Flow Field Analysis And Mass Transfer Model Of MDEA Desulfurization Under High Gravity Field

Natural gas from the underground reservoir often contains a certain amount of H2S, CO2, H2O and other impurities. However, these groups have a great influence on natural gas gathering, transportation and utilization. In particular, the hydrogen sulfide not only causes corrosion of equipment and pipeline but also is toxic and harmful, which leads adverse impact on the environment and human health.Therefore, it is indispensable to purify the sour natural gas before utilization. Currently, the methods used to desulfurize can be divided into dry and wet technologies. In wet desulphurization, MDEA solution is widely used as the desulphurizer.The traditional desulfurization using MDEA solution and recipe MDEA solution mainly takes place in a conventional packed column or a plate column, which principally relies on gravity to achieve the gas-liquid mass transfer process and has a series of defects such as large volume of mass transfer equipment, low production intensity and poor selectivity. In contrast, in the high gravity field, the micro-mixing and mass transfer process has been greatly enhanced, the liquid surface update quickly and the gas-liquid contact area has been significantly increased. It can be speculated that the mass transfer is intense and the residence time is short in the rotating packed bed. As a result, the high gravity technology used in the MDEA desulfurization can not only enhance the mass transfer process, but also beneficial to the selective absorption process.In the paper, based on the computational fluid dynamics theory, a physical model of rotating packed bed was established via the finite volume method in flow field simulation software. The analysis of the flow field of the two-dimensional model was carried out after selecting the appropriate model and solving methods, which was completed on the base of reasonable meshing and boundary conditions setting including to the actual structure of rotating packed bed, the basic size of packing and so on. The liquid flow field, for example radial velocity, tangential velocity and distribution of turbulent kinetic energy, was analyzed when it came to different inlet velocity and rotating speed. In addition, it focused on the analysis of change in radial velocity, tangential velocity and pressure in the gas flow field.Based on the analysis of flow field and the structure of the rotating packed bed, the surface renewal rate of liquid flow, from the radial and tangential of rotating packed bed, was taken in to consideration and the liquid mass transfer coefficient theoretical model was established adopting liquid mass transfer surface renewal theory according to the basic size of packing. While, the gas mass transfer coefficient model was established based on the correlation put forward by Onda and others. What’s more, the change trend of the liquid and the gas mass transfer coefficient under different operation conditions was compared and analyzed in the study.