Syngas,orsynthesis gas,is a mixture ofhydrogenandcarbon monoxide,[1]in various ratios. The gas often contains somecarbon dioxideandmethane.It is principally used for producingammoniaormethanol.Syngas is combustible and can be used as a fuel.[2][3][4]Historically, it has been used as a replacement forgasoline,when gasoline supply has been limited; for example,wood gaswas used to power cars in Europe duringWWII(in Germany alone half a million cars were built or rebuilt to run on wood gas).[5]
Production
editSyngas is produced bysteam reformingorpartial oxidationof natural gas or liquid hydrocarbons, orcoalgasification.[6]
C + H2O → CO + H2[1]
CO + H2O → CO2+ H2[1]
C + CO2→ 2CO[1]
Steam reforming of methane is anendothermic reactionrequiring 206 kJ/mol of methane:
- CH4+ H2O → CO + 3 H2
In principle, but rarely in practice,biomassand related hydrocarbon feedstocks could be used to generatebiogasandbiocharinwaste-to-energygasification facilities.[7]The gas generated (mostly methane and carbon dioxide) is sometimes described assyngasbut its composition differs from syngas. Generation of conventional syngas (mostly H2and CO) from waste biomass has been explored.[8][9]
Composition, pathway for formation, and thermochemistry
editThe chemical composition of syngas varies based on the raw materials and the processes. Syngas produced by coal gasification generally is a mixture of 30 to 60% carbon monoxide, 25 to 30% hydrogen, 5 to 15% carbon dioxide, and 0 to 5% methane. It also contains lesser amount of other gases.[10]Syngas has less than half theenergy densityofnatural gas.[11]
The first reaction, between incandescent coke and steam, is strongly endothermic, producing carbon monoxide (CO), and hydrogenH
2(water gasin older terminology). When the coke bed has cooled to a temperature at which the endothermic reaction can no longer proceed, the steam is then replaced by a blast of air.
The second and third reactions then take place, producing anexothermic reaction—forming initially carbon dioxide and raising the temperature of the coke bed—followed by the second endothermic reaction, in which the latter is converted to carbon monoxide. The overall reaction is exothermic, forming "producer gas" (older terminology). Steam can then be re-injected, then air etc., to give an endless series of cycles until the coke is finally consumed. Producer gas has a much lower energy value, relative to water gas, due primarily to dilution with atmospheric nitrogen. Pure oxygen can be substituted for air to avoid the dilution effect, producing gas of much highercalorific value.
In order to produce more hydrogen from this mixture, more steam is added and thewater gas shiftreaction is carried out:
- CO + H2O → CO2+ H2
The hydrogen can be separated from the CO2bypressure swing adsorption(PSA),amine scrubbing,andmembrane reactors.A variety of alternative technologies have been investigated, but none are of commercial value.[12]Some variations focus on new stoichiometries such as carbon dioxide plus methane[13][14]or partialhydrogenationof carbon dioxide. Other research focuses on novel energy sources to drive the processes including electrolysis, solar energy, microwaves, and electric arcs.[15][16][17][18][19][20]
Electricity generated fromrenewable sourcesis also used to process carbon dioxide and water into syngas throughhigh-temperature electrolysis.This is an attempt to maintaincarbon neutralityin the generation process.Audi,in partnership with company named Sunfire, opened a pilot plant in November 2014 to generatee-dieselusing this process.[21]
Syngas that is not methanized typically has a lower heating value of 120 BTU/scf.[22]Untreated syngas can be run in hybrid turbines that allow for greater efficiency because of their lower operating temperatures, and extended part lifetime.[22]
Uses
editSyngas is used as a source of hydrogen as well as a fuel.[12]It is also used to directly reduceiron oretosponge iron.[23]Chemical uses include the production ofmethanolwhich is a precursor toacetic acidand many acetates; liquid fuels andlubricantsvia theFischer–Tropsch processand previously theMobilmethanol to gasolineprocess;ammoniavia theHaber process,which converts atmospheric nitrogen (N2) into ammonia which is used as afertilizer;andoxo alcoholsvia an intermediate aldehyde.
See also
edit
References
edit- ^abcdSpeight, James G. (2002).Chemical and process design handbook.McGraw-Hill handbooks. New York, NY: McGraw-Hill. p. 566.ISBN978-0-07-137433-0.
- ^"Syngas Cogeneration / Combined Heat & Power".Clarke Energy.Archivedfrom the original on 27 August 2012.Retrieved22 February2016.
- ^Mick, Jason (3 March 2010)."Why Let it go to Waste? Enerkem Leaps Ahead With Trash-to-Gas Plans".DailyTech.Archived fromthe originalon 4 March 2016.Retrieved22 February2016.
