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Current status of corrosion issues: The company currently has a 1.8 Mt/a wax oil hydrogenation unit, a 1.5 Mt/a residue hydrogenation unit, and a 600 kt/a diesel hydrogenation unit. In them, the separation of the reactants from the gas phase in the paraffin oil hydrogenation and residue oil hydrogenation units employs a thermal hydrocracking process. Companies attach great importance to the management of corrosion control for the high-pressure heat exchangers and high-pressure air coolers in the hydrogenation reaction effluent system, and they use materials of high quality for these cooling equipment. Therefore, there have been no leaks in the high-pressure heat exchangers and high-pressure air coolers over the past 3 years. The basic information of the residue/wax oil hydrogenation high-pressure heat exchanger and the high-pressure air cooler is shown in Tables 4 and 5 respectively. Process anti-corrosion measures and management experience (1) Raw material quality control: The crude oil used in the plant’s processing must meet the design requirements; the contents of sulfur, nitrogen, chlorine, and metals in the raw materials, as well as the hydrogen chloride content in the fresh hydrogen, should all be strictly kept within the designated ranges, with regular analyses conducted. Calculate parameters such as the crystallization temperature of ammonium chloride in the reaction effluent system, the Kp value for ammonium hydrogen sulfide, the water injection volume, and the concentration of ammonium hydrosulfide in acidic water. (2) The key process anti-corrosion measure for the hydrogenation reaction effluent system is water injection. If conditions permit, sufficient amount of flushing water should be injected to ensure that the concentrations of NH4HS and NH4Cl are reduced to the desired levels, and to effectively transfer Cl- from the gas phase to the aqueous phase. (3) For high-pressure heat exchangers, water should be injected into the pipes upstream of those where ammonium chloride deposition occurs, with the injection point located near the inlet header of the heat exchanger. It is recommended to use intermittent water injection, along with nozzles that can distribute water evenly. It is ensured that the mass fraction of liquid water remaining after injection at the water injection site is not less than 25%. Meanwhile, it is verified that the total amount of water injected during intermittent water injection does not exceed the oil-water separation capacity of the hydrodesorption reactor effluent air cooler (REAC) system, thereby preventing corrosion in subsequent equipment due to water carried in the oil from the hydrodesorption reactor as a result of overload. The start and end of water injection can be determined based on the pressure difference of the high-pressure heat exchanger or the high-pressure heat transfer coefficient K value. (4) For high-pressure air coolers, continuous water injection should be provided before their inlet. Ensure that 25% of the total water injection volume remains in liquid form at the injection site, and control the mass fraction of high-water-content NH4HS to be less than 4%. Water injection must not be stopped or reduced under the pretext of water conservation.