CS249457B1 - Method of calcium compounds removal - Google Patents

Abstract

Mostly magnesium, magnesium-calcium oxidic or hydroxylic raw materials are removed from calcium oxide or the products of its hydration by selective deposition at 0 to 100 ° C with a solution containing at least one organic base (alkylamine, alkanolamine, najo monoethanolamine) with ammonia or ammonium hydroxide, in an amount corresponding to the desired amount the level of spillage and / or oxidized, respectively. hydroxide raw materials. The remaining magnesium oxide and / or hydration products thereof with unloaded components from the solution separates, e.g. filtration, centrifugation, generally in combination with washing and drying. The method is usually associated with early production pure CaCO3 and is suitable for production magnesium oxide or products of its hydration, any desired amount of calcium oxide.

Description

The invention relates to a process for removing calcium compounds from predominantly magnesium or magnesium-calcium oxide or hydroxide raw materials, in particular from magnesite, dolomagnesite, dolomite, calcareous dolomite or dolomitic limestone, as well as from technical magnesium oxide.

Magnesite is an important mineral raw material for the production of refractory materials and various magnesium compounds and products derived therefrom. In nature, it is usually contaminated mainly by iron, silicon and calcium compounds, reducing the possibilities for its technical use. Magnesite with a high content of calcium compounds is usually called dolomagnesite.

Dolomite is the most common rock-forming carbonate after limestone and with regard to its chemical composition / 30.4% by weight. CaO, 21.7 wt. MgO, 47.9 wt. CO 2 has an important use not only in iron and steel production, but is also an important chemical raw material for the production of magnesium, calcium and carbon dioxide compounds.

If dolomite contains up to 50 8 limestone, it is referred to as calcareous dolomite. When limestone contains up to 50% dolomite, it is often called dolomite limestone.

Among the magnesium compounds, magnesium oxide is of particular importance as an essential component of basic refractory materials in the steel industry, as well as in the production of fused magnesium oxide for the electrical industry; light and active forms of magnesia, usable in the engineering industry for the treatment of sheet metal surfaces for transformers, in the pulp and paper industry at the so-called. Magnesium bisulfite process for the production of pulp, in the rubber and plastics industry as an additive, resp. filler for rubbers and plastics, in the oil processing industry as a catalyst and catalyst carrier, in the construction industry in preparation, so-called. Sorel mortar, in the pharmaceutical industry for the preparation of neutralizers, pastes, powders and the like.

Among calcium compounds, extensive use has e.g. calcium carbonate, in particular, as a filler, additive or pigment in the plastics, rubber, dye, paper, pharmaceutical, food, chemical, malt and ceramic industries.

Magnesium oxide and calcium carbonate can be prepared from dolomite, dolomagnesite or dolomitic limestone by partial thermal decomposition to the first stage at a temperature of about 800 ° C, depending on the reaction conditions. Both compounds, however, exist in the resulting product in the form of a powder mixture from which they cannot be separated from one another by known physical processes.

Among the chemical processes, the most selective is the leaching of the magnesium oxide with ammonium carboxylate solutions, in particular the aqueous solution of ammonium formate in which the calcium carbonate does not dissolve.

Magnesium hydroxide according to U.S. Pat. AO 180 284, basic magnesium carbonate according to MS. AO 196 905 or magnesium carbonate trihydrate according to U.S. Pat.

AO 194,644 and 208,296.

Podlá čs. AO 199 323 leaching with aqueous solutions of sulphate, nitrate or ammonium chloride produces the corresponding magnesium salts which are further converted to basic magnesium carbonate or oxalate.

These compounds are intermediates in the production of magnesium oxide. Other methods of leaching magnesium oxide from calcareous dolomite are disclosed in Romanian patents 59,712 and 59,779.

Thermal decomposition of dolomite into the second stage at a temperature above 900 ° C produces a mixture of oxides containing theoretically 41.7% by weight. MgO and 58.3 wt. CaO. Nor can the two components be separated by physical processes. The method of increasing the magnesium oxide content of the product thus prepared is solved by Cs. AO 190 976. It is based on the fact that a suspension is prepared from dolomite calcite, which is treated with nitric acid or ammonium nitrate, respectively. ammonium formate or ammonium acetate and an insoluble residue is separated from the suspension.

