Studies on activated carbon produced from thermal gasification of biomass wastes

Abstract

Conditions for the optimal production of activated carbon from biomass waste through thermal gasification techniques were studied in this research. Operation of the Biomass Thermal Conversion System (BTCS) gasifier at fuel-to-air ratio between 0.7 and 2.1 resulted in increased char production from 20% to 40% of the fuel input. Varying other operating parameters such as gasifier throughput (fuel feedrate), fuel moisture level, and gasifying temperature affected production rates and char adsorption qualities. The average iodine number of BTCS char ranged from 285-356. Performance characteristic curves (adsorption isotherms) were developed to assess the ability of the activated carbon in the char to adsorb organic contaminants (measured in terms of chemical oxygen demand, COD) and heavy metals from solution. At equilibrium concentrations greater than 80 mg/l COD, BTCS char was shown to reduce higher wastewater COD levels than an equivalent weight of a commercial activated carbon used in this study. At a loading rate of 20 g carbon/100 ml of approximately 100 ppm solution of heavy metal, 95.5% removal rates were achieved for mercury (Hg) and lead (Pb), 88% for Cr, while lower removal rates were obtained for As, Cd, Cu, Co and Se. The performance characteristic curves obtained could be used as a tool in the modification of waste water treatment plant operations using activated carbon derived from biomass waste.