EVAPORATION OF FRUITS. 9 



labor, have resulted in the retention of driers of the cabinet, or 

 stack, type even when apples are the only fruit dried. The wide- 

 spread and increasing use of the kiln drier has been brought about 

 by the low first cost of the kilns, the relatively large capacity, the 

 large extent to which labor-saving machinery may be made to re- 

 place handwork, and to< a certain degree, because their construction 

 and operation are well understood by fruit growers and by the labor 

 available in the apple-growing districts. 



A kiln evaporator plant consists of a two-story building divided 

 into two portions, one of which contains workrooms in which the 

 fruit is received and prepared for drying, with storage rooms for 

 fresh and dry fruit, the other containing the kilns or drying rooms. 

 The individual kiln is the unit of structure, and plants of any desired 

 capacity are obtained by constructing a series of such units. 



THE INDIVIDUAL KILN. 



The individual kiln consists of a structure two stories in height, 

 the first, or ground, floor being occupied by a furnace inclosed in a 

 concrete or masonry room for distributing the heat, as shown in 

 Figure l y and the second floor, which is of slat construction, serving 

 as the drying floor. The walls extend above the drying floor far 

 enough to give sufficient headroom for working in the kiln and sup- 

 port the roof, which is fitted with ventilators for removing the 

 moisture-laden air as it rises from the material being dried. 



The ground plan and cross section of a typical kiln are illustrated 

 in Figure 1. It will be noted that the kiln is 20 by 20 feet, the 

 standard dimensions of a kiln of this type. The distance from the 

 furnace floor to the drying floor is usually 16 feet and should never 

 be less than 14 feet, as uniform distribution of heat to the drying 

 floor can not be obtained with a height less than this. In order to 

 give sufficient headroom for the storage room or workroom on the 

 second floor along the side of the kiln, the roof on one side is not as 

 steep as on the other side. The roof is so constructed that the ridge 

 is in the middle of the kiln, with the ventilators along the ridge. 



Foundation. — The foundation walls for the kiln may consist of 

 any suitable material, their depth being determined by the nature 

 of the subsoil and the character of the building material to be used 

 for the superstructure. Concrete is the best foundation material, 

 as, when once properly set, it is impossible for water to get under 

 .it and cause damage by freezing. Whatever the material used, the 

 foundation walls should be of sufficient size to support the building 

 without settling, as even slight settling throws the machinery out 

 of alignment and causes leaks in the heating apparatus and in 

 the hopper. If the walls of the kiln are to be of frame construction, 

 the foundation is usually 2-J feet above the surface of the ground, 

 in order to make room for the air vents, to have the floors of the 

 preparation room sufficiently high to prevent decay, and to give 

 ample room for the circulation of air beneath it, as part of the 

 air supply for the kiln must pass- under this floor. When the walls 

 of the kiln are of stone, brick, or masonry of any sort, the founda- 

 tion is carried up only to the surface of the ground or far enough 

 above to make it level, and the walls are started directly on this. The 

 air ducts, described later, are placed in the walls below the level 



25497°— 23 2 



