ARTIFICIAL DRYING OF FORAGE CROPS 19 



warmed by passing over heated portions of the exterior of the combus- 

 tion chamber (note drawing of Dutch-oven type of furnace, fig. 9). 

 The furnace gases may be still further diluted by providing an opening 

 just ahead of the drier inlet, although this is not essential. 



Furnace design may be of either the cylindrical or rectangular cross 

 section (figs. 9 and 10). The rectangular-cross-section furnace is 

 usually termed the Dutch- oven type. These two general types of 

 furnaces are adaptable for burning either oil or gas fuels. 



The problem of utilizing solid fuels in drying forage is one requiring 

 special consideration so that the drying gases are rendered smokeless 

 and do not contain incandescent particles of flying ash. Oil- or gas- 

 burning equipment possesses advantages that place the coal- or coke- 

 burning furnace at a disadvantage for hay driers unless a mechanical 

 stoker is available. 



In order not to localize the combustion of the fuel in too small a space 

 it has been found that, with the fuel oil used at Jeanerette, from 1.75 to 

 2 pounds of oil may be fired per hour per cubic foot of combustion 

 space* This quantity of oil has a heat value of about 33,000 B. t. u. 



In drying hay the combustion of fuel capable of generating approxi- 

 mately 5,500,000 B. t. u. of heat energy was required to evaporate 3,000 

 pounds of water per hour. On this basis a combustion chamber with a 

 volume of from 165 to 175 cubic feet is needed. For practical purposes 

 the dimensions might be as follows : Width 4 feet, height to top of arch 

 5 feet, and length to bridge wall 10 feet. 



The combustion of gaseous fuels is relatively simple, requiring only 

 a suitable mixing carburetor. For oil fuels it is essential that there be 

 smokeless combustion, which can be accomplished only by thorough 

 atomization of fuel. Under ordinary conditions, satisfactory results 

 are more certain if oil having a specific gravity less than 0.93 is used. 

 This specific gravity corresponds to 20.6° A. P. I. (American Petro- 

 leum Institute) . Fuels heavier than this usually require preheating 

 equipment in order to insure proper combustion. 



Power Requirements 



In forage drying, power is needed for the following purposes : 



1. Processing the undried forage. This includes chopping, chop- 

 ping and shredding, or crushing, depending upon the type of drier and 

 the operator's preference. 



2. Conveying the drying gases to the drier from the furnace, and 

 removing them after they have performed their work in vaporizing the 

 moisture from the forage. 



3. Transporting the dried forage to a storage structure or processing 

 plant either by a drag conveyor or a pneumatic system or a combination 

 of both. 



4. Miscellaneous uses such as operating fuel pump and blower for 

 the burner, rotating the drum or actuating the apron conveyor of the 

 drier, operating the unloading hoist, baling or grinding the dried 

 material, etc. 



The choice of the power unit depends somewhat on its availability 

 and the cost per unit of energy. From the standpoint of convenience, 



