CA1078626A - Treatment of carbothermically produced aluminum - Google Patents
Treatment of carbothermically produced aluminumInfo
- Publication number
- CA1078626A CA1078626A CA254,485A CA254485A CA1078626A CA 1078626 A CA1078626 A CA 1078626A CA 254485 A CA254485 A CA 254485A CA 1078626 A CA1078626 A CA 1078626A
- Authority
- CA
- Canada
- Prior art keywords
- aluminum
- aluminum carbide
- melt
- gas
- carbide
- 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.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B21/00—Obtaining aluminium
- C22B21/02—Obtaining aluminium with reducing
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B21/00—Obtaining aluminium
- C22B21/06—Obtaining aluminium refining
- C22B21/064—Obtaining aluminium refining using inert or reactive gases
Abstract
TREATMENT OF CARBOTHERMICALLY PRODUCED ALUMINUM
Abstract of the Disclosure A process is set forth for reducing the aluminum carbide content of aluminum produced via carbothermic processes which comprises contacting the aluminum contaminated with aluminum car-bide with reactive gases so as to cause the aluminum carbide to react and separate from the aluminum. The aluminum is recovered and the residue can be recycled back to the furnace without additional chemical treatment.
Abstract of the Disclosure A process is set forth for reducing the aluminum carbide content of aluminum produced via carbothermic processes which comprises contacting the aluminum contaminated with aluminum car-bide with reactive gases so as to cause the aluminum carbide to react and separate from the aluminum. The aluminum is recovered and the residue can be recycled back to the furnace without additional chemical treatment.
Description
7~
This invention relates to a process for the reducing of aluminum carbide content of aluminum produced via carbother-mic processes.
The production of aluminum by carbothermic processes has long been known in the art and there are numerous patents and literature articles which describe processes of this general type. A carbothermic process involves reacting an aluminum oxide containing compound with a reductant which is usually carbon aluminum carbide or a mixture thereof in an electric furnace so as to reduce the aluminum oxide to metallic aluminum. Although the reaction on first impression would appear to be a very simple one, i.e., the reduction of aluminum oxide to aluminum, the art has long been plagued with the inescapable fact that substantially pure aluminum is not obtained via conventional carbothermic processes and, in fact, the product which is tapped from the furnace is alumin~lm contaminated with aluminum carbide. The amount ,f contamiLation ~4ith ~lumlnum car'~ide varies dependin~ upon the ' ~
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.
.:
''' ' ,. - 1 - '' , . . .:, . ' . .. ,. . :'' . :' .. : ., ~17~
particular carbothermic process which is carried out but, in ~eneral, conventional carbothermic processes result in the pro-duction of aluminum which is contaminated by 10-20% by weight of aluminum carbide.
As can well be appreciated, the present standards for commercially pure aluminum do not allow a significant quantity of aluminum carbide to be present and, as such, the furnace pro-duct from most carbothermic reduction processes has to be sub-jected to further proeessing steps in order to reduce the alu-minum carbide content to an acceptable level. ~he art is wellaware of a wide variety of processes which have been heretofore suggested by the workers in this art for reducing the aluminum carbide content from the produck of a carbothermic reduction fur-nace and, in general, these processes have been time consuming, expensive, and evidently not economically feasible as is evi-denced by the fact that there is no known commercial process practiced today for the preparation of commercially pure aluminum via a carbothermic reduction process.
One particular aspect to the problem o~ reducing the aluminum earbide content resides in the fact that the art has found out that it is relatively easy to reduce the aluminum carbide content of at least a portion of the aluminum produced by a carbothermic reduction process by simply letting the fur-nace melt cool so that an aluminum carbide matrix is formed whereby said aluminum carbide matrix squeezes out aluminum to thé surface of the melt wherein this aluminum can be removed by any suitable technique, including decanting. The aluminum which is removed in this manner is greatly diminished in aluminum carbide content but only a small portion of the availa~le aluminum is recovered.
It is also known to enhance the yield of aluminum from a carbothermic reduction process by utilizing a mechanical working. A technique of this type subjects moving equipment under severe stress to very hot and corrosive conditions.
There are also conventional techniques in the prior art such as fluxing with metallic salts which can diminish the amount of aluminum carbide contamination but the molten salts mix with the carbide so removed, and it is costly to remove the carbide from the salt so that the carbide can be recycled to the furnace. Without such recycIe, the power cons~ption and furnace size become uneconomical in comparison w1th prior art methods practiced commercially for making aluminum.
DESCRIP~ION OF THE P ÆFERRED EMBODIMENT
~ The novel process of this invention i5 carried out simply by contacting a mixture of aluminum contaminated with aluminum carbide in the molten state with certain gases which interact with or operate upon aluminum carbide so as to prevent the formation of an aluminum carbide matrix which would entrap the aluminum and recovering substantially pure aluminum. Treat~
ment with the gases in accordance with techniques of this invention involve blowlng the gas through the body of the melt of aluminum and aluminum carbide. This is conveniently accomplished by pouring the mixture of aluminum and aluminum carbide into a suitable receptacle which is provided with ports or inlets through which the particular reactive gas or mixture of gases is passed under pressure so that the gas passes through the body of the melt and reacts with the aluminum carbid<.
