The purpose of coal preparation is to remove the harmful substances from the raw coal by mechanical methods, to obtain commercial coal that meets the quality requirements, and to meet the quality requirements of various industrial coals. In recent years, my country's coal preparation industry has developed rapidly, the number of coal preparation plants has increased, and coal preparation technology has been further accelerated. But there are still many problems. With the continuous development of computer technology, automatic control technology, distributed control technology, PLC and other high-tech, it has laid a solid foundation for coal preparation automation.

The project site is located in the Gold Ocean Industrial Park of China Coal Gold Group in Beizhouzhuang Town, Shanyin County, Shuozhou City, northwestern Shanxi. The project is a coal preparation plant with a raw coal processing capacity of 12 million t/a, using a combined process of heavy medium cyclone and pressure filtration. As shown below:

The project adopts NA400 series programmable controller as the core. On the one hand, the host computer platform communicates with PLC via Ethernet, receives the operator's control commands, and completes the start and stop of the plant-wide equipment and the adjustment of process parameters. On the other hand, through Ethernet, various product indexes and process parameters in the production process can be transmitted to the dispatch room. So that the whole mine can arrange human resources and material resources uniformly, and realize safe and efficient production.

System configuration and description

This system includes power distribution system, PLC control system, host computer monitoring system and field equipment system.

The system block diagram is shown below.

1. Distribution System

Realize power supply to various PLC cabinets, belt conveyors, scrapers, pumps and sensors. The power distribution cabinet is shown below:

Distribution Cabinet

2.PLC control system

PLC control system realizes on-site density, pressure, button collection and real-time control of on-site equipment. The PLC stations of the raw coal system, the main washing system, the concentration system, the pressure filtration system and other auxiliary production systems constitute the workshop equipment layer network. This layer uses the most widely used PROFIBUS bus technology in the world today. The most advanced NA-400 series control system and industrial Ethernet of Nanda Automation Technology Co., Ltd. are used as the hardware platform of the coal washing plant's automation system. The network topology diagram of the PLC cabinet of the washing control system is shown in the following figure:

The factory-wide centralized control (including closed-loop) system is equipped with the following PLC stations:

(1) PLC station of raw coal heavy medium separation control system >>>

Located in the power distribution room of the main plant, it is the PLC cabinet of the No. 0 DP main station and the PLC cabinet of the No. 1 and No. 2 DP substations. Mainly monitor the raw coal grading screen, heavy medium shallow trough, de-intermediate screen, magnetic separator, block coal centrifuge, mixed medium pump, thin medium pump, belt conveyor, scraper and other equipment in the main plant and related signal detection. It also controls the diversion and automatic water replenishment of 5 diversion boxes and 13 auto-regulation valves.

(2) PLC station of slime heavy medium system >>>

Located in the power distribution room of the main plant, it is the PLC cabinet of the No. 3 DP substation, which mainly controls the separation equipment of 13mm or less coal.

(3) PLC station of hydrocyclone separation system>>>

Located in the power distribution room of the main plant, it is the PLC cabinet of No. 4 DP substation, which mainly controls the sorting equipment of the final coal below 0.5mm.

(4) PLC station of raw coal preparation system >>>

It is located in the power distribution room of the raw coal workshop, in the PLC cabinets of DP substations 5 and 6. It mainly monitors and detects related signals of 13 coal feeders, belt conveyors, scraper machines, sewage pumps, belt conveyor iron removers, classification screens and other equipment.

(5) PLC station of concentration and tail coal pressure filtration system >>>

Located in the power distribution room of the filter press workshop, it mainly monitors the tail coal filter press system and related pumps, belts, and scrapers.

(6) PLC station of inferior coal and gangue storage and transportation system>>>

A power distribution room on the roof of inferior coal bunker is set. In the PLC cabinet of No. 7 DP substation, it mainly controls and inspects belts and other equipment.

(7) PLC station for storage and transportation system of end coal and lump coal>>>

A power distribution room at the top of the coal bunker is provided. In the PLC cabinet of No. 8 DP substation, it mainly controls and inspects belts and other equipment.

(8) PLC station in air compressor room>>>

It is located in the power distribution room of the air compressor room and is the PLC cabinet of the DP substations No. 9 and No. 10, which mainly controls the low-pressure fan and detects the shaft temperature.

The PLC main station, the computer monitoring and management station of the upper monitoring system, and the data collection station all communicate through Ethernet or optical fiber to form a control layer network. The field layer uses the PROFIBUS bus. The bus system consists of transmission technology, communication technology protocols, general rules and special rules.

The project selects the redundant PLC in the NA400 high-performance programmable controller: CPU401-0501 as the centralized controller of the whole plant. Among them, a large number of E3 and inverter with Devicenet communication interface are used in the system. Choose CMM401-0106 communication module in NA400 series for network control. The protection of the various types of belts in the system, such as pulling rope, deviation, stall and blockage, is collected through the Dupline bus. The CMM401-0411 serial communication module in the South NA400 series is selected to communicate with its master station to collect real-time field protection signals, which greatly improves the reliability of the system and the safety of production.

3. Host computer monitoring system

The upper computer consists of one engineer station and three operator stations. Choose GE's IFIX configuration software, and use industrial Ethernet to realize the communication between the field controller and 4 host computers to configure the system.

The main screens include:

① Interface of main workshop 1

② Interface of main workshop 2

③Interface of storage and transportation system

Through the automated centralized control system, not only can the sub-control system be monitored in the centralized control room, but software can also be used to monitor, debug, and program the system. Reduce the amount of equipment maintenance and repair, and reduce the burden on operating personnel.

Since the system was put into operation, the equipment has been running well, and the entire system has not had any failures. It has been unanimously praised by the leaders and operators of the coal preparation center.