U.S. patent application number 13/963445 was filed with the patent office on 2014-02-13 for high carbon spent pot lining and methods of fueling a furnace with the same.
The applicant listed for this patent is Alcoa Inc.. Invention is credited to Francis Caron, Dany Drapeau, Denis Guay.
Application Number | 20140041560 13/963445 |
Document ID | / |
Family ID | 49004028 |
Filed Date | 2014-02-13 |
United States Patent
Application |
20140041560 |
Kind Code |
A1 |
Caron; Francis ; et
al. |
February 13, 2014 |
HIGH CARBON SPENT POT LINING AND METHODS OF FUELING A FURNACE WITH
THE SAME
Abstract
A method of creating and using a high-carbon spent pot lining
(SPL) as a fuel, including delining the high-carbon spent pot
lining from an electrolytic cell and combusting the SPL in a
furnace.
Inventors: |
Caron; Francis; (Quebec,
CA) ; Guay; Denis; (Quebec, CA) ; Drapeau;
Dany; (Quebec, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Alcoa Inc. |
Pittsurgh |
PA |
US |
|
|
Family ID: |
49004028 |
Appl. No.: |
13/963445 |
Filed: |
August 9, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61681199 |
Aug 9, 2012 |
|
|
|
61788617 |
Mar 15, 2013 |
|
|
|
Current U.S.
Class: |
110/342 ;
44/605 |
Current CPC
Class: |
C10L 5/48 20130101; F23G
5/033 20130101; F23G 5/02 20130101; F23G 5/46 20130101; F23G
2201/701 20130101; F23G 7/003 20130101; Y02E 20/363 20130101; F23G
2206/201 20130101; C25C 3/08 20130101; F23G 5/08 20130101; Y02E
20/30 20130101 |
Class at
Publication: |
110/342 ;
44/605 |
International
Class: |
C10L 5/48 20060101
C10L005/48; F23G 5/08 20060101 F23G005/08 |
Claims
1. A method of creating a high-carbon spent pot lining (SPL) fuel,
comprising: delining a spent pot lining from an electrolytic cell;
and pulverizing the spent pot lining to create a spent pot lining
fuel, wherein the spent pot lining comprises at least 65% by weight
carbon compounds content, based on a total weight of the spent pot
lining, with the remainder comprising one or more of oxygen
compounds, cyanide compounds, fluoride compounds, sodium compounds,
aluminum compounds, and silicon compounds.
2. The method of claim 1, wherein the delining of the spent pot
lining comprises: removing a 1.sup.st bath layer; removing a metal
layer; removing a 2.sup.nd bath layer; cleaning a cathode block;
breaking the cathode block; removing the cathode block; and
removing the side blocks (27), wherein the spent pot lining
consists essentially of the cathode block.
3. The method of claim 2, further comprising: combining the spent
pot lining with an enriching compound to create an enriched SPL
having at least 65% carbon content, based on a total weight of the
enriched SPL, wherein pulverizing the spent pot lining to create a
spent pot lining fuel comprises pulverizing the enriched SPL.
4. A method of using the SPL fuel of claim 1 as a furnace fuel,
comprising: feeding a fuel comprising the SPL fuel to a burner; and
combusting the fuel in the burner to generate a thermal energy and
directing the thermal energy to a furnace.
5. The method of claim 4, wherein the fuel further comprises a
supplemental fuel, and wherein the SPL fuel comprises between 50%
and 80% of the fuel.
6. The method of claim 5, wherein the fuel comprises no more than
50% supplemental fuel.
7. The method of claim 6, wherein the SPL fuel is an enriched
SPL.
8. A method of using the SPL fuel of claim 3 as a furnace fuel,
comprising: feeding a fuel comprising the enriched SPL fuel to a
burner; and combusting the fuel in the burner to generate a thermal
energy and directing the thermal energy to a furnace.
9. The method of claim 8, wherein the fuel further comprises a
supplemental fuel, and wherein the enriched SPL fuel comprises
between 50% and 80% of the fuel.
10. The method of claim 1, wherein: the SPL fuel has a particle
size of at most 150 .mu.m, and the SPL fuel has trace amounts or
less of HAP, the SPL fuel has trace amounts or less of BPC's, the
SPL fuel has trace amounts or less of Dioxine, and the SPL fuel has
trace amounts or less of Furan.
11. The method of claim 10, wherein the SPL fuel comprises: at most
5% by weight oxygen compounds content, based on the total weight of
the SPL fuel; at most 0.5% by weight cyanide compounds content,
based on the total weight of the SPL fuel; at most 10% by weight
fluoride compounds content, based on the total weight of the SPL
fuel; at most 10% by weight sodium compounds content, based on the
total weight of the SPL fuel; at most 5% by weight aluminum
compounds content, based on the total weight of the SPL fuel; and
at most 5% by weight silicon content, based on the total weight of
the SPL fuel.
12. The method of claim 11, wherein the SPL fuel has a heat value
of at least 18,400 kJ/Kg.
13. The method of claim 3, wherein the enriching compound
comprises: at least 80% by weight carbon compounds content, based
on a total weight of the enriching smelting residue; at most 5% by
weight oxygen compounds content, based on the total weight of the
enriching smelting residue; at most 0.1% by weight cyanide
compounds content, based on the total weight of the enriching
smelting residue; at most 5% by weight fluoride compounds content,
based on the total weight of the enriching smelting residue; at
most 5% by weight sodium compounds content, based on the total
weight of the enriching smelting residue; at most 5% by weight
aluminum compounds content, based on the total weight of the
enriching smelting residue; and at most 1% by weight silicon
content, based on the total weight of the enriching smelting
residue.
