This paper analyzes the coal to char stages of char formation of six coals of different ranks by using Fourier transform infrared coupled w ith attenuated total reflectance(ATR-FTIR).The chars w ere obtained by coal p...This paper analyzes the coal to char stages of char formation of six coals of different ranks by using Fourier transform infrared coupled w ith attenuated total reflectance(ATR-FTIR).The chars w ere obtained by coal pyrolysis carried out at temperature range of 450~700℃.The data obtained show s the pragmatic disappearance of the aliphatic hydrogen content w ith increasing char formation temperature.Numerical evaluation of the spectra enabled the determination of aromaticity,fa.The aromaticity w as found to be betw een 0.66~0.79 for lignite,0.75~0.90 for sub-bituminous,0.84~1.00 for low volatile bituminous,0.83~1.00 for high volatile bituminous,0.94~1.00 for semi-anthracite,and 0.97~1.00 for anthracite respectively.With increasing rank of coal samples,spectra exhibit rising aromaticity and enhanced condensation of aromatic rings,w hereas the aliphatic chain lengths decrease.展开更多
This study investigated the isothermal gasification reactivity of biomass char （BC） and coal char （CC） blended at mass ratios of 1：3, 1：1, and 3：1 via isothermal thermogravimelric analysis （TGA） at 900, 950, ...This study investigated the isothermal gasification reactivity of biomass char （BC） and coal char （CC） blended at mass ratios of 1：3, 1：1, and 3：1 via isothermal thermogravimelric analysis （TGA） at 900, 950, and 1000℃ under CO2. With an increase in BC blending ra- tio, there were an increase in gasification rate and a shortening of gasification time. This could be attributed to the high specific surface area of BC and the high uniformity of carbon structures in CC when compared to those in BC. Three representative gas-solid kinetic models, namely, the volumetric model （VM）, grain model （GM）, and random pore model （RPM）, were applied to describe the reaction behavior of the char. Among them, the RPM model was considered the best model to describe the reactivity of the char gasification reaction. The activa- tion energy of BC and CC isothermal gasification as determined using the RPM model was found to be 126.7 kJ/mol and 210.2 kJ/mol, re- spectively. The activation energy was minimum （123.1 kJ/mol） for the BC blending ratio of 75%. Synergistic effect manifested at all mass ratios of the blended char, which increased with the gasification temperature.展开更多
The authors proposed an integrated gasification fuel cell zero-emission system.The coal char gasification is discussed using high temperature and concentration of CO_(2) produced by solid oxide fuel cells and oxy-fuel...The authors proposed an integrated gasification fuel cell zero-emission system.The coal char gasification is discussed using high temperature and concentration of CO_(2) produced by solid oxide fuel cells and oxy-fuel combustion.The gasification is simulated by Aspen plus based on Gibbs free energy minimization method.Gasification model of pulverized coal char is computed and analyzed.Effects of gas flow rate,pressure,preheating temperature,heat losses on syngas composition,reaction temperature,lower heating value and carbon conversion are studied.Results and parameters are determined as following.The optimum O_(2) flow rate is 20 kg/h.The reaction temperature decreases from 1645 to 1329℃when the CO_(2)flow rate increases from 0 to 5 kg/h,the CO_(2) flow rate should be operated reasonably;lower heating value reduces and reaction temperature increases as the pressure increases;compared to the CO_(2) preheating,O_(2) preheating has greater influence on reaction temperature and lower heating value.展开更多
This study was to examine the influence of reactions of char–O2and char–steam on the char reactivity evolution.A newly-designed fixed-bed reactor was used to conduct gasification experiments using Victorian brown co...This study was to examine the influence of reactions of char–O2and char–steam on the char reactivity evolution.A newly-designed fixed-bed reactor was used to conduct gasification experiments using Victorian brown coal at800 °C. The chars prepared from the gasification experiments were then collected and subjected to reactivity characterisation(ex-situ reactivity) using TGA(thermogravimetric analyser) in air. The results indicate that the char reactivity from TGA was generally high when the char experienced intensive gasification reactions in 0.3%O2in the fixed-bed reactor. The addition of steam into the gasification not only enhanced the char conversion significantly but also reduced the char reactivity dramatically. The curve shapes of the char reactivity with involvement of steam were very different from that with O2 gasification, implying the importance of gasifying agents to char properties.展开更多
