Title of Invention

A CARBON ELECTRODE AND METHOD OF MAKING THEREOF

Abstract The present invention provides a method of making a carbon electrode, suitable for use as an anode in an aluminum reduction cell, which comprises mixing an aggregate, comprising a mixture of particulate shot coke, and a particulate carbonaceous material other than shot coke with coal tar pitch or petroleum pitch or a combination of these pitches at an elevated temperature to form a paste wherein said aggregate comprises a combination of coarse, medium, and fine particles and said particulate shot coke may comprise a majority of said fine particles, and said paste comprises from 80 to 90%, by weight, of said aggregate and from 10 to 20%, by weight, of said pitch; forming said paste into a solid body; and baking said solid body at an elevated temperature to form said carbon electrode.
Full Text The present invention relates to an electrode for use
in the manufacture of aluminum by molten salt electrolysis
of aluminum oxide. More particularly, it relates to an
electrode, specifically to an anode, for use in aluminum
reduction cells.
It has been known to manufacture aluminum by molten
salt electrolysis of aluminum oxide dissolved in a bath of
the fluorides of aluminum and sodium, or cryolite, using a
carbon anode. Usually, such an electrolysis process is
conducted at about 900° to 1000° Centigrade. In this
process, the carbon anode is consumed by oxidation due to
the oxygen produced by the decomposition of aluminum oxide
to the aluminum metal.
In commercial anode production processes, calcined
sponge petroleum cokes or coal tar pitch cokes, along with
recycled carbon anode remnants or butts, are used to
provide an aggregate which is bound with coal tar pitch or
a combination of coal tar and petroleum pitches
(combination pitch) and subsequently shaped and heated at
an elevated temperature, e.g. about 1100°C, to form the
commercial anode. The manufacture of such commercial
anodes requires a coke that has low volatile matter,
vanadium and nickel under 500ppm and sulfur under 4%, by
weight, and preferably under 3%, by weight. Such coke is
preferably calcined, sponge coke. Shot coke, with its
higher impurity levels, more isotropic structure and
higher thermal expansion coefficient when calcined has
never been successfully used for such commercial anodes.


In particular, carbon anodes, made from an aggregate
comprising more than 5%, by weight, shot coke, exhibit a
propensity for thermal shock cracking due to the high
coefficient of thermal expansion and the anode strength is
weakened due to the difficulty in binding shot coke
particles with coal tar or combination pitch. As a
result, the anode scrap rates are unacceptably high and
anode carbon loss in the aluminum reduction cells creates
a serious and unacceptable disruption to the smelting
process.
When discussing petroleum coke, it is essential to
recognize that there are three different types of coking
processes and the petroleum coke produced from each is
distinctly different. These processes - delayed, fluid
and flexicoking - are all effective in converting heavy
hydrocarbon oil fractions to higher value, lighter
hydrocarbon gas and liquid fractions and concentrating the
contaminants (sulfur, metals, etc.) in the coke.
Petroleum coke from the delayed process is described
as delayed sponge, shot or needle coke depending on its
physical structure. Shot is most prevalent when running
the unit under severe conditions with very heavy crude oil
residuum containing a high proportion of asphaltenes.
Needle coke is produced from selected aromatic feedstocks.
Although the chemical properties are most critical, the
physical characteristics of each coke type play a major
role in the final application of the coke. For example,
sponge coke is more porous and contains greater surface
area; if the quality is acceptable, it may be sold to the


calcining industry as a raw material for anode coke
production where it has a higher value. Shot coke looks
like BB's, has much less surface area and is harder; it is
almost always sold as a fuel coke for a relatively low
value. Needle coke's unique structure lends to its use
for graphitized electrodes. Unlike the others, needle
coke is a product (not a by-product) which the refinery
intentionally produces from selected hydrocarbon
feedstocks.
Shot coke is characterized by small round spheres of
coke, the size of BB's, loosely bound together.
Occasionally, they agglomerate into ostrich egg sized
pieces. While shot coke may look like it is entirely made
up of shot, most shot coke is not 100% shot.
Interestingly, even sponge coke may have some measurement
of embedded shot coke. A low shot coke percentage in
petroleum coke is preferably specified for anode grades of
petroleum coke.
Shot coke, while useful as a fuel, is less valuable
than sponge coke which can be used to prepare the more
valuable carbon anodes. It is therefore desirable to find
a way to use the less valuable shot coke in an application
having a greater value, i.e. to manufacture carbon anodes,
provided said carbon anodes do not have poor quality.
SUMMARY OF THE INVENTION
Preferably, in accordance with the present invention,
the aggregate comprises more than 5%, by weight, of shot


