A modified internal-loop airlif reactor (MIALR) with a continuous slurry phase was studied to investigate the local hydrodynamic characteristics, including gas holdup, bubble size, bubble rise velocity and local mas...A modified internal-loop airlif reactor (MIALR) with a continuous slurry phase was studied to investigate the local hydrodynamic characteristics, including gas holdup, bubble size, bubble rise velocity and local mass transfer properties. Based on the analysis of geometrical construction and fluid properties of gas and slurry, MIALR was divided into six flow regions. In these flow regions, the local hydrodynamic characteristics were investigated over a wide range of operating variables. Furthermore, a new method was developed to measure the dissolved oxygen concentration. The volumetric mass-transfer coefficient in six flow regions was also calculated for comparison.展开更多
Hydrodynamics of airlift loop reactors was studied in detail experimentally andtheoretically.An internal airlift loop reactor was designed and set up for this study.An instru-mentation system based on the electrochemi...Hydrodynamics of airlift loop reactors was studied in detail experimentally andtheoretically.An internal airlift loop reactor was designed and set up for this study.An instru-mentation system based on the electrochemical method was adapted to measure local gas holdup andliquid velocity.A two-dimensional two-fluid model based on the first principles was established andimplemented to model the flow in airlift loop reactors.A corrected turbulent model was incorporatedin the simulation.The shear rate,shear stress and energy dissipation are evaluated from the flowfield.The numerically predicted results and experimental data obtained from this work as well as thesereported in literature are analyzed and compared.展开更多
Epoxidation of cyclohexene to cyclohexene oxide was studied in a new type reactor—the ultrasound airlift loop reactor. The influences of ultrasound intensity, molar ratio of isobutyraldehyde to cyclohexene and oxy-ge...Epoxidation of cyclohexene to cyclohexene oxide was studied in a new type reactor—the ultrasound airlift loop reactor. The influences of ultrasound intensity, molar ratio of isobutyraldehyde to cyclohexene and oxy-gen gas flow rate on the conversion of cyclohexene and selectivity of cyclohexene oxide were investigated and dis-cussed, and the optimal operation condition was found, under which 95.2% conversion of cyclohexene and 90.7% selectivity of cyclohexene oxide were achieved. The ultrasonic airlift loop reactor utilizes the synergistic effect of sonochemsitry and higher oxygen transfer rate. Possible reaction mechanisms were outlined and the reason of ul-trasound promotion of epoxidation reactionwas analyzed.展开更多
Inter-phase mass transfer is important to the design and performance of airlift loop reactors for either chemical or biochemical applications, and a good measurement technique is crucial for studying mass transfer in ...Inter-phase mass transfer is important to the design and performance of airlift loop reactors for either chemical or biochemical applications, and a good measurement technique is crucial for studying mass transfer in multiphase systems. According to the model of macro-scale mass transfer in airlift loop reactors, it was proved that the airlift loop reactor can be regarded as a continuous stirred tank reactor for measuring mass transfer coefficient. The calculated mass transfer coefficient on such a basis is different from the volumetric mass transfer coefficient in the macro-scale model and the difference is discussed. To describe the time delay of the probe response to the change of oxygen concentration in the liquid phase, a model taking into account the time constant of response is es-tablished. Sensitivity analysis shows that this model can be used to measure the volumetric mass transfer coefficient. Applying this model to the measurement of volumetric mass transfer coefficient in the loop reactor, results that co-incide with the turbulence theory in the literate were obtained.展开更多
A new process for the direct chlorination of 2-chloro-5-methylpyridine to yield 2-chloro-5-chloro-methylpyridine in an airlift loop reactor (ALR) has been studied.Five main reaction conditions including TR,na/ns,cp,Qg...A new process for the direct chlorination of 2-chloro-5-methylpyridine to yield 2-chloro-5-chloro-methylpyridine in an airlift loop reactor (ALR) has been studied.Five main reaction conditions including TR,na/ns,cp,Qg and dD/dR were optimized.The average molar yield and purity of 2-chloro-5-chloromethylpyridine obtained were 79% and 98.5% respectively under the optimum operating conditions.Finally,the efficiency for the preparation of 2-chloro-50chloromethylpyridine with ALR and stirred tank reactor(STR) respectively was compared.展开更多