14. The method of claim 13, wherein the enriching compound has a
heat value of at least 18,400 kJ/Kg
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 61/681,199, filed on Aug. 9, 2012, and U.S.
Provisional Application No. 61/788,617, filed on Mar. 15, 2013. The
disclosure of U.S. Provisional Applications Nos. 61/681,199 and
61/788,617 are hereby incorporated by reference in their entirety
for all purposes.
COPYRIGHT NOTIFICATION
[0002] This application includes material which is subject to
copyright protection. The copyright owner has no objection to the
facsimile reproduction by anyone of the patent disclosure, as it
appears in the Patent and Trademark Office files or records, but
otherwise reserves all copyright rights whatsoever.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates to a high-carbon spent pot
lining. More particularly, the present invention relates to methods
of obtaining and using a high-carbon spent pot lining ("SPL") as a
fuel source.
[0005] 2. Description of the Related Art
[0006] Electrolysis of alumina within an electrolytic cell is the
major industrial process for the production of aluminum metal. In
an electrolytic cell, an electrical current passed between an anode
and a cathode within a bath of molten cryolite containing dissolved
alumina. The electrical current causes the deposition of aluminum
metal on the cathode. Often, the electrolytic cell is configured as
a large tank or cell with carbon or graphite lining materials to
contain the molten electrolytic bath (also called the "pot
lining"). When the cathode is also made of carbon or graphite
materials, portions of the lining may also serve as part of the
cathode system. Most aluminum electrolytic cells employ carbon
blocks as the pot lining and/or cathode. In addition, the
electrolytic cell may include insulation materials, such as
refractory brick lining, and a metal shell to define and/or
thermally insulate the electrolytic cell.
[0007] During operation of the electrolytic cell, contaminants from
the molten electrolytic bath and/or metal oxides associated with
the electrolytic reaction migrate into the pot lining. Once the pot
lining has reached the end of its life span it is removed from the
electrolytic cell for disposal. Recycling and/or reuse of the spent
pot lining ("SPL") is complicated because it includes both the
original pot lining material (such as carbon or graphite) and
contaminants from the molten electrolytic bath, such as metal
oxides, cyanide, sodium containing materials, and fluoride
compounds subject to environmental use restrictions. In addition,
because of the contamination, the carbon content of the SPL may be
reduced. In some examples, the carbon content of an SPL may be
reduced to less than 50% carbon hindering its use as a fuel
source.
SUMMARY OF THE INVENTION
[0008] The present invention relates to a high-carbon spent pot
lining ("SPL"), and more particularly, to methods of obtaining and
using a high-carbon SPL as a fuel source.
[0009] Additional goals and advantages of the present invention
will become more evident in the description of the figures, the
detailed description of the invention, and the claims. The
foregoing and/or other aspects and utilities of the present
invention may be achieved by providing a method of creating a
high-carbon spent pot lining (SPL) fuel, including delining a spent
pot lining from an electrolytic cell, and pulverizing the spent pot
lining to create a spent pot lining fuel, wherein the spent pot
lining comprises at least 65% by weight carbon compounds content,
based on a total weight of the spent pot lining, with the remainder
comprising one or more of oxygen compounds, cyanide compounds,
fluoride compounds, sodium compounds, aluminum compounds, and
silicon compounds.
[0010] In another embodiment, the delining of the spent pot lining
includes removing a 1.sup.st bath layer, removing a metal layer,
removing a 2.sup.nd bath layer, cleaning a cathode block, breaking
the cathode block, removing the cathode block, and removing the
side blocks (27), wherein the spent pot lining consists essentially
of the cathode block.
[0011] In another embodiment, the method of delining of the spent
pot lining further includes combining the spent pot lining with an
enriching compound to create an enriched SPL having at least 65%
carbon content, based on a total weight of the enriched SPL, and
wherein pulverizing the spent pot lining to create a spent pot
lining fuel includes pulverizing the enriched SPL.
[0012] The foregoing and/or other aspects and utilities of the
present invention may be achieved by providing a method of using an
SPL fuel including feeding a fuel comprising the SPL fuel to a
burner, and combusting the fuel in the burner to generate a thermal
energy and directing the thermal energy to a furnace.
[0013] In another embodiment, the fuel further includes a
supplemental fuel, and wherein the SPL fuel comprises between 50%
and 80% of the fuel.
[0014] In another embodiment, the fuel includes no more than 50%
supplemental fuel.
[0015] In another embodiment, the SPL fuel is an enriched SPL.
[0016] In another embodiment, the method of using the enriched SPL
fuel as a furnace fuel includes feeding a fuel comprising the
enriched SPL fuel to a burner, and combusting the fuel in the
burner to generate a thermal energy and directing the thermal
energy to a furnace.
[0017] In another embodiment, the fuel further includes a
supplemental fuel, and wherein the enriched SPL fuel includes
between 50% and 80% of the fuel.
