CA1115065A - Metallothermal process for the simultaneous production of magnesium and cement or calcium and cement - Google Patents
Metallothermal process for the simultaneous production of magnesium and cement or calcium and cementInfo
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- CA1115065A CA1115065A CA332,944A CA332944A CA1115065A CA 1115065 A CA1115065 A CA 1115065A CA 332944 A CA332944 A CA 332944A CA 1115065 A CA1115065 A CA 1115065A
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Abstract
ABSTRACT OF THE DISCLOSURE
The invention relates to a new process for the simultaneous production of magnesium and cement from calcined dolomite or calcium and cement from calcined lime.
According to the invention calcined dolomite or calcined lime is reduced under a pressure lower than 10 torr and at a temperature of 1300 to 1600 °C with a reducing agent containing silicon and aluminium in a weight ratio of 4:1 to 1:1, wherein the total amount of silicon and aluminium comprises 50 to 100 % by weight. 100 to 200 parts by weight of the reducing agent are applied to convert 600 to 800 parts by weight of calcined dolomite or 700 to 1000 parts by weight of calcined lime.
In contrast to the known procedures, the new method according to the invention provides cement as by-product instead of a useless slag.
The invention relates to a new process for the simultaneous production of magnesium and cement from calcined dolomite or calcium and cement from calcined lime.
According to the invention calcined dolomite or calcined lime is reduced under a pressure lower than 10 torr and at a temperature of 1300 to 1600 °C with a reducing agent containing silicon and aluminium in a weight ratio of 4:1 to 1:1, wherein the total amount of silicon and aluminium comprises 50 to 100 % by weight. 100 to 200 parts by weight of the reducing agent are applied to convert 600 to 800 parts by weight of calcined dolomite or 700 to 1000 parts by weight of calcined lime.
In contrast to the known procedures, the new method according to the invention provides cement as by-product instead of a useless slag.
Description
6~; :
~ he in~ention relates to a metallothermal process for the simultaneous production of ~agnesium and cement or calcium and ement.
As known, magnesium and calcium are generally produced by electrolyzing the melt o:E their salts.
~ he salts /generally chlorides/ are electrolyzed at about 700 to 900 C. A disad~antage o~ this method is that it requires extremely pure starting materials 3 completely free of water, which can be prepared o~ly by a sophisticated and lengthy procedure requiring much la~our and energy.
Several attempts have been made to elaborate large-scale methods for the production of magnesium from dolomite /CaCO3 MgC03/ and calcium from limestone /CaC03/, two ~ -minerals occurring abundantly in nature. According to these methods dolomite or limestone are ~irst calci~ed9 and the resulting calcined products tCaO MgO or CaO/ are subjected to metallothermal reduction. ~len silicon is applied as `
reducing agent, calcinea dolomite con~erts into magnesium according to the equation
~ he in~ention relates to a metallothermal process for the simultaneous production of ~agnesium and cement or calcium and ement.
As known, magnesium and calcium are generally produced by electrolyzing the melt o:E their salts.
~ he salts /generally chlorides/ are electrolyzed at about 700 to 900 C. A disad~antage o~ this method is that it requires extremely pure starting materials 3 completely free of water, which can be prepared o~ly by a sophisticated and lengthy procedure requiring much la~our and energy.
Several attempts have been made to elaborate large-scale methods for the production of magnesium from dolomite /CaCO3 MgC03/ and calcium from limestone /CaC03/, two ~ -minerals occurring abundantly in nature. According to these methods dolomite or limestone are ~irst calci~ed9 and the resulting calcined products tCaO MgO or CaO/ are subjected to metallothermal reduction. ~len silicon is applied as `
reducing agent, calcinea dolomite con~erts into magnesium according to the equation
2/CaO MgO/ ~ Si = 2 CaO SiO2 ~ 2 Mg, whereas calcined lime yields calcium according to the equation 4 CaO ~ Si = 2 CaO Si02 t 2 Ca.
~hen aluminium is used as reducing agent in the metallothermal processes9 magnesium or calcium is formed according to the equations
~hen aluminium is used as reducing agent in the metallothermal processes9 magnesium or calcium is formed according to the equations
3/CaO MgO/ ~ 2 Al = 3 CaO A1203 ~ 3 Mg 6 CaO ~ 2 Al = 3 CaO A12O3 ~ 3 Ca ;~
Up to now these methods could not compete with electrolytical techniques, since they yield9 beside the aimed ~1 -. . . - ~ ~
product, extre~el~ large a~ounts o~ useless slag. According to theoretical calculations, 3.6 tons of slag with a ~-composition of 2 GaO SiO2 are formed in the silicothermal production of l -ton of magnesiu~, whereas in the alumino--5 thermal process the production of l ton of magnesium is acco~panied with the formation of 3.72 tons of slag with a composition of 3 CaO Al203. In the production of calcium 2.14 tons of 2 CaO SiO2 or 2.24 tons of 3 ~aO A1203 are formed together wlth one ton of the re~uired product.