coke and may comprise up to 90%, by weight, of shot coke.
The shot coke must be calcined to remove most of the
volatiles prior to use in the method of the invention.
The calcined shot coke may be milled to provide fine
particles. For the purposes of the present invention,
fine particles are defined as those whereby 100% will pass
through a 60 mesh, Tyler Sieve Size and approximately 70%
or more will pass through a 200 mesh U.S. Standard Sieve
Size.
The milling process to obtain the above fine
particles is common knowledge in the art and need not be
disclosed herein.
The particulate shot coke may have a sulfur content
of up to 8%, by weight. It is generally undesirable for
the coke utilized in the manufacture of carbon electrodes
for use in an aluminum reduction cell to have a sulfur
content of greater than about 4%.
The remainder of the aggregate may comprise any
particulate carbonaceous material that is suitable for
preparing carbon electrodes, including recycled anode
butts, for use in aluminum reduction cells. Such
carbonaceous materials are well known in the art.
Preferably, said carbonaceous material is selected
from the group consisting of sponge, needle or pitch
cokes, and recycled carbon electrode remnants.


It has now been discovered that a satisfactory carbon
electrode, suitable for use in an aluminum reduction cell
may be prepared from a particulate carbonaceous,
aggregate, preferably comprising more than 5%, by weight,
of shot coke.
Thus, the present invention provides a method of
making a carbon electrode, suitable for use as an anode in
an aluminum reduction cell, which comprises mixing an
aggregate, comprising a mixture of particulate shot coke,
recycled anode butts, and a particulate carbonaceous
material other than shot coke with coal tar pitch or
combination pitch at an elevated temperature to form a
paste wherein said aggregate comprises a combination of
coarse, medium, and fine particles =and said paste
comprises up to about 90%, by weight, of said aggregate
and from about 10 to about 20%, by weight, of said coal
tar pitch or combination pitch; forming said paste into a
solid body; and baking said solid body at an elevated
temperature to form said carbon electrode.
DETAILED DESCRIPTION
In the method of the invention, the aggregate is
combined with a coal tar pitch binder or a combination
pitch binder.
Coal tar pitch is a residue produced by distillation
or heat treatment of coal tar. It is a solid at room
temperature, consists of a complex mixture of numerous
predominantly aromatic hydrocarbons and heterocyclics, and


exhibits a broad softening range instead of a defined
melting temperature. Petroleum pitch is a residue from
heat treatment and distillation of petroleum fractions.
It is solid at room temperature, consists of a complex
mixture of numerous predominantly aromatic and alkyl-
substituted aromatic hydrocarbons, and exhibits a broad
softening range instead of a defined melting temperature.
Combination pitch is a mixture or combination of coal tar
pitch and petroleum pitch.
The hydrogen aromaticity in coal tar pitch (ratio of
aromatic to total content of hydrogen atoms) varies from
0.7 to 0.9. The hydrogen aromaticity (ratio of aromatic
to total hydrogen atoms) varies between 0.3 and 0.6. The
aliphatic hydrogen atoms are typically present in alkyl
groups substituted on aromatic rings or as naphthenic
hydrogen.
The aggregate utilized in the method of the present
invention comprises a mixture of fine, medium and coarse
particles. The mesh sizes for the fine particles are
defined above. Medium particles will pass through a 4
mesh Tyler sieve and be retained on a 60 mesh screen.
Coarse particles, which may also contain recycled anode
butts, will be retained on a 16 mesh Tyler screen. It is
noted, however, that coarse particles having a mesh size
of over 2.5 mesh are generally to be excluded from the
aggregates utilized in the method of the present
invention.


