摘要:蒸馏操作是炼油、石化生产中一个十分重要的环节，蒸馏塔的控制直接影响到工厂的产品质量、产量和能量的消耗。而作为蒸馏塔系统中一个重要的组成部分，回流罐的运行情况直接影响着塔顶物料平衡，进而影响整个精馏塔的运行情况。因此，若回流罐系统的控制存在问题，则将会对整个蒸馏塔的运行造成不利的影响。本文采用西门子S7-200系列PLC对石油蒸馏塔的回流罐液位进行控制，提高液位控制的准确性和安全性，使液位达到较为理想的效果。结合模拟量模块EM235、液位传感器等，组成一个基于S7-200系列PLC的石油蒸馏塔回流罐液位控制系统，实现对回流罐液位的控制与检测。在设计中运用PLC中的PID来实现对液位的控制，建立起闭环控制系统。设计回流罐液位PID控制程序 ，采用组态王6.53软件设计组态画面，实现系统的模拟运行与调试。

关键词：可编程控制器(PLC)；回流罐液位；PID控制

Abstract:Distillation operation is a very important link in oil refining and petrochemical production. Distillation column control has the direct influence on the quality of plant products, production and consumption of energy. As one of the important part of the distillation system, situation of backflow can directly influence the material balance, which affects the operation of the whole of the column. Therefore, if the control of the backflow system exists problems, it will have an adverse influence on the distillation column operation. This paper adopts Siemens S7-200series PLC for backflow liquid level control, improve control accuracy and safety, so that the liquid level reaches the ideal effect. Combined with the analog module EM235, liquid level sensors, composed of a series of distillation column based on S7-200PLC constant liquid level control system, realize the backflow liquid level detection and control. In the design of the extensive use of PID in the PLC to achieve the level of control, establishment of closed loop control system. Design of reflux tank of liquid level control procedures PID and By Kingview 6.53software design configuration screen, the system simulation run and debug. 

Key words：Programmable Logic Controller(PLC); Backflow cans level; PID control