Method for preparing high-purity magnesium oxide from waste refractory material by an environmentally friendly wet metallurgical application process and magnesium oxide prepared by the method

Abstract

The present invention provides a method for preparing high-purity magnesium oxide from waste refractory material through an environmentally friendly wet metallurgical process, and magnesium oxide prepared by the method, comprising: a step of separating leach liquor from residue by solid-liquid separation after leaching magnesium-containing waste refractory material (step S10); a step of purifying the leach liquor from impurities (step S20); a step of powderizing the leach liquor after the impurity purification leaching step to prepare magnesium-containing powder (step S30); a step of heat treating the magnesium-containing powder to prepare magnesium oxide (step S40); and a step of washing the heat-treated magnesium oxide to increase purity (step S50).

Description

Technical Field

[0001] This invention relates to a method for preparing high-purity magnesium oxide from waste refractory materials using an environmentally friendly hydrometallurgical process, and the magnesium oxide prepared by the method. More specifically, it relates to a method for preparing high-purity magnesium oxide (MgO) in an environmentally friendly manner from existing secondary resources that are recycled into refractory materials or from waste refractory materials that have been landfilled, through processes such as leaching, purification, and washing. Background Technology

[0002] Magnesium oxide, also known as magnesia, is typically an oxide form of magnesium with a high melting point and hygroscopic properties.

[0003] Most magnesia is produced from magnesite, a natural carbonate mineral. Magnesia can be classified according to heat treatment temperature or raw material. Lightly calcined magnesia is produced from magnesite at temperatures between 600°C and 1400°C, while heavily calcined magnesia is produced at temperatures between 1400°C and 2200°C. Furthermore, fused magnesia is produced by melting magnesite at temperatures above 2800°C. Seawater magnesia is also produced from seawater through precipitation and roasting.

[0004] Magnesium oxide prepared at high temperatures is used as a raw material for refractory materials. More than 70% of the magnesium oxide produced in this way is used as refractory materials, while the remaining 30% is used in various industries such as agriculture, medicine, optics, nuclear reactors, and rocket propellants, depending on the type of application.

[0005] In South Korea's steel industry, refractory materials containing MgO-C are used in electric furnaces and steel ladles for ironmaking. After use, these materials are discarded, and a portion of them are reused.

[0006] Recycling methods include wet methods to remove nitrogen and aluminum from waste refractory materials, followed by physical screening to improve the purity of magnesium oxide, and dry methods to burn and gasify carbon to improve the purity of magnesium oxide. However, the purity is usually below 97%, and most waste refractory materials are reused as refractory materials. Reports on processes for preparing high-purity magnesium oxide from waste refractory materials are very few.

[0007] In South Korea, magnesium oxide production is limited to a single smelting company that produces over 98% pure magnesium oxide from seawater using a wet process as described above, but this is also limited to self-production and sales.

[0008] Therefore, South Korea, lacking its own magnesium mines, relies entirely on imports for its magnesium oxide, and the supply is insufficient. Consequently, there is an urgent need to develop processes for recovering magnesium oxide from waste refractory materials, and to develop a process for producing high-purity magnesium oxide using environmentally friendly and economical smelting techniques.

[0009] Generally, compared to currently prevalent commercial processes, the disadvantage of environmentally friendly processes lies in their economic limitations due to the high cost of the chemicals and reaction equipment used. Therefore, research is needed to shorten the number of steps and prepare high-purity magnesium oxide in an environmentally friendly manner by applying commercially available conventional processes. Summary of the Invention

[0010] Technical issues

[0011] To address the aforementioned problems, the present invention aims to provide an environmentally friendly method for recovering high-purity magnesium oxide from waste refractory materials using an environmentally friendly hydrometallurgical process that simplifies the process. This method utilizes a simplified, environmentally friendly process to recover magnesium oxide, which is entirely imported into South Korea.

[0012] The technical problem to be solved by the present invention is not limited to the technical problems mentioned above. Those skilled in the art to which the present invention pertains can clearly understand the unmentioned technical problems or other technical problems through the following description.