[0018] The foregoing and/or other aspects and utilities of the
present invention may be achieved by providing a method of using an
SPL, wherein the SPL fuel has a particle size of at most 150 .mu.m,
and the SPL fuel has trace amounts or less of HAP, the SPL fuel has
trace amounts or less of BPC's, the SPL fuel has trace amounts or
less of Dioxine, and the SPL fuel has trace amounts or less of
Furan.
[0019] In another embodiment, the SPL fuel includes at most 5% by
weight oxygen compounds content, based on the total weight of the
SPL fuel, at most 0.5% by weight cyanide compounds content, based
on the total weight of the SPL fuel, at most 10% by weight fluoride
compounds content, based on the total weight of the SPL fuel, at
most 10% by weight sodium compounds content, based on the total
weight of the SPL fuel, at most 5% by weight aluminum compounds
content, based on the total weight of the SPL fuel, and at most 5%
by weight silicon content, based on the total weight of the SPL
fuel.
[0020] In another embodiment, the SPL fuel has a heat value of at
least 18,400 kJ/Kg.
[0021] The foregoing and/or other aspects and utilities of the
present invention may be achieved by providing a method of using an
enriched SPL fuel as a furnace fuel, wherein the enriching compound
includes at least 80% by weight carbon compounds content, based on
a total weight of the enriching smelting residue, at most 5% by
weight oxygen compounds content, based on the total weight of the
enriching smelting residue, at most 0.1% by weight cyanide
compounds content, based on the total weight of the enriching
smelting residue, at most 5% by weight fluoride compounds content,
based on the total weight of the enriching smelting residue, at
most 5% by weight sodium compounds content, based on the total
weight of the enriching smelting residue, at most 5% by weight
aluminum compounds content, based on the total weight of the
enriching smelting residue, and at most 1% by weight silicon
content, based on the total weight of the enriching smelting
residue.
[0022] In another embodiment, the enriching compound has a heat
value of at least 18,400 kJ/Kg
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] These and/or other aspects and advantages of the present
invention will become apparent and more readily appreciated from
the following description of the various embodiments, taken in
conjunction with the accompanying drawings of which:
[0024] FIGS. 1-2 illustrate an exemplary electrolytic cell that can
be delined to obtain a high-carbon SPL according to embodiments of
the present invention.
[0025] FIG. 3 illustrates a method of delining an electrolytic cell
to obtain a high-carbon SPL according to an embodiment of the
present invention.
[0026] FIGS. 4-7 illustrate methods of using a high-carbon SPL as a
furnace fuel according embodiments of the present invention.
[0027] FIG. 8 illustrates an apparatus configured to use a
high-carbon SPL as a fuel according to embodiments of the present
invention.
[0028] The drawings referenced above are not necessarily to scale,
with emphasis instead generally being placed upon illustrating the
principles of the present invention. Further, some features may be
exaggerated to show details of particular components. These
drawings/figures are intended to be explanatory and not restrictive
of the invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0029] Reference will now be made in detail to the various
embodiments of the present invention. The embodiments are described
below to provide a more complete understanding of the components,
processes and apparatuses of the present invention. Any examples
given are intended to be illustrative, and not restrictive.
Throughout the specification and claims, the following terms take
the meanings explicitly associated herein, unless the context
clearly dictates otherwise. The phrases "in some embodiments" and
"in an embodiment" as used herein do not necessarily refer to the
same embodiment(s), though they may. Furthermore, the phrases "in
another embodiment" and "in some other embodiments" as used herein
do not necessarily refer to a different embodiment, although they
may. As described below, various embodiments of the present
invention may be readily combined, without departing from the scope
or spirit of the present invention.
[0030] As used herein, the term "or" is an inclusive operator, and
is equivalent to the term "and/or," unless the context clearly
dictates otherwise. The term "based on" is not exclusive and allows
for being based on additional factors not described, unless the
context clearly dictates otherwise. In addition, throughout the
specification, the meaning of "a," "an," and "the" include plural
references. The meaning of "in" includes "in" and "on."
[0031] All physical properties that are defined hereinafter are
measured at 20.degree. to 25.degree. Celsius unless otherwise
specified.
[0032] When referring to any numerical range of values herein, such
ranges are understood to include each and every number and/or
fraction between the stated range minimum and maximum. For example,
a range of about 0.5-6% would expressly include all intermediate
values of about 0.6%, 0.7%, and 0.9%, all the way up to and
including 5.95%, 5.97%, and 5.99%. The same applies to each other
numerical property and/or elemental range set forth herein, unless
the context clearly dictates otherwise.
[0033] As used herein, "enriching" means the act or process of
adding a compatible material fuel to a first material or fuel. For
example, an SPL fuel may be enriched with another source of carbon
fuel, such as carbon containing residues from other compatible
smelting processes.
[0034] FIGS. 1-2 illustrate an exemplary electrolytic cell for the
production of aluminum. As illustrated in FIGS. 1-2, an
electrolytic cell (1) may include an anode (not illustrated), a
cathode (2), a current collector (4), and a steel shell (7). The
steel shell (7) may support a sidewall lining (3) and insulations
bricks (5) configured to contain and insulate a molten electrolytic
bath (15). In some embodiments, the electrolytic cell (1) further
includes an insulation layer (6) between the cathode (2) and the
insulations bricks (5). In some embodiments, the insulation layer
(6) is composed of alumina. In some aluminum electrolytic cells,
the cathode (2) and the sidewall lining (3) include carbon or
graphite materials. For example, in some embodiments, the cathode
(2) and sidewall lining (3) are made of amorphous, graphitic or
graphitized carbon blocks. In some embodiments, the carbon blocks
are made of an anthracite aggregate mixed with a coal-tar pitch
binder. In some embodiments, a ramming paste (8) may be used to
fill the joints between the carbon joints to create a liquid-tight
pot lining. In some embodiments, the ramming paste (8) includes an
anthracite filler and a coal-tar pitch binder.
[0035] An aluminum electrolytic cell pot lining has a typical
operational life of about 2 to 6 years. After which, the
electrolytic cell is shut down, the pot lining is removed and
disposed off, and the electrolytic cell is cleaned and prepared for
re-lining. During operation, the electrical current supplied to the
electrolytic cell maintains the electrolytic bath in a molten
state. However, after shutting down, any remaining aluminum metal
and electrolytic bath solidifies.
[0036] FIG. 3 illustrates a method of delining an electrolytic cell
(1) to obtain a high-carbon SPL according to an embodiment of the
present invention.
[0037] As illustrated in FIG. 3, in one embodiment, a method of
delining an electrolytic cell to obtain a high-carbon SPL (20)
includes the following operations; removing a 1.sup.st bath layer
(21); removing a metal layer (22); removing a 2.sup.nd bath layer
(23); cleaning a cathode block (24); breaking the cathode block
(25); removing the cathode block (26); and removing the side blocks
(27).
[0038] In one embodiment of the present invention, and with
reference to FIGS. 2-3, removing a 1.sup.st bath layer in operation
(21) includes the physical break up and removal of the solidified
electrolytic bath (15). As some non-limiting examples, removing the
1.sup.st bath layer in operation (21) may include physically
removing (e.g. by jack hammering bath components and/or siphoning
the dust generated from removing the bath components) the
solidified electrolytic bath (15) from the electrolytic cell (1).
For example, in one embodiment, an excavator equipped with a bucket
is used to break up and collect large pieces of the solidified
electrolytic bath (15).
[0039] In some electrolytic cell operations, a residual metal layer
(16) may remain in the electrolytic cell (1) after shut-down. In
one embodiment of the present invention, removing the metal layer
(16) in operation (22) includes removing the solid metal layer (16)
from the electrolytic cell (1) after removal of the 1.sup.st bath
layer in operation (21). Physical means may be used to remove the
solid metal layer (16). For example, an excavator equipped with a
pneumatic drill may be used to take off and/or break the metal
layer (16) and pick it up.
[0040] As illustrated in FIG. 2, in some embodiments, a 2.sup.nd
layer of solidified bath (17) may be present underneath the metal
layer (16) after shut down of the electrolytic cell (1). In one
embodiment of the present invention, removing the 2.sup.nd bath
layer (17) in operation (23) includes physical break up and removal
of the 2.sup.nd solidified electrolytic bath layer (17). As some
non-limiting examples, removing the 2.sup.nd solidified
electrolytic bath layer (17) in operation (23) may include
physically removing (e.g. by jack hammering bath components and/or
siphoning the dust generated from removing the bath components) the
2.sup.nd solidified electrolytic bath layer (17) from the
electrolytic cell (1).
[0041] In one embodiment of the present invention, and with
reference to FIGS. 2-3, cleaning a cathode block in operation (24)
includes removal of any remaining solidified electrolytic bath
after operations (21-23). For example, in one embodiment, a vacuum
is used to siphon dust or small debris generated from removing the
solidified electrolytic bath (15), the metal layer (16), and/or the
2.sup.nd solidified electrolytic bath layer (17) remaining in the
electrolytic cell (1) after operations (21-23).
[0042] In another embodiment of the present invention, after
cleaning the cathode block in operation (24), the cathode block is
removed in operations (25-26). Removal of the cathode block in
operations (25-26) may include physically breaking up (e.g. by jack
hammering or drilling) and removing the cathode block (2). For
example, in one embodiment, excavators equipped with pneumatic
drills and/or buckets are used to break up and collect large pieces
of the cathode block (2).
[0043] In some embodiments, a ramming paste (8) joins the cathode
block (2) and the sidewall lining (3). In such cases, the breaking
of the cathode block in operation (25) is configured to avoid the
ramming paste (8) and the sidewall lining (3). For example, in one
embedment, the breaking of the cathode block in operation (25)
includes breaking up the cathode block (2) from a center thereof
towards the sides in order to avoid touching the joints defined by
the ramming paste (8) and/or the sidewall lining (3). In some
embodiments, the cathode block (2) removed in operations (25-26)
does not include substantial amounts of the ramming paste (8) or
the sidewall lining (3).
[0044] In some embodiments, the presence of an insulation layer (6)
between the cathode (2) and the insulations bricks (5) allows the
removal of the cathode block (2) separate from the insulation
bricks (5). For example, in one embodiment, the cathode block (2)
removed in operations (25-26) does not include substantial amounts
of the insulations bricks (5).
[0045] In one embodiment of the present invention, the cathode
block (2) removed in operations (25-26) is used to create a
high-carbon SPL.
[0046] In another embodiment of the present invention, after the
cathode block (2) is removed in operations (25-26), the remaining
ramming paste (8) and/or sidewall lining (3) are broken up and
removed from the electrolytic cell (1). Removal of the sidewall
lining (3) in operation (27) may include physically breaking up
(e.g. by jack hammering or drilling) and removing the sidewall
lining (3) and/or ramming paste (8). For example, in one
embodiment, excavators equipped with pneumatic drills and/or
buckets are used to break up and collect large pieces of the
sidewall lining (3) and/or ramming paste (8).
[0047] In some embodiments of the invention, the spent pot lining
materials obtained in operations (25-26) are segregated from the
spent pot lining materials obtained in operation (27). In some
embodiments, the spent pot lining materials obtained in operations
(25-26) do not include substantial amounts of the ramming paste (8)
or the sidewall lining (3). In some embodiments, the spent pot
lining materials obtained in operations (25-26) do not include
substantial amounts of the solidified electrolytic bath (15), the
metal layer (16), the 2.sup.nd solidified electrolytic bath layer
(17), and/or the insulations bricks (5). In some embodiments, the
spent pot lining materials obtained in operations (25-26) consist
essentially of portions of the cathode block (2).
[0048] As illustrated in FIG. 3, in one embodiment of the present
invention a high-carbon SPL is obtained from the delining method
(20). In one embodiment, the high-carbon SPL includes the spent pot
lining materials obtained in operations (25-26). In another
embodiment, the high-carbon SPL includes the cathode block (2)
obtained in operations (25-26). In some embodiments, the
high-carbon SPL consists essentially of the cathode block (2)
obtained in operations (25-26). In other embodiments, the
high-carbon SPL does not include substantial amounts of the
solidified electrolytic bath (15), the metal layer (16), the
2.sup.nd solidified electrolytic bath layer (17), and/or the
insulations bricks (5) obtained from the delining method (20).
[0049] In one embodiment of the present invention, the high-carbon
SPL has a carbon content of at least 50% by weight. In another
embodiment, the carbon content of the high-carbon spent pot lining
is at least about 55%, at least about 60%, at least about 65%, at
least about 70%, at least about 75%, at least about 80%, at least
about 85%, at least about 95%, and at least about 98%.
[0050] In another embodiment, the high-carbon SPL includes less
than 50% non-carbon compounds. For example, in one embodiment, the
high-carbon SPL includes at least 65% carbon content by weigh with
the remainder including one or more of oxygen compounds, cyanide
compounds, fluoride compounds, sodium compounds, aluminum
compounds, and silicon compounds.
[0051] In another embodiment, the high-carbon SPL does not contain
measurable amounts of, or contains only trace amounts of regulated
environmental contaminants affecting the use of carbon as a fuel.
For example, in one embodiment, the high-carbon SPL contains only
trace amounts of organic air toxins, such as dioxins and furans. In
another embodiment, the use of the high-carbon SPL does not produce
measurable amounts of, or produces only trace amounts of, hazardous
air pollutants (HAP), polychlorinated biphenyls (PCBs), hazardous
metal air pollutants (e.g., mercury, arsenic, chromium, nickel), or
acid gases (e.g., hydrochloric acid (HCl), hydrogen fluoride).
[0052] Table 1 illustrates a composition of two example high-carbon
SPLs obtained according to embodiments of the present invention. As
illustrated in Table 1, embodiments of a high-carbon SPL contain at
least 65% carbon content, and no more than 10% of oxygen compounds,
cyanide compounds, fluoride compounds, sodium compounds, aluminum
compounds, or silicon compounds.
TABLE-US-00001 TABLE 1 High Carbon SPL Composition Embodiment 1 (%)
Embodiment 2 (%) Carbon Compounds >65 >75 Oxygen Compounds
<5 <5 Cyanide Compounds <0.5 <0.2 Fluoride Compounds
<10 <7 Sodium Compounds <10 <7 Aluminum Compounds <5
<3 Silicon Compounds <5 <1
[0053] In another embodiment of the invention, the high-carbon SPL
is combined with an enriching compound to further increase the
carbon content of the resulting enriched high-carbon SPL. For
example, in one embodiment of the present disclosure, the
high-carbon SPL is combined with other carbon containing materials
to create an enriched high-carbon SPL. In one embodiment, the
high-carbon SPL is enriched by combining it with compatible smelter
residues, such as carbon anode or cathode production byproducts.
Table 3 illustrates a composition of compatible enriching compounds
that can be used to enrich the high-carbon SPL according to
embodiments of the present invention. As illustrated in Table 3,
Embodiment 1 represents an exemplary carbon anode fabrication
process residue usable as an enriching compound. Embodiment 2 is an
exemplary carbon anode cleaning process residue usable as an
enriching compound. In one embodiment of the present invention, a
high-carbon SPL having at least 50% carbon content by weight is
enriched with one or more enriching compounds to create an enriched
high-carbon SPL having at least a 75% carbon content by weight. In
another embodiment of the present invention, a high-carbon SPL
having at least a 75% carbon content by weight is enriched with one
or more enriching compounds to create an enriched high-carbon SPL
having at least a 80% carbon content by weight.
TABLE-US-00002 TABLE 3 Enriching Compound Composition Embodiment 1
(%) Embodiment 2 (%) Carbon Compounds >80 >90 Oxygen
Compounds <5 <2 Cyanide Compounds <0.1 <0.1 Fluoride
Compounds <5 <5 Sodium Compounds <5 <2 Aluminum
Compounds <5 <2 Silicon Compounds <1 <1
[0054] FIGS. 4-8 illustrate methods of using a high-carbon SPL as a
fuel according embodiments of the present invention.
