Rare earth oxide was prepared via direct pyrolysis of rare earth chloride solution. Based on this technique, a new-type jet-flow pyrolysis reactor was designed, and then the fluid dynamics (pressure and velocity) insi...Rare earth oxide was prepared via direct pyrolysis of rare earth chloride solution. Based on this technique, a new-type jet-flow pyrolysis reactor was designed, and then the fluid dynamics (pressure and velocity) inside the reactor was numerically simulated using a computational fluid dynamics method. The self-produced pressure (p) and the fuel inlet velocity (v) satisfied a quadratic function,p=0.06v2+0.23v?4.49. To fully utilize the combustion-generated heat in pyrolysis of rare earth chloride, an appropriate external pressure p=v2+3v?4.27 should be imposed at the feed inlet. The 1.25- and 1.5-fold increase of feed inlet diameter resulted in decline of adsorption dynamic pressure, but the intake of rare earth chloride increased by more than 30% and 60%, respectively. The fluid flow in the reactor was affected by the feeding rate; the fluid flow peaked near the throat of venturi and gradually smoothed down at the jet-flow reactor’s terminal along with the sharp decline of feeding rate.展开更多
In this study, the mercury adsorption characteristics of HBr-modified fly ash in an entrained-flow reactor were investigated through thermal decomposition methods. The results show that the mercury adsorption performa...In this study, the mercury adsorption characteristics of HBr-modified fly ash in an entrained-flow reactor were investigated through thermal decomposition methods. The results show that the mercury adsorption performance of the HBr-modified fly ash was enhanced significantly. The mercury species adsorbed by unmodified fly ash were Hg Cl2,Hg S and Hg O. The mercury adsorbed by HBr-modified fly ash, in the entrained-flow reactor,existed in two forms, Hg Br2 and Hg O, and the HBr was the dominant factor promoting oxidation of elemental mercury in the entrained-flow reactor. In the current study, the concentration of Hg Br2 and Hg O in ash from the fine ash vessel was 4.6 times greater than for ash from the coarse ash vessel. The fine ash had better mercury adsorption performance than coarse ash, which is most likely due to the higher specific surface area and longer residence time.展开更多
The oxidative coupling of methane （OCM） to ethylene over a perovskite titanate catalyst in a fixed bed reactor was studied experimentally and numerically. The two-dimensional steady state model accounted for separat...The oxidative coupling of methane （OCM） to ethylene over a perovskite titanate catalyst in a fixed bed reactor was studied experimentally and numerically. The two-dimensional steady state model accounted for separate energy equations for the gas and solid phases coupled with an experimental kinetic model. A lumped kinetic model containing four main species CH4, O2, COx （CO2, CO）, and C2 （C2H4 and C2H6） was used with a plug flow reactor model as well. The results from the model agreed with the experimental data. The model was used to analyze the influence of temperature and feed gas composition on the conversion and selectivity of the reactor performance. The analytical results indicate that the conversion decreases, whereas, C2 selectivity increases by increasing gas hourly space velocity （GHSV） and the methane conversion also decreases by increasing the methane to oxygen ratio.展开更多
Biodiesel industrial production based on a solid base catalyst in a fixed-bed was simulated. The lab and bench scale experiments were carded out effectively, in which the kinetic model is established and it can descri...Biodiesel industrial production based on a solid base catalyst in a fixed-bed was simulated. The lab and bench scale experiments were carded out effectively, in which the kinetic model is established and it can describe the transesterification reaction well. The Antoine equation of biodiesel is regressed with the vapor-liquid data cited of literature. The non-random two liquid （NRTL） model is applied to describe the system of fatty acid methyl ester （FAME）, methanol and glycerol and parameters are obtained. The Ternary phase map is obtained from Aspen Plus via the liquid-liquid equilibrium （LLE） data. In order to describe the production in a fixed-bed performs in industrial scale after being magnified 1 000 times, the Aspen Plus simulation is employed, where two flowsheets are simulated to predict material and energy consumption. The simulation results prove that at least 350. 42 kW energy consumption can be reduced per hour to produce per ton biodiesel compared with data reported in previous references.展开更多
The simulation was made based on the model of pipe-shell reactor that was established by the model of global kinetics of synthesis of dimethyl ether from syngas over a bifunctional catalyst. The results of simulation ...The simulation was made based on the model of pipe-shell reactor that was established by the model of global kinetics of synthesis of dimethyl ether from syngas over a bifunctional catalyst. The results of simulation showed that the selectivity for dimethyl ether （DME） and the conversion of CO were higher but the hot spot was kept below the temperature limit of the pipe-shell reactor. The suitable diameter of the pipe was φ38×2 mm, and the length of the pipe was 5.8 m. The optimal process conditions of the reactor were that the pressure was 5 MPa, the temperature of the cooling water was 240 ℃, and the temperature of the raw gas at inlet of the reactor was 220 ℃. The production of this reactor was 102800 t/y （ton per year） under these conditions.展开更多
A three-phase reactor mathematical model was set up to simulate and design a three-phase bubble column reactor for direct synthesis of dimethyl ether （DME） from syngas, considering both the influence of part inert c...A three-phase reactor mathematical model was set up to simulate and design a three-phase bubble column reactor for direct synthesis of dimethyl ether （DME） from syngas, considering both the influence of part inert carrier backmixing on transfer and the influence of catalyst grain sedimentation on reaction. On the basis of this model, the influences of the size and reaction conditions of a 100000 t/a DME reactor on capacity were investigated. The optimized size of the 10000 t/a DME synthesis reactor was proposed as follows： diameter 3.2 m, height 20 m, built-in 400 tube heat exchanger （Ф 38×2 mm）, and inert heat carrier paraffin oil 68 t and catalyst 34.46 t. Reaction temperature and pressure were important factors influencing the reaction conversion for different size reactors. Under the condition of uniform catalyst concentration distribution, higher pressure and temperature were proposed to achieve a higher production capacity of DME. The best ratio of fresh syngas for DME synthesis was 2.04.展开更多
