Coal pyrolysis is a fundamental reaction in the thermal processing and utilization of coal.Investigating the behavior and kinetics of coal pyrolysis is crucial for optimizing,designing,and developing a composite riser...Coal pyrolysis is a fundamental reaction in the thermal processing and utilization of coal.Investigating the behavior and kinetics of coal pyrolysis is crucial for optimizing,designing,and developing a composite riser for the staged pyrolysis gasification process of pulverized coal.In this study,the non-isothermal pyrolysis behavior and kinetics of coal were examined at different heating rates(30,50,100,300,500,700,and 900℃/min)using thermogravimetry(TG)coupled with Fourier-transform infrared spectroscopy.Analysis of the TG/derivative TG(TG/DTG)curves indicated that coal pyrolysis mainly occurred between 300℃ and 700℃.Higher heating rates led to more volatiles being released from the coal,and a higher temperature was required to achieve rapid pyrolysis.Kinetic analysis showed that both the model-free methods(Friedman,Flynn-Wall-Ozawa,and Kissinger-Akahira-Sunose)and the model-based method(Coats-Redfern)effectively describe the coal pyrolysis process.The change in the Ea values between the two kinetic models was consistent throughout the pyrolysis process,and the most probable mechanism was the F2 model(secondary chemical reaction).In addition,the heating rate did not change the overall reaction order of the pyrolysis process;however,a higher heating rate resulted in a decrease in the Ea value during the initial pyrolysis stage.展开更多
In this work, the extractive distillation with heat integration process is extended to separate the pressure-insensitive benzene-cyclohexane azeotrope by using furfural as the entrainer. The optimal design of extracti...In this work, the extractive distillation with heat integration process is extended to separate the pressure-insensitive benzene-cyclohexane azeotrope by using furfural as the entrainer. The optimal design of extractive distillation process is established to achieve minimum energy requirement using the multi-objective genetic algorithm, and the results show that energy saving for this heat integration process is 15.7%. Finally, the control design is performed to investigate the system's dynamic performance, and three control structures are studied. The pressure-compensated temperature control scheme is proposed based on the first two control structures, and the dynamic responses reveal that the feed disturbances in both flow rate and benzene composition can be mitigated well.展开更多
In order to explore the advantages of self-heat recuperative distillation(SHRD) process, the design and control of the SHRD process was studied for the separation of n-butanol and iso-butanol mixtures. The economic su...In order to explore the advantages of self-heat recuperative distillation(SHRD) process, the design and control of the SHRD process was studied for the separation of n-butanol and iso-butanol mixtures. The economic superiority of SHRD process is presented when a comparison on the total annual cost(TAC) of the conventional distillation process, the vapor recompression distillation process and the SHRD process was made. For the SHRD process, 37.74% and 11.35% savings of TAC can be achieved as compared to the conventional distillation process and vapor recompression distillation process, respectively. The dynamic characteristics of this promising SHRD sequence had been studied, and the dynamic responses demonstrated that 10% changes in both feed flow rate and feed composition can be well handled by the control strategy with dual-temperature control. It is proven that the SHRD system not only can provide economical savings but also can operate normally with good controllability.展开更多
Decreasing petroleum reserves and growing alternative fuels requirements have promoted the study of biodiesel production. In this work, two thermally coupled reactive distillation designs for biodiesel production were...Decreasing petroleum reserves and growing alternative fuels requirements have promoted the study of biodiesel production. In this work, two thermally coupled reactive distillation designs for biodiesel production were investigated, and the sensitivity analysis was conducted to obtain the appropriate design values. The thermodynamic analysis and economics evaluation were performed to estimate the superiority of the thermally coupled designs over the base case. The proposed biodiesel production processes were simulated using the simulator Aspen Plus, and calculation results show that the exergy loss and economic cost in the two thermally coupled designs can be greatly reduced. It is found that the thermally coupled side-stripper reactive distillation design provides more economic benefits than the side-rectifier one. The dynamic performance of the thermally coupled side-stripper design was investigated and the results showed that the proposed control structure could effectively handle large feed disturbances.展开更多
Investigations on the pyrolysis and kinetic behaviors during pyrolysis of fossil fuel samples, such as coal, are fundamental for developing the related technology and practical application. In this work, pyrolysis beh...Investigations on the pyrolysis and kinetic behaviors during pyrolysis of fossil fuel samples, such as coal, are fundamental for developing the related technology and practical application. In this work, pyrolysis behavior and kinetics in the pyrolysis process of a coal sample were investigated by the thermogravimetric analyzer at a heating rate of 10, 40, 70,100, 200, and 500 °C/min, respectively. The pyrolysis process could be divided into four stages according to the TG/DTG curves. The first stage was mainly attributed to the removal of volatiles, and the second peak was the polycondensation reaction between the volatile components. It was found that more volatiles could be released from coal during pyrolysis at higher heating rate and the higher pyrolysis temperature was necessary for a rapid pyrolysis process. Kinetic analysis revealed that both the model-free(KAS and FWO) and the Coats-Redfern methods were suitable to describing the pyrolysis process, and the variation of activation energy(E) with the two types of kinetic models was consistent during the whole pyrolysis process. Furthermore, the heating rate did not alter the reaction sequence of the whole pyrolysis process, but higher heating rate could make the E value of the initial pyrolysis stage smaller.展开更多