.
'. ' ', ' ' 7 ~
~he number and size of the inlets is obviously not critical but what is reguired is that the gas pass through the body of the melt so as to be able to act upon the aluminum carbide and react therewith.
Another way of accomplishing the same is to cause a high velocity stream of gas to impin~e upon and penetrate the aluminum-aluminum carbide mixture. Suitable examples of this technique include a plasma torch operating in an environment of air as well as the use of a lance.
It is to be understood that if a mixture of aluminum and aluminum carbide is simply heated in air so that the air only contacts the surface thereo~ that effective reduction of a$uminum carbide content simply will not be obtained. This invention requires that the reactive gas be passed through the melt so that it has an opportunity to xeact with the aluminum carbide and prevent the formation of an al~minum-aluminum carbide matrïx.
The gases that can be utilized in the novel process of this in~ention are not narrowly critical and they can be characterized ~y stating that they must include oxygen, for example in the form of air, carbon monoxide, caxbon dioxide, or water vapor. It is to be understood that there can be other components in the gaseous mixture providing that oxygen and/or an oxidizing compound such as carbon monoxide, C02, or H20 are present. Thus, for example, the reactive gases can be mixtures of oxygen or carbon monoxide with inert gases such as nitrogen, argon, etc. Air would be useful in the instant process. In some cases the mixture of reactive gases can include materials such as chlorine or other halogens but in situations of this type it is extremely important that the concentration of the chlorine be controlled to low concentrationsr i. eO~ no more - 4 - ' .
~ an about 20 weight percent of the total mixture, in order to assure that the resldue will be directly recyclible to the reduc-tion furnace without additional chemical treatment. It is to be immediately understood that a treatment with 100 percent chlorine is not within the scope of this invention since the chlorine would react with the aluminum carbide and aluminum in such a manner as to produce products which cannot be directly recycled back to the urnace. An example of a mixture of a gas containing chlorine which is operable in the novel process of ~his invention would be a mixture of nitrogen, carbon monoxide and chlorine, wherein chlorine was about 10 weight percent of the total mixture.
The temperature at which the process of this invention i~ carried out is also not narrowly critical and all that is re- .
quired is,that it be carried out at a temperature which is sufficiently high to keep the aluminum-aluminum carbide mixture in a fluid state. The uppermost t~mperature is determined by the initial amount of aluminum carbide in solution with the alumi-num. For example, with 20~ A14C3 in solution with aluminum the initial temperature of gassing must be about 2100C. With an i~itial carbide content of 2%, the uppermost temperature can be as low as 1600C. Quite ob~iously,-excessively high temperatures should be avoided in order to prevent the aluminum from being lost to the atmosphere by volatilization. In general, it has been found that temperatures within the range of 660 ~o 2100C
and more preferably, from 700 to 1600C can be ef~ectively employed. The amounk of gas which is used is also not narrowly critical and any convenient flow xate can be employed in order to obtain the desired results. It should appear quite obYious that, in general, a low flow rate will mean that the reaction will take longer to accomplish for the very simple reason that it will take longer for the gas to interact with the aluminum _5_ , .
.
,- - : .
Il 107~Z6 carbide and prevent the formation of the matrix. Additionally, too high a flow rate, although not detrimental to the reaction, .
will involve waste in that the gas will be passed through the mixture at a rate faster than it can react with the aluminum carbide which is present. Addi~ionally, some gases are more effective than other gases so that the exact flow rate utilized .
would also depend on the partic~lar gas which is being used. :
In general, however, it has been found that flow rates of : .
from about 0.02to about 5 liters per minute for each 100 grams : -.
of melt to be de-carbonized and, more preferably, from .04 to .06 liters per minute will ke sufficien~ to accomplish the task -of reducing the aluminum carbide contamination. .
It i.s.understood that gassing i~ accordance with this invention can be carried out at a substantially cons.tant temperature, although~ quite obviously, it is preferre~ to allow the aluminum-aluminum carbide melt to cool while ~:
.assing to within the temperature ranges above set forth.
It is also to be understood that the flow rate of gas need not be continuous but can rather be an intermittent oper- : :
ation if such is desired. Thus, gas can be charged at certain spaced intervals. This operation is within the scope of thls - ¦
invention. It is also to be understood that the flow rate of gas used may not be a constant one, but can be raised and lowered as conditions require.
The time during which the novel process of this in-vention is carried out is also not narrowly critical and, quite obviously, it is carried out until the amount of aluminum carbide is decreased to acceptable levels. Factors which govern ..
the amount of time with which the reaction is carried out ob~ ously include the ~low rate of the cxidizing gas beiny . , . .
