Project background
  • Project background

Project background

The broad variety of properties of solid biofuels poses a big challenge in particular to combustion technologies. Apart from emissions and corrosion related problems, ash melting and slag formation in the grate section of combustion units is an issue of main relevance in the field of biomass combustion. Ash slagging occurs as a result of interactions between boiler type, fuel composition and combustion temperature. Whereas these phenomena are well documented and understood for fossil fuels, information for predicting the occurrence of slagging of biomass fuels is still scarce.

The ash fusion test is the only standardised method currently available for the description of the ash melting properties of solid biofuels, but the application of the method is limited with regard to the fuel quality. The quality of prediction is declining with decreasing quality of the wood fuels, and even worse for other solid biomass. Moreover, results do insufficiently predict the ash melting properties of biomass fuels under real combustion conditions.

As there is no reliable method available for the ash melting behaviour of solid biomass, a respective normative regulation has not been included in the recently developed product standards for wooden biofuels (EN 14961 Part 2 – Part 5), which is considered a major drawback for future development of the high quality end consumer market for wood pellets. Thus, there is an urgent need for the development of a test method which is applicable for biomass fuels and significant with regard to the combustion behaviour. Several test methods have been investigated in previous studies, but predictions and test results have scarcely been evaluated regarding their significance with regard to the practical performance of the fuel during combustion.

In the project information is gathered about available methods to determine the slagging behaviour focusing on the identification of approaches that could be further developed resulting in a standard test method for the prediction of biomass ash melting behaviour under real combustion conditions.