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H2S removal Process Explained

Posted by Antony Thomas at Monday, October 31, 2011

 H2S removal Process

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,

ironchelate 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 auto circulation 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 sulfi de 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.

Installations: Presently, 160 licensed units are in operation with four

units under construction.

Reference: Heguy, D. L. and G. L. Nagl, “Consider optimized Iron-Redox

processes to remove sulfur,” Hydrocarbon Processing, January 2003, pp.


Licensor: Gas Technology Products LLC, a Merichem Co.


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