The Shell–Paques process, also known by the trade name of Thiopaq O&G,
is a gas
desulfurization Desulfurization or desulphurisation is a chemical process for the removal of sulfur from a material. This involves either the removal of sulfur from a molecule (''e.g.'' A=S → A:) or the removal of sulfur compounds from a mixture such as oil refin ...
technology for the removal of
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 ...
from natural-, refinery-, synthesis- and
biogas
Biogas is a mixture of gases, primarily consisting of methane, carbon dioxide and hydrogen sulphide, produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste and food waste. I ...
. The process was initially named after the
Shell Oil
Shell plc is a British multinational oil and gas company headquartered in London, England. Shell is a public limited company with a primary listing on the London Stock Exchange (LSE) and secondary listings on Euronext Amsterdam and the New ...
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
Sulfide (British English also 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 l ...
into 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 ...
. 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
The Claus process is the most significant gas desulfurizing process, recovering elemental sulfur from gaseous hydrogen sulfide. First patented in 1883 by the chemist Carl Friedrich Claus, the Claus process has become the industry standard.
The ...
.
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 (H
2S) from the
sour gas
Sour gas is natural gas or any other gas containing significant amounts of hydrogen sulfide (H2S).
Natural gas is usually considered sour if there are more than 5.7 milligrams of H2S per cubic meter of natural gas, which is equivalent to approxim ...
according to:
:H
2S + NaOH → NaHS + H
2O
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 O
2 → S + NaOH
Combined reaction equation:
:H
2S + ½ O
2 → S + H
2O
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
''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, b ...
'' in the bioreactor. These natural, living microorganisms present in the bioreactor catalyse the sulfur conversions and are, by their nature, resilient and adaptive.
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
Sulfidation (British spelling also sulphidation) is a process of installing sulfide ions in a material or molecule. The process is widely used to convert oxides to sulfides but is also related to corrosion and surface modification.
Inorganic, mate ...
,
LPG, hydrotreater offgas and fuel gas.
See also
*
Flue-gas desulfurization
Flue-gas desulfurization (FGD) is a set of technologies used to remove sulfur dioxide () from exhaust flue gases of fossil-fuel power plants, and from the emissions of other sulfur oxide emitting processes such as waste incineration.
Methods
...
References
{{DEFAULTSORT:Shell-Paques process
Industrial processes
Shell plc