Carbon Cycle in A Steelmaking Mill: Recycling of Kish Graphite and Its Subsequent Application for Steelmaking Carburant

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The recycling and utilization of kish graphite associated with steel slag are of great significance to achieve a circular economy and environmental protection. This study explored a recycling process that combined gravity separation and flotation, and the feasibility of carburant preparation from kish graphite was determined. During the recycling process, the concentrate of a teeter bed separator went into a flotation tank, then the rougher flotation concentrate was re-ground four times and underwent cleaning flotation five times. The final concentrate held a yield of 20.28%, a grade of 94.85%, and a recovery rate of 95.32% and a kish-graphite-based carburant was prepared. The results indicated that recycling the kish graphite from steelmaking slag with a gravity-flotation process and using it as a carburant for steelmaking is a feasible route for its resource utilisation and an effective carbon emission reduction technology. kish graphite steelmaking slag recycling carburant Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 1 Introduction Iron and steel are the most used metals in industry. In 2021, the crude steel production in the world was 1,951 million tons, with an average growth rate of 4.06% from 2000 to 2021. In the process of steel making, 12–15% of the steel output is waste slag (Shen H et al., 2003; Wang Q et al., 2013 ; Guo J et al., 2018 ). Therefore, iron and steel smelting slags are the metallurgical solid waste products produced in the largest amounts, which results in severe environmental pollution and a waste of resources without proper disposal. In addition to using steelmaking slag in construction, environmental management, and agriculture after simple treatment, the recovery of valuable substances in steelmaking slag is another essential measure for environmental protection and to achieve a circular world economy (Suvendu D et al., 2020 ; Giulio D et al., 2021 ; Pan S et al., 2017 ; Aiyuan Met et al., 2018). Among these valuable substances, kish graphite, which precipitates because the solubility of excess carbon in molten iron decreases as the iron cools (Naraghi R et al., 2014 ), has remarkable recycling value. Kish graphite in the steel industry’s desulphurized slag and dust has a high degree of crystallinity comparable to that of natural flake graphite (Das B et al., 2006 ; Jiang Y et al., 2018; Lung K S et al., 2022; Mahieux P Y et al., 2008; Branca T A et al., 2020). Walker (JUN et al., 1957) and Eitaro (EITARO M et al., 1959) studied the crystal structure of kish graphite and compared it with those of other graphite types. It was found that the layer spacing of kish graphite is smaller than that of natural flake graphite, and the crystal structure of kish graphite is well crystallized. In 1963, Walker and Bunergee (JUN et al., 1963) studied the morphology of kish graphite and the effect of air oxidation. They found that there were some holes on the surface of the purified graphite sheet. They speculated that kish graphite would form a crystal structure with Fe and other impurity elements as the core. Hydrochloric acid alone could not completely remove the impurities in kish graphite. In 1996, Nishimoto (Nishimoto H et al., 1996 ) studied the photoelectronic properties of kish graphite, showing that the initial states of the kish graphite photoelectrons are symmetric. In 2001, Bourelle (Bourelle E et al., 2001 ) studied the surface morphology of kish graphite by scanning electron microscopy (SEM), and an iron doping test was carried out at 2800°C to measure the resistivity before and after doping. The results showed that the doped iron occurred in two forms. When iron clusters spread on the graphite matrix to form pores, the resistivity was low. When iron clusters diffused on the graphite matrix to form small mounds, the resistivity was high. Many researchers have carried out kish graphite recycling research to obtain a substitute for natural graphite, a critical raw material. Laverty (Laverty P D et al., 1994) proposed the separation and purification process of sieving, hydraulic classification, flotation, and pickling. A graphite concentrate of over 70% grade was obtained after flotation and 95% after pickling. In 2008, Kazmi (Kazmi K R et al., 2008) optimized the leaching parameters, including the acid concentration, liquid–solid ratio, time, and temperature. The graphite grade was 92.48% when hydrochloric acid was used, and it was 99.38% when hydrofluoric acid was further used. Li (Jihui L et al., 2021 ) designed an ideal physical separation process for kish graphite, which involved dry separation, flotation, ultrasonic dissociation, and magnetic separation. Graphite concentrates with grades above 95% were obtained after this physical recycling and above 99% after acid leaching. Kish graphite’s applications have attracted many researchers’ attention. An (An J et al., 2015 ) prepared a graphene nanofilm with kish graphite and sulfuric acid as an effective intercalating agent. He noted that high-grade graphite could prepare large-diameter thin graphene nanofilms. The average diameter reached 6.7 mm, and the thickness reached 5 nm. Li (Jihui L et al., 2021 ) found that the pore structure of kish-graphite-based expanded graphite provided it with excellent oil absorption capabilities. Kumari (Kumari T S D et al., 2016) and Wang (Shutao W et al., 2017) successfully prepared a graphite anode material in a battery using modified kish graphite. In the graphite flotation process, a large number of coarse and heavy impurity particles in steel slag will sink to the bottom of the flotation tank, affecting the feasibility of the process. Thus, gravity separation with a large processing capacity should be added for pretreatment to solve this problem. In terms of practical application, the above methods are either too small to be applied for large quantities or they require too high of a graphite purity, which will undoubtedly increase the cost of the recycling and purification of kish graphite. Graphite-based carburant is a high-quality carburizing material that is frequently utilized in steelmaking. Kish graphite comes from iron and steel smelting. After sorting and purification, its main impurity is iron, and other harmful elements are not present. Thus, kish graphite has advantages as the raw material of carburant. This study aimed to develop a separation process that combined teeter bed separator (TBS) pretreatment and flotation to recycle kish graphite with a high recovery rate and high quality from steelmaking slag and to prepare kish-graphite-based carburant that met the requirements of industrial standards. Based on the results of this paper, we aim to provide a theoretical foundation for the scientific research and practice of the recycling and application of valuable substances in steelmaking slags. 2 Materials and methods 2.1 Materials The raw samples were desulfurized steelmaking slags provided by Qingdao Special Iron and Steel Co., Ltd in Shandong province, China. Observations showed that the desulfurized steelmaking slags contained large steel particles with sizes > 3 mm, which contained almost no graphite and were too hard to be broken. Thus, 3 mm was selected as the classification size. The particles that passed through a 3-mm screen were taken as the experimental object. The carbon content of the particles with sizes < 3 mm fraction was 20.18%. Raw steelmaking slags with different particle sizes are shown in Fig. 1 . 2.2 Separation process In the overall separation process in Fig. 2 , the TBS was used for preliminary separation. The TBS underflow as tailings overflowed into the subsequent separation process, first through the rougher. The rougher overflowed into the subsequent multi-stage grinding and flotation process, and the obtained concentrate was the flotation product. The rougher underflow entered scavenger I. The scavenger overflow combined with the multi-stage flotation underflow and entered the grinder as middling, which was then was carried to scavenger II. The overflow of scavenger II returned to the multi-stage grinder and flotation process, and the underflow became the flotation tailings, which were combined with the underflow of the TBS and scavenger I. 2.3 X-ray fluorescence (XRF) The samples were analyzed by an XRF spectrometer (Thermo Fei, USA). A rhodium target was selected as the tube target, and the voltage and current were set to 60 kV and 150 mA, respectively. The contents of each component in the samples were analyzed. 