The low-load operating parameters of the catalytic cracking unit at Guangdong Petrochemical ensure stable quality

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At 8 a.m. on May 17, Wang Shimin, the chief operator of the fluid catalytic cracking unit at Guangdong Petrochemical, reviewed the key parameters as usual before the shift change. On the control room screens, the slide valve pressure drop remained stable at above 40 kPa, while the temperature of the regenerated two-phase mixture fluctuated steadily between 680 and 681 degrees Celsius. “This class is all set. ”Wang Shimin breathed a sigh of relief. The catalytic cracking unit is the core equipment in refining and petrochemical enterprises; it is known as the “heart” of a refinery. Recently, the fluid catalytic cracking unit has been operating at a low load of 65%. It is now facing a series of technical challenges, including a decrease in material linear velocity, poorer stability of catalyst fluidization, easy disruption of the thermal balance between the two reactors, fluctuations in steam generation from external heat removal, and increased pressure regarding environmental protection controls. Facing multiple challenges, the unit’s technical team and key operators focused on tackling two core issues: “maintaining stable fluidization and steam production during external heat extraction” and “ensuring stable fluidization in both the reactor and regenerator while preventing catalyst leakage.” To address issues such as abnormal fluidization in the external heat removal system and unstable steam generation, operators conducted round-the-clock adjustments for 8 consecutive hours. They precisely controlled the slide valve position at 15% ± 1%, while simultaneously optimizing the volume and distribution of fluidization air. Local density was strictly kept below 750 kg/m³. As a result, the catalyst circulation pathway was restored, ensuring continuous and stable steam generation through external heat removal. To address the issues of unstable fluidization and the risk of catalyst leakage in the two reactors, the team spent 12 hours making meticulous adjustments. As a result, the slide valve pressure drop was kept steadily above 40 kPa. The pressures in both reactors were regulated such that the inlet linear velocity at the top of the settler remained between 18 and 21 m/s, while the linear velocity in the regenerator cyclone was controlled within 18 to 23 m/s. The differential pressure between the two reactors was optimized to range from 15 to 45 kPa. These measures eliminated potential risks of catalyst channeling and maldistribution, thereby reducing catalyst loss to an optimal level. Meanwhile, fractionation, absorption stabilization, thermal processes, and environmental protection systems are optimized concurrently: the circulation rate of stabilized slurry and the bottom temperature of the tower are stabilized, while system pressure and desorption gas flow rate are strictly controlled ； Closely monitor the temperature at each section of the waste heat boiler to prevent risks of overheating and vaporization ； Dynamically adjust the amounts of ammonia spraying and alkali injection, and intensify the slurry replacement process to effectively reduce the risks of ammonia escape and scaling, thereby ensuring that environmental protection indicators are met throughout the entire process. After a week of continuous optimization and meticulous control, the fluid catalytic cracking unit has fully adapted to operating at a low load of 65%. All process parameters remain stable and controllable; the catalyst is in a good fluidized state. The thermal balance between the two reactors is stable, and external heat removal results in steady steam generation. The product quality is 100% compliant with standards. Energy consumption has significantly decreased compared to before the adjustments. Environmental emissions remain within regulatory limits throughout the process, with no unexpected fluctuations occurring at any point. This stable operation under low load has not only honed the emergency response and precise operational capabilities of the cadres and employees at Guangdong Petrochemical, but also provided valuable experience for the plant’s long-term flexible production and its ability to cope with fluctuations in operating conditions.