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{{Short description|Fossil fuel derived from other hydrocarbon sources}}
{{Short description|Fossil fuel derived from other hydrocarbon sources}}
{{Distinguish|synthetic gasoline}}
{{Distinguish|synthetic gasoline}}
'''Syngas''', or '''synthesis gas''', is a [[fuel gas]] mixture consisting primarily of [[hydrogen]], [[carbon monoxide]], and very often some [[carbon dioxide]]. The name comes from its use as [[Reaction intermediate|intermediate]]s in creating [[synthetic natural gas]] (SNG)<ref name="Beychok">{{cite book |last1=Beychok |first1=M R |title=Process and environmental technology for producing SNG and liquid fuels |date=1975 |publisher=Environmental Protection Agency |oclc=4435004117 |osti=5364207 }}{{page needed|date=November 2021}}</ref> and for producing [[ammonia]] or [[methanol]]. Syngas is combustible and can be used as a fuel of [[internal combustion engine]]s.<ref>{{Cite web|title=Syngas Cogeneration / Combined Heat & Power|website=[[Clarke Energy]]|url=http://www.clarke-energy.com/gas-type/synthesis-gas-syngas/|access-date=22 February 2016|archive-date=27 August 2012|archive-url=https://web.archive.org/web/20120827024737/http://www.clarke-energy.com/gas-type/synthesis-gas-syngas/|url-status=live}}</ref><ref>{{Cite web|title=Why Let it go to Waste? Enerkem Leaps Ahead With Trash-to-Gas Plans|first=Jason|last=Mick|date=3 March 2010|website=[[DailyTech]]|url=http://www.dailytech.com/Why+Let+it+go+to+Waste++Enerkem+Leaps+Ahead+With+TrashtoGas+Plans/article17817.htm|access-date=22 February 2016|url-status=dead|archive-url=https://web.archive.org/web/20160304054919/http://www.dailytech.com/Why+Let+it+go+to+Waste++Enerkem+Leaps+Ahead+With+TrashtoGas+Plans/article17817.htm|archive-date=4 March 2016}}</ref><ref>{{cite journal |last1=Boehman |first1=André L. |last2=Le Corre |first2=Olivier |title=Combustion of Syngas in Internal Combustion Engines |journal=Combustion Science and Technology |date=15 May 2008 |volume=180 |issue=6 |pages=1193–1206 |doi=10.1080/00102200801963417 |s2cid=94791479 }}</ref> Historically, it has been used as a replacement for gasoline, when gasoline supply has been limited; for example, [[wood gas]] was used to power cars in Europe during [[World War II|WWII]] (in Germany alone half a million cars were built or rebuilt to run on wood gas).<ref>{{Cite web|url=https://www.lowtechmagazine.com/2010/01/wood-gas-cars.html|title=Wood gas vehicles: firewood in the fuel tank|website=LOW-TECH MAGAZINE|access-date=2019-06-13|archive-date=2010-01-21|archive-url=https://web.archive.org/web/20100121081440/https://www.lowtechmagazine.com/2010/01/wood-gas-cars.html|url-status=live}}</ref> However, it has less than half the [[energy density]] of [[natural gas]].<ref name="Beychok" />
'''Syngas''', or '''synthesis gas''', is a mixture of [[hydrogen]] and [[carbon monoxide]],<ref name=":0">{{Cite book |last=Speight |first=James G. |title=Chemical and process design handbook |date=2002 |publisher=McGraw-Hill |isbn=978-0-07-137433-0 |series=McGraw-Hill handbooks |location=New York, NY |page=566}}</ref> in various ratios. The gas often contains some [[carbon dioxide]] and [[methane]]. <!--I dont believe it: The name comes from its use as [[Reaction intermediate|intermediate]]s in creating [[synthetic natural gas]] (SNG)<ref name="Beychok">{{cite book |last1=Beychok |first1=M R |title=Process and environmental technology for producing SNG and liquid fuels |date=1975 |publisher=Environmental Protection Agency |oclc=4435004117 |osti=5364207 }}{{page needed|date=November 2021}}</ref>--> It is principally used for producing [[ammonia]] or [[methanol]]. Syngas is combustible and can be used as a fuel.<ref>{{Cite web|title=Syngas Cogeneration / Combined Heat & Power|website=[[Clarke Energy]]|url=http://www.clarke-energy.com/gas-type/synthesis-gas-syngas/|access-date=22 February 2016|archive-date=27 August 2012|archive-url=https://web.archive.org/web/20120827024737/http://www.clarke-energy.com/gas-type/synthesis-gas-syngas/|url-status=live}}</ref><ref>{{Cite web|title=Why Let it go to Waste? Enerkem Leaps Ahead With Trash-to-Gas Plans|first=Jason|last=Mick|date=3 March 2010|website=[[DailyTech]]|url=http://www.dailytech.com/Why+Let+it+go+to+Waste++Enerkem+Leaps+Ahead+With+TrashtoGas+Plans/article17817.htm|access-date=22 February 2016|url-status=dead|archive-url=https://web.archive.org/web/20160304054919/http://www.dailytech.com/Why+Let+it+go+to+Waste++Enerkem+Leaps+Ahead+With+TrashtoGas+Plans/article17817.htm|archive-date=4 March 2016}}</ref><ref>{{cite journal |last1=Boehman |first1=André L. |last2=Le Corre |first2=Olivier |title=Combustion of Syngas in Internal Combustion Engines |journal=Combustion Science and Technology |date=15 May 2008 |volume=180 |issue=6 |pages=1193–1206 |doi=10.1080/00102200801963417 |s2cid=94791479 }}</ref> Historically, it has been used as a replacement for [[gasoline]], when gasoline supply has been limited; for example, [[wood gas]] was used to power cars in Europe during [[World War II|WWII]] (in Germany alone half a million cars were built or rebuilt to run on wood gas).<ref>{{Cite web|url=https://www.lowtechmagazine.com/2010/01/wood-gas-cars.html|title=Wood gas vehicles: firewood in the fuel tank|website=LOW-TECH MAGAZINE|access-date=2019-06-13|archive-date=2010-01-21|archive-url=https://web.archive.org/web/20100121081440/https://www.lowtechmagazine.com/2010/01/wood-gas-cars.html|url-status=live}}</ref>