~he in~ention aims at -the elimination of the abo~e disad~antages of the silicothermal or aluminothermal produc tion of magnesium or calcium by providing an easily perform-able, economical large-scale method for the metallothermal production of these two alkaline earth metals.
~ow it has been found that when preparing magnesium ;;
from calcined dolomite or calcium from calcined lime, cement is obtained as valuable by-product in addition to the two `
metals~ if the reduction is performed with an appropriate amount of a reducing agent containing silicon and aluminium ;~
in a Si:Al weight ratio of 4:1 to l:l. Tn the process lOO to 200 parts by weight of the reducing agent are applied to con~er-t 600 to 800 parts by weight of calcined dolomite or 700 to 1000 parts by weight of calcined lime. When magnesium is to be prepared, one can also proceed by adding not more than 200 parts by weight of calcined lime to 600 to 800 parts by weight of calcined dolomite, and reducing this mixture with 100 to 200 parts by weight of the reducing agent.
Accordingly, the invention is based on the recogni-tion that if a reducing agent containing silicon and alu-minium in the weight ratios defined abo~e is applîed, and the , .
X ,' , . . ... ..
xa-tio of the reducing agent to the starting substance ls maintained within the above limits, the silicothermal or aluminother~al process yields cement as by-product instead of a useless slag. ~s it appears frorn the above ratios, the - 5 mixtures of the starting substance and the reducing agent contain relati~el~ high amounts of calclum oxide~ ~s men-tioned above~ specific ad~antages arise in the production of magnesium when an additional amount of calcium oxide is added to -the calcined dolomite prior to starti~g the metallother~al reduction. ~hese facts are in stri~ing contrast with the prior e*forts, where it was attempted to keep the proportion of calcium oxide at the minimum in order to decrease the amount of slag. On the contrary, according to the in~ention, it is essential to process mixtures with relati~ely high calcium oxide contents, since this ensures the formation of cement as by-product instead of a slag.
According to a fur-ther ~ariant of the in~ention a reducing agent also containing calcium is applied. ~his is again in contrast wi-th the former efforts. The significance of the presence of calcium can èasily be understood on the basis of the equation 5 lCaO MgO/ t Ca t. 2 Si = 2 /3 CaO ~ Si.02/ + 5 Mg ~his equation shows that calcium also participates in the reduction of calcined dolomite as a reducing agent. Of course, in the processing of calcined lime calcium has no reducing effect but simply increases the yield. ~he reason ~` -for the use of/calcium-containing reducing agent in the processing of calcined lime is that CaSi allo~ is the most ; easily a~ailable of the reduoing agents applicable in 30 practice. ~he calcium content o* this reducing agent ~;
.
-............ , : . . ~ ;- . ~ . ..... . .
increases the yield o~ the aimed product.
~s mentioned abo~e, substances containing silicon and aluminium in a weight ratio of ~:l to 1:1 are applied as ;
reducing agents. ~he total silicon and aluminium content of the reducing agent may vary between 50 to lO0 % ~his means that simple mixtures or alloys of silicon and alùminium con-taining the two metals in the abo~e weight ratio can be utilized as reducing agents in the process of the invention.
However, reducing agents containing other subs-tances in addi tion to aluminium and silicon can be utili~ed as well. As mentioned above, reducing agents also containing calcium are preferred. ~he calcium content o~ these reducing agents may ;~
amount to 30 % by weight; they contain generally 1 to 30 ~0 by weight of calcium. ~he reducing agents utilized in practice are generally iron-containing alloys or mixtures of such alloys. ~he iron content of the reducing agent may amount to 25 % by weight; the reducing agent contains generally 0.1 to 25 ~0 by weight of iron. ~s reducing agent appropriate mi~tures of silicoaluminium, ferrosLlicon, calciumsilicon, silicoaluminiumcalcium and ferrosilico-aluminiumcalcium alloys can be used, wherein the ratio of silicon to alum m ium, the total silicon and aluminium content, and the calcium and iron content meets the above requirements.
Of course, single alloys with appropriate compositions can `
be used as well.
~ he reduction itself is performed in apparatuses utili~ed for silicothermal and aluminothermal processes according to known techniques, at a temperature of 1300 to 1600 C under a pressure o~ less than 10 torr, until the development of magnesium or calcium vapours ceases.
