A new coal staged conversion poly-generation system combined coal combustion and pyrolysis has been developed for clean and high efficient utilization of coal.Coal is the first pyrolysed in a fluidized pyrolyzer.The p...A new coal staged conversion poly-generation system combined coal combustion and pyrolysis has been developed for clean and high efficient utilization of coal.Coal is the first pyrolysed in a fluidized pyrolyzer.The pyrolysis gas is then purified and used for chemical product or liquid fuel production.Tar is collected during purification and can be processed to extract high value product and to make liquid fuels by hydro-refining.Semi-coke from the pyrolysis reactor is burned in a circulating fluidized bed(CFB)combustor for heat or power generation.The system can realize coal multiproduct generation and has a great potential to increase coal utilization value.A 1 MW poly-generation system pilot plant and a 12 MW CFB gas,tar,heat and power poly-generation system was erected.The experimental study focused on the two fluidized bed operation and characterization of gas,tar and char yields and compositions.The results showed that the system could operate stable,and produce about 0.12 m^(3)/kg gas with 22 MJ/m^(3)heating value and about 10 wt%tar when using Huainan bituminous coal under pyrolysis temperature between 500 and 600℃.The produced gases were mainly H_(2),CH_(4),CO,CO_(2),C_(2)H_(4),C_(2)H_(6),C_(3)H_(6)and C_(3)H_(8).The CFB combustor can burn semi-coke steadily.The application prospect of the new system was discussed.展开更多
In this study,the thermogravimetric analysis(TGA)method has been used to evaluate the kinetic behavior of biomass,coal and its blends during oxyfuel co-combustion.The thermogravimetric results have been evaluated by t...In this study,the thermogravimetric analysis(TGA)method has been used to evaluate the kinetic behavior of biomass,coal and its blends during oxyfuel co-combustion.The thermogravimetric results have been evaluated by the Coats-Redfern method and validated by Criado’s method.TG and DTG curves indicate that as the oxygen concentration increases the ignition and burn out temperatures approach a lower temperature region.The combustion characteristic index shows that biomass to coal blends of 28%and 40%respectively can achieve enhanced combustion up to 60%oxygen enrichment.In the devolatilization region,the activation energies for coal and blends reduce while in the char oxidation region,they increase with rise in oxygen concentration.Biomass,however,indicates slightly different combustion characteristic of being degraded in a single step and its activation energies increase with rise in oxygen concentration.It is demonstrated in this work that oxygen enrichment has more positive combustion effect on coal than biomass.At 20%oxygen enrichment,28%and 40%blends indicate activation energy of 132.8 and 125.5 kJ·mol^-1 respectively which are lower than coal at 148.1 kJ·mol^-1 but higher than biomass at 81.5 kJ·mol^-1 demonstrating synergistic effect of fuel blending.Also,at char combustion step,an increase in activation energy for 28%blend is found to be 0.36 kJ·mol^-1 per rise in oxygen concentration which is higher than in 40%blend at 0.28 kJ·mol^-1.展开更多
Pyrolytic lignin, the water-insoluble fraction in bio-oil, often shows a high content and has strong intermolecular interactions with other compounds in bio-oil. In order to obtain pure pyrolytic lignin and facilitate...Pyrolytic lignin, the water-insoluble fraction in bio-oil, often shows a high content and has strong intermolecular interactions with other compounds in bio-oil. In order to obtain pure pyrolytic lignin and facilitate the utilization of aqueous phase obtained from water extraction of bio-oil, methanol–water extraction method was employed to further separate the bio-oil water-insoluble phase in this paper. Different technologies, including Fourier transform infrared spectroscopy, gel permeation chromatography, and nuclear magnetic resonance, were adopted to characterize the structures of pyrolytic lignins with different activities obtained through this method. Both the heating value and the polymerization degree of high-molecular-weight pyrolytic lignin were higher than those of low-molecular-weight pyrolytic lignin. The molecular weight distribution of high-molecular-weight pyrolytic lignin was relatively wider, among which the contents of dimers to pentamers all accounted for 12% –18%,while the low-molecular-weight pyrolytic lignin mainly consisted of trimers(75.38%). The pyrolytic lignins had similar basic structures, both of which contained syringyl and guaiacyl units, whereas the low-molecular-weight pyrolytic lignin had more abundant syringyl units, reactive carbonyl groups and hydroxyl groups. Meanwhile,thermogravimetric study revealed that the final char residue yield of low-molecular-weight pyrolytic lignin was lower than that of high-molecular-weight pyrolytic lignin.展开更多
