PLC Automatic Control System

At present, the control level of domestic and foreign beer production (saccharification, fermentation section) can be divided into four grades

(1) PID manual control

Its main feature is that the valve is manual. The analog signals in the production process such as temperature, pressure, liquid level, flow rate, turbidity, and electrical conductivity are collected by conventional decentralized instruments, and then displayed centrally or on-site. Set the start and stop, the valve is operated by the workers to the scene. In this way, the beer production process parameters cannot be reliably implemented, the consistency is poor, the beer quality is greatly affected by human factors, and the labor intensity of the workers is very large, the main production equipment and devices cannot work in a better state, the raw materials The utilization rate is low, the energy consumption of the product is large, it is impossible to use more complex advanced technology to produce beer, and the production cost is high.

(2) PLC semi-automatic control mode (centralized manual control)

It is represented by a mosaic simulation screen. Its main feature is that the valve mostly adopts pneumatic or electric automatic valve. Take measures such as data collectors to collect various process quantities and enter the control room. Generally, a mosaic simulation screen or a host computer is installed. Display various process parameters such as temperature, flow rate, pressure, liquid level and the opening status of motors and valves on the simulation screen or host computer, and monitor the production process. On the stage, the valve is opened and the motor is started and stopped remotely to meet the process requirements, and the key data in the production is recorded manually. However, due to the frequent intervention of operators, the quality and taste of beer also fluctuate greatly, and the labor intensity of workers is also relatively large.

(3) PC + data acquisition card

Represented by industrial PC plus various data acquisition cards, various signals in the process control are sent to the data acquisition card inserted in the industrial PC slot through the corresponding transmitter at the periphery, and each signal is displayed on the PC screen. Various production process parameters are used to control the start and stop of valves, pumps, motors and other equipment to meet process production requirements. At present, many domestic brewery fermentation workshops use this system for control. To a certain extent, the problem of beer production process control is solved, but there are the following shortcomings: a. The system reliability is poor. b. The screen is rigid and lacks the flexible program script control function of general industrial control configuration software. At the same time, the security of the system itself is poor, and it is difficult to establish an effective operation level and authority system. c. The scalability of the system is poor. d. Due to the large drift of peripheral devices, the control accuracy of the system is greatly affected by the four seasons of the year, and the control effect is not ideal.

(4) Distributed control system

Advanced computer control technology, multi-layer network structure and advanced control algorithm are used to automatically control the production process. The main feature is that PLC is used as the lower computer. At present, there are DCS (distributed control system) control system and (FCS field bus control system) control system. In this control method, the control unit in the lower computer network generally adopts PLC, which has high reliability (generally can work continuously and reliably for 20 years), stable performance, and the upper computer network is compatible with various communication protocols (such as TCP/IP protocol). ), and the standard database, which are hung on the local Ethernet subnet, which is convenient for information integration management and function expansion. But the main disadvantage is the large investment in one time.