Ultrasonic airlift loop reactor （UALR） shows potential and wide application for wastewater treatment. In this paper the performance and efficiency of UALR in dimethoate degradation were presented. The effects of O3 ...Ultrasonic airlift loop reactor （UALR） shows potential and wide application for wastewater treatment. In this paper the performance and efficiency of UALR in dimethoate degradation were presented. The effects of O3 flow rate, ultrasonic intensity and initial concentration of dimethoate on degradation rate were investigated. UALR imposed a synergistic effect combining sonochemical merit with high O3 transfer rate. The results showed that UALR not only increased degradation rate, but also was better than the simole sum of degradation by O3 and ultrasound separately. Under the operation conditions of O3 flow of 0.34 m^3·h^-1, ultrasonic intensity 3.71 W.cm^-2, and initial concentration of dimethoate at 20 mg·L^- 1, the degradation rate of dimethoate increased to 80%. UALR seems an advisable choice for treating organic wastewater and this process may have wide application prospect in industry.展开更多
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
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...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-5-chloromethylpyridine with ALR and stirred tank reactor (STR) respectively was compared.展开更多
Residence time distribution (RTD) analysis of liquid phase was conducted in an internal airlift loop reactor (AL) and a bubble column (BC) with the tracer response technique. These data were simulated and compared thr...Residence time distribution (RTD) analysis of liquid phase was conducted in an internal airlift loop reactor (AL) and a bubble column (BC) with the tracer response technique. These data were simulated and compared through several flow mixing models. The modeling results of two-parameter model indicated that there were higher ratio of full mixing zones and lower ratio of bypass flow in AL than in BC. Then a completely mixed-plug flow parallel combined (four-parameter) model was established. Modeling results show that it is more precise and more obvious than two-parameter model.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
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
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
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
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
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
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
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
Pneumatically agitated slurry reactors,including bubble column reactors and airlift loop reactors(ALRs),are important gas-liquid-solid multiphase reactors.These reactors have been widely applied in many processes,espe...Pneumatically agitated slurry reactors,including bubble column reactors and airlift loop reactors(ALRs),are important gas-liquid-solid multiphase reactors.These reactors have been widely applied in many processes,especially in the biological fermentation and energy chemical industry,due to their low shear stress,good mixing,perfect mass-/heat-transfer properties,and relatively low costs.To further improve the performance of slurry reactors(i.e.,mixing and mass/heat transfer)and to satisfy industrial require-ments(e.g.,temperature control,reduction of back-mixing,and product separation),the process intensi-fication of slurry reactors is essential.This article starts by reviewing the latest advancements in the intensification of mixing and mass/heat transfer in these two types of reactors.It then summarizes process-intensification methods for mixing and separation that allow continuous production in these slurry reactors.Process-intensification technology that integrates directional flow in an ALR with simple solid-liquid separation in a hydrocyclone is recommended for its high efficiency and low costs.This arti-cle also systematically addresses vital considerations and challenges,including flow regime discrimina-tion,gas spargers,solid particle effects,and other concerns in slurry reactors.It introduces the progress of numerical simulation using computational fluid dynamics(CFD)for the rational design of slurry reactors and discusses difficulties in modeling.Finally,it presents conclusions and perspectives on the design of industrial slurry reactors.展开更多
Slurry reactors are popular in many industrial processes,involved with numerous chemical and biological mixtures,solid particles with different concentrations and properties,and a wide range of operating conditions.Th...Slurry reactors are popular in many industrial processes,involved with numerous chemical and biological mixtures,solid particles with different concentrations and properties,and a wide range of operating conditions.These factors can significantly affect the hydrodynamic in the slurry reactors,having remarkable effects on the design,scale-up,and operation of the slurry reactors.This article reviews the influences of fluid physical properties,solid particles,and operating conditions on the hydrodynamics in slurry reactors.Firstly,the influence of fluid properties,including the density and viscosity of the individual liquid and gas phases and the interfacial tension,has been reviewed.Secondly,the solid particle properties(i.e.,concentration,density,size,wettability,and shape)on the hydrodynamics have been discussed in detail,and some vital but often ignored features,especially the influences of particle wettability and shape,as well as the variation of surface tension because of solid concentration alteration,are highlighted in this work.Thirdly,the variations of physical properties of fluids,hydrodynamics,and bubble behavior resulted from the temperature and pressure variations are also summarized,and the indirect influences of pressure on viscosity and surface tension are addressed systematically.Finally,conclusions and perspectives of these notable influences on the design and scale-up of industrial slurry reactors are presented.展开更多
Local hydrodynamics in the riser of an external loop airlift reactor （EL-ALR） are identified and the performances of three drag models are evaluated in computational fluid dynamics simulation. The simulation results...Local hydrodynamics in the riser of an external loop airlift reactor （EL-ALR） are identified and the performances of three drag models are evaluated in computational fluid dynamics simulation. The simulation results show that the Schiller-Naumann drag model underestimated the local gas holdup at lower superficial gas velocity whereas the Tomiyama drag model overestimated that at higher superficial gas velocity. By contrast, the dual-bubble-size （DBS）-local drag model gave more reasonable radial and axial distri-butions of gas holdup in all cases. The reason is that the DBS-local drag model gave correct values of the lumped parameter, i,e., the ratio of the drag coefficient to bubble diameter, for varying operating conditions and radial positions. This ratio is reasonably expected to decrease with increasing superficial gas velocity and be smaller in the center and larger near the wall. Only the DBS-local drag model correctly reproduced these trends. The radial profiles of the axial velocity of the liquid and gas predicted by the DBS-local model also agreed well with experimental data.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
文摘Ultrasonic airlift loop reactor （UALR） shows potential and wide application for wastewater treatment. In this paper the performance and efficiency of UALR in dimethoate degradation were presented. The effects of O3 flow rate, ultrasonic intensity and initial concentration of dimethoate on degradation rate were investigated. UALR imposed a synergistic effect combining sonochemical merit with high O3 transfer rate. The results showed that UALR not only increased degradation rate, but also was better than the simole sum of degradation by O3 and ultrasound separately. Under the operation conditions of O3 flow of 0.34 m^3·h^-1, ultrasonic intensity 3.71 W.cm^-2, and initial concentration of dimethoate at 20 mg·L^- 1, the degradation rate of dimethoate increased to 80%. UALR seems an advisable choice for treating organic wastewater and this process may have wide application prospect in industry.
