Method for producing high-purity magnesium oxide from waste refractory materials by an environmentally friendly hydrometallurgical process, and magnesium oxide produced thereby

Abstract

The present invention provides a method for producing high-purity magnesium oxide from waste refractory material by an environmentally friendly hydrometallurgical process, the method including the steps of leaching magnesium-containing waste refractory material, performing solid-liquid separation, and separating a leachate from a residue (S10); purifying and leaching impurities from the leachate (S20); powdering the leachate that has been subjected to the purifying and leaching step to produce a magnesium-containing powder (S30); heat-treating the magnesium-containing powder to produce magnesium oxide (S40); and washing the heat-treated magnesium oxide to highly purify it (S50). The present invention also provides a method for producing high-purity magnesium oxide from waste refractory material by an environmentally friendly hydrometallurgical process.

Description

[Technical Field]

[0001] The present invention relates to a method for producing high-purity magnesium oxide from waste refractory materials by an environmentally friendly hydrometallurgical process, and the magnesium oxide produced thereby. More specifically, the present invention relates to a method for producing high-purity magnesium oxide (MgO) by processes such as leaching, refining, and washing using waste refractory materials that have been recycled as secondary resources for conventional refractory materials or disposed of in landfills. [Background technology]

[0002] Magnesium oxide, commonly called magnesia, is an oxide form of magnesium that has a high melting point and is hygroscopic.

[0003] It is mostly produced from magnesite, a natural carbonate mineral. Magnesia can be classified by heat treatment temperature and raw material. Light-burned magnesia is produced from magnesite at 600-1400°C, while heavy-burned magnesia is produced at 1400-2200°C. Electrofused magnesia is produced by melting magnesite at over 2800°C. Seawater magnesia is produced by precipitation from seawater and calcination.

[0004] Magnesium oxide produced at high temperatures is used as a raw material for refractories. Therefore, more than 70% of the produced magnesium oxide is used as refractories, and the remaining 30% is used in various industrial fields such as agriculture, medicine, optics, nuclear reactors, and rocket propellants.

[0005] In the Korean steel industry, refractories containing MgO-C are used in electric furnaces and steelmaking ladles, but they are discarded after use, and some are reused.

[0006] Reuse methods include a wet method in which nitrogen and aluminum in the waste refractory are controlled and the purity of MgO in the waste refractory is increased through a physical separation process, and a dry method in which carbon is burned and vaporized to increase the purity of MgO in the waste refractory.However, the purity is approximately 97% or less, and the waste refractory is reused as a refractory material in the waste refractory, and there have been very few reports of processes for producing high-purity MgO from waste refractory.

[0007] As mentioned above, a certain domestic smelting company produces more than 98% magnesium oxide from seawater using a wet process, but the magnesium oxide is simply internalized.

[0008] Therefore, Korea, which does not have any magnesium mines, imports all of its MgO and is currently short of supply. For this reason, it is extremely urgent to develop a process to recover MgO from waste refractory materials, and a process to produce high-purity MgO through an environmentally friendly and economical smelting process is required.

[0009] The disadvantage of conventional environmentally friendly smelting processes is the considerable cost of the chemicals and reaction equipment used, and the economic viability is limited compared to currently common commercial processes. Therefore, research is needed to reduce the number of process steps by applying conventional commercial processes and produce environmentally friendly high-purity MgO. Summary of the Invention [Problem to be solved by the invention]

[0010] The object of the present invention is to solve the above-mentioned problems by providing an environmentally friendly method for producing high-purity MgO from waste refractory materials, which is entirely imported in Japan, by simplifying the process and applying an environmentally friendly hydrometallurgical process.

[0011] The problems that the present invention aims to solve are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0012] In order to achieve the above object, the present invention provides a method for producing high-purity magnesium oxide from waste refractory material by an environmentally friendly hydrometallurgical process, including the steps of leaching magnesium-containing waste refractory material, performing solid-liquid separation, and separating the leachate from the residue (S10); purifying and leaching impurities from the leachate (S20); powdering the leachate that has been subjected to the purifying and leaching step to produce a magnesium-containing powder (S30); heat-treating the magnesium-containing powder to produce magnesium oxide (S40); and washing the heat-treated magnesium oxide to highly purify it (S50).

[0013] According to an embodiment of the present invention, the magnesium-containing waste refractory material may contain 30% to 55% by weight of magnesium.

[0014] According to one embodiment of the present invention, the method may further include a step of crushing / crushing the magnesium-containing waste refractory material before the step of leaching the magnesium-containing waste refractory material, performing solid-liquid separation, and separating the leachate from the residue.

[0015] According to one embodiment of the present invention, the crushed / ground magnesium-containing waste refractory material may have an average particle size of 100 mesh or less.

[0016] According to one embodiment of the present invention, in step S10, the magnesium-containing waste refractory material may be leached using a sulfuric acid solution having a molar concentration of 1M to 7M.

[0017] According to one embodiment of the present invention, step S10 can be carried out under the conditions that the solid (g) / liquid (mL) ratio of the magnesium-containing waste refractory material to the sulfuric acid solution is 1 / 10 to 3 / 10, the reaction temperature is 100°C or less, and the stirring speed is 100 to 400 RPM.

