Estimating the higher heating value of biomass fuels from basic analysis data

The heating value is one of the most important properties of biomass fuels for design calculations or numerical simulations of thermal conversion systems for biomass. There are a number of formulae proposed in the literature to estimate the higher heating value (HHV) of biomass fuels from the basic analysis data, i.e. proximate, ultimate and chemical analysis composition. In the present paper, these correlations were evaluated statistically based on a larger database of biomass samples collected from the open literature. It was found that the correlations based on ultimate analysis are the most accurate. The correlations based on the proximate data have low accuracy because the proximate analysis provides only an empirical composition of the biomass. The correlations based on the bio-chemical composition are not reliable because of the variation of the components properties. The low accuracy of previous correlations is mainly due to the limitation of samples used for deriving them. To achieve a higher accuracy, new correlations were proposed to estimate the HHV from the proximate and ultimate analyses based on the current database. The new correlation between the HHV and dry ash content of biomass (in weight percent, wt%) (i.e. HHV (MJ/kg) = 19.914-0.2324 Ash) could be conveniently used to estimate the HHV from proximate analysis. The new formula, based on the composition of main elements (in wt%) C, H, and O (i.e. HHV (MJ/kg)=-1.3675+0.3137C+0.7009H+0.0318O*), is the most accurate one, with more than 90% predictions in the range of ±5% error.