EP0713928A1 - Procédé et dispositif pour la préparation de nitrite de sodium - Google Patents

Procédé et dispositif pour la préparation de nitrite de sodium Download PDF

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Publication number
EP0713928A1
EP0713928A1 EP95118544A EP95118544A EP0713928A1 EP 0713928 A1 EP0713928 A1 EP 0713928A1 EP 95118544 A EP95118544 A EP 95118544A EP 95118544 A EP95118544 A EP 95118544A EP 0713928 A1 EP0713928 A1 EP 0713928A1
Authority
EP
European Patent Office
Prior art keywords
cathode
nitrite
sodium nitrite
nitrate
sodium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP95118544A
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German (de)
English (en)
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EP0713928B1 (fr
Inventor
Hans Jürgen Eisen
Christian Dr. Tragut
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BASF SE
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BASF SE
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Filing date
Publication date
Application filed by BASF SE filed Critical BASF SE
Publication of EP0713928A1 publication Critical patent/EP0713928A1/fr
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Publication of EP0713928B1 publication Critical patent/EP0713928B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/14—Alkali metal compounds

Definitions

  • the invention relates to a method and a device for producing sodium nitrite from solutions with sodium nitrate.
  • a method of this type is known from DE-A1 31 25 616.
  • the sodium nitrite solution (approx. 25-35% NaNO2, 2-6% NaNO3, small amounts of NaHCO3 and Na2SO3, approx. 58-72% H2O) originating from the alkaline scrubbing of nitrogen oxide gases of the nitric acid low-pressure system is initially in a precoat filter filtered to remove solid residues such as silica etc.
  • the filtered so-called raw solution is largely concentrated in evaporators upon crystallization of sodium nitrite. This results in a crystallized mash with a solids content of approx.
  • the raw solution used in this process may only be evaporated to the extent that the ratio of NaNO2 / NaNO3 in the salt-free mother liquor is not less than 3.
  • the ratio of NaNO2 / NaNO3 in the salt-free mother liquor is not less than 3.
  • the specification of the low-nitrate sodium nitrite solution only allows a sodium nitrate content of max. 0.3%. This necessitates the production from washed sodium nitrite salt and condensed water; i.e. Sodium nitrite must first be crystallized out, separated off by centrifuges and washed and finally redissolved in water.
  • the invention has for its object to overcome the aforementioned disadvantages and to provide a method which enables a significantly higher yield of sodium nitrite at a lower cost.
  • This object is achieved in that the sodium nitrate is converted to sodium nitrite by electrochemical reduction and then separated off.
  • the process according to the invention differs essentially from the known process in that the filtered crude solution is subjected to the electrochemical reduction (hereinafter referred to as ECR for short) of the sodium nitrate introduced to sodium nitrite before the sodium nitrite is separated off.
  • ECR electrochemical reduction
  • the filtered crude sodium nitrite solution is cooled to -10 ° C. for the electrolysis.
  • the pH can be carefully lowered beforehand with a little nitric acid, just to the extent that no nitrous development occurs. Na hydrogen carbonate and Na carbonate are converted into Na nitrate.
  • the electrolysis is carried out in such a way that nitrate ions are selectively reduced to nitrite ions on the cathode of an electrolytic cell.
  • the construction of the cell must ensure that the nitrite ions present in the salt solution at the anode are not oxidized to the nitrate.
  • a reduction of the nitrate to lower oxidation levels of the nitrogen than in the nitrite must be avoided by choosing the appropriate cathode and by suitable electrolysis conditions.
  • the anodic oxidation of the nitrite can be avoided by separating the anode and cathode spaces by means of a cation exchange membrane or a diaphragm.
  • the aqueous solution of a mineral acid with a typical concentration of 2% to 5%, preferably sulfuric or nitric acid is in the anode compartment, which ensures a sufficiently high conductivity of the anolyte.
  • water is converted to oxygen and hydronium ions, which can reach the cathode compartment through the diaphragm or the cation exchange membrane.
  • the anode itself is realized in the usual way, e.g. B. as an expanded metal electrode with a low oxygen overvoltage.
  • the electrolysis can also be carried out in an undivided cell. Then through Selection of the electrode material and the electrolysis conditions ensure that no oxidation of the nitrite at the anode can take place, for example by iron anodes in an alkaline electrolyte solution.
  • the sodium nitrite and sodium nitrate-containing salt solution flows through the cathode compartment.
  • the nitrate ion is reduced to nitrite, with water being produced using hydronium ions.
  • This cathode consists of a porous silver electrode with a large surface area and great catalytic activity, which enables a selective reduction of the nitrate to nitrite at a high current density.
  • the electrode can consist of a bed of metal powder provided with electrical contact or of a sintered metal plate.
  • Metal powder as well as sintered metal plate can be obtained by alkaline leaching of a silver-aluminum or silver-alkaline earth alloy in the manner in which a Raney catalyst is produced. Before leaching, this alloy is brought into the appropriate shape by grinding or producing a porous sintered metal plate.
  • the nitrite / nitrate solution flows through the electrode.
  • the flow can be perpendicular or parallel to the current direction and ensures a sufficiently high mass transfer on the electrode surface down to the lowest nitrate concentrations.
  • the electrolysis can be carried out in one step to such an extent that the nitrate content of the converted catholyte corresponds to the required specification of low-nitrate solution.
  • the process according to the invention is suitable not only for improving the known process for the production of sodium nitrite, but also for the production of nitrite from nitrate solutions which are obtained, for example, from natural saltpetre deposits.
  • the advantages of the process according to the invention can be seen on the one hand in that the nitrite yield is at a maximum.
  • the sodium nitrite supplied in the raw solution remains almost quantitatively
  • the equivalent amount of sodium nitrite is additionally generated by the electrochemical reaction (ECR) of the sodium nitrate.
  • ECR electrochemical reaction
  • the available amount of sodium nitrite, based on the nitrogen used increases considerably compared to the known method, namely by at least 30%.
  • the nitrate-free (nitrate-free) sodium nitrite solution obtained by the process according to the invention can be further processed directly to 40% sodium nitrite solution and sodium nitrite salt. This can be done in one step in such a way that sodium nitrite solution is removed at a sufficiently high concentration level during evaporation (duplexes, triplexes) and adjusted to the desired sodium nitrite concentration with solution from the electrolysis and the remaining sodium nitrite solution is concentrated to salt in the crystallizer.
  • the process of crystallization, separation, drying, cooling and conditioning of the sodium nitrite salt is the same as in the known process.
  • a block diagram illustrating the sequence of such a method using the invention can be seen in the drawing.
  • a crude sodium nitrite solution which still contains 2 to 6% by weight of sodium nitrate, is fed to the filtration 2 at the point indicated by the arrow 1.
  • part of this solution becomes directly the Electrolysis 3 supplied according to the invention.
  • the resulting sodium nitrite solution is partially evaporated in a concentration stage 4 and then mixed in a mixer 6 with a stream branched off via line 5 after the electrolysis 3.
  • the resulting low-nitrite solution (S) with a content of 39 to 41% by weight sodium nitrite is drawn off at 7.
  • Part of the solution formed in the concentration stage 4 is fed to a crystallization stage 9 via a line 8.
  • the resulting salt is separated in the separation stage 10.
  • the remaining mother liquor is returned via line 11 to crystallization stage 9.
  • the sodium nitrite salt separated off in the separation stage 10 is dried in the drying stage 12, cooled and conditioned and drawn off at 13.
  • Part of the filtered crude solution is fed via line 14 to a further concentration stage 15.
  • the resulting nitrite solution which still has a sodium nitrate content of 6 to 10% by weight, is mixed in a mixer 16 with a portion of the crude nitrite solution drawn off through line 17 after the filtration 2.
  • the resulting nitrite solution has a sodium nitrite content of 39 to 41% by weight and a sodium nitrate content of 2 to 4% by weight. It is deducted at 21.
  • nitrite solution obtained at concentration stage 4 is fed via line 19 to a mixer 20, where it is combined via line 18 with a portion of the crude solution filtered. This produces a nitrite solution with 39 to 41% by weight sodium nitrite and 1 to 2% by weight sodium nitrate, which is drawn off at 21.
EP95118544A 1994-11-24 1995-11-24 Procédé et dispositif pour la préparation de nitrite de sodium Expired - Lifetime EP0713928B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4441937 1994-11-24
DE4441937A DE4441937A1 (de) 1994-11-24 1994-11-24 Verfahren und Vorrichtung zur Herstellung von Natriumnitrit

