Abstract
Despite recent progress, NOx is still a major problem in biomass combustion, especially when using fuels with high nitrogen contents. The aim of this work was to determine the minimum NOx emissions achievable by applying primary measures in small-scale biomass grate furnaces. For this purpose, a new benchmark for furnaces using double air staging was defined on the basis of three different plants. An experimental study with different biomass fuels was conducted in two of these plants to systematically improve this benchmark.The results show that the new NOx benchmark using double air staging is up to 39 % lower than values achieved with conventional single air staging. Furthermore, this new benchmark was improved by extending the reduction zone, additionally reducing the NOx by up to 30 %. Secondary flue gas recirculation and partial load further reduced the NOx emissions.By combining the primary measures investigated in the 70-kW furnace, NOx emissions were achieved that were up to 70 % lower than those from other small-scale furnaces described in the literature. This efficiency also applies to fuels with a high nitrogen content, so that secondary NOx reduction measures can be avoided in most cases in furnaces in the future by taking this approach.
Published Version
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