影响全密度聚乙烯装置挤压造粒系统长周期运行的因素及对策

Influencing factors of long period operation of extrusion granulation system in a full density polyethylene plant and their countermeasures

分析了中国石油兰州石化公司30万t/a全密度聚乙烯装置中挤压造粒系统长周期运行的影响因素,提出了整改措施。结果表明,当生产负荷为37.0 t/h时,将反应器中异戊烷体积分数调整至约7.2%,有效地降低了粉料的黏度,避免了在输送过程中黏结现象的发生。在粉料振动筛至缓冲罐的弯管处开设1个观察口,定期从此处清理块状物,这样可以有效降低挤压造粒机的停车次数。将粉料缓冲罐料位由之前的50%～60%调整为20%～30%,同时在其锥部增设2台氮气振荡器,定时进行氮气吹扫,可缓解堵塞现象。

The influencing factors were analyzed for the long period operation of extrusion granulation system in a 300 kt/a full density polyethylene plant of Lanzhou Petrochemical Company, PetroChina, and the corresponding measures were put forward. The results showed that by means of reducing the volume fraction of isopentane in reactor to about 7.2% at 37.0 t/h of production load, the cohesiveness of polyethylene powders was effectively decreased, and the caking was lightened along the way to extruder. By setting up a viewport at the bent tube from vibration screen of powder product to buffer tank and removing block regularly, the shutdown frequency of extruder was decreased evidently. Though adjusting the stock level of buffer from 50%-60% to 20% -30% and installing 2 sets of nitrogen gas oscillator at the conic section to purge the buffer periodically, the bridge plugging was released.