An automated ash fusion test for characterisation of the behaviour of ashes from biomass and coal at elevated temperatures

Abstract

The benefits of blending biomass with coal for power generation include less CO2 emissions and a reduced dependency on non-renewable fossil fuels. However, there is a need to understand the role of biomass during direct combustion and co-firing, particularly in terms of the effect of biomass use on ash slagging and fouling. A new image analysis based technique has been developed to characterise the behaviour of ashes from biomass, coal and coal/biomass blends using a single heating test at elevated temperatures. It is a reproducible test that combines the conventional ash fusion test, dilatometry and sinter strength test by means of image analysis. An oven is used to heat the cylindrical ash pellets from room temperature to 1520°C, while the in-built camera captures still images of the samples throughout the temperature range. An automated image analysis code has been developed to provide behaviour profiles for each ash sample (across the temperature range) by quantifying dimensional changes upon heating. The error for the determined ash characteristic temperatures is approximately 15°C, which is approximately 50% lower than for a conventional ash fusion test. Cylindrical ash samples from 9 biomasses (corn stover, DDG, DDGS, miscanthus, olive residue, wheat shorts, wheat, rapeseed, sunflower seed) and a standard UK coal (Daw Mill) were tested using this method and each was found to produce unique profiles.