Based on the quasi-steady-state approximation, the dynamic equation of char combustion in the oxidation zone of underground coal gasification (UCG) was derived. The parameters of the dynamic equation were determined a...Based on the quasi-steady-state approximation, the dynamic equation of char combustion in the oxidation zone of underground coal gasification (UCG) was derived. The parameters of the dynamic equation were determined at 900℃ using a thermo-gravimetric (TG) analyzer connected to a flue gas analyzer and this equation. The equation was simplified for specific coals, including high ash content, low ash content, and low ash fusibility ones. The results show that 1) the apparent reaction rate constant increases with an increase in volatile matter value as dry ash-free basis,2) the effective coefficient of diffusion decreases with an increase in ash as dry basis, and 3) the mass transfer coefficient is independent of coal quality on the whole. The apparent reaction rate constant, mass-transfer coefficient and effective coefficient of diffusion of six char samples range from 7.51×104 m/s to 8.98×104 m/s, 3.05×106 m/s to 3.23×106 m/s and 5.36×106 m2/s to 8.23×106 m2/s at 900℃, respectively.展开更多
For low-income communities in South Africa,coal is the most common solid fuel which is burnt in a variety of devices,including imbaulas and cast-iron stoves.The present work was conducted with the aim of determining t...For low-income communities in South Africa,coal is the most common solid fuel which is burnt in a variety of devices,including imbaulas and cast-iron stoves.The present work was conducted with the aim of determining the effect of the fuel particle size on the performance of coal,typically sourced in low-income households in townships in South Africa,and to subsequently compare the performance with a feed char of a common cast iron stove.Four fuel particle sizes of 15,20,30,and 40 mm,as well as a composite of the sizes were tested at 550C,against their untreated coal analogues to evaluate the thermal performance of each fuel.The thermal performance assessment metrics are ignition time,water boiling time,heat transfer and combustion efficiencies,while CO and CO_(2)emissions were measured for the calculations of CO/CO_(2)ratios.Ignition times were found to decrease from coals to chars and to decrease with increasing particle size.The effects of fuel type on the water boiling time were only observed in the later stages of the burn cycle,with the char boiling a 2 L batch of water in an average 24 min,while the coals reported an average boiling time of 20 min.Heat transfer efficiencies showed no significant variation with fuel type or particle size,with the average efficiency for the coals and that of the chars being around 66%.The fuels’performance was better gauged by the combustion efficiency,which was found to improve marginally from the coal fuels to the chars,and to increase with increasing particle size.Results from this testwork could contribute to the performance inventories from the combustion of domestic coal mined in South Africa in a typical cast iron stove which is used in informal settlements.展开更多
This study examined an isothermal CO2 gasification of four chars prepared via two different methods,i.e.,conventional and microwave-assisted pyrolysis,by the approach of thermogravimetric analysis.Physical,chemical,an...This study examined an isothermal CO2 gasification of four chars prepared via two different methods,i.e.,conventional and microwave-assisted pyrolysis,by the approach of thermogravimetric analysis.Physical,chemical,and structural behaviours of chars were examined using ultimate analysis,X-ray diffraction,and scanning electronic microscopy.Kinetic parameters were calculated by applying the shrinking unreacted core(SCM)and random