CA1115966A - Method of extracting magnesium from magnesium oxides - Google Patents
Method of extracting magnesium from magnesium oxidesInfo
- Publication number
- CA1115966A CA1115966A CA332,411A CA332411A CA1115966A CA 1115966 A CA1115966 A CA 1115966A CA 332411 A CA332411 A CA 332411A CA 1115966 A CA1115966 A CA 1115966A
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Abstract
ABSTRACT
A process for extracting magnesium from compounds con-taining magnesium oxides is disclosed, The process is carried out at lower temperatures and pressures than previous processes which does not melt the dross. The process comprises the steps of mixing magnesium oxide and calcium oxide with aluminum, com-pressing the mixture, heating the compressed mixture uniformally to a temperature in the range of 800-1100°C. under controlled pressure to vaporize the magnesium, and condensing the vaporized magnesium on a cooled surface.
A process for extracting magnesium from compounds con-taining magnesium oxides is disclosed, The process is carried out at lower temperatures and pressures than previous processes which does not melt the dross. The process comprises the steps of mixing magnesium oxide and calcium oxide with aluminum, com-pressing the mixture, heating the compressed mixture uniformally to a temperature in the range of 800-1100°C. under controlled pressure to vaporize the magnesium, and condensing the vaporized magnesium on a cooled surface.
Description
This invention relates to the ex-traction of magnesium from magnesium oxides. More particularly~ the in~ention relates to a process for extracting magnesium from compounds containing magnesium oxides.
One of the main sources of magnesium metal produced on an industrial scale is dolomite which is a carbonate of calcium and magnesium. The magnesium metal is produced using a reduction process and in the past silicon or ferrosilicon has been the reducing agent. This process is ~nown as the Pidgeon process. In the case when the starting material is calcined dolomite the fol-lowing reaction occurs:
(A) 2(CaO. MgO) ~ Si = 2 Mg + (CaO)2SiO2 According to this process -the magnesium metal is liberated from the intimate mixture in the vapor state leaving a bi-calcium silicate as a dross.
In -the past, this type of operation has been carried out at reduced pressure and with furnace temperatures up to about 1500C., and at these temperatures the dross is in a mol-ten state at the end of the reduction step. Thus, the starting material must be contained in a crucible or other container to prevent the liquid dross from spreading over the floor of the furnace. Further-more, these high temperatures lead to high maintenance costs of the furnaces due to the frequent need to change the refractory linings which have only a limited life at these temperatures.
Examples of these processes are described by Van Embden in U.S.
Patent 2,252,052 Cooper in U.S~ Patent 2,429,66~ and Ar-tru and Marchal in French Paten-t 762,671. The process defined ln this French Patent requires the addition o~ a third component, alumina~
to act as a melting medium but does not -take any part in the chemical action defined in formula tA).
Furthermore, with the high te~nperatures of the known processes of producing magnesium metal, a high degree of contam~
ination occurs because as well as magnesium o-ther metals are also vaporized and subsequently condensed in the reduction pro-cess. These other metals are present as impurities in the mag-nesium oxide and include for e~ample, calcium, lead, antimony, manganese, nickel, silicon, tin, copper, iron and others.
The problem of high temperatures can be overcome in part by making use of the silicothermic process in the solid state. Unlike known methods this process does not require high temperatures, thus the dross does not become molten and can be extracted from the furnace in the solid state. In this process an intimate mixture of fine powders is prepared and compacted or compressed into blocks consisting of calcined dolomite and a re-ducing agent and it is possible to achieve distillation of the magnesium whilst limiting the tempera~ures of the reaction to below the melting point of the blocks. By achieving this lower temperature, ~he degree of contamination is considerably reduced.
It is one purpose o~ the presen-t invention to provide a process which can be carried out at temperatures below the melting point of the starting materials and this is achieved in part by replacing the silicon either in whole or in part with aluminum.