2.4 X-ray diffraction (XRD) An X-ray diffractometer (Brucker D8 ADVANCE, Germany) was used to analyze the inorganic mineral phases in the samples. The test step width was 0.01°, the scanning speed was 5°/min, and the scanning range was 5°–90°. 2.5 Scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDS) A scanning electron microscope (MERLIN Compact, USA) and an energy dispersive X-ray spectrometer (HORIBA EX-350, China) were used to analyze the samples. Before the test, a proper amount of each sample was mixed with epoxy resin and a curing agent. The mixture was put into a vacuum device for curing and then removed for polishing. Finally, the surface of the polished active sample was sprayed with gold and analyzed by the scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDS) instrument. 2.6 Elemental analysis Carbon and sulfur (CS) as well as oxygen, nitrogen, and hydrogen (ONH) elemental analyses were performed using a CS/ONH elemental analyzer (Elementar, Germany). The elements Fe, Ca, Mn, Al, and P were analyzed using an Agilent ICPOES730 (USA) inductively coupled plasma atomic emission spectrometer. 2.7 Flotation A 0.5-L single-cell flotation tank was used for flotation tests, with a rotor speed of 6.5 m/s and an air charging rate of 0.07 m 3 /h. Weighed samples were moistened and added to the flotation tank. Then, water was added to the flotation tank. The rotor was turned on to stir the slurry for 2 min, the collector (kerosene) was added, and the mixture was stirred for 1 min. Then, an appropriate amount of frother (sec-octanol) was added, and the mixture was stirred for 20 s. The gas valve was then opened. The air entered the flotation tank, dispersing under the action of the rotor, and acted with frother to form stable bubbles, which combined with the target mineral and then floated. In the above process, the rotor rotated at a high speed to produce shear action, which completed the dispersion and mixing of the pulp, reagents, and bubbles. The scraper was opened when the foam was stable. The graphite concentrate gathered in the foam layer at the top of the flotation tank and was scraped out by the scraper to complete the separation of the concentrate and impurities; the scraping time was 2 min. The amount of collector, the amount of foaming agent, and the concentration of pulp were the main factors affecting the flotation effect. In order to obtain the best flotation index, we changed the three experimental conditions in the flotation experiment. Based on the data from the flotation test, the beneficiation efficiency was determined. The beneficiation efficiency is defined as follows (Pankratov P I et al., 1970): $$\eta {\text{=}}\frac{{ε - {\gamma _j}}}{{\left( {100 - \alpha } \right)}} \times 100\%$$ , where \(\eta\) is the beneficiation efficiency, \(ε\) is the recovery, \({\gamma _j}\) is the concentrate yield, and \(\alpha\) is the feed grade. 2.8 Grinding Grinding can achieve the dissociation of graphite and steel slag, thereby improving the subsequent concentrate grade and beneficiation efficiency. The grinding equipment was a rod mill equipped for wet grinding. The tank was filled to 40% with steel rods, and the sample was then added to the tank, supplemented by the appropriate amount of water. The rod mill tank was put on the mill’s roller with the lid fastened, and the mill speed was 132 r/min. The yield and grade of ± 0.3 mm were measured after grinding 2.9 Carburant preparation Carburant was prepared by the mold-forming method. A 50-g graphite sample was weighed, starch binder was added to the sample to a content of 1%, and the mixture was stirred evenly. Then, an appropriate amount of water was sprayed into the sample to a content of 14%, and the mixture was thoroughly stirred again. The stirred sample was added to the mold, locked, and placed on a pressure machine for molding and pressing. The compressive strength of the kish graphite was tested by a pressure testing machine after preparation. 3 Results and Discussion 3.1 Mineralogy characteristics of samples The author previously proposed a process to remove coarse and heavy impurities in advance by air separation. However, this air separation method requires strict dust removal measures. Otherwise, material loss or environmental pollution will occur, which limits the application of the air separation method to a certain extent. To overcome the shortcomings of this previous method, this paper used TBS, a gravity-based separator, with water as the medium to pretreat the steelmaking slag samples. The particles with sizes < 3 mm were pre-sorted by the TBS to remove the large impurity particles. The TBS overflow product (TBSO), whose carbon content was 63.91%, was used in all subsequent tests. The particle size distribution of the TBSO was obtained by a sieving test. Images of the TBSOs with different particle sizes and histograms of the yield and grade distributions of the different particle sizes of the TBSO are shown in Fig. 3 . The grades of particles in the ranges of > 1 mm, 1.0–0.5 mm, 0.5–0.3 mm, 0.3–0.2 mm, 0.2–0.15 mm, and < 0.15 mm were 5.87%, 16.58%, 28.35%, 30.59%, 50.59%, and 41.16%, respectively. With the decrease in size, the carbon content gradually increased. The 0.2–0.15 mm group had the highest grade of 52.53%. However, the carbon content of the < 0.15 mm fraction decreased again. It was inferred from this observation that this group contained fine powder impurities. The mineral chemical analysis obtained by XRF for the ash of the sample (Table 1 ) showed that iron was the main impurity. Figure 4 (a) shows the XRD pattern of the TBSO. The kish graphite had a high crystallinity and graphitization degree. Figure 4 (b) shows the XRD pattern of the ash sample. The impurities in the ash sample were mainly composed of calcium albite, hematite, and quartz. This result is consistent with kish graphite formation theory and the mineral chemical analysis results. The SEM-EDS results are shown in Fig. 5 . The graphite in the TBSO exhibited a typical flaky structure, and the main impurity elements in the selected area were Fe and O. Table 1 Mineral chemical analysis results of the ash of TBSO. composition Fe 2 O 3 SiO 2 Al 2 O 3 Others Content /% 82.65 7.98 1.90 7.47 3.2 Separation and recovery of kish graphite The optimal flotation conditions were explored, including the amount of collector (kerosene), frother (sec-octanol), and pulp concentration. Based on the concentrate grade and recovery, the experimental results (Fig. 6 ) showed that optimal flotation conditions were a 1500 g/t collector dosage, 300 g/t frother dosage, and 50 g/L pulp concentration. Under such conditions, the concentrate grade and recovery reached 68.04% and 96.44%, respectively. Since the calculation method of the beneficiation efficiency was only applicable to the case of a high sample grade, we used the concentrate grade and recovery as the evaluation indices. 