226 



CEMENTS, LIMES, AND PLASTERS. 



or natural-cement kiln the pot or lower portion of the kiln is an inverted 

 oval in shape, with one or more draw-chutes or doors at the side. This 

 results in a certain amount of concentration of the heat, as the draft 

 is localized near the base of the kiln owing to the effects of the draw- 

 openings. The Campbell kiln-pot, instead of being an inverted egg- 

 shaped mass of solid masonry, is an open grating in the form of an in- 



t 86 x- 



TIG. 37. Sections of kilns used in natural -cement plants. (After Gillmore.) 



verted cone. In Figs. 38 and 39 the construction details of the kiln 

 are clearly shown. It will be seen in the front elevation that an open 

 space is left all around the pot, between the grating and the supporting 

 walls of the kiln, so that the drawer has free access to all parts of the 

 grating in case of choking or other difficulty. The openings in the grating 

 distribute the air-supply so that the draft is uniform throughout the 

 kiln. 



It is stated * that the cost of reconstructing the iron-cased kilns of 

 the Milwaukee Cement Company on the Campbell pattern was about 

 $250 per kiln. For a stone kiln the cost of reconstruction would be 

 somewhat higher. A new Campbell kiln, however, would cost some- 

 what less than a new kiln of ordinary pattern, for the iron "pot" will 

 displace more than its equivalent value of brick and labor. 



The Campbell kilns in use at the plant of the Milwaukee Cement 

 Company hold a charge equivalent to about 400 barrels (265 Ibs. each) 

 of cement. This is drawn at the rate of 125 to 130 barrels per day, 



* Engineering News, Dec. 23, 1897. 



