Design And DCS Realization Of Control System In LNG Refrigeration

China is one of the biggest coke-producing countries. Coke-oven gas is produced when making coke. Most coke-oven gas is buring directly causing environment pollution and resource waste. Using novel liquefaction process technology, Tiancheng Technology of Taiyuan Company produced LNG (liquefied natural gas) from Coke-oven gas. This new technology is the first creation, and its control system is not perfect until now. This article first analyzes problems and methods of industry control in and then designs a new process control program which combined the characteristics of new technology and requirements of process control.This article first describes the preparation process and requirements of the LNG liquefaction from coke oven gas, and then designs control programs of plate heat exchanger and compressor. Compressor surge is a major issue, and anti-surge control is the puzzle of industrial automation, and also is main content of this paper. Based on the similarity principle, applications for anti-surge in compressor is proposed in this paper. A new type of anti-surge controller is designed through pressure limiting and settings of surge line, control line and security line. Expander refrigeration is the main equipment for refrigeration technique. by analyzing the impact of the efficiency factor, this paper proposes a method to improve the efficiency of the expander and another method for safety chain in DCS control. Under the characteristics of distillation process, the paper designs methods of optimal control in distillation.Using MACSV system of demestic DCS, according to the new features and the control program of our papers, we design it from system type, hardware configuration, system wiring, software configuration, automatic control system design. The schemes, such as automatic plate heat exchanger, anti-surge control, is first applied to DCS. Configurations of operation interface is completed according to principles of intuitive screen, easy management and online parameter changing.The DCS system is safe and reliable since it has been put into operation. It improves production efficiency, but also reduce number of parking in production trouble and labor intensity. Also the product quality has been improved. The results of this paper also are models for promoting the popularization of domestic DCS system.