142 DESCRIPTION OF IMPORTANT FISHERIES AND THEIR PRODUCTS 



fish pulp although this press is reputed to have been designed for the 

 pressing of citrus pulp. Low upkeep costs and small space requirements 

 are two other significant advantages that have gained the entry of this 

 type of press into the fish meal industry which for so many years was 

 dominated by the screw press. 



Drying. From the press, the press cake is conveyed through a wet mill 

 to the drier. The wet mill is a disintegrator type of a mill whose purpose 

 is to break up the press cake into a granular material of uniform size, 

 thereby insuring a better and more even drying in the subsequent drying 

 operation. 



There are several types of fish meal driers in use but two seem to 

 predominate. One is the direct heat rotary drier where the granular press 

 cake is introduced at the hot end of the kilns and as it slowly moves 

 down the slightly inclined kiln tube, the press cake, in contact with the 

 hot combustion gases of the burner, slowly loses its moisture to the gases, 

 thereby cooling them. The burner is recessed in the kiln so that the wet 

 press cake is not in direct contact with the flame. 



Another type of drier in common use is the steam tube drier. In this 

 rotary drier the drying of the press cake is accomplished by heat from 

 the steam tubes which run the full length of the drier. By the rotary 

 action, the press cake constantly drops over and around the steam tubes, 

 thereby causing a gentle and efficient drying of the press cake. Both of 

 the above mentioned kilns can give a very excellent fish meal free from 

 any recognizable sign of thermal damage. It is, however, very important 

 that the operator of the drying kiln maintains proper control of the drying 

 at all times by constantly watching rates of input and output and, in 

 particular, by keeping a close watch on the temperature of kiln gases, 

 humidity of exhaust, and remaining moisture content of the dried fish 

 meal. 



A third type of fish meal drier recently introduced into the fish meal 

 industry, here and abroad, is the airlift drier. In this type of drier, 

 ascending hot combustion gases meet the descending wet press cake in 

 a tower of proper design, and by carefully regulating the temperature 

 and volume of the gas and the amount of press cake, the manufacturer 

 claims that a fish meal of superior quality may be obtained at minimum 

 cost. Steam jacketed batch driers once so popular in small fish meal 

 operations and continuous fire tube rotary driers are not in use any more. 



The dried press cake is removed at the end of the kiln by various 

 simple devices, depending on circumstances. In the direct-fired rotary 

 kiln, the separation of the large volume of combustion gases from the 

 fluffy fish meal requires elaborate cyclone construction. This problem 

 does not seem so difficult with the steam tube rotary drier where the 



