Design and evaluation of a drum-type rice hull carbonizer and the manually-operated briquette molder for biocoal fuel production and for agricultural applications

Abstract

A drum-type rice hull carbonizer and a manually-operated briquette molder were designed and evaluated at the Department of Agricultural Engineering, Central Philippine University (CPU), Iloilo City from June 1999 to April 2000. The carbonizer was made of salvage petrol-drum opened at the top where rice hull is loaded for carbonization. A steel cover with T-chimney was provided to serve as exhaust for burned gases. A 2 1/2-in. electric blower was provided for the carbonizer to supply air necessary for combustion. The briquette molder, on the other hand, is made of steel pipe having a diameter of 15.5 cm and a height of 13.5 cm. Twelve pieces of 2-cm diameter shafting were distributed centrally in the molder cylinder to create holes on the briquette necessary for proper combustion. Results showed that the carbonizer has a loading capacity of 22.5 to 33.75 kg of rice hull per batch. Carbonization time ranged from 43 to 65 minutes. The percentage CRH produced per load is 30.7% and an average of 16 pieces biocoal fuel is produced per load in the carbonizer. Physical properties of CRH produced from the carbonizer were found out to be of higher water holding capacity, with 3.49 to 3.72 times of the original weight. Each biocoal fuel weighs about 484.5 to 531.1 g and has a heating value of 2,407.7 kcal/kg. The fuel can be ignited within 2 to 5 minutes and sustain a burning time of 45 to 65 minutes. No significant effect was observed when using CRH as soil conditioner for growing radish. However, the use of CRH as feed supplement for Cobb broilers showed that birds fed with commercial feeds mixed with 5% CRH significantly increased their feed consumption which resulted in an increase in their live weight gain. Cost analysis showed that for an investment cost of P5,700.00 and with a capacity to produce 128 pieces of biocoal fuel per day, the cost to produce a piece of biocoal fuel is P1.80. At a selling price of P3.00 per piece and at an operating period of 8 hours per day, 20 days per month, and 10 months per year, the return on investment is 539 percent. Payback period is 1.85 months and the benefit-cost ratio is 0.65.