A sulfur recovery unit for processing an acid gas feed to recover elemental sulfur, the sulfur recovery unit comprising: a reaction furnace, the reaction furnace configured to burn the acid gas feed, an oxygen source, and a fuel gas to create a furnace outlet stream, the reaction furnace comprises a main burner and a reaction chamber, the main burner is configured to heat the acid gas feed, the oxygen source, and the fuel gas to a minimum reaction temperature, wherein the acid gas feed comprises hydrogen sulfide, wherein the hydrogen sulfide is converted to the elemental sulfur in the reaction chamber; a waste heat boiler fluidly connected to the reaction furnace, the waste heat boiler configured to capture heat from the furnace outlet stream to create a cooled stream, wherein the heat captured from the furnace outlet stream is operable to heat a water feed to create steam; a condenser fluidly connected to the waste heat boiler, the condenser configured to condense the cooled stream to produce a waste gas stream and a condensed stream, wherein the waste gas stream comprises sulfur-containing contaminants, and wherein the condensed stream comprises the elemental sulfur; a tail gas analyzer installed after the condenser; a thermal oxidizer fluidly connected to the condenser, the thermal oxidizer configured to burn the waste gas stream, the oxygen source, and the fuel gas to create a sulfur dioxide rich stream, wherein a conversion of the sulfur-containing contaminants to sulfur dioxide is operable to occur in the thermal oxidizer, wherein the sulfur dioxide rich stream comprises the sulfur dioxide; and a sulfur dioxide scrubbing unit fluidly connected to the thermal oxidizer, the sulfur dioxide scrubbing unit configured to remove an amount of sulfur dioxide from the sulfur dioxide rich stream to create an effluent stream and a recycle stream, the recycle stream comprising the amount of sulfur dioxide, wherein the recycle stream is recycled to the reaction furnace. a reaction furnace, the reaction furnace configured to burn the acid gas feed, an oxygen source, and a fuel gas to create a furnace outlet stream, the reaction furnace comprises a main burner and a reaction chamber, the main burner is configured to heat the acid gas feed, the oxygen source, and the fuel gas to a minimum reaction temperature, wherein the acid gas feed comprises hydrogen sulfide, wherein the hydrogen sulfide is converted to the elemental sulfur in the reaction chamber; a waste heat boiler fluidly connected to the reaction furnace, the waste heat boiler configured to capture heat from the furnace outlet stream to create a cooled stream, wherein the heat captured from the furnace outlet stream is operable to heat a water feed to create steam; a condenser fluidly connected to the waste heat boiler, the condenser configured to condense the cooled stream to produce a waste gas stream and a condensed stream, wherein the waste gas stream comprises sulfur-containing contaminants, and wherein the condensed stream comprises the elemental sulfur; a tail gas analyzer installed after the condenser; a thermal oxidizer fluidly connected to the condenser, the thermal oxidizer configured to burn the waste gas stream, the oxygen source, and the fuel gas to create a sulfur dioxide rich stream, wherein a conversion of the sulfur-containing contaminants to sulfur dioxide is operable to occur in the thermal oxidizer, wherein the sulfur dioxide rich stream comprises the sulfur dioxide; and a sulfur dioxide scrubbing unit fluidly connected to the thermal oxidizer, the sulfur dioxide scrubbing unit configured to remove an amount of sulfur dioxide from the sulfur dioxide rich stream to create an effluent stream and a recycle stream, the recycle stream comprising the amount of sulfur dioxide,