'. , ' ... ,,, ~" " 1~
Z~
utilized, as well as the temperature and the amount of carbide contamination. It is quite obvious, however, that sampling techniques can easily determine when the reaction has progressed to the point that the aluminum carbide contamination has been reduced to desired levels.
The manner in which the reactive gas or gases affects the aluminum carbide is not completely understood but it has been observed that when aluminum contaminated with aluminum carbide is contacted in accordance with the novel process of this invention, the aluminum carbide is changed so that it becomes readily separable from the aluminum. This change is evidenced by the fact that the aluminum carbide separates from the aluminum product -- usually in the form of a foam-like material which can be removed from the aluminum mass by any con~entional technique including skimming and/or decantation.
One particularly significant advantage of the instant process is that ~he reaction product, containing aluminum carbide, for example, the foam previously referred to can be directly recycled back to the reduction furnace without additional chemical treatment~ This advantage is of tremendous importance since as can be readily appreciated, additional chemical treatments are expensive and time consuming which detract from the overall economy of any operation. This is to be immediately distinguished from the heretorore practiced prior art processes involving the use of fluxes wherein the residue after removal of aluminum was not, could not, be recycled directly back to reduction furnaces without expensive chemical treatment.
A particularly preferred embodiment of the novel -process of this invention resides in those situations wh_rein . , ' , ,' '~
..... ,.
.
7~362~
~-hc aluminum }~iny trc~lted is contaminated with no more than al)ou~ 5 ~eight percent o~ aluminum carbide. It has becn ~ound that wl~n a f~cd ma~ri~l containillc3 ~his pcrccnta~e of alumin~
carbide is trea~ed in acc~rdanc~ with the novel proccss of this invcntion, the ~luminum carbidc is changcd to a rc~dily scparab]e form and aluminum can be recovered which meets the specifications of con~ercially pure aluminum.
EXA*IPLE 1 A mixiure of 186.88 grams of aluminum contaminated with 3.12 grams o~ aluminum carbide (1.64 weight percent alumin~m J carbide) was melted and while in the molten state ~hr3~e~ with Tri-gas* at a flow rate o~ 0.5 liters per minute for 10 minu~es.
The temperature during this time was 1045C. Ater the treat-ment for 10 minute~, the metal was poured o~f and analyze~ for aluminum carbide content.
The aluminum carbide level was so low that it was below detection limits, i.e., less than 0.2%. A sample of un1uxed electrolytic metal showed 0.2% aluminum carbide b~ the same test.
~ri-gas - 80 Vol. % Mitrogen - 10 Vol. ~ Chlorine - 10 ~ol. % Carbon Monoxide `~ EXAMPLE 2 A charge of 401 grams of aluminum and 8 grams of aluminum carbide (about 2 weight percent aluminum carbide) was heated to 1510C. and homogenized by stirring. Air was blown through ~le me~t at 0-6 liters per minute for four minutes~
The sample was cooled to 1100C and s~immed. Air was again blown at 0.7 liters per minute ~or 1 minute. The melt was skimmed and allowed to freeze.
,' ~ .
. .
, 1, 78~;
I Analysis of the product showed that the aluminum carbide ¦ content had been reduced to 0.73 weight percent~
I I
: ` ~ 9 ~ ' :' ' ' ~`
. ': ~ '`, .
'.`
.~...... ... ~ r 7136z~E~
A charge of 4474 grams of aluminum and 44 grams of carbon fines tenough to produce about 4 weight percent a~uminum carbide) was heated to 1740C and homogenized by stirring.
Carbon dioxide gas was blown through the melt at approximately
This invention relates to a process for the reducing of aluminum carbide content of aluminum produced via carbother-mic processes.
The production of aluminum by carbothermic processes has long been known in the art and there are numerous patents and literature articles which describe processes of this general type. A carbothermic process involves reacting an aluminum oxide containing compound with a reductant which is usually carbon aluminum carbide or a mixture thereof in an electric furnace so as to reduce the aluminum oxide to metallic aluminum. Although the reaction on first impression would appear to be a very simple one, i.e., the reduction of aluminum oxide to aluminum, the art has long been plagued with the inescapable fact that substantially pure aluminum is not obtained via conventional carbothermic processes and, in fact, the product which is tapped from the furnace is alumin~lm contaminated with aluminum carbide. The amount ,f contamiLation ~4ith ~lumlnum car'~ide varies dependin~ upon the ' ~
-''~..
.
.:
''' ' ,. - 1 - '' , . . .:, . ' . .. ,. . :'' . :' .. : ., ~17~
particular carbothermic process which is carried out but, in ~eneral, conventional carbothermic processes result in the pro-duction of aluminum which is contaminated by 10-20% by weight of aluminum carbide.
As can well be appreciated, the present standards for commercially pure aluminum do not allow a significant quantity of aluminum carbide to be present and, as such, the furnace pro-duct from most carbothermic reduction processes has to be sub-jected to further proeessing steps in order to reduce the alu-minum carbide content to an acceptable level. ~he art is wellaware of a wide variety of processes which have been heretofore suggested by the workers in this art for reducing the aluminum carbide content from the produck of a carbothermic reduction fur-nace and, in general, these processes have been time consuming, expensive, and evidently not economically feasible as is evi-denced by the fact that there is no known commercial process practiced today for the preparation of commercially pure aluminum via a carbothermic reduction process.