[0018] According to one embodiment of the present invention, step S20 can be performed by using the leachate obtained in step S10 as a leaching agent, adding the magnesium-containing waste refractory material to the leaching agent, and then separating the leachate from the residue.

[0019] According to one embodiment of the present invention, the step S20 can be repeatedly performed by using the first leachate as a leaching agent, adding the magnesium-containing waste refractory material to the leaching agent, and then separating the second leachate from the residue.

[0020] According to one embodiment of the present invention, step S20 can be carried out under the conditions that the solid (g) / liquid (L) ratio of the magnesium-containing waste refractory material and the leaching agent is 5 to 30, the reaction temperature is 100°C or less, and the stirring speed is 100 to 400 RPM.

[0021] According to one embodiment of the present invention, the pH of the leaching solution after the purification and leaching of impurities in step S20 may be 7 or more.

[0022] According to one embodiment of the present invention, step S30 can be carried out for 30 minutes to 2 hours under the conditions that the steam temperature is 45° C. or more and the stirring speed is 25 RPM or more.

[0023] According to an embodiment of the present invention, the heat treatment in step S40 can be performed at a temperature of 1000° C. to 1500° C. for 30 minutes to 6 hours.

[0024] According to an embodiment of the present invention, the heat treatment in step S40 can be performed at a temperature of 1200° C. to 1500° C. for 3 to 6 hours.

[0025] According to one embodiment of the present invention, at least one of the residue generated in step S20, the distillate generated in step S30, and the exhaust gas components generated in step S40 can be reused in step S10.

[0026] According to one embodiment of the present invention, in step S50, the heat-treated magnesium oxide may be washed with distilled water at a solid (g) / liquid (mL) ratio of the heat-treated magnesium oxide to distilled water of 1 / 1 to 1 / 10, at a temperature of 20°C to 50°C, for 5 to 50 minutes.

[0027] According to one embodiment of the present invention, step S50 can be performed once or repeated 2 to 5 times.

[0028] According to one embodiment of the present invention, the heat treatment in step S40 is performed at a temperature of 1200° C. to 1500° C. for 3 to 6 hours, and step S50 is repeated 2 to 5 times.

[0029] To achieve the above object, there is provided magnesium oxide produced by a method for producing high-purity magnesium oxide from the above waste refractory material by an environmentally friendly hydrometallurgical process. [Effects of the Invention]

[0030] The method for producing high-purity magnesium oxide from waste refractories according to the present invention can produce environmentally friendly high-purity magnesium oxide (MgO) with controlled impurities such as Fe, Al, Si, and Ca by recycling the waste refractories into secondary resources of conventional refractories or by using environmentally friendly hydrometallurgical processes from the waste refractories that have been disposed of in landfills.

[0031] In addition, in the method for producing magnesium oxide according to the present invention, an alkaline solution can be produced from the washing solution in the washing step to highly purify MgO, and SO2 gas generated during heat treatment can be produced into sulfuric acid in a subsequent catalytic process. The distillate in the powdering process can be used to produce sulfuric acid, thereby effectively reducing wastewater generated. Thus, an environmentally friendly hydrometallurgical process can be implemented to produce environmentally friendly high-purity magnesium oxide. [Brief explanation of the drawings]

[0032] [Figure 1]1 is a process flow diagram of a method for producing high-purity magnesium oxide from waste refractory materials through a hydrometallurgical separation and purification process in one embodiment of the present invention. [Figure 2] 1 is an XRD pattern of a magnesium-containing powder in one embodiment of the present invention. [Figure 3] 1 is an XRD pattern of magnesium oxide recovered after heat treatment in one embodiment of the present invention. [Figure 4] 1 shows an XRD pattern of high-purity magnesium oxide recovered after washing in one embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

[0033] The object of the present invention is to solve the above-mentioned problems by providing an environmentally friendly method for producing high-purity MgO from waste refractory materials, which is entirely imported in Japan, by simplifying the process and applying an environmentally friendly hydrometallurgical process. DETAILED DESCRIPTION OF THE INVENTION

[0034] Before describing the present invention in detail, it should be understood that the terms and words used in this specification should not necessarily be interpreted as being limited to their ordinary or dictionary meanings, and that the inventors of the present invention may appropriately define and use the concepts of various terms in order to explain their invention in the best possible manner, and further, that these terms and words should be interpreted as having meanings and concepts that correspond to the technical ideas of the present invention.

[0035] In other words, the terms used in this specification are used only to describe preferred embodiments of the present invention, and are not intended to specifically limit the content of the present invention. It should be understood that these terms are defined in consideration of various possibilities of the present invention.

[0036] Furthermore, in this specification, unless the context clearly indicates otherwise, it should be understood that singular expressions may include plural expressions, and similarly, even when plural expressions are used, they may also include the singular meaning.

[0037] Throughout this specification, when a component is described as "comprising" another component, unless otherwise specifically stated, this does not mean that it excludes any other component, but rather that it may further include any other component.