pore(RPM)models.Moreover,char-CO2 gasification was further simulated by using Aspen Plus to investigate thermodynamic performances in terms of syngas composition and cold gas efficiency(CGE).The microwave-induced char has the largest C/H mass ratio and most ordered carbon structure,but the smallest gasification reactivity.Kinetic analysis indicates that the RPM is better for describing both gasification conversion and reaction rates of the studied chars,and the activation energies and pre-exponential factors varied in the range of 78.45–194.72 kJ/mol and 3.15–102,231.99 s−1,respectively.In addition,a compensation effect was noted during gasification.Finally,the microwave-derived char exhibits better thermodynamic performances than the conventional chars,with the highest CGE and CO molar concentration of 1.30%and 86.18%,respectively.Increasing the pyrolysis temperature,gasification temperature,and CO2-to-carbon molar ratio improved the CGE.展开更多
Dephosphorization behavior of monazite concentrate with charred coal at high temperature was investigated.It is found that the roast temperature is the main factor for the dephosphorization of the monazite.The high de...Dephosphorization behavior of monazite concentrate with charred coal at high temperature was investigated.It is found that the roast temperature is the main factor for the dephosphorization of the monazite.The high dephosphorization efficiency can be reached at the temperatures ranging from 1 200 to 1 400°C.When the monazite pellets,made by pressing mixture of the monazite,charred coal and water into mould,were roasted at 1 400°C for 2 h,98%of phosphorus was removed from the monazite pellets.The roast time has little effect on the dephosphorization efficiency.Meanwhile,the particle size of the charred coal also has great influence on the dephosphorization efficiency of the monazite,and it is better to control particle size around 150μm,while Fe and Fe2O3 have neglectable effect on the dephosphorization of the monazite.展开更多
In the current research process of coal rank char gasification reaction in China, it is found that particle size has different influence on the gasification reactivity of coal char of different ranks. Therefore, monod...In the current research process of coal rank char gasification reaction in China, it is found that particle size has different influence on the gasification reactivity of coal char of different ranks. Therefore, monodisperse pulverized coal was prepared from eight kinds of coal chars of different ranks in entrained-flow gasifier. The particle size and gasification temperature of coal char were analyzed for these samples. The degree of influence of carbon dioxide gasification reaction. Through research and analysis, the performance differences of these samples under different carbon conversion rates were compared, and the sample reaction under high carbon conversion rates was discussed. The experimental results show that the orderliness of the microcrystalline structure of coal char is directly proportional to the rank of coal, while the gasification activity of coal char is inversely proportional to the rank of coal. Therefore, for different coal ranks, the influence of coal char particle size on coal char gasification reaction is different. According to the experiments, smaller coal char size and higher gasification temperature can promote the reactivity of higher-order coal gasification. In order to clarify the correlation between particle size and gasification reactivity of coal chars with different ranks, this paper discussed this issue.展开更多
In this investigation, SAXS and XRD were used to investigate both the physical and chemical changes in six coals of different ranks subjected to heat treatment. The specific surface area which gives an indication of t...In this investigation, SAXS and XRD were used to investigate both the physical and chemical changes in six coals of different ranks subjected to heat treatment. The specific surface area which gives an indication of the reactivity of the coal (measures surface area available for reaction) was determined to be in the range of 70.04 - 260.40 m<sup>2</sup>/cm<sup>3</sup> particle volume for lignite from 450°C - 700°C. The specific surface area was determined to be in the range of 51.58 - 239.00 m<sup>2</sup>/cm<sup>3</sup> particle