Systems and processes for treating acid gas from a sour gas stream are provided. A chemical looping combustion (CLC) process is provided that uses CaCO.sub.3 to capture sulfur from the acid gas and produce CaSO.sub.4. An acid gas treatment unit may receive an acid gas from an acid gas removal unit and produce the CaSO.sub.4 and various gas and air streams for use in heat exchangers for steam production. The acid gas treatment unit may include a fuel reactor, an oxidizer reactor, and a calciner reactor. Another acid gas treatment unit may include a fuel reactor that includes the calciner function and an oxidizer reactor. A selective membrane module may be disposed between the sour gas stream and an acid gas removal unit to produce a H.sub.2S and CO.sub.2 permeate that is mixed with the acid gas stream provided to the acid gas treatment unit.

The process for configuring or reconfiguring a sulfur removal plant having a plurality of Claus units that is greater than the number of downstream tail gas treating units (TGTUs) allows for the regeneration of one of the Claus units without shutting down any of the downstream TGTUs or the other Claus units. Specifically, the regeneration tail gas can be diverted to the reaction furnace of an in-service Claus unit, thereby allowing excess oxygen to be used to regenerate the Claus unit more efficiently, and without exceeding environmental SO2 emission requirements.

A system includes an outlet flowline from an activated carbon bed, a bypass flowline, a furnace, and a control system. The outlet flowline is configured to flow an acid gas stream out of the activated carbon bed after the activated carbon bed has removed benzene, toluene, and xylene from the acid gas stream. The bypass flowline includes a bypass valve and provides an alternative flow path for the acid gas stream exiting the activated carbon bed. The furnace includes a burner configured to combust at least a portion of the acid gas stream. The control system includes a temperature sensor and a controller. The temperature sensor is configured to measure a furnace temperature. The controller is configured to reduce a percent opening of the bypass valve based on the measured furnace temperature.

A process for production of elemental sulfur from a feedstock gas including from 15% to 100 vol % H2S and a stream of sulfuric acid, the process including: a) providing a Claus reaction furnace feed stream substoichiometric oxygen with respect to the Claus reaction, b) directing to a reaction furnace zone operating at elevated temperature such as above 900 C., c) directing to a sulfuric acid evaporation zone downstream said reaction furnace zone, d) cooling to provide a cooled Claus converter feed gas, e) directing to contact a material catalytically active in the Claus reaction, f) withdrawing a Claus tail gas and elemental sulfur, g) directing to a Claus tail gas treatment plant, with the associated benefit of a process involving injection of sulfuric acid in a sulfuric acid evaporation zone allowing high temperature combustion of said feedstock gas, including impurities, without cooling from evaporation and decomposition of sulfuric acid.