A three stage equilibrium model is developed for coal gasification in the Texaco type coal gasifiersbased on Aspen Plus to calculate the composition of product gas, carbon conversion, and gasification teml^erature. Th...A three stage equilibrium model is developed for coal gasification in the Texaco type coal gasifiersbased on Aspen Plus to calculate the composition of product gas, carbon conversion, and gasification teml^erature. The model is divided into three stages including pyrolysis and combustion stage, char gas reaction stage, and gas p.hase reaction stage. Part of the water produced in thepyrolysis and combust!on stag.e is assumed to be involved inthe second stage to react with the unburned carbon. Carbon conversion is then estimated in the second stage by steam participation ratio expressed as a function of temperature. And the gas product compositions are calculated from gas phase reactions in the third stage. The simulation results are consistent with published experimental data.展开更多
Mineral matter in a residue(RC G)from coal gasification(CG)was removed by two-stage acid leaching.Hierarchical activated carbon(HAC)was prepared by activating RC Gwith CO2.The performance of HAC on removing methylene ...Mineral matter in a residue(RC G)from coal gasification(CG)was removed by two-stage acid leaching.Hierarchical activated carbon(HAC)was prepared by activating RC Gwith CO2.The performance of HAC on removing methylene blue(MB)from an aqueous solution was investigated.HAC was characterized by N2 adsorption–desorption isotherm,Fourier transform infrared spectroscopy,and scanning electron microscopy.The results show that HAC exhibits hierarchical pore structure with high specific surface area(862.76 m2·g-1)and total pore volume(0.684 cm3·g-1),and abundant organic functional groups.The adsorption equilibrium data of MB on HAC are best fitted to the Redlich-Peterson.The kinetic data show that the pseudo-first-order model is more suitable at low MB concentration,while the advantages of the pseudo-second-orderand the Elovich models are more obvious as the concentration increases.According to the thermodynamic parameters,the HAC-MB adsorption process is spontaneous and endothermic.展开更多
During underground coal gasification （UCG）, whereby coal is converted to syngas in situ, a cavity is formed in the coal seam. The cavity growth rate （CGR） or the moving rate of the gasification face is affected by...During underground coal gasification （UCG）, whereby coal is converted to syngas in situ, a cavity is formed in the coal seam. The cavity growth rate （CGR） or the moving rate of the gasification face is affected by controllable （operation pressure, gasification time, geometry of UCG panel） and uncontrollable （coal seam properties） factors. The CGR is usually predicted by mathematical models and laboratory experiments, which are time consuming, cumbersome and expensive. In this paper, a new simple model for CGR is developed using non-linear regression analysis, based on data from 1 l UCG field trials. The empirical model compares satisfactorily with Perkins model and can reliably predict CGR.展开更多
The idea of the transformation of coal in underground into synthetic gas so-called syngas is interested in world in many centuries. Underground Coal Gasification （UCG） is an in-situ technique to recover the fuel or ...The idea of the transformation of coal in underground into synthetic gas so-called syngas is interested in world in many centuries. Underground Coal Gasification （UCG） is an in-situ technique to recover the fuel or feedstock value of coal that is not economically available through conventional recovery technologies. Today, less than one sixth of the world＇s coal is economically accessible. Today, similarly to all other countries in the world also in Slovakia there is an interest in the revival and perfection of the UCG technology. From the viewpoint of content the research is directed toward to increasing heating capacity of syngas. From the standpoint of the methods used the research can be divided into 2 approaches： experiments in UCG laboratory and mathematical modeling, including simulation studies. Both approaches have helped to discover complicated relationships during UCG and they will be the subject of this paper. The most important factors are methods, the humidity of the coal, heat losses, temperatures in relevant zones, the composition of oxidation agents and the permeability of the coal. The calorific value of syngas was found generally to be 0.55-4.45 MJ.Nm^-3 with a maximum of 25.51 MJ.m^-3 if only air is used as the oxidation agent. Where a mixture of air and oxygen is used, calorific values in the range 0.43-6.38 MJ.m^-3 were generally obtained, with maximum 27.53 MJ·m^-3. Analysis was carried out on these big differences in order to improve UCG.展开更多
