TRIES.
A similar type of furnace answers for the manufacture of phosphorus; the materials sup plied are phosphoric acid and coke. The phos phorus comes out as a vapor and is caught in a flue and condensed. Both calcium carbide and phosphorus may be made continuously, by pro viding means for feeding the furnace with new material and carrying off the product.
In the aluminum furnace a continuous cur rent is employed, the positive electrode being at the top, so that the current may pass downward through the fused mass to the negative elec trode, which may be of either iron or carbon. The liquid is thus electrolyzed on the wet prin ciple. The metallic oxide alumina is fed into a fused mass of fluoride of aluminum and sodium (cryolite, AlFs), the fluoride being electrolyzed. The oxygen uniting with carbon at the negative electrode the metal collects at the bottom, and may be drawn off through a tap-hole, the process being continuous. Over 150,000,000 pounds of aluminum are annually produced by electrical furnaces in the United States, and large factories have recently been built at Whitney, N. C.
The electric furnace has been tried for smelting a great variety of ores, with many in teresting results. Several concerns announce success in smelting zinc ores in the electric fur nace, one being at Keokuk, Iowa, where there is cheap hydroelectric power. It is practically certain that within a few years there will be considerable electrolytic smelting in localities where electricity is obtainable in large quantity at low cost.
The smelting of iron ores in an electric fur nace was begun in Italy, where Captain Stassano patented a furnace in 1898, and by 1900 ferro alloys were being produced commercially, and to-day ferroalloys are generally and preferably made in electric furnaces, of which 114 were known to be in operation and 30 building in different countries just before the European war of 1914. Of these 14 were in the United States, and the majority in Germany, Austria, France and Sweden. These electric furnaces do not pretend to compete with the great blast furnaces in cheap production of iron and steel, but their product is superior in the cat: uf alloys of known exact percentage, and the de mand for such steels being constant and increas ing, the future of the electric furnace is assured. As the cost of electrolytic iron becomes lowered there is a tendency to introduce the furnaces for commercial iron in regions where coal is scarce, as in California. There are large de posits of iron ore in Southern California which are liable to become of commercial importance when electrolytic reduction is better developed, as they have the advantages of cheap oil as a reducing agent.
The first electric iron-making furnace at Shasta, Cal., was completed in 1907, being of
the HeronIt type, 1,500 kilowatt, three-bhase re duction furnace. It had to be rebuilt and rebuilt again, and was not deemed a commercial success until 1911. The furnace proper is a well-burned lime and 121/4 pounds oi quartz. With coke at $6 a ton and power at $16 a kilo watt year, the cost of these items and for con sumed electrodes is $6.87 per ton of pig iron product.
New electric furnaces under construction have an average capacity of 41/4 tons. A 25 ton furnace and another of 22 tons were com pleted at Bruckhausen, Germany, just before the war broke out. In 1911 Gerrhany produced over 60,C00 tons of electrolytic iron or almost as much as all other countries comhined. The United States production is now (1916) nearly as large. The HeronIt furnace, developed in France, is the most popular type and is used in California, South Ohicago, Worcester and other places in the United States. The first Swedish furnace was the Kjellin, which was superseded by the Rochling-Rodenhauser, and steel shell 27 feet long, 13 wide and 12 high. The bottom slopes toward the tap-hole which is centrally placed in front. There are five 24-inch stacks, extending 15 feet above the roof. Cylin drical graphite electrodes are used one foot in diameter and four feet long. They last about 30 days, but the working is made continuous by fastening a new one to the stump of the one partially consumed. Three service transformers supply three-phase current at 40 to 80 volts to the efectrodes. They are each 750 kilowatts, and are water-cooled and oil-immersed. The metal is drawn off three times in every 24 hours. It is not necessary to shut off the current during the charging, so the operation is continuous. The charging is done by cars, running to a plat form at the level of the ton of the shafts. A normal charge is 500 pounds of magnetite iron ore, 140 pounds of charcoal, 3% pounds of is especially adapted to refining molten metal. It is built in sizes up to 15 tons capacity, some thing like a great steel converter. having an enormous steel tank, mounted on rollers and tipped sidev.-ays for pouring. One of these has been installed at Landstown, Pa., and uses 300 kilowatts, furnished by a 25-cycle current at 480 volts.
The success of the electric furnace in the iron and steel industry is due to the fact that the product of these furnaces is much purer than the blast furnace, and this notwithstand ing the blast furnace product has been vastly improved in purity, Pure iron is essential to making alloy steels with a known percentage of this or that other metal, required for pro ducing certain results. For further details con sult 'Electric Furnaces for Making Iron and Steel,' issued by the Bureau of Mines.