Shell–Paques process

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The Shell–Paques process, also known by the trade name of Thiopaq O&G, [1] is a gas desulfurization technology for the removal of hydrogen sulfide from natural-, refinery-, synthesis- and biogas. The process was initially named after the Shell Oil and Paques purification companies. After accession of a dedicated joint venture by the founders, Paqell B.V., the trade name for applications in the Oil & Gas industry was changed to "THIOPAQ O&G". It is based on the biocatalytical conversion of sulfide into elemental sulfur. It operates at near-ambient conditions of temperature, about 30-40 °C, and pressure which results in inherent safety. It is an alternative to, for example, the Claus process.

Hydrogen sulfide Poisonous, corrosive and flammable gas

Hydrogen sulfide is the chemical compound with the formula H
2
S
. It is a colorless chalcogen hydride gas with the characteristic foul odor of rotten eggs. It is very poisonous, corrosive, and flammable.

Biogas mixture of different gases produced by the breakdown of organic matter in the absence of oxygen

Biogas refers to a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen. Biogas can be produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste or food waste. Biogas is a renewable energy source.

Sulfide salt or other derivative of hydrogen sulfide or organic compound having the structure RSR (R ≠ H)

Sulfide (British English sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. Sulfide also refers to chemical compounds large families of inorganic and organic compounds, e.g. lead sulfide and dimethyl sulfide. Hydrogen sulfide (H2S) and bisulfide (SH-) are the conjugate acids of sulfide.

Contents

Process chemistry

Each reaction can be applied individually or sequentially as dictated by the characteristics of the stream to be treated. The process consist of three main sections: An absorber (gas washing section), a bioreactor (sulfide oxidation and regeneration of washing liquid) and Sulfur handling section as shown in the figure below:

The washing step uses a dilute alkaline solution to remove hydrogen sulfide (H2S) from the sour gas according to:

Sour gas is natural gas or any other gas containing significant amounts of hydrogen sulfide (H2S).

H2S + NaOH → NaHS + H2O

The loaded washing liquid is transported to a bioreactor where a biocatalyst oxidises the aqueous NaHS to elemental sulfur with about 95% selectivity according to:

NaHS + ½ O2 → S + NaOH

Combined reaction equation:

H2S + ½ O2 → S + H2O

The regenerated washing liquid is sent back to the washing column.

The controlled partial oxidation of sulfide to elemental sulfur (2) is catalyzed by naturally occurring microorganisms of the genus Halothiobacillus in the bioreactor. These natural, living microorganisms present in the bioreactor catalyse the sulfur conversions and are, by their nature, resilient and adaptive.

Halothiobacillus is a genus in the Gammaproteobacteria. Both species are obligate aerobic bacteria; they require oxygen to grow. They are also halotolerant; they live in environments with high concentrations of salt or other solutes, but don't require them in order to grow.

In many situations the process can be used for sulfur removal and recovery. When sulfur recovery is desired, the elemental sulfur produced in the aerobic bioreactor will be separated from the aqueous effluent in a separator inside of the reactor. The excess sulfur will be removed as aqueous slurry or cake of up to 65% dry solids content. There are several options for handling this slurry and to convert it into products for sulfuric acid generation, fertiliser or fungicide.

The system is flexible and has several processing options that have ready application in the petroleum refinery or petrochemical complex for managing a variety of sulfur-containing streams including sulfidic caustic, LPG, hydrotreater offgas and fuel gas.

Liquefied petroleum gas chemical compound

Liquefied petroleum gas or liquid petroleum gas, also referred to as simply propane or butane, are flammable mixtures of hydrocarbon gases used as fuel in heating appliances, cooking equipment, and vehicles.

See also

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