[0038] In addition, in the following description of the present invention, it is possible to omit detailed descriptions of configurations that are deemed to obscure the gist of the present invention, such as publicly known technologies including conventional technologies.

[0039] The present invention will be described in more detail below.

[0040] According to the present invention, as shown in the process flow chart of Figure 1 below, there is provided a method for producing high-purity magnesium oxide from waste refractory material by an environmentally friendly hydrometallurgical process, including a step (S10) of leaching magnesium-containing waste refractory material, performing solid-liquid separation, and separating a leachate from a residue; a step (S20) of purifying and leaching impurities from the leachate; a step (S30) of powdering the leachate that has been subjected to the step of purifying and leaching impurities to produce a magnesium-containing powder; a step (S40) of heat-treating the magnesium-containing powder to produce magnesium oxide; and a step (S50) of washing the heat-treated magnesium oxide to highly purify it.

[0041] In one embodiment of the present invention, the magnesium-containing waste refractory material may include one or more materials selected from the group consisting of dolomite (MgO-CaO-based refractory material), magnesia-carbon (MgO-C-based refractory material), magnesia (MgO-based refractory material), magnesia-chromium (MgO-Cr2O3-based refractory material), alumina, and silica, which can withstand temperatures of 1,500° C. As a specific example, the magnesium-containing waste refractory material may be MgO-C waste refractory material.

[0042] The magnesium-containing waste refractory material may contain 30% to 55% by weight or 35% to 50% by weight of magnesium (Mg). The magnesium-containing waste refractory material may further contain, in addition to magnesium, any one or more of calcium (Ca), iron (Fe), sodium (Na), potassium (K), aluminum (Al), silicon (Si), and carbon (C).

[0043] When the magnesium-containing waste refractory material further contains any one or more of calcium (Ca), iron (Fe), sodium (Na), potassium (K), aluminum (Al), silicon (Si), and carbon (C) in addition to magnesium, the calcium content may be 0.01 wt% to 0.5 wt%, the iron content may be 0.01 wt% to 1 wt%, the sodium content may be 0.001 wt% to 0.3 wt%, the potassium content may be 0.001 wt% to 0.3 wt%, the aluminum content may be 0.1 wt% to 5 wt%, the silicon content may be 0.01 wt% to 1 wt%, and the carbon content may be 1 wt% to 25 wt%.

[0044] In one embodiment of the present invention, the method may further include a step of crushing / crushing the magnesium-containing waste refractory material before the step of leaching the magnesium-containing waste refractory material, performing solid-liquid separation, and separating the leachate from the residue.

[0045] The magnesium-containing waste refractory material can be crushed / pulverized using a conventional crusher, which may include at least one selected from the group consisting of a jaw crusher, a gyratory crusher, a roller crusher, a cone crusher, a hammermill crusher, a tumbling mill, a vibration mill, an attrition mill, a ball mill, a rod mill, a pebble mill, and an autogeneous mill.

[0046] The crushed / pulverized magnesium-containing waste refractory material may have an average particle size of 100 mesh or less, 10 to 100 mesh, or 30 to 100 mesh. When the magnesium-containing waste refractory material is crushed and pulverized within the above ranges and then subjected to subsequent leaching and extraction processes, the recycling rate of the magnesium component contained in the waste refractory material can be improved, and process time and costs can be reduced.

[0047] In one embodiment of the present invention, in step S10, the magnesium-containing waste refractory material is leached and subjected to solid-liquid separation to separate the leachate and the residue.

[0048] When leaching the magnesium-containing waste refractory material, an acidic solution can be used as a leaching agent, and the acidic solution may contain at least one acid selected from the group consisting of nitric acid, hydrochloric acid, sulfuric acid, and perchloric acid. As a specific example, the leaching agent may be a sulfuric acid solution.

[0049] The leaching of the magnesium-containing waste refractory material in the above step S10 can be carried out using a sulfuric acid solution having a molar concentration of 1 M to 7 M, 3 M to 7 M, or 4 M to 6 M. When the magnesium-containing waste refractory material is leached using a sulfuric acid solution having a molar concentration in the above range, the leaching rate of Mg can be increased and the co-leaching rate of impurities such as Fe, Al, Ca, and Si can be reduced.

[0050] The above step S10 can be carried out under the conditions that the solid (g) / liquid (mL) ratio of the magnesium-containing waste refractory material to the sulfuric acid solution is 1 / 10 to 3 / 10, the reaction temperature is 100°C or less, and the stirring speed is 100 to 400 RPM.

[0051] As a specific example, the step S10 can be carried out under the conditions that the solid-liquid ratio of the magnesium-containing waste refractory material to the sulfuric acid solution is 1 / 10 to 1.5 / 10, the reaction temperature is 80°C to 100°C, and the stirring speed is 150 to 250 RPM.

[0052] In one embodiment of the present invention, the residue separated by the solid-liquid separation contains low-grade valuable metals and carbon (C), which can be utilized as low-grade and medium-grade carbon (C).

[0053] In one embodiment of the present invention, step S20 may be a step for purifying impurities of the leachate separated in step S10 by a leaching method.

