THE ROTARY KILN. 



487 



The blast-fans are so arranged that the reserve fan could be placed 

 in service in case of accident to the operating fan before kilns have 

 time to cool to any great extent; after the kiln has cooled or when 

 starting the kiln for burning clinker, it requires several hours to heat 



DETAIL PLAN OF VARIABLE SPEED MECHANISM f 



FIG. 121. Coal-burning arrangement, International Portland Cement Co. 

 (B. F. Sturtevant Co.) 



kiln to a proper temperature for the complete combustion of the pul- 

 verized coal. The blast-fans in most cases draw their supply of air 

 directly from the kiln-room. In some plants, however, the inlet to- 

 blast-fans are connected with the clinker-coolers or the other parts of the 



