System and process for producing and recovering elemental sulfur

Abstract

A straight-through four reactor system and process is disclosed for obtaining high levels of sulfur recovery from acid gas at a cost equal to or less than that required for a standard modified four reactor Claus system. Two conventional Claus reactors and two cold bed adsorption (CBA) reactors are in series. Four condensers are provided, one disposed before each of the Claus and CBA catalytic reactors. A first heater and a first bypass line is disposed between the second condenser and the second catalytic reactor (second Claus reactor) and a second heater and a second bypass line is disposed between the third condenser and the third catalytic reactor (first CBA reactor). The system is designed to operate either with both CBA reactors in a recovery mode or with one CBA reactor in a regeneration mode and the other CBA reactor in a recovery mode. When both reactors are operating in the recovery mode, the system is similar to the standard modified Claus system. But when one of the CBA reactors is in a regeneration mode, effluent from the third condenser is heated in the second heater and directed to the CBA reactor on regeneration. Sulfur is vaporized from the regenerating CBA reactor and is recovered in the fourth condenser. Effluent from the fourth condenser is then passed through the CBA reactor in recovery mode before it passes to the incinerator.