US-12618164-B2 - Electrode attachment assembly, cell and method of use

Abstract

Electrode attachment assemblies for electrolytic cells and electrolytic cells having one or more electrode attachment assemblies and the method of using the same are provided that comprise a carbon-containing electrode and one or more deformable attachment elements in direct or indirect contact with said carbon-containing electrode, wherein said one or more deformable attachment elements will deform at a stress lower than the stress that results in fracture of the carbon-containing electrode to accommodate the expansion of the carbon-containing electrode when in use.

Inventors

• James Patrick Nehlsen
• WILLIAM F. SCHULZE

Assignees

• VERSUM MATERIALS US, LLC

Dates

Publication Date

20260505

Application Date

20201104

Claims (20)

1. 1 . An electrode attachment assembly for an electrolytic cell comprising a carbon-containing electrode and one or more deformable attachment elements in direct or indirect contact with said carbon-containing electrode, wherein said one or more deformable attachment elements will deform at a stress lower than the stress that results in fracture of the carbon-containing electrode to accommodate the expansion of the carbon-containing electrode when in use, wherein the one or more deformable elements comprise fully annealed copper.
2. 2 . The electrode attachment assembly of claim 1 wherein said one or more deformable attachment elements at no time exerts more than 8,000 psi of stress on any portion of the carbon-containing electrode.
3. 3 . The electrode attachment assembly of claim 1 wherein at no time said one or more deformable attachment elements exerts more than 6,000 psi of stress on any portion of the carbon-containing electrode.
4. 4 . The electrode attachment assembly of claim 1 wherein said one or more deformable attachment elements deform at a pressure between from 4,000 to 10,000 psi of stress.
5. 5 . The electrode attachment assembly of claim 1 wherein said one or more deformable attachment elements deform at a pressure between from 4,000 to 8,000 psi of stress.
6. 6 . The electrode attachment assembly of claim 1 wherein no portion of the electrode assembly comprises a polymer.
7. 7 . The electrode attachment assembly of claim 1 wherein said fully annealed copper has mechanical properties conforming to ASTM O60 temper.
8. 8 . The electrode attachment assembly of claim 1 wherein said one or more deformable attachment elements comprises copper alloy C11000.
9. 9 . The electrode attachment assembly of claim 1 wherein said one or more deformable attachment elements have a yield strength at 0.5% extension less than 10,000 psi.
10. 10 . The electrode attachment assembly of claim 1 wherein said deformable attachment device comprises one or more selected from compression bands, straps, screws, threaded bolts, rods, threaded rods, posts, or shafts.
11. 11 . The electrode attachment assembly of claim 1 wherein said deformable attachment device comprises one or more selected from springs, coil springs, bolts, screws, bracings, crush washers, U- or C-shaped hanger bars, C-shaped clamps.
12. 12 . The electrode attachment assembly of claim 1 wherein said deformable attachment device comprises one or more selected from conical washers, spring washers, crush washers, elastomeric pads, gaskets or washers.
13. 13 . The electrode attachment assembly of claim 1 wherein said deformable attachment element comprises one or more bolts.
14. 14 . The electrode attachment assembly of claim 1 wherein said carbon-containing electrode comprises carbon selected from ungraphitized carbon, graphitized carbon, low-permeability carbon, high-permeability carbon, carbon fiber, pressed carbon powder, mesocarbon microbeads, carbon impregnated with metals, carbon coated with a thin layer of metal, carbon diamond, coal or petroleum-derived coke.
15. 15 . The electrode attachment assembly of claim 1 wherein said carbon-containing electrode is a monolithic structure, or a composite structure.
16. 16 . The electrode attachment assembly of claim 1 wherein said carbon-containing electrode is a shaped mass of compressed carbon comprising a form of coal or petroleum-derived coke and a pitch binder, baked to densify, harden, and to carbonize the pitch.
17. 17 . The electrode attachment assembly of claim 1 wherein said one or more deformable elements deforms to accommodate the expansion of the carbon-containing electrode by about 0.1% to about 1.0% without said one or more deformable elements exerting stress on the carbon-containing electrode in excess of the fracture strength of said carbon-containing electrode.
18. 18 . The electrode attachment assembly of claim 1 wherein said one or more deformable elements deforms elasticly.
19. 19 . The electrode attachment assembly of claim 1 wherein said one or more deformable elements deforms plasticly.