As well as -the reaction identified as formula (A), other possible chemical reactions include the following formulas invol~ing dolomite, magnesium oxide and aluminum:
(B) 3(CaO MgO) + 2Al = 3 Mg + (CaO)3 A1203 (C) 8tCaO. MgO) -~ 4MgO -~ 8Al =
12Mg -~ (CaO)3A1203 + (CaO)s(A1203)3 (D) 5(CaO MgO) + 4MgO + 6Al = 9Mg -~ (CaO)s(A1203)3 (E) 5(CaO. ~gO) + 2Al + Si =
5Mg + (CaO)3A1203 + (CaO)2 SiO2 (F) 17(CaO MgO) + 4MgO + 6Al + 6Si =
21Mg + (CaO~s(A1203)3 + 6(CaO)2SiO2 s~
The (E) and (F) formulas represent reactions when dolomite, magnesium oxide and a mixture of two reducing agents, silicon and aluminum are used~ The dolomite may be replaced by a mixture o~ calcium oxide and magnesium oxide from any source provided the proportions of the mixture of oxides correspond to the stoichiometric ratio of dolomite.
The process of the present invention is carried out by first taking a measured amount of powdered aluminum, and in some cases the addition of ferrosilicon, magnesium oxide and calcium oxide, mixing these powders together and compressing them into a block for reduction by means of heating in a furnace un~er control-led pressure. The heating need not exceed 1100C and is prefer-ably in the range of 800 - 1100C. Under these temperature con-ditions and at a controlled pressure, the magnesium metal vaporizes and is recovered by condensation leaving behind an exhausted dross in the solid state consisting of a particular calcium aluminate or more generally a stoichiometric e~uivalent mixture of other alumi-nates. If a mixture of two reducing agents is used, the dross contains calcium silicate and calcium aluminate If the two reducing agents are used under the working conditions according to the present lnvention, the agents work together in a synegistic manner.
In the past this process was not feasible due to the scarcity of the required raw materials Eowever, in recent years there has been a demand for a magnesium oxide and calcium oxide of a high purity and these have been obtained using calcination of the respective carbonates or making use of precipitation pro-cesses followed by subsequent drying o~ the corresponding oxides.
Furthermore, aluminum in granular form or chip form is now avail-able in large quantities from a machining process or from scrap.
This alumino-ther~c process carried out in the solid state has a number of advantages over known processes of recover-5~
ing magnesium metal. One advantage i5 that, due to the lowerreaction temperature, it is possible to produce a much purer magnesium metal because the lower temperatures avoid the dis-tillation of other metals in the magnesium metal. Furthermore, it has been found that a greater magnesium content may be used in the starting mix, thus resulting in a higher output of magnesium from a single furnace. Still further, by keeping the temperature below 1100C there is less wear in the reaction furnace which tends to keep operating and maintenance costs down.
The present invention provides a process of extracting magnesium from compounds containing magnesium oxides comprising the steps of mixing magnesium oxides and calcium oxide with alumi-num, and in some cases ferrosilicon, compressing the mixture, heat-ing the compressed mixture uniformally to a tamperature in the range of 800 - 1100C~, under a controlled pressure to vaporize magnesium, and condensing the vaporized magnesium on a cooled sur-faceO
In a preferred embodiment the proportion by weight of the various components of the mixture should correspond to the stoichiometric ratio and preferably the mixture contains 2 0 -
One of the main sources of magnesium metal produced on an industrial scale is dolomite which is a carbonate of calcium and magnesium. The magnesium metal is produced using a reduction process and in the past silicon or ferrosilicon has been the reducing agent. This process is ~nown as the Pidgeon process. In the case when the starting material is calcined dolomite the fol-lowing reaction occurs:
(A) 2(CaO. MgO) ~ Si = 2 Mg + (CaO)2SiO2 According to this process -the magnesium metal is liberated from the intimate mixture in the vapor state leaving a bi-calcium silicate as a dross.
