Abstract This paper introduces the application of PROFIBUS fieldbus technology in a blast furnace system. It describes the principles and shortcomings of traditional field control systems, analyzes the functions and characteristics of automation systems based on fieldbus control, illustrates the communication mechanism of the PROFIBUS network through a system communication network topology diagram, presents the method for implementing communication software, and introduces the application of the bus in the Wuhan Iron and Steel Group's blast furnace.
Preface
Industrial fieldbus technology has become one of the most closely watched technologies in the automation industry in recent years, bringing significant advancements to automation control technology. Traditional field-level control systems are not open, have poor integrability, and are difficult to guarantee in terms of reliability. Fieldbus Control Systems (FCS) use a single communication cable to connect field devices (intelligent devices with communication interfaces), replacing 4-20mA/24VDC signals with digital communication to perform functions such as field device control, monitoring, and remote parameterization. It offers many advantages, with significant strengths in industrial automation, including high integration, simple configuration, convenient design and installation, easy maintenance and expansion, and savings in hardware and software investment, enabling advanced field device management functions. Fieldbus has been widely applied in various fields, such as power monitoring and energy management.
Wuhan Iron and Steel's (WISCO) Ironmaking Plant began experimenting with fieldbus technology in 2003 with the construction of its No. 6 blast furnace, marking the first time such a system was used in a blast furnace system nationwide. Shortly after the No. 6 blast furnace began operation, an accident caused a fire in the main control building, damaging almost all the electrical wiring in the furnace top charging and hot blast stove systems. Traditional field-level control would have required at least two weeks to restore operations. However, thanks to the fieldbus system, which significantly reduced the number of cables used, production was restored in just three days, more than ten days ahead of schedule. This highlighted the powerful advantages of the fieldbus control system over traditional field control methods in terms of maintenance and emergency repair. The application of fieldbus technology at WISCO's Ironmaking Plant has greatly improved the control and stability of the blast furnace's electrical equipment. It has since been adopted by other blast furnaces and has achieved excellent results in the ironmaking plant.
II. Current Status and Shortcomings of Traditional Blast Furnace Automated Control Systems
The blast furnace system mainly consists of the furnace top charging system, the trough and trough feeding system, the hoisting system, the pulverized coal injection system, the hot blast stove system, the furnace front tapping area system, and the INBA slag treatment system. The production process is complex, there are many dispersed points, and the environmental conditions are special, which places very high demands on electrical equipment. This results in a very complex electrical automation system with a high failure rate and a large amount of maintenance.
Currently, the control systems used in blast furnaces in my country are primarily based on traditional field control methods. One key characteristic of traditional field-level and workshop-level automated monitoring and information integration systems (including distributed control systems based on PCs, PLCs, and DCS products) is that the connection between field-level devices and controllers is one-to-one (one I/O point to one control point on the device). This I/O wiring method transmits 4-20mA (analog signals) or 24VDC (digital signals). (See Figure 1.)
As we can see from the figure, this traditional field-level automated monitoring system has several drawbacks:
(1) Weak information integration capabilities;
(2) The system is not open, has poor integrability, and lacks professionalism;
(3) Reliability is not easy to guarantee. Its main drawback is the bottleneck phenomenon at the host entry point.
Due to the large number and dispersed locations of equipment and facilities at the site, signals entering the PLC must undergo A/D and D/A conversion processes, resulting in reduced accuracy. This forces the PLC to lengthen its scan cycle, degrading the overall performance of the main unit and threatening the real-time performance of various signals from the blast furnace. Consequently, this affects the stability and reliability of the blast furnace control system.
The principle and characteristics of a fieldbus-based automated control system for blast furnaces
Profibus is the only fully integrated H1 (process) and H2 (factory automation) fieldbus solution, and it is an open fieldbus standard that is independent of the manufacturer. With the Profibus standard system, devices from different manufacturers do not require special adjustments to their interfaces to communicate. Profibus can be used for high-speed, time-critical data transmission, as well as for a wide range of complex communication applications.
Based on application characteristics, Profibus is divided into three compatible versions: Profibus-DP, Profibus-FMS, and Profibus-PA. Among them, Profibus-DP (H2) is an optimized high-speed communication connection designed specifically for communication between automatic control systems and device-level distributed I/O. It can be used for high-speed data transmission in distributed control systems, with a transmission rate of up to 12 Mbit/s, and is generally used to form a single master station system.
Profibus enables the networking of distributed digital controllers from the field level to the shop floor. The system consists of master and slave stations. The master station controls bus data communication; when it gains bus control (token), it can proactively send messages without external request. Slave stations are peripheral devices, typically including input/output devices, controllers, drivers, and measurement transmitters. They do not have bus control; they only acknowledge received messages or send messages to the slave station when requested by the master station.
Fieldbus is a network and control system that uses individual, distributed, digital, and intelligent measurement and control devices as network nodes, connected by a bus to exchange information and jointly complete automatic control functions. It is suitable for replacing expensive parallel transmission lines for 24V DC and 4-20mA measurement signals. While saving on wiring and equipment, it also provides field-level control functions for the Ethernet system of Wuhan Iron and Steel Plant. Its principle is shown in Figure 2 below:
From the diagram, we can see that fieldbus has the following main advantages:
(1) Reduce equipment (such as isolators and terminal points) to save engineering costs.
(2) Because the D/A and A/D conversion processes are eliminated, the signal accuracy r is improved.
(3) It can avoid signal blockage caused by the convergence of detection signals from thousands of detection points and control points at the DCS entrance, and instead delegate the control function to the field, increasing the reliability of the system.
(4) Simple configuration, easy installation, operation and maintenance;
(5) It adopts an IP67 protection rating, making it fully suitable for the harsh environment of the blast furnace site.
Bus monitoring and configuration methods for the Sifang Iron and Steel Plant
4.1 Bus interface with PLC
The Wuhan Iron and Steel Plant uses Schneider Electric PLCs (Quantum series). These PLCs employ PTQ modules for bus configuration. The PTQ modules support the Profibus-DP industrial bus protocol and offer strong scalability. One PTQ module is mounted on the rack, using the Profibus-DP protocol to acquire data from the industrial bus and control the operation of field devices. The bus is configured using the GSD file provided by Turner and the ProSoft Configuration Builder bus configuration software. The configured file is then imported into the Schneider Electric PLC programming software Concept, and the program monitors and operates the bus devices. The configuration diagram is shown in Figure 3.
4.2 Computer monitoring
In the bus monitoring screen, we use Wonderware's Intouch software for monitoring, which can monitor the communication status of each bus module. When a bus alarm occurs, we can quickly identify the faulty device through the bus, effectively improving the time for fault repair.
V. Application Effects and Future Prospects
The adoption of fieldbus avoids the need for extensive point-to-point cable laying, reduces the difficulty of line laying design and construction complexity, saves investment, installation, commissioning and maintenance costs, facilitates maintenance, reduces the number of blast furnace shutdowns, and brings direct economic benefits to the ironmaking plant, achieving good results.
Faced with the challenges of the industrial technology revolution, we should seize the opportunities. The application of fieldbus technology in automation control systems will undoubtedly have an increasingly wide range of applications and scope, playing a positive role in promoting our development.
References
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