热旁路塔压控制系统中两种不合理的流程设计分析

The Analysis on Two Unreasonable Flowsheet Configurations in the Distillation Column Hot Vapor Bypass Pressure Control Scheme

精馏塔热旁路塔压控制系统的控制方案设计中,常会出现两种不合理的流程设置:一种是将热旁路与冷凝液管线混合后再进入回流罐,另一种是热旁路控制阀由固定压差控制。分析了这两种流程设置对精馏塔压力控制系统造成的不利影响:前者会造成精馏塔压力波动和控制不稳定,后者则易造成控制混乱。相应的改正措施:冷凝液和热旁路气体应分别单独从回流罐底、罐顶进料;采用"浮动压差"控制器来控制热旁路控制阀。

In the distillation column hot vapor bypass pressure control scheme there are always to appeav two sorts of unreasonable flowsheet configurations： one is that the hot vapor line and the condensate line are mixed together before entering the reflux drum, the other is that the hot vapor bypass control valve is controlled by the fixed pressure difference. The disadvantageous effects caused by these two configurations are analyzed： the former can cause the distillation column pressure fluctuations and instability, the later can experience frequent control confusions. Therefore the corresponding modified measures are： the condensate should enter the bottom section and the hot vapor should enter the top section of the reflux drum individually and ＂floating pressure difference＂ controller is used to control the hot vapor bypass control valve.