Impact of configuration of Heat Exchanging Internals on Symmetric Behavior of Bubble Dynamics of a Bubble Column
Ahmed Jasim1, and Muthanna Al-Dahhan*
1,*Chemical Engineering and Biochemical Engineering Department
Missouri University of Science and Technology, Rolla, MO 65409-1230. USA
Bubble column reactors have many industrial applications including processes with exothermic reactions, such as F-T synthesis for converting syn gas to liquid fuels. Heat Removal internals are used to keep these processes at a desired temperature. Earlier studies reported that internals alter the hydrodynamics, mixing pattern, bubble dynamics, heat and mass transfer and hence the bubble column performance. There is no unified geometrical standard of internals design in the open literature to optimize these parameters in bubble column reactor equipped with internals. Uniform distribution of the internals over the cross- sectional area impact the flow field in the reactor. Accordingly, in this work three different configurations were studied. First configuration is a hexagonal arrangement of 30 tubes with 0.5 inch outside diameter of each tube. Second configuration is a very uniform circular arrangement of 30 tubes of 0.5 inch outside diameter, in which two types of tube end bottom shape were investigated, which are tapered and U-Tube. The third configuration is also a uniform circular arrangement but of 8 tubes of 1 inch outside diameter of each. These configurations have same cross-section area covering 25% of the column's cross-section area to simulate those used if F-T process. Hexagonal arrangement by virtue of its geometric configuration creates distinguished free areas between the edges and column wall which would cause extreme channeling for the majority of gas to flow through. Hence uniform circular arrangement was studied to see the effect of free surface formation in hexagonal arrangement.This study aimed to investigate the impact of these heat exchanging tubes on bubble dynamics and the symmetric behavior of bubble dynamics in bubble column by studying local radial profiles of each of gas hold up, gas-liquid interfacial area, bubble density, bubble chord length, and bubble rise velocity at r/R= -0.9, -0.6,-0.3, 0, 0.3, 0.6, 0.9 in the fully developed region by using 4-point optical fiber probe. The experimental work was carried out in a 14 cm inner diameter Plexiglas bubble column using air-water semi batch system. The gas introduced into the column at velocities (5, 15, 30, and 45) cm/s based on free cross-section area of the column. The results and finding will be presented and discussed in this presentation
Keywords: Bubble column, internals gas hold up, gas-liquid interfacial area, bubble density, bubble chord length, bubble rise velocity.