Abstract: This paper mainly introduces the integrated design concept and features of the three-electric system (EIC) of the computer control system for the 265m² sintering machine in the new district sintering plant. The design includes instrumentation and control design, computer control system design, electrical control design, and the implementation of control functions. Keywords: 265m² sintering machine; integrated three-electric system design; automatic control; FCS; 1. Introduction The No. 1 265 m² sintering machine in the new district sintering plant uses a computer to automatically control the main process production line. This control system adopts an integrated three-electric system (EIC) control method, which mainly includes instrumentation and control design, computer control system design, and electrical control design. Considering the advanced nature, accuracy, and stability of each system of the sintering machine, the Modicon TSX Quantum series control system from Schneider Electric was selected. While absorbing the design advantages of the original three 105 m² sintering machines in the sintering plant, this design not only avoids the shortcomings of the previous three sintering machines but also optimizes the control system. After establishing the input and output signals, a control model is established, and the process control relationship is determined, improving the control level and accuracy of the sintering machine. The following section will discuss the instrumentation and control design, computer control system design, and electrical control design in detail. 2. Instrumentation and Control Design Based on the technical requirements of the 265m² sintering machine, rigorous analysis was conducted on the selection and design of the instrumentation and control equipment. The main design contents include: 2.1 Ignition Furnace Temperature Control System Ignition furnace combustion control is a crucial part of the sintering machine control. The accuracy and stability of this system directly affect the quality of the sintered ore. Ignition furnace temperature control can be selected via a cascade control system or single-loop control on the screen according to actual conditions, with seamless manual/automatic switching. When using cascade control, the operator inputs the ignition furnace set temperature into the host computer temperature regulator according to process requirements. The measured value PV of the temperature regulator is selected as the high value temperature of the ignition section, and PID calculation is performed with the set temperature. The output of the temperature regulator is used as the setting for the gas flow regulator. The opening of the gas flow regulating valve FV-701 (FZ) is automatically controlled. In single-loop control, the operator inputs the gas flow regulating valve setting according to actual conditions, and PID calculation is performed with the measured value to stabilize the furnace temperature within the specified range. The air volume is input by the operator on the host computer according to the actual situation. In addition, calculations for gas and air flow rate temperature and pressure compensation are required. [align=center]Figure 1 Schematic diagram of ignition furnace temperature control[/align] 2.2 Combustion Air Flow Control System The combustion air flow control uses an HV-701 (HZ) valve. The operator can manually control the opening of the HV-701 (HZ) valve according to production needs by referring to the combustion air flow rate value (FI-701) displayed on the computer screen using a handheld device. When the actual air flow rate is less than a certain value, the gas pressure shut-off valve and the low-pressure gas shut-off valve will be automatically shut off. 2.3 Gas Pressure Control System To ensure stable combustion in the ignition furnace, negative feedback control is used for the main gas pipe pressure. Its operation mode is divided into manual and automatic modes. - Manual Mode (M): The operator can manually control the opening of the PV-701 valve to adjust the gas pressure by referring to the gas pressure value (PI-701) displayed on the computer screen using a handheld device. - Automatic Mode (A): The operator inputs the setpoint value SP of the gas pressure on the computer screen. The computer then performs PID calculations based on the deviation between the measured gas pressure value PV (PI-701) and the setpoint value SP, automatically controlling the opening of the PV-701 valve to keep the gas pressure stable within the setpoint range. The following diagram shows the gas pressure regulation control schematic: [align=center] Figure 2 Gas Pressure Regulation Control Schematic[/align] Note: PIC - Pressure PID Control Function Block; PIK - Pressure Regulation Actuator; PT - Pressure Transmitter; SP - Pressure Setpoint; PV - Pressure Measured Value; e - Pressure Deviation. 3. Computer Control System Design Using computer control can greatly improve production efficiency. Through remote control, production time is saved and the production pace is accelerated. The 1# 265 m2 sintering machine uses a computer to automatically control the main process production line. The control system adopts an integrated instrumentation and electrical approach, with Modicon TSX Quantum series PLCs handling the sequential and loop control of the entire process. Communication between the control station and monitoring station is achieved via an industrial Ethernet ring network, ensuring stable and accurate data exchange between the various systems of the sintering machine. 3.1 Hardware Structure To optimize the hardware system configuration and utilization, the Quantum PLC products were thoroughly researched, and various modules were selected appropriately. This resulted in a technologically advanced, fully functional, easily expandable, and highly network-enabled system. The system consists of five client computers and two servers. The sintering main control room has three client computers and one server, while the batching room has one client computer and one server. This allows for monitoring of the fuel, batching, sintering cooling, and finished product screening sections. All systems are connected to the industrial Ethernet ring network via a switch. Hardware configuration: ※ Dell computer, PIII/1G/256GB/80GB/40DVD ※ Monitor, 21″ Dell, 1248×1024 ※ Ethernet card, 10/100Mbps adaptive Software configuration: ※ Monitoring software, MP7 ※ Operating system, Windows 2000 Pro Chinese version ※ Programming software, Concept 2.6 sr2 3.2 network communication The entire