Method for preparing magnesia carbon brick by using salt lake bischofite as raw material and magnesia carbon brick

Abstract

The invention discloses a method for preparing a magnesia carbon brick by using salt lake bischofite as a raw material and the magnesia carbon brick. The method comprises the following steps: obtaining the salt lake bischofite by using a dissolution-precipitation method, and preparing high-purity magnesium oxide powder by using a direct decomposition method; grinding, drying, briquetting and calcining the high-purity magnesium oxide powder to obtain high-purity sintered magnesia; the preparation method comprises the following steps: crushing high-purity magnesite clinker into high-purity magnesite clinker particle materials with different particle sizes, mixing the high-purity magnesite clinker particle materials with graphite, asphalt, metal silicon and phenolic resin according to a certain proportion and a certain filling sequence, and pressing into a magnesia carbon brick blank; and roasting the magnesia carbon brick blank at constant temperature and at fixed time to prepare the formed magnesia carbon brick. The indexes of the prepared magnesia carbon brick completely meet the MT-14A standard requirements in magnesia carbon GB / T22589-2017. The magnesia carbon brick prepared by using the salt lake bischofite as the raw material has the excellent performances of high purity, high density, low impurity and the like, the product index is stable, the comprehensive benefit is excellent, meanwhile, the problem of'magnesium harm 'in the salt lake potash fertilizer production process is solved, and the reuse efficiency of salt lake resources is improved.

Description

Technical Field

[0001] This invention relates to the field of magnesium-carbon brick preparation technology, specifically to a method for preparing magnesium-carbon bricks using salt lake water magnesium chloride as raw material, and the magnesium-carbon bricks themselves. Background Technology

[0002] Magnesia-carbon bricks are an indispensable core refractory product in steel metallurgical production, with applications covering key equipment in the steelmaking process, such as electric furnaces, converters, and ladles. These machines operate at high temperatures, typically exceeding 1500°C, under extreme conditions of strong erosion from molten steel and slag, placing extremely high demands on the high-temperature resistance, erosion resistance, and structural stability of the refractory materials. Therefore, the quality and supply stability of magnesia-carbon bricks directly affect the continuity, safety, and product quality of steel production, making them a "basic building material" supporting the efficient operation of the steel industry.

[0004] my country possesses abundant salt lake resources, among which the magnesium chloride reserves of the Qarhan Salt Lake are particularly outstanding, reaching 1.8 billion tons, making it an important global magnesium resource reserve base. At the same time, the potash fertilizer (KCl) production process in the salt lake area generates a large amount of by-product brine, which is a high-concentration salt solution remaining after potash fertilizer extraction. The most important active component in the brine is magnesium chloride hydrate (MgCl2・6H2O).

[0005] Statistics show that potash fertilizer companies accumulate up to 30 million tons of magnesium chloride hydrate annually from old brine. From a resource perspective, magnesium chloride hydrate is a high-quality magnesium source; however, from the perspective of the current industry situation, these large-scale accumulations of magnesium chloride hydrate have long failed to be utilized efficiently. Instead, due to problems such as accumulation and storage, they pose a potential threat to the ecological environment of salt lakes and surrounding production facilities. This phenomenon is referred to in the industry as "magnesium hazard," which is the dual contradiction of idle magnesium resources and environmental pressure.

[0006] Against this backdrop, the industry is currently facing two major pain points: (1) Raw material bottleneck: the purity of raw materials is unstable, production costs are high and the development of high-end raw materials is limited; (2) Resource contradiction: the problem of "magnesium hazard" is becoming increasingly prominent, and the industry has not yet formed a mature process for preparing magnesium carbon bricks using salt lake brine (or its by-product hydrate magnesium chloride) as raw material.

[0007] In conclusion, addressing the current bottlenecks in magnesia-carbon brick production, resolving the "magnesium hazard" problem in salt lakes, and achieving comprehensive resource utilization are inevitable logical outcomes. Summary of the Invention

[0008] Based on the aforementioned technical problems, this invention breaks away from the traditional reliance on the magnesite-fused magnesia route for magnesia-carbon bricks, instead using brine (a byproduct of potash fertilizer production in salt lakes) as a starting point to construct a completely new raw material supply chain. The aim is to provide a method for preparing magnesia-carbon bricks using salt lake magnesia minerals as raw material, and to produce magnesia-carbon bricks themselves.

