Process Intensification of CO₂ Absorption with MEA in a Rotating Packed Bed: Experimental Evaluation and Analysis

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Adizov This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6601658/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The emission of carbon dioxide (CO₂) from industrial sources, particularly power plants, remains one of the leading contributors to global climate change. While conventional post-combustion CO₂ capture technologies are effective, they are often limited by high energy consumption and large equipment size. Rotating Packed Bed (RPB) technology offers a promising solution through process intensification and improved mass transfer. This study presents an experimental investigation of a laboratory-scale RPB absorber designed for CO₂ capture using aqueous monoethanolamine (MEA) solutions. The effects of rotor speed, MEA concentration, and liquid-to-gas (L/G) ratio on CO₂ capture efficiency and the overall volumetric gas-phase mass transfer coefficient \(\:\left({K}_{{G}^{a}}\right)\) were systematically examined. The results showed that increasing rotor speed significantly improved both CO₂ capture efficiency and KGa due to enhanced centrifugal acceleration and better gas–liquid contact. Higher MEA concentrations led to improved capture performance, attributed to increased reaction kinetics, while elevated L/G ratios further enhanced absorption efficiency and reduced the Height of Transfer Unit (HTU). The findings confirm the suitability of RPB technology for efficient and compact CO₂ absorption systems, with strong potential for industrial applications. MEA solvent postcombustion CO2 capture process Intensification rotating packed bed Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction The global demand for energy has consistently increased in recent years, driven by population growth and rapid technological advancements [ 1 ]. Consequently, energy-related carbon dioxide (CO₂) emissions have also escalated, reaching 31.5 gigatonnes in 2021 [ 2 ]. As CO₂ is the most significant anthropogenic greenhouse gas (GHG) contributing to global warming, the need for sustainable mitigation strategies is urgent. The International Energy Agency (IEA) has identified Carbon Capture, Utilization, and Storage (CCUS) as a critical technology for reducing GHG emissions and addressing climate change [ 3 ]. At the same time, global reserves of sweet natural gas are being depleted [ 4 ], leading to growing interest in developing sour gas reservoirs that often contain high CO₂ concentrations—up to 80% in some cases [ 5 ]. The presence of CO₂, along with hydrogen sulfide and other impurities, makes sour gas processing technically challenging. CO₂ is highly corrosive, endangering the integrity of pipelines and process equipment. Therefore, efficient and scalable CO₂ separation technologies are essential for both natural gas purification and environmental compliance. Among the three main CO₂ capture approaches—pre-combustion, oxy-fuel combustion, and post-combustion capture (PCC)—chemical absorption-based PCC is the most mature and widely applied technology [ 6 ]. Its compatibility with existing infrastructure has enabled commercial-scale deployment, particularly for power plants and industrial facilities [ 7 ]. However, conventional PCC systems typically employ packed bed (PB) columns for CO₂ absorption and solvent regeneration. These columns are bulky, expensive, and limited by poor mass transfer rates, especially when operating with viscous, concentrated solvents such as monoethanolamine (MEA) [ 7 ]. To overcome these limitations, Rotating Packed Bed (RPB) technology has emerged as a promising process intensification solution. By replacing gravitational flow with centrifugal acceleration, RPBs significantly enhance gas–liquid mass transfer rates and reduce equipment size. In RPBs, the liquid is distributed at the rotor center and flows radially outward through the packing as thin films, while the gas flows countercurrently from the outer edge toward the center [ 14 – 18 ]. This configuration facilitates intense phase contact, improves mixing, and enables the use of high-viscosity solvents such as concentrated MEA (> 55 wt%) [ 8 – 10 ]. RPBs have been successfully applied across a range of industries, including distillation, oxidation, crystallization, polymerization, and biodiesel production [ 14 – 18 ]. In the context of CO₂ capture, several studies have demonstrated the potential of RPBs to improve absorption efficiency and reduce regeneration energy [ 12 – 13 , 21 ]. For example, Joel et al. [ 11 ] developed a rate-based RPB absorber model using MEA in Aspen Plus®, coupled with Fortran®. Their simulations showed that absorber volume could be reduced by a factor of 12 compared to conventional PB columns—highlighting the compactness and efficiency of RPBs. Despite these advantages, process intensification in RPBs is inherently complex due to simultaneous phenomena involving mass transfer, heat transfer, and fluid dynamics [ 21 , 22 ]. Accurate modeling of RPB performance remains a significant challenge, particularly at industrial scale. Many existing models rely on simplifying assumptions that, while suitable for lab-scale units, may not hold for scaled-up operations, potentially resulting in discrepancies in performance prediction [ 23 ]. Moreover, due to the complex internal flow behavior, experimental data alone is insufficient to fully understand RPB hydrodynamics. Three-dimensional computational fluid dynamics (CFD) simulations have been proposed to gain deeper insight into flow characteristics, pressure fields, and velocity distributions, though such studies remain limited [ 19 , 20 ]. In light of these considerations, further research and model development are essential for optimizing RPB systems for CO₂ capture. The unique advantages of RPBs—compactness, high mass transfer efficiency, and compatibility with concentrated solvents—position this technology as a leading candidate for next-generation carbon capture systems. 2. Materials and Methods 2.1. Materials In this study, pure monoethanolamine (MEA) was used as the solvent. The MEA was sourced from the Mubarek Gas Processing Plant with a purity of > 99%. A gas mixture of CO₂ and air was also used in the experiments. Aqueous MEA solutions with mass concentrations of 30%, 50%, 70%, and 90% were prepared using distilled water. The gas mixtures consisted of 85% CO₂ and 15% air. 2.2. Experimental Part The experimental setup was assembled at the "Processes and Apparatuses of Chemical Technology" laboratory of the Institute of General and Inorganic Chemistry of the Academy of Sciences of the Republic of Uzbekistan. The schematic diagram of the experimental system is shown in Fig. 1 . The system includes an RPB absorber, reservoirs for lean and rich MEA, a gas cylinder filled with pure CO₂, a pump for circulating the lean MEA solution, a compressor for air injection, a GC-7860 gas chromatograph for gas analysis, and flow meter gas and liquid for measuring the flow rates of both the gas mixture and the solvent. Figure 1 shows the setup of the experimental RPB (Rotating Packed Bed) absorber used for CO₂ capture, where lean MEA is introduced as the absorbing solvent and exits as rich MEA after capturing CO₂. The experiment begins with the supply of a gas mixture containing 15% CO₂ and 85% air from the cylinder (4) through the compressor (5), which provides the required pressure. The gas then flows through the globe valves (11) and the gas flow meter (10) into the rotating packed bed (RPB) absorber. Simultaneously, a monoethanolamine (MEA) solution is pumped from the liquid tank (2) using a pump (8), passes through the liquid flow meter (9), and is also fed into the absorber. Inside the RPB, which is equipped with SS316 stainless steel packing, the liquid is distributed via a stationary distributor containing five sets of holes (each set has five 1 mm holes spaced 72° apart) along the inner edge of the packing. Due to centrifugal force, the liquid moves radially outward through the packing and is collected at the bottom of the stationary casing. In contrast, the gas enters from the outer stationary casing, flows inward through the packing counter-currently to the liquid flow, and exits through the central pipe of the rotor. This counter-current flow is intensified by the high rotational speed of the packing, driven by the motor (1), which enhances mass transfer efficiency. During this process, CO₂ from the gas mixture is absorbed by the MEA solution. The CO₂-depleted gas (lean gas) exits through the rotor's central pipe and is directed to the CO₂ analyzer (6) to monitor residual CO₂ concentration. The CO₂-rich MEA (rich MEA) is collected at the bottom in the storage tank (3) for further regeneration. This setup simulates an industrial CO₂ capture process using an advanced rotating packed bed technology. The inlet and outlet CO₂ concentrations were measured using a GC-7860 gas chromatograph. The rotor speed was varied from 0 to 2400 rpm. The centrifugal field in the RPB enables the formation of thinner liquid films and smaller droplets. This system is capable of operating at higher gas–liquid flow ratios due to its reduced tendency for flooding. One of the most critical advantages of this configuration is its ability to significantly enhance mass transfer coefficients—by an order of magnitude—thereby reducing equipment size compared to conventional packed bed columns. The axial height of the packing was 3.0 cm, while the inner and outer diameters were 5 cm and 14 cm, respectively. The MEA solution was pumped into the rotating packed bed with a flow rate ranging from 0.161 to 0.567 L/min. The CO₂–air gas mixture entered from the stationary casing and flowed radially inward through the packing. The CO₂ concentration in the inlet gas was maintained at 15% of the total mixture volume. The gas flow rate was 13.4 L/min, and the liquid flow rate ranged from 0.161 to 0.567 L/min. A steady state was typically reached within 7–12 minutes, monitored by the outlet CO₂ concentration. All experiments were conducted at an ambient temperature of approximately 25°C and under atmospheric pressure. 