CA1093280A - Removal of iron from magnesite ore - Google Patents
Removal of iron from magnesite oreInfo
- Publication number
- CA1093280A CA1093280A CA288,501A CA288501A CA1093280A CA 1093280 A CA1093280 A CA 1093280A CA 288501 A CA288501 A CA 288501A CA 1093280 A CA1093280 A CA 1093280A
- Authority
- CA
- Canada
- Prior art keywords
- iron
- magnesite
- chloride
- magnesium chloride
- magnesium
- 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
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F5/00—Compounds of magnesium
- C01F5/02—Magnesia
- C01F5/06—Magnesia by thermal decomposition of magnesium compounds
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
REMOVAL OF IRON FROM MAGNESITE ORE
ABSTRACT OF THE DISCLOSURE
Iron carbonate distributed through the magnesium carbonate lattice of magnesite may be removed to produce a high grade magnesium oxide having a low residual iron content by reacting the magnesite with magnesium chloride and oxygen .
ABSTRACT OF THE DISCLOSURE
Iron carbonate distributed through the magnesium carbonate lattice of magnesite may be removed to produce a high grade magnesium oxide having a low residual iron content by reacting the magnesite with magnesium chloride and oxygen .
Description
The present invention relates to the treatment of magnesite ores.
Magnesite is a mineral ore form of magnesium in which the magnesium is present mainly as magnesium carbonate. Gangue constituents associated with the ore, such as talc, free silica and hematite, are readily removed. Usually varying quantities of finely dispersed iron carbonate occur in the magnesium carbonate lattice.
The presence of such iron carbonate is detri-mental to some end uses of the magnesite. For example, one major use of magnesite is in the formation of refractory magnesium oxide and the presence of small quan~ities of iron consumes carbon in basic oxygen furnace applications and opens the refractory structure for slag penetration.
Since the iron values are present in the lattice structure of the magnesite, it cannot be removed by con-ventional means, such as magnetic separation from the calcined product. It has previoUSly been suggested to remove the iron as gaseous iron chloride by treating the ore with chlorine gas at an elevated temperature. While this procedure removes the iron, it suffers from the dis-advantage that considerable excess quantities of chlorine are required, necessitating recovery, purification and recycle of large volumes of chlorine containing gas.
It has now been surprisingly found that iron may be removed from magnesite in a procedure whîch does not require the elaborate techniques associated with the prior art handling of large volumes of chlorine-containing gas.
rn accordance with the present invention, the magnesite ore, usually after initial beneficiation to ~0932~0 remove gangue constituents, is treated with magnesium chloride in the presence of oxygen to form iron chloride from the iron constituents of the ore, the treatment being carried out at a temperature sufficient to vola-tilize the iron chloride. The procedure is accompanied by the production of magnetic iron oxide which is removed by magnetic separation.
The magnesium chloride used in the present invention is anhydrous magnesium chloride which may be purchased as such or formed by dehydration of magnesium chloride hexahydrate at elevated temperature.
In the latter case, there is usually hydration of some of the magnesium chloride to magnesium oxychloride, so that the dehydrated magnesium chloride has less than 50% active chlorine, usually about 45 to about 48 active chlorine.
The dehydration of hydrated magnesium chloride may be carried out under a variety of conditions, for example, an initial heating for 2 hours at 100F
followed by heating for 1 hour at 240F.
The mixture of reactants is heated above the temperature necessary to effect the reaction, that is abo~e about 600C, for example, up to about 1200C, to - cause decomposition of the magnesium carbonate to magnesium oxide. The ability of magnesium chloride to act as a chlorinating agent is particularly beneficial, since this material remains in the final product as magnesium oxide and does not contaminate the final product.
Volatilized iron chloride produced in the reac-tion is removed from the system and condensed. Followingcompletion of the chlorination reaction, the product is subjected to magnetic separation techniques to xemove further quantities of iron, which are present as magnetic iron oxide formed under the oxidizing conditions of the process. In this invention, therefore, iron removal from the magnesite is achieved as volatilized iron chloride, supplemented by separation of magnetic iron oxides associa--ted with the product.
