The environmental concerns resulting from coal-fired power generation that produces large amounts of CO_(2)and fly ash are of great interest.To mitigate,this study aims to develop a novel carbonated CO_(2)-fly ash-bas...The environmental concerns resulting from coal-fired power generation that produces large amounts of CO_(2)and fly ash are of great interest.To mitigate,this study aims to develop a novel carbonated CO_(2)-fly ash-based backfill(CFBF)material under ambient conditions.The performance of CFBF was investigated for different fly ash-cement ratios and compared with non-CO_(2)reacted samples.The fresh CFBF slurry conformed to the Herschel-Bulkley model with shear thinning characteristics.After carbonation,the yield stress of the fresh slurry increased significantly by lowering fly ash ratio due to gel formation.The setting times were accelerated,resulting in approximately 40.6%of increased early strength.The final strength decreased when incorporating a lower fly ash ratio(50%and 60%),which was related to the existing heterogeneous pores caused by rapid fluid loss.The strength increased with fly ash content above 70%because additional C-S(A)-H and silica gels were characterized to precipitate on the grain surface,so the binding between particles increased.The C-S(A)-H gel was developed through the pozzolanic reaction,where CaCO_(3)was the prerequisite calcium source obtained in the CO_(2)-fly ash reaction.Furthermore,the maximum CO_(2)uptake efficiency was 1.39 mg-CO_(2)/g-CFBF.The CFBF material is feasible to co-dispose CO_(2)and fly ash in the mine goaf as negative carbon backfill materials,and simultaneously mitigates the strata movement and water lost in post-subsurface mining.展开更多
The rapidly increasing demand for energy in China leads to the construction of new power plants all over the country. Coal, as the main fuel resource of those power plants, results in increasing problems with the disp...The rapidly increasing demand for energy in China leads to the construction of new power plants all over the country. Coal, as the main fuel resource of those power plants, results in increasing problems with the disposal of solid residues from combustion and off gas cleaning. This investigation describes chances for the utilization of fly ash from coal-fired power plants in China. After briefly comparing the situation in China and Germany, the status of aluminum recycling from fly ash and the ad- vantages for using fly ash in concrete products are introduced. Chemical and physical analyses of Chinese fly ash samples, e.g., X-ray diffraction (XRD), ICP (Inductive Coupled Plasma) and particle size analysis, water requirement, etc. are presented. Rea- sonable amounts of aluminum were detected in the samples under investigation, but for recovery only sophisticated procedures are available up to now. Therefore, simpler techniques are suggested for the first steps in the utilization of Chinese fly ash.展开更多
Thermal processes are emerging as promising solutions to recovering phosphorus and other nutrient elements from anaerobic digestates.The feasibility of nutrient element recovery depends largely on the fates of nutrien...Thermal processes are emerging as promising solutions to recovering phosphorus and other nutrient elements from anaerobic digestates.The feasibility of nutrient element recovery depends largely on the fates of nutrient elements and heavy metals during thermal processing.This study assesses the partitioning of macronutrients(N,P,K,Na,Ca and Mg)and heavy metals(Zn,Cu,and Mn)between condensed and gaseous phases during thermal conversion of cattle slurry digestates in gas atmospheres of pyrolysis,combustion,and gasification processes.This study also assesses the chemical forms of macronutrients retained in combustion ashes.The partitioning of elements between condensed and gaseous phases was quantified by mass balances based on elemental analyses of char and ash residues.The char and ash residues were prepared in a fixed-bed,batch reactor at temperatures within the range 800-1000°C.Powder X-ray diffraction was used to identify the chemical forms of macronutrient elements in combustion ashes.Volatilisation of P was low(<20%)when the digestates were heated in inert and oxidising atmospheres,whereas a reducing atmosphere volatilized P to a major extent(~60%at 1000°C).Oxidising atmospheres increased volatilisation of N but suppressed volatilisation of K,Na,and Zn.Volatilisation of the following elements was low(<30%)in all investigated operating conditions:Ca,Mg,Mn,and Cu.The combustion ashes contained both high concentrations of P(around 7 w/w%)and acceptable concentrations of regulated heavy metals(Cu,and Zn)for application on agricultural and forest soils in Finland.Phosphorous was retained in the combustion ashes in the form of whitlockite.This form of P is expected to be available to plants when the ashes are added to soil.展开更多
CO2 capturing, transport and sequestration by pressurized water dissolution and reacting by natural alkali lime and magnesia in coal fly ash or other sources become an industrial advantageous sequestration option resu...CO2 capturing, transport and sequestration by pressurized water dissolution and reacting by natural alkali lime and magnesia in coal fly ash or other sources become an industrial advantageous sequestration option resulting in green waste solutions or solid fines. Mg and Ca containing minerals are reacting with CO2 to form carbonates. Various types of fly ash materials may react with CO2 to form carbonate regarding ash composition and reaction parameters. Mineral sequestration of CO2 will also allow using the products in cement industry or as cement material in constructions with low cost. This paper discussed progress on coal mining filling by carbonation method using coal fly ash of Soma, Yatagan, Afsin Elbistan Power Stations. Other filler materials containing coal mine waste shale, fly ashes and foam concrete, and additives were searched for pretreatment methods to enhance cement reactivity;and in analyzing the structural changes to identify reaction paths and potential barriers.展开更多
基金The authors would like to make an appreciation to the National Natural Science Foundation of China(No.51874280)the Fundamental Research Funds of the Central Universities(No.2021ZDPY0211)for financial support.
