铬系催化剂生产HDPE牌号切换的工艺调整

分析了用铬系催化剂生产高密度聚乙烯(HDPE)的工艺、生产特点及关键步骤.铬系催化剂进入聚合釜前,必须经高温活化处理约35 h.用铬系催化剂生产的HDPE典型牌号HD4801向HD5420转产,必须调节好流化气速,将反应温度从104 5℃降至99.8℃,可在20h内完成.HD4801和HD5420的密度相差不大,但是熔体流动速率相差较大,所以转产时,需平稳控制HDPE粉料密度、适当调整反应温度及乙烯浓度.

Process adjustment for grade transition in HDPE production with chromium catalyst

The author analyzed the technology,production characteristics and key procedures of producing high density polyethylene(HDPE) with chromium catalyst.The chromium catalyst had to be activated for 35 hours at high temperature before being fed into the reactor.The fluidizing gas velocity should be properly adjusted and the reaction temperature should be lowered from 104.5 ℃ to 99.8 ℃ in less than 20 hours once starting the grade transition from typical HD4801 to HD5420 in the production with chromium catalyst.There was little difference in density but wide discrepancy in melt flow rate between the two grades.Therefore,the density of HDPE powder should be controlled stably and the reaction temperature and ethylene concentration should be regulated properly during the period of grade transition.