The stability analysis of horizontal wells is essential for a successful underground coal gasification(UCG)operation.In this paper,a new 3D coupled thermo-mechanical numerical modeling is proposed for analyzing the st...The stability analysis of horizontal wells is essential for a successful underground coal gasification(UCG)operation.In this paper,a new 3D coupled thermo-mechanical numerical modeling is proposed for analyzing the stability of UCG horizontal wells.In this model,the effect of front abutment stresses,syngas pressure,syngas temperature and thermal stresses is considered to predict the mud weight window and drilling mud pressure during UCG process.The results show that the roof caving in UCG panel has a greatest impact on the stability of horizontal well.Moreover,when the time of coal gasification is increased,the well convergence increases and for more stability it is necessary to increase the drilling mud pressure.This research was carried out on the M2 coal seam in Mazino coal deposit(Iran).The results showed that the mud weight window for horizontal well drilling is between 0 and 33 MPa.The appropriate stress for the maximum stability of the horizontal well,taking all the thermal and mechanical parameters into account,is 28 MPa.The suggested numerical method is a comprehensive and consistent way for analyzing the stability of horizontal wells in UCG sites.展开更多
The scope of the present paper is to investigate the suitability of a mathematical model for Circulating Fluidized Bed (CFB) coal combustion (developed by the International Energy Agency), to predict and simulate the ...The scope of the present paper is to investigate the suitability of a mathematical model for Circulating Fluidized Bed (CFB) coal combustion (developed by the International Energy Agency), to predict and simulate the performance of the 100 kWth CFB for air-blown biomass gasification. The development of a mathematical model allows to simulate the operative conditions during biomass gasification, control the quality of the synthesis gas and improve the gasifier design. The geometrical, mechanical, hydro dynamical and thermo chemical features were introduced in the model by properly setting the input file and, some changes have been made in the code to assure the final convergence. A sensitivity analysis has been performed to study the variation in the input parameters of the program, and it has been finally verified by comparing the results with the empirical data collected during coal and wood combustion tests. The program, in the same case, could not successfully run;probably depending on wood char density value. For these reason the influence of char density will be investigated. The model predicts the development of tar and other hydrocarbons, valuating the agreement between the measured and calculated efficiency. A further development, to consider solid biomass, with a certain volatile percentages (20% - 40%), as a fuel has been previewed and analyzed. Finally some investigations have been carried out to provide some useful indications for future developments of the code, in the biomass gasification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 gasification kinetic modelling of two Victorian brown coal(Yallourn and Maddingley)chars and the validity for entrained flow gasification were investigated in this study.The study was conducted in a thermogravimet...The gasification kinetic modelling of two Victorian brown coal(Yallourn and Maddingley)chars and the validity for entrained flow gasification were investigated in this study.The study was conducted in a thermogravimetric analyzer(TGA)at 750–1100℃,30%–90%CO_(2)concentration using different char particle sizes within 20–106 mm.It was found that random pore model and modified volumetric model are applicable for TGA results,but volumetric model and grain model are not.The effect of particle size under106 mm on gasification rate is very limited.Activation energies of Maddingley char and Yallourn char in CO_(2)gasification are 219–220 and 197–208 k J/mol,respectively.The pre-exponential factors are in the same order of magnitude,and they increased as particle size decreased.A mathematical model was developed to predict carbon conversion over time for entrained flow gasification of Victorian brown coal chars at 1000–1400℃.展开更多
Using a newly developed experimental setup,the features and advantages of an autothermal single-casing atmospheric sub-bituminous coal fluidized bed air-blown gasifier,combining a combustion and gasification section,a...Using a newly developed experimental setup,the features and advantages of an autothermal single-casing atmospheric sub-bituminous coal fluidized bed air-blown gasifier,combining a combustion and gasification section,and mixing the dispersed phase(inert material,char)and heat exchange between them through an annular transfer device,have been revealed.To increase the efficiency of the gasifier,an experimental-computational method was developed find the conditions for optimal operation,combining changing the annular flow's geometry and regulating the primary air for gasification.A simple and reliable multizone thermodynamic calculation model makes it possible to predict the composition of char and syngas in the gasification section with acceptable accuracy.This method confirmed that a two-section fluidized bed gasifier can provide efficient gasification of solid fuels and is suitable for use in small-scale cogeneration plants.Syngas with a heating value of 3.6-4.5 MJ/m^(3)and CGE of 38.2%-42.3%was obtained in the experimental setup without optimizing the primary air flow rate.With optimization,the indicators increased to the heating value of syngas of 5.20-5.34 MJ/m^(3)and CGE of 42.5%-50.0%.With heat regeneration of 0.8,CGE increases to 70%.展开更多