3.3 Stage grinding and cleaner test After removing coarse impurities by TBS, the graphite samples still contained many aggregates of graphite and fine impurity particles. In these aggregates, impurities were irregularly attached to the surfaces of the graphite flakes. Grinding dissociation and recleaning were carried out to remove these impurities. According to Fig. 7 , the conditions of the one-stage grinding–rougher flotation system were tested. Since the sizes of graphite flakes affect their economic value and large-flake graphite has a superior floatability and a faster flotation rate, large flakes need to be protected during production (Sun K et al., 2017). According to Fig. 8 (a), when the grinding time was 6 min, the yield of flakes with sizes of > 0.3 mm was 45.07%, and the grade was 76.87%. Since the yield of flakes with sizes > 0.3 mm decreased rapidly after 6 min, 6 min was chosen as the best grinding time. According to Fig. 8 (b), the concentrate grade and beneficiation efficiency increased with the continuous increase in the grinding time. After one roughing, one grinding, and one cleaning process, the concentrate grade reached 77.08%, and the material still needed further grinding and recleaning. For the second-stage grinding and recleaning, according to Fig. 8 (c), when the grinding time was 4 min, the yield of flakes with sizes > 0.3 mm was 49.47%, and the grade was 82.18%. According to Fig. 8 (d), the concentrate grade and beneficiation efficiency increased with the grinding time. The recleaner concentrate grade was 83.36% and the beneficiation efficiency was 61.25% in the fourth minute. After 4 min, the yield of flakes with sizes > 0.3 mm decreased significantly, so the second-stage grinding fineness test was determined to be 4 min. After one stage of roughing and two stages of grinding and cleaning, the concentrate grade reached 83.36%, but the concentrate still did not reach the value required by the standard for high-carbon graphite, so it was still necessary to carry out third and fourth stages of grinding and cleaning. As shown in Fig. 8 (e), (f), (g), and (h), the optimal grinding times in the third and fourth stages were 4 and 2 min, respectively. The corresponding grades reached 90.13% and 93.95%, and the beneficiation efficiencies reached 73.08% and 76.32%, respectively. 3.4 Regrinding flotation test of middling According to Fig. 9 , when the grinding time was less than 6 min, the grade of the concentrate increased, but when the grinding time exceeded 6 min, the grade of the concentrate began to decline. As shown in Fig. 8 , this may have been because the grinding time and fineness increased, which led to a low flotation selectivity. Therefore, the optimal grinding time was determined to be 6 min. The yield was 12.63%, the grade was 67.12%, and the beneficiation efficiency of the concentrate was 78.41%. 3.5 Closed-circuit flotation SEM images of the final product from the closed-circuit process is shown in Fig. 10 . The yield was 20.28%, the grade was 94.85%, and the recovery of the final product of kish graphite treated by this process was 95.32%, achieving the purpose of the experiment. The yield, grade, and distribution rate of the flake graphite with flake sizes of > 0.3 mm were 50.62%, 95.48%, and 50.95%, respectively, which would ensure a high utilization value for the kish graphite concentrate. Figure 10 (a), (b), and (c) show SEM images at different magnifications. The graphite surface was still smooth at higher magnifications, indicating that multi-stage grinding ensured that the kish graphite contained very few impurities. 3.6 Preparation of carburant Four grades (95%, 90%, 85%, and 75%) of kish graphite concentrates were used to prepare the carburant samples (named KCE-95, KCE-90, KCE-85, and KCE-75, respectively). The compressive strengths of the four carburant products were greater than 688.28 N, meeting the requirements for long-distance transportation. An image of the kish-graphite-based carburant samples is shown in Fig. 11 (a) The industrial analysis results of the kish concentrate and carburant products are shown in Table 2 . The elemental content analysis results of the carburant products are shown in Fig. 11 (b). The fixed carbon content of the KCE-95 was 94.76%, the ash content was 4.28%, the volatile fraction was 0.96%, and sulfur content was 0.0874%. This met the FC94-level standard industry requirement (China Standardization, 2015). For KCE-90, the fixed carbon content was 90.18%, the ash content was 8.54%, the volatile fraction was 1.28%, and the sulfur content was 0.1452%. Thus, this sample met the FC90-level industry standard requirements. The other two samples did not meet the industry standard requirements. However, the kish graphite contained more iron than the amount specified in the FC90-level industry standard. The actual production of the carburant can be adjusted according to the specific steelmaking needs. Due to the high content of iron in the steel slag accompanied by graphite, the product grade of the graphite carburants produced will be improved. However, the carburizing effect in actual production needs to be evaluated. Table 2 Industrial analysis results of carburant products. Product number Fixed carbon/% (Dry basis) Ash/% (Dry basis) Volatile/% (Dry basis) KCE-95 94.76 4.28 0.96 KCE-90 90.18 8.54 1.28 KCE-85 84.05 13.87 2.08 KCE-75 75.74 21.69 2.57 Using kish graphite to prepare graphite carburants has good prospects. In the process of iron and steel smelting, with the wide range of applications of the converter process in the steelmaking process, the carbon content of steel may not meet the standard requirements. Thus, adding carburant to molten steel has become a conventional steelmaking process (Chen J et al., 2012 ). Due to its relatively unique forming environment, kish graphite has different impurity compositions from those of natural graphite. Kish graphite impurities are mainly iron, but iron has no side effects on steelmaking and does not need to be entirely removed from kish graphite concentrate, reducing the difficulty of separating the impurities. Therefore, using kish graphite to prepare carburant and returning it to the furnace has unique advantages to promote the recycling of iron and steel resources in the industry (Zhu Z Y et al., 2012; Kleimt I B et al., 2012; Cao L et al., 2018 ; Kozhukhov A A, 2012). 4 Conclusions In this study, a new combined approach for recycling kish graphite from steel slag was developed, and high-grade kish graphite concentrate was successfully obtained. Moreover, kish graphite-based carburant products with excellent quality that could be used back in the steelmaking process were prepared. In this way, a partial carbon cycle in the steel mill would be created to reduce carbon emissions. The developed multi-stage grinding and flotation process system can be designed and operated at the industrial level to recover and reuse valuable resources from industrial waste. It contributes significantly to the study on recycling valuable resources to meet the skyrocketing demand and closed-loop recycling approach with an economically feasible process. (1) TBS pre-separation followed by grinding and flotation was effective for kish graphite beneficiation. Rougher concentrate with a yield of 90.48%, grade of 68.04%, and recovery of 96.44% was obtained by the TBS. The final concentrate product with a yield of 67.07%, grade of 94.85%, and recovery of 99.54% was finally obtained by a closed-circuit flotation process involving one rougher and one scavenger step, four grinding steps, and five cleaning steps, where the middling was returned to the first cleaner. (2) The obtained kish-graphite-based carburant met the quality requirements of a high-quality carburant. Two carburant products, KCE-95 and KCE-90, met the industry standards. The fixed carbon content of the carburant product KCE-95 was 94.76%, the ash content was 4.28%, the volatile fraction was 0.96%, and the sulfur content was 0.0874%. For KCE-90, the fixed carbon content was 90.18%, the ash content was 8.54%, the volatile fraction was 1.28%, and the sulfur content was 0.1452%. (3) Recycling the kish graphite from steelmaking slag by combining TBS, stage grinding, and flotation and using it as a carburant back in the steelmaking process is a new and feasible idea for steelmaking slag resource utilization. It is significant for promoting a circular economy in iron and steel yards. Declarations Ethics approval and consent to participate ： Not applicable. Consent for publication ： Not applicable. Availability of data and materials ： The authors confirm that the data supporting the findings of this study are available within the article. Competing interests ： No, I declare that the authors have no competing interests as defined by BMC, or other interests that might be perceived to influence the results and/or discussion reported in this paper. Acknowledgements: This research was supported by the National Natural Science Foundation of China under Grant No. 52004294, the Open Foundation of State Key Laboratory of Mineral Processing under Grant No. BGRIMM-KJSKL-2019-19, and the Fundamental Research Funds for the Central Universities under Grant No. 2021YQHH01. CRediT authorship contribution statement Jihui Li: Conceptualization, Funding acquisition, Writing - review & editing, Supervision. Zeyang Xu: Writing - review & editing, Roles/Writing - original draft. Ronghao Yang: Data Curation. Lingling Ren: Validation. Liqiang Ma: Project Administration. Gen Huang: Formal analysis, Methodology, Supervision. Shuang Zhang: Investigation, Resources. Zhenghong Huang: Supervision. References Shen H, Forssberg E. 