Catalytic combustion of CH4/air in monolith reactor is simulated using a commercial computational fluid dy-namic code. The user subroutines to describe the heterogeneous reaction at the channel wall in a single channe...Catalytic combustion of CH4/air in monolith reactor is simulated using a commercial computational fluid dy-namic code. The user subroutines to describe the heterogeneous reaction at the channel wall in a single channel and at the channel walls in the whole reactor are incorporated into the program. The correctness of the method is verified by com-paring the simulation results with the experimental data for the whole reactor. Furthermore, it is observed that the model based on the whole reactor is more reasonable than that based on a single channel. Therefore, using the former, the effects of operating conditions such as inlet gas velocity, temperature, concentration and catalyst loading on methane conversion are investigated.展开更多
The performance of binary particles mixing and gas-solids contacting,which is considered qualitatively to have a significant influence on the heat transfer in internal heated circulating fluidized beds,is carefully in...The performance of binary particles mixing and gas-solids contacting,which is considered qualitatively to have a significant influence on the heat transfer in internal heated circulating fluidized beds,is carefully investigated by means of a numerical approach in the newly developed high solids-flux downer lignite pyrolyzer(φ0.1 m×6.5 m).Since binary particles are used in this system,a reasonably validated 3 D,transient,multi-fluid model,in which three heat transfer modes relating to the convection,conduction and radiation are considered,is adopted to simulate the flow behavior,temperature profiles as well as volatile contents.The simulation results showed that the solids stream impinges the left wall surface initially and turns towards the right wall in the further downward direction and then shrinks during this process resulting in that the solids concentrate a little more at the central region.In the further downward section of the downer,the particle flow disperses near the right wall and develops uniformly.Meanwhile,the coal phase is slowly heated in the downer and it is found that most of the heat absorbed by the coal is from the convection heat transfer mode.To explore the heat transfer mechanism more quantitatively,two indexes(mixing index and contacting index)are proposed,and it is found that the mixing index initially increased fast and later remained at a relatively flat state.For the contact index,it shows a trend with a first rising and then falling,finally rising continuously.Also,it is found that the convection heat transfer is closely correlated to the contacting status of gas-coal which indicates that the improving of the gas-coal contacting efficiency should be an effective way to strengthen the coal particle heating process.展开更多
Axial gas-liquid separators have been adopted in fission gas removal systems for the development of thorium molten salt reactors. In our previous study, we observed an unsteady flow phenomenon in which the flow patter...Axial gas-liquid separators have been adopted in fission gas removal systems for the development of thorium molten salt reactors. In our previous study, we observed an unsteady flow phenomenon in which the flow pattern is directly dependent on the backpressure in a gas-liquid separator; however, the underlying flow mechanism is still unknown. In order to move a step further in clarifying how the flow pattern evolves with a variation in backpressure, a large eddy simulation(LES) was adopted to study the flow field evolution. In the simulation, an artificial boundary was applied at the separator outlet under the assumption that the backpressure increases linearly. The numerical results indicate that the unsteady flow feature is captured by the LES approach, and the flow transition is mainly due to the axial velocity profile redistribution induced by the backpressure variation. With the increase in backpressure,the axial velocity near the downstream orifice transits from negative to positive. This change in the axial velocity sign forces the unstable spiral vortex to become a stable rectilinear vortex.展开更多
Verification of operation parameters of VVER-1200 NPP Simulator installed at Nuclear Training Center, VINATOM has been performed. This simulator has been supplied for Vietnam in the framework of IAEA TC Project VIE201...Verification of operation parameters of VVER-1200 NPP Simulator installed at Nuclear Training Center, VINATOM has been performed. This simulator has been supplied for Vietnam in the framework of IAEA TC Project VIE2010 on Developing Nuclear Power Infrastructure—Phase II hosted by the Vietnam Atomic Energy Agency (VAEA). The comparison of the main parameters in nominal power operation with design data given in safety analysis report of VVER-1200/V392M as well as Ninh Thuan FSSAR is presented. In this study, the reactor coolant coast-down transient is investigated using the VVER-1200 NPP simulator. The simulated results performed in the simulator through switching off one reactor coolant pump in comparisons with experiment results performed in VVER-1000 reactor are given. The similarity between the measured and simulated results shows that the thermal hydraulic characteristics and the control protection systems are modeled in a reasonable way. A good agreement in operating parameters was found between the VVER-1200 NPP simulator and VVER-1200/V392M’s PSAR.展开更多
