SULFREEN Process by Lurgi Oel-Gas-Chemie GmbH

Catalytic purification of Claus tail gas or lean H2S waste gas for an overall sulfur recovery ranging from 99% to 99.9%. Different versions of the SULFREEN process are available.

SULFREEN Process by Lurgi Oel-Gas-Chemie GmbH

The SULFREEN process is based on the well-known Claus reaction in which the components H2S and SO2 in tail gas—are catalytically converted into elemental sulfur. The process occurs in the gas phase; the operating conditions being those at which the tail gas leaves the upstream Claus plant. The catalyst, which is arranged in fixed beds, consists of impregnated activated alumina, the properties of which are similar to those of Claus catalysts. Tail gas leaving the Claus plant at temperatures of 120°C to 140°C passes through one of the two reactors (1) (2), where most of the H2S and SO2 are converted into elemental sulfur and adsorbed on the catalyst.

The sulfur-laden catalyst is regenerated by using part of the Claus plant tail gas. The regeneration gas is heated in a gas/gas-heat exchanger (6), using the heat in the hot offgases from the incineration unit (3). A gas-fired heat exchanger, a direct-fired heater or an electrical heater can also be used for heating purposes. The desorbed sulfur contained in the hot regeneration gas is recovered in the sulfur condenser (4) (5). The regeneration-gas blower (7) serves for overcoming the pressure drop of the closed regeneration loop. After subsequent cooling of the catalyst bed with purified tailgas, the reactor (1) (2), is again ready to be switched to adsorption.

If high COS and CS2 concentrations are expected to be present in the tailgas, a modified version of the process, named HYDROSULFREEN, is available. The HYDROSULFREEN process includes a pretreatment of the tail gas in an hydrolysis and oxidation reactor, located upstream of the SULFREEN reactors. For sulfur recoveries up to 99.9%, the DOXOSULFREEN process can be applied. This process includes an additional direct oxidation step downstream of the SULFREEN reactors.

Economics: SULFREEN investment amounts to 30–45% of the Claus unit cost for the conventional version, and 50–85% for the improved versions. Operating costs are much lower than for solvent-based processes.

Licensor: Lurgi Oel-Gas-Chemie GmbH


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