[0009] This invention protects a method for preparing magnesia-carbon bricks using magnesium chloride from salt lake water as a raw material, the specific steps of which are as follows: Step 1, Impurity Removal: After drying the magnesium chloride from the salt lake, the dried magnesium chloride from the salt lake is dissolved in anhydrous ethanol in batches to form a MgCl2 solution; Step 2, Preparation of high-purity magnesium oxide powder: First, filter the above MgCl2 solution to separate the KCl and NaCl insoluble substances in the solution; then, separate the ethanol and magnesium chloride water from the filtered MgCl2 solution; finally, calcine and heat-preserving the separated magnesium chloride water to prepare high-purity magnesium oxide powder. Step 3, preparation of high-purity sintered magnesia: After the above high-purity magnesium oxide powder is fully mixed with agate balls and anhydrous ethanol, it is ground, dried, shaped into balls and calcined to obtain high-purity sintered magnesia. Step 4, Crushing: The above-mentioned high-purity sintered magnesia is crushed into high-purity sintered magnesia particles of different sizes for later use; Step 5, Mixing: The high-purity sintered magnesia particles of different sizes are mixed with graphite, asphalt, silicon metal and phenolic resin in a certain proportion and in a certain order. The mixture is pressed into magnesia-carbon brick blanks under the action of pressure equipment and mold. Step 6, Firing of Magnesia-Carbon Bricks: The above-mentioned magnesia-carbon brick blanks are fired at a constant temperature for a set time and then naturally cooled to produce magnesia-carbon bricks.

[0010] Further, in step 1, the magnesium chloride is dried at 120°C for 12 hours, and the mass ratio of the magnesium chloride from the salt lake to anhydrous ethanol in the MgCl2 solution is 1:3.

[0011] Further, in step 2, filtration is performed using a vacuum filtration flask; the filtered MgCl2 solution is then separated from the ethanol and magnesium chloride water using a rotary evaporator via evaporation-precipitation; the separated magnesium chloride water is placed in a corundum crucible and then placed in a box-type resistance furnace at 4-5℃·min. -1 The temperature is increased to 550-600℃ at a certain rate for calcination, and then held at that temperature for 1-1.5 h to prepare high-purity magnesium oxide powder.

[0012] Further, in step 3, firstly, high-purity magnesium oxide powder and agate balls are thoroughly mixed, with the mass ratio of agate balls to high-purity magnesium oxide powder being 10:1. The mixture is then placed in a laboratory planetary ball mill and milled at a speed of 600 r·min⁻¹ for 1 hour, with the particle size controlled at 1.2-1.5 μm. Next, the mixture of milled high-purity magnesium oxide powder and anhydrous ethanol is dried in an oven at 80-100℃ for 2 hours and then pressed into 30mm*40mm ball blanks using a briquetting machine. Finally, the ball blanks are calcined in a high-temperature box-type resistance furnace at 1600℃ for 2 hours and then cooled to room temperature with the furnace to obtain high-purity sintered magnesia.

[0013] Furthermore, in step 4, the high-purity sintered magnesia is crushed into high-purity sintered magnesia particle sizes of 5-3mm, 3-1mm, 1-0mm, and 200 mesh by a small jaw crusher.

[0014] Further, in step 5, the high-purity sintered magnesia granules (5-3mm: 3-1mm: 1-0mm: 200 mesh: graphite: bitumen: silicon metal: phenolic resin) are mixed in a mass fraction ratio of 30:25:15:15:10:1:1:3. To ensure that the high-purity sintered magnesia granules are uniformly coated with graphite, the mixture is added in the following order: high-purity sintered magnesia granules (5-3mm, 3-1mm, 1-0mm), phenolic resin, graphite, high-purity sintered magnesia granules (200 mesh), bitumen, and silicon metal. The mixture is then pressed into a 200 mm * 150 mm * 100 mm rectangular magnesia-carbon brick blank with a weight of 20 kg under the action of a 1200 MPa pressurizing device and a mold.

[0015] Furthermore, in step 6, the magnesia-carbon brick blank is baked in an oven at a constant temperature of 200°C for 36 hours and then naturally cooled to produce magnesia-carbon bricks.

[0016] This invention also protects magnesia-carbon bricks prepared by the above method, wherein the magnesia-carbon bricks have an MgO content greater than 78%, a C content greater than 14%, a flexural strength greater than 10 MPa, a compressive strength greater than 40 MPa, and a bulk density greater than 3.4 g·cm³. -3 Its indicators fully comply with the MT-14A standard requirements in GB / T22589-2017 for magnesia-carbon bricks.

