Method for producing high purity magnesium oxide from waste refractory material by eco-friendly hydrometallurgy application process and magnesium oxide produced by method

Abstract

The present invention provides a method for preparing high-purity magnesium oxide from a waste refractory material by an eco-friendly hydrometallurgy application process and magnesium oxide prepared by the method, comprising: a step (step S10) of leaching a magnesium-containing waste refractory material and then separating a leachate and a residue by solid-liquid separation; a step (step S20) for purifying and leaching impurities in the leachate; a step (step S30) for preparing a magnesium-containing powder by powdering the leach solution that has undergone the impurity purification leaching step; a step (step S40) for preparing magnesium oxide by heat-treating the magnesium-containing powder; and a step (step S50) for washing the heat-treated magnesium oxide to increase the purity of the magnesium oxide.

Description

Technical Field

[0001] The present invention relates to a method for preparing high-purity magnesium oxide from waste refractory materials through an environmentally friendly hydrometallurgical application process and magnesium oxide prepared by the method. More specifically, the present invention relates to a method for environmentally friendly preparation of high-purity magnesium oxide (MgO) by using waste refractory materials that are currently reused as secondary resources for refractory materials or landfilled through processes such as leaching, purification, and washing. Background Art

[0002] Generally, magnesium oxide, also known as magnesia, is an oxide form of magnesium with a high melting point and hygroscopicity.

[0003] Most of it is prepared from magnesite, a natural carbonate mineral. Magnesia can be classified according to the heat treatment temperature or raw materials. Light-burned magnesia is prepared from magnesite at a temperature of 600°C to 1400°C. On the contrary, dead-burned magnesia is prepared at a temperature of 1400°C to 2200°C. And fused magnesia is prepared by melting magnesite at a temperature above 2800°C. Moreover, seawater magnesia is prepared from seawater through precipitation and roasting.

[0004] Magnesium oxide prepared at a high temperature is used as a raw material for refractories. More than 70% of the magnesium oxide thus prepared is used as refractories, and the remaining 30% is used in various industrial fields such as agriculture, medicine, optics, atomic reactors, and rocket propellants according to different types.

[0005] In the steel industry in Korea, refractories containing MgO-C are used in electric furnaces and steel ladles for ironmaking, and are discarded after use, and a part of them is reused.

[0006] Reuse methods include methods of removing nitrogen, aluminum, etc. in waste refractories by wet methods and then improving the purity of magnesium oxide in waste refractories through physical screening processes, and methods of burning and gasifying carbon by dry methods to improve the purity of magnesium oxide in waste refractories. However, its purity is about 97% or less, and most of the waste refractories are reused as refractories, and there are very few reports on the process of preparing high-purity magnesium oxide from waste refractories.

[0007] In Korea, the preparation of magnesium oxide is only carried out in a certain smelting company by the above-mentioned wet process from seawater to prepare more than 98% of magnesium oxide, but it is limited to self-production and self-sale.

[0008] Therefore, all magnesium oxide in Korea without magnesium-related mines depends on imports and the supply is insufficient. Thus, there is an urgent need to develop a process for recovering magnesium oxide from waste refractory materials, and a preparation process for preparing high-purity magnesium oxide through a smelting process that combines environmental protection and economy is required.

[0009] Generally, compared with the currently popular commercialized processes, the disadvantage of environmentally friendly processes is that they are limited in terms of economy due to the high cost of the chemical reagents and reaction equipment used. Therefore, research is needed to shorten the number of process steps by applying commercialized conventional processes and to prepare high-purity magnesium oxide in an environmentally friendly manner. Summary of the Invention

[0010] Technical Problem

[0011] In order to solve the above problems, an object of the present invention is to provide an environmentally friendly method for recovering magnesium oxide, which is entirely imported in Korea, from waste refractory materials with high purity by simplifying the environmentally friendly hydrometallurgical application process.

[0012] The technical problems to be solved by the present invention are not limited to the above-mentioned technical problems, and those of ordinary skill in the technical field to which the present invention pertains can clearly understand unmentioned technical problems or other technical problems through the following description.

[0013] Technical Solution

[0014] In order to achieve the above object, the present invention provides a method for preparing high-purity magnesium oxide from waste refractory materials through an environmentally friendly hydrometallurgical application process, including: step S10 of leaching magnesium-containing waste refractory materials and then separating the leachate and residue through solid-liquid separation; step S20 of purifying impurities in the leachate; step S30 of powdering the leachate after the impurity purification leaching step to prepare magnesium-containing powder; step S40 of heat-treating the magnesium-containing powder to prepare magnesium oxide; and step S50 of washing the heat-treated magnesium oxide to increase its purity.

[0015] According to an embodiment of the present invention, the magnesium-containing waste refractory materials may contain 30 wt% to 55 wt% of magnesium.

[0016] According to an embodiment of the present invention, before the step of separating the leachate and residue through solid-liquid separation after leaching the magnesium-containing waste refractory materials, a step of crushing or pulverizing the magnesium-containing waste refractory materials may further be included.

[0017] According to an embodiment of the present invention, the average particle size of the crushed or pulverized magnesium-containing waste refractory materials may be 100 mesh or less.

[0018] According to an embodiment of the present invention, in step S10, the magnesium-containing waste refractory materials may be leached using a sulfuric acid solution with a molar concentration of 1M to 7M.

[0019] According to an embodiment of the present invention, 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 below 100 °C, and the stirring speed is 100 RPM to 400 RPM.

