CBA for Claus tail gas cleanup

In a process for catalytic conversion of a gaseous stream containing hydrogen sulfide wherein said stream is subjected to an oxidation step to produce a reaction mixture in which hydrogen sulfide and sulfur dioxide are present in a molar ratio of about 2:1 and wherein the sulfur content of said reaction mixture is substantially reduced by first passing said mixture through a series of at least two Claus reactors with associated liquid sulfur condensers, and then passing the resulting Claus effluent through a CBA cleanup step involving at least two interchangeable CBA reactors wherein said Claus effluent at all times passes through at least one of said CBA reactors being sufficiently regenerated to further convert and condense the sulfur for a time sufficient to allow said other interchangeable CBA reactor to be regenerated by thermal removal of deposited sulfur followed by cooling of the sulfur-denuded CBA reactor, the improvement comprising:

• (a) maintaining the reaction conditions of a lead Claus reactor such that the effluent temperature of said reactor is from 600.degree. to 800.degree. F., thus promoting hydrolysis of COS and CS.sub.2 ;
• (b) diverting, periodically, a stream of said 600.degree. to 800.degree. F. effluent of said lead Claus reactor to the CBA reactor having deposited sulfur on the catalyst bed of said CBA reactor, thereby vaporizing and removing said deposited sulfur and regenerating said CBA catalyst bed;
• (c) returning the effluent of said CBA reactor being regenerated during said period of regeneration to a point downstream from said lead Claus reactor and downstream from where said stream is diverted but upstream to a subsequent second Claus reactor;
• and
• (d) cooling the sulfur-denuded CBA reactor before returning it to the cleanup mode for further removal of sulfur from the effluent of said Claus reactors.