The simulation of a high-temperature gas-cooled reactor pebble-bed module(HTR-PM) plant is discussed.This lumped parameter model has the form of a set differential algebraic equations(DAEs) that include stiff equation...The simulation of a high-temperature gas-cooled reactor pebble-bed module(HTR-PM) plant is discussed.This lumped parameter model has the form of a set differential algebraic equations(DAEs) that include stiff equations to model point neutron kinetics.The nested approach is the most common method to solve DAE,but this approach is very expensive and time-consuming due to inner iterations.This paper deals with an alternative approach in which a simultaneous solution method is used.The DAEs are discretized over a time horizon using collocation on finite elements,and Radau collocation points are applied.The resulting nonlinear algebraic equations can be solved by existing solvers.The discrete algorithm is discussed in detail;both accuracy and stability issues are considered.Finally,the simulation results are presented to validate the efficiency and accuracy of the simultaneous approach that takes much less time than the nested one.展开更多
Numerical simulation on the flow,heat transfer and cracking reactions in commercial fluid catalyticcracking(FCC)riser reactors were carried out employing the developed turbulent gas-solid two-phase flow-reac-tion mode...Numerical simulation on the flow,heat transfer and cracking reactions in commercial fluid catalyticcracking(FCC)riser reactors were carried out employing the developed turbulent gas-solid two-phase flow-reac-tion model for FCC riser reactors given in Part Ⅰ of the present paper.Detailed information about the turbulentflow fields in the riser reactor obtained revealed the basic characteristics of the gas-solid two-phase turbulentflows when heat transfer and catalytic cracking reactions were co-existing in the riser.Results showed that thedistributions of the flow,the turbulence kinetic energy and the catalyst particle concentration are not uniform inthe axial,radial and tangential directions.The most complicated part of the riser reactor is the feed injectingzone.The complicated configuration of the turbulent gas-solid two-phase flows would exert a great influence onthe results of interphase heat transfer and cracking reactions.展开更多
Different mathematical models for ethylene furnace reactor tubes were reviewed. On the basis of these models a new mathematical simulation approach for reactor tubes based on computational fluid dynamics （CFD） techn...Different mathematical models for ethylene furnace reactor tubes were reviewed. On the basis of these models a new mathematical simulation approach for reactor tubes based on computational fluid dynamics （CFD） technique was presented. This approach took the flow, heat transfer, mass transfer and thermal cracking reactions in the reactor tubes into consideration. The coupled reactor model was solved with the SIMPLE algorithm. Some detailed information about the flow field, temperature field and concentration distribution in the reactor tubes was obtained, revealing the basic characteristics of the hydrodynamic phenomena and reaction behavior in the reactor tubes. The CFD approach provides the necessary information for conclusive decisions regarding the production optimization, the design and improvement of reactor tubes, and the new techniques implementation.展开更多
Compared with the traditional radial flow reactors(RFRs), the double-ring RFRs possess advantages including lower pressure drop, shorter flow path and greater flow area. According to the Ergun's equation and the c...Compared with the traditional radial flow reactors(RFRs), the double-ring RFRs possess advantages including lower pressure drop, shorter flow path and greater flow area. According to the Ergun's equation and the continuity equation, a two-dimensional hydrodynamic model was established to describe the hydrodynamic behavior in the double-ring RFRs. The successive over-relaxation(SOR) method was applied to solve the two-dimensional hydrodynamic model. The flow assignment parameters(T_i) of mass flow in the inner channel to the outer catalyst bed and the inner catalyst bed were optimized by the Powell method. Simulations showed the trend of change in gas distribution uniformity along the axial direction and the weight hourly space velocity(WHSV) with the variation of reactor size. The model can be used to analyze the reasonability of dehydrogenation reactor design, and it can also provide quantitative reference for the design of new double-ring RFRs.展开更多
In this work,by establishing a three-dimensional physical model of a 1000-ton industrial multi-jet combustion reactor,a hexahedral structured grid was used to discretize the model.Combined with realizable k–εmodel,e...In this work,by establishing a three-dimensional physical model of a 1000-ton industrial multi-jet combustion reactor,a hexahedral structured grid was used to discretize the model.Combined with realizable k–εmodel,eddy-dissipation-concept,discrete-ordinate radiation model,hydrogen 19-step detailed reaction mechanism,air age user-defined-function,velocity field,temperature field,concentration field and gas arrival time in the reactor were numerically simulated.The Euler–Lagrange method combined with the discrete-phase-model was used to reveal the flow characteristics of particles in the reactor,and based on this,the effects of the reactor aspect ratios,central jet gas velocity and particle size on the flow field characteristics and particle back-mixing degree in the reactor were investigated.The results show that with the decrease of aspect ratio in the combustion reactors,the velocity and temperature attenuation in the reactor are intensified,the vortex phenomenon is aggravated,and the residence time distribution of nanoparticles is more dispersed.With the increase in the central jet gas velocities in reactors,the vortex lengthens along the axis,the turbulence intensity increases,and the residence time of particles decreases.The back-mixing degree and residence time of particles in the reactor also decrease with the increase in particle size.The simulation results can provide reference for the structural regulation of nanoparticles and the structural design of combustion reactor in the process of gas combustion synthesis.展开更多