- ^Boehman, André L.; Le Corre, Olivier (15 May 2008). "Combustion of Syngas in Internal Combustion Engines".Combustion Science and Technology.180(6): 1193–1206.doi:10.1080/00102200801963417.S2CID94791479.
- ^"Wood gas vehicles: firewood in the fuel tank".LOW-TECH MAGAZINE.Archivedfrom the original on 2010-01-21.Retrieved2019-06-13.
- ^Beychok, Milton R. (1974)."Coal gasification and the Phenosolvan process"(PDF).Am. Chem. Soc., Div. Fuel Chem., Prepr.; (United States).19(5).OSTI7362109.S2CID93526789.Archived fromthe original(PDF)on 3 March 2016.
- ^"Sewage treatment plant smells success in synthetic gas trial - ARENAWIRE".Australian Renewable Energy Agency.11 September 2019.Archivedfrom the original on 2021-03-07.Retrieved2021-01-25.
- ^Zhang, Lu; et al. (2018). "Clean synthesis gas production from municipal solid waste via catalytic gasification and reforming technology".Catalysis Today.318:39–45.doi:10.1016/j.cattod.2018.02.050.ISSN0920-5861.S2CID102872424.
- ^Sasidhar, Nallapaneni (November 2023)."Carbon Neutral Fuels and Chemicals from Standalone Biomass Refineries"(PDF).Indian Journal of Environment Engineering.3(2): 1–8.doi:10.54105/ijee.B1845.113223.ISSN2582-9289.S2CID265385618.Retrieved29 December2023.
- ^"Syngas composition".National Energy Technology Laboratory, U.S. Department of Energy.Archivedfrom the original on 27 March 2020.Retrieved7 May2015.
- ^Beychok, M R (1975).Process and environmental technology for producing SNG and liquid fuels.Environmental Protection Agency.OCLC4435004117.OSTI5364207.[page needed]
- ^abHiller, Heinz; Reimert, Rainer; Stönner, Hans-Martin (2011). "Gas Production, 1. Introduction".Ullmann's Encyclopedia of Industrial Chemistry.doi:10.1002/14356007.a12_169.pub3.ISBN978-3527306732.
- ^"dieBrennstoffzelle.de - Kvaerner-Verfahren".diebrennstoffzelle.de.Archivedfrom the original on 2019-12-07.Retrieved2019-12-17.
- ^EU patent 3160899B1,Kühl, Olaf, "Method and apparatus for producing h2-rich synthesis gas", issued 12 December 2018
- ^"Sunshine to Petrol"(PDF).Sandia National Laboratories. Archived fromthe original(PDF)on February 19, 2013.RetrievedApril 11,2013.
- ^"Integrated Solar Thermochemical Reaction System".U.S. Department of Energy.Archivedfrom the original on August 19, 2013.RetrievedApril 11,2013.
- ^Matthew L. Wald (April 10, 2013)."New Solar Process Gets More Out of Natural Gas".The New York Times.Archivedfrom the original on November 30, 2020.RetrievedApril 11,2013.
- ^Frances White."A solar booster shot for natural gas power plants".Pacific Northwest National Laboratory.Archivedfrom the original on April 14, 2013.RetrievedApril 12,2013.
- ^Foit, Severin R.; Vinke, Izaak C.; de Haart, Lambertus G. J.; Eichel, Rüdiger-A. (8 May 2017). "Power-to-Syngas: An Enabling Technology for the Transition of the Energy System?".Angewandte Chemie International Edition.56(20): 5402–5411.doi:10.1002/anie.201607552.PMID27714905.
- ^US patent 5159900A,Dammann, Wilbur A., "Method and means of generating gas from water for use as a fuel", issued 3 November 1992
- ^"Audi in new e-fuels project: synthetic diesel from water, air-captured CO2 and green electricity;" Blue Crude "".Green Car Congress.14 November 2014.Archivedfrom the original on 27 March 2020.Retrieved29 April2015.
- ^abOluyede, Emmanuel O.; Phillips, Jeffrey N. (May 2007). "Fundamental Impact of Firing Syngas in Gas Turbines".Volume 3: Turbo Expo 2007.Proceedings of the ASME Turbo Expo 2007: Power for Land, Sea, and Air. Volume 3: Turbo Expo 2007. Montreal, Canada: ASME. pp. 175–182.CiteSeerX10.1.1.205.6065.doi:10.1115/GT2007-27385.ISBN978-0-7918-4792-3.
- ^Chatterjee, Amit (2012).Sponge iron production by direct reduction of iron oxide.PHI Learning.ISBN978-81-203-4659-8.OCLC1075942093.[page needed]