Implementation of Blast Furnace Gas Water Spray Cooling Control System Based on PLC and OPC

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Implementation of Blast Furnace Gas Water Spray Cooling Control System Based on PLC and OPC

Minggang Zheng, Zhifang Jiang, Xiaohui Zhu School of Mechanical and Electrical Engineering

Shandong Jianzhu University

Jinan, China

Abstract—An automatic control system based on PLC was panel and ABB ACS510 frequency converter. The hardware

designed according to big flow, high temperature and maximum structural diagram of the system is shown in figure 1.

cooling temperature 55 of the blast furnace gas. To realize closed-loop control of temperature, the system collected inlet and outlet gas temperature using temperature sensors. According to the change in temperature, PLC automatically changed the working water spray capacity by regulating the output frequency of frequency converter automatically. Considering the big noise and long distance from monitoring room, a remote control system was designed to help operators in DCS control room monitor and operate the water cooling equipment. The system enhances the automation of water spray cooling system, and it has great practical and spreading values.

Keywords-Siemens S7-200PLC; OPC; water spray cooling system; remote control

Figure1. Hardware structural diagram of the system.

I. INTRODUCTION

There is a set of electrical control cabinet, which is mainly PLC controller, AD/DA converting module and touch panel (HMI). All the parameters can be directly set by HMI or the remote control computer. There are also signal insulation modules and low voltage electrical component parts in the control cabinet. Manually open inlet ball valve v20 of the gas circuit, the inlet and outlet ball valves v11, v12 of the filter. Start II. SYSTEM INTRODUCTION AND WORKING PRINCIPLE

the solenoid value B21 of the gas circuit and pneumatic control valve B11 at first, the gas circuit starts to work, then start the 2.1 System Introduction

The system consists of host computer (remote control water pump P11 or P12, one pump works and the other prepares computer), PLC controller and extended modules, 2 frequency to work, and the lance begins to spray water at this moment.

The system collects the inlet and outlet hot resistance converters (one-work, one-standby), 2 water pumps (one-work,

one-standby), main water circuit, main gas circuit, water spray temperature and automatically generates frequency converter mechanism (grouping control cabinet and two-fluid lance) and opening, working water jet capacity of the lance, and the

number of the working lance according to the target temperature measuring control system.

temperature so that the outlet temperature can meet the

The hardware of the system: Siemens S7-200 PLC requirements. When stop the system, close the frequency CPU226, digital I/O module EM223, analog modules EM231, converter and water pump at first, and water supply stops at EM235, the extended slave station module EM277 once, after some time (can be defined), stop the solenoid value

B21, and the gas circuit stops. The system automatically turns to PROFIBUS-DP, Siemens PC547B IPC, Siemens bus connector

and interface card CP5611, Siemens K-TP178Micro touch

The blast furnace gas can be used as personal fuel gas in metallurgical enterprise and can also be supplied for civilian use after dust abatement. The required gas temperature of the gas pipeline is below 55 , but the temperature of the gas from TRT is still above 180 , so it is necessary to reduce the gas temperature with spray water before the gas entering gas pipeline. Because of the big noise in working site, two ways-local control and remote control are set in the water spray cooling system. IPC of the remote control is located in TRT control room, which is convenient to operate and monitor the device for the workers. The system can greatly improve the recoverability rate of the blast furnace gas, and it also has significant environmental and economic benefit.

2.2 Working Principle

The two-fluid lance sprays water in the direction of gas flow. The system controls the main water circuit and the main gas circuit according to the selected parameters (water pressure, gas pressure, the number of the working lance and the target temperature). The cooling water absorbs heat and evaporates by mixing with hot gas in mist form to reduce the gas temperature. The temperature is measured by hot resistance, one in inlet and two in outlet. The control system checks the inlet and outlet temperature to realize PID closed-loop control. Working principle of the whole system is shown in figure 2.

another control way once serious warning occurs, and we can

also manually start the lance.

Figure2. Working principle of the system.

PLC program consists of the main program, the extended module check, frequency converter check, pressure release, reducing temperature scanning, start, alarm, analog quantity processing, PID control and AD conversion. The main program flowchart is shown in figure 3.