[0054] As a specific example, step S20 can be performed by using the leachate obtained in step S10 as a leaching agent, adding magnesium-containing waste refractory material to the leaching agent to cause a leaching reaction, and then separating the leachate from the residue.

[0055] In one embodiment of the present invention, step S20 can be performed once or repeatedly 2 to 5 times. Specifically, the first leachate is used as a leaching agent, the magnesium-containing waste refractory material is introduced into the leaching agent, and then the second leachate and the residue are separated.

[0056] For example, when step S20 is performed once, the first-stage leaching solution separated in step S10 is used as a leaching agent, and the magnesium-containing waste refractory material is introduced into the first-stage leaching agent for leaching. After that, the second-stage leaching solution and the residue are separated, and the second-stage leaching solution can be used to perform the subsequent extraction process.

[0057] As another example, when step S20 is performed twice, the first-stage leaching solution separated in step S10 may be used as a leaching agent, and the magnesium-containing waste refractory material may be introduced into the first-stage leaching agent for leaching, followed by separation into a second-stage leaching solution and a residue. Next, the second-stage leaching solution may be used as a leaching agent, and the magnesium-containing waste refractory material may be introduced into the second-stage leaching agent for leaching, followed by separation into a third-stage leaching solution and a residue. The third-stage leaching solution may then be used to perform the subsequent extraction step.

[0058] In one embodiment of the present invention, step S20 can be carried out for 5 to 120 minutes under the following conditions: a solid (g) / liquid (L) ratio of the magnesium-containing waste refractory material and the leaching agent is 5 to 30, a reaction temperature is 100°C or less, and a stirring speed is 100 to 400 RPM.

[0059] As a specific example, the step S20 can be carried out for 30 to 120 minutes under the conditions that the solid (g) / liquid (L) ratio of the magnesium-containing waste refractory material and the leaching agent is 7 to 15, the reaction temperature is 80 to 100°C, and the stirring speed is 150 to 250 RPM.

[0060] In one embodiment of the present invention, the pH of the leachate after the impurity purification and leaching step in step S20 may be 7 or higher, 7 to 10, or 7.7 to 9. By adjusting the pH within the above range, the impurities Fe, Al, and Si contained in the leachate separated in step S10 can be completely precipitated and removed, and the removal rate of Ca can be increased.

[0061] In one embodiment of the present invention, after the impurity purification and leaching process in step S20, a solution containing high Mg concentration of 30 g / L to 90 g / L in the solution can be obtained, and impurities such as Fe, Al, and Si can be effectively removed.

[0062] Of the leachate and residue separated after the purification and leaching of the impurities, the leachate can be supplied to the subsequent extraction step, and the residue can be added during the leaching in step S10.

[0063] In one embodiment of the present invention, the leachate separated in step S10 may be subjected to a purification leaching step of removing impurities in step S20, and the obtained leachate may be powdered to produce a magnesium-containing powder.

[0064] The powdering step of the magnesium-containing raffinate can be performed by vacuum distillation or spray drying, etc. As a specific example, the powdering step of the magnesium-containing raffinate can be performed by vacuum distillation.

[0065] The step S30 can be carried out for 30 minutes to 2 hours or 1 minute to 1 hour and 30 minutes under the conditions of a steam temperature of 45°C or higher or 45 to 60°C and a stirring speed of 25 RPM or higher or 50 to 110 RPM, thereby evaporating and drying all of the water in the leachate to obtain a dry powder containing sulfuric acid and Mg.

[0066] The distillate evaporated in step S30 can be further recovered and reused as distilled water to be added to prepare the sulfuric acid solution in the leaching step S10.

[0067] The resulting magnesium-containing powder can be supplied to a subsequent heat treatment step.

[0068] In one embodiment of the present invention, step S40 may be a step of producing magnesium oxide (MgO) by heat treating the magnesium-containing powder obtained in step S30.

[0069] The heat treatment in the above step S40 can be carried out at a temperature of 1000° C. to 1500° C. or 1200° C. to 1500° C. for 30 minutes to 6 hours or 3 hours to 6 hours, thereby making it possible to recover powdery MgO.

[0070] When the heat treatment is performed in step S40, SO2-containing exhaust gas may be generated, and the SO2-containing exhaust gas can be converted into sulfuric acid through a separate catalytic process. The sulfuric acid thus produced can be reused to produce a sulfuric acid solution when leaching in step S10.

[0071] In one embodiment of the present invention, step S50 may be a step of purifying the powdered MgO obtained in step S40 by washing it.

[0072] In the step S50, the heat-treated magnesium oxide is washed with distilled water to remove impurities, especially Ca.

[0073] The step S50 can be carried out under the condition that the solid (g) / liquid (mL) ratio of the heat-treated magnesium oxide to the distilled water is 1 / 1 to 1 / 10, 1 / 2 to 1 / 10, or 1 / 2 to 1 / 3.

[0074] In the step S50, the heat-treated magnesium oxide may be washed with distilled water at a temperature of 20°C to 50°C, or 20°C to 30°C for 5 to 50 minutes, or 20 to 30 minutes.

