Research on the Application of Energy Saving Technology of Electromagnetic Heating in Plastic Industry in the Heating System of Extrusion Machine Zhao Zongbin, Zhu Binxiang, Yang Dali 2, Li Jinrong, Zhang Jiangwen, Li Mingzhang 2 (1. Hefei General Machinery Research Institute, Hefei 230031, China; 2. Shandong Jintai Energy Saving Technology Co., Ltd. , Liaocheng, Shandong 252000) The production environment has serious thermal pollution. By analyzing the working principle of the extruder heating system and the power of the original resistance heating system in a plastic pipe manufacturing enterprise, the energy-saving technology of the enterprise's extruder has been successfully implemented in energy-saving technological transformation. The results show that under the premise of meeting the requirements of the production process, the electromagnetic heating technology achieves rapid, efficient, and safe heating, and the energy-saving rate is more than 25%.
The extruder heating system of a plastic tube manufacturing enterprise uses the traditional resistance coil heating method to heat the raw material in the extruder barrel. There are three disadvantages to the resistance ring heating method: (1) The resistance ring is easily burned due to high temperature aging, and the service life is short and the maintenance volume is large. (2) Low utilization of thermal energy and serious energy waste. The heat conversion efficiency of the resistive ring heating is only about 35%, and 65% of the heat is lost to the surrounding environment. (3) Thermal pollution in the surrounding production environment. Especially in summer, the ambient temperature of the workshop exceeds 45C, not only the working environment of the workers is poor, but also the use of axial fans to reduce the temperature increases the production cost of the company. 10. In view of this, this paper has been widely used in heavy oil extraction, gas pipeline plugging, The electromagnetic heating technology in oil storage tank insulation, bitumen filling, plastic coating and thermosetting glass production 12-3 The energy-saving technological transformation of the enterprise's extruder heating system was implemented, and good energy-saving effects were achieved.
1 Electromagnetic Heating Energy Saving Technology Principles and Features 1.1 Principle of Electromagnetic Heating Technology Electromagnetic heating technology is an energy-saving technology that converts electric energy into heat based on Faraday's electromagnetic induction principle. The technology uses an electromagnetic heating controller to invert the AC380V and 50Hz input voltage into a DC alternating current source, and then converts the direct current into a high frequency current with a frequency of 20 to 40 kHz. A high-speed, high-frequency current flows through the coil to generate high-speed changes. Changing the magnetic field, electrical energy is converted into magnetic energy. The magnetic field lines in the magnetic field generate numerous small eddy currents in the metal body when the magnetic field lines pass through the magnetic conductive metal material, causing a magnetic field inside the metal, causing the metal iron molecules and atoms to violently rub and generate heat themselves. Metal self-heating, heat conversion rate of up to 95% H. Electromagnetic heating technology as shown.
The principle of electromagnetic heating of insulating and insulating layer Fig. 1.2 Application of electromagnetic heating technology in the heating system of the extruder and its characteristics The application of electromagnetic heating technology in the heating system of the extruder is to use the principle of electromagnetic induction to heat the metal barrel itself to heat The raw material in the barrel, and a certain thickness of insulation material is added outside the barrel, which greatly reduces heat loss and improves the efficiency of thermal energy utilization. Since the electromagnetic heating coil itself does not generate heat and is made of insulating material and high-temperature cable, there is no problem that the resistance wire is oxidatively blown at high temperatures to reduce its service life.
Electromagnetic heating technology compared with resistance heating, has the following six characteristics: (1) electromagnetic heating host equipment through intelligent closed-loop control and comprehensive protection features, long-term stable operation, design life of up to 10 years, the heating coil long-term durable maintenance-free ,Reduce the cost of secondary maintenance; (2) The electromagnetic heating method is internal heat type, reduce heat loss, and at the same time the external burden layer thermal insulation cotton and insulation board, improve the thermal energy utilization; (3) fast heating, shorten the pre Heat and temperature increase time, increase productivity, heat evenly at the same time, improve the finished product rate; (4) The heat dissipation to the surrounding production environment is extremely low, the workshop work environment is improved, save the cost of cooling; (5) The heating power is only the original resistance heating total The power of 30% ~ 60%, to reduce the workload of existing transformers, increasing the margin of the transformer. (6) The temperature control is more accurate (1 C), reducing the temperature change inertia, avoiding the disadvantages of resistance heating temperature drifting up and down, ensuring product quality.
