Mannheim process

Mannheim process
Process typeChemical
Industrial sector(s)Chlor-Alkali industry
FeedstockSodium chloride, sulfuric acid
Product(s)Hydrogen chloride, sodium sulfate

The Mannheim process is an industrial process for the production of hydrogen chloride and sodium sulfate from sulfuric acid and sodium chloride.[1] The Mannheim furnace is also used to produce potassium sulfate from potassium chloride.[2] 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 The furnace was developed at Verein Chemischer Fabriken in Mannheim [de] at the turn of the 20th century[3] and superseded earlier furnace designs formerly used for the same purpose.[4]

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 6 m (20 ft) 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.[5]

The process involves intermediate formation of sodium bisulfate, an exothermic reaction that occurs at room temperature:

NaCl + H2SO4 → HCl + NaHSO4

The second step of the process is endothermic, requiring energy input:

NaCl + NaHSO4 → HCl + Na2SO4

Temperatures in the range 600-700 °C are required.[5]

References

  1. ^ Helmold Plessen (2000). "Sodium Sulfates". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a24_355. ISBN 978-3-527-30673-2.
  2. ^ H. Schultz; G. Bauer; E. Schachl; F. Hagedorn; P. Schmittinger (2005). "Potassium Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a22_039. ISBN 978-3-527-30673-2.
  3. ^ DE 137906, "Mechanischer Calcinirofen bzw. Sulfatofen", published 1903-01-08, issued 1900-08-12 
  4. ^ Laury, Napoleon Arthur (1927). Hydrochloric Acid and Sodium Sulfate. Chemical catalog Company, Incorporated. ISBN 978-0-598-81795-2.
  5. ^ a b Riegel, Emil Raymond (1974). Kent, James Albert (ed.). Riegel's Handbook of Industrial Chemistry (7th ed.). New York: Van Nostrand Reinhold. p. 132. ISBN 978-0-442-24347-0.