Application: Removal of hydrogen sulfide (H2S) from a large range of gas streams giving a sulfur production of 0.1–20 tpd. Gas applications include: natural gas, amine tail gas, enhanced oil recovery CO2 recycle, refinery gases, geothermal, syngas, offshore production gas, digester offgas and offgas from wastewater treatment plants. The full range of H2S concentrations (from a few ppmv to almost 100%v of H2S) can be treated to 1 ppmv H2S. Turndown properties—both on H2S concentration and total gas flow—are very good, and the process shows excellent flexibility. If gas flows become too large (in excess of 10 million Nm3/d) the combination of an amine unit coupled to a SulFerox unit becomes more economical. The sulfur product can be obtained as a filter cake or alternatively as molten sulfur of high quality. The sulfur cake can be land filled as a nonhazardous waste or-depending on local regulations-directly used as a fertilizer.
SulFerox is a redox-based process that converts H2S in sour gas to elemental sulfur (S) in the contactor through reaction with a proprietary aqueous ferric iron chelate solution. Various contactor types are available, such as sparged towers, spray towers and pipeline contactors. The sparged tower is the most versatile contactor and will be selected whenever pressure drop allows. After contacting the sour gas and SulFerox solution in the (sparged tower) contactor, the gas/liquid mixture is separated. In the separator, the solution and treated gas is separated yielding the treated sweet gas—leaving the unit via an optional knockout vessel—and the depleted SulFerox solution.
After optional degassing, the reduced iron chelate solution is regenerated via reaction of Fe2+ back to Fe3+
with oxygen from an air source in the regenerator vessel. Via a thickener vessel, part of the solution is sent for filtration and sulfur recovery; the major portion of the stream is returned to the contactor.
In addition, the resulting filtrate is returned to the process for maximum solution recovery, thus, optimally using the chelate solution. Depending on the feed gas conditions, the contactor and separator can be combined in one vessel as can be done with the regenerator and surge vessel. This gives a two-vessel configuration suited for amine regenerator offgas.
Operating conditions: Operating pressures vary from just over atmospheric to 500 psig. The SulFerox process itself operates at temperatures of 110°F–140°F. However, the feed gas temperature can be between 75°F–130°F. The feed gas must be free of hydrocarbon liquids. Gas at other conditions may need pretreatment first (cooling, dew pointing). Although the applicability of the SulFerox process is very wide, some feed gas contaminants such as high levels of NH3, HCN and SO2 might affect the economics of the process.
Licensor: Shell Global Solutions International B.V.
