KR20090004036A - Manufacturing methods of magnesium compounds from waste mgo-c refractories - Google Patents

Abstract

A manufacturing method of magnesium compounds from waste magcarbone-C(MgO-C) refractory is provided to manufacture magnesium hydroxide and magnesium oxide compound of a high purity with a high yield by recycling waste magcarbone brick disused by reclamation. A manufacturing method of magnesium compounds from waste magcarbone-C(MgO-C) refractory comprises steps of: pulverizing waste magnesia carbon brick; reacting the pulverized waste magnesia carbon brick with a strong acid, filtering the pulverized waste magnesia carbon brick and separating a liquor; agitating a filtered liquor, reacting the filtered liquor with a base and producing a magnesium hydroxide; drying generated magnesium compounds; and incinerating obtained magnesium compounds to 600~800°C. The acid comprises a hydrochloric acid.

Description

Technical Field [0001] The present invention relates to a method for producing a magnesium compound from a waste magnesium carbide refractory. BACKGROUND ART [0002] MgO-C REFRACTORIES,

1 is a photograph of sludge obtained after reacting a waste refractory with strong hydrochloric acid.

2 is a photograph of a crystal of magnesium chloride (MgCl ₂ ) obtained according to the present invention.

3 is a graph showing particle size distribution of magnesium hydroxide obtained according to the present invention.

4 is a graph showing particle size analysis results for the solid content of magnesium hydroxide obtained according to the present invention.

5A and 5B show the results of EDS and XRD analysis of the MgO samples prepared according to the present invention, respectively.

The present invention relates to a method for recycling a refractory used in a converter or the like, and more particularly to a method for producing a magnesium compound in a pulverized refractory.

The steel industry uses a large amount of resources and energy to produce steel products and generates various kinds of by-products. The byproducts include slag of rock components, dust and harmful by-products of exhaust gas collection process, iron oxide and waste refractory Occurs. The amount of landfill is decreasing as slag, which is a typical by-product of steel, is recycled as whole road slabs or recycling of dust and sludge increases. However, much of the interior materials of various materials used in blast furnace, Torpedo Ladel Car, converter, RH vacuum degassing furnace, etc. are buried in waste.

The refractories used in electric furnaces and the like are dolomite (MgO-CaO refractory), magnesia-carbon (MgO-C refractory; hereafter referred to as "mag carbon refractory") which can withstand temperatures of 1,500 ° C (SK 26) there may be mentioned hereinafter, referred to as "MAG chrome refractory"), alumina and silica-based and the like; chromium quality (MgO-Cr ₂ O ₃ based refractory material - hereinafter), quality magnesia (MgO-based refractory), magnesia. Refractory bricks in electric furnaces are operated according to the demand of steel, but refractory materials of 1,000 tons or more per month are almost discarded, and research on the refractory materials to be discarded is still insufficient.

Regarding the recycling of waste refractory, for example, in Japanese Patent No. 10-388005, metal iron, free CaO, and hexavalent chromium components contained in the magnesium-based waste refractory are removed and the residue remaining is recycled as a refractory, A method for producing a Mg component eluted from MgO with an MgSO4 aqueous solution and using the byproduct thereof has been disclosed. In addition, Patent Document 10-491993 discloses a method for producing a hexavalent chrome To remove waste refractory, and to obtain Cr2O5 from the removed hexavalent chromium.

On the other hand, Japanese Patent Laid-Open No. 10-605711 discloses a method of manufacturing a refractory composition by adding sodium silicate, sodium hexametaphosphate, liquid phenol resin, or the like to a magnesium carbon waste refractory.

As described above, the conventional art relating to the recycling of waste refractory materials is only to the extent that it is desired to remove undesired components and then discard them or use them as refractories again. Further, attempts have been made to extract and recycle part of the composition in some of the magnesium-based refractories, but there has been no such attempt in the magnesium-based refractories.

In practice, the magnesium carbide refractories are recovered when they are not mixed with other refractories, and are used again as refractory materials after being processed with MgO clinker. However, when refractories such as alumina are mixed, it is known that all of the refractories are currently buried.

