Abstract: This paper introduces the basic principle of the primary dust removal system in Tangshan Iron and Steel Group's No. 1 steelmaking plant, as well as the features of the Controlllogix 5000 series programmable controller and RSView32, in accordance with the process requirements of the primary dust removal system. The paper elaborates on the hardware and software design of the control system and realizes the control of the primary dust removal system in Tangshan Iron and Steel Group's No. 1 steelmaking plant.
Keywords: Controllogix 5000, RSView32, ControlNet, EtherNet
The primary dusting control system based on PLC
ZHAO Xin-xiang
(The Automatization Co. of tangshan Iron &Steel Group Co.Ltd, Tangshan Hebei 063016,China)
Abstract: For the priamy dusting system processes the request, introduces the basic principles of dust control system, as well as Contrllogix 5000 series of programmable controllers, RSView32 characteristics on the first Tangshan Iron and Steel steel-making, Described the control system hardware and software design, realized the priamy dusting control system on the first Tangshan Iron and Steel steel-making.
Key words: Controllogix 5000, RSview32, ControlNet, EtherNet
Overview
The automatic control system for gas recovery and primary dust removal in Tangshan Iron and Steel's 150t converter adopts PLC technology. The control system uses a ControlLogix 5000 series programmable controller, connected to I/O modules via ControlNet network to achieve remote control data exchange. The lower-level programming software is RSLogix5000, and the upper-level monitoring software is RSview32. Main functions include: adjusting and controlling various process equipment or processes based on operator commands, data settings, and signals from field detectors on the HMI (Human-Machine Interface); real-time data acquisition, processing, and transmission of process and equipment status data to the upper-level computer for display; and handling and displaying fault alarms.
1. Process Introduction
The primary dust removal process for converters comprises two parts: flue gas purification and coal gas recovery. The process is as follows: After being collected by a movable fume hood, the converter flue gas enters a vaporization cooling system for cooling. After being cooled through the vaporization cooling flue, the temperature drops from 1450–1600℃ to approximately 900℃. It then enters a dust collection tower, which combines a scrubbing tower with an annular venturi tube to form a high-efficiency dust collection tower. Following further dehydration in a vortex dehydrator, the gas enters a blower through pipelines. Its powerful suction capacity removes the large amount of dust generated during the blowing process.
The converter flue gas purification system consists of a fan, frequency converter, motor, lubrication system, etc.; the converter gas recovery system consists of a bypass valve, three-way valve, water-sealed check valve, gas venting and ignition system, and overall measurement system, etc. The production process flow is shown in Figure 1.
Figure 1. Flowchart of primary dust removal in converter
2. Control System Hardware Composition
The primary dust removal fan and gas recovery control system of Tangshan Iron and Steel Group's No. 1 Steel Rolling Mill consists of one PLC, two HMIs, a printer, special testing equipment (CO analyzer), conventional testing equipment (resistance thermometer, flow transmitter, pressure transmitter, etc.), regulating valves, and network communication equipment.
Hardware components: Processor 1756-L62, analog input module (power distribution) 1756-IF6CIS, RTD input module 1756-IR6I, digital input module 1756-IM16I, digital output module 1756-OW16I, and network modules including ControlNet module 1756-CNB and EtherNet module 1756-ENBT. See Figure 2 for the hardware system configuration.
Figure 2 Hardware configuration of primary dust removal system
2.1 Features of Controllogix 5000
The Logix 5000 system features flexible network types and structures. By inserting different types of communication modules, the system can form ControlNet networks, Ethernet networks, connect DeviceNet devices, and perform serial and DH/RIO communication. Network structures can be bus-based, tree-based, etc., offering great convenience and flexibility. The ControlLogix platform provides high-speed data transmission through the backplane. Through a well-organized data structure, CPUs can perform reliable, time-sensitive produce/consume communication.
The Contrllogix5000 template is a fully intelligent template. All modules are intelligently designed, and each channel of each module can be configured according to user requirements, depending on the module type. It features hot-swappable functionality, self-diagnosis, time stamping, module identification, flash memory upgrade, electronic fuses, and individual isolation. The sampling rate of each module can be set individually.
