Experimental Investigation On Mass Transfers Of Gas-Liquid And Liquid-Liquid Phases In Different Microchannels

This paper focuses on the researches of the mass transfer in a microchannel reactor. Experiments on absorption of carbon dioxide in water and the extraction between kerosene, water and acetic acid have been carried out in a rectangular metal microchannel etched by ultra-fast laser and 3 groups of glass capillaries. The rectangular metal microchannel and the glass capillaries have a hydrodynamic diameter of 90μm and capillary diameters around 500μm respectively. The aim of this work is to investigate the behaviors of the gas-liquid and liquid-liquid mass transfer in a microchannel.It has been proved to be feasible to make a microchannel by ultra-fast laser and also it is proper to seal the metal microchannel by mechanic method in favor of silicone rubber. The experiments can be operated in range of some liquid velocities and the normal glass capillaries have been utilized as well. Our work has shown that in glass capillaries the liquid side volumetric mass transfer coefficient has more influence by the superficial liquid velocity of 0.08～1.27m/s rather than the superficial gas velocity of 0.84～7.64m/s. Similar conclusions can be attained in the rectangular metal microchannel that the superficial liquid velocity is the dominated factor in mass transfer rather than the superficial gas velocity, but compared to the glass capillaries, the mass transfer coefficient is extraordinarily high due to the notable reduction of the hydrodynamic diameter and the length of diffusion distance and it has a good foreground in industry. Liquid-liquid mass transfer experiment showed that the microchannel has a predominance especially in gas-liquid and gas-liquid-solid catalytical reactions. Further analysis suggest that in a microchannel the mass transfer of different phases relies on the molecular diffusion under laminar flow and in low liquid velocity thus extraordinarily high efficiency and low liquid velocity are the main characteristics of mass transfer in a microchannel. Due to the notable reduction of the characterizing size new problems such as the control of experimental operation and the analysis of the results have been presented. For instance, apparutus which has a characterizing size under 400μm can only work in a limited range. These practical problems need to be worked out in the future experimental research on mass transfer in a microchannel. Microchannel reactors still have a lot of problems suspended such as a high cost in fabrication and the"numbering up". The mass production of microreators in chemical industry still has a long way to go.