Calcium salt solutions resulting from extraction; it can be treated by simultaneous deposition of ammonia and carbon dioxide to form pure calcium carbonate and the corresponding ammonium salt, thereby achieving recycling of the extractant in the reaction process.

In this way, calcium oxide can only be partially removed so that the product formed has a composition in the range of 26.3% CaO and 72.4% MgO to 43.0% CaO and 52.5%, depending on the annealed condition.

However, in addition to the advantages mentioned in the said certificate, the disadvantage of such a process is only a partial separation of calcium oxide from magnesium oxide, on the other hand, difficult filterability, washability and dehydration of the resulting product, complicating the manufacturing operations necessary for further processing into refractory mixtures.

The way of reducing the calcium content in magnesite or in dolomagnesite is solved by MS. AO 194 133. It is based on the fact that the magnesium raw material is fired at 800 to 1700 ° C and achieves an annealing loss of 0.3 to 5% by mass, and is treated with an aqueous nitrate solution for this calcinate adjusted to a particle size below 3C mm. % ammonium having a concentration of 3 to 50 wt. at a temperature above 15 ° C, preferably at 70 to 160 ° C, and then the solid phase is separated from the reaction mixture. .

The disadvantage of this method is only the partial separation of the calcium compounds and the necessity to operate at elevated solution temperatures under optimum conditions, as well as the fact that the leached calcium compound solution is not used in the next production cycle for leaching further feedstock.

A method is known for producing magnesium oxide and / or its hydration products from predominantly magnesium or magnesium-calcium, and therefrom mainly carbonate or toxic raw materials, which is based on the selective leaching of calcium oxide and / or calcium hydroxide with a solution of at least one organic base and at least one salt. inorganic and / or organic acids with an organic nitrogen base or bases. The disadvantage of this process is the lower technical availability of organic nitrogen bases compared to ammonia.

These disadvantages of the foregoing processes are overcome by the process of the present invention based mainly on the selective leaching of calcium oxide and its hydration products from a mixture with magnesium oxide, its hydration products and possible admixtures of insoluble silicon, iron, aluminum and other magnesium-derived compounds. raw materials.

According to the present invention, a process for removing calcium compounds from predominantly magnesium or magnesium-calcium oxide and / or hydroxide raw materials, generally associated with the manufacture; · by carrying out a thermal decomposition of the raw material in the case of the carbonate form from the obtained bile and / or oxides, the calcium oxide and / or its hydration products are selectively leached at 0 to 100 ° C with a solution containing at least one organic base together with ammonia and / or ammonium hydroxide and at least one inorganic and / or organic acid forming a water-soluble calcium salt, with at least one organic nitrogen base and ammonium hydroxide, in a total amount corresponding to the desired degree of leaching of the calcium and / or oxide fraction. respectively. the hydroxide feedstock and the remaining magnesium oxide and / or its hydration products, optionally with unleached components, are separated from the solution, e.g. by filtration, centrifugation, generally in conjunction with washing and drying.

An advantage of the process according to the invention is the technical simplicity not requiring a technically overly demanding apparatus, a low number of technological steps in the removal of calcium compounds to form relatively pure magnesium oxide and / or its hydration products, and optionally in the production of fine-grained calcium carbonate. An advantage is also the partial replacement of organic nitrogen bases with more technically accessible ammonia in the preparation of the leaching solution.

A further advantage is the possibility of utilizing a wide range of calcium-calcium starting materials, and the method can also be used for the purification of other magnesium oxide obtained, manufactured or commercially available or its hydration products. Another advantage is the fact that calcium removal is generally a closed production cycle, as the regenerated leaching solution, containing mainly salts of the used nitrogen bases, returns to be reused for selective leaching of calcium oxide and / or calcium hydroxide from another fraction of calcium-calcium fret. raw materials.

The calcium carbonate produced has a high purity (above 99% by weight) and, when used with organic acid salts in the leaching solution, does not contain any other substances which, after its thermal decomposition, remain in the resulting calcium oxide or its hydration product.

Magnesium oxide or its hydration product, depending on the leaching conditions, contains predetermined resp. required, if necessary, only trace amounts of calcium oxide, as well as admixtures of iron, silicon and other elements derived from the starting magnesite, dolomite or other magnesium or magnesium oxide, respectively. magnesium-calcium raw material.