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Industrial Experiment of Steelmaking in a Top-Bottom-Side Blown Converter with Slag Splashing Process[J]. Steel Res Int, 2012,83(1). Kleimt IB, Schlautmann RNM, Weinberg IM et al. Optimierte Prozessführung zur ressourceneffizienten Stahlerzeugung im Konverterprozess[J]. Chem Ing Tech, 2012,84(10). Cao L, Wang Y, Liu Q et al. Physical and Mathematical Modeling of Multiphase Flows in a Converter[J]. ISIJ Int, 2018,58(4). Kozhukhov AA. Study of the efficiency of using process dust in a layer of foamed slag in an oxygen converter[J]. Metallurgist. 2011;54:9–10. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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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-3336245","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":232908891,"identity":"f268d66a-a26d-4612-8708-c18c6dd3d3f1","order_by":0,"name":"Jihui Li","email":"","orcid":"","institution":"China University of Mining and Technology-Beijing","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Jihui","middleName":"","lastName":"Li","suffix":""},{"id":232908892,"identity":"b8483cd6-4e3b-4efa-b6b3-7e15c4a85cea","order_by":1,"name":"Zeyang Xu","email":"","orcid":"","institution":"China University of Mining and Technology-Beijing","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zeyang","middleName":"","lastName":"Xu","suffix":""},{"id":232908893,"identity":"b20d8078-daa1-45bb-8310-877242011b90","order_by":2,"name":"Ronghao Yang","email":"","orcid":"","institution":"China University of Mining and Technology-Beijing","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Ronghao","middleName":"","lastName":"Yang","suffix":""},{"id":232908894,"identity":"f5a21a5d-3507-4806-b48c-a1d6fb80c5c8","order_by":3,"name":"Lingling Ren","email":"","orcid":"","institution":"China University of Mining and Technology-Beijing","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Lingling","middleName":"","lastName":"Ren","suffix":""},{"id":232908895,"identity":"45e8d775-0380-4b30-8d39-75dbde50a68c","order_by":4,"name":"Liqiang Ma","email":"","orcid":"","institution":"China University of Mining and Technology-Beijing","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Liqiang","middleName":"","lastName":"Ma","suffix":""},{"id":232908896,"identity":"f344c447-c7cd-4bd5-bd4a-806ecc1dee7d","order_by":5,"name":"Gen Huang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA30lEQVRIiWNgGAWjYBACA2QOM0OFhJw8KVoYmxnOWBgbNpCkhbGtIpHhAAEt5hLJzx5++WWTxz8jO/1x4TyJBMYG5oePbuDRYjkjzdxYti+tWOJG7sbmmdsk8tgZ2IyNc/A57EaCmbRkz+HEDRJALbzbJIoZG3jYpPFrSf8G1PIfqmWORGLDAYJacswkP/w4ANXSQIyWM2/KpBkbkhNnnHm7cfaMYxLGhs2E/HI8fZvkjz92if3tuRs+F9TUycmzNz98jE8LCDDztqFwCSgHAcYff4hQNQpGwSgYBSMXAABg7FCjCZ9qhwAAAABJRU5ErkJggg==","orcid":"","institution":"China University of Mining and Technology-Beijing","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Gen","middleName":"","lastName":"Huang","suffix":""},{"id":232908897,"identity":"14ee69d5-5cb5-44b7-bcb6-bb3175bbd46f","order_by":6,"name":"Shuang Zhang","email":"","orcid":"","institution":"China Nonferrous Metal Industry’s Foreign Engineering and Construction Co., Ltd. Beijing","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Shuang","middleName":"","lastName":"Zhang","suffix":""},{"id":232908898,"identity":"75a17b13-cf03-4295-9a3a-2af114f241f7","order_by":7,"name":"Zhenghong Huang","email":"","orcid":"","institution":"Tsinghua University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zhenghong","middleName":"","lastName":"Huang","suffix":""}],"badges":[],"createdAt":"2023-09-08 04:59:19","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3336245/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3336245/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":43375304,"identity":"d6c1de9c-8f99-41ae-955e-d836abc9f616","added_by":"auto","created_at":"2023-09-19 16:15:09","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":503184,"visible":true,"origin":"","legend":"\u003cp\u003eImages of (a) all particle sizes, (b) particles with sizes \u0026gt;3 mm, and (c) particles with sizes \u0026lt;3 mm in raw steelmaking slags.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-3336245/v1/6414fa18864a9118e40f1de7.png"},{"id":43375302,"identity":"3a1cc425-df5a-46b1-8a29-884802dbae5c","added_by":"auto","created_at":"2023-09-19 16:15:09","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":149923,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of separation process.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-3336245/v1/67cf1b08a0eab6c22c49f233.png"},{"id":43375303,"identity":"6462adfc-f6bb-4308-a995-a02d3cb19c44","added_by":"auto","created_at":"2023-09-19 16:15:09","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":161263,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Images of samples with different particle sizes, and (b) histograms of yield and grade distributions for different particle sizes of teeter bed separator output product (TBSO).\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-3336245/v1/0595239ccdf98e6332e3c05f.png"},{"id":43375306,"identity":"e7aa65ad-5467-4103-b797-911e46228f62","added_by":"auto","created_at":"2023-09-19 16:15:09","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":75537,"visible":true,"origin":"","legend":"\u003cp\u003e(a) X-ray diffraction (XRD) patterns for the raw sample and (b) XRD patterns for the ash sample of the TBSO.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-3336245/v1/05ace6c249febff897022b56.png"},{"id":43375311,"identity":"3eee1bd9-a327-443d-b032-c09f3b71e42d","added_by":"auto","created_at":"2023-09-19 16:15:10","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":226540,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Scanning electron microscopy (SEM) and (b) energy spectrum of TBSO.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-3336245/v1/c530c0131aff12356f15ef1f.png"},{"id":43375307,"identity":"91248a18-75c4-4cbd-99d6-839a8ebe26b8","added_by":"auto","created_at":"2023-09-19 16:15:09","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":217148,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Test results of the amount of rough-selected collector (300 g/t frother dosage and 50 g/L pulp concentration), (b) amount of rough-selected frother (1500 g/t collector dosage and 50 g/L pulp concentration), and (c) concentration of rough-selected pulp (1500 g/t collector dosage and 300 g/t frother dosage).\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-3336245/v1/e12a02307d683ff347c664d2.png"},{"id":43376325,"identity":"2d68493b-9d6f-483f-8076-5ebfb0ffb654","added_by":"auto","created_at":"2023-09-19 16:23:09","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":17417,"visible":true,"origin":"","legend":"\u003cp\u003eFlow chart of single-stage grinding–rougher flotation.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-3336245/v1/cd19409ca9e8332296054229.png"},{"id":43375309,"identity":"ee6f61b7-73ec-481d-8378-f16bb5816ce9","added_by":"auto","created_at":"2023-09-19 16:15:09","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":300893,"visible":true,"origin":"","legend":"\u003cp\u003eInfluence of grinding time on the fineness, concentrate grade, and beneficiation efficiency: (a, b) first stage, (c, d) second stage, (e, f): third stage, and (g, h): fourth stage.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-3336245/v1/8e0a00654271f42fb3b4e9d4.png"},{"id":43376326,"identity":"39985d31-d896-4734-a6c9-bf6a18632a21","added_by":"auto","created_at":"2023-09-19 16:23:09","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":172822,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Influence of grinding time on the particle size distribution and (b) influences of grinding time on the yield, beneficiation efficiency, and grade.