Method for preparing low-calcium magnesium oxide by purifying high-calcium magnesite

Abstract

The invention discloses a method for preparing low-calcium magnesium oxide by purifying high-calcium magnesite, and belongs to the technical field of metal ore upgrading processing. According to the invention, a method of first calcining and then mixing is adopted, raw material waste is avoided, hydrochloric acid is taken as a chlorinating agent, experiment cost is greatly reduced, utilization of low-grade magnesite is increased, resource waste is reduced, high-quality low-calcium magnesium oxide (WCaO is less than 1.00%) is finally obtained, and the process flow is simple and easy to operate.

Description

Technical Field

[0001] The invention belongs to the technical field of metal ore quality improvement and processing, and specifically relates to a method for purifying high-calcium magnesite to prepare low-calcium magnesium oxide. Background Art

[0002] Magnesite is the main natural mineral raw material for refractory materials, which can be divided into two types: rhombohedral crystalline magnesite and dense and high-hardness amorphous magnesite.

[0003] my country is rich in magnesite resources. Two-thirds of the world's magnesite reserves are concentrated in China, and one-half of the output is provided by China. China plays a pivotal role in the world magnesite market.

[0004] High-purity magnesium oxide usually refers to magnesium oxide products with a magnesium oxide content (w) higher than 98% or even 99%. High-purity magnesium oxide has high thermal conductivity, large thermal expansion coefficient, good light transmittance, excellent insulation and alkali resistance at high temperatures, and is an important raw material for high-temperature heat-resistant and thermal insulation materials.

[0005] The main impurities in magnesite are calcium and silicon, and a relatively mature process has been formed for the removal of impurity silicon. According to the different impurity contents of magnesite, magnesite can be divided into low-grade (W MgO <46%) and high grade (W MgO ≥46%). Although my country's natural magnesite resources are very rich, after decades of mining, high-grade magnesite has become less and less, and in some areas it can no longer meet production needs. Low-grade magnesite cannot be directly used in the production of high-end products due to excessive impurity calcium, resulting in a waste of magnesite resources. Therefore, from a long-term perspective, in order to make better use of resources, the impurity calcium of magnesite is removed by wet method, and low-grade magnesite is turned into high-quality refractory materials that can be calcined to solve the problems of low utilization rate of magnesite resources and shortage of high-grade magnesite.

[0006] Patent CN110775992A discloses a method for preparing high-purity magnesium oxide by purifying magnesite. The method uses a method of mixing magnesite and magnesium chloride and calcining them to remove calcium. While obtaining low-calcium magnesium oxide, it inevitably causes the evaporation and waste of a portion of magnesium chloride (1). This method innovatively proposes a method of calcining magnesite first and then reacting it in hydrochloric acid, which can avoid the waste of magnesium chloride during the calcination process and help reduce experimental costs. Summary of the invention

[0007] In view of the above shortcomings, the present invention provides a high calcium magnesite (W CaO ≥6%) to purify and prepare low calcium magnesium oxide (W CaOThe method of reducing the content of magnesium oxide to less than 1% provides a new way to produce high-purity magnesium oxide and makes more effective use of low-grade magnesite.

[0008] The scheme adopted by the present invention is as follows:

[0009] A method for purifying high-calcium magnesite to prepare low-calcium magnesium oxide comprises the following steps:

[0010] (1) High calcium magnesite (W CaO ≥6%) is crushed, ground, and sieved to obtain magnesite powder, and the magnesite powder is calcined at high temperature to obtain a calcined product;

[0011] (2) mixing the calcined product obtained in step (1) with hydrochloric acid in proportion and stirring to prepare a mixed slurry;

[0012] (3) stirring the mixed slurry obtained in step (2), heating and keeping the mixture warm, filtering and washing with water to obtain a washed product;

[0013] (4) calcining the washed product obtained in step (3) at high temperature to obtain low-calcium magnesium oxide (W CaO <1.00%).

[0014] The above method for purifying high-calcium magnesite to prepare low-calcium magnesium oxide, wherein:

[0015] Preferably, in step (1), the calcination temperature is 900° C.-1000° C., and the calcination time is 1 h-2 h.

[0016] Preferably, in step (1), the particle size of the magnesite powder does not exceed 100 mesh.

[0017] Preferably, in step (2), the concentration of hydrochloric acid is 3%-8%.

[0018] Preferably, in step (2), the solid-liquid ratio of the calcined product and hydrochloric acid is 1: (3-7) g / ml.

[0019] Preferably, in step (3), the stirring rate is 150 rpm-300 rpm, the heating temperature is 70° C.-90° C., and the insulation time is 30 min-90 min.

