Coal gasification fly ash(CGFA)is an industrial solid waste from the coal circulating fluidized bed(CFB)gasification process,and it needs to be effectively disposed to achieve sustainable development of the environmen...Coal gasification fly ash(CGFA)is an industrial solid waste from the coal circulating fluidized bed(CFB)gasification process,and it needs to be effectively disposed to achieve sustainable development of the environment.To realize the application of CGFA as a precursor of porous carbon materials,the physicochemical properties of three kinds of CGFA from industrial CFB gasifiers are analyzed.Then,the activation potential of CGFA is acquired via steam activation experiments in a tube furnace reactor.Finally,the fluidization activation technology of CGFA is practiced in a bench-scale CFB test rig,and its advantages are highlighted.The results show that CGFA is characterized by a high carbon content in the range of 54.06%–74.09%,an ultrafine particle size(d50:16.3–26.1 μm),and a relatively developed pore structure(specific surface area SSA:139.29–551.97 m^(2)·g^(-1)).The proportion of micropores in CGFA increases gradually with the coal rank.Steam activation experiments show that the pore development of CGFA mainly includes three stages:initial pore development,dynamic equilibrium between micropores and mesopores and pore collapse.The SSA of lignite fly ash(LFA),subbituminous fly ash(SBFA)and anthracite fly ash(AFA)is maximally increased by 105%,13%and 72%after steam activation;the order of the largest carbon reaction rate and decomposition ratio of steam among the three kinds of CGFA is SBFA>LFA>AFA.As the ratio of oxygen to carbon during the fluidization activation of LFA is from 0.09 to 0.19,the carbon conversion ratio increases from 14.4%to 26.8%and the cold gas efficiency increases from 6.8%to 10.2%.The SSA of LFA increases by up to 53.9%during the fluidization activation process,which is mainly due to the mesoporous development.Relative to steam activation in a tube furnace reactor,fluidization activation takes an extremely short time(seconds)to achieve the same activation effect.It is expected to further improve the activation effect of LFA by regulating the carbon conversion ratio range of 27%–35%to create pores in the initial development stage.展开更多
The coal gasification fly ash(CGFA) is an industrial solid waste from coal gasification process and needs to be effectively disposed for environmental protection and resource utilization.To further clarify the feasibi...The coal gasification fly ash(CGFA) is an industrial solid waste from coal gasification process and needs to be effectively disposed for environmental protection and resource utilization.To further clarify the feasibility of CGFA to prepare porous carbon materials,the physicochemical properties of ten kinds of CGFA from circulating fluidized bed(CFB) gasifiers were analyzed in detail.The results of proximate and ultimate analysis show that the CGFA is characterized with the features of near zero moisture content,low volatile content as low as 0.90%-9.76%,high carbon content in the range of 37.89%-81.62%,and ultrafine particle size(d50=15.8-46.2 μm).The automatic specific surface area(SSA) and pore size analyzer were used to detect the pore structure,it is found that the pore structure of CGFA is relatively developed,and part of the CGFA has the basic conditions to be used directly as porous carbon materials.From SEM images,the microscopic morphology of the CGFA is significantly different,and they basically have the characteristics of loose and porous structure.XRD and Roman spectroscopy were used to characterize the carbon structure.The result shows that the CGFA contains abundant amorphous carbon structure,and thus the CGFA has a good reactivity and a potential to improve pore structure through further activation.Through thermal gravimetric analysis,it can be concluded that the order of reactivity of the CGFA under CO_(2) atmosphere has a good correlation with the degree of metamorphism of the raw coal.The gasification reactivity of the CGFA is generally consistent with the change trend of micropores combined with the pore structure.According to the physicochemical properties,the CGFA has a good application prospect in the preparation of porous carbon materials.展开更多
The poor-reactivity anthracite urgently needs more ways for large-scale and high-quality utilization.Due to the advantage of good fuel adaptability,the circulating fluidized bed(CFB)gasification technology has the pot...The poor-reactivity anthracite urgently needs more ways for large-scale and high-quality utilization.Due to the advantage of good fuel adaptability,the circulating fluidized bed(CFB)gasification technology has the potential of high-quality utilization of anthracite.In this paper,one kind of anthracite from Shanxi province,China,was employed to be gasified in a pilot-scale CFB gasifier.It is found that at the operating temperature of 1049℃and oxygen concentration of 60.75%,the gas with a concentration of combustibles of 66%and a low heating value of 7.93 MJ/m^(3)(at about 25℃and 101.325 kPa)was produced in the CFB gasification process.However,the overall gasification efficiency was not desired because a