Ammonsulfat zur selektiven nicht-katalytischen Stickoxidreduktion von Zementwerksabgasen
Research output: Thesis › Doctoral Thesis
Two ammonium sulphate-containing residues, which were due to their composition not utilisable, were the origin of this research doctoral thesis. Within this research work for both residual materials, the application for selective non-catalytic reduction of NOx (SNCR-process) of exhaust gas from cement plants was suggested. The SNCR technique is deemed to be best available technology for NOx removal in cement plants, whereupon urea and ammonia is generally used as reducing agent. Denitrification with ammonium sulphate is applied rarely and to date hardly investigated. Since little experience with ammonium sulphate was available, initially the suitability for NOx removal of commercial 40% ammonium sulphate solution was investigated in 5 different industrial furnace systems with cyclone preheating. For comparison, also 40% urea solution and 25% ammonia solution were tested. Furthermore, secondary emissions such as SO2, NH3 and CO, which may result from the addition of the reducing agents, were analysed. The reduction efficiency and the interactions with the cement production process were investigated accordingly under operational conditions, whereby the results gain in importance for the practical application. Afterwards the suitability of the ammonium sulphate-containing residues was reviewed with consideration to the content of active ingredient, contaminants, storage and conveying behaviour as well as corrosion performance. As far as possible the residues were also tested in line with field tests in cement plants. For an improved comprehension of the results from the field tests important parameters, which were used to quantify the reduction efficiency and the secondary emissions, were plotted according to the molar ratio and theoretically discussed in consideration of the influence of temperature, retention time and intermixture. The results of these theoretical considerations are generally adequate for the interpretation of the results from SNCR-tests and therefore suitable for optimisation of every SNCR-equipment. It was demonstrated that ammonium sulphate from a technical point of view is perfectly appropriate for NOx removal in cement plants. However, the application of commercial ammonium sulphate is according to the actual price situation only economical, if a considerably improved reduction efficiency can be achieved in comparison to e.g. urea. Within the field tests it was shown, that in many cement plants the reduction effect of ammonium sulphate was better compared with urea. With low-priced ammonium sulphate containing residues the application of ammonium sulphate is additionally favourable. In two cement plants it was demonstrated, that also the ammonium sulphate-containing residues are effective reducing agents and that a large-scale application is possible. In this context during the research work a patent with the title “use of an ammonia-releasing residue” was successfully applied.