12 CIRCULAR «3, U. S. DEPARTMENT OF AGRICULTURE 



2. When the apron-conveyor drier was used to dry chopped soy- 

 bean hay. the drying proved to he very uneven and poor, the average 

 discharge moisture content being approximately 20 percent. At this 

 moisture content it is doubtful if artificially dried forage will keep in 



good condition, free from mold and spoilage. 



3. Cowpea hay in the apron-conveyor drier presented much the 

 same problem as to nonimiformity of drying as did soybean hay. 



-i. The data for the 1935 season for the rotary drier were taken when 

 the material was further reduced by passing it through a hammer miU 

 after it had been cut in a silage cutter. The power requirements per 

 1.000 pounds of water evaporated were greater for clrying soybean hay 

 in 1935 than in 1934. The heat required per unit of material dried was 

 about the same, but the hourly evaporation was increased from 770 

 to S66 pounds or an increase of 13 percent. In drying alfalfa there also 

 appears to be an increase in thermal efficiency as well as capacity of 

 the drier due to the shredding of the undried forage with a hammer 

 mill. 



5. Data taken on the effect of maturity on power and fuel require- 

 ments showed that the 120-day growth Otootan soybean hay required 

 slightly less power and fuel for dehydration than 80-day growth hay 

 of the same variety. This difference was not due to initial moisture 

 content of the green material. 



6. The thermal capacity for evaporating moisture is affected 

 materially when the forage is reduced to fine particles. The inner 

 parts of the forage plant come in more direct contact with the drying 

 gases when chopped and shredded than when left whole as they are in 

 the apron-conveyor drier. 



Data were also taken on several commercial driers operating on 

 neighboring plantations. The performance of these driers are sum- 

 marized in table 3 under the heading of ' 'Single-drum' ' and ''* Triple- 

 drum. ' " So far as the data show the large commercial driers were some- 

 what more efficient in the utilization of heat than the small experi- 

 mental units. 



USE OF DRIERS 

 CAPACITY 



Alfalfa when cut for hay may contain more than 70 percent moisture. 

 When such material is hauled to the drier and dried immediately, as 

 much as 3,860 pounds of water must be evaporated to produce 2,000 

 pounds of hay containing 12 percent moisture ffig. 6' . If the hay is 

 left in the swath for several hours its moisture content may be reduced 

 to about qq percent. Under such conditions it will be necessary for 

 the machine to evaporate approximately 1.930 pounds of water to 

 produce a ton of hay at 12 percent moisture. In the latter case the 

 capacity of the drier in tons of hay per hour may be twice as great as 

 with 70-percent moisture content forage. 



The capacity of a dryer will also depend somewhat upon the kind 

 of forage and the degree of processing before it is fed to the machine. 

 TVith drum dryers the fineness and uniformity of chopping greatly 

 influence the performance of the machine. Alfalfa, some varieties of 

 clover, and meadow grasses usually dry much easier than soybean hay 

 or other coarse-stem plants. The capacity of a hay drier is frequently 

 referred to in terms of tons of dried material delivered per hour. While 

 this method gives an indication as to what tonnage may be expected 