network is divided into two levels of control: control level and monitoring and management level. The control level connects four PLCs through optical fiber to form an industrial Ethernet ring network with a communication rate of 100Mb/s; the sintering and cooling system and the batching system are connected to remote substations through coaxial cables; all frequency converters are connected to the PLCs through the MB+ network to form an MB+ subnet. The monitoring and management level adopts a C/S structure and communicates with the four PLCs in real time through a switch. It is also considered to reserve an interface for another sintering machine and an interface for the secondary system. If a plant-level information management network is added, optical fiber Ethernet can be used to connect to the production management network through a database server to realize the rapid query and sharing of production data. 3.3 Software development of the control system The functions of the control software of this system are divided into several parts: equipment interlock control, PID adjustment, network data communication, parameter acquisition and monitoring, and fault alarm processing. The computer software for the entire sintering machine process production control is completed by Concept2.6, and the process monitoring screen is completed using MP7 monitoring software. The specific work is as follows: (1) Hardware system configuration, determining the slot of the template, and the I/O address of each module. The first task of programming is to configure the PLC hardware, determine the position of each module in the Quantum PLC station, assign addresses to I/O modules, determine the Ethernet address, and define the communication information between stations. (2) Compile ladder diagram and function block diagram programs to complete the control of various equipment. Program according to the process requirements to realize the control functions proposed by the process. Adopt the modular idea and use the software's derived function blocks to write the more repetitive parts in independent function blocks (DFB), which is convenient for finding problems and also saves the storage space of the PLC. Use ladder diagrams to complete the actions of switching quantities, and use function block diagrams to simulate the engineering quantity conversion, PID loop control, etc. (3) Operation interface configuration design: Compile the process monitoring screen according to the process requirements, establish historical trends for the main data: ignition furnace combustion temperature, gas main pressure, gas main flow, etc.; realize the monitoring of the operation status of each equipment, parameter alarm, valve adjustment and other functions. 3.3 System implementation functions The optimized control system for Laiwu Steel's No. 1 265m² sintering machine achieves automatic control of five main parts and 13 subsystems: fuel, batching, sintering and cooling, finished product screening, and main fan room. It completes the sequential start-up, stop, and interlocking control according to the system flow, as well as CRT screen monitoring. Each system's fully automatic, semi-automatic, and remote manual control modes are logically interlocked, with only one control mode active at a time, avoiding unnecessary operational confusion. During operation, if a single device in any system malfunctions, upstream devices stop simultaneously, downstream devices stop sequentially, and audible and visual alarms are triggered. 4. Electrical Control Design The main design contents of the electrical control section include the design of the flux fuel system, batching system, sintering and cooling system, and finished product screening system. 4.1 Flux Fuel System Design This includes separate control of fuel feeding and fuel crushing. The fuel feeding system mainly delivers raw materials from the raw material yard to the fuel crushing system via different feed lines. In remote mode, it is divided into fully automatic, semi-automatic, and remote manual modes. Select the fully automatic mode on the screen. The system automatically selects the silo based on the material level. It determines the running direction and feeding point of the conveyor belt and walking mechanism based on the silo's inventory level. Select the start/stop mode and press the corresponding start/stop button; the system will automatically start/stop the relevant equipment sequentially. For semi-automatic mode, manual selection of the fuel silo is required based on the material level displayed on the screen. In cases where the system lacks interlocking conditions due to malfunctions or requires operation of individual equipment, the remote manual mode is used. This mode is considered for all controlled equipment in the system. The fuel crushing system primarily feeds raw materials (anthracite and coke powder) from the raw material yard into the crusher via the fuel feeding system. After crushing, the raw materials are fed into the batching system's silos #7 and #8 for later use. The remote mode is the same as the fully automatic mode selected on the screen and the feeding system . 4.2 Batching System Design It includes three parts: the batching system, the mixing and batching system, and the mixed material feeding system. Each part is designed with fully automatic, semi-automatic, and remote manual switching modes. (1) The fully automatic mixing system on the batching tank has 5 ore bins and three material preparation models to choose from: 5-to-2 model, 5-to-3 model, and 5-to-4 model. Before feeding, the process personnel select one of the models according to production needs. After selection (e.g., selecting the 5-to-2 model), the system automatically judges the inventory of the 5 ore bins and selects the 2 bins with the lowest inventory to start material preparation. If one of the ore bins is full during the material preparation process, the system automatically selects the bin with the lowest inventory from the other 3 unused bins and automatically switches to that bin. The system will not stop, that is, the system achieves uninterrupted bin switching. Similarly, when the inventory of all 5 ore bins reaches the required level, a stop command is issued and the material feeding system stops smoothly. The semi-automatic mode is that the manual selection of ore bins is based on the inventory of each bin, and the number of bins to be used is selected according to production needs. The system prepares material according to the selected bins. No model is involved in the control. When the selected bin is full, a