A coupled system simulating both firebox and reactor is established to study the naphtha pyrolysis in an industrial tubular furnace.The firebox model is based on zone method including combustion,radiation,and convecti...A coupled system simulating both firebox and reactor is established to study the naphtha pyrolysis in an industrial tubular furnace.The firebox model is based on zone method including combustion,radiation,and convection to simulate heat transfer in the furnace.A two-dimensional recirculation model is proposed to estimate the flow field in furnace.The reactor model integrates the feedstock reconstruction model,an auto-generator of detail kinetic schemes,and the reactor simulation model to simulate the reaction process in the tubular coil.The coupled simulation result is compared with industrial process and shows agreement within short computation time.展开更多
Microstructural analysis and fatigue crack propagation behavior of three types of rail steels, was performed. These are premium pearlitic, austenitic manganese （AM） and bainitic rail steels. Rectangular un-notched a...Microstructural analysis and fatigue crack propagation behavior of three types of rail steels, was performed. These are premium pearlitic, austenitic manganese （AM） and bainitic rail steels. Rectangular un-notched and notched test specimens were machined from railheads of each material using electrical discharge machining （EDM） and used for the mechanical properties and fatigue evaluation respectively. Bainitic steel has the highest yield strength, ultimate strength, and strain to failure as compared to both pearlitic and austenitic manganese steels. Fatigue studies showed that the crack speed for the bainitic steel is lower than that for the pearlitie and the AM steels over the entire range of the energy release rate. The bainitic steel exhibits a higher rate of crack deceleration in the second stage, as indicated by the lower slope of the fatigue crack propagation kinetics curve in comparison with the pearlitic and manganese rail steels. This attests to the superior fatigue damage tolerance of the bainitic rail steel in comparison to pearlitic and austenitic manganese rail steels. Microstructural analysis of the three rail steels revealed that bainitic steel has a more intricate structure than AM and pearlitic steels. AM steel shows very few signs of being work hardened or toughened, which usually increases the mechanical properties of the material. As the number of alloying elements increase, the microstructure of the steel becomes more complex, resulting in the increase of mechanical properties and fatigue fracture resistance of bainitic rail steel.展开更多
A new generic reaction in the form of PC_i→PC_m+[i,m]→PC_m+λi,m coke+surplusage has been proposed for describing the catalytic cracking behavior of petroleum narrow cuts or pseudo-components(PCs),where the rate con...A new generic reaction in the form of PC_i→PC_m+[i,m]→PC_m+λi,m coke+surplusage has been proposed for describing the catalytic cracking behavior of petroleum narrow cuts or pseudo-components(PCs),where the rate constant formula is derived from the transition state theory and the coking amount is correlated to the properties of the intermediate substance [i,m].In composing the cracking reaction network for feedstock and product oils,only the product PC m of the proposed generic reaction is used,which together with a criterion for excluding exothermic reactions,distinctly reduces the number of reactions in the network.With the proposed cracking reaction scheme coupled with special pseudo-components,a predictive one-dimensional steady state model for fluid catalytic cracking risers is formulated in the sense that for a given riser and given catalyst,the model parameters are independent of stock oils,product schemes and other operational conditions.The great correlating and predicting capability of the resulted model is tested with production data in different scenarios of four commercial risers.展开更多
This work aims to investigate the intrinsic kinetics of thermal dimerization of C_5 fraction in the reactive distillation process. Experiments are conducted in an 1000-m L stainless steel autoclave under some selected...This work aims to investigate the intrinsic kinetics of thermal dimerization of C_5 fraction in the reactive distillation process. Experiments are conducted in an 1000-m L stainless steel autoclave under some selected design conditions. By means of the weighted least squares method, the intrinsic kinetics of thermal dimerization of C_5 fraction is established, and the corresponding pre-exponential factor as well as the activation energy are determined. For example, the pre-exponential factor A is equal to 4.39×105 and the activation energy E4 a is equal to 6.58×10J/mol for the cyclopentadiene dimerization reaction. The comparison between the experimental and calculated results shows that the kinetics model derived in this work is accurate and reliable, which can be used in the design of reactive distillation columns.展开更多
基金Supported by the National Natural Science Foundation of China(U1462206)
文摘A coupled system simulating both firebox and reactor is established to study the naphtha pyrolysis in an industrial tubular furnace.The firebox model is based on zone method including combustion,radiation,and convection to simulate heat transfer in the furnace.A two-dimensional recirculation model is proposed to estimate the flow field in furnace.The reactor model integrates the feedstock reconstruction model,an auto-generator of detail kinetic schemes,and the reactor simulation model to simulate the reaction process in the tubular coil.The coupled simulation result is compared with industrial process and shows agreement within short computation time.
文摘Microstructural analysis and fatigue crack propagation behavior of three types of rail steels, was performed. These are premium pearlitic, austenitic manganese （AM） and bainitic rail steels. Rectangular un-notched and notched test specimens were machined from railheads of each material using electrical discharge machining （EDM） and used for the mechanical properties and fatigue evaluation respectively. Bainitic steel has the highest yield strength, ultimate strength, and strain to failure as compared to both pearlitic and austenitic manganese steels. Fatigue studies showed that the crack speed for the bainitic steel is lower than that for the pearlitie and the AM steels over the entire range of the energy release rate. The bainitic steel exhibits a higher rate of crack deceleration in the second stage, as indicated by the lower slope of the fatigue crack propagation kinetics curve in comparison with the pearlitic and manganese rail steels. This attests to the superior fatigue damage tolerance of the bainitic rail steel in comparison to pearlitic and austenitic manganese rail steels. Microstructural analysis of the three rail steels revealed that bainitic steel has a more intricate structure than AM and pearlitic steels. AM steel shows very few signs of being work hardened or toughened, which usually increases the mechanical properties of the material. As the number of alloying elements increase, the microstructure of the steel becomes more complex, resulting in the increase of mechanical properties and fatigue fracture resistance of bainitic rail steel.
基金Supported by the National Natural Science Foundation of China(21676012)the Fundamental Research Funds for the Central Universities(Project YS1404)the National High Technology Research and Development Program of China(2007AA04Z191)
文摘A new generic reaction in the form of PC_i→PC_m+[i,m]→PC_m+λi,m coke+surplusage has been proposed for describing the catalytic cracking behavior of petroleum narrow cuts or pseudo-components(PCs),where the rate constant formula is derived from the transition state theory and the coking amount is correlated to the properties of the intermediate substance [i,m].In composing the cracking reaction network for feedstock and product oils,only the product PC m of the proposed generic reaction is used,which together with a criterion for excluding exothermic reactions,distinctly reduces the number of reactions in the network.With the proposed cracking reaction scheme coupled with special pseudo-components,a predictive one-dimensional steady state model for fluid catalytic cracking risers is formulated in the sense that for a given riser and given catalyst,the model parameters are independent of stock oils,product schemes and other operational conditions.The great correlating and predicting capability of the resulted model is tested with production data in different scenarios of four commercial risers.
文摘This work aims to investigate the intrinsic kinetics of thermal dimerization of C_5 fraction in the reactive distillation process. Experiments are conducted in an 1000-m L stainless steel autoclave under some selected design conditions. By means of the weighted least squares method, the intrinsic kinetics of thermal dimerization of C_5 fraction is established, and the corresponding pre-exponential factor as well as the activation energy are determined. For example, the pre-exponential factor A is equal to 4.39×105 and the activation energy E4 a is equal to 6.58×10J/mol for the cyclopentadiene dimerization reaction. The comparison between the experimental and calculated results shows that the kinetics model derived in this work is accurate and reliable, which can be used in the design of reactive distillation columns.
