Editing Coal (section)

==Uses==
Most coal is used as fuel. 27.6% of world energy was supplied by coal in 2017 and Asia used almost three-quarters of it.<ref>{{cite web |title=Primary energy |url=https://www.bp.com/en/global/corporate/energy-economics/statistical-review-of-world-energy/primary-energy.html |access-date=5 December 2018 |publisher=[[BP]]}}</ref> Other large-scale applications also exist. The [[energy density]] of coal is roughly 24 [[megajoule]]s per kilogram<ref>{{cite web |last=Fisher |first=Juliya |year=2003 |title=Energy Density of Coal |url=http://hypertextbook.com/facts/2003/JuliyaFisher.shtml |url-status=live |archive-url=https://web.archive.org/web/20061107152122/http://hypertextbook.com/facts/2003/JuliyaFisher.shtml |archive-date=7 November 2006 |access-date=25 August 2006 |work=The Physics Factbook}}</ref> (approximately 6.7 [[kilowatt-hours]] per kg). For a coal power plant with a 40% efficiency, it takes an estimated {{convert|325|kg|abbr=on}} of coal to power a 100&nbsp;W lightbulb for one year.<ref>{{cite web |date=2000-10-03 |title=How much coal is required to run a 100-watt light bulb 24 hours a day for a year? |url=http://science.howstuffworks.com/question481.htm |url-status=live |archive-url=https://web.archive.org/web/20060807235142/http://science.howstuffworks.com/question481.htm |archive-date=7 August 2006 |access-date=25 August 2006 |work=Howstuffworks}}</ref>

===Electricity generation===
{{Main|Coal-fired power station}}[[File:Grand Junction Trip 92007 098.JPG|thumb|[[Castle Gate Power Plant]] near Helper, Utah, US]]
[[File:Ashtabulacoalcars e2.jpg|thumb|Coal rail cars]]
[[File:Komatsu bulldozer pushing coal in Power plant Ljubljana (winter 2017).jpg|thumb|[[Bulldozer]] pushing coal in [[Ljubljana Power Station]], Slovenia]]
In 2022, 68% of global coal use was used for electricity generation.<ref name=":0" />{{Rp|page=11}} 
Coal burnt in [[list of coal power stations|coal power stations]] to [[electricity generation|generate electricity]] is called '''thermal coal'''. It is usually pulverized and then burned in a furnace with a [[boiler]].<ref name="World Coal">[http://www.worldcoal.org/coal/uses-of-coal/coal-electricity/ Total World Electricity Generation by Fuel (2006)] {{webarchive|url=https://web.archive.org/web/20151022093430/http://www.worldcoal.org/coal/uses-of-coal/coal-electricity/|date=22 October 2015}}. Source: IEA 2008.</ref> The furnace heat converts boiler water to [[steam]], which is then used to spin [[turbine]]s which turn [[electrical generator|generators]] and create electricity.<ref>{{cite web |title=Fossil Power Generation |url=http://w1.siemens.com/responsibility/en/environment/portfolio/fossil_power_generation.htm |url-status=dead |archive-url=http://arquivo.pt/wayback/20090929225531/http://w1.siemens.com/responsibility/en/environment/portfolio/fossil_power_generation.htm |archive-date=29 September 2009 |access-date=23 April 2009 |publisher=Siemens AG}}</ref> The [[thermodynamic efficiency]] of this process varies between about 25% and 50% depending on the pre-combustion treatment, turbine technology (e.g. [[supercritical steam generator]]) and the age of the plant.<ref>J. Nunn, A. Cottrell, A. Urfer, L. Wibberley and P. Scaife, [http://www.docstoc.com/docs/80110435/TA-28-Vic-elec-grid-YED-2000-Final "A Lifecycle Assessment of the Victorian Energy Grid"] {{webarchive|url=https://web.archive.org/web/20160902132119/http://www.docstoc.com/docs/80110435/TA-28-Vic-elec-grid-YED-2000-Final|date=2 September 2016}}, Cooperative Research Centre for Coal in Sustainable Development, February 2003, p. 7.</ref><ref>{{cite web |title=Neurath F and G set new benchmarks |url=http://www.alstom.com/Global/Power/Resources/Documents/Brochures/neurath-fandg-supercritical-steam-power-plant-new-benchmarks.pdf |url-status=live |archive-url=https://web.archive.org/web/20150401132704/http://www.alstom.com/Global/Power/Resources/Documents/Brochures/neurath-fandg-supercritical-steam-power-plant-new-benchmarks.pdf |archive-date=1 April 2015 |access-date=21 July 2014 |publisher=Alstom}}</ref> 

