13-1 Introduction

The fine coal and rock particles produced in underground mining are called the dust. The sizes of the particles are denoted by their diameter in micrometers����m��. The dust that is suspended in and moved with the air in ventilation flow is the airborne dust [2] and that which settles down on the floor is the settle dust [3]. Dust concentration is the amount of airborne dust contained one unit of air volume. It is generally represented by the total weight in milligrams per cubic meter or sometimes by number of dust particles in one cubic centimeter of air volume. The airborne dust is the most hazardous both from health and safety points of view:

A. Coal dust as a heath hazard [4] to the miners: If the miners work

in a dust environment for long period of time, the inhaled [5] coal dust could cause health hazards ranging from minor bronchial disorders [6] to pneumoconiosis [7]or silicosis [8].

B. Degradation [9] of the working environment by coal dust: If the air

at the area is filled with airborne dust, it very difficult to make the visual inspection [10] required constantly for operating the machine and roof conditions. This may tend to accidents.

C. Coal dust as cause of dust explosion [11]: when the concentration of the airborne dust with particle sizes ranging from 25 to 100mm reaches certain limits, dust explosion will occur.

13-2 Major Dust Sources

A. Coal cutting and loading are the major sources of dust production in longwall mining. Following coal cutting by the shearer��s drum, coal is broken by spiral vanes or scrolls, resulting in more dust.

B. Coal is further broken down and more dust is produced during conveying by AFC and at the transfer points [12] where the AFC empties into the stage loader, which in turn dumps into the belt conveyor.

C. The modern powered supports exert high resistance to the roof. Thus, the roof rock and the head coal are crushed and produce a certain amount of coal dusts that are rich in silica content.

13-3 Dust Prevention and Control

A. To correctly select the optimum operational parameters and to improve the cutting technique: they are the effective methods for reducing the dust production. For examples, increasing the haulage speed of the shearer can reduce the size of coal lumps [13] and decrease dust generation and properly reducing the drum speed can reduce the airborne dust blown away by the rotation. The cutting horizon control can effectively reduce the source of the silica dust. The natural ��-rays system of machine steering is an advanced method for automatic horizon control of shearer��s drum.

B. Control of the air flow and air velocity: It is necessary to provide sufficient air volume and velocity to dilute [14] the airborne dust concentration and/or carry it away from the face area. To assure sufficient air volume and air velocity at face area, air leakages [15]

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