Volatile organic compounds(VOCs)are generally toxic and harmful substances that can cause health and environmental problems.The removal of VOCs from polymers has become a key problem.The effective devolatilization to ...Volatile organic compounds(VOCs)are generally toxic and harmful substances that can cause health and environmental problems.The removal of VOCs from polymers has become a key problem.The effective devolatilization to remove VOCs from high viscous fluids such as polymer is necessary and is of great importance.In this study,the devolatilization effect of a rotating packed bed(RPB)was studied by using polydimethylsiloxane as the viscous fluid and acetone as the VOC.The devolatilization rate and liquid phase volume(KLa)have been evaluated.The results indicated that the optimum conditions were the high-gravity factor of 60,liquid flow rate of 10 L·h^(-1),and vacuum degree of 0.077 MPa.The dimensionless correlation of KLa was established,and the deviations between predicted and experimental values were less than±28%.The high-gravity technology will result in lower mass transfer resistance in the devolatilization process,enhance the mass transfer process of acetone,and improve the removal effect of acetone.This work provides a promising path for the removal of volatiles from polymers in combination with high-gravity technology.It can provide the basis for the application of RPB in viscous fluids.展开更多
A number of studies have been reported on the applications of supercritical fluids to polymeric processes. The presence of volatiles can affect the end-use properties of polymer materials. Therefore, these volatiles m...A number of studies have been reported on the applications of supercritical fluids to polymeric processes. The presence of volatiles can affect the end-use properties of polymer materials. Therefore, these volatiles must be reduced to a level below the maximum permissible limit. Conventional heat-relevant techniques for polymer devolatilization sometimes have limited effectiveness. Devolatilization with supercritical fluids, however, can enhance removal of volatiles from polymers. A model for diffusion-limited extraction is used to characterize dynamic supercritical fluid devolatilization of spherical polymer particles. The rate of supercritical fluid devolailization for styrene/polystyrene system is measured at 343 K and 18 MPa and at CO2 flow rate of 1.93, 3.27 and 5.62 L·min^-1, respectively. The model analysis, which is consistent with experimental results, indicates that the supercritical fluid devolatilization is not solubility-limited but diffusion-limited when CO2 flow rate is above 4.00 L·min^-1.展开更多
An isothermal kinetic study of a novel technique for reducing agglomerated iron ore by volatiles released by pyrolysis of lean-grade non-coking coal was carried out at temperature from 1050 to 1200℃ for 10-120 min. T...An isothermal kinetic study of a novel technique for reducing agglomerated iron ore by volatiles released by pyrolysis of lean-grade non-coking coal was carried out at temperature from 1050 to 1200℃ for 10-120 min. The reduced samples were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and chemical analysis. A good degree of metallization and reduction was achieved. Gas diffusion through the solid was identified as the reaction-rate-controlling resistance; however, during the initial period, particularly at lower temperatures, resistance to interfacial chemical reaction was also significant, though not dominant. The apparent rate constant was observed to increase marginally with decreasing size of the particles constituting the nuggets. The apparent activation energy of reduction was estimated to be in the range from 49.640 to 51.220 kJ/mol and was not observed to be affected by the particle size. The sulfur and carbon contents in the reduced samples were also determined.展开更多
A general model of coal particle devolatilization has been presented. The difference between the Fu-Zhang model and the previous ones is that the equivalent activation energy, E, and the equivalent frequency factor, K...A general model of coal particle devolatilization has been presented. The difference between the Fu-Zhang model and the previous ones is that the equivalent activation energy, E, and the equivalent frequency factor, K_0, of coal particle devolatilization are independent of the coal type, but depending only on the final temperature, T_∞ , and heating rate of the coal particles. The relationship between E/K_0 and T_∞ has been obtained and found universal for all coal ranks. The present model has been examined by using the experimental data of sixteen coal types. The comparison of calculations with experiments show that the Fu-Zhang model is able to predict more accurately the coal devolatilization at different heating rates, with different particle diameters and various coal types. This model can also be used for modelling coal devolatilization in fluidized beds.展开更多
The coal devolatilzation process of different coals was studied by means of thermogravimetric analysis method. The experimental results and the kinetic parameters of devolatilization, K and E1 have been obtained. A ma...The coal devolatilzation process of different coals was studied by means of thermogravimetric analysis method. The experimental results and the kinetic parameters of devolatilization, K and E1 have been obtained. A mathematical model for coal devolatilization has been proposed, and the model is simple and practical. The predictions of the model are shown to be in agreement with experimental results.展开更多
