高压聚乙烯装置中冷器黏壁现象的原因分析及对策

Reason analysis and countermeasures of inner wall-sticking behavior in intercooler of high pressure polyethylene unit

分析了中国石油兰州石化公司20万t/a高压聚乙烯(LDPE)装置二次压缩机中冷器发生黏壁现象的原因及其影响因素,并结合装置的实际运行情况,提出相应的对策。结果表明,二次压缩机一段聚合产生的聚合物处于熔融态,其随着高压乙烯气体进入中冷器进行冷却时,会发生自聚而黏附在中冷器内壁上。在生产过程中,应降低第4反应区过氧化物浓度,减少其中二叔丁基过氧化物(DTBP)的含量,控制第4反应区出口脉冲阀的脉冲强度为40 MPa,脉冲持续时间为0.50 s,脉冲周期为80 s,控制较高的反应后系统温度,使过氧化物尽可能完全分解。另外,可在润滑油中加入抗氧剂,并在其注入槽中加装氮封,以减缓乙烯自聚。

The reasons and influencing factors of inner wallsticking behavior of intercooler in a 200 kt/a high pressure polyethylene unit of Lanzhou Petrochemical Company were analyzed, and the corresponding countermeasures were proposed according to the actual operating condition. The results showed that the molten selfpolymerization product formed in the first zone of secondary compressor could stick onto the inner wall of intercooler when it went into the intercooler with high pressure ethylene gas together. During the operation, the peroxide con- centration in the 4th reaction zone should be reduced,the ditert-butyl peroxide （DTBP） content init should also be reduced, and the strength of the pulse valve in the 4th reaction zone ought to be controlled to 40 MPa, the pulse length for O. 50 s, the pulse cycle to 80 s,the system temperature after reaction should high to decompose the peroxides as completely as possible. Moreover, the antioxidants could be added in the lubricant, and the nitrogen seal could be used in the lubricantfeeding vessel to slow down ethylene polymerized.