[0075] The step S50 can be carried out once or repeatedly 2 to 5 times. As a specific example, the step S50 can be carried out 2 to 3 times.

[0076] After washing the MgO, the pH may be 10 or higher, 10 to 13, or 10.2 to 12.5.

[0077] The washing solution obtained after washing the heat-treated MgO with distilled water in step S50 may contain Ca as an impurity. The washing solution can be left in the air to remove Ca and used to prepare an alkaline solution with a pH of 10 or higher.

[0078] In one embodiment of the present invention, by controlling the heat treatment temperature and time in step S40 and the number of washings and the solid-liquid ratio in step S50, it is possible to minimize the loss of Mg and improve the removal rate of Ca, thereby producing higher purity MgO.

[0079] As a specific example, when MgO that has been heat-treated in step S40 at a temperature of 1200°C to 1500°C for 3 to 6 hours is washed with distilled water two to three times, the loss of Mg can be minimized while the removal rate of Ca can be improved.

[0080] The present invention also provides high-purity magnesium oxide produced by the above-mentioned method for producing high-purity magnesium oxide by an environmentally friendly hydrometallurgical process.

[0081] As described above, the method for producing high-purity magnesium oxide by an environmentally friendly hydrometallurgical process according to the present invention, and the magnesium oxide produced thereby, have been described and shown in the drawings. However, the above description and the illustrations in the drawings only describe and show the core configuration for understanding the present invention, and in addition to the processes and devices described and shown in the drawings, processes and devices not otherwise described or shown can be appropriately applied and used to carry out the present invention.

[0082] Hereinafter, the present invention will be described in detail with reference to examples. However, the examples according to the present invention can be modified in various ways, and the scope of the present invention is not to be construed as being limited to the examples described below. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0083] <Example> In the following, as the magnesium-containing waste refractory material, MgO-C waste refractory material having the valuable metal components (wt%) shown in Table 1 below was used as the raw material.

[0084] [Table 1]

[0085] Example 1: One-stage leaching of MgO-C waste refractory material MgO-C waste refractory material having an average particle size of 60 mesh or less was leached using 1M, 3M, 5M, and 7M sulfuric acid (H2SO4) solutions as leaching agents, respectively. The leaching process was carried out under the following conditions: a solid / liquid ratio of MgO-C waste refractory material / sulfuric acid solution was 1 / 10, a reaction temperature was 90°C, and a stirring speed was 200 rpm.

[0086] Table 2 below shows the leachate composition (mg / L) after leaching with 1M sulfuric acid. As can be seen from Table 2, only about 50% of Mg was leached from the initial 120 minutes. On the other hand, in the case of Ca, the leaching rate gradually decreased from an initial 95.1% to only 85.8%. Furthermore, in the case of Fe, Al, and Si, the leaching rate decreased as the pH increased. Fe was precipitated and removed without leaching from the 90-minute mark, Al was precipitated and removed from the 15-minute mark, and Si was precipitated and removed from the 45-minute mark.

[0087] When leaching was performed using 1M sulfuric acid, the initial pH rose from 4.1 to 6.7 after 120 minutes. This was because the MgO in the waste refractory material was a basic substance, and the sulfuric acid solution used was weakly concentrated. In conclusion, the 1M sulfuric acid experiment confirmed that valuable metal impurities such as Fe, Al, and Si could be removed, but that only about 50% of Mg was leached.

[0088] [Table 2]

[0089] The results of leaching with 3M sulfuric acid are shown in Table 3 below. As can be seen from Table 3, the initial leaching rate of Mg increased from 75.5% to 93.7% at 60 minutes from the beginning. At this time, unlike the leaching with 1M sulfuric acid, all of the Ca, Fe, and Al were leached. This is due to the SO4 in the 3M sulfuric acid. 2- The total amount was leached at a concentration and pH of 1M. That is, when 3M sulfuric acid was used, the leaching rate of Mg also increased, reaching 93.7%, but the total amount of other impurities such as Ca, Fe, and Al was leached, confirming that the concentration of impurities was higher than that of leaching with 1M sulfuric acid. In this case, the pH was below 0.1.

[0090] [Table 3]

[0091] Table 4 below shows the results of leaching with 5M sulfuric acid. As can be seen from Table 4, from the beginning to 120 minutes, the initial leaching rate for Mg started at 68.9%, and increased to 95.8% at 60 minutes. In addition, in the case of Ca, the leaching rate started at 87.1% at the first 5 minutes, but decreased significantly over time, reaching 36.2% at 120 minutes. This is because, compared to 3M sulfuric acid, the leaching rate of Ca was 87.1% at 5 minutes, and decreased significantly over time to 36.2% at 120 minutes. 2- It is believed that the concentration of CaSO4 was relatively high and the pH was low, causing precipitation of CaSO4.

[0092] In the case of Si, it precipitates in SiO2 through a similar reaction.

[0093] On the other hand, it can be seen that the leaching rate of Fe and Al was completely leached at low pH. In other words, when 5M sulfuric acid was used, the leaching rate of Mg could be increased to over 95%, and the impurities of Ca and Si could be controlled.

