Complex utilization of washery wastes and environmental protection

The problems of the large scale utilization, detoxification and disposal of washery waste are being attacked in the USSR by the widespread investigation and study of the physical, chemical and technological properties of the mining and cleaning wastes in various coalfields. These wastes differ widely in composition and properties. They can be regarded as sources of both minerals and fuel (residual coal) and can be used effectively as a fuel and chemical (reducing) agent in various thermal treatment processes. Derivatographic, X-ray structural and other physico-chemical methods of investigation have shown that the thermal treatment of mineral wastes involves complicated phase transformations, including combustion of the organic matter, dehydration and restructuring of the minerals and partial vitrification in the heat-treated product. Complex investigation of the mineral fractions of coals show that most of the wastes should be regarded as a new and effective source of secondary fuel-mineral material for various sectors of industry; promising methods of utilization can already be specified. A discussion is also presented of closed-cycle water-slurry systems, purification of gases discharged to the atmosphere and, minimizing coal losses.