[0055] As illustrated in FIG. 4, a general method of using a
high-carbon SPL as a fuel includes injecting a fuel having
high-carbon SPL into a burner to produce a thermal energy (e.g.
heat and/or flame) in operation (110), and directing the thermal
energy to a furnace via the burner in operation (112).
[0056] FIG. 5 illustrates a method of heating a furnace using a
high-carbon SPL according to another embodiment of the present
invention. As illustrated in FIG. 5, a method of heating a furnace
with a high-carbon SPL fuel includes injecting a fuel having
high-carbon SPL into a burner to produce thermal energy (110);
directing the thermal energy to a furnace (e.g. into, onto) via the
burner (112); and modifying the high-carbon SPL fuel content of
fuel in operation (114), followed by reiterating operations 110 and
112.
[0057] FIG. 6 illustrates a method of heating a furnace using a
high-carbon SPL according to another embodiment of the present
invention. As illustrated in FIG. 3, a method of heating a furnace
with a high-carbon SPL fuel includes recovering high-carbon SPL
from an electrolytic cell (1) in operation (116), co-feeding the
high-carbon SPL fuel and another fuel (e.g. combustible air) into a
burner (118), and directing a thermal energy (e.g. heat, flame)
from the burner to a furnace (e.g. into/onto the furnace) in
operation (120). In some embodiments of the present invention,
recovering high-carbon SPL from an electrolytic cell (1) refers to
obtaining a high-carbon SPL by delining an electrolytic cell (1)
through operations (25-26) described above. In other embodiments,
recovering high-carbon SPL from an electrolytic cell (1) includes
delining an electrolytic cell (1) to obtain a high-carbon SPL,
grinding and/or purifying the high-carbon SPL to a particle size
suitable for injection into the burner of operation (118). In one
embodiment, after delining the electrolytic cell to obtain the
high-carbon SPL, a purifying operation is completed to further
remove non-carbon contaminants (e.g. insulating brick, solidified
bath, and alumina) prior to grinding the high-carbon SPL.
[0058] FIG. 7 illustrates another method according to an embodiment
of the present disclosure. As illustrated in FIG. 7, a method of
using a high-carbon SPL as a fuel includes delining an electrolytic
cell (1) to obtain a high-carbon SPL (122); grinding the
high-carbon SPL into fuel-sized particles (124); co-feeding the
high-carbon SPL and another fuel (e.g. combustible air, natural
gas) into a burner (118); directing a thermal energy from the
burner to a furnace (120); and scrubbing off-gases to recover
fluoride compounds in operation (126).
[0059] FIG. 8 illustrates an apparatus configured to use a
high-carbon SPL according to embodiments of the present invention.
In one embodiment, FIG. 8 illustrates an apparatus (200) configured
to use a high-carbon SPL under one or more of the aforementioned
methods of using a high-carbon SPL as a fuel. As illustrated in
FIG. 8, an apparatus (200) includes a solid fuel container (210); a
supplemental fuel container (212); a burner system (216); a furnace
(218); and a scrubber (224).
[0060] In an embodiment of the present invention, the solid fuel
container (210) is configured to store and provide a solid fuel to
the burner system (216). In some embodiments, the solid fuel
includes a high-carbon SPL. In one embodiment, the high-carbon SPL
is obtained from an electrolytic cell via delining operations
(25-26). In another embodiment, the solid fuel has a carbon content
of at least 65% by weight, 80% by weight, and 90% by weight. In
another embodiment, the solid fuel includes a high-carbon SPL with
a carbon content of at least 65% by weight, 80% by weight, and 90%
by weight. In another embodiment, the solid fuel includes an
enriched high-carbon SPL with a carbon content of at least 65% by
weight, 80% by weight, and 90% by weight. In some embodiments, the
solid fuel consists essential of high-carbon SPL. In some
embodiments, the solid fuel consists essential of enriched SPL. In
another embodiment, the solid fuel includes a high-carbon SPL with
a carbon content of at least 75% and/or an enriched high-carbon SPL
with a carbon content of at least 80% by weight.
[0061] In one embodiment of the present invention, the solid fuel
produces a specific heat value when combusted in the burner (217)
making it suitable for use as a fuel for a furnace (218). For
example, Table 4 illustrates heat values for a high-carbon SPL fuel
and for compatible enriching compounds according to embodiments of
the present disclosure.
TABLE-US-00003 TABLE 4 Heat Value Embodiment 1 (kJ/kg) Embodiment 2
(kJ/kg) SPL Fuel Composition >18,400 >24,000 Enriching
Residue >18,400 >24,000 Composition
[0062] In one embodiment, the high-carbon SPL obtained from an
electrolytic cell via delining operations (25-26) has a heat value
of at least 18,400 kJ/Kg. In another embodiment, the enriched SPL
has a heat value of at least 18,400 kJ/Kg. In yet another
embodiment, the solid fuel has a heat value of at least 18,400
kJ/Kg.
[0063] In another embodiment, the high-carbon SPL obtained from an
electrolytic cell via delining operations (25-26) has a heat value
of at least 24,000 kJ/Kg. In another embodiment, the enriched SPL
has a heat value of at least 24,000 kJ/Kg. In yet another
embodiment, the solid fuel has a heat value of at least 24,000
kJ/Kg.
[0064] In an embodiment of the present invention, the solid fuel is
sized according to the requirements of the burner system (216),
such as a dual-fuel combustion burner system. For example, in some
embodiments, the solid fuel has an average particle size less than
150 micrometers (.mu.m). In another embodiment, the solid fuel has
an average particle size less than 90 micrometers (.mu.m). In some
embodiments, the size of the solid fuel is adjusted by sizing the
high-carbon SPL or enriched SPL in the solid fuel. For example, in
some embodiments, the high-carbon SPL or enriched SPL has an
average particle size less than 150 micrometers (.mu.m). In another
embodiment, the high-carbon SPL or enriched SPL has an average
particle size less than 90 micrometers (.mu.m).
[0065] In some embodiments, the average particle size is obtain
through physical means, such as pounding, pressing, crushing, or
pulverizing the solid fuel to a desired particle size. In some
embodiments, the average particle size of the high-carbon SPL is:
at least about 0.1 mm; at least about 0.2 mm; at least about 0.3
mm; at least about 0.4 mm; at least about 0.5 mm; at least about
0.6 mm; at feast about 0.7 mm; at least about 0.8 mm; at least
about 0.9 mm; at least about 1 mm; at least about 1.1 mm; at least
about 1.2 mm; at least about 1.5 mm; at least about 1.8 mm; at
least about 2 mm; at least about 2.5 mm; at least about 3 mm; at
least about 3.5 mm; at least about 4 mm; at least about 4.5 mm; or
at least about 5 mm. In some embodiments, the average particle size
of the high-carbon SPL fuel is: not greater than about 0.1 mm; not
greater than about 0.2 mm; not greater than about 0.3 mm; not
greater than about 0.4 mm; not greater than about 0.5 mm; not
greater than about 0.6 mm; not greater than about 0.7 mm; not
greater than about 0.8 mm; not greater than about 0.9 mm; not
greater than about 1 mm; not greater than about 1.1 mm; not greater
than about 1.2 mm; not greater than about 1.5 mm; not greater than
about 1.8 mm; not greater than about 2 mm; not greater than about
2.5 mm; not greater than about 3 mm; not greater than about 3.5 mm;
not greater than about 4 mm; not greater than about 4.5 mm; or not
greater than about 5 mm.
[0066] In one embodiment, about 95% of the high-carbon SPL has an
average size of not greater than 0.5 mm, where substantially all
(e.g. 100%) of the high-carbon SPL has an average size of not
greater than 1.0 mm.
[0067] In another embodiment, the particle size of the solid fuel,
the high-carbon SPL, or the enriched SPL is adjusted to improve the
destruction of cyanide compounds. For example, Table 2 illustrates
ranges of SPL fuel particle sizes according to one embodiment of
the invention.
TABLE-US-00004 TABLE 2 SPL particle size <90 um <150 um (%)
95% 100%
[0068] In an embodiment of the present invention, the apparatus
(200) includes a supplemental fuel container (212) configured to
store and provide a supplemental fuel to the burner system (216).
In some embodiments, the supplemental fuel is an oil, such as fuel
oil (e.g. #2, #4, or #6), biofuel, diesel, or combinations thereof.
In some embodiments, the supplemental fuel is a gas, such as
natural gas (e.g. at least about 95% methane), propane, or
liquefied petroleum gasses (e.g. mix of propane and butane). In
other embodiments, the supplemental fuel is a combination of a fuel
oil and a gas.
[0069] In an embodiment of the present invention, the apparatus
(200) includes a burner system (217) configured to received and
combust one or more fuels from the solid fuel container (210) or
the supplemental fuel container (212).
[0070] In some embodiments, after a grinding step, a high carbon
SPL is fed into solid fuel container (210) and retained until the
high-carbon SPL is fed into the burner system (217) with or without
feeding of a supplemental fuel to the burner system (217) from the
supplemental fuel container (212).
[0071] For example, in some embodiments, high-carbon SPL from the
fuel container (210) and a supplemental fuel (e.g. fuel oil or
natural gas) from the supplemental fuel container (212) are
directed into the burner system (216). In one embodiment, the
burner system (216) is equipped with a controller, such as a
programmable logic controller (PLC) injection system capable of
modifying the amount of solid fuel and supplemental fuel injected
into the burner system (216). In another embodiment, the burner
system (216) is capable of controlling the rate that at least one
of the solid fuel from the fuel container (210) and the
supplemental fuel (e.g. fuel oil or natural gas) from the
supplemental fuel container (212) are provided to the burner (216).
In other embodiments, the burner system (217) is equipped with a
mechanical injection system configured to adjust a ratio or feed
rate of the solid fuel and supplemental fuel injected into the
burner system (216).
[0072] In some embodiments, the burner system (217) increases the
amount of solid fuel to supplemental fuel, decreases the amount of
solid fuel to supplemental fuel, increases a rate of fuel injection
to the burner system (217) while keeping the ratio of solid fuel
the same, or decreases a rate of fuel injection to the burner
system (217) while keeping the ratio of solid fuel the same.