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==Production==
Syngas can be produced from many sources, including natural gas, coal, biomass, or virtually any hydrocarbon feedstock, by reaction with steam ([[steam reforming]]), carbon dioxide ([[dry reforming]]) or oxygen ([[partial oxidation]]). It is a crucial intermediate resource for production of hydrogen, ammonia, methanol, and synthetic hydrocarbon fuels. It is also used as an intermediate in producing [[synfuel|synthetic petroleum]] for use as a [[fuel]] or [[lubricant]] via the [[Fischer–Tropsch process]] and previously the [[Mobil]] [[Gas to liquids#Methanol to Gasoline process (MTG)|methanol to gasoline]] process.
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Syngas is produced by [[steam reforming]] or [[partial oxidation]] of natural gas or liquid hydrocarbons, or [[coal]] [[gasification]].<ref>{{cite journal |last1=Beychok |first1=Milton R. |title=Coal gasification and the Phenosolvan process |journal=Am. Chem. Soc., Div. Fuel Chem., Prepr.; (United States) |date=1974 |volume=19 |issue=5 |osti=7362109 |s2cid=93526789 |url=http://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/19_5_ATLANTIC%20CITY_09-74_0085.pdf |archive-url=https://web.archive.org/web/20160303221005/http://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/19_5_ATLANTIC%20CITY_09-74_0085.pdf |archive-date=3 March 2016 }}</ref>


{{chem2|C + H2O -> CO + H2}}<ref name=":0" />
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Production methods include [[steam reforming]] of natural gas or liquid hydrocarbons to produce hydrogen, the [[gasification]] of coal,<ref>{{cite journal |last1=Beychok |first1=Milton R. |title=Coal gasification and the Phenosolvan process |journal=Am. Chem. Soc., Div. Fuel Chem., Prepr.; (United States) |date=1974 |volume=19:5 |osti=7362109 |s2cid=93526789 |url=http://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/19_5_ATLANTIC%20CITY_09-74_0085.pdf |archive-url=https://web.archive.org/web/20160303221005/http://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/19_5_ATLANTIC%20CITY_09-74_0085.pdf |archive-date=3 March 2016 }}</ref> [[biomass]], and in some types of [[waste-to-energy]] gasification facilities.


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{{chem2|CO + H2O -> CO2 + H2}}<ref name=":0" />
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==Production==
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The 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.<ref>{{cite web|title=Syngas composition|url=http://www.netl.doe.gov/research/coal/energy-systems/gasification/gasifipedia/syngas-composition|publisher=National Energy Technology Laboratory, U.S. Department of Energy|access-date=7 May 2015|archive-date=27 March 2020|archive-url=https://web.archive.org/web/20200327190358/http://www.netl.doe.gov/research/coal/energy-systems/gasification/gasifipedia/syngas-composition|url-status=live}}</ref>


{{chem2|C + CO2 -> 2CO }}<ref name=":0" />
The main reaction that produces syngas, [[steam reforming]], is an [[endothermic reaction]] with 206 kJ/mol methane needed for conversion.