A few [[integrated gasification combined cycle]] (IGCC) power plants have been built, which burn coal more efficiently. Instead of pulverizing the coal and burning it directly as fuel in the steam-generating boiler, the [[coal gasification|coal is gasified]] to create [[syngas]], which is burned in a [[gas turbine]] to produce electricity (just like natural gas is burned in a turbine). Hot exhaust gases from the turbine are used to raise steam in a [[heat recovery steam generator]] which powers a supplemental [[steam turbine]]. The overall plant efficiency when used to provide [[combined heat and power]] can reach as much as 94%.<ref>[http://ipaper.ipapercms.dk/DONGENERGY/Internet/UK/ThermalPower/AVVbrochure2012UK/ Avedøreværket] {{webarchive|url=https://web.archive.org/web/20160129110317/http://ipaper.ipapercms.dk/DONGENERGY/Internet/UK/ThermalPower/AVVbrochure2012UK/|date=29 January 2016}}. Ipaper.ipapercms.dk. Retrieved on 11 May 2013.</ref> IGCC power plants emit less local pollution than conventional pulverized coal-fueled plants. Other ways to use coal are as [[coal-water slurry fuel]] (CWS), which was developed in the [[Soviet Union]], or in [[magnetohydrodynamic generator|an MHD topping cycle]]. However these are not widely used due to lack of profit.

In 2017 38% of the world's electricity came from coal, the same percentage as 30 years previously.<ref>{{cite web |date=2018-06-15 |title=The most depressing energy chart of the year |url=https://www.vox.com/energy-and-environment/2018/6/15/17467164/energy-chart-renewables-coal-climate-change |access-date=30 October 2018 |publisher=Vox}}</ref> In 2018 global installed capacity was 2[[terawatt|TW]] (of which 1TW is in China) which was 30% of total electricity generation capacity.<ref name="Cornot-Gandolfe 2018">{{cite book |last1=Cornot-Gandolfe |first1=Sylvie |url=https://www.ifri.org/sites/default/files/atoms/files/cornot_gandolphe_coal_exit_2018.pdf |title=A Review of Coal Market Trends and Policies in 2017 |date=May 2018 |publisher=Ifri |archive-url=https://web.archive.org/web/20181115153650/https://www.ifri.org/sites/default/files/atoms/files/cornot_gandolphe_coal_exit_2018.pdf |archive-date=2018-11-15 |url-status=live}}</ref> The most dependent major country is South Africa, with over 80% of its electricity generated by coal;<ref>{{cite web |title=Energy Revolution: A Global Outlook |url=https://www.drax.com/wp-content/uploads/2018/12/Energy-Revolution-Global-Outlook-Report-Final-Dec-2018-COP24.pdf |url-status=live |archive-url=https://web.archive.org/web/20190209123738/https://www.drax.com/wp-content/uploads/2018/12/Energy-Revolution-Global-Outlook-Report-Final-Dec-2018-COP24.pdf |archive-date=2019-02-09 |access-date=7 February 2019 |publisher=Drax}}</ref> but China alone generates more than half of the world's coal-generated electricity.<ref>{{cite news |date=28 March 2021 |title=China generated over half world's coal-fired power in 2020: study |url=https://www.reuters.com/article/us-climate-change-china-coal/china-generated-over-half-worlds-coal-fired-power-in-2020-study-idUSKBN2BK0PZ |access-date=14 September 2021 |work=[[Reuters]] |quote=China generated 53% of the world's total coal-fired power in 2020, nine percentage points more that five years earlier}}</ref> Efforts around the world to reduce the use of coal have led some regions to switch to natural gas and [[renewable energy]]. In 2018 coal-fired power station [[capacity factor]] averaged 51%, that is they operated for about half their available operating hours.<ref>{{Cite report |url=https://endcoal.org/wp-content/uploads/2020/03/BoomAndBust_2020_English.pdf |title=Boom and Bust 2020: Tracking the Global Coal Plant Pipeline |last1=Shearer |first1=Christine |last2=Myllyvirta |first2=Lauri |date=March 2020 |publisher=[[Global Energy Monitor]] |last3=Yu |first3=Aiqun |last4=Aitken |first4=Greig |last5=Mathew-Shah |first5=Neha |last6=Dallos |first6=Gyorgy |last7=Nace |first7=Ted |access-date=27 April 2020 |archive-url=https://web.archive.org/web/20200327062155/https://endcoal.org/wp-content/uploads/2020/03/BoomAndBust_2020_English.pdf |archive-date=27 March 2020 |url-status=usurped}}</ref>

===Coke===
{{Main|Coke (fuel)}}
[[File:Coke Ovens Abercwmboi.jpg|right|thumb|Coke oven at a [[smokeless fuel]] plant in [[Wales]], United Kingdom]]