large amount of gasification fly ash(GFA)escaped and its yield was up to 22%.In this case,the cold gas efficiency was below 48%and the carbon conversion ratio was only 62%.Further analysis reveals that the GFA was featured with a developed pore structure and the specific surface area(S_(BET))reached 277 m^(2)/g.This indicates such GFA has a potential to use as activated carbon(AC)or AC precursor.Basis on this,steam activation experiments of the GFA produced were conducted to investigate the activation characteristics of GFA and thereby to determine its activation potential.Experimental results indicate that increasing temperature sharply accelerated the activation process,while did not impair the maximum activation effect.After activation,the S_(BET)of GFA maximumly increased by 63%,reaching452 m^(2)/g.With the progress of activation,the pore structure of GFA presents a three-stage evolution process:development,dynamic balance,and collapse.Such a process can be divided and quantified according to the carbon loss.In order to achieve an optimal activation of GFA,the carbon loss shall be controlled at~15%.This work provides a new scheme for high-quality utilization of anthracite.展开更多
Geopolymer is a material with high early strength.However,the insufficient durability properties,such as long-term strength,acid-base resistance,freeze-thaw resistance,leaching toxicity,thermal stability,sulfate resis...Geopolymer is a material with high early strength.However,the insufficient durability properties,such as long-term strength,acid-base resistance,freeze-thaw resistance,leaching toxicity,thermal stability,sulfate resistance and carbonation resistance,restrain its practical application.Herein,a longterm stable geopolymer composite with high final strength(ASK1)was synthesized from shell coal gasification fly ash(SFA)and steel slag(SS).Additionally,a geopolymer composite with high early strength(ASK2)was also synthesized for comparison.The results showed that ASK1 exhibited better performance on freezing-thawing resistance,carbonization resistance and heavy metals stabilization compared to the ASK2 at long-term curing.Raising the curing temperature could accelerate the unconfined compressive strength(UCS)development at initial curing ages of 3 to 7 d.Both ASK1 and ASK2 exhibited excellent acid-base and sulfate corrosion resistance.An increase for UCS was seen under KOH solution and MgSO_(4)solution corrosion for ASK1.All leaching concentrations of heavy metals out of the two geopolymers were below the standard threshold,even after 50 freezingthawing cycles.Both ASK1 and ASK2 geopolymer concrete exhibited higher sustainability and economic efficiency than Portland cement concrete.The result of this study not only provides a suitable way for the utilization of industrial solid waste in civil and environmental engineering,but also opens a new approach to improve the long-term stabilities of the geopolymers.展开更多
基金financially supported by the Special Research Assistant Fund Project of Chinese Academy of Sciences.
文摘Coal gasification fly ash(CGFA)is an industrial solid waste from the coal circulating fluidized bed(CFB)gasification process,and it needs to be effectively disposed to achieve sustainable development of the environment.To realize the application of CGFA as a precursor of porous carbon materials,the physicochemical properties of three kinds of CGFA from industrial CFB gasifiers are analyzed.Then,the activation potential of CGFA is acquired via steam activation experiments in a tube furnace reactor.Finally,the fluidization activation technology of CGFA is practiced in a bench-scale CFB test rig,and its advantages are highlighted.The results show that CGFA is characterized by a high carbon content in the range of 54.06%–74.09%,an ultrafine particle size(d50:16.3–26.1 μm),and a relatively developed pore structure(specific surface area SSA:139.29–551.97 m^(2)·g^(-1)).The proportion of micropores in CGFA increases gradually with the coal rank.Steam activation experiments show that the pore development of CGFA mainly includes three stages:initial pore development,dynamic equilibrium between micropores and mesopores and pore collapse.The SSA of lignite fly ash(LFA),subbituminous fly ash(SBFA)and anthracite fly ash(AFA)is maximally increased by 105%,13%and 72%after steam activation;the order of the largest carbon reaction rate and decomposition ratio of steam among the three kinds of CGFA is SBFA>LFA>AFA.As the ratio of oxygen to carbon during the fluidization activation of LFA is from 0.09 to 0.19,the carbon conversion ratio increases from 14.4%to 26.8%and the cold gas efficiency increases from 6.8%to 10.2%.The SSA of LFA increases by up to 53.9%during the fluidization activation process,which is mainly due to the mesoporous development.Relative to steam activation in a tube furnace reactor,fluidization activation takes an extremely short time(seconds)to achieve the same activation effect.It is expected to further improve the activation effect of LFA by regulating the carbon conversion ratio range of 27%–35%to create pores in the initial development stage.
基金This work was financially supported by the Special Research Assistant Fund Project of Chinese Academy of Sciences.
