Enhancement of claus tail gas treatment by sulfur dioxide-selective membrane technology and sulfur dioxide-selective absorption technology

A system for recovering sulfur from an acid gas feed, the system comprising:

• a Claus process, the Claus process configured to convert a combined Claus feed to produce a Claus outlet gas stream and a recovered sulfur stream, wherein the combined Claus feed comprises the acid gas feed and an absorption process outlet stream, wherein the acid gas feed comprises hydrogen sulfide such that the acid gas feed has a hydrogen sulfide concentration, wherein the absorption process outlet stream comprises sulfur dioxide, wherein the Claus outlet gas stream comprises sulfur-containing compounds, hydrogen sulfide, and sulfur dioxide;
• wherein the recovered sulfur stream comprises elemental sulfur,
• a thermal oxidizer fluidly connected to the Claus process, the thermal oxidizer configured to convert sulfur-containing compounds and hydrogen sulfide in the Claus outlet gas stream to sulfur dioxide to produce a thermal oxidizer outlet stream, wherein the thermal oxidizer outlet stream comprises the sulfur dioxide and water vapor;
• a gas treatment unit fluidly connected to the thermal oxidizer, the thermal oxidizer configured to cool the thermal oxidizer outlet stream to produce a process condensed water stream and a dehydrated stream, wherein the dehydrated stream comprises sulfur dioxide;
• a membrane sweeping unit fluidly connected to the gas treatment unit, the membrane sweeping unit configured to separate sulfur dioxide from a sweep membrane feed to produce a sweep membrane residue stream and a sulfur dioxide enriched air feed, wherein the sweep membrane feed is separated from the dehydrated stream, wherein the membrane sweeping unit comprises a membrane, wherein the sulfur dioxide permeates through the membrane of the membrane sweeping unit to a permeate side of the membrane, wherein the sweep membrane residue stream comprises sulfur dioxide;
• a pressure differential driven membrane unit fluidly connected to the gas treatment unit, the pressure differential driven membrane configured to separate sulfur dioxide from a pressure differential driven membrane feed to produce a pressure driven residue stream and a pressure driven permeate recycle stream, wherein the pressure differential driven membrane feed is separated from the dehydrated stream, wherein the pressure differential driven membrane unit comprises a pressure driven membrane, wherein the pressure driven membrane has a permeate side and a feed side, wherein the sulfur dioxide permeates from the feed side of the pressure driven membrane to the permeate side of the pressure driven membrane, wherein the pressure driven permeate recycle stream has a permeate pressure, wherein the permeate pressure is below atmospheric pressure;
• a recycle pressure treatment unit fluidly connected to the pressure differential driven membrane unit, the recycle pressure treatment unit configured to increase the permeate pressure of the pressure driven permeate recycle stream to above atmospheric pressure;
• and
• a sulfur dioxide absorption process fluidly connected to the membrane sweeping unit and the pressure differential driven membrane feed, the sulfur dioxide absorption process configured to produce the absorption process outlet stream and a stack feed, the sulfur dioxide absorption process configured to separate sulfur dioxide from a residue stream, wherein the residue stream comprises the sweep membrane residue stream and the pressure driven residue stream, wherein the stack feed is below an allowable sulfur dioxide emission limit.

A system for recovering sulfur from an acid gas feed, the system comprising the steps of:

• a feed treatment unit, the feed treatment unit configured to condense water vapor in the acid gas feed to produce a feed recovered water stream and a carbon dioxide membrane feed, wherein the carbon dioxide membrane feed comprises carbon dioxide and hydrogen sulfide, wherein the acid gas feed has a hydrogen sulfide concentration;
• a carbon dioxide membrane unit fluidly connected to the feed treatment unit, the carbon dioxide membrane unit configured to separate carbon dioxide from the carbon dioxide membrane feed to produce a carbon dioxide permeate and a hydrogen sulfide retentate, wherein the carbon dioxide membrane unit comprises a carbon dioxide-selective membrane, wherein the carbon dioxide permeate has a carbon dioxide permeate pressure, wherein the carbon dioxide permeate pressure is below atmospheric pressure;
• a feed pressure treatment unit fluidly connected to the carbon dioxide membrane unit, the feed pressure treatment unit configured to increase the carbon dioxide permeate pressure of the carbon dioxide permeate to produce a carbon dioxide enriched feed, wherein the carbon dioxide permeate pressure of the carbon dioxide enriched feed is above atmospheric pressure;
• a Claus process fluidly connected to the feed pressure treatment unit, the Claus process configured to convert an enriched acid gas stream to produce a Claus outlet gas stream and a recovered sulfur stream, wherein the enriched acid gas stream comprises the hydrogen sulfide retentate and an absorption process outlet stream, wherein the absorption process outlet stream comprises sulfur dioxide, wherein the Claus outlet gas stream comprises sulfur-containing compounds, hydrogen sulfide, and sulfur dioxide;
• wherein the recovered sulfur stream comprises elemental sulfur,
• a thermal oxidizer fluidly connected to the Claus process, the thermal oxidizer configured to convert sulfur-containing compounds and hydrogen sulfide in the Claus outlet gas stream to sulfur dioxide to produce a thermal oxidizer outlet stream, wherein the thermal oxidizer outlet stream comprises the sulfur dioxide and water vapor;
• a gas treatment unit fluidly connected to the thermal oxidizer, the thermal oxidizer configured to cool the thermal oxidizer outlet stream to produce a process condensed water stream and a dehydrated stream, wherein the dehydrated stream comprises sulfur dioxide;
• a membrane sweeping unit fluidly connected to the gas treatment unit, the membrane sweeping unit configured to separate sulfur dioxide in the dehydrated stream to produce a sweep membrane residue stream and a sulfur dioxide enriched air feed, wherein the membrane sweeping unit comprises a membrane, wherein the sulfur dioxide permeates through the membrane of the membrane sweeping unit to a permeate side of the membrane, wherein the sweep membrane residue stream comprises sulfur dioxide;
• and
• a sulfur dioxide absorption process fluidly connected to the membrane sweeping unit, the sulfur dioxide absorption process is configured to produce the absorption process outlet stream and a stack feed, the sulfur dioxide absorption process configured to separate sulfur dioxide from the sweep membrane residue stream, wherein the stack feed is below an allowable sulfur dioxide emission limit.