Ash utilisation. The utilisation of CCPs from coal-fired power plants has developed over decades. The basic technical, physical and chemical properties of the ashes are addressed in product and application standards and regulations. In general terms, the DEBCO project has demonstrated that the solid by-products generated during the co-firing in dedicated plants at low co-firing ratios can also be utilised as construction materials. The co-firing of specific biomass materials is already covered by the European Standard EN 450-1 for fly ash for concrete. The biomass properties and the co-firing levels are limited to guarantee that the key properties of the fly ash materials do not change significantly. In order to extend the co-firing of biomass to higher levels, the utilisation paths of by-products need to be analysed and the impact of co-firing need to be assessed. The intention is to minimise the quantities of material that need to be sent to disposal to land. For the use in or as construction materials, the requirements in European standards, which have to be considered for the placing on the market of coal ash, as well as national standards, for the application in the countries, have to be considered. The possible uses of CCPs could be: - In cement; - In concrete; - Road constructions; - Aggregates. The specific technical and other requirements for fly ashes for different applications are established by European standards, and these are listed in Table 12. The requirements for fly ash for the use as a constituent of blended cements and of concrete established in the European Standards are given in Table 13. For the use in concrete, some additional physical parameters are defined in EN 450-1:2005 and listed in Table 14. For the evaluation of the impact of co-firing of different biomass / materials on the properties of ashes it is recommended to consider the following issues: - If the ash from co-firing is to be used for the same purpose as the ash from coal, the impact on the chemical and physical properties should be minimal or negligible. - Different biomass materials have different chemical compositions and will have different impacts on the chemical compositions of the ashes resulting from co-firing with hard coal or lignite. The results of the work carried out within the DEBCO project show significant variability in the ash chemistry even when co-firing relatively well-defined wood pellets. - The lower the ash content of the co-firing material, the lower the impact ...