While the applicants do not wish to be bound thereto, it is theorized that the procedure of the present invention operates in the following way. Oxygen causes decomposition of the magnesium chloride, producing chlorine and magnesium oxide. The chlorine reacts with the iron in the lattice forming gaseous iron chloride which then separates from the solid phase. At the high temperatures of operation, some of the iron chloride is oxidized by oxygen and/or any water vapor, to form Fe2O3 and/or Fe304, which deposits from the gaseous phase and may contaminate the magnesium oxide. Unreacted iron chloride is removed from the system while contaminating quantities of magnetic iron oxide may be readily separated from the magnesium oxide since it is now in a discrete form as opposed to interstitial dispersion in the magnesite.
Chlorine and/or hydrogen chloride formed by oxidation of the iron chloride may react with additional quantities of chemically-bound iron and/or may be used for generation of magnesium chloriae for use in the process.
In the latter procedure, the off-gases from the reaction, after condensation of iron chloride, are passed into a bed of uncalcined magnesite, to form magnesium chloride by reaction with the magnesite. In this way, off-gases from the system are purified of possible noxious gases and may be vented to atmosphere in non-polluting manner.
The quantity of magnesium chloride used in the present invention may vary widely, depending on the technique employed. Typically, the concentration is about 1 to about 1.9 times the stoichiometric quantity required to convert all the iron present in the magnesite to ferric chloride. Greater than stoichiometric quan-tities usually are used to promote reaction with the iron values.
Similarly, the quantity of oxygen used in the atmosphere may vary widely, for example, up to about 6 times the stoichiometric requirement for conversion of the magnesium chloride to magnesium oxide and chloride.
Higher concentrations tend to promote reaction speed.
The magnesite and magnesium chloride may be reacted in any convenient oxygen-containing atmosphere, such as air or coal burner gas atmosphere. Generally, the atmosphere contains oxygen in the desired concen-tration and one or more inert gases, such as nitrogen and carbon dioxide.
The process of the invention may be carried out in a variety of ways, generally involving intimate association of particulate magnesite and particulate magnesium chloride. It is preferred to carry out the reaction in a fluidized bed of the particles to facili-tate iron chloride removal, although the mixture may be heated in a loose blended form or a briquetted form to effect the desired iron,removal.
The process of the present invention is capable of rapidly and efficiently decreasing the iron content of magnesite without introducing other contaminants so that the total iron content of the calcined product is less than 1%, which is considered tolerable for many magnesium oxide uses, in a procedure which does not involve the prior art difficulties and which is non-polluting.
~093280 Further purification of the magnesite or magnesi~m oxide to decrease the already low concentrations of alumina and silica may be achieved by reacting the magnesite with alkali to solubilize the alumina and silica and thereafter leaching the reaction mixture to remove the solubilized material. The alkali treatment may be effected using sodium carbonate.
The alkali treatment may be carried out simultaneously with the magnesium chloride treatment, or may be carried out in a separate step. In this way, magnesium oxide of purity greater than 99% MgO may be obtained.
The invention is illustrated by the following Example:
Example 1 40g of magnesite flotation concentrate were blended with 5.7g of approximately -65 mesh dehydrated magnesium chloride (having an active chlorine content of 44.g%) and heated at 1000C for 1 hour in a 1 inch diameter fluidized bed system employing a total gas flow rate of 0.46 l/min.
The magnesite concentrate had a particle size distribution and chemical composition as outlined in the following Table I:
Mesh Size wt. %
.
+80 0.71 -80+10~ 1.33 -100+150 9.20 -150~200 26.73 -200-~250 8.53 -250-~325 30.64 -3~5 22.~6 Element %
MgO 43.30 Fe23 2.69( ) CaO 0.25 A123 0.16 SiO2 0.14 L.O.I. 54.60 (3) 101.14 otes:
(1) This value corresponds to a total iron content of 1.88% which in turn corresponds to a total iron content after calcining of 4.14%.
Magnesite is a mineral ore form of magnesium in which the magnesium is present mainly as magnesium carbonate. Gangue constituents associated with the ore, such as talc, free silica and hematite, are readily removed. Usually varying quantities of finely dispersed iron carbonate occur in the magnesium carbonate lattice.
The presence of such iron carbonate is detri-mental to some end uses of the magnesite. For example, one major use of magnesite is in the formation of refractory magnesium oxide and the presence of small quan~ities of iron consumes carbon in basic oxygen furnace applications and opens the refractory structure for slag penetration.
