Study On Two Phase Flow Of Chemical Process With The CFD Method

There are many kinds of different systems included in chemical industrial two phase flow, such as gas-droplet, gas-solid, liquid-solid, liquid-bubble, and so on. Their flow patterns are of great difference because of their difference in the physical properties of their two phases, the operating conditions and the process environment. It's known that flow characters of the two phase flow is very complex. Both the fluid mechanics of the porous SiC tray and the gas-solid two phase flow of the fluidised bed reactor in catalytic cracking unit were studied in this paper. The main contents are as follows:Firstly, as for the porous SiC tray, the Porous Model provided by CFX was known to have reference value and predictive value for modelling of the flow problems in the porous/pure fluid area through the study on the the Porous Model in CFX. And then, the flow of two-dimensional single-phase on the porous tray was modelled using the Porous Model to acquire the dry pressure drop. It came to that the change curve of the dry pressure drop following the F was the same to the experimental results. The wet pressure drop from the gas-droplet two phase simulation corresponded to the experimental results. It was proved that air and water had better distribution, larger contact area and more drastic velocity disturbance on the porous tray compared to that on the sieve tray from both the water volme faction and the air velocity vector.Secondly, as for the fluidised reactor, the mixed C4 and the raw petrol gas in the reactor before transformation depart directly without any disturbance and mixture after they enter the reactor. Therefore, not only did the structure of the previous reactor go against the reaction of the reactant and the catalyst particle, but also made low utilization ratio of the reactants. The catalyst particle had uneven distribution in the whole reactor. In the radial direction, the particles mainly concentrated on the center of the reactor so that the raw materials near the wall couldn't contact and react with the catalyst particles. In the axial direction,the raw petrol gas nearly wasn't able to react because of the low volume fraction of the particle in the upper part of the reactor. The two kinds of feed pipes and the relative dimension of the reactor were improved and optimized accroding to the analysis of the simulation results from modelling the structure of the previous reactor. The distribution situation of the catalyst particles in the reactor had achieved significant improvements.Not only was the distribution of the particles more even, but also involved the wall of the reactor. Such distribution could promote the react near the wall and increased the utilization rate of the raw materials.