Method of operating a diaphragm electrolytic cell

• US 20070045105A1
• Filed: 08/31/2005
• Published: 03/01/2007
• Est. Priority Date: 08/31/2005
• Status: Active Grant

• Current Assignee: Eagle US 2 LLC (TTWF LP)
• Original Assignee: PPG Industries Ohio Incorporated (Nouryon BV)
• Inventors: Fast, Robert, Schussler, Henry, Garrard, Berry, Richardson, Steven, Cimini, Joseph
• Granted Patent: US 7,618,527 B2
• Time in Patent Office: Days
• US Class Current: 204/230.200
• CPC Class Codes: C25B 1/46 in diaphragm cells
• CPC Class Codes: C25B 13/08 based on organic materials
• CPC Class Codes: C25B 15/00 Operating or servicing cells

Abstract

Describes a method for lowering the flow of liquid anolyte through perforations in the diaphragm of a diaphragm electrolytic cell, e.g., a chlor-alkali diaphragm electrolytic cell, comprising introducing ceramic fiber into the anolyte compartment of the electrolytic cell, e.g., during cell operation. The benefits described for lowering the flow of anolyte liquor through the diaphragm of a chlor-alkali diaphragm electrolytic cell are increasing the concentration of alkali metal hydroxide, e.g., sodium hydroxide, and decreasing the concentration of hypochlorite ion, e.g., sodium hypochlorite, in the catholyte liquor. Also describes introducing dopant material and/or fibers comprising halogen-containing polymer, e.g., fluorocarbon polymer fibers, into the anolyte compartment of the electrolytic cell in conjunction with the addition of ceramic fiber into the anolyte compartment, e.g., during cell operation.

Claims

1. A method for improving the operation of an electrolytic cell comprising an anolyte compartment, a catholyte compartment and a diaphragm separating the anolyte and catholyte compartments wherein liquid anolyte is introduced into the anolyte compartment and flows through the diaphragm into the catholyte compartment, which method comprises introducing ceramic fiber into the anolyte compartment in amounts sufficient to lower the flow of liquid anolyte through the diaphragm into the catholyte compartment.

2. The method of claim 1 wherein the electrolytic cell is a chlor-alkali electrolytic cell.

3. The method of claim 2 wherein the diaphragm of the electrolytic cell is a synthetic diaphragm.

4. The method of claim 1 wherein the ceramic fiber is chosen from fibers comprising the oxides, nitrides, carbides, borides and silicates of metals or semi-metals chosen from zirconium, titanium, silicon, aluminum, boron, magnesium and mixtures of such metal or semi-metal oxides, nitrides, carbides, borides and silicates.

5. The method of claim 4 wherein the ceramic fiber is chosen from fibers comprising at least one of the oxides of silicon, aluminum and zirconium.

6. The method of claim 5 wherein ceramic fiber is introduced into the anolyte compartment while the cell is operating.

7. In the method of operating a chlor-alkali electrolytic cell comprising an anolyte compartment, a catholyte compartment and a diaphragm separating the anolyte and catholyte compartments, wherein aqueous alkali metal chloride is introduced continuously into the anolyte compartment and passes through the diaphragm into the catholyte compartment which contains catholyte liquor comprising alkali metal hydroxide and wherein the concentration of alkali metal hydroxide in the catholyte liquor is less than the desired concentration, the improvement comprising introducing ceramic fiber into the anolyte compartment in amounts sufficient to increase the concentration of alkali metal hydroxide in the catholyte liquor.

8. The method of claim 7 wherein the diaphragm of the chlor-alkali electrolytic cell is a synthetic diaphragm and the alkali metal chloride is sodium chloride.

9. The method of claim 8 wherein the ceramic fiber is chosen from fibers comprising the oxides, nitrides, carbides, borides and silicates of metals or semi-metals chosen from zirconium, titanium, silicon, aluminum, boron, magnesium and mixtures of such metal or semi-metal oxides, nitrides, carbides, borides and silicates.

10. The method of claim 9 wherein the ceramic fiber is chosen from fibers comprising at least one of the oxides of silicon, aluminum and zirconium.

11. The method of claim 9 wherein the ceramic fiber is at least partially resistant to the corrosive conditions within the anolyte compartment.

12. The method of claim 11 wherein ceramic fibers are introduced into the anolyte compartment while the cell is operating.

13. The method of claim 12 wherein dopant materials are added to the anolyte in conjunction with the ceramic fibers.

14. The method of claim 13 wherein fibers comprising halogen-containing polymer are added in conjunction with the ceramic fibers.

15. The method of claim 12 wherein fibers comprising fluorocarbon polymer are added in conjunction with the ceramic fibers.

16. The method of claim 15 wherein dopant materials are added to the anolyte in conjunction with the ceramic fibers.

17. In the operation of a chlor-alkali electrolytic cell comprising an anolyte compartment, a catholyte compartment and a microporous diaphragm separating the anolyte and catholyte compartments, wherein aqueous alkali metal chloride is introduced continuously into the anolyte compartment and percolates through the diaphragm into the catholyte compartment, which contains catholyte liquor comprising alkali metal hydroxide and hypochlorite ion, and wherein the concentration of hypochlorite ion in the catholyte liquor is more than the desired concentration, the improvement comprising introducing ceramic fiber into the anolyte compartment in amounts sufficient to lower the concentration of hypochlorite ion in the catholyte liquor.

18. The method of claim 17 wherein the diaphragm of the chlor-alkali electrolytic cell is a synthetic diaphragm and the alkali metal chloride is sodium chloride.

19. The method of claim 18 wherein the ceramic fiber is chosen from fibers comprising at least one of the oxides of silicon, aluminum and zirconium.

20. The method of claim 19 wherein at least one of dopant material, fibers comprising fluorocarbon polymer and mixtures of dopant material and fluorocarbon polymer fibers are added to the anolyte compartment in conjunction with the ceramic fibers.