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METHOD OF UTILIZATION.

At present gas circulation is used in the Swedish type of furnace in order to cool the superheated brickwork of the crucible and to carry up through the stack a volume of gas that is large enough and hot enough to bring about reduction in the stack.

This method has been the subject of a great deal of discussion.

OBJECTIONS.

The following are the principal objections to the circulation of gas in the electric furnace:

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(1) The moisture of the charge, the CO2 of the flux, and the CO2 gas naturally produced in the furnace are returned in a large part to the crucible and react on the unconsumed carbon by the reactions—

CO+C=2C0
H2O+C=H,+CO.

(2) The reactions noted materially cool the smelting zone of the furnace, which is its most vital working part.

(3) The system is cumbersome and expensive, and soon reaches the maximum of useful effect.

In order to overcome the objections mentioned it has been proposed to keep the ore in the shaft at a low red heat, and then to allow the CO gas produced by reduction in the crucible to rise slowly up through the charge, thus giving it the best opportunity of producing the maximum amount of CO2. In the circulation of gas, as has been pointed out by Richards," it is not the increased volume of the circulating gas that performs the reduction, as it is evident that when the amount of gas passing through the furnace is increased two or three times its velocity is also increased to that extent, and therefore its contact with the ore is only one-half to one-third as long. Such being the case, the only value of circulating a part of the gas escaping from the top of the shaft, so far as the problem of reduction is concerned, is that the charge in the shaft is kept at the temperature necessary for reduction, but, on the other hand, the CO2 returned to the crucible is reduced by C to CO, and thus one aim of electricfurnace reduction is defeated, namely, the removal of the oxygen from the ore with a minimum amount of carbon.

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Nevertheless there are objections to the methods that have been proposed for obviating the difficulties connected with the present method of gas circulation which may be briefly stated as follows:

(1) It would probably be difficult to heat successfully the charge in the stack by means of surface electrodes embedded in the walls of the shaft.

(2) As at a low red heat (say 480° C.) reduction takes place slowly, the volume in the shaft would have to be large in order to

a Richards, J. W., Gas circulation in electrical reduction furnaces: Trans. Am. Electrochem, Soc., vol. 21, 1912, p. 403.

give the charge time enough to be reduced in passing through the shaft.

(3) The use of burnt limestone, where shaft reduction is attempted, would introduce an unnecessarily large quantity of fine material into the charge.

(4) The water-cooled plates in the arch of the crucible, although useful, would not of themselves form a satisfactory substitute for the introduction of cold gas beneath the roof of the crucible.

As has been stated by Leffler," one of the engineers of the JernKontoret, gas circulation would be abandoned for a more simple and practicable method if such should be discovered.

However, the use of gas circulation at Trollhättan seems to be necessary, at least with the Swedish type of furnace. If this be true, efforts to improve the system ought to be directed somewhat along the following lines:

As is now done at Trollhättan, that part of the gas from the top of the shaft that is to be circulated could be drawn through a "Cottrell system" for the removal of the solid particles of ore and flux, by means of the circulating fan, and forced through a regenerator filled with coke heated electrically to such a temperature as to bring about the reduction of the CO2 to CO. The gas at the same time would be heated, but not to a temperature too high to absorb heat as it entered the crucible, and would thus pass up into the shaft at such a temperature as to readily effect reduction. Part of the excess waste gases could then be burned in a jacket around the shaft of the furnace so as to prevent radiation losses; the waste gases from the jacket could be passed to a preheater and completely burned, whereby the charge, minus the reducing agent, would be dried and raised to a temperature high enough to admit of the ore being reduced as soon as or soon after it was introduced into the stack.

The obvious advantages of such a system would be the doing away with the introduction of water vapor into the gas, as is.done by the present system of scrubbing the gas; the removal of CO, from the gas; and the raising of the temperature of the circulating gas.

Although the system as above outlined is just as cumbersome and expensive as the present method, it would probably be more effective.

OTHER METHODS SUGGESTED.

Some of the methods suggested as improvements are:

(1) Calcining the limestone outside of the furnace. This subject is discussed in a later section dealing with the comparison of the Swedish and Californian types of furnaces.

a Leffler, J. A., In discussion of Richards's paper on "Gas Circulation in Electrical Reduction Furnaces": Trans. Am. Electrochem. Soc., vol. 21, 1912, p. 412.

(2) Preheating the ore.-Judging by experience gained in California, the writer believes that the preheating of the charge is beneficial, for the following reasons: (a) It dries the charge and thus permits a more accurate weighing of the same, which is especially important in the electric reduction furnaces; (b) the initial temperature of the charge on entering the stack is thus sufficiently high to permit its being reduced immediately.

(3) Smelting of fine ores.-The authors are privileged to quote from a communication from Electro-Metals, Ltd., in regard to this matter, as follows:

As was explained in our first publication on this subject, the object of this plant [at Trollhättan] was to determine the relative merits of electric smelting as compared with ordinary blast-furnace smelting. For this reason the work has been carried out under widely varying conditions and with different kinds of ore and fuel. In consequence the results are by no means uniform and scarcely suitable for conclusions based on the average figures.

One object of some importance in Sweden was to determine the proportion of ore concentrates which could be used. The results prove that a large proportion of concentrates is detrimental to smooth running and good results.

This is readily understood from the fact that only about one-third as much charcoal is used as in the blast furnace, and concentrates therefore have an increased tendency to choke the passage of the gas.

As will be seen from the above, it is not feasible to use a large proportion of fine material in making up the charge for the electric furnace. This limitation, however, does not prevent the smelting of fine ores, for they may be sintered.