The hydrodynamics in a gas-solid airlift loop reactor was investigated systematically using experimental measurements and CFD simulation. In the experiments, the time averaged parameters, such as solid frac- tion and ...The hydrodynamics in a gas-solid airlift loop reactor was investigated systematically using experimental measurements and CFD simulation. In the experiments, the time averaged parameters, such as solid frac- tion and particle velocity, were measured by optical fiber probe. In the simulation, the modified Gidaspow drag model accounting for the interparticles clustering was incorporated into the Eulerian-Eulerian CFD model with particulate-phase kinetic theory. Predicted values of solid fraction and particle velocity were compared with experimental results, validating the drag model and the simulation. The results show that the profiles of particle velocity and solid fraction are uniform in annulus. However, the core-annulus structure appears in other three regions (draft tube region, bottom region and particle diffluence region), which presents the similar heterogeneous feature of aggregative fluidization usually occurred in nor- mal fiuidized beds. Simulated profiles of particle residence time distribution indicate that the airlift loop reactor should be characterized by near perfect mixing.展开更多
A novel fiber optic probe system and a set of commercial ultrasonic Doppler velocimeters have been used to study the hydrodynamic behavior of a three phase airlift loop (TPAL) slurry reactor. Experiments have been ...A novel fiber optic probe system and a set of commercial ultrasonic Doppler velocimeters have been used to study the hydrodynamic behavior of a three phase airlift loop (TPAL) slurry reactor. Experiments have been carried out in a loop reactor with 100 mm inner diameter and 2.5 m height, in which air, tap water and silica gel particles are used as the gas, liquid and solid phase, respectively. The radial profile of gas holdup, bubble size, bubble rising velocity, liquid circulating velocity, and the influence of the main operating conditions such as superficial gas velocity and solids concentration have been studied experimentally in the TPAL slurry reactor. The experimental results show that the bubble characteristics are different in various flow regimes and the radial profiles of some hydrodynamic parameters in the TPAL slurry reactor are more uniform than those in traditional three phase reactors. The distribution of the bubble size and bubble rising velocity can be described by a lognormal function. The influence of superficial gas velocity on the hydrodynamic parameters is more remarkable than that of the solids concentration.展开更多
The objective of this work is to study the reactive crystallization in an airlift-loop reactor(ALR)using the precipitation of Ni(OH)_2 as a model reaction.The growth of Ni(OH)_2 particles in an ALR and a stirred tank ...The objective of this work is to study the reactive crystallization in an airlift-loop reactor(ALR)using the precipitation of Ni(OH)_2 as a model reaction.The growth of Ni(OH)_2 particles in an ALR and a stirred tank was quantified by scanning electronic microscope(SEM),X-ray diffraction(XRD),laser particle analyzer,tap densitometer and optical microscope,and the growth process of Ni(OH)_2 particles is analyzed.It is found that the Ni(OH)_2 particles prepared in an ALR have a better sphericity than those in a stirred tank and the growth of Ni(OH)_2 particle tap density mainly depends on the size of crystallites:the bigger the size of crystallites,the bigger the tap density is.Based on these,the growth process of Ni(OH)_2 particles in ALR is elaborated.Crystallites precipitated from solution aggregate to form large particles with much void.These constituting crystallites continue to grow up,that takes up the void inside particles and makes the tap density increase.展开更多
Oilfield produced water is large quantities of salty water trapped in underground formations and subsisted under high temperatures and pressures that are brought to the surface along with oil during production. Produc...Oilfield produced water is large quantities of salty water trapped in underground formations and subsisted under high temperatures and pressures that are brought to the surface along with oil during production. Produced water(PW) contains a lot of pollutants such as hydrocarbons and metals, this water must be treated before disposal. Therefore, different techniques are being used to treat produced water. Electrocoagulation is an efficient treatment technique involving the dissolution of anodes and formation of electro-coagulants, while the simultaneous generation of H_2 bubbles at the cathode leads to the pollutant removal by flotation. Electrocoagulation(EC)method is one of the most promising and widely used processes to treat oilfield produced water. In the present work, a conventional internal-loop(draught tube) airlift reactor was utilized as electrocoagulation/flotation cell for PW treatment by inserting two aluminum electrodes in the riser section of the airlift reactor. The EC airlift reactor was operated in a batch mode for the liquid phase. Different experimental parameters were studied on the oil and turbidity removal efficiencies such as current density, initial pH, electrocoagulation time, and air injection.The experimental results showed that mixing of the oil droplets in the PW was accomplished using only the liquid recirculation resulted by H_2 microbubbles generated by EC process which enhanced the oil removal. The experimental results further showed that the EC time required achieving ≥ 90% oil removal efficiency decreases from 46 to 15 min when operating current density increases from 6.8 to 45.5 mA·cm^(-2). This reactor type was found to be highly efficient and less energy consuming compared to conventional existing electrochemical cells which used mechanical agitation.展开更多
