Effect Of Solids On Gas-liquid Mass Transfer Characteristics In A Gas-liquid-solid Three Phase Stirred Tank

Gas-liquid-solid multi-phase stirred reactor has extensive applications in the petrochemical,biochemical,pharmaceutical and other process industries.The gas-liquid mass transfer process is very complex in multi-phase stirred reactors,and it is affected by various factors such as impeller type,operation mode and material properties.In order to improve the gas-liquid mass transfer efficiency,structural parameters and operating parameters of the reactor have been studied by many scholars.A variety new of impellers improve the power and mass transfer performance compared with traditional impellers,which also makes the relevant chemical process more efficient.With the development of basic theory and the further improvement of the computational fluid dynamics software,there are many new ideas and methods in the design of the stirred impellers.Gas liquid mixing process is often accompanied by solid catalyst,biomass and other solid phase,the addition of solids further increases the complexity of the gas-liquid mass transfer.However,the conclusions about the effects of different types,sizes and concentrations of particles on mass transfer are not consistent.In this paper,based on the recent CFD simulation,a new type of disc turbine impeller is proposed.The gas-dispersion and mass transfer performance of the JDT are determined experimentally.The effects of the addition of solid particles on the gas-liquid system,especially the mass transfer,have been studied.This paper is aiming at further optimizing the impeller type,clarifying the influence of different factors on the mass transfer performance,and providing the reference for the design and industrialization of the reactor.The experiment is divided into two parts.First of all,the power consumption,gas holdup and mass transfer performance of the JDT(D=0.19 m)in gas-liquid system are studied in a stirred tank with a diameter of 0.48 m and a liquid level of 0.48 m.At the same time,the effect of the addition of solid phase on the power consumption,gas holdup and mass transfer performance is studied.In order to better evaluate the performance of the JDT,take HEDT and PDT as comparisons.Secondly,the influence of the addition of solid phase on the mass transfer performance of HEDT + 2WHU impeller combination is studied in a stirred tank with a diameter of 0.48 m and a liquid level of 0.857 m.Based on the above experimental data,the correlation coefficients of Np,? and kLa are obtained at influencing factors.The results show that:first,for single impeller,JDT shows better power and mass transfer performance in the gas-liquid and gas-liquid three-phase system.The RPD of JDT and JDT-2 is higher by 4%than PDT and 8%than HEDT.The JDT and JDT-1 paddle were about 7%higher than HEDT and PDT when the superficial gas velocity was greater than 0.024 m/s in terms of mass transfer and gas holdup.When solids are added to the gas-liquid system,the RPD for all impeller increases,and the? and kLa are reduced by about 5%compared with in two phases system.The concentration of solid phase has little effect on kLa.Secondly,the kLa for HEDT+2WHU is decreased in three phase system compared with in tow phase system.And kLa is decreasing with the increase of solid concentration.