Operations

Excerpt from "Iron and Steel Production in America by Frank Popplewell Manchester University Press 1906. Publication No. XXI

An account of a visit to America between September 1903 and April 1904

The Wharton plant at Port Oram, N.J., consists of three blast-furnaces in all. Of these, the oldest was working at the time of the writer's visit on foundry iron, and does not call for any special consideration. The two more recently erected structures had the following dimensions: Height, 100 ft.; diameter (boshes), 21 ft.; diameter (hearth) 14 ft.; number of tuyeres, 16; air-blast, 42,000 cubic feet per minute; temperature, 1,100°F.; output, 450 tons per day. The furnaces were working on basic iron, and since the Ores are sulphur-free, there was no occasion to keep down the temperature. The burden was 21,400 lbs. ore, 12,000 lbs. Coke.

This plant was working on New Jersey magnetites exclusively. The ore is found at Hibernia, about 12 miles distant, in a seam 748 feet thick, and is mined underground by drilling and blasting. It then undergoes concentration at the mine head, and the product is worth about $2 per ton. .. The raw ore contains 45-52 per cent. of iron. It is concentrated up to 59-62 per cent. of iron. There are two varieties of concentrates--"lump ore," in pieces of about 2 in. diameter, and “fines. The latter is treated as a separate ore, and cannot, on account of its dusty character, be used to a greater extent than about 12 percent of the total charge. It has none of the binding properties of Mesabi ore, and gives great trouble in slipping. The lump ore is extremely hard, and the life of a furnace lining smelting it is correspondingly short. One of the furnaces of this plant required repairing after a twentyseven months' run.

The fuel employed is a Western Pennsylvania mountain coke, dusty, and of not very high quality. It is well adapted, however, for standing the burden of 100 ft. of hard ore.

The arrangement for cooling the boshes was a series of bronze cooling-boxes, such as are employed in the large furnaces of the West. Generally speaking, the steel cooling-plate is in favour in the East, and the bronze cooling-boxes in the West. It has been seen, however, that boxes were the cooling device adopted in the reconstruction of the Lebanon furnaces; while it is noteworthy that cooling plates are in use at the furnaces of the Pennsylvania Steel Co., at Harrisburg, and a modified form of the same device at the Ohio steel works, Youngstown, Ohio, which comprises some of the largest furnaces in existence. But, as the manager of the Wharton plant pointed out, the Harrisburg furnaces are small, and

a real comparative test yet remains to be made between the two arrangements as applicable to large furnaces. The furnaces are filled by means of skip-hoists charged from bins. Two men on a single electric larry fill and weigh all the material for one furnace, and one man on the top operates the hoist and bells. Steam, not electric power, is employed in this latter operation.

A Uehling casting-machine has given fairly satisfactory results, but it is found that very frequent repairs are necessitated. The wheels of the mould wear down the rail; and the moulds themselves, being fixed at both ends, have no room to expand and contract with changes of temperature, and are constantly cracking. They have to be replaced at the rate of one a day. A simple modification has accordingly been devised, whereby the moulds are placed in the same direction as the travelling belt, instead of across it; and this arrangement allows of their being attached to the belt by one of their ends only. There is thus perfectly free play for the forces of expansion and contraction in the mould.

The Concentration of the Ore. Two methods of concentration are in use for enriching the ore, both depending upon the attraction of an electro-magnet for the pure magnetite and the rejection by the same of non-magnetic particles. • In the older method, the ore as it comes from the mine in lumps is hand-picked upon a slowly-travelling belt and divided into two parts. The first consists of large lumps of ore containing about 52 per cent. of iron, which are sent to the furnace and smelted directly. The rock which is thrown out, and which was formerly rejected as valueless, contains on an average 28 per cent. of iron, and is now subjected to further treatment. It is Crushed and cobbed, and then passed over two drums, in the interior of which are strong permanent magnets. The pure magnetite is retained momentarily on the second drum, thrown off from that on to a travelling belt, and delivered into the car. The pure sand drops off the first drum, and is also collected. The "middlings," that is, the lumps which still contain both magnetite and sand, are carried half-way to the second drum and then thrown off. They are re-crushed and retreated. Somewhat less than half the original residue is obtained as ore, but it has an iron-content of 62 percent. The cost of treatment of such an amount of residue 'as will yield one ton of these rich concentrates is $1.10. The sand separated in this process is very pure, and is in great demand for cement manufacture. It commands a price sufficient to cover the cost of operating.

The newer method which it is proposed to install altogether consists in first grinding all the ore mined until it will pass through a 2 in. mesh. The whole is then passed over Ball-Norton two-cylinder magnets, which differentiate it into lumps of pure magnetite, and lumps of impure magnetite. (The latter may consist of as much as 50 per cent magnetite.)

This second half is then re-crushed and treated as before, when a further crop of pure magnetite, in•lumps of smaller size, is obtained. By this method there are obtained from the original ore. about six parts of magnetite (containing 59--60 per cent.), and about four parts of sand (containing still about 10 per cent. of magnetite). The cost of operation is only 10 cents per ton of finished magnetite, whereas in the former method 28 cents per ton were consumed in hand-picking alone. About 100 tons of mined ore are operated daily at the present time.