[0020] According to an embodiment of the present invention, in the above step S20, the leaching solution obtained in the above step S10 can be used as a leaching agent, and the magnesium-containing waste refractory material can be put into the leaching agent for leaching, and then the leaching solution and the residue can be separated.

[0021] According to an embodiment of the present invention, in the above step S20, the following process can be repeated: using the previous-stage leaching solution as a leaching agent, putting the magnesium-containing waste refractory material into the leaching agent for leaching, and then separating the latter-stage leaching solution and the residue.

[0022] According to an embodiment of the present invention, the above step S20 can be carried out under the conditions that the solid (g) / liquid (L) ratio of the magnesium-containing waste refractory material to the sulfuric acid solution is 5 to 30, the reaction temperature is below 100 °C, and the stirring speed is 100 RPM to 400 RPM.

[0023] According to an embodiment of the present invention, in the above step S20, the pH of the leaching solution after the impurity purification leaching step can be 7 or more.

[0024] According to an embodiment of the present invention, the above 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.

[0025] According to an embodiment of the present invention, in the above step S40, the heat treatment can be carried out at a temperature of 1000 °C to 1500 °C for 30 minutes to 6 hours.

[0026] According to an embodiment of the present invention, in the above step S40, the heat treatment is carried out at a temperature of 1200 °C to 1500 °C for 3 hours to 6 hours.

[0027] According to an embodiment of the present invention, in the above step S10, one or more of the residue generated in step S20, the distillate generated in step S30, and the waste gas components generated in step S40 can be reused.

[0028] According to an embodiment of the present invention, the above step S50 can use distilled water to wash the heat-treated magnesium oxide for 5 minutes to 50 minutes under the conditions that the solid (g) / liquid (mL) ratio of the heat-treated magnesium oxide to the distilled water is 1 / 1 to 1 / 10 and the temperature is 20 °C to 50 °C.

[0029] According to an embodiment of the present invention, the above step S50 can be carried out once or repeated 2 to 5 times.

[0030] According to an embodiment of the present invention, in the above step S40, the heat treatment can be performed at a temperature of 1200 °C to 1500 °C for 3 hours to 6 hours, and the above step S50 can be repeated 2 to 5 times.

[0031] To achieve the above object, the present invention provides magnesium oxide prepared by using the method for preparing high-purity magnesium oxide from waste refractory materials through the above environmentally friendly wet smelting application process.

[0032] Effects of the Invention

[0033] The method for preparing high-purity magnesium oxide from waste refractory materials of the present invention utilizes waste refractory materials that can be reused as secondary resources for refractory materials or buried through the existing environmentally friendly wet smelting application process to prepare high-purity magnesium oxide with impurities such as iron (Fe), aluminum (Al), silicon (Si), and calcium (Ca) removed in an environmentally friendly manner.

[0034] Moreover, in the method for preparing magnesium oxide of the present invention, an alkaline solution can be prepared from the washing liquid in the washing step for high-purifying magnesium oxide. If sulfur dioxide (SO2) gas is generated during the heat treatment, it can be prepared into sulfuric acid through a subsequent catalyst process, and the generated wastewater can be effectively reduced by using the distillate in the powder chemical process when preparing sulfuric acid, thereby enabling the environmentally friendly wet smelting application process and preparing high-purity magnesium oxide in an environmentally friendly manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a process flow diagram of a method for preparing high-purity magnesium oxide from waste refractory materials through a wet smelting process according to an embodiment of the present invention. [[ID=2%]]

[0036] Figure 2 It is an X-ray diffraction (XRD) pattern of magnesium-containing powder according to an embodiment of the present invention.

[0037] Figure 3 It is an X-ray diffraction pattern of magnesium oxide recovered after heat treatment according to an embodiment of the present invention.

[0038] Figure 4 It is an X-ray diffraction pattern of high-purity magnesium oxide recovered after washing according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The object of the present invention is to provide an environmentally friendly method for recovering magnesium oxide, which is all imported in Korea, from waste refractory materials with high purity through an environmentally friendly wet smelting application process that simplifies the process.

[0040] Embodiments of the Present Invention

[0041] Before explaining the present invention in detail, it should be noted that the terms or words used in this specification should not be unconditionally construed in accordance with the ordinary or dictionary meanings. The inventors of the present invention can appropriately define and use the concepts of various terms in order to explain the present invention in the best way. Furthermore, these terms or words should be construed as meanings and concepts consistent with the technical idea of the present invention.

[0042] That is, the terms used in this specification are only used to explain the preferred embodiments of the present invention, rather than being used with the intention of specifically limiting the content of the present invention. These terms are defined in consideration of various possibilities of the present invention.

[0043] Also, in this specification, unless the context clearly indicates otherwise, singular expressions may include plural expressions, and similarly, plural expressions may also include singular expressions.

[0044] Throughout this specification, when a structural element is referred to as "including" other structural elements, unless there is a particularly contrary meaning recorded, it may mean that any other structural elements may also be included, rather than excluding any other structural elements.

[0045] Also, in the following process of explaining the present invention, structures that are judged to be likely to unnecessarily confuse the gist of the present invention will be omitted, for example, detailed descriptions of well-known technologies including prior arts.

[0046] Hereinafter, the present invention will be described in more detail.