Pressurized oxy-fuel combustion is a potential combustion technology with high efficiency and low-cost CO_(2)capture capacity.However,there is currently limited research on the basic experimental due to the difficulty...Pressurized oxy-fuel combustion is a potential combustion technology with high efficiency and low-cost CO_(2)capture capacity.However,there is currently limited research on the basic experimental due to the difficulty of experiments,with the predominant focus residing in low-pressure regimes and a dearth of exploration in high-pressure environments.Since the ignition and devolatilization is as the initial step,contributes significantly to the process of coal combustion,this study examines the ignition and devolatilization characteristics of single bituminous coal and anthracite particles in O_(2)/CO_(2)condition under pressures of 0.1 to 4MPa using a visualized high-pressure drop tube furnace(HP-DTF).The dynamic combustion process at this high-pressure environment is captured,facilitating the determination of ignition delay time(IDT)and devolatilization time(DT)of single-particle coal.The results demonstrate that the IDT of coal particles will be lengthened relative to the ambient pressure under the fixed oxygen volume fraction.Bituminous coal and anthracite exhibit homogeneous ignition and heterogeneous ignition respectively.Bituminous coal initially experiences a rapid increase in IDT,followed by a gradual decrease;the drastic change of gas phase properties and the release of volatiles are the main factors leading to the increase of ignition delay,comparing to with 0.1MPa pressured oxy-fuel combustion.The promotion of volatile ignition occurs as a result of increased oxygen partial pressure and a higher heat transfer coefficient,which leads to the shortening of the subsequent IDT.Also,the devolatilization time of bituminous coal showed a positive correlation with pressure,and the value at 4 MPa is about twice that at atmospheric pressure.In summary,this study of the coal ignition deepens the understanding of flame characteristics in the pressure oxygen combustion,which lays a solid foundation for the future pressured oxy-fuel combustion industrial application.展开更多
The removal of a volatile organic compound (VOC) from high viscous liquid was carried out in a rotat-ing packed bed (RPB) in this study. The mixed liquid of syrup and acetone was used as simulated high viscous polymer...The removal of a volatile organic compound (VOC) from high viscous liquid was carried out in a rotat-ing packed bed (RPB) in this study. The mixed liquid of syrup and acetone was used as simulated high viscous polymer solution with acetone as the volatile compound. The influence of the rotating speed of RPB, liquid viscos-ity, liquid flow rate, vacuum degree, and initial acetone content in the liquid on acetone removal efficiency was in-vestigated. The experimental results indicated that the removal efficiency increased with increasing rotating speed and initial acetone content in the viscous liquid and decreased with increasing liquid viscosity and flow rate. It was also observed that acetone removal efficiency increased with an increasing vacuum degree and reached 58% at a vacuum degree of 0.1 MPa. By the comparison with a flash tank devolatilizer, it was found that acetone removal ef-ficiency in RPB increased by about 67%.展开更多
Seven Chinese coals ranking from anthracite to sub-bituminous fromthe Shanxi province were selected for study to forecast thecombustion and NO_x emission behavior. Three UK, one Indonesia andone South Africa coal was ...Seven Chinese coals ranking from anthracite to sub-bituminous fromthe Shanxi province were selected for study to forecast thecombustion and NO_x emission behavior. Three UK, one Indonesia andone South Africa coal was included in the study for reference. A flatflame-turbulent jet apparatus was employed to assess flame stability,ignition performance and NO_x emission behavior for the initial stageof devolatilization and combustion. This apparatus can simulateparticle heating rates, maximum temperatures and the influence of theturbulent Fluid interactions on the fate of volatiles.展开更多
The diffusion coefficient of volatiles in polymer solutions is a crucial parameter to describe the mass transfer efficiency and ability of volatiles.In this research,polyolefin elastomer(POE)was used as a polymer,and ...The diffusion coefficient of volatiles in polymer solutions is a crucial parameter to describe the mass transfer efficiency and ability of volatiles.In this research,polyolefin elastomer(POE)was used as a polymer,and cyclohexane was used as a volatile.A gravimetric analysis was applied to measure the diffusion coefficient of cyclohexane in POE.The devolatilization rate of the POE-cyclohexane system under different conditions was measured.The effects of temperature,film sample thickness,and initial concentration of volatiles on the devolatilization rate were discussed.Based on the devolatilization rate data,the average diffusion coefficient of cyclohexane in POE was obtained by fitting with a mathematical model.The experimental results indicate that the devolatilization rate increased with increasing temperature and initial concentration of volatiles,but it decreased with increasing sample thickness.As the thickness increased,the overall diffusion resistance increased.As the temperature increased,the molecular movement increased,resulting in the increase of average diffusion coefficient.The relationship between the diffusion coefficient of the POE-cyclohexane system and temperature follows the Arrhenius law.The diffusion activation energy E=6201.73 J/mol,and the pre-exponential factor of the diffusion coefficient D0=2.64×10^(-10) m^(2)/s.This work can provide basic data for exploring the devolatilization of POE polymers and serves as a useful reference for enhancing the effect of devolatilization.展开更多
