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Nigerian Journal of Technology

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Pyrolytic analysis of cocoa pod for biofuel production

A.O. Akinola, J.F. Eiche, P.O. Owolabi, A.P. Elegbeleye

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




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