SMOKE AND DUST ABATEMENT COTTRELL. 663 



occasioned, a new stack was also built 50 feet in internal diameter 

 and 506 feet high, the chamber and stack costing over a million dol- 

 lars, and yet the company considered this a good investment on ac- 

 count of the values recovered from the dust settled by the chamber. 

 Nor is this by any means the largest of the copper-smelting plants in 

 this countr3^ In fact, the same company has another. Ihree times 

 this size, only 175 miles away, at Anaconda. This is mentioned to 

 give some idea of the magnitude of the problems confronting the 

 engineer in smelter-smoke control and the amount of skill and money 

 already expended toward their solution. 



APPLICATION OF CENTRIFUGAI. FORCE. 



Centrifugal force may be applied to remove suspended particles 

 in one of two main ways. In the first of these the gas is brought 

 tangentiall}^ into a stationary container of circular horizontal cross 

 section and withdrawn vertically upward through the axis of the 

 container, as in the well-known type of cyclone dust catcher, while 

 the dust particles tend to be thrown out to the periphery and finally 

 drop down into a receptacle provided for them beneath. In the 

 second method the gases are passed axially through a rapidly ro- 

 tating cylindrical shell, preferably provided with some form of 

 baffles. The dust collects on the shell wall and baffles and may be 

 removed from them in various ways. 



The first of these methods is in very general use for gases con- 

 taining fairly coarse dusts, but its efficiency falls off very rapidly, 

 as might be expected, when we come to deal with smaller particles, 

 and on reaching what we usually understand as fume or smoke the 

 depositing action is practically nil. 



The revolving shell type is much more efficient in this regard, but 

 the size and high speed necessary in such machinery for treating the 

 large volumes of gases met with in most instances w^here it would be 

 of interest have made it rather impractical and it has not come into 

 general use. 



ELECTRIC A L. PRECIPITATION . 



The last method of fume and dust collection to which attention 

 will here lie drawn depends upon the use of high potential electrical 

 discharges. This has a somewhat special interest for the Smith- 

 sonian Institution, not merely on account of the interesting scientific 

 problems which surround it, but also because some three years ago 

 a group of patents pertaining to the subject were offered to the 

 Institution as the basis for a new and unique form of endowment for 

 scientific research. Out of this has grown the Eesearch Corpora- 

 tion, an organization incorporated to administer the technical and 

 business developments of these and other patents and inventions 



