Water leaching of herbaceous biomass bales to reduce sintering and corrosion

Abstract

Two different leaching treatments (immersion and irrigation) were applied to the biomass bales of two different herbaceous solid biofuels (barley straw and tall wheatgrass) in order to improve their sintering and corrosion behaviour during combustion. Six immersion treatments (1 h with and without stirring, and 5 h, 1 day and 2 days without stirring) and two irrigation treatments with tap water (900 L and 1800 L) were tested. The bales made of barley straw were of high-density 140 kg/m3) whereas the density of tall wheatgrass bales was lower (80 kg/m3). After the leaching treatment, bales were dried naturally indoors. Sintering and corrosion tests along with chemical elemental analyses, X-ray diffraction and SEM analyses were performed on the lixiviated biomass. An immersion treatment of 5 h reduced the sintering and corrosion potential of both types of bales to an acceptable level. In high-density bales, the irrigation treatment (1800 L) provided similar sintering and corrosion reductions than those obtained when the 5 h immersion treatment was applied. However, in low-density bales, the immersion treatments provided much better results than irrigation leaching systems, probably in connection with their different degrees of compaction. The naturally drying process of the lixiviated bales can be considerably long, particularly after immersing high-density bales. The drying period to reach a moisture level of 20% w.b, was longer than 100 days for high-density bales and shorter than 20 days for low-density bales.