Steam reforming of methane is an [[endothermic reaction]] requiring 206 kJ/mol of methane:
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The first reaction, between incandescent coke and steam, is strongly endothermic, producing carbon monoxide (CO), and hydrogen {{chem|H|2}} ([[water gas]] in 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.
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:{{chem2|CH4 + H2O -> CO + 3 H2}}
In principle, but rarely in practice, [[biomass]] and related hydrocarbon feedstocks could be used to generate [[biogas]] and [[biochar]] in [[waste-to-energy]] gasification facilities.<ref>{{Cite web|title=Sewage treatment plant smells success in synthetic gas trial - ARENAWIRE|url=https://arena.gov.au/blog/logan-gasification-sewage-treatment-plant/|access-date=2021-01-25|website=Australian Renewable Energy Agency|date=11 September 2019 |language=en-AU|archive-date=2021-03-07|archive-url=https://web.archive.org/web/20210307141645/https://arena.gov.au/blog/logan-gasification-sewage-treatment-plant/|url-status=live}}</ref> The gas generated (mostly methane and carbon dioxide) is sometimes described as ''syngas'' but its composition differs from syngas. Generation of conventional syngas (mostly H<sub>2</sub> and CO) from waste biomass has been explored.<ref>{{cite journal | last=Zhang | first=Lu | display-authors=etal | title=Clean synthesis gas production from municipal solid waste via catalytic gasification and reforming technology | journal=Catalysis Today | volume=318 | year=2018 | issn=0920-5861 | doi=10.1016/j.cattod.2018.02.050 | pages=39–45| s2cid=102872424 }}</ref><ref>{{Cite journal |last=Sasidhar |first=Nallapaneni |date=November 2023 |title=Carbon Neutral Fuels and Chemicals from Standalone Biomass Refineries |url=https://www.ijee.latticescipub.com/wp-content/uploads/papers/v3i2/B1845113223.pdf |access-date=29 December 2023 |journal=Indian Journal of Environment Engineering |issn=2582-9289 |volume=3 |issue=2|pages=1–8 |doi=10.54105/ijee.B1845.113223 |s2cid=265385618}}</ref>


==Composition, pathway for formation, and thermochemistry==
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The second and third reactions then take place, producing an [[exothermic 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, CO. 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 higher calorific value.
⚫
The 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.<ref>{{cite web|title=Syngas composition|url=http://www.netl.doe.gov/research/coal/energy-systems/gasification/gasifipedia/syngas-composition|publisher=National Energy Technology Laboratory, U.S. Department of Energy|access-date=7 May 2015|archive-date=27 March 2020|archive-url=https://web.archive.org/web/20200327190358/http://www.netl.doe.gov/research/coal/energy-systems/gasification/gasifipedia/syngas-composition|url-status=live}}</ref> Syngas has less than half the [[energy density]] of [[natural gas]].<ref name="Beychok">{{cite book |last1=Beychok |first1=M R |title=Process and environmental technology for producing SNG and liquid fuels |date=1975 |publisher=Environmental Protection Agency |oclc=4435004117 |osti=5364207 }}{{page needed|date=November 2021}}</ref>
When used as an intermediate in the large-scale, industrial synthesis of hydrogen (principally used in the production of [[ammonia]]), it is also produced from [[natural gas]] (via the steam reforming reaction) as follows:


⚫
The first reaction, between incandescent coke and steam, is strongly endothermic, producing carbon monoxide (CO), and hydrogen {{chem|H|2}} ([[water gas]] in 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.
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:<chem>CH4 + H2O -> CO + 3H2</chem>


⚫
The second and third reactions then take place, producing an [[exothermic 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 higher [[calorific value]].
In order to produce more hydrogen from this mixture, more steam is added and the [[Water-gas shift reaction|water gas shift]] reaction is carried out:
In order to produce more hydrogen from this mixture, more steam is added and the [[Water-gas shift reaction|water gas shift]] reaction is carried out:
:{{chem2|CO + H2O -> CO2 + H2}}


