CS201636B1 - Method of producing homogeneous clinker based on dolomite - Google Patents

Description

The present invention relates to a novel process for producing dolomagical clinkers for refractory linings.

Increasing the proportion of steel produced in oxygen converters and high-performance electric furnaces imposes new requirements on the quantity and quality of the refractory materials used to burn these furnace aggregates.

A comparison of the basic materials used so far, such as magnesium (MgO), dolomium (CaO. MgO) and lime (CaO), shows that the concentration of the refractory component and the admixture is important over the lifetime of higher temperature intensified steel furnaces. and the physicochemical properties of the refractory base.

Boron, ferric, alumina and silicon dioxide are considered to be harmful primates.

Based on exquisite washing and years of practical experience, it has been established to use oxygen converters and electric arc furnaces as the most advantageous dolomagnesic, tar-powered building materials with a certain content of lime and magnesia, made from dolomagnesic clinkers. The magnesium content e in these building materials ranges from 70 to 95%, the polluting primates are limited so that boric oxide must not be more than 0.01%, iron oxide not more than 0.3%, aluminum oxide not more than

201 636

201 030

0,5%, silicon dioxide not more than 0,2%.

The simplest apflaob for preparing low-magnesia elines for the production of refractory building materials consists of mixing pure magnesia and dolomite, obtained by calcining natural magnesite and dolomite, mixing them, briquetting and firing in high-temperature shaft or rotary kilns. The product obtained always has the characteristic properties given by the origin of the starting materials.

Since the CSSR does not have natural magnesites of the required purity, eu chemical purification procedures for natural magnesites with the aim of obtaining pure magnesia elines with a magnesia content of 97.5 to 99.5% and low-magnesia elines are added for this purpose. net dolomite or dolomite obtained from natural domestic deposits.

None of the real processes for producing chemically pure magnesium is the nitrate process and its variants.

As the raw material for the production of magnesia elinks, this epdeob is intended to calculate natural magnesite with different contents of silicon, iron, aluminum and calcium foams. While the silica, ferric and aluminum oxides are transferred to, or remain in, an insoluble residue upon dissolution of magnesium with nitric acid and subsequent neutralization with ammonia and separated by filtration, the dissolved calcium oxide as well as the dissolved magnesium oxide is aged in solution in the form of eoli. Similarly, when dissolving calcined magnesite in ammonium nitrate solution, only calcium oxide and magnesium oxide dissolve. The other constituents of calcined magnesite remain in an insoluble residue. The solution thus obtained always contains unreacted ammonium nitrate in addition to magnesium and calcium nitrate (see CSP 164 318, 163 638, 161 494),

When the magnesium is precipitated from the solution with ammonia, the presence of calcium in the solution causes contamination of the magnesium precipitate according to the concentration in which the calcium is present in the solution.

Most of the time, however, it dries calcium in solution, which, after the magnesium has been precipitated, works on the fertilizer - ammonium reed. The presence of calcium nitrate in this product at a concentration above 4% worsens its sales.

Therefore, processes for removing calcium, in particular from mixed magnesium-calcium nitrate or chloride solutions, have been developed to remove it, such as carbonate, by precipitation using carbon dioxide, ammonium carbonate or magnesium carbonate (non-queonite). After removal of the calcium, pure magnesium hydroxide is then precipitated by the addition of ammonia, which by calcination and elimination and obtaining a pure magnesium eline. The precipitation of calcium oxide extends the scope of the pure magnesia production operation and reduces the recovery of magnesium oxide from the raw material to the end product, a more calcium precipitated film is required, the greater the magnesia side.

For the chemical production of magnesia by the nitrate process, dolomitic magnesites, which are separated from magnesites in the mined

201 03B of utility timber in heavy liquids or by flotation. These materials contain from 5 to 25% calcium oxide per fired state, depending on the location of the feedstock.

