CA1133447A - Method for processing solid raw materials such as minerals and ores, more particularly spathic magnesite ore - Google Patents
Method for processing solid raw materials such as minerals and ores, more particularly spathic magnesite oreInfo
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- CA1133447A CA1133447A CA341,983A CA341983A CA1133447A CA 1133447 A CA1133447 A CA 1133447A CA 341983 A CA341983 A CA 341983A CA 1133447 A CA1133447 A CA 1133447A
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- grain
- magnesite
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03B—SEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS
- B03B1/00—Conditioning for facilitating separation by altering physical properties of the matter to be treated
- B03B1/02—Preparatory heating
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B1/00—Preliminary treatment of ores or scrap
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- Environmental & Geological Engineering (AREA)
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- Organic Chemistry (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
Abstract of the Disclosure A method of beneficiating spathic magnesite ore depends upon a special characteristic thereof that has been realized, namely that it decrepitates or disintegrates into grains when heated to temperatures below its chemical conversion reaction temperatures whereas its common impurities do not.
The ore is therefor heated to such a temperature below its calcining temperature and the resultant material graded according to grain size when the finer grain fraction will be enriched with the magnesite and the coarser grain fraction will be enriched with the usual calcite and/or dolomite impurities.
Depending upon the degree of purity required one would select smaller and smaller grain size fractions for increasing purity and, for example, one would then discard fractions of grain sizes greater than 5 mm, 3mm or 1 mm as waste. The separated finer grain size fraction can be subjected to a second decrepitating step.
The ore is therefor heated to such a temperature below its calcining temperature and the resultant material graded according to grain size when the finer grain fraction will be enriched with the magnesite and the coarser grain fraction will be enriched with the usual calcite and/or dolomite impurities.
Depending upon the degree of purity required one would select smaller and smaller grain size fractions for increasing purity and, for example, one would then discard fractions of grain sizes greater than 5 mm, 3mm or 1 mm as waste. The separated finer grain size fraction can be subjected to a second decrepitating step.
Description
1~33447 METHOD FOR PROCESSING SOLID RAW MATERIALS SUCH AS MINERALS
AND ORES, MORE PARTICULARLY SPATHIC MAGNESITE ORE
Eield of the Invention This invention relates to a method for processing solid raw materials such as minerals, ores, or the like, the constit-uents of which are of different chemical composition and/or structure. More particularly the invention relates to a method for beneficiating spathic magnesite ore, by separation into individual constituents, especially for the purpose of enrich~ng a main constituent by separating out the remaining constituent, or constituents, as an impurity.
Review of the Prior Art Since magnesite was first used, in the middle of the second half of the l9th century (German Patent 5,869), as a refractory raw material for basic furnace linings in the steel industry, this mineral has belonged, with calcite and dolomite which are mineralogically related, to the technically important carbonates, especially in the refractories industry where it is in universal use, although mainly for lining steel-and cement-making equipment. The annual world production of magnesite, including salt-water magnesite tabout 2 million tons per annum), is about 7 million tons. In contrast to dolomite and calcite, which can be found practially everywhere in any desired amounts and qualities, workable deposits of magnesite are few. In addition to this, very high-purity material is required since, in its main field of application, namely the refractories industry, relatively small amounts of impurities render the material useless, as will be explained hereinafter in greater detail. There is thus a considerable amount of processing and beneficiating in the magnesite-treatment industry.
As a result of a difference in origin, raw magnesite appears in two types of deposit, namely as a crypto-crystalline or gel-magnesite and as a crystalline or spathic magnesite.
Gel-magnesite is obtained as a product of metamorphic conversion of ultra-basic rock, mainly serpentiniteS~ by reaction with ascendent C02-containing solutions. The pattern of this conversion is given, in a simplified form, in the following equation:
Mg3 t(oH)4 Si205~ + 3 C02 --~3 Mg C03 + 2 SiO2 + 2 H20 Serpentine Magnesite As may be gathered from the above reaction equation, the main impurity in this gel-magnesite, which is mainly lenticular or appears in veins of widely varying thickness, is SiO2 in the form of quartz or chalcedony, occurring in edge areas, veins, or finely divided, depending upon the layout of the deposit.
In contrast to gel-magnesite, which has a dense appear-ance, spathic magnesite is mainly coarsely crystalline and of metasomatic origin. It is formed from dolomites, or dolomitic lime, by the addition of magnesium and the simultaneous elimination of calcium. Depending upon the completeness of the expulsion and exchange reactions, the main impurities in this magnesite are dolomite and calcite, together with talc, mica, chlorite, quartz and pyrite, and the weathering product limonite thereof.
~33447 Since the middle of the 1930's, sea-water has been used as a source of MgO, in addition to the natural deposits of gel- and spathic-magnesite, Mg (OH) being recovered by ion-exchange reaction (Mg2+ from sea-water for Ca2+ from burned dolomite) and being processed into MgO. The impurities eliminated in this manufacturing process are different from those in natural magnesite, for example B203, and the benefic-iating problems are therefore different from those encountered with gel-magnesite and especially with spathic magnesite.
As already indicated hereinbefore, the value of a magnesite to the refractories industry is dependent mainly upon the amount and composition of its impurities, since these diminish the refractory properties to a greater or lesser extent.
The following Table 1 shows the main compounds which can be formed from the impurities, with their melting and decomposition points, in comparison with pure periclase.
