Kinetics of Auto-Gasification of Poultry Litter

Abstract

Thermochemical conversion of poultry litter is the efficient route for its disposal, as well as energy recovery from it. The ultimate analysis of poultry litter indicates that it has sufficient oxygen in itself to convert all the carbon to gaseous products. In order to verify the role of biomass oxygen in the gasification of poultry litter, thermo gravimetric analysis (TGA) of poultry litter was carried out with a nitrogen and air environment with particle size ranging from 100 microns to 3 mm and at a heating rate of 5 to 50°C/min. Heating of poultry litter at a rate less than 15°C/min in static air or nitrogen environment has resulted in complete gasification yielding ash at less than 600°C. This establishes the auto gasification of poultry litter by the oxygen present in the litter itself. Poultry litter is highly porous and a continuous reaction model seems to apply. Using the TGA data, the kinetics of auto gasification of poultry litter was elucidated at a heating rate of 5°C/min with static air and nitrogen separately. There are four zones. The first zone represents moisture removal between 30°C and 120°C, the second zone of thermal degradation between 200°C and 310°C, the third zone between 310°C and 440°C and the forth zone between 440°C and 600°C. The first order rate equation was used to evaluate the rate constant. The effect of temperature on rate constant was explained using the Arrhenius equation. The values of Arrhenius frequency factors (A) and activation energies (E) for static air and nitrogen environments coincide with each other in magnitude, proving the feasibility of auto gasification once again. The calculated weight loss using kinetic parameters was found to match the experimental weight loss satisfactorily.