At present, hot water boilers only use computers to monitor the operating parameters of hot water boilers. The operation of the hot water boiler must be adjusted manually. To truly realize the automatic control of hot water boilers, it is not enough to use computer remote monitoring. On the one hand, it is impossible to make the hot water boiler run at a higher efficiency, on the other hand, it is impossible to achieve the purpose of real energy saving.

The China Coal Mining Energy Co., Ltd. Maying Mine is located in the south of Maying Village, Maying Township, northwest of Shanyin County, and about 36km southeast of Shanyin County. The boiler room is located in the Maying Coal Industry Park. Two SZL7-1.0/115/70-AⅡ coal-fired hot water boilers and one SZL4.2-1.0/115/70-AⅡ coal-fired hot water boiler are selected. Two 7MW boilers were in operation during the heating period. A 4.2MW boiler is running during non-heating period. As shown below,

The system is composed of programmable controller, frequency converter, blower, induced draft fan, pump motor, sensor and so on. Take NA400 series programmable controller as the core. On the one hand, it communicates with the PLC through the console and receives control commands from the manager. On the other hand, it communicates with each inverter to start and stop control of the blower, induced draft fan, circulation pump and make-up pump, etc., and the motor speed setting. The operator can also understand the operation status of each boiler on site through the operation console at any time, and start and stop control of the motors such as fans and water pumps.

System configuration and description

This system includes power distribution system, PLC control system, on-site local box, upper computer monitoring system and sensor system. The system block diagram is shown below.

1. Power distribution system

Realize power supply to on-site blowers, induced draft fans, grate, circulation pumps, make-up pumps, coal feeding system, demineralized water and sensors. The power distribution cabinet is shown below:

　Distribution Cabinet

2. PLC control system

Using the most advanced NA-400 series control system and industrial Ethernet of Nanda Auto Technology Co., Ltd. as the automation system hardware platform of the boiler room. The PLC control system realizes the real-time control of the on-site temperature, pressure and flow of the boiler and the on-site equipment. The network topology of the boiler control system is shown in the figure below.

The on-site PLC cabinet is shown below:

NA400 redundant PLC cabinet

3. On-site operation box

Complete manual control of the boiler on site. Through the on-site "local/remote" switching button, when the knob is selected as the "local" mode, the boiler equipment can be started and stopped locally in the local state.

4. Host computer monitoring system

The upper computer is composed of an operator station and an engineer station. Picture of field equipment shown in the figure below.

　　Host computer monitoring system

The main screen includes:

① Main interface of technological process　

② Manual operation interface

③ Historical report query

5. Sensor system

Realize the pressure (economizer of boiler furnace negative pressure, water pressure, economizer, into the water, boiler water pressure, outlet suction fan outlet pressure, filter, etc.), temperature (furnace temperature, economizer in water temperature, water economizer outlet water temperature, water temperature, the temperature of return water main, etc.), flow (main flow of water supply and return water main flow, filling water flow, softened water, etc.) in real-time monitoring.

Since the system was put into operation in May 2012, the equipment has been running well and the entire system has not experienced any failures. Received unanimous praise from coal mine leaders and operating workers.