Carbon Consumption and Adsorption-Regeneration of H2S on Activated Carbon for Coke Oven Flue Gas Purification

Carbon Consumption and Adsorption-Regeneration of H2S on Activated Carbon for Coke Oven Flue Gas Purification | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Carbon Consumption and Adsorption-Regeneration of H2S on Activated Carbon for Coke Oven Flue Gas Purification Yuting Lin, Yuran Li, Zhicheng Xu, Junxiang Guo, Tingyu Zhu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-335006/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract Carbon consumption of activated carbon varies with the sulfur-containing products. In this work, differential thermogravimetric (DTG), electron paramagnetic resonance (ESR), X-ray photoelectron spectroscopy (XPS), and temperature programmed desorption (TPD) were used to reveal the adsorption-regeneration process of H 2 S and the effect of adsorption products on carbon consumption. H 2 S reacts with the C=C bond to form C-S bond as an intermediate state, followed by the formation of elemental sulfur. It directly sublimates at approximately 380 °C , about 30 °C higher than the decomposition temperature of H 2 SO 4 . In the thermal regeneration process, the elemental sulfur in the form of monoclinic sulfur (S 8 ) first breaks into infinitely long chain molecules (S ∞ ) and then into small molecules, finally into sulfur vapor. The desorption of elemental sulfur consumes less oxygen and carbon functional groups, reducing the chemical carbon consumption by 59.8% than H 2 SO 4 . The compressive strength reduces less due to its slight effect on the disordered graphitic structure. H 2 S also reacts with the C=O bond to form H 2 SO 3 or H 2 SO 4 . The desorption of H 2 SO 3 does not require carbon consumption. The decomposition of H 2 SO 4 needs to react with C=C bond to release SO 2 , CO 2 , and CO, and the compressive strength of activated carbon significantly decreases. The carbon consumption originates from two aspects, the one from the regeneration of sulfur-containing products is more than twice of the other one from the decomposition of oxygen-containing functional groups. Environmental Engineering activated carbon hydrogen sulfide elemental sulfur chemical carbon consumption physical carbon abrasion Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction Due to the leakage of coke oven gas from the furnace wall, coke oven flue gas contains approximately 200 mg/m 3 H 2 S in addition to 150 mg/m 3 SO 2 , and this issue must then be ameliorated by oxidation (Vinod and Tawfik, 2013). Activated carbon treatment of H 2 S and SO 2 in flue gas is an environmentally friendly and effective purification technology (Braghiroli et al., 2019, Grzyb et al., 2009, Liu et al., 2003, Nguyen-Thanh et al., 2005, Rubio and Izquierdo, 2010). However, more than 20% of the operation cost per year is attributed to the supplement of activated carbon for activated carbon technology. The proportion of operation cost is calculated based on the coke oven flue gas purification project from ACRE Coking and Refractory Engineering Consulting Corporation in Hebei province, China. Therefore, the carbon consumption should be reduced for sustainable development and cleaner production. Carbon consumption of activated carbon purification technology is obvious different under different industrial flue gas. For a long-term operation of activated carbon purification device, it is found that the carbon consumption in sintering flue gas purification is 1.15 ~ 1.2 times higher than that in coke oven flue gas purification. The both flue gas has a similar NO concentration about 300 ~ 400 ppm and total sulfur concentration about 200 ~ 300 ppm. While sintering flue gas only contains SO 2 , but coke oven flue gas includes 30 ~ 50% H 2 S except SO 2 . Carbon consumption consists of physical carbon consumption and chemical carbon consumption. The main influencing factors of physical carbon consumption include the moving speed of activated carbon, wear resistance and compressive strength, which is no significant diversity between the two devices. The chemical carbon consumption is from the regeneration of the sulfur-containing components. That is, the presence of H 2 S may decrease the carbon consumption. At present, there is little research on the effects of H 2 S on carbon consumption of activated carbon for flue gas purification. Both H 2 S and SO 2 in coke oven flue gas can cause sulfur species deposition on the activated carbon, which are usually treated by thermal regeneration to recover the reaction activity (Li et al., 2019a, Qi et al., 2014, Silas et al., 2018). SO 2 is combined with basic functional groups to generate H 2 SO 4 (Guo et al., 2013, Karatepe et al., 2008, Xu et al., 2018). H 2 S can be oxidized to sulfur, H 2 SO 3 and H 2 SO 4 , which depend on the activated carbon surface properties and the atmosphere. H 2 S associates with the oxygen functional groups on the activated carbon surface, producing H 2 SO 4 and elemental sulfur. With O 2 in the atmosphere, H 2 S can be oxidized to elemental sulfur, and then to produce gaseous SO 2 (Li et al., 2019a). In the thermal regeneration process, H 2 SO 4 can react with activated carbon to release SO 2 and simultaneously produce CO and CO 2 , which are the main sources of the chemical carbon consumption (Li et al., 2019b). H 2 SO 3 decomposes at lower temperature, so its chemical carbon consumption is essentially negligible (Kim et al., 2019). Currently, the transformation of elemental sulfur in the regeneration process and its chemical carbon consumption are rarely studied. The physical carbon abrasion is related to the mechanical strength of the activated carbon as well as the moving speed of the activated carbon in the reactor. Regeneration will alter the lattice structure of the activated carbon and then affect its mechanical strength. To date, few studies have focused on this issue. The adsorption products determine the carbon consumption at different degrees. Therefore, the deposition products of three typical sulfur-containing components were prepared on activated carbon in various adsorption atmospheres, and then the regeneration process was studied to elucidate the effect of sulfur containing substances on the physical structure and chemical characteristics of activated carbon. The sources of physical carbon abrasion and chemical carbon consumption were studied, and the strategy of reducing carbon consumption was put forward. 2. Material and methods 2.1 Activated carbon preparation The anthracite-based activated carbon (AC) is from Shanxi province. The material in the lab was pulverized, sieved to 20 - 60 mesh (0.25 - 0.85 mm), rinsed by deionized water, filtered and dried in a drying oven at 110 °C for 20 h; the activated carbon thus treated was marked as fresh AC. The fresh AC sample was pretreated in a fixed bed reactor with a diameter of 30 mm, with 1.50 ± 0.01 g sample charged, and then reacted with the mixture gas at a gas hourly space velocity of 5700 h -1 at 150 °C for 300 min. Four samples named blank sample and AC 1 - AC 3 were obtained in different gas: blank sample, N 2 ; AC 1 , 50 ppm SO 2 and 150 ppm H 2 S; AC 2 , 200 ppm SO 2 ; AC 3 , 200 ppm SO 2 and 5% O 2 , with the balance N 2 . The total molar contents of the sulfur substances, the adsorption time and the activated carbon used in the experiment were the same for the AC 1 - AC 3 samples. 2.2 Experimental conditions The thermal regeneration process on the activated carbon samples was investigated in the above-mentioned fixed bed reactor. The regeneration process was carried out in N 2 and the gas flow rate was 180 ± 5 mL/min at a heating rate of 5 °C/min from 150 °C to the final temperature of 450 °C. The regenerated activated carbon was labeled as AC-re. The outlet concentration of the gas component was tested online by a Fourier transform infrared (FTIR) spectrometer (Tensor 27, Bruker, Germany). The integral area of the thermal regeneration curves could be used to calculate the CO and CO 2 contents with a minimum standard deviation of approximately 2%. And the same calculation method was also used for the temperature programmed desorption (TPD) curves obtained at a heating rate of 5 °C/min from 150 °C to 900 °C. Chemical carbon consumption referred to the sum of CO and CO 2 emitted per gram of activated carbon (mmol/g) during the regeneration. 2.3 Characterization methods Elemental analysis was conducted using an Elemental Analyzer (Vario EL, Elementar, Germany). The C, N, H and S contents were characterized on the dry ash free (daf) basis of the AC samples with a minimum standard deviation of approximately 0.2%, and the O content was calculated by the difference method. A simultaneous thermogravimetric (TG) analyzer (LABSYS EVO, SETARAM LABSYS, France) was used to test the TG and differential TG (DTG) curves over the 30 – 900 °C range at a heating rate of 5 °C/min in N 2 . 50 mg analytically pure sulfur and 50 mg activated carbon were packed in a suprasil quartz glass tube, and heated in air. The characterization methods of pore structure, graphite structure, X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance infrared Fourier transform (DRIFT) spectra were represented in detail elsewhere (Fang et al., 2013, Li et al., 2018). The electron paramagnetic resonance (ESR) spectra were measured to test the form of elemental sulfur on an X-band spectrometer (EMXplus-9.5/12, Bruker, USA) at room temperature, 150 °C and 400 °C. Mechanical strength was measured using a compression strength tester (HNYQ6000, Huatong, China) and a wear resistance tester (MHXT-2D, Tianguan, China), that were customized according to the GB 30202.3-2013 standard. The average value was obtained after three tests with an error of 1% for wear resistance and 3% for compression strength. 3. Results and discussion 3.1 Decomposition mechanism of sulfur products To determine the differences in the sulfur-containing adsorption products, an elemental analysis of various AC samples was carried out, and the results are shown in Table 1. The sulfur contents of the AC 1 - AC 3 samples are basically the same and significantly higher than that of the blank sample due to the strong adsorption capacity of activated carbon for H 2 S and SO 2 . For AC 1 - AC 3 samples, there is no clear difference in the sulfur and oxygen contents with a deviation of 2%. According to the previous study (Li et al., 2019a), the desulfurization efficiency of the three atmospheres used in the work can reach approximately 95% so that the sulfur contents of the three products are basically the same. Table 1 Elemental composition of the activated carbon samples (wt%) Samples C H N S O Fresh AC 79.10 1.19 0.99 0.34 18.38 Blank 79.27 1.31 1.02 0.44 17.96 AC 1 75.71 1.31 0.97 1.87 20.14 AC 2 76.15 1.13 1.07 1.79 19.78 AC 3 75.82 1.20 0.97 1.83 20.18 Fig. 1 shows the proportions of the elemental sulfur, SO 3 2- and SO 4 2- calculated from the data in Fig. S1. SO 4 2- and elemental sulfur (Liu et al., 2015, Menezes et al., 2018, Qiu et al., 2019) constitute the majority of sulfur products on the activated carbon surface for the four samples. The proportion of elemental sulfur in AC 1 is 65.8%, indicating that the oxidation products of H 2 S are mostly elemental sulfur. AC 2 contains approximately 20.8% H 2 SO 3 , because H 2 SO 3 can be formed by the reaction of SO 2 and H 2 O in the atmosphere without O 2 . However, due to the oxidation of oxygen-containing functional groups on the AC surface, H 2 SO 3 will be oxidized to H 2 SO 4 (Guo et al., 2013). The SO 4 2- content in AC 3 is greater than 60%, because SO 2 is adsorbed at the active site first and then is easily oxidized to H 2 SO 4 in the presence of O 2 . According to the analysis of the elemental content and XPS spectra, the total sulfur content is basically the same for AC 1 - AC 3 , and the difference lies in the forms of sulfur-containing products. The elemental sulfur accounts for the majority of the sulfur species in AC 1 , while AC 2 contains 20.8% H 2 SO 3 , and the main sulfur product in AC 3 is H 2 SO 4 . The existence form of sulfur-containing products is determined by the adsorption atmosphere of different sulfur components with SO 2 and H 2 S. The XPS results of carbon and oxygen functional groups are shown in Table. S1 and S2. As shown in Fig. 2 (a), compared with the blank sample, the amount of C=C and C=O bonds of AC 1 clearly decrease, while the C-S bond increases. According to previous studies (Silas et al., 2018), in the process of H 2 S oxidation, the C=C bond and C=O bond have been broken by H 2 S, and then the C-S bond and S-O bond are generated as intermediate products. The C-S bond tends to form elemental sulfur, while the S-O bond is likely to form H 2 SO 4 . For the AC 2 and AC 3 samples, there is no clear change in the carbon functional groups. After the thermal regeneration, the content of C-S bond in blank sample significantly decreases, due to the release of its own sulfur in the process of regeneration. The content of C=C bond basically changes little due to few sulfur compounds in the blank sample to react with C=C bond. For AC 1 - AC 3 samples, the main change is reflected in the reduction of C=C and C-S bonds, and the increase of the C=O and C-O bond. The C=C bond reacts with H 2 SO 4 to release SO 2 . The C-S bond is unstable and easily decomposes to release elemental sulfur at high temperature. The C=O and C-O bonds are more stable than the other carbon functional groups, so that the total amount of