In industries such as chemical and pharmaceutical, reactors are key equipment, and their performance and efficiency directly affect the quality and output of products. However, traditional reactor control methods often have problems such as human operation errors and unstable equipment operation. In order to solve these challenges, it is particularly important to choose a PLC (programmable logic controller) control system suitable for reactors.
When choosing a PLC control system, we need to consider the number of control points. The number of control points refers to the number of signals that need to be monitored and controlled in the system, including digital input and output points, analog input and output points. If the reactor has a small number of control points, PLC is a suitable choice because its I/O modules can be flexibly configured to meet simple control needs. However, when the number of control points is large and the control logic is more complex, it may be necessary to consider using a DCS (distributed control system). DCS uses multiple controllers to better meet complex control needs. But in many small and medium-sized reactor applications, PLC is more common due to its economy and flexibility.
Consider the scale and control requirements of the reactor
Small reactor
For small laboratory or pilot-scale reactors, the control parameters are relatively few, and only a few parameters such as temperature and stirring speed may need to be controlled. At this time, you can choose a small PLC control system, such as the Siemens S7-1200 series or the Mitsubishi FX3U series. These small PLCs have enough I/O points (input/output points) to connect basic equipment such as temperature sensors and stirring motors, and their programming is relatively simple to meet basic control needs.
Large reactors
Reactors used in large industrial production often need to control multiple parameters, such as temperature, pressure, liquid level, flow, stirring speed, etc., and have high requirements for control accuracy and reliability. In this case, you need to choose a medium or large PLC control system, such as the Siemens S7-1500 series or the Rockwell ControlLogix series. These PLCs have more I/O points, can process signals from multiple sensors and actuators at the same time, and have fast processing speed and large storage capacity. They can run complex control algorithms, such as advanced PID control (proportional-integral-derivative control) and multivariable control algorithms.
Select according to control accuracy requirements
High-precision control requirements
If the control accuracy of the reactor for parameters such as temperature and pressure is required to be within ±1℃ or ±0.1MPa, it is necessary to select a PLC system with high-precision analog input/output modules. For example, some high-precision analog input modules can accurately measure sensor signals to 12-bit or 16-bit resolution, thereby more accurately collecting parameters in the reactor. At the same time, the PLC itself should have strong computing power to support complex control algorithms to achieve high-precision control.
General precision control requirements
For reactors that do not require particularly high control accuracy, such as some reactors for chemical product production that do not require very strict product quality, a control accuracy of about ±5℃ or ±0.5MPa can meet the requirements. In this case, a conventional precision PLC system can be selected, which is relatively low in price and more cost-effective.
Consider reliability and stability
High reliability requirements
In the control of reactors in the chemical, pharmaceutical and other industries, due to the continuity and safety requirements of the production process, the PLC control system must have high reliability. Choose a PLC system with redundant functions, such as dual CPU redundancy, dual power supply redundancy, I/O redundancy, etc. Redundant design can ensure that when one component fails, another redundant component can immediately take over the work, so that the system can run uninterruptedly. At the same time, the mean time between failures (MTBF) index of the PLC should be considered. The higher the MTBF value, the better the reliability of the system.
General reliability requirements
For some reactors in non-critical production links, such as small reagent preparation reactors, the reliability requirements are relatively low. You can choose an ordinary single CPU, single power supply PLC system, but you must also ensure its basic quality and stability, such as choosing products with good brand reputation and quality certification.
Compatibility with other equipment
Reactor PLC control systems usually need to be integrated with other equipment, such as host computer monitoring software, various sensors, actuators, etc. When selecting a PLC system, consider the compatibility of its communication interface and communication protocol. For example, the PLC should have common communication interfaces, such as Ethernet interface, RS-485 interface, etc., to facilitate data transmission and remote monitoring with the host computer. At the same time, PLC must be able to support multiple industrial communication protocols, such as Modbus, Profibus, OPC, etc., so as to communicate with sensors and actuators produced by different manufacturers.