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The hydrogen can be separated from the {{CO2}} by [[pressure swing adsorption]] (PSA), [[amine scrubbing]], and [[membrane reactor]]s. A variety of alternative technologies have been investigated, but none are of commercial value.<ref name=Ullmann>{{cite book |doi=10.1002/14356007.a12_169.pub3|chapter=Gas Production, 1. Introduction |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2011 |last1=Hiller |first1=Heinz |last2=Reimert |first2=Rainer |last3=Stönner |first3=Hans-Martin |isbn=978-3527306732 }}</ref> Some variations focus on new stoichiometries such as carbon dioxide plus methane<ref>{{Cite web|url=http://www.diebrennstoffzelle.de/wasserstoff/herstellung/kvaerner.shtml|title=dieBrennstoffzelle.de - Kvaerner-Verfahren|website=www.diebrennstoffzelle.de|access-date=2019-12-17|archive-date=2019-12-07|archive-url=https://web.archive.org/web/20191207063249/http://www.diebrennstoffzelle.de/wasserstoff/herstellung/kvaerner.shtml|url-status=live}}</ref><ref>{{cite patent |country=EU |number=3160899B1 |status=patent |title=Method and apparatus for producing h2-rich synthesis gas |gdate=12 December 2018 |inventor1-last=Kühl |inventor1-first=Olaf }}</ref> or partial [[hydrogenation]] of carbon dioxide. Other research focuses on novel energy sources to drive the processes including electrolysis, solar energy, microwaves, and electric arcs.<ref name="Sunshine to Petrol">{{cite web|title=Sunshine to Petrol|url=http://energy.sandia.gov/wp/wp-content/gallery/uploads/S2P_SAND2009-5796P.pdf|publisher=Sandia National Laboratories|access-date=April 11, 2013|archive-date=February 19, 2013|archive-url=https://web.archive.org/web/20130219194404/http://energy.sandia.gov/wp/wp-content/gallery/uploads/S2P_SAND2009-5796P.pdf|url-status=dead}}</ref><ref name="SunShot">{{cite web|title=Integrated Solar Thermochemical Reaction System|url=http://www1.eere.energy.gov/solar/sunshot/csp_sunshotrnd_pnnl.html|publisher=U.S. Department of Energy|access-date=April 11, 2013|archive-date=August 19, 2013|archive-url=https://web.archive.org/web/20130819063840/http://www1.eere.energy.gov/solar/sunshot/csp_sunshotrnd_pnnl.html|url-status=live}}</ref><ref name="NYT41013">{{cite news|title=New Solar Process Gets More Out of Natural Gas|url=https://www.nytimes.com/2013/04/11/business/energy-environment/new-solar-process-gets-more-out-of-natural-gas.html|access-date=April 11, 2013|newspaper=The New York Times|date=April 10, 2013|author=Matthew L. Wald|archive-date=November 30, 2020|archive-url=https://web.archive.org/web/20201130012407/https://www.nytimes.com/2013/04/11/business/energy-environment/new-solar-process-gets-more-out-of-natural-gas.html|url-status=live}}</ref><ref name="PNNL41113">{{cite web|title=A solar booster shot for natural gas power plants|url=http://www.pnnl.gov/news/release.aspx?id=981|publisher=Pacific Northwest National Laboratory|access-date=April 12, 2013|author=Frances White|archive-date=April 14, 2013|archive-url=https://web.archive.org/web/20130414234802/http://www.pnnl.gov/news/release.aspx?id=981|url-status=live}}</ref><ref>{{cite journal |last1=Foit |first1=Severin R. |last2=Vinke |first2=Izaak C. |last3=de Haart |first3=Lambertus G. J. |last4=Eichel |first4=Rüdiger-A. |title=Power-to-Syngas: An Enabling Technology for the Transition of the Energy System? |journal=Angewandte Chemie International Edition |date=8 May 2017 |volume=56 |issue=20 |pages=5402–5411 |doi=10.1002/anie.201607552 |pmid=27714905 }}</ref><ref>{{cite patent |country=US |number=5159900A |status=patent |title=Method and means of generating gas from water for use as a fuel |gdate=3 November 1992 |inventor1-last=Dammann |inventor1-first=Wilbur A. }}</ref>
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:<chem>CO + H2O -> CO2 + H2</chem>

The hydrogen must be separated from the {{CO2}} to be able to use it. This is primarily done by [[pressure swing adsorption]] (PSA), [[amine scrubbing]], and [[membrane reactor]]s.

