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In the present paper a novel process of the coal ash treatment was developed and analyzed: a high-pressure autoclave HCl leaching of the coal bottom and fly ash from an Omsk coal-fired power plant. This process was applied to extract aluminum from the coal ash into a chloride solution, which can further be used as a coagulant for water treatment. The Al extraction efficiency in this process can reach over 90 % at certain process parameters discussed in the present study. Kinetics of the leaching process were evaluated using different kinetic (e.g. shrinking core) models. A semi-empirical equation was proposed for description of the kinetics of the leaching process as a function of the HCl concentration, solid-to-liquid ratio and temperature. Different mechanisms of the leaching process were also discussed and proposed. Water treatment by the obtained Al-chloride showed good results compared to an industrial coagulant; the treated water parameters were within the limits recommended by the World Health Organization for drinkable water.
Dmitry Valeev; Irina Kunilova; Andrei Shoppert; Cristian Salazar-Concha; Alex Kondratiev. High-pressure HCl leaching of coal ash to extract Al into a chloride solution with further use as a coagulant for water treatment. Journal of Cleaner Production 2020, 276, 123206 .
AMA StyleDmitry Valeev, Irina Kunilova, Andrei Shoppert, Cristian Salazar-Concha, Alex Kondratiev. High-pressure HCl leaching of coal ash to extract Al into a chloride solution with further use as a coagulant for water treatment. Journal of Cleaner Production. 2020; 276 ():123206.
Chicago/Turabian StyleDmitry Valeev; Irina Kunilova; Andrei Shoppert; Cristian Salazar-Concha; Alex Kondratiev. 2020. "High-pressure HCl leaching of coal ash to extract Al into a chloride solution with further use as a coagulant for water treatment." Journal of Cleaner Production 276, no. : 123206.
Sandy grade alumina is a valuable intermediate material that is mainly produced by the Bayer process and used for manufacturing primary metallic aluminum. Coal fly ash is generated in coal-fired power plants as a by-product of coal combustion that consists of submicron ash particles and is considered to be a potentially hazardous technogenic waste. The present paper demonstrates that the Al-chloride solution obtained by leaching coal fly ash can be further processed to obtain sandy grade alumina, which is essentially suitable for metallic aluminum production. The novel process developed in the present study involves the production of amorphous alumina via the calcination of aluminium chloride hexahydrate obtained by salting-out from acid Al-Cl liquor. Following this, alkaline treatment with further Al2O3 dissolution and recrystallization as Al(OH)3 particles is applied, and a final calcination step is employed to obtain sandy grade alumina with minimum impurities. The process does not require high-pressure equipment and reutilizes the alkaline liquor and gibbsite particles from the Bayer process, which allows the sandy grade alumina production costs to be to significantly reduced. The present article also discusses the main technological parameters of the acid treatment and the amounts of major impurities in the sandy grade alumina obtained by the different (acid and acid-alkali) methods.
Dmitry Valeev; Andrei Shoppert; Alexandra Mikhailova; Alex Kondratiev. Acid and Acid-Alkali Treatment Methods of Al-Chloride Solution Obtained by the Leaching of Coal Fly Ash to Produce Sandy Grade Alumina. Metals 2020, 10, 585 .
AMA StyleDmitry Valeev, Andrei Shoppert, Alexandra Mikhailova, Alex Kondratiev. Acid and Acid-Alkali Treatment Methods of Al-Chloride Solution Obtained by the Leaching of Coal Fly Ash to Produce Sandy Grade Alumina. Metals. 2020; 10 (5):585.
Chicago/Turabian StyleDmitry Valeev; Andrei Shoppert; Alexandra Mikhailova; Alex Kondratiev. 2020. "Acid and Acid-Alkali Treatment Methods of Al-Chloride Solution Obtained by the Leaching of Coal Fly Ash to Produce Sandy Grade Alumina." Metals 10, no. 5: 585.
The chemical and mineral composition of the red mud from the Ural Aluminum Plant were studied by XRF, XRD, and Mössbauer spectroscopy. Experiments on reductive smelting of red mud were carried out in a range of temperatures (1650–1750 °C) to recover iron from the aluminum production waste with maximum efficiency. It was found that it is possible to obtain pig iron with a high content of titanium, phosphorus, and vanadium, and low sulfur content. The efficiency of iron recovery at 1750 °C was found to be around 98%. Thermodynamic calculations were carried out to assist in finding the optimal conditions for the process (e.g., carbon content, furnace temperature, slag liquidus temperature). It was also found that the pig iron phase obtained at 1650 to 1700 °C is not separated from the slag phase into ingot compared with the sample obtained at 1750 °C. Pig iron obtained at 1750 °C can be used to produce molds for the steel-casting equipment.
Dmitry Valeev; Dmitry Zinoveev; Alex Kondratiev; Dmitry Lubyanoi; Denis Pankratov. Reductive Smelting of Neutralized Red Mud for Iron Recovery and Produced Pig Iron for Heat-Resistant Castings. Metals 2019, 10, 32 .
AMA StyleDmitry Valeev, Dmitry Zinoveev, Alex Kondratiev, Dmitry Lubyanoi, Denis Pankratov. Reductive Smelting of Neutralized Red Mud for Iron Recovery and Produced Pig Iron for Heat-Resistant Castings. Metals. 2019; 10 (1):32.
