Magnetic Ore Milling Work - 7

Magnetic Ore Milling Work - 7

As to the next step in the process, we may now quote again from the article in the Iron

Age: "While Mr. Edison and his associates were working on the problem of cheap

concentration of iron ore, an added difficulty faced them in the preparation of the

concentrates for the market. Furnacemen object to more than a very small proportion of

fine ore in their mixtures, particularly when the ore is magnetic, not easily reduced. The

problem to be solved was to market an agglomerated material so as to avoid the

drawbacks of fine ore. The agglomerated product must be porous so as to afford access of

the furnace- reducing gases to the ore. It must be hard enough to bear transportation, and

to carry the furnace burden without crumbling to pieces. It must be waterproof, to a

certain extent, because considerations connected with securing low rates of freight make

it necessary to be able to ship the concentrates to market in open coal cars, exposed to

snow and rain. In many respects the attainment of these somewhat conflicting ends was

the most perplexing of the problems which confronted Mr. Edison. The agglomeration of

the concentrates having been decided upon, two other considerations, not mentioned

above, were of primary importance--first, to find a suitable cheap binding material; and,

second, its nature must be such that very little would be necessary per ton of

concentrates. These severe requirements were staggering, but Mr. Edison's courage did

not falter. Although it seemed a well-nigh hopeless task, he entered upon the

investigation with his usual optimism and vim. After many months of unremitting toil

and research, and the trial of thousands of experiments, the goal was reached in the

completion of a successful formula for agglomerating the fine ore and pressing it into

briquettes by special machinery."

This was the final process requisite for the making of a completed commercial product.

Its practice, of course, necessitated the addition of an entirely new department of the

works, which was carried into effect by the construction and installation of the novel

mixing and briquetting machinery, together with ex- tensions of the conveyors, with

which the plant had already been liberally provided.

Briefly described, the process consisted in mixing the concentrates with the special

binding material in machines of an entirely new type, and in passing the resultant pasty

mass into the briquetting machines, where it was pressed into cylindrical cakes three

inches in diameter and one and a half inches thick, under successive pressures of 7800,

14,000, and 60,000 pounds. Each machine made these briquettes at the rate of sixty per

minute, and dropped them into bucket conveyors by which they were carried into drying

furnaces, through which they made five loops, and were then delivered to crossconveyors

which carried them into the stock-house. At the end of this process the

briquettes were so hard that they would not break or crumble in loading on the cars or in

transportation by rail, while they were so porous as to be capable of absorbing 26 per

cent. of their own volume in alcohol, but repelling water absolutely-- perfect "old soaks."

Thus, with never-failing persistence and patience, coupled with intense thought and hard

work, Edison met and conquered, one by one, the complex difficulties that confronted

him. He succeeded in what he had set out to do, and it is now to be noted that the product

he had striven so sedulously to obtain was a highly commercial one, for not only did the

briquettes of concentrated ore fulfil the purpose of their creation, but in use actually

tended to increase the working capacity of the furnace, as the following test, quoted from

the Iron Age, October 28, 1897, will attest: " The only trial of any magnitude of the

briquettes in the blast-furnace was carried through early this year at the Crane Iron

Works, Catasauqua, Pennsylvania, by Leonard Peckitt.

"The furnace at which the test was made produces from one hundred to one hundred and

ten tons per day when running on the ordinary mixture. The charging of briquettes was

begun with a percentage of 25 per cent., and was carried up to 100 per cent. The

following is the record of the results:

RESULTS OF WORKING BRIQUETTES AT THE CRANE FURNACE

Quantity of Phos- Man- Date Briquette Tons Silica phorus Sulphur ganese

Working Per Cent. January 5th 25 104 2.770 0.830 0.018 0.500

January 6th 37 1/2 4 1/2 2.620 0 740 0.018 0.350 January 7th 50 138 1/2 2.572 0.580

0.015 0.200 January 8th 75 119 1.844 0.264 0.022 0.200 January 9th 100 138 1/2 1.712

0.147 0.038 0.185

"On the 9th, at 5 P.M., the briquettes having been nearly exhausted, the percentage was

dropped to 25 per cent., and on the 10th the output dropped to 120 tons, and on the 11th

the furnace had resumed the usual work on the regular standard ores.

"These figures prove that the yield of the furnace is considerably increased. The Crane

trial was too short to settle the question to what extent the increase in product may be

carried. This increase in output, of course, means a reduction in the cost of labor and of

general expenses.

"The richness of the ore and its purity of course affect the limestone consumption. In the

case of the Crane trial there was a reduction from 30 per cent. to 12 per cent. of the ore

charge.

"Finally, the fuel consumption is reduced, which in the case of the Eastern plants, with

their relatively costly coke, is a very important consideration. It is regarded as possible

that Eastern furnaces will be able to use a smaller proportion of the costlier coke and

correspondingly increase in anthracite coal, which is a cheaper fuel in that section. So far

as foundry iron is concerned, the experience at Catasauqua, Pennsylvania, brief as it has

been, shows that a stronger and tougher metal is made."