. ~ ~
TABLE I
Melting and decomposition points of minerals formed from magnesite impurities, as compared with periclase Mineral Chemical Melting point C
Composition (Decomp. point) Periclase MgO 2~800 Spinell MgO Al23 2~135 Dicalcium silicate 2 CaO SiO2 2~130 Forsterite 2 MgO SiO2 1,890 Magnesium ferrite MgO Fe23 1~750 Montecellite CaO MgO SiO2 1~500 Merwinite 3 CaO MgO 2SiO2 (1~575) Dicalcium ferrite 2 CaO Fe203 1~436 Brownmillerite 4 CaO Al23 Fe23 lt415 Tricalcium silicate 3 CaO SiO2 (1,900) Because of the detrimental effect of even small amounts of impurities upon the refractory properties of magnesite, no effort is spared to reduce the impurities in raw magnesite to an acceptable minimum, in order to meet the requirements for a modern basic refractory material. Some of the methods used are simple and traditional, some are highly sophisiticated and costly. They may be separated roughly into physical and chemical processes (for a comprehensive survey see Viktor Weiss, "Die Aufbereitung von Magnesit", Handbuch der Keramik, Verlag Schmid GmbH, Freiburg 1968). The following are the most important physical proces~es: hand sifting, sorting-classification, magnetic separation, sorting by gravity, flotation, and processes invo~ing light and laser optics.
Chemical processes are used far less frequently, and some even involve dissolving all of the material to be processed and re-covering the MgO by a kind of separating procedure. These process-es are therefore for use in large-scale production of high-purity MgO, as described, for example, in German application document No:
21 07 844, and are therefore not treatments in the actual meanlng of the word.
Depending upon the degree of intergrowth and structural configuration, silicate impurities and accompanying minerals containing iron are relatively easily separated from raw magnesite, although some of the processes used (flotation) are very cost-intensive. It is much more difficult, and sometimes impossible, to separate the carbonate impurities such as calcite and dolomite, since their material similarity to magnesite is so pronounced that only properties very difficult to distinguish can be used as a basis for processing, as shown in Table II below:
TABLE II
PROPERTIES OF MAGNESITE, DOLOMITE AND CALCITE
Magnesite Dolomite Calcite Chemical composition Mg C03 CaMg(C3)2 CaC03 Crystal structure trigonal trigonal trigonal Cleavability (1011) (1011) (1011) Mohs hardness 4-4,5 3,5 - 4 3 Density (g/cm3) 2,95-3,05 2.85-2,95 2,72 Magn. su~ceptibility (x 10 cgs) x 2-5 1 -0,35 x Handbuch der Keramik, page 6, Verlag Schmid, Freiburg 1968.
Problems similar to those described above, in connection with the removal of impurities from raw magnesite, also arise with other raw materials, especially minerals and ores which, prior to further processing must be largely freed from accompanying sub-stances, either because such substances act, as impurities, toimpede further direct processing, or because they make it difficult, or even impossible, to achieve reaction or conversion, for example, of ores in arc- or blast-furnaces.
Definition of the Invention It is therefore the purpose of the invention to provide a method of the type mentioned at the beginning hereof, which will ma~e it possible to proce~s solid raw materials economically by grading, especially minerals and ores such as spathic magnesite ore.
According to the invention there is provided a method for beneficiating spathic magnesite ore which can be decrepitated by separating therefrom the calcite and/or dolomite, characterized by the steps of:
heating the spathic magnesite ore to a temperature sufficient to decrepitate it and enrich it with a fine-grain fraction or fractions, the said temPerature beinq between 400 and 1100C, below the calcining temperature of magnesium carbonate and above the calcining temperature of magnesite respectively;
after decrepitation grading the spathic magnesite ore into at least two grain-size fractions, the coarser fraction being enriched with calcite and/or dolomite and the finer fraction with magnesite;
and subsequently separating the said grain-size fractions.
Decrepitation, as is known, means explosive grain disintegration at temperatures below chemical-conversion reaction, which goes far beyond brittleness or cracking of the material and leads spontaneously, i.e. without external assistance, if the increased temperature is disregarded, to great changes from the initial grain-size in the direction of finer grains.
After the grain-size fractions have been separated, provision may be made for at least the finest grain-size fraction to be subjected to a further decrepitating step, followed by grading and separating. Furthermore, the method according to the invention may be conducted in such a manner that the raw material is heated to a temperature sufficient to cause decrepitation of the main constituent, but not of the remaining constitutent(s) which is to be removed as an impurity.
Provision may be made for the magnesite-enriched grain fraction(s) to be separated, after the heat-treatment, at a grain-size below the intergrowth grain-size of the carbonate impurities calcite and/or dolomite to be separated.
Separation of the grain-size fractions may be carried out by screening, especially dry-screening and/or by air-separation, the temperature of the material, during separation,being preferably between 20 and 700C. In the treatment of spathic magnesite ore, depending upon the degree of purity required, grain-size fractions above 5,3, or 1 mm may be discarded as waste, while the finer fractions are recovered as processed treated product. It is also possible to combine a plurality of grain-size fractions into processed treated magnesite of different qualitites.