\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-3336245/v1/a2bd5db36baf5afc7d7249f5.png"},{"id":43375312,"identity":"3a34abe5-9739-4378-8340-9ab03f26103c","added_by":"auto","created_at":"2023-09-19 16:15:11","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":125536,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of closed-circuit final concentrate product (a, b, and c are concentrate product at different magnifications).\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-3336245/v1/ed6dceb1f40fda5a77d4a085.png"},{"id":44704410,"identity":"5c2cf7bc-c05b-4f02-93e9-299b8b942f4f","added_by":"auto","created_at":"2023-10-16 16:07:50","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2372630,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3336245/v1/ad0e2c54-f7b5-4ea7-9eca-f5b7e24d355c.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Carbon Cycle in A Steelmaking Mill: Recycling of Kish Graphite and Its Subsequent Application for Steelmaking Carburant","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eIron and steel are the most used metals in industry. In 2021, the crude steel production in the world was 1,951\u0026nbsp;million tons, with an average growth rate of 4.06% from 2000 to 2021. In the process of steel making, 12\u0026ndash;15% of the steel output is waste slag (Shen H et al., 2003; Wang Q et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Guo J et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Therefore, iron and steel smelting slags are the metallurgical solid waste products produced in the largest amounts, which results in severe environmental pollution and a waste of resources without proper disposal. In addition to using steelmaking slag in construction, environmental management, and agriculture after simple treatment, the recovery of valuable substances in steelmaking slag is another essential measure for environmental protection and to achieve a circular world economy (Suvendu D et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Giulio D et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Pan S et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Aiyuan Met et al., 2018). Among these valuable substances, kish graphite, which precipitates because the solubility of excess carbon in molten iron decreases as the iron cools (Naraghi R et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), has remarkable recycling value.\u003c/p\u003e \u003cp\u003eKish graphite in the steel industry\u0026rsquo;s desulphurized slag and dust has a high degree of crystallinity comparable to that of natural flake graphite (Das B et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Jiang Y et al., 2018; Lung K S et al., 2022; Mahieux P Y et al., 2008; Branca T A et al., 2020). Walker (JUN et al., 1957) and Eitaro (EITARO M et al., 1959) studied the crystal structure of kish graphite and compared it with those of other graphite types. It was found that the layer spacing of kish graphite is smaller than that of natural flake graphite, and the crystal structure of kish graphite is well crystallized. In 1963, Walker and Bunergee (JUN et al., 1963) studied the morphology of kish graphite and the effect of air oxidation. They found that there were some holes on the surface of the purified graphite sheet. They speculated that kish graphite would form a crystal structure with Fe and other impurity elements as the core. Hydrochloric acid alone could not completely remove the impurities in kish graphite.\u003c/p\u003e \u003cp\u003eIn 1996, Nishimoto (Nishimoto H et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1996\u003c/span\u003e) studied the photoelectronic properties of kish graphite, showing that the initial states of the kish graphite photoelectrons are symmetric. In 2001, Bourelle (Bourelle E et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2001\u003c/span\u003e) studied the surface morphology of kish graphite by scanning electron microscopy (SEM), and an iron doping test was carried out at 2800\u0026deg;C to measure the resistivity before and after doping. The results showed that the doped iron occurred in two forms. When iron clusters spread on the graphite matrix to form pores, the resistivity was low. When iron clusters diffused on the graphite matrix to form small mounds, the resistivity was high.\u003c/p\u003e \u003cp\u003eMany researchers have carried out kish graphite recycling research to obtain a substitute for natural graphite, a critical raw material. Laverty (Laverty P D et al., 1994) proposed the separation and purification process of sieving, hydraulic classification, flotation, and pickling. A graphite concentrate of over 70% grade was obtained after flotation and 95% after pickling. In 2008, Kazmi (Kazmi K R et al., 2008) optimized the leaching parameters, including the acid concentration, liquid\u0026ndash;solid ratio, time, and temperature. The graphite grade was 92.48% when hydrochloric acid was used, and it was 99.38% when hydrofluoric acid was further used. Li (Jihui L et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) designed an ideal physical separation process for kish graphite, which involved dry separation, flotation, ultrasonic dissociation, and magnetic separation. Graphite concentrates with grades above 95% were obtained after this physical recycling and above 99% after acid leaching.\u003c/p\u003e \u003cp\u003eKish graphite\u0026rsquo;s applications have attracted many researchers\u0026rsquo; attention. An (An J et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) prepared a graphene nanofilm with kish graphite and sulfuric acid as an effective intercalating agent. He noted that high-grade graphite could prepare large-diameter thin graphene nanofilms. The average diameter reached 6.7 mm, and the thickness reached 5 nm. Li (Jihui L et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) found that the pore structure of kish-graphite-based expanded graphite provided it with excellent oil absorption capabilities. Kumari (Kumari T S D et al., 2016) and Wang (Shutao W et al., 2017) successfully prepared a graphite anode material in a battery using modified kish graphite.\u003c/p\u003e \u003cp\u003eIn the graphite flotation process, a large number of coarse and heavy impurity particles in steel slag will sink to the bottom of the flotation tank, affecting the feasibility of the process. Thus, gravity separation with a large processing capacity should be added for pretreatment to solve this problem. In terms of practical application, the above methods are either too small to be applied for large quantities or they require too high of a graphite purity, which will undoubtedly increase the cost of the recycling and purification of kish graphite. Graphite-based carburant is a high-quality carburizing material that is frequently utilized in steelmaking. Kish graphite comes from iron and steel smelting. After sorting and purification, its main impurity is iron, and other harmful elements are not present. Thus, kish graphite has advantages as the raw material of carburant.\u003c/p\u003e \u003cp\u003eThis study aimed to develop a separation process that combined teeter bed separator (TBS) pretreatment and flotation to recycle kish graphite with a high recovery rate and high quality from steelmaking slag and to prepare kish-graphite-based carburant that met the requirements of industrial standards. Based on the results of this paper, we aim to provide a theoretical foundation for the scientific research and practice of the recycling and application of valuable substances in steelmaking slags.