Risk assessment of ammonium salt crystallisation in wax oil hydrogenation cooling exchange equipment

Aiming at the tube bundle of wax oil hydrogenation air cooler in a petrochemical enterprise, the crystallisation law and flow deposition distribution of ammonium salt in multi-fluid environment are comprehensively studied by combining process analysis with numerical simulation prediction. Based on the process modelling of the hydrogenation heat exchange system and the multiphase flow distribution of the easily crystallised components, the fugacity coefficient method is used to fit and correct the ammonium salt crystallisation equilibrium curve. The multiphase flow model and discrete phase model are used to predict and analyse the deposition position and deposition amount of ammonium chloride crystallisation. The results show that the crystallisation temperature of ammonium chloride in the system is 206°C, and there is a crystallisation risk of ammonium chloride in the air cooler. The non-uniform flow field leads to the distribution difference of multiphase flow. As the flow progresses, the fluid of each phase in the pipeline begins to stratify and is stable after a certain distance, and the water phase is enriched at the bottom of the pipeline. The particle retention rate of ammonium chloride particles near the inlet pipe is larger, reaching 10.07%. [Received: June 30, 2023; Accepted: June 24, 2024]