By the above nitrate process, very pure magnesite clinker, MgO (97.5 to 99.5%), and the calcium, which also contains the starting material, is recovered from the process in the form of hardly recoverable waste. From magnesia, the dolomagnesium clinker is then made by adding an appropriate amount of dolomite so that the resulting product has 4-29% lime and 70-95% magnesium, with a content of other impurities of about 1%. However, the disadvantages of such a process are that the added dolomite a and introduces desirable impurities of ferric and silicon dioxide, and both components are difficult to homogenize, resulting in a decrease in the quality of the dolomagnesium clinkers. These disadvantages are overcome by the method of the present invention.

The production of homogeneous dolomagnesium clinkers according to the present invention consists in the deliberate use of the presence of calcium nitrate in solutions obtained in the leaching of calcined magnesite or calcined dolomitic magnesia by nitric acid or ammonium nitrate by calculating the quality of the final product of homogeneous dolomagnesium clinker. which is used in the product - ammonium liqueur according to CSN and a proportion of calcium oxide, which is precipitated from the nitrate solution as carbonate into a common precipitate with magnesium hydroxide, from which after filtering, washing, drying and calcination, briquetting and sintering produces dolomagnesium eline a predetermined content of lime as determined by its use. If necessary, the CaO: MgO ratio in the nitrate solution is corrected prior to the carbonate hydroxide precipitation by addition of the appropriate component in the form of a solution prepared by separately dissolving the appropriate magnesium calcine or, as a last resort, precipitating and separating only excess calcium oxide as carbonate.

Depending on the calcium nitrate content of the solution after filtering off the mixed precipitate, which are based on the calcium nitrate content of the brine solution, carbonate and ammonia, ammonium carbonate or magnesium carbonate hydrate is added to the solution and the required amount of carbonate ions is added to the solution. the magnesium nitrate content of the solution after filtering off the mixed precipitate is supplied in advance or simultaneously or additionally with the required amount of ammonia required by chemical equilibrium for a certain degree of magnesium precipitation in the form of magnesium hydroxide. In addition to magnesium hydroxide and calcium carbonate, the mixed precipitate may also contain magnesium carbonate.

The process according to the invention is based on the precipitation of a solution containing 10 to 45 wt. % of magnesium nitrate and calcium nitrate with carbon dioxide and ammonia or ammonium carbonate and ammonia or hydrate of magnesium carbonate and ammonia, in all cases in an amount corresponding to a molar ratio of COg: Ca of 0,8 to 1,5, preferably 1,0 to 1, 2 and ammonia in an NH 3: Mg molar ratio of 2 to 5, preferably 3.0 to 3.5 at 20 to 90 ° C, preferably at 20 to 30 ° C ►

201 030 and a mixture of magnesium hydroxide 8 with calcium carbonate, and optionally also magnesium carbonate, and a filtering or other known procedures, washed with water and worked by drying, calcining, briquetting and sintering at 1650 ° C to 1900 ° C, not dolomegnaic eline.

It is possible to use different diluent addition steps. It is possible to precisely precipitate calcium by introducing ammonia and carbon dioxide in a molar ratio of 2NH 3: CO ₂ or ammonium carbonate, and then immediately carry out the ammonia precipitation. It is also possible to precipitate a solution of nitrates by simultaneously injecting carbon dioxide and ammonia in an NH 3: CO 2 molar ratio of greater than 2. In that case, aa magnesium hydroxide begins to precipitate acre as aa and terminates the abaorption of all carbonate. In addition, it is also possible to precipitate ammonia and a magnesium hydroxide, and the resulting suapensation, and to precipitate calcium as calcium carbonate or with the aid of carbon dioxide or by adding ammonium carbonate in solution or in solid form.

Example no

For the production of homogeneous dolomagnesium clinker aa used the calcine of waste from flotation of magnesite composition:

SiO ₂ 11.32%

CaO 12,10%

Fe ₂ 0 ₃ 6.48%

MgO 68.1%.

