Effect of ammonia and ammonium compounds on wet-limestone flue gas desulfurization process from a coal-based power plant - Preliminary industrial scale study

摘要

The paper encompasses a review and presents the influence of ammonia and ammonium ions on wet flue gas desulfurization (WFGD) absorber based on results of an preliminary industrial scale study. Subject of the study was a WFGD with total maximum flue gas flow capacity equal to 1,500,000 Nm(3)/h, fed from four hard-coal fueled boilers equipped with SNCR based on urea injection. In this study, effects of SNCR operation and ammonia slip on the absorption slurry pH and NH4+ concentration are considered. It was shown, that an increase in ammonia concentration present in the flue gas upstream the WFGD increases the pH of absorption slurry, a critical parameter in the control of WFGD operation, limestone dissolution and gypsum formation. Moreover, analysis of particulate matter upstream and downstream the absorber shows, that the WFGD as a source of particulate matter increases the content of ammonium species in the PM due to the entrainment and evaporation by 3,9 times, as average. Results show that a SNCR system combined with a WFGD can achieve higher concentrations of NF4+ ions in the absorption slurry (up to 768 mg/L), gypsum slurry (up to 858 mg/L) and raw wastewater (up to 891 mg/L) compared to the more commonly used SCR. Results indicate, that the wastewater must be additionally treated prior the discharge to the environment.