[0020] Preferably, in step (4), the calcination temperature is 400° C.-500° C., and the calcination time is 1 h-3 h.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] (1) The present invention adopts a method of calcining first and then mixing, thereby avoiding the waste of raw materials;

[0023] (2) This experiment uses hydrochloric acid as the chlorinating agent, which greatly reduces the experimental cost;

[0024] (3) The method of the present invention increases the utilization of low-grade magnesite and reduces the waste of resources;

[0025] (4) The method of the present invention obtains high-quality low-calcium magnesium oxide (W CaO <1.00%), the process is simple and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a process flow chart for preparing low-calcium magnesium oxide by purifying high-calcium magnesite according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, wherein the process flow of the present invention for preparing low-calcium magnesium oxide by purifying high-calcium magnesite is as follows: Figure 1 shown.

[0028] Comparative Example 1

[0029] High calcium magnesite (W CaO =6.59%) was crushed, ground, and sieved through a 100-mesh sieve to obtain magnesite powder, which was placed in a muffle furnace and calcined at 900°C for 1 hour. The calcined product was mixed and stirred with 3% hydrochloric acid in a ratio of 1:5 to prepare a mixed slurry, which was placed in a magnetic stirring pot, stirred at a rate of 300 rpm and heated at 60°C for 20 minutes, filtered, and washed with water. The washed product was calcined at 400°C for 1 hour in a muffle furnace to obtain low-calcium magnesium oxide (W CaO =1.21%).

[0030] Comparative Example 2

[0031] High calcium magnesite (W CaO =6.59%) was crushed, ground, and sieved through a 100-mesh sieve to obtain magnesite powder, which was placed in a muffle furnace and calcined at 900°C for 1 hour. The calcined product was mixed and stirred with 3% hydrochloric acid in a ratio of 1:3 to prepare a mixed slurry, which was placed in a magnetic stirring pot, stirred at a rate of 300 rpm and heated at 50°C for 30 minutes, filtered, and washed with water. The washed product was calcined at 400°C for 1 hour in a muffle furnace to obtain low-calcium magnesium oxide (W CaO =1.46%).

[0032] Comparative Example 3

[0033] High calcium magnesite (WCaO =6.59%) was crushed, ground, and sieved through a 100-mesh sieve to obtain magnesite powder, which was placed in a muffle furnace and calcined at 900°C for 1 hour. The calcined product was mixed and stirred with 2% hydrochloric acid in a ratio of 1:3 to prepare a mixed slurry, which was placed in a magnetic stirring pot, stirred at a rate of 300 rpm and heated at 70°C for 30 minutes, filtered, and washed with water. The washed product was calcined at 400°C for 1 hour in a muffle furnace to obtain low-calcium magnesium oxide (W CaO =1.31%).

[0034] Example 1

[0035] High calcium magnesite (W CaO =6.59%) was crushed, ground, and sieved through a 100-mesh sieve to obtain magnesite powder, which was placed in a muffle furnace and calcined at 900°C for 1 hour. The calcined product was mixed and stirred with 3% hydrochloric acid in a ratio of 1:5 to prepare a mixed slurry, which was placed in a magnetic stirring pot, stirred at a rate of 300 rpm and heated at 70°C for 30 minutes, filtered, and washed with water. The washed product was calcined at 400°C for 1 hour in a muffle furnace to obtain low-calcium magnesium oxide (W CaO =0.68%).

[0036] Example 2

[0037] High calcium magnesite (W CaO =6.59%) was crushed, ground, and sieved through a 100-mesh sieve to obtain magnesite powder, which was placed in a muffle furnace and calcined at 1000°C for 2 hours. The calcined product was mixed and stirred with 5% hydrochloric acid in a ratio of 1:7 to prepare a mixed slurry, which was placed in a magnetic stirring pot, stirred at a rate of 300 rpm, heated at 70°C for 30 minutes, filtered, and washed with water. The washed product was calcined at 500°C for 3 hours in a muffle furnace to obtain low-calcium magnesium oxide (W CaO =0.52%).

[0038] Example 3

[0039] High calcium magnesite (W CaO=6.59%) was crushed, ground, and sieved through a 200-mesh sieve to obtain magnesite powder, which was placed in a muffle furnace and calcined at 900°C for 1 hour. The calcined product was mixed and stirred with 8% hydrochloric acid in a ratio of 1:7 to prepare a mixed slurry, which was placed in a magnetic stirring pot, stirred at a rate of 300 rpm and heated at 70°C for 30 minutes, filtered, and washed with water. The washed product was calcined at 500°C for 2 hours in a muffle furnace to obtain low-calcium magnesium oxide (W CaO =0.41%).