This paper investigates steady-state and dynamic simulation of an industrial fixed-bed ethylene oxide reactor. A mathematical heterogeneous one-dimensional model is developed for simulation of reactor performance in t...This paper investigates steady-state and dynamic simulation of an industrial fixed-bed ethylene oxide reactor. A mathematical heterogeneous one-dimensional model is developed for simulation of reactor performance in the presence of long term deactivation of silver/a-alumina catalyst. In this paper, steady-state model of the reactor is solved and results of steady state simulation are fed to dynamic simulator as initial condition. When results of dynamic simulation are compared with industrial reactor data, it is found that there were good agreements between simulation results and industrial data. The proposed model is also validated by industrial process data for a period of 1100 operating days.展开更多
The final goal of this applied research is to simulate a Natural Gas Combined Cycle (NGCC) power plant with a CO2 capture unit. The originality of this investigation is the integration of a methanation process to prod...The final goal of this applied research is to simulate a Natural Gas Combined Cycle (NGCC) power plant with a CO2 capture unit. The originality of this investigation is the integration of a methanation process to produce the natural gas of the power plant from the captured CO2. The objective of this first part of the investigation is to simulate a methanation reactor for the production of methane using 1 kg/hr. of captured carbon dioxide containing 95% mol. CO2 and 5% mol. H2O. To reach this goal, Aspen Plus software and the Redlich-Kwong-Soave equation of state with modified Huron-Vidal mixing rules are utilized. Three parameters are considered in order to maximize the production of CH4 production: 1) temperature, varying from 250°C to 300°C, 2) pressure varying between 10 atm to 40 atm and 3) [H2/CO2] ratio which varies between 2 to 6. The maximum production of methane of 0.875 kmol/hr. was obtained for the following operating conditions: [H2/CO2] ratio of 3.5, at relatively low temperature (250°C - 270°C) and high pressures 30 and 40 atm.展开更多
Unsteady-state operation has been widely applied in chemical engineering, such as optimizing a process, increasing yield and saving energy, etc. But the knowledge of the flow characteristics in bubble column reactors(...Unsteady-state operation has been widely applied in chemical engineering, such as optimizing a process, increasing yield and saving energy, etc. But the knowledge of the flow characteristics in bubble column reactors(BCRs) under unsteady state control is far from enough. In order to study the flow structures in this operation, the volume of fluid (VOF) model and the standard k-ε model to simulate the evolution of gas-liquid flow in BCRs under the start-up state are combined. For both the symmetry and asymmetry flow, the layout of the gas-inlets, the gas-in velocity, the liquid viscosity and the aspect ratio of the BCR all have effects on the liquid velocity distribution. The simulation results could provide some information for the design and scale-up of the BCRs.展开更多
A three-dimensional geometric model was set up for the oxidative coupling of methane(OCM) fixed bed reactor loaded with Na_3PO_4-Mn/SiO_2/cordierite monolithic catalyst,and an improved Stansch kinetic model was establ...A three-dimensional geometric model was set up for the oxidative coupling of methane(OCM) fixed bed reactor loaded with Na_3PO_4-Mn/SiO_2/cordierite monolithic catalyst,and an improved Stansch kinetic model was established to calculate the OCM reactions using the computational fluid dynamics method and Fluent software.The simulation conditions were completely the same with the experimental conditions that the volume velocity of the reactant is 80 ml·min^(-1) under standard state,the CH_4/O_2 ratio is 3 and the temperature and pressure is800 ℃ and 1 atm,respectively.The contour of the characteristic parameters in the catalyst bed was analyzed,such as the species mass fractions,temperature,the heat flux on side wall surface,pressure,fluid density and velocity.The results showed that the calculated values matched well with the experimental values on the conversion of CH4 and the selectivity of products(C_2H_6,C_2H_4,CO,CO_2 and H_2) in the reactor outlet with an error range of±4%.The mass fractions of CH_4 and O_2 decreased from 0.600 and 0.400 at the catalyst bed inlet to 0.445 and0.120 at the outlet,where the mass fractions of C_2H_6,C_2H_4,CO and CO_2 were 0.0245,0.0460,0.0537 and 0.116,respectively.Due to the existence of laminar boundary layer,the mass fraction contours of each species bent upwards in the vicinity of the boundary layer.The volume of OCM reaction was changing with the proceeding of reaction,and the total moles of products were greater than reactants.The flow field in the catalyst bed maintained constant temperature and pressure.The fluid density decreased gradually from 2.28 kg·m^(-3) at the inlet of the catalyst bed to 2.18 kg·m^(-3) at the outlet of the catalyst bed,while the average velocity magnitude increased from 0.108 m·s-1 to 0.120 m·s^(-1).展开更多
Carbon dioxide(CO2),the main gas emitted from fossil burning,is the primary contributor to global warming.Circulating fluidized bed reactor(CFBR)is proved as an energy-efficient method for post-combustion CO2 capture....Carbon dioxide(CO2),the main gas emitted from fossil burning,is the primary contributor to global warming.Circulating fluidized bed reactor(CFBR)is proved as an energy-efficient method for post-combustion CO2 capture.The numerical simulation by computational fluid dynamics(CFD)is believed as a promising tool to study CO2 adsorption process in CFBR.Although three-dimensional(3D)simulations were proved to have better predicting performance with the experimental results,two-dimensional(2D)simulations have been widely reported for qualitative and quantitative studies on gas-solid behavior in CFBR for its higher computational efficiency recently.However,the discrepancies between 2D and 3D simulations have rarely been evaluated by detailed study.Considering that the differences between the 2D and 3D simulations will vary substantially with the changes of independent operating conditions,it is beneficial to lower computational costs to clarify the effects of dimensionality on the numerical CO2 adsorption runs under various operating conditions.In this work,the comparative analysis for CO2 adsorption in 2D and 3D simulations was conducted to enlighten the effects of dimensionality on the hydrodynamics and reaction behaviors,in which the separation rate,species distribution and hydrodynamic characteristics were comparatively studied for both model frames.With both accuracy and computational costs considered,the viable suggestions were provided in selecting appropriate model frame for the studies on optimization of operating conditions,which directly affect the capture and energy efficiencies of cyclic CO2 capture process in CFBR.展开更多