In -the past, this type of operation has been carried out at reduced pressure and with furnace temperatures up to about 1500C., and at these temperatures the dross is in a mol-ten state at the end of the reduction step. Thus, the starting material must be contained in a crucible or other container to prevent the liquid dross from spreading over the floor of the furnace. Further-more, these high temperatures lead to high maintenance costs of the furnaces due to the frequent need to change the refractory linings which have only a limited life at these temperatures.
Examples of these processes are described by Van Embden in U.S.
Patent 2,252,052 Cooper in U.S~ Patent 2,429,66~ and Ar-tru and Marchal in French Paten-t 762,671. The process defined ln this French Patent requires the addition o~ a third component, alumina~
to act as a melting medium but does not -take any part in the chemical action defined in formula tA).
Furthermore, with the high te~nperatures of the known processes of producing magnesium metal, a high degree of contam~
ination occurs because as well as magnesium o-ther metals are also vaporized and subsequently condensed in the reduction pro-cess. These other metals are present as impurities in the mag-nesium oxide and include for e~ample, calcium, lead, antimony, manganese, nickel, silicon, tin, copper, iron and others.
The problem of high temperatures can be overcome in part by making use of the silicothermic process in the solid state. Unlike known methods this process does not require high temperatures, thus the dross does not become molten and can be extracted from the furnace in the solid state. In this process an intimate mixture of fine powders is prepared and compacted or compressed into blocks consisting of calcined dolomite and a re-ducing agent and it is possible to achieve distillation of the magnesium whilst limiting the tempera~ures of the reaction to below the melting point of the blocks. By achieving this lower temperature, ~he degree of contamination is considerably reduced.
It is one purpose o~ the presen-t invention to provide a process which can be carried out at temperatures below the melting point of the starting materials and this is achieved in part by replacing the silicon either in whole or in part with aluminum.
As well as -the reaction identified as formula (A), other possible chemical reactions include the following formulas invol~ing dolomite, magnesium oxide and aluminum:
(B) 3(CaO MgO) + 2Al = 3 Mg + (CaO)3 A1203 (C) 8tCaO. MgO) -~ 4MgO -~ 8Al =
12Mg -~ (CaO)3A1203 + (CaO)s(A1203)3 (D) 5(CaO MgO) + 4MgO + 6Al = 9Mg -~ (CaO)s(A1203)3 (E) 5(CaO. ~gO) + 2Al + Si =
5Mg + (CaO)3A1203 + (CaO)2 SiO2 (F) 17(CaO MgO) + 4MgO + 6Al + 6Si =
21Mg + (CaO~s(A1203)3 + 6(CaO)2SiO2 s~
The (E) and (F) formulas represent reactions when dolomite, magnesium oxide and a mixture of two reducing agents, silicon and aluminum are used~ The dolomite may be replaced by a mixture o~ calcium oxide and magnesium oxide from any source provided the proportions of the mixture of oxides correspond to the stoichiometric ratio of dolomite.
The process of the present invention is carried out by first taking a measured amount of powdered aluminum, and in some cases the addition of ferrosilicon, magnesium oxide and calcium oxide, mixing these powders together and compressing them into a block for reduction by means of heating in a furnace un~er control-led pressure. The heating need not exceed 1100C and is prefer-ably in the range of 800 - 1100C. Under these temperature con-ditions and at a controlled pressure, the magnesium metal vaporizes and is recovered by condensation leaving behind an exhausted dross in the solid state consisting of a particular calcium aluminate or more generally a stoichiometric e~uivalent mixture of other alumi-nates. If a mixture of two reducing agents is used, the dross contains calcium silicate and calcium aluminate If the two reducing agents are used under the working conditions according to the present lnvention, the agents work together in a synegistic manner.
In the past this process was not feasible due to the scarcity of the required raw materials Eowever, in recent years there has been a demand for a magnesium oxide and calcium oxide of a high purity and these have been obtained using calcination of the respective carbonates or making use of precipitation pro-cesses followed by subsequent drying o~ the corresponding oxides.