stop command is issued and the material feeding system stops smoothly. The remote manual mode is used when the system is not interlocked due to an abnormality or when it is necessary to operate a single device. It is not recommended to use this mode during normal production. All controlled devices in this system have been designed with this mode in mind. There is a logical interlock between the three control modes, and only one control mode is active at any given time, which avoids unnecessary confusion in operation. If a single device fails during system operation, the upstream devices will stop simultaneously, the downstream devices will stop sequentially, and there will be an audible and visual alarm. (2) The mixing and batching system mainly consists of 13 wide-belt feeders, 2 screw feeders, and a mixing belt conveyor under 15 ore bins. Its primary function is to feed the mixed material, fuel, flux, return ore, and dust ash in a specific ratio, and then convey them to the mixer via the mixing belt conveyor. All 13 wide-belt feeders and 2 screw feeders under the 15 ore bins utilize PID digital frequency conversion speed control technology. Closed-loop regulation of the 15 feeding devices is achieved by comparing the actual instantaneous flow rate with the set target value. The electronic scale accuracy is approximately 0.5%, and the feeding error is approximately 1-1.5%. When the production conditions are unstable, such as large and irregular fluctuations in instantaneous flow rate, cumulative adjustment can be used. Specifically, the cumulative flow rate per unit time (generally set at 5 seconds) is taken as the PV value and compared with the set flow rate SP for adjustment. In order to improve the accuracy of the proportioning, a sequential delay acquisition method was adopted, that is, the instantaneous flow rate of scale 1 is delayed by 5 seconds with scale 2, scale 2 and scale 3 are delayed by 5 seconds, scale 4 and scale 5 are delayed by 5 seconds, and so on. In this way, within a batch of feeding, under the condition that the total number of given materials remains unchanged, the proportioning control of different materials can be realized, and better accuracy control can be achieved. Within a given time, the given error is compared with the cumulative error per unit time (i.e., the integral of the instantaneous flow rate error and time). If it is greater than the given error, the screen prompts and the sound and light alarm is set to prevent the instantaneous alarm from affecting production. Otherwise, no alarm is set. The given error range can be adjusted at any time according to the production conditions. (3) The mixing material feeding system mainly controls the interlocking control of 4 conveyor belt machines and 2 mixers. In order to ensure the integrity of the system and the simplicity and intuitiveness of the operation, we combined the logic control of the start/stop operation of the mixing material feeding system and the mixing and batching system into one control. There are two start-up methods: simultaneous start-up of the wide-band feeder and the belt conveyor, and separate start-up of the wide-band feeder and the belt conveyor. The system starts the corresponding belt conveyor and feeder sequentially with a delay, following the reverse material flow sequence. There are two stop-up methods: simultaneous stop of the wide-band feeder and the belt conveyor, and separate stop of the wide-band feeder and the belt conveyor. The control mechanism is the same as above. 4.3 Sintering Cooling System Design Controlled equipment includes: roller feeder, roller distributor, sintering machine, combustion fan, single-tooth roller crusher, annular cooler, and plate feeder. Remote operation is divided into automatic and remote manual modes. In automatic mode, the start/stop methods are further divided according to process requirements: sequential start, simultaneous start, sequential stop, and simultaneous stop. In remote mode, the PLC first checks whether the online controlled equipment meets the starting conditions: (1) whether the main circuit power supply is normal, (2) whether the control circuit power supply is normal, and (3) whether the equipment has a fault selection switch position is correct. If the conditions are met, a start-up signal is sent. If there is no such signal, it indicates that the system does not meet the starting conditions. The signal indicating that the conditions are not met can be viewed through the monitoring screen. Select the fully automatic mode on the screen, select the start/stop mode, and press the corresponding sequential start or simultaneous start/stop or simultaneous stop button. The system will automatically start/stop the relevant equipment in sequence. 4.4 Finished Product Screening System Design Mainly controls the operation of 21 conveyor belts, such as "Cheng-1 Conveyor Belt Machine" and "Zhuan 9-1 Conveyor Belt Machine". Two modes are designed: remote automatic and remote manual. In automatic mode, the start/stop modes are divided into sequential start, simultaneous start, sequential stop, and simultaneous stop according to the process requirements. Because this sintering machine process uses one sintering machine with two finished product lines, the two lines can cross-feed via a shared conveyor belt. By selecting different combinations of conveyor belts (9-1, 9-2, 1-1 vibrating screen, 1-2 vibrating screen, 1-1 conveyor belt, 1-2 conveyor belt), various combined production lines can be achieved. Each production line controls the sintering and cooling system. 5. Conclusion Since its commissioning, the project has been very successful. It achieved daily production in just 7 days, setting a record for the fastest production of sintering machines in China. The advanced automatic control system played an important role in the smooth commissioning and rapid production of the sintering machine. Based on the control of the original three sintering machines, the control system has been refined and optimized, making it reach the leading level in China in terms of both the smoothness of operation after commissioning and the stability of production status. It has broad prospects for industrialization and promotion. References [1] 265m2 sintering machine control function specification [2] 265m2 sintering machine automatic control system maintenance manual of Laiwu Steel Group Yinshan Steel Co., Ltd. [3] "Variable Frequency Drive World" 2005 Issue 1 [4] "Laiwu Steel Technology" 2004 Issue 4 [5] Modicon TSX Quantum series software manual [6] Modicon TSX Quantum series hardware manual