In this way, when the impurities in the waste magnesium carbide refractory are relatively small, they can be recycled through a relatively simple process. However, in the case where a relatively large amount of impurities such as alumina is contained, there is almost no method that can be recycled.

DISCLOSURE OF THE INVENTION In order to solve the problems of the prior art described above, it is an object of the present invention to provide a method for recycling a mag carbon waste refractory.

The present invention also aims to provide a method for producing a magnesium compound of high purity such as magnesium hydroxide and magnesium oxide from a waste mica carbon refractory which is mostly being treated by landfill.

According to an aspect of the present invention, there is provided a method for producing a magnesium compound from a waste magnesium carbide (MgO-C) refractory, comprising the steps of: (a) pulverizing a waste magnesium carbonitride; (b) reacting the pulverized waste magnesium carbide refractory material with a strong acid and filtering it to separate the filtrate; (c) reacting the filtrate with a base with stirring to produce magnesium hydroxide. In the present invention, stirring may be carried out at room temperature or at a temperature of 100 DEG C or lower.

In the present invention, the acid preferably includes hydrochloric acid.

The present invention also provides a method for producing a magnesium compound, comprising: (d) drying a magnesium compound; And (e) calcining the obtained magnesium compound to 600 to 800 占 폚.

In the present invention, the pH of the step (c) is preferably 8 or more, more preferably 8 to 9.

In the present invention, it is preferable that the step (a) is pulverized so that the 100 mesh pass fraction becomes 100%.

Hereinafter, the present invention will be described in detail by explaining preferred embodiments of the present invention.

In the present invention, high-value-added magnesium hydroxide and magnesium oxide compounds are produced from the waste magnesium carbide refractory that has been disposed of.

First, the waste magnesium carbide refractory is crushed (step (a)). According to a preferred embodiment of the present invention, it is preferable that the particle size of the waste mag carbon in the pulverization step is 100% of 100 mesh. If the particle size of the waste mag carbon is not 100% after passing 100 mesh after the pulverization, unreacted MgO will be present when reacting with strong hydrochloric acid in the subsequent process, and the recycling rate of the magnesium component will eventually be low, There is a problem that time and cost increase.

Then, while adding a strong acid such as HCl to the pulverized waste carbon, gradually increase the reaction temperature, and react at 100 to 300 ° C with care not to boil the solution. If the reaction temperature is excessively increased, the reaction proceeds rapidly but there is a problem that the reaction solution may boil.

When the pulverized refractory material is pulverized and reacted with strong hydrochloric acid such as HCl, a MgCl ₂ solution can be prepared from the waste mag carbon as shown in the following chemical formulas (1) and (2).

The MgCl ₂ solution thus prepared is filtered to separate the solution from the remaining residue (step (b)). The separated residue is mostly composed of carbon, and contains a part of MgO, Al ₂ O ₃ , SiO ₂ , Fe ₂ O ₃ and the like.

Subsequently, in step (c), a magnesium compound is formed by reacting the filtrate with a base such as ammonium hydroxide under atmospheric pressure with stirring. Of course, in the present invention, in addition to ammonium hydroxide, another base having a hydroxyl group such as sodium hydroxide can be used as a base. However, sodium and the like remain in the final product, and the purity of the product is low.

At this time, the amount of ammonium hydroxide to be added is preferably added until the pH of the solution becomes 8 - 9. If the pH is less than 8, the recovery rate of the magnesium compound is lowered. Further, the aluminum or iron component can coprecipitate with the magnesium hydroxide, so that the magnesium hydroxide finally produced contains aluminum and iron components as impurities. In addition, when the pH is 9 or more, ammonium hydroxide is unnecessarily added, which is undesirable. Further, since the filtrate to be discharged finally becomes strong alkaline, it may cause environmental pollution when discharged into wastewater.

When the pH of the solution of the precipitation reaction is 8 to 9, when the precipitation reaction is completed, the aluminum and iron components are present in the solution, so that they can be separated from the precipitate through filtration.

Then, the resulting precipitate is filtered and dried at an appropriate temperature, for example, 100 DEG C to obtain a powder of the magnesium hydroxide compound (step (d)). The magnesium hydroxide thus obtained can be calcined at a temperature of 600 to 800 ° C, for example, 700 ° C, and magnesium oxide powder can be obtained through a reaction represented by the following formula (6) (step (e)).

