LIME-BURNING. 



99 



TABLE 33. 



HEAT AND FUEL THEORETICALLY REQUIRED IN BURNING ONE TON OF 



LIMESTONE. 



The above results are to be regarded only as approximations to 

 the truth, because the chemical data on which the calculations are 

 based are not accurately determined, but the figures suffice to show 

 the great economy in fuel consumption which comes from the use of 

 highly magnesian limestone. 



Types of lime-kilns. The types of kilns employed in lime-burning 

 may be grouped as follows: 



(i) 



Intermittent kilns | 

 Continuous kilns ) 



( limestone and fuel fed ) 



Vertical kiln, mixed feed. . . . [ (2) 



( in alternate layers j 



Vertical kiln, separate feed. . .limestone and fuel not in contact (3) 

 Ring or chamber kiln (4) 



(1) Intermittent kilns are those in which each burning of a charge 

 constitutes a separate operation. The kiln is charged, burned, cooled, 

 and the charge is drawn; then the kiln is again charged, and so on. 

 The disadvantages of this intermittent mode of operation are obvious; 

 and kilns of this type are consequently employed only where there is a 

 slight or very irregular demand for the product. Old kilns of this kind 

 can still be seen in farming regions, where charges of lime are burned 

 as the neighborhood demand requires. 



These primitive kilns were * " rudely constructed of stone, and 

 were located on the side of a hill, so that the top was easily accessible 



* Blatchley, S. W. 29th Ann. Rep. Indiana Dept. Geology, pp. 225-227, 1904. 