Local hydrodynamics of a gas–liquid–solid system,such as bubble circulation regime,gas holdup,liquid velocity and axial profile of solid concentration,are studied in a two-stage internal loop airlift reactor.Empiric...Local hydrodynamics of a gas–liquid–solid system,such as bubble circulation regime,gas holdup,liquid velocity and axial profile of solid concentration,are studied in a two-stage internal loop airlift reactor.Empirical correlations for gas holdup and liquid velocity are proposed to ease the reactor design and scale-up.Different bubble circulation regimes were displayed in the first(lower) and second(upper) stages.Increasing superficial gas velocity and solid loading can promote regime transition of the second stage,and the gas holdup of the second stage is higher than that of the lower stage.In addition,the effects of solid loading on bubble behaviour are experimentally investigated for each stage.It is found that bubble size in the downcomer decreases with the presence of solid particles,and bubble size distribution widens under higher superficial gas velocity and lower solid loading.展开更多
New modified combination mathematical models including the pores blocking models and the cake layer models were developed to describe the continuous cross-flow microfiltration in an airlift external loop slurry reacto...New modified combination mathematical models including the pores blocking models and the cake layer models were developed to describe the continuous cross-flow microfiltration in an airlift external loop slurry reactor. The pores blocking models were created based on the standard blocking law and the intermediate blocking law, and then the cake layer models were developed based on the hydrodynamic theory in which the calculation method of porosity of cake layer was newly corrected. The Air-Water-FCC equilibrium catalysts cold model experiment was used to verify the relevant models.Results showed that the calculated values fitted well with experimental data with a relative error of less than 10%.展开更多
In this paper, a 2-D airlift reactor was developed. The streamline and hydrodynamic parameters were measured in a 2-D airlift loop reactor(ALR)with different draft baffles. Three regimes were observed under different ...In this paper, a 2-D airlift reactor was developed. The streamline and hydrodynamic parameters were measured in a 2-D airlift loop reactor(ALR)with different draft baffles. Three regimes were observed under different conditions. Particle image velocimetry(PIV)measurement showed that the liquid velocity distribution in horizontal direction presented different profiles in the three regimes. The length, the height and the spacing of draft baffles were applied in the experiments to optimize the ALR structure. It was found that the draft tube structure is of great importance in determining the hydrodynamics of ALRs. Additionally, the experimental results may serve as a step to the further optimization and design of ALR.展开更多
In this work, the overall gas hold-up in the riser and down-comer of three internal airlift reactors with a working volume of 10.5, 32 and 200 l at the range of temperatures 18℃ - 21℃, under atmospheric pressure was...In this work, the overall gas hold-up in the riser and down-comer of three internal airlift reactors with a working volume of 10.5, 32 and 200 l at the range of temperatures 18℃ - 21℃, under atmospheric pressure was simulated using Com-putational Fluid Dynamics (CFD). The range of superficial gas velocity was 0.5 - 3 cm/s. The three reactors geometrically were similar to each other. CFD simulation and experimental data showed that the gas hold-up in the riser and down-comer increased by increasing the reactor scale. It was concluded that the simulated data were in good agreement with the experimental ones obtained from the literature.展开更多
Oxygen, concentration distributions of the liquid and gas phases along the axial direction of an airlift loop reactor have been calculated for various gas superficial velocities and oxygen consumption rates with water...Oxygen, concentration distributions of the liquid and gas phases along the axial direction of an airlift loop reactor have been calculated for various gas superficial velocities and oxygen consumption rates with water and CMC solutions respectively by applying the axial backmixing model to the riser and the downcomer and the complete mixing model for the separator. The results show that the dissolved oxygen concentration is zero at the bottom part of the downcomer when the rate of dissolved oxygen consumption by microorganisms is very high.展开更多