[0094] [Table 4]

[0095] The results of leaching with 7M sulfuric acid are shown in Table 5 below. As can be seen from Table 5, the initial leaching rate for Mg increased from 79.9% for the first 45 minutes to 95.8% at 30 minutes. It can also be seen that the leaching rate for Ca was only 17%, and no leaching was observed for Si.

[0096] When compared to the other experimental conditions above, 3M and 5M sulfuric acid, SO4 2- Because the concentration of sulfuric acid is relatively high, the leaching rate of Ca is low and almost no Si is leached. On the other hand, the leaching rates of Fe and Al are 100% and 98%, respectively, at low pH. In other words, the higher the concentration of sulfuric acid, the better the leaching rate of Mg, and the higher the SO42- It was confirmed that the incorporation of Ca and Si can be controlled by increasing the concentration of

[0097] [Table 5]

[0098] Example 2: Purification and leaching of impurities from waste MgO refractory materials The leaching solutions using 3M, 5M, and 7M sulfuric acid solutions were further used as leaching agents to carry out purification leaching experiments of impurities.

[0099] The reason for excluding 1M is that when leaching using a 1M sulfuric acid solution, the pH is already quite high at 6.7 or higher, and it was judged that the leaching of Mg in the two-stage leaching would be significantly less.

[0100] The 3M, 5M, and 7M sulfuric acid solutions were selected because the final pH of the first-stage leaching solution was about pH 0.03, pH -0.6, and pH -0.9, respectively, which was low enough to leach out the magnesium contained in the waste refractory material that was fed in. The composition (mg / L) of the first-stage leaching solution used as the leaching solution during the impurity purification and leaching process was measured and is shown in Table 6 below.

[0101] [Table 6]

[0102] The results of the impurity purification and leaching process using a first-stage leaching solution of 3M sulfuric acid are shown in Table 7. The temperature during the impurity purification and leaching reaction was adjusted to 90°C, the solid-liquid ratio to 1 / 10, and the stirring speed to 200 rpm.

[0103] As a result, the amount of Mg leached was 45,600 mg / L, and the other impurities Fe, Al, and Si were all precipitated as the pH rose from the initial value to 8.56 and were not analyzed. In the case of Ca, 342 mg / L was finally present in the solution.

[0104] [Table 7]

[0105] The results of the impurity purification and leaching process using a first-stage leaching solution of 5M sulfuric acid are shown in Table 8. The temperature during the impurity purification and leaching reaction was adjusted to 90°C, the solid-liquid ratio to 1 / 10, and the stirring speed to 200 rpm.

[0106] As a result, the amount of Mg leached reached 52,600 mg / L, while the other impurities Fe, Al, and Si gradually decreased as the pH increased from an initial value of 5.21 to a final value of 7.81, and all of them precipitated and were not analyzed. In the case of Ca, 157 mg / L was ultimately present in the solution.

[0107] [Table 8]

[0108] The results of the impurity purification and leaching process using a first-stage leaching solution of 7M sulfuric acid are shown in Table 9. The temperature during the impurity purification and leaching reaction was adjusted to 90°C, the solid-liquid ratio to 1 / 10, and the stirring speed to 200 rpm.

[0109] As a result, the amount of Mg leached reached 51,600 mg / L, and the pH only increased to -0.1. Unlike the leaching with 3M and 5M sulfuric acid, the final solution contained 555 mg / L Fe, 158 mg / L Al, and 37.6 mg / L Si. The final pH was -0.1, which allowed further purification and leaching experiments to be carried out using this solution.

[0110] [Table 9]

[0111] The results of the impurity purification and leaching process using a two-stage leaching solution of 7M sulfuric acid are shown in Table 10. Here, the temperature during the impurity purification and leaching reaction was adjusted to 90°C, the solid-liquid ratio to 1 / 10, and the stirring speed to 200 rpm.

[0112] As a result, the leaching amount of Mg reached 58,300 mg / L, and as the pH increased to 8.23, Fe, Al, and Si precipitated and were not analyzed at all. In the case of Na, the leaching amount continued to decrease, because the Na in the solution precipitated as Na2SO4 as the pH increased.

[0113] [Table 10]

[0114] Example 3: Purification leaching process of impurities using 5M sulfuric acid solution with solid-liquid ratio Tables 11 and 12 below show the results of the solid-liquid ratio during the impurity purification leaching process using a first-stage leaching solution in which 5M sulfuric acid solution was used as the leaching agent. The temperature during the impurity purification leaching reaction was adjusted to 90°C and the stirring speed to 200 rpm.

[0115] The solid-liquid ratio experiment has the effect of concentrating the Mg in the solution rather than the leaching rate of Mg in the sample during two-stage leaching, and at the same time, it is a process that automatically increases the pH to control impurities such as Fe, Al, and Si. Therefore, the specific gravity of the sample added is very important. This is because when the residue generated after the impurity purification leaching process is further leached in one stage, it is mixed with new sample and used, which allows the amount of sample that must be added in the first stage leaching process to be calculated.

