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CN-121338543-B - Electrodialysis method and device

CN121338543BCN 121338543 BCN121338543 BCN 121338543BCN-121338543-B

Abstract

The invention belongs to the technical field of membrane separation and relates to an electrodialysis method for avoiding hydrogen production, which comprises the following steps of (1) adding a raw material aqueous solution to an electrodialysis device, and (2) adding aqueous solutions of salts with different valence states of polyvalent metals M to a cathode chamber and an anode chamber of the electrodialysis device, wherein in the method, the molar ratio of relatively high valence cations of the metals M in the feed to the cathode chamber to relatively low valence cations of the metals M in the feed to the anode chamber is at least 1:10, wherein the metals M are selected from iron, nickel, manganese or cobalt, and the metals M in the feed to the cathode chamber are the same as the metals M in the feed to the anode chamber. The invention also includes an electrodialysis system for carrying out the method of the invention. The invention can effectively inhibit the hydrogen output of the cathode chamber, thereby effectively reducing the explosion-proof grade of the electrodialysis device and simultaneously realizing cost and energy consumption reduction.

Inventors

  • ZHANG PENG

Assignees

  • 巴斯夫新材料有限公司

Dates

Publication Date
20260512
Application Date
20251216

Claims (14)

  1. 1. A method of electrodialysis to avoid hydrogen production, characterized in that the method comprises the steps of: (1) Adding the aqueous feed solution to an electrodialysis unit, and (2) Aqueous solutions of salts of different valence states of the polyvalent metal M are added to the cathode and anode compartments of the electrodialysis device, Wherein in the process the molar ratio of the relatively higher valence cations of the polyvalent metal M added to the feed to the cathode compartment to the relatively lower valence cations of the polyvalent metal M added to the feed to the anode compartment is at least 1:10, Wherein the polyvalent metal M is selected from iron, nickel, manganese or cobalt, wherein the polyvalent metal M added to the feed to the cathode chamber is the same as the polyvalent metal M added to the feed to the anode chamber.
  2. 2. Electrodialysis process according to claim 1, wherein in the process the molar ratio of the relatively higher valence cations of the polyvalent metal M added to the feed to the cathode compartment to the relatively lower valence cations of the polyvalent metal M added to the feed to the anode compartment is at least 10:1.
  3. 3. Electrodialysis process according to claim 1, wherein the anions of the salts of polyvalent metal M of different valences are also identical.
  4. 4. Electrodialysis process according to claim 1, wherein aqueous solutions of salts of different valence of the polyvalent metal M are added from the buffer tank to the cathode and anode compartments.
  5. 5. The electrodialysis process according to any one of claims 1-4, wherein the process further comprises: (3) The stream from the cathode compartment and the stream from the anode compartment are mixed in a recycle loop and the resulting mixture is split and added as feed to step (2) to the cathode compartment and the anode compartment of the electrodialysis device, respectively, wherein the molar ratio of the relatively higher valent cations of the polyvalent metal M to the relatively lower valent cations of the polyvalent metal M in the mixture is at least 1:10.
  6. 6. Electrodialysis process according to claim 5, wherein the molar ratio of the relatively higher valence cations of the polyvalent metal M to the relatively lower valence cations of the polyvalent metal M in the mixture is at least 10:1.
  7. 7. An electrodialysis process according to claim 5 wherein the circulation loop comprises a surge tank and the resulting mixture is split from the surge tank and added as feed to step (2) to the cathode and anode compartments of the electrodialysis device, respectively.
  8. 8. An electrodialysis process according to any one of claims 1 to 4, 6,7 wherein the feed flow to the anode compartment in step (2) is at least 3 times the feed flow to the cathode compartment by weight.
  9. 9. Electrodialysis process according to claim 8, wherein the feed flow to the anode compartment in step (2) is at least 5 times the feed flow to the cathode compartment by weight.
  10. 10. An electrodialysis process according to any one of claims 1 to 4, 6, 7, 9 wherein the pH at the outlet of the anode compartment is controlled to be 10 or higher.
  11. 11. Electrodialysis process according to any one of claims 1 to 4, 6, 7, 9, wherein the pH at the outlet of the cathode compartment is controlled in the range of 2.5 to 6.
  12. 12. Electrodialysis process according to claim 11, wherein the pH at the outlet of the cathode compartment is controlled in the range of 3.5 to 5.
  13. 13. Electrodialysis process according to any one of claims 1 to 4, 6, 7, 9, 12, wherein the salts of polyvalent metal M of different valence are the salts of Fe 3+ and the salts of Fe 2+ , the corresponding anions of the salts of different valence being monovalent or divalent anions.
  14. 14. The electrodialysis method according to any one of claims 1-4, 6, 7, 9, 12, wherein the aqueous feed solution added in step (1) is an aqueous Na 2 SO 4 solution and the different valence salts of the polyvalent metal M added in step (2) are Fe 2 (SO 4 ) 3 and FeSO 4 .