⚫
A variety of alternative technologies have been investigated, but none are of commercial value.<ref name=Ullmann>{{cite book |doi=10.1002/14356007.a12_169.pub3|chapter=Gas Production, 1. Introduction |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2011 |last1=Hiller |first1=Heinz |last2=Reimert |first2=Rainer |last3=Stönner |first3=Hans-Martin |isbn=978-3527306732 }}</ref> Some variations focus on new stoichiometries such as carbon dioxide plus methane<ref>{{Cite web|url=http://www.diebrennstoffzelle.de/wasserstoff/herstellung/kvaerner.shtml|title=dieBrennstoffzelle.de - Kvaerner-Verfahren|website=www.diebrennstoffzelle.de|access-date=2019-12-17|archive-date=2019-12-07|archive-url=https://web.archive.org/web/20191207063249/http://www.diebrennstoffzelle.de/wasserstoff/herstellung/kvaerner.shtml|url-status=live}}</ref><ref>{{cite patent |country=EU |number=3160899B1 |status=patent |title=Method and apparatus for producing h2-rich synthesis gas |gdate=12 December 2018 |inventor1-last=Kühl |inventor1-first=Olaf }}</ref> or partial hydrogenation of carbon dioxide. Other research focuses on novel energy sources to drive the processes including electrolysis, solar energy, microwaves, and electric arcs.<ref name="Sunshine to Petrol">{{cite web|title=Sunshine to Petrol|url=http://energy.sandia.gov/wp/wp-content/gallery/uploads/S2P_SAND2009-5796P.pdf|publisher=Sandia National Laboratories|access-date=April 11, 2013|archive-date=February 19, 2013|archive-url=https://web.archive.org/web/20130219194404/http://energy.sandia.gov/wp/wp-content/gallery/uploads/S2P_SAND2009-5796P.pdf|url-status=dead}}</ref><ref name="SunShot">{{cite web|title=Integrated Solar Thermochemical Reaction System|url=http://www1.eere.energy.gov/solar/sunshot/csp_sunshotrnd_pnnl.html|publisher=U.S. Department of Energy|access-date=April 11, 2013|archive-date=August 19, 2013|archive-url=https://web.archive.org/web/20130819063840/http://www1.eere.energy.gov/solar/sunshot/csp_sunshotrnd_pnnl.html|url-status=live}}</ref><ref name="NYT41013">{{cite news|title=New Solar Process Gets More Out of Natural Gas|url=https://www.nytimes.com/2013/04/11/business/energy-environment/new-solar-process-gets-more-out-of-natural-gas.html|access-date=April 11, 2013|newspaper=The New York Times|date=April 10, 2013|author=Matthew L. Wald|archive-date=November 30, 2020|archive-url=https://web.archive.org/web/20201130012407/https://www.nytimes.com/2013/04/11/business/energy-environment/new-solar-process-gets-more-out-of-natural-gas.html|url-status=live}}</ref><ref name="PNNL41113">{{cite web|title=A solar booster shot for natural gas power plants|url=http://www.pnnl.gov/news/release.aspx?id=981|publisher=Pacific Northwest National Laboratory|access-date=April 12, 2013|author=Frances White|archive-date=April 14, 2013|archive-url=https://web.archive.org/web/20130414234802/http://www.pnnl.gov/news/release.aspx?id=981|url-status=live}}</ref><ref>{{cite journal |last1=Foit |first1=Severin R. |last2=Vinke |first2=Izaak C. |last3=de Haart |first3=Lambertus G. J. |last4=Eichel |first4=Rüdiger-A. |title=Power-to-Syngas: An Enabling Technology for the Transition of the Energy System? |journal=Angewandte Chemie International Edition |date=8 May 2017 |volume=56 |issue=20 |pages=5402–5411 |doi=10.1002/anie.201607552 |pmid=27714905 }}</ref><ref>{{cite patent |country=US |number=5159900A |status=patent |title=Method and means of generating gas from water for use as a fuel |gdate=3 November 1992 |inventor1-last=Dammann |inventor1-first=Wilbur A. }}</ref>
Some of the Carbon gets turned into carbon nanotubes<ref>{{cite journal |last1=Kim |first1=Yongil |last2=Nishikawa |first2=Eiichi |last3=Kioka |first3=Toshihide |title=An underwater arc discharge method of CNT production using carbon electrode physical vibration |journal=Journal of Plasma and Fusion |volume=8 |date=2009 |s2cid=133690319 |citeseerx=10.1.1.361.5540 }}</ref> Syngas in principle can be produced from many kinds of wastes.<ref>{{cite patent |country=US |number=5311830A |status=patent |title=Method of energetic and material utilization of waste goods of all kind and device for implementing said method |gdate=17 May 1994 |inventor1-last=Kiss |inventor1-first=Gunter H. }}</ref><ref>{{cite patent |country=US |number=5980858A |status=patent |title=Method for treating wastes by gasification |gdate=9 November 1999 |inventor1-last=Fujimura |inventor1-first=Hiroyuki |inventor2-last=Hirayama |inventor2-first=Yoshio |inventor3-last=Fujinami |inventor3-first=Shosaku |inventor4-last=Takano |inventor4-first=Kazuo }}</ref> As an example Logan City Council, Australia, will use a waste gasification process to dramatically shrink the volume of waste needing to be trucked off site and produce syngas to power the facility. Once wastewater is treated to kill off harmful pathogens and bacteria, the remaining biosolids will be heated to high temperatures to produce a syngas mixture made up of mostly hydrogen, carbon monoxide, methane and carbon dioxide.<ref>{{Cite web|title=Sewage treatment plant smells success in synthetic gas trial - ARENAWIRE|url=https://arena.gov.au/blog/logan-gasification-sewage-treatment-plant/|access-date=2021-01-25|website=Australian Renewable Energy Agency|language=en-AU|archive-date=2021-03-07|archive-url=https://web.archive.org/web/20210307141645/https://arena.gov.au/blog/logan-gasification-sewage-treatment-plant/|url-status=live}}</ref> The syngas produced in waste-to-energy gasification facilities can be used e.g. to generate electricity.