A new developed external loop airlift slurry reactor, which was integrated with gas–liquid–solid three-phase mixing, mass transfer, and liquid–solid separation simultaneously, was deemed to be a promising slurry re...A new developed external loop airlift slurry reactor, which was integrated with gas–liquid–solid three-phase mixing, mass transfer, and liquid–solid separation simultaneously, was deemed to be a promising slurry reactor due to its prominent advantages such as achieving continuous separation of clear liquid from slurry and cyclic utilization of solid particles without any extra energy, energy-saving, and intrinsic safety design. The principal operating parameters, including gas separator volume, handling capacity, and superficial gas velocity, are systematically investigated here to promote the capabilities of mixing, mass transfer, and yield in the pilot external loop airlift slurry reactor. The influences of top clearance and throughput of the clear liquid on flow regime and gas holdup in the riser, liquid circulating velocity, and volumetric mass transfer coefficient with a typical high solid holdup and free of particles are examined experimentally. It was found that increasing the gas separator volume could promote the liquid circulating velocity by about 14.0% at most. Increasing the handling capacity of the clear liquid from 0.9 m3·h-1 to 3.0 m3·h-1 not only could increase the output without any adverse consequences, but also could enhance the liquid circulating velocity as much as 97.3%. Typical operating conditions investigated here can provide some necessary data and guidelines for this new external loop airlift slurry reactor to upgrade its performances.展开更多
The external loop airlift reactor(ELALR)is widely used for gasliquid reactions.It’s advantage of good heat and mass transfer rates compared to conventional bubble column reactors.In the case of fermentation applicati...The external loop airlift reactor(ELALR)is widely used for gasliquid reactions.It’s advantage of good heat and mass transfer rates compared to conventional bubble column reactors.In the case of fermentation application where a medium is highly viscous and coalescing in nature,internal in riser helps in the improvement of the interfacial area as well as in the reduction of liquidphase back mixing.The computational fluid dynamic(CFD)as a tool is used to design and scaleup of sectionalized external loop airlift reactor.The present work deals with computational fluid dynamics(CFD)techniques and experimental measurement of a gas holdup,liquid circulation velocity,liquid axial velocity,Sauter mean bubble diameter over a broad range of superficial gas velocity 0.0024≤UG≤0.0168 m s 1.The correlation has been made for bubble size distribution with specific power consumption for different plate configurations.The effects of an internal on different mass transfer models have been completed to assess their suitability.The predicted local mass transfer coefficient has been found higher in the sectionalized external loop airlift reactor than the conventional ELALR.展开更多
In this paper, the principles of airlift loop reactor in gas-liquid and gas-liquid-solid systems are extended to gas-solid system. The models on bed average voidage in draft tube and the particle circulation velocity ...In this paper, the principles of airlift loop reactor in gas-liquid and gas-liquid-solid systems are extended to gas-solid system. The models on bed average voidage in draft tube and the particle circulation velocity in a gas-solid loop reactor are deduced. The experiments are also conducted on a Φ600mm×7000mm reactor. The catalyst voidage and catalyst circulation velocity are measured at different radial and axial positions in draft tube and annulus, respectively. The experimental data are analyzed systemically and represented satisfactorily by the proposed models.展开更多
文摘A modified internal-loop airlif reactor (MIALR) with a continuous slurry phase was studied to investigate the local hydrodynamic characteristics, including gas holdup, bubble size, bubble rise velocity and local mass transfer properties. Based on the analysis of geometrical construction and fluid properties of gas and slurry, MIALR was divided into six flow regions. In these flow regions, the local hydrodynamic characteristics were investigated over a wide range of operating variables. Furthermore, a new method was developed to measure the dissolved oxygen concentration. The volumetric mass-transfer coefficient in six flow regions was also calculated for comparison.
基金Supported by the National Natural Science Foundation of China.
文摘Hydrodynamics of airlift loop reactors was studied in detail experimentally andtheoretically.An internal airlift loop reactor was designed and set up for this study.An instru-mentation system based on the electrochemical method was adapted to measure local gas holdup andliquid velocity.A two-dimensional two-fluid model based on the first principles was established andimplemented to model the flow in airlift loop reactors.A corrected turbulent model was incorporatedin the simulation.The shear rate,shear stress and energy dissipation are evaluated from the flowfield.The numerically predicted results and experimental data obtained from this work as well as thesereported in literature are analyzed and compared.
基金Supported by Qinglan Project Foundation of Jiangsu Province and Doctoral Dissertation Innovate Foundation of Nanjing Uni-versity of Technology (No.BSCS200508).