[0047] According to the present invention, as shown in the process flow chart of Figure 1 , a method for preparing high-purity magnesium oxide from waste refractory materials through an environmentally friendly hydrometallurgical application process is provided, including: a step of separating the leachate and the residue by solid-liquid separation after leaching the magnesium-containing waste refractory materials (step S10); a step of purifying the impurities of the leachate obtained above (step S20); a step of pulverizing the leachate obtained through the impurity purification leaching step above to prepare a magnesium-containing powder (step S30); a step of heat-treating the magnesium-containing powder above to prepare magnesium oxide (step S40); and a step of washing the heat-treated magnesium oxide above to make it highly pure (step S50).

[0048] In an embodiment of the present invention, the magnesium-containing waste refractory materials may include one or more of dolomite-based (MgO-CaO-based refractory materials), magnesite-carbon-based (MgO-C-based refractory materials), magnesite-based (MgO-based refractory materials), magnesite-chromium-based (MgO-Cr2O3-based refractory materials), alumina-based, and silica-based refractory materials that can withstand temperatures above 1500°C. Specifically, for example, the magnesium-containing waste refractory materials may be MgO-C waste refractory materials.

[0049] The above-mentioned magnesium-containing waste refractory material may contain 30 wt% to 55 wt% or 35 wt% to 50 wt% of magnesium (Mg). And, in addition to magnesium, the above-mentioned magnesium-containing waste refractory material may further contain one or more of calcium (Ca), iron (Fe), sodium (Na), potassium (K), aluminum (Al), silicon (Si), and carbon (C).

[0050] When the above-mentioned magnesium-containing waste refractory material contains one or more of calcium, iron, sodium, potassium, aluminum, silicon, and carbon in addition to magnesium, the content of calcium may be 0.01 wt% to 0.5 wt%, the content of iron may be 0.01 wt% to 1 wt%, the content of sodium may be 0.001 wt% to 0.3 wt%, the content of potassium may be 0.001 wt% to 0.3 wt%, the content of aluminum may be 0.1 wt% to 5 wt%, the content of silicon may be 0.01 wt% to 1 wt%, and the content of carbon may be 1 wt% to 25 wt%.

[0051] In one embodiment of the present invention, before the step of separating the leachate and the residue by solid-liquid separation after leaching the magnesium-containing waste refractory material, a step of crushing the magnesium-containing waste refractory material may further be included.

[0052] The crushing of the above-mentioned magnesium-containing waste refractory material can be carried out using a conventional crusher. For example, the above-mentioned crusher may include one or more selected from the group consisting of a jaw crusher, a gyratory crusher, a roller crusher, a cone crusher, a hammermil crusher, a tumbling mill, a vibration mill, an attrition mill, a ball mill, a rod mill, a pebble mill, and an autogenous mill.

[0053] The average particle size of the crushed magnesium-containing waste refractory material may be 100 mesh or less, 10 mesh to 100 mesh, or 30 mesh to 100 mesh. When the magnesium-containing waste refractory material is crushed by a crusher to the above range and then followed by subsequent leaching process and extraction process, etc., the recycling rate of the magnesium component contained in the waste refractory material can be increased, and the process time and cost can be saved.

[0054] In one embodiment of the present invention, in step S10, the leachate and the residue may be separated by solid-liquid separation after leaching the magnesium-containing waste refractory material.

[0055] When leaching the magnesium-containing waste refractory material described above, an acidic solution can be used as the leaching agent. For example, the acidic solution can contain one or more selected from the group consisting of nitric acid, hydrochloric acid, sulfuric acid, and perchloric acid. Specifically, for example, the leaching agent can be a sulfuric acid solution.

[0056] In the above step S10, the magnesium-containing waste refractory material can be leached using a sulfuric acid solution with a molar concentration of 1M to 7M, 3M to 7M, or 4M to 6M. When leaching the magnesium-containing waste refractory material using a sulfuric acid solution with a molar concentration within the above range, the co-leaching rate of impurities such as iron, aluminum, calcium, and silicon can be reduced while increasing the leaching rate of magnesium.

[0057] 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 below 100°C, and the stirring speed is 100 RPM to 400 RPM.

[0058] Specifically, for example, the above 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 RPM to 250 RPM.

[0059] In an embodiment of the present invention, the residue separated by solid-liquid separation described above contains low-grade valuable metals and carbon (C), and can be used as low-grade or medium-grade carbon.

[0060] In an embodiment of the present invention, the above step S20 can be a step of purifying the impurities in the leaching solution separated in the above step S10 by a leaching method.

[0061] Specifically, for example, in the above step S20, the leaching solution obtained in the above step S10 can be used as the leaching agent, and the magnesium-containing waste refractory material can be put into the leaching agent for leaching reaction, and then the leaching solution and the residue can be separated.

[0062] In an embodiment of the present invention, the above step S20 can be carried out once or repeated 2 to 5 times. Specifically, the following process can be repeated: using the previous-stage leaching solution as the leaching agent, putting the magnesium-containing waste refractory material into the leaching agent for leaching, and then separating the latter-stage leaching solution and the residue.

[0063] As an example, when carrying out the above step S20 once, the first-stage leaching solution separated in the above step S10 can be used as the leaching agent, and the magnesium-containing waste refractory material can be put into the first-stage leaching agent for leaching, and then the second-stage leaching solution and the residue can be separated. Among them, the second-stage leaching solution can be used for the subsequent extraction process.

[0064] For another example, in the case of performing the above-mentioned step S20 twice, a separated leachate in the above-mentioned step S10 can be used as a leaching agent. After putting magnesium-containing waste refractory into the above-mentioned first-stage leaching agent for leaching, the second-stage leachate and residue are separated. Then, the second-stage leachate is used as a leaching agent, and after putting magnesium-containing waste refractory into the above-mentioned second-stage leaching agent for leaching, the third-stage leachate and residue are separated. Among them, the third-stage leachate can be used for the subsequent extraction process.