these two carbon functional groups changes little but their proportion increases. The decrease in the C=C bond is most obvious for AC 3 , which is related to the fact that the highest H 2 SO 4 content among the three samples is observed on AC 3 . As shown in Fig. 2 (b), compared with the blank sample, the C=O bond amount of AC 1 clearly decreases and the OH amount increases, due to the combination of the C=O bond with free H in H 2 S. For AC 2 and AC 3 , the OH amount obviously decreases, due to the form H 2 SO 4 or H 2 SO 3 through the combination of the OH site with SO 2 . In the thermal regeneration process, COOH and OH can be decomposed below 450 °C and mainly from carboxyls, lactones and anhydrides (Vivovilches et al., 2014), which is an important reason for the loss of the carbon functional groups. While the C=O bond amount increases significantly, due to their stable chemical properties. To further illustrate the decomposition process of the sulfur products in activated carbon, in situ DRIFT spectra are carried out with the results shown in Fig. 2 (c) and (d). H 2 SO 3 (872 cm - 1 ) and H 2 SO 4 (1090 cm - 1 ) are observed in the adsorption process, particularly for the AC 2 and AC 3 samples, but their amount decreases during the regeneration process. Due to the adsorption amount of acid SO 2 , the alcohol (OH) (1240 cm -1 ) decreases while alkyl ether (1020 cm - 1 ) increases in the AC 2 and AC 3 samples. In the regeneration process, the reduction of the S-O bond (1150 cm - 1 ) is most significant in AC 3 , representing the decomposition of sulfuric acid. Another important change is the decomposition of carboxylic acid (1080 cm -1 ). Carboxylic acid on the activated carbon surface decomposes below 450 °C, which is an important reason for the reduction in the denitrification efficiency of the activated carbon after regeneration. In the regeneration process, the chemical carbon consumption comes from the decomposition of oxygen-containing functional groups and the reaction of activated carbon with H 2 SO 4 . Carboxyls, lactones and anhydrides with COOH and OH groups can be decomposed below 450 °C. The thermal decomposition of functional groups is independent with the type of sulfur-containing products. The thermal regeneration of sulfur-containing products results in the reduction of the C=C bond amount. The C=C bond reacts with H 2 SO 4 to produce CO and CO 2 . 3.2 Effect of sulfur products regeneration on chemical carbon consumption Fig. 3 shows the SO 2 concentration for the AC 1 - AC 3 samples during the TPD process. The decomposition temperature range of H 2 SO 3 is 150 ~ 300 °C, and H 2 SO 4 decomposes at 300 ~ 450 °C (Lin et al., 2018). Therefore, the regeneration temperature is set at 450 °C for the complete desorption of SO 2 . At approximately 380 °C, a main peak of the H 2 SO 4 decomposition is observed. A shoulder peak of SO 2 desorption is observed in AC 2 at 150 ~ 300 °C because the H 2 SO 3 decomposition temperature is lower than that of H 2 SO 4 (Kim et al., 2019). The peak areas of AC 1 - AC 3 in the range of 300 ~ 450 °C are 37523, 46112 and 67321, basically proportional to the H 2 SO 4 contents of 33.1%, 39.7% and 60.7% calculated from the XPS spectra as given in Fig. 1. There are no clear differences between the total sulfur contents of the three adsorbed samples, while the concentration of the desorbed SO 2 from AC 1 is significantly lower than AC 2 and AC 3 , indicating that the most of the sulfur in AC 1 decomposes in the form of elemental sulfur instead of SO 2 . Table 2 Elemental analysis of the activated carbon samples after the TPD process (wt%) Samples C H N S O Blank 86.12 1.97 0.61 0.39 10.91 AC 1 86.16 1.67 1.09 0.44 10.64 AC 2 87.23 1.81 1.37 0.41 9.18 AC 3 88.02 1.77 1.01 0.52 8.68 The results of elemental analysis of various samples after the TPD process are shown in Table 2. Compared with the data in Table 1, the sulfur and oxygen contents in AC 1 - AC 3 samples decrease during the TPD process, due to the decomposition of the sulfur species and oxygen functional groups at high temperature (Lin et al., 2018). The sulfur content shows slight differences among the three samples, showing that the three samples have similar values of the total desorption amount of the sulfur species. However, clear differences among the three samples are observed for the oxygen content. The oxygen content of AC 1 is significantly higher than those of AC 2 and AC 3 . It is inferred that the desorption process of elemental sulfur is different from that of H 2 SO 4 , with H 2 SO 4 releasing more oxygen during the desorption process. Fig. 4 show the results for the SO 2 desorption and chemical carbon consumption of the three samples during the regeneration process. The SO 2 desorption in AC 1 is much lower than that in AC 2 and AC 3 , because the elemental sulfur desorption cannot be detected by FTIR. AC 1 has the smallest carbon consumption, because of the largest component of elemental sulfur. For AC 2 , some H 2 SO 3 can be decomposed directly at lower temperature, thus reducing the release of CO and CO 2 . AC 3 consumes the most carbon, mainly due to the reaction of sulfuric acid and carbon. The carbon consumption of blank sample can be used to calculate the decomposition of oxygen-containing functional groups during regeneration. As shown in Table 3, according to the comparison of the oxygen content between the activated carbon and blank sample, about 6% of the oxygen-containing functional groups are consumed in the regeneration process. For AC 1 , the total carbon consumption during regeneration is 0.28 mmol/g, of which 75% comes from the thermal decomposition of oxygen-containing functional groups and 25% originates from the reaction between C and H 2 SO 4 . For AC 3 sample, the total carbon consumption during regeneration is 0.68 mmol/g, including 31% from its own thermal decomposition and 69% from its reaction with H 2 SO 4 . The desorption of elemental sulfur consumes less oxygen and carbon functional groups, reducing the chemical carbon consumption by 59.8% than H 2 SO 4 . In AC 3 , the carbon consumption caused by the regeneration of sulfur-containing products is more than twice of that caused by the decomposition of oxygen-containing functional groups, which indicates that the most important carbon consumption for the activated carbon used is caused by the reaction of C and H 2 SO 4 . Table 3 SO 2 recovery and carbon consumption of the AC samples Samples S (mmol/g) Carbon Consumption (mmol/g) Adsorption (H 2 S and SO 2 ) Desorption (SO 2 ) CO CO 2 Total C/S blank 0 0 0.04 0.17 0.21 / AC 1 0.76 0.15 0.06 0.22 0.28 0.45 AC 2 0.73 0.39 0.16 0.44 0.60 1.00 AC 3 0.77 0.36 0.20 0.48 0.68 1.12 * Blank refers to the blank activated carbon without adsorption. Unlike H 2 SO 4 and H 2 SO 3 , elemental sulfur cannot be determined during the desorption process. To further evaluate the morphology of sulfur products, DTG characteristics were used to measure the total weight loss at various temperature ranges, with the results shown in Fig. 5. The peak at 350 °C represents the decomposition of H 2 SO 4 , while elemental sulfur directly sublimates at approximately 380 °C. Based on the temperature peak position, AC 1 mainly contains elemental sulfur and a small amount of H 2 SO 4 , and AC 2 contains less H 2 SO 4 than AC 3 . H 2 SO 4 and a small amount of elemental sulfur are found on the surface of AC 3 . The differences between the peak area of DTG curves and that of SO 2 , CO and CO 2 content curves are the content of elemental sulfur. And elemental sulfur in AC 1 is the highest, which is consistent with the results in Fig. 1. It can be concluded from the DTG curves that the elemental sulfur sublimates at 350 ~ 400 °C, which is of great significance to guide the design for industrial flue gas purification by activated carbon process. Electron Spin Resonance was used to calculate the average chain length of sulfur by dividing the number of electron spin (Terada et al., 2020). The ESR spectrogram is shown in Fig. S3. Where E (in spins per gram) is the amount of electron spin of samples, N A (6.022ⅹ10 23 mol -1 ) is Avogadro constant. It is difficult to test the electron spin of activated carbon because of its magnetism. So, the results of elemental sulfur were used to characterize the properties of elemental sulfur produced by adsorption on activated carbon, as shown in Fig.6. When the elemental sulfur rises from room temperature to 150 ℃, the chain length of sulfur has no obvious change, and the average value is about 2´10 6 . It is difficult for orthorhombic sulfur to exist at 150 ℃, the sulfur form at this temperature is monoclinic sulfur (S 8 ) (Terada et al., 2020). Each sulfur atom forms covalent single bond with the other two sulfur atoms in sp 3 hybrid orbit (Brandi et al., 2019). When the temperature continues to rise up to 254 ℃, the electron spin number of sulfur is close to 0, the S 8 ring structure breaks into infinitely long chain molecules (S ∞ ) which are twisted back together. The temperature continues to rise to 400 ℃, the average chain length of sulfur decreases to 0.7ⅹ10 6 , the sulfur becomes vapor, and there are S 8 , S 6 , S 2 and other molecules in the vapor (Lau et al., 2017). For the composition of sulfur vapor, the energy barriers of ·S 2 · and ·S 6 · are only 209.45 kJ/mol (Song et al., 2019). It is the lowest energy barriers of the ring opening reaction of S 8 , which indicates that the reaction is easy to occur when the S 8 chain breaks. The energy barrier of ·S 4 · is 447.07 kJ/mol (Jones and Ballone, 2003), which is difficult to occur. Therefore, only three products of S 2 , S 6 , S 8 are calculated when calculating the equilibrium sulfur vapor products. According to principle of minimum free energy (Catone et al., 2019), the volume fraction of each component for sulfur vapor at 400 ℃ is 3.7% for S 2 ，56.4% for S 6 and 39.9% for S 8 . At the adsorption temperature, the state of elemental sulfur is monoclinic sulfur, which is composed of S 8 ring molecules. When the activated carbon is regenerated, the temperature rise first causes the S 8 ring structure to break into infinitely long chain molecules (S ∞ ). Above 254 °C, the long chain sulfur breaks into small molecules, such as S 6 and S 2 . At 400 °C, the sulfur becomes vapor, and the volume fraction of each component for sulfur vapor is 3.7% for S 2 , 56.4% for S 6 and 39.9% for S 8 . Table 4 shows the reactions of sulfur-containing substances with activated carbon in the adsorption-regeneration process. C(O) represents the oxygen functional groups on the activated carbon surface. Table 4 Reactions for adsorption-regeneration process of sulfur-containing substances on activated carbon Process Change of reactants Reaction Participating functional groups No. Adsorption Adsorption and oxidation of SO 2 SO 2 →H 2 SO 3 OH (1) (2) SO 2 →H 2 SO 4 Oxidation of H 2 S H 2 S→S(s) Reactant: C=O, C=C Intermediate product: C-S, S-O (3) (4) (5) H 2 S→H 2 SO 3 H 2 S→H 2 SO 4 Regeneration Regeneration of sulfur products H 2 SO 4 +C→SO 2 +CO+H 2 O 2H 2 SO 4 +2C→2SO 2 +CO 2 + 2H 2 O H 2 SO 3 →SO 2 +H 2 O S(s)→S(g) C=C (6) (7) (8) (9) Decomposition of carbon-functional groups C(O)→CO 2 carboxyls, lactones and anhydrides (10) (11) C(O)→CO The carbon consumption partly depends on the existence form of sulfur-containing products, in addition to the thermal decomposition of functional groups. The desorption of elemental sulfur consumes less oxygen and carbon functional groups, with 59.8% less chemical carbon consumption than H 2 SO 4 . The carbon consumption caused by the regeneration of sulfur-containing products is less than that by the decomposition of functional groups with elemental sulfur as the main products. 3.3 Influence of sulfur products regeneration on physical carbon abrasion To investigate the influence of sulfur products regeneration on the AC physical structure, the pore structures were analyzed before and after the regeneration. The results are shown in Table 5. In comparison with the blank sample, the specific surface area and pore volume of AC 1 - AC 3 clearly decrease due to the sediment of sulfur substances on the activated carbon surface. Moreover, the specific surface area of AC 1 decreases by 11% and that of AC 3 decreases by 20%. This phenomenon is ascribed to the different volumes of elemental sulfur and H 2 SO 4 . The volume of elemental sulfur is 13.6 cm 3 /mol, while that of sulfuric acid is 53.5 cm 3 /mol, and that of H 2 SO 3 is 79.6 cm 3 /mol (Lau et al., 2017). Therefore, when elemental sulfur rather than H 2 SO 4 is deposited on the activated carbon surface, the decrease in the specific surface area is not obvious. After thermal regeneration, both the specific surface area and pore volume increase because of the partial decomposition of the functional groups. The pore size of the activated carbon is restored to the level of the fresh activated carbon, and even increases after the regeneration. Table 5 Characterization of the various AC before and after regeneration Sample S BET (m 2 /g) V m (mL/g) V t (mL/g) Be-re Af- re Be- re Af-re Be- re Af-re Fresh AC 196 0.070 0.087 Blank 198 221 0.070 0.070 0.091 0.096 AC 1 175 215 0.065 0.073 0.076 0.096 AC 2 161 200 0.059 0.070 0.076 0.093 AC 3 157 199 0.059 0.070 0.069 0.093 *Be-re is the abbreviation of before-regeneration. Af-re is the abbreviation of after-regeneration. The graphite microcrystalline structure of the AC samples before and after regeneration was shown in Fig. 7. Raman spectra of all samples displays two peaks including the disorder (D) peak at 1360 cm -1 reflecting the structural defects and the graphite (G) peak at 1600 cm -1 reflecting the sp 2 carbon atoms in the graphene sidewalls. The ratio of the peak intensity (I D /I G ) represents the degree of disorder in the graphite microcrystalline structure on activated carbon (Zhang et al., 2019). The D and G peaks of various AC samples are basically the same prior to regeneration. The D peaks of AC 1 - AC 3 samples clearly increase after regeneration, while the G peak does not change much, so that the I D / I G value increases significantly, particularly for AC 3 . This indicates that regeneration can significantly improve the disorder in the activated carbon. From the macroscopic point of view, the activated carbon structure can also be characterized by compressive strength and wear resistance, which are tested before and after regeneration, with results shown in Fig. 8. There is little difference between the wear resistance values before and after regeneration, while the compressive strength clearly decreases, especially for the AC 2 and AC 3 samples, indicating that the reaction of C and H 2 SO 4 destroys the integrity of the carbon structure. The compressive strength and wear resistance decrease on regenerated activated carbon, leading to the increase in the amount of small granular activated carbon, and finally increase the physical carbon abrasion. 