The structural evolution of the chars from pyrolysis of biomass components （cellulose, hemicellulose and lignin） in a xenon lamp radiation reactor was investigated. The elemental composition analysis showed that the...The structural evolution of the chars from pyrolysis of biomass components （cellulose, hemicellulose and lignin） in a xenon lamp radiation reactor was investigated. The elemental composition analysis showed that the C content increased at the expense of H and O contents during the chars formation. The values of AH/C/ZSO/c for the formation of cellulose and hemicellulose chars were close to 2, indicating that dehydration was the dominant reaction. Meanwhile, the value was more than 3 for lignin char formation, suggesting that the occurrence of demethoxylation was prevalent. FTIR and XRD analyses further disclosed that the cellulose pyrolysis needed to break down the stable crystal structure prior to the severe depolymerization. As for hemicellulose and lignin pyrolysis, the weak branches and linkages decomposed firstly, followed by the major decomposition. After the devolatilization at the main pyrolysis stage, the three components encountered a slow carbonization process to form condensed aromatic chars. The SEM results showed that the three components underwent different devolatilization behaviors, which induced various surface mornhologies of the chars.展开更多
Bio-oil from biomass pyrolysis cannot directly substitute traditional fuel due to compositional deficiencies.Catalytic hydrodeoxygenation(HDO)is the critical and efficient step to upgrade crude bio-oil to high-quality...Bio-oil from biomass pyrolysis cannot directly substitute traditional fuel due to compositional deficiencies.Catalytic hydrodeoxygenation(HDO)is the critical and efficient step to upgrade crude bio-oil to high-quality bio-jet fuel by lowering the oxygen content and increasing the heating value.However,the hydrocracking reaction tends to reduce the liquid yield and increase the gas yield,causing carbon loss and producing hydrocarbons with a short carbon-chain.To obtain high-yield bio-jet fuel,the elucidation of the conversion process of biomass catalytic HDO is important in providing guidance for metal catalyst design and optimization of reaction conditions.Considering the complexity of crude bio-oil,this review aimed to investigate the catalytic HDO pathways with model compounds that present typical bio-oil components.First,it provided a comprehensive summary of the impact of physical and electronic structures of both noble and non-noble metals that include monometallic and bimetallic supported catalysts on regulating the conversion pathways and resulting product selectivity.The subsequent first principle calculations further corroborated reaction pathways of model compounds in atom-level on different catalyst surfaces with the experiments above and illustrated the favored C-O/C-O scission orders thermodynamically and kinetically.Then,it discussed hydrogenation effects of different H-donors(such as hydrogen and methane)and catalysts deactivation for economical and industrial consideration.Based on the descriptions above and recent researches,it also elaborated on catalytic HDO of biomass and bio-oil with multi-functional catalysts.Finally,it presented the challenges and future prospective of biomass catalytic HDO.展开更多
