REPORT ON OPERATION OF THE FURNACE FROM AUGUST, 1911, TO MAY, 1912.

The furnace was again put into operation in August, 1911, and
was in continuous operation up to July, 1912, when it was relined.
In May, 1912, a report was submitted to the Jern Kontoret by the
engineers in charge of the operation of the furnace from August,
1911, up to that time. The following summary is taken from an
abstract of the report that appeared in Metallurgical and Chemical
Engineering, July, 1912, p. 413:

Results of operation of furnace from August, 1911, to May, 1912.

Iron, in ore, per cent.

Iron, in burden, per cent_.

Weight of slag per ton of iron, kg-

60.95
66. 84
323

Volume of circulating gas, cubic meters per second.....

0.24

The variation in the charcoal and power consumption per ton of iron produced, depending upon the iron content of the ore used, is shown in the following tabulation, taken from the article mentioned above:

Variation in power and charcoal consumption.

lowing limits:

The composition of the pig iron produced varied between the fol

The composition of the gases produced varied as follows:

The ratio of CO to CO, by volume varied from 4.8 to 1.8. The calorific power of the gas per cubic meter varied from 2,035 to 2,569, an average of 2,297 calories, or from 57.5 to 72.7 calories per cubic foot.

The oxygen ratio of the slags produced varied from 2.09 to 1.23. Analysis of the slags showed the following variations in composition:

The temperatures of the iron and the slag issuing from the furnace varied as follows:

Iron, °C

Slag, °C

1, 230 to 1, 420 1,290 to 1, 460

In September, 1912, the Jern-Kontoret leased the plant at Trollhättan to the Strömsnäs Iron Works, which has since worked it as a commercial plant. The final report on the research work at Trollhättan, as well as a report on similar commercial installations elsewhere, has now been published. A summary of the report, as furnished by Electro-Metals, of London, is largely presented below.

Use of concentrates. The proportion of concentrates ought not to exceed 20 per cent of the ore charged. This figure, however, does not appear to be final, as in a somewhat modified furnace of the same type constructed later at the plant of the Uddeholm Co. at Hagfors 25 per cent of concentrates is used without any difficulty.

Power consumption. The power consumption per ton of pig iron varies in proportion to the iron content in the ore. A poor ore and a pig iron high in silicon and manganese require more power than rich ore and pig iron low in silicon and manganese. For such iron the power consumption averages only 2,067 kilowatt-hours per ton of pig iron—that is, there is obtained 4.22 tons of pig iron per kilowatt-year, or 3.10 tons per horsepower-year.

Charcoal consumption. The charcoal consumption per ton of pig iron varies from 20 to 24 hectoliters (57 to 68 bushels), depending on the quality of the charcoal and the charge. Coke, unless mixed with charcoal, is unsuitable for this furnace.

"Abstract of report, Iron and Coal Trades Rev., vol. 86, 1913, p. 714.

Consumption of electrodes.-The consumption of electrodes at Trollhättan has been reduced to less than 3 kilograms per ton of pig iron. At Hagfors it has amounted to as much as 6 to 9 kilograms. This discrepancy is explained by the fact that the electrode consumption is increased in proportion to the higher power consumption for a poor charge, and is further increased by the more efficient circulation of gases and higher carbon dioxide content in the gas. The lower electric load per unit of surface at the Hagfors furnaces also contributes to the higher electrode consumption at this plant.

Cost of repairs.-The cost of repairs is lower than was at first expected. In the manufacture of pig iron containing silicon and manganese the cost for repairs is higher than in producing pig iron with a low content of those elements.

Quality of the pig iron.-The silicon content does not vary more than in the product of an ordinary blast furnace. The phosphorus content is lower than when the same quality of charge is used in an ordinary blast furnace, owing to the lower consumption of charcoal in the electric furnace. The sulphur content is, however, slightly higher in the product of the electric furnace. However, it should be observed that both at Trollhättan and at Hagfors unroasted ores have been used without any difficulty arising from the sulphur present.

The quality of the pig iron from the electric furnace has been highly commended. It acts particularly well in the open-hearth furnace, and steel made from it is certainly not inferior to steel made from ordinary pig iron. E. Odelberg, managing director of the Strömsnäs Iron Works, states that the electric pig iron is "of the very best quality for the open-hearth process and, as regards the uniformity of the silicon content, fully as uniform as iron from an ordinary blast furnace." A. Herleinus, managing director of the Uddeholm Co., states that "the electric pig iron has been used with satisfactory results, both for the open-hearth, Bessemer, and Lancashire processes. Generally speaking, there has been no difficulty in obtaining pig iron of uniform quality, although slightly better uniformity may possibly be obtained with a very carefully conducted blast furnace."

Value of the gas.-At the plant of the Uddeholm Co., at Hagfors, the gas from the furnaces has been used with very good results for heating the open-hearth furnaces. It is estimated that the value of the gas obtained per ton of pig iron may be taken at 2.50 kroner (about $0.67).

With regard to the furnace that was used, the report expresses the opinion that its construction and general dimensions have been found to be suitable. A summary of the most important figures relating to the economic results is presented in Table 4 following.