'`:
. ~ I
. . .
The ~ixt~re of the ~tar-ting su~-tances is powdered and brlquetted. Appropriate briquattes can be formed from the mixtures generally under a pressure of 500 to 2000 kiloponds/cm2 The briquettes, either as such or op~ionally after hardening and/or preheating, are filled into the cobbing chamber, kept at 1300 to 1600 ~, of a furnace filled with an inert protecting gas. ~he furnace is closed, the internal pressure is decreased to below 10 *orr, and heating is continued, whereupon the briquettes warm up to 1300 to 1600 ~ and the metallothermal reaction takes place. ;~
~he magnesium or calcium ~apours formed are collected in the condenser of the furnace, where magnesium or calcium preci-pitates in crystalline form. At the end of the process the temperature of the condenser drops, since no further ~agnesium or calcium vapour precipitates in -the condenser.
Depending on the composition of the mixture of -the starting substance and the reducing agent, the dimensions of ;
the furnace, the temperature and other parameters, reduction is completed generally within 4 to 12 hours.
At the end of the reaction the furnace is refilled with an inert protecting gas, and the cement clinker formed is removed from the cobbing chamber, whereas crystalline magnesium or calcium is removed from the condenser. ~he process can then be restarted. It is preferred to operate the furnace in cyclic manner.
As protecting gas preferably argon is applied.
~ he cement clinker removed from the cob~:ing chamber of the furnace contains 20 to 25 yO by weight of SiO2, 6 to 12 % by weight of A1203 and 62 to 69 % by weight of CaO~
furthermore optionally up to 2 % by weight of MgO and/or X "
.
, ~. . . .
_ 7 ~
up -to 6 ~0 by welght of iron. hs the composition of this product corresponds to that of portland cement, it can be utilized as binding agent in the building lndustry.
~he most important advantage of the new process accordlng to the in~ention is that it pro~ldes an econo~ical method for the large-sc~le production of magneslum and cal-cium. Utilizing the process of the in~ention the disadvantage of the prior silicothermal and aluminother~al processes, i.e.
the formation of large amounts of useless slag, also causing environ~ental protection problems, can be avoided completely, since all of the products formed in the new process can be utilized.
~ he process of the invention is easy to per~orm and requires no specific technological operations or specific equipment. ~he process can be performed in the apparatuses commonly used for silicothermal and aluminothermal opera-tions, pro~ided that a pressure lower than 10 torr and te~peratures of 1300 to 1600 ~ can be maintained in them.
The invention is elucida-ted in detail by the aid of the ~ollowing non-limiting Examples.
xample 1 ,~1 638 parts by weight of calcined dolomite and 71 parts by weight o~ calcined lime are admixed with 100 parts by weight of a reducing agent containing 70 % by weight of silicon and 30 % by weight of aluminium, and the mixture is pul~erized by grinding. ~he powder is briquetted, and the briquettes are cobbed at 1500 C under a pressure of 10 2 torr. As a min product of this process 155 parts by weight of magnesium separate in the condenser of the furnace. As by-product, 656 parts by weight of cement containing 66 ~o ~ .
8 - ~ r~r~
by weight of CaO, 23.5 % by weight of SiO21 9 ~0 by weight of A1203 and 1~5 ~0 by weight o~ MgO re~ain in the cobbing chamber of the furnace.
xample 2 699 parts by weight of calcined dolomite are admixed with 125 parts by weigh-t of a reducing agent con-taining 56 ~o by weight o~ silicon, 24 % by ~eight of aluminium and 20 by weight of calcium, and the mixture is pul~erized by grindingO ~he powder is briquetted 9 and the briquettes are cobbed at 1400 C under a pressure of 10 3 torr until the e~olution of magnesium vapours cease. As a main product 173 par-ts by weight of magnesium are obtained. ~he by-product i.s 660 parts by weight of cement containing 66.5 % by weight of aaO, 23 % by weight of SiO25 10 % by weight of A1203 and 5 0.5 % by weight of MgO, ~xample 3 668.5 parts by weight of calcined dolomite and 35.5 parts by weight of calcined lime are admixed with 112.5 parts by weight of a reducing agent c~ntaining 62 %
by weight of silicon, 27 % by weight of alu~inium and 11 %
by weight of calcium, and the mixture is ground. ~he resulting powder is briquetted~ and the briquettes are cobbed at ;~-1600 a under a pressure of 10 torr until the de~elopment ;
of magnesium vapour ceases. As a main product 164 parts by weight of magnesium are obtained. As a by-product 665 parts by weight of cement are formed with essentially the same composition as indicated in Example 1.