Since the iron values are present in the lattice structure of the magnesite, it cannot be removed by con-ventional means, such as magnetic separation from the calcined product. It has previoUSly been suggested to remove the iron as gaseous iron chloride by treating the ore with chlorine gas at an elevated temperature. While this procedure removes the iron, it suffers from the dis-advantage that considerable excess quantities of chlorine are required, necessitating recovery, purification and recycle of large volumes of chlorine containing gas.
It has now been surprisingly found that iron may be removed from magnesite in a procedure whîch does not require the elaborate techniques associated with the prior art handling of large volumes of chlorine-containing gas.
rn accordance with the present invention, the magnesite ore, usually after initial beneficiation to ~0932~0 remove gangue constituents, is treated with magnesium chloride in the presence of oxygen to form iron chloride from the iron constituents of the ore, the treatment being carried out at a temperature sufficient to vola-tilize the iron chloride. The procedure is accompanied by the production of magnetic iron oxide which is removed by magnetic separation.
The magnesium chloride used in the present invention is anhydrous magnesium chloride which may be purchased as such or formed by dehydration of magnesium chloride hexahydrate at elevated temperature.
In the latter case, there is usually hydration of some of the magnesium chloride to magnesium oxychloride, so that the dehydrated magnesium chloride has less than 50% active chlorine, usually about 45 to about 48 active chlorine.
The dehydration of hydrated magnesium chloride may be carried out under a variety of conditions, for example, an initial heating for 2 hours at 100F
followed by heating for 1 hour at 240F.
The mixture of reactants is heated above the temperature necessary to effect the reaction, that is abo~e about 600C, for example, up to about 1200C, to - cause decomposition of the magnesium carbonate to magnesium oxide. The ability of magnesium chloride to act as a chlorinating agent is particularly beneficial, since this material remains in the final product as magnesium oxide and does not contaminate the final product.
Volatilized iron chloride produced in the reac-tion is removed from the system and condensed. Followingcompletion of the chlorination reaction, the product is subjected to magnetic separation techniques to xemove further quantities of iron, which are present as magnetic iron oxide formed under the oxidizing conditions of the process. In this invention, therefore, iron removal from the magnesite is achieved as volatilized iron chloride, supplemented by separation of magnetic iron oxides associa--ted with the product.
While the applicants do not wish to be bound thereto, it is theorized that the procedure of the present invention operates in the following way. Oxygen causes decomposition of the magnesium chloride, producing chlorine and magnesium oxide. The chlorine reacts with the iron in the lattice forming gaseous iron chloride which then separates from the solid phase. At the high temperatures of operation, some of the iron chloride is oxidized by oxygen and/or any water vapor, to form Fe2O3 and/or Fe304, which deposits from the gaseous phase and may contaminate the magnesium oxide. Unreacted iron chloride is removed from the system while contaminating quantities of magnetic iron oxide may be readily separated from the magnesium oxide since it is now in a discrete form as opposed to interstitial dispersion in the magnesite.
Chlorine and/or hydrogen chloride formed by oxidation of the iron chloride may react with additional quantities of chemically-bound iron and/or may be used for generation of magnesium chloriae for use in the process.
In the latter procedure, the off-gases from the reaction, after condensation of iron chloride, are passed into a bed of uncalcined magnesite, to form magnesium chloride by reaction with the magnesite. In this way, off-gases from the system are purified of possible noxious gases and may be vented to atmosphere in non-polluting manner.
The quantity of magnesium chloride used in the present invention may vary widely, depending on the technique employed. Typically, the concentration is about 1 to about 1.9 times the stoichiometric quantity required to convert all the iron present in the magnesite to ferric chloride. Greater than stoichiometric quan-tities usually are used to promote reaction with the iron values.
Similarly, the quantity of oxygen used in the atmosphere may vary widely, for example, up to about 6 times the stoichiometric requirement for conversion of the magnesium chloride to magnesium oxide and chloride.
Higher concentrations tend to promote reaction speed.
The magnesite and magnesium chloride may be reacted in any convenient oxygen-containing atmosphere, such as air or coal burner gas atmosphere. Generally, the atmosphere contains oxygen in the desired concen-tration and one or more inert gases, such as nitrogen and carbon dioxide.
The process of the invention may be carried out in a variety of ways, generally involving intimate association of particulate magnesite and particulate magnesium chloride. It is preferred to carry out the reaction in a fluidized bed of the particles to facili-tate iron chloride removal, although the mixture may be heated in a loose blended form or a briquetted form to effect the desired iron,removal.