[0017] Compared with existing technologies, the present invention has the following beneficial effects: This invention uses salt lake brine as raw material, obtaining high-purity magnesium chloride from old salt lake brine using a dissolution-precipitation method, and preparing high-purity magnesium oxide powder through direct decomposition. The high-purity magnesium oxide powder is then ground, dried, briquetted, and calcined to obtain high-purity sintered magnesia. This high-purity sintered magnesia is crushed into particles of different sizes, then mixed with graphite, asphalt, silicon metal, and phenolic resin in a specific ratio and order, and pressed into magnesia-carbon brick blanks. The magnesia-carbon brick blanks are then fired at a constant temperature for a set time and naturally cooled to produce magnesia-carbon bricks. The prepared magnesia-carbon bricks have an MgO content greater than 78%, a carbon content greater than 14%, a flexural strength greater than 10 MPa, a compressive strength greater than 40 MPa, and a bulk density greater than 3.4 g·cm³. -3 Its indicators fully comply with the MT-14A standard requirements in GB / T22589-2017 for magnesium carbon.

[0018] This invention utilizes magnesium chloride from salt lake water as a raw material to prepare magnesia-carbon bricks. These bricks exhibit high purity, high density, and low impurities, resulting in stable product performance and excellent overall benefits. Simultaneously, it solves the "magnesium toxicity" problem in the production of potash fertilizer from salt lakes, filling a gap in my country's magnesia-carbon brick production using salt lake brine as a raw material and improving the efficiency of salt lake resource reuse. Furthermore, the developed process for preparing magnesia-carbon bricks from magnesium chloride from salt lake water not only provides a stable, low-cost, high-end raw material for magnesia-carbon brick production and solves the problem of unstable fused magnesia grade in Liaoning Province, but also provides a direction for alternatives to fused magnesia after resource depletion and environmental restrictions in Liaoning. This promotes the coordinated economic development of the salt lake region with the steel and refractory materials industries, possessing significant technical value and economic and social significance. Attached Figure Description

[0019] Figure 1 This is a flowchart of the preparation process of the present invention; Figure 2 This is a SEM image of the sintered magnesia of the present invention; Figure 3 This is a physical image of the magnesia-carbon brick prepared according to the present invention. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1 A method for preparing magnesia-carbon bricks using salt lake water magnesia stone as raw material (1) Removal of impurities The hydrous magnesium chloride from the Qarhan Salt Lake in Qinghai Province was dried at 120℃ for 12 hours to obtain naturally crystalline hydrous magnesium chloride. The chemical composition (w) of the hydrous magnesium chloride is: MgCl₂·6H₂O 98.12%, NaCl 0.39%, KCl 0.24%, CaO 0.12%, SiO₂ 0.06%, with Mg as the main component. 2+ Cl - The minor component is K + Na + and Ca 2+ Then, 50 kg of magnesium chloride from the salt lake was dissolved in anhydrous ethanol in batches, with the mass ratio of magnesium chloride to anhydrous ethanol being 1:3, to form a MgCl2 solution.

[0022] (2) Preparation of high-purity magnesium oxide powder First, the MgCl2 solution was filtered using a vacuum filtration flask to separate the insoluble KCl and NaCl from the solution. Then, the filtered MgCl2 solution was subjected to a rotary evaporator to separate the ethanol and magnesium chloride water using an evaporation-precipitation method. Finally, the separated magnesium chloride water was placed in a corundum crucible and then placed in a box-type resistance furnace, heated at 5℃·min. -1 The temperature was increased to 550℃ and calcined, then held for 1 hour to prepare high-purity magnesium oxide powder.

[0023] (3) Preparation of high-purity sintered magnesia First, high-purity magnesium oxide powder and agate balls are thoroughly mixed, with the mass ratio of agate balls to high-purity magnesium oxide powder being 10:1. The mixture is then placed in a laboratory planetary ball mill and milled at a speed of 600 r·min. -1 The high-purity magnesium oxide powder was ball-milled for 1 hour, and the particle size was controlled at 1.303 μm. Then, the mixture of ball-milled high-purity magnesium oxide powder and anhydrous ethanol was dried in an oven at 80°C for 2 hours and then pressed into 30 mm * 40 mm ball blanks on a briquetting machine. Finally, the ball blanks were placed in a high-temperature box-type resistance furnace at 1600°C and calcined for 2 hours. After cooling to room temperature with the furnace, high-purity sintered magnesia was obtained.

