A method for increasing sulfur recovery from an acid gas feed comprising the steps of introducing the acid gas feed and a sulfur dioxide enriched air stream to a Claus process to produce a product gas stream, introducing the product gas stream to a thermal oxidizer to produce a flue gas stream, cooling the flue gas stream to produce a cooled take-off stream, separating the cooled take-off stream into a saturated gas stream, heating the saturated gas stream to produce a membrane gas stream, introducing the membrane gas stream to a membrane sweeping unit, the membrane sweeping unit comprises a membrane, the sulfur dioxide in the membrane gas stream permeates the membrane of the membrane sweeping unit, introducing a sweep air stream, the sweep air stream collects the sulfur dioxide to create the sulfur dioxide enriched air stream.