[0065] In an embodiment of the present invention, the above-mentioned step S20 can be carried out for 5 minutes to 120 minutes under the conditions that the solid (g) / liquid (L) ratio of magnesium-containing waste refractory to sulfuric acid solution is 5 to 30, the reaction temperature is below 100 °C, and the stirring speed is 100 RPM to 400 RPM.

[0066] Specifically, for example, the above-mentioned step S20 can be carried out for 30 minutes to 120 minutes under the conditions that the solid (g) / liquid (L) ratio of magnesium-containing waste refractory to the leaching agent is 7 to 15, the reaction temperature is 80 °C to 100 °C, and the stirring speed is 150 RPM to 250 RPM.

[0067] In an embodiment of the present invention, the pH of the leachate after the impurity purification leaching step in the above-mentioned step S20 can be 7 or more, 7 to 10, or 7.7 to 9. When the pH is adjusted within the above range, all of the impurities iron, aluminum, and silicon contained in the leachate separated in step S10 can be removed by precipitation, and the removal rate of calcium can be increased.

[0068] In an embodiment of the present invention, after performing the impurity purification leaching process in the above-mentioned step S20, a solution with a high concentration of magnesium with a magnesium concentration in the solution as high as 30 g / L to 90 g / L can be obtained, and iron, aluminum, and silicon as impurities can be effectively removed.

[0069] The leachate in the leachate and residue separated after the above-mentioned impurity purification leaching can be supplied to the subsequent extraction process, and the residue can be put in during the leaching in the above-mentioned step S10.

[0070] In an embodiment of the present invention, the following steps can be carried out: for the leachate separated in the above-mentioned step S10, a magnesium-containing powder is prepared by powdering the leachate obtained after the impurity purification leaching step in step S20.

[0071] The powdering step of the above-mentioned magnesium-containing raffinate can be carried out by vacuum distillation or spray drying, etc. Specifically, for example, the powdering step of the above-mentioned magnesium-containing raffinate can be carried out by vacuum distillation.

[0072] The above step S30 can be carried out for 30 minutes to 2 hours or 1 hour to 1 hour and 30 minutes under the conditions that the steam temperature is above 45°C or 45°C to 60°C and the stirring speed is above 25 RPM or 50 RPM to 110 RPM. Through this, all the moisture in the above leachate can be evaporated and dried to obtain a dry powder in powder form containing sulfuric acid and magnesium.

[0073] The distilled liquid evaporated in the above step S30 can be recycled and reused as the distilled water for preparing the sulfuric acid solution in the leaching step of the above step S10.

[0074] The obtained magnesium-containing powder can be supplied to the subsequent heat treatment step.

[0075] In an embodiment of the present invention, the above step S40 can be a step of preparing magnesium oxide (MgO) by heat-treating the magnesium-containing powder obtained in the above step S30.

[0076] In the above step S40, the heat treatment 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. Through this, magnesium oxide in powder form can be recovered.

[0077] When the heat treatment is carried out in the above step S40, waste gas containing sulfur dioxide will be generated. The waste gas containing sulfur dioxide can be prepared into sulfuric acid through an additional catalyst process, and the prepared sulfuric acid can be reused in the preparation of the sulfuric acid solution during the leaching in the above step S10.

[0078] In an embodiment of the present invention, the above step S50 can be a step of purifying by washing the magnesium oxide in powder form obtained in the above step S40.

[0079] The above step S50 can use distilled water to wash the heat-treated magnesium oxide to remove impurities, especially calcium.

[0080] The above step S50 can be carried out under the condition that the solid (g) / liquid (mL) ratio of the heat-treated magnesium oxide to distilled water is 1 / 1 to 1 / 10, 1 / 2 to 1 / 10 or 1 / 2 to 1 / 3.

[0081] The above step S50 can use distilled water to wash the heat-treated magnesium oxide for 5 minutes to 50 minutes or 20 minutes to 30 minutes under the temperature condition of 20°C to 50°C, 20°C to 30°C.

[0082] The above step S50 can be carried out once or repeated 2 to 5 times. Specifically, for example, the above step S50 can be repeated 2 to 3 times.

[0083] After washing, the pH of the above magnesium oxide can be 10 or more, 10 to 13, or 10.2 to 12.5.

[0084] The washing liquid obtained by washing the heat-treated magnesium oxide with distilled water in the above step S50 will contain calcium as an impurity. The above washing liquid can be used to remove calcium by being placed in the atmosphere and can be used when preparing an alkaline solution with a pH of 10 or more.

[0085] In an embodiment of the present invention, the loss of magnesium can be minimized while increasing the removal rate of calcium according to the heat treatment temperature and time in the above step S40 and the number of washing times and solid-liquid ratio in the above step S50, so that magnesium oxide with higher purity can be prepared.

[0086] Specifically, for example, when magnesium oxide heat-treated at a temperature of 1200°C to 1500°C for 3 hours to 6 hours in the above step S40 is used as an object and washed repeatedly with distilled water 2 to 3 times, the loss of magnesium can be minimized while increasing the removal rate of calcium.

[0087] Moreover, the present invention can provide high-purity magnesium oxide prepared by the above method for preparing high-purity magnesium oxide through an environmentally friendly hydrometallurgical application process.