Example 4 638 parts by weight of calcined dolomite and 71 30 parts by weight of calcined llme are admixed with 123 parts - ;
.~ ~
- 9~
by weight of a reducing agent con-taining 57 % by weight of silicon, 24.~ yO by weight of aluminium and 18.6 ~0 by weight of iron. ~he mixture is pulveri~ed by grinding, and the powder is briquetted~ ~he br1quettes are cobbed at 130G a - 5 under a pressure of 10 4 torr until the de~elopment of ~agnesiu~ vapours ceases. 156 parts by weigh-t of magnesium are obtained as a main product. As a by-product, 675 parts by weight of cement containing 68.4 ~0 by weight of CaO, 21.0 ~0 by weight of SiO2, 7.0 ~o by weight of A1203, 0.5 yo by weight of ~gO and 3.1 ~o by weight of iron are obtained.
Example 5 699 parts by weight of calcined dolomite are ~ -admixed with 148 parts by weight of a reducing agent containing ~7 % by weight of silicon, 20 % by weight of aluminiu~, 17 yO by weight of calcium and 16 % by weight of iron. ~he mixture is pulverized by grinding, and the powder is briquetted. ~he briquettes are cobbed at 1550 C under a pressure o~ 10 1 torr until the development of magnesium vapours cease~.~he process yields 171 parts by weight of magnesium as main product and 677 parts by weight of cement, containing 64.0 ~0 by weight of CaO, 19.7 % by weight of SiO2, 11.3 % by weight of A1203, 1.8 % by weight of MgO and 3.1 ~0 by w~ight of iron, as by-product.
Exarnple 6 668.5 parts by weight of calcined dolomi-te and 35.5 parts by weight of calcined lime are admixed with 135 5 parts by weight o~ a reducing agent containing 51.7 yo by weight of silicon, 22 1 ~0 by weight of aluminium, 9.2 yO by weight of calcium and I7 % by weight of iron. ~he mixture is pulverized by grinding, and the powder is briquetted. ~he '`~7 - 10 ~ b~ ~i briquettes are cobbed at 1450 C under a pressure of 10 2 torr un-til the development of magnesium vapours ceases. ~he process yields 166 parts by welght of magnesium as main product and 671 parts by weight of cement, containing 65.0 %
by weight of CaO, 24 0 ~0 by weight of SiO2, 7.7 ~0 by weight of A1203, 0.2 % by weight of MgO and 3~ O by weight of iron as by-product.
~ `~, ~14 parts by weight of calcined lime are admixed with 100 parts by weight of a reducing agent con-taining 70 %
by weight of silicon and 30 ~0 by weight of alu~inium. ~he mixture is pulveri~ed by grinding, the powder is briquetted, and the briquettes are cobbed at 1500 C under a pressure of 10 3 torr until the development of calcium vapours ceases.
~he process yields 258 parts by weight of calcium as main product and 656 parts by weight of cement, containing 64.5 %
by weight of CaO, 23.6 % by weight of SiO2, 11.4 % by weight of A1203 and 0.5 % by weight of MgO, as by-product.
,' ;-814 parts by weight of calcined lime are admixed ~-with 135 parts by weight of a reducing agent containing 52 % by weight of silicon, 22 % by weight of aluminium and 26 % by weight of calcium. ~he mixture is ground, the result-ing powder is briquetted, and the briquettes are oobbed at 1600 C under a pressure of 10 1 torr until the development of calcium vapours ceases. ~he process yields 294 parts by weight of calcium as main product and 650 parts by weight of cement, containing 66.7 yO by weight of CaO, 22.8 ~ by weight of SiO2, 9.9 % by weight of A1203 and 006 % by weight of MgO, as by-product.
```~! :
hxc~mple 9 814 parts by weight of calcined lime are admixea with 123 parts by weight of a reducing agent containing 57 %
by weight of silicon 9 24 % by weight of aluminium and 19 %
- 5 by weight of iron. The mixture is pulveri~ed by grinding) the resulting powder is briquetted, and the briquettes are cobbed at 1450 C under a pressure of 10 4 -torr until the develop-~ent of calcium vapours ceases. ~he process yield~ 254 parts by weight of calcium as main product and 680 parts by weight of cement, containing 64.8 yO by weight of CaO, 22.7 yO by weight of SiO2, 8.5 % by weight of A1203, 0.3 % by weight of is MgO and 3.7 yO b~ weight of iron, as by-product.
.
814 parts by weigh-t of calcined lime are admixed with 158 parts by weight of a reducing agent containing 44.3 yO by weight of silicon, 19.0 yO by weight of aluminium 22.2 yO by weight of calcium and 14.5 % by weight of iron.
