Limestone-based wet flue gas desulfurization process
AssigneeGeneral Electric Company
InventorsEli Gal, Michael L. Mengel
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Abstract
The limestone dissolution rate for limestone-containing slurries used in wet flue gas desulfurization (WFGD) systems is enhanced by the addition of ammonium ions. The ammonium ions may be obtained by incorporating into the limestone-containing slurry gaseous or aqueous ammonia and/or a water-soluble ammonium salt, such as ammonium sulfate, ammonium chloride, or ammonium carbonate. Increasing the limestone dissolution rate for limestone-containing slurries used in WFGD systems allows courser limestone particles, lower limestone stoichiometry and lower slurry recycle rates to be employed, thereby saving capital and operating costs. The ammonium ions may be recovered and reused in the process.
Claims11
A wet flue gas desulfurization process comprising the steps of:
- (a) bringing a sulfur-containing flue gas into contact with an aqueous limestone-containing slurry which includes a limestone-dissolution rate enhancing effective amount of ammonium ions in an absorber;
- (b) forcing oxidation air into the absorber so as to oxidize sulfite therein to sulfate;
- (c) removing desulfurized gas from the absorber;
- and
- (d) recovering the ammonium ions from the slurry and recycling the recovered ammonium ions to the absorber;
- wherein
- step (d) includes the steps of:
- (I) transferring a stream of the slurry containing the ammonium ions from the absorber to a filtration tank;
- (II) bringing the slurry into contact with calcium hydroxide within the filtration feed tank, while concurrently sparging the filtration feed tank with air so as to strip ammonia from the slurry and form an ammonia-lean slurry and an ammonia-rich air stream;
- (III) dewatering and washing the ammonia-lean slurry so as to obtain a gypsum cake having less than 5 ppm ammonia;
- and
- (IV) mixing at least a portion of the ammonia-rich air stream obtained according to step (II) with the oxidation air prior to the absorber so that a mixture of the ammonia-rich air stream and the oxidation air is forced into the absorber during practice of step (b) to thereby provide a source of the ammonium ions therein.
Dependencies are inferred from the claim text.