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The first shutdown for maintenance of the two sulfur units at the Shunbei Oilfield Combined Station, as well as the green shutdown of the sulfur recovery unit in the First Refining Operations Department, are among the more successful cases of sulfur unit shutdowns in recent years. The two sulfur units at the Shunbei Oilfield Combined Station have been shut down for maintenance. These units were put into operation in 2023, with a daily capacity to process 110,000 cubic meters of sour gas; they are key facilities for the treatment of natural gas sulfides. In December 2025, it completed its first comprehensive shutdown for maintenance and successfully resumed production. During the maintenance process, Oil Production Plant 4 adopted a combination of shutdown-based and non-shutdown maintenance methods to coordinate the project schedule over different time periods. Experts from the Puguang Gas Field in Zhongyuan Oilfield were invited to provide on-site guidance, enabling the work to proceed safely and efficiently despite extreme conditions such as severe winter weather and sandstorms. The sulfur recovery unit in the First Refining Division was shut down in a green manner. In March 2026, this unit adopted a thermal nitrogen flushing process to continuously purge the Claus system, transferring the accumulated sulfur to the exhaust gas treatment unit where it was subjected to hydrogenation reduction and absorption treatment. Throughout the entire process, the sulfur dioxide content in the exhaust gases remained below 70 mg/m³, which is far below the **standard** of 400 mg/m³, ensuring 100% compliance with emission standards at all times. This process effectively avoids the risks of overheating of the catalyst bed and excessive emissions, reflecting the concept of green shutdown with environmental control. CNOOC Huizhou Petrochemical’s 240 kt/a sulfur recovery unit underwent its first green shutdown. During this shutdown, issues such as excessive SO₂ emissions and difficulties in amine liquid recovery arose. By implementing measures including using gas to flush sulfur-containing flue gases into the hydrogenation process, performing sealed purging of the towers, and optimizing the amine removal process, a successful green shutdown for maintenance was achieved for the first time, providing a technical reference for large-scale similar facilities.