3.4 Total carbon consumption in engineering applications The total carbon consumption in engineering applications includes chemical carbon consumption and physical carbon abrasion. In this work, two factories using activated carbon technology for flue gas purification were investigated. One is for sintering flue gas purification to capture SO 2 , and the other is for coke oven flue gas purification to simultaneously remove SO 2 and H 2 S. The results are shown in Table 6. For sintering flue gas purification, the total carbon consumption is about 55% of the total charge per year; among them, the physical carbon abrasion is about 38%, and the chemical carbon consumption is about 17%. The physical carbon abrasion is twice more than chemical carbon consumption. The total carbon consumption is approximately 48% for coke oven flue gas, lower than that for sintering flue gas. The high content of H 2 S depresses the carbon consumption in the regeneration process compared with the same content of SO 2 . Table 6 Comparison of total carbon consumption between sintering flue gas and coke oven flue gas Sintering flue gas Coke oven flue gas Total gas volume (Nm 3 /h) 2,800,000 300,000 Inlet SO 2 (ppm) 200~300 50~100 Inlet H 2 S (ppm) / 150~200 Outlet SO 2 (ppm) 20 10 Outlet H 2 S (ppm) / 15 Total AC loading (t) 12,000 2500 Total AC consumption (t/a) 6600 1200 Physical carbon abrasion 38% 35% Chemical carbon consumption 17% 13% In order to reduce carbon consumption, the following strategies can be considered. Use air screen sorting devices to reduce physical carbon abrasion. With the increase of operation time, the particle size of activated carbon becomes smaller and smaller. The small particles and dust fill in the gap of activated carbon bed increasing the resistance of flue gas. An efficient balance vibrating screen in the activated carbon conveying system is commonly used to screen out small particles, but this measure will undoubtedly greatly increase the physical carbon abrasion between the particles and particle with vibrating screen. In order to solve this problem, an air screen sorting device for activated carbon was developed in the project. Driven by the upstream hot air flow, the dust and small particles in the activated carbon were gradually fluidized, suspended, and finally separated under the traction of the upstream air flow. This process reduces the collision and friction between the particles and vibrating screen, and then greatly reduces the physical carbon abrasion. Select a high-quality activated carbon to reduce chemical carbon consumption. In engineering, the main quality index of activated carbon includes sulfur capacity, wear resistance, compressive strength, ignition point, and particle size distribution etc. In this work, it is found that elemental sulfur generated by H 2 S can reduce the chemical carbon consumption of activated carbon. Therefore, the activated carbon with less C=O bond should be selected under the premise of ensuring the above quality index, which can effectively reduce the production of H 2 SO 4 and greatly reduces the chemical carbon consumption. 4. Conclusions H 2 S can react with the C=C bond on the activated carbon surface to form C-S bond as an intermediate state, followed by the formation of elemental sulfur. It directly sublimates at approximately 380 °C, about 30 °C higher than the decomposition temperature of H 2 SO 4 . So, the regeneration temperature should be determined according to the sublimation temperature of elemental sulfur in the engineering application. At the adsorption temperature, the state of elemental sulfur is monoclinic sulfur in the form of S 8 ring molecules. When the activated carbon is regenerated, the temperature rise first causes the S 8 ring structure to break into infinitely long chain molecules (S ∞ ). When the activated carbon is heated above 254 °C, the long chain sulfur breaks into small molecules. At 400 °C, the sulfur becomes vapor, and the volume fraction of each component for sulfur vapor is 3.7% for S 2 , 56.4% for S 6 and 39.9% for S 8 . The desorption process of elemental sulfur consumes less oxygen and carbon functional groups, reducing the chemical carbon consumption by 59.8% than H 2 SO 4 ; due to the slight effect on the disordered graphitic structure, its compressive strength is reduced less. H 2 S also reacts with the C=O bond to form H 2 SO 3 and H 2 SO 4 . The decomposition of H 2 SO 3 does not require carbon consumption. The deposited H 2 SO 4 reacts with the C=C bond to generate SO 2 , which is the cardinal reaction of the thermal regeneration. In addition, H 2 SO 4 decomposition improves the ratio of the disordered graphitic structure. About 6% of the oxygen-containing functional groups are consumed in the regeneration process, and most of these functional groups are carboxyls, lactones and anhydrides. The carbon consumption caused by the regeneration of sulfur-containing products is more than that caused by the decomposition of oxygen-containing functional groups. From the data of engineering project, the total carbon consumption of coke oven flue gas is slightly lower than that of sintering flue gas. H 2 S will depress the carbon consumption in the thermal regeneration process compared with SO 2 . To reduce carbon consumption, the following two strategies can be considered. Use air screen sorting devices to reduce the collision between activated carbon and vibrating screen, and then significantly reduces the physical carbon abrasion. Select the activated carbon with less C=O bond to reduce the production of H 2 SO 4 , and then greatly reduce the chemical carbon consumption. Declarations Ethics approval and consent to participate : This manuscript has been developed in compliance with ethical standards. Consent for publication : This manuscript does not contain data from any individual person. Availability of data and materials: The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. Consent to participate : The authors voluntarily agreed to participate in this research study. Consent to publish : The authors agree to publish the article in the Environmental Science and Pollution Research. Competing interests : The authors declare that they have no competing interests. Funding : This work was supported by the National Key Research and Development Program of China (No. 2017YFC0210600) and the National Natural Science Foundation of China (No. U1810209). The role of the funding body is in the design of the study, analysis, and interpretation of data. Authors Contributions : Yuting Lin: Conceptualization, Methodology, Formal analysis, Writing- Original draft preparation. Yuran Li.: Resources, Writing - Review & Editing. Zhicheng Xu: Visualization, Investigation. Junxiang Guo: Supervision. Tingyu Zhu: Resources, Supervision. Acknowledgments: This work was supported by the National Key Research and Development Program of China (No. 2017YFC0210600) and the National Natural Science Foundation of China (No. U1810209). References Braghiroli F L, Bouafif H, Koubaa A. Enhanced SO 2 adsorption and desorption on chemically and physically activated biochar made from wood residues [J]. 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Fuel , 2019, 257:324-331. https://doi.org/ 10.1016/j.fuel.2019.116038 Supplementary Files Graphicsummary.tif supportinginformation.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Major Revision 08 May, 2021 Reviewers invited by journal 20 Apr, 2021 Editor invited by journal 31 Mar, 2021 Editor assigned by journal 18 Mar, 2021 First submitted to journal 16 Mar, 2021 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-335006","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":22781334,"identity":"3c9bad08-eccf-4d53-8643-4e71642dcbe5","order_by":0,"name":"Yuting Lin","email":"","orcid":"","institution":"Institute of Process Engineering Chinese Academy of Sciences","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yuting","middleName":"","lastName":"Lin","suffix":""},{"id":22781335,"identity":"1fb72656-6608-4dbd-9cb6-5b4ac581dd8f","order_by":1,"name":"Yuran Li","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAApUlEQVRIiWNgGAWjYFAC5oYDHwxI08LYcHAGyVqYeUjSYHD7YONhm4I7cgzshx8w/NxBjJZziQ2HcwyeGTPwpBkw9p4hRssZRpCWw4kNDDkMzIxtxGqxMDhc38D/hhQtDAaHExgkiLVFEqjlYI/BM8M2iWcGB3uJ0cJ3hvnwhx9/7sjz8yc/fPCTGC0KB8DUAQY2MEkMkG+AahkFo2AUjIJRgBMAAKHjN+/+hhd2AAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0003-0131-9622","institution":"Institute of Process Engineering Chinese Academy of Sciences","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Yuran","middleName":"","lastName":"Li","suffix":""},{"id":22781336,"identity":"50757c3e-6b77-4cab-b370-331fada29d98","order_by":2,"name":"Zhicheng Xu","email":"","orcid":"","institution":"Institute of Process Engineering Chinese Academy of 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02:08:42","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-335006/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-335006/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":8387397,"identity":"aaa79a64-7685-4c19-8fe8-368b1907e25f","added_by":"auto","created_at":"2021-04-23 20:57:31","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":42840,"visible":true,"origin":"","legend":"S 2p peaks from XPS for the activated carbon samples","description":"","filename":"ScreenShot20210423at3.45.39PM.png","url":"https://assets-eu.researchsquare.com/files/rs-335006/v1/4f643e188042f2e7d24ed599.png"},{"id":8387838,"identity":"06c12d3b-4ebf-450a-9350-380525d291cb","added_by":"auto","created_at":"2021-04-23 21:00:31","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":404739,"visible":true,"origin":"","legend":"Content of carbon (a) and oxygen functional groups (b) in the samples \nin situ DRIFT spectra of the samples before (c) and after (d) regeneration\n","description":"","filename":"ScreenShot20210423at3.45.47PM.png","url":"https://assets-eu.researchsquare.com/files/rs-335006/v1/fd3732478883fd76e95f4402.png"},{"id":8387396,"identity":"ac90380e-97e0-4591-ac04-76353977cfae","added_by":"auto","created_at":"2021-04-23 20:57:30","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":43435,"visible":true,"origin":"","legend":"SO2 concentration during the TPD process for the activated carbon samples","description":"","filename":"ScreenShot20210423at3.45.55PM.png","url":"https://assets-eu.researchsquare.com/files/rs-335006/v1/b6d0ae85d9faecdf7a77b157.png"},{"id":8387400,"identity":"3e3d792a-1c25-463a-93bc-fe5d657ee721","added_by":"auto","created_at":"2021-04-23 20:57:31","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":68615,"visible":true,"origin":"","legend":"CO (a) and CO2 (b) concentration during the regeneration process","description":"","filename":"ScreenShot20210423at3.46.03PM.png","url":"https://assets-eu.researchsquare.com/files/rs-335006/v1/74f49f2ea5f27360f29a9dbf.png"},{"id":8387106,"identity":"0d14439d-cf8b-4441-8d5d-581730ea79cb","added_by":"auto","created_at":"2021-04-23 20:54:31","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":160997,"visible":true,"origin":"","legend":"DTG curves for the absorbed AC","description":"","filename":"ScreenShot20210423at3.46.14PM.png","url":"https://assets-eu.researchsquare.com/files/rs-335006/v1/f1bc8b48423f26645d4d2dba.png"},{"id":8387837,"identity":"5aa12743-4b2f-403d-ab3c-70d00c41bd5d","added_by":"auto","created_at":"2021-04-23 21:00:31","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":47205,"visible":true,"origin":"","legend":"Morphological changes of elemental sulfur during adsorption-regeneration process","description":"","filename":"ScreenShot20210423at3.46.22PM.png","url":"https://assets-eu.researchsquare.com/files/rs-335006/v1/22e86326f4532bc577e5c8b4.png"},{"id":8387402,"identity":"9e3e6407-f6d3-4877-8cd6-391738fb7182","added_by":"auto","created_at":"2021-04-23 20:57:31","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":99567,"visible":true,"origin":"","legend":"Raman spectra for various AC samples before and after regeneration","description":"","filename":"ScreenShot20210423at3.46.32PM.png","url":"https://assets-eu.researchsquare.com/files/rs-335006/v1/fcc756a7a2dfb4b6cfcfdf86.png"},{"id":8387403,"identity":"c1b68a1f-5dfb-43ec-b45d-9750e1c57a2d","added_by":"auto","created_at":"2021-04-23 20:57:31","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":30989,"visible":true,"origin":"","legend":"Wear resistance and compressive strength of the AC samples before and after regeneration\n*Be-re is the abbreviation of before-regeneration. Af-re is the abbreviation of after-regeneration.