It will be appreciated from the foregoing that for removing calcium compounds to form magnesium oxide and / or its hydration products according to the present invention (wherein the hydration product is a substance or a system of substances resulting from the interaction of water molecules with solid magnesium oxide), particularly suitable magnesium and hydrogen. the magnesium-calcium raw material is relatively pure dolomite, doomagnesite, but also magnesite and other magnesium and magnesium-calcium raw materials, mainly in the form of carbonates and oxides.

The carbonate magnesium-calcium raw materials are thermally expanded at a temperature above 900 ° C to form oxides. Conditions ensuring complete decomposition of the calcium carbonate to calcium oxide are preferred. The oxide raw materials according to the invention are, in addition to magnesium oxide, a mixture of magnesium and calcium oxides, also products of their partial or clamped hydration. However, the process according to the invention can also be used for refining magnesium oxide and / or magnesium hydroxide from calcium oxide and / or calcium hydroxide, since the product is a much purer magnesium oxide or hydroxide than used as feedstock into the process.

Suitable organic bases are, in particular, technically available nitrogen bases such as alkylamines and their derivatives, e.g. diethylamine, dibutylamine, ethylenediamine, piperidine, alkanolamines and derivatives thereof, e.g. monoethanolamine-4-aminoethanol / HOCB 2 Cl 2 NB 3, diethanolamine / HO 1 1 CH 2/4 H, 1-amino-2-propanol CH 3 CH 3 OH / CH 2 NH 3 3-diamino-2-propanol 2-CH 2 OH / CH 2 OH, 2-ethoxyethylamine CH ₃ CH ₂ OCH ₉ CH ₂ NH ₂ and i.

In addition to these individual organic nitrogen bases, mixtures thereof or mixtures thereof can also be applied. systems containing anions of several inorganic or organic acids, but suitable? most preferably, from the standpoint of production stability, only one organic nitrogen base is used in addition to ammonia and / or ammonium hydroxide.

Most suitable are organic nitrogen bases containing at least one carbon atom bonded to the carbon atom per molecule and salts thereof, e.g. monoethanolamine chloride, diethanolamine chloride, monoethanolamine formate, monoethanolamine acetate, monoethanolamine propionate and the like. Of the ammonium salts, most preferred are formate and ammonium acetate.

If the aim of the method of removing calcium compounds according to the invention is to prepare magnesium oxide or its hydration products with a defined or predetermined content of calcium component, for example calcium oxide, then less than the stoichiometric amount of leaching solution corresponding to the desired leaching degree is used. constituents of roast.

In cases where a practically complete leaching of the lime component from the roast and / or oxide feedstocks is used, at least a stoichiometric, preferably above-stoichiometric amount of leaching solution calculated on the leachable lime component content of the leached feedstock should be used.

The carbon dioxide for precipitating the calcium carbonate of the present invention can be used both as pure carbon dioxide and in admixture with air, nitrogen, carbon monoxide, methane, and other gases that do not react with the leach solution components.

In such cases, when using carbon dioxide-containing gases, this method can additionally be used as well as a method for concentrating the by-gas, e.g. carbon monoxide.

Carbon dioxide obtained by thermal decomposition of limestone, dolomite, magnesite and the like, in particular after separation of the solid particles, may also be used,

The leaching aqueous solution of the calcium salt of the corresponding acid (hydrochloric acid, nitric, formic, acetic, propionic, etc.) from insoluble magnesium oxide and / or its hydration products, as well as insoluble compounds of silicon, iron and other elements present in the starting raw material, separated by conventional methods, e.g. by filtration or centrifugation.

Of the filtrate, by treatment with carbon dioxide at a temperature of 0 to 100 ° C, most preferably at a temperature of 20 to 70 ° C, at a pH of 7 to 12, most preferably at a pH of 7.5 to 9, at a gas pressure of 0.09 to 2 MPa. at 0.1 to 0.3 MPa, easily filterable and sedatable calcium carbonate precipitates, which can be separated by conventional methods, e.g. by filtration, decantation, centrifugation and the like.

From the leaching solution used before its re-use, respectively. by recirculation, it is advisable to remove carbon dioxide, either by heating, by blowing with indifferent gas or by air, by suction, etc.

A suitable method for removing carbon dioxide from the leaching solution is also to bind it by adding calcium oxide or hydroxide. Particularly suitable is the addition of low-grade calcium oxide or hydroxide, which is omitted in various manufacturing processes.