\u003c/p\u003e"},{"header":"2 Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Materials\u003c/h2\u003e \u003cp\u003eThe raw samples were desulfurized steelmaking slags provided by Qingdao Special Iron and Steel Co., Ltd in Shandong province, China. Observations showed that the desulfurized steelmaking slags contained large steel particles with sizes\u0026thinsp;\u0026gt;\u0026thinsp;3 mm, which contained almost no graphite and were too hard to be broken. Thus, 3 mm was selected as the classification size. The particles that passed through a 3-mm screen were taken as the experimental object. The carbon content of the particles with sizes\u0026thinsp;\u0026lt;\u0026thinsp;3 mm fraction was 20.18%. Raw steelmaking slags with different particle sizes are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Separation process\u003c/h2\u003e \u003cp\u003eIn the overall separation process in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the TBS was used for preliminary separation. The TBS underflow as tailings overflowed into the subsequent separation process, first through the rougher. The rougher overflowed into the subsequent multi-stage grinding and flotation process, and the obtained concentrate was the flotation product. The rougher underflow entered scavenger I. The scavenger overflow combined with the multi-stage flotation underflow and entered the grinder as middling, which was then was carried to scavenger II. The overflow of scavenger II returned to the multi-stage grinder and flotation process, and the underflow became the flotation tailings, which were combined with the underflow of the TBS and scavenger I.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 X-ray fluorescence (XRF)\u003c/h2\u003e \u003cp\u003eThe samples were analyzed by an XRF spectrometer (Thermo Fei, USA). A rhodium target was selected as the tube target, and the voltage and current were set to 60 kV and 150 mA, respectively. The contents of each component in the samples were analyzed.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 X-ray diffraction (XRD)\u003c/h2\u003e \u003cp\u003eAn X-ray diffractometer (Brucker D8 ADVANCE, Germany) was used to analyze the inorganic mineral phases in the samples. The test step width was 0.01\u0026deg;, the scanning speed was 5\u0026deg;/min, and the scanning range was 5\u0026deg;\u0026ndash;90\u0026deg;.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Scanning electron microscopy\u0026ndash;energy-dispersive X-ray spectroscopy (SEM-EDS)\u003c/h2\u003e \u003cp\u003eA scanning electron microscope (MERLIN Compact, USA) and an energy dispersive X-ray spectrometer (HORIBA EX-350, China) were used to analyze the samples. Before the test, a proper amount of each sample was mixed with epoxy resin and a curing agent. The mixture was put into a vacuum device for curing and then removed for polishing. Finally, the surface of the polished active sample was sprayed with gold and analyzed by the scanning electron microscopy\u0026ndash;energy-dispersive X-ray spectroscopy (SEM-EDS) instrument.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Elemental analysis\u003c/h2\u003e \u003cp\u003eCarbon and sulfur (CS) as well as oxygen, nitrogen, and hydrogen (ONH) elemental analyses were performed using a CS/ONH elemental analyzer (Elementar, Germany). The elements Fe, Ca, Mn, Al, and P were analyzed using an Agilent ICPOES730 (USA) inductively coupled plasma atomic emission spectrometer.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.7 Flotation\u003c/h2\u003e \u003cp\u003eA 0.5-L single-cell flotation tank was used for flotation tests, with a rotor speed of 6.5 m/s and an air charging rate of 0.07 m\u003csup\u003e3\u003c/sup\u003e/h. Weighed samples were moistened and added to the flotation tank. Then, water was added to the flotation tank. The rotor was turned on to stir the slurry for 2 min, the collector (kerosene) was added, and the mixture was stirred for 1 min. Then, an appropriate amount of frother (sec-octanol) was added, and the mixture was stirred for 20 s. The gas valve was then opened. The air entered the flotation tank, dispersing under the action of the rotor, and acted with frother to form stable bubbles, which combined with the target mineral and then floated. In the above process, the rotor rotated at a high speed to produce shear action, which completed the dispersion and mixing of the pulp, reagents, and bubbles. The scraper was opened when the foam was stable. The graphite concentrate gathered in the foam layer at the top of the flotation tank and was scraped out by the scraper to complete the separation of the concentrate and impurities; the scraping time was 2 min. The amount of collector, the amount of foaming agent, and the concentration of pulp were the main factors affecting the flotation effect. In order to obtain the best flotation index, we changed the three experimental conditions in the flotation experiment.\u003c/p\u003e \u003cp\u003eBased on the data from the flotation test, the beneficiation efficiency was determined. The beneficiation efficiency is defined as follows (Pankratov P I et al., 1970):\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\eta {\\text{=}}\\frac{{ε - {\\gamma _j}}}{{\\left( {100 - \\alpha } \\right)}} \\times 100\\%$$\u003c/div\u003e\u003c/div\u003e,\u003c/p\u003e \u003cp\u003ewhere \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\eta\\)\u003c/span\u003e\u003c/span\u003e is the beneficiation efficiency, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(ε\\)\u003c/span\u003e\u003c/span\u003e is the recovery, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\gamma _j}\\)\u003c/span\u003e\u003c/span\u003e is the concentrate yield, and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\alpha\\)\u003c/span\u003e\u003c/span\u003e is the feed grade.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e2.8 Grinding\u003c/h2\u003e \u003cp\u003eGrinding can achieve the dissociation of graphite and steel slag, thereby improving the subsequent concentrate grade and beneficiation efficiency. The grinding equipment was a rod mill equipped for wet grinding. The tank was filled to 40% with steel rods, and the sample was then added to the tank, supplemented by the appropriate amount of water. The rod mill tank was put on the mill\u0026rsquo;s roller with the lid fastened, and the mill speed was 132 r/min. The yield and grade of \u0026plusmn;\u0026thinsp;0.3 mm were measured after grinding\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e2.9 Carburant preparation\u003c/h2\u003e \u003cp\u003eCarburant was prepared by the mold-forming method. A 50-g graphite sample was weighed, starch binder was added to the sample to a content of 1%, and the mixture was stirred evenly. Then, an appropriate amount of water was sprayed into the sample to a content of 14%, and the mixture was thoroughly stirred again. The stirred sample was added to the mold, locked, and placed on a pressure machine for molding and pressing. The compressive strength of the kish graphite was tested by a pressure testing machine after preparation.\u003c/p\u003e \u003c/div\u003e"},{"header":"3 Results and Discussion","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Mineralogy characteristics of samples\u003c/h2\u003e \u003cp\u003eThe author previously proposed a process to remove coarse and heavy impurities in advance by air separation. However, this air separation method requires strict dust removal measures. Otherwise, material loss or environmental pollution will occur, which limits the application of the air separation method to a certain extent. To overcome the shortcomings of this previous method, this paper used TBS, a gravity-based separator, with water as the medium to pretreat the steelmaking slag samples.\u003c/p\u003e \u003cp\u003eThe particles with sizes\u0026thinsp;\u0026lt;\u0026thinsp;3 mm were pre-sorted by the TBS to remove the large impurity particles. The TBS overflow product (TBSO), whose carbon content was 63.91%, was used in all subsequent tests. The particle size distribution of the TBSO was obtained by a sieving test. Images of the TBSOs with different particle sizes and histograms of the yield and grade distributions of the different particle sizes of the TBSO are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The grades of particles in the ranges of \u0026gt;\u0026thinsp;1 mm, 1.0\u0026ndash;0.5 mm, 0.5\u0026ndash;0.3 mm, 0.3\u0026ndash;0.2 mm, 0.2\u0026ndash;0.15 mm, and \u0026lt;\u0026thinsp;0.15 mm were 5.87%, 16.58%, 28.35%, 30.59%, 50.59%, and 41.16%, respectively. With the decrease in size, the carbon content gradually increased. The 0.2\u0026ndash;0.15 mm group had the highest grade of 52.53%. However, the carbon content of the \u0026lt;\u0026thinsp;0.15 mm fraction decreased again. It was inferred from this observation that this group contained fine powder impurities.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe mineral chemical analysis obtained by XRF for the ash of the sample (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) showed that iron was the main impurity. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e (a) shows the XRD pattern of the TBSO. The kish graphite had a high crystallinity and graphitization degree. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e (b) shows the XRD pattern of the ash sample. The impurities in the ash sample were mainly composed of calcium albite, hematite, and quartz. This result is consistent with kish graphite formation theory and the mineral chemical analysis results. The SEM-EDS results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. The graphite in the TBSO exhibited a typical flaky structure, and the main impurity elements in the selected area were Fe and O.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMineral chemical analysis results of the ash of TBSO.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ecomposition\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOthers\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eContent /%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e82.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.47\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Separation and recovery of kish graphite\u003c/h2\u003e \u003cp\u003eThe optimal flotation conditions were explored, including the amount of collector (kerosene), frother (sec-octanol), and pulp concentration. Based on the concentrate grade and recovery, the experimental results (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) showed that optimal flotation conditions were a 1500 g/t collector dosage, 300 g/t frother dosage, and 50 g/L pulp concentration. Under such conditions, the concentrate grade and recovery reached 68.04% and 96.44%, respectively. Since the calculation method of the beneficiation efficiency was only applicable to the case of a high sample grade, we used the concentrate grade and recovery as the evaluation indices.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Stage grinding and cleaner test\u003c/h2\u003e \u003cp\u003eAfter removing coarse impurities by TBS, the graphite samples still contained many aggregates of graphite and fine impurity particles. In these aggregates, impurities were irregularly attached to the surfaces of the graphite flakes. Grinding dissociation and recleaning were carried out to remove these impurities. According to Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, the conditions of the one-stage grinding\u0026ndash;rougher flotation system were tested.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSince the sizes of graphite flakes affect their economic value and large-flake graphite has a superior floatability and a faster flotation rate, large flakes need to be protected during production (Sun K et al., 2017). According to Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (a), when the grinding time was 6 min, the yield of flakes with sizes of \u0026gt;\u0026thinsp;0.3 mm was 45.07%, and the grade was 76.87%. Since the yield of flakes with sizes\u0026thinsp;\u0026gt;\u0026thinsp;0.3 mm decreased rapidly after 6 min, 6 min was chosen as the best grinding time. According to Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (b), the concentrate grade and beneficiation efficiency increased with the continuous increase in the grinding time. After one roughing, one grinding, and one cleaning process, the concentrate grade reached 77.08%, and the material still needed further grinding and recleaning.\u003c/p\u003e \u003cp\u003eFor the second-stage grinding and recleaning, according to Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (c), when the grinding time was 4 min, the yield of flakes with sizes\u0026thinsp;\u0026gt;\u0026thinsp;0.3 mm was 49.47%, and the grade was 82.18%. According to Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (d), the concentrate grade and beneficiation efficiency increased with the grinding time. The recleaner concentrate grade was 83.36% and the beneficiation efficiency was 61.25% in the fourth minute. After 4 min, the yield of flakes with sizes\u0026thinsp;\u0026gt;\u0026thinsp;0.3 mm decreased significantly, so the second-stage grinding fineness test was determined to be 4 min.\u003c/p\u003e \u003cp\u003eAfter one stage of roughing and two stages of grinding and cleaning, the concentrate grade reached 83.36%, but the concentrate still did not reach the value required by the standard for high-carbon graphite, so it was still necessary to carry out third and fourth stages of grinding and cleaning. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (e), (f), (g), and (h), the optimal grinding times in the third and fourth stages were 4 and 2 min, respectively. The corresponding grades reached 90.13% and 93.95%, and the beneficiation efficiencies reached 73.08% and 76.32%, respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Regrinding flotation test of middling\u003c/h2\u003e \u003cp\u003eAccording to Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e, when the grinding time was less than 6 min, the grade of the concentrate increased, but when the grinding time exceeded 6 min, the grade of the concentrate began to decline. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, this may have been because the grinding time and fineness increased, which led to a low flotation selectivity. Therefore, the optimal grinding time was determined to be 6 min. The yield was 12.63%, the grade was 67.12%, and the beneficiation efficiency of the concentrate was 78.41%.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Closed-circuit flotation\u003c/h2\u003e \u003cp\u003eSEM images of the final product from the closed-circuit process is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e. The yield was 20.28%, the grade was 94.85%, and the recovery of the final product of kish graphite treated by this process was 95.32%, achieving the purpose of the experiment. The yield, grade, and distribution rate of the flake graphite with flake sizes of \u0026gt;\u0026thinsp;0.3 mm were 50.62%, 95.48%, and 50.95%, respectively, which would ensure a high utilization value for the kish graphite concentrate. Figure\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e (a), (b), and (c) show SEM images at different magnifications. The graphite surface was still smooth at higher magnifications, indicating that multi-stage grinding ensured that the kish graphite contained very few impurities.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e3.6 Preparation of carburant\u003c/h2\u003e \u003cp\u003eFour grades (95%, 90%, 85%, and 75%) of kish graphite concentrates were used to prepare the carburant samples (named KCE-95, KCE-90, KCE-85, and KCE-75, respectively). The compressive strengths of the four carburant products were greater than 688.28 N, meeting the requirements for long-distance transportation. An image of the kish-graphite-based carburant samples is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e (a) The industrial analysis results of the kish concentrate and carburant products are shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The elemental content analysis results of the carburant products are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e (b). The fixed carbon content of the KCE-95 was 94.76%, the ash content was 4.28%, the volatile fraction was 0.96%, and sulfur content was 0.0874%. This met the FC94-level standard industry requirement (China Standardization, 2015). For KCE-90, the fixed carbon content was 90.18%, the ash content was 8.54%, the volatile fraction was 1.28%, and the sulfur content was 0.1452%. Thus, this sample met the FC90-level industry standard requirements. The other two samples did not meet the industry standard requirements. However, the kish graphite contained more iron than the amount specified in the FC90-level industry standard. The actual production of the carburant can be adjusted according to the specific steelmaking needs. Due to the high content of iron in the steel slag accompanied by graphite, the product grade of the graphite carburants produced will be improved. However, the carburizing effect in actual production needs to be evaluated.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eIndustrial analysis results of carburant products.