Gasification is an efficient method of producing clean synthetic gas which can be used as fuel for electric generation and chemical for industries use. Gasification process simulation of coal inside a generic two-stag...Gasification is an efficient method of producing clean synthetic gas which can be used as fuel for electric generation and chemical for industries use. Gasification process simulation of coal inside a generic two-stage entrained flow gasifier to produce syngas was undertaken. Numerical simulation of the oxygen blown coal gasification process inside a two-stage entrained coal gasifier is studied with the commercial CFD solver ANSYS FLUENT. The purpose of this study is to use CFD simulation to improve understanding of the gasification processes in the state of art two-stage entrained flow coal gasifier. Three dimensions, Navier-Stokes equations and species transport equations are solved with the eddy-breakup reaction model to predict gasification processes. The influences of coal/water slurry concentration and O2/coal ratio on the gasification process are investigated. The coal-to-water slurry concentrations in this study were 0.74 and O2/coal ratio is 0.91. Coal slurry fed the predicted concentration of 47.7% and CO was 25% with higher syngas heating value of 27.65 MJ/kg. The flow behavior in the gasifier, especially the single fuel injection design on the second stage, is examined and validated against available data in the literature.展开更多
This paper presents a new approach to study the process of coal gasification. Non-linear programming techniques are used to determine the value of the model parameters that depends on coal species and experimental con...This paper presents a new approach to study the process of coal gasification. Non-linear programming techniques are used to determine the value of the model parameters that depends on coal species and experimental conditions and thus minimize the difference between experimental results and model predictions. Model predictions being in good agreement with the experimental results show that this method of combining model with experiment is effective for modeling complex processes.展开更多
By considering the features of fluidized-bed reactors and the kinetic mechanism of biomass gasification,a steady-state,isothermal,one-dimensional and twophase mathematical model of biomass gasification kinetics in bub...By considering the features of fluidized-bed reactors and the kinetic mechanism of biomass gasification,a steady-state,isothermal,one-dimensional and twophase mathematical model of biomass gasification kinetics in bubbling fluidized beds was developed.The model assumes the existence of two phases–a bubble and an emulsion phase–with chemical reactions occurring in both phases.The axial gas dispersion in the two phases is accounted for and the pyrolysis of biomass is taken to be instantaneous.The char and gas species CO,CO_(2),H_(2),H_(2)O,CH_(4) and 8 chemical reactions are included in the model.The mathematical model belongs to a typical boundary value problem of ordinary differential equations and its solution is obtained by a Matlab program.Utilizing wood powder as the feedstock,the calculated data show satisfactory agreement with experimental results and proves the effectiveness and reliability of the model.展开更多
Gasification temperature measurement is one of the most challenging tasks in an entrained-flow gasifier and often requires indirect calculation using the soft-sensor method,a parameter prediction method using other pa...Gasification temperature measurement is one of the most challenging tasks in an entrained-flow gasifier and often requires indirect calculation using the soft-sensor method,a parameter prediction method using other parameters that are more easily measurable and using correlation equations that are widely accepted in the gasification field for the temperature data.Machine learning is a non-linear prediction method that can adequately act as a soft sensor.Furthermore,the recurrent neural network(RNN)has the function of memorization,which makes it capable of learning how to deal with temporal order.In this paper,the oxygen-coal ratio,CH_(4)content and CO_(2)content determined through the