Chicago/Turabian StyleDmitry Valeev; Dmitry Zinoveev; Alex Kondratiev; Dmitry Lubyanoi; Denis Pankratov. 2019. "Reductive Smelting of Neutralized Red Mud for Iron Recovery and Produced Pig Iron for Heat-Resistant Castings." Metals 10, no. 1: 32.
Red mud is a by-product of alumina production from bauxite ore by the Bayer method, which contains considerable amounts of valuable components such as iron, aluminum, titanium, and scandium. In this study, an approach was applied to extract iron, i.e., carbothermic reduction roasting of red mud with sodium and potassium carbonates followed by magnetic separation. The thermodynamic analysis of iron and iron-free components’ behavior during carbothermic reduction was carried out by HSC Chemistry 9.98 (Outotec, Pori, Finland) and FactSage 7.1 (Thermfact, Montreal, Canada; GTT-Technologies, Herzogenrath, Germany) software. The effects of the alkaline carbonates’ addition, as well as duration and temperature of roasting on the iron metallization degree, iron grains’ size, and magnetic separation process were investigated experimentally. The best conditions for the reduction roasting were found to be as follows: 22.01% of K2CO3 addition, 1250 °C, and 180 min of duration. As a generalization of the obtained data, the mechanism of alkaline carbonates’ influence on iron grain growth was proposed.
Dmitry Zinoveev; Pavel Grudinsky; Andrey Zakunov; Artem Semenov; Maria Panova; Dmitry Valeev; Alex Kondratiev; Valery Dyubanov; Alexander Petelin; Dmitry Valeev. Influence of Na2CO3 and K2CO3 Addition on Iron Grain Growth during Carbothermic Reduction of Red Mud. Metals 2019, 9, 1313 .
AMA StyleDmitry Zinoveev, Pavel Grudinsky, Andrey Zakunov, Artem Semenov, Maria Panova, Dmitry Valeev, Alex Kondratiev, Valery Dyubanov, Alexander Petelin, Dmitry Valeev. Influence of Na2CO3 and K2CO3 Addition on Iron Grain Growth during Carbothermic Reduction of Red Mud. Metals. 2019; 9 (12):1313.
Chicago/Turabian StyleDmitry Zinoveev; Pavel Grudinsky; Andrey Zakunov; Artem Semenov; Maria Panova; Dmitry Valeev; Alex Kondratiev; Valery Dyubanov; Alexander Petelin; Dmitry Valeev. 2019. "Influence of Na2CO3 and K2CO3 Addition on Iron Grain Growth during Carbothermic Reduction of Red Mud." Metals 9, no. 12: 1313.
Fly ash landfills that accumulate a by-product of coal combustion and gasification represent a permanent threat to the surrounding environment due to many factors (air and water pollution, soil contamination, wildlife poisoning, etc). Moreover, disposed coal fly ash may contain significant amounts of valuable elements that are not extracted and potentially wasted. To improve the above situation, a combined ash treatment process was developed for utilisation of the coal fly ash waste from coal-fired power stations. The ash treatment includes three stages: 1) magnetic separation of an iron-containing fraction, 2) carbon separation by floatation, and 3) extraction of aluminum by the autoclave hydrochloric acid leaching. The lab-scale results of the ash treatment applied to the Ekibastuz brown coal fly ash from the Omsk power stations (Russia) were presented and discussed. The XRD analysis showed that the fly ash consists primarily of quartz, mullite and magnetite. It was found that the magnetic fraction separated at the first stage is enriched in magnetite (over 20 wt. %), the carbon content in the concentrate after flotation increases to 27 wt. %, and 90-95 % of aluminum can be extracted during the autoclave acid leaching. The SEM analysis showed that the magnetite phase is grown on the surface of alumosilicate spheres as ~1 μm cubic crystals. The effect of the autoclave temperature and exposure time on the Al extraction efficiency was also investigated and analysed in the present paper. The optimal autoclave temperature and exposure time were found to achieve the maximum Al extraction efficiency. It was also found by the SEM microanalysis that further extraction of aluminum is not economically feasible since the remaining Al is evenly surrounded by SiO2 in the fly ash particles.
D. Valeev; I. Kunilova; A. Alpatov; A. Mikhailova; M. Goldberg; A. Kondratiev. Complex utilisation of ekibastuz brown coal fly ash: Iron & carbon separation and aluminum extraction. Journal of Cleaner Production 2019, 218, 192 -201.
AMA StyleD. Valeev, I. Kunilova, A. Alpatov, A. Mikhailova, M. Goldberg, A. Kondratiev. Complex utilisation of ekibastuz brown coal fly ash: Iron & carbon separation and aluminum extraction. Journal of Cleaner Production. 2019; 218 ():192-201.
Chicago/Turabian StyleD. Valeev; I. Kunilova; A. Alpatov; A. Mikhailova; M. Goldberg; A. Kondratiev. 2019. "Complex utilisation of ekibastuz brown coal fly ash: Iron & carbon separation and aluminum extraction." Journal of Cleaner Production 218, no. : 192-201.