In large-scale circulating fluidized bed （CFB） boilers, it is common to use multiple cyclones in parallel for the capture of solids, assuming that gas-solid flow to be the same in the cyclones. This article presents...In large-scale circulating fluidized bed （CFB） boilers, it is common to use multiple cyclones in parallel for the capture of solids, assuming that gas-solid flow to be the same in the cyclones. This article presents a study investigating gas-solid flow through six parallel cyclones in a CFB cold test rig. The six cyclones were located asymmetrically on the left and right walls of the riser. Solid volume fraction and particle velocity profiles at the riser outlets and in the horizontal ducts were measured using a fiber optical probe. Cyclone pressure drop and solid circulating rate were measured for each individual cyclone. Measure- ments showed good agreement as to the non-uniform distribution of the gas-solid flow, which occurred mainly across the three cyclones on one side： the middle cyclones on both sides had higher particle veloc- ities. Conversely, the solid volume fractions, solid fluxes and solid circulating rates of the middle cyclones were lower than those of the other four cyclones. The apparent reason for the flow non-uniformity among the cyclones is the significant flow non-uniformity at the riser outlets. Under typical operating conditions, the solid volume fractions at the riser outlets had a deviation of up to 26% whereas the solid circulating rates at the stand pipes, 7%. These results are consistent with most other studies in the literature.展开更多
Slow pyrolysis of a typical high-ash lignite in China was carried out in atmospheres of N_(2),20%CO_(2)/N_(2),40%CO_(2)/N_(2),and 60%CO_(2)/N_(2)in a fixed bed reactor.The evolution of char,tar,and gases in yield and ...Slow pyrolysis of a typical high-ash lignite in China was carried out in atmospheres of N_(2),20%CO_(2)/N_(2),40%CO_(2)/N_(2),and 60%CO_(2)/N_(2)in a fixed bed reactor.The evolution of char,tar,and gases in yield and characteristics,and the physico-chemical characteristics of chars in different atmospheres were compared.Results revealed that CO_(2)almost behaves as an inert gas in the evolution of char and CO before 600℃.The decrease in char and CO_(2)yields and the increase in CO yield at temperatures higher than 600℃are ascribed to the occurrence of char-CO_(2)gasification.The higher the CO_(2)level present in the atmosphere,the higher the severity of the gasification becomes.Introducing CO_(2)into the atmosphere raises tar and water yields but cuts down H_(2),CH_(4),and C_(2)H_(6)yields.The promotion of tar yield results from the higher phenols and aliphatics yields in the presence of CO_(2).The reduction of H_(2)yield is associated with the increase in water yield,while the decline of light hydrocarbon gases is connected with the suppression effects of CO_(2)on methyl decomposition.The role of inherent minerals was also investigated by comparing product yields from raw coal and demineralized coal.The comparison indicated that the char-CO_(2)gasification rate is sharply reduced to nearly zero without the catalytic effects of calcium,iron,and magnesium minerals.The evolution of tar and light hydrocarbon gases in the CO_(2)-containing atmosphere greatly depends on inherent minerals.Without minerals,tar yield is inhibited in the presence of CO_(2).In the absence of minerals,CO_(2)hardly has influences on CH_(4)and C_(2)H_(6)yields.展开更多
In this work,the forms of potassium and chlorine from oxy-fuel co-combustion of lignite coal and corn stover under atmospheric pressure were investigated.In order to check transitional stage,the feedstocks were combus...In this work,the forms of potassium and chlorine from oxy-fuel co-combustion of lignite coal and corn stover under atmospheric pressure were investigated.In order to check transitional stage,the feedstocks were combusted stepwise,first by pyrolysis to form coke under N2 environment and later by coke combustion into the ash at 850℃ in O_(2)/CO_(2) atmosphere.The results show that an increase in blend ratio from 15%to 40%results in an increase in water-soluble potassium in the feedstock and the ashes from 0.15%to 0.4%and 0.015%to 0.038%in weight respectively.The water-soluble potassium is present mainly as KCl and K2SO4.For ammonium acetate soluble potassium,a similar trend to water-soluble potassium is presented but with a much lower content of potassium.The bound potassium in the fuel matrix exists,likely in the form of AlKSi_(2)O_(6).Chlorides are present mainly in the form of KCl which is the dominant water-soluble compound.展开更多
