Application of Thermogravimetry for Determination of Carbon Content in Biomass Ash as an Indicator of the Efficiency of the Combustion Process

The determination of the amount of residual carbon in biomass ash is important not only for the assessment of the efficiency of biomass fuel combustion but also as one of the criteria for the estimation of biomass ash potential use. In this paper carbon content in biomass ash was analysed by applying two methods: total organic carbon analysis (TOC) and thermogravimetric analysis (TGA) in an inert (N2) and oxidizing (O2) atmosphere. The amount of inorganic (carbonate) carbon can be directly calculated from the TGA curve and the obtained results are in a good agreement with the ones obtained using TOC analyser. On the other hand, the quantitative determination of organic and elemental carbon by TGA is not straight-forward since the temperature range of their oxidation overlaps with dehydration temperature of portlandite that is a constituent of biomass ash. It can be concluded that a basic version of the thermogravimetric analyzer can be used for the determination of inorganic carbon in ash samples, but for total organic carbon determination, it is recommended to use hyphenated techniques, for example, TGA-MS or TGA-FTIR that allows quantitation of evolved gases (CO2 and H2O)