process analysis of a 3000-t/d coal-water slurry gasifier are used as input parameters for the soft sensor of the gasification temperature.The RNN model and back propagation(BP)neural network model are then established with training-set data from gasification results.Compared with prediction set data from the gasification results,the RNN model is found to be much better than the BP neural network based on important indexes such as the mean square error(MSE),mean absolute error(MAE)and standard deviation(SD).The results show that the MSE of the prediction set of the RNN model is 6.25℃,the MAE is 10.33℃and the SD is 3.88℃,respectively.The overall accuracy,the average accuracy and the stability effects are well within the accepted ranges for the results as such.展开更多
Non-isothermal method was used to study gasification characteristics of three coal chars and one biomass char.Four chars were made from anthracite coal（A）,bituminous coal（B）,lignite coal（L）,and wood refuse（W）,...Non-isothermal method was used to study gasification characteristics of three coal chars and one biomass char.Four chars were made from anthracite coal（A）,bituminous coal（B）,lignite coal（L）,and wood refuse（W）,respectively.The gasification process was studied by random pore model（RPM）,unreacted core model（URCM）and volumetric model（VM）.With an increase in metamorphic grade,the gasification reactivity of coal char decreased,and the gasification reactivity of biomass char was close to that of low metamorphic coal char.With an increase in heating rate,the gasification of all samples moved towards high temperature zone,and the whole gasification time decreased.It was concluded from kinetics analysis that the above-mentioned three models could be used to describe the gasification process of coal char,and the RPM fitted the best among the three models.In the RPM,the activation energies of gasification were193.9,225.3 and 202.8 kJ/mol for anthracite coal char,bituminous coal char and lignite coal char,respectively.The gasification process of biomass char could be described by the URCM and VM,while the URCM performed better.The activation energy of gasification of wood refuse char calculated by the URCM was 282.0 kJ/mol.展开更多
The gasification reactivities of three kinds of different coal ranks(Huolinhe lignite,Shenmu bituminous coal,and Jincheng anthracite)with CO_(2) and H_(2)O was carried out on a self-made pressurized fixed-bed reactor ...The gasification reactivities of three kinds of different coal ranks(Huolinhe lignite,Shenmu bituminous coal,and Jincheng anthracite)with CO_(2) and H_(2)O was carried out on a self-made pressurized fixed-bed reactor at increased pressures(up to 1.0 MPa).The physicochemical characteristics of the chars at various levels of carbon conversion were studied via scanning electron microscopy(SEM),X-ray diffraction(XRD),and BET surface area.Results show that the char gasification reactivity increases with increasing partial pressure.The gasification reaction is controlled by pore diffusion,the rate decreases with increasing total system pressure,and under chemical kinetic control there is no pressure dependence.In general,gasification rates decrease for coals of progressively higher rank.The experimental results could be well described by the shrinking core model for three chars during steam and CO_(2) gasification.The values of reaction order n with steam were 0.49,0.46,0.43,respectively.Meanwhile,the values of reaction order n with CO_(2) were 0.31,0.28,0.26,respectively.With the coal rank increasing,the pressure order m is higher,the activation energies increase slightly with steam,and the activation energy with CO_(2) increases noticeably.As the carbon conversion increases,the degree of graphitization is enhanced.The surface area of the gasified char increases rapidly with the progress of gasification and peaks at about 40%of char gasification.展开更多
基金Supported by the Major State Basic Research Development Program of China(2012CB720500)the National Natural Science Foundation of China(U1162202,61174118)+1 种基金the National Science Fund for Outstanding Young Scholars(61222303)Shanghai Leading Academic Discipline Project(B504)
文摘A three stage equilibrium model is developed for coal gasification in the Texaco type coal gasifiersbased on Aspen Plus to calculate the composition of product gas, carbon conversion, and gasification teml^erature. The model is divided into three stages including pyrolysis and combustion stage, char gas reaction stage, and gas p.hase reaction stage. Part of the water produced in thepyrolysis and combust!on stag.e is assumed to be involved inthe second stage to react with the unburned carbon. Carbon conversion is then estimated in the second stage by steam participation ratio expressed as a function of temperature. And the gas product compositions are calculated from gas phase reactions in the third stage. The simulation results are consistent with published experimental data.
