Objectives and Problems to be resolved: The use of bio fuels in dedicated plants or as a secondary fuel in coal co-combustion are feasible options for effective CO2 reduction. However, these fuels can lead to significantly increased deactivation of SCR-DeNOx-catalysts in the flue gas cleaning system of power plants. The consequences are high follow-up costs as well as higher emissions of NOx and trace elements. Hence, the deactivation constitutes a major obstacle for an increasing share of bio fuels in (co-)combustion. The project therefore exploits complementary experience to investigate fundamental processes in SCR-DeNOx-catalysts during (co-)combustion of biomass and bio waste fuels such as wood, straw, peat and sewage sludge. The main objective of the project is to evaluate and investigate the transformation and deactivation mechanisms concerning alkalis, heavy metals, and phosphor and derive optimised regeneration techniques. Description of the work: Within the project consortium experience of power plant operators from former deactivation tests using wood and straw for (co-)combustion in the Scandinavian countries and observations made at co-combusting sewage sludge in Germany are summarised and completed by the knowledge of a catalyst producer. Additional input is given through knowledge in full-scale regeneration methods. Furthermore, two research institutes will perform systematic studies with synthetic and combustion simulating flue gases in lab-and bench-scale test facilities using advanced measurement techniques with the aim to identify and partly quantify the main mechanisms and parameters that lead to deactivation and mercury oxidation. The work is focussed on the influence of single parameters, relevant combustion conditions, flue gas composition and conversion as well as the use of additives on the occurrence of poisoning elements in the gaseous and particle bound phase. Feasible changes in catalytic structure or composition are studied. The work of one partner considers the determination of mercury oxidation mechanisms at standard DCR-DeNOx-catalysts to suggest an increase oxidation rate for effective removal of mercury in the down stream gas cleaning units. Combustion conditions or fuel blends that should be avoided will also be determined. The available regeneration methods are optimised. Full scale tests at four plants for wood, straw and sewage sludge (co-) combustion equipped with standard and "bio-optimised" catalysts provide different flue gas compositions for the tests and will be used to validate results and prove their full-scale applicability. Expected Results and Exploitation Plans: If the follow-up costs of catalyst deactivation cannot be significantly reduced, they will become a considerable negative argument for the use of bio fuels in large-scale power plants. The aim of this project is to help plant operators and utilities to calculate the risk related to the use of specific bio fuels and therefore minimise these inestimable costs. In the next years the US will become a huge market for SCR technology. Experts expect problems similar to bio fuel co-combustion due to the composition of US coals. Since these are sub-bituminous, higher alkali and trace element content will promote catalytic deactivation. An increased knowledge on process parameters promoting deactivation combined with the development of resistant and optimised catalysts as well as optimised regeneration processes will enhance the competitiveness in non-European markets.
Funding SchemeCSC - Cost-sharing contracts