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Hydrogen sulfide (H₂S) is a very toxic and pungent gas that causes problems in both the upstream and downstream oil and gas industry. The process of removing H₂S is known as gas sweetening, by either iron sponge H₂S scrubbers (forming [[iron sulfide]]) or chemical scavengers. Typical H₂S scavengers used in the oilfield are amine based chemicals<ref>Production chemicals for the oil and gas industry</ref>. They can be roughly categorized into regenerative and non-regenerative H₂S scavengers. ==Regenerative H2S scavengers== ===Chemicals=== In large production facilities, the most economic solution to remove H₂S in the gas process stream is to install a regenerative system for treating the sour gas<ref>M. Pandey, SPE, Oil and Natural Gas Corp. Ltd. , Process Optimization in Gas Sweetening Unit - A Case Study, International Petroleum Technology Conference, 21-23 November 2005, Doha, Qatar</ref>. After absorbing the H₂S, the chemical is then regenerated, usually by heating and reused in the system. The separated H₂S is treated by a modified [[Claus process]] to form elemental sulfur. Several types of amine solutions can be used as the absorbent depending on the sour gas specifications. Typical amines are: *[[Ethanolamine|Monoethanolamine(MEA)]] *[[Diethanolamine|Diethanolamine (DEA)]] *[[Methyl_diethanolamine|N-methyldiethanolamine (MDEA)]] *[[Diisopropylamine]] *[[Diglycolamine (DGA)]], ''also known as 2-(2-aminoethoxy)ethanolamine'' Most modern amine gas sweetening processes are MDEA-based, which typically only absorbs H₂S. MEA, DEA and DGA typically absorb other acid gases as well (i.e. CO₂) besides H₂S. ===Application processes=== [[Amine gas treating]] can be utilized to remove H₂S in the gas stream. ==Non-regenerative H2S scavengers== ===Chemicals=== [[File:Triazine_isomers.png|frame|right|Triazine]] This type of scavenger can be divided into the following categories<ref>T. Salma, M.L. Briggs, Baker Petrolite; D.T. Herrmann, E.K. Yelverton, British Petroleum , "Hydrogen Sulfide Removal from Sour Condensate Using Non-Regenerable Liquid Sulfide Scavengers: A Case Study", SPE Rocky Mountain Petroleum Technology Conference, 21-23 May 2001, Keystone, Colorado</ref>. Triazine scavengers are the most commonly used<ref>Yaser K. Al-Duailej, Saleh H. Al-Mutairi, and Adel Y. Al-Humaidan, SPE, Saudi Aramco Oil Company, "Evaluation of Triazine-Based H2S Scavengers for Stimulation Treatments", SPE/DGS Saudi Arabia Section Technical Symposium and Exhibition, 4-7 April 2010, Al-Khobar, Saudi Arabia</ref>. *[[Triazine]] - alkaline and can cause carbonate scaling *Solid scavengers (generally zinc or iron based materials) *Oxidizing chemicals (e.g. NaClO₂, NaBrO₃, NaNO₂, etc.) *[[Aldehydes]] **[[Glyoxal]] - can be applied in neutral, acidic, and alkaline conditions *Metal carboxylates and chelates **Both water and oil soluble high valence metal chelates have been used as H₂S scavengers for treating drilling fluids and contaminated water and oil streams. ===Application processes=== Non-generative H₂S scavengers are typically applied via a in-line injection quail to finely disperse the liquid chemical into the gas stream to maximize reaction. ==Lessons learned== *H₂S scavenger increases the pH of the water and can cause severe carbonate scale<ref>Meiliza Sumestry, SPE and Hendy Tedjawidjaja, PT Medco E&P Indonesia, " Case Study : Calcium Carbonate Scale Inhibitor Performance Degradation due to H₂S Scavenger Injection in Semoga Field", North Africa Technical Conference and Exhibition, 20-22 February 2012, Cairo, Egypt</ref>. *Over-reacted H₂S scavenger can form polymeric sulfar deposit<ref>Susan R. Schieman / HCI Travis, Solids-Free HS Scavenger Improves Performance and Operational Flexibility, SPE International Symposium on Oilfield Chemistry, 16-19 February 1999, Houston, Texas</ref>. *Performance of H₂S scavenger can be improved by increasing resident time or adding a static mixer<ref>J.G.R. Eylander, H.A. Holtman, Nederlandse Aardolie Maatschappij; T. Salma, M. Yuan, M. Callaway, J.R. Johnstone, Baker Petrolite, The Development of Low-Sour Gas Reserves Utilizing Direct-Injection Liquid Hydrogen Sulphide Scavengers, SPE Annual Technical Conference and Exhibition, 30 September-3 October 2001, New Orleans, Louisiana</ref>. *The dosage of H₂S scavenger is calculated based on the amount of sulfur to be removed. ==Reference== <references /> [[Category:Production Chemistry]] [[Category:Oilfield Chemicals]]

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