Simulation of Gas Oil Hydrotreater Heat Exchange Tube and Crystallization Prediction of NH4Cl by Thermodynamic Equilibrium

The hydrotreater system heat exchanger is one of the main pieces of heat exchange equipment in petrochemical enterprises. In recent years, oil resources have shown a deterioration trend of high sulfur and high acid content, with corrosion risk being prominent in oil processing. Taking the multi-medium flow corrosion risk of the hydrotreater heat exchanger pipeline in a petrochemical enterprise as the research object, based on the parameter characteristics of corrosive NH(3 )and HCl media under a high-temperature and high-pressure environment, the ammonium salt crystallization and deposition mechanism under multi-phase flow is revealed. The thermodynamic equilibrium curve is modified based on the thermodynamic principle and fugacity coefficient variation, and the prediction model of ammonium chloride crystallization in hydrotreater heat exchanger under high temperature and high pressure is constructed according to the modification. This study uses the mixture model, the flow-thermal coupling method, and the discrete phase model method to carry out the numerical simulation of multiphase flow and the numerical prediction of particle distribution characteristics in the heat exchanger pipeline of the hydrotreater heat exchange equipment, so as to realize the quantitative prediction of the particle crystallization deposition distribution in the pipeline. The results show that with the decrease of temperature, the crystallization occurs first on both sides of the center of the tube bundle, and more crystallization occurs in the lower half of the U-shaped tube, which may seriously lead to problems such as pipe blockage and under-deposit corrosion.