It will be seen that the invention is based upon the 1133~'~7 surprising knowledge that it is possible in the case of spathic magnesite ore, to use decrepitation occurring during heat-treatment for a special thermo-mechanical separation process which, in the case of spathic magnesite, produces separation of calcite and/or dolomite. This decrepitation behaviour, which has long been known to occur in many minerals, for example in heavy spar barite has hitherto not been observed in spathic magnesite, for example and has therefore not been described in the relevant technical literature. This so-far largely neglected property of spathic magnesite is of particular interest and value, since it provides a clear distinction from dolomite and calcite which can be used according to the invention. In spite of their often spathiform formation, dolomite and calcite do not behave in this way, and this fact can be made use of in processing lS teclmiques.
In a method according to the invention, use is made of the magnesite-specific property described above, by heating a grain-size of raw magnesite adapted to the furnace unit, but not too far below the intergrowth grain-size, in a heat-treatment unit (e.g. a multi-stage furnace, rotary kiln, fluidized-bed reactor, or suspension-type heat-exchanger), to a temperature of between 400 and 1100C, preferably between 400C and the calcining temperature of magnesium carbonate, or between 700 and 900C, for not less than 45 minutes, preferably between 60 and 90 minutes. This is then separated into various grain-size fractions entirely by screening or sifting. This produces enrichment of the non-decrepitating carbonates and impurities in the coarser fractions, so that most of these can be separated.
~33447 In the case of silicate impurities, SiO2 enrichment is obtained, also in the coarser fractions, by means of stratified silicates (e.g. chlorite) and coarser quartz inclusions, since here again, the heat-treatment produces no qrain disintegration. Thus by applying the method according to the invention to spathic magnesite ore, it is possible in many cases to obtain a reduction in the SiO2 content of the processed magnesite, corresponding to a reduction in CaO.
The particular advantage of the method according to the invention, as compared with conventional grading and beneficiating processes, is to he perceived in that, in the case of spathic magnesite ore, methods directed specifically to carbonate impurities in raw magnesite may be integrated, without any difficulty, into the predetermined flow of material in a magnesite-processing installation, and may thus be incorporated very economically into existing production lines. The processing of materials to be treated according to the invention, especially spathic magnesite ore, is, of course, also facilitated by the fact that decrepitation results in considerable breaking-down of the material, especially of spathic magnesite ore.
The invention is explained in more detail hereinafter with the aid of several examples.
_ g _ Decrepitating spathic magnesite of the following composition:
CaO 5,93 SiO2 0,55 % by weight
AND ORES, MORE PARTICULARLY SPATHIC MAGNESITE ORE
Eield of the Invention This invention relates to a method for processing solid raw materials such as minerals, ores, or the like, the constit-uents of which are of different chemical composition and/or structure. More particularly the invention relates to a method for beneficiating spathic magnesite ore, by separation into individual constituents, especially for the purpose of enrich~ng a main constituent by separating out the remaining constituent, or constituents, as an impurity.
Review of the Prior Art Since magnesite was first used, in the middle of the second half of the l9th century (German Patent 5,869), as a refractory raw material for basic furnace linings in the steel industry, this mineral has belonged, with calcite and dolomite which are mineralogically related, to the technically important carbonates, especially in the refractories industry where it is in universal use, although mainly for lining steel-and cement-making equipment. The annual world production of magnesite, including salt-water magnesite tabout 2 million tons per annum), is about 7 million tons. In contrast to dolomite and calcite, which can be found practially everywhere in any desired amounts and qualities, workable deposits of magnesite are few. In addition to this, very high-purity material is required since, in its main field of application, namely the refractories industry, relatively small amounts of impurities render the material useless, as will be explained hereinafter in greater detail. There is thus a considerable amount of processing and beneficiating in the magnesite-treatment industry.
As a result of a difference in origin, raw magnesite appears in two types of deposit, namely as a crypto-crystalline or gel-magnesite and as a crystalline or spathic magnesite.
Gel-magnesite is obtained as a product of metamorphic conversion of ultra-basic rock, mainly serpentiniteS~ by reaction with ascendent C02-containing solutions. The pattern of this conversion is given, in a simplified form, in the following equation:
Mg3 t(oH)4 Si205~ + 3 C02 --~3 Mg C03 + 2 SiO2 + 2 H20 Serpentine Magnesite As may be gathered from the above reaction equation, the main impurity in this gel-magnesite, which is mainly lenticular or appears in veins of widely varying thickness, is SiO2 in the form of quartz or chalcedony, occurring in edge areas, veins, or finely divided, depending upon the layout of the deposit.
In contrast to gel-magnesite, which has a dense appear-ance, spathic magnesite is mainly coarsely crystalline and of metasomatic origin. It is formed from dolomites, or dolomitic lime, by the addition of magnesium and the simultaneous elimination of calcium. Depending upon the completeness of the expulsion and exchange reactions, the main impurities in this magnesite are dolomite and calcite, together with talc, mica, chlorite, quartz and pyrite, and the weathering product limonite thereof.
~33447 Since the middle of the 1930's, sea-water has been used as a source of MgO, in addition to the natural deposits of gel- and spathic-magnesite, Mg (OH) being recovered by ion-exchange reaction (Mg2+ from sea-water for Ca2+ from burned dolomite) and being processed into MgO. The impurities eliminated in this manufacturing process are different from those in natural magnesite, for example B203, and the benefic-iating problems are therefore different from those encountered with gel-magnesite and especially with spathic magnesite.
