Extended thermal stage sulfur recovery process

A process for recovering sulfur in a sulfur recovery unit, the process comprising the steps of:

• introducing an acid gas feed to a reaction furnace, where the acid gas feed comprises hydrogen sulfide;
• introducing a fuel gas to the reaction furnace;
• introducing air feed to the reaction furnace, where the air feed comprises oxygen;
• reacting the hydrogen sulfide and oxygen in the reaction furnace at a minimum reaction temperature to produce a reaction effluent, where the reaction effluent comprises elemental sulfur and sulfur dioxide, where the reaction effluent is at the minimum reaction temperature;
• introducing the reaction effluent to a wasteheat stage of an extended boiler stage;
• reducing the temperature of the reaction effluent from the minimum reaction temperature to a boiler section outlet temperature to produce a cooled effluent, where the cooled effluent comprises hydrogen sulfide, sulfur dioxide, and sulfur-containing contaminants, where the temperature of the reaction effluent is reduced by capturing heat energy;
• introducing the cooled effluent to a catalytic extension of the extended boiler stage, where the catalytic extension comprises a catalyst, where the catalytic extension has a gross hourly space velocity between 3000 h−1 and 6000 h−1;
• reacting the hydrogen sulfide, sulfur dioxide, and sulfur-containing contaminants in the catalytic extension to produce a boiler catalytic effluent, where the boiler catalytic effluent comprises elemental sulfur, where the boiler catalytic effluent is at a boiler catalytic effluent temperature;
• introducing the boiler catalytic effluent to a condenser, where the boiler catalytic effluent comprises elemental sulfur;
• reducing the boiler catalytic effluent temperature such that the elemental sulfur condenses to form liquid sulfur and a gases stream;
• introducing the gases stream to a thermal oxidizer, where the gases stream comprises hydrogen sulfide and sulfur-containing contaminants;
• introducing an air stream to the thermal oxidizer, where the air stream comprises oxygen;
• reacting the hydrogen sulfide and sulfur-containing contaminants with the oxygen to produce an oxidizer outlet stream, where the oxidizer outlet stream comprises sulfur dioxide;
• introducing the oxidizer outlet stream to a scrubbing unit;
• and
• separating the sulfur dioxide in the scrubbing unit to produce a recycle stream and an effluent gases, where the recycle stream comprises sulfur dioxide.