Electrodialytic process for the conversion of impure soda values to sodium hydroxide and carbon dioxide

• US 4,238,305 A
• Filed: 10/29/1979
• Issued: 12/09/1980
• Est. Priority Date: 10/29/1979
• Status: Expired due to Term

• Current Assignee: HMC Patents Holding Co., Inc. (Gentek Incorporated)
• Original Assignee: Allied Chemical Corporation (Honeywell International Inc.)
• Inventors: Gancy, Alan B., Jenczewski, Theodore J.
• Primary Examiner(s): Prescott, Arthur C.
• Application Number:
  US06/088,781
• Time in Patent Office: 407 Days
• Field of Search: 204/180 P, 204/301
• US Class Current: 204/538
• CPC Class Codes: B01D 61/445 with bipolar membranes; Water splitting
• CPC Class Codes: C01D 1/04 Hydroxides

Abstract

An electrodialytic process for the conversion of soda sources containing anionic and optionally nonionic impurities to high purity, high strength sodium hydroxide and carbon dioxide gas is disclosed.

Claims

1. A process for the production of high strength, high purity NaOH and CO₂ from soda values in an electrodialysis cell having an anode and a cathode compartment separated by base and acid zones, which comprises the steps of:

(a) introducing an aqueous soda solution having NaHCO₃, Na₂ CO₃, trona or mixtures thereof to an acid zone of the electrodialysis cell located between a cation permselective face of a bipolar membrane and one face of a cation permselective membrane;

(b) introducing an aqueous NaOH solution to a base zone of the cell located between an anion permselective face of a bipolar membrane and the other face of said cation permselective membrane;

(c) passing direct electric current through the electrodialysis cell thereby producing H₂ CO₃ and CO₂ gas from the soda solution in the acid zone and producing a NaOH-enriched stream in the base zone;

(d) withdrawing the NaOH-enriched product stream from the base zone; and

(e) withdrawing H₂ CO₃ and CO₂ gas and partially depleted soda solution from the acid zone.

2. A process as described in claim 1 wherein the Na₂ CO₃ content in the soda solution introduced in step (a) is less than about 12 weight percent.

3. A process as described in claim 1 wherein in step (a) the soda values have been at least in part derived from sodium carbonate crystallizer mother liquid purge.

4. A process as described in claim 1 wherein the soda values in step (a) are at least in part derived from trona pond water.

5. A process as described in claim 1 wherein the soda values in step (a) are at least in part derived from uncalcined trona.

6. A process as described in claim 5 wherein the initial concentration of NaHCO₃ is less than about 5 weight percent and that of Na₂ CO₃ is less than about 6.2 weight percent.

7. A process as described in claim 1 wherein the NaOH product stream from step (d) is contacted with CO₂ gas to form Na₂ CO₃.

8. A process as described in claim 1 wherein the aqueous soda solution contains sodium bicarbonate from the Solvay ammonia-soda process.