[0088] As described above, the method for preparing high-purity magnesium oxide through an environmentally friendly hydrometallurgical application process of the present invention and the magnesium oxide prepared by this method are shown through the description and the drawings. However, the above description and illustration only show the core structure for understanding the present invention. For processes and devices not additionally described and illustrated except for the processes and devices shown in the above description and drawings, they can be appropriately applied and used for implementing the present invention.

[0089] Hereinafter, examples will be described in detail for specifically explaining the present invention. However, the examples of the present invention can be deformed into various other forms, and the scope of the present invention should not be construed as being limited to the examples described in detail below. The examples of the present invention are only provided to more completely explain the present invention to ordinary technical personnel in the technical field to which the present invention pertains.

[0090] Examples

[0091] Hereinafter, as a magnesium-containing waste refractory, MgO-C waste refractory having the valuable metal components (weight percentage) shown in Table 1 below is used as a raw material.

[0092] Table 1

[0093] Magnesium Calcium Iron Sodium Potassium Aluminum Silicon Carbon 35-50 0.1-0.3 0.1-0.5 0.01-0.1 0.01-0.1 0.5-2 0.1-0.5 10-20

[0094] Example 1: One-stage leaching of MgO-C waste refractory

[0095] 1M, 3M, 5M, and 7M sulfuric acid (H2SO4) solutions were used as leaching agents to leach MgO-C waste refractory materials with an average particle size of less than 60 mesh. The above leaching process was carried out under the conditions of a solid / liquid ratio of MgO-C waste refractory materials / sulfuric acid solution of 1 / 10, a reaction temperature of 90°C, and a stirring speed of 200 rpm.

[0096] Table 2 below shows the leachate composition (mg / L) from 1M sulfuric acid leaching results. As shown in Table 2, only approximately 50% of magnesium was leached from the initial leaching time to 120 minutes. Conversely, the calcium leaching rate was confirmed to gradually decrease from an initial 95.1% to 85.8%. Furthermore, the leaching rates of iron, aluminum, and silicon decreased with increasing pH. Iron was no longer leached from 90 minutes onwards and was removed by precipitation, while aluminum was removed by precipitation from 15 minutes onwards. The portion of silicon leached from 45 minutes onwards was also removed by precipitation.

[0097] When leaching with 1M sulfuric acid, the pH increased from 4.1 to 6.7 after 120 minutes. This is because the magnesium oxide in the scrap refractory is alkaline and the concentration of the sulfuric acid solution used was low. In conclusion, the 1M sulfuric acid experiment confirmed that while valuable metals such as iron, aluminum, and silicon, which are impurities, could be removed, the magnesium leaching rate was only approximately 50%.

[0098] Table 2

[0099]

[0100] Table 3 below shows the results of 3M sulfuric acid leaching. As shown in Table 3, the magnesium leaching rate increased from 75.5% to 93.7% at 60 minutes from the start. In this case, unlike the 1M sulfuric acid leaching, all calcium, iron, and aluminum were leached. This is because the SO4 content in 3M sulfuric acid increases. 2- The concentration and pH were completely leached. Specifically, it was confirmed that when 3M sulfuric acid was used, the leaching rate of magnesium also increased to 93.7%, but the remaining impurities, such as calcium, iron, and aluminum, were all leached, resulting in a higher concentration of impurities than when leaching with 1M sulfuric acid. In this case, the pH was 0.1 or less.

[0101] Table 3

[0102]

[0103] Moreover, the following Table 4 shows the leaching results with 5M sulfuric acid. As shown in Table 4, it can be confirmed that from the start to 120 minutes, the leaching rate of magnesium increases from 68.9% at the start to 95.8% at the 60-minute time point. Also, it can be seen that the leaching rate of calcium significantly decreases over time starting from 87.1% at the initial 5 minutes and decreases to 36.2% at the 120-minute time point. This is judged to be due to the relatively higher concentration of SO4 2- and lower pH compared to 3M sulfuric acid, resulting in precipitation as calcium sulfate (CaSO4).

[0104] Also, silicon precipitates as silicon dioxide (SiO2) due to a reaction similar to the above.

[0105] Conversely, it can be confirmed that the leaching rates of iron and aluminum are completely leached due to the low pH. That is, it can be seen that when using 5M sulfuric acid, the leaching rate of magnesium can be increased to over 95%, and calcium and silicon as impurities can be removed.

[0106] Table 4

[0107]

[0108] Moreover, the following Table 5 shows the leaching results with 7M sulfuric acid. As shown in Table 5, it can be seen that from the initial stage to 45 minutes, the leaching rate of magnesium increases from 79.9% at the initial stage to 95.8% at 30 minutes. Also, it can be confirmed that the leaching rate of calcium is only 17%, and silicon is not leached at all.

[0109] Compared with 3M and 5M sulfuric acid as the other experimental conditions mentioned above, since the concentration of SO4 2- is relatively very high, the leaching rate of calcium decreases, and most of the silicon is not leached. Conversely, it can be seen that due to the low pH, the leaching rates of Fe and Al are 100% and 98% respectively. That is, it can be confirmed that the higher the concentration of sulfuric acid, the higher the leaching rate of magnesium, and the incorporation of calcium and silicon can be controlled due to the increase in the concentration of SO4 2- .

[0110] Table 5

[0111]

[0112]

[0113] Example 2: Impurity purification leaching of waste refractory magnesium oxide

[0114] The leachates using 3M, 5M, and 7M sulfuric acid solutions respectively were reused as leaching agents to conduct impurity purification leaching experiments.

