LIME AND CEMENT INDUSTRIES 709 



the older processes. Crude or fuel oil is used at all the American 

 factories where this type of furnace is employed. Producer gas 

 could no doubt be employed. It is claimed by Johnson that this 

 type of kiln is used only at those works where the mixed mate- 

 rials will not adhere with sufficient firmness to permit molding 

 into bricks. 



Dome kiln (pi. 14). This is one of the oldest types used, and is 

 the simplest. The kiln is charged by placing kindling at the bot- 

 tom, and then alternate layers of coal and slurry cake are put on, 

 till the kiln is full enough. The fire is then started, and burns 

 slowly upward through the mass, the temperature gradually in- 

 creasing. The doors at the bottom are then opened and the 

 clinkers discharged through them. The kiln is recharged for an- 

 other burning. The recharging occurs about once in a week or 10 

 days. The proportion of underburned and overburned clinker 

 depends on the relative amount of fuel and slurry used. As fuel 

 burns out, fresh material can be added at the top, or the whole 

 mass can be allowed to burn out and be removed without recharg- 

 ing the kiln. There is much waste heat, which is sometimes 

 utilized for drying the slurry, but the utilization of this should in 

 no way interfere with the working of the kiln. 



When the kiln is intermittent in its action, there is of course 

 a great loss in heat. There is probably also much cost for re- 

 pairs, as the heating and cooling tend to crack the walls. This 

 kiln is rather expensive in fuel and produces an output averaging 

 only 3 to 6 tons of cement a day in a month's run. A good deal 

 of sorting and picking of the clinker is required to exclude the 

 underburnt and vitrified material. Till 1889 these were the only 

 kilns in this country. 



Dietzsch kiln (pi. 15). This is continuous in its action, and has 

 been in use in some works for a number of years being patented 

 in 1884. The fuel used in it is generally coal slack, and the cost 

 of calcination, comparing this with the " bottle " kiln is small, 

 but the slurry has to be dried before introduction, and there is 