[0013] Technical solution

[0014] To achieve the above objectives, the present invention provides a method for preparing high-purity magnesium oxide from waste refractory materials using an environmentally friendly hydrometallurgical process, comprising: step S10, leaching magnesium-containing waste refractory materials and then separating the leachate and residue by solid-liquid separation; step S20, purifying the impurities in the leachate; step S30, pulverizing the leachate after the impurity purification leaching step into magnesium-containing powder; step S40, heat-treating the magnesium-containing powder to prepare magnesium oxide; and step S50, washing the heat-treated magnesium oxide to achieve high purity.

[0015] According to one embodiment of the present invention, the above-mentioned magnesium-containing waste refractory material may contain 30 to 55% by weight of magnesium.

[0016] According to one embodiment of the present invention, before the step of separating the leachate and residue by solid-liquid separation after leaching the magnesium-containing waste refractory material, a step of crushing / pulverizing the magnesium-containing waste refractory material may be included.

[0017] According to one embodiment of the present invention, the average particle size of the crushed / pulverized magnesium-containing waste refractory material can be below 100 mesh.

[0018] According to an embodiment of the present invention, step S10 above can be performed by leaching magnesium-containing waste refractory materials with a sulfuric acid solution of a molar concentration of 1M to 7M.

[0019] According to an embodiment of the present invention, step S10 can be carried out under the following conditions: the solid (g) / liquid (mL) ratio of magnesium-containing waste refractory material to 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 step S20, the leachate obtained in step S10 can be used as a leaching agent. Magnesium-containing waste refractory material is added to the leaching agent for leaching, and then the leachate and residue are separated.

[0021] According to an embodiment of the present invention, the following steps can be repeated in step S20: using the first-stage leachate as a leaching agent, adding magnesium-containing waste refractory material to the leaching agent for leaching, and then separating the second-stage leachate from the residue.

[0022] According to an embodiment of the present invention, step S20 can be carried out under the following conditions: the solid (g) / liquid (L) ratio of magnesium-containing waste refractory material 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.

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

[0024] According to one embodiment of the present invention, step S30 can be carried out for 30 minutes to 2 hours under the conditions of steam temperature above 45°C and stirring speed above 25 RPM.

[0025] According to one embodiment of the present invention, in step S40 above, 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 one embodiment of the present invention, in step S40 above, the heat treatment is carried out at a temperature of 1200°C to 1500°C for 3 to 6 hours.

[0027] According to an embodiment of the present invention, in 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, step S50 can be performed by washing the heat-treated magnesium oxide with distilled water for 5 to 50 minutes under the conditions that the solid (g) / liquid (mL) ratio of the heat-treated magnesium oxide to distilled water is 1 / 1 to 1 / 10 and the temperature is 20°C to 50°C.

[0029] According to one embodiment of the present invention, step S50 can be performed once or repeated two to five times.

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

[0031] To achieve the above objectives, the present invention provides magnesium oxide prepared by the above-described method for preparing high-purity magnesium oxide from waste refractory materials using an environmentally friendly hydrometallurgical process.

[0032] The effects of the invention

[0033] The present invention provides a method for preparing high-purity magnesium oxide from waste refractory materials. This method utilizes existing secondary resources that can be reused as refractory materials or waste refractory materials that have been landfilled, and uses an environmentally friendly hydrometallurgical process to prepare high-purity magnesium oxide by removing impurities such as iron (Fe), aluminum (Al), silicon (Si), and calcium (Ca) in an environmentally friendly manner.

[0034] Furthermore, in the magnesium oxide preparation method of the present invention, an alkaline solution can be prepared from the washing liquid in the washing step for high-purity magnesium oxide. If sulfur dioxide (SO2) gas is generated during heat treatment, it can be prepared into sulfuric acid through the subsequent catalyst process. The wastewater generated can be effectively reduced by using the distillate in the powdering process when preparing sulfuric acid, thereby realizing an environmentally friendly hydrometallurgical application process and preparing high-purity magnesium oxide in an environmentally friendly manner. Attached Figure Description

[0035] Figure 1 This is a process flow diagram of a method for preparing high-purity magnesium oxide from waste refractory materials by hydrometallurgical process according to an embodiment of the present invention.