As already indicated hereinbefore, the value of a magnesite to the refractories industry is dependent mainly upon the amount and composition of its impurities, since these diminish the refractory properties to a greater or lesser extent.
The following Table 1 shows the main compounds which can be formed from the impurities, with their melting and decomposition points, in comparison with pure periclase.
. ~ ~
TABLE I
Melting and decomposition points of minerals formed from magnesite impurities, as compared with periclase Mineral Chemical Melting point C
Composition (Decomp. point) Periclase MgO 2~800 Spinell MgO Al23 2~135 Dicalcium silicate 2 CaO SiO2 2~130 Forsterite 2 MgO SiO2 1,890 Magnesium ferrite MgO Fe23 1~750 Montecellite CaO MgO SiO2 1~500 Merwinite 3 CaO MgO 2SiO2 (1~575) Dicalcium ferrite 2 CaO Fe203 1~436 Brownmillerite 4 CaO Al23 Fe23 lt415 Tricalcium silicate 3 CaO SiO2 (1,900) Because of the detrimental effect of even small amounts of impurities upon the refractory properties of magnesite, no effort is spared to reduce the impurities in raw magnesite to an acceptable minimum, in order to meet the requirements for a modern basic refractory material. Some of the methods used are simple and traditional, some are highly sophisiticated and costly. They may be separated roughly into physical and chemical processes (for a comprehensive survey see Viktor Weiss, "Die Aufbereitung von Magnesit", Handbuch der Keramik, Verlag Schmid GmbH, Freiburg 1968). The following are the most important physical proces~es: hand sifting, sorting-classification, magnetic separation, sorting by gravity, flotation, and processes invo~ing light and laser optics.
Chemical processes are used far less frequently, and some even involve dissolving all of the material to be processed and re-covering the MgO by a kind of separating procedure. These process-es are therefore for use in large-scale production of high-purity MgO, as described, for example, in German application document No:
21 07 844, and are therefore not treatments in the actual meanlng of the word.
Depending upon the degree of intergrowth and structural configuration, silicate impurities and accompanying minerals containing iron are relatively easily separated from raw magnesite, although some of the processes used (flotation) are very cost-intensive. It is much more difficult, and sometimes impossible, to separate the carbonate impurities such as calcite and dolomite, since their material similarity to magnesite is so pronounced that only properties very difficult to distinguish can be used as a basis for processing, as shown in Table II below:
TABLE II
PROPERTIES OF MAGNESITE, DOLOMITE AND CALCITE
Magnesite Dolomite Calcite Chemical composition Mg C03 CaMg(C3)2 CaC03 Crystal structure trigonal trigonal trigonal Cleavability (1011) (1011) (1011) Mohs hardness 4-4,5 3,5 - 4 3 Density (g/cm3) 2,95-3,05 2.85-2,95 2,72 Magn. su~ceptibility (x 10 cgs) x 2-5 1 -0,35 x Handbuch der Keramik, page 6, Verlag Schmid, Freiburg 1968.
Problems similar to those described above, in connection with the removal of impurities from raw magnesite, also arise with other raw materials, especially minerals and ores which, prior to further processing must be largely freed from accompanying sub-stances, either because such substances act, as impurities, toimpede further direct processing, or because they make it difficult, or even impossible, to achieve reaction or conversion, for example, of ores in arc- or blast-furnaces.
Definition of the Invention It is therefore the purpose of the invention to provide a method of the type mentioned at the beginning hereof, which will ma~e it possible to proce~s solid raw materials economically by grading, especially minerals and ores such as spathic magnesite ore.
According to the invention there is provided a method for beneficiating spathic magnesite ore which can be decrepitated by separating therefrom the calcite and/or dolomite, characterized by the steps of:
heating the spathic magnesite ore to a temperature sufficient to decrepitate it and enrich it with a fine-grain fraction or fractions, the said temPerature beinq between 400 and 1100C, below the calcining temperature of magnesium carbonate and above the calcining temperature of magnesite respectively;
after decrepitation grading the spathic magnesite ore into at least two grain-size fractions, the coarser fraction being enriched with calcite and/or dolomite and the finer fraction with magnesite;
and subsequently separating the said grain-size fractions.
Decrepitation, as is known, means explosive grain disintegration at temperatures below chemical-conversion reaction, which goes far beyond brittleness or cracking of the material and leads spontaneously, i.e. without external assistance, if the increased temperature is disregarded, to great changes from the initial grain-size in the direction of finer grains.
After the grain-size fractions have been separated, provision may be made for at least the finest grain-size fraction to be subjected to a further decrepitating step, followed by grading and separating. Furthermore, the method according to the invention may be conducted in such a manner that the raw material is heated to a temperature sufficient to cause decrepitation of the main constituent, but not of the remaining constitutent(s) which is to be removed as an impurity.
Provision may be made for the magnesite-enriched grain fraction(s) to be separated, after the heat-treatment, at a grain-size below the intergrowth grain-size of the carbonate impurities calcite and/or dolomite to be separated.
Separation of the grain-size fractions may be carried out by screening, especially dry-screening and/or by air-separation, the temperature of the material, during separation,being preferably between 20 and 700C. In the treatment of spathic magnesite ore, depending upon the degree of purity required, grain-size fractions above 5,3, or 1 mm may be discarded as waste, while the finer fractions are recovered as processed treated product. It is also possible to combine a plurality of grain-size fractions into processed treated magnesite of different qualitites.
