Limitation Of Gas-Liquid Mass Transfer In Turbulence And Its Application

In traditional mass transfer theories, the limitation of gas-liquid mass transfer is phase equilibrium. The fluid turbulence can shorten the time that the system takes to achieve equilibrium. However, it can be observed that the mass transfer limitation in the flowing system often different from equilibrium in daily life, such as, the carbon dioxide desorbs from flowing sodas. In chemical industry, gas-liquid often contact in flow condition to strengthen mass transfer process. However, the high degree of turbulence is not always benefit for gas absorption. Hence, the definition of gas-liquid mass transfer limitation, which is different from phase equilibrium, is introduced in this study.Six different one-component systems were treated as research objects, including:water, ethanol, acetic acid, isopropyl alcohol, normal propyl alcohol and acetone. One-component phase equilibrium systems were prepared and tested at constant temperature. The close system, which reached equilibrium, was fixed on water-bath-shaking-table and moved in horizontal uniform circular motion. The instantaneous data of system pressure and temperature were collected by online acquisition system. The experiments under different liquid volumes, temperatures and rotating speeds verified that the limitation of one-component vapor-liquid mass transfer could be an analogy with saturated vapor pressure. This limitation value was only related to reduced temperature and Reynolds number. The dynamic balance deviation ratio of one-component system contented r=7.4388×10-4(Tr)2.61(Re)066in the application range of7000<Re<19000and0.4375<Tr<0.6951. The maximum calculation error of the correlation was10%.The dynamic mass transfer limitation was also different from equilibrium in multi-components system. The CO2-H2O, CO2-C2H5OH and different concentrations of CO2-C2H5OH-H2O systems were chosen as research systems. The saturated liquid was pumped into circulation line by peristaltic pump. The instantaneous system temperature and pressure data were measured by online acquisition system. Based on the experimental results in one-component system, the correlation between dynamic balance deviation ratio of CO2-H2O system, Reynolds number and ratio of liquid-gas viscosity was gained by experimental data as: in the application range of7500<Re<42000and288.15<T<303.15K. This correlation was also appropriated for CO2-C2H5OH and different concentrations of CO2-C2H5OH-H2O systems. The maximum calculation error of the correlation was10%.The mechanism of liquid flow affects on the limitation of gas-liquid mass transfer was verified to be different from temperature by Aspen Plus program. The physical model and model assumption were built on experimental systems. The instantaneous voidages in experimental processes under different temperatures and flow velocities were calculated by FORTRAN program. In the temperature range of278.15-303.15K, the flow velocity range of1-3m/s and pipe inner diameter range of10-15mm, the bubble voidage in the pipe accorded with According to the correlation of voidage, the system pressure of dynamic balance was expressedComparing the simulation results with experimentaldata in the CO2-H2O system, the maximum model calculation error was less than10%. The simulation results were satisfied in this research.The theory of dynamic gas-liquid mass transfer balance was used to analyze the CO2absorption process by MDEA aqueous in rotating packed bed (RPB). In different experimental conditions, the absorption rates of CO2all increased to maximum first then decreased with the RPB rotating speed increasing. The high turbulence degree of liquid was not benefit for CO2absorption. In this way, the high rotating speed of RPB was not always good for gas absorption. The theoretical analysis was confirmed with experimental results in RPB. The theories in this research cloud explain the optimal rotating speed in the gas absorption process in RPB well.