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

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

[0038] Figure 4 This is an X-ray diffraction pattern of high-purity magnesium oxide recovered after washing, according to an embodiment of the present invention. Detailed Implementation

[0039] The purpose of this invention is to provide an environmentally friendly method for recovering magnesium oxide from waste refractory materials in high purity through a simplified and environmentally friendly hydrometallurgical process, which is entirely dependent on imports by South Korea.

[0040] Embodiments of the present invention

[0041] Before describing the invention in detail, it should be noted that the terms or vocabulary used in this specification should not be unconditionally limited to their usual or dictionary meanings. The inventors of the invention may appropriately define and use the concepts of various terms in order to best illustrate the invention. Furthermore, these terms or vocabulary should be interpreted as meanings and concepts consistent with the technical ideas of the invention.

[0042] That is, the terminology used in this specification is only for describing preferred embodiments of the invention and is not intended to specifically limit the content of the invention. These terms are defined in view of the various possibilities of the invention.

[0043] Furthermore, in this specification, unless the context explicitly indicates otherwise, the singular expression may include the plural expression, and similarly, the plural expression may include the singular expression.

[0044] Throughout this specification, when a structural element is referred to as "including" other structural elements, unless otherwise stated, it means that any other structural elements may be included, rather than excluding any other structural elements.

[0045] Furthermore, in the following description of the present invention, structures that are deemed potentially obscuring the essence of the invention, such as detailed descriptions of known technologies including the prior art, will be omitted.

[0046] The present invention will now be described in more detail.

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

[0048] In one embodiment of the present invention, the aforementioned magnesium-containing waste refractory material may comprise one or more of the following groups: dolomite (MgO-CaO type refractory material), magnesia-carbonaceous (MgO-C type refractory material), magnesia (MgO type refractory material), magnesia-chromium (MgO-Cr2O3 type refractory material), alumina, and silica, all capable of withstanding temperatures above 1500°C. Specifically, the aforementioned magnesium-containing waste refractory material may be MgO-C waste refractory material.

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

[0050] In the case where the aforementioned magnesium-containing waste refractory material contains one or more of the following elements besides magnesium: calcium, iron, sodium, potassium, aluminum, silicon, and carbon, the content of calcium may be from 0.01% to 0.5% by weight, the content of iron may be from 0.01% to 1% by weight, the content of sodium may be from 0.001% to 0.3% by weight, the content of potassium may be from 0.001% to 0.3% by weight, the content of aluminum may be from 0.1% to 5% by weight, the content of silicon may be from 0.01% to 1% by weight, and the content of carbon may be from 1% to 25% by weight.

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

[0052] The crushing / pulverization of the aforementioned magnesium-containing waste refractory materials can be carried out using conventional pulverizers. For example, the aforementioned pulverizers may include one or more selected from the group consisting of jaw crushers, rotary crushers, roller crushers, cone crushers, hammer mills, tumbling mills, vibrating mills, attrition mills, ball mills, rod mills, pebble mills, and autogeneous mills.

[0053] The average particle size of the crushed / pulverized magnesium-containing waste refractory materials can be below 100 mesh, 10 to 100 mesh, or 30 to 100 mesh. By crushing the magnesium-containing waste refractory materials into the above-mentioned range and then performing subsequent leaching and extraction processes, the reuse rate of the magnesium content in the waste refractory materials can be improved, and process time and costs can be reduced.

[0054] In one embodiment of the present invention, step S10 can be performed by solid-liquid separation after leaching magnesium-containing waste refractory materials to separate the leachate and residue.

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

[0056] In step S10 above, magnesium-containing waste refractory materials can be leached using sulfuric acid solutions with molar concentrations of 1M to 7M, 3M to 7M, or 4M to 6M. When using sulfuric acid solutions with molar concentrations within the above ranges to leach magnesium-containing waste refractory materials, the leaching rate of magnesium can be increased while the co-leaching rate of impurities such as iron, aluminum, calcium, and silicon can be reduced.

[0057] The above step S10 can be carried out under the following conditions: the solid (g) / liquid (mL) ratio of magnesium-containing waste refractory material to sulfuric acid solution is 1 / 10 to 3 / 10, the reaction temperature is below 100℃, and the stirring speed is 100RPM to 400RPM.