The aggregate is combined and mixed with the coal tar
pitch or combination pitch. There are numerous mixing
schemes in the art. Any of them may be adapted for shot
coke use, simply by treating the shot aggregate in the
same way as the current aggregate is combined with the
pitch.
It is important that the aggregate and the pitch are
mixed together at an elevated temperature, e.g. greater
than 150°C, in order to coat the particles with pitch,
penetrate the pitch and the fine particles into the
internal pores of the medium and coarse particles and fill
the interstitial aggregate volume with the pitch and the
fine particles.
After mixing the aggregate and the coal tar pitch for
1 to 45 minutes, e.g. from 10 to 20 minutes, a paste is
formed.
The paste may be formed into a solid body, by methods
known in the art, e.g. pressing or vibroforming, prior to
baking to form the electrode.
The green electrode is baked at an elevated
temperature to provide a carbon electrode suitable for use
in an aluminum reduction cell. Preferably, the green
electrode is baked at a temperature of from 1000°C to
1200°C, e.g. about 1100oC entigrade for a time sufficient
for the green electrode to reach a temperature within the
preferred range.


The baking may take place in open or closed furnaces,
as is well known in the art.
The method of the invention provides carbon
electrodes having characteristics including density, air
permeability, compressive strength, modulus of elasticity,
thermal conductivity, coefficient of thermal conductivity,
air reactivity, and carboxy-reactivity which are within
acceptable ranges for aluminum smelters.
In another aspect of the present invention, there is
provided a carbon electrode, suitable for use an anode in
an aluminum reduction cell, which comprises (a) an
aggregate comprising a mixture of particulate shot coke
and a particulate carbonaceous material other than shot
coke, and (b) a coal tar or combination pitch binder,
wherein said aggregate comprises a combination of coarse,
medium, and fine particles and said particulate shot coke
comprises a majority of said fine particulates.
In said electrode, preferably said particulate shot
coke is prepared by screening and milling shot coke from a
delayed coker to provide a particulate mixture comprising
at least 30%, by weight, particles that are fine.
Preferably the particulate carbonaceous material in
the electrode is selected from the group consisting of
sponge, needle or pitch cokes, and recycled carbon
electrode remnants.


While the invention has been described in a preferred
embodiment as a method of utilizing shot coke as fine
particles to provide a satisfactory carbon electrode, it
is also within the scope of the invention, as described,
to utilize shot coke to provide the coarse and medium
particles that make up the carbon electrodes of this
invention.
In this aspect of the present invention, the fines
may comprise shot coke, e.g., milled shot coke, or some
other particulate carbonaceous material, e.g., fine
particulates from the delayed coking of heavy hydrocarbon
oil fractions. In this aspect of the method of this
invention and the resulting carbon electrodes, like the
above preferred embodiment, the aggregate will preferably
comprise from 10 to 50 weight percent fine particulates,
from 10 to 50 weight percent medium particulates and from
5 to 50 weight percent coarse particulates.
Any of the above, novel electrodes or electrodes made
by the method of the present invention may be used, in a
method for producing aluminum by the molten salt
electrolysis of aluminum oxide which comprises
electrolyzing aluminum oxide dissolved in a molten salt at
an elevated temperature by passing a direct current
through an anode to a cathode disposed in said molten salt
wherein said anode is any of the above electrodes.
Although there has been hereinabove described a
specific electrode useful for molten salt electrolysis of
aluminum oxide to aluminum in accordance with the present


invention for the purpose of illustrating the manner in
which the invention may be used to advantage, it should be
appreciated that the invention is not limited thereto.
That is, the present invention may suitably comprise,
consist of, or consist essentially of the recited
elements. Further, the invention illustratively disclosed
herein suitably may be practiced in the absence of any
element which is not specifically disclosed herein.
Accordingly, any and all modifications, variations or
equivalent arrangements which may occur to those skilled
in the art, should be considered to be within the scope of
the present invention as defined in the appended claims.

