High swelling ramming paste for aluminum electrolysis cell

• US 20040178063A1
• Filed: 03/12/2003
• Published: 09/16/2004
• Est. Priority Date: 03/12/2003
• Status: Active Grant

• Current Assignee: Alcan Incorporated (Rio Tinto Limited)
• Original Assignee: Alcan Incorporated (Rio Tinto Limited)
• Inventors: Chen, Weixia, Lavigne, Lise, Bergeron, Emmanuel, Mirchi, Amir A., Bergeron, Jules
• Granted Patent: US 7,186,357 B2
• Time in Patent Office: Days
• US Class Current: 204/280
• CPC Class Codes: C04B 2235/3217 Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
• CPC Class Codes: C04B 2235/3232 Titanium oxides or titanates, e.g. rutile or anatase
• CPC Class Codes: C04B 2235/3409 Boron oxide, borates, boric acids, or oxide forming salts thereof, e.g. borax
• CPC Class Codes: C04B 2235/3813 Refractory metal borides
• CPC Class Codes: C04B 2235/3826 Silicon carbides
• CPC Class Codes: C04B 2235/422 Carbon
• CPC Class Codes: C04B 2235/48 Organic compounds becoming part of a ceramic after heat treatment, e.g. carbonising phenol resins
• CPC Class Codes: C04B 2235/77 Density
• CPC Class Codes: C04B 2235/96 Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
• CPC Class Codes: C04B 2235/9607 Thermal properties, e.g. thermal expansion coefficient
• CPC Class Codes: C04B 2235/9615 Linear firing shrinkage
• CPC Class Codes: C04B 35/013 containing carbon C04B35/103 takes precedence
• CPC Class Codes: C04B 35/528 obtained from carbonaceous particles with or without other non-organic components
• CPC Class Codes: C04B 35/58071 based on titanium borides
• CPC Class Codes: C04B 35/66 Monolithic refractories or refractory mortars, including those whether or not containing clay making or repairing of linings F27D1/16
• CPC Class Codes: C25C 3/08 Cell construction, e.g. bottoms, walls, cathodes

Abstract

A new ramming paste for aluminum reduction cell cathodes is a high swelling cold ramming paste made of a blend of pitch, light oil diluent and an aggregate comprising a mixture of anthracite and crushed anode butts or calcined coke. The presence of the crushed anode butts or calcined coke increases the sodium swelling index of the paste by about four times higher than that of regular ramming pastes. This new high swelling cold ramming paste may also contain an amount of a refractory hard material, such as TiB₂.

Claims

1. A high swelling cold ramming paste for use in joining components of electrolytic cells for the electrolysis of alumina for the production of aluminum, comprising a mixture of pitch, a light oil and a carbonaceous aggregate, said aggregate containing anthracite and crushed anode butts or calcined coke with the crushed anode butts or calcined coke comprising up to 20% by weight of the total aggregate.

2. A high swelling cold ramming paste according to claim 1 wherein the crushed anode butts or calcined coke comprise about 15 to 20% by weight of the total aggregate.

3. A high swelling cold ramming paste according to claim 1 containing 10 to 15% by weight of said pitch.

4. A high swelling cold ramming paste according to claim 3 containing about 5 to 10% by weight of said light oil.

5. A high swelling cold ramming paste according to claim 4 wherein the light oil has a boiling point in the range of about 210-355°

C.

6. A high swelling cold ramming paste according to claim 1 which further comprises particles of a refractory hard material.

7. A high swelling cold ramming paste according to claim 5 which comprises about 30 to 60% by weight titanium diboride, about 10 to 15% by weight pitch, about 5 to 10% by weight light oil and the balance a carbonaceous aggregate comprising anthracite and crushed anode butts where the crushed anode butts represent about 15 to 20% by weight of the total carbonaceous aggregates.

8. A method of making a high swelling cold ramming paste for use in joining components of electrolytic cells for the electrolysis of alumina for the production of aluminum which comprises mixing together pitch, light oil and a carbonaceous aggregate comprising anthracite and crushed anode butts with the crushed anode butts comprising up to 20% by weight of the total aggregate, said mixing being carried out at about 9.0 to 130°

C. for about 20 to 50 minutes.

9. A method according to claim 8 wherein there are mixed together about 10 to 15% by weight pitch, about 5 to 10% by weight light oil and the balance carbonaceous aggregate comprising anthracite and crushed anode butts wherein the crushed anode butts represent about 15 to 20% by weight of the total aggregate.

10. A process for forming the cathode lining of an electrolytic cell for the electrolysis of alumina for the production of aluminum, said lining being made up of adjacent carbonaceous blocks having joint spaces therebetween, comprising the steps of introducing into said joint spaces a high swelling cold ramming paste comprising a mixture of pitch, light oil and a carbonaceous aggregate comprising a mixture of anthracite and crushed anode butts with the crushed anode butts comprising about 15 to 20% by weight of the total aggregate, compacting the paste within the joint spaces and thereafter baking the blocks and cemented joints at a temperature and for a time sufficient to carbonize the ramming paste and form a continuous lining structure.

11. A process according to claim 10 wherein the ramming paste is inserted into the joint spaces as a series of layers, with tamping between added layers.

12. A process according to claim 11 wherein a top layer is applied comprising a mixture of pitch, light oil, titanium diboride and a carbonaceous aggregate comprising a mixture of anthracite and crushed anode butts with the crushed anode butts comprising about 15 to 12% by weight of the total aggregate.

13. A process according to claim 12 wherein the layer of high swelling cold ramming paste immediately below the top layer containing titanium diboride is not tamped before adding the top layer and the two layers are tamped together.

14. A process for forming the cathode lining of an electrolytic cell for the electrolysis of alumina for the production of aluminum, said lining being made up of adjacent carbonaceous blocks having joint spaces therebetween, comprising the steps of introducing into said joint spaces a high swelling cold ramming paste as a series of layers with tamping between added layers except the layer before the top layer and tamping the two top layers together, and thereafter baking the blocks and cemented joints at a temperature and for a time sufficient to carbonize the ramming paste and form a continuous lining structure.

15. The process according to claim 14 wherein the top layer is applied to a thickness of about 2.5 to 12.5 cm.

16. The process according to claim 15 wherein the top layer has a density at least 25% greater than the density of the layers below.