基金Projects(51204040,U1202274)supported by the National Natural Science Foundation of ChinaProjects(2010AA03A405,2102AA062303)supported by the National High-tech Research and Development Program of China+1 种基金Project(2012BAE01B02)supported by the National Science and Technology Support Program of ChinaProject(N130702001)supported by the Fundamental Research Funds for the Central Universities,China
文摘Rare earth oxide was prepared via direct pyrolysis of rare earth chloride solution. Based on this technique, a new-type jet-flow pyrolysis reactor was designed, and then the fluid dynamics (pressure and velocity) inside the reactor was numerically simulated using a computational fluid dynamics method. The self-produced pressure (p) and the fuel inlet velocity (v) satisfied a quadratic function,p=0.06v2+0.23v?4.49. To fully utilize the combustion-generated heat in pyrolysis of rare earth chloride, an appropriate external pressure p=v2+3v?4.27 should be imposed at the feed inlet. The 1.25- and 1.5-fold increase of feed inlet diameter resulted in decline of adsorption dynamic pressure, but the intake of rare earth chloride increased by more than 30% and 60%, respectively. The fluid flow in the reactor was affected by the feeding rate; the fluid flow peaked near the throat of venturi and gradually smoothed down at the jet-flow reactor’s terminal along with the sharp decline of feeding rate.
基金Financial support from the National High Technology Research and Development Program of China (No. 2013AA065404)Program of Introducing Talents of Discipline to Universities of China (111 Project, B12034)Fundamental Research Funds for the Central Universities (13ZD04) is gratefully acknowledged
文摘In this study, the mercury adsorption characteristics of HBr-modified fly ash in an entrained-flow reactor were investigated through thermal decomposition methods. The results show that the mercury adsorption performance of the HBr-modified fly ash was enhanced significantly. The mercury species adsorbed by unmodified fly ash were Hg Cl2,Hg S and Hg O. The mercury adsorbed by HBr-modified fly ash, in the entrained-flow reactor,existed in two forms, Hg Br2 and Hg O, and the HBr was the dominant factor promoting oxidation of elemental mercury in the entrained-flow reactor. In the current study, the concentration of Hg Br2 and Hg O in ash from the fine ash vessel was 4.6 times greater than for ash from the coarse ash vessel. The fine ash had better mercury adsorption performance than coarse ash, which is most likely due to the higher specific surface area and longer residence time.
文摘The oxidative coupling of methane （OCM） to ethylene over a perovskite titanate catalyst in a fixed bed reactor was studied experimentally and numerically. The two-dimensional steady state model accounted for separate energy equations for the gas and solid phases coupled with an experimental kinetic model. A lumped kinetic model containing four main species CH4, O2, COx （CO2, CO）, and C2 （C2H4 and C2H6） was used with a plug flow reactor model as well. The results from the model agreed with the experimental data. The model was used to analyze the influence of temperature and feed gas composition on the conversion and selectivity of the reactor performance. The analytical results indicate that the conversion decreases, whereas, C2 selectivity increases by increasing gas hourly space velocity （GHSV） and the methane conversion also decreases by increasing the methane to oxygen ratio.
基金The National Basic Research Program of China(973Program)(No.2010CB732206)the National Natural Science Foundation of China(No.21076044,21276050)
文摘Biodiesel industrial production based on a solid base catalyst in a fixed-bed was simulated. The lab and bench scale experiments were carded out effectively, in which the kinetic model is established and it can describe the transesterification reaction well. The Antoine equation of biodiesel is regressed with the vapor-liquid data cited of literature. The non-random two liquid （NRTL） model is applied to describe the system of fatty acid methyl ester （FAME）, methanol and glycerol and parameters are obtained. The Ternary phase map is obtained from Aspen Plus via the liquid-liquid equilibrium （LLE） data. In order to describe the production in a fixed-bed performs in industrial scale after being magnified 1 000 times, the Aspen Plus simulation is employed, where two flowsheets are simulated to predict material and energy consumption. The simulation results prove that at least 350. 42 kW energy consumption can be reduced per hour to produce per ton biodiesel compared with data reported in previous references.
基金Development Project of Shanghai Priority Academic Discipline and Development of Research Projects of China Petroleum and Natural Gas Corporation (No.03js-079)
文摘The simulation was made based on the model of pipe-shell reactor that was established by the model of global kinetics of synthesis of dimethyl ether from syngas over a bifunctional catalyst. The results of simulation showed that the selectivity for dimethyl ether （DME） and the conversion of CO were higher but the hot spot was kept below the temperature limit of the pipe-shell reactor. The suitable diameter of the pipe was φ38×2 mm, and the length of the pipe was 5.8 m. The optimal process conditions of the reactor were that the pressure was 5 MPa, the temperature of the cooling water was 240 ℃, and the temperature of the raw gas at inlet of the reactor was 220 ℃. The production of this reactor was 102800 t/y （ton per year） under these conditions.
