Abstract : This paper is the first to integrate wireless sensing technology, automatic positioning technology, remote video monitoring technology and industrial Ethernet into the fully automatic control system of coke quenching car, which solves the bottleneck problem of fully automatic vehicle control in harsh coking environments.
Keywords: coke quenching car; wireless sensing; automatic positioning; remote video monitoring; industrial Ethernet
China is a major coke producer, but most coking plants have relatively outdated equipment. Furthermore, the extensive production control model of the coking industry is gradually failing to keep pace with the automation process of modern production. Accurate and reliable fully automatic control technology is an inevitable trend in the technological development of my country's coking industry, and also a key technical challenge. This paper designs a fully automatic coke quenching car control system.
1. Fully Automated Production Operation Process of Coke Quenching Car
The main function of the coke quenching car is to transport the coke pushed out of the coke oven to the water spraying tower, where high-pressure ammonia water is sprayed to cool the coke from a high temperature of 1100℃ to nearly 200℃. The cooled coke is then transported to the coke cooling platform for unloading and cooling. The coke quenching car mainly consists of four main actions: receiving coke, quenching coke, unloading coke, and traveling. Based on their sequential relationship, a workflow diagram for the fully automatic coke quenching car is determined, as shown in Figure 1.
2. Overall Structure of the Control System
The entire control system is divided into two parts: the vehicle-mounted part and the ground part [1]. The vehicle-mounted part is the signal acquisition center, data center and control center of the entire system. The embedded control computer of the vehicle-mounted part is the core of the entire system, and is the data center and control center of the system. The aforementioned locomotive operation recording and intelligent operation functions are all performed in the embedded control computer. The ground part is mainly divided into three parts.
(1) Production plan entry and locomotive status display;
(2) Data integration of peripheral systems: The PLC in the central control room is connected to the water distribution tower system through fiber optic communication, and the I/O points are electrically connected to collect information from the coke drying platform;
(3) The operation of video monitoring equipment is used to monitor the automatic operation of the coke quenching car through the locomotive's operation video.
2.1 Design of Ground-Based Control System
The main functions of the ground control system are implemented in the central control room, such as plan entry and locomotive status display.
(1) Position detection system
The position detection system consists of an address generator, an coded cable, an address receiver box, an address detector, and a Siemens PLC module. Based on inductive wireless technology, the address receiver box, located at a point on the coded cable, receives a specific combination of analog signals. The address detector then decomposes this signal into a digital signal and sends it to the Siemens PLC module, providing data to other subsystems.
(2) Data communication system
The data communication system comprises both industrial communication (RS-485) and Ethernet (TCP/IP) communication modes. Both communication methods simultaneously and redundantly transmit critical action and limit signals, ensuring stable system operation.
The advantages of industrial wireless Ethernet (TCP/IP) communication include high communication efficiency, which can reach more than 10M/S. Video image signals and digital signals are usually transmitted in this way.
(3) Video surveillance system
The video surveillance system mainly consists of coke oven monitoring cameras, vehicle-mounted monitoring cameras, vehicle-mounted video, remote monitoring video, video processors, and wireless communication networks.
The coke oven camera is installed on the coke oven and is responsible for monitoring the operating status of the entire quenching car track. The vehicle-mounted monitoring camera monitors the details around the vehicle, the video processor is responsible for converting the image signals, and the monitoring video is displayed in real time to support human operation. The structure of the video monitoring system is shown in Figure 4.
(4) Remote control system
The remote control system primarily transmits data from a host computer to a ground-based control PLC, which then relays the data to the onboard PLC via a communication network. The onboard PLC controls the operation of the frequency converter and electric valves, enabling remote operation of the locomotive and completion of production tasks. The structure of the remote control system is shown in Figure 5.
2.2 Design of Vehicle Control System
The main equipment of the vehicle control system is an embedded industrial computer and an S7-400HPLC group. The subsystems include: automatic travel control system, automatic coking control system, automatic coking extinguishing control system, automatic coking unloading control system, and fault detection and alarm system [2].
(1) Embedded industrial computer
The embedded industrial computer is the core of the entire system, serving as its data center and control center. It primarily records and analyzes all historical data generated during locomotive operation, performing statistical analysis to guide the locomotive in achieving automated operation. After acquiring the coking plan, the embedded industrial computer can control the locomotive to complete various operations based on the plan and process requirements.
(2) Redundant S7-400 HPLC group
The S7-400H is designed in a redundant manner, allowing it to continue operating after any event occurs. All major components in the S7-400HPLC group are dual-purpose, including the following components designed as dual-purpose devices: the CPU power supply module PS40710A, the hardware CPU417-4H connecting the two CPUs, and the communication module CP443-1.