The process of the present invention is capable of rapidly and efficiently decreasing the iron content of magnesite without introducing other contaminants so that the total iron content of the calcined product is less than 1%, which is considered tolerable for many magnesium oxide uses, in a procedure which does not involve the prior art difficulties and which is non-polluting.
~093280 Further purification of the magnesite or magnesi~m oxide to decrease the already low concentrations of alumina and silica may be achieved by reacting the magnesite with alkali to solubilize the alumina and silica and thereafter leaching the reaction mixture to remove the solubilized material. The alkali treatment may be effected using sodium carbonate.
The alkali treatment may be carried out simultaneously with the magnesium chloride treatment, or may be carried out in a separate step. In this way, magnesium oxide of purity greater than 99% MgO may be obtained.
The invention is illustrated by the following Example:
Example 1 40g of magnesite flotation concentrate were blended with 5.7g of approximately -65 mesh dehydrated magnesium chloride (having an active chlorine content of 44.g%) and heated at 1000C for 1 hour in a 1 inch diameter fluidized bed system employing a total gas flow rate of 0.46 l/min.
The magnesite concentrate had a particle size distribution and chemical composition as outlined in the following Table I:
Mesh Size wt. %
.
+80 0.71 -80+10~ 1.33 -100+150 9.20 -150~200 26.73 -200-~250 8.53 -250-~325 30.64 -3~5 22.~6 Element %
MgO 43.30 Fe23 2.69( ) CaO 0.25 A123 0.16 SiO2 0.14 L.O.I. 54.60 (3) 101.14 otes:
(1) This value corresponds to a total iron content of 1.88% which in turn corresponds to a total iron content after calcining of 4.14%.
(2) Mainly as carbon dioxide
(3) This value is greater than 100% due to in-accuracies in analysis.
The gas used in the fluidized bed was a simulated coal burner gas containing 23 vol.% CO2, 0.40 vol. % SO2, 1.75 vol.% H2O vapor, 1.2 vol. ~ 2 and the balance nitrogen. The concentration of magnesium chloride used corresponds to about 1~25 times the stoichiometric value and the quantity of oxygen used corresponds to about 1.1 times the stoichiometric value.
15.6g of main product (magnesium oxide) was re-covered and after magnetic separation, analysis disclosed the residual total iron content of 0.25 wt.% indicating that removal of iron was about 94% complete. After recovery of deposits from the reactor wall and accounting for magnetics separated, a total product yield of 86% was realized.
~0 xample 2 10 yms. of macJnesite conccntrate o~ the comE~osi-tions SeL fOrLh in Table I was mixed with 1.9~ gms. of of 44.9% having an average particle size of -65 mesh), corresponding '~o 1.8 times the stoichiometric quantity required, and the mixture was compacted in a die to form a briquette of dimension 1 1/4" diameter and 1/2" thick.
The briquette was cut into three pieces which were heated in a horizontal tube with about 2.1 times the stoichio-metric volume of air flowing through the tube at 1000C for 60 minutes.
The solid product was found to have a cream-n white colour and analysis revealed an iron content of 0.59%. The briquette segments had partially disintegrated to powder and the remaining lumps were friable and fell apart on handling.
Example 3 Different samples of magnesite concentrate were calcined with sodium hydroxide and sodium carbonate at about 1200C for 1 hour. After cooling, the roasted material was leached with hot (80C) alkaline water to remove solubles.
It was found in each case that about 75% of the initial silica and alumina concentrations had been solubilized by the treatments.
Modifications are possible within the scope of the invention.
The gas used in the fluidized bed was a simulated coal burner gas containing 23 vol.% CO2, 0.40 vol. % SO2, 1.75 vol.% H2O vapor, 1.2 vol. ~ 2 and the balance nitrogen. The concentration of magnesium chloride used corresponds to about 1~25 times the stoichiometric value and the quantity of oxygen used corresponds to about 1.1 times the stoichiometric value.
15.6g of main product (magnesium oxide) was re-covered and after magnetic separation, analysis disclosed the residual total iron content of 0.25 wt.% indicating that removal of iron was about 94% complete. After recovery of deposits from the reactor wall and accounting for magnetics separated, a total product yield of 86% was realized.