volume for sub-bituminous;440.60 - 241.70 m<sup>2</sup>/cm<sup>3</sup> particle volume for light volatile bituminous;452.71 - 247.73 m<sup>2</sup>/cm<sup>3</sup> particle volume for high volatile bituminous;349.11 - 347.52 m<sup>2</sup>/cm<sup>3 </sup>particle volume for semi-anthracite and 333.60 - 125.34 m<sup>2</sup>/cm<sup>3</sup> particle volume for anthracite respectively. On the other hand, the aromaticity was determined in the range of 0.66 - 0.76 for lignite;0.67 to 0.80 for sub-bituminous;0.91 - 0.97 for light volatile bituminous;0.93 - 0.99 for high volatile bituminous;0.96 - 1.00 for semi-anthracite and 0.96 to 0.99 for anthracite respectively. The porosity, pore size distribution associated with SAXS and the other crystallite parameters identified with XRD were also determined. Links between the physical and chemical parameters were established.展开更多
基金Supported by the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation of South Africa(Coal Research Chair Grant No.86880)
文摘This paper analyzes the coal to char stages of char formation of six coals of different ranks by using Fourier transform infrared coupled w ith attenuated total reflectance(ATR-FTIR).The chars w ere obtained by coal pyrolysis carried out at temperature range of 450~700℃.The data obtained show s the pragmatic disappearance of the aliphatic hydrogen content w ith increasing char formation temperature.Numerical evaluation of the spectra enabled the determination of aromaticity,fa.The aromaticity w as found to be betw een 0.66~0.79 for lignite,0.75~0.90 for sub-bituminous,0.84~1.00 for low volatile bituminous,0.83~1.00 for high volatile bituminous,0.94~1.00 for semi-anthracite,and 0.97~1.00 for anthracite respectively.With increasing rank of coal samples,spectra exhibit rising aromaticity and enhanced condensation of aromatic rings,w hereas the aliphatic chain lengths decrease.
基金financially supported by the National Natural Science Foundation of China (No. 51104014)
文摘This study investigated the isothermal gasification reactivity of biomass char （BC） and coal char （CC） blended at mass ratios of 1：3, 1：1, and 3：1 via isothermal thermogravimelric analysis （TGA） at 900, 950, and 1000℃ under CO2. With an increase in BC blending ra- tio, there were an increase in gasification rate and a shortening of gasification time. This could be attributed to the high specific surface area of BC and the high uniformity of carbon structures in CC when compared to those in BC. Three representative gas-solid kinetic models, namely, the volumetric model （VM）, grain model （GM）, and random pore model （RPM）, were applied to describe the reaction behavior of the char. Among them, the RPM model was considered the best model to describe the reactivity of the char gasification reaction. The activa- tion energy of BC and CC isothermal gasification as determined using the RPM model was found to be 126.7 kJ/mol and 210.2 kJ/mol, re- spectively. The activation energy was minimum （123.1 kJ/mol） for the BC blending ratio of 75%. Synergistic effect manifested at all mass ratios of the blended char, which increased with the gasification temperature.
基金National Basic Research Program of China(No.2012CB215404,2012CB215406)the National Natural Science Foundation of China(No.51261120378)for financial support of this work.
文摘The authors proposed an integrated gasification fuel cell zero-emission system.The coal char gasification is discussed using high temperature and concentration of CO_(2) produced by solid oxide fuel cells and oxy-fuel combustion.The gasification is simulated by Aspen plus based on Gibbs free energy minimization method.Gasification model of pulverized coal char is computed and analyzed.Effects of gas flow rate,pressure,preheating temperature,heat losses on syngas composition,reaction temperature,lower heating value and carbon conversion are studied.Results and parameters are determined as following.The optimum O_(2) flow rate is 20 kg/h.The reaction temperature decreases from 1645 to 1329℃when the CO_(2)flow rate increases from 0 to 5 kg/h,the CO_(2) flow rate should be operated reasonably;lower heating value reduces and reaction temperature increases as the pressure increases;compared to the CO_(2) preheating,O_(2) preheating has greater influence on reaction temperature and lower heating value.
