Sulfur recovery process could solve acidic gas dilemma offshore

Prosernat has expanded its range of process technologies through the acquisition of Germany's ITS Reaktortechnik. ITS owned a sulfur recovery technology developed by Linde in the 1980s, originally commercialized as Clinsulf, but later known as SmartSulf.

Prosernat has expanded its range of process technologies through the acquisition of Germany's ITS Reaktortechnik. ITS owned a sulfur recovery technology developed by Linde in the 1980s, originally commercialized as Clinsulf, but later known as SmartSulf.

To date, the SmartSulf process has been employed mainly in upstream and downstream applications onshore. However, Prosernat sees strong potential for the development of offshore reservoirs with high levels of acidic gas, where the handling of hydrogen sulfide (H2S) has presented major problems for operating companies.

The process is designed to treat H2S in direct oxidation mode for conversion to sulfur. According to Vincent Simonneau, Prosernat's sulfur business development manager, SmartSulf can recover up to 99% of the sulfur content, and due to its free-of-flame concept, the equipment can be incorporated into the process facilities of an offshore production platform. Until now, sulfur recovery has been virtually impossible offshore. SmartSulf could also be used on a vessel and can tolerate fluctuations caused by waves. A typical footprint, Simonneau said, would be 3 m long x 6 m wide x 6 m high (9.8 x 19.7 x 19.7 ft). The system could be used to treat up to 20 MMcf/d (0.56 MMcm/d) of feed gas or amine acid gas in one train, he adds, producing commercial-grade sulfur that would be stored on the platform for subsequent offloading to a barge.

SmartSulf continuously removes the reaction heat generated by the Claus reaction directly in the catalyst bed rather than in a downstream heat exchanger. This maintains a fixed temperature throughout the catalyst bed close to the optimum for the chemical equilibrium, resulting in much higher sulfur recovery rates, Prosernat says. The heat exchanger comprises thermoplates with large clearances - the space in between the plates is filled with a catalyst, leading to efficient temperature control.

Feed gas containing a concentration of H2S (up to 15%) is mixed with a stoichiometric deficiency of air from an air blower. The gas mixture is heated and enters the catalytic reactor, which contains two catalyst beds. In the upper bed the catalyst converts one-third of the H2S to elemental sulfur, some sulfur dioxide (SO2), and water (H2O). The residual H2S and the SO2 react in the lower bed to form elemental sulfur, according to the Claus reaction.

The lower bed's heat exchanger cools the process gas at the outlet to a temperature close or slightly above the sulfur dew point. This shifts the chemical equilibrium toward more sulfur formation, maximizing sulfur recovery efficiency. Process gas exiting the reactor enters a sulfur condenser where the gas is cooled and liquid sulfur formed is separated out. If the H2S content of the feed gas leads to a reaction temperature that would become too high, a recycle blower can be installed, sending part of the product gas from the reactor outlet back to the pre-heater, with the residual gas routed to the consumer as product gas. •

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