Study of physical and chemical properties of coal concentration wastes with a purpose of their utilization as secondary raw materilal

Abstract

Involvement of production wastes into the economy turnover, in particular flotation wastes at coal concentration is an actual task. OJSC “MMK-Ugol” flotation wastes studied aimed at their utilization in facilities for burning high-ash coals, as well as utilization as thinning and combustible additive to clay burden for production of ceramic bricks. In the course of thermo-analytical study by applying the STA 449 NETZSCH synchronous thermal analyzer in a dynamic mode with a heating speed of 10 oC/min in an airflow 30 sm 3 /min within the temperature interval 30–1000  oC, the lowest combustion heat of the carbon-bearing material determined. Besides, the following parameters were determined: mass variation during calcination, variation and speed of the sample mass variation, the process heat effect, the temperature of the beginning, end and maximum progress of thermal effects. It was determined, that the biggest mass loss was observed within the temperature range of 450–600° С , that makes 65–67% of the whole mass of organic share of the coal. The maximum speed of combustion corresponds to the temperature 540–563° С . The lowest combustion heat of the wastes under study was 15.9 MJ/kg. Based on results of the thermo-analytical study, technical analysis and heat-engineering calculations, a possibility of flotation wastes utilization justified. The wastes should be used in the mixture up to 20% with a regular coal as a raw material in the furnaces of low temperature boiling bedchamber for coal concentrate drying. Analysis of flotation wastes chemistry showed, that they have high specific surface (56.8×10 3 m 2 /kg), high dispersion, soaking ability, swelling ability and due to considerable clay substance content they are a plastic material. It enables to use them as a fuel-bearing and thinning additive into the clay burden for production of ceramic bricks. Optimal amount of thinning and combustible additive to clay burden for production of ceramic bricks by semi-dry method determined, application of which after more uniform sintering will result in improving strength indices of the bricks (up to 30–40%), energy saving (up to 30%). Besides, it will exclude necessity to add black coal to the burden and increase productivity of sintering furnaces.