It will be seen that the invention is based upon the 1133~'~7 surprising knowledge that it is possible in the case of spathic magnesite ore, to use decrepitation occurring during heat-treatment for a special thermo-mechanical separation process which, in the case of spathic magnesite, produces separation of calcite and/or dolomite. This decrepitation behaviour, which has long been known to occur in many minerals, for example in heavy spar barite has hitherto not been observed in spathic magnesite, for example and has therefore not been described in the relevant technical literature. This so-far largely neglected property of spathic magnesite is of particular interest and value, since it provides a clear distinction from dolomite and calcite which can be used according to the invention. In spite of their often spathiform formation, dolomite and calcite do not behave in this way, and this fact can be made use of in processing lS teclmiques.
In a method according to the invention, use is made of the magnesite-specific property described above, by heating a grain-size of raw magnesite adapted to the furnace unit, but not too far below the intergrowth grain-size, in a heat-treatment unit (e.g. a multi-stage furnace, rotary kiln, fluidized-bed reactor, or suspension-type heat-exchanger), to a temperature of between 400 and 1100C, preferably between 400C and the calcining temperature of magnesium carbonate, or between 700 and 900C, for not less than 45 minutes, preferably between 60 and 90 minutes. This is then separated into various grain-size fractions entirely by screening or sifting. This produces enrichment of the non-decrepitating carbonates and impurities in the coarser fractions, so that most of these can be separated.
~33447 In the case of silicate impurities, SiO2 enrichment is obtained, also in the coarser fractions, by means of stratified silicates (e.g. chlorite) and coarser quartz inclusions, since here again, the heat-treatment produces no qrain disintegration. Thus by applying the method according to the invention to spathic magnesite ore, it is possible in many cases to obtain a reduction in the SiO2 content of the processed magnesite, corresponding to a reduction in CaO.
The particular advantage of the method according to the invention, as compared with conventional grading and beneficiating processes, is to he perceived in that, in the case of spathic magnesite ore, methods directed specifically to carbonate impurities in raw magnesite may be integrated, without any difficulty, into the predetermined flow of material in a magnesite-processing installation, and may thus be incorporated very economically into existing production lines. The processing of materials to be treated according to the invention, especially spathic magnesite ore, is, of course, also facilitated by the fact that decrepitation results in considerable breaking-down of the material, especially of spathic magnesite ore.
The invention is explained in more detail hereinafter with the aid of several examples.
_ g _ Decrepitating spathic magnesite of the following composition:
CaO 5,93 SiO2 0,55 % by weight
2 3 0,16 (calculated with no burning loss) MgO 92,83 was treated in a laboratory electric-furnace at 850C for 120 min.
Mineralogically detectable impurities were dolomite, calcite, chlorite and pyrite or limonite.
TABLE I I I
Comparison of grain-size at charge and discharge.
Grain-size (mm) Charge (% by weight) Discharge ~% by weight) ~ 6 1,2 6-5 8,6 1,7 5-3 53,2 7,4
Mineralogically detectable impurities were dolomite, calcite, chlorite and pyrite or limonite.
TABLE I I I
Comparison of grain-size at charge and discharge.
Grain-size (mm) Charge (% by weight) Discharge ~% by weight) ~ 6 1,2 6-5 8,6 1,7 5-3 53,2 7,4
3-2 22,7 11,7 2-1 13,5 18,4 1-0,5 0,8 17,5 0,5-0,2 - 22,4 0,2-0,1 - 15,2 0,1-0 - 5,7 Table IV below shows CaO enrichment or impoverishment in individual grain fractions.
1133~47 TABLE IV
Analytical data on grain fractions of spathic magnesite processed according to the invention.
Fraction (mm) SiO2 A123 Fe2 3 CaO MgO % by Weight 6-5 4,46 0,23 0,45 21,73 73,00 5-2 2,06 0,61 0,38 12,88 83,97 3-2 0,51 0,14 0,38 9~21 89~69 2-1 0.51 0~17 0,51 5~87 92,85 1-0,5 0,28 0,18 0,42 3.85 95~20 0,5-0,2 0,22 0,12 0,43 3~91 95,25 0,2-0~1 0,34 0,12 0,40 4,34 97,75 0,1-0 0,27 0,17 0,44 4,23 94,84 Disregarding the 6-5 mm grain-size fraction discharged, i.e. 1.7% by weight, this produced 98.3% of two qualities of processed magnesite. The CaO content in quality I had been reduced by 32% in comparison with the initial material, as may be gathered from Table V below:
TABLE V
Qualities obtainable from the grain fractions in Table III
F~actio~
Yield 22 3 2 3CaO MgO
A' Quality 1 ~l mm 60,8% 0,28 0,14 0,42 4,04 95,07 Quality 2 5-1 mm 37,5% Or82 0,24 0,44 8,29 90~11 Waste 6-5 mm 1,7% 4,46 0,23 0,4521,73 73.00 1~33447 Example 2 A spathic magnesite containing dolomite and calcite and, as secondary additional constituents, chlorite and pyrite or limonite, and of the following composition:
CaO 5,82 SiO2 1.15 A1230,18 % by weight Fe230,79 (calculated with no burning loss) ~qgo 91,96 10 was calcined by the method according to the invention, in a multi-stage furnace, at 900C. Additional mechanical stressing of the material inside the furnace produced a reduction of the initial grain-size surpassing that produced by decrepitation, as shown in Table VI below:
TABLE VI
- Comparison of grain-size at charge and discharge.
