11-1 The Main Functions of Ventilation [1]

Ventilation is one of the most important aspects of longwall mining. The main functions of ventilation in longwall mining is:

A. Supply of fresh air at tolerable heat and humidity levels [2] for the mine workers to breathe.

B. Removal of noxious gasses from the mine atmosphere that are produced from the coal seam and mining equipment.

11-2 Ventilation Systems

The type of ventilation system used in a longwall mine is dependant upon the conditions found at each mine. The most influential factor [3] in the choice of ventilation system is the amount of gas that is present in the mine atmosphere. If the mine is considerably gassy, the gas in the mine has to be removed from the working panel as quickly and safely as possible.

The most common types of ventilation systems found in U.K are:

A.��U�� System

This is the simplest form, the mining district [4] is developed using two raises [5], both being maintained in front of the face for retreating mining. Ventilation of the method can employ two, or even three parallel intake and return gates [6]. The intake and return gates are drawn off [7] behind the face. The system is called reverse system as the intake air travels in the reverse direction to the return air. The raises, intake return gates are maintained behind the face in gob area [8] for advancing mining while ventilation flow and pressure distribution across the gob area increasing the air leakage [9]. The system has a smaller air leakage for retreating face, but it has a longer and changing ventilation lines, and a larger air leakage for advancing face. The system is suitable for coal seams that have very low gas emission rates.

B.��U�� System with Local Gob Edge [10] Ventilation

This system is used when retreating face with just two gates, the return gate being chocked [11] to keep it open. A duct [12] is installed from the return gate across the support line into the return gate behind the face and the airflow through the duct is usually of the order of 1/3 of the total face quantity, The flow is maintained by the use of a compressed air powered airmover [13]. Such a system merely provides scouring of the gob edge at the return end of the face and it only applicable to low gas emissions.

C."Z" System
With the "Z" system, the lower intake is a pre-formed gate

[1][2][3]��һҳ