Processing Ash and Slag Wastes from Thermal Power Stations. Part 1

Abstract

In accordance with the national energy strategy, the development of coal-fired power stations in Russia, especially in Siberia and the Far East, calls for utilization of their ash and slag wastes. The total quantity of ash and slag in Russian tailings exceeds 1.5 billion t. These wastes cover an area of more than 220 km². The utilization of these wastes is no more than 10%. The most promising approaches are utilization of the wastes in construction materials or road building, or a hybrid approach in which valuable metals are extracted during the production of construction materials. Some fly ash can be used in agriculture. The physicochemical properties of ash and slag waste and correspondingly their applicability and the choice of technology will be determined by the mineral component of the coal and the methods by which the coal is burned. In order to use fly ash in construction, dry processing methods for ash and slag waste must be introduced. On the one hand, that involves greater capital expenditures on equipment and structures for storage, classification, crushing, and grinding of the ash and slag waste, as well as means of modifying their properties. On the other, increased transportation and organizational barriers must be expected. Examples of proposed processing technologies based on metal extraction and the production of construction materials are presented. To obtain iron-bearing concentrates, single-stage magnetic separation is mainly employed. However, the resulting quality of the concentrate is unsatisfactory. A better approach to the extraction of metals from ash and slag waste is flotation. At the same time, the available data indicate that the application of flotation may be limited by economic and organizational factors and associated environmental hazards. The conclusion is that the use of such technologies at thermal power stations that are already in operation is possible, with state support.