6 



CIRCULAR 443, U. S. DEPARTMENT OF AGRICULTURE 



A furnace was connected to one end of the drum and an exhaust fan 

 to the other. The dried forage passed from the drum through the 

 fan and was blown into a dust collector or cyclone. This machine was 

 inefficient because of the short chying zone or length of travel and 

 period of exposure of the material in the drier. 



For increasing the efficiency of this machine a cylinder 2 feet in 

 diameter and 20 feet long was installed inside and concentrical with 

 the large drum (fig. 5). This cylinder was connected to the furnace 

 and to the feeder for the undried material at the furnace end of the 

 drier. At the opposite end the 2-foot cylinder was open and ended 

 3 feet from the end of the outer cylinder. An exhaust fan was con- 

 nected to the outer shell at the furnace end in such a manner as to 

 move the furnace gases together with the chopped hay first through 

 the inner cylinder and back through the outer cylinder. The dried 

 forage, after passing through the fan, was blown into a dust collector. 



Conveyor 

 green forage 



Figure 5.— Revolving-drum drier used in forage-drying experiments at Iberia Livestock Experiment 



Station. 



This reverse current or two-pass system lengthened the evaporating 

 zone and greatly increased the efficiency of the machine. 



From 1931 to 1936, inclusive, the apron-conveyor and double -drum 

 driers, were used in drying about 300 tons of hay, including alfalfa, 

 pasture grass, clovers, and soybean hay. Approximately 250 tons were 

 used in feeding tests with dairy animals, and the remaining portion 

 with beef cattle. In operating these experimental driers records were 

 kept of the tonnage handled, the power, labor, and fuel requirements, 

 and the moisture content of the forage before and after chying. As 

 time permitted, trips were made to farms operating forage driers in 

 Louisiana, where similar data were obtained. 



Observations of the various factors entering into the dehydration of 

 forage takes into account a large number of factors, many of which are 

 rather difficult to measure with any degree of precision. A drying 

 machine handling such a bulky product as forage must of itself be large 

 and any attempt to measure ah' velocities, temperatures, or make 

 hydrometric measurements of the drying gases are only an approxima- 

 tion. It is furthermore impossible to make check runs on the average 

 lot of forage because of the wide range of moisture contents which it 

 has before entering the drier. The presence of weeds and mixtures of 

 other kinds of forage enter into the actual test work and provide data 

 which are somewhat difficult to interpret. 



The performance of the apron-conveyor and rotary driers located at 

 Iberia Livestock Experiment Station were observed especially as to 

 the power, labor, and fuel requirements for various kinds of crops, for 



