Fluidized Bed Combustion of Wet Biomass Fuel (Olive Husks)

Abstract

The present paper reports on experiments of fluidized bed combustion of dry and wet olive husks. The olive husks are a biogenic residue of the olive oil industry, accounting for around 80 % of olive mass on wet basis. They have residual water content up to 70 % and rather high heating value (i.e. 22.3 MJ/kg on dry basis). Huge production of olive husks occurs seasonally in the Mediterranean area, posing problems for proper disposal and valorisation because of the difficulty to store this material for long times. The research demonstrated that the olive husks can be smoothly and effectively burnt in fluidized bed with high combustion efficiency and very low emissions of pollutants and solid particulate in a bed temperature range between 800 and 850 °C. The energy balance on the combustor shows that a fraction of 10-15 % of the heat input can be directly extracted from the fluidized bed, the remaining being available in the hot flue gases. The focus was also on the emissions of nitrogen oxide. The research can have practical application for small scale and local installation, e.g. at olive oil factory, as demonstrated by the experimental campaign at pilot scale.