With the development of the chemical industry, production is becoming increasingly complex, large-scale, high-speed, and automated. To ensure stable, reliable, and safe production, the parameter detection and automatic control of the production process must meet higher requirements. PLC (Programmable Logic Controller) systems can meet these requirements and play a crucial role in the design of production process control systems and the protection of mechanical safety.
PLC systems can program various control algorithms to achieve closed-loop control, automating chemical production processes and controlling them under optimal conditions. This reduces raw material and power consumption, lowers production costs, and achieves high quality and high output. It also reduces human error, ensures production safety, prevents accidents from occurring or escalating, and extends equipment lifespan while improving equipment utilization.
Currently, over 200 manufacturers worldwide produce more than 300 varieties of PLC system products, primarily used in industries such as automotive (23%), grain processing ( 16.4 %), chemical/pharmaceutical ( 14.6 %), metal/mining ( 11.5 %), and pulp/paper ( 11.3 %). In the chemical industry, specific applications mainly involve switch logic control, widely used for single-machine control, multi-machine group control, and even automated production line control, as well as closed-loop control of analog quantities such as temperature, pressure, and flow. For example, in sulfuric acid production, temperature control plays a decisive role. The roasting intensity and temperature, as well as the gas concentration, in the furnace pre-process determine the normality of temperature and gas concentration in various parts of the conversion process, and the conversion rate. The application of PLC systems can adjust the interactions and influences between different temperatures and gas concentrations, thereby achieving safe control of the production process. In chemical process control, a PLC system mainly consists of five parts: a central processing unit, a memory, input/output modules, a programmer, and operating modes (online programming and offline programming).
Furthermore, in the petroleum processing industry, large rotating units are crucial components of the equipment, such as the main blowers, gas compressors, flue gas turbines, and steam turbines in catalytic cracking units. These units have high power output and operate under harsh conditions, making emergency shutdown or lockout protection for these devices essential in the event of a sudden accident.
The interlocking-self-protection system of the heavy oil catalytic cracking gas compressor unit of Shenyang Paraffin Chemical Co., Ltd. was constructed using a PLC system. It has performed stably in subsequent production processes and has repeatedly protected the unit and production equipment in the event of an accident, greatly reducing the risk of accidents.
Currently, the application of PLC systems in my country's petrochemical industry has made great progress. Several companies in Shanghai, Hangzhou, Dalian, and Suzhou are now able to produce small and medium-sized PLC systems and apply them in industrial production.
