Process for producing a concentrated aqueous sodium hydroxide solution

Patent metadata

Field	Value
Publication number	US-11465907-B2
Application number	US-202016953404-A
Country	US
Kind code	B2
Filing date	Nov 20, 2020
Priority date	Nov 12, 2013
Publication date	Oct 11, 2022
Grant date	Oct 11, 2022

Abstract

A method for producing a concentrated aqueous sodium hydroxide solution from a purge stream deriving from a sodium carbonate, or sesquicarbonate, or wegsheiderite crystallizer, or sodium bicarbonate crystallizer, said purge stream comprising sodium carbonate and/or bicarbonate, and at least 1% of sodium chloride or sodium sulfate and a soluble impurity from an ore deposit comprising at least one of the following elements: As, Ba, B, Ca, Co, K, Li, Mo, P, Pb, Se, Sn, Sr, Te, Tl, Ti, V, and W, to be purified, the method comprising: causticizing at least 50 mol. % of the sodium carbonate into a caustic solution and into a calcium carbonate mud with lime and water; separating the mud from the caustic solution; concentrating the caustic solution by removing part of the water to obtain a concentrated caustic solution comprising at least 25% NaOH, and a crystallized solid comprising sodium carbonate and sodium chloride and/or sulfate; and separating the crystallized solid from the concentrated caustic solution, said crystallized solid to be disposed of or to be further valorized.

First claim

I claim:

1. A method for producing a concentrated aqueous sodium hydroxide solution from a purge stream derived from an anhydrous sodium carbonate crystallizer, or a sodium carbonate monohydrate crystallizer, or a sodium carbonate decahydrate crystallizer, or a sodium sesquicarbonate crystallizer, or a wegsheiderite crystallizer, or a sodium bicarbonate crystallizer, said purge stream comprising:
sodium carbonate and/or sodium bicarbonate from a sodium carbonate or sodium bicarbonate ore deposit selected from the group consisting of: trona ore, nahcolite ore, and wegscheiderite ore,
at least 1% by weight of a sodium salt selected from the group consisting of sodium chloride, sodium sulfate and mixtures thereof, and
at least one soluble salt or at least one soluble impurity from said sodium carbonate or sodium bicarbonate ore deposit, said soluble salt or soluble impurity comprising at least one of the following elements selected from the group consisting of: As, Ba, B, Ca, Co, K, Li, Mo, P, Pb, Se, Sn, Sr, Te, Tl, Ti, V, and W,
said concentrated aqueous sodium hydroxide solution comprising:
at least 25% by weight of NaOH,
said method comprising the following steps:
f) adding lime to the purge stream, in presence of water, to causticize at least 50 mol. % of the sodium from sodium carbonate and/or sodium bicarbonate, into an aqueous sodium hydroxide solution and into a calcium carbonate mud;
g) separating the calcium carbonate mud from the aqueous sodium hydroxide solution;
h) concentrating the aqueous sodium hydroxide solution by removing part of the water to obtain:
the concentrated aqueous sodium hydroxide solution comprising at least 25% NaOH, and to crystallize a solid comprising sodium carbonate and comprising sodium chloride and/or sulfate,
i) separating the crystallized solid comprising sodium carbonate and sodium chloride and/or sulfate from the concentrated aqueous sodium hydroxide solution;
j) valorizing the concentrated aqueous sodium hydroxide solution as a salable sodium hydroxide solution or recycling at least one part of the concentrated aqueous sodium hydroxide solution to the anhydrous sodium carbonate crystallizer, or to the sodium carbonate monohydrate crystallizer, or to the sodium carbonate decahydrate crystallizer, or to the sodium sesquicarbonate crystallizer, or to the sodium bicarbonate crystallizer, or to processes upstream of the anhydrous sodium carbonate crystallizer, or of the sodium carbonate monohydrate crystallizer, or of the sodium carbonate decahydrate crystallizer, or of the sodium sesquicarbonate crystallizer, or of the sodium bicarbonate crystallizer;
and wherein the at least one soluble salt or the at least one soluble impurity comprising at least one element selected from the group consisting of: As, Ba, Be, Bi, B, Ca, Co, Cu, F, K, Li, Mo, P, Pb, Se, Sn, Sr, Te, Tl, Ti, V, and W,
is at least partially removed at steps f) to i) from the purge stream.

2. The method of claim 1 wherein the at least one soluble salt or the at least one soluble impurity from the trona ore deposit or from the nahcolite ore deposit, comprises at least one element selected from the group consisting of: Ca, Cl, Cu, Pb, S, Se, Te, Tl that is at least partially removed at steps h) to i) from the purge stream.

