368 Figure 2- Percentage of research work in coking coal optimization in 2000-2024 2. METHODOLOGY The high ash Indian coking coal (ash > 35%, W-V & VI) coal have NGM greater than 25% at the desired specific gravity of cut (Formidable category, extremely difficult to wash). Due to intimate mixing of finely disseminated coal and shale, these coals are poorly liberated; even progressive crushing to 15/13 mm does not provide significant clean coal yield. 2.1 The New Bhojudih Washery (2.0 Mtpa) is one of the NLW coal washery of Bharat Coking Coal Limited (BCCL; A subsidiary of Coal India Limited) having its headquarter at Dhanbad (Jharkhand).The washery is located at Bhojudih, P.O-Sathaldih, Purulia district of West Bengal. The washery is designed to wash washery grade, W-V coal (avg ash-38%) from Seam-I, II & III, North-Tisra OC Mine of Lodna Area, Jharia Coalfield of BCCL. The screen analysis of raw coal (50 mm) feed to the washery is described in Table 1 and float & sink data of 50 mm is mentioned at Table 2. This is three-product washery producing clean coal (18% ash), middlings (<40% ash) and rejects (> 60% ash). Table 1 - Screen-cum-ash analysis Size (mm) Wt % Ash % 50-25 49.7 39.3 25-13 18.4 37.9 13-6 9.2 37.3 6-3 7.3 36.5 3-0.5 6.9 35.1 -0.5 8.5 34.5 Total 100.0 38.0 Table 2 - Screen-cum-ash analysis Float & sink analysis (50 – 0 mm) Size (mm) 50-25 25-13 13-6 Mass % 49.7 18.4 9.2 Sp. Gr. Float Float Float Wt% Ash% Wt% Ash% Wt% Ash% < 1.40 1.8 14.6 3.2 14.2 5.0 12.0 1.40 – 1.50 18.0 21.1 20.6 20.1 21.0 19.2 1.50 – 1.60 30.3 30.3 28.4 29.6 25.9 29.4 1.60 – 1.70 19.1 38.2 14.1 38.8 10.7 36.3
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