Based on the practice, this paper expounds the use of intelligent PID regulator, and hopes to provide some reference and experience for the majority of battery production automation technology practitioners.
[Abstract] NMP recycling is an important part of lithium battery production. Utilizing the PID regulator of Yudian to accurately control the temperature of the recycling process, it can greatly improve the purity of recycling and greatly save the cost of expensive NMP materials. Based on the practice, this paper expounds the use of intelligent PID regulator, and hopes to provide some reference and experience for the majority of battery production automation technology practitioners.
[Key words] NMP recycling; lithium battery production line; intelligent PID regulator
[Chinese Library Classification Number] TQ [Document Identification Code] A [Article Number] 1007-1865 (2014)
[Author] Gao Xianfang (1985-), male, Zhaoqing, graduated from Xiamen University, majoring in industrial control application engineering.
[Author] Luo Jianhui (1984-), male, Loudi, graduated from Huaqiao University, mainly engaged in industrial control application engineering.
An Application of Yudian AI Series PID Controller in the NMP Recovery system of Lithium Battery Industry
Xianfang Gao Jianhui Luo
(Yudian Automation Technology Co., Ltd., Xiamen 361006, China)
The NPC(N-methyl-2-pyrrolidone) recovery is an essential part in the lithium battery producing. Using the professional PID controller from Yudian company to achieve precise control on the recovery temperature, can improve the purity of recovery greatly, and We have, by press this paper, to share our work and offer some experience to the related persons engaged in the industry automation Work.
Keywords: NMP Recovery;Producing of Lithium Battery;Artificial Intelligence PID controller
1 NMP recovery principle
NMP-methylpyrrolidone is a liquid which is condensed with methylamine by using Y-butyrolactone as a raw material. It is highly volatile and highly permeable. It has a pH of 7-9, is flammable and explosive, and is produced in lithium batteries. Widely used in applications. In the lithium battery electrode manufacturing process, the coating opportunity generates high temperature NMP exhaust gas. If the exhaust tower absorbs the environmental standards and directly discharges, it will cause the waste of expensive NMP. The NMP in the exhaust gas can generally be recovered by a freeze recovery method. The principle of recovery is to use a cooling water to cool the high temperature air containing NMP through a water-gas heat exchanger, so that the NMP in the exhaust gas is separated from the air in a liquid form and then collected and purified to achieve the purpose of recovery. After the exhaust gas is concentrated to a certain concentration, the NMP can be condensed and recovered by the freezing method. See Figure 1 below for the principle.
Figure 1 Principle of NMP recovery
Pic.1 Principle of NMP Recovery
2 PID regulator application
2.1 The project proposes that the control cabinet of an NMP recycling line in the factory area of ​​Shenzhen BYD Lithium Battery Co., Ltd. is mainly composed of Proface GP-4000 HMI of Japan and Siemens S7-200 PLC. The control of the recovery temperature uses PLC's built-in PID calculation. But the control effect has not been ideal. The company's process department applied for the transformation of the equipment. After investigation by the engineering department, it was found that the valve adjustment to the temperature change was lagging due to the certain delay of the change of the valve opening degree. Causes frequent fluctuations in temperature above and below the set value. After the project was established, the project leader decided to use the Yudian AI-719 series high-precision intelligent PID regulator instrument to transform the equipment, and replaced the original PID calculation function by the PLC with a professional temperature PID regulator.
According to the customer's request, Yudian engineers selected the model AI-719-A-I4-X3-L5-S4. This regulator has the following functions and performance: 0.1-level precision linear current analog input, analog output, with two normally open relay alarms, RS485 module supports AIBUS and MODBUS RTU protocol; built-in intelligent PID and standard PID dual algorithm Select, fine control mode, measuring the sampling rate 12.5 times per second, the minimum control period is 0.24 seconds.
The customer chose this AI-719 regulator for closed-loop control of the proportional valve for cooling feed water in NMP recovery to control the temperature in the recovery vessel to the appropriate target value. The control principle is shown in Figure 2.