In this paper,the structure and characteristics of the NS high-efficiency composite trays based on the doublelayer aperture jet sieve plate and compositely structured packing were investigated.The effect of aperture a...In this paper,the structure and characteristics of the NS high-efficiency composite trays based on the doublelayer aperture jet sieve plate and compositely structured packing were investigated.The effect of aperture and opening ratio of plate on the fluid dynamics of the NS high-efficiency composite trays,such as the dry tray pressure drop,the wet tray pressure drop,the entrainment,the froth height,the leakage and mass transfer characteristics,were investigated.As a result, the low pressure drop,the high efficiency and the high capacity are the main advantages of the NS high-efficiency composite trays compared to other types of trays.According to this study,small aperture is useful for reducing the pressure drop and entrainment with a high mass transfer efficiency;while large aperture can achieve high capacity and efficiency in a broader operating range at the same pressure drop and entrainment.展开更多
To study the hydrodynamic characteristics of gas-solid-phase flow in a pulse riser,a dense discrete particle model considering particle collisions and solid volume fraction is used.The core-annular flow in the enlarge...To study the hydrodynamic characteristics of gas-solid-phase flow in a pulse riser,a dense discrete particle model considering particle collisions and solid volume fraction is used.The core-annular flow in the enlarged-diameter section of the pulse riser is described,which can be destroyed with a high superficial gas velocity.The particle trajectory crossing effect and particle-particle and particle-wall collisions in the reduced-diameter section of the pulse riser can also destroy the core-annular flow and enhance the gas-solid interaction.The solid volume fraction exhibits an S-type distribution at different solid mass rates.The distribution of axial velocity,radial velocity,and relative slip velocity is investigated by analyzing the simulated results at different pulse riser diameter ratios.A suitable pulse riser diameter ratio can improve the performance of the pulse riser.展开更多
The thermogravimetry analyzer coupled with the pyrolysis gas chromatography/time-of-flight mass spectrometry technology was used in this study to investigate the mass loss behavior and volatile release characteristics...The thermogravimetry analyzer coupled with the pyrolysis gas chromatography/time-of-flight mass spectrometry technology was used in this study to investigate the mass loss behavior and volatile release characteristics of a bituminous coal. The results showed that with an increasing heating rate, the characteristic parameters and TG/DTG curves shifted obviously to the higher temperature region. The pyrolysis of a bituminous coal at different heating rates can be divided into two stages according to the Coats-Redfern(C-R) plots. The activation energy obtained from the C-R method is 50.21—85.14 kJ/mol and 5.14—7.24 kJ/mol at a heating rate range of 8—300 °C/min for the first and second pyrolysis stages, respectively. Aromatic hydrocarbons were dominant in the volatile products during fast pyrolysis of the coal, followed by the olefins, whereas the phenols were the third major components. With the increase of pyrolysis temperature, the heavy components in the volatile species increased; meanwhile the phenol cracking reactions were intensified. The carbon number of olefins was mainly concentrated in 3—9, and the aromatics were mainly composed of the compounds of C_6—C_(13).This study can provide a basic reference for fast pyrolysis of coal and other thermal chemical conversion processes.展开更多
To meet the requirements for fast and efficient gas-solid separation at the outlet of a gas-solid concurrent downflow fluidized bed(downer),a new horizontal gas-solid rapid separator was designed based on the joint ac...To meet the requirements for fast and efficient gas-solid separation at the outlet of a gas-solid concurrent downflow fluidized bed(downer),a new horizontal gas-solid rapid separator was designed based on the joint action of centrifugal and inertial forces.Under the same experimental conditions,a fluid catalytic cracking(FCC)catalyst was used as the material(with a particle density of 1500 kg/m3 and a mean particle size of 45.8μm)to experimentally investigate the effects of the insertion length of gas outlet pipe,the bypass cylinder,the gas outlet direction,and the secondary separation structure on the separator performance.The results showed that with an inlet gas flow rate of 14.5 m/s and a gas phase solid content of 60―835 g/m3,the downer system achieved a gas-solid separation efficiency of above 99.5%,with the separator’s pressure drop within 1846 Pa(when the separator included a bypass cylinder and a secondary separation structure with a proper insertion length of gas outlet pipe).展开更多
基金the financial support from the National Natural Science Foundation of China(Grant No.21576293 and 21576294)。