基金the financial support from the Scientific Research Program of Taiyuan University (23TYQN23)
文摘Volatile organic compounds(VOCs)are generally toxic and harmful substances that can cause health and environmental problems.The removal of VOCs from polymers has become a key problem.The effective devolatilization to remove VOCs from high viscous fluids such as polymer is necessary and is of great importance.In this study,the devolatilization effect of a rotating packed bed(RPB)was studied by using polydimethylsiloxane as the viscous fluid and acetone as the VOC.The devolatilization rate and liquid phase volume(KLa)have been evaluated.The results indicated that the optimum conditions were the high-gravity factor of 60,liquid flow rate of 10 L·h^(-1),and vacuum degree of 0.077 MPa.The dimensionless correlation of KLa was established,and the deviations between predicted and experimental values were less than±28%.The high-gravity technology will result in lower mass transfer resistance in the devolatilization process,enhance the mass transfer process of acetone,and improve the removal effect of acetone.This work provides a promising path for the removal of volatiles from polymers in combination with high-gravity technology.It can provide the basis for the application of RPB in viscous fluids.
基金Supported by the National Natural Science Foundation of China (No. 20576123).
文摘A number of studies have been reported on the applications of supercritical fluids to polymeric processes. The presence of volatiles can affect the end-use properties of polymer materials. Therefore, these volatiles must be reduced to a level below the maximum permissible limit. Conventional heat-relevant techniques for polymer devolatilization sometimes have limited effectiveness. Devolatilization with supercritical fluids, however, can enhance removal of volatiles from polymers. A model for diffusion-limited extraction is used to characterize dynamic supercritical fluid devolatilization of spherical polymer particles. The rate of supercritical fluid devolailization for styrene/polystyrene system is measured at 343 K and 18 MPa and at CO2 flow rate of 1.93, 3.27 and 5.62 L·min^-1, respectively. The model analysis, which is consistent with experimental results, indicates that the supercritical fluid devolatilization is not solubility-limited but diffusion-limited when CO2 flow rate is above 4.00 L·min^-1.
基金financial support from Technical Quality Improvement Programme (TEQIP) phase-IIJadavpur University towards fellowship is also acknowledged
文摘An isothermal kinetic study of a novel technique for reducing agglomerated iron ore by volatiles released by pyrolysis of lean-grade non-coking coal was carried out at temperature from 1050 to 1200℃ for 10-120 min. The reduced samples were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and chemical analysis. A good degree of metallization and reduction was achieved. Gas diffusion through the solid was identified as the reaction-rate-controlling resistance; however, during the initial period, particularly at lower temperatures, resistance to interfacial chemical reaction was also significant, though not dominant. The apparent rate constant was observed to increase marginally with decreasing size of the particles constituting the nuggets. The apparent activation energy of reduction was estimated to be in the range from 49.640 to 51.220 kJ/mol and was not observed to be affected by the particle size. The sulfur and carbon contents in the reduced samples were also determined.
文摘A general model of coal particle devolatilization has been presented. The difference between the Fu-Zhang model and the previous ones is that the equivalent activation energy, E, and the equivalent frequency factor, K_0, of coal particle devolatilization are independent of the coal type, but depending only on the final temperature, T_∞ , and heating rate of the coal particles. The relationship between E/K_0 and T_∞ has been obtained and found universal for all coal ranks. The present model has been examined by using the experimental data of sixteen coal types. The comparison of calculations with experiments show that the Fu-Zhang model is able to predict more accurately the coal devolatilization at different heating rates, with different particle diameters and various coal types. This model can also be used for modelling coal devolatilization in fluidized beds.
文摘The coal devolatilzation process of different coals was studied by means of thermogravimetric analysis method. The experimental results and the kinetic parameters of devolatilization, K and E1 have been obtained. A mathematical model for coal devolatilization has been proposed, and the model is simple and practical. The predictions of the model are shown to be in agreement with experimental results.
