Abstract:

The flue gas desulfurization system of catalytic cracking unit is prone to fouling and blockage, equipment corrosion and other problems during operation, which affects the long-term operation of the flue gas desulfurization system. Through analysis, it is known that the main reason for scaling and blocking of the flue gas desulfurization system is that the average calcium hardness of the fresh water used in the absorption tower is 175 mg/L, which is much higher than the recommended value for system operation(65 mg/L). After being absorbed, SO_x in the flue gas reacts with Ca²⁺ in the fresh water to generate CaSO₄ precipitation. At the same time, the paper also analyzes the H₂SO₄ dew point corrosion of the absorption tower caused by SO_x encountering water, the erosion of catalyst particles, and the pitting corrosion of the system caused by Cl^- in the liquid. By selecting the external drainage of the unit with low content of Ca and Cl to replace the fresh water, optimizing the operation and strictly controlling the total hardness of tower bottom slurry to be no more than 100 mg/L, total dissolved salts(TDS) to be no more than 106 mg/L, total suspended solids(TSS) to be no more than 2,500 mg/L, mass concentration of chloride ions to be no more than 750 mg/L, system pH value of 6.5～7.0, etc., the equipment failure problems and maintenance frequency have decreased significantly, and the pipeline replacement cycle has increased from three months to more than one year. The scaling and corrosion problems of the system have been effectively controlled to ensure the long-term operation of the system.

Key words: catalytic cracking unit, flue gas desulfurization, fouling, blockage, corrosion, quality of make-up water, pH value, particulate matter;

摘要：

催化裂化装置烟气脱硫系统在运行过程中易出现结垢堵塞、设备腐蚀等问题，影响烟气脱硫系统的长周期运行。通过分析得知导致烟气脱硫系统结垢堵塞的主要原因：吸收塔所用新鲜水的平均钙硬度为175 mg/L,远大于系统运行建议值(65 mg/L),烟气中的SO_x被吸收后与新鲜水中的Ca²⁺反应生成CaSO₄沉淀。同时，还分析了SO_x遇水对吸收塔的H₂SO₄露点腐蚀、催化剂颗粒物的冲蚀、液体所含Cl^-对系统造成的点蚀等问题。通过选择Ca, Cl含量低的装置外排水替代新鲜水，优化操作，严格控制塔底浆液总硬度不大于100 mg/L、总溶解盐(TDS)不大于106 mg/L、总悬浮物(TSS)不大于2 500 mg/L、氯离子质量浓度不大于750 mg/L、系统pH值在6.5～7.0等措施，设备故障问题与检修频次明显下降，管道更换周期由3个月升至1 a以上。系统结垢与腐蚀问题得到有效控制，保证了系统的长周期运行。

关键词: 催化裂化装置, 烟气脱硫, 结垢, 堵塞, 腐蚀, 补水水质, pH值, 颗粒物