EP1344845A1 - Pitch-impregnated refractory brick - Google Patents
Pitch-impregnated refractory brick Download PDFInfo
- Publication number
- EP1344845A1 EP1344845A1 EP02005613A EP02005613A EP1344845A1 EP 1344845 A1 EP1344845 A1 EP 1344845A1 EP 02005613 A EP02005613 A EP 02005613A EP 02005613 A EP02005613 A EP 02005613A EP 1344845 A1 EP1344845 A1 EP 1344845A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- pitch
- bricks
- lining
- impregnated
- resins
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
- C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
- C25C3/085—Cell construction, e.g. bottoms, walls, cathodes characterised by its non electrically conducting heat insulating parts
Definitions
- the invention is related to the improvement of refractory materials for the lining of electrolytic reduction cells as used for the winning of aluminium by molten salt electrolysis.
- FIG. 1 A typical example of a reduction cell lining is shown in Figure 1.
- the bottom of the electrolysis basin consists of carbon or graphite cathode blocks (1).
- Steel collector bars (2) are embedded in the cathode blocks and serve as electrical connection to the outside of the potshell (3).
- Carbon materials (4) are also used as a major part of the side wall lining of the cell, particularly in contact with the liquid metal pad on the cathode bottom as well as with the electrolytic melt above the metal.
- the main component of the electrolyte is molten cryolite. It contains a few percent of dissolved alumina and some other additives such as aluminium and calcium fluoride.
- the cell operating temperatures range from 950 to 970°C.
- fireclay bricks (5) are commonly applied as back material of the carbon cathode bottom and carbon side wall lining.
- the carbon materials at the hot or front face of the electrolysis cell are pervious to the cryolitic melt.
- the fireclay bricks are impregnated by cryolite, react with it and are partially converted to a magma-like slag.
- electrolyte constituents penetrate deeper into the refractory lining, degrade its insulation capacity and cause swelling and softening of the fireclay bricks. The insulating and structural conditions become even worth when the light-weight insulation bricks (6) in the outer zone of the potshell lining are affected.
- the objective of the invention is to effectively improve the resistance of the refractory, especially of the fireclay bricks against cryolite. This can be achieved by filling the open pore volume of the refractory bricks with impregnating pitch.
- the procedure of pitch impregnation is carried out as follows: The refractory bricks are placed in an impregnation autoclave where they are pre-heated to 150 - 250°C. Preheating of the bricks can also be done outside the autoclave prior to the impregnation process. The autoclave and the bricks are evacuated. Thereafter the bricks are flooded with liquid impregnating pitch. After pitch flooding pressure of 5 - 10 bar is applied (compressed air or nitrogen) to press the liquid pitch into the open pores. When thorough impregnation is completed, the pitch is withdrawn and the bricks are taken out from the autoclave.
- the impregnated bricks may be directly used in the reduction cell lining if their number is limited. During heating up of the reduction cell, fumes and volatiles are released from the pitch due to its carbonization. Therefore, good ventilation and fume collection is required at the cell operating temperature. For environmental reasons it is more advantageous to subject the pitch-impregnated refractory bricks to a carbonization or coking process in dedicated furnaces up to 1000°C.
- the cryolite resistance of normal, non-impregnated fireclay bricks was compared with pitch-impregnated heat-treated fireclay bricks by two testing methods, namely the "finger” and the "cup” test. Both well-established tests showed distinct differences in cryolite resistance between the two preceding types of bricks.
- the non-impregnated fireclay brick is strongly attacked and a substantial portion of the brick material is dissolved and scorified.
- the pitch-impregnated brick did practically not indicate any sign of surface erosion and slagging. Plant tests proved this result and the favourable behaviour of the pitch-impregnated fireclay bricks.
- the pitch-impregnated bricks are preferably laid adjacent to the carbon (4) or graphite lining materials (7), i.e. under the cathode blocks and below or behind the carbon material in the side lining.
