Pyrolytic analysis of cocoa pod for biofuel production

Abstract

This study carried out pyrolytic conversion of cocoa pod husk in a refurbished fixed bed type 17.4 litres capacity electric thermal reactor. The process was studied by heating 1 kg of dried sample at an average size of 20 mm x 30 mm x 1.9 mm and moisture content of 13.78% at four different temperatures (300 ⁰C, 400 ⁰C, 500 ⁰C and 600 ⁰C) using two electrical heating coils of 2.5 kW each. Bio-oil and bio-gas were produced and characterized. The average heating values of bio-oil and bio-gas were 36.23 MJ/kg and 35.24 MJ/kg respectively. These were higher to that obtainable from other fuels like Coal (27 MJ/kg) and Ethanol (29.7 MJ/kg). Physiochemical properties of bio-oil gave an average value of 0.9543 g/ml³ for density, and 1.88 mm²/s for viscosity. The density is similar to that of diesel fuel (0.83 g/ml) but lower in viscosity (3.10 mm²/s). Gas chromatography analysis of bio-gas shows that CO₂, CO, CH₄, H₂S and H₂O contents increased with increase in pyrolysis temperature. From the ultimate analyses carried out, the pyrolysis process produced bio-oil with an average of 75% carbon composition, 6.61 % hydrogen, 7.11 % oxygen, 0.16 % nitrogen and 0.007% sulphur. The proximate analysis showed bio-oil has an average of 25.57 % volatile matter and 58.44 % fixed carbon. Results showed that pyrolysis is an efficient and sustainable means of converting cocoa pod husk into rich sources of useful biofuel.

Keywords: pyrolysis, fixed-bed reactor, proximate analysis, ultimate analysis, volatile matter