Wood waste generated during the processing of unproductive rubber trees for timber can be economically utilised for co-production of energy and activated carbon. The feasibility of getting commercial grade activated carbon from rubberwood has been established by experimental studies in a laboratory type rotary activator at FRIM. Powder carbon with decolourising characteristics equivalent to methylene blue value of 395 mg/g was obtained with overall yield of 10 per cent based on dried wood having 6.5 % moisture.
The process involves carbonisation of sized rubberwood (25 x 15 x 6 mm thick) in a tray pyrolyser at 450°C. The product distribution obtained during pyrolysis was char = 31.8%, tar and liquids = 33.5% and combustible gases =3 4.7%. The Char is crushed and classified to 2.80.5mm size and subjected to steam/CO2 activation in an externally heated activator at 900°C. The product obtained with a yield or 33% was tested for its decolourising properties. The apparent residence time was 26 mins. during which the bulk density of carbon decreased from 0.19 to 0.134 g/ml indicating substantial generation of internal porosity. In addition the progressive increase of methylene blue value from 96 to 395 mg/g with decreasing yields from 44.615% reinforces the impartation or activity.
Further, by controlled pyrolysis through partial combustion it is feasible to recover combustible gases amounting to 225 kg/100kg of dry wood with heating value of 1200 kcal/kg (5MJ/kg) with 55% recovery of heat. These gases can be clean combusted for thermal application or can generate electrical power though diesel generating Set. It is estimated that 100 kg of dry wood can give 10 kg of activated carbon and 45 kWh of power.
Key words: wood wastes, carbonisation, steam activation, heat recovery.
Correspondence: Hoi Why Kong, Forest Research Institute Malaysia, Kepong, 52109, Kuala Lumpur, Malaysia
Telefax: +60-3-6367753
E-mail: salleh@frim.my