174 GEOLOGY OF OHIO. 



day throwing out waste heat enough to dry all the daily product twenty 

 times over. 



There have been several attempts made by manufacturers to 

 use this absolutely wasted heat from the kilns. No method worthy of 

 general adoption has yet been devised. In one place the kilns are lo- 

 cated in a leanto building alongside the main shop. The kiln shed is 

 made tight and has an iron roof. The heat arising is accumulated under 

 this iron roof and directed into the upper stories of the main building, 

 through a row of openings. There being no outlet above in the main 

 building the claim is made that the hot air is forced as it cools to descend 

 by displacement and as it goes downward it dries the wares exposed on 

 the floors. The air current is finally allowed free exit at the bottom. 

 The operators and inventors of this system, which they call " Down draft 

 drying" lay great stress on its benefits. In addition to the heat of kilns, 

 however, the boilers are in the center of the factory on the lower floor 

 and the heat radiated from this source is in itself no small factor in keep- 

 ing the drying conditions up to the mark. In addition to this economy 

 of drying, the generation of power is accomplished by use of a high 

 grade Corliss engine, so that the best economy of steam consumption 

 possible with the use of non-condensing engines is attained. 



In another place, the kilns themselves are located in the basement of 

 the building, which when completed will contain several stories of slatted 

 floors above. The heated air rises in this case directly through the wares 

 and escapes at the roof in ventilators. 



In still another place the wares are placed in the kiln in a semi-dry con- 

 dition and by use of a fan system connecting all the kilns in the place ; 

 the heat is abstracted from a cooling kiln and, mixed with the proper 

 quantity of ccol air from outside, is blown into the newly set kiln; by 

 this means the temperature is slowly increased until 230° or 250° or even 

 300° is attained, when the burning proper is commenced. Though this 

 is a drying process, it is attained in the kiln, and not in the dryers, and 

 it is conducted on material in which the moisture is not to exceed five 

 per cent at most. It would be hardly applicable to the proces of paving 

 material made from stiff mud, which must be approximately dry before 

 being set in the kilns. 



Though there are grave objections to the use of any of these three 

 plans, j-et they are all based on the proper line of action; the improve- 

 ments which will come to the drying process are sure to be in this line, 

 for in the burning and cooling of clay wares of any kind there is more 

 heat wasted than will dry twenty times the output, and the recovery of 

 the necessary portion of it is only a question of time. With this 

 economy would come the less important but much needed use of high 

 grade power generation, by which the full value of the fuel in the boiler 

 room can be secured. 



