关键词:

双峰聚乙烯, 牌号切换, 催化剂切换, 停留时间分布, 优化

Abstract:

The Borstar technology contains a loop reactor and a fluidized bed reactor connecting in series. Aiming at minimizing the grade transition time and the quantity of off-specification product, a grade transition model involving catalyst changeover was presented for this process. Meanwhile, the models of instantaneous and cumulative polyethylene properties, including melt index and polymer density in each reactor, were presented for the tanks-in-series process involving catalyst changeover. The results showed that if grade transition involved catalyst changeover, the recommended optimal strategy was to feed new catalyst step by step. Further more, it is necessary to consider the respective demands for manipulated variable profiles by old and new catalysts and the effect of old catalyst mass fraction on resin properties in each reactor. In this way, the transition time was remarkably reduced, the sharp fluctuation of manipulated variables was restrained and the profiles of polymer properties were smoothed up.

Key words:

双峰聚乙烯, 牌号切换, 催化剂切换, 停留时间分布, 优化