(4) Sintering. The advantages derived from sintering in electric-furnace work would be as follows: (a) The fine material would be caked in lumps, permitting free passage of the gases up through the charge in the shaft, and as the lumps would be porous they would be readily reduced, and (b) the fine ore would be preheated; that is, the hot sintered ore could be charged directly into the shaft at reduction temperature.

(5) Increasing the size of the unit.-The electric reduction furnaces now in operation vary in size as regards their horsepower from 1,500 up to 3,500. The largest yet designed requires 7,500 kilowatts and is at a plant in Sweden. As can be readily understood, it is important that the size of the unit be made as large as possible, and it is quite probable that larger furnaces will be built.

(6) Increasing the general efficiency of the furnace.-Improvements will probably be along the following lines: (a) The utilization of the waste gases; (b) the securing of a high-power factor; (c) the correction of induction losses; and (d) the perfecting of the single-phase furnace as recommended by Catani."

a Catani, R., Large electric furnaces in the electrometallurgy or iron and steel: Trans. Am. Electrochem. Soc., vol. 15, 1909, p. 168.

STATUS OF THE IRON INDUSTRY IN THE WESTERN STATES.

At the presenti time the only important iron-reduction plant west of the Mississippi River is at Pueblo, Colo. The plant has six stacks, twelve 50-ton open-hearth furnaces, two 15-ton Bessemer converters, four 400-ton furnaces, and two 250-ton furnaces. That there are no other large iron-reduction plants in the West is due largely to the fact that there is lacking in that part of the country, especially in California, the grade of coal necessary for making a suitable metallurgical coke. Then, too, although there are several known large iron-ore deposits scattered throughout the Western States, not much attention has in the past been paid to this class of deposits.

For nearly half a century after the discovery of gold in California the prospector along the Pacific coast looked for gold-bearing rock only. In recent years the discovery of valuable deposits of copper in California gave the prospector the copper craze, so to speak. In prospecting he looked for iron only as an indication of the presence of copper; that is, if he came across an iron deposit he looked upon it as a gossan or capping, and at once examined it for gold and copper, as his experience had taught him that gold is frequently found near the surface in rock of similar appearance and copper at a greater depth. It is well known that there are many deposits that yield oxidized ores above water level and sulphides below, so it is easy to understand why the prospector should have mistaken a true iron deposit for a deposit of the nature just mentioned. Even such iron ores as those in Shasta County were never seriously considered as such by prospectors. The miners in that part of the country commonly believe that iron indicates the presence of copper, and they insist that copper will be found below the iron.

IRON-ORE DEPOSITS ON THE PACIFIC COAST.

As above stated, it has long been known that there are large deposits of iron ore in Nevada, Arizona, and California, especially in southern California. As has been pointed out by Jones," most of the present known deposits of the Southwest have been discovered in places where there has been more or less erosion. Owing to the erosion, faces of ore several hundred feet in height, and of as great or greater width, are shown in certain intersecting gulches. Intrusions in limestone beds are common in the desert regions of Arizona, western Nevada, and California, and, as Jones states, there is in these regions scarcely a range of this nature that does not show some ledges of iron or float ore, and he ventures the assertion that syste

a Jones, C. C., Iron ores of the southwest: Paper read before the American Mining Congress, September, 1910; published in Min. and Min., vol. 31, April, 1911, p. 574.

matic prospecting and mining would uncover as great bodies of ore as have been already accidentally exposed by erosion.

For some time past the railway and oil interests of California have been systematically acquiring iron-ore holdings. For example, Jones states that in 1911 the Union Oil Co., through its subsidiary company, the California Industrial Co., was reported to hold an aggregate proven tonnage of 300,000,000 tons, one-third being in California. and two-thirds in Lower California, Mexico. This company has acquired these properties for the reason that they believe the problem of using oil as a reducing agent will ultimately be solved, and thus permit the establishment of an iron and steel industry in that section of the country. The Southern Pacific Railroad Co., operating under the name of the Iron Chief Mining Co., controls several deposits throughout the State, one of which is in Riverside County, some 140 miles from Los Angeles. Jones' states that it has some 30,000,000 tons of proven ore of such a nature that it can be mined cheaply. The average analysis of the ore is claimed to show 64 per cent iron and phosphorus within the Bessemer limit.

In addition to these deposits Jones also mentioned the following: At Scotts Siding, 190 miles east of Los Angeles, where 10,000,000 tons of ore have been blocked out, there being three times that quantity of ore on the property; in the Providence Mountains, 236 miles from Los Angeles, is a deposit of 5,000,000 tons of soft hematite, of Bessemer quality, that can be mined with a steam shovel; 12 miles west of Silver Lake Station and 230 miles east of Los Angeles is a deposit owned by the Colorado Fuel & Iron Co. that it states shows over 13,000,000 tons of ore that can be mined with steam shovels. In addition to the deposits named there are the Minarets deposits in Madera County, which are at present inaccessible, being about 80 miles from the railroad, but it is thought that a railroad line will soon be built into this district, thus making them accessible both to San Francisco and Los Angeles. It is stated that this is one of the largest deposits of iron ore to be found anywhere in the United States. As a result of his investigation Jones is of the opinion that there is 200,000,000 tons of available high-grade ore in southern California alone within 300 miles of Los Angeles, and that the ore can be laid down at Los Angeles at a cost of $3.50 to $4 per ton. If these figures are correct, there is a basis for the hope that an iron industry will be established on the Pacific coast, provided there can be found a commercially feasible process that will permit the utilization for metallurgical purposes of those fuels that are available in that part of the country.

a Jones, C. C., Op. cit., p. 53.

b Jones, C. C., Idem.

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