Sulfur Recovery Info

The right sulfur recovery process is the least expensive process that will reliably achieve the required sulfur recovery efficiency. The sulfur recovery efficiency required for a given plant is almost always dictated by environmental regulations, which vary from state to state and from country to country. Most environmental regulations use a sliding scale for recovery efficiency that is based on the size of the sulfur recovery plant (a notable exception being the U.S. EPA regulations for sulfur plants in petroleum refineries), with larger plants requiring higher recovery efficiencies to minimize the amount of sulfur dioxide (SO2) emitted to the local area. Some regulations also consider the acid gas quality in setting the required recovery efficiency, acknowledging the greater expense in recovering sulfur from dilute and/or contaminated acid gas streams.

The discussions below are intended to give a general idea of the recovery capabilities of the sulfur recovery processes offered by Ortloff. Since the recovery efficiency of these processes is extremely dependent on the nature of the acid gas stream to be processed and other factors specific to each plant location, contact Ortloff for information regarding a specific application. The Sulfur Recovery Information Checklist lists the data needed by Ortloff for an evaluation. Budget quality pricing information can also be obtained quickly by contacting Ortloff.

Large SRU/TGCU Plant

Modified Claus Process

The modified Claus process is the workhorse in sulfur recovery, and is used worldwide in more plants than any other process. In the typical modified Claus process, the acid gas feed is partially oxidized to generate sulfur dioxide, which then reacts with the remaining hydrogen sulfide (H2S) over a catalyst to produce sulfur. Most Claus sulfur plants contain two or three catalytic stages and can achieve 94-97% sulfur recovery efficiency. The Claus process is usually followed by a Tailgas Thermal Oxidizer to incinerate all of the sulfur compounds in the sulfur plant tailgas to SO2 before dispersing the effluent to the atmosphere. Claus plant sulfur is normally of very high quality, “Texas bright” and free of contaminants.

Detailed process information is available on the Modified Claus Process page.

2Cold Bed Adsorption Process

The conventional Claus sulfur recovery process is limited by reaction equilibrium considerations to sulfur recoveries in the range of 94-97%. For applications requiring an intermediate level (97.5-99.5%) of sulfur recovery, the so-called “sub-dewpoint” Claus process can be used. This process extends the capability of the Claus process by operating the Claus reaction at a lower temperature, so that the sulfur produced by the reaction condenses. Since the Claus reaction occurs in the gas phase, this liquid sulfur does not inhibit the reaction like sulfur vapor does, resulting in a favorable shift in the reaction equilibrium and higher sulfur conversion.

Amoco Corporation developed and licenses the most widely used sub-dewpoint Claus process, the Cold Bed Adsorption (CBA) sulfur recovery process. Ortloff has completed a number of CBA projects, with additional plants currently under construction. The application of Ortloff’s proprietary know-how and design features in key areas of these plants have allowed them to be, without question, the most successful CBA process sulfur recovery plants installed and operated to date. The CBA process is a cyclic process that employs switching valves in very demanding sulfur vapor services that have typically caused significant operation and maintenance problems in all other CBA plants. Ortloff’s proprietary Sulfur Vapor Valve Assemblies have functioned flawlessly without operational or leakage problems in the CBA plants designed by Ortloff.

Detailed process information is available on the Cold Bed Adsorption Process page.

3Modified Claus Process with Tailgas Cleanup

In applications where a high level (more than 99.5%) of overall sulfur recovery is required, Ortloff has chosen to employ the modified Claus process coupled with an amine-based tailgas cleanup process. We believe this process is the best widely-proven technology available in the industry for achieving overall sulfur recovery performance up to 99.9%. Ortloff has performed the detailed process engineering, specification, and design of more than fifteen amine-based tailgas cleanup units.

The tailgas cleanup process reduces all of the sulfur compounds in the tailgas leaving the front-end Claus sulfur plant back to hydrogen sulfide, then uses selective amine absorption to remove the H2S while allowing most of the carbon dioxide (CO2) to “slip” by. The H2S and CO2 removed by the amine are stripped from the amine and recycled back to the Claus plant, allowing an overall sulfur recovery in excess of 99.5%. Depending on the performance required, the effluent from the tailgas cleanup unit can contain as little as 10 PPM of H2S. This effluent is normally routed to a Tailgas Thermal Oxidizer to incinerate the H2S and any other remaining sulfur compounds to SO2 before dispersion to the atmosphere.

Detailed process information is available on the Modified Claus Process with Tailgas Cleanup page.