System Overview

The intelligent local ventilation system for coal mines is a multi-functional, highly efficient, and energy-saving automatic control device that ensures normal production in coal mines. It integrates the mine's local ventilation control system with local ventilation fans. The system is equipped with specially designed local ventilation fans, monitoring sensors, and other monitoring signals that are connected to a PLC automatic control system for closed-loop control. This changes the current situation in China where local ventilation fans lack effective monitoring and control, organically combining effective mine management with safe equipment operation. This reduces the hazards caused by gas in mine development faces, improving equipment safety while ensuring normal mine production.

This system consists of a host computer, local ventilation fans, a variable frequency speed control device, intelligent control, and air distributors.

Composition and Function

(1) Product Composition

The device consists of a variable frequency drive, PLC, switching components, methane concentration sensor, temperature sensor, anemometer, carbon monoxide sensor, dust sensor, broadcast system, network system, and the fan unit itself (see Figure 2).

The explosion-proof switch is placed at the mine's power distribution point and connected to the mine's ring network switch, ensuring both uninterrupted power supply and network connectivity. The connection between the explosion-proof switch and the intelligent variable frequency drive can be via network cable or fiber optic cable. For short distances (within 100 meters), a network cable is used; for longer distances, fiber optics are used. The intelligent variable frequency drive has built-in Ethernet and fiber optic interfaces. Video and sensor data are transmitted via Ethernet to the host computer in the dispatch room.

(2) Function and Principle

Speed Control Device Operating Modes: The control mode is set based on the collected methane, temperature, wind speed, CO, and dust signals.

According to the regulations, conventional speed control is based on methane concentration and has three operating modes: "automatic ventilation mode," "automatic methane discharge mode," and "manual frequency setting mode."

Automatic Ventilation Mode

For low-gas mines, when the methane concentration at the working face heading and return air area does not exceed the set value, the speed control device operates in automatic ventilation mode. The fan speed is controlled comprehensively based on roadway air volume, temperature, CO content, and dust content. If any of these parameters exceed the set value, the speed control device will automatically increase the speed and increase the air supply (upper frequency limit) until the exceeding signal returns to below the set safety value. Then, the fan speed will decrease (lower frequency limit). During this process, the methane concentration must remain within the normal range; any exceeding will immediately switch to the automatic methane discharge mode.