文摘Epoxidation of cyclohexene to cyclohexene oxide was studied in a new type reactor—the ultrasound airlift loop reactor. The influences of ultrasound intensity, molar ratio of isobutyraldehyde to cyclohexene and oxy-gen gas flow rate on the conversion of cyclohexene and selectivity of cyclohexene oxide were investigated and dis-cussed, and the optimal operation condition was found, under which 95.2% conversion of cyclohexene and 90.7% selectivity of cyclohexene oxide were achieved. The ultrasonic airlift loop reactor utilizes the synergistic effect of sonochemsitry and higher oxygen transfer rate. Possible reaction mechanisms were outlined and the reason of ul-trasound promotion of epoxidation reactionwas analyzed.
基金Supported by the Specialized Research Fund for the Program of Higher Education (No.20050003030) and byTsinghua-Zhongda Postdoctoral Fellowship Program (No.20283600131).
文摘Inter-phase mass transfer is important to the design and performance of airlift loop reactors for either chemical or biochemical applications, and a good measurement technique is crucial for studying mass transfer in multiphase systems. According to the model of macro-scale mass transfer in airlift loop reactors, it was proved that the airlift loop reactor can be regarded as a continuous stirred tank reactor for measuring mass transfer coefficient. The calculated mass transfer coefficient on such a basis is different from the volumetric mass transfer coefficient in the macro-scale model and the difference is discussed. To describe the time delay of the probe response to the change of oxygen concentration in the liquid phase, a model taking into account the time constant of response is es-tablished. Sensitivity analysis shows that this model can be used to measure the volumetric mass transfer coefficient. Applying this model to the measurement of volumetric mass transfer coefficient in the loop reactor, results that co-incide with the turbulence theory in the literate were obtained.
基金Natural Science Foundation of Tianjin(No.013605711)National Natural Science Foundation of China(No.20176040)
文摘A new process for the direct chlorination of 2-chloro-5-methylpyridine to yield 2-chloro-5-chloro-methylpyridine in an airlift loop reactor (ALR) has been studied.Five main reaction conditions including TR,na/ns,cp,Qg and dD/dR were optimized.The average molar yield and purity of 2-chloro-5-chloromethylpyridine obtained were 79% and 98.5% respectively under the optimum operating conditions.Finally,the efficiency for the preparation of 2-chloro-50chloromethylpyridine with ALR and stirred tank reactor(STR) respectively was compared.
基金supports by the National Natural Science Foundation of China(Grant Nos.20806090,20976190and20776155).
文摘The hydrodynamics in a gas-solid airlift loop reactor was investigated systematically using experimental measurements and CFD simulation. In the experiments, the time averaged parameters, such as solid frac- tion and particle velocity, were measured by optical fiber probe. In the simulation, the modified Gidaspow drag model accounting for the interparticles clustering was incorporated into the Eulerian-Eulerian CFD model with particulate-phase kinetic theory. Predicted values of solid fraction and particle velocity were compared with experimental results, validating the drag model and the simulation. The results show that the profiles of particle velocity and solid fraction are uniform in annulus. However, the core-annulus structure appears in other three regions (draft tube region, bottom region and particle diffluence region), which presents the similar heterogeneous feature of aggregative fluidization usually occurred in nor- mal fiuidized beds. Simulated profiles of particle residence time distribution indicate that the airlift loop reactor should be characterized by near perfect mixing.
文摘A novel fiber optic probe system and a set of commercial ultrasonic Doppler velocimeters have been used to study the hydrodynamic behavior of a three phase airlift loop (TPAL) slurry reactor. Experiments have been carried out in a loop reactor with 100 mm inner diameter and 2.5 m height, in which air, tap water and silica gel particles are used as the gas, liquid and solid phase, respectively. The radial profile of gas holdup, bubble size, bubble rising velocity, liquid circulating velocity, and the influence of the main operating conditions such as superficial gas velocity and solids concentration have been studied experimentally in the TPAL slurry reactor. The experimental results show that the bubble characteristics are different in various flow regimes and the radial profiles of some hydrodynamic parameters in the TPAL slurry reactor are more uniform than those in traditional three phase reactors. The distribution of the bubble size and bubble rising velocity can be described by a lognormal function. The influence of superficial gas velocity on the hydrodynamic parameters is more remarkable than that of the solids concentration.