[0058] For example, step S10 can be carried out under the following conditions: the solid-liquid ratio of magnesium-containing waste refractory material to 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 one embodiment of the present invention, the residue separated by solid-liquid separation contains low-grade valuable metals and carbon (C), which can be utilized as low-grade or medium-grade carbon.

[0060] In one embodiment of the present invention, step S20 may be a step of purifying the impurities in the leachate separated in step S10 by leaching.

[0061] For example, in step S20 above, the leachate obtained in step S10 can be used as a leaching agent. Magnesium-containing waste refractory material is added to the leaching agent to carry out a leaching reaction, and then the leachate and residue are separated.

[0062] In one embodiment of the present invention, step S20 can be performed once or repeated two to five times. Specifically, the following steps can be repeated: using the first-stage leachate as a leaching agent, adding magnesium-containing waste refractory material to the leaching agent for leaching, and then separating the second-stage leachate from the residue.

[0063] As an example, when performing step S20 once, the first leaching solution separated in step S10 can be used as a leaching agent. Magnesium-containing waste refractory material is added to the first leaching agent for leaching, and then the second leaching solution and residue are separated. The second leaching solution can be used for the subsequent extraction process.

[0064] As another example, if step S20 is performed twice, the first stage of leachate separated in step S10 can be used as a leaching agent. Magnesium-containing waste refractory material is added to the first stage leaching agent for leaching, and then the second stage leachate and residue are separated. The second stage leachate is then used as a leaching agent. Magnesium-containing waste refractory material is added to the second stage leaching agent for leaching, and then the third stage leachate and residue are separated. The third stage leachate can be used for the subsequent extraction process.

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

[0066] For example, step S20 can be carried out for 30 to 120 minutes under the following conditions: the solid (g) / liquid (L) ratio of magnesium-containing waste refractory material to 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 one embodiment of the present invention, the pH of the leachate obtained from the impurity purification leaching step in step S20 can be 7 or higher, 7 to 10, or 7.7 to 9. When the pH is adjusted to the above range, all the impurities iron, aluminum, and silicon contained in the leachate separated in step S10 can be precipitated and removed, thereby improving the calcium removal rate.

[0068] In one embodiment of the present invention, after the impurity purification and leaching process in step S20, a solution containing a high concentration of magnesium with a magnesium concentration of up to 30 g / L to 90 g / L can be obtained, which can effectively remove iron, aluminum and silicon as impurities.

[0069] The leachate separated after the above-mentioned impurities are purified and leached, and the leachate in the residue can be supplied to the subsequent extraction process, while the residue can be added during the leaching in step S10 above.

[0070] In one embodiment of the present invention, the following steps may be taken: for the leachate separated in step S10 above, magnesium-containing powder is prepared by pulverizing the leachate obtained after the impurity purification leaching step in step S20.

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

[0072] Step S30 described above can be carried out for 30 minutes to 2 hours or 1 hour to 1 hour and 30 minutes under conditions of steam temperature above 45°C or between 45°C and 60°C and stirring speed above 25 RPM or between 50 RPM and 110 RPM. This process can completely evaporate the moisture in the above leachate and dry it to obtain a dry powder containing sulfuric acid and magnesium.

[0073] The distillate evaporated in step S30 can be recycled and reused as distilled water used in the leaching step of step S10 to prepare sulfuric acid solution.

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

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

[0076] In step S40 above, 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. This allows the recovery of magnesium oxide in powder form.

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

[0078] In one embodiment of the present invention, step S50 may be a step of purifying magnesium oxide in powder form by washing it in step S40.

[0079] In step S50 above, impurities, especially calcium, can be removed by washing the heat-treated magnesium oxide with distilled water.

[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 be performed by washing the heat-treated magnesium oxide with distilled water for 5 to 50 minutes or 20 to 30 minutes at temperatures of 20°C to 50°C or 20°C to 30°C.

[0082] The above step S50 can be performed once or repeated two to five times. For example, the above step S50 can be repeated two to three times.

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

[0084] The washing solution obtained after washing the heat-treated magnesium oxide with distilled water in step S50 above will contain calcium as an impurity. The calcium in this washing solution can be removed by exposing it to the atmosphere, and it can be used when preparing alkaline solutions with a pH above 10.