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eProduct number\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFixed carbon/% (Dry basis)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAsh/% (Dry basis)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eVolatile/% (Dry basis)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKCE-95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e94.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.96\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKCE-90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e90.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.28\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKCE-85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e84.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e13.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.08\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKCE-75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e75.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e21.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.57\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eUsing kish graphite to prepare graphite carburants has good prospects. In the process of iron and steel smelting, with the wide range of applications of the converter process in the steelmaking process, the carbon content of steel may not meet the standard requirements. Thus, adding carburant to molten steel has become a conventional steelmaking process (Chen J et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Due to its relatively unique forming environment, kish graphite has different impurity compositions from those of natural graphite. Kish graphite impurities are mainly iron, but iron has no side effects on steelmaking and does not need to be entirely removed from kish graphite concentrate, reducing the difficulty of separating the impurities. Therefore, using kish graphite to prepare carburant and returning it to the furnace has unique advantages to promote the recycling of iron and steel resources in the industry (Zhu Z Y et al., 2012; Kleimt I B et al., 2012; Cao L et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Kozhukhov A A, 2012).\u003c/p\u003e \u003c/div\u003e"},{"header":"4 Conclusions","content":"\u003cp\u003eIn this study, a new combined approach for recycling kish graphite from steel slag was developed, and high-grade kish graphite concentrate was successfully obtained. Moreover, kish graphite-based carburant products with excellent quality that could be used back in the steelmaking process were prepared. In this way, a partial carbon cycle in the steel mill would be created to reduce carbon emissions. The developed multi-stage grinding and flotation process system can be designed and operated at the industrial level to recover and reuse valuable resources from industrial waste. It contributes significantly to the study on recycling valuable resources to meet the skyrocketing demand and closed-loop recycling approach with an economically feasible process.\u003c/p\u003e \u003cp\u003e(1) TBS pre-separation followed by grinding and flotation was effective for kish graphite beneficiation. Rougher concentrate with a yield of 90.48%, grade of 68.04%, and recovery of 96.44% was obtained by the TBS. The final concentrate product with a yield of 67.07%, grade of 94.85%, and recovery of 99.54% was finally obtained by a closed-circuit flotation process involving one rougher and one scavenger step, four grinding steps, and five cleaning steps, where the middling was returned to the first cleaner.\u003c/p\u003e \u003cp\u003e(2) The obtained kish-graphite-based carburant met the quality requirements of a high-quality carburant. Two carburant products, KCE-95 and KCE-90, met the industry standards. The fixed carbon content of the carburant product KCE-95 was 94.76%, the ash content was 4.28%, the volatile fraction was 0.96%, and the sulfur content was 0.0874%. For KCE-90, the fixed carbon content was 90.18%, the ash content was 8.54%, the volatile fraction was 1.28%, and the sulfur content was 0.1452%.\u003c/p\u003e \u003cp\u003e(3) Recycling the kish graphite from steelmaking slag by combining TBS, stage grinding, and flotation and using it as a carburant back in the steelmaking process is a new and feasible idea for steelmaking slag resource utilization. It is significant for promoting a circular economy in iron and steel yards.\u003c/p\u003e "},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003eThe authors confirm that the data supporting the findings of this study are available within the article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003eNo, I declare that the authors have no competing interests as defined by BMC, or other interests that might be perceived to influence the results and/or discussion reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u003c/strong\u003e This research was supported by the National Natural Science Foundation of China under Grant No. 52004294, the Open Foundation of State Key Laboratory of Mineral Processing under Grant No. BGRIMM-KJSKL-2019-19, and the Fundamental Research Funds for the Central Universities under Grant No. 2021YQHH01.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCRediT authorship contribution statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eJihui Li: \u003c/strong\u003eConceptualization, Funding acquisition, Writing - review \u0026amp; editing, Supervision. \u003cstrong\u003eZeyang Xu: \u003c/strong\u003eWriting - review \u0026amp; editing, Roles/Writing - original draft.\u003cstrong\u003e Ronghao Yang: \u003c/strong\u003eData Curation. \u003cstrong\u003eLingling Ren: \u003c/strong\u003eValidation.\u003cstrong\u003e Liqiang Ma: \u003c/strong\u003eProject Administration. \u003cstrong\u003eGen Huang:\u003c/strong\u003e Formal analysis, Methodology, Supervision. \u003cstrong\u003eShuang Zhang:\u003c/strong\u003e Investigation, Resources. \u003cstrong\u003eZhenghong Huang: \u003c/strong\u003eSupervision.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eShen H, Forssberg E. 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Metallurgist. 2011;54:9\u0026ndash;10.\u003c/span\u003e\u003c/li\u003e\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":"kish graphite, steelmaking slag, recycling, carburant","lastPublishedDoi":"10.21203/rs.3.rs-3336245/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3336245/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe reclamation management of the solid waste produced by iron and steel enterprises is an urgent problem. The recycling and utilization of kish graphite associated with steel slag are of great significance to achieve a circular economy and environmental protection. This study explored a recycling process that combined gravity separation and flotation, and the feasibility of carburant preparation from kish graphite was determined. During the recycling process, the concentrate of a teeter bed separator went into a flotation tank, then the rougher flotation concentrate was re-ground four times and underwent cleaning flotation five times. The final concentrate held a yield of 20.28%, a grade of 94.85%, and a recovery rate of 95.32% and a kish-graphite-based carburant was prepared. The results indicated that recycling the kish graphite from steelmaking slag with a gravity-flotation process and using it as a carburant for steelmaking is a feasible route for its resource utilisation and an effective carbon emission reduction technology.\u003c/p\u003e","manuscriptTitle":"Carbon Cycle in A Steelmaking Mill: Recycling of Kish Graphite and Its Subsequent Application for Steelmaking Carburant","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-09-19 16:15:03","doi":"10.21203/rs.3.rs-3336245/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":"7c3f4634-a1ea-4b24-a1fa-c35144a925ef","owner":[],"postedDate":"September 19th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2023-12-01T11:29:17+00:00","versionOfRecord":[],"versionCreatedAt":"2023-09-19 16:15:03","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3336245","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3336245","identity":"rs-3336245","version":["v1"]},"buildId":"FbvkV6FR0MCFSLy54lSbu","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}