基金Support by the Victorian State Government under its Energy Technology Innovation Strategy programme and the 12th Five-Year Plan of National Science and Technology of China(2012BAA04B02)
文摘This study was to examine the influence of reactions of char–O2and char–steam on the char reactivity evolution.A newly-designed fixed-bed reactor was used to conduct gasification experiments using Victorian brown coal at800 °C. The chars prepared from the gasification experiments were then collected and subjected to reactivity characterisation(ex-situ reactivity) using TGA(thermogravimetric analyser) in air. The results indicate that the char reactivity from TGA was generally high when the char experienced intensive gasification reactions in 0.3%O2in the fixed-bed reactor. The addition of steam into the gasification not only enhanced the char conversion significantly but also reduced the char reactivity dramatically. The curve shapes of the char reactivity with involvement of steam were very different from that with O2 gasification, implying the importance of gasifying agents to char properties.
基金Projects 59906014, 50276066 and 20207014 supported by National Natural Science Foundation of China
文摘Based on the quasi-steady-state approximation, the dynamic equation of char combustion in the oxidation zone of underground coal gasification (UCG) was derived. The parameters of the dynamic equation were determined at 900℃ using a thermo-gravimetric (TG) analyzer connected to a flue gas analyzer and this equation. The equation was simplified for specific coals, including high ash content, low ash content, and low ash fusibility ones. The results show that 1) the apparent reaction rate constant increases with an increase in volatile matter value as dry ash-free basis,2) the effective coefficient of diffusion decreases with an increase in ash as dry basis, and 3) the mass transfer coefficient is independent of coal quality on the whole. The apparent reaction rate constant, mass-transfer coefficient and effective coefficient of diffusion of six char samples range from 7.51×104 m/s to 8.98×104 m/s, 3.05×106 m/s to 3.23×106 m/s and 5.36×106 m2/s to 8.23×106 m2/s at 900℃, respectively.
基金acknowledge the DS&T and NRF(Coal Research Chair Grant Nos.86880)of SA for financing this investigation.
文摘For low-income communities in South Africa,coal is the most common solid fuel which is burnt in a variety of devices,including imbaulas and cast-iron stoves.The present work was conducted with the aim of determining the effect of the fuel particle size on the performance of coal,typically sourced in low-income households in townships in South Africa,and to subsequently compare the performance with a feed char of a common cast iron stove.Four fuel particle sizes of 15,20,30,and 40 mm,as well as a composite of the sizes were tested at 550C,against their untreated coal analogues to evaluate the thermal performance of each fuel.The thermal performance assessment metrics are ignition time,water boiling time,heat transfer and combustion efficiencies,while CO and CO_(2)emissions were measured for the calculations of CO/CO_(2)ratios.Ignition times were found to decrease from coals to chars and to decrease with increasing particle size.The effects of fuel type on the water boiling time were only observed in the later stages of the burn cycle,with the char boiling a 2 L batch of water in an average 24 min,while the coals reported an average boiling time of 20 min.Heat transfer efficiencies showed no significant variation with fuel type or particle size,with the average efficiency for the coals and that of the chars being around 66%.The fuels’performance was better gauged by the combustion efficiency,which was found to improve marginally from the coal fuels to the chars,and to increase with increasing particle size.Results from this testwork could contribute to the performance inventories from the combustion of domestic coal mined in South Africa in a typical cast iron stove which is used in informal settlements.
基金This work was financially supported by the National Key Research and Development Program of China(2017YFB0602601)the Key Research and Development Program of Ningxia Hui Autonomous Region(2019BCH01001).
