Improvement of Electric Heating Method for Chemical Equipment

Technical Improvement of Electric Heating Method for Chemical Equipment Huang Luji Feng Yeliang2 Luo Yingjun3 (1. Zhengzhou Urban Construction Technical School, Zhengzhou 450051, China; 2. Zhongyuan Dahua Group Co., Ltd., Liyang 457000, Henan, China; 3. Henan Chemical Research Institute Institute, Henan Zhengzhou industrial equipment temperature control stability and accuracy.

5:B Article ID: 1003―3467 (2004) 10―0041―01 In recent years, electric heating equipment has become more and more widely used in chemical production. Compared with traditional steam and fuel heating methods, the use of electric heating method of the reactor, distiller has a convenient, quick response and so on. However, heating and heating are generally controlled by turning on or off the contactor KM to turn on or off the number of electric heating elements, and the number of heating elements and the power combination are determined during the design and manufacture of the equipment, and the actual production environment, The number of materials and other factors are changed with the actual production conditions, especially in the thermal insulation control, it is difficult to adjust the number of heating elements to balance the generated heat with the required heat, so the heating elements have to be frequently turned on and off. There are disadvantages such as excessive overshoot, lag in response, etc., which make the stability and accuracy of the temperature control drastically lower.

1 Improvement measures 1.1 Control principle of the electric heating method of the improved chemical equipment The drawback of the traditional electric heating chemical equipment is that the heating element cannot produce continuously adjustable heating amount according to actual production needs, so the continuous adjustable heating amount is technologically improved. The essential. The use of a bidirectional thyristor as the actuator of the electric heating device, coupled with PID control can well solve this problem. Bidirectional thyristors are stationary high-power electronic components that have the advantages of rapidity, small size, no noise, and no wear. By adjusting the phase of the trigger signal of the bidirectional thyristor gate, the conduction angle of the bidirectional thyristor in each half cycle of the alternating current can be controlled, and the stepless continuous adjustment of the output voltage of the bidirectional thyristor can be realized, so that the heating element can generate continuously adjustable heating amount. PID control is a predictive control method integrating proportional, differential and integral control. In the control process, closed-loop thermostatic control can be realized. The system can determine the appropriate heating voltage and heating current according to the actual production conditions. When the temperature exceeds the set value, the heating output can be reduced or stopped; when the temperature is lower than the set value, the heating output starts to increase.

1.2 After the improvement of the circuit after technical improvement, the thyristor PID heating control is adopted. In the PID closed-loop control loop, platinum resistance and temperature transmitter are used to realize the detection and signal conversion of the actual temperature of the control object, and the converted electrical signal is transmitted. To the temperature control instrument input. The PID control algorithm of the temperature control instrument compares the detection signal with the set value to determine the size of the output signal and transmit the output signal to the flip-flop of the triac. The trigger of the bidirectional thyristor receives the output signal from the temperature-controlled instrument and adjusts the phase of the trigger signal according to the magnitude of the signal, thereby controlling the conduction angle of the thyristor, controlling the magnitude of the voltage output to the heating element, and achieving continuous adjustment of the heating amount. Complete closed-loop temperature control. If the chemical equipment itself has a PLC control, the temperature control instrument can be omitted and the PID control algorithm of the PLC can be directly used to achieve the control.

2 Improved effect The improved bidirectional thyristor PID heating control method adopts stepless voltage regulation heating technology instead of traditional segmented heating control to achieve continuous adjustment of the heating amount, and the system can be automatically based on factors such as production environment, material quantity and other factors. Adjusting the voltage and current output to the heating element not only effectively reduces the overshoot, but also speeds up the system's reaction speed, improves the system's sensitivity, and significantly improves the stability and accuracy of the temperature control. In addition, the rated current of the H22 bidirectional thyristor can reach more than 1000A, and the peak voltage can reach 2200V in forward and reverse directions, which can meet the heating requirements of various chemical applications. Temperature control instrument PID proportional, integral, differential parameters can be adjusted in real time, which can achieve optimal control results.