478 



MARINE PRODUCTS OF COMMERCE 



Direct-Heat Drier. This type of drier is composed of a furnace in which the 

 heat is generated. Hot gases are forced through a cyhnder which is shghtly de- 

 clined from the furnace. The size of these cyhnder s varies from 4 to 6 feet in 

 diameter and 40 to 50 feet in length. They are mounted on trunion rings and 

 slowly rotated. Inside the cylinders are fixed fins or plates which carry the meal up 

 toward the top and then spill it back through the hot gases passing through the 



DeoooKiziNc 5c»</oe^te ToiA/en 



Fig. 22-7. Renneburg steam tube drier with 



cylinder. The wet meal enters the cylinder near the furnace, and the rotation of 

 cylinder and fins gradually work the meal towards the opposite or discharge end 

 of the drier. 



Considerable care is required in adjusting the heat of the gases in the drying 

 cylinder since a high temperature may scorch the meal and considerably reduce 

 the protein content. Since fish meal for animal feeding is purchased on protein 

 value, most processors carefully regulate the heat used in drying. 



In some driers a forced draft is employed. A blower pulls the hot gases through 

 the drier, and the exhaust from the blower goes into a cyclone separator. Small 

 particles of fish meal are separated from the gases in the cyclone, and the gases are 

 returned to the furnace where any objectionable odors are destroyed by burning. 



Steam-Tube Drier. The steam-tube drier resembles the direct-heat drier in out- 

 ward appearance, but differs from it on the inside. Steam tubes are arranged in 

 concentric circles with a header at each end. The steam inlet and outlet are 

 centered in the axis of the drier and fitted with suitable stuffing boxes to retain 

 the steam pressure. 



As the drier cylinder rotates, the fins on the inside lift the fish meal, carry it 

 toward the top, and drop it through the spaces between the steam tubes. The 

 blower carries away the warm moist air and deposits the small particles of meal 

 in a cyclone separator. The gases are taken care of in the same manner as described 

 for the direct-heat drier. 