One particular aspect to the problem o~ reducing the aluminum earbide content resides in the fact that the art has found out that it is relatively easy to reduce the aluminum carbide content of at least a portion of the aluminum produced by a carbothermic reduction process by simply letting the fur-nace melt cool so that an aluminum carbide matrix is formed whereby said aluminum carbide matrix squeezes out aluminum to thé surface of the melt wherein this aluminum can be removed by any suitable technique, including decanting. The aluminum which is removed in this manner is greatly diminished in aluminum carbide content but only a small portion of the availa~le aluminum is recovered.
It is also known to enhance the yield of aluminum from a carbothermic reduction process by utilizing a mechanical working. A technique of this type subjects moving equipment under severe stress to very hot and corrosive conditions.
There are also conventional techniques in the prior art such as fluxing with metallic salts which can diminish the amount of aluminum carbide contamination but the molten salts mix with the carbide so removed, and it is costly to remove the carbide from the salt so that the carbide can be recycled to the furnace. Without such recycIe, the power cons~ption and furnace size become uneconomical in comparison w1th prior art methods practiced commercially for making aluminum.
DESCRIP~ION OF THE P ÆFERRED EMBODIMENT
~ The novel process of this invention i5 carried out simply by contacting a mixture of aluminum contaminated with aluminum carbide in the molten state with certain gases which interact with or operate upon aluminum carbide so as to prevent the formation of an aluminum carbide matrix which would entrap the aluminum and recovering substantially pure aluminum. Treat~
ment with the gases in accordance with techniques of this invention involve blowlng the gas through the body of the melt of aluminum and aluminum carbide. This is conveniently accomplished by pouring the mixture of aluminum and aluminum carbide into a suitable receptacle which is provided with ports or inlets through which the particular reactive gas or mixture of gases is passed under pressure so that the gas passes through the body of the melt and reacts with the aluminum carbid<.
.
'. ' ', ' ' 7 ~
~he number and size of the inlets is obviously not critical but what is reguired is that the gas pass through the body of the melt so as to be able to act upon the aluminum carbide and react therewith.
Another way of accomplishing the same is to cause a high velocity stream of gas to impin~e upon and penetrate the aluminum-aluminum carbide mixture. Suitable examples of this technique include a plasma torch operating in an environment of air as well as the use of a lance.
It is to be understood that if a mixture of aluminum and aluminum carbide is simply heated in air so that the air only contacts the surface thereo~ that effective reduction of a$uminum carbide content simply will not be obtained. This invention requires that the reactive gas be passed through the melt so that it has an opportunity to xeact with the aluminum carbide and prevent the formation of an al~minum-aluminum carbide matrïx.
The gases that can be utilized in the novel process of this in~ention are not narrowly critical and they can be characterized ~y stating that they must include oxygen, for example in the form of air, carbon monoxide, caxbon dioxide, or water vapor. It is to be understood that there can be other components in the gaseous mixture providing that oxygen and/or an oxidizing compound such as carbon monoxide, C02, or H20 are present. Thus, for example, the reactive gases can be mixtures of oxygen or carbon monoxide with inert gases such as nitrogen, argon, etc. Air would be useful in the instant process. In some cases the mixture of reactive gases can include materials such as chlorine or other halogens but in situations of this type it is extremely important that the concentration of the chlorine be controlled to low concentrationsr i. eO~ no more - 4 - ' .
~ an about 20 weight percent of the total mixture, in order to assure that the resldue will be directly recyclible to the reduc-tion furnace without additional chemical treatment. It is to be immediately understood that a treatment with 100 percent chlorine is not within the scope of this invention since the chlorine would react with the aluminum carbide and aluminum in such a manner as to produce products which cannot be directly recycled back to the urnace. An example of a mixture of a gas containing chlorine which is operable in the novel process of ~his invention would be a mixture of nitrogen, carbon monoxide and chlorine, wherein chlorine was about 10 weight percent of the total mixture.
The temperature at which the process of this invention i~ carried out is also not narrowly critical and all that is re- .
quired is,that it be carried out at a temperature which is sufficiently high to keep the aluminum-aluminum carbide mixture in a fluid state. The uppermost t~mperature is determined by the initial amount of aluminum carbide in solution with the alumi-num. For example, with 20~ A14C3 in solution with aluminum the initial temperature of gassing must be about 2100C. With an i~itial carbide content of 2%, the uppermost temperature can be as low as 1600C. Quite ob~iously,-excessively high temperatures should be avoided in order to prevent the aluminum from being lost to the atmosphere by volatilization. In general, it has been found that temperatures within the range of 660 ~o 2100C
and more preferably, from 700 to 1600C can be ef~ectively employed. The amounk of gas which is used is also not narrowly critical and any convenient flow xate can be employed in order to obtain the desired results. It should appear quite obYious that, in general, a low flow rate will mean that the reaction will take longer to accomplish for the very simple reason that it will take longer for the gas to interact with the aluminum _5_ , .