[0115] 1M was excluded because it was judged that when leaching with a 1M sulfuric acid solution, the pH was as high as over 6.7, and in the two-stage leaching, the leaching of magnesium would be negligible.

[0116] In the case of sulfuric acid with concentrations of 3M, 5M, and 7M, the final pH values of the first-stage leachate are about pH 0.03, pH -0.6, and pH -0.9, which are sufficiently low to leach the magnesium contained in the waste refractory materials placed in it, so they are selected. The composition (mg / L) of the first-stage leachate used as the leachate during the impurity purification leaching process is measured and shown in Table 6 below.

[0117] Table 6

[0118] Sulfuric acid concentration Magnesium Calcium Iron Sodium Potassium Aluminum Silicon pH 3M 39400 292 328 10.6 5 998 83.7 0.03 5M 40300 105.7 328 10.3 5 998 8.4 -0.6 7M 40300 50.8 328 10.1 5 985 0 -0.9

[0119] Moreover, Table 7 below shows the results of the impurity purification leaching process using the first-stage leachate of 3M sulfuric acid. Among them, during the impurity purification leaching reaction, the temperature is adjusted to 90°C, the solid-liquid ratio is adjusted to 1 / 10, and the stirring speed is adjusted to 200 rpm.

[0120] As a result, the leaching amount of magnesium reaches 45600 mg / L. As the pH rises from the beginning to 8.56, all of the remaining impurities, iron, aluminum, and silicon, precipitate, so they are not analyzed. Calcium exists in the final solution at a concentration of 342 mg / L.

[0121] Table 7

[0122]

[0123]

[0124] Moreover, Table 8 below shows the results of the impurity purification leaching process using the first-stage leachate of 5M sulfuric acid. Among them, during the impurity purification leaching reaction, the temperature is adjusted to 90°C, the solid-liquid ratio is adjusted to 1 / 10, and the stirring speed is adjusted to 200 rpm.

[0125] As a result, the leaching amount of magnesium reaches 52600 mg / L. As the pH rises from the initial 5.21 to the final 7.81, the remaining impurities, iron, aluminum, and silicon, gradually decrease and all precipitate, so they are not analyzed. Calcium exists in the final solution at a concentration of 157 mg / L.

[0126] Table 8

[0127]

[0128] Moreover, Table 9 below shows the results of the impurity purification leaching process using the first-stage leachate of 7M sulfuric acid. Among them, during the impurity purification leaching reaction, the temperature is adjusted to 90°C, the solid-liquid ratio is adjusted to 1 / 10, and the stirring speed is adjusted to 200 rpm.

[0129] As a result, the leaching amount of Mg reached 51,600 mg / L. Different from the leaching with 3M and 5M sulfuric acid, since the pH only rose to -0.1, iron, aluminum, and silicon existed in the final solution at concentrations of 555 mg / L, 158 mg / L, and 37.6 mg / L respectively. Since the pH was -0.1, another impurity purification leaching experiment was carried out using it.

[0130] Table 9

[0131]

[0132] The results of the impurity purification leaching process using the second-stage leaching solution of 7M sulfuric acid are shown in Table 10 below. Among them, during the impurity purification leaching reaction, the temperature was adjusted to 90 °C, the solid-liquid ratio was adjusted to 1 / 10, and the stirring speed was adjusted to 200 rpm.

[0133] As a result, the leaching amount of Mg reached 58,300 mg / L. As the pH rose to 8.23, iron, aluminum, and silicon were not analyzed due to precipitation. The leaching amount of sodium can be regarded as continuously decreasing because as the pH increased, sodium in the solution formed sodium sulfate precipitate (Na2SO4).

[0134] Table 10

[0135]

[0136]

[0137] Example 3: Impurity purification leaching process with varying solid-liquid ratio using 5M sulfuric acid solution

[0138] The following Tables 11 and 12 show the results with varying solid-liquid ratio in the impurity purification leaching process using the first-stage leaching solution with 5M sulfuric acid solution as the leaching agent. Among them, during the impurity purification leaching reaction, the temperature was adjusted to 90 °C, and the stirring speed was adjusted to 200 rpm.

[0139] Since the experiment based on the solid-liquid ratio has the effect of concentrating the leaching rate of magnesium in the solution more than that in the sample during the second-stage leaching, and at the same time, controls impurities such as iron, aluminum, and silicon by automatically increasing the pH, the specific gravity of the sample put in is particularly important. This is because the residue generated after the impurity purification leaching process is remixed with a new sample during the first-stage leaching and used, so that the amount of sample to be put in during the first-stage leaching process can be calculated.

[0140] Table 11 shows the results of the composition (mg / L) of the second-stage leachate measured in the impurity purification leaching process with a solid-liquid ratio of 7.5% (solution: 500 mL / sample: 37.5 g). In this case, Mg is leached to 53400 mg / L, the leaching amount of calcium is 137.5 mg / L, and since the pH increases to 7.5 over time, iron, aluminum, and silicon are not analyzed due to precipitation.

[0141] Table 11

[0142]

[0143] The following Table 12 shows the results of the composition (mg / L) of the second-stage leachate measured in the impurity purification leaching process with a solid-liquid ratio of 15% (solution: 500 mL / sample: 75 g). In this case, Mg is leached to 56200 mg / L, calcium is leached to 117.5 mg / L, and since the pH of the solution increases from 7.11 at the beginning to 7.94 after 30 minutes, iron, aluminum, and silicon are not analyzed due to precipitation.