[0024] (4) Broken The above-mentioned high-purity sintered magnesia is crushed into high-purity sintered magnesia particle size materials of 5-3mm, 3-1mm, 1-0mm and 200 mesh by a small jaw crusher, and then set aside for later use.

[0025] (5) Mixing To ensure that the high-purity sintered magnesia particles are uniformly coated with graphite, the following mixture is added in the following order by mass fraction: 30% high-purity sintered magnesia particles (5-3mm), 25% high-purity sintered magnesia particles (3-1mm), 15% high-purity sintered magnesia particles (1-0mm), 3% phenolic resin, 10% graphite, 15% high-purity sintered magnesia particles (200 mesh), 1% bitumen, and 1% metallic silicon. The mixture is then pressed into rectangular magnesia-carbon brick blanks (200mm x 150mm x 100mm) under a 1200MPa pressure device and mold, with a weight of 20kg.

[0026] (6) Firing of magnesia-carbon bricks The above-mentioned magnesia-carbon brick blanks were fired in an oven at a constant temperature of 200℃ for 36 hours, and then naturally cooled to produce magnesia-carbon bricks. Sampling and testing were conducted according to GB / T 10325-2012 Sampling Inspection Rules for Acceptance of Shaped Refractory Products; GB / T 2997-2000 tested the bulk density and apparent porosity of samples after heat treatment at 200℃; GB / T 5072-2008 tested the room temperature compressive strength of samples after heat treatment at 200℃; and GB / T 3002-2004 tested the high-temperature flexural strength of samples after holding at 1400℃ for 0.5 hours.

[0027] Finally, the magnesia-carbon bricks prepared by the above method were measured to have an MgO content greater than 78%, a C content greater than 14%, a flexural strength greater than 10 MPa, a compressive strength greater than 40 MPa, and a bulk density greater than 3.4 g·cm³. -3 Its indicators fully comply with the MT-14A standard requirements in GB / T22589-2017 for magnesia-carbon bricks. Note: The above indicators were tested according to national standards; therefore, no compensation was provided for the testing process.

[0028] From the appendix Figure 2 SEM images of sintered magnesia show that the high-purity magnesia from the salt lake exhibits high density and small grain size. The microstructure indicates that the formation of high-density magnesia is inevitably accompanied by a decrease in porosity, requiring fewer and smaller pores within the material. Its main components are Mg, O, Si, and Ca. The periclase phase in the salt lake magnesia is uniformly and orderly distributed, and no obvious intergranular phase aggregation regions were found throughout the observation range.

[0029] Comparative Example 1 1. Comparison of chemical composition of raw materials Based on a comparison of the chemical indicators of raw materials, salt lake sintered magnesia has a high MgO content and few impurities. For alkaline refractory materials, this can improve their refractoriness, enhance their erosion resistance, improve their thermal shock stability, and reduce the impact of impurities.

[0030] Table 1 Chemical composition of raw materials (wt%) 2. Comparison of Magnesia-Carbon Brick Indicators Table 2 Comparison of Magnesia-Carbon Brick Indicators (wt%) MgO (%) C (%) Flexural strength (Mpa) Compressive strength (Mpa) Apparent porosity (%) Bulk density (g / cm3) Magnesia-carbon brick prepared from Liaoning 97.5% fused magnesia 78.42 14.31 10.26 39.56 3.33 2.97 Magnesia-carbon brick prepared from sintered magnesia from salt lake (i.e. Example 1) 80.82 15.13 10.45 40.41 3.21 3.14 Based on the comparison of chemical indicators of magnesia-carbon bricks, magnesia-carbon bricks prepared from salt lake sintered magnesia (i.e., the magnesia-carbon bricks of this application) have higher main content, and their C% content, flexural strength, and compressive strength are all superior to those prepared from 97.5% fused magnesia. By optimizing the MgO content, C content, flexural strength, and compressive strength, the ability of magnesia-carbon bricks to resist slag erosion and mechanical scouring can be improved, thus extending the service life of magnesia-carbon bricks.