基金financial support from the National Natural Science Foundation of China(51762042)the(2019PT-18)+1 种基金the Science and Technology Program of Shaanxi Province(2017GY-136,2018GY-086)the Shaanxi Province Education Department Key Scientific Research Project(18JS123)。
文摘Mineral matter in a residue(RC G)from coal gasification(CG)was removed by two-stage acid leaching.Hierarchical activated carbon(HAC)was prepared by activating RC Gwith CO2.The performance of HAC on removing methylene blue(MB)from an aqueous solution was investigated.HAC was characterized by N2 adsorption–desorption isotherm,Fourier transform infrared spectroscopy,and scanning electron microscopy.The results show that HAC exhibits hierarchical pore structure with high specific surface area(862.76 m2·g-1)and total pore volume(0.684 cm3·g-1),and abundant organic functional groups.The adsorption equilibrium data of MB on HAC are best fitted to the Redlich-Peterson.The kinetic data show that the pseudo-first-order model is more suitable at low MB concentration,while the advantages of the pseudo-second-orderand the Elovich models are more obvious as the concentration increases.According to the thermodynamic parameters,the HAC-MB adsorption process is spontaneous and endothermic.
文摘During underground coal gasification （UCG）, whereby coal is converted to syngas in situ, a cavity is formed in the coal seam. The cavity growth rate （CGR） or the moving rate of the gasification face is affected by controllable （operation pressure, gasification time, geometry of UCG panel） and uncontrollable （coal seam properties） factors. The CGR is usually predicted by mathematical models and laboratory experiments, which are time consuming, cumbersome and expensive. In this paper, a new simple model for CGR is developed using non-linear regression analysis, based on data from 1 l UCG field trials. The empirical model compares satisfactorily with Perkins model and can reliably predict CGR.
文摘The idea of the transformation of coal in underground into synthetic gas so-called syngas is interested in world in many centuries. Underground Coal Gasification （UCG） is an in-situ technique to recover the fuel or feedstock value of coal that is not economically available through conventional recovery technologies. Today, less than one sixth of the world＇s coal is economically accessible. Today, similarly to all other countries in the world also in Slovakia there is an interest in the revival and perfection of the UCG technology. From the viewpoint of content the research is directed toward to increasing heating capacity of syngas. From the standpoint of the methods used the research can be divided into 2 approaches： experiments in UCG laboratory and mathematical modeling, including simulation studies. Both approaches have helped to discover complicated relationships during UCG and they will be the subject of this paper. The most important factors are methods, the humidity of the coal, heat losses, temperatures in relevant zones, the composition of oxidation agents and the permeability of the coal. The calorific value of syngas was found generally to be 0.55-4.45 MJ.Nm^-3 with a maximum of 25.51 MJ.m^-3 if only air is used as the oxidation agent. Where a mixture of air and oxygen is used, calorific values in the range 0.43-6.38 MJ.m^-3 were generally obtained, with maximum 27.53 MJ·m^-3. Analysis was carried out on these big differences in order to improve UCG.
文摘The stability analysis of horizontal wells is essential for a successful underground coal gasification(UCG)operation.In this paper,a new 3D coupled thermo-mechanical numerical modeling is proposed for analyzing the stability of UCG horizontal wells.In this model,the effect of front abutment stresses,syngas pressure,syngas temperature and thermal stresses is considered to predict the mud weight window and drilling mud pressure during UCG process.The results show that the roof caving in UCG panel has a greatest impact on the stability of horizontal well.Moreover,when the time of coal gasification is increased,the well convergence increases and for more stability it is necessary to increase the drilling mud pressure.This research was carried out on the M2 coal seam in Mazino coal deposit(Iran).The results showed that the mud weight window for horizontal well drilling is between 0 and 33 MPa.The appropriate stress for the maximum stability of the horizontal well,taking all the thermal and mechanical parameters into account,is 28 MPa.The suggested numerical method is a comprehensive and consistent way for analyzing the stability of horizontal wells in UCG sites.
文摘The scope of the present paper is to investigate the suitability of a mathematical model for Circulating Fluidized Bed (CFB) coal combustion (developed by the International Energy Agency), to predict and simulate the performance of the 100 kWth CFB for air-blown biomass gasification. The development of a mathematical model allows to simulate the operative conditions during biomass gasification, control the quality of the synthesis gas and improve the gasifier design. The geometrical, mechanical, hydro dynamical and thermo chemical features were introduced in the model by properly setting the input file and, some changes have been made in the code to assure the final convergence. A sensitivity analysis has been performed to study the variation in the input parameters of the program, and it has been finally verified by comparing the results with the empirical data collected during coal and wood combustion tests. The program, in the same case, could not successfully run;probably depending on wood char density value. For these reason the influence of char density will be investigated. The model predicts the development of tar and other hydrocarbons, valuating the agreement between the measured and calculated efficiency. A further development, to consider solid biomass, with a certain volatile percentages (20% - 40%), as a fuel has been previewed and analyzed. Finally some investigations have been carried out to provide some useful indications for future developments of the code, in the biomass gasification
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.