Furthermore, aluminum in granular form or chip form is now avail-able in large quantities from a machining process or from scrap.
This alumino-ther~c process carried out in the solid state has a number of advantages over known processes of recover-5~
ing magnesium metal. One advantage i5 that, due to the lowerreaction temperature, it is possible to produce a much purer magnesium metal because the lower temperatures avoid the dis-tillation of other metals in the magnesium metal. Furthermore, it has been found that a greater magnesium content may be used in the starting mix, thus resulting in a higher output of magnesium from a single furnace. Still further, by keeping the temperature below 1100C there is less wear in the reaction furnace which tends to keep operating and maintenance costs down.
The present invention provides a process of extracting magnesium from compounds containing magnesium oxides comprising the steps of mixing magnesium oxides and calcium oxide with alumi-num, and in some cases ferrosilicon, compressing the mixture, heat-ing the compressed mixture uniformally to a tamperature in the range of 800 - 1100C~, under a controlled pressure to vaporize magnesium, and condensing the vaporized magnesium on a cooled sur-faceO
In a preferred embodiment the proportion by weight of the various components of the mixture should correspond to the stoichiometric ratio and preferably the mixture contains 2 0 -
2.5 parts by weight magnesium oxide, 1 5 - 2.0 parts by weight calcium oxide and 1.0 - 1.5 parts by weight aluminum. The com-pounds should preferably be in powder or granular form before mixing. In one embodiment the mixture is compacted into a block which may then be heated uniformally so that the temperature difference across the block does not exceed 100C. In still another embodiment the block is formed integral with an electrical heating conductor and in yet a further embodiment tbe block is formed as a hollow column with the heating conductor formed as a helical coil within the blockO
In a preferred embodiment the process is carried out in a lower portion of an electric furnace, the lower portion r ~ 4 ~
, ~
, ~
5~
having an insulated lining and the block being spaced from the lining. An upper portion forms the cooled surface for condensing the magnesium metal thereon and is joined to the lower portion to form an enclosed sealed chamber. The pressure may be controlled by an exhaust pump and a filtex prevents vapori~ed magnesium from passing through to the pump. Separate condensation chambers, which are removable, may be provided, each condensation chamber having a cooled surface therein.
In drawings which illustrate embodiments of the invention, Fig. 1 is a diagrammatic cross sectional view through one embodiment of an electric furnace suitable for the process of the present invention.
Fig. 2 is a side view, partly in cross section, of an electrical hea-ting conductor together with the compounds in a solid compressed form shaped as a hollow column structure for insertion-in the electric furnace shown in Fig. 1.
~ ig. 3 is a diagrammatic cross sectional view through another embodiment of an electric furnace having at least one separate condensation chamber.
Fig. 4 is a top plan view of the electric furnace shown in Fig. 3.
Fig. 1 and 2 illustrate an electric furnace suitable ~or the process of this in~ention. The furnace has a top bell-shaped portion 10 and a lower cylindrical portion 11 which define a substæntially cylindrical chamber. The top and lower portions 10 and 11 are joined together in a detachable manner at flange 12 to form a sealed chamber, the joint 12 being provided with a suitable seal in order to maintain the sealed chamber. The lower portion 11 is lined internally with refrac-tory material 13 and constitutes the heating chamber or reduction chamber of the fur-nace. A block or charge 14 of the compounds to be heated are 36~
placed in the lower portion 11 spaced apart from the ref:ractory lining 13 so that as the metal in the charge vaporizes due to heat the vapor can escape from the sides as well as the top of the charge 14.