~0 xample 2 10 yms. of macJnesite conccntrate o~ the comE~osi-tions SeL fOrLh in Table I was mixed with 1.9~ gms. of of 44.9% having an average particle size of -65 mesh), corresponding '~o 1.8 times the stoichiometric quantity required, and the mixture was compacted in a die to form a briquette of dimension 1 1/4" diameter and 1/2" thick.
The briquette was cut into three pieces which were heated in a horizontal tube with about 2.1 times the stoichio-metric volume of air flowing through the tube at 1000C for 60 minutes.
The solid product was found to have a cream-n white colour and analysis revealed an iron content of 0.59%. The briquette segments had partially disintegrated to powder and the remaining lumps were friable and fell apart on handling.
Example 3 Different samples of magnesite concentrate were calcined with sodium hydroxide and sodium carbonate at about 1200C for 1 hour. After cooling, the roasted material was leached with hot (80C) alkaline water to remove solubles.
It was found in each case that about 75% of the initial silica and alumina concentrations had been solubilized by the treatments.
Modifications are possible within the scope of the invention.
Claims (5)
1. A process for the treatment of magnesite containing iron values, which comprises heating a mixture of magnesite and anhydrous magnesium chloride in an atmosphere containing molecular oxygen at a temperature of at least about 600°C
to cause formation of volatile iron chloride from at least part of the iron values which volatilizes from the solid magnesium oxide and to form magnesium oxide having a low residual iron content, and subjecting the magnesium oxide product resulting from said heating step to magnetic separa-tion to remove any magnetic iron oxide which may be formed in said reaction.
to cause formation of volatile iron chloride from at least part of the iron values which volatilizes from the solid magnesium oxide and to form magnesium oxide having a low residual iron content, and subjecting the magnesium oxide product resulting from said heating step to magnetic separa-tion to remove any magnetic iron oxide which may be formed in said reaction.
2. The process of claim 1 wherein said magnesium chloride is anhydrous magnesium chloride having an active chlorine concentration of about 45 to about 48%.
3. The process of claim 1 wherein the quantity of magnesium chloride utilized is about 1 to about 1.9 times the stoichiometric quantity of magnesium chloride required to convert all the iron present in the magnesite to ferric chloride.
4. The process of claim 1, 2 or 3 carried out in a fluidized bed.
5. The process of claim 1, 2 or 3 including solubi-lizing silica and/or alumina in said magnesite and leaching said solubilized material.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB4361176 | 1976-10-20 | ||
| GB43611/76 | 1976-10-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1093280A true CA1093280A (en) | 1981-01-13 |
Family
ID=10429526
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA288,501A Expired CA1093280A (en) | 1976-10-20 | 1977-10-07 | Removal of iron from magnesite ore |
Country Status (3)
| Country | Link |
|---|---|
| AT (1) | AT356060B (en) |
| BR (1) | BR7707023A (en) |
| CA (1) | CA1093280A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4642133A (en) * | 1980-08-20 | 1987-02-10 | Outokumpu Oy | Process for chlorinating volatilization of metals which are present in oxidic iron ores or concentrates |
| CN104152688A (en) * | 2014-08-21 | 2014-11-19 | 营口东吉科技（集团）有限公司 | Quality improving and impurity reducing method of low-grade magnesite |
| CN112094106A (en) * | 2020-08-19 | 2020-12-18 | 辽宁东和新材料股份有限公司 | Preparation method of large-crystal magnesia with low silicon dioxide content |
-
1977
- 1977-10-07 CA CA288,501A patent/CA1093280A/en not_active Expired
- 1977-10-19 AT AT747477A patent/AT356060B/en not_active IP Right Cessation
- 1977-10-20 BR BR7707023A patent/BR7707023A/en unknown
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4642133A (en) * | 1980-08-20 | 1987-02-10 | Outokumpu Oy | Process for chlorinating volatilization of metals which are present in oxidic iron ores or concentrates |
| CN104152688A (en) * | 2014-08-21 | 2014-11-19 | 营口东吉科技（集团）有限公司 | Quality improving and impurity reducing method of low-grade magnesite |
| CN112094106A (en) * | 2020-08-19 | 2020-12-18 | 辽宁东和新材料股份有限公司 | Preparation method of large-crystal magnesia with low silicon dioxide content |
Also Published As
| Publication number | Publication date |
|---|---|
| BR7707023A (en) | 1978-08-15 |
| ATA747477A (en) | 1979-09-15 |
| AT356060B (en) | 1980-04-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |