Preparation method of magnesium carbonate
The preparation method of heating and mixing solves the problem of unstable performance of magnesium carbonate products produced by the brine-soda ash method, and prepares petal-shaped magnesium carbonate, which improves its dispersibility and mechanical properties in specific material fields and expands its application range.
Patent Information
- Application Number
- CN202511120948.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-12
- Publication Date
- 2025-11-07
Smart Images
Figure CN120903533A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of magnesium carbonate production, and particularly relates to a preparation method of magnesium carbonate. BACKGROUND
[0002] Magnesium carbonate is a white to yellow solid crystal or crystal powder. It can resist high temperature and is difficult to dissolve in water, acetone and liquid ammonia, but it is easily soluble in aqueous ammonium salt solution. Magnesium carbonate can be used as a refractory material, a heat preservation material for boilers and pipelines, and for manufacturing magnesium salt, magnesium oxide, ink, glass, toothpaste, rubber filler and the like. The preparation methods of magnesium carbonate include precipitation method, hydrothermal method, sodium carbonate method, soda ash method, bauxite double decomposition method, brine-soda ash method and the like.
[0003] Among them, the brine-soda ash method for producing magnesium carbonate is to use brine to react with soda ash (sodium carbonate) to prepare magnesium carbonate. The principle is that magnesium ions (such as magnesium chloride) in brine react with carbonate ions in soda solution to generate magnesium carbonate precipitate, and the reaction formula is: MgCl2 + Na2CO3 = MgCO3↓ + 2NaCl.
[0004] At present, in the process of producing magnesium carbonate by the brine-soda ash method, low-temperature brine is preferentially mixed with lye (the temperature is not higher than 40 DEG C), and then a precipitation reaction is carried out. The crystal form of the slurry after mixing is rod-shaped, and the crystal form is gradually changed from rod-shaped to petal-shaped after pyrolysis at 60 DEG C. The filter cake is formed after dehydration, and the filter cake is washed, dried and sieved, and finally the magnesium carbonate product (the crystal form is a mixture of rod-shaped and petal-shaped) is obtained. The performance of this product is unstable, and the solubility in water is relatively low, which may affect the application effect in some dissolution systems; the relative hardness, strength and other physical properties may not meet the requirements of specific materials or industrial fields. SUMMARY
[0005] In order to solve the above technical problems, the present application provides a preparation method of magnesium carbonate. The raw materials are heated before mixing reaction, and the obtained magnesium carbonate is petal-shaped. The product structure is regular, the powder particles are uniform, and when added in the fields of plastics, rubber, coatings and the like, it can be well dispersed, and the mechanical properties of the material (such as strength and material flowability) can be improved; it is suitable for the fields of environmental protection new materials, battery additives, medical video and the like which have high safety requirements.
[0006] To achieve this technical purpose, the present application adopts the following scheme: The present application provides a preparation method of magnesium carbonate, comprising the following steps: S1, raw material pretreatment: removing impurities and insoluble substances in brine and soda solution; S2, raw material heating: heating the raw materials brine and soda solution respectively, and keeping warm for standby; S3, reaction precipitation: the heated brine and soda solution are slowly mixed in proportion, and slowly reacted under stirring; S4, solid-liquid separation and washing: the slurry after reaction is subjected to solid-liquid separation, and the filter cake is washed; S5, filter cake scattering and drying: the filter cake after washing is scattered and dried to remove water, to obtain the magnesium carbonate product.
[0007] Further, the preferred scheme of the present application is: In step S2, the brine and soda solution are heated to 65-70 DEG C respectively.
[0008] The heating mode in step S2 is indirect heating.
[0009] In step S3, the molar ratio of magnesium ions in the brine to carbonate ions in the soda solution is 1.6:1.6.
[0010] In step S3, the reaction temperature is 60-65 DEG C, the pH is 8-10, the stirring speed is 280-300 rpm, and the reaction time is 3 hours.
[0011] In step S4, the filter cake is washed with softened water.
[0012] In step S5, the drying temperature is 120-140 DEG C, and the crystal form of the magnesium carbonate product is petal-shaped.
[0013] Compared with the prior art, the present application has the following beneficial effects: The present application uses brine and alkali solution of the same concentration, indirect heat exchange is carried out by a steam heat exchanger, the material temperature is heat exchanged to the required production temperature, then the brine and alkali solution are mixed and reacted, the slurry after reaction is filtered and washed, the filter cake is sent to a dryer for drying, and the filter cake after drying is crushed, graded, weighed and packaged. The present application uses a steam heat exchanger for indirect heat exchange, the process parameters are easy to control, the impurities brought in by direct steam injection and direct heating are greatly reduced, the cleanliness of the material is further ensured, and the quality of the final product is high, and the application range is wider. BRIEF DESCRIPTION OF DRAWINGS
[0014] Figure 1 The flow chart of the preparation method of magnesium carbonate in the embodiments of the present application; Figure 2 The crystal form diagram of the magnesium carbonate product in Example 1 of the present application; Figure 3 The crystal form diagram of the magnesium carbonate product in Comparative Example 1 of the present application. DETAILED DESCRIPTION
[0015] In order to fully understand the purpose, features and effects of the present application, the following specific embodiments are described in detail, but the present application is not limited to this.