.
,- - : .
Il 107~Z6 carbide and prevent the formation of the matrix. Additionally, too high a flow rate, although not detrimental to the reaction, .
will involve waste in that the gas will be passed through the mixture at a rate faster than it can react with the aluminum carbide which is present. Addi~ionally, some gases are more effective than other gases so that the exact flow rate utilized .
would also depend on the partic~lar gas which is being used. :
In general, however, it has been found that flow rates of : .
from about 0.02to about 5 liters per minute for each 100 grams : -.
of melt to be de-carbonized and, more preferably, from .04 to .06 liters per minute will ke sufficien~ to accomplish the task -of reducing the aluminum carbide contamination. .
It i.s.understood that gassing i~ accordance with this invention can be carried out at a substantially cons.tant temperature, although~ quite obviously, it is preferre~ to allow the aluminum-aluminum carbide melt to cool while ~:
.assing to within the temperature ranges above set forth.
It is also to be understood that the flow rate of gas need not be continuous but can rather be an intermittent oper- : :
ation if such is desired. Thus, gas can be charged at certain spaced intervals. This operation is within the scope of thls - ¦
invention. It is also to be understood that the flow rate of gas used may not be a constant one, but can be raised and lowered as conditions require.
The time during which the novel process of this in-vention is carried out is also not narrowly critical and, quite obviously, it is carried out until the amount of aluminum carbide is decreased to acceptable levels. Factors which govern ..
the amount of time with which the reaction is carried out ob~ ously include the ~low rate of the cxidizing gas beiny . , . .
'. , ' ... ,,, ~" " 1~
Z~
utilized, as well as the temperature and the amount of carbide contamination. It is quite obvious, however, that sampling techniques can easily determine when the reaction has progressed to the point that the aluminum carbide contamination has been reduced to desired levels.
The manner in which the reactive gas or gases affects the aluminum carbide is not completely understood but it has been observed that when aluminum contaminated with aluminum carbide is contacted in accordance with the novel process of this invention, the aluminum carbide is changed so that it becomes readily separable from the aluminum. This change is evidenced by the fact that the aluminum carbide separates from the aluminum product -- usually in the form of a foam-like material which can be removed from the aluminum mass by any con~entional technique including skimming and/or decantation.
One particularly significant advantage of the instant process is that ~he reaction product, containing aluminum carbide, for example, the foam previously referred to can be directly recycled back to the reduction furnace without additional chemical treatment~ This advantage is of tremendous importance since as can be readily appreciated, additional chemical treatments are expensive and time consuming which detract from the overall economy of any operation. This is to be immediately distinguished from the heretorore practiced prior art processes involving the use of fluxes wherein the residue after removal of aluminum was not, could not, be recycled directly back to reduction furnaces without expensive chemical treatment.
A particularly preferred embodiment of the novel -process of this invention resides in those situations wh_rein . , ' , ,' '~
..... ,.
.
7~362~
~-hc aluminum }~iny trc~lted is contaminated with no more than al)ou~ 5 ~eight percent o~ aluminum carbide. It has becn ~ound that wl~n a f~cd ma~ri~l containillc3 ~his pcrccnta~e of alumin~
carbide is trea~ed in acc~rdanc~ with the novel proccss of this invcntion, the ~luminum carbidc is changcd to a rc~dily scparab]e form and aluminum can be recovered which meets the specifications of con~ercially pure aluminum.
EXA*IPLE 1 A mixiure of 186.88 grams of aluminum contaminated with 3.12 grams o~ aluminum carbide (1.64 weight percent alumin~m J carbide) was melted and while in the molten state ~hr3~e~ with Tri-gas* at a flow rate o~ 0.5 liters per minute for 10 minu~es.
The temperature during this time was 1045C. Ater the treat-ment for 10 minute~, the metal was poured o~f and analyze~ for aluminum carbide content.
The aluminum carbide level was so low that it was below detection limits, i.e., less than 0.2%. A sample of un1uxed electrolytic metal showed 0.2% aluminum carbide b~ the same test.
~ri-gas - 80 Vol. % Mitrogen - 10 Vol. ~ Chlorine - 10 ~ol. % Carbon Monoxide `~ EXAMPLE 2 A charge of 401 grams of aluminum and 8 grams of aluminum carbide (about 2 weight percent aluminum carbide) was heated to 1510C. and homogenized by stirring. Air was blown through ~le me~t at 0-6 liters per minute for four minutes~
The sample was cooled to 1100C and s~immed. Air was again blown at 0.7 liters per minute ~or 1 minute. The melt was skimmed and allowed to freeze.
,' ~ .
. .
, 1, 78~;
I Analysis of the product showed that the aluminum carbide ¦ content had been reduced to 0.73 weight percent~
I I
: ` ~ 9 ~ ' :' ' ' ~`
. ': ~ '`, .