文摘The coal gasification fly ash(CGFA) is an industrial solid waste from coal gasification process and needs to be effectively disposed for environmental protection and resource utilization.To further clarify the feasibility of CGFA to prepare porous carbon materials,the physicochemical properties of ten kinds of CGFA from circulating fluidized bed(CFB) gasifiers were analyzed in detail.The results of proximate and ultimate analysis show that the CGFA is characterized with the features of near zero moisture content,low volatile content as low as 0.90%-9.76%,high carbon content in the range of 37.89%-81.62%,and ultrafine particle size(d50=15.8-46.2 μm).The automatic specific surface area(SSA) and pore size analyzer were used to detect the pore structure,it is found that the pore structure of CGFA is relatively developed,and part of the CGFA has the basic conditions to be used directly as porous carbon materials.From SEM images,the microscopic morphology of the CGFA is significantly different,and they basically have the characteristics of loose and porous structure.XRD and Roman spectroscopy were used to characterize the carbon structure.The result shows that the CGFA contains abundant amorphous carbon structure,and thus the CGFA has a good reactivity and a potential to improve pore structure through further activation.Through thermal gravimetric analysis,it can be concluded that the order of reactivity of the CGFA under CO_(2) atmosphere has a good correlation with the degree of metamorphism of the raw coal.The gasification reactivity of the CGFA is generally consistent with the change trend of micropores combined with the pore structure.According to the physicochemical properties,the CGFA has a good application prospect in the preparation of porous carbon materials.
基金financially supported by the Special Research Assistant Project,Chinese Academy of Sciences。
文摘The poor-reactivity anthracite urgently needs more ways for large-scale and high-quality utilization.Due to the advantage of good fuel adaptability,the circulating fluidized bed(CFB)gasification technology has the potential of high-quality utilization of anthracite.In this paper,one kind of anthracite from Shanxi province,China,was employed to be gasified in a pilot-scale CFB gasifier.It is found that at the operating temperature of 1049℃and oxygen concentration of 60.75%,the gas with a concentration of combustibles of 66%and a low heating value of 7.93 MJ/m^(3)(at about 25℃and 101.325 kPa)was produced in the CFB gasification process.However,the overall gasification efficiency was not desired because a large amount of gasification fly ash(GFA)escaped and its yield was up to 22%.In this case,the cold gas efficiency was below 48%and the carbon conversion ratio was only 62%.Further analysis reveals that the GFA was featured with a developed pore structure and the specific surface area(S_(BET))reached 277 m^(2)/g.This indicates such GFA has a potential to use as activated carbon(AC)or AC precursor.Basis on this,steam activation experiments of the GFA produced were conducted to investigate the activation characteristics of GFA and thereby to determine its activation potential.Experimental results indicate that increasing temperature sharply accelerated the activation process,while did not impair the maximum activation effect.After activation,the S_(BET)of GFA maximumly increased by 63%,reaching452 m^(2)/g.With the progress of activation,the pore structure of GFA presents a three-stage evolution process:development,dynamic balance,and collapse.Such a process can be divided and quantified according to the carbon loss.In order to achieve an optimal activation of GFA,the carbon loss shall be controlled at~15%.This work provides a new scheme for high-quality utilization of anthracite.
基金funded by the Jiangxi Academy of Water Science and Engineering Open Project Fund(No.2021SKSG04)the National Natural Science Foundation of China(No.51979011)+1 种基金the Central Non-Profit Scientific Research Fund for Institutes(Nos.CKSF2021483/CL,CKSF2023359/HL,and CKSF2023397/HL)the Knowledge Innovation Program of Science and Technology Bureau of Wuhan,China(No.CKSD2022360/CL)。
文摘Geopolymer is a material with high early strength.However,the insufficient durability properties,such as long-term strength,acid-base resistance,freeze-thaw resistance,leaching toxicity,thermal stability,sulfate resistance and carbonation resistance,restrain its practical application.Herein,a longterm stable geopolymer composite with high final strength(ASK1)was synthesized from shell coal gasification fly ash(SFA)and steel slag(SS).Additionally,a geopolymer composite with high early strength(ASK2)was also synthesized for comparison.The results showed that ASK1 exhibited better performance on freezing-thawing resistance,carbonization resistance and heavy metals stabilization compared to the ASK2 at long-term curing.Raising the curing temperature could accelerate the unconfined compressive strength(UCS)development at initial curing ages of 3 to 7 d.Both ASK1 and ASK2 exhibited excellent acid-base and sulfate corrosion resistance.An increase for UCS was seen under KOH solution and MgSO_(4)solution corrosion for ASK1.All leaching concentrations of heavy metals out of the two geopolymers were below the standard threshold,even after 50 freezingthawing cycles.Both ASK1 and ASK2 geopolymer concrete exhibited higher sustainability and economic efficiency than Portland cement concrete.The result of this study not only provides a suitable way for the utilization of industrial solid waste in civil and environmental engineering,but also opens a new approach to improve the long-term stabilities of the geopolymers.