This paper investigated the effect of the pressures,reaction atmospheres and coal ash species on the ash fusibility with high-pressure thermogravimetric analysis(PTGA)apparatus and X-ray diffraction(XRD)analysis.Each ...This paper investigated the effect of the pressures,reaction atmospheres and coal ash species on the ash fusibility with high-pressure thermogravimetric analysis(PTGA)apparatus and X-ray diffraction(XRD)analysis.Each specimen analyzed by XRD was observed for the mineral conversion and formation of new minerals with the pressures under different atmospheres.These results indicate that the pressure restrains the transformation and decomposition of minerals.Many low-temperature minerals are still present under the elevated pressure.The different reaction atmospheres have different effects on the formation of coal ash minerals.Under the N_(2)atmosphere,the present microcline may decrease the melting temperature of coal ash.And later,it transforms into sanidine at high pressure;thus,the melting temperature of coal ash may increase.Under the CO_(2)atmosphere,the minerals such as microcline,lomonitite,geothite and illite are still present with the increase in pressure;this may reduce the melting temperature.While under the H_(2)O atmosphere,there are magnetite and anorthoclase,which may produce the low-temperature eutectics decreasing the melting temperature.The coal ash abundance in basic oxides or higher SiO_(2),Fe_(2)O_(3),K_(2)O and Na_(2)O has lower melting temperature.While the ash sample with more SiO_(2)and Al_(2)O_(3)and less Fe_(2)O_(3)and basic oxides may lead to higher melting temperature.展开更多
Non-thermal plasma technology has been regarded as a promising alternative technology for NOx removal. The understanding of NO2 reduction characteristics is extremely important since NO2 reduction could lower the tota...Non-thermal plasma technology has been regarded as a promising alternative technology for NOx removal. The understanding of NO2 reduction characteristics is extremely important since NO2 reduction could lower the total NO oxidation rate in the plasma atmosphere. In this study, NO2 reduction was experimentally investigated using a non-thermal plasma reactor driven by a pulsed power supply for different simulated gas compositions and operating parameters. The NO2 reduction was promoted by increasing the specific energy density （SED）, and the highest conversion rates were 33.7%, 42.1% and 25.7% for Ar, N2/Ar and O2/Ar, respectively. For a given SED, the NO2 conversion rate had the order N2/Ar 〉 Ar 〉 02/Ar. The highest energy yield of 3.31 g/kWh was obtained in N2/Ar plasma and decreased with increasing SED; the same trends were also found in the other two gas compositions. The conversion rate decreased with increasing initial NO2 concentration. Furthermore, the presence of N2 or O2 led to different reaction pathways for NO2 conversion due to the formation of different dominating reactive radicals.展开更多
基金This work was supported by the National High technology Research and Development Program of China(863 Pro-gram)(No.2007AA05Z334,2013AA051203)International Cooper-ation Project(2011DFR60190)the program of introducing talents of discipline to University(B08026).
文摘A new coal staged conversion poly-generation system combined coal combustion and pyrolysis has been developed for clean and high efficient utilization of coal.Coal is the first pyrolysed in a fluidized pyrolyzer.The pyrolysis gas is then purified and used for chemical product or liquid fuel production.Tar is collected during purification and can be processed to extract high value product and to make liquid fuels by hydro-refining.Semi-coke from the pyrolysis reactor is burned in a circulating fluidized bed(CFB)combustor for heat or power generation.The system can realize coal multiproduct generation and has a great potential to increase coal utilization value.A 1 MW poly-generation system pilot plant and a 12 MW CFB gas,tar,heat and power poly-generation system was erected.The experimental study focused on the two fluidized bed operation and characterization of gas,tar and char yields and compositions.The results showed that the system could operate stable,and produce about 0.12 m^(3)/kg gas with 22 MJ/m^(3)heating value and about 10 wt%tar when using Huainan bituminous coal under pyrolysis temperature between 500 and 600℃.The produced gases were mainly H_(2),CH_(4),CO,CO_(2),C_(2)H_(4),C_(2)H_(6),C_(3)H_(6)and C_(3)H_(8).The CFB combustor can burn semi-coke steadily.The application prospect of the new system was discussed.