The top portion lO is provided wi-th a suitable cooling means (not shown). The top portion 10 constitutes the condensa-tiOIl chamber for the magnesium vapors which are set free during the course of the reduction from the charge 14. The top portion 10 and the lower portion ll are both made from suitable material preferably metal which has suitable s-trength to withstand the mechanical and thermal stresses to which the ~urnace is subjected, A controlled pressure is maintained within the sealed chamber by means of a suitable suction through a conduit 15 preferably con nected to an exhaust pump. A pressure sensing device may be included in the sealed chamber, and in a preferred embodiment a filter is supplied on this exhaust conduit 15 to prevent metallic vapors passing to the exhaust pump.
The charge 14 is shown in more detail in Fig. 2 and is constructed in the form of a hollow column. The struc-ture 2a of electrical conducting elements 16 are formed in a helix and the mass of compounds are compacted or compressed :in spaces 17 between the helical elements 16 which are suitably connected at their terminals 1~ to electrical connections provided within the furnace. The charge 14 is then heated by elec-trical resistance to the desired temperature, and the conductor elements 16 maintain a uniform temperaturc throughout the charge 1~. I'he preparation of the charge 14 takes place outside the furnace wherein the mix-ture of compounds is first prepared and then compacted between these elements 16 prior to installation in the furnace. In the embodiment shown the charge 14 has electrical conductor elements 16 in the form of a helical coil. It will be apparent to those skilled in the art that other configurations of electrical 5~
conductor elements could also be employed in the charge, such conductor elements could take almost any shape provided the mass of the charge was evenly heated For example, conductor elements may be installed within the hollow column as shown in ~ig. 2.
In operation powders of magnesium oxide, calcium oxide and aluminum and in some cases ferrosilicon in powder or granule form are mixed together according to the fol~owing weight ratios, Magnesium o~ide 2.0 - 2.5 parts by weight Calcium oxide 1.5 - 2.0 parts by weight Aluminum 1.0 - 1.5 parts by weight After mixing, these compounds are compacted or compressed to a charge 14 such as that shown in Fig. 2. The mixture is compressed within the conductor elements 16 so that the compounds are evenly compressed and form a column or sel~ sustaining mass that retains its shape when left. In this form the charge 14 is placed within the furnace, the terminals 18 connected to the terminals within the furnace, the top portion 10 of the furnace located on and sealed to the flange 12, and gases are drawn through conduit 15 inside the sealed chamber. The conductor elements 16 commence heating the block evenly and the temperature o the block in-creases to within the range of 800 - 1100C. At this temperature, the temperature range through the block does not exceed 100C.
At this temperature the magnesium vaporizes and commences to be set free from the charge 14, these vapors exit from the outside and the inside of the column structure and also on top o~ the column, the vapors pass upwards from -the hot lower portion of the furnace into the top portion 10 where they condense against the cooled surface of the top portion 10. The condensed ~ag-nesium metal forms crystals on these cooled surfaces, and this process continues while the temperature of the block is main-tained at between 8Q0 and 1100C until all the magnesium metal . ' ~
s~
has been released from the block and condensed in the cooled surface. After a pre~set time the power to the conductor ele~
ments 16 is turned off to allow the furnace to commence cooling, and the exhaust pump is stoppedO Before the furnace is cooled, the top portion 10 is removed and the hot charge 14, which has still retained its structure because the highest temperature reached was below the melting temperature, is removed from the furnace and replaced with a new charge 14~ At the same time, the magnesium crystals are scraped off the inside surface of the top portion 10 whlch is then replaced on top o~ the lower portion 11, the flange 12 connected and the process recommenced~
Fig. 3 and 4 show another embodiment o~E the furnace in which a top portion 20 has four condensation chambers 21 spaced around the periphery of the top portion 20. These condensation chambers 21 are joined to the top portion 20 by flanges 22 and e~ch chamber 21 has an exhaust conduit 23 at the far end to suck the metallic vapors into the condensation chambers 21 Each of the condensation chambers ~1 has cooling means surrounding it so that the magnesium metal condenses on the walls oE the chambers 210 After the chambers 21 have become full, then it is merely necessary to uncouple the flanges 22, take off the chambers 21, and replace them with new chambers 21. In this way less down time is needed, and the scraping may be carried out when the condensa-tion chambers 21 are separated from the furnaceO
Tests carried out using -the apparatus illustrated in Figs. 1 and 2 have shown that as much as 25% by weight of the charge mixture of magnesium has been recovered Erom each batchO
The following table summarizes the results of tests carried out on the extraction of magnesium from diEferent compo-nents. The results confirm the recovery percentages achi0ved with this process~ The mixtures used in these tests correspond to the proportions to comply with the formulas A to F.