- the new refractory brick for the lining of aluminium reduction cells is characterized in that the open pore volume of fireclay bricks or other ceramic bricks is fully impregnated with pitch or resins of high carbon residue to provide a superior resistance of the impregnated bricks against components and reaction products of cryolite-based melts as well as against molten aluminium.
Abstract
The invention relates to an improvement of refractory materials for the lining of electrolytic
reduction cells used for the winning of aluminum by molten salt electrolysis.
If the refractory brick consists of ceramic material having an open pore volume which is filled
with pitch or resins of high carbon residue the resistance of the refractory against cryolite is
improved. Further improvements can be made by impregnating the carbon materials with
pitch or resins of high carbon residue.
Description
The invention is related to the improvement of refractory materials for the lining of electrolytic
reduction cells as used for the winning of aluminium by molten salt electrolysis.
A typical example of a reduction cell lining is shown in Figure 1. The bottom of the electrolysis
basin consists of carbon or graphite cathode blocks (1). Steel collector bars (2) are embedded
in the cathode blocks and serve as electrical connection to the outside of the potshell
(3). Carbon materials (4) are also used as a major part of the side wall lining of the cell, particularly
in contact with the liquid metal pad on the cathode bottom as well as with the electrolytic
melt above the metal. The main component of the electrolyte is molten cryolite. It contains
a few percent of dissolved alumina and some other additives such as aluminium and
calcium fluoride. The cell operating temperatures range from 950 to 970°C.
Various types of fireclay bricks (5) are commonly applied as back material of the carbon
cathode bottom and carbon side wall lining. The carbon materials at the hot or front face of
the electrolysis cell are pervious to the cryolitic melt. For this reason, the fireclay bricks are
impregnated by cryolite, react with it and are partially converted to a magma-like slag. As
time proceeds, electrolyte constituents penetrate deeper into the refractory lining, degrade its
insulation capacity and cause swelling and softening of the fireclay bricks. The insulating and
structural conditions become even worth when the light-weight insulation bricks (6) in the
outer zone of the potshell lining are affected.
The objective of the invention is to effectively improve the resistance of the refractory, especially
of the fireclay bricks against cryolite. This can be achieved by filling the open pore volume
of the refractory bricks with impregnating pitch. The procedure of pitch impregnation is
carried out as follows: The refractory bricks are placed in an impregnation autoclave where
they are pre-heated to 150 - 250°C. Preheating of the bricks can also be done outside the
autoclave prior to the impregnation process. The autoclave and the bricks are evacuated.
Thereafter the bricks are flooded with liquid impregnating pitch. After pitch flooding pressure
of 5 - 10 bar is applied (compressed air or nitrogen) to press the liquid pitch into the open
pores. When thorough impregnation is completed, the pitch is withdrawn and the bricks are
taken out from the autoclave.
The impregnated bricks may be directly used in the reduction cell lining if their number is
limited. During heating up of the reduction cell, fumes and volatiles are released from the
pitch due to its carbonization. Therefore, good ventilation and fume collection is required at
the cell operating temperature. For environmental reasons it is more advantageous to subject
the pitch-impregnated refractory bricks to a carbonization or coking process in dedicated
furnaces up to 1000°C.
The cryolite resistance of normal, non-impregnated fireclay bricks was compared with pitch-impregnated
heat-treated fireclay bricks by two testing methods, namely the "finger" and the
"cup" test. Both well-established tests showed distinct differences in cryolite resistance between
the two preceding types of bricks. The non-impregnated fireclay brick is strongly attacked
and a substantial portion of the brick material is dissolved and scorified. The pitch-impregnated
brick did practically not indicate any sign of surface erosion and slagging. Plant
tests proved this result and the favourable behaviour of the pitch-impregnated fireclay bricks.
In the reduction cells, the pitch-impregnated bricks are preferably laid adjacent to the carbon
(4) or graphite lining materials (7), i.e. under the cathode blocks and below or behind the
carbon material in the side lining.
