Removal of Sulfur Dioxide and Nitric Oxide From a Flue Gas Stream By Two Sodium Alkalis of Various Sizes

The primary purpose of this research effort was to examine the dry removal of SO₂ and NO from a flue gas stream by injecting two sodium additives into a pilot bag house system. The additives tested were NaHCO₃ and Na₂CO₃ dusts with mass mean diameters ranging from approximately 30 to 200 microns. The Na₂CO₃ was obtained by decomposing the NaHCO₃ (with heat) prior to testing. The bag house temperature was maintained at either 250 or 300 degrees F.

It was demonstrated that 70% SO₂ removal can be attained with NaHCO₃ powders that have mass mean diameters of 32 and 52 microns at stoichiometric ratios of 0.8 and 1.3, respectively. The rate of mass transfer limited the desulfurization capacity of NaHCO₃ powders with mass mean diameters greater than 50 microns. The rate of chemical reaction limited the SO₂ removal capability of the smallest NaHCO₃ additive tested (mass mean diameter = 32 microns). Decomposition of NaHCO₃ to Na₂CO₃ in bulk before injection yielded poorer SO₂ removal.

It was also demonstrated that 7 to 36% of the NO was removed simultaneously with SO₂ by the NaHCO₃ additives with mass mean diameters smaller than 120 microns. This removal was inversely dependent on the system temperature. No appreciable NO removal was observed with Na₂CO₃ injection.