106 



CEMENTS, LIMES, AND PLASTERS. 



lime can be discharged into a car run in under the cooling-cone or on 

 the floor. The heated air which ordinarily would accumulate around 

 the cooling-cone is discharged into the ash-pit under the grates, which 

 adds considerably to the efficiency of the furnace. Arrangement can 

 also be made for placing a steam-jet in the hot-air passage so as to pro- 

 vide forced draft if desired. 



TABLE 34. 

 DIMENSIONS OF KEYSTONE LIME-KILNS. 



Many patents have been taken out to cover improvements in various 

 details of the ordinary lime-kiln. One of these patented devices is 

 shown in Fig. 23, where boilers are inserted in the kiln arches so as to 

 utilize the waste heat of the kiln. The boilers, in turn, are used to 

 develop the power needed for running drills, hoists, and other machinery 

 in the quarry and mill. 



(4) Ring or chamber kilns. Chamber kilns of the Hoffman type, 

 though never used in America, are in somewhat extensive use in Europe 

 for both lime and Portland-cement burning. They are described 

 briefly on pages in connection with the burning of Portland cement. 

 When used for burning lime in Europe, a fuel consumption of 400 to 

 450 Ibs. coal per ton (2000 Ibs.) of burned lime is attained in common 

 practice, while lower consumption can be expected under favorable 

 conditions. The Hoffman kiln is, of course, a great improvement in 

 both economy and qua'ity of product on the old style of vertical kiln, 

 but it is doubtful if it gives better results than the modern 'kilns now 

 in use in the more important American lime-plants. 



Gen. Q. A. Gillmore stated * in 1871 that a Hoffman kiln used for 

 lime-burning at Llandulas, Wales, produced about 80 tons of lime per 

 day at the following detailed cost: 



Cost of quarrying stone, including tools $0 . 31 



Charging kiln 0.10- 



Drawing kiln . 07 



Wages of burners . 07- 



Fuel at $1.75 per ton Q.37 



Managing expenses, etc [ . 0.31} 



Cost of lime per ton $1 . 25 



* Gillmore, Q. A. A practical treatise on Coignet-Be"ton and other artificial 

 stone, pp. 71-72, 1871. 