As a result of XRD analysis, the calcined product at 700 ° C can be confirmed to be magnesium oxide powder in which magnesium hydroxide is not remained.

Hereinafter, the principle of obtaining magnesium hydroxide in the present invention can be explained as follows.

Magnocarbon waste refractory is magnesium oxide (MgO) as its main component. Generally, MgO is a ceramic material having a high water absorption property, and therefore magnesium hydroxide (Mg (OH) ₂ ) can be produced by the following reaction mechanism by reacting with water.

However, the reaction did not proceed even when the reaction temperature was raised to the boiling point of water (100 ° C). This is presumably because carbon is bound to the waste refractory.

To accelerate the reaction, the reaction was accelerated by adding a base to water and the reaction was carried out by adding sodium hydroxide (NaOH) to the pulmonary refractory. However, even when sodium hydroxide was added, generation of magnesium hydroxide was not observed.

MgO can react with hydrochloric acid to produce magnesium chloride (MgCl ₂ ) by the following reaction mechanism. The magnesium chloride thus produced is dissolved in water and ionized.

When a base is added to a solution that is ionized with magnesium cations and chlorine anions, it will precipitate with magnesium hydroxide by the following reaction mechanism.

Hereinafter, the present invention will be described in more detail with reference to specific examples.

The components of the waste mica carbon refractory used in this example are shown in Table 1 below.

ingredient Content (wt%) MgO 76.7 SiO ₂ 3.54 Al ₂ O ₃ 3.16 CaO 1.82 Fe ₂ O ₃ 0.80 K ₂ O 0.07 MnO 0.06 Na ₂ O 0.06 TiO ₂ 0.06 Zn 0.04 Zr <0.01 Ig. loss (estimated graphite) 13.64

Pre-treatment of Magcarbon Waste Refractories

To 500 g of pulverized refractory material having a particle size of 100 mesh or less, 500 mL of strong hydrochloric acid was added, and the mixture was heated at a boiling point (about 250 ° C) for about 13 hours and cooled to room temperature. As shown in Fig. 1, the reaction sludge had needle-like crystals formed therein, which was confirmed to be magnesium chloride. The magnesium chloride crystals were covered with carbon material and the magnesium chloride was very soluble in water, so washing with cooling water or cooled hydrochloric acid was attempted, but separation was very difficult.

At this time, when water was added to the reaction product cooled to room temperature, a yellow solution and a black precipitate were formed. The solution was heated to a suitable temperature (about 100 DEG C) and then filtered to separate the solution and the precipitate. The isolated black solids were dried and weighed to give 102.5 g. This corresponds to about 20.5% of the initial weight of the sample of the mag carbon waste refractory, so that it is understood that 79.5% of the inorganic component is dissolved in the solution. From the analysis results of the waste refractory component in Table 1, considering that the magnesium oxide content is 76.7 wt% and the Ig.Loss estimated by graphite is 13.64%, the inorganic components of the first sample are all dissolved except for about 7 wt% it means.

The resulting yellow solution is heated to be concentrated and then crystallized at a low temperature to obtain magnesium chloride (MgCl ₂ ) crystals as shown in FIG.

Example 1

The magnesium chloride obtained through the pretreatment process has a difficulty in separating magnesium because of its high solubility in water. Thus, a 28-30% ammonium hydroxide (NH ₄ OH) solution was slowly added to the yellowish filtrate to lower the solubility of the magnesium chloride. As a result, a white ammonium hydroxide precipitate was obtained by the reaction of ammonium hydroxide and magnesium chloride.

Then, the magnesium hydroxide precipitate was separated by using a centrifuge and then dried to obtain a solid content of about 424.3 g. This corresponds to about 76 wt% in terms of the amount of magnesium oxide contained in the waste refractory.

3 is a graph showing the particle size distribution of the obtained magnesium hydroxide. As can be seen from FIG. 3, it was found that very fine particles having a main average particle diameter of about 8 mu m were formed. In addition, although small particles as small as 0.15 μm are observed, it can be seen that the particle distribution appears to be fairly uniform.