[0085] In one embodiment of the present invention, magnesium loss can be minimized while calcium removal rate can be increased by adjusting the heat treatment temperature and time in step S40 and the number of washes and solid-liquid ratio in step S50, thereby producing magnesium oxide with higher purity.

[0086] For example, when magnesium oxide that has been heat-treated at 1200°C to 1500°C for 3 to 6 hours in step S40 is used as the object, and it is repeatedly washed with distilled water 2 to 3 times, the calcium removal rate can be improved while minimizing the loss of magnesium.

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

[0088] The above description and accompanying drawings illustrate the method for preparing high-purity magnesium oxide using an environmentally friendly hydrometallurgical process and the magnesium oxide prepared by the method. However, the above description and drawings only describe and illustrate the core structure for understanding the present invention. In addition to the processes and apparatus shown in the above description and accompanying drawings, the processes and apparatus not additionally described and illustrated may be used for appropriate application in carrying out the present invention.

[0089] Hereinafter, embodiments are described in detail to illustrate the present invention. However, the embodiments of the present invention can be modified into many other forms, and the scope of the present invention should not be construed as limited to the embodiments detailed below. The embodiments of the present invention are provided merely to illustrate the present invention more completely to those skilled in the art.

[0090] Example

[0091] The following uses MgO-C waste refractory material with the valuable metal composition (weight percentage) shown in Table 1 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 materials

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

[0096] Table 2 below shows the composition (mg / L) of the leachate from 1M sulfuric acid leaching. As shown in Table 2, only about 50% of the magnesium was leached from the beginning to 120 minutes. Conversely, it can be confirmed that the calcium leaching rate gradually decreased from the initial 95.1% to 85.8%. Furthermore, it can be confirmed that the leaching rates of iron, aluminum, and silicon decreased with increasing pH. Iron stopped leaching from the 90-minute mark and was removed due to precipitation; Al was removed due to precipitation from the 15-minute mark; and silicon was partially removed due to precipitation starting from the 45-minute mark.

[0097] When leaching with 1M sulfuric acid, the pH rose from 4.1 to 6.7 at the 120-minute mark. This is because magnesium oxide in the waste refractory material is alkaline, and the concentration of the sulfuric acid solution used was low. In conclusion, the 1M sulfuric acid experiment confirmed that although valuable metals such as iron, aluminum, and silicon, which are impurities, can be removed, the magnesium leaching rate is only about 50%.

[0098] Table 2

[0099]

[0100] Furthermore, Table 3 below shows the leaching results of 3M sulfuric acid. As shown in Table 3, it can be seen that from the start to 120 minutes, the magnesium leaching rate increased from 75.5% to 93.7% at time point 60 minutes. In this case, unlike the leaching with 1M sulfuric acid, calcium, iron, and aluminum were completely leached, which is due to the presence of SO4 in the 3M sulfuric acid. 2- The concentration and pH of the magnesium were completely leached out. That is, it can be confirmed that when using 3M sulfuric acid, although the magnesium leaching rate also increased to 93.7%, all other impurities such as calcium, iron, and aluminum were also leached out, resulting in a higher concentration of impurities compared to leaching with 1M sulfuric acid. Under these conditions, the pH was below 0.1.

[0101] Table 3

[0102]

[0103] Furthermore, Table 4 below shows the leaching results of 5M sulfuric acid. As shown in Table 4, it can be confirmed that from the start to 120 minutes, the magnesium leaching rate increased from 68.9% at the beginning to 95.8% at time point 60 minutes. Furthermore, it can be seen that the calcium leaching rate decreased significantly over time, starting from 87.1% at the initial 5 minutes, decreasing to 36.2% at time point 120 minutes. This indicates that compared to 3M sulfuric acid, due to SO42-... 2- The concentration of calcium sulfate is relatively high and the pH is lower, so it precipitates as calcium sulfate (CaSO4).

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

[0105] Conversely, it can be confirmed that 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, which are impurities, can be removed.

[0106] Table 4

[0107]

[0108] Furthermore, Table 5 below shows the leaching results of 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 increased from 79.9% to 95.8% after 30 minutes. It can also be confirmed that the leaching rate of calcium was only 17%, while silicon was not leached at all.

