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

Authors: Haozhe Jin; Xinyu Liu; Xiaofei Liu; Chao Wang; Dexiao Fu

Addresses: National Safety Engineering Technology Research Center for Pressure Vessels and Pipeline, Hefei General Machinery Research Institute, No. 888, Changjiang West Road, Hefei, Anhui Province, 230031, China; Key Laboratory of Fluid Transmission Technology of Zhejiang Province, Zhejiang Sci-Tech University, No. 928, 2nd Street, Xiasha Higher Educational Zone, Hangzhou, Zhejiang Province, 310018, China ' Institute of Flow-Induced Corrosion, Zhejiang Sci-Tech University, Hangzhou, Zhejiang, 310018, China; Zhejiang Academy of Special Equipment Science, No. 211, Kaixuan Road, Shangcheng District, Hangzhou, Zhejiang, 310020, China ' Institute of Flow-Induced Corrosion, Zhejiang Sci-Tech University, Hangzhou, Zhejiang, 310018, China ' Institute of Flow-Induced Corrosion, Zhejiang Sci-Tech University, Hangzhou, Zhejiang, 310018, China ' Institute of Flow-Induced Corrosion, Zhejiang Sci-Tech University, Hangzhou, Zhejiang, 310018, China

Abstract: 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]

Keywords: wax oil hydrotreater; heat exchange equipment; crystallisation of NH4Cl; multiphase flow; risk assessment.

DOI: 10.1504/IJOGCT.2026.150567

International Journal of Oil, Gas and Coal Technology, 2026 Vol.39 No.1, pp.76 - 96

Received: 28 Jun 2023
Accepted: 24 Jun 2024
Published online: 17 Dec 2025 *

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