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Charges as high as one metric ton have been processed and furthermore it has been ound that the energy required is in the order of 1,800 kilowatts ~or the complete reduction of one metric ton based on the recovery o~ 25% by weight of ~agnesium from each charge,
In a preferred embodiment the process is carried out in a lower portion of an electric furnace, the lower portion r ~ 4 ~
, ~
, ~
5~
having an insulated lining and the block being spaced from the lining. An upper portion forms the cooled surface for condensing the magnesium metal thereon and is joined to the lower portion to form an enclosed sealed chamber. The pressure may be controlled by an exhaust pump and a filtex prevents vapori~ed magnesium from passing through to the pump. Separate condensation chambers, which are removable, may be provided, each condensation chamber having a cooled surface therein.
In drawings which illustrate embodiments of the invention, Fig. 1 is a diagrammatic cross sectional view through one embodiment of an electric furnace suitable for the process of the present invention.
Fig. 2 is a side view, partly in cross section, of an electrical hea-ting conductor together with the compounds in a solid compressed form shaped as a hollow column structure for insertion-in the electric furnace shown in Fig. 1.
~ ig. 3 is a diagrammatic cross sectional view through another embodiment of an electric furnace having at least one separate condensation chamber.
Fig. 4 is a top plan view of the electric furnace shown in Fig. 3.
Fig. 1 and 2 illustrate an electric furnace suitable ~or the process of this in~ention. The furnace has a top bell-shaped portion 10 and a lower cylindrical portion 11 which define a substæntially cylindrical chamber. The top and lower portions 10 and 11 are joined together in a detachable manner at flange 12 to form a sealed chamber, the joint 12 being provided with a suitable seal in order to maintain the sealed chamber. The lower portion 11 is lined internally with refrac-tory material 13 and constitutes the heating chamber or reduction chamber of the fur-nace. A block or charge 14 of the compounds to be heated are 36~
placed in the lower portion 11 spaced apart from the ref:ractory lining 13 so that as the metal in the charge vaporizes due to heat the vapor can escape from the sides as well as the top of the charge 14.
The top portion lO is provided wi-th a suitable cooling means (not shown). The top portion 10 constitutes the condensa-tiOIl chamber for the magnesium vapors which are set free during the course of the reduction from the charge 14. The top portion 10 and the lower portion ll are both made from suitable material preferably metal which has suitable s-trength to withstand the mechanical and thermal stresses to which the ~urnace is subjected, A controlled pressure is maintained within the sealed chamber by means of a suitable suction through a conduit 15 preferably con nected to an exhaust pump. A pressure sensing device may be included in the sealed chamber, and in a preferred embodiment a filter is supplied on this exhaust conduit 15 to prevent metallic vapors passing to the exhaust pump.
The charge 14 is shown in more detail in Fig. 2 and is constructed in the form of a hollow column. The struc-ture 2a of electrical conducting elements 16 are formed in a helix and the mass of compounds are compacted or compressed :in spaces 17 between the helical elements 16 which are suitably connected at their terminals 1~ to electrical connections provided within the furnace. The charge 14 is then heated by elec-trical resistance to the desired temperature, and the conductor elements 16 maintain a uniform temperaturc throughout the charge 1~. I'he preparation of the charge 14 takes place outside the furnace wherein the mix-ture of compounds is first prepared and then compacted between these elements 16 prior to installation in the furnace. In the embodiment shown the charge 14 has electrical conductor elements 16 in the form of a helical coil. It will be apparent to those skilled in the art that other configurations of electrical 5~
conductor elements could also be employed in the charge, such conductor elements could take almost any shape provided the mass of the charge was evenly heated For example, conductor elements may be installed within the hollow column as shown in ~ig. 2.