==Uses==
Syngas is used as a fuel and as a source of hydrogen<ref name=Ullmann/> Use of electricity to extract carbon dioxide from water and then water gas shift to syngas has been trialled by the US Naval Research Lab.{{citation needed|date=March 2021}} This process becomes cost effective if the price of electricity is below $20/MWh.<ref>{{cite web|url=https://www.technologyreview.com/s/508051/a-cheap-trick-enables-energy-efficient-carbon-capture/|title=A Cheap Trick Enables Energy-Efficient Carbon Capture|first=Prachi|last=Patel|website=technologyreview.com|access-date=7 April 2018|archive-date=9 November 2018|archive-url=https://web.archive.org/web/20181109031855/https://www.technologyreview.com/s/508051/a-cheap-trick-enables-energy-efficient-carbon-capture/|url-status=live}}</ref>{{irrelevant citation|date=March 2021|reason=Doesn't reference energy production or per MWh pricing, only carbon capture.}}


Electricity generated from [[renewable energy|renewable sources]] is also used to process carbon dioxide and water into syngas through [[high-temperature electrolysis]]. This is an attempt to maintain [[carbon neutrality]] in the generation process. [[Audi]], in partnership with company named Sunfire, opened a pilot plant in November 2014 to generate [[e-diesel]] using this process.<ref>{{cite news|title=Audi in new e-fuels project: synthetic diesel from water, air-captured CO2 and green electricity; "Blue Crude"|url=http://www.greencarcongress.com/2014/11/20141114-audibluecrude.html|access-date=29 April 2015|work=Green Car Congress.|date=14 November 2014|archive-date=27 March 2020|archive-url=https://web.archive.org/web/20200327190343/https://www.greencarcongress.com/2014/11/20141114-audibluecrude.html|url-status=live}}</ref>
Electricity generated from [[renewable energy|renewable sources]] is also used to process carbon dioxide and water into syngas through [[high-temperature electrolysis]]. This is an attempt to maintain [[carbon neutrality]] in the generation process. [[Audi]], in partnership with company named Sunfire, opened a pilot plant in November 2014 to generate [[e-diesel]] using this process.<ref>{{cite news|title=Audi in new e-fuels project: synthetic diesel from water, air-captured CO2 and green electricity; "Blue Crude"|url=http://www.greencarcongress.com/2014/11/20141114-audibluecrude.html|access-date=29 April 2015|work=Green Car Congress.|date=14 November 2014|archive-date=27 March 2020|archive-url=https://web.archive.org/web/20200327190343/https://www.greencarcongress.com/2014/11/20141114-audibluecrude.html|url-status=live}}</ref>
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Syngas that is not methanized typically has a lower heating value of 120 BTU/[[Standard cubic foot|scf]] .<ref name="synheat">{{cite conference |last1=Oluyede |first1=Emmanuel O. |last2=Phillips |first2=Jeffrey N. |title=Volume 3: Turbo Expo 2007 |chapter=Fundamental Impact of Firing Syngas in Gas Turbines |conference=Proceedings of the ASME Turbo Expo 2007: Power for Land, Sea, and Air. Volume 3: Turbo Expo 2007 |location=Montreal, Canada |date=May 2007 |pages=175–182 |publisher=ASME |doi=10.1115/GT2007-27385 |isbn=978-0-7918-4792-3 |citeseerx=10.1.1.205.6065 }}</ref> Untreated syngas can be run in hybrid turbines that allow for greater efficiency because of their lower operating temperatures, and extended part lifetime.<ref name="synheat" />
Syngas that is not methanized typically has a lower heating value of 120 BTU/[[Standard cubic foot|scf]] .<ref name="synheat">{{cite conference |last1=Oluyede |first1=Emmanuel O. |last2=Phillips |first2=Jeffrey N. |title=Volume 3: Turbo Expo 2007 |chapter=Fundamental Impact of Firing Syngas in Gas Turbines |conference=Proceedings of the ASME Turbo Expo 2007: Power for Land, Sea, and Air. Volume 3: Turbo Expo 2007 |location=Montreal, Canada |date=May 2007 |pages=175–182 |publisher=ASME |doi=10.1115/GT2007-27385 |isbn=978-0-7918-4792-3 |citeseerx=10.1.1.205.6065 }}</ref> Untreated syngas can be run in hybrid turbines that allow for greater efficiency because of their lower operating temperatures, and extended part lifetime.<ref name="synheat" />