~he mixture is pul~eri~ed by grinding, the resulting powder is briquetted, and the briquettes are cobbed at 1550 C under a pressure bf 10 3 torr. ~he process yields 298 parts by weight of calciu~ as main product and 675 parts by weight of cement, containing 62.9 % by weight of CaO, 23.5 % by weight of SiO2, 9.6 yO by weight of ~1203, 0.7 % by weight of MgO
and 3.3 ~o b~ weight of iron, as by-product.
: .. . .. : . . ..
Up to now these methods could not compete with electrolytical techniques, since they yield9 beside the aimed ~1 -. . . - ~ ~
product, extre~el~ large a~ounts o~ useless slag. According to theoretical calculations, 3.6 tons of slag with a ~-composition of 2 GaO SiO2 are formed in the silicothermal production of l -ton of magnesiu~, whereas in the alumino--5 thermal process the production of l ton of magnesium is acco~panied with the formation of 3.72 tons of slag with a composition of 3 CaO Al203. In the production of calcium 2.14 tons of 2 CaO SiO2 or 2.24 tons of 3 ~aO A1203 are formed together wlth one ton of the re~uired product.
~he in~ention aims at -the elimination of the abo~e disad~antages of the silicothermal or aluminothermal produc tion of magnesium or calcium by providing an easily perform-able, economical large-scale method for the metallothermal production of these two alkaline earth metals.
~ow it has been found that when preparing magnesium ;;
from calcined dolomite or calcium from calcined lime, cement is obtained as valuable by-product in addition to the two `
metals~ if the reduction is performed with an appropriate amount of a reducing agent containing silicon and aluminium ;~
in a Si:Al weight ratio of 4:1 to l:l. Tn the process lOO to 200 parts by weight of the reducing agent are applied to con~er-t 600 to 800 parts by weight of calcined dolomite or 700 to 1000 parts by weight of calcined lime. When magnesium is to be prepared, one can also proceed by adding not more than 200 parts by weight of calcined lime to 600 to 800 parts by weight of calcined dolomite, and reducing this mixture with 100 to 200 parts by weight of the reducing agent.
Accordingly, the invention is based on the recogni-tion that if a reducing agent containing silicon and alu-minium in the weight ratios defined abo~e is applîed, and the , .
X ,' , . . ... ..
xa-tio of the reducing agent to the starting substance ls maintained within the above limits, the silicothermal or aluminother~al process yields cement as by-product instead of a useless slag. ~s it appears frorn the above ratios, the - 5 mixtures of the starting substance and the reducing agent contain relati~el~ high amounts of calclum oxide~ ~s men-tioned above~ specific ad~antages arise in the production of magnesium when an additional amount of calcium oxide is added to -the calcined dolomite prior to starti~g the metallother~al reduction. ~hese facts are in stri~ing contrast with the prior e*forts, where it was attempted to keep the proportion of calcium oxide at the minimum in order to decrease the amount of slag. On the contrary, according to the in~ention, it is essential to process mixtures with relati~ely high calcium oxide contents, since this ensures the formation of cement as by-product instead of a slag.
According to a fur-ther ~ariant of the in~ention a reducing agent also containing calcium is applied. ~his is again in contrast wi-th the former efforts. The significance of the presence of calcium can èasily be understood on the basis of the equation 5 lCaO MgO/ t Ca t. 2 Si = 2 /3 CaO ~ Si.02/ + 5 Mg ~his equation shows that calcium also participates in the reduction of calcined dolomite as a reducing agent. Of course, in the processing of calcined lime calcium has no reducing effect but simply increases the yield. ~he reason ~` -for the use of/calcium-containing reducing agent in the processing of calcined lime is that CaSi allo~ is the most ; easily a~ailable of the reduoing agents applicable in 30 practice. ~he calcium content o* this reducing agent ~;
.
-............ , : . . ~ ;- . ~ . ..... . .
increases the yield o~ the aimed product.
~s mentioned abo~e, substances containing silicon and aluminium in a weight ratio of ~:l to 1:1 are applied as ;
reducing agents. ~he total silicon and aluminium content of the reducing agent may vary between 50 to lO0 % ~his means that simple mixtures or alloys of silicon and alùminium con-taining the two metals in the abo~e weight ratio can be utilized as reducing agents in the process of the invention.
