230 



CEMENTS, LIMES, AND PLASTERS. 



layers. About a week suffices for the passage through the kiln of any 

 particular mass of material. These small kilns produce about 100 to 

 125 barrels (265 Ibs. each) of cement per day. 



The larger kilns are 54 feet from extreme base to top. Viewed 

 from the outside they appear to be cylinders 54 feet high and 16 feet 

 in diameter. Their interior space, however, is 10 feet in diameter at 

 the top, enlarging to 12 feet at a point 18 feet above the base. Below 

 this level, though the interior walls still slope outward, the space is 

 really contracted by the occurrence of a conical mass of brickwork in 

 the center of the kiln. This cone throws the downcoming clinker toward 

 the draw-gates at the sides. A 9-inch lining of fire-brick is set around 

 the kiln space proper. This is followed by 9 inches of common brick, 

 and the space between the common-brick lining and the exterior kiln 

 shell (which is j-inch iron) is filled with clay. A kiln of this size and 

 type will produce 150 barrels of cement per day. 



FIG. 42. Kilns and kiln-housing, Speed plant, Speeds, Ind. 



The coal used in these kilns is bituminous nut and slack mixed from 

 Pittsburg or Jellico. About 25.6 Ibs. of coal are required to burn a 

 barrel of cement (265 Ibs.), equivalent to a fuel consumption of about 

 9.5 per cent on weight of cement produced. 



