Method for the removal of mercury and nitrogen oxides from combustion flue gas
AssigneeInfilco Degremont Inc.
InventorsKy Dangtran, Troy C. Holst
Life of this patent
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Abstract
The process is by injection of calcium chloride into the combustor and lowering the flue gas temperature in sufficient time to enhance oxidation of mercury and nitrogen oxides into more soluble products prior to their absorption in a wet scrubber. The additive also increases the alkalinity and the pH of the scrubber water, therefore, favorably increasing the absorption of the pollutants. The flue gas is then cooled to ambient temperature or less to enhance the removal of mercury.
Claims25
A process for removing Hg and NOx from combustion flue gas generated by combustion of carbonaceous material comprising:
- a) providing said carbonaceous material and at least one additive compound selected from the group consisting of alkali earth metal, chlorine, and mixtures thereof, to a combustor to facilitate formation in situ of HCl acid and MO or M(OH)2 in the flue gas generated by the combustor;
- b) generating excess MO and M(OH)2 in the combustor to increase alkalinity and pH;
- c) converting gaseous Hg and HCl into HgCl2 by cooling Hg and HCl containing flue gas;
- d) converting gaseous NO and MO or M(OH)2 into a more soluble form of nitrogen oxides;
- e) quenching the HgCl2 and the NOx containing flue gas to about 70-90° C.;
- f) separating Hg in the form of HgCl2 and the soluble form of nitrogen oxides with a majority of ash generated by the combustor from the flue gas;
- g) cooling the flue gas in the presence of water to about 45-50° C.;
- h) removing residual HgCl2 and remaining soluble nitrogen oxides from the flue gas;
- i) condensing fugitive elemental Hg by contacting the flue gas with further cooling fluid to reduce flue gas temperature to substantially ambient temperature or lower;
- and
- j) separating condensed fugitive elemental Hg from the flue gas.
A process for removing Hg from combustion flue gas generated by combustion of carbonaceous material comprising:
- a) providing said carbonaceous material and a chlorine containing substance to a combustor to facilitate formation of HCl acid in the flue gas;
- b) converting gaseous Hg and HCl into HgCl2 by cooling Hg and HCl containing flue gas;
- c) quenching the HgCl2 containing flue gas to about 70°-90° C.;
- d) separating Hg in the form of HgCl2 from the flue gas;
- e) cooling the flue gas in the presence of water to about 45°-50° C.;
- f) removing residual HgCl2 and condensed water vapor from the flue gas;
- g) condensing fugitive elemental Hg by contacting the flue gas with further cooling fluid to reduce flue gas temperature to substantially ambient temperature or lower;
- and
- h) separating condensed fugitive elemental Hg from the flue gas.
A process for reducing NOx containing flue gas generated by combustion of carbonaceous material comprising:
- a) providing said carbonaceous material and alkali earth metal containing substance for a combustor to facilitate formation in situ of MO or M(OH);
- b) generating excess MO and M(OH)2 in the combustor to increase alkalinity and pH;
- c) converting gaseous NO and MO or M(OH)2 into a more soluble form of nitrogen oxides;
- and
- d) quenching the NOx containing flue gas to about 70-90° C.;
- e) separating the soluble form of nitrogen oxides with a majority of ash generated in the combustor from the flue gas;
- f) cooling the flue gas in the presence of water to about 45-50° C.;
- and
- g) removing remaining soluble nitrogen oxides from the flue gas.
Dependencies are inferred from the claim text.