1. Introduction Due to the emission of smoke and dust, China's atmospheric environment has suffered serious pollution, making flue gas purification equipment a focus of attention. Currently, the main flue gas purification equipment options are electrostatic precipitators (ESPs) and bag filters. ESPs are significantly affected by boiler operating conditions and load variations, and their ability to capture fine particles is limited. Bag filters, on the other hand, have lower initial investment, higher dust removal efficiency (over 99.9%), fewer auxiliary equipment, and can capture dust that is difficult to recover from ESPs. Therefore, bag filters are gradually becoming an important choice. The dust removal process of a bag filter mainly includes three parts: collection, cleaning, and ash discharge. The dust collection unit, as the name suggests, filters air containing smoke and dust through filter bags, trapping the smoke and dust inside the bags while the purified air is discharged from the outlet. The dust removal unit is a crucial component of the dust collector. As dust accumulates in the filter bags, it obstructs the discharge of purified air. Therefore, regular dust removal is necessary. By controlling isolation valves and pulse valves, heated air is fed into the filter bags. The heated bags expand, and combined with the airflow, the dust falls onto the conveyor belt and is transported to the ash hopper. The schematic diagram is shown in Figure 1. [align=center] Figure 1 Schematic diagram of a baghouse dust collector[/align] 2 Overall Design of the Control System 2.1 Overall Design The electrical control system of the baghouse dust collector mainly includes the design of the high-voltage and low-voltage sections. The high-voltage section mainly refers to the introduction of a 10kV high-voltage power supply and its distribution to various control systems, as well as the control of the high-pressure fan. The low-pressure section design encompasses: control of flue gas temperature within the flue gas duct, control of the gas source temperature, control of the collection system, control of the high-pressure blower station, control of ash conveying and unloading, and control of the ash removal system, among others. To ensure reliable system operation, a Siemens S7-300 programmable logic controller (PLC) is used to acquire digital and analog signals from the field and transmit these signals to a host computer via Ethernet. The host computer then transmits control signals to the PLC via Ethernet as needed, enabling the PLC to output control parameters for each controlled object. Simultaneously, WinCC 5.2 configuration software is used for real-time remote monitoring of the equipment, including real-time display of field switch quantities, real-time display of analog quantities, real-time modification of lower-level operating parameters, fault alarms, and recording of operating parameters. Information transmission from the lower-level computer to the host computer utilizes Ethernet to achieve centralized monitoring of the operating status of all field equipment, improving transmission quality and enabling information resource sharing. 2.2 Ethernet Communication Design Scheme In early practice, communication between PLC and WinCC often adopted the PROFIBUS fieldbus communication method. Although this method has a fast data transmission speed, the data transmission area is limited (maximum 64 bytes), and the hardware cost is very high, requiring hardware such as CP5412, EM277 PROFIBUS-DP, and PROFIBUS bus. With the rapid development of information technology, Ethernet technology has been widely developed in information networks due to its advantages of high transmission speed, low power consumption, easy installation, good compatibility, good openness, and support for many devices. In this design, Ethernet is mainly used to complete the information transmission between the host computer and the slave computer. It can easily meet the following design requirements: (1) Devices from different manufacturers can be easily interconnected, which can solve the compatibility and interoperability problems of devices from different manufacturers in the control system; (2) High transmission rate, up to 10~100Mbps; (3) Remote access and sharing/access to multiple databases can be easily realized; (4) Low hardware and software costs, with a variety of software development environments and hardware devices for users to choose from. The hardware selection for Industrial Ethernet is relatively simple. Its main function is to interconnect PLC devices with remote monitoring host computers and workstations equipped with WinCC to achieve system data transmission and monitoring. The host computer connects to the PLC via the CP1613 communication module. Since an S7-300 PLC is used on-site, the SIMATI S7 Protocol Suite communication driver needs to be installed. After installation, channel units need to be established, with each channel unit serving as a port for only one lower-level hardware driver. On the on-site lower-level end, a CP343-1 communication processor is used to connect the S7-300 PLC to the Industrial Ethernet. This module has its own processor, which reduces the