Study of fish feed pelleting process in a basket granulator

The production of pelleted aquaculture feeds from wet raw materials should reasonably be carried out in a basket granulator. The operation process of the basket granulator is not well studied. Rational parameters of its operation have no scientific grounds. A basket granulator is designed for pelleting of wet raw materials and producing feed for fish and their fry in the form of pellets with a diameter of 0.5 of 2 mm and a moisture content of 25 to 40%. Experimental studies were carried out to determine rational parameters of pelleting that provide high productivity. The pelleting process of wet raw material was studied at the rotation frequency of three extrusion blades of the granulator 37.8, 45.8, and 50.3 rpm and efficiency, respectively, 231, 274, and 291 kg∙h^-1. It has been established that the process of pellet formation in the basket granulator is cyclic and consists of pellet formation, reverse movement of material, and relaxation. Increasing the speed of the granulator’s working parts will lead to a decrease in the cycle duration of the impact of the parts on the material due to a decrease in the relaxation period, while the duration of the periods of pellet formation and reverse movement of the material remain constant. The duration of the relaxation period and the whole cycle of impact of the parts decrease almost linearly when increasing the rotational speed, but their duration decreases insignificantly when the frequency exceeds 47 rpm. The efficiency of the basket granulator can be increased both by increasing the number of working parts and increasing their rotary speed, but these methods have limitations associated with increasing the energy intensity of the process and the granulator design. The influence of rheological properties of raw materials and their moisture content on the pelleting process should be studied in the course of further research to justify the rational duration of periods in the working cycle of the basket granulator.

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