Technological tests were carried out and a waste-free technology for processing coal sludge and waste tailings of coal preparation plants was developed. As a result of R&D the level of development of coal preparation in Russia and foreign countries was assessed. Substantial composition of samples of overlying tailings of coal preparation plants was studied. Technological tests were carried out, on the basis of which an ecologically clean, waste-free technology of enrichment of waste tailings with application of screw separators as the main enrichment equipment was developed. The possibility of obtaining high-quality secondary fuel with the Ad index less than 20 %; iron-containing concentrate with the mass fraction of iron not less than 62 %, which can be suitable for application in metallurgical industry or can be used in heavy-medium separation for coal preparation, has been shown. The tailings can be used as sand for construction works.

The basic design of the enrichment stand for semi-industrial testing of raw materials was designed. Design documentation for the enrichment stand was developed, including: general scheme; electrical circuit diagram; general view drawing; specification; operation manual.

The enrichment stand for semi-industrial tests of raw materials was manufactured and assembled, the acts of enrichment stand manufacturing were drawn up. Semi-industrial tests were carried out on the bench for taking indicators on representative samples weighing at least 2000 kg according to the technological schemes of enrichment developed during the laboratory tests. As a result of semi-industrial tests (hereinafter referred to as SIT) on the recommended technological scheme developed on the basis of the results of the research work, performed on the lying tailings of coal preparation plants, the data for the development of general technical solutions (hereinafter referred to as GTS) and technical regulations were obtained. According to the developed magnetic-gravity technology in PPI the possibility of obtaining coal concentrate with Ad index less than 20 %, iron-containing concentrate with mass fraction of iron not less than 62 % and tailings suitable as sand for construction works GOST 8736-2014 was confirmed. The report on semi-industrial tests on the topic "Processing of tailings of coal preparation plants in order to obtain commercial coal concentrate" and the act of semi-industrial tests on the stand were drawn up.

The OTRs were developed for drawing up the technological regulations for designing a pilot technological line for obtaining commercial products from technogenic wastes with a capacity of 20 tons per hour for feedstock. As a result of general technical solutions the following tasks were solved: development of detailed technology for obtaining coal concentrate from technogenic tailings (overlying tailings) of coal preparation plants; selection of necessary equipment for processing of technogenic tailings (overlying tailings) of coal preparation plants; basic design of pilot production technological line as a part of pilot processing plant.

The prospect of implementing a project to engage in the processing of waste tailings from coal preparation plants was confirmed. Tailings processing will allow solving several urgent issues, in particular, obtaining high-quality secondary fuel with minimal extraction costs using environmentally friendly technology at low energy costs.