SPRAY CHARACTERIZATION OF TWIN FLUID EXTERNAL MIX ATOMIZATION OF PYROLYSIS OIL

The development of biomass-based energy conversion technologies has gradually been intensified throughout the last decade. The route based on pressurized entrained flow biomass gasification has an important role in this development. However, the issues of logistics and handling of the biomass requires thorough and detailed process integration studies in order to find optimal ways of implementation of this technology. An interesting approach is to liquefy the biomass via fast pyrolysis to produce a bio-oil, which then could be disintegrated into the gasifier. In order to better understand how a generic type of externally gas-assisted atomizer performs for pyrolysis oil, spray characterization based on high-speed photography and case-independent image analysis were performed. Three different parameters were varied in order to study the atomization performance for the considered nozzle: The ambient pressure, the pyrolysis oil temperature, and the length of external extension of the prefilming center bluff body in the nozzle. It was found that an increase in ambient pressure and corresponding load as well as an extension of the center bluff body of the nozzle led to degradation in atomization performance. On the other hand, a moderate temperature increase that affects the fluid properties in a favorable way improved the atomization performance. In all considered cases for the tested nozzle, a notable fraction of the droplets in the spray were found in the large-size tail of the size distributions and it is uncertain whether this may have an effect on the fuel conversion in the gasification process.