'.`
.~...... ... ~ r 7136z~E~
A charge of 4474 grams of aluminum and 44 grams of carbon fines tenough to produce about 4 weight percent a~uminum carbide) was heated to 1740C and homogenized by stirring.
Carbon dioxide gas was blown through the melt at approximately
2 liters per minute for 32 minutes at which time the melt was at 1000 ~25C.
The melt container was tipped to a horizontal position and 665 grams of product wa~ poured out. This was a pourable yield, at approximately 1000C, of 14.7 percent o~ the starting material.
Analysis of the poured product showed that the aluminum carbide content was reduced to 0.89 weight percent. `
A charge o~ 4452 grams o~ aluminum and 44 grams of carbon (enough to produce about 4 weight percent aluminum carbide was heated to 1910C and homogenized by stirring. Carbon dioxide gas was blown through the melt at approximately 2 liters per minute for 3 minutes at which time the melt was at 1000 ~25C.
The melt conta1ner was tipped to a horizontal position and 400 grams of product was poured out. This was a pourable ~yleld, at approximately 1000C, o~ 8.9 percent of the starting material. ~ `
Analysis of the poured product showed that the aluminum carbide content~was reduced to 0.44 weight peraent. `
EXAMPLE S
A charge of 4452 grams of aluminum and 44 grams of carbon fines (enough to produce about 4 weight percent aluminum oarbide) was heated to 1810C and homogenized by stirring~ Wate - 10 - ~ " :' Il ~ . T ~
vapor gas (steam) was blown through the melt at approxima~ely 2 liters per minute for 15 minutes at which time the melt was at 1000 +25C.
The melt container was tipped to a horizontal position and 1159 grams of product was poured out. This was a pourable yield, at approximately 1000C, of 25.7 percent of the starting material.
Analysis of the poured product showed that the aluminum carbide content was reduced to 1.26 weight percent.
A charge of 4425 grams of aluminum and 44 grams of carbon fines (enou~h to produc~ about 4 weight percent aluminum carbide~ was heated to 176SC and homogenized by stirring. Water vapor gas (steam) was blown through the mel~ at approximately 2 liters per minute for 10 minutes at which time the melt was at 1~75C.
The melt co~tainer was tipped to a horizontal position and 1577 grams of product was poured out. This was a pourable yield, at approximately 1000C, of 35.3 percent of the starting material.
~ nalysis of the poured product showed that the aluminum carbide content waS reduced to 1.43 weight percent.
A charge of 4489 grams of aluminum and 44 grams of carbon fines (enough to produce about 4 weight percent aluminum carbide) was heated to 1730C and homogenized by stirring. Carbon monoxide (85%) - chlorine (15~) gas mix* was blown through the melt at approximately 2 liters per minute for 12 minutes at which time the melt was at 1000 +25C.
* Volume Percent . ~ ~
` ' :.
.
. .
.' r~
' I' ,~ . : . .
.
-. , . . : , .
' .
10786,'Z6 The melt container was tipped to a horizontal position and 658 grams of product was poured out. This was a pourable yield, at approximately 1000C, of 14.5 percent of the starting ma~erial.
Analysis of the poured product showed that the aluminum .
carbide content was reduced to 0.79 weight percent.
EX~MPLE 8 A charge comprising aluminum contamina~ed with 3 weight -percent of aluminum carbide is subjected to the action of a plasma torch in an environment of air such that the charge is flowable at approximately 900C. A residue comprising alumina, aluminum carbide and aluminum is skimmed, approximately 60% of the weight o the charge is recovered as pourable aluminum con-taini less thar 0.2% al~inum ca~bide.
Il 1 ;
. , ,~
:
f
The melt container was tipped to a horizontal position and 665 grams of product wa~ poured out. This was a pourable yield, at approximately 1000C, of 14.7 percent o~ the starting material.
Analysis of the poured product showed that the aluminum carbide content was reduced to 0.89 weight percent. `
A charge o~ 4452 grams o~ aluminum and 44 grams of carbon (enough to produce about 4 weight percent aluminum carbide was heated to 1910C and homogenized by stirring. Carbon dioxide gas was blown through the melt at approximately 2 liters per minute for 3 minutes at which time the melt was at 1000 ~25C.
The melt conta1ner was tipped to a horizontal position and 400 grams of product was poured out. This was a pourable ~yleld, at approximately 1000C, o~ 8.9 percent of the starting material. ~ `
Analysis of the poured product showed that the aluminum carbide content~was reduced to 0.44 weight peraent. `
EXAMPLE S
A charge of 4452 grams of aluminum and 44 grams of carbon fines (enough to produce about 4 weight percent aluminum oarbide) was heated to 1810C and homogenized by stirring~ Wate - 10 - ~ " :' Il ~ . T ~
vapor gas (steam) was blown through the melt at approxima~ely 2 liters per minute for 15 minutes at which time the melt was at 1000 +25C.