[0073] In one embodiment of the present invention, the fuel
provided to the burner system (217) includes between about 50%-80%
solid fuel and about 50% and 20% supplemental fuel. In some
embodiments, the solid fuel provided to the burner (217) has a
carbon content of at least 65% by weight, 80% by weight, and 90% by
weight. In some embodiments, the solid fuel provided to the burner
(217) a heat value of at least 18,400 kJ/Kg.
[0074] In other embodiments of the present invention, the fuel
provided to a burner to produce thermal energy is a combination of
solid fuel and a supplemental fuel. For example, in some
embodiments, the fuel provided to a burner system (217) to generate
a thermal energy include a high-carbon SPL in an amount of at least
about 50 wt. %; at least about 55 wt. %; at least about 60 wt. %;
at least about 65 wt. %; at least about 70 wt. %; at least about 75
wt. %; at least about 80 wt. %; at least about 85 wt. %; at least
about 90 wt. %; at least about 95 wt. %; or at least about 100 wt.
%.
[0075] In another embodiment, the fuel provided to a burner system
(217) to generate a thermal energy includes a solid fuel in an
amount of at least about 50 wt. %; at least about 55 wt. %; at
least about 60 wt. %; at least about 65 wt. %; at least about 70
wt. %; at least about 75 wt. %; at least about 80 wt. %; at least
about 85 wt. %; at least about 90 wt. %; at least about 95 wt. %;
or at least about 100 wt. %.
[0076] In another embodiment, the fuel provided to a burner system
(217) to generate a thermal energy include a solid fuel with an
enriched SPL in an amount of at least about 50 wt. %; at least
about 55 wt. %; at least about 60 wt. %; at least about 65 wt. %;
at least about 70 wt. %; at least about 75 wt. %; at least about 80
wt. %; at least about 85 wt. %; at least about 90 wt. %; at least
about 95 wt. %; or at least about 100 wt. %.
[0077] In one embodiment of the present invention, a feed rate or
amount of solid fuel or supplemental fuel is modified according to
operation parameters of the furnace. For example, in one
embodiment, at the start-up of the burner system (217), the fuel
provided is mostly, if not wholly, comprises of supplemental fuel
from the supplemental fuel container (212). In another embodiment,
after a predetermined time, for example once a flame of combustion
is established, the fuel provided to the burner system (217) is
modified to increase a solid fuel/high-carbon SPL content. For
example, the fuel may be modified to include at least 55 wt. %, 75
wt. %, or 80 wt % solid fuel/high-carbon SPL.
[0078] In one embodiment, the solid fuel is gravity fed to the
burner (217). In another embodiment, the solid fuel is fed into the
burner (217) via a carrier gas (e.g. pressurized air, at a
modifiable flow rate).
[0079] In yet another embodiment, once the burner system (217) has
been operating for some time, the fuel content provided to the
burner system (217) is modified to reduce a content of solid
fuel/high-carbon SPL to enable burner system (217) shut off and
prevent any solid fuel from entering a furnace (218).
[0080] In an embodiment of the present invention, the apparatus
(200) includes a furnace (218). In one embodiment, the high-carbon
SPL is provided to a furnace (218) for combustion. In one
embodiment, the furnace (218) is in communication with the burner
system (216), and a thermal energy from the burner system (216) is
supplied to the furnace (218) (e.g. directed onto/into the
furnace). In one embodiment, the furnace (218) includes an enclosed
combustion chamber with a combustion system power rating of at
least 3 MW. For example, in one embodiment, the furnace (218) is a
casthouse furnace with one or more burners forming the burner
system (217).
[0081] In another example, the thermal energy is supplied to an
aluminum furnace (218) to melt/assist in processing of the aluminum
metal charge within the aluminum furnace (218).
[0082] In some embodiments, burners forming the burner system (217)
may be directed toward the charge in the furnace (218) or angled
away from the charge (e.g. such that heat is applied to the furnace
walls, which then heats the charge through conduction and
convection). In another embodiment, directing refers to pointing
the burners forming the burner system (217) toward an external wall
of the furnace (218) (e.g. sidewall and/or end), which in turn
heats the furnace's walls and thus, the charge within.
[0083] In some embodiments, aluminum metal ingots (220) are
processed in and produced from the aluminum furnace (218), along
with associated off-gases (222) exhausted from the burner system
(216) or furnace (218).
[0084] In some embodiments, the apparatus (200) includes a scrubber
(224). In some embodiments, off-gasses produced by the burner
system (217) or furnace (218) are scrubbed by the scrubber (224) to
remove pollutants or contaminants. For example, in some
embodiments, the off-gases may include fluoride compounds, which
are then scrubbed by the scrubber (224). In some embodiments, the
scrubber (224) cleans the off-gases 226 (removes the fluorides
compounds) and/or recovers AlF.sub.3 materials present therein. In
some embodiments, the recovered AlF.sub.3 can be reused in the
electrolytic cell (1) as an electrolytic bath component.
[0085] As used herein, "scrubbing" means to the process of removing
impurities or undesirable components by chemical means. In one
non-limiting embodiment, scrubbing is done through a cleansing
system that recovers fluoride emissions from a gaseous exhaust by
contacting the gaseous exhaust with an absorptive feed (e.g.
alumina).
[0086] Although a few embodiments of the present invention have
been shown and described, it will be appreciated by those skilled
in the art that changes may be made in these embodiments without
departing from the principles and spirit of the present invention,
the scope of which is defined in the appended claims and their
equivalents.
* * * * *