Union Carbide Chemicals & Plastics Technology Corporation

Cansolv Technologies Inc.

Paul J Parisi

Leo Ernest Hakka

John Nicolas Sarlis

Patrick M Ravary

Sulphur dioxide is removed from gas streams by contacting the gas stream with an absorbing medium containing an amine capable of forming an amine salt, heat stable salt and sulfite. The level of heat stable salt is selected such that during the regeneration process of the sulphur dioxide rich amine, the pH of the absorbing medium is at a selected level or below when the level of sulfite in the absorbing medium has been reduced to a specified value. The amine that absorbs the sulphur dioxide has a pKa less than that of sulfite. If the absorbent includes a diamine, then the spent absorbing medium is regenerated under conditions such that at least one amine group remains in salt form.

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The invention relates to a method of confining sulfur dioxide for storage or transportation under safe conditions. The method of the invention comprises the steps of (a) contacting a sulfur dioxide-containing gas stream with an absorbing medium comprising water and a water-soluble amine absorbent having at least one amine group with a pKa value greater than about 7 and at least one other amine group with a pKa value less than about 6.5 so that the at least one amine group with a pKa value greater than about 7 irreversibly absorbs sulfur dioxide in salt form rendering the amine absorbent non-volatile and the at least one other amine group with a pKa value less than about 6.5 reversibly absorbs sulfur dioxide, to thereby saturate the absorbing medium with sulfur dioxide against a partial pressure of sulfur dioxide of no more than about 1 atmosphere at 25&deg; C.; and (b) charging the absorbing medium saturated with sulfur dioxide obtained in step (a) into a container for storage or transportation.

Safe storage and transportation of sulfur dioxide

Improved processes are disclosed for the removal of hydrogen sulfide from feed streams by conversion of hydrogen sulfide and sulfur dioxide to elemental sulfur and water, e.g. Claus process. The feed stream of the present invention is divided into two split streams wherein one is incinerated to form sulfur dioxide in the presence of oxygen. The sulfur dioxide is then separated from the water, nitrogen and other impurities and combined with the other split stream to form a reactor feed which is passed to a sulfur reaction zone for conversion to elemental sulfur. Due to the rejection of water, nitrogen and other impurities from the reactor inlet stream, a higher concentration of hydrogen sulfide and sulfur dioxide can be achieved in the sulfur reaction zone. As a result, the processes of the present invention can be used to increase the throughput of existing Claus process plants and reduce the size of new Claus process plants.

Removal of hydrogen sulfide

Processes for the removal of sulfur dioxide from gas streams, e.g., stack gases, are disclosed wherein the absorption occurs in the presence of a diamine. The first amine group, i.e., stronger amine group, of the diamine is in salt form, having sulfite anions associated therewith, and absorbs by a sulfite/bisulfite absorption mechanism. The second amine groups absorbs sulfur dioxide in free base form. The sulfite salt on the first amine group is maintained by controlling the level of heat stable salts in the absorbent. Both the first and second amine groups can be conveniently regenerated together, e.g., by steam stripping.

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Saint Lambert, Canada

Paul J Parisi