CS201234B1 - Method of producing magnesia-calcareous clinker of high purity - Google Patents

Description

The present invention relates to a novel process for producing high purity magnesium calcium clinker in the production of pure magnesium clinker from domestic magnesite raw materials. By the process of the present invention, a more complete utilization of the starting magnesite feedstock is obtained and high purity magnesium calcium clinker is obtained.

The expansion of steel production in oxygen converters and electric arc furnaces is subject, inter alia, to the availability of suitable refractory materials.

Over the years, it has been settled to use dolomite, magnesium or dolomagrass materials, generally tar-tared, to localize these baking containers according to local conditions. A common condition for all the abovementioned species is the minimum content of co-contaminants of ferric oxide, aluminum oxide, silicon dioxide and in particular boric oxide.

With the development of pure low-boron magnesia technology in recent years, there has been a gradual transition from the conversion of oxygen converters to fast-moving dolomite building materials to magnesia and dolomagnesia. Depending on the working conditions of the furnace vessel, in particular according to the time dependence of the slag quality change, a magnesium or dolomagnesium lining containing up to 30% calcium oxide is selected.

The first dolomagnesium clinkers began to be used after it was shown that by removing the boron oxide in the production of magnesia from seawater by over-heating, not

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201 234 is the increased lime content in magnesia as a defect, but on the contrary, it extends the life of the lining just in the most challenging working conditions of oxygen converters and electric arc furnaces.

Not the current world production of pure magnesia or dolomagnazi clinkers about 3 mil. tonnes per year, account for 98% of the maritime States. The production of these materials by the reprocessing of differently contaminated magnesite has not reached any significant significance. In addition to the general finding that the most intensive refining effect has technologies based on the dissolution of magnesia eubstance in mineral acids, in purification of the solution and in the ultimate conversion of magnesia to solid state, the conditions of optimal technology are not yet clearly formulated. The main criterion of such hydrometallurgical processes is the purity of the product, and it is considered realistic and desirable to have a magnesium oxide content above 99.5% for ferric oxide contents below 0.1%. Given the energy intensity and complexity of the processes for producing pure magnesia from natural magnesites, it is very important that neither the feedstock nor the product contain boron.

For chemical processing for the production of pure magnesium, inferior magnesite raw materials with a high content of calcium, iron and silicon, or waste from the treatment of magnesite raw materials are generally offered.

One of the real technologies of chemical production of magnesium is the dissolution of total or partially calcined contaminated magnesite with hydrochloric acid. After oxidation in trivalent iron solution, pH adjustment and filtration, the solution encompasses magnesium and calcium chlorides. Its thermal decomposition at temperatures of 600 - 700 ° C yields magnesium and contains calcium chloride and hydrochloric acid, which is returned to the solvent of the magnesite feedstock.

The magnesium-calcium chloride mixture is not suitable for the production of dense magnesium clinker and therefore the soluble components must be washed with water. Hydrated oxygen is obtained! magnesium and a dilute calcium chloride solution with a lower magnesium chloride content. The hydrated magnesium oxide is then calcined, briquetted and sintered to a dense magnesium clinker. The scrubbing water is descaled using carbon dioxide (e.g., flue gas of calcined magnesite furnaces) and the addition of magnesium oxide. The resulting calcium carbonate and the liberated chloride ion from the calcium chloride are wetted with added magnesium cyanide. The calcium carbonate separated by filtration together with the addition of non-agglomerated hydrated magnesium oxide is a waste of the process. The descaled water containing magnesium chloride is fully utilized in the production process.

The described process has advantages over seawater production in that the product obtained contains more than 99.5% of magnesium oxide and is not contaminated with boron oxide. The disadvantage, however, is its relatively high energy intensity compared to production from seawater. This difficulty is further emphasized by the fact that almost all the calcium oxide entering the process and the magnesite raw material has to be eliminated by a relatively complex chemical operation, resulting in ethers of the useful ingredient.

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- magnesium oxide.

The essence of the production of high-calcium magnesium clinker according to the present invention is the production of dolomagnesia by 70-95% of magnesium and 5-30% of calcium cyanide by mixing a mixture of magnesium oxide and magnesium chloride with water and mashed with water and mixed with water. carbon dioxide to convert calcium chloride to calcium carbonate. The resulting mixture of magnesium hydroxide and calcium carbonate is then dewatered, calcined, briquetted, and fired to a dense, high purity magnesium calcium eline. At a low calcium chloride content in magnesium oxide, the lime content in the slurry! before or during carbonation by adding calcium milk to the desired value of the CaO: MgO ratio in the magnesium product.

