tendent of mines contained substantially the following conclusions relative to the experiments: Canadian magnetite ores can be as economically smelted as hematites by the electrothermic process. Ores of high sulphur content can be made into pig iron containing only a few thousandths of 1 per cent of sulphur. The silicon content can be varied as required for the class of pig that is to be produced. Charcoal, which can be cheaply produced from mill refuse or wood that could not otherwise be utilized, and peat coke can be substituted for coke without being briquetted with the ore. A ferronickel pig practically free from sulphur and of fine quality can be produced from roasted nickeliferous pyrrhotite. Titaniferous iron ores containing up to 5 per cent of titanium can be successfully treated by the electrothermic process. This conclusion is based upon an experiment made with an ore containing 17.82 per cent of titanic acid, yielding a pig iron of good quality. The electrical horsepower-year used per ton of pig produced during these experiments was about 0.277. As noted later, an average of 18 months' running at Trollhättan, Sweden, indicated that the electrical horsepower-year used per ton of pig produced was 0.340. After the Government had discontinued its tests the experimental plant was acquired by the Lake Superior Corporation, and for a time was employed for the semicommercial production of ferronickel pig, but up to the present time no other electric pig-iron reduction furnace plants have been installed in Canada. This lack of plants is not because the reduction of iron ores in the electric furnace has not met the expectations of the commission, but because the peculiar economic and geographic conditions in Canada have not seemed to warrant, to the present time, the introduction of the electric furnace for the production of pig iron. DEVELOPMENT OF THE ELECTRIC IRON-REDUCTION FURNACE IN SWEDEN. The development of the electric iron-reduction furnace in Sweden has been due to the following reasons: In Sweden the conditions are somewhat analogous to those found in Canada, that is, there are iron ores, but no coal for coking. There is, however, this difference between the conditions in Canada and in Sweden-in Sweden, as also in California, the ores are for the most part high in their iron content and rather free from impurities. Moreover, as has been indicated by Sundbarg", the iron industry has been well established in Sweden for some hundreds of years. The ores have been smelted in a blast furnace, charcoal for the most part having been used as a reducing agent, and Swedish charcoal iron is known the world over for its purity. However, it has long been a Sundbarg, A. G., Sweden, its people and its industries, 1904. apparent to those familiar with the situation that there would have to be some innovation in order to enable Swedish iron manufacturers FIGURE 3.-First type of shaft furnace used in experiments of Grönwall, Lindblad, and Stalhane. to keep the cost of production down. Each year has seen an increase in the cost of charcoal, because wood for making charcoal is becoming scarce owing to the depletion of the forests and the increased production of wood pulp. These facts caused Swedish engineers to turn their attention to the possibilities of electric smelting. EXPERIMENTS OF GRÖNWALL, LINDBLAD, AND STALHANE, DOMNARFVET, SWEDEN. The first electric-furnace smelting experiments made in Sweden were conducted by Grönwall, Lindblad, and Stalhane. The types. of furnaces used by them are shown in figures 3, 4, and 5. The construction of the fur nace shown in figure 3, is described by Yngstrom as follows: It was a shaft furnace Iwith the hearth lined with stamped silica. In the bottom of the hearth there were three channels: One in the middle leading to the tap hole for the pig iron, and one on each side. The latter communicated with two receptacles placed outside the shaft and filled with iron. The bottom of these receptacles was formed by blocks of granite packed on copper plates and connected with the electric-current supply. The furnace FIGURE 4.-Second type of shaft furnace used by Grönwas started with an air wall, Lindblad, and Stalhane. blast as an ordinary blast furnace, and when sufficient iron had collected on the hearth the air blast was cut off and the electric current turned on. The a Yngstrom, Lars, Electric production of iron from iron ore at Domnarfvet, Sweden: Engineer (London), vol. 109, Feb. 25, 1910, p. 206. idea was that the current entering the furnace through the iron by one of the channels would melt the charge in its passage to the opposite channel. It was possible to work the furnace in this manner during short periods, but it proved impossible to make the hearth durable. In part this was due to the fact that at the high temperatures used the silica became conductive of electricity. The furnace was therefore reconstructed in the manner shown in figure 4. The general principle of the design was the same as in the first furnace, but the lower portion of the furnace was of more solid construction. The electric current was introduced at opposite sides of the furnace. The most important alteration was, however, Lindblad, and Stalhane. opment of the type that FIGURE 5.-Third type of furnace used by Grönwall, later proved successful and is now being successfully operated in Sweden and Norway. In the work of developing this furnace to a feasible and commercial success these men were ably assisted by the engineers and capitalists of Sweden. An agreement was made with the Trafikaktiebolaget Grangesberg Oxelosund which enabled them to carry out their experiments on a large scale at the Domnarfvet Iron Works. Although the preliminary work on the furnace at Domnarfvet was begun in April, 1906, the furnace was not operated until April, 1907. Experimental work was conducted with it during the summer of 1907. The furnace is shown in figure 6. As the shaft of the furnace is low and open at the top, large quantities of charcoal were consumed at the top of the open shaft, and the gas escaping from the furnace consisted almost entirely of carbon monoxide. Based on the data obtained during the operation of this furnace, a new furnace was constructed. This furnace, which is shown in figure 7, higher, was closed at the top, and was so constructed as to permit the return to the crucible of a part of the gas I I FIGURE 6.-First type of furnace used FIGURE 7.-Second type of furnace used at Domat Domnarfvet, Sweden. narfvet, Sweden. passing from the top of the shaft. The furnace has been described in detail by Yngstrom in his report. EXPERIMENTS OF THE JERN-KONTORET, TROLLHÄTTAN, SWEDEN. The experimental runs conducted at Domnarfvet satisfied those interested in the undertaking so well that it was decided to go a step farther and to construct and perfect a furnace of a size suitable for commercial purposes. a Yngstrom, Lars, Electric production of iron from iron ore at Domnarfvet, Sweden: Engineer (London), vol. 109, Mar. 4, 1910, p. 237. DESCRIPTION OF FURNACE, This work was undertaken by the Jern-Kontoret, an association of the ironmasters of Sweden. Realizing the importance of the work to the iron industry of that country, the association voted $90,000 for the pur pose of putting up a plant and developing the process. The Swedish Government also assisted the project to the extent of furnishing power at a nominal figure from the plant at Trollhättan. Plans and sectional elevations of this furnace are shown in figures 8 to 11. The following description is taken from the official report delivered by the engineers to the Jern-Kontoret: " The four electrodes project through the roof in a slanting position at an angle of 65° to the horizontal. At the openings in the roof the electrodes are surrounded by cooling jackets of copper provided at the top with asbestos packing "Leffler, J. A., and Odelberg, E., Redogörelse för Jern-Kontoret's Försoksverk I Trollhättan, May 31, 1911. Abstract: Iron and Coal Trades Rev., vol. 82, 1911, pp. 957, 1010. |