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Current status of corrosion problems The corrosion and control of the company's aromatic hydrocarbon extraction unit is the focus and difficulty of anti-corrosion management of the entire plant process. Especially after the start of the second cycle of the unit (the first cycle ran for 3 years without replacing the solvent), multiple heat exchangers of the unit frequently leaked, which brought many unstable factors to the production and safety of the unit. The specific leakage cases of aromatic hydrocarbon extraction units in recent years are shown in Table 6. As can be seen from Table 6, since the start of construction in October 2017, the aromatic hydrocarbon extraction unit has leaked 13 times from solvent-related equipment alone, averaging once per quarter (excluding steam heat exchanger leaks). Such high-frequency leaks seriously affect the safe production of the unit and the completion of production tasks. Process anti-corrosion measures and management (1) Strictly control operating temperature: The boiling point of sulfolane is 285°C. Under normal conditions, it begins to decompose at 180°C, and will obviously decompose into other degradation products such as sulfur dioxide and butadiene at 230°C. Excessively high temperature is an important reason for the decomposition of sulfolane. Strictly controlling the bottom temperature of the extractive distillation tower and recovery tower within 175°C can eliminate the problem of sulfolane decomposition caused by excessive temperature. (2) Prevent oxygen from leaking into the extraction system: The low-point diversion valve and high-point vent valve of the extraction system must be sealed with wire plugs to prevent internal leakage of the valves. When the device starts nitrogen replacement, the system oxygen mass fraction should be controlled below 0.3%. When filling and replenishing sulfolane, it must be under N2 protection. Regularly check the working conditions of the solvent tank, wet solvent tank top breathing valve, and nitrogen self-operated valve to prevent oxygen from entering the solvent. (3) The air in the equipment and instruments that have been cut out for maintenance must be purged and replaced with N2 according to the procedure before being put into use to avoid bringing a large amount of oxygen into the solvent system. (4) Open the regeneration tower: Corrosive impurities are inevitably produced during the production process, and the presence of these impurities also accelerates solvent deterioration. The regeneration tower uses vacuum distillation to remove high molecular polymers and impurities in sulfolane. The regeneration tower is a key equipment for purifying solvents. While removing decomposition products, it can also remove impurities carried in the raw materials and improve the quality of the solvent. (5) Add solvent filtration facilities to control the chlorine content in the solvent and keep its pH value no less than 8.