Experimental Study Of Liquid Flow And Axial Dispersion Performance In Multiphase Monolithic Reactors

Compared with traditional multiphase reactors, multiphase monolithic reactors possess many advantages such as lower pressure drop, high mass transfer rate and large surface area, which make them an attractive alternative to traditional multiphase reactors. Therefore, it is significant to thoroughly study multiphase monolithic reactors. Liquid flow and axial dispersion performance in different multiphase monolithic reactors was studied in this paper, so as to provide basics for the design, operation and scale-up of such reactors.The "tracer-response" experimental study was conducted in three types of cell density (50cpsi, 100cpsi,400cpsi) integral and segmented multiphase monolithic reactors separately, with tap water as liquid phase, air as gas phase, nozzle/glass beads static distributor as liquid distributor, operated at superficial liquid velocities of 0.0283～0.0637m/s and superficial gas velocities of 0.0490～0.2942m/s, in cocurrent downflow mode. The "tracer-response" concentration vs. time data were measured at different superficial gas/liquid velocities using conductivity probe method and the corresponding bed pressure drop vs. time data were measured at the same time using pressure sensors.Based on the experimental data, the influence of superficial gas/liquid velocities on the degree of axial dispersion was analyzed, the effect of superficial gas/liquid velocities and cell density on the average residence time, the bed pressure drop, the average liquid holdup and the average liquid slug length was studied, and the Peclet number correlation reflecting the degree of axial dispersion was obtained in nozzle liquid distributor integral multiphase monolithic reactors; the comparison of the influence of superficial gas/liquid velocities on the average residence time, the bed pressure drop, the average liquid holdup and the average liquid slug length, and of the degree of axial dispersion in the two liquid distributors integral and segmented multiphase monolithic reactors was done. The results show that:In nozzle liquid distributor integral multiphase monolithic reactors:(1) The degree of axial dispersion decreases with increase of superficial liquid velocities and increases with increase of superficial gas velocities.(2) With superficial liquid velocities increasing, the average residence time decreases, the average bed pressure drop, the average liquid holdup and the average liquid slug length increases; with superficial gas velocities increasing, the average residence time, the average bed pressure drop, the average liquid holdup and the average liquid slug length all decreases; with cell density increasing, the average residence time increases, the average bed pressure drop and the average liquid holdup decreases, the average liquid slug length first increases and then decreases.(3) The error of the obtained Peclet number correlation reflecting the degree of axial dispersion is mostly within±30%, which shows that the Peclet number correlation is able to predict the degree of axial dispersion in multiphase monolithic reactors.Comparison shows that:(1) The influence of superficial gas/liquid velocities on the average residence time, the bed pressure drop, the average liquid holdup and the average liquid slug length in segmented multiphase monolithic reactors is almost consistent with that in integral multiphase monolithic reactors.(2) The degree of axial dispersion is less when using nozzle as liquid distributor.(3) To decrease axial dispersion, redistribution segment can be set in multiphase monolithic reactors with avoiding backmixing and energy consumption being considered.