Coke is a solid carbonaceous residue that is used in manufacturing steel and other iron-containing products.<ref name="World Coal Steel">{{cite web|title=How is Steel Produced?|url=https://www.worldcoal.org/coal/uses-coal/how-steel-produced|publisher=[[World Coal Association]]|access-date=April 8, 2017|url-status=live|archive-url=https://web.archive.org/web/20170412114829/https://www.worldcoal.org/coal/uses-coal/how-steel-produced|archive-date=12 April 2017|date=2015-04-28}}</ref> Coke is made when [[metallurgical coal]] (also known as ''coking coal'') is baked in an oven without oxygen at temperatures as high as 1,000&nbsp;°C, driving off the volatile constituents and fusing together the fixed carbon and residual ash. Metallurgical coke is used as a fuel and as a [[reducing agent]] in [[smelting]] iron ore in a [[blast furnace]].<ref>[http://www.steelonthenet.com/cost-bof.html Blast furnace steelmaking cost model] {{webarchive|url=https://web.archive.org/web/20160114013811/http://www.steelonthenet.com/cost-bof.html |date=14 January 2016 }}. Steelonthenet.com. Retrieved on 24 August 2012.</ref> The carbon monoxide produced by its combustion reduces [[hematite]] (an [[iron oxide]]) to iron.
:{{chem2|2 Fe2O3 + 6 CO -> 4 Fe + 6 CO2}}
[[Pig iron]], which is too rich in dissolved carbon, is also produced.

The coke must be [[Coke strength after reaction|strong enough]] to resist the weight of overburden in the blast furnace, which is why coking coal is so important in making steel using the conventional route. Coke from coal is grey, hard, and porous and has a heating value of 29.6 MJ/kg. Some coke-making processes produce byproducts, including [[coal tar]], [[ammonia]], light oils, and [[coal gas]].

[[Petroleum coke]] (petcoke) is the solid residue obtained in [[oil refining]], which resembles coke but contains too many impurities to be useful in metallurgical applications.

===Production of chemicals===
[[File:Coal to chemicals routes diagram.jpg|upright=1.35|thumb|Production of chemicals from coal]]

Chemicals have been produced from coal since the 1950s. Coal can be used as a feedstock in the production of a wide range of chemical fertilizers and other chemical products. The main route to these products was [[coal gasification]] to produce [[syngas]]. Primary chemicals that are produced directly from the syngas include [[methanol]], [[hydrogen]], and [[carbon monoxide]], which are the chemical building blocks from which a whole spectrum of derivative chemicals are manufactured, including [[olefins]], [[acetic acid]], [[formaldehyde]], ammonia, [[urea]], and others. The versatility of [[syngas]] as a precursor to primary chemicals and high-value derivative products provides the option of using coal to produce a wide range of commodities. In the 21st century, however, the use of [[coalbed methane]] is becoming more important.<ref>{{Cite web|title=Coal India begins process of developing Rs 2,474 crore CBM projects {{!}} Hellenic Shipping News Worldwide|url=https://www.hellenicshippingnews.com/coal-india-begins-process-of-developing-rs-2474-crore-cbm-projects/|website=www.hellenicshippingnews.com|access-date=2020-05-31}}</ref>

Because the slate of chemical products that can be made via coal gasification can in general also use feedstocks derived from [[natural gas]] and [[petroleum]], the chemical industry tends to use whatever feedstocks are most cost-effective. Therefore, interest in using coal tended to increase for higher oil and natural gas prices and during periods of high global economic growth that might have strained oil and gas production.

Coal to chemical processes require substantial quantities of water.<ref>{{Cite web|title=Coal-to-Chemicals: Shenhua's Water Grab|url=http://www.chinawaterrisk.org/opinions/coal-to-chemicals-shenhuas-water-grab-2/|website=China Water Risk|language=en-US|access-date=2020-05-31}}</ref> Much coal to chemical production is in China<ref name=OILDRUM9371>{{cite web|title=China's Coal to Chemical Future|url=http://www.theoildrum.com/node/9371|publisher=The Oil Drum.Com|access-date=3 March 2013|author=Rembrandt|format=Blog post by expert|date=2 August 2012}}</ref><ref name=ICIS022712>{{cite news|title=China develops coal-to-olefins projects, which could lead to ethylene self-sufficiency|url=http://www.icis.com/Articles/2012/02/27/9535534/china-develops-coal-to-olefins-projects-which-could-lead-to-ethylene.html|author= Yin, Ken|access-date=3 March 2013|newspaper=ICIS Chemical Business|date=27 February 2012}}</ref> where coal dependent provinces such as [[Shanxi]] are struggling to control its pollution.<ref>{{cite news |title=Smog war casualty: China coal city bears brunt of pollution crackdown |url=https://www.reuters.com/article/us-china-pollution-economy-insight/smog-war-casualty-china-coal-city-bears-brunt-of-pollution-crackdown-idUSKCN1NV2RB |work=[[Reuters]] |date=27 November 2018}}</ref>