20. 20 . The electrode attachment assembly of claim 1 wherein said one or more deformable elements exert less than 8,000 psi of stress on the carbon-containing electrode after 0.5% expansion of the carbon-containing electrode.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a National Stage filing under 35 U.S.C. 371 of International Patent Application No. PCT/US2020/058775, which claims priority to U.S. provisional application 63/057,561 filed on Sep. 8, 2020, the entire contents of both are incorporated herein by reference thereto for all allowable purposes. BACKGROUND OF THE INVENTION The industrial generation of elemental fluorine (F2) and related fluorinated gases such as nitrogen trifluoride (NF3) occurs primarily in electrolytic cells. For fluorine gas generation especially, the anodes of such cells are made from carbon. To function, the anodes must be connected to a source of electrical power such that electrical current can flow between the cathodes and anodes. Making a reliable connection to the anodes in a fluorine cell is challenging due to the very aggressive chemical conditions found in such cells. The liquid electrolyte used in such cells is typically a molten salt mixture of potassium fluoride (KF) and hydrogen fluoride (HF). To generate NF3, ammonium fluoride is used in place of or in addition to KF. This electrolyte, combined with the elevated operating temperature and the anodic potential applied to the anodes, creates highly corrosive conditions that tend to attack the metallic components of the anode connection apparatus. Furthermore, for efficient and stable operation, the electrical resistance of the connection to the anodes must start and remain low throughout the lifetime of the anode. Any deterioration in the electrical connection to the anode is known to cause breakage of the anode, as thoroughly described by Ring and Royston (Australian Atomic Energy Commission Report E281, 1973, ISBN 0 642 99601 6). Many ways to attach a carbon anode to the electrical source and/or other support member have been suggested in the prior art including those disclosed in U.S. Pat. No. 5,290,413 (circumferential metal sleeve around the anode top), U.S. Pat. No. 3,041,266A (metal hanger bar with the anodes attached via several bolts), JP7173664A (threaded bolts inserted first through a metal bar and then into the carbon anode), U.S. Pat. No. 5,688,384 (screws in the top of the carbon anode), KR100286717 B1 (carbon anode is held between two metal plates by bolts), CN102337491 A (clamping plates), U.S. Pat. No. 8,349,164 (clamping plates), Zhao, et al. (clamping plate), U.S. Pat. No. 6,210,549 (C-shaped anode hanger bar and a threaded rod). Despite the many different attachment methods, the carbon anodes fracture during use in electrolysis after a period of time. The fracture of the carbon anode renders the cell unusable and requires that at least some portion of the cell be rebuilt. There is therefore a need in the art to extend the life of the carbon electrodes in an electrolytic cell. BRIEF SUMMARY OF THE INVENTION This invention provides an electrode attachment assembly and an electrolytic cell comprising an electrode attachment assembly, said electrode attachment assembly comprising a carbon-containing electrode and one or more deformable attachment elements in direct or indirect contact with said carbon-containing electrode, wherein said one or more deformable attachment elements will deform at a stress below the fracture strength of the carbon-containing electrode to accommodate the expansion of the carbon-containing electrode when in use. In another embodiment, this invention provides an electrolytic cell comprising one or more electrode attachment assemblies of the present invention, a container, an electrical distribution member, an electrolytic bath and one or more oppositely charged electrodes. In yet another embodiment, this invention provides a method or use of the electrolytic cell to manufacture fluorine-containing materials comprising the step of introducing electrical energy into said electrolytic cell to cause chemical reactions at said carbon-containing electrode and said one or more oppositely charged electrodes to produce fluorine-containing materials at said carbon-containing electrode. This invention provides the benefit of a cell and electrode attachment assemblies, which may be anode attachment assemblies that reduce the tendency of carbon electrodes (anodes) to fracture, thereby extending the life of the electrodes, which enables longer cell operation, lowers maintenance costs by reducing the frequency of rebuilding cells and improves safety. Broken electrodes (anodes) can sometimes cause electrical shorting inside the cell or lead to electrical arcing, resulting in damage to many of the cell's internal components. This invention further provides electrode attachment assemblies (anode attachment assemblies) possessing good electrical contact and resistance to corrosion. Corrosion of the electrical connection to the carbon electrode may also be reduced by keeping the connection points and metallic components “dry”, that is, preferably above the surface of the liquid electrolyte. Cells mad