USE OF WASTE COAL AND ORES IN The use of waste anthracite coal'in connection with the dust or refuse ores in blast furnaces is an invention of the writer, on which a patent is pending.
The waste coal is passed through a screen, and the clean dirt, as free from slate and impurity as it is possible to make it, is crushed between heavy, smooth rollers until it is perfectly fine, and in this condition is ready for admixture with a proper quantity of iron ores.
The finer particles of the ores rejected by our large blast-furnaces are collected, with such cheap ores as may be available from the anthracite mines or other localities, and the whole passed through heavy, smooth, iron rollers, and crushed to powder. In this condition it is passed through a stream of water in which it is violently agitated, and then allowed to precipitate in successive tanks. The richer ores will be the first to precipitate, and the most distant sediments will be the leanest. In this manner, ores of any given richness can be obtained from a lean matrix or seam, and the only objec tion against their use will be their cost, or the cost of mining, since the cost of crushing and precipitating is merely nominal. But the washing and precipitating will not be necessary with rich ores. Such have only to be crushed. In the condition above de scribed, the ores are ready for admixture with the coal-dust in such proportions as experience may dictate, but not above one part of coal to one of ore or flux.
The third process is to burn and slack a sufficiency of lime for flux, and mix the whole in given proportions in the state of brick mortar. The mass can then be moulded by hand as bricks are moulded, and dried and stacked away for use; or they can be made and pressed in machinery, and stacked away to dry without the process of sun drying.
When sufficiently dried, the blocks are ready for the furnace, and the materials are so intimately mixed and so minute in particles that the carbonizing and deodorizing process is complete, and the burden arrives at the melting zone in a state ready for fusion.
This process has been tried on a small scale and found to work admirably; but it is here mentioned only as a means to economize the waste of the anthracite mines.
We expect most of our extensive coal-operators will be pleased to give away the waste coal, provided it is taken without cost or inconvenience to them. The cost then will depend on the transportation and the preparation of the material. The cost of crushing and mixing would not exceed 50 cents per ton, and five tons would be required to pro duce one ton of iron. One ton of fine ore yielding 45 per cent., and two tons of lean ore yielding 30 per cent., would, when crushed and cleaned, be less than 21 tons, yielding an average of 40 per cent. of metal in the furnace, at an average cost, delivered on the ground, of $2.50 per ton.
The lime might cost $3 per ton to transport and burn. The whole cost of a ton of metal would stand thus:— This, under ordinary circumstances, might be reduced one-fourth, since the figures above are all given at maximum rates. But, at the full rates for the best ores, the margin lies in the difference in the price of coal, since the preparation of the five tons of mixture would not exceed half the cost of coal as now used in the furnaces.