EP0093319B1 - Procédé de préparation électrolytique de chlore et de soude caustique à partir de sel contenant des sulfates - Google Patents

Procédé de préparation électrolytique de chlore et de soude caustique à partir de sel contenant des sulfates Download PDF

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Publication number
EP0093319B1
EP0093319B1 EP83103829A EP83103829A EP0093319B1 EP 0093319 B1 EP0093319 B1 EP 0093319B1 EP 83103829 A EP83103829 A EP 83103829A EP 83103829 A EP83103829 A EP 83103829A EP 0093319 B1 EP0093319 B1 EP 0093319B1
Authority
EP
European Patent Office
Prior art keywords
brine
partial stream
stream
sulphate
salt
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.)
Expired
Application number
EP83103829A
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German (de)
English (en)
Other versions
EP0093319A2 (fr
EP0093319A3 (en
Inventor
Rolf Dr. Schäfer
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.)
Bayer AG
Original Assignee
Bayer AG
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Filing date
Publication date
Application filed by Bayer AG filed Critical Bayer AG
Publication of EP0093319A2 publication Critical patent/EP0093319A2/fr
Publication of EP0093319A3 publication Critical patent/EP0093319A3/de
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Classifications

    • 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
    • C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
    • 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
    • C25B15/00—Operating or servicing cells
    • C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
    • C25B15/087—Recycling of electrolyte to electrochemical cell

Definitions

  • the present invention relates in particular to processes for the electrolytic production of chlorine and sodium hydroxide solution from sulfate-containing salt, in which the brine is circulated.
  • the impurities in the salt are enriched in the brine circuit if they are not removed by continuous cleaning operations except for residual levels that are tolerable during electrolysis. After passing through the electrolysis cell, the brine is acidified and dechlorinated. In the further course of the brine cycle, there are process and plant-related variants. The majority of large-scale plants are still amalgam plants, most of them have open salt dissolving stations. In this case, an alkalization of the brine is required before reactivation in order to safely avoid emissions of residual chlorine. Usually, the necessary excess of sodium hydroxide solution is added at the time of re-saturation, so that the hydroxides of magnesium and iron also precipitate out during the dissolving process.
  • Calcium carbonate and barium sulfate are then precipitated by adding barium compounds and soda. Soda and caustic soda are used in excess in order to achieve the most complete precipitation possible. Barium compounds are added in the deficit so that they are fully implemented.
  • a certain sulfate content in the brine is tolerable. In the membrane process, the tolerable limit of a few g / l is determined by the membranes currently available. It is expected that sulfate-resistant membranes will also be available in the future. In the case of the amalgam process with graphite anodes, the graphite burnup, which increases with the sulfate content, determines the upper limit. When using titanium anodes, relatively high sulfate contents of up to 30 g sulfate / l can be controlled in the amalgam process.
  • a process for sulfate removal without precipitation chemicals for converting sodium sulfate-containing sodium chloride salt into a NaCl brine which can be used in the diaphragm process and is largely reduced in sulfate content.
  • the sulfate-containing salt is partially dissolved in water, resulting in an aqueous solution containing Na 2 SO 4 / NaCl and solid, pure NaCl. Pure Glauber's salt is separated from the solution by cooling crystallization, the remaining NaCl solution, which is reduced in sulfate content, can be recycled into the electrolysis.
  • EP-A-8470 It is also known from EP-A-8470 to prevent an accumulation of chlorate in the brine circuit by partial flow treatment of an alkali halide-containing solution with hydrochloric acid, halogen oxyacids / salts being broken down to an acceptable level.
  • the object of the present invention is to provide a process which does not require the relatively expensive barium compounds for sulfate precipitation and in which there are also no difficulties in removing the other impurities such as magnesium and iron.
  • the sulfate can be removed from the circulating brine under certain additional conditions as a Glauber's salt by cooling crystallization without adversely affecting the electrolysis process.
  • the present invention accordingly relates to the combination of Glauber's salt cooling crystallization precipitation, chlorate removal and the precipitation of the further impurities.
  • the embodiment of the process according to the invention is particularly preferred in which, after the brine has been re-strengthened, the calcium ions introduced as an impurity with the salt are first precipitated as calcium carbonate and then further impurities are precipitated by adding sodium hydroxide, and that Precipitated is filtered off together. This results in an excellent filterable brine.
  • the possible accumulation of chlorate in the brine circuit can be avoided within a few minutes by decomposing the chlorate with a relatively high excess of hydrochloric acid.
  • the chlorate removal from a partial stream is sufficient to keep the chlorate content in the brine circuit at a tolerable value.
  • it is sufficient to keep the partial flow for the chlorate removal in the order of magnitude for the amount of hydrochloric acid necessary for the acidification for the dechlorination.
  • the volume flow of the first partial flow is preferably about half to double the volume flow of hydrochloric acid. 15 to 25%, more preferably about 20%, hydrochloric acid is preferably used. Hydrochloric acid diluted in this way is still sufficient to bring about chlorate decomposition.
  • Glauber's salt precipitation can be carried out according to known laws without any problems.
  • the strong dependence of the solubility of the Glauber's salt in concentrated brine on the temperature is known.
  • the solubility of Glauber's salt, expressed in g SOJI is approx. 15 at 5 ° C and approx. 10 at 0 ° C.
  • the parameters determining the Glauber's salt cooling crystallization precipitation can be specified in a simple manner for the other parameters present in a technical electrolysis cell.
  • a sodium chloride salt with 0.5% sulfate content is also used to strengthen a brine that has been depleted in the electrolysis cell by 40 g / l, so a partial flow of 2% of the brine flow to 5 ° C to cool so that the sulfate introduced when 40 g of salt are dissolved per 1 brine is removed. With more cooling, the partial flow for the cooling crystallization can be kept smaller.
  • the brine in this second partial stream is preferably cooled to temperatures between -5 and 10 ° C., particularly preferably to temperatures between 0 and 5 ° C.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Inorganic Chemistry (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