[0040] Example 4

[0041] High calcium magnesite (W CaO =6.59%) was crushed, ground, and sieved through a 200-mesh sieve to obtain magnesite powder, which was placed in a muffle furnace and calcined at 1000°C for 2 hours. The calcined product was mixed and stirred with 8% hydrochloric acid in a ratio of 1:3 to prepare a mixed slurry, which was placed in a magnetic stirring pot, stirred at a rate of 150 rpm and heated at 80°C for 30 minutes, filtered, and washed with water. The washed product was calcined at 500°C for 2 hours in a muffle furnace to obtain low-calcium magnesium oxide (W CaO =0.39%).

[0042] Example 5

[0043] High calcium magnesite (W CaO =6.59%) was crushed, ground, and sieved through a 200-mesh sieve to obtain magnesite powder, which was placed in a muffle furnace and calcined at 1000°C for 2 hours. The calcined product was mixed and stirred with 8% hydrochloric acid in a ratio of 1:5 to prepare a mixed slurry, which was placed in a magnetic stirring pot, stirred at a rate of 300 rpm and heated at 90°C for 30 minutes, filtered, and washed with water. The washed product was calcined at 500°C for 2 hours in a muffle furnace to obtain low-calcium magnesium oxide (W CaO =0.32%).

[0044] Example 6

[0045] High calcium magnesite (W CaO=6.59%) was crushed, ground, and sieved through a 100-mesh sieve to obtain magnesite powder, which was placed in a muffle furnace and calcined at 1000°C for 2 hours. The calcined product was mixed and stirred with 8% hydrochloric acid in a ratio of 1:5 to prepare a mixed slurry, which was placed in a magnetic stirring pot, stirred at a rate of 300 rpm and heated at 90°C for 60 minutes, filtered, and washed with water. The washed product was calcined at 500°C for 2 hours in a muffle furnace to obtain low-calcium magnesium oxide (W CaO =0.24%).

[0046] Example 7

[0047] High calcium magnesite (W CaO =6.59%) was crushed, ground, and sieved through a 100-mesh sieve to obtain magnesite powder, which was placed in a muffle furnace and calcined at 1000°C for 2 hours. The calcined product was mixed and stirred with 8% hydrochloric acid in a ratio of 1:5 to prepare a mixed slurry, which was placed in a magnetic stirring pot, stirred at a rate of 300 rpm and heated at 90°C for 90 minutes, filtered, and washed with water. The washed product was calcined at 500°C for 2 hours in a muffle furnace to obtain low-calcium magnesium oxide (W CaO =0.21%).

Claims

1. A method for purifying high-calcium magnesite to prepare low-calcium magnesium oxide, characterized in that: The following steps are involved: Step 1. crushing, grinding and sieving high-calcium magnesite to obtain magnesite powder; calcining the magnesite powder at high temperature to obtain a calcined product; Step 2. Mixing the calcined product and hydrochloric acid in proportion and stirring to prepare a mixed slurry; Step 3. Stirring the mixed slurry and heating and keeping it warm, filtering and washing with water to obtain a washed product; Step 4. calcining the washed product at high temperature to obtain low-calcium magnesium oxide.

2. The method for purifying high-calcium magnesite to prepare low-calcium magnesium oxide according to claim 1, characterized in that: The mass fraction of CaO in the high-calcium magnesite is not less than 6%; the mass fraction of CaO in the low-calcium magnesium oxide is less than 1.00%.

3. The method for purifying high-calcium magnesite to prepare low-calcium magnesium oxide according to claim 1, characterized in that: In step 1, during the high-temperature calcination process, the calcination temperature is 900° C. to 1000° C., and the calcination time is 1 h to 2 h; the particle size of the sieved magnesite powder does not exceed 100 mesh.

4. The method for purifying high-calcium magnesite to prepare low-calcium magnesium oxide according to claim 1, characterized in that: In step 2, the mass concentration of hydrochloric acid is 3% to 8%.

5. The method for purifying high-calcium magnesite to prepare low-calcium magnesium oxide according to claim 4, characterized in that: When the calcined product is mixed with hydrochloric acid, the solid-liquid ratio is calcined product: hydrochloric acid = 1: (3-7) g / ml.

6. The method for purifying high-calcium magnesite to prepare low-calcium magnesium oxide according to claim 1, characterized in that: In step 3, the stirring rate is 150 rpm to 300 rpm, the heating temperature is 70° C. to 90° C., and the insulation time is 30 min to 90 min.

7. The method for purifying high-calcium magnesite to prepare low-calcium magnesium oxide according to claim 1, characterized in that: In step 4, the calcination temperature is 400° C. to 500° C., and the calcination time is 1 h to 3 h.

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