Description

Electrodialysis method and device Technical Field The present invention relates to an electrodialysis method. More particularly, the present invention relates to an electrodialysis method that improves safety. The invention also relates to an electrodialysis system. Background Electrodialysis is a membrane separation technology for realizing ion separation and purification in solution by utilizing the action of an ion exchange membrane and a direct current electric field, and is widely applied to the fields of sea water desalination, wastewater treatment, material purification and the like. The electrodialysis device includes a cathode compartment and an anode compartment, and a cathode membrane, an anode membrane, and a bipolar membrane disposed between the anode compartment and the cathode compartment. Hydrogen is by-produced in the cathode compartment during electrodialysis. Hydrogen gas has very wide explosion limit (4.0% -75.6%), so that the safety of the device is greatly influenced. For this reason, the building of the electrodialysis device is generally designed according to class a, the plant cost is relatively high, and the design standard of other electric equipment in the workshop is also improved, so that the whole investment cost is high, and the safety risk in the whole production process is high. Accordingly, there is a need for an electrodialysis method that is capable of effectively suppressing hydrogen production from the cathode compartment, thereby effectively reducing the explosion-proof rating of the electrodialysis device, while achieving cost and energy consumption reduction. In addition, there is a need for electrodialysis systems that can be used to carry out such electrodialysis methods. Disclosure of Invention In order to solve the problems in the prior art, the invention provides an electrodialysis method and an electrodialysis system. By the method, the hydrogen output of the cathode chamber is effectively inhibited, so that the process safety is improved, and the process cost is saved. One aspect of the invention relates to an electrodialysis method for avoiding hydrogen production, the method comprising the steps of: (1) Adding the aqueous feed solution to an electrodialysis unit, and (2) Aqueous solutions of salts of different valence states of the polyvalent metal M are added to the cathode and anode compartments of the electrodialysis device, Wherein in the process the molar ratio of relatively higher valence cations of the metal M added to the feed to the cathode compartment to relatively lower valence cations of the metal M added to the feed to the anode compartment is at least 1:10, preferably at least 1:1, more preferably at least 10:1, Wherein the metal M is selected from iron, nickel, manganese or cobalt, preferably the metal M is iron, wherein the metal M added to the feed to the cathode compartment is the same as the metal M added to the feed to the anode compartment, preferably the anions of the different valence salts of the polyvalent metal M are also the same. In another aspect, the invention relates to an electrodialysis system comprising an electrodialysis device comprising a cathode compartment and an anode compartment, and a circulation device in fluid communication with the cathode compartment and the anode compartment of the electrodialysis device for receiving and mixing a stream from the cathode compartment with a stream from the anode compartment, and recycling the resulting mixture to the cathode compartment and the anode compartment. The invention can effectively inhibit the hydrogen production of the cathode chamber and the oxygen production of the anode chamber. Moreover, the invention can also improve the electric efficiency of the whole device and reduce the energy consumption. This can bring beneficial effects on both existing electrodialysis devices and on newly built electrodialysis devices. The safety of the whole device can be effectively improved for the existing electrodialysis device, and the invention is more important for preparing the newly built electrodialysis device, because the method and the system of the invention enable the explosion-proof level of the device to be reduced from zone 0 to zone 2 or even to a non-explosion-proof zone, so that a plurality of measures and a large amount of investment related to the explosion-proof zone can be effectively avoided. Generally, non-explosion-proof equipment may reduce investment by about half relative to area 0 explosion-proof equipment. Drawings Fig. 1 is an exemplary schematic diagram of a prior art electrodialysis embodiment. Fig. 2 is an exemplary schematic of an embodiment of the present invention. Fig. 3 is an exemplary schematic of another embodiment of the present invention. Detailed Description The present invention will be described in further detail by the following detailed description. These specific embodiments are given for illustrative purposes only and are not intended