In operation powders of magnesium oxide, calcium oxide and aluminum and in some cases ferrosilicon in powder or granule form are mixed together according to the fol~owing weight ratios, Magnesium o~ide 2.0 - 2.5 parts by weight Calcium oxide 1.5 - 2.0 parts by weight Aluminum 1.0 - 1.5 parts by weight After mixing, these compounds are compacted or compressed to a charge 14 such as that shown in Fig. 2. The mixture is compressed within the conductor elements 16 so that the compounds are evenly compressed and form a column or sel~ sustaining mass that retains its shape when left. In this form the charge 14 is placed within the furnace, the terminals 18 connected to the terminals within the furnace, the top portion 10 of the furnace located on and sealed to the flange 12, and gases are drawn through conduit 15 inside the sealed chamber. The conductor elements 16 commence heating the block evenly and the temperature o the block in-creases to within the range of 800 - 1100C. At this temperature, the temperature range through the block does not exceed 100C.
At this temperature the magnesium vaporizes and commences to be set free from the charge 14, these vapors exit from the outside and the inside of the column structure and also on top o~ the column, the vapors pass upwards from -the hot lower portion of the furnace into the top portion 10 where they condense against the cooled surface of the top portion 10. The condensed ~ag-nesium metal forms crystals on these cooled surfaces, and this process continues while the temperature of the block is main-tained at between 8Q0 and 1100C until all the magnesium metal . ' ~
s~
has been released from the block and condensed in the cooled surface. After a pre~set time the power to the conductor ele~
ments 16 is turned off to allow the furnace to commence cooling, and the exhaust pump is stoppedO Before the furnace is cooled, the top portion 10 is removed and the hot charge 14, which has still retained its structure because the highest temperature reached was below the melting temperature, is removed from the furnace and replaced with a new charge 14~ At the same time, the magnesium crystals are scraped off the inside surface of the top portion 10 whlch is then replaced on top o~ the lower portion 11, the flange 12 connected and the process recommenced~
Fig. 3 and 4 show another embodiment o~E the furnace in which a top portion 20 has four condensation chambers 21 spaced around the periphery of the top portion 20. These condensation chambers 21 are joined to the top portion 20 by flanges 22 and e~ch chamber 21 has an exhaust conduit 23 at the far end to suck the metallic vapors into the condensation chambers 21 Each of the condensation chambers ~1 has cooling means surrounding it so that the magnesium metal condenses on the walls oE the chambers 210 After the chambers 21 have become full, then it is merely necessary to uncouple the flanges 22, take off the chambers 21, and replace them with new chambers 21. In this way less down time is needed, and the scraping may be carried out when the condensa-tion chambers 21 are separated from the furnaceO
Tests carried out using -the apparatus illustrated in Figs. 1 and 2 have shown that as much as 25% by weight of the charge mixture of magnesium has been recovered Erom each batchO
The following table summarizes the results of tests carried out on the extraction of magnesium from diEferent compo-nents. The results confirm the recovery percentages achi0ved with this process~ The mixtures used in these tests correspond to the proportions to comply with the formulas A to F.
:
5~$~;
Z; _, . _ H
O ~ ~ O C~
O O ~ C~ L~
¢ L~ LO ~ d~ L~
E-~
E-__~.
_~
tog LO
~q .~ .~ ~
H ~ ~D I I I I ,_1 1 1 ¢ r-l ~
~ ¢~rl O _ ,~
:~ ¢ .
CO
~Ct S~ 00 00 0~ L~
O ,_ a~ I o o o I o O ~ ~ +~ .
