Thermo Gravimetric Study on Thermal and Combustion Characteristics of Thai Lignite, Rice Husk, and their Mixtures
The combustion behavior and characteristics of Thai lignite, rice husk, and their blends in different proportions were investigated in a thermogravimetric analyzer. In each thermogravimetric test, a 15-mg sample (lignite/biomass/blend) was heated in the analyzer furnace from 30 °C to 900 °C, using dry air as a furnace gas. Three test series, aimed at studying the effects of (i) lignite and biomass proportions in the blend, (ii) heating rate, and (iii) flow rate of the furnace gas on the TG/DTG profiles (characterizing the decomposition behavior of the samples), were performed. The characteristic temperatures were obtained from the analysis of TG/DTG curves for the selected fuel options and operating conditions. The kinetic parameters were determined for a model predicting the time-related decomposition of lignite/biomass blends for different operating conditions, using the Coats-Redfern method. The experimental results revealed excellent combustion properties of both selected fuels. However, rice husk exhibited higher thermal and combustion reactivity, compared to Thai lignite, and therefore can be used as a secondary/reburn fuel in fuel-staged co-firing systems, leading to lower environmental impacts. Keywords - Thai lignite, Rice husk, Thermogravimetric analysis, Operating conditions, Kinetic parameters.