[0016] Referring to Figure 1 The present application provides a preparation method of magnesium carbonate, comprising the following steps: S1, raw material pretreatment: removing impurities and insoluble substances in brine and soda solution; Brine: The brine produced by solar salt needs to be filtered to remove impurities such as silt, and soft water is used to dilute and adjust the concentration (magnesium ion content) to the appropriate concentration range.
[0017] If other metal ions (such as calcium, iron) are contained in the brine, they need to be removed in advance to avoid affecting the purity of the product.
[0018] Soda: A sodium carbonate solution with a certain concentration is prepared and filtered to remove insoluble substances.
[0019] The concentration of brine (calculated as magnesium ions) and soda is 1.6±0.05 mol / L. The appropriate concentration is conducive to the precipitation reaction. If the concentration of the raw material is too high, the reaction will be violent, the gap between the crystals will be small, and the precipitate will be fine, affecting filtration. If the concentration of the raw material is too low, there will be less precipitate, increasing the frequency of liquid preparation circulation and increasing the production cost.
[0020] S2, heating of raw materials: heating the raw material brine and soda solution to 65~70℃ respectively, and keeping warm for standby; the preferred heating method is indirect heating.
[0021] In an embodiment, a shell and tube heat exchanger is used, the hot fluid is steam, and the cold fluid is the raw material medium. The raw material brine and soda solution are heated to the required production temperature by indirect heat exchange between steam and raw material medium for subsequent production.
[0022] Indirect heat exchange is carried out by using a steam heat exchanger, the process parameters are easy to control, and the impurities brought in by direct steam injection and direct heating are greatly reduced, further ensuring the cleanliness of the material and the quality of the final product.
[0023] Heating all the raw materials to the required production temperature at once before mixing can reduce the changes in the appearance of the material caused by pyrolysis heating, leading to uncontrollable factors such as particle size.
[0024] S3, reaction precipitation: slowly mix the heated brine and soda solution in proportion, and slowly react under stirring conditions; The molar ratio of magnesium ions in brine to carbonate ions in soda solution is 1.6:1.6, with a slight excess of soda, which can ensure the complete precipitation of magnesium ions.
[0025] The reaction temperature is controlled at 60-65 DEG C and the pH is controlled at 8-10 during the reaction, which can promote the generation of magnesium carbonate precipitation and avoid the generation of impurities other than magnesium carbonate; the stirring speed is 280-300 rpm and the reaction time is 3 hours, and the appropriate stirring speed and reaction time are conducive to controlling the size of the material particle size and facilitating subsequent slurry solid-liquid separation, washing and other operations.
[0026] The reaction time should be moderate, too short time relatively small particles, otherwise the larger particles; temperature deviation is large, which will affect the reaction slurry particle size and the purity of the final product (magnesium carbonate main content).
[0027] Appropriate stirring can promote the uniformity of the slurry reaction, but too fast speed may damage the structure of the precipitate, and the stirring speed in the present application is preferably 280-300 rpm.
[0028] S4, solid-liquid separation and washing: the slurry after the reaction is subjected to solid-liquid separation, and then soft water is added to wash the filter cake to remove the absorbed impurities such as chloride ions in the filter cake until no chloride ions are detected in the washing liquid, thereby obtaining a magnesium carbonate filter cake, and the filtrate (mainly containing sodium chloride) can be recycled or discharged after treatment.
[0029] The solid-liquid separation method uses one of the prior art methods, such as a filter pressing method.
[0030] S5, filter cake scattering and drying: the filter cake after washing is scattered by a scattering machine and then dried to remove water to obtain a magnesium carbonate product.
[0031] The drying temperature is 120-140 DEG C, and the crystal form of the magnesium carbonate product is petal-shaped.
[0032] In some embodiments, the dried magnesium carbonate product can be crushed, graded, etc. according to customer requirements to produce finished products with particle sizes meeting customer requirements. Example 1
[0033] S1, raw material pretreatment Brine: the bitter brine produced by salt drying is first filtered to remove impurities such as mud and sand, and then the calcium, iron and other metal ions are removed, and the magnesium ion content is adjusted to 1.6 mol / L by using soft water dilution.
[0034] Soda ash: take the soda ash to configure a 1.6 mol / L sodium carbonate solution, and filter to remove insoluble substances.