文摘The gasification kinetic modelling of two Victorian brown coal(Yallourn and Maddingley)chars and the validity for entrained flow gasification were investigated in this study.The study was conducted in a thermogravimetric analyzer(TGA)at 750–1100℃,30%–90%CO_(2)concentration using different char particle sizes within 20–106 mm.It was found that random pore model and modified volumetric model are applicable for TGA results,but volumetric model and grain model are not.The effect of particle size under106 mm on gasification rate is very limited.Activation energies of Maddingley char and Yallourn char in CO_(2)gasification are 219–220 and 197–208 k J/mol,respectively.The pre-exponential factors are in the same order of magnitude,and they increased as particle size decreased.A mathematical model was developed to predict carbon conversion over time for entrained flow gasification of Victorian brown coal chars at 1000–1400℃.
基金funding from the Ministry of Science and Higher Education of the Russian Federation (Ural Federal University Program of Development within the Priority-2030 Program)is gratefully acknowledged.
文摘Using a newly developed experimental setup,the features and advantages of an autothermal single-casing atmospheric sub-bituminous coal fluidized bed air-blown gasifier,combining a combustion and gasification section,and mixing the dispersed phase(inert material,char)and heat exchange between them through an annular transfer device,have been revealed.To increase the efficiency of the gasifier,an experimental-computational method was developed find the conditions for optimal operation,combining changing the annular flow's geometry and regulating the primary air for gasification.A simple and reliable multizone thermodynamic calculation model makes it possible to predict the composition of char and syngas in the gasification section with acceptable accuracy.This method confirmed that a two-section fluidized bed gasifier can provide efficient gasification of solid fuels and is suitable for use in small-scale cogeneration plants.Syngas with a heating value of 3.6-4.5 MJ/m^(3)and CGE of 38.2%-42.3%was obtained in the experimental setup without optimizing the primary air flow rate.With optimization,the indicators increased to the heating value of syngas of 5.20-5.34 MJ/m^(3)and CGE of 42.5%-50.0%.With heat regeneration of 0.8,CGE increases to 70%.
文摘Gasification is an efficient method of producing clean synthetic gas which can be used as fuel for electric generation and chemical for industries use. Gasification process simulation of coal inside a generic two-stage entrained flow gasifier to produce syngas was undertaken. Numerical simulation of the oxygen blown coal gasification process inside a two-stage entrained coal gasifier is studied with the commercial CFD solver ANSYS FLUENT. The purpose of this study is to use CFD simulation to improve understanding of the gasification processes in the state of art two-stage entrained flow coal gasifier. Three dimensions, Navier-Stokes equations and species transport equations are solved with the eddy-breakup reaction model to predict gasification processes. The influences of coal/water slurry concentration and O2/coal ratio on the gasification process are investigated. The coal-to-water slurry concentrations in this study were 0.74 and O2/coal ratio is 0.91. Coal slurry fed the predicted concentration of 47.7% and CO was 25% with higher syngas heating value of 27.65 MJ/kg. The flow behavior in the gasifier, especially the single fuel injection design on the second stage, is examined and validated against available data in the literature.
文摘This paper presents a new approach to study the process of coal gasification. Non-linear programming techniques are used to determine the value of the model parameters that depends on coal species and experimental conditions and thus minimize the difference between experimental results and model predictions. Model predictions being in good agreement with the experimental results show that this method of combining model with experiment is effective for modeling complex processes.
基金the National Natural Science Foundation of China(Grant No.50606037).
文摘By considering the features of fluidized-bed reactors and the kinetic mechanism of biomass gasification,a steady-state,isothermal,one-dimensional and twophase mathematical model of biomass gasification kinetics in bubbling fluidized beds was developed.The model assumes the existence of two phases–a bubble and an emulsion phase–with chemical reactions occurring in both phases.The axial gas dispersion in the two phases is accounted for and the pyrolysis of biomass is taken to be instantaneous.The char and gas species CO,CO_(2),H_(2),H_(2)O,CH_(4) and 8 chemical reactions are included in the model.The mathematical model belongs to a typical boundary value problem of ordinary differential equations and its solution is obtained by a Matlab program.Utilizing wood powder as the feedstock,the calculated data show satisfactory agreement with experimental results and proves the effectiveness and reliability of the model.
