Granulation in technology for utilization of industrial waste materials

Abstract

Technology is presented for the utilization of dust, captured by electric filters of a cement production rotary kiln, with preparation of granulated potassium-lime fertilizer in a drum pelletizer. The binder used is an aqueous solution of potassium, prepared by mixing sinter dust with water and unconditioned granules in the ratio S:L = 1:5. The size of the dried granules is not more than 5 mm, strength in compression 1.2‐1.6 MPa, and this satisfies the requirements for granulated fertilizer. With the aim of utilizing overburden chalk rocks from iron deposits of the Lebedinskii and Stoilenskii Mining and Concentration Combines granulation technology is developed for chalk as an improver for soil deoxidation. It is established that the most effective binder material is bentonite. The optimum weight of bentonite clay per ton of chalk is 2‐3 kg. The granules obtained satisfy the requirements for a granulated fertilizer with respect to size, strength and moisture content. During development of industrial production in the economic revolution of the country ever greater amounts of natural resources are involved. However, the degree of the rational use is very low. About 70% of industrial expenditure in CIS countries is consumed in feedstock, materials, fuel, electrical energy, and at the same time about 10‐70% of starting materials is converted into waste discharged into the atmosphere or volumes of water. In ferrous and nonferrous metallurgy, and also in the production of fertilizer and chemical preparations obtaining concentrates is an obligatory production operation with which it is necessary to grind natural materials, accompanied by an increase in the dispersion of mineral waste materials (that is undesirable from an ecological point of view) and an increase in the amount of them. With known assumptions, it is possible to confirm that the level of the harmful effect on the natural environment of substances contained in dumps is proportional to their dispersion and volume. The practice of operating tailing and slurry pits indicates that they serve as a source of water and atmospheric contamination. In view of the exhaustion of natural resources, it may be suggested that these pits and dumps with time are converted from objects for burying waste materials into reservoirs for storing unclaimed mineral masses undergoing a specific treatment cycle and containing components that it will be necessary to extract in the future. Aggregation of technogenic powders by granulation may be considered as the next step in converting mineral waste material into a source of conditioned technogenic raw material. In order to store powders in pelletized form, powder with binding properties is mainly recommended, i.e., calcium ashes from thermal power stations, cement kiln dust, etc. [1]. A method has also been proposed in [2] for immobilizing and storing condensed harmful substances by processing them with a protective binder solution (aluminosilicate solution of nepheline in a 10‐20% solution of sulfuric or hydrochloric acid) followed by hardening and molding.