KINETICS OF BIOMASS AND SEWAGE-SLUDGE PYROLYSIS - THERMOGRAVIMETRIC AND SEALED REACTOR STUDIES

Biomass and sewage sludge decomposition is studied by a competitive mo del consisting of weight loss and char formation reactions. Non-linear optimization technique is used to simulate the experimental curves ob tained by TGA by minimizing the sum of the squares functions. Pre-expo nential factors and activation energy are obtained for both the reacti ons for heating rates of 10, 20 and 40 K/min for acacia wood, bagasse, rice husk, and sewage sludge respectively. The order of the reactions determined for sewage sludge are much higher than that of other bioma ss materials, whereas the activation energies are lower. Isothermal ex perimental studies resulted in much higher yields of char for all the four samples, and experiments carried out at various initial nitrogen gas pressures confirm that vapour-solid interactions are the cause of secondary char formation. Rice husk and sewage sludge yield higher amo unts of secondary char due to the catalytic effect of the inorganics p resent in higher amounts in these samples.