2.3. Chemical Reactions between CO₂, Water, and MEA The primary mechanisms of the reaction between carbon dioxide (CO₂) and monoethanolamine (MEA) have been investigated using two distinct approaches: the zwitterion mechanism and the termolecular mechanism. According to studies by Aboudheir et al. [ 24 ], a series of chemical reactions describing the interaction of CO₂ with aqueous MEA solutions have been proposed. These reactions cover the key stages of the absorption process, including the formation of intermediate compounds and equilibrium transformations. Water ionization: $$\:2{H}_{2}O\leftrightarrow\:O{H}^{-}+{H}_{3}{O}^{+}$$ 1 Water undergoes spontaneous dissociation, producing hydroxide ions ( \(\:O{H}^{-}\) ) and hydronium ions ( \(\:{H}_{3}{O}^{+}\) ). This reaction plays an important role in the acid–base processes occurring in the solution. Dissociation of dissolved CO₂ in water: $$\:{CH}_{2}+{H}_{2}O\leftrightarrow\:HC{O}_{3}^{-}+{H}_{3}{O}^{+}$$ 2 When carbon dioxide (CO₂) dissolves in water, it reacts with water molecules to form carbonic acid ( \(\:{H}_{2}C{O}_{3}\) ), which rapidly dissociates into bicarbonate ions ( \(\:HC{O}_{3}^{-}\) ) and hydronium ions ( \(\:{H}_{3}{O}^{+}\) ). The dissociation of bicarbonate proceeds as follows: $$\:HC{O}_{3}^{-}+{H}_{2}O\leftrightarrow\:C{O}_{3}^{2-}+{H}_{3}{O}^{+}$$ 3 Bicarbonate ( \(\:HC{O}_{3}^{-}\) ) can further dissociate to form carbonate ions ( \(\:C{O}_{3}^{2-}\) ) and hydronium ions ( \(\:{H}_{3}{O}^{+}\) ), which contributes to a decrease in the solution's pH. Zwitterion formation reaction during the interaction of MEA with CO₂: $$\:C{O}_{2}+{RNH}_{2}\leftrightarrow\:RN{H}_{2}^{+}CO{O}^{-}$$ 4 The amino group of monoethanolamine ( \(\:{RNH}_{2}\) ) reacts with CO₂ to form a zwitterion ( \(\:RN{H}_{2}^{+}CO{O}^{-}\) ), where the carboxylate group carries a negative charge and the amine group becomes protonated. Deprotonation of the zwitterion and formation of the carbamate: $$\:RN{H}_{2}^{+}CO{O}^{-}+{RNH}_{2}\leftrightarrow\:RN{H}_{3}^{+}+RNHCO{O}^{-}$$ 5 The zwitterion reacts with an additional MEA molecule, resulting in the formation of a protonated MEA ( \(\:RN{H}_{3}^{+}\) ) and a carbamate ion ( \(\:RNHCO{O}^{-}\) ). Hydrolysis of carbamate and its reverse conversion to bicarbonate: $$\:RN{H}_{2}^{+}CO{O}^{-}+{H}_{2}O\leftrightarrow\:{H}_{3}{O}^{+}+RNHCO{O}^{-}$$ 6 Carbamate may undergo hydrolysis, resulting in the release of a hydronium ion ( \(\:{H}_{3}{O}^{+}\) ) and partial regeneration of the carbamate structure. Dissociation of protonated MEA: $$\:RN{H}_{3}^{+}+{H}_{2}O\leftrightarrow\:{RNH}_{2}+{H}_{3}{O}^{+}$$ 7 The protonated form of monoethanolamine ( \(\:RN{H}_{3}^{+}\) ) can donate a proton to water, returning to its neutral amine form ( \(\:{RNH}_{2}\) ), thereby influencing the pH of the solution. Formation of bicarbonate: $$\:C{O}_{2}+O{H}^{-}\leftrightarrow\:HC{O}_{3}^{-}$$ 8 CO₂ can also react with hydroxide ions ( \(\:O{H}^{-}\) ), to form bicarbonate ( \(\:HC{O}_{3}^{-}\) ), which is a significant reaction in alkaline environments. Yu et al. [ 25 ] identified three key processes that govern CO₂ absorption using MEA within a pseudo-first-order reaction framework: molecular diffusion, physical dissolution, and chemical interaction. As noted by Arunvilas et al. [ 26 ], the chemical reaction between CO₂ and MEA occurs almost instantaneously. After CO₂ enters the liquid phase via physical absorption, it rapidly transforms into various chemical species. The greatest resistance to mass transfer is associated with the step involving the movement of CO₂ from the bulk gas phase to the gas–liquid interface. 2.4. Theoretical Analysis Method 2.4.1. Evaluation of Mass Transfer Efficiency in RPB The mass transfer performance in a rotating packed bed (RPB) is determined by a combination of parameters, among which the overall volumetric gas-phase mass transfer coefficient ( \(\:{K}_{{G}^{a}}\) ). plays a central role. This coefficient provides a quantitative measure of the intensity of mass transfer between the gas and liquid phases, which is essential for the design and optimization of RPB systems. In general, the coefficient ( \(\:{K}_{{G}^{a}}\) ) can be determined using the following expression [ 27 , 28 ]: $$\:{K}_{{G}^{a}}=\frac{{G}_{1}}{\pi\:PZ({r}_{out}^{2}-{r}_{in}^{2})}\int\:\frac{1}{({y}_{{CO}_{2}}-{y}_{{CO}_{2}}^{*})}d\left(\frac{{y}_{{CO}_{2}}}{1-{y}_{{CO}_{2}}}\right)$$ 9 where P — the total pressure, Z — the axial height of the packing in the RPB, \(\:{r}_{in}\) and \(\:{r}_{out}\) represent the inner and outer radii of the packing, respectively. \(\:{G}_{1}\) denotes the inert gas flow rate. \(\:{y}_{{CO}_{2}}\) and \(\:{y}_{{CO}_{2}}^{*}\) refer to the mole fraction of CO₂ in the gas phase and the equilibrium mole fraction of CO₂, respectively. Since the interaction between CO₂ and the aqueous solution of monoethanolamine (MEA) is characterized by a very fast chemical reaction, it is reasonable to assume that \(\:{y}_{{CO}_{2}}^{*}=0\) . This assumption simplifies the integration of the mass transfer equation, leading to the following expression (Eq. 10 ): $$\:{K}_{{G}^{a}}=\frac{{G}_{1}}{\pi\:PZ({r}_{out}^{2}-{r}_{in}^{2})}\times\:\left[ln\frac{{y}_{in}(1-{y}_{out)}}{{y}_{out}(1-{y}_{in)}}+\left(\frac{1}{1-{y}_{in}}+\frac{1}{1-{y}_{out}}\right)\right]$$ 10 where \(\:{y}_{in}\) and \(\:{y}_{out}\) are the mole fractions of CO₂ in the gas phase at the inlet and outlet, respectively. Additionally, the CO₂ capture efficiency \(\:\left({\eta\:}\right)\) defined as the ratio of the amount of CO₂ removed to its initial amount in the gas stream, is calculated using the following equation (Eq. 11 ): $$\:\eta\:=\left[1-\frac{{y}_{out}(1-{y}_{in})}{{y}_{in}(1-{y}_{out})}\:\right]\times\:100\%$$ 11 This expression provides a quantitative assessment of CO₂ absorption efficiency in the RPB, which is essential for further analysis and scaling of gas purification processes. These parameters form the basis for optimizing the design characteristics of the unit and selecting appropriate operating conditions for the process. 3. Results and discussions 3.1. Effect of rotational speed on CO₂ capture efficiency The energy requirements of a Rotating Packed Bed (RPB) are closely linked to the rotor speed, which also plays a crucial role in determining the capture efficiency. To achieve an optimal balance between energy consumption and capture performance, it is important to investigate the relationship between rotor speed and separation efficiency. In this work, the rotor speed was varied in the range of 0 rmp to 2400 rpm. This range was selected based on the maximum operational frequency of the motor (3000 rmp), while 0 rmp was included as a reference point to evaluate the influence of rotation in comparison to a stationary packed bed. A 30% MEA (monoethanolamine) aqueous solution and a synthetic flue gas containing 15% CO₂ were used in this study. Figure 3 illustrates the effect of rotation speed on CO₂ capture efficiency under the following operating conditions: 30% MEA concentration, temperature of 25°C, and pressure of 101,325 N/m². The results indicate a positive correlation between rotor speed and CO₂ capture efficiency. This trend is consistent with findings reported by Burns et al. [ 29 , 30 ], which suggest that the rotation of the absorber enhances mass transfer due to the combined action of droplet and film flows. Figure 3 demonstrates the relationship between rotor speed and CO₂ capture efficiency in a Rotating Packed Bed (RPB) system. The rotational speed was varied from 0 to approximately 2700 rpm, and the corresponding CO₂ capture efficiency was recorded. As shown in the Fig. 3 , a clear positive correlation exists between the rotor speed and the CO₂ capture efficiency. At low rotational speeds (e.g., 0–500 rpm), a sharp increase in capture efficiency is observed, indicating the significant impact of initial rotational motion on mass transfer. This enhancement can be attributed to the increased centrifugal force, which intensifies the liquid film and droplet dispersion within the packing, thereby improving gas–liquid contact. Beyond 500 rpm, the increase in efficiency continues but at a more moderate, linear rate. At approximately 2700 rpm, the CO₂ capture efficiency reaches around 75%, suggesting that higher rotational speeds further improve the absorption process, although with diminishing marginal returns. Figure 4 shows the variation of the overall gas-phase overall mass transfer coefficient \(\:\left({K}_{{G}^{a}}\right)\) as a function of rotor speed in a Rotating Packed Bed (RPB) system. The experiments were conducted using a 30% MEA solution under standard conditions. The results reveal a clear upward trend: as the rotor speed increases from 0 to approximately 2500 rpm, the value of \(\:\left({K}_{{G}^{a}}\right)\) significantly rises—from about 0.2 to over 3.5 kmol·kPa⁻¹·m⁻³·h⁻¹. This substantial enhancement can be attributed to the intensified centrifugal forces and improved gas-liquid contact at higher rotational speeds, which promote the thinning of the liquid film, the dispersion of droplets, and an increase in interfacial area for mass transfer. At lower speeds (0–750 rpm), the increase in \(\:\left({K}_{{G}^{a}}\right)\) is relatively moderate, indicating the initial contribution of mechanical rotation to overcoming natural convection limitations. Beyond 1000 rpm, the growth becomes more pronounced, with the steepest rise observed between 2000 and 2500 rpm, suggesting a nonlinear relationship likely influenced by turbulence and droplet entrainment. These findings are consistent with the theory that RPB systems provide intensified mass transfer by reducing diffusion resistance and enhancing the surface renewal rate. Thus, optimizing rotor speed is a key parameter in designing energy-efficient CO₂ absorption systems with high mass transfer performance. 3.2. Effect of MEA concentration on CO 2 capture efficiency, Mass transfer coefficient \(\:\left({\varvec{K}}_{{\varvec{G}}^{\varvec{a}}}\right)\) and Height of Transfer Unit (HTU). In this study, the impact of varying monoethanolamine (MEA) concentrations on CO 2 capture efficiency and the overall volumetric mass transfer coefficient was thoroughly examined under controlled conditions. The experimental data obtained from different concentrations of MEA (30%, 50%, 70%, and 90% by weight) are analyzed, and their implications for CO 2 absorption efficiency and mass transfer are discussed below. The results, as shown in Fig. 5 , demonstrate a clear upward trend in CO 2 capture efficiency with increasing MEA concentration. At the lowest MEA concentration (30%), the capture efficiency was around 40%, while at the highest concentration (90%), it reached nearly 80%. This behavior is attributed to the increase in hydroxide ions per unit volume as the MEA concentration increases. Hydroxide ions are crucial in the absorption process, as they react with CO 2 , enhancing the overall absorption rate. These findings are consistent with previous studies by Freguia and Rochelle [ 31 ], who observed that the reaction rate of a pseudo-first-order reaction depends directly on the concentration of MEA. As MEA concentration rises, the reaction rate increases, leading to higher CO 2 absorption. This phenomenon explains why higher MEA concentrations are more effective in capturing CO 2 . Furthermore, these results align with reports by Jassim et al. [ 32 ], which found that higher concentrations of MEA result in lower CO 2 penetration due to improved absorption kinetics. The second aspect of the study focused on the effect of MEA concentration on the overall volumetric mass transfer coefficient. As illustrated in Fig. 6 , the increase in MEA concentration is correlated with a rise in the mass transfer coefficient. This indicates that the efficiency of mass transfer improves as MEA concentration increases. This result can be explained by the enhanced CO 2 absorption rate, which is a direct consequence of higher MEA concentration. With more hydroxide ions available to react with CO 2 , the rate of mass transfer increases, improving the overall performance of the CO 2 capture process. However, while higher MEA concentrations improve both CO 2 capture efficiency and mass transfer, there are practical considerations to address. As the MEA concentration increases, so does the solvent viscosity, which leads to thicker liquid films and a reduction in the driving force for mass transfer. This trade-off between increased capture efficiency and reduced mass transfer efficiency at higher MEA concentrations must be considered when optimizing the process for industrial applications. The experimental data also reveal the relationship between MEA concentration and the Height of Transfer Unit (HTU), as shown in Fig. 6 . HTU values were found to increase with decreasing MEA concentration. This result suggests that a higher concentration of MEA leads to a lower HTU, indicative of improved mass transfer efficiency at higher concentrations. The decrease in HTU can be attributed to the enhanced absorption kinetics at higher MEA concentrations, which leads to a more efficient overall mass transfer process. While the results demonstrate the benefits of higher MEA concentrations for CO 2 capture, several practical challenges must be considered. Higher MEA concentrations not only improve CO 2 capture but also increase the risk of equipment corrosion, which is a significant concern in industrial applications. Additionally, the increase in solvent viscosity at higher MEA concentrations can lead to operational challenges related to fluid dynamics and mass transfer resistance. Therefore, it is essential to identify the optimal MEA concentration that maximizes CO 2 capture while minimizing the adverse effects of increased viscosity and potential corrosion. Further studies are needed to evaluate the trade-offs between these factors and to explore the impact of other process variables, such as temperature, pressure, and flow rates, on the overall efficiency of the CO 2 capture process. 3.3. Effect of liquid to gas ratio on CO 2 capture efficiency, volumetric mass transfer coefficient \(\:\left({\varvec{K}}_{{\varvec{G}}^{\varvec{a}}}\right)\) and Height of Transfer Unit (HTU) The effect of varying the liquid to gas ratio (L/G) on CO 2 capture efficiency is shown in Fig. 7 . As observed, the CO 2 capture efficiency increases significantly with higher liquid to gas ratios. At the lowest L/G ratio (0.01 L/G), the capture efficiency is approximately 55%, and it steadily rises to nearly 90% at the highest L/G ratio (0.04 L/G). This indicates that increasing the liquid flow rate or decreasing the gas flow rate leads to a higher absorption of CO 2 , thus improving the overall CO 2 capture performance. The increase in CO 2 capture efficiency with higher L/G ratios can be attributed to the increased solvent availability for CO 2 absorption. At higher liquid flow rates, there is a larger volume of MEA solution in contact with the CO 2 -laden gas, which provides more active sites for the absorption process. The findings are consistent with previous research indicating that a higher L/G ratio improves the efficiency of gas-liquid absorption processes by enhancing the contact time between the CO 2 and the solvent. Figure 8 shows the relationship between the liquid to gas ratio (L/G) and both the overall mass transfer coefficient \(\:\left({K}_{{G}^{a}}\right)\) and Height of Transfer Unit (HTU). As the L/G ratio increases, the mass transfer coefficient also increases, reaching its highest value at an L/G ratio of 0.04 L/G. This is consistent with the observed increase in CO 2 capture efficiency, as higher mass transfer rates correspond to better absorption of CO 2 . At higher liquid flow rates, there is more solvent available to absorb CO 2 , which leads to faster absorption and, therefore, a higher mass transfer coefficient. This is indicative of more efficient mass transfer between the gas and liquid phases. Conversely, the HTU decreases as the L/G ratio increases. At lower L/G ratios, HTU is higher, indicating that more space is required to achieve the same level of CO 2 absorption. As the L/G ratio increases, the absorption efficiency improves, and the required HTU decreases. The decrease in HTU with increasing L/G ratio suggests that the process of CO 2 absorption becomes more efficient as the liquid flow rate increases. With more solvent available, the mass transfer efficiency improves, reducing the required height of the absorption column. From the two figures (Fig. 7 – 8 ), it is evident that there is an inverse relationship between the mass transfer coefficient and HTU. As the mass transfer coefficient increases, the HTU decreases, and vice versa. This inverse relationship is typical in absorption processes, where improved mass transfer leads to more efficient CO 2 absorption and, as a result, reduces the amount of space (HTU) needed for the same level of CO 2 capture. The results highlight the importance of optimizing the liquid to gas ratio to achieve maximum CO 2 capture efficiency. Increasing the liquid flow rate improves both the mass transfer coefficient and CO 2 capture efficiency, while simultaneously reducing HTU. However, it is important to consider the operational costs associated with higher liquid flow rates, such as increased energy consumption for pumping and potential equipment wear. Moreover, the optimal liquid to gas ratio should balance the trade-off between increasing CO 2 capture efficiency and minimizing energy and operational costs. Further experiments are needed to explore the effect of varying other parameters, such as gas flow rate, pressure, and temperature, to achieve a comprehensive understanding of the factors influencing the CO 2 absorption process. 4. Conclusions This study experimentally investigated the performance of a Rotating Packed Bed (RPB) absorber for CO₂ capture using aqueous monoethanolamine (MEA) solutions under various operating conditions. The influence of rotor speed, MEA concentration, and liquid-to-gas (L/G) ratio on CO₂ capture efficiency, overall mass transfer coefficient \(\:\left({K}_{{G}^{a}}\right)\) , and Height of Transfer Unit (HTU) was systematically analyzed. The results demonstrated a clear positive correlation between rotor speed and CO₂ capture efficiency, with an observed enhancement from approximately 40% at low speeds to over 75% at around 2700 rpm. This increase was accompanied by a significant rise in the overall mass transfer coefficient, highlighting the role of centrifugal acceleration in intensifying gas–liquid interactions. Increasing MEA concentration from 30–90% wt significantly improved CO₂ capture efficiency and mass transfer performance due to enhanced reaction kinetics. However, the associated increase in solvent viscosity presents practical trade-offs that must be considered during process design. A similar trend was observed in HTU reduction, confirming more efficient mass transfer at higher MEA concentrations. Furthermore, the study revealed that higher liquid-to-gas ratios substantially enhance CO₂ absorption efficiency and \(\:\left({K}_{{G}^{a}}\right)\) while reducing HTU, demonstrating the importance of solvent availability and interfacial area in optimizing absorber performance. Nonetheless, the energy and operational costs associated with increased solvent flow must be carefully balanced. Overall, the findings confirm that RPB technology is a highly effective process intensification approach for post-combustion CO₂ capture. The insights gained from this study provide valuable data for designing, scaling up, and optimizing industrial CO₂ absorption systems using RPBs. Declarations Author Contribution Alisher U. Auesbaev (Corresponding Author) — Conceptualization, Supervision, Writing – Original Draft, Experimental Design.Bobirjon Z. Adizov — Experimental Investigation, Data Collection, Visualization. References Aydin G, et al., 2016. Energy consumption modelling using artificial neural networks: The case of the world’s highest consumers. Energy Sources, Part B Econ Plan Policy.11, 212–219. Hong WY. 2022. A techno-economic review on carbon capture, utilisation and storage systems for achieving a net-zero CO 2 emissions future. Carbon Capture Science & Technology. 3:100044. EIA. Energy information administration. Department of Energy; 2010. Tan L.S., et al., 2012. Factors affecting CO 2 absorption efficiency in packed column: A review. Journal of Industrial and Engineering Chemistry. 18(6), 1874-1883. Tan L.S., et al., 2012. Removal of high concentration CO 2 from natural gas at elevated pressure via absorption process in packed column. Journal of Natural Gas Chemistry. 21(1), 7-10. Wang M, et al., 2011. Post-combustion CO capture with chemical absorption: a state-of-the-art review. Chem Eng Res Des. 89:1609–1624. Lawal A, et al., 2012. Demonstrating full-scale post-combustion CO capture for coal-fired power plants through dynamic modelling and simulation. Fuel. 101:115–128. Oko E, et al., 2018. Study of intercooling for rotating packed bed absorbers in intensified solvent-based CO 2 . Appl Energy. 223, 302–316. Jassim MS, et al., 2007. Carbon dioxide absorption and desorption in aqueous monoethanolamine solutions in a rotating packed bed. Ind Eng Chem Res, 46:2823–2833. Cheng H-H, et al., 2013. Thermal regeneration of alkanolamine solutions in a rotating packed bed. Int J Greenh Gas Control, 16:206–216. Joel AS, et al., 2014, Process analysis of intensified absorber for post-combustion CO 2 capture through modelling and simulation. Int J Greenh Gas Control. 21:91–100. Borhani T.N, et al., 2019. Process modelling, validation and analysis of rotating packed bed stripper in the context of intensified CO 2 capture with MEA. Journal of Industrial and Engineering Chemistry, 75:285–295. Im D, et al., 2020. Modeling, simulation and optimization of the rotating packed bed (RPB) absorber and stripper for MEA-based carbon capture. Comput Chem Eng, 143:107102. Lin C.C. and Chen Y.W., 2011, Performance of a cross-flow rotating packed bed in removing carbon dioxide from gaseous streams by chemical absorption. Int. J. Greenhouse Gas Control. 5, 668-675. Agarwal L, et al., 2010, Process Intensification in HiGee Absorption and Distillation: Design Procedure and Applications. Ind. Eng. Chem. Res., 49, 10046-10058. Chen, Y.H., 2010. A continuous-flow biodiesel production process using a rotating packed bed, Bioresour. Technol., 101, 668–673. Lin C.C., et al., 2008. Feasibility of a cross-flow rotating packed bed in removing carbon dioxide from gaseous streams. Separ. Purif. Tech., 62, 507–512. Das A; et al., 2008. Continuous biosorption in rotating packed-bed contactor, Ind. Eng. Chem. Res., 47, 4230–4235. Llerena-Chavez H and Larachi F. 2009. Analysis of flow in rotating packed beds via CFD simulations - Dry pressure drop and gas flow maldistribution. Chem. Eng. Sci., 64, 2113-2126. Yang W. et al., 2010, Computational fluid dynamic simulation of fluid flow in a rotating packed bed, Chem. Eng. J., 156, 582-587. Borhani T.N., 2018, Process modelling and analysis of intensified CO 2 capture using monoethanolamine (MEA) in rotating packed bed absorber. J. Clean. Prod., 204, 1124-1142. Dimoliani M., 2021, Modeling and Parametric Investigation of Rotating Packed Bed Processes for CO 2 Capture and Mineralisation, Chem. Eng. Trans, 88, 187-192. Hendry J.R., 2020, Pressure drop and flooding in rotating packed beds, Chem. Eng. Proc. Proc. Intensif., 151, 107908. Aboudheir A, et al., 2003. Kinetics of the reactive absorption of carbon dioxide in high CO 2 ‐loaded, concentrated aqueous monoethanolamine solutions. Chem Eng Sci. 58, 5195‐5210. Yu Y.S, et al., 2010. Multi‐field synergy study of CO 2 capture process by chemical absorption. Chem Eng Sci. 65, 3279‐3292. Aroonwilas A et al., 1999. Behavior of the mass‐transfer coefficient of structured packings in CO2 absorbers with chemical reactions. Ind Eng Chem Res. 38, 2044‐2050. Wu S.Y., et al., 2017. Mass- transfer performance for CO 2 absorption by 2-(2-aminoethylamino)ethanol solution in a rotating packed bed, Energy Fuels. 