Eucalyptus bark ash removal by acetic acid leaching: response surface optimization and slagging/fouling tendency evaluation

The inorganic matters in biomass contain quite a lot of alkali and alkaline-earth metals (AAEMs) which cause slagging/fouling while combustion, limiting the utilization of biomass. This study investigated the de-ash treatment and ash characteristics of eucalyptus bark (EB) after washing by water and acetic acid, respectively. In particular, the optimal washing condition was investigated by response surface methodology. For water washing, the optimal condition was 67.80 min, 58.87 °C, and 50.34:1 liquid-solid-ratio, while it was 87.72 min, 2.36 mol/L, and 49.55:1 liquid-solid-ratio for acetic acid washing. The ash in EB (Raw-ash) contains a large amount of AAEMs, while the ash of treated EB (WL-Ash, AL-Ash) mainly containing CaO. The de-ash treatment increased the melting temperature of the ash. Acetic acid is better than water for ash removal, with a shorter leaching time, smaller liquid-solid-ration, milder temperature, and lower tendency to slagging.