Carbon dioxide blasting

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A method of blasting coal that has been undercut, topcut, or sheared. Into one end of a seamless high-grade molybdenum-steel cylinder 2 to 3 in (5.08 to 7.62 cm) in diameter and 36 to 60 in (91.44 to 152.4 cm) long is put a cartridge containing a mixture of potassium perchlorate and charcoal with an electric match. The other end is sealed by a metal disk weaker than the shell and held in place by a cap that has holes at about 45 degrees to the axis of the cylinder. The cylinder is filled with liquid carbon dioxide at a pressure of 1,000 psi (6.9 MPa) and inserted in a borehole with the cap holes pointing outward. The heating mixture is lit and raises the gas pressure so that the disk is sheared; the carbon dioxide escaping through the angular holes tends to hold the cylinder in place, and break and push the coal forward. If the gas pressure is not enough to break the coal, the cylinder, if not properly set, will be blown from the borehole. The cylinder can be used over and over. It is claimed that a greater portion of lump coal is obtained than with ordinary explosives. Some smelters loosen slag in the same way. Hess
Source: Dictionary of Mining, Mineral, and Related Terms


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