31, 14053–14059. Xie C.X., et al., 2018. Low-concentration CO 2 capture from natural gas power plants using a rotating packed bed reactor, Energy Fuels. 33, 1713–1721. Burns J.R., et al., 2000. Process intensification: operating characteristics of rotating packed beds— determination of liquid hold‐up for a high‐voidage structured packing. Chem Eng Sci. 55, 2401‐2415. Burns J.R., et al., 2003. Measurement of liquid film thickness and the determination of spin‐up radius on a rotating disc using an electrical resistance technique. Chem Eng Sci. 58, 2245‐2253. Freguia S and Rochelle G.T., 2003. Modeling of CO 2 capture by aqueous monoethanolamine. AIChE J. 49, 1676‐1686. Jassim M.S., et al., 2007. Carbon dioxide absorption and desorption in aqueous monoethanolamine solutions in a rotating packed bed. Ind Eng Chem Res. 46, 2823‐2833. Additional Declarations No competing interests reported. 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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-6601658","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":470286449,"identity":"9c5f07ee-426e-432b-b56e-fb296f0305a6","order_by":0,"name":"Auesbaev Alisher","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABDElEQVRIiWNgGAWjYDACdsYGZiiTDUTIgYgDD/BpYUbTYgzWkoBXCxghtCQ2gEh8WvibmZs/F1Tckzc43v7swY+Kw+nzww4/BNpiJ6fbgF2LxGHGNukZZ4oNN5w5Y27Yc+Zw7sbbaQZALcnGZgdwWAPUwszblsC44UYOmwRvW1ruxtkJIC0HErfh0CJ/mLH5M++/BPsN958/k/z7Ly3dcHb6B7xaDA4zNkjzNiQkbrjBYAZk2CTIS+fgt8UQ5BeeYwnJM8/kmBvLHLMx3CCdU3AgwQC3X+SOtz/+zFOTYNt3/Pizh29qJOTlZ6dv/vChwk4Op/cxnQpWaUCschCQbyBF9SgYBaNgFIwEAACnQmPItvtYuQAAAABJRU5ErkJggg==","orcid":"","institution":"Institute of General and Inorganic Chemistry of the Academy of Sciences of the Republic of Uzbekistan, Tashkent","correspondingAuthor":true,"prefix":"","firstName":"Auesbaev","middleName":"","lastName":"Alisher","suffix":""},{"id":470286451,"identity":"e82ff879-e298-40b9-808e-c7b485eb2d9b","order_by":1,"name":"Bobirjon Z. Adizov","email":"","orcid":"","institution":"Institute of General and Inorganic Chemistry of the Academy of Sciences of the Republic of Uzbekistan, Tashkent","correspondingAuthor":false,"prefix":"","firstName":"Bobirjon","middleName":"Z.","lastName":"Adizov","suffix":""}],"badges":[],"createdAt":"2025-05-06 09:53:32","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6601658/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6601658/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":84551769,"identity":"4212dded-552f-4634-af73-252776dcf5a0","added_by":"auto","created_at":"2025-06-13 10:32:29","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1057416,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental set‐up for CO\u003csub\u003e2\u003c/sub\u003e capture.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-6601658/v1/c4b69da49aef2a6bb079ff00.png"},{"id":84551394,"identity":"b7a1649a-7a06-4c1f-8c25-22a8d9669e73","added_by":"auto","created_at":"2025-06-13 10:24:28","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":17805,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 3.\u003c/strong\u003e \u003cem\u003eEffect of rotational speed on CO₂ capture efficiency using 30% MEA solution at 25 °C and atmospheric pressure (101,325 N/m²).\u003c/em\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6601658/v1/310ed64888e4756b5169550a.png"},{"id":84551417,"identity":"21363137-3837-4a84-b54f-1267e08ae0e9","added_by":"auto","created_at":"2025-06-13 10:24:29","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":485289,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 4.\u003c/strong\u003e\u003cem\u003eEffect of rotational speed on the overall gas-phase mass transfer coefficient \u003c/em\u003e(\u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003eG\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003ea\u003c/em\u003e\u003c/sup\u003e)\u003cem\u003e\u0026nbsp;and height of transfer unit using 30% MEA solution at 25 °C and atmospheric pressure (101,325 N/m²)\u003c/em\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6601658/v1/ae909d41539b3a660d745370.png"},{"id":84551393,"identity":"101dc5a3-3258-4774-838c-92747172781a","added_by":"auto","created_at":"2025-06-13 10:24:28","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":15456,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 5.\u003c/strong\u003e The effect of monoethanolamine concentration on CO\u003csub\u003e2\u003c/sub\u003e capture efficiency. Experimental conditions: Liquid flow rate = 0.23 l/min; Gas flow rate = 13.4 l/min; Inlet CO\u003csub\u003e2\u003c/sub\u003e concentration = 15%; Pressure = 101.325 N/m²; Temperature = 25°C; Rotational speed = 1500 rpm\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6601658/v1/89a79d5f2e4f0e46d1bdac7f.png"},{"id":84551411,"identity":"00a9dc17-f47b-44e2-aaf4-108d3aaa15b9","added_by":"auto","created_at":"2025-06-13 10:24:29","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":25989,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 6.\u003c/strong\u003e The effect of monoethanolamine concentration on volumetric mass transfer coefficient and height of transfer unit. Experimental conditions: Liquid flow rate = 0.23 l/min; Gas flow rate = 13.4 l/min; Inlet CO\u003csub\u003e2\u003c/sub\u003e concentration = 15%; Pressure = 101.325 N/m²; Temperature = 25°C; Rotational speed = 1500 rpm\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6601658/v1/9ef48909413738e0edd071a6.png"},{"id":84551406,"identity":"4e06bd00-6d77-45ce-bccb-583f3834e369","added_by":"auto","created_at":"2025-06-13 10:24:29","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":193838,"visible":true,"origin":"","legend":"\u003cp\u003eFigure 7. The effect of liquid to gas ratio on CO\u003csub\u003e2\u003c/sub\u003e capture efficiency. Experimental conditions: Liquid flow rate = 0.161-0.567 l/min; Gas flow rate = 13.4 l/min; Inlet CO\u003csub\u003e2\u003c/sub\u003e concentration = 15%; Pressure = 101.325 N/m²; Temperature = 25°C; Rotational speed = 1500 rpm\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6601658/v1/dc9a8768dabf399214233a6b.png"},{"id":84552460,"identity":"ed84e345-0bd6-49df-9ab2-c424cd6ea84e","added_by":"auto","created_at":"2025-06-13 10:40:29","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":640938,"visible":true,"origin":"","legend":"\u003cp\u003eFigure 8. The effect of liquid to gas ratio on overall mass transfer coefficient \u0026nbsp;and Height of Transfer Unit (HTU). Experimental conditions: Liquid flow rate = 0.161-0.567 l/min; Gas flow rate = 13.4 l/min; Inlet CO\u003csub\u003e2\u003c/sub\u003e concentration = 15%; Pressure = 101.325 N/m²; Temperature = 25°C; Rotational speed = 1500 rpm\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6601658/v1/f8abe8797f2fda340df613a0.png"},{"id":102749545,"identity":"d66236d4-c3e1-4961-a325-f8c220aa4652","added_by":"auto","created_at":"2026-02-16 09:12:48","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2621817,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6601658/v1/1aba358e-8fff-4d4d-b4cd-bcb0a2a3569c.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Process Intensification of CO₂ Absorption with MEA in a Rotating Packed Bed: Experimental Evaluation and Analysis","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe global demand for energy has consistently increased in recent years, driven by population growth and rapid technological advancements [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Consequently, energy-related carbon dioxide (CO₂) emissions have also escalated, reaching 31.5 gigatonnes in 2021 [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. As CO₂ is the most significant anthropogenic greenhouse gas (GHG) contributing to global warming, the need for sustainable mitigation strategies is urgent. The International Energy Agency (IEA) has identified Carbon Capture, Utilization, and Storage (CCUS) as a critical technology for reducing GHG emissions and addressing climate change [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAt the same time, global reserves of sweet natural gas are being depleted [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], leading to growing interest in developing sour gas reservoirs that often contain high CO₂ concentrations\u0026mdash;up to 80% in some cases [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The presence of CO₂, along with hydrogen sulfide and other impurities, makes sour gas processing technically challenging. CO₂ is highly corrosive, endangering the integrity of pipelines and process equipment. Therefore, efficient and scalable CO₂ separation technologies are essential for both natural gas purification and environmental compliance.\u003c/p\u003e \u003cp\u003eAmong the three main CO₂ capture approaches\u0026mdash;pre-combustion, oxy-fuel combustion, and post-combustion capture (PCC)\u0026mdash;chemical absorption-based PCC is the most mature and widely applied technology [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Its compatibility with existing infrastructure has enabled commercial-scale deployment, particularly for power plants and industrial facilities [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. However, conventional PCC systems typically employ packed bed (PB) columns for CO₂ absorption and solvent regeneration. These columns are bulky, expensive, and limited by poor mass transfer rates, especially when operating with viscous, concentrated solvents such as monoethanolamine (MEA) [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTo overcome these limitations, Rotating Packed Bed (RPB) technology has emerged as a promising process intensification solution. By replacing gravitational flow with centrifugal acceleration, RPBs significantly enhance gas\u0026ndash;liquid mass transfer rates and reduce equipment size. In RPBs, the liquid is distributed at the rotor center and flows radially outward through the packing as thin films, while the gas flows countercurrently from the outer edge toward the center [\u003cspan additionalcitationids=\"CR15 CR16 CR17\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. This configuration facilitates intense phase contact, improves mixing, and enables the use of high-viscosity solvents such as concentrated MEA (\u0026gt;\u0026thinsp;55 wt%) [\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRPBs have been successfully applied across a range of industries, including distillation, oxidation, crystallization, polymerization, and biodiesel production [\u003cspan additionalcitationids=\"CR15 CR16 CR17\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. In the context of CO₂ capture, several studies have demonstrated the potential of RPBs to improve absorption efficiency and reduce regeneration energy [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. For example, Joel et al. [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] developed a rate-based RPB absorber model using MEA in Aspen Plus\u0026reg;, coupled with Fortran\u0026reg;. Their simulations showed that absorber volume could be reduced by a factor of 12 compared to conventional PB columns\u0026mdash;highlighting the compactness and efficiency of RPBs.