Blast Furnace Burden Preparation with Reference to High Ash Coke

THE primary objectives in iron smelting are high output, low coke, rate and smooth operation.
The aspect of coke economy is somewhat complex when working with an iron rich burden and a high ash coke
since the ash of the coke contributes a major part of
the total slag.Where, as in India, the sulphur content
of ore and coke is low , the minimum workable slag volume mn be taken as 350 kg. of slag per metric ton of pig iron. It is worth noting that the Fairless works in America has successfully operated with slag volumes as low as 300 kg. per metric ton.For an ore containing 62 per cent iron, 3 per cent silica and 4 per cent alumina the relationship
between per cent ash in the coke and the coke rate nece-ssary to give 350 kg. of slag is as plotted in graph 1, line AOB. Also on this graph line COD represents appro-ximately the coke rate likely to be attained with optimum practice. As the coke ash is reduced below 17.5 per cent it becomes necessary to add silica sand as a fluxing agent and this explains the reduced benefit of lower ash in
the coke to the left of point O.
If a hypothetical furnace is operating at point P two steps are required to bring it to 0, the point of optimum working. Firstly, the coke ash roust he reduced from 21 per cent to 17.5 per cent(P to Q). This is it problem for the coal washeries and is already well appreciated and being dealt with. Secondly, it is necessary to lower the coke rate from Q to 0 and the present paper considers
burden preparation as a means of achieving this aim.