The University of Tennessee Research Foundation

Atul C Sheth

William A Butler

Robert L Solomon

Howard R Herrigel

Darryll G Rasnake

Gregory L Wilson

Jeffrey K Holt

The specification discloses a desulfurization process for use in a fossel fuel combustion process involving the generation of a flue gas product containing sulfur oxides and halogen compounds wherein an alkali metal compound is contacted with the gas resulting in the removal of sulfur oxides from the gas and formation of a water-soluble residue comprising alkali metal sulfates and alkali metal halides, which residue is collected from the gas before the gas is released to the environment. The process is adapted to recover the alkali metal ions from the collected residue for use in supplying the alkali metal ions that are contacted with the gas and for limiting the presence co-collected halogen ions within the recovered alkali metal ions. The process comprises dissolving the collected residue in water to form an aqueous solution thereof having a pH of less than about 8 so that sulfate ions, halogen ions and alkali metal ions are present in the solution. Thereafter, the solution is contacted with a weak base anion-exchange resin having bicarbonate groups associated therewith that exchange with sulfate and halogen ions in the solution so that the sulfate and halogen ions become associated with the resin and the bicarbonate groups become associated with the alkali metal ions in the solution. As a result, the alkali metal ions are separated from the sulfate ions and halogen ions for use in supplying the alkali metal compound that is contacted with the gas.

Desulfurization process

The specification discloses a spent seed recovery and regeneration process for an MHM power plant employing an alkali metal salt seed material such as potassium salt wherein the spent potassium seed in the form of potassium sulfate is collected from the flue gas and reacted with calcium hydroxide and carbon monoxide in an aqueous solution to cause the formation of calcium sulfate and potassium formate. The pH of the solution is adjusted to supress formation of formic acid and to promote precipitation of any dissolved calcium salts. The solution containing potassium formate is then employed to provide the potassium salt in the form of potassium formate or, optionally, by heating the potassium formate under oxidizing conditions to convert the potassium formate to potassium carbonate.

Recovery and regeneration of spent MHD seed material by the formate

Alkali metal sulfates are converted to a sulfur-free form by dissolving the alkali metal sulfate in water to produce an aqueous solution containing alkali metal ions and sulfate ions at a pH below about 8, and then passing the solution through a weak base, anion exchange resin having bicarbonate ions associated therewith that exchange with the sulfate ions so that the sulfate ions become associated with the resin and the bicarbonate ions become associated with the alkali metal ions in the solution. The resin can be regenerated to the bicarbonate form by treatment with an ammonium hydroxide solution followed by contact with carbon dioxide and the regeneration by-products are commercially useful.

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Tullahoma, TN, United States of America

Atul C Sheth