\u003c/p\u003e \u003cp\u003eDespite these advantages, process intensification in RPBs is inherently complex due to simultaneous phenomena involving mass transfer, heat transfer, and fluid dynamics [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Accurate modeling of RPB performance remains a significant challenge, particularly at industrial scale. Many existing models rely on simplifying assumptions that, while suitable for lab-scale units, may not hold for scaled-up operations, potentially resulting in discrepancies in performance prediction [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Moreover, due to the complex internal flow behavior, experimental data alone is insufficient to fully understand RPB hydrodynamics. Three-dimensional computational fluid dynamics (CFD) simulations have been proposed to gain deeper insight into flow characteristics, pressure fields, and velocity distributions, though such studies remain limited [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn light of these considerations, further research and model development are essential for optimizing RPB systems for CO₂ capture. The unique advantages of RPBs\u0026mdash;compactness, high mass transfer efficiency, and compatibility with concentrated solvents\u0026mdash;position this technology as a leading candidate for next-generation carbon capture systems.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Materials\u003c/h2\u003e \u003cp\u003eIn this study, pure monoethanolamine (MEA) was used as the solvent. The MEA was sourced from the Mubarek Gas Processing Plant with a purity of \u0026gt;\u0026thinsp;99%. A gas mixture of CO₂ and air was also used in the experiments. Aqueous MEA solutions with mass concentrations of 30%, 50%, 70%, and 90% were prepared using distilled water. The gas mixtures consisted of 85% CO₂ and 15% air.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Experimental Part\u003c/h2\u003e \u003cp\u003eThe experimental setup was assembled at the \"Processes and Apparatuses of Chemical Technology\" laboratory of the Institute of General and Inorganic Chemistry of the Academy of Sciences of the Republic of Uzbekistan. The schematic diagram of the experimental system is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The system includes an RPB absorber, reservoirs for lean and rich MEA, a gas cylinder filled with pure CO₂, a pump for circulating the lean MEA solution, a compressor for air injection, a GC-7860 gas chromatograph for gas analysis, and flow meter gas and liquid for measuring the flow rates of both the gas mixture and the solvent.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the setup of the experimental RPB (Rotating Packed Bed) absorber used for CO₂ capture, where lean MEA is introduced as the absorbing solvent and exits as rich MEA after capturing CO₂. The experiment begins with the supply of a gas mixture containing 15% CO₂ and 85% air from the cylinder (4) through the compressor (5), which provides the required pressure. The gas then flows through the globe valves (11) and the gas flow meter (10) into the rotating packed bed (RPB) absorber. Simultaneously, a monoethanolamine (MEA) solution is pumped from the liquid tank (2) using a pump (8), passes through the liquid flow meter (9), and is also fed into the absorber. Inside the RPB, which is equipped with SS316 stainless steel packing, the liquid is distributed via a stationary distributor containing five sets of holes (each set has five 1 mm holes spaced 72\u0026deg; apart) along the inner edge of the packing. Due to centrifugal force, the liquid moves radially outward through the packing and is collected at the bottom of the stationary casing. In contrast, the gas enters from the outer stationary casing, flows inward through the packing counter-currently to the liquid flow, and exits through the central pipe of the rotor. This counter-current flow is intensified by the high rotational speed of the packing, driven by the motor (1), which enhances mass transfer efficiency. During this process, CO₂ from the gas mixture is absorbed by the MEA solution. The CO₂-depleted gas (lean gas) exits through the rotor's central pipe and is directed to the CO₂ analyzer (6) to monitor residual CO₂ concentration. The CO₂-rich MEA (rich MEA) is collected at the bottom in the storage tank (3) for further regeneration. This setup simulates an industrial CO₂ capture process using an advanced rotating packed bed technology. The inlet and outlet CO₂ concentrations were measured using a GC-7860 gas chromatograph.\u003c/p\u003e \u003cp\u003eThe rotor speed was varied from 0 to 2400 rpm. The centrifugal field in the RPB enables the formation of thinner liquid films and smaller droplets. This system is capable of operating at higher gas\u0026ndash;liquid flow ratios due to its reduced tendency for flooding. One of the most critical advantages of this configuration is its ability to significantly enhance mass transfer coefficients\u0026mdash;by an order of magnitude\u0026mdash;thereby reducing equipment size compared to conventional packed bed columns.\u003c/p\u003e \u003cp\u003eThe axial height of the packing was 3.0 cm, while the inner and outer diameters were 5 cm and 14 cm, respectively. The MEA solution was pumped into the rotating packed bed with a flow rate ranging from 0.161 to 0.567 L/min. The CO₂\u0026ndash;air gas mixture entered from the stationary casing and flowed radially inward through the packing. The CO₂ concentration in the inlet gas was maintained at 15% of the total mixture volume. The gas flow rate was 13.4 L/min, and the liquid flow rate ranged from 0.161 to 0.567 L/min. A steady state was typically reached within 7\u0026ndash;12 minutes, monitored by the outlet CO₂ concentration. All experiments were conducted at an ambient temperature of approximately 25\u0026deg;C and under atmospheric pressure.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Chemical Reactions between CO₂, Water, and MEA\u003c/h2\u003e \u003cp\u003eThe primary mechanisms of the reaction between carbon dioxide (CO₂) and monoethanolamine (MEA) have been investigated using two distinct approaches: the zwitterion mechanism and the termolecular mechanism.\u003c/p\u003e \u003cp\u003eAccording to studies by Aboudheir et al. [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], a series of chemical reactions describing the interaction of CO₂ with aqueous MEA solutions have been proposed. These reactions cover the key stages of the absorption process, including the formation of intermediate compounds and equilibrium transformations.\u003c/p\u003e \u003cp\u003eWater ionization:\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:2{H}_{2}O\\leftrightarrow\\:O{H}^{-}+{H}_{3}{O}^{+}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWater undergoes spontaneous dissociation, producing hydroxide ions (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:O{H}^{-}\\)\u003c/span\u003e\u003c/span\u003e) and hydronium ions (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{H}_{3}{O}^{+}\\)\u003c/span\u003e\u003c/span\u003e). This reaction plays an important role in the acid\u0026ndash;base processes occurring in the solution.\u003c/p\u003e \u003cp\u003eDissociation of dissolved CO₂ in water:\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:{CH}_{2}+{H}_{2}O\\leftrightarrow\\:HC{O}_{3}^{-}+{H}_{3}{O}^{+}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhen carbon dioxide (CO₂) dissolves in water, it reacts with water molecules to form carbonic acid (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{H}_{2}C{O}_{3}\\)\u003c/span\u003e\u003c/span\u003e), which rapidly dissociates into bicarbonate ions (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:HC{O}_{3}^{-}\\)\u003c/span\u003e\u003c/span\u003e) and hydronium ions (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{H}_{3}{O}^{+}\\)\u003c/span\u003e\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe dissociation of bicarbonate proceeds as follows:\u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$$\\:HC{O}_{3}^{-}+{H}_{2}O\\leftrightarrow\\:C{O}_{3}^{2-}+{H}_{3}{O}^{+}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eBicarbonate (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:HC{O}_{3}^{-}\\)\u003c/span\u003e\u003c/span\u003e) can further dissociate to form carbonate ions (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:C{O}_{3}^{2-}\\)\u003c/span\u003e\u003c/span\u003e) and hydronium ions (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{H}_{3}{O}^{+}\\)\u003c/span\u003e\u003c/span\u003e), which contributes to a decrease in the solution's pH.\u003c/p\u003e \u003cp\u003eZwitterion formation reaction during the interaction of MEA with CO₂:\u003cdiv id=\"Equ4\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ4\" name=\"EquationSource\"\u003e\n$$\\:C{O}_{2}+{RNH}_{2}\\leftrightarrow\\:RN{H}_{2}^{+}CO{O}^{-}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e4\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eThe amino group of monoethanolamine (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{RNH}_{2}\\)\u003c/span\u003e\u003c/span\u003e) reacts with CO₂ to form a zwitterion (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:RN{H}_{2}^{+}CO{O}^{-}\\)\u003c/span\u003e\u003c/span\u003e), where the carboxylate group carries a negative charge and the amine group becomes protonated.\u003c/p\u003e \u003cp\u003eDeprotonation of the zwitterion and formation of the carbamate:\u003cdiv id=\"Equ5\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ5\" name=\"EquationSource\"\u003e\n$$\\:RN{H}_{2}^{+}CO{O}^{-}+{RNH}_{2}\\leftrightarrow\\:RN{H}_{3}^{+}+RNHCO{O}^{-}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e5\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eThe zwitterion reacts with an additional MEA molecule, resulting in the formation of a protonated MEA (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:RN{H}_{3}^{+}\\)\u003c/span\u003e\u003c/span\u003e) and a carbamate ion (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:RNHCO{O}^{-}\\)\u003c/span\u003e\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eHydrolysis of carbamate and its reverse conversion to bicarbonate:\u003cdiv id=\"Equ6\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ6\" name=\"EquationSource\"\u003e\n$$\\:RN{H}_{2}^{+}CO{O}^{-}+{H}_{2}O\\leftrightarrow\\:{H}_{3}{O}^{+}+RNHCO{O}^{-}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e6\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eCarbamate may undergo hydrolysis, resulting in the release of a hydronium ion (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{H}_{3}{O}^{+}\\)\u003c/span\u003e\u003c/span\u003e) and partial regeneration of the carbamate structure.