512 Transactions. 



neither would appear in the pig. However, the form of this ore is against 

 any hope of successful utilization in the blast furnace, even if the purity 

 made it worth while. Possibly the first suggestion to briquette such ores 

 was made by Mr. Pharazyn before the Wellington Philosophical Society 

 in 1869, and to this day those ignorant of metallurgical history vainly 

 hope for success along this line. The problem of utilizing finely divided 

 ore on the blast furnace arises wherever iron is smelted (flue-dust and fine 

 stuff) ; but so far no method of briquetting or sintering has ever been 

 successful, beyond making possible the use of the product to the extent of 

 about 10 per cent, of the total charge. The very nature of the briquetting 

 process is against the product holding solid under the high temperature 

 and gi-eat pressure of the modem furnace, and in the same way sintering 

 (or fritting a mass of ore and coal together to form what some fancifully 

 term ferro-carbon) cannot be efficacious beyond the temperature at which 

 fritting takes place. Metallurgical experience throughout the world has 

 made the fallacy of such ideas an axiom. At the most, a fritted product 

 can be made which will stand quick passage through a low shaft furnace, 

 and give a molten semi-steel containing under 2 per cent, carbon, which is 

 quite useless commercially. The prospect of large works using Taranaki 

 sand seems hopeless unless the ore is valuable enough to justify electrical 

 treatment, or unless some cheaper electrical furnace is introduced. At pre- 

 sent electrical furnaces use only expensive charcoal or coke as the source 

 of the carbon chemically necessary for reduction, and the necessary heat 

 is provided by electricity separately generated, while all the products of 

 combustion are wasted. But if powdered coal in excess (thousands of tons 

 of coaldust are destroyed every year in New Zealand as valueless) were 

 fed in with ironsand to the top of a small shaft furnace, and the waste 

 gases burnt under boilers to produce the small quantity of electricity 

 needed to quickly carbonize and melt the already white-hot mass of 

 mingled reduced iron and particles of coke, it is probable a much cheaper 

 process would result. Assuming that the ore, fuel, and air are highly pre- 

 heated by the waste gases, and remembering how efficient powdered coal 

 is as a heating agent, it should be possible to smelt ironsand at the expense 

 in fuel of 30 cwt. of coaldust, which presupposes an efficiency of about 

 20 per cent. Even in Taranaki this should not cost over £1 a ton, and if 

 the low figure of 30 per cent, is taken as the concentration factor of the 

 sand we would have — 



Table II. — Taranaki Pig. 

 (Magnetic concentrate, 30 per cent, of original sand ; iron, 56 per cent. ; Ti02, 10 per 



cent. ; phosphorus, 0'3 per cent. ; sulphur, trace. Electric furnace, 60 tons per 



week. Cost, £25,000). 



Grey Pig for Foundry. 



Ore, 6 tons (mining, 2s. 6d. ; drj'ing, 6d. ; concentrating, Is. 6d.) 



30 cwt. powdered coal 



5 cwt. limestone . . 



Labour 



Repairs 



Interest and depreciation . . 



At furnace . . 



Worth in Glasgow, July, 1914. 



66 