基金Financed by the International Cooperation Foundation for ChinaUSA(NSFC-NSF 51661125012)。
文摘In this study,the thermogravimetric analysis(TGA)method has been used to evaluate the kinetic behavior of biomass,coal and its blends during oxyfuel co-combustion.The thermogravimetric results have been evaluated by the Coats-Redfern method and validated by Criado’s method.TG and DTG curves indicate that as the oxygen concentration increases the ignition and burn out temperatures approach a lower temperature region.The combustion characteristic index shows that biomass to coal blends of 28%and 40%respectively can achieve enhanced combustion up to 60%oxygen enrichment.In the devolatilization region,the activation energies for coal and blends reduce while in the char oxidation region,they increase with rise in oxygen concentration.Biomass,however,indicates slightly different combustion characteristic of being degraded in a single step and its activation energies increase with rise in oxygen concentration.It is demonstrated in this work that oxygen enrichment has more positive combustion effect on coal than biomass.At 20%oxygen enrichment,28%and 40%blends indicate activation energy of 132.8 and 125.5 kJ·mol^-1 respectively which are lower than coal at 148.1 kJ·mol^-1 but higher than biomass at 81.5 kJ·mol^-1 demonstrating synergistic effect of fuel blending.Also,at char combustion step,an increase in activation energy for 28%blend is found to be 0.36 kJ·mol^-1 per rise in oxygen concentration which is higher than in 40%blend at 0.28 kJ·mol^-1.
基金Supported by the National Science and Technology Supporting Plan Through Contract(2015BAD15B06)the National Natural Science Foundation of China(51276166)+1 种基金the National Basic Research Program of China(2013CB228101)Guangdong Province Key Laboratory of Efficient and Clean Energy Utilization(2013A061401005)
文摘Pyrolytic lignin, the water-insoluble fraction in bio-oil, often shows a high content and has strong intermolecular interactions with other compounds in bio-oil. In order to obtain pure pyrolytic lignin and facilitate the utilization of aqueous phase obtained from water extraction of bio-oil, methanol–water extraction method was employed to further separate the bio-oil water-insoluble phase in this paper. Different technologies, including Fourier transform infrared spectroscopy, gel permeation chromatography, and nuclear magnetic resonance, were adopted to characterize the structures of pyrolytic lignins with different activities obtained through this method. Both the heating value and the polymerization degree of high-molecular-weight pyrolytic lignin were higher than those of low-molecular-weight pyrolytic lignin. The molecular weight distribution of high-molecular-weight pyrolytic lignin was relatively wider, among which the contents of dimers to pentamers all accounted for 12% –18%,while the low-molecular-weight pyrolytic lignin mainly consisted of trimers(75.38%). The pyrolytic lignins had similar basic structures, both of which contained syringyl and guaiacyl units, whereas the low-molecular-weight pyrolytic lignin had more abundant syringyl units, reactive carbonyl groups and hydroxyl groups. Meanwhile,thermogravimetric study revealed that the final char residue yield of low-molecular-weight pyrolytic lignin was lower than that of high-molecular-weight pyrolytic lignin.
基金Supported by the National Natural Science Foundation of China(51276166)the National Basic Research Program of China(2013CB228101)the National Science and Technology Supporting Plan Through Contract(2015BAD15B06)
文摘The structural evolution of the chars from pyrolysis of biomass components （cellulose, hemicellulose and lignin） in a xenon lamp radiation reactor was investigated. The elemental composition analysis showed that the C content increased at the expense of H and O contents during the chars formation. The values of AH/C/ZSO/c for the formation of cellulose and hemicellulose chars were close to 2, indicating that dehydration was the dominant reaction. Meanwhile, the value was more than 3 for lignin char formation, suggesting that the occurrence of demethoxylation was prevalent. FTIR and XRD analyses further disclosed that the cellulose pyrolysis needed to break down the stable crystal structure prior to the severe depolymerization. As for hemicellulose and lignin pyrolysis, the weak branches and linkages decomposed firstly, followed by the major decomposition. After the devolatilization at the main pyrolysis stage, the three components encountered a slow carbonization process to form condensed aromatic chars. The SEM results showed that the three components underwent different devolatilization behaviors, which induced various surface mornhologies of the chars.