, (mm) ChargeDischarge (% by weight) A ~ 6 0,6 6-5 7,4 1,08 5-3 S5,0 1,12 3-2 24,1 2,30 2-1 11,6 13,00 1-0,5 1v3 23,00 0,5-0,2 - 21,00 0,2-0,1 - 21,50 0~1-0 - 17,00 1~33447 Table VII shows CaO enrichment or impverishment in the individual fractions:
TABLE VII
Analytical data on individual grain fractions of spathic 5 magnesite processed according to the invention.
Fraction (mm) SiO2 A1203 Fe203 CaO MgO (~ by weight) 6-5 14,68 0,79 0,27 38,12 45,98 5-3 8,68 0,34 0,34 37,92 52,62 3-2 7,04 0,36 0,32 26,71 65,41 2-1 2,97 0,26 0,28 9,40 86,99 1-0,50,74 0,16 0,80 5~30 92,94 0,5-0,20,51 0,18 1,01 3,59 94,64 0,2-0,10,51 0,12 0,81 3,67 94,83 0,1-0 0.64 0,16 0,98 4,43 93,73 A spathic magnesite which was of high grade in the raw state and contained only minimal amounts of impurities in the form of dolomite, calcite, chlorite, and pyrite, was treated at 880C in a fluidized-bed reactor and thereby processed according to the invention.
The composition of the raw magnesite was as follows:
CaO 2,02 SiO2 0-74 A123 0,36 % by weight Fe23 0,71 MgO 95,96 il33~ ~7 The grain-size analyses given in Table VIII below indicate that effective decrepitation takes place even in the fine range:
TABLE VIII
Comparison of grain-size at charge and discharge (mm) Charge Discharge (% by weight) ~ 0.1 20 10 0,1-0,06 25 13 ~ 0,06 55 77 Analytical data on the above three fractions are compared in Table IX below:
TABLE IX
Analytical data on three grain fractions of spathic magnesite processed according to the invention Fraction (mm) SiO2 A123 Fe203 CaO MgO (% by weight) ~ 0~1 1.60 0,64 0,63 4,86 92,04 0,1-0,06 0,80 0,30 0~62 1,87 96,13 ~ 0.06 0,62 0,34 0,74 1.68 96~44 The above analytical data show that in spite of the very low CaO content of the raw material, this was clearly reduced still further by the method according to the invention.
11334 *7 EX~MPLE 4 A coarsely crystalline spathic magnesite, containing dolomite, calcite and chlorite impurities, and of the following composition:
CaO 4,94 SiO2 0,64 A1230,21 ~ by weight Fe230,53 (calculated with no burning loss) MgO 93,56 was treated by the method according to the invention, in a laboratory electric furnace, for 2 hours, at 600C, i.e. below ~ 1 J~carb 0~5 C/f~f or/
A the-dec~rb~ g temperature. The grain-size reduction produced by decrepitation is shown in Table X.
TABLE X
Comparison of grain-size at charge and discharge (mm) ChargeDischarge (% by weight) - 6-5 5 1,5 5-3 32 10,1 3-2 30 12,2 2-1 33 18,2 1-0,5 - 18,2 0,5-0,2 - 24,7 0,2-0,1 - 9,7 0,1-0 - 5,4 Table XI shows the increase or decrease in CaO content in the individual fractions:
TABLE XI
Analytieal data on individual yrain fractions of spathie magnesite by the method according to the invention Fraetion (mm) SiO2 A123 Fe23 CaO MgO (% by weight) 6-5 2,77 0,170,39 15,39 81,19 5-3 1,39 0,310,62 11,74 85,83 3-2 1,22 0,310,48 6,75 91,15 2-1 0,71 0,290,78 ~,85 93,26 1-0,5 0,40 0,180,45 2,96 95,90 0,5-0,2 0~29 0,120,43 3,27 95,76 0,2-0,1 0,29 0,190,48 3,16 95,76 0,1-0 0,28 0,140,42 3,04 96,03 An 88.4% yield makes it possible to produee two qualities. Quality 1 has 36% less CaO than the initial material;
waste, estimated at 11,6% may be improved by a seeond treatment:
TABLE XII
Qualities obtainable rom the grain fraetions in Table XI
Fraetion Yield SiO2 A1203 Fe203 CaO MgO
Quality 1 ~ 1 mm 58,0% 0,33 0,15 0,44 3,13 95,83 Quality 2 3-1 mm 30,4% 0,92 0,29 0,66 5,61 92,41 Waste 6-3 mm 11,6% 1,53 0,29 0,59 12,21 85,23
1133~47 TABLE IV
Analytical data on grain fractions of spathic magnesite processed according to the invention.
