Pelletized and powdered iron hydroxide for hydrogen sulfide control: a solid H₂S scavenger for biogas, landfill gas, and other sulfur-bearing streams, supplied in bulk with the equipment and technical support to run it.
H₂S removal media is a solid, reactive medium that takes hydrogen sulfide (H₂S) out of a gas stream, or out of the anaerobic process that generates it, by binding the sulfur to a metal. Interra Global's media is iron hydroxide, iron(III) oxide-hydroxide, FeO(OH). The iron binds hydrogen sulfide chemically, as iron sulfide, rather than holding it by physical adsorption, and when a small amount of oxygen is present the iron sulfide converts to elemental sulfur and reactive iron hydroxide is restored, so the media keeps working through many cycles before it is spent. Interra Global supplies it in bulk in two forms: FerroSorp® pellets, loaded into gas-phase vessels, and iron hydroxide powders, FerroSorp DGR and the house-brand iSORB IronMaxx, dosed directly into anaerobic digesters. H₂S removal media in pellet form is a solid H₂S scavenger, typically the choice for hydrogen sulfide removal where the gas is wet and variable and the operator wants sulfur control that does not depend on biological activity or liquid chemical handling. Because the reaction converts captured sulfide to elemental sulfur and restores the iron, a pellet bed typically carries far more sulfur per changeout than a liquid scavenger or a non-regenerating solid, and the powders act ahead of the gas phase altogether, binding sulfur in the digestate before sulfate-reducing bacteria turn it into hydrogen sulfide. Method comparison, including liquid scrubbing, biological treatment, and chemical dosing, is on the hydrogen sulfide removal page; this page covers the media. PELLETS AND POWDERS FerroSorp SK. Pelletized iron hydroxide for gas-phase desulfurization in fixed and moving bed vessels, produced with granulating and drying methods that give the pellet high form stability, abrasion hardness, and reactivity. SK is the grade Interra Global typically supplies for wet, variable gas such as raw biogas and landfill gas. Properties and documents are on the FerroSorp SK product page. FerroSorp SLH. The second FerroSorp pellet grade for gas-phase desulfurization, based on the same iron hydroxide chemistry and produced with the same granulating and drying methods. Properties and documents are on the FerroSorp SLH product page. FerroSorp DGR. Iron hydroxide powder, dosed into the digester feedstock rather than loaded into a vessel: its fine particle size and high iron content bind sulfur in the digestate before it leaves the digester as hydrogen sulfide in the biogas, which lowers the sulfide load on everything downstream. Properties and documents are on the FerroSorp DGR product page. iSORB IronMaxx. The house-brand iron desulfurization powder, developed for the North American market with high iron content and a low level of non-iron byproducts, suitable for most digester types and dosed through Interra Global's automated powder-to-slurry dosing system where dust-free handling is wanted. Properties and documents are on the iSORB IronMaxx product page. HOW IRON HYDROXIDE REMOVES HYDROGEN SULFIDE The chemistry is the same in both forms. In the gas phase, hydrogen sulfide reacts with iron hydroxide to form iron sulfide and water. With a small amount of oxygen in the stream, the iron sulfide then converts to elemental sulfur, which stays in the pellet, and the iron returns to its hydroxide form to react again. That regeneration is what gives the media its loading: sulfur accumulates in the pellet pores across many cycles, and the bed is changed out when the accumulated sulfur blocks access to the iron. Both reactions release heat, and the regeneration reaction releases considerably more than the capture reaction, which is why gas moisture and oxygen are managed in service and why a changeout follows the manufacturer's procedure. In the digester, the powder binds sulfur before it can leave as hydrogen sulfide in the biogas, and the iron sulfide it forms leaves with the digestate instead of entering the gas. H₂S SCAVENGERS AND WHERE SOLID MEDIA FITS An H₂S scavenger is a chemical that removes hydrogen sulfide from a gas or a liquid by reacting with it. Liquid scavengers react the sulfide to a product that leaves in the spent liquid, which is replenished as it is used up; solid scavengers hold the sulfur in a bed of media that the gas passes through, and the bed is changed out when it is spent. FerroSorp pellets are a solid scavenger: the sulfur stays in the pellet as elemental sulfur and leaves the site as a solid at changeout, rather than as a liquid waste stream. Where the gas is wet and its flow and sulfide concentration vary, as in biogas and landfill gas, solid iron media are typically better suited to the duty than liquid scavengers. MEDIA, VESSELS, AND ADDITIVES H₂S removal media sits in the middle of a line that runs from the digester to the gas outlet. The powders and Interra Global's digester additives go into the process, correcting conditions inside an operating digester; the pellets go into a gas-phase vessel downstream, treating the stream after it leaves. The Vacuum Adsorption Vessel is the bulk media vessel built for the pellets, loaded through top manways and emptied through a dump door at changeout, and the Automated Powder-to-Slurry Dosing System converts the powders to slurry under integrated controls. Media, vessel, dosing equipment, and additives for a digester therefore come from one supplier on one purchase order, and Interra Global reviews operating conditions and provides performance estimates across them on request. TYPICAL APPLICATIONS
