Combustion of liquid bio-fuels in an internal circulating fluidized bed

The paper presents novel experimental results for the combustion of liquid bio-fuels in an internal circulating fluidized bed (ICFB). A 20 kW experimental facility equipped with an air-assisted injector has been used. Reliable operation, high combustion efficiency and limited temperature increase along the combustion riser tube have been attained at different operating conditions. However, CO emission has been rather higher than expected. A form of micro-explosive behaviour of the fuel has been experienced at relatively low bed temperatures (710–730 °C), but this behaviour was significantly less intense than in bubbling fluidized beds. A mathematical model of the combustion of liquid fuels has been adapted to ICFB conditions. The comparison between model and experimental results demonstrates that the efficiency of fuel-air mixing has a crucial role on combustion behaviour. Poor contact between air and fuel in the bottom half of the riser is responsible for high CO levels measured during the experiments. On the whole, the research demonstrates that the proposed liquid injection process could be suitable for application in co-gasification or for incineration of liquid wastes.