\n","description":"","filename":"ScreenShot20210423at3.46.39PM.png","url":"https://assets-eu.researchsquare.com/files/rs-335006/v1/122b1512d57c41f53b49aea7.png"},{"id":13688559,"identity":"7ecf7aa6-2e4d-4606-9825-e89020a6cf5f","added_by":"auto","created_at":"2021-09-17 12:25:51","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":941805,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-335006/v1/4334e892-5787-4324-ac9d-39df51646cf5.pdf"},{"id":8387399,"identity":"d5d77100-9bed-4295-b0d3-d6f6b0ec830d","added_by":"auto","created_at":"2021-04-23 20:57:31","extension":"tif","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":230296,"visible":true,"origin":"","legend":"","description":"","filename":"Graphicsummary.tif","url":"https://assets-eu.researchsquare.com/files/rs-335006/v1/86422d511d5f13a4af9c1952.tif"},{"id":8387098,"identity":"dc3344ae-d737-49a7-9602-1e6651b94191","added_by":"auto","created_at":"2021-04-23 20:54:30","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":782646,"visible":true,"origin":"","legend":"","description":"","filename":"supportinginformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-335006/v1/252e6928cbaa0dd212a01252.docx"}],"financialInterests":"","formattedTitle":"Carbon Consumption and Adsorption-Regeneration of H2S on Activated Carbon for Coke Oven Flue Gas Purification","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eDue to the leakage of coke oven gas from the furnace wall, coke oven flue gas contains approximately 200 mg/m\u003csup\u003e3\u003c/sup\u003e H\u003csub\u003e2\u003c/sub\u003eS in addition to 150 mg/m\u003csup\u003e3\u003c/sup\u003e SO\u003csub\u003e2\u003c/sub\u003e, and this issue must then be ameliorated by oxidation (Vinod and Tawfik, 2013). Activated carbon treatment of H\u003csub\u003e2\u003c/sub\u003eS and SO\u003csub\u003e2\u003c/sub\u003e in flue gas is an environmentally friendly and effective purification technology (Braghiroli et al., 2019, Grzyb et al., 2009, Liu et al., 2003, Nguyen-Thanh et al., 2005, Rubio and Izquierdo, 2010). However, more than 20% of the operation cost per year is attributed to the supplement of activated carbon for activated carbon technology. The proportion of operation cost is calculated based on the coke oven flue gas purification project from ACRE Coking and Refractory Engineering Consulting Corporation in Hebei province, China. Therefore, the carbon consumption should be reduced for sustainable development and cleaner production.\u003c/p\u003e\n\u003cp\u003eCarbon consumption of activated carbon purification technology is obvious different under different industrial flue gas. For a long-term operation of activated carbon purification device, it is found that the carbon consumption in sintering flue gas purification is 1.15 ~ 1.2 times higher than that in coke oven flue gas purification. The both flue gas has a similar NO concentration about 300 ~ 400 ppm and total sulfur concentration about 200 ~ 300 ppm. While sintering flue gas only contains SO\u003csub\u003e2\u003c/sub\u003e, but coke oven flue gas includes 30 ~ 50% H\u003csub\u003e2\u003c/sub\u003eS except SO\u003csub\u003e2\u003c/sub\u003e. Carbon consumption consists of physical carbon consumption and chemical carbon consumption. The main influencing factors of physical carbon consumption include the moving speed of activated carbon, wear resistance and compressive strength, which is no significant diversity between the two devices. The chemical carbon consumption is from the regeneration of the sulfur-containing components. That is, the presence of H\u003csub\u003e2\u003c/sub\u003eS may decrease the carbon consumption. At present, there is little research on the effects of H\u003csub\u003e2\u003c/sub\u003eS on carbon consumption of activated carbon for flue gas purification.\u003c/p\u003e\n\u003cp\u003eBoth H\u003csub\u003e2\u003c/sub\u003eS and SO\u003csub\u003e2\u003c/sub\u003e in coke oven flue gas can cause sulfur species deposition on the activated carbon, which are usually treated by thermal regeneration to recover the reaction activity (Li et al., 2019a, Qi et al., 2014, Silas et al., 2018). SO\u003csub\u003e2\u003c/sub\u003e is combined with basic functional groups to generate H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e (Guo et al., 2013, Karatepe et al., 2008, Xu et al., 2018). H\u003csub\u003e2\u003c/sub\u003eS can be oxidized to sulfur, H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e, which depend on the activated carbon surface properties and the atmosphere. H\u003csub\u003e2\u003c/sub\u003eS associates with the oxygen functional groups on the activated carbon surface, producing H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e and elemental sulfur. With O\u003csub\u003e2\u003c/sub\u003e in the atmosphere, H\u003csub\u003e2\u003c/sub\u003eS can be oxidized to elemental sulfur, and then to produce gaseous SO\u003csub\u003e2\u003c/sub\u003e (Li et al., 2019a). In the thermal regeneration process, H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e can react with activated carbon to release SO\u003csub\u003e2\u003c/sub\u003e and simultaneously produce CO and CO\u003csub\u003e2\u003c/sub\u003e, which are the main sources of the chemical carbon consumption (Li et al., 2019b). H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e decomposes at lower temperature, so its chemical carbon consumption is essentially negligible (Kim et al., 2019). Currently, the transformation of elemental sulfur in the regeneration process and its chemical carbon consumption are rarely studied. The physical carbon abrasion is related to the mechanical strength of the activated carbon as well as the moving speed of the activated carbon in the reactor. Regeneration will alter the lattice structure of the activated carbon and then affect its mechanical strength. To date, few studies have focused on this issue.\u003c/p\u003e\n\u003cp\u003eThe adsorption products determine the carbon consumption at different degrees. Therefore, the deposition products of three typical sulfur-containing components were prepared on activated carbon in various adsorption atmospheres, and then the regeneration process was studied to elucidate the effect of sulfur containing substances on the physical structure and chemical characteristics of activated carbon. The sources of physical carbon abrasion and chemical carbon consumption were studied, and the strategy of reducing carbon consumption was put forward.\u003c/p\u003e"},{"header":"2. Material and methods","content":"\u003cp\u003e\u003cem\u003e2.1 Activated carbon preparation\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe anthracite-based activated carbon (AC) is from Shanxi province. The material in the lab was pulverized, sieved to 20 - 60 mesh (0.25 - 0.85 mm), rinsed by deionized water, filtered and dried in a drying oven at 110 \u0026deg;C for 20 h; the activated carbon thus treated was marked as fresh AC. The fresh AC sample was pretreated in a fixed bed reactor with a diameter of 30 mm, with 1.50 \u0026plusmn; 0.01 g sample charged, and then reacted with the mixture gas at a gas hourly space velocity of 5700 h\u003csup\u003e-1\u003c/sup\u003e at 150 \u0026deg;C for 300 min. Four samples named blank sample and AC\u003csub\u003e1\u003c/sub\u003e - AC\u003csub\u003e3\u003c/sub\u003e were obtained in different gas: blank sample, N\u003csub\u003e2\u003c/sub\u003e; AC\u003csub\u003e1\u003c/sub\u003e, 50 ppm SO\u003csub\u003e2\u003c/sub\u003e and 150 ppm H\u003csub\u003e2\u003c/sub\u003eS; AC\u003csub\u003e2\u003c/sub\u003e, 200 ppm SO\u003csub\u003e2\u003c/sub\u003e; AC\u003csub\u003e3\u003c/sub\u003e, 200 ppm SO\u003csub\u003e2\u003c/sub\u003e and 5% O\u003csub\u003e2\u003c/sub\u003e, with the balance N\u003csub\u003e2\u003c/sub\u003e. The total molar contents of the sulfur substances, the adsorption time and the activated carbon used in the experiment were the same for the AC\u003csub\u003e1\u003c/sub\u003e - AC\u003csub\u003e3\u003c/sub\u003e samples.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e2.2 Experimental conditions\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe thermal regeneration process on the activated carbon samples was investigated in the above-mentioned fixed bed reactor. The regeneration process was carried out in N\u003csub\u003e2\u003c/sub\u003e and the gas flow rate was 180 \u0026plusmn; 5 mL/min at a heating rate of 5 \u0026deg;C/min from 150 \u0026deg;C to the final temperature of 450 \u0026deg;C. The regenerated activated carbon was labeled as AC-re. The outlet concentration of the gas component was tested online by a Fourier transform infrared (FTIR) spectrometer (Tensor 27, Bruker, Germany). The integral area of the thermal regeneration curves could be used to calculate the CO and CO\u003csub\u003e2\u003c/sub\u003e contents with a minimum standard deviation of approximately 2%. And the same calculation method was also used for the temperature programmed desorption (TPD) curves obtained at a heating rate of 5 \u0026deg;C/min from 150 \u0026deg;C to 900 \u0026deg;C. Chemical carbon consumption referred to the sum of CO and CO\u003csub\u003e2\u003c/sub\u003e emitted per gram of activated carbon (mmol/g) during the regeneration.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e2.3 Characterization methods\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eElemental analysis was conducted using an Elemental Analyzer (Vario EL, Elementar, Germany). The C, N, H and S contents were characterized on the dry ash free (daf) basis of the AC samples with a minimum standard deviation of approximately 0.2%, and the O content was calculated by the difference method.\u003c/p\u003e\n\u003cp\u003eA simultaneous thermogravimetric (TG) analyzer (LABSYS EVO, SETARAM LABSYS, France) was used to test the TG and differential TG (DTG) curves over the 30 \u0026ndash; 900\u0026thinsp;\u0026deg;C range at a heating rate of 5\u0026thinsp;\u0026deg;C/min in N\u003csub\u003e2\u003c/sub\u003e. 50 mg analytically pure sulfur and 50 mg activated carbon were packed in a suprasil quartz glass tube, and heated in air.\u003c/p\u003e\n\u003cp\u003eThe characterization methods of pore structure, graphite structure, X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance infrared Fourier transform (DRIFT) spectra were represented in detail elsewhere (Fang et al., 2013, Li et al., 2018).\u003c/p\u003e\n\u003cp\u003eThe electron paramagnetic resonance (ESR) spectra were measured to test the form of elemental sulfur on an X-band spectrometer (EMXplus-9.5/12, Bruker, USA) at room temperature, 150 \u0026deg;C and 400 \u0026deg;C.\u003c/p\u003e\n\u003cp\u003eMechanical strength was measured using a compression strength tester (HNYQ6000, Huatong, China) and a wear resistance tester (MHXT-2D, Tianguan, China), that were customized according to the GB 30202.3-2013 standard. The average value was obtained after three tests with an error of 1% for wear resistance and 3% for compression strength.\u003c/p\u003e"},{"header":"3. Results and discussion","content":"\u003cp\u003e\u003cem\u003e3.1 Decomposition mechanism of sulfur products\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eTo determine the differences in the sulfur-containing adsorption products, an elemental analysis of various AC samples was carried out, and the results are shown in Table 1. The sulfur contents of the AC\u003csub\u003e1\u003c/sub\u003e - AC\u003csub\u003e3\u003c/sub\u003e samples are basically the same and significantly higher than that of the blank sample due to the strong adsorption capacity of activated carbon for H\u003csub\u003e2\u003c/sub\u003eS and SO\u003csub\u003e2\u003c/sub\u003e. For AC\u003csub\u003e1\u003c/sub\u003e - AC\u003csub\u003e3\u003c/sub\u003e samples, there is no clear difference in the sulfur and oxygen contents with a deviation of 2%. According to the previous study (Li et al., 2019a), the desulfurization efficiency of the three atmospheres used in the work can reach approximately 95% so that the sulfur contents of the three products are basically the same.