CPU's communication workload and allows for the establishment of additional connections. First, the Ethernet address of the CP343-1 is defined. In the network configuration software of SIMATI, a new network link is inserted into the CPU module, and the link type is set to TCP connection. Then, a network communication ID number is defined; each network connection uses a unique ID number. The PLC software uses different ID numbers to identify different network connections. After the link is established, it is connected to a network switch via an Ethernet cable to complete the system configuration and network setup as shown in Figure 2. [align=center] Figure 2 Configuration diagram of CP1613 and CP343-1[/align] 3 Design Evaluation 3.1 System Hardware Design and Features (1) The low-voltage section uses 4 GGD type distribution cabinets: incoming line cabinet, valve control cabinet, output control cabinet and PLC control cabinet, as well as collection hood control box, manual ash unloading control cabinet, manual ash cleaning control box, etc. The power supply is sent to the power module after isolation transformer and AC voltage stabilizer, which ensures the stability and reliability of the PLC power supply. The PLC configuration of the system mainly includes: central processing unit CPU315, power supply unit PS307, interface modules IM361, IM360, digital input unit SM321, digital output unit SM322, analog input unit SM331, communication module CP343-1 and rack. (2) In order to prevent the AC line in the low-voltage cabinet from interfering with the PLC system, the output modules of the PLC are all 24V DC output type with opto-isolation. The output points drive the intermediate relays. Moreover, the intermediate relays that need to be connected to 220V AC voltage are placed in other cabinets. (3) The dust collector needs to control 48 offline valves. Each offline valve drives 8 pulse valves, for a total of 384 pulse valves. Using the traditional control method, this part would require a total of 432 PLC output control points. In order to reduce the project cost and save PLC output points, a matrix circuit was designed. In the end, only 186 digital outputs are needed, which reduces the number of PLC output points and reduces the system cost. 3.2 Software design and characteristics of the system (1) The lower-level PLC program is written using the standard software package Step7 for simatic programmable logic controller configuration and programming. The system program design adopts the structured and modular programming concept: the action control of the 8 pulse valves in the pulse backflushing system is compiled into an FC2 module; the control of the pulse backflushing automatic system is also compiled into an FC1 module. In the functional module fc1, fc2 is called, and then in the program loop execution organization block ob1, fc1 is called again. This modular programming idea can make the programming ideas clear and easy to implement; on the other hand, the program code can be reduced by function calls, and the storage space of the program in the PLC can be reduced. (2) The design of the upper computer monitoring system uses Siemens WinCC5.2 configuration software. Through standard interfaces such as ActiveX, OPC, and SQL, it can easily communicate with other software and hardware systems. The database function of the WinCC background and the global script editor based on C language make the dynamic configuration of objects very flexible, convenient and fast. Among them, the project function is only effective in the actual project on which it is created, so it can be easily modified and reduce unnecessary time waste on site. The project function is a C function and can be written or modified as needed. In addition, the system design implements a hierarchical management login mechanism. Engineers can modify data settings, while ordinary operators can only perform monitoring operations. For the detection data, soft matrix technology is used to achieve multi-point status monitoring. For the nonlinear state of the field analog signals, a computer-based piecewise linearization method is employed. All field parameters are categorized and stored in the database in real time, greatly facilitating real-time online operation for field process personnel. 4. Conclusion Ethernet, as an open network, has been widely developed and applied in the field of industrial control, especially in monitoring systems. It enables more convenient and faster information transmission and allows for remote monitoring, achieving high-quality communication with relatively low networking costs. A good human-machine interface enriches human-machine interaction and provides strong self-diagnostic functions, effectively improving the system's safe operation level. The PLC matrix circuit design simplifies the PLC output nodes, giving it a high cost-performance ratio. Practical applications by companies such as Taigang and Jiaogang show that this design is stable and reliable in performance, facilitates process parameter modification, adapts to complex field conditions, meets the actual needs of users, and creates significant economic and social benefits, demonstrating strong practicality.