Читать книгу Coal-Fired Power Generation Handbook - James Speight G., James G. Speight - Страница 54

Auger mining is analogous to wood drilling; the coal is extracted from a seam (which outcrops to the surface) by the use of large-diameter augers.

This particular method for the recovery of coal was developed mainly in the period following World War II. An attractive aspect of the method is the relatively low cost of the equipment since the technique essentially involves boring a series of parallel horizontal holes into a coal seam.

The technique is frequently employed in open pit mines where the thickness of the overburden at the high-wall section of the mine is too great for further economic mining. This, however, should not detract from the overall concept and utility of auger mining as it is also applicable to underground operations. As the coal is discharged from the auger spiral, it is collected for transportation to the coal preparation plant or to the market.

In this technique, the miners drill a series of horizontal holes into the coal bed with a large auger (drill) powered by a diesel or gasoline engine. These augers are typically approximately 200 feet long and drill holes between 2 and 7 feet in diameter to depths of up to 300 feet in the coal seam and the coal is moved out as the drill turns farther into the seam. As these enormous drills bore into the coal seam, they discharge coal like a wood drill producing wood shavings.

Additional auger lengths are added as the cutting head of the auger penetrates further under the high wall into the coal. Penetration continues until the cutting head drifts into the top or bottom, as determined by the cuttings returned, into a previous hole, or until the maximum torque or the auger is reached. Penetration in an auger operation may vary from a few feet up to 200 feet, depending on the pitch of the coal seam, the seam thickness, and the physical characteristics of the strata immediately above the coal seam. The better the roof strata and the more level the coal seam, the deeper the penetration.