[0109] Compared to the 3M and 5M sulfuric acid used as the other experimental conditions mentioned above, due to SO4 2- The concentration of sulfuric acid is relatively high, thus reducing the leaching rate of calcium and leaving most of the silicon unleached. Conversely, due to the low pH, the leaching rates of Fe and Al are 100% and 98%, respectively. This confirms that the higher the concentration of sulfuric acid, the higher the leaching rate of magnesium, which can be attributed to SO42-. 2- The concentration of calcium and silicon is increased to control the mixing of calcium and silicon.

[0110] Table 5

[0111]

[0112]

[0113] Example 2: Purification and Leaching of Impurities in Waste Magnesium Oxide Refractory Materials

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

[0115] The reason for excluding 1M is that when using 1M sulfuric acid solution for leaching, the pH will be as high as 6.7 or higher, and the leaching of magnesium in the second stage will be negligible.

[0116] In the case of 3M, 5M, and 7M sulfuric acid, the final pH of the first-stage leachate is sufficiently low, around pH 0.03, pH -0.6, and pH -0.9, respectively, which is sufficient to leach the magnesium contained in the waste refractory material, and therefore it is selected accordingly. The composition (mg / L) of the first-stage leachate used as the leachate in 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] Furthermore, Table 7 below shows the results of the impurity purification leaching process using a 3M sulfuric acid first-stage leachate. During the impurity purification leaching reaction, the temperature was adjusted to 90°C, the solid-liquid ratio to 1 / 10, and the stirring speed to 200 rpm.

[0120] As a result, the magnesium leaching concentration reached 45,600 mg / L. As the pH rose from the initial concentration to 8.56, the remaining impurities, iron, aluminum, and silicon, all precipitated and were therefore not analyzed. Calcium was present in the final solution at a concentration of 342 mg / L.

[0121] Table 7

[0122]

[0123]

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

[0125] As a result, the leaching concentration of magnesium reached 52,600 mg / L. As the pH increased from the initial 5.21 to the final 7.81, the remaining impurities, iron, aluminum, and silicon, gradually decreased and precipitated completely, thus not being analyzed. Calcium was present in the final solution at a concentration of 157 mg / L.

[0126] Table 8

[0127]

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

[0129] As a result, the leaching concentration of Mg reached 51,600 mg / L. Unlike the leaching with 3M and 5M sulfuric acid, because the pH only rose to -0.1, iron, aluminum, and silicon were present 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, a second impurity purification leaching experiment was conducted using this pH.

[0130] Table 9

[0131]

[0132] The results of the impurity purification leaching process using 7M sulfuric acid two-stage leaching solution are shown in Table 10 below. During the impurity purification leaching reaction, the temperature was adjusted to 90℃, the solid-liquid ratio to 1 / 10, and the stirring speed 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 leached due to precipitation. The leaching amount of sodium can be considered to have continuously decreased because, with the increase of pH, sodium in the solution precipitates as sodium sulfate (Na2SO4).

[0134] Table 10

[0135]

[0136]

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

[0138] Tables 11 and 12 below show the results of the solid-liquid ratio during the impurity purification leaching process using a 5M sulfuric acid solution as the leaching agent in a single-stage leaching solution. During the impurity purification leaching reaction, the temperature was adjusted to 90°C and the stirring speed to 200 rpm.

[0139] Because experiments based on the solid-liquid ratio can concentrate magnesium in the solution more effectively than magnesium in the sample during the two-stage leaching process, and because the pH is automatically increased to control impurities such as iron, aluminum, and silicon, the specific gravity of the sample added is particularly important. This is because the residue generated after the impurity purification leaching process is mixed with the new sample from the first-stage leaching, allowing the calculation of the amount of sample to be added in the first-stage leaching process.

[0140] Table 11 shows the results of the two-stage leachate composition (mg / L) measured in the impurity purification leaching process at a solid-liquid ratio of 7.5% (solution: 500 mL / sample: 37.5 g). Under these conditions, Mg was leached to 53400 mg / L, and calcium was leached to 137.5 mg / L. Since the pH increased to 7.5 over time, iron, aluminum, and silicon were not analyzed due to precipitation.

