Design, fabrication and evaluation of fish meal pelletizing machine

Abstract

A 113.1kg/h fish meal pellet processing machine which produced 4mm diameter pellet, with an average length of 6mm was designed and fabricated. Design values of 210 was used for the maximum angle that the hopper wall formed with the vertical in the discharge zone, a critical stress of 1.3kPa of the ground particulate materials, and a density of 2.4521kg/m3 of the particulate materials, were used to obtain a hopper smallest outlet diameter of 12.7cm with a capacity of 24,118cm3 which proved efficient for the pelletizing machine. Two 3-cm diameter shafts carried the speed reduction gears with the perforated disc attached to the roller cutters on one end, while at the other end a 5hp motor was connected to the speed reduction gear by pulleys with diameters of 6cm and 12cm respectively. The speed reduction was 1:5 over a motor speed of 2000rpm. The fish meal pelletizing machine utilized 4kg of ingredients to produce 3.77kg pellets at an efficiency of 94.2%. The percentage loss due to unprocessed ground particulate materials was 5.8%.The moisture content of the fish meal pellets after 7days of drying in open air was 26.5% (wet basis). When tested for floatation, the pellets stayed afloat for 9 days, while the un-dried pellets only remained afloat for 2days. A combination of the weight of the twin roller cutters and the addition of some starch to the ground particulate materials assisted the compacting and gelatinization of pellet formed. This machine will be useful to medium and small scale aquaculture farmers and also reduce the need for foreign sources of fish meal in the aquaculture industry, thus conserving foreign exchange.

Keywords: Ground particulate materials; mixing; compacting; gelatinizing; pelletizing