Claims (6)

1. Procédé de production de chlore et de lessive de soude à partir d'un sel formé de chlorure de sodium contenant un sulfate par électrolyse, dans lequel une saumure de chlorure de sodium contenant un sulfate circule entre l'appauvrissement de la saumure en chlorure de sodium dans la cellule électrolytique et le rétablissement de la force de la saumure par dissolution de sel contenant un sulfate, la saumure par dissolution de sel contenant un sulfate, la saumure étant débarrassée du chlore par acidification à l'acide chlorhydrique après avoir quitté la cellule électrolytique et le sulfate introduit avec le sel dans la saumure est éliminé de cette dernière en même temps que d'autres impuretés, caractérisé en ce que
a) un premier courant partiel, auquel l'acide chlorhydrique nécessaire pour l'acidification de la saumure, est détourné du circuit de saumure, le courant partiel est réuni avec le courant principal de saumure après une durée de séjour suffisante pour décomposer le chlorate contenu dans le courant partiel, formé lors de l'électrolyse, et
b) un second courant partiel est détourné du courant de saumure, le second courant partiel est refroidi de manière à faire cristalliser une quantité de Na2S04' 10H20 correspondant au sulfate total introduit dans la saumure, le magma cristallin est séparé et le second courant partiel est réuni avec le courant principal de saumure, et
. c) la saumure est renforcée à un pH de 6 à 8,5 par l'addition d'hydroxyde de sodium.
2. Procédé suivant la revendication 1, caractérisé en ce que, après le renforcement de la saumure, les ions calcium introduits comme impureté avec le sel sous forme de carbonate de calcium sont tout d'abord précipités par addition de carbonate de sodium, puis d'autres impuretés sont précipitées par addition ultérieure d'hydroxyde de sodium et le précipité est séparé en commun par filtration.
3. Procédé suivant la revendication 1 ou 2, caractérisé en ce qu'on entretient dans le circuit de saumure une teneur en sulfate de 10 à 30 gil, de préférence de 15 à 25 g/I.
4. Procédé suivant l'une des revendications 1 à 3, caractérisé en ce que le refroidissement de la saumure est effectué dans le second courant partiel à une température de -5 à 10 °C, de préférence de 0 à 5 °C.
5. Procédé suivant l'une des revendications 1 à 4, caractérisé en ce qu'on introduit dans le premier courant partiel de l'acide chlorhydrique à 15-25 %.
6. Procédé suivant l'une des revendications 1 à 5, caractérisé en ce que le flux volumique du premier courant partiel correspond environ à une quantité allant de la moitié au double de l'acide chlorhydrique nécessaire pour acidifier la saumure pour l'élimination du chlore.
EP83103829A 1982-05-03 1983-04-20 Procédé de préparation électrolytique de chlore et de soude caustique à partir de sel contenant des sulfates Expired EP0093319B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19823216418 DE3216418A1 (de) 1982-05-03 1982-05-03 Verfahren zur elektrolytischen herstellung von chlor und natronlauge aus sulfathaltigem salz
DE3216418 1982-05-03

Publications (3)

Publication Number Publication Date
EP0093319A2 EP0093319A2 (fr) 1983-11-09
EP0093319A3 EP0093319A3 (en) 1984-02-08
EP0093319B1 true EP0093319B1 (fr) 1986-07-30

Family

ID=6162527

Family Applications (1)

Application Number Title Priority Date Filing Date
EP83103829A Expired EP0093319B1 (fr) 1982-05-03 1983-04-20 Procédé de préparation électrolytique de chlore et de soude caustique à partir de sel contenant des sulfates

Country Status (3)

Country Link
EP (1) EP0093319B1 (fr)
JP (1) JPS58199882A (fr)
DE (2) DE3216418A1 (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3345898A1 (de) * 1983-12-20 1985-07-04 Bayer Ag, 5090 Leverkusen Verfahren zur entfernung von sulfat aus elektrolysesole
US5126019A (en) * 1989-11-16 1992-06-30 Texas Brine Corporation Purification of chlor-alkali membrane cell brine
US5028302A (en) * 1989-11-16 1991-07-02 Texas Brine Corporation Purification of chlor-alkali membrane cell brine
GB9815173D0 (en) 1998-07-13 1998-09-09 Nat Power Plc Process for the removal of sulphate ions
CN112321046A (zh) * 2020-09-24 2021-02-05 四川永祥股份有限公司 淡盐水浓母液盐回收系统

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3407128A (en) * 1967-03-13 1968-10-22 Ciba Ltd Process for the manufacture of chlorine, sodium hydroxide and hydrogen by the electrolysis of sodium chloride in mercury cells
FR2376907A1 (fr) * 1977-01-06 1978-08-04 Kestner App Evaporateurs Procede de traitement, de sel sulfate precipite au cours de l'evaporation de soude caustique de cellules a diaphragme
DE2837313A1 (de) * 1978-08-26 1980-03-13 Metallgesellschaft Ag Verfahren zur elektrolyse waessriger alkalihalogenid-loesungen
DE3037818C2 (de) * 1980-10-07 1985-08-14 Hoechst Ag, 6230 Frankfurt Verfahren zur Herstellung von Natriumbisulfat

Also Published As

Publication number Publication date
DE3364877D1 (en) 1986-09-04
EP0093319A2 (fr) 1983-11-09
EP0093319A3 (en) 1984-02-08
DE3216418A1 (de) 1983-11-03
JPS58199882A (ja) 1983-11-21

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