After a CPU failure, the backup CPU automatically establishes a synchronous connection with the primary CPU. The backup CPU issues a Link-up request, and the primary station, after disabling deletion, copying, and block generation functions, sends all data to the backup CPU. The primary station then runs a user program that, after disabling all alarms and interrupts, sends dynamic data that has changed since the last update to the linked backup CPU.
(3) Automatic walking control system
The automatic travel control system mainly uses an on-board PLC to control a frequency converter, which in turn controls the motor speed and adjusts the travel speed.
Based on the vehicle's workflow, the target position for the automatic movement of the coke quenching car is calculated. The current position is detected by a position detection system, and the positional difference is calculated. The PLC program controls the inverter's operating frequency to achieve automatic movement of the coke quenching car. During movement, the position detection system continuously updates the current position value, and the PID feedback adjustment continuously corrects the movement frequency to achieve accurate alignment.
The structure of the self-propelled control system is shown in Figure 6.
(4) Automatic focus control system
The automatic coke-attaching control system mainly operates through an onboard PLC, limit switches, a position detection system, and a data communication system. When the fully automatic coke quenching car reaches the coke-attaching position, it automatically detects whether it has reached the set position and the coke quenching car door closing signal. It also checks whether other equipment is ready via the communication system, and then sends a coke-pushing permission signal to the ground-based central control PLC system. The structure of the automatic coke-attaching and coke-quenching control system is shown in Figure 7.
(5) Automatic coke quenching control system
The automatic coke quenching control system is mainly completed through vehicle-mounted PLC, ground control PLC, water spray tower control PLC, position detection system and data communication system.
Because the coke inside the vehicle is at a high temperature of 1100℃, there is a 5-10 second delay between the control signal being sent and the water valve fully opening, allowing ammonia water to spray from the storage tank to the nozzles. Therefore, the position detection system detects that the fully automatic coke quenching car is 10m away from the quenching tower and sends a signal to the water pump via the data communication system to ensure that the quenching nozzles in the water spraying tower have already started spraying water when the quenching car enters the water spraying tower. After the set water spraying program is completed, it automatically enters the next working state. The structure of the automatic water spraying coke quenching control system is shown in Figure 8.
(6) Automatic coke unloading control system
The automatic coke unloading control system is mainly completed by vehicle-mounted PLC, ground control PLC, coke drying table control PLC, position detection system and data communication system [3].
The coke unloading area typically has three sections where coke is unloaded in rotation. The unloading section is numbered based on the remaining coke in the coke drying platform. Because the unloading platform is longer than the hopper and the coke must be evenly distributed on it, a low speed is required during the unloading process. The system either enters a resting state or directly enters the next round of coke receiving based on the planned coke discharge time from the furnace. The structure of the automatic coke unloading control system is shown in Figure 9.
(7) Fault detection and alarm system
The fault detection system mainly monitors the operation of all systems through a host computer and issues alarms.
Location detection system: If the detected location data is discontinuous or there is no data, an alarm should be triggered immediately, stopping automatic operation and switching to manual operation.
Automatic driving system: During automatic driving, the system uses a position detection system to check whether the vehicle is moving and whether the direction of movement is correct. If any abnormality is detected, the automatic driving system will exit.
Automatic coking control system: Detects the closing signal of the truck bed door. If it fails to close for an extended period or the closing signal malfunctions, it stops automatic coking and issues an alarm.
Automatic water spraying and coke quenching control system: If no feedback signal is sent to the PLC system for a long time after the start signal is issued, the automatic water spraying and coke quenching system is judged to be faulty and manual intervention is required.
Automatic coke unloading control system: If there is no feedback signal from the coke unloading platform to the PLC system for a long time after the coke quenching car arrives at the coke unloading platform area, the automatic coke unloading control system is judged to be faulty and manual intervention is required.
3. Summary
The design of the fully automatic control system for the coke quenching car leverages current industrial automation technology, based on the key points of the automation industry: "detection and perception + efficient communication + digital networking + intelligent control + collaborative output + effective feedback," as well as the principle of "unified management + decentralized control," with the ultimate goal of achieving fully automatic operation of the coke quenching car equipment.
References
[1] Liang Wei. Design and Application of Automatic Control System for Dry Quenching Coke [D]. Wuhan: Wuhan University of Science and Technology, 2008.
[2] Liu, Liankai. Development of Computer System for Four Major Locomotive Interlocking Systems in Coke Ovens [D]. Chengdu: University of Electronic Science and Technology of China, 2006.
[3] Zhu Tianlong. Research on Three-Vehicle Interlocking System Based on Wireless Induction