[0141] Table 11

[0142]

[0143] Table 12 below shows the results of the two-stage leachate composition (mg / L) measured in the impurity purification leaching process at a solid-liquid ratio of 15% (solution: 500 mL / sample: 75 g). Under these conditions, Mg was leached to 56200 mg / L, and calcium to 117.5 mg / L. Because the solution pH increased from 7.11 initially to 7.94 after 30 minutes, iron, aluminum, and silicon were not analyzed due to precipitation.

[0144] Table 12

[0145]

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

[0147] A two-stage leachate with adjusted pH is obtained through an impurity purification process. The solution and magnesium-containing powder are then obtained by vacuum distillation.

[0148] The vacuum distillation experiment was conducted for 1 hour at a steam temperature of 45°C and a stirring speed of 25 RPM or higher. Under these conditions, the solution recovered by distillation was reused in the preparation of sulfuric acid.

[0149] The following Figure 2 The X-ray diffraction analysis results of the powder obtained after vacuum distillation are shown. The main peaks are in the calcium sulfate series, magnesium sulfate (MgSO4) series, and magnesium hydroxide sulfate (Mg(OH)4SO4) series. This confirms that impurities such as iron, silicon, and aluminum were completely removed through the impurity purification process, leaving only magnesium and calcium residues.

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

[0151] The powders obtained after vacuum distillation were 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.

[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 temperatures above 1200°C was magnesium oxide. ICP analysis was used to calculate the purity of the obtained magnesium oxide.

[0153] The ICP analysis results are shown in Table 13 below. It confirmed that the calcium content was less than 0.61% (0.61% > Ca). X-ray diffraction analysis showed that the calcium in the powder existed as calcium sulfate with a minor peak. Under these conditions, the purity of the prepared magnesium oxide was 97.8%.

[0154] Table 13

[0155]

[0156] Example 6: High-purity magnesium oxide washed with distilled water

[0157] To achieve high purity in the prepared magnesium oxide, washing experiments were conducted using distilled water at different solid-liquid ratios to remove calcium. The experiments were carried out at room temperature for no more than 30 minutes.

[0158] The results are shown in Table 14 below. Table 14 shows the results of washing magnesium oxide obtained by heat treatment at 1200°C for 30 minutes with water. Under these conditions, when washing with a solid-liquid ratio of 1 / 10 (magnesium oxide: 3.1 g, distilled water: 31 mL), it can be seen 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 washing magnesium oxide after heat treatment at 1200℃ to 1500℃ for 3 hours. It was confirmed that washing 3.1g of magnesium oxide with 31mL of distilled water resulted in a loss of less than 0.5g, with magnesium losses decreasing to 59mg / L, 46mg / L, and 31mg / L respectively. The magnesium loss decreased with increasing heat treatment temperature. Under these conditions, the pH of the solution after washing was confirmed to be pH 10.5, pH 11.2, and pH 11.6, respectively, depending on the heat treatment temperature.

[0162] Table 15

[0163]

[0164]

[0165] Tables 14 and 15 show the magnesium oxide loss and impurity removal with increasing heat treatment time and temperature. Specifically, the heat treatment time must be at least 30 minutes to minimize magnesium loss, and a heat treatment temperature of 1200°C can slightly reduce magnesium loss.

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

[0167] As shown in Table 16, the amount of magnesium lost decreases slightly with increasing heat treatment temperature, which can be confirmed by the pH after washing. Under these conditions, the amount of calcium removed in the second wash is significantly increased compared to the first wash.

[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 obtained after two washings, after drying at a temperature above 80°C and performing ICP analysis, converting the resulting magnesium oxide to oxide. As shown in Table 17, the purity of the prepared magnesium oxide is 99.76%, indicating that a considerably high purity magnesium oxide was prepared. Furthermore, the X-ray diffraction analysis results of the prepared magnesium oxide are as follows... Figure 4 As shown.

[0171] Table 17

[0172]

[0173] Industrial availability

[0174] The present invention provides a method for preparing high-purity magnesium oxide from waste refractory materials. This method utilizes existing secondary resources that can be reused as refractory materials or waste refractory materials that have been disposed of through landfilling. Through an environmentally friendly hydrometallurgical process, high-purity magnesium oxide is prepared in an environmentally friendly manner, removing impurities such as iron, aluminum, silicon, and calcium.

