The advanced fieldbus control system in the world, namely SIEMENS PCS7 control system, is adopted in No.4 converter project of No.3 Steelmaking Plant of Masteel. Among them, the Profibus PA bus technology, which is rarely used in metallurgical industry, is first used in the instrument control system of Masteel, which completely changes the traditional measurement and control mode and makes the technical level of the whole instrument control system among the international advanced level.

SIEMENS PCS7 series PLC is used in the secondary control system, which is connected with PROFIBUS DP network, and the bus instrument control equipment is connected to the industrial control network through DP / PA link (linker). The purpose of “centralized management and decentralized control” is truly realized. At the same time, the full digital communication mode has strong anti-interference ability and high accuracy of measurement and control. With the help of the characteristics of digital two-way transmission and advanced equipment management software, it can realize remote parameter setting, collect rich instrument information, facilitate equipment fault diagnosis and improve management status. The process control level is composed of two-level computers, which are connected to the basic level PLC through industrial Ethernet, and rely on the control model and database to guide, manage and track the first level control system. It is an open industrial control system with the concept of factory integration.

I. system composition

The basic level adopts a set of PCS7 PLC as the controller of caster. Its CPU type is as416-2dp, and has communication function. It can be connected with im-153, im-157 communication cards of expansion unit and frequency converter through PROFIBUS DP control network. The expansion unit uses et-200m and linker as sub station. The control software is step 7 and integrated with Siemens process equipment management software PDM. The control level adopts Siemens industrial computer as the monitoring station, which is connected with PLC through fast industrial Ethernet (based on TCP / IP Protocol). The system runs SIEMENS PCS7 fully integrated software based on Windows 2000.

1. Hardware structure

Figure 1 only shows the configuration of the system related to instruments.

Design of converter industrial control system based on Industrial Ethernet, PLC and bus technology

PC1 is the monitoring station of upper computer, et200 is the remote station of electronic control system. The linker is one of the slave stations of PCS7, and it is also the PA master station of field bus instrument and control equipment. The coupler of network components realizes the connection between all PROFIBUS PA field instruments and DP bus, which can transmit more detection and control information and obtain the self diagnosis information of bus equipment at the same time. In the whole control system, the instrument control system has only one field control box except for the common operation station and corresponding primary detection elements.

2. Software configuration

The operation station software is PCS7 software, the network platform is Windows 2000, PCS7 has its own database, and provides monitoring screen and PLC configuration tool. The configuration software in PCS7 is STEP7 and Siemens process equipment management software PDM.

The operation station mainly provides a human-computer interface between users and all system functions, through which all kinds of personnel can access the system resources within their respective authority. For example, the operator can call out the process display screen, observe the parameters, status, trend and alarm of the process loop, and realize the operation and parameter adjustment of the process loop. The process engineer can configure the process, display screen and process control database for other configuration work. Software engineers can enter the software development environment, write, debug and execute user applications.

System maintenance personnel can observe the working condition of each equipment in the system, and diagnose these equipment.

II. System functions

4. The electric drive and instrument control of all equipment in converter system engineering adopt centralized control and centralized monitoring mode to realize the basic automatic control with PLC as the center.

1. Production process distribution

(1) Main raw material system

Hot metal pouring station; Scrap supply.

(2) By-product system

Flux feeding (1 belt conveyor ~ 5 belt conveyor); Flux feeding (4 × converter body).

(3) Ferroalloy system

Converter ferroalloy supply, feeding.

(4) 4# converter and auxiliary facilities

Converter body; Bottom blowing system; Top blowing oxygen and slag splashing for furnace protection; Converter and lance cooling water; The water seal between the movable hood and the flue of the furnace mouth; Cooling water for movable smoke hood, oxygen lance mouth and feeding mouth; Nitrogen sealing system; The car under the stove.

(5) 4. Argon blowing station

Alloy feeding; Top blowing oxygen and argon; Bottom blowing argon.

