Thermodynamic and kinetic study of lignocellulosic wastes gasification

ROSA RODRIGUEZ; GERMÁN MAZZA; MARCELO ECHEGARAY; ANABEL FERNANDEZ; DANIELA ZALAZAR GARCÍA; GERMÁN MAZZA

Gasification

InTechOpen

Año: 2018;

In this chapter, the kinetic behaviour during the steam gasification of sawdust, plum and olive pits were investigated by thermogravimetric analysis where the loss weight is measured with the temperature variation at different heating rates (5, 10 and 15 K/min). The weight loss and their derivatives curves show that the gasification takes place in three visible stages. The kinetic study was carried out using Coats Redfern methods. The Ginstling ? Brounstein model showed better fit. The obtained activation energy values vary between 70 -100 kJ/mol for the pyrolysis stage for all studied agro-industrial wastes. On the other hand, a thermodynamic model was proposed to predict the five wastes gasification process, considering the char and tar production. The proposed model allows it to perform a parametric study, analyzing the process variables´ effect on the exergetic efficiency. The higher temperatures favour the endothermic reactions as the H2 and CO formation reactions. Therefore, in the product, moles of H2 and CO increase and consequently the exergy efficiency of the process. Increasing the equivalence ratio value, H2, CO and CH4 contents decrease, thus the calorific value of the produced gas and the exergetic efficiency decrease. In addition, the CO2 and H2O presences in the syngas composition diminish its calorific value and the exergetic efficiency. Considering the influence of supply steam/biomass ratio, the exergetic efficiency decrease with the growth of this parameter.