Implementation Of Electromagnetic Induction-Heating Cylinder Dryer In Paper Mill And The PLC Control System

As the current situation of paper-making industry, Hot Oil Cylinder Dryer and Stream Cylinder Dryer are still being used widely in many paper mills domestically and internally. But many disadvantages were exposed during the decades of production, such as low utilization of energy, high cost of device, pollution of the environment, frequent accidents, and so on .With the growing shortage of energy and the development of people's consciousness to protect environment, many factories are improving their old devices and developing new and efficient facilities. In order to reform the traditional cylinder dryer, which is the most energy-consuming device in the paper-making process, it is necessary to find out a convenient way of heating without any pollution."Induction Heating" is appropriate, for it is safe, efficient and with uniformity for heating. In addition, it has been used in smelting and automotive industry successfully. The innovation of this paper is to apply "Induction Heating" to paper-making cylinder dryer. Based on this idea, a medium-sized electromagnetic induction heating cylinder dryer was designed, which has a diameter of 1200mm and a width of 400mm . Besides, by using SIEMENS S7-200 serial PLC products, the control systems were developed, which are low-cost, with high degree of accuracy and convenient operation. In the test for about one year, it runs stably, meeting all of requirements of production and saving energy apparently. Consequently, the conclusion can be made that, with promising future in market, it can replace the traditional hot-oil and stream cylinder dryers.This thesis expounds the process of developing induction heating dryer, including the elements of induction-heating power supply, the design of cylinder dryer,the process of paper-making, selection of PLC control system modules, and control algorithm. The main content is about:(1) analysis of the disadvantages of traditional cylinder dryers; introduction of elements on induction heating, and current development as well as application of induction-heating power supply.(2) analysis of two types of induction-heating power supply-parallel mode and serial mode; compare of their features respectively; introduction of several methods of capacity controlling, choice of the PWM & PWM method; deduction of the relationship among the power, the phase-angle,and angular-frequency; a brief explanation of the control circuit.(3) compare of the two reasonable compounding modes of cylinder dryer and dry ovens;introduction of the all paper-making flow process, constituted with dry ovens and cylinder dryer; illumination of the mechanism of humid gas circulation system; choice of the equipments to measure prodcedure parameters, along with the determination of the mode and amount of PLC modules according to the practice.(4) the way of writing the PLC control program based on the PID algorithm; explanation of the principles of filtering algorithms, PID algorithm and their amelioration; application of many algorithms to the codes, such as "sliding mean-value filtering algorithm with deadzone'7'Differential ahead PID algorithm'V'PID algorithm with dead-zone"and "Partial differential PID algorithm", improving the quality of control.