\u003c/p\u003e\n\u003cp\u003eTable 1 Elemental composition of the activated carbon samples (wt%)\u003c/p\u003e\n\u003ctable border=\"1\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e\u003cstrong\u003eSamples\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e\u003cstrong\u003eC\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e\u003cstrong\u003eH\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e\u003cstrong\u003eN\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e\u003cstrong\u003eS\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e\u003cstrong\u003eO\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003eFresh AC\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e79.10\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e1.19\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e0.99\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e0.34\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e18.38\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003eBlank\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e79.27\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e1.31\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e1.02\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e0.44\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e17.96\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003eAC\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e75.71\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e1.31\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e0.97\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e1.87\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e20.14\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003eAC\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e76.15\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e1.13\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e1.07\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e1.79\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e19.78\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003eAC\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e75.82\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e1.20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e0.97\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e1.83\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"92\"\u003e\n\u003cp\u003e20.18\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eFig. 1 shows the proportions of the elemental sulfur, SO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e and SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e calculated from the data in Fig. S1. SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e and elemental sulfur (Liu et al., 2015, Menezes et al., 2018, Qiu et al., 2019) constitute the majority of sulfur products on the activated carbon surface for the four samples. The proportion of elemental sulfur in AC\u003csub\u003e1\u003c/sub\u003e is 65.8%, indicating that the oxidation products of H\u003csub\u003e2\u003c/sub\u003eS are mostly elemental sulfur. AC\u003csub\u003e2\u003c/sub\u003e contains approximately 20.8% H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e, because H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e can be formed by the reaction of SO\u003csub\u003e2\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003eO in the atmosphere without O\u003csub\u003e2\u003c/sub\u003e. However, due to the oxidation of oxygen-containing functional groups on the AC surface, H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e will be oxidized to H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e (Guo et al., 2013). The SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e content in AC\u003csub\u003e3\u003c/sub\u003e is greater than 60%, because SO\u003csub\u003e2\u003c/sub\u003e is adsorbed at the active site first and then is easily oxidized to H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e in the presence of O\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e\n\u003cp\u003eAccording to the analysis of the elemental content and XPS spectra, the total sulfur content is basically the same for AC\u003csub\u003e1\u003c/sub\u003e - AC\u003csub\u003e3\u003c/sub\u003e, and the difference lies in the forms of sulfur-containing products. The elemental sulfur accounts for the majority of the sulfur species in AC\u003csub\u003e1\u003c/sub\u003e, while AC\u003csub\u003e2\u003c/sub\u003e contains 20.8% H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e, and the main sulfur product in AC\u003csub\u003e3\u003c/sub\u003e is H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e. The existence form of sulfur-containing products is determined by the adsorption atmosphere of different sulfur components with SO\u003csub\u003e2\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003eS.\u003c/p\u003e\n\u003cp\u003eThe XPS results of carbon and oxygen functional groups are shown in Table. S1 and S2. As shown in Fig. 2 (a), compared with the blank sample, the amount of C=C and C=O bonds of AC\u003csub\u003e1\u003c/sub\u003e clearly decrease, while the C-S bond increases. According to previous studies (Silas et al., 2018), in the process of H\u003csub\u003e2\u003c/sub\u003eS oxidation, the C=C bond and C=O bond have been broken by H\u003csub\u003e2\u003c/sub\u003eS, and then the C-S bond and S-O bond are generated as intermediate products. The C-S bond tends to form elemental sulfur, while the S-O bond is likely to form H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e. For the AC\u003csub\u003e2\u003c/sub\u003e and AC\u003csub\u003e3\u003c/sub\u003e samples, there is no clear change in the carbon functional groups. After the thermal regeneration, the content of C-S bond in blank sample significantly decreases, due to the release of its own sulfur in the process of regeneration. The content of C=C bond basically changes little due to few sulfur compounds in the blank sample to react with C=C bond. For AC\u003csub\u003e1\u003c/sub\u003e - AC\u003csub\u003e3\u003c/sub\u003e samples, the main change is reflected in the reduction of C=C and C-S bonds, and the increase of the C=O and C-O bond. The C=C bond reacts with H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e to release SO\u003csub\u003e2\u003c/sub\u003e. The C-S bond is unstable and easily decomposes to release elemental sulfur at high temperature. The C=O and C-O bonds are more stable than the other carbon functional groups, so that the total amount of these two carbon functional groups changes little but their proportion increases. The decrease in the C=C bond is most obvious for AC\u003csub\u003e3\u003c/sub\u003e, which is related to the fact that the highest H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e content among the three samples is observed on AC\u003csub\u003e3\u003c/sub\u003e.\u003c/p\u003e\n\u003cp\u003eAs shown in Fig. 2 (b), compared with the blank sample, the C=O bond amount of AC\u003csub\u003e1\u003c/sub\u003e clearly decreases and the OH amount increases, due to the combination of the C=O bond with free H in H\u003csub\u003e2\u003c/sub\u003eS. For AC\u003csub\u003e2\u003c/sub\u003e and AC\u003csub\u003e3\u003c/sub\u003e, the OH amount obviously decreases, due to the form H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e or H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e through the combination of the OH site with SO\u003csub\u003e2\u003c/sub\u003e. In the thermal regeneration process, COOH and OH can be decomposed below 450 \u0026deg;C and mainly from carboxyls, lactones and anhydrides (Vivovilches et al., 2014), which is an important reason for the loss of the carbon functional groups. While the C=O bond amount increases significantly, due to their stable chemical properties.\u003c/p\u003e\n\u003cp\u003eTo further illustrate the decomposition process of the sulfur products in activated carbon, in situ DRIFT spectra are carried out with the results shown in Fig. 2 (c) and (d). H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e (872 cm\u003csup\u003e-\u003c/sup\u003e\u003csup\u003e1\u003c/sup\u003e) and H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e (1090 cm\u003csup\u003e-\u003c/sup\u003e\u003csup\u003e1\u003c/sup\u003e) are observed in the adsorption process, particularly for the AC\u003csub\u003e2\u003c/sub\u003e and AC\u003csub\u003e3\u003c/sub\u003e samples, but their amount decreases during the regeneration process. Due to the adsorption amount of acid SO\u003csub\u003e2\u003c/sub\u003e, the alcohol (OH) (1240 cm\u003csup\u003e-1\u003c/sup\u003e) decreases while alkyl ether (1020 cm\u003csup\u003e-\u003c/sup\u003e\u003csup\u003e1\u003c/sup\u003e) increases in the AC\u003csub\u003e2\u003c/sub\u003e and AC\u003csub\u003e3\u003c/sub\u003e samples. In the regeneration process, the reduction of the S-O bond (1150 cm\u003csup\u003e-\u003c/sup\u003e\u003csup\u003e1\u003c/sup\u003e) is most significant in AC\u003csub\u003e3\u003c/sub\u003e, representing the decomposition of sulfuric acid. Another important change is the decomposition of carboxylic acid (1080 cm\u003csup\u003e-1\u003c/sup\u003e). Carboxylic acid on the activated carbon surface decomposes below 450 \u0026deg;C, which is an important reason for the reduction in the denitrification efficiency of the activated carbon after regeneration.\u003c/p\u003e\n\u003cp\u003eIn the regeneration process, the chemical carbon consumption comes from the decomposition of oxygen-containing functional groups and the reaction of activated carbon with H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e. Carboxyls, lactones and anhydrides with COOH and OH groups can be decomposed below 450 \u0026deg;C. The thermal decomposition of functional groups is independent with the type of sulfur-containing products. The thermal regeneration of sulfur-containing products results in the reduction of the C=C bond amount. The C=C bond reacts with H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e to produce CO and CO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.2 Effect of sulfur products regeneration on chemical carbon consumption\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eFig. 3 shows the SO\u003csub\u003e2\u003c/sub\u003e concentration for the AC\u003csub\u003e1\u003c/sub\u003e - AC\u003csub\u003e3\u003c/sub\u003e samples during the TPD process. The decomposition temperature range of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e is 150 ~ 300 \u0026deg;C, and H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e decomposes at 300 ~ 450 \u0026deg;C (Lin et al., 2018). Therefore, the regeneration temperature is set at 450 \u0026deg;C for the complete desorption of SO\u003csub\u003e2\u003c/sub\u003e. At approximately 380 \u0026deg;C, a main peak of the H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e decomposition is observed. A shoulder peak of SO\u003csub\u003e2\u003c/sub\u003e desorption is observed in AC\u003csub\u003e2\u003c/sub\u003e at 150 ~ 300 \u0026deg;C because the H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e decomposition temperature is lower than that of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e (Kim et al., 2019). The peak areas of AC\u003csub\u003e1\u003c/sub\u003e - AC\u003csub\u003e3\u003c/sub\u003e in the range of 300 ~ 450 \u0026deg;C are 37523, 46112 and 67321, basically proportional to the H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e contents of 33.1%, 39.7% and 60.7% calculated from the XPS spectra as given in Fig. 1. There are no clear differences between the total sulfur contents of the three adsorbed samples, while the concentration of the desorbed SO\u003csub\u003e2\u003c/sub\u003e from AC\u003csub\u003e1\u003c/sub\u003e is significantly lower than AC\u003csub\u003e2\u003c/sub\u003e and AC\u003csub\u003e3\u003c/sub\u003e, indicating that the most of the sulfur in AC\u003csub\u003e1\u003c/sub\u003e decomposes in the form of elemental sulfur instead of SO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e\n\u003cp\u003eTable 2 Elemental analysis of the activated carbon samples after the TPD process (wt%)\u003c/p\u003e\n\u003ctable border=\"1\" width=\"552\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd width=\"134\"\u003e\n\u003cp\u003eSamples\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003eC\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003eH\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003eN\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003eS\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003eO\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"134\"\u003e\n\u003cp\u003eBlank\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e86.12\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e1.97\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e0.61\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e0.39\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e10.91\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"134\"\u003e\n\u003cp\u003eAC\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e86.16\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e1.67\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e1.09\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e0.44\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e10.64\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"134\"\u003e\n\u003cp\u003eAC\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e87.23\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e1.81\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e1.37\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e0.41\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e9.18\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"134\"\u003e\n\u003cp\u003eAC\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e88.02\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e1.77\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e1.01\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e0.52\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"84\"\u003e\n\u003cp\u003e8.68\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe results of elemental analysis of various samples after the TPD process are shown in Table 2. Compared with the data in Table 1, the sulfur and oxygen contents in AC\u003csub\u003e1\u003c/sub\u003e - AC\u003csub\u003e3 \u003c/sub\u003esamples decrease during the TPD process, due to the decomposition of the sulfur species and oxygen functional groups at high temperature (Lin et al., 2018). The sulfur content shows slight differences among the three samples, showing that the three samples have similar values of the total desorption amount of the sulfur species. However, clear differences among the three samples are observed for the oxygen content. The oxygen content of AC\u003csub\u003e1\u003c/sub\u003e is significantly higher than those of AC\u003csub\u003e2\u003c/sub\u003e and AC\u003csub\u003e3\u003c/sub\u003e. It is inferred that the desorption process of elemental sulfur is different from that of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e, with H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e releasing more oxygen during the desorption process.