E~ E~ .~
1~~ . ~ .... _ _ . _ _ __, , . _ -:-- -W
~ ~ ~ _ CC ~ ~ ~ ' ~Z C) p~`
~:` P~ ~1 00 O ~ ~
~1 ~ rlC` ~ ~ ~ ., C~ ~ O I I I I O O .
. _.. ~_ P~ ~ . -O ~
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H LO ~1 ~ 6) E-~ P. ~S) C~) ~ 5) cr~
~ S::l I I O O' O I O' O O , ,. _ ~ _ I ~
rl ~
~ 0 a~ 0 ~ ~ o o ~) oo ~ Ltl ~ ~ ~ o n o c~
g ~3 L~ N
O 5 ~ C) O ~tH
~ O . . .. _ _ ~ .
. ~ ' ~1 ~
_ . ~ ~ ~ a ~ I~ .
$;
Charges as high as one metric ton have been processed and furthermore it has been ound that the energy required is in the order of 1,800 kilowatts ~or the complete reduction of one metric ton based on the recovery o~ 25% by weight of ~agnesium from each charge,
Claims (12)
1. A process of extracting magnesium from compounds containing magnesium oxides comprising the steps of mixing mag-nesium oxide and calcium oxide with aluminum, compressing the mixture, heating the compressed mixture uniformally to a tempera-ture in the range of 800 - 1,100°C under controlled pressure to vaporize the magnesium, and condensing the vaporized magnesium on a cooled surface.
2. The process according to claim 1 wherein the mixture contains 2.0 - 2.5 parts by weight magnesium oxide, 1.5 - 2.0 parts by weight calcium oxide, and 1.0 - 1.5 parts by weight alu-minum, and the mixing occurs with the compounds in powder form.
3. The process according to claim 1, wherein magnesium oxide and calcium oxide are mixed with aluminum and ferrosilicon.
4. The process according to claim 3, wherein the mix-ture contains 2.0 - 2.5 parts by weight magnesium oxide, 1.5 -2.0 parts by weight calcium oxide and 1.0 - 1.5 parts by weight aluminum and ferrosilicon, and the mixing occurs with the compounds in powder form.
The process according to claim 1 wherein the mixture is compacted into a block, and wherein the block is heated uniformally so that temperature differences accross the block do not exceed 100°C.
6. The process according to claim 5 wherein the block is formed integral with an electrical heating conductor.
7. The process according to claim 6 wherein the block is formed as a hollow column and wherein the heating conductor is formed as a helical coil within the block.
8. The process according to claim 6 wherein the block is formed of a plurality of rings and wherein the heating elements forming the electrical heating conductor are positioned between the rings.
9 The process according to claim 6 wherein the block is placed in a lower heating portion of an electrical furnace, the lower portion having an insulated lining, the block being spaced from the lining, and a top portion forming the cooled sur-face is joined to the lower portion to form an enclosed sealed chamber.
10. The process according to claim 1 or claim 3 wherein the controlled pressure is maintained by an exhaust pump and a fil-ter prevents vaporized magnesium from passing into the pump.
11. The process according to claim 1 or claim 3 inclu-ding removable condensation chambers each having the cooled sur-face therein.
12. The process according to claim 6 wherein the block is extracted from the furnace after the heating step and whilst still hot and replaced with a fresh block.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA332,411A CA1115966A (en) | 1979-07-24 | 1979-07-24 | Method of extracting magnesium from magnesium oxides |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA332,411A CA1115966A (en) | 1979-07-24 | 1979-07-24 | Method of extracting magnesium from magnesium oxides |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1115966A true CA1115966A (en) | 1982-01-12 |
Family
ID=4114773
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA332,411A Expired CA1115966A (en) | 1979-07-24 | 1979-07-24 | Method of extracting magnesium from magnesium oxides |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1115966A (en) |
-
1979
- 1979-07-24 CA CA332,411A patent/CA1115966A/en not_active Expired
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