Method for pyrolyzing heavy magnesium water and device therefor, basic magnesium carbonate

Abstract

The application relates to a method and device for pyrolyzing heavy magnesium water and basic magnesium carbonate, the method comprising: heating the heavy magnesium water; wherein a vacuum treatment is adopted, and the vacuum degree of the vacuum treatment is controlled to perform a first-stage pyrolysis of the heavy magnesium water; the vacuum treatment is stopped according to the first temperature of the heavy magnesium water to perform a second-stage pyrolysis of the heavy magnesium water, and basic magnesium carbonate is obtained. In the first-stage pyrolysis, it is also an induction period of pyrolysis. The heavy magnesium water is heated, and a certain vacuum degree is reached in the pyrolysis process by using the vacuum treatment, the carbon dioxide partial pressure in the pyrolysis is reduced, the induction period of the pyrolysis is controlled, the pyrolysis temperature in the first stage is reduced, the reaction rate of the pyrolysis is accelerated, and the energy consumption is reduced.

Description

Technical Field

[0001] This application relates to the fields of chemical engineering and magnesium smelting technology, and in particular to a method and apparatus for pyrolyzing heavy magnesium water and basic magnesium carbonate. Background Technology

[0002] The pyrolysis of hydrated magnesium hydroxide is a crucial step in the carbonization process of dolomite. Dolomite's main components are calcium carbonate and magnesium carbonate, and it can be used as a raw material for smelting metallic magnesium and extracting magnesium oxide. The pyrolysis of hydrated magnesium hydroxide is one of the key steps in obtaining these components.

[0003] However, in actual production, the pyrolysis process is slow and inefficient due to various conditions. Summary of the Invention

[0004] This application provides a method and apparatus for pyrolyzing magnesium hydroxide and basic magnesium carbonate, in order to solve the technical problem of slow pyrolysis rate of existing magnesium hydroxide pyrolysis methods.

[0005] In a first aspect, this application provides a method for pyrolyzing magnesium hydroxide, the method comprising:

[0006] The magnesium hydroxide solution was heated; among which,

[0007] Vacuum treatment is employed, and the vacuum level of the vacuum treatment is controlled, to carry out the first stage pyrolysis of the heavy magnesium water;

[0008] The vacuum treatment is stopped at the first temperature of the magnesium hydroxide to carry out the second stage pyrolysis of the magnesium hydroxide, thereby obtaining basic magnesium carbonate.

[0009] Optionally, the vacuum degree of the vacuum treatment is 80kPa-90kPa.

[0010] Optionally, the first temperature is 40℃-60℃.

[0011] Optionally, stopping the vacuum treatment based on the first temperature of the magnesium hydroxide to perform a second-stage pyrolysis of the magnesium hydroxide to obtain basic magnesium carbonate includes:

[0012] The vacuum treatment is stopped at the first temperature of the magnesium hydroxide to carry out the second stage pyrolysis of the magnesium hydroxide to obtain basic magnesium carbonate; wherein, the time between the end of pyrolysis and the second temperature of the magnesium hydroxide is set.

[0013] Optionally, the second temperature is 80℃-90℃.

[0014] Optionally, the set time from the end of pyrolysis is 30-60 minutes.

[0015] Optionally, the heating temperature is 120℃-200℃.

[0016] Secondly, this application provides a basic magnesium carbonate, which is prepared by the method described in any one of the embodiments of the first aspect.

[0017] Thirdly, this application provides an apparatus for pyrolyzing magnesium hydroxide, used to implement the method described in any embodiment of the first aspect, the system comprising:

[0018] Pyrolysis system 1, used for pyrolysis of magnesium hydroxide;

[0019] Heating system 2 is used to heat pyrolysis system 1;

[0020] Vacuum system 3 is used to perform vacuum treatment on the pyrolysis system 1 and is connected to the pyrolysis system 1.

[0021] Optionally, the pyrolysis system 1 includes a discharge port 4, which is located at the bottom of the pyrolysis system 1 and is slightly higher than the bottom of the pyrolysis system 1.

[0022] The technical solutions provided in this application have the following advantages compared with the prior art:

[0023] The method for pyrolyzing magnesium hydroxide provided in this application embodiment is also the induction period of pyrolysis in the first stage of pyrolysis.

[0024] Heating the magnesium hydroxide solution and using vacuum treatment to achieve a certain degree of vacuum during pyrolysis reduces the partial pressure of carbon dioxide during pyrolysis, controls the induction period of pyrolysis, lowers the pyrolysis temperature of the first stage, accelerates the pyrolysis reaction rate, and reduces energy consumption. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A schematic flowchart of a method for pyrolyzing magnesium hydroxide provided in an embodiment of this application;

[0028] Figure 2 This is a schematic diagram of the structure of an apparatus for pyrolyzing magnesium hydroxide according to an embodiment of this application; wherein,

[0029] 1-Pyrolysis system, 2-Heating system, 3-Vacuum system, 4-Discharge port, 5-Oil bath, 6-Agitator, 7-Feeding port. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0032] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0033] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0034] Firstly, this application provides a method for pyrolyzing magnesium hydroxide, please refer to [link to relevant documentation]. Figure 1 The method includes:

[0035] S1. Heating the molten magnesium hydroxide; wherein...

[0036] Vacuum treatment is employed, and the vacuum level of the vacuum treatment is controlled, to carry out the first stage pyrolysis of the heavy magnesium water;

[0037] The vacuum treatment is stopped at the first temperature of the magnesium hydroxide to carry out the second stage pyrolysis of the magnesium hydroxide, thereby obtaining basic magnesium carbonate.