On the other hand, other elements or compounds besides magnesium are contained in the filtrate, and other elements except magnesium are present in the ion state in the aqueous solution. That is, impurities such as iron or aluminum, calcium, sodium, and potassium contained in the waste refractory are ionized by the following reaction mechanism by the addition of ammonium hydroxide.

Example 2

A mixed acid of nitric acid and hydrochloric acid was used instead of hydrochloric acid to reduce the pretreatment time of the waste refractory. To 100 g of waste refractory, 200 mL of aqua regia, which is a mixed acid of nitric acid and hydrochloric acid, was added, and the mixture was heated for about 6 hours and cooled to room temperature. Then, 500 mL of water was added and filtrated to obtain a filtrate.

Table 2 below shows the results of analyzing the composition of the filtrate using an inductively coupled plasma spectrometer and comparing it with Example 1.

As can be seen from Table 2, it can be seen that the concentration of magnesium is lower than that of hydrochloric acid when it is pretreated with water. On the other hand, in the case of the remaining elements or compounds except for magnesium, it can be seen that the case of using royal water is higher than the case of using hydrochloric acid. Therefore, it can be seen that there is a difference in the yield and purity of magnesium obtained according to the kind of acid used in the pretreatment, and it is considered that when the waste refractory is treated with hydrochloric acid, the yield and purity of the final magnesium hydroxide can be increased.

Dyed water Strong hydrochloric acid dissolution ingredient wt% wt% Na ₂ O 0.007 0.007 MgO 56.03 68.14 MnO 0.085 0.038 K ₂ O 0.005 0.008 CaO 2.100 1.622 Fe ₂ O ₃ 1.600 1.313 Al ₂ O 3 0.741 0.459 Ti 0.023 0.017 Cu 0.002 - Ni 0.055 - P 0.018 0.012 Sr 0.002 0.001 Cr 1140 mg / kg 821 mg / kg

To the obtained filtrate was added 15 N ammonium hydroxide solution (specific gravity: 0.88, about 28-30%). The addition of ammonium hydroxide solution resulted in the formation of a yellow precipitate at the beginning and a white precipitate as the ammonium hydroxide solution increased. When the ammonium hydroxide solution is added, a yellow precipitate of red color is formed. It is considered that some iron and other metals dissolve when the waste refractory is dissolved by the royal flue, so that coprecipitation occurs during the precipitation reaction of magnesium hydroxide.

Then, the magnesium hydroxide precipitate was centrifuged and dried, and the obtained solid content was subjected to particle size analysis. 4 is a graph showing the result of particle size analysis. From the graph, four particle sizes of 0.15 μm, 3 μm, 11 μm and 40 μm were observed.

According to the results of this test, the method of dissolving the waste refractory by the water of water is shorter than the method of dissolving by the strong hydrochloric acid, but the recovery and the purity are low.

Example 3 Influence of Particle Size of Waste MAG Carbon Refractory

In this example, to examine the influence of the particle diameter of the pulverized refractory material on the extraction of Mg, pulverized into 325 mesh, 100 mesh, 16 mesh, and 6 mesh throughput as shown in Table 2 below. (Specific gravity: 1.19, about 38%) for about 10 hours, and magnesium hydroxide was produced through the above-mentioned process to recover the recovered product.

division #One #2 # 3 #4 Particle size 6 mesh 16 mesh 325 mesh 100 mesh Recovery rate 34% 52% 86% 78%

As can be seen from Table 2, the smaller the particle diameter of the waste mag carbon particles, the higher the recovery rate of magnesium hydroxide. This is because the larger the particle diameter is, the more the reaction proceeds only on the particle surface, and the reaction with the inside of the particle does not proceed easily. When the particle diameter of the waste mag carbon was reduced to about 325 mesh, the recovery rate was about 86% and the recovery rate was about 8% higher than the case of 78% particle diameter passing 100 mesh. Generally, as the particle size decreases, it takes a lot of time and money to crush it to have a smaller particle size. Therefore, it is costly to grind particles of 100 mesh size or more, considering the cost of making particle size of 1/3 of 325 mesh particles. However, the increase of recovery rate is not so great It is uneconomical. For example, when using a pulverizer of the same capacity, it takes about 10 min / kg for 100 mesh and about 30 min / kg for 325 mesh.