Service life and thermal conditions of the electrolytic reduction cell is greatly enhanced by the
pitch-impregnated refractory bricks according to the invention.
Furthermore, it could clearly be demonstrated that the pitch-impregnated bricks are also highly resistant against liquid aluminium in the presence of cryolite-based melts.
Furthermore, it could clearly be demonstrated that the pitch-impregnated bricks are also highly resistant against liquid aluminium in the presence of cryolite-based melts.
Also, other carbonaceous impregnating fluids such as phenolic and/or furane resins can successfully
be applied for the impregnation of refractory lining bricks for aluminium reduction
cells. Therefore the new refractory brick for the lining of aluminium reduction cells is characterized
in that the open pore volume of fireclay bricks or other ceramic bricks is fully impregnated
with pitch or resins of high carbon residue to provide a superior resistance of the impregnated
bricks against components and reaction products of cryolite-based melts as well
as against molten aluminium.
Claims (4)
- Aluminium reduction cell comprising a refractory brick lining, carbon materials used as part of the side wall and/or fireclay materials used as back materials of the cathode bottom and side wall lining,
characterized in that the refractory brick lining consists of ceramic material having an open pore volume which is filled with pitch or resins of high carbon residue. - Aluminium reduction cell according to claim 1 wherein the carbon materials are impregnated with pitch or resins of high carbon residue.
- Aluminium reduction cell according to claim 1 wherein the pores of the fireclay material are filled with impregnating pitch or resins of high carbon residue.
- Aluminium reduction cell according to claim 1 wherein pitch impregnated bricks of fireclay or carbon materials are positioned under the cathode blocks and below or behind the carbon material in the side lining.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP02005613A EP1344845A1 (en) | 2002-03-12 | 2002-03-12 | Pitch-impregnated refractory brick |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP02005613A EP1344845A1 (en) | 2002-03-12 | 2002-03-12 | Pitch-impregnated refractory brick |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| EP1344845A1 true EP1344845A1 (en) | 2003-09-17 |
Family
ID=27763364
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP02005613A Withdrawn EP1344845A1 (en) | 2002-03-12 | 2002-03-12 | Pitch-impregnated refractory brick |
Country Status (1)
| Country | Link |
|---|---|
| EP (1) | EP1344845A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105463506A (en) * | 2016-01-13 | 2016-04-06 | 重庆大学 | Method for separating and recycling electrolytes and carbon in anode carbon residues of aluminum electrolytes |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4071593A (en) * | 1973-11-06 | 1978-01-31 | General Refractories Company | Process for making a pitch impregnated, cold molded refractory article |
| GB1593161A (en) * | 1978-04-28 | 1981-07-15 | Steetley Refractories Ltd | Refractory materials |
| RU2081208C1 (en) * | 1993-04-05 | 1997-06-10 | Товарищество с ограниченной ответственностью "Межотраслевой центр проблем экологии и эффективности производства алюминия" | Method for protection of lining of aluminium electrolyzer |
-
2002
- 2002-03-12 EP EP02005613A patent/EP1344845A1/en not_active Withdrawn
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4071593A (en) * | 1973-11-06 | 1978-01-31 | General Refractories Company | Process for making a pitch impregnated, cold molded refractory article |
| GB1593161A (en) * | 1978-04-28 | 1981-07-15 | Steetley Refractories Ltd | Refractory materials |
| RU2081208C1 (en) * | 1993-04-05 | 1997-06-10 | Товарищество с ограниченной ответственностью "Межотраслевой центр проблем экологии и эффективности производства алюминия" | Method for protection of lining of aluminium electrolyzer |
Non-Patent Citations (1)
| Title |
|---|
| DATABASE WPI Section Ch Week 199807, Derwent World Patents Index; Class M28, AN 1998-075551, XP002210681 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105463506A (en) * | 2016-01-13 | 2016-04-06 | 重庆大学 | Method for separating and recycling electrolytes and carbon in anode carbon residues of aluminum electrolytes |
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