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 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-5-chloromethylpyridine with ALR and stirred tank reactor (STR) respectively was compared.
文摘Residence time distribution (RTD) analysis of liquid phase was conducted in an internal airlift loop reactor (AL) and a bubble column (BC) with the tracer response technique. These data were simulated and compared through several flow mixing models. The modeling results of two-parameter model indicated that there were higher ratio of full mixing zones and lower ratio of bypass flow in AL than in BC. Then a completely mixed-plug flow parallel combined (four-parameter) model was established. Modeling results show that it is more precise and more obvious than two-parameter model.
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 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.
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 (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.
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.
基金supported by the National Key Research and Development Program of China(2016YFB0301701)the National Natural Science Foundation of China(21808234,21878318,and 21938009)+3 种基金the DNL Cooperation Fund,Chinese Academy of Sciences(CAS)(DNL201902)the Strategic Priority Research Program of the CAS(XDA21060400)the QIBEBT and Dalian National Laboratory for Clean Energy of the CAS(QIBEBT ZZBS201803 and QIBEBT I201907)the CAS Key Technology Talent Program.
文摘Pneumatically agitated slurry reactors,including bubble column reactors and airlift loop reactors(ALRs),are important gas-liquid-solid multiphase reactors.These reactors have been widely applied in many processes,especially in the biological fermentation and energy chemical industry,due to their low shear stress,good mixing,perfect mass-/heat-transfer properties,and relatively low costs.To further improve the performance of slurry reactors(i.e.,mixing and mass/heat transfer)and to satisfy industrial require-ments(e.g.,temperature control,reduction of back-mixing,and product separation),the process intensi-fication of slurry reactors is essential.This article starts by reviewing the latest advancements in the intensification of mixing and mass/heat transfer in these two types of reactors.It then summarizes process-intensification methods for mixing and separation that allow continuous production in these slurry reactors.Process-intensification technology that integrates directional flow in an ALR with simple solid-liquid separation in a hydrocyclone is recommended for its high efficiency and low costs.This arti-cle also systematically addresses vital considerations and challenges,including flow regime discrimina-tion,gas spargers,solid particle effects,and other concerns in slurry reactors.It introduces the progress of numerical simulation using computational fluid dynamics(CFD)for the rational design of slurry reactors and discusses difficulties in modeling.Finally,it presents conclusions and perspectives on the design of industrial slurry reactors.
基金supported by the National Natural Science Foundation of China(2187831821808234)+5 种基金the Dalian National Laboratory for Clean Energy Cooperation Fund,CAS(DNL201902)“Transformational Technologies for Clean Energy and Demonstration”,Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)(XDA21060400)Qingdao Institute of Bioenergy and Bioprocess Technology(QIBEBT)and Dalian National Laboratory for Clean Energy(DNL)of CAS(QIBEBT ZZBS201803QIBEBT I201907)Director Innovation Fund of Synthetic Biology Technology Innovation Center of Shandong Province(sdsynbio-2020-ZH02)Project of CNPC-DICP Joint Research Center。
文摘Slurry reactors are popular in many industrial processes,involved with numerous chemical and biological mixtures,solid particles with different concentrations and properties,and a wide range of operating conditions.These factors can significantly affect the hydrodynamic in the slurry reactors,having remarkable effects on the design,scale-up,and operation of the slurry reactors.This article reviews the influences of fluid physical properties,solid particles,and operating conditions on the hydrodynamics in slurry reactors.Firstly,the influence of fluid properties,including the density and viscosity of the individual liquid and gas phases and the interfacial tension,has been reviewed.Secondly,the solid particle properties(i.e.,concentration,density,size,wettability,and shape)on the hydrodynamics have been discussed in detail,and some vital but often ignored features,especially the influences of particle wettability and shape,as well as the variation of surface tension because of solid concentration alteration,are highlighted in this work.Thirdly,the variations of physical properties of fluids,hydrodynamics,and bubble behavior resulted from the temperature and pressure variations are also summarized,and the indirect influences of pressure on viscosity and surface tension are addressed systematically.Finally,conclusions and perspectives of these notable influences on the design and scale-up of industrial slurry reactors are presented.
文摘Local hydrodynamics in the riser of an external loop airlift reactor （EL-ALR） are identified and the performances of three drag models are evaluated in computational fluid dynamics simulation. The simulation results show that the Schiller-Naumann drag model underestimated the local gas holdup at lower superficial gas velocity whereas the Tomiyama drag model overestimated that at higher superficial gas velocity. By contrast, the dual-bubble-size （DBS）-local drag model gave more reasonable radial and axial distri-butions of gas holdup in all cases. The reason is that the DBS-local drag model gave correct values of the lumped parameter, i,e., the ratio of the drag coefficient to bubble diameter, for varying operating conditions and radial positions. This ratio is reasonably expected to decrease with increasing superficial gas velocity and be smaller in the center and larger near the wall. Only the DBS-local drag model correctly reproduced these trends. The radial profiles of the axial velocity of the liquid and gas predicted by the DBS-local model also agreed well with experimental data.
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.
