Biomass woodchip tracking by image analysis in a model of a fixed bed combustor

Abstract

Energy sector sustainability is one of the main concerns in the recent years. Biomass, in form of woodchips, is interesting for direct combustion in external combustion cycles (e.g. supercritical CO2 Brayton cycles) due to the opportunity of using low quality and low environmental impact fuels. In this study, a direct combustion system working with biomass woodchips is investigated by means of an image analysis technique. The system is made up by a screw conveyor and a fixed bed, where the woodchips are processed. The analysed device operates in cold-condition, and woodchips are partially coloured according to their dimensional class to be traced once these reached the bed surface. A proper algorithm was developed to identify the particles size, define and detect macroparticles centres, and evaluate the main particles motion pattern by comparing the centre positions during time. The results were particularly useful to understand potential inefficiencies of the combustion system due to an uneven woodchips distribution. In addition, the results achieved with the proposed test rig and the adopted methodology can also be used to validate results from Discrete Element Modelling (DEM) simulations.