基金supported by the National Natural Science Foundation of China(Grant No.52236011).
文摘Bio-oil from biomass pyrolysis cannot directly substitute traditional fuel due to compositional deficiencies.Catalytic hydrodeoxygenation(HDO)is the critical and efficient step to upgrade crude bio-oil to high-quality bio-jet fuel by lowering the oxygen content and increasing the heating value.However,the hydrocracking reaction tends to reduce the liquid yield and increase the gas yield,causing carbon loss and producing hydrocarbons with a short carbon-chain.To obtain high-yield bio-jet fuel,the elucidation of the conversion process of biomass catalytic HDO is important in providing guidance for metal catalyst design and optimization of reaction conditions.Considering the complexity of crude bio-oil,this review aimed to investigate the catalytic HDO pathways with model compounds that present typical bio-oil components.First,it provided a comprehensive summary of the impact of physical and electronic structures of both noble and non-noble metals that include monometallic and bimetallic supported catalysts on regulating the conversion pathways and resulting product selectivity.The subsequent first principle calculations further corroborated reaction pathways of model compounds in atom-level on different catalyst surfaces with the experiments above and illustrated the favored C-O/C-O scission orders thermodynamically and kinetically.Then,it discussed hydrogenation effects of different H-donors(such as hydrogen and methane)and catalysts deactivation for economical and industrial consideration.Based on the descriptions above and recent researches,it also elaborated on catalytic HDO of biomass and bio-oil with multi-functional catalysts.Finally,it presented the challenges and future prospective of biomass catalytic HDO.
基金financial support of National Key Technologies R & D Program of China (no. 2006BAA03B01-09)International Cooperation Project of MOST (2011FR60190)
文摘In large-scale circulating fluidized bed （CFB） boilers, it is common to use multiple cyclones in parallel for the capture of solids, assuming that gas-solid flow to be the same in the cyclones. This article presents a study investigating gas-solid flow through six parallel cyclones in a CFB cold test rig. The six cyclones were located asymmetrically on the left and right walls of the riser. Solid volume fraction and particle velocity profiles at the riser outlets and in the horizontal ducts were measured using a fiber optical probe. Cyclone pressure drop and solid circulating rate were measured for each individual cyclone. Measure- ments showed good agreement as to the non-uniform distribution of the gas-solid flow, which occurred mainly across the three cyclones on one side： the middle cyclones on both sides had higher particle veloc- ities. Conversely, the solid volume fractions, solid fluxes and solid circulating rates of the middle cyclones were lower than those of the other four cyclones. The apparent reason for the flow non-uniformity among the cyclones is the significant flow non-uniformity at the riser outlets. Under typical operating conditions, the solid volume fractions at the riser outlets had a deviation of up to 26% whereas the solid circulating rates at the stand pipes, 7%. These results are consistent with most other studies in the literature.
基金the National Key R&D Program of China(No.2017YFB0602800)。
文摘Slow pyrolysis of a typical high-ash lignite in China was carried out in atmospheres of N_(2),20%CO_(2)/N_(2),40%CO_(2)/N_(2),and 60%CO_(2)/N_(2)in a fixed bed reactor.The evolution of char,tar,and gases in yield and characteristics,and the physico-chemical characteristics of chars in different atmospheres were compared.Results revealed that CO_(2)almost behaves as an inert gas in the evolution of char and CO before 600℃.The decrease in char and CO_(2)yields and the increase in CO yield at temperatures higher than 600℃are ascribed to the occurrence of char-CO_(2)gasification.The higher the CO_(2)level present in the atmosphere,the higher the severity of the gasification becomes.Introducing CO_(2)into the atmosphere raises tar and water yields but cuts down H_(2),CH_(4),and C_(2)H_(6)yields.The promotion of tar yield results from the higher phenols and aliphatics yields in the presence of CO_(2).The reduction of H_(2)yield is associated with the increase in water yield,while the decline of light hydrocarbon gases is connected with the suppression effects of CO_(2)on methyl decomposition.The role of inherent minerals was also investigated by comparing product yields from raw coal and demineralized coal.The comparison indicated that the char-CO_(2)gasification rate is sharply reduced to nearly zero without the catalytic effects of calcium,iron,and magnesium minerals.The evolution of tar and light hydrocarbon gases in the CO_(2)-containing atmosphere greatly depends on inherent minerals.Without minerals,tar yield is inhibited in the presence of CO_(2).In the absence of minerals,CO_(2)hardly has influences on CH_(4)and C_(2)H_(6)yields.
