Editing Chromium (section)

== Production ==
[[File:Chrom 1.jpg|thumb|left|Piece of chromium produced with [[aluminothermic reaction]]]]
[[File:Chromium - world production trend.svg|upright=1.4|thumb|World production trend of chromium]]
[[File:Chromium zone refined and 1cm3 cube.jpg|left|thumb|Chromium, remelted in a horizontal arc [[Zone melting|zone-refiner]], showing large visible crystal grains]]
Approximately 28.8 million metric tons (Mt) of marketable chromite ore was produced in 2013, and converted into 7.5 Mt of ferrochromium.<ref name="USGS2015Yb">{{cite web|url = http://minerals.usgs.gov/minerals/pubs/commodity/chromium/mcs-2015-chrom.pdf|publisher = United States Geological Survey|access-date = 3 June 2015|title = Mineral Yearbook 2015: Chromium|first = John F|last = Papp|archive-date = 10 January 2019|archive-url = https://web.archive.org/web/20190110210251/https://minerals.usgs.gov/minerals/pubs/commodity/chromium/mcs-2015-chrom.pdf|url-status = live}}</ref> According to John F. Papp, writing for the USGS, "Ferrochromium is the leading end use of chromite ore, [and] stainless steel is the leading end use of ferrochromium."<ref name="USGS2015Yb" />

The largest producers of chromium ore in 2013 have been South Africa (48%), Kazakhstan (13%), Turkey (11%), and India (10%), with several other countries producing the rest of about 18% of the world production.<ref name="USGS2015Yb" />

The two main products of chromium ore refining are [[ferrochromium]] and metallic chromium. For those products the ore smelter process differs considerably. For the production of ferrochromium, the chromite ore (FeCr<sub>2</sub>O<sub>4</sub>) is reduced in large scale in [[electric arc furnace]] or in smaller smelters with either [[aluminium]] or [[silicon]] in an [[aluminothermic reaction]].<ref name="IndMin">{{Cite book|title = Industrial Minerals & Rocks: Commodities, Markets, and Uses|edition = 7th|publisher = SME|date = 2006|isbn = 978-0-87335-233-8|chapter = Chromite|author = Papp, John F.|author2 = Lipin, Bruce R.|name-list-style = amp|chapter-url = https://books.google.com/books?id=zNicdkuulE4C&pg=PA309|access-date = 5 June 2020|archive-date = 10 June 2024|archive-url = https://web.archive.org/web/20240610050310/https://books.google.com/books?id=zNicdkuulE4C&pg=PA309#v=onepage&q&f=false|url-status = live}}</ref>
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[[File:World Chromium Production 2002.svg|thumb|upright=1.4|Chromium ore output in 2002<ref name="USGS2002Yb">{{cite web|url = http://minerals.usgs.gov/minerals/pubs/commodity/chromium/chrommyb02.pdf|publisher = United States Geological Survey|access-date = 16 Feb 2009|title = Mineral Yearbook 2002: Chromium|first = John F.|last = Papp|archive-date = 10 January 2019|archive-url = https://web.archive.org/web/20190110130417/https://minerals.usgs.gov/minerals/pubs/commodity/chromium/chrommyb02.pdf|url-status = live}}</ref>]]
For the production of pure chromium, the iron must be separated from the chromium in a two step roasting and leaching process. The chromite ore is heated with a mixture of [[calcium carbonate]] and [[sodium carbonate]] in the presence of air. The chromium is oxidized to the hexavalent form, while the iron forms the stable Fe<sub>2</sub>O<sub>3</sub>. The subsequent leaching at higher elevated temperatures dissolves the [[chromates]] and leaves the insoluble iron oxide. The chromate is converted by [[sulfuric acid]] into the dichromate.<ref name="IndMin" />

:4 FeCr<sub>2</sub>O<sub>4</sub> + 8 Na<sub>2</sub>CO<sub>3</sub> + 7 O<sub>2</sub> → 8 Na<sub>2</sub>CrO<sub>4</sub> + 2 Fe<sub>2</sub>O<sub>3</sub> + 8 CO<sub>2</sub>

:2 Na<sub>2</sub>CrO<sub>4</sub> + H<sub>2</sub>SO<sub>4</sub> → Na<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub> + Na<sub>2</sub>SO<sub>4</sub> + H<sub>2</sub>O

The dichromate is converted to the chromium(III) oxide by reduction with carbon and then reduced in an aluminothermic reaction to chromium.<ref name="IndMin" />
:Na<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub> + 2 C → Cr<sub>2</sub>O<sub>3</sub> + Na<sub>2</sub>CO<sub>3</sub> + CO
:Cr<sub>2</sub>O<sub>3</sub> + 2 Al → Al<sub>2</sub>O<sub>3</sub> + 2 Cr