Experimental Study And Multi-Scale CFD Simulation Of Novel High Capacity Structured Packings

In the first part of this paper, three types of novel high capacity structured packings are proposed to meet the ever growing demand of industrial chemicals. Based on the previous work on stretching the capacity of structured packings and the successful design experience of BH packings, the high capacity packings are expected to hold a great advantage in both hydrodynamic performance and mass-transfer efficiency.The hydrodynamic performance and mass-transfer efficiency of the new packings is tested in a 500mm diameter column using air-water-oxygen system at ambient pressure and temperature and the results are compared with that of Mellapak125X. As expected, the new packings hold a much larger capacity and relatively higher mass-transfer efficiency. The wet pressure drop of Type A, Type B and Type C decreases by 26.7%、34.2%、40.3% respectively, compared with that of Mellapak125X. The flooding gas velocity of Type A, Type B and Type C is 7.5%,11.3%,15.1% higher than that of Mellapak125X. The HETP values for Type A are 20% lower than that for Mellapak125X. The HETP values for Type B are almost the same as Mellapak125X while the HETP values for Type C are higher than that of Mellapack125X.In the second part, a modified multi-scale approach is proposed to simulate the flow behavior in the new packings. Both 2D and 3D VOF models are applied to get the information of liquid film thickness and effective area. The result of VOF calculation is put into use for wet pressure drop prediction of packing layer by pseudo single-phase CFD simulation. Meanwhile, the influence of gas and liquid velocity on both liquid film thickness and effective area is also analyzed. The average deviation between simulated and experimental values of dry and wet pressure drop is not more than 20%.Apart from the influence of gas, the average liquid film thickness shows a liner trend with the increasing of liquid load. Meanwhile, the effective area is also increasing with a decreasing rate at the same condition. On the other hand, both the average liquid film thickness and effective area perform the same trend with the increasing of gas at fixed liquid load. The average liquid film thickness and effective area remain approximately constant in the preloading zone, while increase significantly in the flooding area. This result indicates that the interaction of gas and liquid is weak in the preloading zone. With both dynamic liquid film thickness and effective area being taken into account, the multi-scale strategy is considered a convenient and useful tool for designing and optimizing the structured packings.