=== Sponge iron ===
==Uses==
Syngas is used to directly reduce [[iron ore]] to [[Direct reduced iron|sponge iron]].<ref>{{cite book |last1=Chatterjee |first1=Amit |title=Sponge iron production by direct reduction of iron oxide |date=2012 |publisher=PHI Learning |isbn=978-81-203-4659-8 |oclc=1075942093 }}{{page needed|date=November 2021}}</ref>
Syngas is used as a source of hydrogen as well as a fuel.<ref name=Ullmann/> It is also used to directly reduce [[iron ore]] to [[Direct reduced iron|sponge iron]].<ref>{{cite book |last1=Chatterjee |first1=Amit |title=Sponge iron production by direct reduction of iron oxide |date=2012 |publisher=PHI Learning |isbn=978-81-203-4659-8 |oclc=1075942093 }}{{page needed|date=November 2021}}</ref> Chemical uses include the production of [[methanol]] which is a precursor to [[acetic acid]] and many acetates; liquid fuels and [[lubricant]]s via the [[Fischer–Tropsch process]] and previously the [[Mobil]] [[Gas to liquids#Methanol to gasoline (MTG) and methanol to olefins|methanol to gasoline]] process; [[ammonia]] via the [[Haber process]], which converts atmospheric nitrogen (N<sub>2</sub>) into ammonia which is used as a [[fertilizer]]; and [[oxo alcohol]]s via an intermediate aldehyde.

=== Methanol and other liquid fuels ===
Syngas is used to produce [[methanol]]. Methanol is a precursor to acetic acid and many acetates. Many liquid fuels can be produced from syngas.
Syngas can be used in the [[Fischer–Tropsch process]] to produce diesel fuel, or converted into e.g. [[methane]], [[methanol]], and [[dimethyl ether]] in [[catalytic]] processes.

=== Ammonia synthesis ===
Syngas is used to produce [[hydrogen]] for the [[Haber process]], which converts atmospheric nitrogen (N<sub>2</sub>) into ammonia, which is used as a [[fertilizer]].


== See also ==
== See also ==
{{Portal|Energy|Renewable energy}}
{{Portal|Energy|Renewable energy}}
{{Div col}}
{{Div col}}
*[[Biochar]]
*[[Biobased economy]]
*[[Biofuels]]
*[[Boudouard reaction]]
*[[Boudouard reaction]]
*[[Claus process]]
*[[Claus process]]

Latest revision as of 11:29, 29 March 2024

Not to be confused with synthetic gasoline.

Syngas, or synthesis gas, is a mixture of hydrogen and carbon monoxide,[1] in various ratios. The gas often contains some carbon dioxide and methane. It is principally used for producing ammonia or methanol. Syngas is combustible and can be used as a fuel.[2][3][4] Historically, it has been used as a replacement for gasoline, when gasoline supply has been limited; for example, wood gas was used to power cars in Europe during WWII (in Germany alone half a million cars were built or rebuilt to run on wood gas).[5]

Production

[edit]

Syngas is produced by steam reforming or partial oxidation of natural gas or liquid hydrocarbons, or coal gasification.[6]

C + H2O → CO + H2[1]

CO + H2O → CO2 + H2[1]

C + CO2 → 2CO[1]

Steam reforming of methane is an endothermic reaction requiring 206 kJ/mol of methane:

CH4 + H2O → CO + 3 H2

In principle, but rarely in practice, biomass and related hydrocarbon feedstocks could be used to generate biogas and biochar in waste-to-energy gasification facilities.[7] The gas generated (mostly methane and carbon dioxide) is sometimes described as syngas but its composition differs from syngas. Generation of conventional syngas (mostly H2 and CO) from waste biomass has been explored.[8][9]

Composition, pathway for formation, and thermochemistry

[edit]

The 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 the energy density of natural gas.[11]

The first reaction, between incandescent coke and steam, is strongly endothermic, producing carbon monoxide (CO), and hydrogen H
2 (water gas in 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 an exothermic 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 higher calorific value.