3. The method of claim 1 wherein at least 66% of sodium chloride present in the purge stream is removed at steps f) to i) in the concentrated aqueous sodium hydroxide solution.

4. The method of claim 1 wherein at least 89% of sulfur expressed as sulfate present in the purge stream is removed at steps f) to i) in the concentrated aqueous sodium hydroxide solution.

5. The method of claim 1 wherein at least 74% of Mg (magnesium) element from the at least one soluble salt or the at least one soluble impurity from the trona ore deposit or the nahcolite ore deposit and present in the purge stream is removed from steps f) to i) in the concentrated aqueous sodium hydroxide solution.

6. The method of claim 1 wherein at least 92% of P (phosphorus) element from the at least one soluble salt or the at least one soluble impurity from the trona ore deposit or the nahcolite ore deposit and present in the purge stream is removed from steps f) to i) in the concentrated aqueous sodium hydroxide solution.

7. The method of claim 1 wherein the concentrated aqueous sodium hydroxide solution comprises at least 114 mg P and at most 460 mg P expressed as PO4/kg.

8. The method of claim 1 wherein the concentrated aqueous sodium hydroxide solution comprises at least 187 mg Si/kg and at most 1970 mg Si/kg.

9. The method of claim 1 wherein the concentrated aqueous sodium hydroxide solution comprises at least 3200 mg S and at most 6684 mg S expressed as SO4/kg.

10. The method of claim 1 , wherein at step h) the weight ratio of sodium carbonate to the sum of the sodium chloride and/or sodium sulfate in crystallized solid is at most 2.

11. The method of claim 1 , wherein at step f) the lime is hydrated lime, or a milk of lime comprising hydrated lime.

12. The method of claim 1 , wherein, at step f), the lime used as quick lime directly in the causticization step or the lime used before hydration to constitute hydrated lime, comprises more than 90% calcium oxide (CaO).

13. The method of claim 1 , wherein the lime is generated by recycle and calcination of the washed calcium carbonate mud.

14. The method of claim 1 , wherein at step f) the lime is quick lime or hydrated lime, and the lime comprises magnesium oxide or magnesium hydroxide wherein the magnesium to calcium molar ratio is less than 0.2 mol/mol.

15. The method of claim 1 , wherein the purge stream comprises Na2CO3 and/or NaHCO 3 in a quantity of at least 7% TA (Total Alkalinity) expressed as equivalent Na2CO3.

16. The method according to claim 1 , wherein the purge stream is a purge derived from a sodium carbonate decahydrate crystallizer, or from a sodium sesquicarbonate crystallizer.

17. The method according to claim 16 , wherein the sodium carbonate decahydrate crystallizer, or the sodium sesquicarbonate crystallizer are crystallizers in which a purge from a sodium carbonate monohydrate crystallizer is treated in order to control the sodium chloride and/or the sodium sulfate of the sodium monohydrate crystallizer.

18. A method for producing a sodium carbonate salt or a sodium bicarbonate salt from a sodium carbonate solution or a sodium bicarbonate solution derived from a sodium carbonate ore or a sodium bicarbonate ore selected from the group consisting of: trona, nahcolite, and wegsheiderite ores, or from a sodium carbonate/bicarbonate lake water, or from a reclaimed solid, or from a mine water, said ores, waters or solid comprising sodium carbonate/bicarbonate, comprising the following steps:
a) optionally pre-treating the sodium carbonate solution or the sodium bicarbonate solution in removing part of organics and/or changing the carbonate or bicarbonate molar ratio in order to obtain an optional pre-treated sodium carbonate solution or sodium bicarbonate solution;
b) crystallizing from the sodium carbonate solution or the sodium bicarbonate solution, or from the optionally pre-treated sodium carbonate solution or sodium bicarbonate solution, a sodium carbonate salt or a sodium bicarbonate salt with one of the means selected from the group consisting of:
evaporation crystallization, cooling evaporation, carbonation crystallization and combinations thereof,
said crystallization step of the sodium carbonate salt or the sodium bicarbonate salt generating a mother liquor, said mother liquor comp

Assignees

• Solvay

Inventors

• Vandendoren Alain

Classifications

• C01D1/22 Primary

  with carbonates or bicarbonates · CPC title

• C01D7/24

  Crystallisation · CPC title

• C22B26/10

  Obtaining alkali metals · CPC title

• C01D5/16

  Purification {(C01D5/145 takes precedence)} · CPC title

• C01D1/42 Primary

  Concentration; Dehydration · CPC title