基金Supported by the National Key Research and Development Program(2016YFB0301701)the National Natural Science Foundation of China(21406236,91434126)+1 种基金the Major National Scientific Instrument Development Project(21427814)Jiangsu National Synergetic Innovation Center for Advanced Materials
文摘The objective of this work is to study the reactive crystallization in an airlift-loop reactor(ALR)using the precipitation of Ni(OH)_2 as a model reaction.The growth of Ni(OH)_2 particles in an ALR and a stirred tank was quantified by scanning electronic microscope(SEM),X-ray diffraction(XRD),laser particle analyzer,tap densitometer and optical microscope,and the growth process of Ni(OH)_2 particles is analyzed.It is found that the Ni(OH)_2 particles prepared in an ALR have a better sphericity than those in a stirred tank and the growth of Ni(OH)_2 particle tap density mainly depends on the size of crystallites:the bigger the size of crystallites,the bigger the tap density is.Based on these,the growth process of Ni(OH)_2 particles in ALR is elaborated.Crystallites precipitated from solution aggregate to form large particles with much void.These constituting crystallites continue to grow up,that takes up the void inside particles and makes the tap density increase.
文摘Oilfield produced water is large quantities of salty water trapped in underground formations and subsisted under high temperatures and pressures that are brought to the surface along with oil during production. Produced water(PW) contains a lot of pollutants such as hydrocarbons and metals, this water must be treated before disposal. Therefore, different techniques are being used to treat produced water. Electrocoagulation is an efficient treatment technique involving the dissolution of anodes and formation of electro-coagulants, while the simultaneous generation of H_2 bubbles at the cathode leads to the pollutant removal by flotation. Electrocoagulation(EC)method is one of the most promising and widely used processes to treat oilfield produced water. In the present work, a conventional internal-loop(draught tube) airlift reactor was utilized as electrocoagulation/flotation cell for PW treatment by inserting two aluminum electrodes in the riser section of the airlift reactor. The EC airlift reactor was operated in a batch mode for the liquid phase. Different experimental parameters were studied on the oil and turbidity removal efficiencies such as current density, initial pH, electrocoagulation time, and air injection.The experimental results showed that mixing of the oil droplets in the PW was accomplished using only the liquid recirculation resulted by H_2 microbubbles generated by EC process which enhanced the oil removal. The experimental results further showed that the EC time required achieving ≥ 90% oil removal efficiency decreases from 46 to 15 min when operating current density increases from 6.8 to 45.5 mA·cm^(-2). This reactor type was found to be highly efficient and less energy consuming compared to conventional existing electrochemical cells which used mechanical agitation.
基金Supported by the State Key Laboratory of Chemical Engineering(SKL-ChE-16B01)China Postdoctoral Science Foundation(2016M601263)
文摘Local hydrodynamics of a gas–liquid–solid system,such as bubble circulation regime,gas holdup,liquid velocity and axial profile of solid concentration,are studied in a two-stage internal loop airlift reactor.Empirical correlations for gas holdup and liquid velocity are proposed to ease the reactor design and scale-up.Different bubble circulation regimes were displayed in the first(lower) and second(upper) stages.Increasing superficial gas velocity and solid loading can promote regime transition of the second stage,and the gas holdup of the second stage is higher than that of the lower stage.In addition,the effects of solid loading on bubble behaviour are experimentally investigated for each stage.It is found that bubble size in the downcomer decreases with the presence of solid particles,and bubble size distribution widens under higher superficial gas velocity and lower solid loading.
基金financially supported by the National Key Research & Development Program of China (2016YFB0301600)
文摘New modified combination mathematical models including the pores blocking models and the cake layer models were developed to describe the continuous cross-flow microfiltration in an airlift external loop slurry reactor. The pores blocking models were created based on the standard blocking law and the intermediate blocking law, and then the cake layer models were developed based on the hydrodynamic theory in which the calculation method of porosity of cake layer was newly corrected. The Air-Water-FCC equilibrium catalysts cold model experiment was used to verify the relevant models.Results showed that the calculated values fitted well with experimental data with a relative error of less than 10%.
基金Supported by the National Natural Science Foundation of China(No.21406157)
文摘In this paper, a 2-D airlift reactor was developed. The streamline and hydrodynamic parameters were measured in a 2-D airlift loop reactor(ALR)with different draft baffles. Three regimes were observed under different conditions. Particle image velocimetry(PIV)measurement showed that the liquid velocity distribution in horizontal direction presented different profiles in the three regimes. The length, the height and the spacing of draft baffles were applied in the experiments to optimize the ALR structure. It was found that the draft tube structure is of great importance in determining the hydrodynamics of ALRs. Additionally, the experimental results may serve as a step to the further optimization and design of ALR.