Fraction (mm) SiO2 A123 Fe2 3 CaO MgO % by Weight 6-5 4,46 0,23 0,45 21,73 73,00 5-2 2,06 0,61 0,38 12,88 83,97 3-2 0,51 0,14 0,38 9~21 89~69 2-1 0.51 0~17 0,51 5~87 92,85 1-0,5 0,28 0,18 0,42 3.85 95~20 0,5-0,2 0,22 0,12 0,43 3~91 95,25 0,2-0~1 0,34 0,12 0,40 4,34 97,75 0,1-0 0,27 0,17 0,44 4,23 94,84 Disregarding the 6-5 mm grain-size fraction discharged, i.e. 1.7% by weight, this produced 98.3% of two qualities of processed magnesite. The CaO content in quality I had been reduced by 32% in comparison with the initial material, as may be gathered from Table V below:
TABLE V
Qualities obtainable from the grain fractions in Table III
F~actio~
Yield 22 3 2 3CaO MgO
A' Quality 1 ~l mm 60,8% 0,28 0,14 0,42 4,04 95,07 Quality 2 5-1 mm 37,5% Or82 0,24 0,44 8,29 90~11 Waste 6-5 mm 1,7% 4,46 0,23 0,4521,73 73.00 1~33447 Example 2 A spathic magnesite containing dolomite and calcite and, as secondary additional constituents, chlorite and pyrite or limonite, and of the following composition:
CaO 5,82 SiO2 1.15 A1230,18 % by weight Fe230,79 (calculated with no burning loss) ~qgo 91,96 10 was calcined by the method according to the invention, in a multi-stage furnace, at 900C. Additional mechanical stressing of the material inside the furnace produced a reduction of the initial grain-size surpassing that produced by decrepitation, as shown in Table VI below:
TABLE VI
- Comparison of grain-size at charge and discharge.
, (mm) ChargeDischarge (% by weight) A ~ 6 0,6 6-5 7,4 1,08 5-3 S5,0 1,12 3-2 24,1 2,30 2-1 11,6 13,00 1-0,5 1v3 23,00 0,5-0,2 - 21,00 0,2-0,1 - 21,50 0~1-0 - 17,00 1~33447 Table VII shows CaO enrichment or impverishment in the individual fractions:
TABLE VII
Analytical data on individual grain fractions of spathic 5 magnesite processed according to the invention.
Fraction (mm) SiO2 A1203 Fe203 CaO MgO (~ by weight) 6-5 14,68 0,79 0,27 38,12 45,98 5-3 8,68 0,34 0,34 37,92 52,62 3-2 7,04 0,36 0,32 26,71 65,41 2-1 2,97 0,26 0,28 9,40 86,99 1-0,50,74 0,16 0,80 5~30 92,94 0,5-0,20,51 0,18 1,01 3,59 94,64 0,2-0,10,51 0,12 0,81 3,67 94,83 0,1-0 0.64 0,16 0,98 4,43 93,73 A spathic magnesite which was of high grade in the raw state and contained only minimal amounts of impurities in the form of dolomite, calcite, chlorite, and pyrite, was treated at 880C in a fluidized-bed reactor and thereby processed according to the invention.
The composition of the raw magnesite was as follows:
CaO 2,02 SiO2 0-74 A123 0,36 % by weight Fe23 0,71 MgO 95,96 il33~ ~7 The grain-size analyses given in Table VIII below indicate that effective decrepitation takes place even in the fine range:
TABLE VIII
Comparison of grain-size at charge and discharge (mm) Charge Discharge (% by weight) ~ 0.1 20 10 0,1-0,06 25 13 ~ 0,06 55 77 Analytical data on the above three fractions are compared in Table IX below:
TABLE IX
Analytical data on three grain fractions of spathic magnesite processed according to the invention Fraction (mm) SiO2 A123 Fe203 CaO MgO (% by weight) ~ 0~1 1.60 0,64 0,63 4,86 92,04 0,1-0,06 0,80 0,30 0~62 1,87 96,13 ~ 0.06 0,62 0,34 0,74 1.68 96~44 The above analytical data show that in spite of the very low CaO content of the raw material, this was clearly reduced still further by the method according to the invention.
11334 *7 EX~MPLE 4 A coarsely crystalline spathic magnesite, containing dolomite, calcite and chlorite impurities, and of the following composition:
CaO 4,94 SiO2 0,64 A1230,21 ~ by weight Fe230,53 (calculated with no burning loss) MgO 93,56 was treated by the method according to the invention, in a laboratory electric furnace, for 2 hours, at 600C, i.e. below ~ 1 J~carb 0~5 C/f~f or/
A the-dec~rb~ g temperature. The grain-size reduction produced by decrepitation is shown in Table X.