[0035] S2, raw material heating: the raw material brine and the soda ash solution are heated to 65 DEG C through a shell and tube heat exchanger, the hot fluid of the shell and tube heat exchanger is steam, and the cold fluid is the raw material medium. After heating, it is kept warm for standby.
[0036] S3, reaction precipitation: the heated brine and soda solution are slowly mixed in the reaction tank at a volume ratio of 1:1, and slowly react under stirring conditions; The reaction temperature is controlled at 60°C, the pH is 8-10, the stirring speed is 280 rpm, and the reaction time is 3 hours.
[0037] S4, solid-liquid separation and washing: the slurry after the reaction is separated by pressure filtration, and then softened water is added to wash the filter cake to remove the absorbed chlorine ions and other impurities in the filter cake until no chlorine ions are detected in the washing liquid, to obtain a magnesium carbonate filter cake. The filtrate (mainly containing sodium chloride) can be recycled and utilized or discharged after treatment.
[0038] S5, filter cake scattering and drying: the washed filter cake is scattered by a scattering machine and then sent to a drying machine for drying at a temperature of 120°C to obtain a magnesium carbonate product.
[0039] The magnesium carbonate is observed by using a Thesken MIRA fourth-generation high-performance scanning electron microscope, as shown in Figure 2 It can be seen that the magnesium carbonate crystal form is petal-shaped. Example 2
[0040] S1, raw material pretreatment Brine: the bitter brine produced by solar salt is first filtered to remove impurities such as mud and sand, and then the calcium, iron and other metal ions are removed, and the magnesium ion content is adjusted to 1.6 mol / L by using soft water dilution.
[0041] Soda: take soda to prepare a 1.6 mol / L sodium carbonate solution, and filter to remove insoluble substances.
[0042] S2, raw material heating: the raw material brine and soda solution are heated to 70°C by a tube heat exchanger, the hot fluid of the tube heat exchanger is steam, and the cold fluid is the raw material medium. After heating, it is kept warm for standby.
[0043] S3, reaction precipitation: the heated brine and soda solution are slowly mixed in the reaction tank at a volume ratio of 1:1, and slowly react under stirring conditions; The reaction temperature is controlled at 65°C, the pH is 8-10, the stirring speed is 300 rpm, and the reaction time is 3 hours.
[0044] S4, solid-liquid separation and washing: the slurry after the reaction is separated by pressure filtration, and then softened water is added to wash the filter cake to remove the absorbed chlorine ions and other impurities in the filter cake until no chlorine ions are detected in the washing liquid, to obtain a magnesium carbonate filter cake. The filtrate (mainly containing sodium chloride) can be recycled and utilized or discharged after treatment.
[0045] S5, the filter cake is scattered and dried: the filter cake after washing is scattered by a scattering machine and then sent to a drying machine for drying at a temperature of 140 DEG C to obtain a magnesium carbonate product. Comparative Example 1
[0046] The preparation method of the magnesium carbonate is basically the same as that of Example 1, and the difference from Example 1 is that: The brine and the soda solution are heated to 60 DEG C respectively.
[0047] When the raw materials are heated to below 65 DEG C, the temperature of the raw materials is reduced during the transportation to the reaction tank for mixing, and the reaction temperature of the materials cannot be guaranteed to be above 60 DEG C. When the reaction temperature is below 60 DEG C, the final product is a mixture of rods and petals, and the performance is relatively poor, and the purity of the magnesium carbonate is relatively low. Figure 3 Comparative Example 2
[0048] The preparation method of the magnesium carbonate is basically the same as that of Example 1, and the difference from Example 1 is that: The brine and the soda solution are heated to 75 DEG C respectively.
[0049] When the raw materials are heated to above 70 DEG C, the temperature of the raw materials is not reduced to below 65 DEG C during the transportation to the reaction tank for mixing, which causes the particle size of the final product to increase, reduces the flowability and dispersibility of the synthetic product, and thus limits the application field of the product. Comparative Example 3
[0050] The preparation method of the magnesium carbonate is basically the same as that of Example 1, and the difference from Example 1 is that: The stirring speed in step S3 is 250 rpm.
[0051] When the stirring speed of the reaction tank is below 280 rpm, the raw materials are not mixed sufficiently, the particle size of the slurry is uneven, the washing effect of the filter cake after filtration is uneven, and the semi-finished product with high chlorine content has high corrosion to the equipment. Comparative Example 4
[0052] The preparation method of the magnesium carbonate is basically the same as that of Example 1, and the difference from Example 1 is that: The stirring speed in step S3 is 350 rpm.
[0053] When the stirring speed of the reaction tank is above 300 rpm, the slurry is stirred too violently, it is difficult to form crystal nucleus, the particle size of the slurry is relatively small, the filtration and washing time is seriously affected, the moisture content of the filter cake is high, and the filter cake is not easy to dry, which increases the production cost. Comparative Example 5
[0054] The preparation method of magnesium carbonate is basically the same as that of example 1, and the difference from example 1 is that: The drying temperature in step S5 is 100℃.