2.3 Principle of Temperature Measurement

Classify the situation of time interval and time variation at first according to the time process of the craft: When start the machine, the smoke capacity is unstable and the smoke temperature is also unstable, so the outlet temperature will fluctuate, and at this time PLC will analyze and process the temperature collection. There are some phases (figure 4): (1) When the outlet gas temperature reaches between upper and lower temperature limits, the frequency converter works between the defined upper and lower frequency, and the running frequency is regulated by PID loop. (2) If the temperature reaches above the upper limit, the system regulates the running frequency range of the frequency converter, and adds 1 to it. The frequency converter works at the new frequency plus 3Hz, and the system begins to timing. If the temperature keeps on a rise, repeat the steps before, and while the temperature stops to increase, stop regulating frequency. (3) When the outlet gas temperature decreases between upper and lower temperature limits, the frequency converter works between the new upper and lower frequency, and the running frequency is regulated by PID loop. (4) If the temperature is lower than the lower limit, the system regulates the running frequency range of the frequency converter, and minus 1. The frequency converter works at the new frequency minus 3Hz. If the temperature continues to decrease, repeat the steps before, and while the temperature stops to decrease, stop regulating frequency, and a regulating period finishes.

The allowable deviation of the target temperature is 0.2 , and PID loop does not work during the range (dashed in figure 4). The sampling period of the temperature is set between 15 to 20 seconds according to experiment.

Figure3. Main program flowchart.

IV. REMOTE COMMUNICATION PRINCIPLE OF THE SYSTEM 4.1 Introduction of OPC

OLE is short for object linking and embedding. OPC (OLE for Process Control) is a standardized, vendor-independent software interface. It is an open and interoperable interface standard which is developed from Windows COM (Component Object Model), DCOM (Distributed COM) and XML (Extensible Markup Language). The equipment is very simple, containing at least one OPC server and one OPC client. Applying OPC server can provide data for the OPC client, and the OPC client retrieves data to make further processing. WinCC can communicate with any PLC using OPC [1]. 4.2 Communication Between OPC Server and WinCC PLC Data communication is made through PROFIBUS DP. The system collects PLC data by way of OPC data acquisition, and then WinCC reads data of OPC server as OPC client [2]. CPU226 provides two RS485 interfaces which can communicate with both PC and touch panel at the same time. CP5611 communicates with S7 PROFIBUS DP by WinCC. It generally uses S7 protocol in DP link, built-in drive, direct support, and can connect 8 PLC [3].

KEPSeverExV4.0 is installed in IPC, equipped with CP5611. Configure PC station CP card as the host station and the device supporting PROFIBUS DP protocol is the slave station. Open KEPServerEx, select appropriate communication protocol to create a new channel, establish corresponding equipment in the channel, and finally create the required variables under the equipment, as shown in figure 7. Open WinCC document by WinCC Explore, import KEP variables, and add variables to variable manager [4]

.

Figure4. Temperature control adjustment diagram.

III. STATE DIAGRAM OF THE SYSTEM

There are two working ways-local control and remote control, which locate in the main control cabinet and remote IPC separately. The local control operation interface is displayed by Siemens touch panel, as shown in figure 5, and

the remote control operation interface is shown in figure 6.

Figure5. Touch panel HMI main menu screen.

There are automatic control and manual control in both local and remote control methods, which is convenient to use the device for the debugging workers and operators.

Figure6. Remote IPC system operating main screen

Figure7. KEPSeverExV4.0 variables

4.3 Data Displayed by Remote IPC

The real-time operation data recorded by WinCC is shown in figure 8, and the record illustrates that the effect of the cooling has been well satisfied the process requirements.

Figure8. The operation data recorded by WinCC.

V. CONCLUSION

The OPC Data Access Server designed in this paper achieves real-time data reading and writing, so it has great practical value. The software of the control system can make data access to the hardware effectively and steadily, and the information exchange between application software is also flexible, which greatly improves interoperability and adaptability of the control system.

The control system has been used in water spray cooling system of Jigang Group Co.,Ltd. NO.4 blast furnace gas pipeline, practical applications prove that the system can display the working site operation data timely and accurately, and it has achieved a good function to reduce the gas temperature.

REFERENCES

[1] Zhijun Xu. Industrial Control Configuration Software and Application.

Beijing: China Machine Press, 2005.7:157-158.

[2] Shi Zhong, Yonghui Bie. Design and Application of Mobile Machinery

in Ports Control System Bbased on WinCC. Science & Technology of Ports, 2007.5:20-22.

[3] Wincc Technical Manual. Siemens Ltd. China.

[4] Changchu Liao. Siemens HMI (touch panel) Configuration and

Application Technology. Beijing: China Machine Press, 2007.1:130-138.

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