H2S Removal LO-CAT Process by Merichem Chemicals & Refinery Services

Application: LO-CAT removes H2S from gas streams and produces elemental sulfur. LO-CAT units are in service treating refinery fuel gas, hydrodesulfurization offgas, sour-water-stripper gas, amine acid gas, claus tail gas and sulfur tank vent gas. Sulfur capacities are typically less than 25 ltpd down to several pounds per day. Key benefits of operation are high (99.9%) H2S removal efficiency, and flexible operation, with virtually 100% turndown capability of H2S composition and total gas flow. Sulfur is recovered as a slurry, filter cake or high-purity molten sulfur. The sulfur cake is increasingly being used in agriculture, but can also be deposited in a nonhazardous landfill.

Description: The conventional configuration is used to process combustible gas and product gas streams. Sour gas contacts the dilute, proprietary, iron chelate catalyst solution in an absorber (1), where the H2S is absorbed and oxidized to solid sulfur. Sweet gas leaves the absorber for use by the refinery. The reduced catalyst solution returns to the oxidizer (2), where sparged air reoxidizes the catalyst solution. The catalyst solution is returned to the absorber. Continuous regeneration of the catalyst solution allows for very low chemical operating costs.

In the patented autocirculation configuration, the absorber (1) and oxidizer (2) are combined in one vessel, but separated internally by baffles. Sparging of the sour gas and regeneration air into the specially designed baffle system creates a series of “gas lift” pumps, eliminating the external circulation pumps. This configuration is ideally suited for treating amine acid gas and sour-water-stripper gas streams.

In both configurations, sulfur is concentrated in the oxidizer cone and sent to a sulfur filter, which can produce filter cake as high as 85% sulfur. If desired, the filter cake can be further washed and melted to produce pure molten sulfur.

Operating conditions: Operating pressures range from vacuum conditions to 1,000 psi. Operating temperatures range from 40°F to 140°F. Hydrogen sulfide concentrations range from a few ppm to 100%. Sulfur loadings range from a few pounds per day to 25+ tons per day. No restrictions on type of gas to be treated; however, some contaminants, such as SO2, may increase operating costs.

Licensor: Merichem Chemicals & Refinery Services LLC, Gas Technology Products Division.