Study On Transport Phenomena About Gas-Liquid Co-current Flow In Structured Packing Column

As the development of green chemical technology, energy saving and consumption reducing become more and more important in chemical industry at present. It is well known that in chemical unit operations distillation, absorption and so on take up a great deal of energy. So it's very important to study on the energy saving in such chemical processes. Since the advantage of gas liquid co-current flow in the aspect of energy saving over other operations, it is necessary to be studied on. The pressure drop and the holdup are respectively tested in a packed column of ID 80 mm filled with Mellapak 350Y. Water and air are as testing medium, with Fv factor from 1 to 5 and liquid flow from 50L/h to 400L/h. From the tested results, it is found when gas Fv factor is fixed, the pressure drop and holdup in the packed bed increase as the liquid spray density increases, while at small gas Fv factor the pressure drop changes not obviously; also when the liquid spray density is fixed, the pressure drop and holdup in the packed bed increase as the liquid spray density increases. The three-dimensional CFD model for gas-liquid co-current flow based on Mellapak 350Y packing is created. VOF method is adopted for simulating flow process and flow field operating at gas-liquid co-current flow state in packed column. With gas Fv factor is 1 to 5 and the liquid flow from 50L/h to 400L/h, the pressure drop and holdup are fitted respectively. And comparing the simulated results with experimental ones, it shows that the gas-liquid co-current model presented in this paper is able to simulate the flow process perfectly.By comparing the simulated and experimental results, it is found that as liquid spray density increases, the pressure drop shows also increase tendency both in the experimental and simulated data and the error is within 20 percent. But at small gas Fv factor as liquid spray density increases, the pressure drop varies a little, even abnormal phenomenon occurs. At one time, by comparing with the condition in gas-liquid counter-current flow published in literature, the pressure drop in co-current flow is about 70 percent of that in counter-current flow.By comparing the simulated and experimental results, it is also found that as liquid spray density increases, the holdup shows increase tendency both in the experimental and simulated data. Also by comparing with the condition in gas-liquid counter-current flow published in literature, the holdup in co-current flow decreases about 50 percent, even more than that in counter-current flow.For the co-current flow operation, by simulating of CFD, it is found that as liquid spray density increases, the wetted specific surface in packed bed increases gradually, while as the gas Fv factor increases, the wetted specific surface decreases gradually. Also the wetted specific surface in packed bed for co-current flow is less than that for counter-current flow.