View source for Mannheim process

{{short description|Industrial process}}
{{Infobox industrial process
| name           = Mannheim process
| image          = 
| caption        = 
| type           = Chemical
| sector         = Chlor-Alkali industry
| technologies   = 
| feedstock      = [[Sodium chloride]], [[sulfuric acid]]
| product        = [[Hydrogen chloride]], [[sodium sulfate]]
| companies      = 
| facility       = 
| inventor       = 
| year           = 
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}}
The '''Mannheim process''' is an industrial process for the production of [[hydrogen chloride]] and [[sodium sulfate]] from [[sulfuric acid]] and [[sodium chloride]].<ref>{{cite journal|author=Helmold Plessen|title=Sodium Sulfates|journal=Ullmann's Encyclopedia of Industrial Chemistry|publisher=Wiley-VCH|year=2000|location=Weinheim|doi=10.1002/14356007.a24_355|isbn=978-3-527-30673-2}}</ref> The Mannheim furnace is also used to produce [[potassium sulfate]] from [[potassium chloride]].<ref name=UllmannK>{{cite encyclopedia|author=H. Schultz |author2=G. Bauer |author3=E. Schachl |author4=F. Hagedorn |author5=P. Schmittinger |chapter=Potassium Compounds|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry|year=2005|publisher=Wiley-VCH|location=Weinheim|doi=10.1002/14356007.a22_039|isbn=978-3-527-30673-2}}</ref>  The Mannheim process is a stage in the [[Leblanc process]] for the production of [[sodium carbonate]].

== Process ==
The process is named after Mannheim furnace, a large cast iron kiln in which it is conducted. The furnace was developed at {{Ill|Verein Chemischer Fabriken in Mannheim|de}} at the turn of the 20th century<ref>{{Cite patent|country=DE|number=137906|title=Mechanischer Calcinirofen bzw. Sulfatofen|pubdate=1903-01-08|gdate=1900-08-12}}</ref> and superseded earlier furnace designs formerly used for the same purpose.<ref>{{Cite book |last=Laury |first=Napoleon Arthur |url=https://hdl.handle.net/2027/mdp.39015078659516?urlappend=%3Bseq=77%3Bownerid=13510798895708989-89 |title=Hydrochloric Acid and Sodium Sulfate |date=1927 |publisher=Chemical catalog Company, Incorporated |hdl=2027/mdp.39015078659516?urlappend=%3Bseq=77 |isbn=978-0-598-81795-2 |language=en}}</ref>

Sodium chloride and sulfuric acid are first fed onto a stationary reaction plate where an initial reaction takes place. The stationary plate is up to {{convert|6|m|ft|0|abbr=on}} in diameter. Rotating rabble arms constantly turn over the mixture and move the intermediate product to a lower plate. The kiln portion of the furnace is constructed with bricks that have high resistance to direct flame, temperature, and acid. The other parts of the furnace are heat and acid resistant. Hot flue gas passes up over the plates carrying out liberated [[hydrogen chloride]] gas. The intermediate product reacts with more sodium chloride in the lower, hotter section of the kiln producing sodium sulfate. This exits the furnace and passes through cooling drums before being milled, screened and sent to product storage facilities.<ref name="Riegel" /> 

The process involves intermediate formation of [[sodium bisulfate]], an exothermic reaction that occurs at room temperature:
:NaCl  +  H<sub>2</sub>SO<sub>4</sub>   →  HCl  +  NaHSO<sub>4</sub>
The second step of the process is endothermic, requiring energy input:
:NaCl  +  NaHSO<sub>4</sub>   →  HCl  +  Na<sub>2</sub>SO<sub>4</sub>
Temperatures in the range 600-700 °C are required.<ref name=Riegel>{{cite book|last1=Riegel|first1=Emil Raymond|editor1-last=Kent|editor1-first=James Albert|title=Riegel's Handbook of Industrial Chemistry|url=https://archive.org/details/handbookofindust0000rieg|url-access=registration|date=1974|publisher=Van Nostrand Reinhold|location=New York|isbn=978-0-442-24347-0|page=[https://archive.org/details/handbookofindust0000rieg/page/132 132]|edition=7th}}</ref>

==References==
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[[Category:Chemical processes]]