\u003c/p\u003e \u003cp\u003eDissociation of protonated MEA:\u003cdiv id=\"Equ7\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ7\" name=\"EquationSource\"\u003e\n$$\\:RN{H}_{3}^{+}+{H}_{2}O\\leftrightarrow\\:{RNH}_{2}+{H}_{3}{O}^{+}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e7\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eThe protonated form of monoethanolamine (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:RN{H}_{3}^{+}\\)\u003c/span\u003e\u003c/span\u003e) can donate a proton to water, returning to its neutral amine form (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{RNH}_{2}\\)\u003c/span\u003e\u003c/span\u003e), thereby influencing the pH of the solution.\u003c/p\u003e \u003cp\u003eFormation of bicarbonate:\u003cdiv id=\"Equ8\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ8\" name=\"EquationSource\"\u003e\n$$\\:C{O}_{2}+O{H}^{-}\\leftrightarrow\\:HC{O}_{3}^{-}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e8\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eCO₂ can also react with hydroxide ions (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:O{H}^{-}\\)\u003c/span\u003e\u003c/span\u003e), to form bicarbonate (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:HC{O}_{3}^{-}\\)\u003c/span\u003e\u003c/span\u003e), which is a significant reaction in alkaline environments.\u003c/p\u003e \u003cp\u003eYu et al. [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] identified three key processes that govern CO₂ absorption using MEA within a pseudo-first-order reaction framework: molecular diffusion, physical dissolution, and chemical interaction. As noted by Arunvilas et al. [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], the chemical reaction between CO₂ and MEA occurs almost instantaneously. After CO₂ enters the liquid phase via physical absorption, it rapidly transforms into various chemical species. The greatest resistance to mass transfer is associated with the step involving the movement of CO₂ from the bulk gas phase to the gas\u0026ndash;liquid interface.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Theoretical Analysis Method\u003c/h2\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e2.4.1. Evaluation of Mass Transfer Efficiency in RPB\u003c/h2\u003e \u003cp\u003eThe mass transfer performance in a rotating packed bed (RPB) is determined by a combination of parameters, among which the overall volumetric gas-phase mass transfer coefficient (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{K}_{{G}^{a}}\\)\u003c/span\u003e\u003c/span\u003e). plays a central role. This coefficient provides a quantitative measure of the intensity of mass transfer between the gas and liquid phases, which is essential for the design and optimization of RPB systems.\u003c/p\u003e \u003cp\u003eIn general, the coefficient (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{K}_{{G}^{a}}\\)\u003c/span\u003e\u003c/span\u003e) can be determined using the following expression [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]:\u003cdiv id=\"Equ9\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ9\" name=\"EquationSource\"\u003e\n$$\\:{K}_{{G}^{a}}=\\frac{{G}_{1}}{\\pi\\:PZ({r}_{out}^{2}-{r}_{in}^{2})}\\int\\:\\frac{1}{({y}_{{CO}_{2}}-{y}_{{CO}_{2}}^{*})}d\\left(\\frac{{y}_{{CO}_{2}}}{1-{y}_{{CO}_{2}}}\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e9\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere \u003cb\u003eP\u003c/b\u003e \u0026mdash; the total pressure, \u003cb\u003eZ\u003c/b\u003e \u0026mdash; the axial height of the packing in the RPB, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{r}_{in}\\)\u003c/span\u003e\u003c/span\u003e and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{r}_{out}\\)\u003c/span\u003e\u003c/span\u003e represent the inner and outer radii of the packing, respectively. \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{G}_{1}\\)\u003c/span\u003e\u003c/span\u003e denotes the inert gas flow rate. \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{y}_{{CO}_{2}}\\)\u003c/span\u003e\u003c/span\u003e and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{y}_{{CO}_{2}}^{*}\\)\u003c/span\u003e\u003c/span\u003e refer to the mole fraction of CO₂ in the gas phase and the equilibrium mole fraction of CO₂, respectively.\u003c/p\u003e \u003cp\u003eSince the interaction between CO₂ and the aqueous solution of monoethanolamine (MEA) is characterized by a very fast chemical reaction, it is reasonable to assume that \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{y}_{{CO}_{2}}^{*}=0\\)\u003c/span\u003e\u003c/span\u003e. This assumption simplifies the integration of the mass transfer equation, leading to the following expression (Eq.\u0026nbsp;\u003cspan refid=\"Equ10\" class=\"InternalRef\"\u003e10\u003c/span\u003e):\u003cdiv id=\"Equ10\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ10\" name=\"EquationSource\"\u003e\n$$\\:{K}_{{G}^{a}}=\\frac{{G}_{1}}{\\pi\\:PZ({r}_{out}^{2}-{r}_{in}^{2})}\\times\\:\\left[ln\\frac{{y}_{in}(1-{y}_{out)}}{{y}_{out}(1-{y}_{in)}}+\\left(\\frac{1}{1-{y}_{in}}+\\frac{1}{1-{y}_{out}}\\right)\\right]$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e10\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{y}_{in}\\)\u003c/span\u003e\u003c/span\u003e and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{y}_{out}\\)\u003c/span\u003e\u003c/span\u003e are the mole fractions of CO₂ in the gas phase at the inlet and outlet, respectively. Additionally, the CO₂ capture efficiency \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\left({\\eta\\:}\\right)\\)\u003c/span\u003e\u003c/span\u003e defined as the ratio of the amount of CO₂ removed to its initial amount in the gas stream, is calculated using the following equation (Eq.\u0026nbsp;\u003cspan refid=\"Equ11\" class=\"InternalRef\"\u003e11\u003c/span\u003e):\u003cdiv id=\"Equ11\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ11\" name=\"EquationSource\"\u003e\n$$\\:\\eta\\:=\\left[1-\\frac{{y}_{out}(1-{y}_{in})}{{y}_{in}(1-{y}_{out})}\\:\\right]\\times\\:100\\%$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e11\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eThis expression provides a quantitative assessment of CO₂ absorption efficiency in the RPB, which is essential for further analysis and scaling of gas purification processes. These parameters form the basis for optimizing the design characteristics of the unit and selecting appropriate operating conditions for the process.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"3. Results and discussions","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Effect of rotational speed on CO₂ capture efficiency\u003c/h2\u003e \u003cp\u003eThe energy requirements of a Rotating Packed Bed (RPB) are closely linked to the rotor speed, which also plays a crucial role in determining the capture efficiency. To achieve an optimal balance between energy consumption and capture performance, it is important to investigate the relationship between rotor speed and separation efficiency. In this work, the rotor speed was varied in the range of 0 rmp to 2400 rpm. This range was selected based on the maximum operational frequency of the motor (3000 rmp), while 0 rmp was included as a reference point to evaluate the influence of rotation in comparison to a stationary packed bed.\u003c/p\u003e \u003cp\u003eA 30% MEA (monoethanolamine) aqueous solution and a synthetic flue gas containing 15% CO₂ were used in this study. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e illustrates the effect of rotation speed on CO₂ capture efficiency under the following operating conditions: 30% MEA concentration, temperature of 25\u0026deg;C, and pressure of 101,325 N/m\u0026sup2;.\u003c/p\u003e \u003cp\u003eThe results indicate a positive correlation between rotor speed and CO₂ capture efficiency. This trend is consistent with findings reported by Burns et al. [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e], which suggest that the rotation of the absorber enhances mass transfer due to the combined action of droplet and film flows.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e demonstrates the relationship between rotor speed and CO₂ capture efficiency in a Rotating Packed Bed (RPB) system. The rotational speed was varied from 0 to approximately 2700 rpm, and the corresponding CO₂ capture efficiency was recorded.\u003c/p\u003e \u003cp\u003eAs shown in the Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e, a clear positive correlation exists between the rotor speed and the CO₂ capture efficiency. At low rotational speeds (e.g., 0\u0026ndash;500 rpm), a sharp increase in capture efficiency is observed, indicating the significant impact of initial rotational motion on mass transfer. This enhancement can be attributed to the increased centrifugal force, which intensifies the liquid film and droplet dispersion within the packing, thereby improving gas\u0026ndash;liquid contact.\u003c/p\u003e \u003cp\u003eBeyond 500 rpm, the increase in efficiency continues but at a more moderate, linear rate. At approximately 2700 rpm, the CO₂ capture efficiency reaches around 75%, suggesting that higher rotational speeds further improve the absorption process, although with diminishing marginal returns.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the variation of the overall gas-phase overall mass transfer coefficient \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\left({K}_{{G}^{a}}\\right)\\)\u003c/span\u003e\u003c/span\u003e as a function of rotor speed in a Rotating Packed Bed (RPB) system. The experiments were conducted using a 30% MEA solution under standard conditions.\u003c/p\u003e \u003cp\u003eThe results reveal a clear upward trend: as the rotor speed increases from 0 to approximately 2500 rpm, the value of \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\left({K}_{{G}^{a}}\\right)\\)\u003c/span\u003e\u003c/span\u003e significantly rises\u0026mdash;from about 0.2 to over 3.5 kmol\u0026middot;kPa⁻\u0026sup1;\u0026middot;m⁻\u0026sup3;\u0026middot;h⁻\u0026sup1;. This substantial enhancement can be attributed to the intensified centrifugal forces and improved gas-liquid contact at higher rotational speeds, which promote the thinning of the liquid film, the dispersion of droplets, and an increase in interfacial area for mass transfer.\u003c/p\u003e \u003cp\u003eAt lower speeds (0\u0026ndash;750 rpm), the increase in \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\left({K}_{{G}^{a}}\\right)\\)\u003c/span\u003e\u003c/span\u003e is relatively moderate, indicating the initial contribution of mechanical rotation to overcoming natural convection limitations. Beyond 1000 rpm, the growth becomes more pronounced, with the steepest rise observed between 2000 and 2500 rpm, suggesting a nonlinear relationship likely influenced by turbulence and droplet entrainment.