Nox REDUCTION IN A PILOT-SCALE MSW GRATE INCINERATOR BY AIR AND FUEL STAGING

摘要

Investigations on the effect of air staging in the furnace of TAMARA were completed, focusing on the primary air distribution along the grate and the utilization of recirculated flue gas instead of primary and secondary air. Furthermore preliminary experiments on the primary side reduction of NO via fuel staging were performed with spherical polyethylene fed in batches into the furnace. Residues from the mechanical-biological pretreatment (MBA) of MSW were utilized as monofuel with a lower calorific value of 7.4 MJ/kg and mixed with RDF to adjust the lower calorific value to 9-10 MJ/kg. The feed rates ranged from 140 to 200 kg/h fuel and 70 to 100 % load respectively. The mean N-content of the fuel components was 1 % mass and 0.7 % mass. For evaluating the reduction potential by the various staging measures CO, CO2, O2 and NO concentrations were analyzed above the fuel bed and behind the boiler of the incinerator. Based on actual findings concerning the NO formation from the volatiles and the fixed carbon the staging experiments with air are discussed in terms of the influence of the fuel/air ratio and the effect of secondary air supply on the NO formation in the furnace at different fuel loads. The influence of the primary air distribution and the interaction with the secondary air supply will be addressed. The effect of the batchwise fuel staging is presented and compared to the air staging measures for NO reduction in the furnace. The results will be correlated to the distribution of the species CO, CO2, O2 and NO above the grate and behind the boiler. Finally the transfer to full-scale MSW incinerators with current furnace geometries will be addressed.