[0116] Table 11 shows the measurement results for the composition (mg / L) of the two-stage leaching solution in the impurity purification leaching process at a solid-liquid ratio of 7.5% (solution: 500 mL / sample: 37.5 g). Mg was leached to 53,400 mg / L, Ca was leached to 137.5 mg / L, and Fe, Al, and Si all precipitated and were not analyzed as the pH increased to 7.5 over time.

[0117] [Table 11]

[0118] Table 12 below shows the measurement results for the composition (mg / L) of the two-stage leaching solution in the impurity purification leaching process at a solid-liquid ratio of 15% (solution: 500 mL / sample: 75 g). During this time, Mg was leached to 56,200 mg / L, and Ca was leached to 117.5 mg / L. Furthermore, Fe, Al, and Si all precipitated and were not analyzed as the solution pH increased from 7.11 initially to 7.94 after 30 minutes.

[0119] [Table 12]

[0120] Example 4: Preparation of Mg-containing powder by vacuum distillation process The secondary leaching solution, the pH of which was adjusted through the impurity purification process, was obtained, and each of these was distilled under reduced pressure to obtain a solution and a powder containing Mg.

[0121] The vacuum distillation experiment was carried out for 1 hour at a vapor temperature of 45°C or higher and a stirring speed of 25 RPM or higher. The solution recovered from the distillation was then used for further production of sulfuric acid.

[0122] Figure 2 below shows the XRD analysis results of the powder obtained after vacuum distillation. The main peaks were CaSO4, MgSO4, and Mg(OH)4SO4. In other words, it was confirmed that impurities such as Fe, Si, and Al were completely removed through the impurity purification process, leaving only Mg and Ca.

[0123] Example 5: Preparation of high purity MgO by heat treatment process After vacuum distillation, the obtained powders were all heat-treated at 1000° C. to 1500° C. The heat treatment process was carried out in an air atmosphere using a box furnace for 30 minutes to 3 hours.

[0124] As a result, the XRD analysis shown in Figure 3 below confirmed that the main peak in the powder obtained by heat treatment at 1200°C or higher was MgO, and the purity of the obtained MgO was calculated by instrumental analysis using ICP.

[0125] ICP analysis confirmed that the powder contained approximately 0.61% Ca as shown in Table 13 below, and XRD analysis revealed that the Ca in the powder existed as a minor peak in the form of CaSO4. The purity of the produced MgO was 97.8%.

[0126] [Table 13]

[0127] Example 6: Purification of MgO by washing with distilled water To purify the produced MgO, a solid-liquid washing experiment was carried out to remove Ca using distilled water. The experiment was carried out at room temperature within 30 minutes.

[0128] The results are shown in Table 14 below. Table 14 shows the results of water washing of MgO obtained by heat treatment at 1200°C for 30 minutes. When washing was performed at a solid-liquid ratio of 1 / 10 (MgO: 3.1 g, distilled water: 31 mL), 2.57 g was removed, resulting in a loss of 82.9% of the sample.

[0129] [Table 14]

[0130] Table 15 below shows the results of first water washing after MgO was obtained by heat treatment at temperatures between 1200°C and 1500°C for 3 hours. When 3.1 g of MgO was washed in 31 mL of distilled water, the amount lost was less than 0.5 g, and the Mg loss was 59 mg / L, 46 mg / L, and 31 mg / L, respectively, confirming that the amount of Mg lost decreases depending on the heat treatment temperature. The pH of the solution after washing was confirmed to be pH 10.5, pH 11.2, and pH 11.6, depending on the heat treatment temperature.

[0131] [Table 15]

[0132] Tables 14 and 15 show the MgO loss and impurity removal amount depending on the heat treatment time and heat treatment temperature. In other words, the heat treatment time must be 30 minutes or more to reduce Mg loss, and the heat treatment temperature of 1200°C can reduce Mg loss slightly.

[0133] Therefore, to obtain high-purity MgO, the sample heat-treated for 3 hours or more was subjected to a second water wash. Specifically, 3.1 g of MgO was washed in 31 mL of distilled water at a temperature of 1200 to 1500°C for 30 minutes. The results are shown in Table 16 below.

[0134] As can be seen from Table 16, as the heat treatment temperature increases, the amount of Mg lost decreases slightly, which can be verified by the pH after washing. At the same time, it can be seen that the amount of Ca removed in the second washing is significantly greater than that in the first washing.

[0135] [Table 16]

[0136] Table 17 below shows the purity of MgO obtained after two washes and drying at 80°C or higher, followed by ICP analysis and conversion to oxide. As can be seen from Table 17, the purity of the produced MgO was 99.76%, demonstrating that very high-purity MgO was produced. The XRD analysis results of the produced MgO are also shown in Figure 4 below.

[0137] [Table 17] [Industrial Applicability]

[0138] The method for producing high-purity magnesium oxide from waste refractories according to the present invention can produce environmentally friendly high-purity magnesium oxide (MgO) with controlled impurities such as Fe, Al, Si, and Ca by recycling the waste refractories into secondary resources of conventional refractories or by using environmentally friendly hydrometallurgical processes from the waste refractories that have been disposed of in landfills.