文摘Coal pyrolysis is a fundamental reaction in the thermal processing and utilization of coal.Investigating the behavior and kinetics of coal pyrolysis is crucial for optimizing,designing,and developing a composite riser for the staged pyrolysis gasification process of pulverized coal.In this study,the non-isothermal pyrolysis behavior and kinetics of coal were examined at different heating rates(30,50,100,300,500,700,and 900℃/min)using thermogravimetry(TG)coupled with Fourier-transform infrared spectroscopy.Analysis of the TG/derivative TG(TG/DTG)curves indicated that coal pyrolysis mainly occurred between 300℃ and 700℃.Higher heating rates led to more volatiles being released from the coal,and a higher temperature was required to achieve rapid pyrolysis.Kinetic analysis showed that both the model-free methods(Friedman,Flynn-Wall-Ozawa,and Kissinger-Akahira-Sunose)and the model-based method(Coats-Redfern)effectively describe the coal pyrolysis process.The change in the Ea values between the two kinetic models was consistent throughout the pyrolysis process,and the most probable mechanism was the F2 model(secondary chemical reaction).In addition,the heating rate did not change the overall reaction order of the pyrolysis process;however,a higher heating rate resulted in a decrease in the Ea value during the initial pyrolysis stage.
基金supported by the National Natural Science Foundation of China(grant number 21476261)the Key Research and Development Plan Project of Shandong Province(grant number 2015GGX107004)
文摘In this work, the extractive distillation with heat integration process is extended to separate the pressure-insensitive benzene-cyclohexane azeotrope by using furfural as the entrainer. The optimal design of extractive distillation process is established to achieve minimum energy requirement using the multi-objective genetic algorithm, and the results show that energy saving for this heat integration process is 15.7%. Finally, the control design is performed to investigate the system's dynamic performance, and three control structures are studied. The pressure-compensated temperature control scheme is proposed based on the first two control structures, and the dynamic responses reveal that the feed disturbances in both flow rate and benzene composition can be mitigated well.
基金Financial supports from the National Natural Science Foundation of China(Grant:21276279 and Grant:21476261)the Fundamental Research Funds for the Central Universities(No.14CX05030ANo.15CX06042A)
文摘In order to explore the advantages of self-heat recuperative distillation(SHRD) process, the design and control of the SHRD process was studied for the separation of n-butanol and iso-butanol mixtures. The economic superiority of SHRD process is presented when a comparison on the total annual cost(TAC) of the conventional distillation process, the vapor recompression distillation process and the SHRD process was made. For the SHRD process, 37.74% and 11.35% savings of TAC can be achieved as compared to the conventional distillation process and vapor recompression distillation process, respectively. The dynamic characteristics of this promising SHRD sequence had been studied, and the dynamic responses demonstrated that 10% changes in both feed flow rate and feed composition can be well handled by the control strategy with dual-temperature control. It is proven that the SHRD system not only can provide economical savings but also can operate normally with good controllability.
基金Financial supports of the National Natural Science Foundation of China(Grant:21276279 and Grant:21476261)the Fundamental Research Funds for the Central Universities(No.14CX05030ANo.15CX06042A)
文摘Decreasing petroleum reserves and growing alternative fuels requirements have promoted the study of biodiesel production. In this work, two thermally coupled reactive distillation designs for biodiesel production were investigated, and the sensitivity analysis was conducted to obtain the appropriate design values. The thermodynamic analysis and economics evaluation were performed to estimate the superiority of the thermally coupled designs over the base case. The proposed biodiesel production processes were simulated using the simulator Aspen Plus, and calculation results show that the exergy loss and economic cost in the two thermally coupled designs can be greatly reduced. It is found that the thermally coupled side-stripper reactive distillation design provides more economic benefits than the side-rectifier one. The dynamic performance of the thermally coupled side-stripper design was investigated and the results showed that the proposed control structure could effectively handle large feed disturbances.
基金the financial support from the National Natural Science Foundation of China(Grant Nos.21576293 and 21576294)
文摘Investigations on the pyrolysis and kinetic behaviors during pyrolysis of fossil fuel samples, such as coal, are fundamental for developing the related technology and practical application. In this work, pyrolysis behavior and kinetics in the pyrolysis process of a coal sample were investigated by the thermogravimetric analyzer at a heating rate of 10, 40, 70,100, 200, and 500 °C/min, respectively. The pyrolysis process could be divided into four stages according to the TG/DTG curves. The first stage was mainly attributed to the removal of volatiles, and the second peak was the polycondensation reaction between the volatile components. It was found that more volatiles could be released from coal during pyrolysis at higher heating rate and the higher pyrolysis temperature was necessary for a rapid pyrolysis process. Kinetic analysis revealed that both the model-free(KAS and FWO) and the Coats-Redfern methods were suitable to describing the pyrolysis process, and the variation of activation energy(E) with the two types of kinetic models was consistent during the whole pyrolysis process. Furthermore, the heating rate did not alter the reaction sequence of the whole pyrolysis process, but higher heating rate could make the E value of the initial pyrolysis stage smaller.