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This process can also be carried out by washing the carbon dioxide scrubbing water from the washing of magnesium oxide containing calcium chloride. In this case, at least a stoichiometric amount of oxide or magnesium hydroxide must be added before or during carbonation.

2-throwing calcium carbonate with carbon dioxide into the hydrated magnesium oxide emulsion also has the advantage that the precipitated calcium carbonate is excreted in very fine crystals on the hydrated magnesium oxide particles, which in subsequent calcination, briquetting and sintering, respectively. Direct-A, clinker processing after pressure filtration, allows a high degree of homogenization of the mixture of calcium oxide in magnesium oxide.

Example

Waste from dry magnetic separation of magnesite raw material roasted at 1200 - 1250 ° C was used for the production of high purity magnesium lime clinker, with the flux from this roasting with the average composition of the mixture:

silicon dioxide Si0 ₂ 9.5 calcium oxide CaO 6.7 iron oxide Fe ₂ ° 3 5.8 magnesium oxide MgO 70.0 loss by annealing 7.7

Dissolution of this feedstock in 20% reverse acid, acidification of the slurry with chlorine, and pH adjustment by the addition of a finely ground magnesia waste and filtration yield a solution of magnesium and calcium chlorides with the effect of converting magnesium oxide to a solution of min. 85% and calcium oxide min. 93.5%. After concentrating the solution to a concentration of about 400 g / l magnesium chloride and thermal decomposition at 670 ° C, a light magnesium oxide containing 9.5% calcium oxide was obtained as magnesium chloride. The obtained magnesium chloride containing calcium chloride was stirred with 8 water in a porosity of 1: 5 and after cooling to 30 ° C by aeration, a slurry of hydrated magnesium oxide was bubbled through a 20% carbon dioxide mixture of 80% air for 20 min. so that over the slope passed min. three times the amount of carbon dioxide relative to the initial calcium chloride content. Then the solid of the slurry was filtered off and washed with water. The calcined solids were determined to contain 7.2% calcium oxide. and 92.5. % magnesium oxide. By sintering the moldings of this material at 1850 ° C for 2 h, compacted dolomagnesium clinker of high purity was obtained.

In the filtrate and washings, 23% of the calcium oxide was initially in the form of calcium chloride. The magnesium chloride content of the water wash filter was proportional to the conversion of calcium chloride to carbonate.

In an uninterrupted production process, the calcium chloride concentration in the light magnesium oxide may be greater by its circulating amount and, after the process has stabilized, virtually all of the dissolved lime will be converted into a magnesium-calcium precipitate upon carbonate precipitation. *

Claims (5)

OBJECT OF THE INVENTION A process for producing high purity magnesium clinker by a thermal decomposition process of a magnesium chloride and calcium chloride solution, characterized in that the mixture of magnesium oxide and calcium chloride obtained by thermal decomposition is mixed with water in a ratio of 1: 3 to 1:10, preferably 1 5 and the slurry thus obtained is saturated with carbon dioxide, pure, slightly mixed with air or flue gas, with a carbon dioxide content of more than 10% vol. until the amount of calcium chloride is converted to carbonate corresponding to the selected MgO: CaO ratio in the final product, which is then obtained by filtering off the solid, washing it and treating the non-dense elinkin by known methods. 2. The process for producing high purity calcium clinker according to claim 1, characterized in that the MgO: CaO ratio in the final product is adjusted by adding calcium oxide in the toy by adding lime milk and thoroughly homogenizing it prior to carbonation. 3. The process for producing high purity magnesium lime clinker according to claim 1, characterized in that the MgO: CaO ratio in the final product is adjusted by adding 95% below 0.04 mm by calcined dolomite or non-calcined finely ground dolomite, containing less than 0.3% iron (III) oxide such that the adjustment of the MgO: CaO ratio is carried out before the slurry is treated with carbon dioxide. 4. A process for the production of high purity magnesium clinker, characterized in that the washing of the water after the lightening of the light magnesium hydroxide from the thermal decomposition of the magnesium chloride solution is made alkaline by the addition of magnesium oxide or hydroxide. 201 234 in excess of magnesium, based on chloride ions released from calcium chloride on its transition to calcium carbonate and saturated with carbon dioxide to reduce the calcium chloride content to 5-15 g / l, whereby the precipitated calcium carbonate together with unreacted hydroxide is obtained separating the solution from the solution by filtration and after washing, drying and comminuting in a mixture of high purity magnesium oxide or calcium hydrate to form a high purity magnesium calcium clinker 5. The process for producing high purity magnesium calcium clinker according to point 4, characterized in and magnesium hydroxide is mixed in the desired MgO: CaO ratio in the final product into the washed light magnesium oxide before or after filtration.