WE CLAIM :
1. A method of making a carbon electrode, suitable
for use as an anode in an aluminum reduction cell, which
comprises mixing an aggregate, comprising a mixture of
particulate shot coke, and a particulate carbonaceous
material other than shot coke with coal tar pitch or
combination pitch at an elevated temperature to form a
paste characterized in that said aggregate comprises a
combination of coarse (including recycled anode butts),
medium, and fine particles and said particulate shot coke
comprises a majority of said fine particles, and said
paste comprises from 80 to 90%, by weight, of said
aggregate and from 10 to 20%, by weight, of said coal tar
pitch or combination pitch; forming said paste into a
solid body; and baking said solid body at an elevated
temperature to form said carbon electrode.
2. The method as claimed in claim 1 wherein said
shot coke comprises more than 5%, by weight, of said
aggregate.
3. The method as claimed in claim 2 wherein said
shot coke comprises up to 90%, by weight, of said
aggregate.
4. The method as claimed in claim 1 wherein said
carbonaceous material is selected from the group
consisting of sponge, needle or coal tar pitch cokes, and
recycled carbon electrode remnants.


5. The method as claimed in claim 1 wherein said
shot coke has a coefficient of thermal expansion of
greater than 20 x 10-7/degrees Centigrade.
6. The method as claimed in claim 1 wherein said
shot coke has a sulfur content of up to 8%, by weight.
7. The method as claimed in claim 1 wherein said
shot coke is prepared by screening and milling shot coke
from a delayed coker to provide a particulate mixture
comprising at least 30%, by weight, of particles that are
fine.
8. The method as claimed in claim 1 wherein said
solid body is subject to compressing or vibrating to form
a green anode prior to baking.
9. The method as claimed in claim 1 wherein said
solid body is baked at a temperature of above 1000°
Centigrade.
10. A method of making a carbon anode for use in an
aluminum reduction cell, in which aluminum oxide is
reduced to molten aluminum metal at an elevated
temperature, which comprises:
(a) mixing an aggregate comprising a mixture of
particulate shot coke, prepared by screening and milling
calcined shot coke to provide a particulate mixture
comprising at least 30%, by weight, particles that are
fine, and a particulate carbonaceous material selected
from the group consisting of sponge, needle or coal tar


pitch cokes, and recycled carbon electrode remnants, with
coal tar or combination pitches at an elevated temperature
to form a paste wherein said aggregate comprises a
combination of coarse, medium, and fine particles and said
particulate shot coke comprises a majority of said fine
particles, and said paste comprises from 80 to 90%, by
weight, of said aggregate and from 10 to 20%, by weight,
of said coal tar or combination pitches;
(b) forming said paste into a solid body; (c)
subjecting said solid body to compression or vibration to
form a green anode; and (d) baking said green anode at an
elevated temperature of greater then 1000°Centigrade to
form said carbon electrode.
11. A carbon electrode, suitable for use as an anode
in an aluminum reduction cell, which comprises (a) an
aggregate comprising a mixture of particulate shot coke
and a particulate carbonaceous material other than shot
coke, and (b) a coal tar pitch or combination pitch
binder, wherein said aggregate comprises a combination of
coarse, medium, and fine particles and said particulate
shot coke comprises a majority of said fine particulates.
12. A method for producing aluminum by the molten
salt electrolysis of aluminum oxide which comprises
electrolyzing aluminum oxide dissolved in a molten salt at
an elevated temperature by passing a direct current
through an anode to a cathode disposed in said molten salt
wherein said anode is the product as claimed in claim 1.


13. A method of making a carbon electrode, suitable
for use as an anode in an aluminum reduction cell, which
comprises mixing an aggregate, comprising a mixture of
particulate shot coke, and a particulate carbonaceous
material other than shot coke with coal tar pitch or
combination pitch at an elevated temperature to form a
paste wherein said aggregate comprises a combination of
coarse (including recycled anode butts), medium, and fine
particles characterized in that said particulate shot coke
comprises more than 5%, by weight, of said aggregate, and
said paste comprises from 80 to 90%, by weight, of said
aggregate and from 10 to 20%, by weight, of said coal tar
pitch or combination pitch; forming said paste into a
solid body; and baking said solid body at an elevated
temperature to form said carbon electrode.


The present invention provides a method of making a
carbon electrode, suitable for use as an anode in an
aluminum reduction cell, which comprises mixing an
aggregate, comprising a mixture of particulate shot coke,
and a particulate carbonaceous material other than shot
coke with coal tar pitch or petroleum pitch or a
combination of these pitches at an elevated temperature to
form a paste wherein said aggregate comprises a
combination of coarse, medium, and fine particles and said
particulate shot coke may comprise a majority of said fine
particles, and said paste comprises from 80 to 90%, by
weight, of said aggregate and from 10 to 20%, by weight,
of said pitch; forming said paste into a solid body; and
baking said solid body at an elevated temperature to form
said carbon electrode.