2 Extrusion machine heating system features of a plastic pipe machine Table 1 Extruder barrel different temperature zone technical parameters No. temperature zone number screw diameter/mm heating temperature/C power/kW 1 zone 2 zone 3 zone 4 zone a plastic pipe The production company adopts a double cone screw extruder, and the heating system uses the traditional resistance ring heating method to heat the raw materials in the barrel. The preheating time is 3h, the total resistance power is 42.8kW. The total length of the extruder screw is about 2200mm. It is divided into 6 temperature zones, except for Zone 1 which does not require cooling, the other 5 temperature zones need to be cooled by fans. The specific technical parameters in each temperature zone are shown in Table 1.
The extruder heating temperature profile is as shown.
Extruder heating temperature characteristic curve 3 Application of electromagnetic heating technology in the heating system of the extruder 3.1 The technical solution Through the above analysis of the extrusion machine heating system process characteristics and the original resistance heating power in a plastic pipe production enterprise, to meet the production Under the premise of process requirements, the total power of the electromagnetic heating is determined to be 30kW. According to the analysis of the power situation of the extruder barrel in different temperature zones, two 15kW electromagnetic heating mainframes are to be used, and two mainframes are installed in a control cabinet. Each host controls three temperature zones, and the control modes are allocated as follows: 1, 3, and 52 zones are controlled by one, and zones 2, 4, and 5-1 are controlled by another.
Fan cooling (small 'change the original way of cooling) Electromagnetic heating system working diagram In the production process, District 1 does not need to reduce the temperature, the first time in the transformation of the bread barrel outside the high temperature insulation insulation material, and then in the insulation material wound inductor coil The other five temperature zones need to be cooled by a fan. In the retrofit, the insulating plate is firstly installed on the barrel to make the cooling air duct, and then the inductor coil is wound on the insulating plate. The insulating plate and the outer wall of the barrel are reserved for fixed gaps. The air inlet and outlet are reserved on the board, the air inlet is connected with the fan, and the fan and the control part use the original system.
The annual electromagnetic heating system of the plastics industry is mainly composed of a control cabinet and a heating coil, and can be seamlessly connected with the extruder. The schematic diagram of its work is shown in the figure.
3.2 Analysis of the effect of energy-saving reform After 3 months of production operation, the application of electromagnetic heating technology in the heating system of the extruder is very good. The following effects are analyzed from the aspects of direct energy-saving effects, indirect effects and temperature accuracy control. Electromagnetic heating energy-saving renovation implementation site as shown.
Fig. 2.2.1 shows the direct energy-saving effect of the electromagnetic heating energy-saving retrofitting. When the original resistance heating method is adopted, the average heating power of the extruder heating system is 16.8 kWh per hour when the heating system is in normal operation. After the electromagnetic heating technology is reformed, the heating system of the extruder is normal. Operating power consumption per hour h; According to the normal production of 300d per year, the annual energy saving after implementing electromagnetic heating energy-saving reform is: 3.2.2 Indirect effect The principle of electromagnetic heating is to use the high temperature coil to generate electricity to generate magneto-thermal conversion, high conversion rate The production process will not cause the wear of the coils, which saves the expense and maintenance cost of the traditional resistance heating that needs regular replacement of the resistance heating sheet, and improves the production efficiency; at the same time, it reduces heat loss to the surroundings and improves the production working environment.
3.2.3 Temperature Accuracy The important index of controlling the heating system of the extruder is to ensure the temperature accuracy of each temperature zone of the barrel. Many plastic pipe products require that the temperature does not fluctuate by more than ±5C. Electromagnetic heating technology is configured rationally and utilized. The PID proportional integrator regulator of the device effectively reduces the temperature rise inertia; the temperature fluctuation is controlled at 1C, and the temperature is accurately controlled. 4 Conclusion In the heating system of the extruder, electromagnetic heating method is used instead of the traditional resistance wire heating method. The operation is stable and reliable. It can not only meet the original production process, but also has significant direct and indirect energy-saving effects, in line with the national energy-saving emission reduction policy. Has a larger promotional value.
However, in order to further ensure the continuous operation of production, reduce the failure rate, improve the temperature control accuracy, we should also strengthen the study of the electromagnetic heating control system, such as the adaptive control of the adjustable parameters for the supply voltage instability 6-6, frequency conversion Application of technology in the temperature control of extruders. In addition, the optimization of electromagnetic heating technology for different processes is still the focus of the next step.
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