\u003c/p\u003e\n\u003cp\u003eFig. 4 show the results for the SO\u003csub\u003e2\u003c/sub\u003e desorption and chemical carbon consumption of the three samples during the regeneration process. The SO\u003csub\u003e2\u003c/sub\u003e desorption in AC\u003csub\u003e1\u003c/sub\u003e is much lower than that in AC\u003csub\u003e2\u003c/sub\u003e and AC\u003csub\u003e3\u003c/sub\u003e, because the elemental sulfur desorption cannot be detected by FTIR. AC\u003csub\u003e1\u003c/sub\u003e has the smallest carbon consumption, because of the largest component of elemental sulfur. For AC\u003csub\u003e2\u003c/sub\u003e, some H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e can be decomposed directly at lower temperature, thus reducing the release of CO and CO\u003csub\u003e2\u003c/sub\u003e. AC\u003csub\u003e3\u003c/sub\u003e consumes the most carbon, mainly due to the reaction of sulfuric acid and carbon.\u003c/p\u003e\n\u003cp\u003eThe carbon consumption of blank sample can be used to calculate the decomposition of oxygen-containing functional groups during regeneration. As shown in Table 3, according to the comparison of the oxygen content between the activated carbon and blank sample, about 6% of the oxygen-containing functional groups are consumed in the regeneration process. For AC\u003csub\u003e1\u003c/sub\u003e, the total carbon consumption during regeneration is 0.28 mmol/g, of which 75% comes from the thermal decomposition of oxygen-containing functional groups and 25% originates from the reaction between C and H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e. For AC\u003csub\u003e3\u003c/sub\u003e sample, the total carbon consumption during regeneration is 0.68 mmol/g, including 31% from its own thermal decomposition and 69% from its reaction with H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e. The desorption of elemental sulfur consumes less oxygen and carbon functional groups, reducing the chemical carbon consumption by 59.8% than H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e. In AC\u003csub\u003e3\u003c/sub\u003e, the carbon consumption caused by the regeneration of sulfur-containing products is more than twice of that caused by the decomposition of oxygen-containing functional groups, which indicates that the most important carbon consumption for the activated carbon used is caused by the reaction of C and H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e.\u003c/p\u003e\n\u003cp\u003eTable 3 SO\u003csub\u003e2\u003c/sub\u003e recovery and carbon consumption of the AC samples\u003c/p\u003e\n\u003ctable border=\"1\" width=\"96%\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"2\" width=\"11%\"\u003e\n\u003cp\u003e\u003cstrong\u003eSamples\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"4\" width=\"35%\"\u003e\n\u003cp\u003e\u003cstrong\u003eS (mmol/g)\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"5\" width=\"39%\"\u003e\n\u003cp\u003e\u003cstrong\u003eCarbon Consumption (mmol/g)\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"13%\"\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"3\" width=\"19%\"\u003e\n\u003cp\u003eAdsorption\u003c/p\u003e\n\u003cp\u003e(H\u003csub\u003e2\u003c/sub\u003eS and SO\u003csub\u003e2\u003c/sub\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"3\" width=\"17%\"\u003e\n\u003cp\u003eDesorption\u003c/p\u003e\n\u003cp\u003e(SO\u003csub\u003e2\u003c/sub\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"15%\"\u003e\n\u003cp\u003eCO\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003eCO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"11%\"\u003e\n\u003cp\u003eTotal\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003eC/S\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"2\" width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003eblank\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"17%\"\u003e\n\u003cp\u003e0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"3\" width=\"17%\"\u003e\n\u003cp\u003e0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"17%\"\u003e\n\u003cp\u003e0.04\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e0.17\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"11%\"\u003e\n\u003cp\u003e0.21\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e/\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"2\" width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003eAC\u003csub\u003e1\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"17%\"\u003e\n\u003cp\u003e0.76\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"3\" width=\"17%\"\u003e\n\u003cp\u003e0.15\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"17%\"\u003e\n\u003cp\u003e0.06\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e0.22\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"11%\"\u003e\n\u003cp\u003e0.28\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e0.45\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"2\" width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003eAC\u003csub\u003e2\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"17%\"\u003e\n\u003cp\u003e0.73\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"3\" width=\"17%\"\u003e\n\u003cp\u003e0.39\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"17%\"\u003e\n\u003cp\u003e0.16\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e0.44\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"11%\"\u003e\n\u003cp\u003e0.60\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e1.00\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"2\" width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003eAC\u003csub\u003e3\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"17%\"\u003e\n\u003cp\u003e0.77\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"3\" width=\"17%\"\u003e\n\u003cp\u003e0.36\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"17%\"\u003e\n\u003cp\u003e0.20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e0.48\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"11%\"\u003e\n\u003cp\u003e0.68\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e1.12\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"79\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"6\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"118\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"13\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"104\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"2\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"13\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"106\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"82\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"72\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"10\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"82\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003csup\u003e*\u003c/sup\u003e \u003csup\u003eBlank refers to the blank activated carbon without adsorption.\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eUnlike H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e, elemental sulfur cannot be determined during the desorption process. To further evaluate the morphology of sulfur products, DTG characteristics were used to measure the total weight loss at various temperature ranges, with the results shown in Fig. 5. The peak at 350 \u0026deg;C represents the decomposition of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e, while elemental sulfur directly sublimates at approximately 380 \u0026deg;C. Based on the temperature peak position, AC\u003csub\u003e1\u003c/sub\u003e mainly contains elemental sulfur and a small amount of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e, and AC\u003csub\u003e2\u003c/sub\u003e contains less H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e than AC\u003csub\u003e3\u003c/sub\u003e. H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e and a small amount of elemental sulfur are found on the surface of AC\u003csub\u003e3\u003c/sub\u003e. The differences between the peak area of DTG curves and that of SO\u003csub\u003e2\u003c/sub\u003e, CO and CO\u003csub\u003e2\u003c/sub\u003e content curves are the content of elemental sulfur. And elemental sulfur in AC\u003csub\u003e1\u003c/sub\u003e is the highest, which is consistent with the results in Fig. 1. It can be concluded from the DTG curves that the elemental sulfur sublimates at 350 ~ 400 \u0026deg;C, which is of great significance to guide the design for industrial flue gas purification by activated carbon process.\u003c/p\u003e\n\u003cp\u003eElectron Spin Resonance was used to calculate the average chain length of sulfur by dividing the number of electron spin (Terada et al., 2020). The ESR spectrogram is shown in Fig. S3.\u003c/p\u003e\n\u003cp\u003e\u003cimg src=\"https://myfiles.space/user_files/58853_cdc0f79cc190fa60/58853_custom_files/img1619206969.png\"\u003e\u003c/p\u003e\n\u003cp\u003eWhere E (in spins per gram) is the amount of electron spin of samples, N\u003csub\u003eA\u003c/sub\u003e (6.022ⅹ10\u003csup\u003e23\u003c/sup\u003e mol\u003csup\u003e-1\u003c/sup\u003e) is Avogadro constant. It is difficult to test the electron spin of activated carbon because of its magnetism. So, the results of elemental sulfur were used to characterize the properties of elemental sulfur produced by adsorption on activated carbon, as shown in Fig.6. When the elemental sulfur rises from room temperature to 150 ℃, the chain length of sulfur has no obvious change, and the average value is about 2\u0026acute;10\u003csup\u003e6\u003c/sup\u003e. It is difficult for orthorhombic sulfur to exist at 150 ℃, the sulfur form at this temperature is monoclinic sulfur (S\u003csub\u003e8\u003c/sub\u003e) (Terada et al., 2020). Each sulfur atom forms covalent single bond with the other two sulfur atoms in sp\u003csup\u003e3\u003c/sup\u003e hybrid orbit (Brandi et al., 2019). When the temperature continues to rise up to 254 ℃, the electron spin number of sulfur is close to 0, the S\u003csub\u003e8\u003c/sub\u003e ring structure breaks into infinitely long chain molecules (S\u003csub\u003e\u0026infin;\u003c/sub\u003e) which are twisted back together. The temperature continues to rise to 400 ℃, the average chain length of sulfur decreases to 0.7ⅹ10\u003csup\u003e6\u003c/sup\u003e, the sulfur becomes vapor, and there are S\u003csub\u003e8\u003c/sub\u003e, S\u003csub\u003e6\u003c/sub\u003e, S\u003csub\u003e2\u003c/sub\u003e and other molecules in the vapor (Lau et al., 2017).\u003c/p\u003e\n\u003cp\u003eFor the composition of sulfur vapor, the energy barriers of \u0026middot;S\u003csub\u003e2\u003c/sub\u003e\u0026middot; and \u0026middot;S\u003csub\u003e6\u003c/sub\u003e\u0026middot; are only 209.45 kJ/mol (Song et al., 2019). It is the lowest energy barriers of the ring opening reaction of S\u003csub\u003e8\u003c/sub\u003e, which indicates that the reaction is easy to occur when the S\u003csub\u003e8\u003c/sub\u003e chain breaks. The energy barrier of \u0026middot;S\u003csub\u003e4\u003c/sub\u003e\u0026middot; is 447.07 kJ/mol (Jones and Ballone, 2003), which is difficult to occur. Therefore, only three products of S\u003csub\u003e2\u003c/sub\u003e, S\u003csub\u003e6\u003c/sub\u003e, S\u003csub\u003e8\u003c/sub\u003e are calculated when calculating the equilibrium sulfur vapor products. According to principle of minimum free energy (Catone et al., 2019), the volume fraction of each component for sulfur vapor at 400 ℃ is 3.7% for S\u003csub\u003e2\u003c/sub\u003e，56.4% for S\u003csub\u003e6\u003c/sub\u003e and 39.9% for S\u003csub\u003e8\u003c/sub\u003e. At the adsorption temperature, the state of elemental sulfur is monoclinic sulfur, which is composed of S\u003csub\u003e8\u003c/sub\u003e ring molecules. When the activated carbon is regenerated, the temperature rise first causes the S\u003csub\u003e8\u003c/sub\u003e ring structure to break into infinitely long chain molecules (S\u003csub\u003e\u0026infin;\u003c/sub\u003e). Above 254 \u0026deg;C, the long chain sulfur breaks into small molecules, such as S\u003csub\u003e6 \u003c/sub\u003eand S\u003csub\u003e2\u003c/sub\u003e. At 400 \u0026deg;C, the sulfur becomes vapor, and the volume fraction of each component for sulfur vapor is 3.7% for S\u003csub\u003e2\u003c/sub\u003e, 56.4% for S\u003csub\u003e6\u003c/sub\u003e and 39.9% for S\u003csub\u003e8\u003c/sub\u003e.\u003c/p\u003e\n\u003cp\u003eTable 4 shows the reactions of sulfur-containing substances with activated carbon in the adsorption-regeneration process. C(O) represents the oxygen functional groups on the activated carbon surface.