. . . that's the classic dilemma with wet scrubbers. Sure, they're capable of removing soluble gases (such as H2S and SO2) from an exhaust stream, but then you have to contend with treating the acidic effluent prior to discharge or recycling. A better approach is to deploy a "dry" or "iron sponge" scrubber. Hydrated iron oxide on a carrier of wood fiber has been used for more than a hundred years to treat gas streams. The basic reaction is:
As you can see, iron oxide reacts with H2S, in the presence of moisture, to yield iron sulfide and water vapor. However, iron oxide would get so bound up with sulfur in the form of iron sulfide that it's efficiency would degrade relatively quickly. Fortunately, iron sulfide can be "regenerated" back into iron oxide with the addition of oxygen, as follows:
Introducing oxygen to the filter media converts iron sulfide to iron oxide and elemental sulfur. The regenerated iron oxide is then fully capable of capturing more H2S. The most efficient way to regenerate filter media is "offline"; that is, one filter vessel is active, while another is being regenerated. This is also the best option for processes that cannot tolerate oxygen, such as RNG upgrading.
Eventually, filter media accumulates enough elemental sulfur that it must be replaced. However, spent media is nonhazardous: it passes the U.S. EPA TCLP standards, is not "readily ignitable" per OSHA, and may be composted, land applied, or disposed of in any landfill.
Iron sponge scrubbers are available from a number of suppliers, but MV Technologies takes the concept a huge step further by adding biological agents to the media to remove numerous non-sulfur bearing species such as VOCs and readily biodegradable organic compounds. MV calls this enhanced media "BAM." BAM media also provides improved re-oxidation of the iron sulfide, which extends filter media life. For example, conventional iron oxide media has a loading capacity of about 0.12 lbs. of H2S per pound of media, while BAM offers a capacity for 0.29 lbs. of H2S per pound of media. This is an iron sponge scrubber on steroids and is why MV Technologies has retrofitted many competitor's systems to use BAM media.
Thus, this technology is usually the most cost effective solution for any H2S removal project for gas conditioning or odor control. Please make an appointment to talk to us for more information, or assistance with any ongoing CHP or H2S Removal applications.
George Voss is a Partner with TransEnergy LLC and Founder/President of Sustainability Business Management. George, a sustainability, distributed energy, & environmental expert, an innovative leader and entrepreneur, offering his expertise to help manufacturers, reps and distributors better understand customer benefits associated with their products/services and realize growth objectives.