文摘The environmental concerns resulting from coal-fired power generation that produces large amounts of CO_(2)and fly ash are of great interest.To mitigate,this study aims to develop a novel carbonated CO_(2)-fly ash-based backfill(CFBF)material under ambient conditions.The performance of CFBF was investigated for different fly ash-cement ratios and compared with non-CO_(2)reacted samples.The fresh CFBF slurry conformed to the Herschel-Bulkley model with shear thinning characteristics.After carbonation,the yield stress of the fresh slurry increased significantly by lowering fly ash ratio due to gel formation.The setting times were accelerated,resulting in approximately 40.6%of increased early strength.The final strength decreased when incorporating a lower fly ash ratio(50%and 60%),which was related to the existing heterogeneous pores caused by rapid fluid loss.The strength increased with fly ash content above 70%because additional C-S(A)-H and silica gels were characterized to precipitate on the grain surface,so the binding between particles increased.The C-S(A)-H gel was developed through the pozzolanic reaction,where CaCO_(3)was the prerequisite calcium source obtained in the CO_(2)-fly ash reaction.Furthermore,the maximum CO_(2)uptake efficiency was 1.39 mg-CO_(2)/g-CFBF.The CFBF material is feasible to co-dispose CO_(2)and fly ash in the mine goaf as negative carbon backfill materials,and simultaneously mitigates the strata movement and water lost in post-subsurface mining.
文摘The rapidly increasing demand for energy in China leads to the construction of new power plants all over the country. Coal, as the main fuel resource of those power plants, results in increasing problems with the disposal of solid residues from combustion and off gas cleaning. This investigation describes chances for the utilization of fly ash from coal-fired power plants in China. After briefly comparing the situation in China and Germany, the status of aluminum recycling from fly ash and the ad- vantages for using fly ash in concrete products are introduced. Chemical and physical analyses of Chinese fly ash samples, e.g., X-ray diffraction (XRD), ICP (Inductive Coupled Plasma) and particle size analysis, water requirement, etc. are presented. Rea- sonable amounts of aluminum were detected in the samples under investigation, but for recovery only sophisticated procedures are available up to now. Therefore, simpler techniques are suggested for the first steps in the utilization of Chinese fly ash.
基金financially supported by the Research Council of Finland grant to NJS(grant#311970)the Finnish Ministry of Agriculture and Forestry(VN/28562/2020-MMM-2).
文摘Thermal processes are emerging as promising solutions to recovering phosphorus and other nutrient elements from anaerobic digestates.The feasibility of nutrient element recovery depends largely on the fates of nutrient elements and heavy metals during thermal processing.This study assesses the partitioning of macronutrients(N,P,K,Na,Ca and Mg)and heavy metals(Zn,Cu,and Mn)between condensed and gaseous phases during thermal conversion of cattle slurry digestates in gas atmospheres of pyrolysis,combustion,and gasification processes.This study also assesses the chemical forms of macronutrients retained in combustion ashes.The partitioning of elements between condensed and gaseous phases was quantified by mass balances based on elemental analyses of char and ash residues.The char and ash residues were prepared in a fixed-bed,batch reactor at temperatures within the range 800-1000°C.Powder X-ray diffraction was used to identify the chemical forms of macronutrient elements in combustion ashes.Volatilisation of P was low(<20%)when the digestates were heated in inert and oxidising atmospheres,whereas a reducing atmosphere volatilized P to a major extent(~60%at 1000°C).Oxidising atmospheres increased volatilisation of N but suppressed volatilisation of K,Na,and Zn.Volatilisation of the following elements was low(<30%)in all investigated operating conditions:Ca,Mg,Mn,and Cu.The combustion ashes contained both high concentrations of P(around 7 w/w%)and acceptable concentrations of regulated heavy metals(Cu,and Zn)for application on agricultural and forest soils in Finland.Phosphorous was retained in the combustion ashes in the form of whitlockite.This form of P is expected to be available to plants when the ashes are added to soil.
文摘CO2 capturing, transport and sequestration by pressurized water dissolution and reacting by natural alkali lime and magnesia in coal fly ash or other sources become an industrial advantageous sequestration option resulting in green waste solutions or solid fines. Mg and Ca containing minerals are reacting with CO2 to form carbonates. Various types of fly ash materials may react with CO2 to form carbonate regarding ash composition and reaction parameters. Mineral sequestration of CO2 will also allow using the products in cement industry or as cement material in constructions with low cost. This paper discussed progress on coal mining filling by carbonation method using coal fly ash of Soma, Yatagan, Afsin Elbistan Power Stations. Other filler materials containing coal mine waste shale, fly ashes and foam concrete, and additives were searched for pretreatment methods to enhance cement reactivity;and in analyzing the structural changes to identify reaction paths and potential barriers.