In order to produce more hydrogen from this mixture, more steam is added and the water gas shift reaction is carried out:

CO + H2O → CO2 + H2

The hydrogen can be separated from the CO2 by pressure swing adsorption (PSA), amine scrubbing, and membrane 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 partial hydrogenation of 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 from renewable sources is also used to process carbon dioxide and water into syngas through high-temperature electrolysis. This is an attempt to maintain carbon neutrality in the generation process. Audi, in partnership with company named Sunfire, opened a pilot plant in November 2014 to generate e-diesel using 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

[edit]

Syngas is used as a source of hydrogen as well as a fuel.[12] It is also used to directly reduce iron ore to sponge iron.[23] Chemical uses include the production of methanol which is a precursor to acetic acid and many acetates; liquid fuels and lubricants via the Fischer–Tropsch process and previously the Mobil methanol to gasoline process; ammonia via the Haber process, which converts atmospheric nitrogen (N2) into ammonia which is used as a fertilizer; and oxo alcohols via an intermediate aldehyde.

See also

[edit]

References

[edit]
  1. ^ a b c d Speight, James G. (2002). Chemical and process design handbook. McGraw-Hill handbooks. New York, NY: McGraw-Hill. p. 566. ISBN 978-0-07-137433-0.
  2. ^ "Syngas Cogeneration / Combined Heat & Power". Clarke Energy. Archived from the original on 27 August 2012. Retrieved 22 February 2016.
  3. ^ Mick, Jason (3 March 2010). "Why Let it go to Waste? Enerkem Leaps Ahead With Trash-to-Gas Plans". DailyTech. Archived from the original on 4 March 2016. Retrieved 22 February 2016.
  4. ^ 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. S2CID 94791479.
  5. ^ "Wood gas vehicles: firewood in the fuel tank". LOW-TECH MAGAZINE. Archived from the original on 2010-01-21. Retrieved 2019-06-13.
  6. ^ Beychok, Milton R. (1974). "Coal gasification and the Phenosolvan process" (PDF). Am. Chem. Soc., Div. Fuel Chem., Prepr.; (United States). 19 (5). OSTI 7362109. S2CID 93526789. Archived from the original (PDF) on 3 March 2016.
  7. ^ "Sewage treatment plant smells success in synthetic gas trial - ARENAWIRE". Australian Renewable Energy Agency. 11 September 2019. Archived from the original on 2021-03-07. Retrieved 2021-01-25.
  8. ^ 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. ISSN 0920-5861. S2CID 102872424.
  9. ^ 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. ISSN 2582-9289. S2CID 265385618. Retrieved 29 December 2023.
  10. ^ "Syngas composition". National Energy Technology Laboratory, U.S. Department of Energy. Archived from the original on 27 March 2020. Retrieved 7 May 2015.
  11. ^ Beychok, M R (1975). Process and environmental technology for producing SNG and liquid fuels. Environmental Protection Agency. OCLC 4435004117. OSTI 5364207.[page needed]
  12. ^ a b Hiller, Heinz; Reimert, Rainer; Stönner, Hans-Martin (2011). "Gas Production, 1. Introduction". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a12_169.pub3. ISBN 978-3527306732.
  13. ^ "dieBrennstoffzelle.de - Kvaerner-Verfahren". www.diebrennstoffzelle.de. Archived from the original on 2019-12-07. Retrieved 2019-12-17.
  14. ^ EU patent 3160899B1, Kühl, Olaf, "Method and apparatus for producing h2-rich synthesis gas", issued 12 December 2018 
  15. ^ "Sunshine to Petrol" (PDF). Sandia National Laboratories. Archived from the original (PDF) on February 19, 2013. Retrieved April 11, 2013.
  16. ^ "Integrated Solar Thermochemical Reaction System". U.S. Department of Energy. Archived from the original on August 19, 2013. Retrieved April 11, 2013.
  17. ^ Matthew L. Wald (April 10, 2013). "New Solar Process Gets More Out of Natural Gas". The New York Times. Archived from the original on November 30, 2020. Retrieved April 11, 2013.
  18. ^ Frances White. "A solar booster shot for natural gas power plants". Pacific Northwest National Laboratory. Archived from the original on April 14, 2013. Retrieved April 12, 2013.
  19. ^ 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. PMID 27714905.
  20. ^ US patent 5159900A, Dammann, Wilbur A., "Method and means of generating gas from water for use as a fuel", issued 3 November 1992 
  21. ^ "Audi in new e-fuels project: synthetic diesel from water, air-captured CO2 and green electricity; "Blue Crude"". Green Car Congress. 14 November 2014. Archived from the original on 27 March 2020. Retrieved 29 April 2015.
  22. ^ a b Oluyede, 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. CiteSeerX 10.1.1.205.6065. doi:10.1115/GT2007-27385. ISBN 978-0-7918-4792-3.
  23. ^ Chatterjee, Amit (2012). Sponge iron production by direct reduction of iron oxide. PHI Learning. ISBN 978-81-203-4659-8. OCLC 1075942093.[page needed]
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