Figure 2 Recovery temperature control process
Pic.2 Control Processing of Recovery Temperature
2.2 Project Implementation In order to achieve the project's functions with minimal cost, the customer programmed the corresponding screen on the original Proface HMI to control and modify the PID regulator settings. The temperature probe also directly uses the originally installed temperature acquisition probe (converts -50 ° C ~ +180 ° C into a 4-20 mA signal to the PLC). The relevant instrument parameters are set as shown in Table 1.
Table 1 PID regulator parameter settings
Tab.1 Parameter Setting On the PID Controller
2.3 After the installation is completed, the user finds that the intelligent PID calculation of the AI-719 regulator is very sensitive and the control effect is good. According to customer experience, the recycling temperature of this recycling line is set to 20 °C, the recycling effect is the best. In the past, when the PLC was controlled, the actual temperature value fluctuated frequently by ±5 °C. After using the Yudian PID regulator, the actual temperature value fluctuated within ±0.8 °C, and the fluctuation frequency was greatly reduced. The purity of NMP recovery has increased by 20% and the project has been successfully accepted. This project has also been rated as a model project, and all NMP recycling systems will be retrofitted and designed with reference to this system in the future.
3 Summary PLC is developing rapidly and the technology is becoming more and more mature, but it is still unable to replace the professional PID regulator in terms of fine temperature control. Yudian AI-719 intelligent PID regulator's high-performance low-power design, and unique technology in PID adjustment, with artificial intelligence adaptive function, more professional than PLC built-in PID algorithm, in the application of temperature control system A good control effect. Because of its strong expandability, this instrument is very flexible in terms of input and output methods and communication, which enables the project to achieve significant results on the basis of low cost and low modification, achieving low investment and high return, and has a good promotion. value.
references
[1] Zhou Weibo. Improvement and construction of NMP waste gas treatment and recovery process for lithium battery electrode coating machine [J]. China Science and Technology Information, 2007, No. 8: 27-28.
[2] Xiamen Yudian Automation Technology Co., Ltd. AI-719/719P Precision Artificial Intelligence Industrial Regulator Instruction Manual (V8.21)[M]. Xiamen: 2013.
Terminology
PID proportional, integral, and derivative.
The PID regulator uses the proportional, integral, and differential calculations to calculate the amount of output for the output meter based on the error of the system.
NMP chemical Chinese name N-methylpyrrolidone, chemical common name or trade name NMP, chemical English name N-methyl-2-pyrrolidone, colorless transparent liquid, boiling point 203 ° C, flash point 95 ° C, miscible with water It is soluble in ether, acetone and various organic solvents. It has a slight ammonia smell and is chemically stable. It does not corrode carbon steel or aluminum and is slightly corrosive to copper. It has the advantages of low viscosity, good chemical and thermal stability, high polarity, low volatility, and infinite miscibility with water and many organic solvents.
PLC Programmable Logic Controller (PLC), which uses a type of programmable memory for storing programs internally, performing user-oriented instructions such as logic operations, sequence control, timing, counting, and arithmetic operations, and Control various types of machinery or production processes through digital or analog inputs/outputs.
HMI is the abbreviation of Human Machine Interface, "human machine interface", also called man-machine interface. The human-machine interface (also known as the user interface or user interface) is the medium for interaction and information exchange between the system and the user, which realizes the conversion between the internal form of information and the acceptable form of human beings.
RS485 A hardware description of the communication interface. It requires only two communication lines to transfer data between two or more devices.
MODBUS was invented in 1979 by Modicon (now a brand of Schneider Electric) and is the world's first bus protocol for industrial sites.
AIBUS is a communication protocol developed by Xiamen Yudian Automation Technology Co., Ltd. for AI series display control instruments. It can realize comprehensive functions with simple instructions. It is characterized by writing parameters and reading functions at the same time, so the parameters are not destroyed when reading. The cycle time, plus the smaller instruction length, has a faster rate than MODBUS.
A proportional valve is a hydraulic valve whose output is proportional to the input signal. It continuously controls the pressure, flow and direction of the flow proportionally to a given input signal.
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