基金financed by International Cooperation Foundation for China-USA,NSFC-NSF 51661125012。
文摘In this work,the forms of potassium and chlorine from oxy-fuel co-combustion of lignite coal and corn stover under atmospheric pressure were investigated.In order to check transitional stage,the feedstocks were combusted stepwise,first by pyrolysis to form coke under N2 environment and later by coke combustion into the ash at 850℃ in O_(2)/CO_(2) atmosphere.The results show that an increase in blend ratio from 15%to 40%results in an increase in water-soluble potassium in the feedstock and the ashes from 0.15%to 0.4%and 0.015%to 0.038%in weight respectively.The water-soluble potassium is present mainly as KCl and K2SO4.For ammonium acetate soluble potassium,a similar trend to water-soluble potassium is presented but with a much lower content of potassium.The bound potassium in the fuel matrix exists,likely in the form of AlKSi_(2)O_(6).Chlorides are present mainly in the form of KCl which is the dominant water-soluble compound.
基金supported by the National Basic Research Program of China(Grant No.2005CB221201)。
文摘This paper investigated the effect of the pressures,reaction atmospheres and coal ash species on the ash fusibility with high-pressure thermogravimetric analysis(PTGA)apparatus and X-ray diffraction(XRD)analysis.Each specimen analyzed by XRD was observed for the mineral conversion and formation of new minerals with the pressures under different atmospheres.These results indicate that the pressure restrains the transformation and decomposition of minerals.Many low-temperature minerals are still present under the elevated pressure.The different reaction atmospheres have different effects on the formation of coal ash minerals.Under the N_(2)atmosphere,the present microcline may decrease the melting temperature of coal ash.And later,it transforms into sanidine at high pressure;thus,the melting temperature of coal ash may increase.Under the CO_(2)atmosphere,the minerals such as microcline,lomonitite,geothite and illite are still present with the increase in pressure;this may reduce the melting temperature.While under the H_(2)O atmosphere,there are magnetite and anorthoclase,which may produce the low-temperature eutectics decreasing the melting temperature.The coal ash abundance in basic oxides or higher SiO_(2),Fe_(2)O_(3),K_(2)O and Na_(2)O has lower melting temperature.While the ash sample with more SiO_(2)and Al_(2)O_(3)and less Fe_(2)O_(3)and basic oxides may lead to higher melting temperature.
基金supported by the National Science Fund for Distinguished Young Scholars (No. 51125025)the National Natural Science Foundation of China (Nos. 51076140, 51206143)
文摘Non-thermal plasma technology has been regarded as a promising alternative technology for NOx removal. The understanding of NO2 reduction characteristics is extremely important since NO2 reduction could lower the total NO oxidation rate in the plasma atmosphere. In this study, NO2 reduction was experimentally investigated using a non-thermal plasma reactor driven by a pulsed power supply for different simulated gas compositions and operating parameters. The NO2 reduction was promoted by increasing the specific energy density （SED）, and the highest conversion rates were 33.7%, 42.1% and 25.7% for Ar, N2/Ar and O2/Ar, respectively. For a given SED, the NO2 conversion rate had the order N2/Ar 〉 Ar 〉 02/Ar. The highest energy yield of 3.31 g/kWh was obtained in N2/Ar plasma and decreased with increasing SED; the same trends were also found in the other two gas compositions. The conversion rate decreased with increasing initial NO2 concentration. Furthermore, the presence of N2 or O2 led to different reaction pathways for NO2 conversion due to the formation of different dominating reactive radicals.