基金This work was supported by the National Basic Research Program of China (2005CB221205)
文摘A three-phase reactor mathematical model was set up to simulate and design a three-phase bubble column reactor for direct synthesis of dimethyl ether （DME） from syngas, considering both the influence of part inert carrier backmixing on transfer and the influence of catalyst grain sedimentation on reaction. On the basis of this model, the influences of the size and reaction conditions of a 100000 t/a DME reactor on capacity were investigated. The optimized size of the 10000 t/a DME synthesis reactor was proposed as follows： diameter 3.2 m, height 20 m, built-in 400 tube heat exchanger （Ф 38×2 mm）, and inert heat carrier paraffin oil 68 t and catalyst 34.46 t. Reaction temperature and pressure were important factors influencing the reaction conversion for different size reactors. Under the condition of uniform catalyst concentration distribution, higher pressure and temperature were proposed to achieve a higher production capacity of DME. The best ratio of fresh syngas for DME synthesis was 2.04.
基金Supported by the National Natural Science Foundation of China (No.20136010 and No.20376005).
文摘Catalytic combustion of CH4/air in monolith reactor is simulated using a commercial computational fluid dy-namic code. The user subroutines to describe the heterogeneous reaction at the channel wall in a single channel and at the channel walls in the whole reactor are incorporated into the program. The correctness of the method is verified by com-paring the simulation results with the experimental data for the whole reactor. Furthermore, it is observed that the model based on the whole reactor is more reasonable than that based on a single channel. Therefore, using the former, the effects of operating conditions such as inlet gas velocity, temperature, concentration and catalyst loading on methane conversion are investigated.
基金supported by the National Natural Science Foundation of China(U1710101)。
文摘The performance of binary particles mixing and gas-solids contacting,which is considered qualitatively to have a significant influence on the heat transfer in internal heated circulating fluidized beds,is carefully investigated by means of a numerical approach in the newly developed high solids-flux downer lignite pyrolyzer(φ0.1 m×6.5 m).Since binary particles are used in this system,a reasonably validated 3 D,transient,multi-fluid model,in which three heat transfer modes relating to the convection,conduction and radiation are considered,is adopted to simulate the flow behavior,temperature profiles as well as volatile contents.The simulation results showed that the solids stream impinges the left wall surface initially and turns towards the right wall in the further downward direction and then shrinks during this process resulting in that the solids concentrate a little more at the central region.In the further downward section of the downer,the particle flow disperses near the right wall and develops uniformly.Meanwhile,the coal phase is slowly heated in the downer and it is found that most of the heat absorbed by the coal is from the convection heat transfer mode.To explore the heat transfer mechanism more quantitatively,two indexes(mixing index and contacting index)are proposed,and it is found that the mixing index initially increased fast and later remained at a relatively flat state.For the contact index,it shows a trend with a first rising and then falling,finally rising continuously.Also,it is found that the convection heat transfer is closely correlated to the contacting status of gas-coal which indicates that the improving of the gas-coal contacting efficiency should be an effective way to strengthen the coal particle heating process.
基金supported by the National Natural Science Foundation of China(Nos.11535009 and 51406114)
文摘Axial gas-liquid separators have been adopted in fission gas removal systems for the development of thorium molten salt reactors. In our previous study, we observed an unsteady flow phenomenon in which the flow pattern is directly dependent on the backpressure in a gas-liquid separator; however, the underlying flow mechanism is still unknown. In order to move a step further in clarifying how the flow pattern evolves with a variation in backpressure, a large eddy simulation(LES) was adopted to study the flow field evolution. In the simulation, an artificial boundary was applied at the separator outlet under the assumption that the backpressure increases linearly. The numerical results indicate that the unsteady flow feature is captured by the LES approach, and the flow transition is mainly due to the axial velocity profile redistribution induced by the backpressure variation. With the increase in backpressure,the axial velocity near the downstream orifice transits from negative to positive. This change in the axial velocity sign forces the unstable spiral vortex to become a stable rectilinear vortex.
文摘Verification of operation parameters of VVER-1200 NPP Simulator installed at Nuclear Training Center, VINATOM has been performed. This simulator has been supplied for Vietnam in the framework of IAEA TC Project VIE2010 on Developing Nuclear Power Infrastructure—Phase II hosted by the Vietnam Atomic Energy Agency (VAEA). The comparison of the main parameters in nominal power operation with design data given in safety analysis report of VVER-1200/V392M as well as Ninh Thuan FSSAR is presented. In this study, the reactor coolant coast-down transient is investigated using the VVER-1200 NPP simulator. The simulated results performed in the simulator through switching off one reactor coolant pump in comparisons with experiment results performed in VVER-1000 reactor are given. The similarity between the measured and simulated results shows that the thermal hydraulic characteristics and the control protection systems are modeled in a reasonable way. A good agreement in operating parameters was found between the VVER-1200 NPP simulator and VVER-1200/V392M’s PSAR.