Example 4: Effect of pH on recovery

In this example, the effect of pH on the precipitation of magnesium hydroxide compound by adding ammonium hydroxide to the filtrate was investigated.

The waste magnesium carbide refractory was pulverized to 100% of 100 mesh throughput, and reacted with strong hydrochloric acid. The magnesium hydroxide compound was prepared by separating the residue and adding a supersaturated solution of ammonium hydroxide to the separated solution at pH 6, 7, 8 and 9 as shown in Table 3, and then the presence of aluminum and iron components was determined from ICP (Inductively Coupled Plasma) analyzer.

division # 5 # 6 # 7 #8 pH 6 7 8 9 Al ₂ O ₃ Excessive presence a very small amount grain grain Fe ₂ O ₃ Excessive presence a very small amount grain grain

As can be seen from the above table, in the case of # 6 and # 7, the aluminum and iron components were not completely solubilized, but precipitates were formed with some hydroxides and co-precipitated with magnesium hydroxide. As shown in # 8 and # 9, when the pH is adjusted to 8 and 9, a trace amount of aluminum and iron components are present. Therefore, it was found that the pH of the solution should preferably be 8 or more.

Example 6

To remove impurities contained in the magnesium hydroxide prepared in Example 1, the solid was washed twice with a weakly alkaline (10% NaOH solution) solution, washed twice with water and then calcined at 700 ° C to obtain about 277.5 g of solid Magnesium oxide (MgO) was obtained. This result corresponds to a yield of 72% as calculated from about 76.7 wt% of MgO contained in 500 g of waste refractory.

FIGS. 5A and 5B show the results of EDS and XRD analysis of the MgO samples, respectively. 5A, only the magnesium peak and the oxygen peak are observed. Other peaks in Fig. 5A are the carbon peaks due to the carbon tape used in the analysis and the Au peaks due to the gold coating for EDS analysis on the sample. On the other hand, it can be seen from the XRD data of FIG. 5B that only peaks are observed at the same positions as the crystals of magnesium hydroxide.

Table 4 below is a graph showing the results of quantitative analysis of the composition of the obtained magnesium oxide compound using an inductively coupled plasma spectrometer (ICP-OES). It was confirmed that the purity of the magnesium oxide was about 99%. In the table, Ig. The chlorine element of the loss is not completely removed in the washing process as an element present in the treatment with strong hydrochloric acid. The presence of other elements does not affect the purity of magnesium oxide in the application range of this study.

ingredient wt% Na ₂ O 0.14 MgO 98.92 K ₂ O 0.03 CaO 0.25 Fe ₂ O ₃ 0.15 MnO 0.01 Al ₂ O ₃ 0.21 TiO ₂ 0.01 Zn 0.02 Si 0.21 Ig. loss (including Cl) 0.25

In this embodiment, when a surfactant such as sodium dodecyl sulfate is added to disperse the magnesium hydroxide particles and then calcined, magnesium oxide of uniform size particles can be obtained.

According to the present invention, high-purity magnesium hydroxide and magnesium oxide compounds can be produced at a high yield by recycling the spent magnesium carbonaceous refractory, which is mostly disposed of by landfill, to produce high value-added chemical products along with waste recycling.

Claims (6)

In a method for producing a magnesium compound from waste magnesium carbide (MgO-C) refractory, (a) pulverizing a spent magnesium carbonaceous refractory; (b) reacting the pulverized waste magnesium carbide refractory material with a strong acid and filtering it to separate the filtrate; (c) reacting the filtrate with a base with stirring to produce magnesium hydroxide. The method according to claim 1, Wherein the acid comprises hydrochloric acid. The method according to claim 1, (d) drying the resulting magnesium compound; And (e) calcining the obtained magnesium compound at 600 to 800 占 폚. The method according to claim 1, Wherein the pH of the step (c) is 8 or more. The method according to claim 1, Wherein the step (a) is milled so that the 100 mesh-passed fraction becomes 100%. The method according to claim 1, Wherein the base is ammonium hydroxide.

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