Combustion process of torrefied wood biomass

Abstract

The present research is focused on investigation of torrefied biomass combustion process and kinetic analysis. Two wood biomass samples (B1 and B2) were torrefied in a specially designed set-up under 1.0 h of residence time, 230, 260 and 290 °C temperatures, and argon atmosphere. The studied materials were characterised in terms of their chemical composition and calorific value. The results showed the improvements of biomass properties towards higher carbon content and low moisture content fuel. The behaviour and comparison of raw and torrefied biomass during the combustion process was investigated by thermal analysis (TG, DTG and DTA). The samples were heated at an ambient temperature up to 700 °C at constant rates: 10, 20 and 40 °C min in air flow. The MS technique was also used simultaneously with TG to determine gaseous products from combustion process (namely NO, CH4, CO2, and H2O). The kinetic parameters were calculated for torrefied biomass combustion using three isoconversional methods: Friedman, Kissinger–Akahira–Sunose and Flynn–Wall–Ozawa. The isoconversional methods were used to find dependency of the activation energy of studied processes on the conversion degree. The kinetic data for raw and torrefied biomass indicates that torrefaction process reduces the activation energy of the studied biomass. The average values of activation energy for biomass combustion e.g. TB1 are E a = 111; 105.2 and 110.4 kJ mol−1 calculated by Friedman, KAS and FWO methods, respectively. For all studied biomass samples, the slight differences between the values of activation energies calculated by Friedman, FWO and KAS methods were obtained.