THE CFD Simulation And Analysis Of Gas Distribution In Distillation Column

Gas flow distribution is an important influential factor for distillation column efficiency. Especially for structured packed columns, which are boomingly used, due to the poor self-distributivity resulted from the lower pressure drop of the structured packing, and the more sensitivity to gas distribution, the influence of gas distribution for structured packed columns is more severe. At present, the research on Gas distributing in packed column is mainly focus on experiment, and the results obtained can hardly be consistent enough to make effective analysis. Computational fluid dynamics (CFD) is undergoing fast development and has found applications in a number of research areas of chemical engineering. For a single phase fluid flow, the CFD technique today can give reliable results on the flow rate distribution even for rather complicated geometrical structure. For gas phase flow in a distillation column, the main factors deciding the flow rate distribution are limited to the open area and geometrical structure of the internals and the superficial velocity.In general, geometrical structures composed of column shell and internals are relatively simple, so, CFD simulation could be expected to give correct results for gas flow rate distribution, and then could be used safely to make reliable analysis of gas flow behaviors in structured packed columns. In this work, we performed CFD simulations for gas phase flow rate distribution in columns with various combinations of different forms of internal structure, its open areas and superficial velocity conditions, and then the simulation results were used to develop a correlation for nonuniformity of column cross section of gas distribution vs the axial position of the section for design purpose. Pipe gas distributor is often applied in small tower. Via CFD simulation, we revealed the influence of velocity of gas feed, position of axial section on the gas phase maldistribution in the column, and proved that velocity of flow has less effect on nonuniformity of gas flow, and it is mainly varied by axial position above the distributor. Bases on the result of simulation we developed a correlation on the axial position and the nonuniformity of gas distribution, so that it can be used in design. In large-scale tower, especially the vacuum tower of the crude unit of refinery, trough-pan liquid-gas distributor is a widely used structure. In this case, the height of packing is relatively small comparing to the diameter of column so, a good gas distribution is every important. In this article we simulated trough-pan liquid-gas distributor's gas flow. By analyzing the simulation result, we proved that velocity of flow has less effect on the nonuniformity of gas distribution, and it mainly determined by axial position of section above the distributor and open area. Bases on the result of simulation we developed a correlation for the nonuniformity of gas distribution varying with the axial position of and the open area...