The reactions taking place in the production of magnesium oxide and / or its hydration products, e.g. from a mixture of oxides may be represented as follows:

x MgO, y CaO f 2y Ha. B - x MgO 4 · y CaA ₂ f 2y B f 2 ^H 2 ° where HA * ⁴ monobasic acid or acid mixtures,

B «nitrogenous base or mixture of nitrogenous bases,

A salt of the acid or acids with a nitrogenous base or bases.

Separation / filtration / of undissolved MgO and admixture from the raw material yields a filtrate containing an aqueous solution of CaA 2 and 2B. That may be carbonated to precipitate pure CaCO ^ y F 2y CaA ₂ Bf yl 4-yl CO ₂ H ₂ O ^ ~ -.> Y _CaCO3 + 2y HA.B to be separated, e.g. filtration, whereby the starting HA.B salt solution is largely regenerated. In order to quantitate the precipitation of the calcium component, it is preferred to have base B in a slight excess above the stoichiometric amount corresponding to the composition of HA.B.

The method according to the invention can be carried out semi-continuously, continuously 1.

Further details of the process as well as other advantages are evident from the examples.

249957

Example 1

100 wt. parts of dolomite having a composition of 54.06 wt. CaCO ₃ , 45.34 wt.%, MgCO ₃ , 0.15 wt. % SiOg, 0.02 wt. 0.03% wt. ^F @ 2 ° 3 ^{, the thermal} Y is decomposed at 1000 ° C and then, after grinding, added in portions to 700 wt. parts of a 20 ° C warm aqueous solution containing 75 wt. parts by weight of ammonium propionate C8H4CO3NH4, 95 wt. parts by weight of C ₂ H ₅ CO _and NH ₃ C ₂ H ₅ OH monoethanolammonium propionate and 20 wt. parts of monoethanolamine H ₂ NC ₂ H ₄ OH.

After stirring for 1 hour, the solution warmed to about 35 ° C by reaction heat is filtered and the undissolved residue containing mainly magnesium oxide is washed with distilled water and dried. The yield is 20 wt. parts by weight of the product of 97.75 wt. MgO, 0.70 wt. CaO, 0.79 wt. % SiO ₂ , 0.25 wt. % Al ₂ O ₃ , 0.25 wt.

Fe ₂ O ₃ (due to annealed condition).

Calcium carbonate precipitates from the filtrate at a temperature of 30-40 ° C by the carbon dioxide introduced at pH 7.5, which is filtered off, washed with water and dried. The filtrate after separation of the calcium carbonate contains a regenerated leaching solution that can be used to leach magnesium oxide from another fraction of the dolomite roast.

Example 2

100 wt. parts of roasted dolomitic lime with a composition of 78.15 wt. CaO, 20.25 wt.

A1, O,

MgO, 0.30 wt. % SiO ₂ , 0.25 wt

% 2 ^ 3 'i / θ ^5% wt. Fe ₂ O ₃ , prepared by thermal decomposition of dolomitic limestone at 1000 ° C, after crushing, is added in portions to 1,400 wt. parts of a 25 C warm aqueous solution containing 96 wt. parts

4 '' 4 2 4 parts of magnesium formate, Mg / HCC> _2/2 and 20 wt. parts of monoethanolamine H ₂ NC ₂ H ₄ OH.

After stirring for one hour, the solution heated to about 45 ° C with a heat of reaction is filtered to give an insoluble residue containing predominantly magnesium oxide and calcium oxide, and the products of their hydration are filtered off on a filter press. The filter cake is suspended in 500 wt. in water, and supplying gaseous carbon dioxide, the leached hydrated calcium oxide is converted to calcium carbonate.

The precipitate containing predominantly partially hydrated magnesium oxide, calcium carbonate and insoluble partially hydrated silicon, aluminum and iron oxides is filtered off, washed with demineralized water and dried. The dry product, calcined at 1000 ° C, has a composition (1 wt.%): 85.10% MgO, 7.50% CaO, 1.30% SiO ₂ , 1.15% ^Al 2 ° 3 ^{and 4 '80} * FeO 3 Calcium carbonate precipitates from the filtrate at 60 ° C with carbon dioxide introduced,

which is filtered off, washed with water and dried. The filtrate after separation of calcium carbonate possible. used to leach an additional fraction of calcium oxide from the roast of dolomitic lime.

