Abstract:

Palm pruning residues are potential pellet raw material, which are quite abundant in regions with hot climates. In pelletizing process, raw material properties and pellet machine features are the main factors affecting the final pellet quality. In this study, 5 mm sieve hole diameter milled palm pruning residues was pelleted using two different pellet dies and two different pelletizing moisture. First die (D1) has 25 mm total length, 17° inlet angle and 10 mm inlet depth. The second die (D2) has 35 mm total length, 33° inlet angle and 5 mm inlet depth. The inlet and outlet hole diameter of both die are 11 mm and 8 mm, respectively. Pelleting moisture is fixed at two different levels as 10% (M10) and 14% (M14). The change of production parameters and pellet physical properties were investigated according to the die type and moisture content parameters. Increasing pelletizing moisture had a positive effect on the production capacity and it was obtained as 82.44, 103.1, 134.05, 145.49 kg h-1 for D1-M10, D1-M14, D2-M10 and D2-M14 pellets, respectively. The increase in pelletizing moisture caused degradation of the pellet forms, which is more evident in the pellets produced in the D1 die. Pellets produced in the D2 die are more compressed and denser and lower moisture content. The increase in total die length resulted in heavier and denser pellet production, resulting in higher production capacity and low specific energy consumption. Pellet durability index (%, ar) of D1-M10, D1-M14, D2-M10 and D2-M14 were measured as 95.53 92.29 and 97.74 98.32, respectively. It was concluded that the longer active die length can tolerate high moisture content pelletizing, and durable pellets can be produced in a wide moisture content range. In addition, die conical dimensions and die length are the factors that needs to be optimized according to different raw materials.

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