8.Ž. 1,0% indeed 1,0%

By leaching this material with nitric acid and filtering off the insoluble residue, a pure solution containing (by weight) 35% magnesium nitrate and 5% calcium nitrate was obtained. 1000 kg of this solution at 22 [deg.] C. were charged into the precipitation reactor, and carbon dioxide and ammonia were fed at the bottom of the vessel. Carbon dioxide aa absorbed 13.2 kg, ammonia 130 kg. A white precipitate formed which was separated from the liquid phase on the drum filter, washed with 2.5 m of water, dried and calcined at 900 ° C, yielding 100 kg of calcine containing 87.7 kg of magnesium oxide and 12 kg of calcium oxide . By briquetting and sintering the moldings at 1800 ° C and obtained a high-quality homogeneous dolomagnesium alinok β content

87.7% of magnesium cyanide, 12% of calcium cyanide, 0.12% of silica, 0.1% of crescent and 0.08% of alumina.

Example 2

To 1000 kg of a solution containing 35% magnesium nitrate and 5% calcium nitrate obtained as in Example 1 was added 30 kg of crystalline ammonium carbonate and after dissolution 120 kg of NH 3 gas were introduced. A white precipitate formed, which was separated by filtration, etc., as in Example 1. It obtained 100 kg of homogeneous dolomagnesium clinker containing 87,7% magnesium cyanide, 12% calcium cyanide and only

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0.3% untreated.

Example 6.3

To 1000 kg of a solution containing 35% magnesium nitrate and 5% calcium nitrate prepared by the same procedure as in Example 1, e, 140 kg of an aqueous suspension containing 30% neeqvehonite was added. After stirring for 30 minutes and by analytical analysis, it was found that 90% of calcium nitrate had reacted to calcium carbonate (which is present as a solid precipitate) according to the equation:

Ca (NO ₃ ) ₂ + MgCO ₃ . 3H ₂ 0 · Mg (NO ₃ ) ₂ + CaCO ₃ ♦ 3H ₂ 0

Ammonia (120 kg) was then suspended at 25 ° C. The resulting precipitate ea was collected by filtration, etc., as shown in Example 1. 1000 kg of homogeneous dolomagnesium clinker were obtained.

Concentration and crystallization of the filtrate produced ammonium salts containing 3.8% calcium nitrate.

The by-product of the process is a brown sludge containing an insoluble residue of magnesium calcine, ammonium, magnesium and calcium nitrates and iron, aluminum and manganese hydroxides, which is elaborated by drying to a granular N-Mg fertilizer.

Claims (4)

Object of the invention A process for the production of homogeneous dolomagnesium clinker from a solution containing magnesium nitrate and calcium nitrate, characterized in that the solution containing 10- 45 wt. % Magnesium nitrate and calcium nitrate precipitated with carbon dioxide and ammonia or ammonium carbonate and ammonia, or a hydrate, magnesium carbonate, and ammonia, in each case in an amount corresponding to a molar ratio of C0 _2: C a equal to 0.8 to 1.5, preferably 1.0 to 1,2 and ammonia in a molar ratio of NH ₃ : Mg = 2.0 to 5.0, preferably 3.0 to 3.5 at 20 to 90 ° C, preferably at 20 to 30 ° C and a mixture of magnesium hydroxide with calcium carbonate and optionally also magnesium carbonate are separated by filtration or other known epochs, washed with water and treated and dried, calcining, briquetting and sintering at a temperature of 1650 to 1900 ° C to form dolomagnesium clinker. 2. The process defined in claim 1, wherein e and in that nitrate solution and on precipitated, first kyeličnikom dioxide and ammonia in a molar ratio of 2 NH _3: 1 CO ₂ or ammonium carbonate and ammonia and the other doeiahnutiu ratio of NH _3: Mg 2.0 to 5, 0th 3. The process defined in claim 1, characterized in that the solution of nitrates súčasnýra precipitated by injection of carbon dioxide and ammonia in a molar ratio of NH _3: C0 ₂ VSCs as a second 4. The method of claim 1, wherein the nitrate solution precipitates the ammonia starch in an amount required by chemical equilibrium for a certain degree of magnesium precipitation as magnesium hydroxide, and then calcium is precipitated into the resulting magnesium hydroxide slurry by introducing carbon dioxide or by adding ammonium carbonate. .