Design Of Temperature Control System Based On PLC On-line Gas Chromatograph Analyzer

The design is the Lanzhou Petrochemical Company quality inspection department on-line quality instrument room research projects, the design of the main to ensure online gas phase chromatography analyzer stability and accuracy for the purpose, the gas phase chromatograph oven temperature control system design.Online gas chromatography is a kind of modernized process detecting instrument is also one of the instrumental analysis to separate a complex mixture, it in oil refining and chemical industry, medical and health, environmental monitoring, food inspection and synthetic materials industry have widely application. The constant temperature box is the core component of the on-line gas chromatograph, and the samples can be analyzed and detected after heat treatment in the constant temperature box. Temperature control system of constant temperature control system stability and accuracy directly affect the accuracy of the results of the analysis of the instrument,and the temperature control accuracy is higher. Constant temperature box under the influence of many factors, for example: by the type and concentration of the test substance, field environment, and a thermostat, thermal insulation materials and temperature control system with a lag, mathematical models are difficult to establish precisely. It is found that the conventional aluminum furnace thermostat, thermal inertia, slow heating rate, temperature control precision low faults, and use the control mode, of online gas phase chromatograph oven temperature control effect is not ideal.Phase compared to conventional aluminum thermostats, air bath temperature control method with fuzzy PID control algorithm, on the online chromatographic analyzer thermostat temperature control has a stronger stability and accuracy. The fuzzy PID algorithm has strong self learning and adaptive ability, to control the mathematical model of the object is not dependent.In this paper, the temperature control technology and development status of on-line gas chromatographic analyzer are described. The working principle and structure of on-line gas chromatographic analyzer are introduced in this paper.Through the understanding of the working principle and structure of the constant temperature box, the mathematical model of constant temperature box is established based on thermodynamics and automatic control principle. Aiming at the disadvantages of the cast aluminum oven instrument selection, control algorithm is introduced into the air bath temperature control and fuzzy PID. In order to improve the accuracy and stability of the temperature control system of fuzzy PID controller of the concrete design method and the theoretical basis of fuzzy control; simulationprove fuzzy PID algorithm has small, fast response, high control precision, validation of in practical application by temperature control system instability, imprecise leads to frequency analysis of the instrument error result is reduced greatly, improve the accuracy of analytical instruments.