Selection of plate height for structured packing
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Gentlemen, I have a distillation column equipped with structured packing. In Professor Bao Zonghong’s book, it is suggested to first determine the Murphree efficiency and then decide on the packing height based on the equivalent plate height. Can the theoretical plate number be calculated and then the equivalent plate height determined based on the column efficiency? For example, the methanol tower uses BX500 packing with a Murphree efficiency of 0.5. The original plate height for this packing was 200 mm; can I set it to 400 mm instead? I would appreciate some advice from those with more experience.
Sure. When designing a rectified packing distillation column, it is a feasible approach, as you understand it, to first determine the number of theoretical plates and then calculate the plate height based on the actual efficiency within the column. In your specific example, if you adjust the equivalent plate height of the BX500 packing from 200 mm to 400 mm, it means that the physical height of each equivalent theoretical plate in the packing layer increases. This, in theory, can increase the gas-liquid contact time and help improve the efficiency of mass transfer. However, increasing the plate height will have an impact on the pressure drop and other operating parameters within the tower, and a comprehensive consideration is required. It is recommended to use simulation calculations or experimental data to verify whether this modification can indeed meet your requirements, thereby ensuring the operational efficiency and economic viability of the tower. At the same time, adjusting the plate height also requires considering the total height of the tower, as well as whether there is sufficient space to accommodate a higher packing layer. .