Reducing dust concn. in mine air - during mechanical coal mining, by emplying hygroscopic pastes on tunnel surfaces

Process for impeding dust formation in coal mines where the extn. of coal is undertaken using curbs and shields to support the surfaces of the tunnels, together with the hygroscopic salt pastes. The exposed roof layers in the tunnels are coated with a layer 1-10mm. thick of a conventional dust-binding paste directly before pressing the shields into position. The paste pref. contains calcium chloride and/or magnesium chloride, and a possesses a partial pressure due to water vapour below that in the air in the tunnel, and the penetration value of the paste is pref. 280-340 (when measured to DIN 51804). The paste pref. consists of a gel of Mg(OH)2 contg. 30-40% of the hygroscopic salts; the paste is pressed into the tunnel surfaces by the shield or prop and prevents the rubbing off of loose particles.