However, reducing agents containing other subs-tances in addi tion to aluminium and silicon can be utili~ed as well. As mentioned above, reducing agents also containing calcium are preferred. ~he calcium content o~ these reducing agents may ;~
amount to 30 % by weight; they contain generally 1 to 30 ~0 by weight of calcium. ~he reducing agents utilized in practice are generally iron-containing alloys or mixtures of such alloys. ~he iron content of the reducing agent may amount to 25 % by weight; the reducing agent contains generally 0.1 to 25 ~0 by weight of iron. ~s reducing agent appropriate mi~tures of silicoaluminium, ferrosLlicon, calciumsilicon, silicoaluminiumcalcium and ferrosilico-aluminiumcalcium alloys can be used, wherein the ratio of silicon to alum m ium, the total silicon and aluminium content, and the calcium and iron content meets the above requirements.
Of course, single alloys with appropriate compositions can `
be used as well.
~ he reduction itself is performed in apparatuses utili~ed for silicothermal and aluminothermal processes according to known techniques, at a temperature of 1300 to 1600 C under a pressure o~ less than 10 torr, until the development of magnesium or calcium vapours ceases.
'`:
. ~ I
. . .
The ~ixt~re of the ~tar-ting su~-tances is powdered and brlquetted. Appropriate briquattes can be formed from the mixtures generally under a pressure of 500 to 2000 kiloponds/cm2 The briquettes, either as such or op~ionally after hardening and/or preheating, are filled into the cobbing chamber, kept at 1300 to 1600 ~, of a furnace filled with an inert protecting gas. ~he furnace is closed, the internal pressure is decreased to below 10 *orr, and heating is continued, whereupon the briquettes warm up to 1300 to 1600 ~ and the metallothermal reaction takes place. ;~
~he magnesium or calcium ~apours formed are collected in the condenser of the furnace, where magnesium or calcium preci-pitates in crystalline form. At the end of the process the temperature of the condenser drops, since no further ~agnesium or calcium vapour precipitates in -the condenser.
Depending on the composition of the mixture of -the starting substance and the reducing agent, the dimensions of ;
the furnace, the temperature and other parameters, reduction is completed generally within 4 to 12 hours.
At the end of the reaction the furnace is refilled with an inert protecting gas, and the cement clinker formed is removed from the cobbing chamber, whereas crystalline magnesium or calcium is removed from the condenser. ~he process can then be restarted. It is preferred to operate the furnace in cyclic manner.
As protecting gas preferably argon is applied.
~ he cement clinker removed from the cob~:ing chamber of the furnace contains 20 to 25 yO by weight of SiO2, 6 to 12 % by weight of A1203 and 62 to 69 % by weight of CaO~
furthermore optionally up to 2 % by weight of MgO and/or X "
.
, ~. . . .
_ 7 ~
up -to 6 ~0 by welght of iron. hs the composition of this product corresponds to that of portland cement, it can be utilized as binding agent in the building lndustry.
~he most important advantage of the new process accordlng to the in~ention is that it pro~ldes an econo~ical method for the large-sc~le production of magneslum and cal-cium. Utilizing the process of the in~ention the disadvantage of the prior silicothermal and aluminother~al processes, i.e.
the formation of large amounts of useless slag, also causing environ~ental protection problems, can be avoided completely, since all of the products formed in the new process can be utilized.
~ he process of the invention is easy to per~orm and requires no specific technological operations or specific equipment. ~he process can be performed in the apparatuses commonly used for silicothermal and aluminothermal opera-tions, pro~ided that a pressure lower than 10 torr and te~peratures of 1300 to 1600 ~ can be maintained in them.
The invention is elucida-ted in detail by the aid of the ~ollowing non-limiting Examples.
xample 1 ,~1 638 parts by weight of calcined dolomite and 71 parts by weight o~ calcined lime are admixed with 100 parts by weight of a reducing agent containing 70 % by weight of silicon and 30 % by weight of aluminium, and the mixture is pul~erized by grinding. ~he powder is briquetted, and the briquettes are cobbed at 1500 C under a pressure of 10 2 torr. As a min product of this process 155 parts by weight of magnesium separate in the condenser of the furnace. As by-product, 656 parts by weight of cement containing 66 ~o ~ .
