Effect of particle size, die rotary speed and amount of urea on physical properties of the produced pellet

Provided pellet by mixing of urea and compost is a kind of nitrogenous fertilizer with gradual release that reduces leaching losses and increases gradual absorption of nitrogen during the growing long season. In this study, the characteristics of the produced pellet such as durability, strength and moisture absorption were examined at two density levels (low and high), three ratio levels of compost and urea fertilizer (1:1, 1:2 and 1:4), particle size of compost at two levels (0.3 and between 0.3 and 0.6mm) and the rotational speed of die roller shaft at four levels (100, 150, 200 and 250rpm). The durability and strength increased by increasing the rotational speed of die roller shaft from 100 to 150rpm, while by increasing from 200 to 250rpm the durability decreased. The results of mean comparison showed that the durability of pellets produced from particles less than 0.3mm increased with increasing the speed from 100 to 150rpm and decreased by increasing the speed from 200 to 250rpm while increasing the effect of speed on the durability was not significant for the pellets produced from particle size between 0.3 and 0.6mm. The results showed that the amount of force, fracture energy and toughness of pellets decreased by increasing the particle size. The durability increased by increasing the density and decreasing the ratio of urea, and the maximum durability was found at the ratio of 1:4 and the high density.