PLC solution for coal injection automation of the

  • Detail

Small and medium-sized blast furnace coal injection automation PLC solution

1 introduction

the application of blast furnace coal injection technology in China began in the 1960s. The former generally uses an ordinary speed regulation system to inject pulverized coal into the furnace directly from the blast furnace tuyere, pulverized anthracite or bituminous coal powder or a mixture of both pulverized coal to replace coke to provide heat and reductant, so as to reduce coking and pig iron costs; At the same time, the thermal system of coal injection adjustable furnace process and improve the workbench state of blast furnace hearth

2 coal injection process

3] according to the principle of heat conduction, in the Zhuhai project, with the cooperation of process technicians, the author optimized and simplified the process of large blast furnace to reduce the investment cost; The blast furnace pulverized coal injection process system is mainly composed of raw coal storage and transportation, pulverized coal preparation, pulverized coal conveying, pulverized coal injection, dry gas preparation and gas supply power system. The process flow is shown in Figure 1. If it is a direct injection process, there is no coal powder conveying part

Figure 1 process flow diagram of blast furnace coal injection system

3 system design

3.1 system design principles

(1) system hardware equipment (including system software) and control application software meet various process control requirements of blast furnace coal injection, and ensure that they are consistent with the development trend of the world control system, and can be updated and upgraded to ensure continuous and stable operation for more than ten years

(2) realize the integration of new generation electrical instruments, data communication network and man-machine operation interface

(3) centralized operation and monitoring, and HMI (CRT operation station) operation is adopted for the equipment on the main process line (pulverization and injection), so as to unify and share the human-machine interface of the electrical instrument system

(4) the control application software has reliability, stability and operability, and is easy to maintain and expand

(5) the selected products are easy to operate, the man-machine interface is Chinese, user-friendly, the system software is universal, the equipment is mature and reliable, and there are achievements and application examples

3.2 system hardware and equipment design

3.2.1 control system hardware and equipment design outline

with the continuous development of automation technology and the rapid progress of computer technology, but the need to bear 4000 vehicles, today's automation control concept has also undergone great changes. In traditional automation solutions, automation control is actually matched by various independent and separate technologies and products of different manufacturers. For example, a large factory is often controlled by process control system, programmable controller, upper monitoring computer, SCADA system and human-machine interface products. In order to combine all these products, it is necessary to use various types of interface software and hardware from different manufacturers to connect, configure and debug

the idea of fully integrated automation is to use one system to complete all the functions that can only be completed by the combination of multiple systems. Applying this solution can greatly simplify the structure of the system and reduce a large number of interface components. The application of fully integrated automation can overcome the boundaries between the upper computer and industrial controller, between continuous control and logical control, and between centralization and decentralization. At the same time, the fully integrated automation solution can also provide a unified technical environment for all automation applications, which mainly includes: (1) unified data management; (2) Unified communication; (3) Unified configuration and programming software; (4) A general network for easy linking

based on this environment, a variety of different technologies can be integrated into an overall platform with a global database under one user interface, so that the interface cost between systems is greatly reduced, and the variety and quantity of spare parts are also greatly reduced. At the same time, technicians can configure, program and monitor all applications under one platform, which can greatly improve the monitoring level and reduce unplanned shutdown time. Also because of the application of a configuration platform, training and engineering become simple, and the cost is greatly reduced

according to the system requirements, Siemens s series PLC system can meet the process requirements of the project. The structure of the equipment conforms to the development of automatic control system in the world and can realize the integrated operation of electric instruments. Ethernet bus structure is adopted for the network. The opening of data communication network system, the integration of man-machine interface and electrical instrument, resource sharing, and the stability and reliability of system software are conducive to the maintenance and expansion of the system. The man-machine interface is Chinese, and the operation is practical and simple. Siemens' fully integrated automation idea is embodied in the solution that can realize PLC and DCS at the same time. Siemens fully integrated automation products are selected for the hardware and network of this system

3.2.2 network system scheme

the basic automatic control system of the project is divided into three control subsystems in process: two sets of pulverized coal preparation system and one set of pulverized coal injection system. The communication between the three systems is realized by Siemens' data network communication technology (Industrial Ethernet). All kinds of power supplies of the system adopt centralized supply and preparation based on UPS power supply, which is practical and convenient for maintenance and management. The network layer of the system is divided into two levels: (1) standard Ethernet server control mode, which facilitates remote operation and network expansion; (2) Fieldbus realizes the unification of field and system

3.2.3 PLC (i/o) interface signal

plc adopts optical isolation module for input and relay module for output. Use the DC power supply of the PLC drive signal to drive the instrument (i/o) signal and RTD signal, connect the PLC with the instrument directly, and complete the instrument signal directly into the PLC. Among them, the analog quantity (i/0) signal is Ma, and RTD is directly detected by the temperature of PLC

