66o 



NATURE 



[February io, 19 i6 



fuel-fired furnaces. These are only some of the most 

 important branches of steel production where the elec- 

 tric furnace is firmly established. 



It has always been recognised that the most serious 

 competitor the electric furnace had to meet was the 

 blast furnace. In this case the coke performs two 

 functions. It has to supply not only the necessary 

 heat, but also the carbon for the reduction of the ore 

 and the carburisation of the metal. It is only the 

 former which can be replaced by electric heat, and 

 the horse-power year would have to be supplied at the 

 extraordinarily low figure of about \\. if it is to com- 

 pete with the modern coke-fired blast furnace. It is 

 not surprising, therefore, that there are few localities 

 which have been found to provide the necessary con- 

 ditions for electrothermic iron-ore smelting. In fact, 

 there <are only two countries where the conditions 

 have permitted headway in this direction to be made, 

 viz., Sweden and California, and of these Sweden is 

 in a much stronger position. Of unusual interest, 

 therefore, is the recent publication of Bulletin No. 344 

 of the Canadian Department of Mines, entitled "The 

 Electrothermic Smelting of Iron Ores in Sweden," by 

 Dr. Alfred Stansfield, who visited Sweden in 1914, 

 inspected the principal smelting works, and made a 

 careful study of the economic operation of the 

 furnaces, reporting on the general position as it affected 

 the possibility of establishing a similar industry in 

 Canada. 



Two main types of furnace exist : (i) the Elektro- 

 metall furnace, in which the ore is preheated and 

 partially reduced in a shaft before it reaches the smelt- 

 ing chamber ; the heating of the ore in the shaft and 

 the chemical reduction of the iron in the ore being 

 materially assisted by the circulation of the furnace 

 gases, which is characteristic of this furnace; (2) 

 furnaces of the Helfenstein, Californian, and Tinfos 

 type, in which there is no provision for preheating the 

 ore. Any shafts, employed are merely for the purpose 

 of introducing the ore charge conveniently, and the 

 main object of the design is to obtain a large and 

 substantial furnace for smelting iron ores by electrical 

 heat. 



In Sweden the Elektrometall furnace has been 

 largely used, and is in regular commercial operation 

 at Domnarfvet, Hagfors, and Trollhattan, but experi- 

 ments are being made with a modified Helfenstein 

 furnace. In Norway, which Dr. Stansfield also 

 visited, the Tinfos furnace is in operation on a mode- 

 rate scale at Notodden. At Domnarfvet there is one 

 4000-h.p. furnace, producing about 30 tons of charcoal 

 iron daily, and the output of the furnaces at the other 

 places mentioned varies for the most part between 

 20 and 25 tons per diem. A considerable variety of 

 irons, open-hearth and Bessemer, acid and basic, are 

 produced. On June 4, 1915, seven furnaces were in 

 operation and ten others in course of construction. 

 The output of the furnaces is not large — compared 

 with the 400 to 500 tons daily output of the hard- 

 driven American coke blast furnace it is small — but it 

 is as large as that of the charcoal blast furnaces which 

 they replace. Dr. Stansfield concludes (p. 7) : — " The 

 electric furnace has now become a dependable and 

 economic appliance for regular commercial use. The 

 iron obtained from it is even better than that from the 

 charcoal-iron blast furnace using the same ores and 

 fuel. The cost of making the iron, using cheap 

 Swedish water-power, is somewhat less than in the 

 charcoal blast furnace. The amount of iron that can 

 be made with a definite supply of charcoal is three 

 times as much in the electric furnace as in the blast 

 furnace. These considerations appear to represent the 

 foundation of the present electric iron-smelting indus- 

 try in Sweden." In fact, in this country the electric 

 furnace is ousting the blast furnace. 

 NO. 2415, VOL. 96] 



That section of Dr. Stansfield's report which deals 

 with the heat distribution and technical efficiency of 

 the Trollhattan Elektrometall furnace is of particular 

 importance. The large shaft of furnaces of this type 

 depends for its effectiveness on the circulation of the 

 gases which ascend from the hearth, as otherwise the 

 contents would not be sufficiently heated, so that the 

 question to be investigated resolves itself into the 

 desirability of the gas circulation system. Does the 

 circulation of the gases cause a large enough economy 

 to justify the expense and inconvenience of the large 

 stack and the circulation apparatus? From calcula- 

 tions made by Messrs. Lefiier and Mystrom, as well 

 as himself, Dr. Stansfield draws the following con- 

 clusions. 



"(i) The heat utilised in the reduction of the iron, 

 melting the pig-iron and slag, and in other necessary 

 parts of the smelting operation, amounts to from 63 to 

 74 per cent, of the whole electrical supply, this figure 

 increasing in the later periods. 



" (2) The principal source of loss is the radiation 

 of heat from the roof and other parts of the furnace 

 and the heat lost in the cooling water supplied to elec- 

 trode holders, collars, and other parts. These losses 

 varied from 31 to 19 per cent, in these tests, decreas- 

 ing in the later periods. 



" (3) The amount of the potential energy or calorific 

 power of the gases escaping from the furnace top 

 varies from 84 to 74 per cent, of the heat equivalent 

 of the electrical supply, and is in each case more than 

 the whole heat utilised in the smelting operation. The 

 object of the gas circulation is to utilise as far as 

 possible, in the furnace stack, the reducing and heat- 

 ing power of the carbon monoxide in the furnace gases ; 

 but even when this has been done to the greatest 

 extent that is practicable, the remaining gas has a 

 heat value greater than the net heat requirements of 

 the smelting operation, or about 75 per cent, of th? 

 whole electrical supply. 



"(4) The sensible heat carried out of the furnace 

 by the escaping gases is unimportant . . . and no con- 

 siderable loss of heat is occasioned in the same manner 

 by the gas circulation system." 



Collecting the results of all the calculations it 

 appears: — "(i) That without circulation the escaping 

 gases have a heat value about equal to the net heat 

 requirements of the furnace; (2) that with the gas 

 circulation about one-fourth the value of the escaping 

 gases is utilised in the furnace, thus saving about 

 II per cent, of the coke and 7 per cent, of the electrical 

 energy." It is evident, therefore, that if the calorific 

 power of the escaping gases could be perfectly utilised 

 the furnace could be run with a small fraction of the 

 power that is needed at present, and that the circulat- 

 ing system only effects about one-fourth of the large 

 saving that is theoretically possible. At present it 

 scarcely looks as though this increased the efficiency 

 of the smelting furnace to an extent commensurate 

 with the complication and expense entailed, particu- 

 larly when it is remembered that the escaping gases 

 could be utilised for converting the pig-iron into steel. 

 Dr. Stansfield's calculation leads him to conclude that 

 the gas produced in making one ton of pig-iron in the 

 electric furnace would almost suffice for the produc- 

 tion of one ton of steel in the open-hearth furnace. 

 H. C. H. Carpenter. 



GEOLOGICAL WORK IN CANADA. 

 nPHE Museum Bulletins of the Geological Survey of 

 ^ Canada include a number of papers on natural 

 history and anthropology, and afford a rapid means 

 for the publication of scientific work. No. 4 ("The 

 Crowsnest Volcanics," by J. D. MacKenzie, 1914) 

 describes igneous rocks from south-west Alberta, and 