\u003c/p\u003e\n\u003cp\u003eTable 4 Reactions for adsorption-regeneration process of sulfur-containing substances on activated carbon\u003c/p\u003e\n\u003ctable border=\"1\" width=\"558\"\u003e\n\u003ctbody\u003e\n\u003ctr style=\"height: 48px;\"\u003e\n\u003ctd style=\"height: 48px;\" width=\"92\"\u003e\n\u003cp\u003eProcess\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 48px;\" width=\"116\"\u003e\n\u003cp\u003eChange of reactants\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 48px;\" width=\"170\"\u003e\n\u003cp\u003eReaction\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 48px;\" width=\"132\"\u003e\n\u003cp\u003eParticipating functional groups\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 48px;\" width=\"47\"\u003e\n\u003cp\u003eNo.\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr style=\"height: 38.4688px;\"\u003e\n\u003ctd style=\"height: 190.469px;\" rowspan=\"5\" width=\"92\"\u003e\n\u003cp\u003eAdsorption\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 76.4688px;\" rowspan=\"2\" width=\"116\"\u003e\n\u003cp\u003eAdsorption and oxidation of SO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 38.4688px;\" width=\"170\"\u003e\n\u003cp\u003eSO\u003csub\u003e2\u003c/sub\u003e\u0026rarr;H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 76.4688px;\" rowspan=\"2\" width=\"132\"\u003e\n\u003cp\u003eOH\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 76.4688px;\" rowspan=\"2\" width=\"47\"\u003e\n\u003cp\u003e(1)\u003c/p\u003e\n\u003cp\u003e(2)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr style=\"height: 38px;\"\u003e\n\u003ctd style=\"height: 38px;\" width=\"170\"\u003e\n\u003cp\u003eSO\u003csub\u003e2\u003c/sub\u003e\u0026rarr;H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr style=\"height: 38px;\"\u003e\n\u003ctd style=\"height: 114px;\" rowspan=\"3\" width=\"116\"\u003e\n\u003cp\u003eOxidation of H\u003csub\u003e2\u003c/sub\u003eS\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 38px;\" width=\"170\"\u003e\n\u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eS\u0026rarr;S(s)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 114px;\" rowspan=\"3\" width=\"132\"\u003e\n\u003cp\u003eReactant: C=O, C=C\u003c/p\u003e\n\u003cp\u003eIntermediate product: C-S, S-O\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 114px;\" rowspan=\"3\" width=\"47\"\u003e\n\u003cp\u003e(3)\u003c/p\u003e\n\u003cp\u003e(4)\u003c/p\u003e\n\u003cp\u003e(5)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr style=\"height: 38px;\"\u003e\n\u003ctd style=\"height: 38px;\" width=\"170\"\u003e\n\u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eS\u0026rarr;H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr style=\"height: 38px;\"\u003e\n\u003ctd style=\"height: 38px;\" width=\"170\"\u003e\n\u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eS\u0026rarr;H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr style=\"height: 144px;\"\u003e\n\u003ctd style=\"height: 217px;\" rowspan=\"3\" width=\"92\"\u003e\n\u003cp\u003eRegeneration\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 144px;\" width=\"116\"\u003e\n\u003cp\u003eRegeneration of sulfur products\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 144px;\" width=\"170\"\u003e\n\u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e+C\u0026rarr;SO\u003csub\u003e2\u003c/sub\u003e+CO+H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n\u003cp\u003e2H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e+2C\u0026rarr;2SO\u003csub\u003e2\u003c/sub\u003e+CO\u003csub\u003e2\u003c/sub\u003e+\u003c/p\u003e\n\u003cp\u003e2H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n\u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e\u0026rarr;SO\u003csub\u003e2\u003c/sub\u003e+H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n\u003cp\u003eS(s)\u0026rarr;S(g)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 144px;\" width=\"132\"\u003e\n\u003cp\u003eC=C\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 144px;\" width=\"47\"\u003e\n\u003cp\u003e(6)\u003c/p\u003e\n\u003cp\u003e(7)\u003c/p\u003e\n\u003cp\u003e(8)\u003c/p\u003e\n\u003cp\u003e(9)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr style=\"height: 38px;\"\u003e\n\u003ctd style=\"height: 73px;\" rowspan=\"2\" width=\"116\"\u003e\n\u003cp\u003eDecomposition of carbon-functional groups\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 38px;\" width=\"170\"\u003e\n\u003cp\u003eC(O)\u0026rarr;CO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 73px;\" rowspan=\"2\" width=\"132\"\u003e\n\u003cp\u003ecarboxyls, lactones and anhydrides\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd style=\"height: 73px;\" rowspan=\"2\" width=\"47\"\u003e\n\u003cp\u003e(10)\u003c/p\u003e\n\u003cp\u003e(11)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr style=\"height: 35px;\"\u003e\n\u003ctd style=\"height: 35px;\" width=\"170\"\u003e\n\u003cp\u003eC(O)\u0026rarr;CO\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe carbon consumption partly depends on the existence form of sulfur-containing products, in addition to the thermal decomposition of functional groups. The desorption of elemental sulfur consumes less oxygen and carbon functional groups, with 59.8% less chemical carbon consumption than H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e. The carbon consumption caused by the regeneration of sulfur-containing products is less than that by the decomposition of functional groups with elemental sulfur as the main products.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.3 Influence of sulfur products regeneration on physical carbon abrasion \u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eTo investigate the influence of sulfur products regeneration on the AC physical structure, the pore structures were analyzed before and after the regeneration. The results are shown in Table 5. In comparison with the blank sample, the specific surface area and pore volume of AC\u003csub\u003e1\u003c/sub\u003e - AC\u003csub\u003e3\u003c/sub\u003e clearly decrease due to the sediment of sulfur substances on the activated carbon surface. Moreover, the specific surface area of AC\u003csub\u003e1\u003c/sub\u003e decreases by 11% and that of AC\u003csub\u003e3\u003c/sub\u003e decreases by 20%. This phenomenon is ascribed to the different volumes of elemental sulfur and H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e. The volume of elemental sulfur is 13.6 cm\u003csup\u003e3\u003c/sup\u003e/mol, while that of sulfuric acid is 53.5 cm\u003csup\u003e3\u003c/sup\u003e/mol, and that of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e is 79.6 cm\u003csup\u003e3\u003c/sup\u003e/mol (Lau et al., 2017). Therefore, when elemental sulfur rather than H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e is deposited on the activated carbon surface, the decrease in the specific surface area is not obvious. After thermal regeneration, both the specific surface area and pore volume increase because of the partial decomposition of the functional groups. The pore size of the activated carbon is restored to the level of the fresh activated carbon, and even increases after the regeneration.\u003c/p\u003e\n\u003cp\u003eTable 5 Characterization of the various AC before and after regeneration\u003c/p\u003e\n\u003ctable border=\"1\" width=\"98%\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"2\" width=\"13%\"\u003e\n\u003cp\u003e\u003cstrong\u003eSample\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"3\" width=\"37%\"\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eS\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003csub\u003eBET\u003c/sub\u003e\u003c/strong\u003e\u003cstrong\u003e (m\u003csup\u003e2\u003c/sup\u003e/g)\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"3\" width=\"25%\"\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eV\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003csub\u003em\u003c/sub\u003e\u003c/strong\u003e\u003cstrong\u003e (mL/g)\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"23%\"\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eV\u003csub\u003et\u003c/sub\u003e\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e (mL/g)\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003eBe-re\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003eAf- re\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"14%\"\u003e\n\u003cp\u003eBe- re\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003eAf-re\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"14%\"\u003e\n\u003cp\u003eBe- re\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003eAf-re\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"13%\"\u003e\n\u003cp\u003eFresh AC\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"28%\"\u003e\n\u003cp\u003e196\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"3\" width=\"28%\"\u003e\n\u003cp\u003e0.070\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"3\" width=\"28%\"\u003e\n\u003cp\u003e0.087\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"13%\"\u003e\n\u003cp\u003eBlank\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e198\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e221\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"14%\"\u003e\n\u003cp\u003e0.070\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e0.070\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"14%\"\u003e\n\u003cp\u003e0.091\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e0.096\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"13%\"\u003e\n\u003cp\u003eAC\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e175\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e215\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"14%\"\u003e\n\u003cp\u003e0.065\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e0.073\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"14%\"\u003e\n\u003cp\u003e0.076\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e0.096\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"13%\"\u003e\n\u003cp\u003eAC\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e161\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e200\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"14%\"\u003e\n\u003cp\u003e0.059\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e0.070\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"14%\"\u003e\n\u003cp\u003e0.076\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e0.093\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"13%\"\u003e\n\u003cp\u003eAC\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e157\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e199\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"14%\"\u003e\n\u003cp\u003e0.059\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e0.070\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd colspan=\"2\" width=\"14%\"\u003e\n\u003cp\u003e0.069\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e0.093\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"95\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"100\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"100\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"58\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"42\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"100\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"36\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"64\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd width=\"100\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e*Be-re is the abbreviation of before-regeneration. Af-re is the abbreviation of after-regeneration.\u003c/p\u003e\n\u003cp\u003eThe graphite microcrystalline structure of the AC samples before and after regeneration was shown in Fig. 7. Raman spectra of all samples displays two peaks including the disorder (D) peak at 1360 cm\u003csup\u003e-1\u003c/sup\u003e reflecting the structural defects and the graphite (G) peak at 1600 cm\u003csup\u003e-1\u003c/sup\u003e reflecting the sp\u003csup\u003e2\u003c/sup\u003e carbon atoms in the graphene sidewalls. The ratio of the peak intensity (I\u003csub\u003eD\u003c/sub\u003e/I\u003csub\u003eG\u003c/sub\u003e) represents the degree of disorder in the graphite microcrystalline structure on activated carbon (Zhang et al., 2019). The D and G peaks of various AC samples are basically the same prior to regeneration. The D peaks of AC\u003csub\u003e1\u003c/sub\u003e - AC\u003csub\u003e3\u003c/sub\u003e samples clearly increase after regeneration, while the G peak does not change much, so that the I\u003csub\u003eD\u003c/sub\u003e / I\u003csub\u003eG\u003c/sub\u003e value increases significantly, particularly for AC\u003csub\u003e3\u003c/sub\u003e. This indicates that regeneration can significantly improve the disorder in the activated carbon.\u003c/p\u003e\n\u003cp\u003eFrom the macroscopic point of view, the activated carbon structure can also be characterized by compressive strength and wear resistance, which are tested before and after regeneration, with results shown in Fig. 8. There is little difference between the wear resistance values before and after regeneration, while the compressive strength clearly decreases, especially for the AC\u003csub\u003e2\u003c/sub\u003e and AC\u003csub\u003e3\u003c/sub\u003e samples, indicating that the reaction of C and H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e destroys the integrity of the carbon structure. The compressive strength and wear resistance decrease on regenerated activated carbon, leading to the increase in the amount of small granular activated carbon, and finally increase the physical carbon abrasion.