Claims

1. A step (S10) of leaching the magnesium-containing waste refractory material, performing solid-liquid separation, and separating the leachate and residue; A step of purifying and leaching impurities from the leaching solution (S20); A step of powdering the leachate obtained by the step of purifying and leaching the impurities to prepare a magnesium-containing powder (S30); Heat-treating the magnesium-containing powder to prepare magnesium oxide (S40); and (S50) a step of purifying the heat-treated magnesium oxide by washing it; The purity of the washed magnesium oxide is 99% or more. A method for producing high-purity magnesium oxide from waste refractory materials by an environmentally friendly hydrometallurgical process.

2. The magnesium-containing waste refractory material contains 30% by weight to 55% by weight of magnesium. A method for producing high purity magnesium oxide from the waste refractory material according to claim 1 by an environmentally friendly hydrometallurgical process.

3. The method further comprises a step of crushing / crushing the magnesium-containing waste refractory material before the step of leaching the magnesium-containing waste refractory material, performing solid-liquid separation, and separating the leachate from the residue. A method for producing high purity magnesium oxide from the waste refractory material according to claim 1 by an environmentally friendly hydrometallurgical process.

4. The crushed / pulverized magnesium-containing waste refractory material has an average particle size of 100 mesh or less. A method for producing high-purity magnesium oxide from the waste refractory material according to claim 3 by an environmentally friendly hydrometallurgical process.

5. The step S10 is characterized in that the magnesium-containing waste refractory material is leached using a sulfuric acid solution having a molar concentration of 1M to 7M. A method for producing high purity magnesium oxide from the waste refractory material according to claim 1 by an environmentally friendly hydrometallurgical process.

6. The step S10 is carried out under the conditions that the solid (g) / liquid (mL) ratio of the magnesium-containing waste refractory material and the sulfuric acid solution is 1 / 10 to 3 / 10, the reaction temperature is 100°C or less, and the stirring speed is 100 to 400 RPM. A method for producing high purity magnesium oxide from the waste refractory material according to claim 5 by an environmentally friendly hydrometallurgical process.

7. The step S20 is performed by using the leaching solution obtained in the step S10 as a leaching agent, adding the magnesium-containing waste refractory material to the leaching agent, and then separating the leaching solution from the residue. A method for producing high purity magnesium oxide from the waste refractory material according to claim 1 by an environmentally friendly hydrometallurgical process.

8. The step S20 is characterized in that a process of using a first-stage leachate as a leachant, introducing magnesium-containing waste refractory material into the leachant, and then separating the second-stage leachate and the residue is repeatedly performed. A method for producing high purity magnesium oxide from the waste refractory material according to claim 7 by an environmentally friendly hydrometallurgical process.

9. The step S20 is carried out under the conditions that the solid (g) / liquid (L) ratio of the magnesium-containing waste refractory material and the leaching agent is 5 to 30, the reaction temperature is 100°C or less, and the stirring speed is 100 to 400 RPM. A method for producing high purity magnesium oxide from the waste refractory material according to claim 8 by an environmentally friendly hydrometallurgical process.

10. The pH of the leaching solution after the purification and leaching step of impurities in step S20 is 7 or more. A method for producing high purity magnesium oxide from the waste refractory material according to claim 1 by an environmentally friendly hydrometallurgical process.

11. The step S30 is performed for 30 minutes to 2 hours under the conditions that the steam temperature is 45°C or higher and the stirring speed is 25 RPM or higher. A method for producing high purity magnesium oxide from the waste refractory material according to claim 1 by an environmentally friendly hydrometallurgical process.

12. The heat treatment in step S40 is performed at a temperature of 1000°C to 1500°C for 30 minutes to 6 hours. A method for producing high purity magnesium oxide from the waste refractory material according to claim 1 by an environmentally friendly hydrometallurgical process.

13. The heat treatment in step S40 is performed at a temperature of 1200°C to 1500°C for 3 to 6 hours. A method for producing high purity magnesium oxide from the waste refractory material according to claim 12 by an environmentally friendly hydrometallurgical process.

14. At least one of the residue generated in step S20, the distillate generated in step S30, and the exhaust gas components generated in step S40 is reused in step S10. A method for producing high purity magnesium oxide from the waste refractory material according to claim 1 by an environmentally friendly hydrometallurgical process.

15. The step S50 is characterized in that the heat-treated magnesium oxide is washed with distilled water at a solid (g) / liquid (mL) ratio of the heat-treated magnesium oxide to distilled water of 1 / 1 to 1 / 10, and at a temperature of 20°C to 50°C for 5 minutes to 50 minutes. A method for producing high purity magnesium oxide from the waste refractory material according to claim 1 by an environmentally friendly hydrometallurgical process.

16. The step S50 is repeated once or twice to five times. A method for producing high purity magnesium oxide from the waste refractory material according to claim 1 by an environmentally friendly hydrometallurgical process.

17. The heat treatment in step S40 is performed at a temperature of 1200°C to 1500°C for 3 to 6 hours. The step S50 is repeated 2 to 5 times. A method for producing high purity magnesium oxide from the waste refractory material according to claim 1 by an environmentally friendly hydrometallurgical process.

18. 10. Magnesium oxide produced by the method of claim 1.

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