基金supported by the Science and Technology Innovation Project of CHN Energy(grant number GJNY-20-119)the Science and Technology Innovation Project of CHN Energy(grant number GJNY-21-91).
文摘Gasification temperature measurement is one of the most challenging tasks in an entrained-flow gasifier and often requires indirect calculation using the soft-sensor method,a parameter prediction method using other parameters that are more easily measurable and using correlation equations that are widely accepted in the gasification field for the temperature data.Machine learning is a non-linear prediction method that can adequately act as a soft sensor.Furthermore,the recurrent neural network(RNN)has the function of memorization,which makes it capable of learning how to deal with temporal order.In this paper,the oxygen-coal ratio,CH_(4)content and CO_(2)content determined through the process analysis of a 3000-t/d coal-water slurry gasifier are used as input parameters for the soft sensor of the gasification temperature.The RNN model and back propagation(BP)neural network model are then established with training-set data from gasification results.Compared with prediction set data from the gasification results,the RNN model is found to be much better than the BP neural network based on important indexes such as the mean square error(MSE),mean absolute error(MAE)and standard deviation(SD).The results show that the MSE of the prediction set of the RNN model is 6.25℃,the MAE is 10.33℃and the SD is 3.88℃,respectively.The overall accuracy,the average accuracy and the stability effects are well within the accepted ranges for the results as such.
基金supported by the China Postdoctoral Science Foundation(2016M600043)the Fundamental Research Funds for the Central Universities(FRF-TP-15-063A1)
文摘Non-isothermal method was used to study gasification characteristics of three coal chars and one biomass char.Four chars were made from anthracite coal（A）,bituminous coal（B）,lignite coal（L）,and wood refuse（W）,respectively.The gasification process was studied by random pore model（RPM）,unreacted core model（URCM）and volumetric model（VM）.With an increase in metamorphic grade,the gasification reactivity of coal char decreased,and the gasification reactivity of biomass char was close to that of low metamorphic coal char.With an increase in heating rate,the gasification of all samples moved towards high temperature zone,and the whole gasification time decreased.It was concluded from kinetics analysis that the above-mentioned three models could be used to describe the gasification process of coal char,and the RPM fitted the best among the three models.In the RPM,the activation energies of gasification were193.9,225.3 and 202.8 kJ/mol for anthracite coal char,bituminous coal char and lignite coal char,respectively.The gasification process of biomass char could be described by the URCM and VM,while the URCM performed better.The activation energy of gasification of wood refuse char calculated by the URCM was 282.0 kJ/mol.
基金supported by the Major State Basic Research Development Program of China(973 Program,Grant No.2006JQJ11131)the National High-Tech R&D program of China(863 program,No.2008AA050302).
文摘The gasification reactivities of three kinds of different coal ranks(Huolinhe lignite,Shenmu bituminous coal,and Jincheng anthracite)with CO_(2) and H_(2)O was carried out on a self-made pressurized fixed-bed reactor at increased pressures(up to 1.0 MPa).The physicochemical characteristics of the chars at various levels of carbon conversion were studied via scanning electron microscopy(SEM),X-ray diffraction(XRD),and BET surface area.Results show that the char gasification reactivity increases with increasing partial pressure.The gasification reaction is controlled by pore diffusion,the rate decreases with increasing total system pressure,and under chemical kinetic control there is no pressure dependence.In general,gasification rates decrease for coals of progressively higher rank.The experimental results could be well described by the shrinking core model for three chars during steam and CO_(2) gasification.The values of reaction order n with steam were 0.49,0.46,0.43,respectively.Meanwhile,the values of reaction order n with CO_(2) were 0.31,0.28,0.26,respectively.With the coal rank increasing,the pressure order m is higher,the activation energies increase slightly with steam,and the activation energy with CO_(2) increases noticeably.As the carbon conversion increases,the degree of graphitization is enhanced.The surface area of the gasified char increases rapidly with the progress of gasification and peaks at about 40%of char gasification.
