Within the recent years the use of bio-waste materials (sewage sludge, waste wood, refuse derived fuel) in dedicated plants (FBC) or as an additional fuel to coal for co-combustion (PF) has been proved to contribute besides CO_2 reduction aspects to a decrease in fuel costs and therefore in energy costs. In addition to possible operational problems major obstacles for an increased use of the energy content of these fuels for heat and power production are the risk of compromising the quality and utilisation of by-products as well as the apprehension of an increase of hazardous air pollutants (HAPs ) emissions, whereas toxic metals and fine particles having a high relevance. Wet FGD or scrubber systems are currently installed on most of the coal-fired utility boilers and in many waste incineration systems in Germany. Although their primary function is to remove SO_2 emissions from flue gas, wet flue gas cleaning systems can also be effective in removing trace elements from boiler flue gases. The main objective of the proposed work is to study the behaviour of trace elements during the use of sewage sludge, waste wood and refuse derived fuels in dedicated plants (FBC) or as an additional fuel to coal for combustion Besides detailed fuel analysis and characterisation the major part of the experimental investigations will be carried out on an available lab-scale flue gas cleaning system The work will consist of the following tasks:
1 ) Determination of the inlet and outlet gas and particulate concentration, characterisation of trace elements by determination of their content as well as their speciation
2) Investigation and analysis of scrubber chemistry regarding trace element removal
3) By-product quality, regarding disposal or utilisation
4) Comparison of results obtained during lab-scale investigations with results from large-scale units. This work is very important for the applicant to complete her research profile in environmental chemistry and trace element emission reduction. In another hand, the outcome of the work will therefore contribute to a further basic understanding about the toxic metal behaviour in coal-feud power plants and applied wet FGD systems.