MANUFACTURING AND PERFORMANCE EVALUATION OF A PROTOTYPE WOOD CHIPPING MACHINE TO PRODUCE MINI-CHIPS

The oversize wood chips are existing in the conventional disc chipper production even with tuning the chipper settings which is not convenient to be used in the some applications that need to small sizes chips as biomass pellets or poultry litter for instances, hence there is an urgent need to produce mini-chips (M_CHIPS) to become abundant for wide range of agricultural utilization within the farm. Thus, the present study aims to manufacture and evaluate the performance a local made prototype wood chipping machine by providing the conventional wood disc chipper with built-in swinging hammer mill and concave screen behind the cutting disc on the same rotating shaft using the pruning residues of mango trees to produce MCHIPS with high quality (uniform chips with minimum fines) and low energy requirement. The performance of the chipping machine was evaluated under operational variables including; three cutting rotational speeds of 750, 1000 and 1250 rpm corresponding to peripheral speeds of 17.66, 23.55 and 29.43 m/s, respectively, three cutting angles of 48°, 50°, 54° and 58°, three concave screen sizes of 12, 16 and 20 mm, where the hammers has the same rotational speed of the cutting disc. The machine performance was investigated taking into consideration the machine productivity, particle size distribution, and energy requirement. The results indicated that, it is recommended to use the prototype chipping machine at cutting speed of 1000 rpm (23.55 m/s), cutting angle of 58° and screen size of 16 m to obtain the best MCHIPS particle size distribution (M_CHIPS ≤3 mm= 6.05 %, M_CHIPS 3-8 mm= 24.07 %, M_CHIPS 8-12mm = 39.95% and M_CHIPS 12-16mm=29.93 %) to achieve regular M_CHIPS with minimum fines at machine productivity of 1.40 Mg/h and consumed energy of 12.35 kW.h/Mg.