8 - ~ r~r~
by weight of CaO, 23.5 % by weight of SiO21 9 ~0 by weight of A1203 and 1~5 ~0 by weight o~ MgO re~ain in the cobbing chamber of the furnace.
xample 2 699 parts by weight of calcined dolomite are admixed with 125 parts by weigh-t of a reducing agent con-taining 56 ~o by weight o~ silicon, 24 % by ~eight of aluminium and 20 by weight of calcium, and the mixture is pul~erized by grindingO ~he powder is briquetted 9 and the briquettes are cobbed at 1400 C under a pressure of 10 3 torr until the e~olution of magnesium vapours cease. As a main product 173 par-ts by weight of magnesium are obtained. ~he by-product i.s 660 parts by weight of cement containing 66.5 % by weight of aaO, 23 % by weight of SiO25 10 % by weight of A1203 and 5 0.5 % by weight of MgO, ~xample 3 668.5 parts by weight of calcined dolomite and 35.5 parts by weight of calcined lime are admixed with 112.5 parts by weight of a reducing agent c~ntaining 62 %
by weight of silicon, 27 % by weight of alu~inium and 11 %
by weight of calcium, and the mixture is ground. ~he resulting powder is briquetted~ and the briquettes are cobbed at ;~-1600 a under a pressure of 10 torr until the de~elopment ;
of magnesium vapour ceases. As a main product 164 parts by weight of magnesium are obtained. As a by-product 665 parts by weight of cement are formed with essentially the same composition as indicated in Example 1.
Example 4 638 parts by weight of calcined dolomite and 71 30 parts by weight of calcined llme are admixed with 123 parts - ;
.~ ~
- 9~
by weight of a reducing agent con-taining 57 % by weight of silicon, 24.~ yO by weight of aluminium and 18.6 ~0 by weight of iron. ~he mixture is pulveri~ed by grinding, and the powder is briquetted~ ~he br1quettes are cobbed at 130G a - 5 under a pressure of 10 4 torr until the de~elopment of ~agnesiu~ vapours ceases. 156 parts by weigh-t of magnesium are obtained as a main product. As a by-product, 675 parts by weight of cement containing 68.4 ~0 by weight of CaO, 21.0 ~0 by weight of SiO2, 7.0 ~o by weight of A1203, 0.5 yo by weight of ~gO and 3.1 ~o by weight of iron are obtained.
Example 5 699 parts by weight of calcined dolomite are ~ -admixed with 148 parts by weight of a reducing agent containing ~7 % by weight of silicon, 20 % by weight of aluminiu~, 17 yO by weight of calcium and 16 % by weight of iron. ~he mixture is pulverized by grinding, and the powder is briquetted. ~he briquettes are cobbed at 1550 C under a pressure o~ 10 1 torr until the development of magnesium vapours cease~.~he process yields 171 parts by weight of magnesium as main product and 677 parts by weight of cement, containing 64.0 ~0 by weight of CaO, 19.7 % by weight of SiO2, 11.3 % by weight of A1203, 1.8 % by weight of MgO and 3.1 ~0 by w~ight of iron, as by-product.
Exarnple 6 668.5 parts by weight of calcined dolomi-te and 35.5 parts by weight of calcined lime are admixed with 135 5 parts by weight o~ a reducing agent containing 51.7 yo by weight of silicon, 22 1 ~0 by weight of aluminium, 9.2 yO by weight of calcium and I7 % by weight of iron. ~he mixture is pulverized by grinding, and the powder is briquetted. ~he '`~7 - 10 ~ b~ ~i briquettes are cobbed at 1450 C under a pressure of 10 2 torr un-til the development of magnesium vapours ceases. ~he process yields 166 parts by welght of magnesium as main product and 671 parts by weight of cement, containing 65.0 %
by weight of CaO, 24 0 ~0 by weight of SiO2, 7.7 ~0 by weight of A1203, 0.2 % by weight of MgO and 3~ O by weight of iron as by-product.
~ `~, ~14 parts by weight of calcined lime are admixed with 100 parts by weight of a reducing agent con-taining 70 %
by weight of silicon and 30 ~0 by weight of alu~inium. ~he mixture is pulveri~ed by grinding, the powder is briquetted, and the briquettes are cobbed at 1500 C under a pressure of 10 3 torr until the development of calcium vapours ceases.
~he process yields 258 parts by weight of calcium as main product and 656 parts by weight of cement, containing 64.5 %
by weight of CaO, 23.6 % by weight of SiO2, 11.4 % by weight of A1203 and 0.5 % by weight of MgO, as by-product.
,' ;-814 parts by weight of calcined lime are admixed ~-with 135 parts by weight of a reducing agent containing 52 % by weight of silicon, 22 % by weight of aluminium and 26 % by weight of calcium. ~he mixture is ground, the result-ing powder is briquetted, and the briquettes are oobbed at 1600 C under a pressure of 10 1 torr until the development of calcium vapours ceases. ~he process yields 294 parts by weight of calcium as main product and 650 parts by weight of cement, containing 66.7 yO by weight of CaO, 22.8 ~ by weight of SiO2, 9.9 % by weight of A1203 and 006 % by weight of MgO, as by-product.