The melt container was tipped to a horizontal position and 1159 grams of product was poured out. This was a pourable yield, at approximately 1000C, of 25.7 percent of the starting material.
Analysis of the poured product showed that the aluminum carbide content was reduced to 1.26 weight percent.
A charge of 4425 grams of aluminum and 44 grams of carbon fines (enou~h to produc~ about 4 weight percent aluminum carbide~ was heated to 176SC and homogenized by stirring. Water vapor gas (steam) was blown through the mel~ at approximately 2 liters per minute for 10 minutes at which time the melt was at 1~75C.
The melt co~tainer was tipped to a horizontal position and 1577 grams of product was poured out. This was a pourable yield, at approximately 1000C, of 35.3 percent of the starting material.
~ nalysis of the poured product showed that the aluminum carbide content waS reduced to 1.43 weight percent.
A charge of 4489 grams of aluminum and 44 grams of carbon fines (enough to produce about 4 weight percent aluminum carbide) was heated to 1730C and homogenized by stirring. Carbon monoxide (85%) - chlorine (15~) gas mix* was blown through the melt at approximately 2 liters per minute for 12 minutes at which time the melt was at 1000 +25C.
* Volume Percent . ~ ~
` ' :.
.
. .
.' r~
' I' ,~ . : . .
.
-. , . . : , .
' .
10786,'Z6 The melt container was tipped to a horizontal position and 658 grams of product was poured out. This was a pourable yield, at approximately 1000C, of 14.5 percent of the starting ma~erial.
Analysis of the poured product showed that the aluminum .
carbide content was reduced to 0.79 weight percent.
EX~MPLE 8 A charge comprising aluminum contamina~ed with 3 weight -percent of aluminum carbide is subjected to the action of a plasma torch in an environment of air such that the charge is flowable at approximately 900C. A residue comprising alumina, aluminum carbide and aluminum is skimmed, approximately 60% of the weight o the charge is recovered as pourable aluminum con-taini less thar 0.2% al~inum ca~bide.
Il 1 ;
. , ,~
:
f
Claims (20)
1. A process for decreasing aluminum carbide contamination of aluminum produced by carbothermic processes, said process comprising:
(A) preparing said aluminum contaminated with up to 20 weight percent of aluminum carbide as a melt at an initial temperature sufficiently high to keep said melt in a fluid state;
(B) blowing said melt with a gas which comprises oxygen, air, carbon dioxide, steam, carbon monoxide, or a mixture of chlorine, nitrogen, and carbon monoxide, wherein chlorine is present in an amount no greater than about 20 weight percent, or mixtures of these gases for a sufficient period of time to prevent the formation of an aluminum-aluminum carbide matrix, whereby said aluminum carbide becomes readily separable from said aluminum;
(C) separating said aluminum carbide from said aluminum in said melt.
(A) preparing said aluminum contaminated with up to 20 weight percent of aluminum carbide as a melt at an initial temperature sufficiently high to keep said melt in a fluid state;
(B) blowing said melt with a gas which comprises oxygen, air, carbon dioxide, steam, carbon monoxide, or a mixture of chlorine, nitrogen, and carbon monoxide, wherein chlorine is present in an amount no greater than about 20 weight percent, or mixtures of these gases for a sufficient period of time to prevent the formation of an aluminum-aluminum carbide matrix, whereby said aluminum carbide becomes readily separable from said aluminum;
(C) separating said aluminum carbide from said aluminum in said melt.
2. The process of claim 1 wherein said gas consists essentially of oxygen or air.
3. The process of claim 1 wherein said gas consists essentially of steam.
4. The process of claim 1 wherein said gas consists essentially of carbon dioxide.
5. The process of claim 1 wherein said gas consists essentially of carbon monoxide.
6. The process of claim 1 wherein said gas is a mixture of chlorine, nitrogen, and carbon monoxide, wherein chlorine is present in an amount no greater than about 20 weight percent.
7. The process of claim 1 wherein said initial temperature varies directly with the initial amount of said aluminum carbide contamination.
8. The process of claim 7 wherein said initial tempera-ture is about 1500°C when said initial amount is 28.
9. The process of claim 1 wherein said blowing is at a flow rate fox said reactive gas of from about 0.02 to about 5 liters per minute for each 100 grams of said melt.
10. The process of claim 9 wherein said flow rate is from 0.04 to 0.06 liters per minute for each 100 grams of said melt.
11. The process of claim 1 wherein said separated aluminum carbide is recycled directly back to a reduction furnace without additional chemical treatment.
12. The process of claim 1 wherein said contamination is no more than about 5 weight percent of said aluminum carbide.
13. The process of claim 1 wherein said preparing of said melt comprises pouring said aluminum contaminated with said aluminum carbide into a receptacle which is provided with inlets through which said gas is passed under pressure so that said gas passes through the body of said melt.