===Liquefaction===
{{Main|Coal liquefaction}}
Coal can be converted directly into [[synthetic fuel]]s equivalent to gasoline or diesel by [[hydrogenation]] or [[carbonization]].<ref>{{cite web|url=http://www.netl.doe.gov/research/Coal/energy-systems/gasification/gasifipedia/direct-liquefaction|title=Direct Liquefaction Processes|publisher=National Energy Technology Laboratory|access-date=16 July 2014|url-status=live|archive-date=25 July 2014|archive-url=https://web.archive.org/web/20140725082303/http://www.netl.doe.gov/research/Coal/energy-systems/gasification/gasifipedia/direct-liquefaction}}</ref> Coal liquefaction emits more carbon dioxide than liquid fuel production from [[crude oil]]. Mixing in biomass and using [[carbon capture and storage]] (CCS) would emit slightly less than the oil process but at a high cost.<ref>{{cite journal |title=Economic and environmental analyses of coal and biomass to liquid fuels |journal=Energy |volume=141|pages=76–86|doi=10.1016/j.energy.2017.09.047|year=2017|last1=Liu|first1=Weiguo|last2=Wang|first2=Jingxin|last3=Bhattacharyya|first3=Debangsu |last4=Jiang|first4=Yuan |last5=Devallance|first5=David|doi-access=free|bibcode=2017Ene...141...76L }}</ref> State owned [[China Energy Investment]] runs a coal liquefaction plant and plans to build 2 more.<ref>{{cite news |title=CHN Energy to build new coal-to-liquid production lines |url=http://en.silkroad.news.cn/2018/0813/106231.shtml |agency=Xinhua News Agency |date=13 August 2018}}</ref>

Coal liquefaction may also refer to the cargo hazard when shipping coal.<ref>{{cite news |title=New IMSBC Code requirements aim to control liquefaction of coal cargoes |url=https://www.hellenicshippingnews.com/new-imsbc-code-requirements-aim-to-control-liquefaction-of-coal-cargoes/ |work=Hellenic Shipping News Worldwide |date=29 November 2018 |access-date=1 December 2018 |archive-date=3 August 2020 |archive-url=https://web.archive.org/web/20200803211939/https://www.hellenicshippingnews.com/new-imsbc-code-requirements-aim-to-control-liquefaction-of-coal-cargoes/ |url-status=dead }}</ref>

===Gasification===
{{Main|Coal gasification|Underground coal gasification}}
Coal gasification, as part of an [[integrated gasification combined cycle]] (IGCC) coal-fired power station, is used to produce [[syngas]], a mixture of [[carbon monoxide]] (CO) and hydrogen (H<sub>2</sub>) gas to fire gas turbines to produce electricity. Syngas can also be converted into transportation fuels, such as [[gasoline]] and [[Diesel fuel|diesel]], through the [[Fischer–Tropsch process]]; alternatively, syngas can be converted into [[methanol]], which can be blended into fuel directly or converted to gasoline via the methanol to gasoline process.<ref>{{cite web |url=http://www.netl.doe.gov/research/coal/energy-systems/gasification/gasifipedia/methanol-to-gasoline |title=Conversion of Methanol to Gasoline |publisher=National Energy Technology Laboratory |access-date=16 July 2014 |url-status=live |archive-url=https://web.archive.org/web/20140717225057/http://www.netl.doe.gov/research/Coal/energy-systems/gasification/gasifipedia/methanol-to-gasoline |archive-date=17 July 2014}}</ref> Gasification combined with Fischer–Tropsch technology was used by the [[Sasol]] chemical company of [[South Africa]] to make chemicals and motor vehicle fuels from coal.<ref>{{Cite news|title=Sasol Is Said to Plan Sale of Its South Africa Coal Mining Unit |url=https://www.bloomberg.com/news/articles/2019-09-18/sasol-is-said-to-plan-sale-of-its-south-africa-coal-mining-unit|newspaper=Bloomberg.com|date=18 September 2019|access-date=2020-05-31}}</ref>

During gasification, the coal is mixed with [[oxygen]] and [[steam]] while also being heated and pressurized. During the reaction, oxygen and water molecules [[oxidize]] the coal into carbon monoxide (CO), while also releasing [[hydrogen]] gas (H<sub>2</sub>). This used to be done in underground coal mines, and also to make [[town gas]], which was piped to customers to burn for illumination, heating, and cooking.

: 3C (''as Coal'') + O<sub>2</sub> + H<sub>2</sub>O → H<sub>2</sub> + 3CO

If the refiner wants to produce gasoline, the syngas is routed into a Fischer–Tropsch reaction. This is known as indirect coal liquefaction. If hydrogen is the desired end-product, however, the syngas is fed into the [[water gas shift reaction]], where more hydrogen is liberated:

: CO + H<sub>2</sub>O → CO<sub>2</sub> + H<sub>2</sub>