Optimization ofsaccharification yield of wood-cellulosic material for bio-ethanol production through mechanical treatment

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A prototype of a fine-crusher (grinder) of wood-cellulosic materials has been constructed with flail-knives and a rotary sieve rotating independently of each other. Pieces of bamboo in batches were fed into the fine-crusher, the crushed material was then treated with pressurized hot water (sub-critical water) to modify its structure and then hydrolyzed into glucose with an enzyme. With an increase in the diameter of the pores of the rotary sieve, the specific energy requirement for fine-crushing decreased remarkably from 500 to 250 kJ/kg, whilethe estimated glucose yield at 200°C decreased negligibly from 38% to 35%. The best rotational speed of the rotor and the diameter of the sieve pores were 1500 rpm and 4 mm, respectively. Additionally, sieve pore diameters of 6 mm and 8 mm was tested to reduce the specific energy requirement, and the acidic hydrolysis showed that such large pore significantly decreased the glucose yield due to too large material produced.A trial at a rotor speed of 2400 rpm showed that finer material was produced and the netenergy requirement did not increase, which implied that further development of the fine-crusher was needed to increase glucose yield at the reduced energy requirement. The results of the additional experiments were partly supported by high-speed video movies taken in the fine-crusher.