Publications (2)

Publication Number Publication Date
EP0713928A1 true EP0713928A1 (fr) 1996-05-29
EP0713928B1 EP0713928B1 (fr) 1998-06-17

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP95118544A Expired - Lifetime EP0713928B1 (fr) 1994-11-24 1995-11-24 Procédé et dispositif pour la préparation de nitrite de sodium

Country Status (2)

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EP (1) EP0713928B1 (fr)
DE (2) DE4441937A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020198726A1 (fr) * 2019-03-28 2020-10-01 Kemin Industries, Inc. Compositions d'extraits à base de plantes à réduction électrochimique pour la cuisson de la viande et procédés associés

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE174737C (fr) *
US2273799A (en) * 1938-12-17 1942-02-17 Nat Carbon Co Inc Process for electrolytic reduction
FR2438010A1 (fr) * 1978-10-06 1980-04-30 Asahi Chemical Ind Procede de preparation de nitrites
DE3125616A1 (de) 1980-07-05 1982-02-11 Basf Ag, 6700 Ludwigshafen Verfahren zur herstellung von festen alkalinitriten
EP0305910A1 (fr) * 1987-09-04 1989-03-08 BASF Aktiengesellschaft Procédé de fabrication de nitrates de métaux alcalins

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE174737C (fr) *
US2273799A (en) * 1938-12-17 1942-02-17 Nat Carbon Co Inc Process for electrolytic reduction
FR2438010A1 (fr) * 1978-10-06 1980-04-30 Asahi Chemical Ind Procede de preparation de nitrites
DE3125616A1 (de) 1980-07-05 1982-02-11 Basf Ag, 6700 Ludwigshafen Verfahren zur herstellung von festen alkalinitriten
EP0305910A1 (fr) * 1987-09-04 1989-03-08 BASF Aktiengesellschaft Procédé de fabrication de nitrates de métaux alcalins

Also Published As

Publication number Publication date
DE59502587D1 (de) 1998-07-23
DE4441937A1 (de) 1996-05-30
EP0713928B1 (fr) 1998-06-17

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