Stretford reactor Sonoma Calpine 3 Plant 4790

The Stretford process was developed during the late 1950s to remove

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 unde ...

(H₂S) from

town gas Coal gas is a flammable gaseous fuel made from coal and supplied to the user via a piped distribution system. It is produced when coal is heated strongly in the absence of air. Town gas is a more general term referring to manufactured gaseous ...

. It was the first liquid phase, oxidation process for converting H₂S into sulfur to gain widespread commercial acceptance. Developed by Tom Nicklin of the

North Western Gas Board The North Western Gas Board was a state-owned utility area gas board providing gas for light and heat to industries and homes in the north-west of England. It was established on 1 May 1949 under the terms of the Gas Act 1948, and dissolved in 197 ...

(NWGB) and the

Clayton Aniline Company The Clayton Aniline Company Ltd. was a British manufacturer of dyestuffs, founded in 1876 by Charles Dreyfus in Clayton, Manchester. Early history Charles Dreyfus was a French emigrant chemist and entrepreneur, who founded the Clayton Aniline Co ...

, in

Manchester Manchester () is a city in Greater Manchester, England. It had a population of 552,000 in 2021. It is bordered by the Cheshire Plain to the south, the Pennines to the north and east, and the neighbouring city of Salford to the west. The t ...

, England, the name of the process was derived from the location of the NWGB's laboratories, in

Stretford Stretford is a market town in Trafford, Greater Manchester, England. It is situated on flat ground between the River Mersey and the Manchester Ship Canal, south of Manchester city centre, south of Salford and north-east of Altrincham. Str ...

. The process uses reduction-oxidation (

redox Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction ...

) chemistry to oxidise the H₂S into elemental sulfur, in an alkaline solution containing

vanadium Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer ( pas ...

as an oxygen carrier. The process earned the NWGB a

Queen's Award to Industry The Queen's Awards for Enterprise is an awards programme for British businesses and other organizations who excel at international trade, innovation, sustainable development or promoting opportunity (through social mobility). They are the highest ...

in 1968. Although it was used in the gas industry for only a relatively short time, the process was licensed by the NWGB and used successfully in a variety of industries worldwide. At the height of its popularity during the 1970s there were more than a dozen companies offering the Stretford technology. By 1987 about 170 Stretford plants had been built worldwide, and more than 100 were still operating in 1992, capable of removing 400,000 tons of sulfur per year. The first US plant was commissioned in 1971 at

Long Beach, California Long Beach is a city in Los Angeles County, California. It is the 42nd-most populous city in the United States, with a population of 466,742 as of 2020. A charter city, Long Beach is the seventh-most populous city in California. Incorporate ...

See also

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