```~! :
hxc~mple 9 814 parts by weight of calcined lime are admixea with 123 parts by weight of a reducing agent containing 57 %
by weight of silicon 9 24 % by weight of aluminium and 19 %
- 5 by weight of iron. The mixture is pulveri~ed by grinding) the resulting powder is briquetted, and the briquettes are cobbed at 1450 C under a pressure of 10 4 -torr until the develop-~ent of calcium vapours ceases. ~he process yield~ 254 parts by weight of calcium as main product and 680 parts by weight of cement, containing 64.8 yO by weight of CaO, 22.7 yO by weight of SiO2, 8.5 % by weight of A1203, 0.3 % by weight of is MgO and 3.7 yO b~ weight of iron, as by-product.
.
814 parts by weigh-t of calcined lime are admixed with 158 parts by weight of a reducing agent containing 44.3 yO by weight of silicon, 19.0 yO by weight of aluminium 22.2 yO by weight of calcium and 14.5 % by weight of iron.
~he mixture is pul~eri~ed by grinding, the resulting powder is briquetted, and the briquettes are cobbed at 1550 C under a pressure bf 10 3 torr. ~he process yields 298 parts by weight of calciu~ as main product and 675 parts by weight of cement, containing 62.9 % by weight of CaO, 23.5 % by weight of SiO2, 9.6 yO by weight of ~1203, 0.7 % by weight of MgO
and 3.3 ~o b~ weight of iron, as by-product.
: .. . .. : . . ..
Claims (9)
1. A process for the simultaneous production of magnesium and cement from calcined dolomite or calcium and cement from calcined lime, characterized in that calcined dolomite or calcined lime is reduced under a pressure lower than 10 torr and at a temperature of 1300 to 1600 °C with a reducing agent containing silicon and aluminium in a Si:Al weight ratio of 4:1 to 1:1, wherein the total amount of silicon and aluminium comprises 50 to 100 % by weight, and 100 to 200 parts by weight of said reducing agent are applied for 600 to 800 parts by weight of calcined dolomite or 700 to 1000 parts by weight of calcined lime.
2. A process as claimed in claim 1 for the simul-taneous production of magnesium and cement, characterized in that 600 to 800 parts by weight of calcined dolomite are admixed with up to 200 parts by weight of calcined lime, and the resulting mixture is reduced with 100 to 200 parts by weight of the reducing agent.
3. A process as claimed in claim 1, characterized in that a reducing agent containing up to 25 % by weight of iron is applied.
4. A process as claimed in claim 1, characterized in that a reducing agent containing up to 30 % by weight of calcium is applied.
5. A process as claimed in claim 1, characterized in that a mixture or an alloy of silicon and aluminium containing the two metals in a weight ratio of 4:1 to 1:1 is applied as reducing agent.
6. A process as claimed 1, characterized in that an alloy or an alloy mixture containing silicon and aluminium in a total amount of 50 to 100 % by weight, up to 30 % by weight of calcium and up to 25 % by weight of iron is applied as reducing agent.
7. A process as claimed in claim 6, characterized in that silicoaluminium, silicoaluminiumcalcium and/or ferro-silicoaluminiumcalcium or a mixture thereof, or a mixture of any of the former alloys and ferrosilicon and/or calcium-silicon is applied as reducing agent.
8. A process as claimed in claim 1, characterized in that reduction is performed in a cyclic operation by placing the powdered and briquetted mixture of the starting substance and the reducing agent in the presence of an inert protecting gas into a furnace equipped with a condenser and heated to 1300 to 1600 °C, decreasing the pressure in the furnace below 10 torr, maintaining the furnace temperature within the above limits, and, after the cessation of magnesium or calcium vapour development, filling the furnace with an inert protecting gas, removing the cement clinker from the furnace and the crystalline magnesium or calcium from the condenser, and restarting the above process.
9. A process as claimed in claim 8, characterized in that argon is applied as inert protecting gas.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA332,944A CA1115065A (en) | 1979-07-31 | 1979-07-31 | Metallothermal process for the simultaneous production of magnesium and cement or calcium and cement |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA332,944A CA1115065A (en) | 1979-07-31 | 1979-07-31 | Metallothermal process for the simultaneous production of magnesium and cement or calcium and cement |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1115065A true CA1115065A (en) | 1981-12-29 |
Family
ID=4114836
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA332,944A Expired CA1115065A (en) | 1979-07-31 | 1979-07-31 | Metallothermal process for the simultaneous production of magnesium and cement or calcium and cement |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1115065A (en) |
-
1979
- 1979-07-31 CA CA332,944A patent/CA1115065A/en not_active Expired
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