基金Project supported by the National Basic Research Program of China (No. 2009CB320603)the National Natural Science Foundation of China (Nos. 60974007 and 60934007)
文摘The simulation of a high-temperature gas-cooled reactor pebble-bed module(HTR-PM) plant is discussed.This lumped parameter model has the form of a set differential algebraic equations(DAEs) that include stiff equations to model point neutron kinetics.The nested approach is the most common method to solve DAE,but this approach is very expensive and time-consuming due to inner iterations.This paper deals with an alternative approach in which a simultaneous solution method is used.The DAEs are discretized over a time horizon using collocation on finite elements,and Radau collocation points are applied.The resulting nonlinear algebraic equations can be solved by existing solvers.The discrete algorithm is discussed in detail;both accuracy and stability issues are considered.Finally,the simulation results are presented to validate the efficiency and accuracy of the simultaneous approach that takes much less time than the nested one.
文摘Numerical simulation on the flow,heat transfer and cracking reactions in commercial fluid catalyticcracking(FCC)riser reactors were carried out employing the developed turbulent gas-solid two-phase flow-reac-tion model for FCC riser reactors given in Part Ⅰ of the present paper.Detailed information about the turbulentflow fields in the riser reactor obtained revealed the basic characteristics of the gas-solid two-phase turbulentflows when heat transfer and catalytic cracking reactions were co-existing in the riser.Results showed that thedistributions of the flow,the turbulence kinetic energy and the catalyst particle concentration are not uniform inthe axial,radial and tangential directions.The most complicated part of the riser reactor is the feed injectingzone.The complicated configuration of the turbulent gas-solid two-phase flows would exert a great influence onthe results of interphase heat transfer and cracking reactions.
文摘Different mathematical models for ethylene furnace reactor tubes were reviewed. On the basis of these models a new mathematical simulation approach for reactor tubes based on computational fluid dynamics （CFD） technique was presented. This approach took the flow, heat transfer, mass transfer and thermal cracking reactions in the reactor tubes into consideration. The coupled reactor model was solved with the SIMPLE algorithm. Some detailed information about the flow field, temperature field and concentration distribution in the reactor tubes was obtained, revealing the basic characteristics of the hydrodynamic phenomena and reaction behavior in the reactor tubes. The CFD approach provides the necessary information for conclusive decisions regarding the production optimization, the design and improvement of reactor tubes, and the new techniques implementation.
文摘Compared with the traditional radial flow reactors(RFRs), the double-ring RFRs possess advantages including lower pressure drop, shorter flow path and greater flow area. According to the Ergun's equation and the continuity equation, a two-dimensional hydrodynamic model was established to describe the hydrodynamic behavior in the double-ring RFRs. The successive over-relaxation(SOR) method was applied to solve the two-dimensional hydrodynamic model. The flow assignment parameters(T_i) of mass flow in the inner channel to the outer catalyst bed and the inner catalyst bed were optimized by the Powell method. Simulations showed the trend of change in gas distribution uniformity along the axial direction and the weight hourly space velocity(WHSV) with the variation of reactor size. The model can be used to analyze the reasonability of dehydrogenation reactor design, and it can also provide quantitative reference for the design of new double-ring RFRs.
基金supported by the National Natural Science Foundation of China(21978088,91534202,51673063)Shanghai Technology Research Leader(20XD1433600)+4 种基金the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutes of High Learningthe Basic Research Program of Shanghai(17JC1402300)the Shanghai City Board of education research and innovation projectthe Fundamental Research Funds for the Central Universities(222201718002)provided by Feringa Nobel Prize Scientist Joint Research Center。
文摘In this work,by establishing a three-dimensional physical model of a 1000-ton industrial multi-jet combustion reactor,a hexahedral structured grid was used to discretize the model.Combined with realizable k–εmodel,eddy-dissipation-concept,discrete-ordinate radiation model,hydrogen 19-step detailed reaction mechanism,air age user-defined-function,velocity field,temperature field,concentration field and gas arrival time in the reactor were numerically simulated.The Euler–Lagrange method combined with the discrete-phase-model was used to reveal the flow characteristics of particles in the reactor,and based on this,the effects of the reactor aspect ratios,central jet gas velocity and particle size on the flow field characteristics and particle back-mixing degree in the reactor were investigated.The results show that with the decrease of aspect ratio in the combustion reactors,the velocity and temperature attenuation in the reactor are intensified,the vortex phenomenon is aggravated,and the residence time distribution of nanoparticles is more dispersed.With the increase in the central jet gas velocities in reactors,the vortex lengthens along the axis,the turbulence intensity increases,and the residence time of particles decreases.The back-mixing degree and residence time of particles in the reactor also decrease with the increase in particle size.The simulation results can provide reference for the structural regulation of nanoparticles and the structural design of combustion reactor in the process of gas combustion synthesis.
文摘This paper investigates steady-state and dynamic simulation of an industrial fixed-bed ethylene oxide reactor. A mathematical heterogeneous one-dimensional model is developed for simulation of reactor performance in the presence of long term deactivation of silver/a-alumina catalyst. In this paper, steady-state model of the reactor is solved and results of steady state simulation are fed to dynamic simulator as initial condition. When results of dynamic simulation are compared with industrial reactor data, it is found that there were good agreements between simulation results and industrial data. The proposed model is also validated by industrial process data for a period of 1100 operating days.
