Sintering reduction of herbaceous biomass when blended with woody biomass: predictive and combustion tests

The objective of this study was to predict and reduce the sintering behaviour of two herbaceous biofuels (triticale and corn straw) by the addition of three woody biofuels (poplar, pine and eucalyptus). Two CIEMAT laboratory in-house methods (disintegration and sieving methods) and the technical specification on ash melting behaviour (CEN/TS 15370-1) were used to predict ash sintering properties of the studied biomasses, and to determine the adequate blends to be used in subsequent combustion pilot plant tests to minimise ash sintering. Moreover, the mechanisms for reducing the slagging and fouling were evaluated and studied by analyses (e.g. ICP-OES and XRD) of biomass and ash collected from the combustion pilot plant (0.5 MWth). Laboratory predictive methods were validated by comparing the information they provided with the results obtained by inspecting and analysing the ash collected in the pilot plant. The sieving and the disintegration methods can be used to predict ash melting behaviour and to select the optimal amount of woody biomass that should be blended with herbaceous biomass. The selected corn straw does not need to be blended with any woody biomass. In contrast, very high concentrations of woody biomass should be added to obtain significant results in reducing the sintering of triticale. These proportions of the woody biomass in the blend could be even clearly higher than 50 wt% (ash basis). The dilution effect seems to be the main mechanism for reducing the sintering.