Sulfur Recovery Unit Process Flow Diagram

The acid gas streams from Amine Recovery Unit (Oil & Gas sector) or from Sour Water Stripping Unit plus Amine Unit (Refinery sector) are sent to Sulfur Recovery Unit where shall be burn with one-third the stoichiometric quantity of air and the hot gases are passed over an alumina catalyst to react sulfur dioxide with unburned hydrogen sulfide to produce free sulfur.

The burner is located in a reaction chamber which may be either a separate vessel or a part of the waste heat boiler. The purpose of the reaction chamber is to allow sufficient time for the combustion reaction to be completed before the gas temperature is reduced in the waste heat boiler.

Ammonia frequently is present in the Claus unit feed streams and must be completely destroyed in the reaction furnace to avoid plugging of equipment with ammonium salts. Specially designed burners and combustion zones have been developed for this purpose. The waste heat boiler removes most of the exothermic reaction heat from gases by steam generation.

Usually, they are arranged so that the gas flows through several tube passes in series with chamber, or ‘‘channels’’, where a portion of the gases may be withdrawn at elevated temperatures to use for reheating the main gas flow stream prior to the catalytic converters. Some elemental sulfur is often condensed and removed from the gas in the waste heat boiler. In some plants a separate condenser is used after the waste heat boiler.

The gas temperature entering the first catalytic converter is controlled at about 218 to 246°C which is necessary to maintain the catalyst bed above sulfur dewpoint in order to avoid saturating the catalyst with sulfur and thereby deactivating the catalyst. The reaction between hydrogen sulfide and sulfur dioxide in the converter is also exothermic. Gases from the converter are cooled in the following condenser for removal of most of the elemental sulfur as liquid.
A Tail Gas Treatment section shall be added to increase sulfur production, the remaining H2S shall be destroyed in final Incinerator and flue gases shall pass to atmosphere via stack.

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