104 CEMENTS, LIMES, AND PLASTERS. 



are charged together in alternate layers. The product, however, is 

 of a much higher grade, for it is not discolored by contact with the fuel, 

 and it contains no fragments of unburned fuel or fuel ashes and clinkers. 

 With average care in feeding and burning, it is probable that at least 

 90 per cent of the product from a kiln of this type will be a well-burned 

 clean white lime, as compared with the 75 or 80 per cent obtainable 

 from mixed-feed kilns. As the fuel-burning apparatus is entirely dis- 

 tinct from the body of the kiln, the firing can be kept under better 

 control, so that the percentage of underburned and overburned material 

 in the product should be materially decreased. 



Kilns of this type are commonly 35 to 50 feet in height and 5 to 8 

 feet in inside diameter, with either two or four fireplaces or "furnaces". 



The Keystone kiln, described in detail below, may be taken as fairly 

 representative of this type of lime-kiln. 



The Keystone kiln is built on Broomell's patent by the Broomell, 

 Schmidt & Steacy Company, of York, Pa. Its construction can be 

 clearly seen from Fig. 22, which shows the kiln with a portion of the 

 shell cut away to exhibit the interior, and with the side wall of the fur- 

 nace removed to show its construction. The kiln from top to floor 

 is a heavy steel shell lined with fire-brick. The base of the kiln below 

 the firing platform is made from very heavy steel plates, reinforced 

 on the inside by numerous stiffening-ribs. The furnaces are carried 

 on steel platforms which extend a sufficient distance in front of the 

 firing-doors to give a convenient working space. In addition to being 

 supported at the inner ends by attachment to the shell of the kiln 

 the steel beams which floor the platforms rest at their outer ends on 

 steel columns. 



In operating this kiln the flame from the coal (or wood) burned 

 in each furnace is directed through two large openings in the kiln shell 

 and lining directly against the limestone which fills the kiln. These 

 openings, as well as the kiln shell and the furnaces, are lined with fire- 

 brick. 



As the lime passes the burning-zone it falls into a " cooling-cone " 

 made of steel plates. This is an inverted hollow frustum of a cone 

 suspended from a heavy cast-iron plate, which in turn is supported 

 by gusset plates riveted to the base of the kiln. The cooling-cone varies 

 from 6 to 6 feet in diameter at top, according to the size of the kiln, 

 and is 7 feet high. The burned and partly cooled lime is drawn from 

 the cone by means of shears or draw-gates at its bottom. These gates 

 are operated by hand-wheels which project outside of the kiln base, 

 thus removing the operator from the dust and heat of the lime. The 



