Selexol is the trade name for an acid gas removal solvent that can separate

acid gas Acid gas is a particular typology of natural gas or any other gas mixture containing significant quantities of hydrogen sulfide (H2S), carbon dioxide (CO2), or similar acidic gases. A gas is determined to be acidic or not after it is mixed with w ...

es such as

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The und ...

and

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

from feed gas streams such as

synthesis gas Syngas, or synthesis gas, is a mixture of hydrogen and carbon monoxide, in various ratios. The gas often contains some carbon dioxide and methane. It is principly used for producing ammonia or methanol. Syngas is combustible and can be use ...

produced by

gasification Gasification is a process that converts biomass- or fossil fuel-based carbonaceous materials into gases, including as the largest fractions: nitrogen (N2), carbon monoxide (CO), hydrogen (H2), and carbon dioxide (). This is achieved by react ...

of coal, coke, or heavy

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...

oils. By doing so, the feed gas is made more suitable for

combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combust ...

and/or further processing. It is made up of dimethyl ethers of polyethylene glycol.{{cite journal , author1=M. Ajhar , author2=M. Travesset , author3=S. Yüce , author4=T. Melin , title = Siloxane removal from landfill and digester gas – A technology overview , year = 2010 , journal =

Bioresource Technology ''Bioresource Technology'' is a peer reviewed scientific journal published biweekly by Elsevier, covering the field of bioresource technology. The journal was established in 1979 as ''Agricultural Wastes'' and renamed to ''Biological Wastes'' in 19 ...

, volume = 101 , issue=9 , pages = 2913–2923 , doi= 10.1016/j.biortech.2009.12.018, pmid=20061140

Process description

In the Selexol process (now licensed by

UOP LLC Honeywell UOP, formerly known as UOP LLC or Universal Oil Products, is an American multi-national company developing and delivering technology to the petroleum refining, gas processing, petrochemical production, and major manufacturing industries. ...

), the Selexol solvent dissolves (absorbs) the

es from the feed gas at relatively high pressure, usually 300 to 2000 psia (2.07 to 13.8 MPa). The rich solvent containing the acid gases is then let down in pressure and/or steam stripped to release and recover the acid gases. The Selexol process can operate selectively to recover

and

as separate streams, so that the hydrogen sulfide can be sent to either a Claus unit for conversion to elemental

sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...

or to a

wet sulfuric acid process The wet sulfuric acid process (WSA process) is a gas desulfurization process. After Danish company Haldor Topsoe introduced this technology in 1987, it has been recognized as a process for recovering sulfur from various process gases in the form ...

unit for conversion to sulfuric acid while, at the same time, the carbon dioxide can be sequestered or used for

enhanced oil recovery Enhanced oil recovery (abbreviated EOR), also called tertiary recovery, is the extraction of crude oil from an oil field that cannot be extracted otherwise. EOR can extract 30% to 60% or more of a reservoir's oil, compared to 20% to 40% using ...

. The Selexol process is similar to the Rectisol process, which uses refrigerated methanol as the solvent. The Selexol solvent is a mixture of the

dimethyl ether Dimethyl ether (DME; also known as methoxymethane) is the organic compound with the formula CH3OCH3, (sometimes ambiguously simplified to C2H6O as it is an isomer of ethanol). The simplest ether, it is a colorless gas that is a useful precurs ...

s of

polyethylene glycol Polyethylene glycol (PEG; ) is a polyether compound derived from petroleum with many applications, from industrial manufacturing to medicine. PEG is also known as polyethylene oxide (PEO) or polyoxyethylene (POE), depending on its molecular w ...

. Selexol is a physical solvent, unlike amine based acid gas removal solvents that rely on a chemical reaction with the acid gases. Since no chemical reactions are involved, Selexol usually requires less energy than the amine based processes. However, at feed gas pressures below about 300 psia (2.07 MPa), the Selexol solvent capacity (in amount of acid gas absorbed per volume of solvent) is reduced and the amine based processes will usually be superior.

References

External links

Selexol Process
Chemical processes Acid gas control Natural gas Oil refining

Process description

See also

References

External links