\u003c/p\u003e \u003cp\u003eThese findings are consistent with the theory that RPB systems provide intensified mass transfer by reducing diffusion resistance and enhancing the surface renewal rate. Thus, optimizing rotor speed is a key parameter in designing energy-efficient CO₂ absorption systems with high mass transfer performance.\u003c/p\u003e \u003cp\u003e \u003cb\u003e3.2. Effect of MEA concentration on CO\u003c/b\u003e \u003csub\u003e \u003cb\u003e2\u003c/b\u003e \u003c/sub\u003e \u003cb\u003ecapture efficiency, Mass transfer coefficient\u003c/b\u003e \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\left({\\varvec{K}}_{{\\varvec{G}}^{\\varvec{a}}}\\right)\\)\u003c/span\u003e\u003c/span\u003e \u003cb\u003eand Height of Transfer Unit (HTU).\u003c/b\u003e\u003c/p\u003e \u003cp\u003eIn this study, the impact of varying monoethanolamine (MEA) concentrations on CO\u003csub\u003e2\u003c/sub\u003e capture efficiency and the overall volumetric mass transfer coefficient was thoroughly examined under controlled conditions. The experimental data obtained from different concentrations of MEA (30%, 50%, 70%, and 90% by weight) are analyzed, and their implications for CO\u003csub\u003e2\u003c/sub\u003e absorption efficiency and mass transfer are discussed below.\u003c/p\u003e \u003cp\u003eThe results, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e, demonstrate a clear upward trend in CO\u003csub\u003e2\u003c/sub\u003e capture efficiency with increasing MEA concentration. At the lowest MEA concentration (30%), the capture efficiency was around 40%, while at the highest concentration (90%), it reached nearly 80%. This behavior is attributed to the increase in hydroxide ions per unit volume as the MEA concentration increases. Hydroxide ions are crucial in the absorption process, as they react with CO\u003csub\u003e2\u003c/sub\u003e, enhancing the overall absorption rate.\u003c/p\u003e \u003cp\u003eThese findings are consistent with previous studies by Freguia and Rochelle [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e], who observed that the reaction rate of a pseudo-first-order reaction depends directly on the concentration of MEA. As MEA concentration rises, the reaction rate increases, leading to higher CO\u003csub\u003e2\u003c/sub\u003e absorption. This phenomenon explains why higher MEA concentrations are more effective in capturing CO\u003csub\u003e2\u003c/sub\u003e. Furthermore, these results align with reports by Jassim et al. [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], which found that higher concentrations of MEA result in lower CO\u003csub\u003e2\u003c/sub\u003e penetration due to improved absorption kinetics.\u003c/p\u003e \u003cp\u003eThe second aspect of the study focused on the effect of MEA concentration on the overall volumetric mass transfer coefficient. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e, the increase in MEA concentration is correlated with a rise in the mass transfer coefficient. This indicates that the efficiency of mass transfer improves as MEA concentration increases. This result can be explained by the enhanced CO\u003csub\u003e2\u003c/sub\u003e absorption rate, which is a direct consequence of higher MEA concentration. With more hydroxide ions available to react with CO\u003csub\u003e2\u003c/sub\u003e, the rate of mass transfer increases, improving the overall performance of the CO\u003csub\u003e2\u003c/sub\u003e capture process.\u003c/p\u003e \u003cp\u003eHowever, while higher MEA concentrations improve both CO\u003csub\u003e2\u003c/sub\u003e capture efficiency and mass transfer, there are practical considerations to address. As the MEA concentration increases, so does the solvent viscosity, which leads to thicker liquid films and a reduction in the driving force for mass transfer. This trade-off between increased capture efficiency and reduced mass transfer efficiency at higher MEA concentrations must be considered when optimizing the process for industrial applications.\u003c/p\u003e \u003cp\u003eThe experimental data also reveal the relationship between MEA concentration and the Height of Transfer Unit (HTU), as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e. HTU values were found to increase with decreasing MEA concentration. This result suggests that a higher concentration of MEA leads to a lower HTU, indicative of improved mass transfer efficiency at higher concentrations. The decrease in HTU can be attributed to the enhanced absorption kinetics at higher MEA concentrations, which leads to a more efficient overall mass transfer process.\u003c/p\u003e \u003cp\u003eWhile the results demonstrate the benefits of higher MEA concentrations for CO\u003csub\u003e2\u003c/sub\u003e capture, several practical challenges must be considered. Higher MEA concentrations not only improve CO\u003csub\u003e2\u003c/sub\u003e capture but also increase the risk of equipment corrosion, which is a significant concern in industrial applications. Additionally, the increase in solvent viscosity at higher MEA concentrations can lead to operational challenges related to fluid dynamics and mass transfer resistance.\u003c/p\u003e \u003cp\u003eTherefore, it is essential to identify the optimal MEA concentration that maximizes CO\u003csub\u003e2\u003c/sub\u003e capture while minimizing the adverse effects of increased viscosity and potential corrosion. Further studies are needed to evaluate the trade-offs between these factors and to explore the impact of other process variables, such as temperature, pressure, and flow rates, on the overall efficiency of the CO\u003csub\u003e2\u003c/sub\u003e capture process.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003e3.3. Effect of liquid to gas ratio on CO\u003c/b\u003e \u003csub\u003e \u003cb\u003e2\u003c/b\u003e \u003c/sub\u003e \u003cb\u003ecapture efficiency, volumetric mass transfer coefficient\u003c/b\u003e \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\left({\\varvec{K}}_{{\\varvec{G}}^{\\varvec{a}}}\\right)\\)\u003c/span\u003e\u003c/span\u003e \u003cb\u003eand Height of Transfer Unit (HTU)\u003c/b\u003e\u003c/p\u003e \u003cp\u003eThe effect of varying the liquid to gas ratio (L/G) on CO\u003csub\u003e2\u003c/sub\u003e capture efficiency is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e. As observed, the CO\u003csub\u003e2\u003c/sub\u003e capture efficiency increases significantly with higher liquid to gas ratios. At the lowest L/G ratio (0.01 L/G), the capture efficiency is approximately 55%, and it steadily rises to nearly 90% at the highest L/G ratio (0.04 L/G). This indicates that increasing the liquid flow rate or decreasing the gas flow rate leads to a higher absorption of CO\u003csub\u003e2\u003c/sub\u003e, thus improving the overall CO\u003csub\u003e2\u003c/sub\u003e capture performance.\u003c/p\u003e \u003cp\u003eThe increase in CO\u003csub\u003e2\u003c/sub\u003e capture efficiency with higher L/G ratios can be attributed to the increased solvent availability for CO\u003csub\u003e2\u003c/sub\u003e absorption. At higher liquid flow rates, there is a larger volume of MEA solution in contact with the CO\u003csub\u003e2\u003c/sub\u003e-laden gas, which provides more active sites for the absorption process. The findings are consistent with previous research indicating that a higher L/G ratio improves the efficiency of gas-liquid absorption processes by enhancing the contact time between the CO\u003csub\u003e2\u003c/sub\u003e and the solvent.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e shows the relationship between the liquid to gas ratio (L/G) and both the overall mass transfer coefficient \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\left({K}_{{G}^{a}}\\right)\\)\u003c/span\u003e\u003c/span\u003e and Height of Transfer Unit (HTU). As the L/G ratio increases, the mass transfer coefficient also increases, reaching its highest value at an L/G ratio of 0.04 L/G. This is consistent with the observed increase in CO\u003csub\u003e2\u003c/sub\u003e capture efficiency, as higher mass transfer rates correspond to better absorption of CO\u003csub\u003e2\u003c/sub\u003e. At higher liquid flow rates, there is more solvent available to absorb CO\u003csub\u003e2\u003c/sub\u003e, which leads to faster absorption and, therefore, a higher mass transfer coefficient. This is indicative of more efficient mass transfer between the gas and liquid phases. Conversely, the HTU decreases as the L/G ratio increases. At lower L/G ratios, HTU is higher, indicating that more space is required to achieve the same level of CO\u003csub\u003e2\u003c/sub\u003e absorption. As the L/G ratio increases, the absorption efficiency improves, and the required HTU decreases. The decrease in HTU with increasing L/G ratio suggests that the process of CO\u003csub\u003e2\u003c/sub\u003e absorption becomes more efficient as the liquid flow rate increases. With more solvent available, the mass transfer efficiency improves, reducing the required height of the absorption column.\u003c/p\u003e \u003cp\u003eFrom the two figures (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e), it is evident that there is an inverse relationship between the mass transfer coefficient and HTU. As the mass transfer coefficient increases, the HTU decreases, and vice versa. This inverse relationship is typical in absorption processes, where improved mass transfer leads to more efficient CO\u003csub\u003e2\u003c/sub\u003e absorption and, as a result, reduces the amount of space (HTU) needed for the same level of CO\u003csub\u003e2\u003c/sub\u003e capture. The results highlight the importance of optimizing the liquid to gas ratio to achieve maximum CO\u003csub\u003e2\u003c/sub\u003e capture efficiency. Increasing the liquid flow rate improves both the mass transfer coefficient and CO\u003csub\u003e2\u003c/sub\u003e capture efficiency, while simultaneously reducing HTU. However, it is important to consider the operational costs associated with higher liquid flow rates, such as increased energy consumption for pumping and potential equipment wear. Moreover, the optimal liquid to gas ratio should balance the trade-off between increasing CO\u003csub\u003e2\u003c/sub\u003e capture efficiency and minimizing energy and operational costs. Further experiments are needed to explore the effect of varying other parameters, such as gas flow rate, pressure, and temperature, to achieve a comprehensive understanding of the factors influencing the CO\u003csub\u003e2\u003c/sub\u003e absorption process.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThis study experimentally investigated the performance of a Rotating Packed Bed (RPB) absorber for CO₂ capture using aqueous monoethanolamine (MEA) solutions under various operating conditions. The influence of rotor speed, MEA concentration, and liquid-to-gas (L/G) ratio on CO₂ capture efficiency, overall mass transfer coefficient \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\left({K}_{{G}^{a}}\\right)\\)\u003c/span\u003e\u003c/span\u003e, and Height of Transfer Unit (HTU) was systematically analyzed.