US 4,078,048 AGranted

Process and apparatus for removing sulfur from stack gases in the form of elemental sulfur

AssigneeCombustion Equipment Associates, Inc.

InventorRavindra M. Nadkarni

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Abstract

Process and apparatus for removing sulfur dioxide from gases such as stack gases. The gases are scrubbed with an alkali metal compound in an aqueous solution to form alkali metal sulfite/sulfate salts which are then reacted with barium sulfide to precipitate barium sulfite/sulfate and form alkali metal sulfide/bisulfide in solution. The alkali metal sulfide/bisulfide is oxidized to form elemental sulfur and regenerated wash liquid; and the barium sulfite/sulfate is reduced by roasting to form the barium sulfide required. In a preferable embodiment, coal is used as both the reductant and fuel in the roasting of the barium sulfite/sulfate and the stack gases from the roasting are scrubbed along with the primary stack gases. As an optional step a portion of the alkali metal sulfite salts may be oxidized to sulfate prior to reaction with barium sulfide.

Claims38

Dependent claims

A process for removing sulfur dioxide in the form of elemental sulfur from gases, comprising the steps of

a. contacting gases containing sulfur dioxide with a scrubbing liquid comprising an aqueous solution of an ammonium or alkali metal compound having an alkaline pH thereby to form an aqueous spent scrubbing liquid containing ammonium or alkali metal sulfite/sulfate salts, the pH of said aqueous spent scrubbing liquid being no lower than about 6;
b. reacting said sulfite/sulfate salts in said aqueous spent scrubbing liquid with an aqueous solution of barium sulfide, the solids concentration of which is below saturation at the temperature of said reacting step, thereby to precipitate insoluble barium salts and form ammonium or alkali metal sulfide/bisulfide in solution without the evolution of gaseous H.sub.2 S;
c. removing said insoluble barium salts from said solution of said sulfide/bisulfide;
d. oxidizing said sulfide/bisulfide solution using as an oxidation catalyst a source of water-soluble polyvalent metal ions dissolved in said solution to precipitate elemental sulfur directly from said solution and to regenerate ammonium or alkali metal compound in solution for recycling as said scrubbing liquid;
and
e. separating said elemental sulfur from said compound in solution.

3 more elements

Dependencies are inferred from the claim text.