文摘The final goal of this applied research is to simulate a Natural Gas Combined Cycle (NGCC) power plant with a CO2 capture unit. The originality of this investigation is the integration of a methanation process to produce the natural gas of the power plant from the captured CO2. The objective of this first part of the investigation is to simulate a methanation reactor for the production of methane using 1 kg/hr. of captured carbon dioxide containing 95% mol. CO2 and 5% mol. H2O. To reach this goal, Aspen Plus software and the Redlich-Kwong-Soave equation of state with modified Huron-Vidal mixing rules are utilized. Three parameters are considered in order to maximize the production of CH4 production: 1) temperature, varying from 250°C to 300°C, 2) pressure varying between 10 atm to 40 atm and 3) [H2/CO2] ratio which varies between 2 to 6. The maximum production of methane of 0.875 kmol/hr. was obtained for the following operating conditions: [H2/CO2] ratio of 3.5, at relatively low temperature (250°C - 270°C) and high pressures 30 and 40 atm.
文摘Unsteady-state operation has been widely applied in chemical engineering, such as optimizing a process, increasing yield and saving energy, etc. But the knowledge of the flow characteristics in bubble column reactors(BCRs) under unsteady state control is far from enough. In order to study the flow structures in this operation, the volume of fluid (VOF) model and the standard k-ε model to simulate the evolution of gas-liquid flow in BCRs under the start-up state are combined. For both the symmetry and asymmetry flow, the layout of the gas-inlets, the gas-in velocity, the liquid viscosity and the aspect ratio of the BCR all have effects on the liquid velocity distribution. The simulation results could provide some information for the design and scale-up of the BCRs.
基金Supported by the National Basic Research Program of China(2005CB221405)
文摘A three-dimensional geometric model was set up for the oxidative coupling of methane(OCM) fixed bed reactor loaded with Na_3PO_4-Mn/SiO_2/cordierite monolithic catalyst,and an improved Stansch kinetic model was established to calculate the OCM reactions using the computational fluid dynamics method and Fluent software.The simulation conditions were completely the same with the experimental conditions that the volume velocity of the reactant is 80 ml·min^(-1) under standard state,the CH_4/O_2 ratio is 3 and the temperature and pressure is800 ℃ and 1 atm,respectively.The contour of the characteristic parameters in the catalyst bed was analyzed,such as the species mass fractions,temperature,the heat flux on side wall surface,pressure,fluid density and velocity.The results showed that the calculated values matched well with the experimental values on the conversion of CH4 and the selectivity of products(C_2H_6,C_2H_4,CO,CO_2 and H_2) in the reactor outlet with an error range of±4%.The mass fractions of CH_4 and O_2 decreased from 0.600 and 0.400 at the catalyst bed inlet to 0.445 and0.120 at the outlet,where the mass fractions of C_2H_6,C_2H_4,CO and CO_2 were 0.0245,0.0460,0.0537 and 0.116,respectively.Due to the existence of laminar boundary layer,the mass fraction contours of each species bent upwards in the vicinity of the boundary layer.The volume of OCM reaction was changing with the proceeding of reaction,and the total moles of products were greater than reactants.The flow field in the catalyst bed maintained constant temperature and pressure.The fluid density decreased gradually from 2.28 kg·m^(-3) at the inlet of the catalyst bed to 2.18 kg·m^(-3) at the outlet of the catalyst bed,while the average velocity magnitude increased from 0.108 m·s-1 to 0.120 m·s^(-1).
基金supported by the National Natural Science Foundation of China(21506181,21506179)Natural Science Foundation of Hunan Province(2020JJ3033,2019JJ40281,2018SK2027,2018RS3088,2019SK2112)+1 种基金Research Foundation of Education Bureau of Hunan Province(18B088)Hunan Key Laboratory of Environment Friendly Chemical Process Integration and Hunan 2011 Collaborative Innovation Center of Chemical Engineering&Technology with Environmental Benignity and Effective Resource Utilization,State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering(2020-KF-11).
文摘Carbon dioxide(CO2),the main gas emitted from fossil burning,is the primary contributor to global warming.Circulating fluidized bed reactor(CFBR)is proved as an energy-efficient method for post-combustion CO2 capture.The numerical simulation by computational fluid dynamics(CFD)is believed as a promising tool to study CO2 adsorption process in CFBR.Although three-dimensional(3D)simulations were proved to have better predicting performance with the experimental results,two-dimensional(2D)simulations have been widely reported for qualitative and quantitative studies on gas-solid behavior in CFBR for its higher computational efficiency recently.However,the discrepancies between 2D and 3D simulations have rarely been evaluated by detailed study.Considering that the differences between the 2D and 3D simulations will vary substantially with the changes of independent operating conditions,it is beneficial to lower computational costs to clarify the effects of dimensionality on the numerical CO2 adsorption runs under various operating conditions.In this work,the comparative analysis for CO2 adsorption in 2D and 3D simulations was conducted to enlighten the effects of dimensionality on the hydrodynamics and reaction behaviors,in which the separation rate,species distribution and hydrodynamic characteristics were comparatively studied for both model frames.With both accuracy and computational costs considered,the viable suggestions were provided in selecting appropriate model frame for the studies on optimization of operating conditions,which directly affect the capture and energy efficiencies of cyclic CO2 capture process in CFBR.
