CFD Simulation Of Two-phase Flow In Uurea Reactor

The urea synthesis tower is the key equipments in the whole urea production process, which is a tower reactor with gas-liquid two-phase coexistence and built-in tray in the high temperature and high pressure operation. In order to strengthen the effect of reaction, the built-in tray is being improved ceaselessly in practice and there appeare many types of tray. The simulation and analysis of gas-liquid two phase flow on the synthesis tower based on computational fluid dynamics has an important theoretical guiding significance in the tray’s improvement, design and operation.This text did numerical simulation analysis of gas-liquid two phase which through different types of tray in the plat of computational fluid dynamics(CFD) software Fluent. Therefore, the reaction space between two adjacent plate of the urea synthesis tower can be seen as a bubbling column and gas-liquid two phase enter it after tray in the way of cocurrent flow. The simulation of this text ignored the chemical reaction of bubble column and material data of bubble column which has reached to reaction equilibrium, material balance and vapor-liquid equilibrium were provided by other calculation software.In the simulation of CFD, turbulence model choose Realizable k-ε, gas-liquid’s transient and dimensional flow in flat sieve tray and waveform tray in the urea reactor were simulated respectively with Euler-Euler two fluid model, the bubble size distribution are simulated in two trays by using population balance model(PBM). The change regulation of average gas holdup was investigated in the effect of different superficial gas; we set 10 groups of bubble size to study the change and distribution of bubbles in the tower when bubbles pass through different perforated plates. The results showed that gas holdup of bubble column and the superficial gas velocity is approximately linear relationship as the superficial gas velocity increases; the distribution of gas in waveform trays more uniform; In the PBM simulation of multi bubble size, The proportion of the number of small bubbles in waveform trays is much more than flat sieve, and that is more conducive to the two phases of mass transfer.The three-dimensional actual model of reactor tower with flat plate is numerical simulated under different inlet velocity with the same mathematical model and boundary conditions in the two-dimensional simulation. The results show that gas phase can be achieved the overall distribution with high gas velocity in the reactor tower, and explored the variation of distribution of gas holdup with tower height’s changing at different inlet gas velocity.