3.2.4 hardware and equipment design of pulverized coal preparation system

the pulverized coal preparation system is equipped with two sets of units, which are divided into a series and B series, to prepare pulverized coal for pulverized coal injection of three blast furnaces. The main process of the pulverized coal preparation system is as follows: the raw coal bunker coal enters the electronic weighing coal feeder through its outlet plug valve, and supplies coal to the coal mill according to the set pulverized coal production volume. While the raw coal is milled by the grinding roller, it is dried by the dry gas sucked into the coal mill. The outlet temperature of the dry gas sent by the heating furnace is 220 ~ 300 ℃, bringing the finer pulverized coal into the separator located on the upper part of the coal mill. The separator returns the unqualified coal to the grinding plate for grinding again. The pulverized coal with qualified fineness enters the bag dust collector with the dry gas through the delivery pipe for collection, and then enters the pulverized coal bunker through the air lock

the main process units and equipment of the pulverized coal preparation system are as follows: raw coal bunker: one for Series A and one for Series B; Coal feeder: one a series and one B series, each equipped with electronic scale, feeding belt speed converter and gate valve; Coal Mills: a series and B series are equipped with a medium speed roller coal mill; Flue gas induced draft fan of hot blast stove: one for Series A and one for Series B; Flue gas heating furnace: a series and B series are equipped with one flue gas heating furnace respectively; Booster fan: one for Series A and one for Series B; Bag type powder collector: one set of a series and one set of B series; Main exhaust fan: one for Series A and one for Series B; Pulverized coal bunker

the above equipment and control points are collected and controlled by two PLCs

3.2.5 hardware and equipment design of pulverized coal injection system

the main process of pulverized coal injection system is as follows: three sets of injection systems are installed in a coal injection workshop with tower structure to inject pulverized coal into three blast furnaces respectively. The injection system includes a pulverized coal bunker and two injection tanks of each injection system. The pulverized coal made in the pulverized coal preparation workshop enters the pulverized coal bunker through the air lock after passing through the bag collector. The pulverized coal sent from the pulverized coal bunker (pcsB) is added to each injection tank alternately, and then the pulverized coal is sent to the blast furnace tuyere by pneumatic force through the main pipe and distributor of the injection tank

the injection tank automatically carries out charging and pressurization, and continuously injects pulverized coal into the blast furnace in turn. The rotation procedure of injection tank is from injection tank 1h1 to injection tank 1h2, and then back to 1h1. When one injection tank reaches the low weight value, the control system will automatically start another injection tank. The activated injection tank must have been filled with pulverized coal and pressurized before the tank being injected reaches the minimum weight setting value, and be in the state of waiting for injection. At the same time, the minimum weight set value signal is also set on the next tank to achieve a smooth conversion

from the bottom of each injection tank to the fluidization cone can help the coal flow stably along the main pipe to the distributor distributed to each tuyere

the main process devices and equipment of pulverized coal injection system are as follows: control of coal filling valve of injection tank; Blow off valve control of injection tank; Charging control; Fluidization regulation control; Secondary air regulation control; Centralized control of pipeline anti blocking

the above control points are collected and controlled by three PLCs

3.3 system and application software design

(1) hardware and operating system requirements

siemens PLC related equipment (as configured above, all CPUs adopt Siemens DP)

industrial computer (Advantech p4/256m ddr/40g/19 "pure screen display)

operating system Windows 2000

(2) development tool

Siemens step 7 V5.2; WINCC 5.1; SIMATIC NET v6.1

(3) the application software

compiles the corresponding control software according to the process requirements in the project, which mainly realizes the following functions:

● pulverizing electrical control system: equipment interlocking control; Coal feeding and grinding control; Heating furnace combustion control; Heating furnace air supply control, hot flue gas air induction control; Powder collection control; Negative pressure control at the inlet of coal mill; Coal mill outlet temperature control; Process parameter measurement and monitoring; Operation data setting; Data processing and transmission; Equipment status monitoring

● injection electrical control system: automatic feeding control of injection tank; Automatic tank replacement control of injection tank; Automatic dispersion control of injection tank; Pressurization control of injection tank; Nitrogen temperature and pressure control; Process parameter measurement and monitoring; Equipment safety interlock control; Data processing and transmission; Equipment status monitoring; Production report

4 conclusion

in Zhuhai Yueyufeng project, five PLCs, Siemens switches and cards using Siemens cpudp adopt PROFIBUS protocol for network communication, and optical fiber transmission technology is used to improve anti electromagnetic interference ability and meet high-speed and long-distance data transmission; So far, the project has achieved good economic results in terms of system stability, work efficiency, reliability and operability. (end)

Copyright © 2011 JIN SHI