基金supported by the Key Project of Chinese National Programs for Fundamental Research and Development(973 Program) (contract number:2005CB221204-5)
文摘In this paper,the structure and characteristics of the NS high-efficiency composite trays based on the doublelayer aperture jet sieve plate and compositely structured packing were investigated.The effect of aperture and opening ratio of plate on the fluid dynamics of the NS high-efficiency composite trays,such as the dry tray pressure drop,the wet tray pressure drop,the entrainment,the froth height,the leakage and mass transfer characteristics,were investigated.As a result, the low pressure drop,the high efficiency and the high capacity are the main advantages of the NS high-efficiency composite trays compared to other types of trays.According to this study,small aperture is useful for reducing the pressure drop and entrainment with a high mass transfer efficiency;while large aperture can achieve high capacity and efficiency in a broader operating range at the same pressure drop and entrainment.
基金This study was supported by the National Natural Science Foundation of China(No.21878335,21576293,and 21576294)the Major Scientific and Technological Innovation Projects in Shandong Province of China(No.2018CXGC0301)+1 种基金the Fundamental Research Funds for the Central Universities(18CX02121A)The authors gratefully acknowledge the financial support from the State Key Laboratory of Heavy Oil Processing and the Shandong Natural Science Foundation(ZR2017QEE006).
文摘To study the hydrodynamic characteristics of gas-solid-phase flow in a pulse riser,a dense discrete particle model considering particle collisions and solid volume fraction is used.The core-annular flow in the enlarged-diameter section of the pulse riser is described,which can be destroyed with a high superficial gas velocity.The particle trajectory crossing effect and particle-particle and particle-wall collisions in the reduced-diameter section of the pulse riser can also destroy the core-annular flow and enhance the gas-solid interaction.The solid volume fraction exhibits an S-type distribution at different solid mass rates.The distribution of axial velocity,radial velocity,and relative slip velocity is investigated by analyzing the simulated results at different pulse riser diameter ratios.A suitable pulse riser diameter ratio can improve the performance of the pulse riser.
基金financial support from the National Natural Science Foundation of China (Grant Nos. 21576293 and 21576294)
文摘The thermogravimetry analyzer coupled with the pyrolysis gas chromatography/time-of-flight mass spectrometry technology was used in this study to investigate the mass loss behavior and volatile release characteristics of a bituminous coal. The results showed that with an increasing heating rate, the characteristic parameters and TG/DTG curves shifted obviously to the higher temperature region. The pyrolysis of a bituminous coal at different heating rates can be divided into two stages according to the Coats-Redfern(C-R) plots. The activation energy obtained from the C-R method is 50.21—85.14 kJ/mol and 5.14—7.24 kJ/mol at a heating rate range of 8—300 °C/min for the first and second pyrolysis stages, respectively. Aromatic hydrocarbons were dominant in the volatile products during fast pyrolysis of the coal, followed by the olefins, whereas the phenols were the third major components. With the increase of pyrolysis temperature, the heavy components in the volatile species increased; meanwhile the phenol cracking reactions were intensified. The carbon number of olefins was mainly concentrated in 3—9, and the aromatics were mainly composed of the compounds of C_6—C_(13).This study can provide a basic reference for fast pyrolysis of coal and other thermal chemical conversion processes.
基金The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China(21576294 and 21706287).
文摘To meet the requirements for fast and efficient gas-solid separation at the outlet of a gas-solid concurrent downflow fluidized bed(downer),a new horizontal gas-solid rapid separator was designed based on the joint action of centrifugal and inertial forces.Under the same experimental conditions,a fluid catalytic cracking(FCC)catalyst was used as the material(with a particle density of 1500 kg/m3 and a mean particle size of 45.8μm)to experimentally investigate the effects of the insertion length of gas outlet pipe,the bypass cylinder,the gas outlet direction,and the secondary separation structure on the separator performance.The results showed that with an inlet gas flow rate of 14.5 m/s and a gas phase solid content of 60―835 g/m3,the downer system achieved a gas-solid separation efficiency of above 99.5%,with the separator’s pressure drop within 1846 Pa(when the separator included a bypass cylinder and a secondary separation structure with a proper insertion length of gas outlet pipe).