基金supported by the Funded by Basic Research Program of Jiangsu(Grants No BK20210238)the National Natural Science Foundation of China(52406127)Postgraduate Research&Practice Innovation Program of Jiangsu Province(5003002304)。
文摘Pressurized oxy-fuel combustion is a potential combustion technology with high efficiency and low-cost CO_(2)capture capacity.However,there is currently limited research on the basic experimental due to the difficulty of experiments,with the predominant focus residing in low-pressure regimes and a dearth of exploration in high-pressure environments.Since the ignition and devolatilization is as the initial step,contributes significantly to the process of coal combustion,this study examines the ignition and devolatilization characteristics of single bituminous coal and anthracite particles in O_(2)/CO_(2)condition under pressures of 0.1 to 4MPa using a visualized high-pressure drop tube furnace(HP-DTF).The dynamic combustion process at this high-pressure environment is captured,facilitating the determination of ignition delay time(IDT)and devolatilization time(DT)of single-particle coal.The results demonstrate that the IDT of coal particles will be lengthened relative to the ambient pressure under the fixed oxygen volume fraction.Bituminous coal and anthracite exhibit homogeneous ignition and heterogeneous ignition respectively.Bituminous coal initially experiences a rapid increase in IDT,followed by a gradual decrease;the drastic change of gas phase properties and the release of volatiles are the main factors leading to the increase of ignition delay,comparing to with 0.1MPa pressured oxy-fuel combustion.The promotion of volatile ignition occurs as a result of increased oxygen partial pressure and a higher heat transfer coefficient,which leads to the shortening of the subsequent IDT.Also,the devolatilization time of bituminous coal showed a positive correlation with pressure,and the value at 4 MPa is about twice that at atmospheric pressure.In summary,this study of the coal ignition deepens the understanding of flame characteristics in the pressure oxygen combustion,which lays a solid foundation for the future pressured oxy-fuel combustion industrial application.
基金Supported by the National Natural Science Foundation of China (20821004)the National High Technology Research and Development Program of China (2006AA030202)the Program for New Century Excellent Talents in University of China(NCET-07-0053)
文摘The removal of a volatile organic compound (VOC) from high viscous liquid was carried out in a rotat-ing packed bed (RPB) in this study. The mixed liquid of syrup and acetone was used as simulated high viscous polymer solution with acetone as the volatile compound. The influence of the rotating speed of RPB, liquid viscos-ity, liquid flow rate, vacuum degree, and initial acetone content in the liquid on acetone removal efficiency was in-vestigated. The experimental results indicated that the removal efficiency increased with increasing rotating speed and initial acetone content in the viscous liquid and decreased with increasing liquid viscosity and flow rate. It was also observed that acetone removal efficiency increased with an increasing vacuum degree and reached 58% at a vacuum degree of 0.1 MPa. By the comparison with a flash tank devolatilizer, it was found that acetone removal ef-ficiency in RPB increased by about 67%.
文摘Seven Chinese coals ranking from anthracite to sub-bituminous fromthe Shanxi province were selected for study to forecast thecombustion and NO_x emission behavior. Three UK, one Indonesia andone South Africa coal was included in the study for reference. A flatflame-turbulent jet apparatus was employed to assess flame stability,ignition performance and NO_x emission behavior for the initial stageof devolatilization and combustion. This apparatus can simulateparticle heating rates, maximum temperatures and the influence of theturbulent Fluid interactions on the fate of volatiles.
基金The authors wish to express their thanks for the financial support from the Polyolefin Elastomer Technology Development project(2020B-2619).
文摘The diffusion coefficient of volatiles in polymer solutions is a crucial parameter to describe the mass transfer efficiency and ability of volatiles.In this research,polyolefin elastomer(POE)was used as a polymer,and cyclohexane was used as a volatile.A gravimetric analysis was applied to measure the diffusion coefficient of cyclohexane in POE.The devolatilization rate of the POE-cyclohexane system under different conditions was measured.The effects of temperature,film sample thickness,and initial concentration of volatiles on the devolatilization rate were discussed.Based on the devolatilization rate data,the average diffusion coefficient of cyclohexane in POE was obtained by fitting with a mathematical model.The experimental results indicate that the devolatilization rate increased with increasing temperature and initial concentration of volatiles,but it decreased with increasing sample thickness.As the thickness increased,the overall diffusion resistance increased.As the temperature increased,the molecular movement increased,resulting in the increase of average diffusion coefficient.The relationship between the diffusion coefficient of the POE-cyclohexane system and temperature follows the Arrhenius law.The diffusion activation energy E=6201.73 J/mol,and the pre-exponential factor of the diffusion coefficient D0=2.64×10^(-10) m^(2)/s.This work can provide basic data for exploring the devolatilization of POE polymers and serves as a useful reference for enhancing the effect of devolatilization.
