Experimental Determination of Bubble Size Distributions in Laboratory Scale Sieve Tray with Mesh

Abstract

Most applications on sieve tray internals were internals additions for increasing bubble area and changing gas liquid contact form to intensify the mass transfer in a tower. An easy improvement to set up a mesh on the sieve tray was proposed in this paper. It was confirmed that foam layer on the sieve tray acts as the main role of mass transfer. The mesh here could turn large bubbles into such small ones that gas would contact with the liquid sufficiently and also could avoid many small bubbles coalescing into large ones. Meanwhile, interfacial area was enlarged greatly, which was of benefit to mass transfer. In addition, the mesh could make small bubbles have a long stay time in trays, an advantage for mass transfer. In this paper, the gas hold-up and tray pressure drop were determined in an air–water system under isothermal conditions. Mean bubble diameter was measured by CCD in a 0.12 m diameter tower, and bubble radial distributions and probability density functions were also determined. The experimental results proved that mesh could obtain more total gas hold-up and reduce the bubble mean diameter greatly but increased the tray pressure drop severely also. The existence of mesh did not change the trend of bubble flow on the tray. The greatest bubbles still concentrated in the center and gradually reduced to the wall along the radial direction; the small bubbles turned into large ones along the height, and the distribution became wider at higher positions.