Growing productivity of mining and processing enterprises entails an increase in the volumes of liquid tailings impoundments and upstream impoundments of ore processing waste. Enterprises face the challenge of minimizing the environmental impact of waste and guaranteeing the sanitary and epidemiological safety of population. The article presents a possibility of recycling one type of such waste (clay-containing concentration tailings of apatite-nepheline and sylvinite ores, coal beneficiation tailings) by using them after preliminary thermochemical treatment as pozzolanic additives to cements and concretes, including concrete mixtures used for soil stabilization, development of territories, reclamation of mine workings, as a component of the insulating layer of landfills for the disposal of municipal solid waste. An analysis of the phase changes of kaolinite, one of the main minerals that make up clay-containing waste, in the temperature range of 200-1,000 °С showed that a change in its mineral form during heat treatment is the main factor in changing its pozzolanic activity. The effect of heat treatment of clay minerals at temperature of 700-800 °C on their pozzolanic activity, estimated by the ability to absorb calcium hydroxide (0.7 g Ca(OH) 2 per 1 g of modified kaolinite), is considered. It is shown that the addition of heat-treated samples (20 % by weight) improves the quality of cement increasing its activity by 15 %, in comparison with the use of unmodified clay minerals. It was proved experimentally that partial replacement of Portland cement with thermally modified kaolinite increases the strength of consolidating stowing mixture by up to 15 %. This approach to processing of ores containing layered silicates, which provides for thermochemical modification of run-of-mine ore, intensifies the processes of tailings thickening and filtering.
Dust control in summer and winter periods is a topical problem associated with conducting open pit mining operations; however, at negative temperatures the additional requirements are imposed on dust suppressants. Preventive compositions are proposed, in which light and heavy gas oils, obtained from catalytic cracking and delayed coking, are used as base components. Involvement of heavy fractions allows to increase the flash point, thereby reducing the flammability of dust suppressant, improve its adhesion properties by increasing the content of polyaromatic hydrocarbons and reduce the cost of the final product. In order to improve low-temperature and adsorption properties of developed dust suppressants, heavy oil residues (cracking residue and tar) are included in their composition in various concentrations: 2-10 wt.%. Alternative compositions of dust suppressants, obtained by water emulsification of vinylated alkyd oligomer, are developed; the ability of this dispersion to form strong films on dusty surfaces is examined. The efficiency of using aqueous solution of vinylated alkyd oligomer as a summer dust suppressant is demonstrated. The results of this study include the development of new preventive compositions with improved low-temperature properties and confirmation of the theoretical part of the study by the results of performance tests on a laboratory facility.Alternative compositions of dust suppressors have been developed, which were obtained by emulsifying a vinyl alkyd oligomer (VAO) in water; the ability of this dispersion to form strong films on dusty surfaces has been studied. The efficiency of using an aqueous solution of vinyl alkyd oligomer in the summer period as a dust suppressant is shown. The results of this study are the development of new prophylactic formulations with improved low-temperature properties and confirmation of the theoretical part of the study by the results of tests of operational characteristics in a laboratory facility.
Extreme dependence of the strength of sinter from its basicity is explained by content in the agglomerate iron and calcium silicates, which form a bundle of strength sinter. Minimum strength of sinter corresponds basicity about 1,2-1,4. This proves the attempts to optimize the technology of this agglomerate with the planning of the experiment. Laboratory experiments have shown that the basicity of sinter with 1,4 at the optimal linear velocity of its sintering about 18,7 mm/min, obtained an acceptable yield ratio not more than 65 %, even at elevated (above 6 %) fuel rate. In order to increase the maximum strength of the agglomerate in this extreme dependence appropriate to increase the content of iron oxide. Found that with the increase in iron content of 1,5 % yield of the agglomerate increases by 1 %. It is noted that the increase in iron content in the agglomerate after the maximum strength can lead to some of its decline, due to increased melting of the charge and decreases the amount of a strength ferritic-calcium binding.
At the present time the demand of manganese is high in Russia. Metallurgy industry lacks of high quality manganese products. They make strict requirements to manganese concentrates for phosphorous content. It is possible to increase the quality of manganese concentrates and to use law-quality manganese raw material in the processing by means of hydrometallurgical processing.
The issues of chemical sulfuric-acid leaching of oxide manganese-containing raw materials in the presence of reducing agents for the purpose of further obtaining high-quality dephosphorus concentrates are considered. The efficiency of using organic acids and alcohols as reducing agents is shown.