Application of the hottest PLC in the automatic co

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Application of PLC in the automatic control system of coke oven gas holder in Angang

1 overview

modern coke ovens produce a large number of by-products coke oven gas due to the continuous increase of furnace capacity and smelting intensity. If coke oven gas is directly released into the air, it will not only cause atmospheric pollution, but also cause a waste of energy. In view of this, Angang gas plant has built a new coke oven gas tank with a volume of 150000 M3 to store coke oven gas. The equipment performance and automatic control of the automatic control system of coke oven gas holder will directly affect the collection and utilization of coke oven gas

this project adopts the PLC redundancy system of ControlLogix series, a new generation control platform of Rockwell Automation Company, which is famous for its high product reliability. In the ControlLogix System, all maintenance and communication are automatically completed by the system, which is more convenient and reliable, and users can write state reading programs to monitor the state of redundant systems at any time

2 hardware configuration of the system

ControlLogix l5550 redundant system is selected for the automatic control system PLC of 150000 m3 coke oven gas holder of Angang. Considering the factors such as long distance, many nodes and anti-interference, ControlNet network type is adopted, which has good anti-interference and redundant network channels, ensures reliable communication and data display of human-machine interface, and is conducive to rapid field data acquisition. The hardware configuration of the system is shown in Figure 1

Figure 1 hardware configuration of the system

1756-l62 module is selected for CPU, 1756-cnbr for communication module, 1756-ib16i for Di, 1756-ob16i for do, and 1756-if16i for AI. 1756-enbt is selected as Ethernet module. In addition to the CPU module, the redundant rack also has a communication module 1756-cnbr, a hot standby module 1756-srm (maintaining the communication between the master and slave racks) and a connecting cable 1756-src3 between the two hot standby modules

the system platform of server and operation station is Windows2000 (server/client version), the upper monitoring software of operation station is RSView 32, and the PLC programming configuration software is rslogix5000. In addition, there is a set of database management system, which uses the OPC interface provided by the network configuration software rslinx to collect data

3 automatic control system

the automatic control system of the gas holder includes the control of the gas holder body and the oil pump station group, but many enterprises can not reach the 1 baseline heat exchange unit, gas inlet and outlet pipes, electric butterfly valves and emergency blow off valves

3.1 oil pump station management

the starting times and running time (hours, minutes, seconds) of two oil pumps in any oil pump station, such as rough surface pumps, are accumulated separately, and the total starting times and running time of the oil station are obtained after adding them. The oil supply pump station is displayed on the main screen for operation management. In addition, a reset button is also set. After pressing it, the times and time return to zero and restart statistics

3.2 manual/automatic control of inlet and outlet valves and blow off valves

the control of inlet and outlet valves and blow off valves is divided into on-site manual and PLC automatic. These two control modes are selected on the field operation box. Field manual operation can operate the equipment through the operation button on the field operation box. PLC can automatically operate the equipment through the operation screen

when operating the inlet and outlet valves/blow off valves on the screen, you must first confirm the following basic operating conditions: select PLC automatic mode on the field operation box + the main switch of the valve is closed + the valve is free of fault. When the three conditions of the steel pipe scaffold fastener experimental machine produced by our company Jinan new era Testing Instrument Co., Ltd. are met at the same time, it is called meeting the basic operating conditions

the inlet and outlet valves are installed on the inlet and outlet pipes of the gasholder, and the blow off valves are installed on the blow off pipes of the gasholder. Manual/automatic switching can be carried out through the pop-up window. The operation can be divided into two ways:

(1) in the manual state, after pressing the manual valve opening button, the signal to open the inlet and outlet valves/blow off valves will be sent, and when pressing the valve closing button, the signal will be closed. There is no external interlocking relationship when manually starting

(2) in the automatic state, the basic operating conditions are met. When the piston rises to 95% of the upper limit (69.3m) volume, or the piston drops to 10% of the lower limit (7.3m), the signal of closing the inlet and outlet valves is sent. To open the valve, it can only be opened by manual state; When the piston reaches 69.3m, that is, 95% of the volume, it sends a signal to open the blow off valve; If the piston recovers to 65.6532m, that is, 90% of the volume, a signal to close the blow off valve will be sent

3.3 composition of the upper monitoring system

this system is divided into seven screens, including "main screen of gas holder monitoring", "monitoring screen of heat exchange unit", "main screen of monitoring", "equipment monitoring screen", "historical trend screen", "alarm screen" and "trend print screen". Each picture can be switched freely

3.3.1 animation display function

in each picture, the actual operation status of each part of the system has animation display function

for example, when the valve is closed, the valve body is displayed in red, and when the valve is open, the valve body is displayed in green; After selecting the working pump and the standby pump, the corresponding words will appear under the pump. When the pump works, the small light will turn green and when it stops, it will turn red; When the limit point comes, the light will be on at the corresponding position; When the cabinet position reaches the upper limit or the lower limit, the filling in the cabinet will turn red. When the upper limit or the lower limit is reached, the filling in the cabinet will turn yellow, which is normally green

3.3.2 integrated alarm function

for the important alarm of the gas holder system, it is displayed on each screen: change color, audible alarm, alarm state record. In addition, there is an alarm summary screen, from which you can view the alarm and event information

3.3.3 historical trend recording function

the system can record the historical curve of oil temperature, flow parameter, pressure parameter, temperature parameter, inlet and outlet pressure, and pressure in the cabinet for up to one day, one week or one month

4 commissioning and operation of automatic control system

according to the overall progress requirements of Angang phase I project, a detailed and common project construction and commissioning scheme has been formulated for the automatic control system of 150000 m3 coke oven gas holder. Complete the drawing design of PLC control system in August; In September, complete the preparation of PLC application software and the production of upper computer monitoring screen; In October, the individual commissioning and linkage commissioning of each system were carried out respectively. The commissioning was basically completed in mid October, and the formal commissioning was carried out in late October. The linkage commissioning of electrical automation was carried out for many times, marking that the automatic control system of 150000 m3 coke oven gas holder has the conditions for production; In November, it was successfully put into production, and many process modifications and commissioning were carried out in the middle, and finally the design process requirements were fully met

5 Conclusion

the automatic monitoring system of 150000 m3 coke oven gas holder in Angang gas plant has been running stably and reliably since it was put into operation in November 2006. The realization of the automatic control system with the advantages of high performance, high reliability and easy to realize complex control functions effectively improves the utilization rate of coke oven gas, reduces the emission of coke oven gas, balances the pressure of coke oven gas pipe, ensures the balanced production of production users, and enhances the secondary utilization of energy and atmospheric environmental protection. (end)

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