8 BULLETIN 927, U. S. DEPARTMENT OF AGRICULTURE. 



A double cyclone is now being manufactured which separates the 

 seeds from the skins and cores in one operation. 



DRYING THE SEED. 



Before the seed obtained from the operations just described is in 

 condition for drying, it is preferable that it be washed and the excess 

 moisture removed. As the seed emerges from the cyclone it is cov- 

 ered with a mucilaginous, slimy coating, and when placed in rotary 

 driers in this condition it sticks to the drying surfaces. This coat- 

 ing also prevents satisfactory treatment in the preliminary removal 

 of water. It has been found that satisfactory washing can be accom- 

 plished by suspending the seed in a stream of hot water and cycloning 

 it out of the mixture by using the ordinary breaker cyclones. In 

 practice this washing is done as follows : The seed is thrown into a 

 funnel set in the inlet part of a centrifugal pump, while a stream 

 of hot water, likewise directed into the funnel, carries the seed with 

 it down into the pump, where the churning action of the rotor 

 breaks up the clumps of seed, suspending each particle separately 

 and discharging the whole mass more or less homogeneously into the 

 washing cyclone. The seed is discharged through the gate quite 

 clean and bright. 



Cyclone waste as it is usually produced contains about 80 per cent 

 of water, while the seed contains from 65 to 70 per cent. One diffi- 

 culty in drying material with such a high moisture content is the 

 cost of the operation. To economize in this respect and at the same 

 time shorten the period of drying, several methods of moisture reduc- 

 tion may be employed. 



A considerable proportion of the excess moisture can be removed 

 by pressure. For this purpose small hydraulic presses of the type 

 used for pressing out apple or grape juice may be used. Cloths are 

 laid on racks, the seed is placed thereon, and the edges of the cloths 

 are folded over, thus forming a cake. Several of these, one above the 

 other, are placed in the press and hydraulic pressure applied. From 

 10 to 15 per cent of moisture can be removed by such treatment. A 

 small press may have a capacity of about 400 pounds of wet seed an 

 hour. 



Moisture reduction by centrifuging has also been tried. In this 

 method 4 the seed is placed in a bag and whirled, as in the ordinary 

 type of laundry centrifuge. The use of a bag prevents the packing 

 of the seed in the machine and facilitates emptying. The moisture 

 content of seed, which originally was about 55 per cent, was found 

 to be reduced to about 51 per cent. A centrifuge of ordinary size 

 (about 3 feet) will handle approximately GOO pounds of seed an hour, 



* Huelsen [W. A. J, 1918. Op. cit., p. 42. 



