Various potential uses of coal from Apsatsky coalfield

Summary

Additional geological exploration and studies of balance reserves of Apsatsky hard coal deposit have shown that these belong to valuable coking coal grades – “Zh”, “KZh” “К”, “КO”, and “OC”. Only a small proportion of coals located near the surface at the depth of up to 20 metres is partly oxidised and belongs to the “CC” grade of steaming coal. The coal ash has low slagging properties and medium ability to pollute convective heating surfaces. In terms of fusibility, the ash belongs to medium-melting: 1200ºC<t_b<1350ºC. The main harmful components in the coal seams are sulfur (S ^d_t ) whose content is below 1.0% and phosphorus (P^d) whose weighted average content is 0.003% and potential maximum content is 0.025%. Thus, coals of Apsatsky deposit are recommended for use in the layered coking process to produce high quality metallurgical coke as well as liquid and gaseous products. At the same time, the oxidised coals are a valuable raw material for burning at modern combined heat and power plants and state district power stations. So one of the main challenges related to operation of Apsatsky coalfield is to produce concentrate with ash (A^d) content below 9.6%. The results of pilot benefication of Apsatsky coals at the leading CPPs in Russia showed that in the course of transportation, storage, coal handling and processing there was a noticeable change in particle size distribution. The percentage of sizes above 25 mm decreased by 2.2-2.5 times and came to less than 30.0% while the total percentage of fine sizes of less than 13 mm increased by more than 30.0%. Most of the concentrate yield belonged to small sizes when washing coals of 0.2-3 mm size while the concentrate ash content was less than 9.0%. Crushing of middlings (fraction of 1550-1800 kg/m³) of plus 25 mm size to 0-3 mm size confirmed feasibility of liberation and additional recovery of up to 15% of concentrate with ash content below 9.6%. Apsatsky coals demonstrate high coking properties. The coefficient of technological value calculated using VUHIN Institute’s methodology has a high rate – 0.97. Mechanical strength of coke in case of individual coking was M40=74%, M25=88%, and M10=8.5%. Coke strength in a hot condition in case of individual coking of coal seams varied between CSR=34.0%-52.0% at CRI=40.0%-54.0%. Commercial blend of Apsatsky coals with other specially selected coking coals has shown significant improvement of the CSR value. Coking properties of Apsatsky coals also significantly improved once concentrate ash content was reduced from 9.6% to 8.0%. All of these factors allow us to place concentrates of Apsatsky coals into the semi-hard coking coal category. In the course of tests and studies of Apsatsky coals it was demonstrated that their dense medium benefication using flotation enables us to produce high quality concentrate at more than 74.0% yield and less than 9.6% ash. When Apsatsky coal concentrates were used at Russian coking plants we managed to obtain blast-furnace and foundry coke of export quality with high performance capability.