PARTITIONING, ABATEMENT AND EMISSION OF NOx AND HN_4~+ ESPECIES IN LARGE SPANISH PCC-FGD POWER PLANTS

摘要

The abatement capacity for NOx and NH_3~+ of wet limestone-based FGD facilities, with re-circulation of the FGD waters and forced oxidation with re-circulation of FGD water streams was investigated in two large Spanish PCC plants (PP1 and PP2). The gaseous streams were sampled IN and OUT-FGD simultaneously with solid and liquid streams in 2007 and 2008 for PP1 and PP2. The levels of NOx were measured by probe while specific trapping solutions were devised for the capture of NH_3~+ (measured as NH_4~+). Abatement of NOx by FGD facilities attained low efficiencies (7-36 %) (no DeNOx are present) resulting in emission levels exceeding the EU directives. A differential NH_4~+speciation and partitioning among FGD streams was produced due to the feed fuel parameters. Most of the NH3 is retained in the gypsum slurry waters from both plants (49-65 %) while lower fractions are retained in gypsum (23-35 % and 8 % for PP1 and PP2, respectively). This resulted in abatement efficiencies of 17-45 % and 73-80 % for PP1 and PP2, respectively with emission values far below the threshold values established in the pollutant release transfer register (PRTR).In view of that more efforts has to be paid on reducing the NOx levels in plants without DeNOx facilities.