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.4 \u003c/em\u003e\u003cem\u003eTotal carbon consumption in engineering applications\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe total carbon consumption in engineering applications includes chemical carbon consumption and physical carbon abrasion. In this work, two factories using activated carbon technology for flue gas purification were investigated. One is for sintering flue gas purification to capture SO\u003csub\u003e2\u003c/sub\u003e, and the other is for coke oven flue gas purification to simultaneously remove SO\u003csub\u003e2\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003eS. The results are shown in Table 6.\u003c/p\u003e\n\u003cp\u003eFor sintering flue gas purification, the total carbon consumption is about 55% of the total charge per year; among them, the physical carbon abrasion is about 38%, and the chemical carbon consumption is about 17%. The physical carbon abrasion is twice more than chemical carbon consumption. The total carbon consumption is approximately 48% for coke oven flue gas, lower than that for sintering flue gas. The high content of H\u003csub\u003e2\u003c/sub\u003eS depresses the carbon consumption in the regeneration process compared with the same content of SO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e\n\u003cp\u003eTable 6 Comparison of total carbon consumption between sintering flue gas and coke oven flue gas\u003c/p\u003e\n\u003ctable border=\"1\" width=\"93%\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd width=\"38%\"\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e\u003cstrong\u003eSintering flue gas\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e\u003cstrong\u003eCoke oven flue gas \u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"38%\"\u003e\n\u003cp\u003eTotal gas volume (Nm\u003csup\u003e3\u003c/sup\u003e/h)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e2,800,000\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e300,000\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"38%\"\u003e\n\u003cp\u003eInlet SO\u003csub\u003e2\u003c/sub\u003e (ppm)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e200~300\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e50~100\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"38%\"\u003e\n\u003cp\u003eInlet H\u003csub\u003e2\u003c/sub\u003eS (ppm)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e/\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e150~200\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"38%\"\u003e\n\u003cp\u003eOutlet SO\u003csub\u003e2\u003c/sub\u003e (ppm)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e10\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"38%\"\u003e\n\u003cp\u003eOutlet H\u003csub\u003e2\u003c/sub\u003eS (ppm)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e/\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e15\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"38%\"\u003e\n\u003cp\u003eTotal AC loading (t)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e12,000\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e2500\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"38%\"\u003e\n\u003cp\u003eTotal AC consumption (t/a)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e6600\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e1200\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"38%\"\u003e\n\u003cp\u003ePhysical carbon abrasion\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e38%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e35%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"38%\"\u003e\n\u003cp\u003eChemical carbon consumption\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e17%\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"30%\"\u003e\n\u003cp\u003e13%\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eIn order to reduce carbon consumption, the following strategies can be considered. Use air screen sorting devices to reduce physical carbon abrasion. With the increase of operation time, the particle size of activated carbon becomes smaller and smaller. The small particles and dust fill in the gap of activated carbon bed increasing the resistance of flue gas. An efficient balance vibrating screen in the activated carbon conveying system is commonly used to screen out small particles, but this measure will undoubtedly greatly increase the physical carbon abrasion between the particles and particle with vibrating screen. In order to solve this problem, an air screen sorting device for activated carbon was developed in the project. Driven by the upstream hot air flow, the dust and small particles in the activated carbon were gradually fluidized, suspended, and finally separated under the traction of the upstream air flow. This process reduces the collision and friction between the particles and vibrating screen, and then greatly reduces the physical carbon abrasion.\u003c/p\u003e\n\u003cp\u003eSelect a high-quality activated carbon to reduce chemical carbon consumption. In engineering, the main quality index of activated carbon includes sulfur capacity, wear resistance, compressive strength, ignition point, and particle size distribution etc. In this work, it is found that elemental sulfur generated by H\u003csub\u003e2\u003c/sub\u003eS can reduce the chemical carbon consumption of activated carbon. Therefore, the activated carbon with less C=O bond should be selected under the premise of ensuring the above quality index, which can effectively reduce the production of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e and greatly reduces the chemical carbon consumption.\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eS can react with the C=C bond on the activated carbon surface to form C-S bond as an intermediate state, followed by the formation of elemental sulfur. It directly sublimates at approximately 380 \u0026deg;C, about 30 \u0026deg;C higher than the decomposition temperature of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e. So, the regeneration temperature should be determined according to the sublimation temperature of elemental sulfur in the engineering application. At the adsorption temperature, the state of elemental sulfur is monoclinic sulfur in the form of S\u003csub\u003e8\u003c/sub\u003e ring molecules. When the activated carbon is regenerated, the temperature rise first causes the S\u003csub\u003e8\u003c/sub\u003e ring structure to break into infinitely long chain molecules (S\u003csub\u003e\u0026infin;\u003c/sub\u003e). When the activated carbon is heated above 254 \u0026deg;C, the long chain sulfur breaks into small molecules. At 400 \u0026deg;C, the sulfur becomes vapor, and the volume fraction of each component for sulfur vapor is 3.7% for S\u003csub\u003e2\u003c/sub\u003e, 56.4% for S\u003csub\u003e6\u003c/sub\u003e and 39.9% for S\u003csub\u003e8\u003c/sub\u003e. The desorption process of elemental sulfur consumes less oxygen and carbon functional groups, reducing the chemical carbon consumption by 59.8% than H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e; due to the slight effect on the disordered graphitic structure, its compressive strength is reduced less.\u003c/p\u003e\n\u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eS also reacts with the C=O bond to form H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e. The decomposition of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e3\u003c/sub\u003e does not require carbon consumption. The deposited H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4 \u003c/sub\u003ereacts with the C=C bond to generate SO\u003csub\u003e2\u003c/sub\u003e, which is the cardinal reaction of the thermal regeneration. In addition, H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e decomposition improves the ratio of the disordered graphitic structure. About 6% of the oxygen-containing functional groups are consumed in the regeneration process, and most of these functional groups are carboxyls, lactones and anhydrides. The carbon consumption caused by the regeneration of sulfur-containing products is more than that caused by the decomposition of oxygen-containing functional groups.\u003c/p\u003e\n\u003cp\u003eFrom the data of engineering project, the total carbon consumption of coke oven flue gas is slightly lower than that of sintering flue gas. H\u003csub\u003e2\u003c/sub\u003eS will depress the carbon consumption in the thermal regeneration process compared with SO\u003csub\u003e2\u003c/sub\u003e. To reduce carbon consumption, the following two strategies can be considered. Use air screen sorting devices to reduce the collision between activated carbon and vibrating screen, and then significantly reduces the physical carbon abrasion. Select the activated carbon with less C=O bond to reduce the production of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e, and then greatly reduce the chemical carbon consumption.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e: This manuscript has been developed in compliance with ethical standards.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e: This manuscript does not contain data from any individual person.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials: \u003c/strong\u003eThe datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e: The authors voluntarily agreed to participate in this research study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to publish\u003c/strong\u003e: The authors agree to publish the article in the Environmental Science and Pollution Research.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e: The authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e: This work was supported by the National Key Research and Development Program of China (No. 2017YFC0210600) and the National Natural Science Foundation of China (No. U1810209). The role of the funding body is in the design of the study, analysis, and interpretation of data.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors Contributions\u003c/strong\u003e:\u003c/p\u003e\n\u003cp\u003eYuting Lin: Conceptualization, Methodology, Formal analysis, Writing- Original draft preparation.\u003c/p\u003e\n\u003cp\u003eYuran Li.: Resources, Writing - Review \u0026amp; Editing.\u003c/p\u003e\n\u003cp\u003eZhicheng Xu: Visualization, Investigation.\u003c/p\u003e\n\u003cp\u003eJunxiang Guo: Supervision.\u003c/p\u003e\n\u003cp\u003eTingyu Zhu: Resources, Supervision.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments: \u003c/strong\u003eThis work was supported by the National Key Research and Development Program of China (No. 2017YFC0210600) and the National Natural Science Foundation of China (No. U1810209).\u003c/p\u003e"},{"header":"References","content":"\u003cp\u003eBraghiroli F L, Bouafif H, Koubaa A. 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In this work, differential thermogravimetric (DTG), electron paramagnetic resonance (ESR), X-ray photoelectron spectroscopy (XPS), and temperature programmed desorption (TPD) were used to reveal the adsorption-regeneration process of H 2 S and the effect of adsorption products on carbon consumption. H 2 S reacts with the C=C bond to form C-S bond as an intermediate state, followed by the formation of elemental sulfur. It directly sublimates at approximately 380 °C , about 30 °C higher than the decomposition temperature of H 2 SO 4 . In the thermal regeneration process, the elemental sulfur in the form of monoclinic sulfur (S 8 ) first breaks into infinitely long chain molecules (S ∞ ) and then into small molecules, finally into sulfur vapor. The desorption of elemental sulfur consumes less oxygen and carbon functional groups, reducing the chemical carbon consumption by 59.8% than H 2 SO 4 . The compressive strength reduces less due to its slight effect on the disordered graphitic structure. H 2 S also reacts with the C=O bond to form H 2 SO 3 or H 2 SO 4 . The desorption of H 2 SO 3 does not require carbon consumption. The decomposition of H 2 SO 4 needs to react with C=C bond to release SO 2 , CO 2 , and CO, and the compressive strength of activated carbon significantly decreases. The carbon consumption originates from two aspects, the one from the regeneration of sulfur-containing products is more than twice of the other one from the decomposition of oxygen-containing functional groups.\u003c/p\u003e","manuscriptTitle":"Carbon Consumption and Adsorption-Regeneration of H2S on Activated Carbon for Coke Oven Flue Gas Purification","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2021-04-23 20:54:28","doi":"10.21203/rs.3.rs-335006/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revision","date":"2021-05-08T09:39:05+00:00","index":"","fulltext":""},{"type":"reviewersInvited","content":"","date":"2021-04-21T00:00:00+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Environmental Science and Pollution Research","date":"2021-04-01T00:00:00+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2021-03-19T00:00:00+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Science and Pollution Research","date":"2021-03-16T20:47:47+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"a054d16e-ccb7-4cdc-9ee2-454d651493df","owner":[],"postedDate":"April 23rd, 2021","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":3865282,"name":"Environmental Engineering"}],"tags":[],"updatedAt":"2021-06-11T15:11:31+00:00","versionOfRecord":[],"versionCreatedAt":"2021-04-23 20:54:28","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-335006","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-335006","identity":"rs-335006","version":["v1"]},"buildId":"-HB7Z8yhvgn0wM9Nzuekk","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}