[0031] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing magnesia-carbon bricks using magnesium chloride from salt lake water as raw material, characterized in that, The specific steps are as follows: Step 1, Impurity Removal: After drying the magnesium chloride from the salt lake, the dried magnesium chloride from the salt lake is dissolved in anhydrous ethanol in batches to form a MgCl2 solution; Step 2, Preparation of high-purity magnesium oxide powder: First, filter the above MgCl2 solution to separate the KCl and NaCl insoluble substances in the solution; then, separate the ethanol and magnesium chloride water from the filtered MgCl2 solution; finally, calcine and heat-preserving the separated magnesium chloride water to prepare high-purity magnesium oxide powder. Step 3, preparation of high-purity sintered magnesia: After the above high-purity magnesium oxide powder is fully mixed with agate balls and anhydrous ethanol, it is ground, dried, shaped into balls and calcined to obtain high-purity sintered magnesia. Step 4, Crushing: The above-mentioned high-purity sintered magnesia is crushed into high-purity sintered magnesia particles of different sizes for later use; Step 5, Mixing: The high-purity sintered magnesia particles of different sizes are mixed with graphite, asphalt, silicon metal and phenolic resin in a certain proportion and in a certain order. The mixture is pressed into magnesia-carbon brick blanks under the action of pressure equipment and mold. Step 6, Firing of Magnesia-Carbon Bricks: The above-mentioned magnesia-carbon brick blanks are fired at a constant temperature for a set time and then naturally cooled to produce magnesia-carbon bricks.

2. The method according to claim 1, characterized in that, In step 1, the magnesium chloride is dried at 120°C for 12 hours, and the mass ratio of the magnesium chloride from the salt lake to anhydrous ethanol in the MgCl2 solution is 1:

3.

3. The method according to claim 1, characterized in that, In step 2, filtration is performed using a vacuum filtration flask; the filtered MgCl2 solution is then separated from the ethanol and magnesium chloride water using a rotary evaporator via evaporation-precipitation; the separated magnesium chloride water is placed in a corundum crucible and then placed in a box-type resistance furnace, heated to 550-600℃ at a rate of 4-5℃·min-1 for calcination, and then held at that temperature for 1-1.5 h to prepare high-purity magnesium oxide powder.

4. The method according to claim 1, characterized in that, In step 3, firstly, high-purity magnesium oxide powder and agate balls are thoroughly mixed, with the mass ratio of agate balls to high-purity magnesium oxide powder being 10:

1. The mixture is then placed in a laboratory planetary ball mill and milled at a speed of 600 r·min⁻¹ for 1 hour, with the particle size controlled at 1.2-1.5 μm. Next, the mixture of milled high-purity magnesium oxide powder and anhydrous ethanol is dried in an oven at 80-100℃ for 2 hours and then pressed into 30mm*40mm ball blanks using a briquetting machine. Finally, the ball blanks are calcined in a high-temperature box-type resistance furnace at 1600℃ for 2 hours and then cooled to room temperature with the furnace to obtain high-purity sintered magnesia.

5. The method according to claim 1, characterized in that, In step 4, the high-purity sintered magnesia is crushed into high-purity sintered magnesia particle sizes of 5-3mm, 3-1mm, 1-0mm, and 200 mesh by a small jaw crusher.

6. The method according to claim 1, characterized in that, In step 5, the high-purity sintered magnesia granules (5-3mm: 3-1mm: 1-0mm: 200 mesh: graphite: bitumen: silicon metal: phenolic resin) are mixed in a mass fraction ratio of 30:25:15:15:10:1:1:

3. To ensure that the high-purity sintered magnesia granules are uniformly coated with graphite, the mixture is added in the following order: high-purity sintered magnesia granules (5-3mm, 3-1mm, 1-0mm), phenolic resin, graphite, high-purity sintered magnesia granules (200 mesh), bitumen, and silicon metal. The mixture is then pressed into a rectangular magnesia-carbon brick blank (200mm*150mm*100mm) under a 1200MPa pressure device and mold, weighing 20kg.

7. The method according to claim 1, characterized in that, In step 6, the magnesia-carbon brick blanks are baked in an oven at a constant temperature of 200℃ for 36 hours and then naturally cooled to produce magnesia-carbon bricks.

8. A magnesia-carbon brick, characterized in that, The magnesia-carbon brick is prepared by the method described in any one of claims 1-7, wherein the magnesia-carbon brick has an MgO content greater than 78%, a C content greater than 14%, a flexural strength greater than 10 MPa, a compressive strength greater than 40 MPa, and a bulk density greater than 3.4 g·cm³. -3 Its indicators fully comply with the MT-14A standard requirements in GB / T22589-2017 for magnesia-carbon bricks.

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