ARTIFICIAL DRYING OF FORAGE CROPS 





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Figure 3.— Revolving-drum type of forage drier, triple-drum design. 



The principles involved in these machines are not new, but the direct 

 exposure of material to be dried to the furnace gases is a practice 

 that has been closely associated with the development of hay driers 

 of various types in the United States. Previously steam was com- 

 monly used, the material to be dried being brought into direct con- 

 tact with or exposed to air heated by steam radiators. Higher effi- 

 ciency in the utilization of heat and elimination of the expense and 

 trouble commonly associated with steam boilers are factors frequently 

 cited in favor of direct application of furnace gases. 



In the apron-conveyor type (fig. 1) the green forage is loaded on an 

 endless screen-wire apron and conveyed through the drying chamber 

 where hot air or furnace gases are circulated through the layer of 

 forage on the apron by means of one or more fans. Driers of this 

 type may have a single endless conveyor, or several conveyors one 

 above the other. As the drying air becomes saturated with moisture 

 it is drawn or allowed to escape from the machine into the atmos- 

 phere. Apron-conveyor driers are not adapted to handling finely 

 chopped forage, especially the single-apron machines, because the 

 apron screen allows a considerable portion of the material to drop 

 through, and the chopped hay. unless it is placed in a comparatively 

 thin layer, forms a mattress practically impervious to the passage 

 of the drying gases. However, crushing the forage by running it 

 through a device patterned after a clothes wringer and cracking the 

 stems, especially the nodes, is found to be of appreciable assistance in 

 drying the forage. 



Drum driers of the single-drum type (fig. 2) , used for drying gran- 

 ular substances such as salt, have the feed end slightly elevated. As 

 the drum revolves the material is picked up by baffles or flights 

 fastened to the inside of the shell and then allowed to fall. Each 

 time some of the material is picked up it falls somewhat closer to 

 the discharge end because of the sloping position of the drum. In 

 drying hay, the drum is placed in a horizontal position and a current of 

 heated air, or furnace gases, is relied upon both for drying and for mov- 

 ing the forage through the machine. The design of the baffles also 

 influences the movement of forage through the driers. When using 

 drum driers it is necessary to chop the forage before it is fed into the 

 machine. In some driers of this type the dry material is drawn into 

 a chamber at the discharge end, from which it is conveyed mechanically 

 to a storage structure. In most cases, however, the dry hay passes 