Claims

1. A method for preparing high-purity magnesium oxide from waste refractory materials using an environmentally friendly hydrometallurgical process, characterized in that, include: Step S10: After leaching the magnesium-containing waste refractory material with a sulfuric acid solution of 1M to 7M, the leachate and residue are separated by solid-liquid separation. Step S20: Using the leachate formed in step S10 as a leaching agent, the impurities in the leachate are purified and removed. The leachate is formed by leaching with a 3M to 7M sulfuric acid solution. Step S30: The leachate obtained from the above impurity purification and leaching step is pulverized to prepare magnesium-containing powder. Step S40: Heat-treat the above-mentioned magnesium-containing powder to prepare magnesium oxide; and Step S50: Wash the magnesium oxide that has undergone the above heat treatment to achieve high purity. The purity of the magnesium oxide obtained from the above washing process is over 99%.

2. The method for preparing high-purity magnesium oxide from waste refractory materials using an environmentally friendly hydrometallurgical process according to claim 1, characterized in that, The aforementioned magnesium-containing waste refractory materials contain 30 to 55 percent magnesium by weight.

3. The method for preparing high-purity magnesium oxide from waste refractory materials using an environmentally friendly hydrometallurgical process according to claim 1, characterized in that, Before the step of separating the leachate and residue by solid-liquid separation after leaching the magnesium-containing waste refractory material, the step of crushing / pulverizing the magnesium-containing waste refractory material is also included.

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

5. The method for preparing high-purity magnesium oxide from waste refractory materials using an environmentally friendly hydrometallurgical process according to claim 1, characterized in that, The above step S10 is carried out under the following conditions: the solid (g) / liquid (mL) ratio of magnesium-containing waste refractory material to sulfuric acid solution is 1 / 10 to 3 / 10, the reaction temperature is below 100℃, and the stirring speed is 100RPM to 400RPM.

6. The method for preparing high-purity magnesium oxide from waste refractory materials using an environmentally friendly hydrometallurgical process according to claim 1, characterized in that, In step S20 above, the leachate obtained in step S10 is used as the leaching agent. Magnesium-containing waste refractory material is added to the leaching agent for leaching, and then the leachate and residue are separated.

7. The method for preparing high-purity magnesium oxide from waste refractory materials using an environmentally friendly hydrometallurgical process according to claim 6, characterized in that, In step S20 above, the following process is repeated: using the first-stage leachate as the leaching agent, magnesium-containing waste refractory material is added to the leaching agent for leaching, and then the second-stage leachate and residue are separated.

8. The method for preparing high-purity magnesium oxide from waste refractory materials using an environmentally friendly hydrometallurgical process according to claim 7, characterized in that, The above step S20 is carried out under the following conditions: the solid (g) / liquid (L) ratio of magnesium-containing waste refractory material to sulfuric acid solution is 5 to 30, the reaction temperature is below 100℃, and the stirring speed is 100 RPM to 400 RPM.

9. The method for preparing high-purity magnesium oxide from waste refractory materials using an environmentally friendly hydrometallurgical process according to claim 1, characterized in that, In step S20 above, the pH of the leachate after the impurity purification and leaching step is above 7.

10. The method for preparing high-purity magnesium oxide from waste refractory materials using an environmentally friendly hydrometallurgical process according to claim 1, characterized in that, The above step S30 is carried out for 30 minutes to 2 hours under the conditions of steam temperature above 45°C and stirring speed above 25 RPM.

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

12. The method for preparing high-purity magnesium oxide from waste refractory materials using an environmentally friendly hydrometallurgical process according to claim 11, characterized in that, In step S40 above, the heat treatment is carried out at a temperature of 1200°C to 1500°C for 3 to 6 hours.

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

14. The method for preparing high-purity magnesium oxide from waste refractory materials using an environmentally friendly hydrometallurgical process according to claim 1, characterized in that, In step S50 above, under the conditions that the solid (g) / liquid (mL) ratio of heat-treated magnesium oxide to 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 to 50 minutes.

15. The method for preparing high-purity magnesium oxide from waste refractory materials using an environmentally friendly hydrometallurgical process according to claim 1, characterized in that, The above step S50 is performed once or repeated 2 to 5 times.

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

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