[0144] Table 12

[0145]

[0146] Example 4: Preparation of magnesium powder by vacuum distillation process

[0147] The second-stage leachate with adjusted pH is obtained through the impurity purification process, and the solution and magnesium-containing powder are obtained by subjecting it to vacuum distillation separately.

[0148] The vacuum distillation experiment is carried out for 1 hour under the conditions of a steam temperature of 45 °C and a stirring speed of 25 RPM or more. In this case, the solution recovered by distillation is reused in the preparation of sulfuric acid.

[0149] The following Figure 2 shows the X-ray diffraction analysis results of the powder obtained after vacuum distillation. The main peaks are the calcium sulfate series, magnesium sulfate (MgSO4) series, and magnesium hydroxide sulfate (Mg(OH)4SO4) series. That is, it can be confirmed that impurities such as iron, silicon, and aluminum are completely removed through the impurity purification process, and only magnesium and calcium remain.

[0150] Example 5: Preparation of high-purity magnesium oxide by heat treatment process

[0151] The powders obtained after vacuum distillation are all heat-treated under the conditions of 1000 °C to 1500 °C. The heat treatment process is carried out for 30 minutes to 3 hours in a box furnace in an air atmosphere.

[0152] As a result, through the following Figure 3X-ray diffraction analysis confirmed that the main peak in the powder obtained by heat treatment at a temperature above 1200 °C was magnesium oxide, and ICP was used for instrumental analysis to calculate the purity of the obtained magnesium oxide.

[0153] The results of ICP analysis are shown in Table 13 below. It was confirmed that the calcium content was about less than 0.61% (0.61% > Ca). From X-ray diffraction analysis, it was known that calcium in the powder existed as a minor peak in the form of calcium sulfate. In this case, the purity of the prepared magnesium oxide was 97.8%.

[0154] Table 13

[0155]

[0156] Example 6: High-purification of magnesium oxide by washing with distilled water

[0157] In order to high-purify the prepared magnesium oxide, washing experiments for removing calcium were carried out with different solid-liquid ratios using distilled water. The experiments were carried out at room temperature within 30 minutes.

[0158] The results are shown in Table 14 below. Table 14 shows the results of water washing of magnesium oxide obtained by heat treatment at 1200 °C for 30 minutes. In this case, when washing with a solid-liquid ratio of 1 / 10 (magnesium oxide: 3.1 g, distilled water: 31 mL), it was known that 2.57 g was removed, resulting in a loss of 82.9% of the sample.

[0159] Table 14

[0160] Magnesium Calcium Iron Sodium Potassium Aluminum Silicon pH Residue, g 12390 284.5 0 3.5 1.1 0 0 9.6 0.53

[0161] Table 15 below shows the results of a single water wash after obtaining magnesium oxide by heat treatment at a temperature of 1200 °C to 1500 °C for 3 hours. It was confirmed that when washing 3.1 g of magnesium oxide with 31 mL of distilled water, the loss amount was all below 0.5 g, and the magnesium loss amount also decreased to 59 mg / L, 46 mg / L, 31 mg / L. The magnesium loss amount decreased with the heat treatment temperature. In this case, it was confirmed that with the heat treatment temperature, the pH of the solution after washing was pH 10.5, pH 11.2, pH 11.6.

[0162] Table 15

[0163]

[0164]

[0165] Tables 14 and 15 show the loss of the prepared magnesium oxide and the removal amount of impurities with the heat treatment time and heat treatment temperature. That is, the heat treatment time must be 30 minutes or more to reduce the loss of magnesium. At the same time, the heat treatment at a temperature of 1200 °C can slightly reduce the loss amount of magnesium.

[0166] Therefore, in order to prepare and obtain high-purity magnesium oxide, the specimens heat-treated for 3 hours or more are washed twice with water. Specifically, 3.1 g of magnesium oxide is washed in 31 mL of distilled water at a temperature of 1200 °C to 1500 °C for 30 minutes. The results are shown in Table 16 below.

[0167] As shown in Table 16, it can be seen that as the heat treatment temperature increases, the amount of magnesium lost decreases slightly, which can be proved by the pH after washing. In this case, compared with the first water wash, the removal amount of calcium in the second water wash increases significantly.

[0168] Table 16

[0169] Heat treatment temperature Magnesium Calcium Sodium Potassium Iron Aluminum Silicon pH Residue, g 1200 12 645 2 2 N·D N·D N·D 10.2 2.76 1400 4.5 642 0.17 1.2 N·D N·D N·D 11.1 2.94 1500 3 648 0.15 1.1 N·D N·D N·D 11.1 2.94

[0170] Table 17 below shows the purity of magnesium oxide when all the magnesium oxide obtained after the second washing is dried at a temperature of 80 °C or higher and then subjected to ICP analysis and converted to oxide. As shown in Table 17, the purity of the prepared magnesium oxide is 99.76%, and it can be seen that high-purity magnesium oxide has been prepared. And, the X-ray diffraction analysis results of the prepared magnesium oxide are as follows Figure 4 shown.

[0171] Table 17

[0172]

[0173] Industrial availability

[0174] The method for preparing high-purity magnesium oxide from waste refractory materials of the present invention utilizes waste refractory materials that can be reused as secondary resources for refractory materials or landfilled through the existing environmental-friendly wet smelting application process to environmentally prepare high-purity magnesium oxide with impurities such as iron, aluminum, silicon, and calcium removed.

