SMOKE AND DUST ABATEMENT COTTRELL. 657 



THE SULPHUR PROBLEM OF THE SMELTERS.' 



The treatment and removal of the really gaseous constituents of 

 these trade wastes become such a special problem of chemical en- 

 gineering in each case that it can hardly be discussed to advantage 

 in the general survey here attempted. There is, however, one case 

 which from its magnitude deserves at least passing comment, viz, 

 the sulphur dioxide gases discharged from smelters operating on the 

 sulphide ores of lead, zinc, and copper, of which the latter, owing to 

 their greater tonnage and higher sulphur content, present the most 

 serious problem. No method has yet been devised which ^r>^ , this 

 from a practical and economic standpoint for all plants of this char- 

 acter. The most generally applicable method thus far employed has 

 been the manufacture of sulphuric acid. The two chief limits to its 

 commercial applicability in many cases are (1) the lack of a local 

 market for the acid, coupled with the difficulty and expense of its 

 transportation to great distances; (2) the great dilution of the sul- 

 phur dioxide with air and other gases in most smelters. 



The greatest single use for sulphuric acid to-day is in the manu- 

 facture of phosphate fertilizer. The proximity of phosphate rock on 

 the one hand, and of a market for the finished superphosphate fer- 

 tilizer on the other, are usually determining conditions in this matter. 

 Perhaps the best example of a smelter favorably located in this re- 

 gard is the Tennessee Copper Co., which has recently installed the 

 largest sulphuric-acid plant in the world. It was driven to this, 

 much against its Avill, by fume litigation, but is now making more 

 from its acid than from its copper output. As stated, however, its 

 location for such business was ideal, with the phosphate deposits of 

 Tennessee and South Carolina as raw material, and the great south- 

 ern cotton belt as market for the finished product at its door. It 

 would be difficult to find another plant of this size so favorably 

 located. 



When it is considered that there are many smelters in the country, 

 most of them in the West, each of which burns off daily from 250 to 

 1,000 tons of sulphur from its ores into the atmosphere, and that eacli 

 ton of sulphur will make three tons of concentrated sulphuric acid 

 and six of superphosphate fertilizer, the industrial problem of its 

 disposition can be better appreciated. 



The cost of smelting in most of the large copper plants of to-day 

 ranges from, say, $1.25 to $2 per ton of ore, depending chiefly on 

 cost of labor, fuel, and power, and as a relatively small per cent of 

 this often represents the difference between running ut a profit or at a 



^ The following four pages treating of the gaseous constituents are taken, with slight 

 revision, from " Smoke Problems of California," Trans. Commonwealth Club of California, 

 vol. 8, No. 9, pp. 487-492, San Francisco, Cal., Sept., 191.".. 



44863°— Sir 1913 42 