2. Top blowing signal display and automatic control

a. Signal display and control

Pressure indication and record in front of oxygen main pressure regulating valve (gas source); On / off state indication and interlock of oxygen emergency shut-off valve; Indication, recording and regulation of pressure behind the pressure regulating valve of oxygen main pipe; Valve position display of oxygen main pressure regulating valve; Oxygen branch flow indication, recording, adjustment, correction calculation; Oxygen branch flow control valve position display; Pressure indication and record after oxygen branch cut-off valve (oxygen blowing pipe inlet); Valve position display of oxygen branch cut-off valve; Cumulative oxygen consumption of one furnace: 4000nm3 / furnace; Accumulated oxygen blowing time of one furnace.

b. Alarm and interlock

Oxygen source pressure low limit alarm; Low low value (LL) alarm and interlock control of oxygen source pressure (interlock with oxygen lance lifting device); Low limit alarm of oxygen branch pipe inlet pressure; Low low value alarm and interlock of oxygen branch pipe inlet pressure (interlock with oxygen lance lifting device); Low limit alarm of oxygen branch pipe flow; Low low value alarm and interlock of oxygen branch pipe flow; Quickly lift the gun and close the branch cut-off valve.

3. Bottom blowing signal display and automatic control

Bottom blowing signal display, automatic control, alarm and interlock are basically the same as top blowing.

4. Process fieldbus configuration

The instrument and control system is tested and controlled by PROFIBUS PA fieldbus.

Although couplers can be directly connected to DP network, they need to occupy one DP address and cannot be expanded. Each linker can expand 5 couplers, and each linker can be connected with up to 30 non explosion proof field bus instruments in non explosion proof area. Therefore, on the premise of balancing economy and system scalability, the hardware configuration mode of one linker with several couplers is adopted. The whole system adopts PROFIBUS PA bus line topology structure. In this mode, the address number of intelligent bus instrument on PA bus is not limited by DP address number, and can be arbitrarily addressed under the corresponding coupler, which is conducive to the expansion and maintenance of bus equipment.

Three system features

Because of the Profibus PA fieldbus technology, all the detection and control instruments adopt the intelligent instrument of full digital communication, which greatly improves the stability and reliability of the system.

(1) High reliability

The network cable replaces the control cable used by all conventional control instruments between the upper and lower platforms of the converter, and all the measurement and control elements are connected to a network line in parallel, and exchange detection and control data with the upper computer in the form of digital communication. At the same time, the internal fault self diagnosis function of the measurement and control elements is realized, The hidden trouble information of the equipment can be predicted to the upper computer before the occurrence of the fault to remind the engineering personnel to eliminate it in time, so as to ensure the safe and smooth production.

(2) High accuracy

Due to the use of digital communication, the actual sampling accuracy and control accuracy are not comparable to analog signals. The technical level has completely entered a new field, providing accurate production parameters for production engineers, which is conducive to optimizing products, controlling production costs, saving energy and reducing consumption.

(3) Flexible system expansion

The node of PA communication network is the measurement and control element, so the addition or deletion of any node will not affect the overall performance of the network. Several groups of PA network can be added or deleted by adding or adding some linkers on DP network cable. Each group of PA can expand 30 measurement and control elements, which is convenient for system expansion and process optimization. The PA network can be distributed anywhere in the factory, which makes it easier to connect with various devices scattered around.

(4) Reduce project cost and quantity

The measuring points are scattered and relatively concentrated between the upper and lower platforms of converter. If the conventional computer control scheme is adopted, not only the wiring is complex, the bridge is numerous, but also the troubleshooting time is long, which is not conducive to the rapid recovery of automatic control process. The adoption of PROFIBUS PA fieldbus technology will greatly save the material cost of cables and bridges and the amount of capital construction and installation. At the same time, it will also cancel the input / output components on the control station, save the cabinet and reduce the area of the control room.

IV. conclusion

On the basis of realizing “three electricity integration”, the control system of No.4 converter in No.3 Steelmaking Plant of Masteel successfully applies Profibus Technology to the whole production process, which improves the control level and reliability of the system and reduces the operation cost. Compared with the conventional system, only the I & C system can save 30% investment. In addition, the embedded process equipment management software PDM reduces the types of other software required, and also reduces the cost of related software. Especially important, because the fieldbus instrument has the self diagnosis function, it can diagnose and maintain the online equipment in advance, eliminate the fault in advance, reduce the downtime, improve the safety of production, greatly reduce the cost of system operation and maintenance, and provide an important technical guarantee for the safe and smooth production of the whole high-efficiency continuous caster.

Editor in charge: GT

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