TABLE X
Comparison of grain-size at charge and discharge (mm) ChargeDischarge (% by weight) - 6-5 5 1,5 5-3 32 10,1 3-2 30 12,2 2-1 33 18,2 1-0,5 - 18,2 0,5-0,2 - 24,7 0,2-0,1 - 9,7 0,1-0 - 5,4 Table XI shows the increase or decrease in CaO content in the individual fractions:
TABLE XI
Analytieal data on individual yrain fractions of spathie magnesite by the method according to the invention Fraetion (mm) SiO2 A123 Fe23 CaO MgO (% by weight) 6-5 2,77 0,170,39 15,39 81,19 5-3 1,39 0,310,62 11,74 85,83 3-2 1,22 0,310,48 6,75 91,15 2-1 0,71 0,290,78 ~,85 93,26 1-0,5 0,40 0,180,45 2,96 95,90 0,5-0,2 0~29 0,120,43 3,27 95,76 0,2-0,1 0,29 0,190,48 3,16 95,76 0,1-0 0,28 0,140,42 3,04 96,03 An 88.4% yield makes it possible to produee two qualities. Quality 1 has 36% less CaO than the initial material;
waste, estimated at 11,6% may be improved by a seeond treatment:
TABLE XII
Qualities obtainable rom the grain fraetions in Table XI
Fraetion Yield SiO2 A1203 Fe203 CaO MgO
Quality 1 ~ 1 mm 58,0% 0,33 0,15 0,44 3,13 95,83 Quality 2 3-1 mm 30,4% 0,92 0,29 0,66 5,61 92,41 Waste 6-3 mm 11,6% 1,53 0,29 0,59 12,21 85,23
Claims (15)
1. A method for beneficiating spathic magnesite ore which can be decrepitated by separating therefrom the calcite and/or dolomite, characterized by the steps of:
heating the spathic magnesite ore to a temperature sufficient to decrepitate it and enrich it with a fine-grain fraction or fractions, the said temperature being between 400 and 1100°C, below the calcining temperature of magnesium carbonate and above the calcining temperature of magnesite respectively;
after decrepitation grading the spathic magnesite ore into at least two grain-size fractions, the coarser fraction being enriched with calcite and/or dolomite and the finer fraction with magnesite;
and subsequently separating the said grain-size fractions.
heating the spathic magnesite ore to a temperature sufficient to decrepitate it and enrich it with a fine-grain fraction or fractions, the said temperature being between 400 and 1100°C, below the calcining temperature of magnesium carbonate and above the calcining temperature of magnesite respectively;
after decrepitation grading the spathic magnesite ore into at least two grain-size fractions, the coarser fraction being enriched with calcite and/or dolomite and the finer fraction with magnesite;
and subsequently separating the said grain-size fractions.
2. A method according to claim 1, characterized in that, after the grain-size fractions have been separated, at least the finer grain-size fraction is subjected to at least one additional decrepitation step, with subsequent grading and separating.
3. A method according to claim 1, characterized in that the treatment temperature is between 700 and 900°C.
4. A method according to claim 2, characterized in that, after the grain-size fractions have been separated, at least the finer grain-size fraction is subjected to at least one additional decrepitation step, with subsequent grading and separating.
5. A method according to any one of claims 1 to 3, characterized in that the treatment time, at the said treatment temperature, is at least 45 minutes.
6. A method according to any one of claims 1 to 3, characterized in that the treatment time, at the said treatment temperature is between 60 and 90 minutes.
7. A method according to any one of claims 1 to 3, characterized in that, after the heat-treatment, the magnesite-enriched grain fraction or fractions are separated at a grain-size below the intergrowth grain-size of the carbonate impurities, calcite and/or dolomite to be separated.
8. A method according to any one of claims 1 to 3, characterized in that the separation is carried out by screening.
9. A method according to any one of claims 1 to 3, characterized in that the separation is carried out by dry-screening.
10. A method according to any one of claims 1 to 3, characterized in that the separation is carried out by air-sifting.
11. A method according to any one of claims 1 to 3, characterized in that the separation is carried out by dry-screening, and in that the separation is carried out with the material at a temperature of between 20 and 700°C.
12. A method according to any one of claims 1 to 3, characterized in that the separation is carried out by air-sifting, and in that the separation is carried out with the material at a temperature of between 20 and 700°C.
13. A method according to any one of claims 1 to 3, characterized in that, in the separating process, a first grain-size fraction of more than 5 mm is discarded as waste, while a second grain-size fraction of up to 5 mm is obtained as a processed product.
14. A method according to any one of claims 1 to 3, characterized in that, in the separating process, a first grain-size fraction of more than 3 mm is discarded as waste, while a second grain-size fraction of up to 3 mm is obtained as a processed product.
15. A method according to any one of claims 1 to 3, characterized in that, in the separating process, a first grain-size fraction of more than 1 mm is discarded as waste, while a second grain-size fraction of up to 1 mm is obtained as a processed product.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19792925899 DE2925899B1 (en) | 1979-06-27 | 1979-06-27 | Process for benefiting decrepitable late magnetite ore |
| DEP2925899.9-24 | 1979-06-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1133447A true CA1133447A (en) | 1982-10-12 |
Family
ID=6074276
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA341,983A Expired CA1133447A (en) | 1979-06-27 | 1979-12-14 | Method for processing solid raw materials such as minerals and ores, more particularly spathic magnesite ore |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1133447A (en) |
| DE (1) | DE2925899B1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115636604A (en) * | 2022-11-09 | 2023-01-24 | 营口菱镁化工集团有限公司 | Method for preparing magnesium oxide particles from low-grade magnesite, feed additive containing magnesium oxide particles, and preparation method and application of feed additive |
-
1979
- 1979-06-27 DE DE19792925899 patent/DE2925899B1/en not_active Withdrawn
- 1979-12-14 CA CA341,983A patent/CA1133447A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115636604A (en) * | 2022-11-09 | 2023-01-24 | 营口菱镁化工集团有限公司 | Method for preparing magnesium oxide particles from low-grade magnesite, feed additive containing magnesium oxide particles, and preparation method and application of feed additive |
| CN115636604B (en) * | 2022-11-09 | 2023-06-27 | 营口菱镁化工集团有限公司 | Method for preparing magnesium oxide particles from low-grade magnesite, feed additive containing particles, and preparation method and application of feed additive |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2925899B1 (en) | 1981-01-08 |
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