氣、液、固三相磁流體化床(生物流體化床)中質傳與流力行為之探討

Abstract

In this experiment, we placed the axial direction of magnetic field on traditional three phase fluidized bed, which were contained the particle of Fe3O4 with diameter 230 microns for carriers, water and CMC solution (Carboxymethyl Cellulose) (0.1%、0.2%) as the liquid phases, air was used as gas phase, to approximation the bioreactor with attachment of the microorganism carrier. The experiment was designed to operate at magnetic LAST mode, we determined the minimum fluidization velocity and drew the phase diagrams in two type of bubble and particle. Then we moved on to the main experiments – gas holdup, pressure fluctuations and axial dispersion coefficient. We used valve technique to determine gas holdup, and we observed the gas holdup decreased when magnetic field intensity increased. The observation was similar with Thompson and Worden (1997) and Snonolikar et al. (1999) but opposite with optical probe method or conductivity probe method stated in the literature. Then we discussed the relationship between the mass of particle and the gas holdup inside the bed. There are two behaviors was used to describing the gas holdup in the magnetic fluidized bed: (1) When the mass of particle was less inside the bed, the volume of bubble was decreased and gas holdup went up when the magnetic field was increased. The behavior of gas holdup was bubble control. (2) When the mass of particle was large inside the bed, the bubble was inhibit inside the fluidized bed easily, and leave the bed until they are perform slug bubble. When the magnetic field was increasing, the bed height was decreased and gas holdup was decreased, too. The behavior of gas holdup was solid control. For pressure fluctuations experiment. The fluctuations was hinges on solid particle flow behavior. In this study, we made the classification of particle flow regime map by visual and observed the pressure fluctuations by it. We find the pressure fluctuations was depend on the particle flow regime and then we can understand the pressure fluctuations from particle flow regime by viaual. The stimulus-response technique was used in the liquid axial dispersion experiment. The result had shown the axial dispersion coefficient went up and then down with increased the magnetic field intensity. Also the maximum value of axial dispersion coefficient was located at the boundary between random regime and jet regime in the particle phase diagram.