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
This study reports an experimental investigation on hydrodynamics and mass transfer characteristics in a 15.6x10-3 m3 external loop airlift reactor for oil-in-water micro-emulsions with oil to water volume ratio （φ...This study reports an experimental investigation on hydrodynamics and mass transfer characteristics in a 15.6x10-3 m3 external loop airlift reactor for oil-in-water micro-emulsions with oil to water volume ratio （φ） rang- ing from 3% to 7% （by volume）. For comparative purposes, experiments were also carried out with water. Increase in φ of micro-emulsion systems results in an increment in the gas holdup and a decrease in the volumetric gas-liquid oxygen transfer coefficient and liquid circulation velocity, attributed to the escalation in the viscosity of mi- cro-emulsions. The gas holdup and volumetric mass transfer coefficient for micro-emulsion systems are signifi- cantly higher than that of water system. Two correlations are developed to predict the gas holdup and oxygen trans- fer coefficient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
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
Two spent yeasts from an ethanol production plant,spent yeast after distillation(SY-AD)and spent yeast after fermentation(SY-AF),were used as low-cost nitrogen sources for ethanol fermentation from sweet sorghum stem ...Two spent yeasts from an ethanol production plant,spent yeast after distillation(SY-AD)and spent yeast after fermentation(SY-AF),were used as low-cost nitrogen sources for ethanol fermentation from sweet sorghum stem juice(SSJ)by a commercial dry yeast(Saccharomyces cerevisiae)in air-locked flasks.SY-AF was the more effective nitrogen source for ethanol fermentation,giving ethanol concentration(P_(E))and ethanol productivity(Q_(E))values of 95.22 g/L and 1.98 g/L·h,respectively.When SY-AF was disrupted by autolysis,and the spent yeast hydrolysate(SYH)obtained was used as a nitrogen supplement.It was found that ethanol production in terms of P_(E)and Q_(E)values increased to 102.20 g/L and 2.83 g/L·h,respectively.When three bioreactors,a stirredtank bioreactor(STR,a typical bioreactor),a column bioreactor with stirrer(CS-R,a tower bioreactor)and an external loop bioreactor(ELR,a low-cost bioreactor with no agitation),were used for ethanol production from the SSJ supplemented with SYH,the fermentation efficiencies of all bioreactors were not different.Appropriate aeration during fermentation(0.31 vvm for 12 h)in the three bioreactors could enhance the Q_(E)value,reaching 3.36 g/L·h.Both the CR-S and ELR could be successfully used for ethanol production from SSJ supplemented with SYH.展开更多
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This study reports an experimental investigation on hydrodynamics and mass transfer characteristics in a 15.6x10-3 m3 external loop airlift reactor for oil-in-water micro-emulsions with oil to water volume ratio （φ） rang- ing from 3% to 7% （by volume）. For comparative purposes, experiments were also carried out with water. Increase in φ of micro-emulsion systems results in an increment in the gas holdup and a decrease in the volumetric gas-liquid oxygen transfer coefficient and liquid circulation velocity, attributed to the escalation in the viscosity of mi- cro-emulsions. The gas holdup and volumetric mass transfer coefficient for micro-emulsion systems are signifi- cantly higher than that of water system. Two correlations are developed to predict the gas holdup and oxygen trans- fer coefficient
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.
基金funded by the Fundamental Fund 2024 of Khon Kaen University,the National Science,Research and Innovation Fund(NSRF),Thailand(Grant.No.200535)the Post Doctoral Training for Frontier Research from Khon Kaen University,Thailand(Grant No.PD2567-04).
文摘Two spent yeasts from an ethanol production plant,spent yeast after distillation(SY-AD)and spent yeast after fermentation(SY-AF),were used as low-cost nitrogen sources for ethanol fermentation from sweet sorghum stem juice(SSJ)by a commercial dry yeast(Saccharomyces cerevisiae)in air-locked flasks.SY-AF was the more effective nitrogen source for ethanol fermentation,giving ethanol concentration(P_(E))and ethanol productivity(Q_(E))values of 95.22 g/L and 1.98 g/L·h,respectively.When SY-AF was disrupted by autolysis,and the spent yeast hydrolysate(SYH)obtained was used as a nitrogen supplement.It was found that ethanol production in terms of P_(E)and Q_(E)values increased to 102.20 g/L and 2.83 g/L·h,respectively.When three bioreactors,a stirredtank bioreactor(STR,a typical bioreactor),a column bioreactor with stirrer(CS-R,a tower bioreactor)and an external loop bioreactor(ELR,a low-cost bioreactor with no agitation),were used for ethanol production from the SSJ supplemented with SYH,the fermentation efficiencies of all bioreactors were not different.Appropriate aeration during fermentation(0.31 vvm for 12 h)in the three bioreactors could enhance the Q_(E)value,reaching 3.36 g/L·h.Both the CR-S and ELR could be successfully used for ethanol production from SSJ supplemented with SYH.