Claims

1. A method for preparing high-purity magnesium oxide from waste refractory materials through an environmentally friendly wet smelting application process, characterized in that, Comprising: Step S10, separating the leaching solution and the residue by solid-liquid separation after leaching the magnesium-containing waste refractory material; Step S20, purifying the impurities in the above-mentioned leaching solution; Step S30, pulverizing the above-mentioned leaching solution after the impurity purification leaching step to prepare magnesium-containing powder; Step S40, heat-treating the above-mentioned magnesium-containing powder to prepare magnesium oxide; And Step S50, washing the above-mentioned heat-treated magnesium oxide to achieve high purity, The purity of the above-mentioned washed magnesium oxide is above 99%.

2. The method for preparing high-purity magnesium oxide from waste refractory materials by an environmentally friendly hydrometallurgical application process according to claim 1, characterized in that, The above-mentioned magnesium-containing waste refractory material contains 30% to 55% by weight of magnesium.

3. The method for preparing high-purity magnesium oxide from waste refractory materials by means of an environmentally friendly wet smelting application process according to claim 1, characterized in that, Before the step of separating the leaching solution and the residue by solid-liquid separation after leaching the magnesium-containing waste refractory material, it further includes a step of crushing / pulverizing the magnesium-containing waste refractory material.

4. The method for preparing high-purity magnesium oxide from waste refractory materials through an environmentally friendly hydrometallurgical application process according to claim 3, characterized in that, The average particle size of the crushed / pulverized magnesium-containing waste refractory material is 100 mesh or less.

5. The method for preparing high-purity magnesium oxide from waste refractory materials through an environmentally friendly hydrometallurgical application process according to claim 1, characterized in that, In the above-mentioned step S10, the magnesium-containing waste refractory material is leached with a sulfuric acid solution having a molar concentration of 1M to 7M.

6. The method for preparing high-purity magnesium oxide from waste refractory materials through an environmentally friendly hydrometallurgical application process according to claim 5, characterized in that, The above-mentioned step S10 is 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 RPM to 400 RPM.

7. The method for preparing high-purity magnesium oxide from waste refractory materials by an environmentally friendly wet smelting application process according to claim 1, characterized in that, In the above-mentioned step S20, the leaching solution obtained in the above-mentioned step S10 is used as the leaching agent, and the magnesium-containing waste refractory material is put into the above-mentioned leaching agent for leaching, and then the leaching solution and the residue are separated.

8. The method for preparing high-purity magnesium oxide from waste refractory materials through an environmentally friendly hydrometallurgical application process according to claim 7, characterized in that, In the above-mentioned step S20, the following process is repeated: using the previous-stage leaching solution as the leaching agent, putting the magnesium-containing waste refractory material into the above-mentioned leaching agent for leaching, and then separating the latter-stage leaching solution and the residue.

9. The method for preparing high-purity magnesium oxide from waste refractory materials through an environmentally friendly hydrometallurgical application process according to claim 8, characterized in that, The above-mentioned step S20 is carried out under the conditions that the solid (g) / liquid (L) ratio of the magnesium-containing waste refractory material to the sulfuric acid solution is 5 to 30, the reaction temperature is 100°C or less, and the stirring speed is 100 RPM to 400 RPM.

10. The method for preparing high-purity magnesium oxide from waste refractory materials through an environmentally friendly hydrometallurgical application process according to claim 1, characterized in that, In the above-mentioned step S20, the pH of the leaching solution after the impurity purification leaching step is 7 or more.

11. The method for preparing high-purity magnesium oxide from waste refractory materials through an environmentally friendly wet smelting application process according to claim 1, characterized in that, The above-mentioned step S30 is 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.

12. The method for preparing high-purity magnesium oxide from waste refractory materials through an environmentally friendly wet smelting application process according to claim 1, characterized in that, In the above-mentioned step S40, the heat treatment is carried out at a temperature of 1000°C to 1500°C for 30 minutes to 6 hours.

13. The method for preparing high-purity magnesium oxide from waste refractory materials by an environmentally friendly hydrometallurgical application process according to claim 12, characterized in that, In the above-mentioned step S40, the heat treatment is carried out at a temperature of 1200°C to 1500°C for 3 hours to 6 hours.

14. The method for preparing high-purity magnesium oxide from waste refractory materials by an environmentally friendly wet smelting application process according to claim 1, characterized in that, In the above-mentioned step S10, one or more of the residue generated in step S20, the distillate generated in step S30, and the waste gas components generated in step S40 are reused.

15. The method for preparing high-purity magnesium oxide from waste refractory materials by an environmentally friendly wet smelting application process according to claim 1, characterized in that, In the above-mentioned step S50, under the conditions that the solid (g) / liquid (mL) ratio of the heat-treated magnesium oxide to the distilled water is 1 / 1 to 1 / 10 and the temperature is 20°C to 50°C, the heat-treated magnesium oxide is washed with distilled water for 5 minutes to 50 minutes.

16. The method for preparing high-purity magnesium oxide from waste refractory materials by an environmentally friendly wet smelting application process according to claim 1, characterized in that, The above-mentioned step S50 is carried out once or repeated 2 to 5 times.

17. The method for preparing high-purity magnesium oxide from waste refractory materials by an environmentally friendly wet smelting application process according to claim 1, characterized in that In the above-mentioned step S40, the heat treatment is carried out at a temperature of 1200°C to 1500°C for 3 hours to 6 hours, The above-mentioned step S50 is repeated 2 to 5 times.

18. A magnesium oxide, characterized in that, Prepared by using the method for preparing high-purity magnesium oxide from waste refractory materials through an environmentally friendly hydrometallurgical application process as described in claim 1.

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