Example 3

100 wt. parts of magnesite with a composition of 45.10 Ϊ wt. MgO, 1.85 wt. CaO, 0.20 ϊ wt. % AlgO 3, 0.50 wt. % Fe ₂ O ₃ , 0.35 wt. SiO ₂ , a loss on ignition of 52.15 wt%, is thermally decomposed at 1000 ° C. The magnesite survivor, ground and sieved with a 0.06 mm aperture, is added in portions up to 500% by stirring. parts by weight of a solution containing 30 wt. parts by weight of ethylenediamine acetate (CH 2 CO 2) (g / ΟΗ, ΝΗ /), 25 wt. parts by weight of ammonium acetate CH 2 CO 3 NH 4 and 20 wt. parts of dietary amine NH / C ₂ H ₄ OH / ₂ ·

After stirring for 1 hour, the insoluble residue was separated from the solution by filtration and then washed with demineralized water. The composition of the dry product after recalculation to the annealed state is

96.85% wt. MgO, 0.35 wt. % CaO, 0.55 wt. % Al ₂ O ₃ , 1.25 wt. Fe ₂ O ₃ , 0.70 ΐ wt. SiO ₂ ·

From the filtrate, the leaching solution is recovered by precipitating the calcium carbonate by feeding in carbon dioxide

Example 4

At a temperature of 1050 ° C and 50 ° C, 100 wt. parts of dolomite having a composition of 30.81 wt. CaO, 21.33 wt. MgO, 0.32 wt. % SiO ₂ , 0.21 wt. Α1 ₂ ^Ο 3 »0,22% w / w

Fe ₂ O ₂ , the annealing loss being 47.1 wt. The so obtained roast is added to 300 wt. parts of water and this suspension is added in portions with stirring to 300 parts by weight of a 40 ° C warm aqueous solution containing 94 parts by weight, parts by weight of ammonium acetate, 34 parts by weight, triisobutylammonium chloride and 50 parts by weight of monoethanolamine.

After 100 min. by stirring, the insoluble residue containing predominantly magnesium oxide and its hydration products are separated by filtration and calcium carbonate precipitates from the filtrate cooled to 28-30 ° C after reaching pH 7.9, which is filtered off, washed with water and dried.

Yield 51.51 wt. parts by weight of calcium carbonate having a content of 99.5% by weight; CaCO2 corresponds to 94% with respect to the calcium oxide content of the feedstock. The undissolved residue after washing and drying at 465 ° C has a composition (% w / w): 97.3% MgO, 0.93% CaO, 0.73% SiO ₂ , 0.81%

A1 ₂ O ₃ and 0,52% Fe ₂ O ₃ -

Claims (4)

Process for removing calcium compounds from predominantly magnesium and / or magnesium-calcium oxide and / or hydroxide raw materials, generally associated with the production of calcium carbonate, characterized in that the starting material in the case of the carbonate form is thermally decomposed from the obtained roast and / or In the case of oxides, calcium oxide and / or its hydration products are selectively leached at 0 to 100 ° C with a solution containing at least one organic base together with ammonia and / or ammonium hydroxide and at least one salt of an inorganic and / or organic acid forming a water-soluble calcium salt , with at least one organic nitrogen base and ammonium hydroxide, in a total amount corresponding to the desired degree of leaching of the lime component and / or the oxide and / or hydroxide feedstock and the remaining magnesium oxide and / or its hydration products, optionally with the hardened components, d of the solution are separated, for example by filtration, centrifugation, as a rule in conjunction with washing and drying. 2. A process according to claim 1, characterized in that the calcium oxide and / or its hydration products are selectively leached with a solution containing alkylamine and / or alkanolamine with ammonia and / or ammonium hydroxide, preferably monoethanolamine with ammonium hydroxide, and an inorganic salt and / or or an organic acid with an alkylamine and / or alkanolamine and an ammonium salt, preferably a salt of hydrochloric acid, nitric acid, formic acid, acetic acid or pinic acid with monoethanolamine and ammonium hydroxide. 3. A process according to claim 1, characterized in that, after separation of the magnesium oxide and / or its hydration products, the solution is at a temperature of 0 to 100 [deg.] C., preferably at a temperature of 20 to 70 [deg.] C., at pH 7. The calcium carbonate is precipitated by separating carbon dioxide and / or ammonium carbonate, preferably pH 7.5 to 9, preferably pH 7.5 to 9. 4. The method of claim 1, wherein the leach solution, preferably after carbon dioxide removal and loss compensation, is used or recycled carefully.