THE CHALLENGE TO USE EXTREMELY LOW VOLATILE AUSTRALIAN WEAK COKING COALS IN THE PRODUCTION OF GOOD QUALITY COKES

摘要

The following conclusions can be drawn from this work: 1. Low Volatile Jellinbah has proven to be a feasible replacement of traditional LV coking coals for coke-making, despite its minor caking properties. 2. Detailed laboratory work done at USIMNAS R&D Center showed that Jellinbah indeed fused and was perfectly bound to the other coals in the blend, as illustrated by microscopic textures. 3. For its high inert content, it does behave as a pressure moderator when compared with the high pressure developing US coals. 4. Pilot oven testing of blends in which the US LV coking coal was replaced by up to 20% of Jellinbah showed essentially no changes in coke quality parameters such as Drum Index, Micum, Micum Slope, Fissure-Free Size and CSR. This was possible because of the unique characteristics of Jellinbah's macerals and because the Brazilian blends already contain adequate fluidity to compensate for Jellinbah's minimum caking properties. 5. Brazilian Steel Mills have purchased and used over 2.1 million tons of Jellinbah at percentages varying from 5 to 16% in blends for extended periods of time. The use of Jellinbah at those levels brought no changes to the expected coke which was aimed at loading into large blast furnaces as in the case of CST (4,405 m~3 inner volume and 14.0 m hearth diameter) and CSN (3,815 m~3 inner volume and 13.0 m hearth diameter). 6. The significance of the utilization of Jellinbah as a blend component is its price differential when compared with traditional LV coals for the same rank contribution (currently over USS 15.00/mt).