[0055] When the drying temperature is lower than 120℃, the filter cake after filtration is a block material with a diameter of about 2cm. When the drying temperature is lower than 120℃, the penetration of heat radiation to the block filter cake is poor, resulting in long drying time, high energy consumption of equipment and other problems, which seriously affect the production efficiency. Comparative example 6
[0056] The preparation method of magnesium carbonate is basically the same as that of example 1, and the difference from example 1 is that: The drying temperature in step S5 is 160℃.
[0057] When the drying temperature is higher than 140℃, the filter cake is periodically dried at this temperature, which causes the actual temperature of the filter cake to rise continuously. Long-term drying at a constant temperature of 140℃ or above will decompose part of the magnesium carbonate and generate part of the magnesium oxide, affecting the use field of the final product. Comparative example 7
[0058] The original two-step preparation method is as follows: The raw materials brine and alkali solution are heated to 35℃, then pumped into the reaction tank for mixing reaction. The obtained slurry is subjected to primary dewatering, washing, beating and pyrolysis, and then subjected to secondary dewatering and washing. The obtained filter cake is sent to a drying machine for drying.
[0059] The magnesium carbonate prepared in the above examples and comparative examples is detected and characterized as follows: 1. Particle size detection, the detection method refers to GB / T19077-2016 “Particle size distribution-laser diffraction method”, and the detection results are shown in the table below.
[0060] Table 1 Effect of stirring speed on product particle size distribution
[0061] 2. Purity detection, the detection method refers to HGT2959-2023 “Industrial hydrated basic magnesium carbonate”, and the detection results are shown in the table below.
[0062] Table 2 Effect of reaction temperature on main content (calculated as magnesium oxide) of product
[0063] 3. Magnetic substance detection, the detection method refers to GB / T37167-2018 “Separation and detection of trace and trace magnetic substances in particulate inorganic powder”, the content of magnetic substances (iron+zinc+chromium+copper) in the magnesium carbonate is detected, and the detection results are shown in the table below.
[0064] Table 3 Magnetic substance content in products prepared by different methods
[0065] The raw material is heated first, and then a one-step reaction is used to produce magnesium carbonate.Compared with the original two-step production process, the one-step process uses steam for heat exchange in the raw material heating, and the process parameters are easier to control.The two-step process uses steam for direct injection pyrolysis of the slurry in the later stage, and the controllability of the process parameters is lower, the slurry has more impurities, and the quality of the final product is relatively low.The one-step process can produce diversified magnesium carbonate products for different customers by adjusting the related controls of the raw material heat exchange temperature, concentration and reaction tank stirring speed.The final product of the two-step production process is a mixture of rod-shaped and petal-shaped, and the final product of the one-step heating process of the application is multi-layer petal-shaped, which greatly reduces the production cost and has a wide range of product applications.
[0066] Finally, it should be noted that the above-mentioned is only the preferred embodiment of the present application, of course, those skilled in the art can modify and change the present application, provided that these modifications and changes belong to the scope of the claims of the present application and its equivalent technology, should be considered as the protection scope of the present application.
Claims
1. A method for producing magnesium carbonate, characterized by, The method comprises the following steps: S1, raw material pretreatment: removing impurities and insoluble substances in brine and soda solution; S2, raw material heating: heating the raw material brine and soda solution respectively and keeping warm for standby; S3, reaction and precipitation: slowly mixing the heated brine and soda solution according to the proportion, and slowly reacting under stirring condition; S4, solid-liquid separation and washing: carrying out solid-liquid separation on the slurry after reaction, and washing the filter cake; S5, filter cake scattering and drying: scattering the filter cake after washing, and drying to remove water to obtain magnesium carbonate product.
2. The method of producing magnesium carbonate according to claim 1, characterized by, In step S2, the brine and soda solution are heated to 65-70 DEG C respectively.
3. The method of producing magnesium carbonate according to claim 1, characterized by, The heating mode in step S2 is indirect heating.
4. The method of producing magnesium carbonate according to claim 1, characterized by, In step S3, the molar ratio of magnesium ions in the brine to carbonate ions in the soda solution is 1.6:1.
6.
5. The method of producing magnesium carbonate according to claim 1, characterized by, In step S3, the reaction temperature is 60-65 DEG C, the pH is 8-10, the stirring speed is 280-300 rpm, and the reaction time is 3 hours.
6. The method of producing magnesium carbonate according to claim 1, characterized by, In step S4, softened water is used to wash the filter cake.
7. The method of producing magnesium carbonate according to claim 1, characterized by, In step S5, the drying temperature is 120-140 DEG C, and the crystal form of the magnesium carbonate product is petal-shaped.