2.2 Features of RSView32
(1) Open industry standards: The widespread application of technologies such as OLE, ActiveX controls, ODBC, and .dbf file format makes RSView32 highly open;
(2) Efficient application tools: Application tools such as project manager, PLC database browser, and command wizard enable engineering technicians to create applications very conveniently and quickly;
(3) Cutting-edge technology: The most advanced computer technology is included in functions such as animation control, trend display, and event detection.
3. Main Program Design of Control System
3.1 Design of Control Program for Primary Dust Collector Fan
The control program flowchart for a primary dust collector fan is shown in Figure 3. In the figure, abnormal fan conditions include: fan bearing temperature too high; motor bearing temperature too high; motor stator temperature too high; excessive motor bearing vibration; low lubricating oil tank level; and low fan cooling water flow. Abnormal inverter conditions include: excessive inverter current; inverter microprocessor protection activation; inverter device alarm. Abnormal high-voltage motor conditions include: comprehensive high-voltage motor fault; and high-voltage motor microprocessor protection activation.
Figure 3 Flowchart of the primary dust collector fan control program
3.2 Design of Gas Recovery and Venting System
The converter gas recovery and venting system consists of a three-way switching valve, a water-sealed check valve, a bypass valve, a gas analysis system, and a venting ignition device. The key control points are ensuring safety and the sequential control of the valves, as shown in Figure 4.
Figure 4. Flowchart of primary dust removal gas recovery control
In this system, if the three-way valve malfunctions and the bypass valve is in automatic operation mode, the bypass valve will automatically open. However, when the three-way valve returns to normal, for safety reasons, the bypass valve is not allowed to close automatically. It must be manually closed after confirming that everything is normal. The system also includes functions such as valve incomplete opening/closing alarms, and timely opening and delayed closing of the fan impeller and various valve flushing shut-off valves according to process requirements.
The venting ignition control is interlocked with the three-way valve. When the three-way valve switches to the gas recovery position, the dust collector PLC sends a extinguishing signal to the gas venting ignition device. Upon receiving the signal, the gas venting ignition device automatically closes, extinguishing the flame and ceasing combustion. When the three-way valve switches to the gas venting side, the dust collector central control room PLC sends an ignition signal to the gas venting ignition device. To ensure timely ignition of the vented gas, the ignition signal is sent three times consecutively. Upon receiving the signal, the gas venting ignition device activates three times, automatically igniting and venting the gas. To prevent the exhaust port from being blocked by dust in the gas, an automatic steam purging device is installed in the pipeline, controlled by the gas venting ignition device itself. When the three-way valve switches to the gas recovery position, the electric ball valve installed on the pipeline automatically opens, starting to purge the venting side pipeline and chimney. After 1.5 minutes of purging, the electric ball valve automatically closes, stopping the purging.
4. Monitoring screen function design and functionality
The graphical monitoring system utilizes the powerful RSView 32 software. The main operation screen includes: the primary dust removal system screen, the oil supply system display screen, the fan instrumentation display screen, the gas recovery system instrumentation display screen, the gas venting point system display screen, the gas recovery total measurement system display screen, the gas recovery instrumentation alarm screen, and the gas recovery system trend graph screen. It is primarily used to control the start and stop of equipment and display the status of each system's equipment and instrument data. The alarm log screen records all equipment fault types, the time of fault occurrence, and the time of recovery. The historical trend screen displays a dynamic curve composed of the current and historical values of each instrument, which can be viewed and printed. The entire system is powerful, easy to operate, and has a beautiful interface.
5. Conclusion
Since its commissioning, the automatic control system for gas recovery and primary dust removal in Tangsteel's 150t converter has demonstrated stable performance, meeting the requirements of the process equipment. It has achieved functions such as automatic speed regulation, automatic recovery, and centralized CRT monitoring. During the commissioning process, it effectively combined advanced technology with applicability to improve the system's automation level, reduce the labor intensity of workers, and enhance the company's economic and social benefits.
References
1. RSView32 User Manual
2. http://www.softwarerockwell.com
3. http://www.gongkong.com