14. In a carbothermic process for producing aluminum in an electric furnace by reacting an aluminum-oxygen compound with a carbon-containing reductant to produce a mixture of aluminum and aluminum carbide which solidifies as an aluminum-aluminum carbide matrix while cooling, the improvement comprising:
(A) while said mixture is a melt in a fluid state at an uppermost temperature determined by an initial amount that is no greater than 5% by weight of said aluminum carbide admixed with said aluminum, sufficiently removing said aluminum carbide from said mixture and reducing said initial amount so that said aluminum remaining therein is substantially pure, said removing comprising the steps of:
(1) passing a gas which consists essentially of oxygen, air, steam, carbon monoxide, carbon dioxide, or a mixture of chlorine, nitrogen, and carbon monoxide, wherein chlorine is present in an amount no greater than about 20 weight percent, for a sufficient period of time to prevent the formation of an aluminum-aluminum carbide matrix, whereby said aluminum carbide separates to the surface of said melt, and (2) skimming said separated aluminum carbide from the said surface, and (B) recycling said skimmed aluminum carbide directly back to said electric furnace without additional chemical treat ment.
(A) while said mixture is a melt in a fluid state at an uppermost temperature determined by an initial amount that is no greater than 5% by weight of said aluminum carbide admixed with said aluminum, sufficiently removing said aluminum carbide from said mixture and reducing said initial amount so that said aluminum remaining therein is substantially pure, said removing comprising the steps of:
(1) passing a gas which consists essentially of oxygen, air, steam, carbon monoxide, carbon dioxide, or a mixture of chlorine, nitrogen, and carbon monoxide, wherein chlorine is present in an amount no greater than about 20 weight percent, for a sufficient period of time to prevent the formation of an aluminum-aluminum carbide matrix, whereby said aluminum carbide separates to the surface of said melt, and (2) skimming said separated aluminum carbide from the said surface, and (B) recycling said skimmed aluminum carbide directly back to said electric furnace without additional chemical treat ment.
15. The process of claim 14 wherein said gas consists essentially of air or oxygen.
16. The process of claim 14 wherein said gas consists essentially of steam.
17. The process of claim 14 wherein said gas consists essentially of carbon dioxide.
18. The process of claim 14 wherein said gas consists essentially of carbon monoxide.
19. The process of Claim 1 wherein said gas consists essentially of a mixture of carbon monoxide and chlorine.
20. The process of claim 14 wherein said gas consists essentially of a mixture of carbon monoxide and chlorine.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/611,794 US3975187A (en) | 1975-02-13 | 1975-09-09 | Treatment of carbothermically produced aluminum |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1078626A true CA1078626A (en) | 1980-06-03 |
Family
ID=24450436
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA254,485A Expired CA1078626A (en) | 1975-09-09 | 1976-06-09 | Treatment of carbothermically produced aluminum |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5232811A (en) |
| AU (1) | AU503487B2 (en) |
| CA (1) | CA1078626A (en) |
| DE (1) | DE2637282A1 (en) |
| FR (1) | FR2323769A1 (en) |
| GB (1) | GB1549794A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH638565A5 (en) * | 1978-11-21 | 1983-09-30 | Alusuisse | METHOD FOR CLEANING ALUMINUM MELTS. |
| US4216010A (en) * | 1979-01-31 | 1980-08-05 | Reynolds Metals Company | Aluminum purification system |
| JPS609836A (en) * | 1983-06-27 | 1985-01-18 | Nippon Light Metal Co Ltd | Treatment of molten aluminum |
| JPH0712228B2 (en) * | 1985-11-25 | 1995-02-08 | ソニー株式会社 | Burst signal phase error detection circuit |
| JPS62152288A (en) * | 1985-12-25 | 1987-07-07 | Mitsubishi Electric Corp | Burst gate pulse generator |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1144014B (en) * | 1958-03-14 | 1963-02-21 | Pechiney Prod Chimiques Sa | Process for the reduction of aluminum oxide with carbon in an electric arc furnace |
| US3149960A (en) * | 1960-11-02 | 1964-09-22 | Reynolds Metals Co | Aluminum degassing system |
-
1976
- 1976-06-09 CA CA254,485A patent/CA1078626A/en not_active Expired
- 1976-08-06 GB GB3289476A patent/GB1549794A/en not_active Expired
- 1976-08-17 AU AU16900/76A patent/AU503487B2/en not_active Expired
- 1976-08-19 DE DE19762637282 patent/DE2637282A1/en not_active Withdrawn
- 1976-08-23 JP JP10104376A patent/JPS5232811A/en active Granted
- 1976-08-25 FR FR7625724A patent/FR2323769A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| DE2637282A1 (en) | 1977-03-17 |
| AU503487B2 (en) | 1979-09-06 |
| JPS6124457B2 (en) | 1986-06-11 |
| FR2323769B1 (en) | 1982-05-28 |
| GB1549794A (en) | 1979-08-08 |
| AU1690076A (en) | 1978-02-23 |
| JPS5232811A (en) | 1977-03-12 |
| FR2323769A1 (en) | 1977-04-08 |
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