SELECTING A PRODUCT Selection typically starts with where the sulfur is to be taken out: in the gas stream, which calls for pellets in a vessel, or in the digester itself, which calls for a powder dosed into the feedstock. For pellets, the inlet H₂S concentration, gas flow, moisture, oxygen availability, and the outlet target set the bed size and the changeout interval, and the grade follows the stream. For powders, feedstock composition, digester type, and current sulfide levels set the dosing rate. Each product page carries the properties and documents for its grade, and Interra Global's technical staff review the operating conditions and recommend a fit when called on, including bed sizing and an estimate of changeout frequency. Every product is supplied in bulk, from bag lots to full container loads, and unlisted grades or sizes are quoted on request. FREQUENTLY ASKED QUESTIONS What is H₂S removal media? A solid medium that takes hydrogen sulfide out of a gas stream, or out of the digester that produces it, by chemical reaction rather than physical adsorption. Interra Global's is iron hydroxide, supplied as FerroSorp pellets for gas-phase vessels and as FerroSorp DGR and iSORB IronMaxx powders for dosing into anaerobic digesters; it is typically the solid medium of choice for hydrogen sulfide control in biogas and landfill gas systems. How does iron hydroxide remove hydrogen sulfide? Hydrogen sulfide reacts with the iron hydroxide to form iron sulfide. With a small amount of oxygen present, the iron sulfide converts to elemental sulfur and the iron hydroxide is restored, so the same iron captures sulfur many times over before the bed is spent. The mechanism section above walks through it. Is H₂S removal media an H₂S scavenger? Yes. A scavenger is any chemical that removes hydrogen sulfide by reacting with it, and iron hydroxide pellets are a solid scavenger: the sulfur stays in the bed as elemental sulfur and leaves at changeout. Liquid scavengers carry the sulfur away in the spent liquid instead. The scavenger section above sets out the difference. Is FerroSorp the same as iron sponge? No. Iron sponge is the traditional iron-based medium, hydrated iron oxide carried on wood chips or a similar support. FerroSorp is a manufactured iron hydroxide pellet. Both rely on iron chemistry to remove hydrogen sulfide. How much sulfur can the media hold before it is changed out? It depends on the gas: moisture, oxygen availability, inlet concentration, pressure, and residence time in the bed all move the number, which is why the loading is estimated per site rather than quoted as a single figure. The product data sheet gives the reference range for each grade, and Interra Global estimates the changeout interval for a given stream on request. Does the media need oxygen or moisture to work? The capture reaction needs the gas to carry moisture, and the regeneration reaction needs a small amount of oxygen. Most biogas and landfill gas streams supply the moisture; oxygen is commonly present in landfill gas and is dosed as a small air bleed in digester gas where it is not. The manufacturer's application guidance gives the operating ranges, and running outside them costs loading. Can the powder be used instead of a vessel? It depends on the feedstock and the outlet specification the gas must meet. Dosing powder into the digester lowers the sulfide that reaches the gas; whether a pellet bed is also needed downstream is assessed per site, and Interra Global reviews the operating conditions on request. What happens to the media when it is spent? Spent pellets carry the sulfur they captured as elemental sulfur, with the remaining iron; a grey coating on the pellets is the visible sign that the bed is saturated. The bed is changed out following the manufacturer's procedure, because spent media exposed to air can continue to react and warm, and the spent material is handled according to its safety data sheet and local rules for the material and the sulfur it carries. Is H₂S removal media hazardous? The safety data sheet for each grade gives its classification and handling requirements. The operating hazard in service is heat: the regeneration reaction is exothermic, so a bed opened to air at changeout, or a vessel with a leak, can warm quickly if the oxygen and moisture conditions are not managed. The changeout guidelines on the equipment and product pages cover the procedure. |
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