文摘In this work, the overall gas hold-up in the riser and down-comer of three internal airlift reactors with a working volume of 10.5, 32 and 200 l at the range of temperatures 18℃ - 21℃, under atmospheric pressure was simulated using Com-putational Fluid Dynamics (CFD). The range of superficial gas velocity was 0.5 - 3 cm/s. The three reactors geometrically were similar to each other. CFD simulation and experimental data showed that the gas hold-up in the riser and down-comer increased by increasing the reactor scale. It was concluded that the simulated data were in good agreement with the experimental ones obtained from the literature.
基金Project supported partially by the Foundation of Chinese Academy of Sciences.
文摘Oxygen, concentration distributions of the liquid and gas phases along the axial direction of an airlift loop reactor have been calculated for various gas superficial velocities and oxygen consumption rates with water and CMC solutions respectively by applying the axial backmixing model to the riser and the downcomer and the complete mixing model for the separator. The results show that the dissolved oxygen concentration is zero at the bottom part of the downcomer when the rate of dissolved oxygen consumption by microorganisms is very high.
基金supported by the National Natural Science Foundation of China (Nos. 21808234,21878318)the DNL Cooperation Fund,CAS(DNL201902)+3 种基金“Transformational Technologies for Clean Energy and Demonstration”, Strategic Priority Research Program of the CAS(XDA21060400)QIBEBT and Dalian National Laboratory for Clean Energy of the CAS(QIBEBT ZZBS201803,QIBEBT I201907)CAS Key Technology Talent ProgramProject of CNPC-DICP Joint Research Center。
文摘A new developed external loop airlift slurry reactor, which was integrated with gas–liquid–solid three-phase mixing, mass transfer, and liquid–solid separation simultaneously, was deemed to be a promising slurry reactor due to its prominent advantages such as achieving continuous separation of clear liquid from slurry and cyclic utilization of solid particles without any extra energy, energy-saving, and intrinsic safety design. The principal operating parameters, including gas separator volume, handling capacity, and superficial gas velocity, are systematically investigated here to promote the capabilities of mixing, mass transfer, and yield in the pilot external loop airlift slurry reactor. The influences of top clearance and throughput of the clear liquid on flow regime and gas holdup in the riser, liquid circulating velocity, and volumetric mass transfer coefficient with a typical high solid holdup and free of particles are examined experimentally. It was found that increasing the gas separator volume could promote the liquid circulating velocity by about 14.0% at most. Increasing the handling capacity of the clear liquid from 0.9 m3·h-1 to 3.0 m3·h-1 not only could increase the output without any adverse consequences, but also could enhance the liquid circulating velocity as much as 97.3%. Typical operating conditions investigated here can provide some necessary data and guidelines for this new external loop airlift slurry reactor to upgrade its performances.
文摘The external loop airlift reactor(ELALR)is widely used for gasliquid reactions.It’s advantage of good heat and mass transfer rates compared to conventional bubble column reactors.In the case of fermentation application where a medium is highly viscous and coalescing in nature,internal in riser helps in the improvement of the interfacial area as well as in the reduction of liquidphase back mixing.The computational fluid dynamic(CFD)as a tool is used to design and scaleup of sectionalized external loop airlift reactor.The present work deals with computational fluid dynamics(CFD)techniques and experimental measurement of a gas holdup,liquid circulation velocity,liquid axial velocity,Sauter mean bubble diameter over a broad range of superficial gas velocity 0.0024≤UG≤0.0168 m s 1.The correlation has been made for bubble size distribution with specific power consumption for different plate configurations.The effects of an internal on different mass transfer models have been completed to assess their suitability.The predicted local mass transfer coefficient has been found higher in the sectionalized external loop airlift reactor than the conventional ELALR.
文摘In this paper, the principles of airlift loop reactor in gas-liquid and gas-liquid-solid systems are extended to gas-solid system. The models on bed average voidage in draft tube and the particle circulation velocity in a gas-solid loop reactor are deduced. The experiments are also conducted on a Φ600mm×7000mm reactor. The catalyst voidage and catalyst circulation velocity are measured at different radial and axial positions in draft tube and annulus, respectively. The experimental data are analyzed systemically and represented satisfactorily by the proposed models.