Documents:

03693-kolnp-2006-abstract.pdf

03693-kolnp-2006-assignment.pdf

03693-kolnp-2006-claims.pdf

03693-kolnp-2006-correspondence others.pdf

03693-kolnp-2006-correspondence-1.1.pdf

03693-kolnp-2006-description(complete).pdf

03693-kolnp-2006-form-1.pdf

03693-kolnp-2006-form-3-1.1.pdf

03693-kolnp-2006-form-3.pdf

03693-kolnp-2006-form-5.pdf

03693-kolnp-2006-international publication.pdf

03693-kolnp-2006-international search authority report.pdf

03693-kolnp-2006-pct request form.pdf

03693-kolnp-2006-priority document.pdf

3693-KOLNP-2006-ABSTRACT 1.1.pdf

3693-kolnp-2006-assignment.pdf

3693-KOLNP-2006-CLAIMS 1.1.pdf

3693-KOLNP-2006-CORRESPONDENCE 1.1.pdf

3693-KOLNP-2006-CORRESPONDENCE.pdf

3693-kolnp-2006-correspondence1.2.pdf

3693-KOLNP-2006-DESCRIPTION (COMPLETE) 1.1.pdf

3693-KOLNP-2006-EXAMINATION REPORT REPLY RECIEVED.pdf

3693-kolnp-2006-examination report.pdf

3693-KOLNP-2006-FORM 1 1.1.pdf

3693-kolnp-2006-form 18.1.pdf

3693-kolnp-2006-form 18.pdf

3693-KOLNP-2006-FORM 2.pdf

3693-KOLNP-2006-FORM 3 1.1.pdf

3693-kolnp-2006-form 3.pdf

3693-kolnp-2006-form 5.pdf

3693-KOLNP-2006-FORM-27-1.pdf

3693-KOLNP-2006-FORM-27.pdf

3693-kolnp-2006-gpa.pdf

3693-kolnp-2006-granted-abstract.pdf

3693-kolnp-2006-granted-claims.pdf

3693-kolnp-2006-granted-description (complete).pdf

3693-kolnp-2006-granted-form 1.pdf

3693-kolnp-2006-granted-form 2.pdf

3693-kolnp-2006-granted-specification.pdf

3693-KOLNP-2006-OTHERS.pdf

3693-kolnp-2006-others1.1.pdf

3693-KOLNP-2006-PA.pdf

3693-KOLNP-2006-PETITION UNDER RULE 137-1.1.pdf

3693-KOLNP-2006-PETITION UNDER RULE 137.pdf

3693-kolnp-2006-reply to examination report.pdf


Patent Number 248742
Indian Patent Application Number 3693/KOLNP/2006
PG Journal Number 33/2011
Publication Date 19-Aug-2011
Grant Date 17-Aug-2011
Date of Filing 07-Dec-2006
Name of Patentee CII CARBON LLC
Applicant Address 2021 LAKESHORE DRIVE SUITE 200 NEW ORLEANS LA
Inventors:
# Inventor's Name Inventor's Address
1 EDWARDS, LESLIE, C. 2021 LAKESHORE DRIVE SUITE 200 NEW ORLEANS LA 70122
2 LOVE, RICHARD, O. P.O.BOX 98,ROUTE 2,SOUTH RAVENSWOOOD WV 26164
3 ROSS, J. ANTHONY P.O. BOX 98, ROUTE 2, SOUTH RAVENSWOOOD WV 26164
4 MORGAN, WILLIAM, ROGERS, JR. 1627 STATE ROUTE 271N POST OFFICE BOX 500 HAWESVILLE KY 42348
5 VOGT, M., FRANZ 2021 LAKESHORE DRIVE SUITE 200 NEW ORLEANS LA 70122
PCT International Classification Number C25B 11/12
PCT International Application Number PCT/US2005/017910
PCT International Filing date 2005-05-23
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10/874,508 2004-06-22 U.S.A.