\u003c/p\u003e \u003cp\u003eThe results demonstrated a clear positive correlation between rotor speed and CO₂ capture efficiency, with an observed enhancement from approximately 40% at low speeds to over 75% at around 2700 rpm. This increase was accompanied by a significant rise in the overall mass transfer coefficient, highlighting the role of centrifugal acceleration in intensifying gas\u0026ndash;liquid interactions.\u003c/p\u003e \u003cp\u003eIncreasing MEA concentration from 30\u0026ndash;90% wt significantly improved CO₂ capture efficiency and mass transfer performance due to enhanced reaction kinetics. However, the associated increase in solvent viscosity presents practical trade-offs that must be considered during process design. A similar trend was observed in HTU reduction, confirming more efficient mass transfer at higher MEA concentrations.\u003c/p\u003e \u003cp\u003eFurthermore, the study revealed that higher liquid-to-gas ratios substantially enhance CO₂ absorption efficiency and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\left({K}_{{G}^{a}}\\right)\\)\u003c/span\u003e\u003c/span\u003e while reducing HTU, demonstrating the importance of solvent availability and interfacial area in optimizing absorber performance. Nonetheless, the energy and operational costs associated with increased solvent flow must be carefully balanced.\u003c/p\u003e \u003cp\u003eOverall, the findings confirm that RPB technology is a highly effective process intensification approach for post-combustion CO₂ capture. The insights gained from this study provide valuable data for designing, scaling up, and optimizing industrial CO₂ absorption systems using RPBs.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAlisher U. Auesbaev (Corresponding Author) \u0026mdash; Conceptualization, Supervision, Writing \u0026ndash; Original Draft, Experimental Design.Bobirjon Z. Adizov \u0026mdash; Experimental Investigation, Data Collection, Visualization.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAydin G, et al., 2016. Energy consumption modelling using artificial neural networks: The case of the world\u0026rsquo;s highest consumers. Energy Sources, Part B Econ Plan Policy.11, 212\u0026ndash;219. \u003c/li\u003e\n\u003cli\u003eHong WY. 2022. A techno-economic review on carbon capture, utilisation and storage systems for achieving a net-zero CO\u003csub\u003e2\u003c/sub\u003e emissions future. Carbon Capture Science \u0026amp; Technology. 3:100044.\u003c/li\u003e\n\u003cli\u003eEIA. Energy information administration. Department of Energy; 2010.\u003c/li\u003e\n\u003cli\u003eTan L.S., et al., 2012. Factors affecting CO\u003csub\u003e2\u003c/sub\u003e absorption efficiency in packed column: A review. Journal of Industrial and Engineering Chemistry. 18(6), 1874-1883.\u003c/li\u003e\n\u003cli\u003eTan L.S., et al., 2012. Removal of high concentration CO\u003csub\u003e2\u003c/sub\u003e from natural gas at elevated pressure via absorption process in packed column. Journal of Natural Gas Chemistry. 21(1), 7-10.\u003c/li\u003e\n\u003cli\u003eWang M, et al., 2011. Post-combustion CO capture with chemical absorption: a state-of-the-art review. Chem Eng Res Des. 89:1609\u0026ndash;1624.\u003c/li\u003e\n\u003cli\u003eLawal A, et al., 2012. Demonstrating full-scale post-combustion CO capture for coal-fired power plants through dynamic modelling and simulation. Fuel. 101:115\u0026ndash;128. \u003c/li\u003e\n\u003cli\u003eOko E, et al., 2018. Study of intercooling for rotating packed bed absorbers in intensified solvent-based CO\u003csub\u003e2\u003c/sub\u003e. Appl Energy. 223, 302\u0026ndash;316.\u003c/li\u003e\n\u003cli\u003eJassim MS, et al., 2007. Carbon dioxide absorption and desorption in aqueous monoethanolamine solutions in a rotating packed bed. Ind Eng Chem Res, 46:2823\u0026ndash;2833. \u003c/li\u003e\n\u003cli\u003eCheng H-H, et al., 2013. Thermal regeneration of alkanolamine solutions in a rotating packed bed. Int J Greenh Gas Control, 16:206\u0026ndash;216. \u003c/li\u003e\n\u003cli\u003eJoel AS, et al., 2014, Process analysis of intensified absorber for post-combustion CO\u003csub\u003e2\u003c/sub\u003e capture through modelling and simulation. Int J Greenh Gas Control. 21:91\u0026ndash;100. \u003c/li\u003e\n\u003cli\u003eBorhani T.N, et al., 2019. Process modelling, validation and analysis of rotating packed bed stripper in the context of intensified CO\u003csub\u003e2\u003c/sub\u003e capture with MEA. Journal of Industrial and Engineering Chemistry, 75:285\u0026ndash;295. \u003c/li\u003e\n\u003cli\u003eIm D, et al., 2020. Modeling, simulation and optimization of the rotating packed bed (RPB) absorber and stripper for MEA-based carbon capture. Comput Chem Eng, 143:107102.\u003c/li\u003e\n\u003cli\u003eLin C.C. and Chen Y.W., 2011, Performance of a cross-flow rotating packed bed in removing carbon dioxide from gaseous streams by chemical absorption. Int. J. Greenhouse Gas Control. 5, 668-675.\u003c/li\u003e\n\u003cli\u003eAgarwal L, et al., 2010, Process Intensification in HiGee Absorption and Distillation: Design Procedure and Applications. Ind. Eng. Chem. Res., 49, 10046-10058.\u003c/li\u003e\n\u003cli\u003eChen, Y.H., 2010. A continuous-flow biodiesel production process using a rotating packed bed, Bioresour. Technol., 101, 668\u0026ndash;673.\u003c/li\u003e\n\u003cli\u003eLin C.C., et al., 2008. Feasibility of a cross-flow rotating packed bed in removing carbon dioxide from gaseous streams. Separ. Purif. Tech., 62, 507\u0026ndash;512.\u003c/li\u003e\n\u003cli\u003eDas A; et al., 2008. Continuous biosorption in rotating packed-bed contactor, Ind. Eng. Chem. Res., 47, 4230\u0026ndash;4235.\u003c/li\u003e\n\u003cli\u003eLlerena-Chavez H and Larachi F. 2009. Analysis of flow in rotating packed beds via CFD simulations - Dry pressure drop and gas flow maldistribution. Chem. Eng. Sci., 64, 2113-2126. \u003c/li\u003e\n\u003cli\u003eYang W. et al., 2010, Computational fluid dynamic simulation of fluid flow in a rotating packed bed, Chem. Eng. J., 156, 582-587.\u003c/li\u003e\n\u003cli\u003eBorhani T.N., 2018, Process modelling and analysis of intensified CO\u003csub\u003e2\u003c/sub\u003e capture using monoethanolamine (MEA) in rotating packed bed absorber. J. Clean. Prod., 204, 1124-1142.\u003c/li\u003e\n\u003cli\u003eDimoliani M., 2021, Modeling and Parametric Investigation of Rotating Packed Bed Processes for CO\u003csub\u003e2\u003c/sub\u003e Capture and Mineralisation, Chem. Eng. Trans, 88, 187-192.\u003c/li\u003e\n\u003cli\u003eHendry J.R., 2020, Pressure drop and flooding in rotating packed beds, Chem. Eng. Proc. Proc. Intensif., 151, 107908.\u003c/li\u003e\n\u003cli\u003eAboudheir A, et al., 2003. Kinetics of the reactive absorption of carbon dioxide in high CO\u003csub\u003e2\u003c/sub\u003e‐loaded, concentrated aqueous monoethanolamine solutions. Chem Eng Sci. 58, 5195‐5210.\u003c/li\u003e\n\u003cli\u003eYu Y.S, et al., 2010. Multi‐field synergy study of CO\u003csub\u003e2\u003c/sub\u003e capture process by chemical absorption. Chem Eng Sci. 65, 3279‐3292. \u003c/li\u003e\n\u003cli\u003eAroonwilas A et al., 1999. Behavior of the mass‐transfer coefficient of structured packings in CO2 absorbers with chemical reactions. Ind Eng Chem Res. 38, 2044‐2050.\u003c/li\u003e\n\u003cli\u003eWu S.Y., et al., 2017. Mass- transfer performance for CO\u003csub\u003e2\u003c/sub\u003e absorption by 2-(2-aminoethylamino)ethanol solution in a rotating packed bed, Energy Fuels. 31, 14053\u0026ndash;14059. \u003c/li\u003e\n\u003cli\u003eXie C.X., et al., 2018. Low-concentration CO\u003csub\u003e2\u003c/sub\u003e capture from natural gas power plants using a rotating packed bed reactor, Energy Fuels. 33, 1713\u0026ndash;1721.\u003c/li\u003e\n\u003cli\u003eBurns J.R., et al., 2000. Process intensification: operating characteristics of rotating packed beds\u0026mdash; determination of liquid hold‐up for a high‐voidage structured packing. Chem Eng Sci. 55, 2401‐2415.\u003c/li\u003e\n\u003cli\u003eBurns J.R., et al., 2003. Measurement of liquid film thickness and the determination of spin‐up radius on a rotating disc using an electrical resistance technique. Chem Eng Sci. 58, 2245‐2253.\u003c/li\u003e\n\u003cli\u003eFreguia S and Rochelle G.T., 2003. Modeling of CO\u003csub\u003e2\u003c/sub\u003e capture by aqueous monoethanolamine. AIChE J. 49, 1676‐1686.\u003c/li\u003e\n\u003cli\u003eJassim M.S., et al., 2007. Carbon dioxide absorption and desorption in aqueous monoethanolamine solutions in a rotating packed bed. Ind Eng Chem Res. 46, 2823‐2833.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"MEA solvent, postcombustion, CO2 capture, process Intensification, rotating packed bed","lastPublishedDoi":"10.21203/rs.3.rs-6601658/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6601658/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe emission of carbon dioxide (CO₂) from industrial sources, particularly power plants, remains one of the leading contributors to global climate change. While conventional post-combustion CO₂ capture technologies are effective, they are often limited by high energy consumption and large equipment size. Rotating Packed Bed (RPB) technology offers a promising solution through process intensification and improved mass transfer. This study presents an experimental investigation of a laboratory-scale RPB absorber designed for CO₂ capture using aqueous monoethanolamine (MEA) solutions. The effects of rotor speed, MEA concentration, and liquid-to-gas (L/G) ratio on CO₂ capture efficiency and the overall volumetric gas-phase mass transfer coefficient \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\left({K}_{{G}^{a}}\\right)\\)\u003c/span\u003e\u003c/span\u003e were systematically examined. The results showed that increasing rotor speed significantly improved both CO₂ capture efficiency and KGa due to enhanced centrifugal acceleration and better gas\u0026ndash;liquid contact. Higher MEA concentrations led to improved capture performance, attributed to increased reaction kinetics, while elevated L/G ratios further enhanced absorption efficiency and reduced the Height of Transfer Unit (HTU). The findings confirm the suitability of RPB technology for efficient and compact CO₂ absorption systems, with strong potential for industrial applications.\u003c/p\u003e","manuscriptTitle":"Process Intensification of CO₂ Absorption with MEA in a Rotating Packed Bed: Experimental Evaluation and Analysis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-13 10:24:24","doi":"10.21203/rs.3.rs-6601658/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"58d149f8-ba59-4f28-b539-2ac7750ca681","owner":[],"postedDate":"June 13th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-02-15T15:09:31+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-13 10:24:24","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6601658","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6601658","identity":"rs-6601658","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}