文摘This study examined an isothermal CO2 gasification of four chars prepared via two different methods,i.e.,conventional and microwave-assisted pyrolysis,by the approach of thermogravimetric analysis.Physical,chemical,and structural behaviours of chars were examined using ultimate analysis,X-ray diffraction,and scanning electronic microscopy.Kinetic parameters were calculated by applying the shrinking unreacted core(SCM)and random pore(RPM)models.Moreover,char-CO2 gasification was further simulated by using Aspen Plus to investigate thermodynamic performances in terms of syngas composition and cold gas efficiency(CGE).The microwave-induced char has the largest C/H mass ratio and most ordered carbon structure,but the smallest gasification reactivity.Kinetic analysis indicates that the RPM is better for describing both gasification conversion and reaction rates of the studied chars,and the activation energies and pre-exponential factors varied in the range of 78.45–194.72 kJ/mol and 3.15–102,231.99 s−1,respectively.In addition,a compensation effect was noted during gasification.Finally,the microwave-derived char exhibits better thermodynamic performances than the conventional chars,with the highest CGE and CO molar concentration of 1.30%and 86.18%,respectively.Increasing the pyrolysis temperature,gasification temperature,and CO2-to-carbon molar ratio improved the CGE.
基金Project(59804003)supported by the National Natural Science Foundation of China
文摘Dephosphorization behavior of monazite concentrate with charred coal at high temperature was investigated.It is found that the roast temperature is the main factor for the dephosphorization of the monazite.The high dephosphorization efficiency can be reached at the temperatures ranging from 1 200 to 1 400°C.When the monazite pellets,made by pressing mixture of the monazite,charred coal and water into mould,were roasted at 1 400°C for 2 h,98%of phosphorus was removed from the monazite pellets.The roast time has little effect on the dephosphorization efficiency.Meanwhile,the particle size of the charred coal also has great influence on the dephosphorization efficiency of the monazite,and it is better to control particle size around 150μm,while Fe and Fe2O3 have neglectable effect on the dephosphorization of the monazite.
文摘In the current research process of coal rank char gasification reaction in China, it is found that particle size has different influence on the gasification reactivity of coal char of different ranks. Therefore, monodisperse pulverized coal was prepared from eight kinds of coal chars of different ranks in entrained-flow gasifier. The particle size and gasification temperature of coal char were analyzed for these samples. The degree of influence of carbon dioxide gasification reaction. Through research and analysis, the performance differences of these samples under different carbon conversion rates were compared, and the sample reaction under high carbon conversion rates was discussed. The experimental results show that the orderliness of the microcrystalline structure of coal char is directly proportional to the rank of coal, while the gasification activity of coal char is inversely proportional to the rank of coal. Therefore, for different coal ranks, the influence of coal char particle size on coal char gasification reaction is different. According to the experiments, smaller coal char size and higher gasification temperature can promote the reactivity of higher-order coal gasification. In order to clarify the correlation between particle size and gasification reactivity of coal chars with different ranks, this paper discussed this issue.
文摘In this investigation, SAXS and XRD were used to investigate both the physical and chemical changes in six coals of different ranks subjected to heat treatment. The specific surface area which gives an indication of the reactivity of the coal (measures surface area available for reaction) was determined to be in the range of 70.04 - 260.40 m<sup>2</sup>/cm<sup>3</sup> particle volume for lignite from 450°C - 700°C. The specific surface area was determined to be in the range of 51.58 - 239.00 m<sup>2</sup>/cm<sup>3</sup> particle volume for sub-bituminous;440.60 - 241.70 m<sup>2</sup>/cm<sup>3</sup> particle volume for light volatile bituminous;452.71 - 247.73 m<sup>2</sup>/cm<sup>3</sup> particle volume for high volatile bituminous;349.11 - 347.52 m<sup>2</sup>/cm<sup>3 </sup>particle volume for semi-anthracite and 333.60 - 125.34 m<sup>2</sup>/cm<sup>3</sup> particle volume for anthracite respectively. On the other hand, the aromaticity was determined in the range of 0.66 - 0.76 for lignite;0.67 to 0.80 for sub-bituminous;0.91 - 0.97 for light volatile bituminous;0.93 - 0.99 for high volatile bituminous;0.96 - 1.00 for semi-anthracite and 0.96 to 0.99 for anthracite respectively. The porosity, pore size distribution associated with SAXS and the other crystallite parameters identified with XRD were also determined. Links between the physical and chemical parameters were established.
