催化裂化装置烟气洗涤塔腐蚀原因分析

阐述了中国石油化工股份有限公司金陵分公司3.5 Mt/a催化裂化装置烟气脱硫脱硝系统核心设备投运后出现的腐蚀状况。该装置烟气洗涤塔在投用4个月后,顶部塔壁局部区域陆续发生了多处腐蚀穿孔,蚀孔周围塔壁出现了严重的腐蚀减薄现象,筒体壁厚由原来13.0 mm局部减薄到5.5 mm。从设备运行的环境、设备腐蚀的机理、设备设计制造的结构、选用的材料、施工质量等方面对烟气洗涤塔顶部塔壁的腐蚀原因进行了分析,认为SO3/H2SO4和HNO3酸液是造成腐蚀的主要介质,腐蚀环境中水气p H值达2.5~3.5,呈强酸性。针对这些问题提出将设备筒体材质升级为304L、降低原料硫含量、改进工艺操作参数、加强腐蚀监控等整改措施,2014年3月装置停工检修中更换了烟气洗涤塔上部筒体,材质选用304L,目前设备运行良好。

Analysis of Corrosion Causes of FCCU Flue Gas Scrubber

The corrosion which occurred in the main equipment of flue gas desulfurization and denitration system of the 3. 5 MM TPY fluid catalytic cracking unit of SINOPEC Jinling Company after the system came into operation is described. The corrosion perforation and corrosion thinning were found on the internal wall of the scrubber overhead 4 months after operation. The thickness of the scrubber shell was reduced to 5.5 mm from 13.0 mm. The corrosion causes of the flue gas scrubber were analyzed in respect of operation conditions, corrosion mechanisms of equipment, structure design of equipment, material selection and construction quality, etc. It was concluded that the main culprits of corrosion are SO2/H2SO4 and HNO3 liquids. The pH value of water vapor in corrosion environment was as high as 2.5 ~ 3.5 which is acidic. The following effective measures were adopted to deal with these problems such as upgrading the shell material to 304L stainless steel, reducing sulfur in FCCU feedstock, optimizing operation parameters and strengthening corrosion monitoring, etc. The equipment has been operating satisfactorily ever since.