[0038] Specifically, in step S1 above, during the first stage of pyrolysis, a vacuum treatment is performed to achieve the above-mentioned vacuum level. During this process, the heating rate is high, and the heavy magnesium water is rapidly heated to 20℃-30℃. Then, the heating rate is controlled to 1℃ / min, and the heavy magnesium water is slowly heated to the first temperature.

[0039] In some embodiments, the heating temperature is 120°C-200°C.

[0040] In this embodiment, an oil bath heating method is used, and the oil temperature is adjusted to suit different pyrolysis processes. This not only increases the temperature difference and improves the efficiency of continuous pyrolysis, but also changes the energy source from traditional weather heat or liquefied petroleum gas to electricity. The positive effects of controlling the heating temperature to 120℃-200℃ include controlling the heating rate of the magnesium hydroxide solution, which facilitates the induction of crystal growth. Specifically, the heating temperature can be 120℃, 140℃, 160℃, 180℃, 200℃, etc.

[0041] In some embodiments, the vacuum degree of the vacuum treatment is 80 kPa-90 kPa.

[0042] In this embodiment, the pyrolysis reaction is endothermic and generates gas; the aforementioned vacuum treatment is beneficial to the reaction. Vacuuming increases both the reaction rate and crystallization speed, allowing for control of crystal size. Retaining some material during discharge can serve as seed crystals for the next production cycle, further increasing crystal size. The first stage of pyrolysis is also the induction period. Vacuum treatment achieves a certain vacuum level during the pyrolysis process, reducing the partial pressure of carbon dioxide during pyrolysis, controlling the induction period, lowering the pyrolysis temperature, accelerating the reaction rate, and reducing energy consumption. Controlling the vacuum level to 80kPa-90kPa has the following positive effects: it effectively accelerates the pyrolysis rate and promotes the growth of basic magnesium carbonate crystals. If the vacuum level is too high, it may excessively lower the boiling point of the solution, causing boiling and water evaporation, thus damaging the vacuum system. If the vacuum level is too low, it will not effectively increase the pyrolysis rate and will not allow for effective control of the product crystal size. Specifically, the vacuum degree of this vacuum treatment can be 80 kPa, 82 kPa, 84 kPa, 86 kPa, 88 kPa, 90 kPa, etc.

[0043] In some embodiments, the first temperature is 40°C-60°C.

[0044] In this embodiment, the positive effect of stopping the vacuum treatment when the temperature of the aforementioned magnesium hydroxide solution reaches a first temperature is as follows: If the vacuum treatment is not stopped as the temperature rises, the solution will boil, causing water evaporation and damaging the vacuum system. If the first temperature is too high, water evaporation will occur to some extent, affecting the vacuum system; if the first temperature is too low, the solution may not yet be supersaturated at low temperatures, making it impossible to effectively control the crystal morphology during vacuuming. Specifically, the first temperature can be 40℃, 45℃, 50℃, 55℃, 60℃, etc.

[0045] In some embodiments, stopping the vacuum treatment based on a first temperature of the magnesium hydroxide to perform a second-stage pyrolysis of the magnesium hydroxide to obtain basic magnesium carbonate includes:

[0046] The vacuum treatment is stopped at the first temperature of the magnesium hydroxide to carry out the second stage pyrolysis of the magnesium hydroxide to obtain basic magnesium carbonate; wherein, the time between the end of pyrolysis and the second temperature of the magnesium hydroxide is set.

[0047] In some embodiments, the second temperature is 80°C-90°C.

[0048] In some implementations, the set time for the end of pyrolysis is 30-60 minutes.

[0049] In this embodiment, when the temperature of the magnesium hydroxide solution reaches a second temperature, a time interval is set between the end of pyrolysis. The positive effects are: accelerating the pyrolysis rate and increasing product yield. If the second temperature is too high, it will increase the energy consumption of the pyrolysis section to some extent; if the second temperature is too low, it will reduce the product yield to some extent. Specifically, the second temperature can be 80℃, 82℃, 84℃, 86℃, 88℃, 90℃, etc.

[0050] Setting the time between the end of pyrolysis and the end of the process to 30-60 minutes has the following positive effects: it ensures complete pyrolysis and controls product yield. If this time is too long, pyrolysis may be completed to some extent, eliminating the need for further heating; if this time is too short, pyrolysis may not be complete to some extent, affecting product yield. Specifically, this time can be 30 minutes, 40 minutes, 50 minutes, 60 minutes, etc.

[0051] Secondly, this application provides a basic magnesium carbonate, which is prepared by the method described in any one of the embodiments of the first aspect.

[0052] In this embodiment, the magnesium hydroxide solution after the second stage of pyrolysis is filtered and calcined to obtain basic magnesium carbonate with a diameter greater than 300 μm. The product morphology is controlled to be spherical, which facilitates subsequent spherical pressing.

[0053] The above method can not only accelerate the pyrolysis rate and reduce pyrolysis energy consumption, but also increase the particle size of basic magnesium carbonate, which is of great significance for improving the efficiency of the magnesium-calcium separation process in the aluminothermic process and subsequent production.

[0054] Thirdly, this application provides an apparatus for pyrolyzing magnesium hydroxide; please refer to [link to relevant documentation]. Figure 2 The system is configured to implement the method described in any embodiment of the first aspect, wherein the system comprises:

[0055] Pyrolysis system 1, used for pyrolysis of magnesium hydroxide;

[0056] Heating system 2 is used to heat pyrolysis system 1;

[0057] Vacuum system 3 is used to perform vacuum treatment on the pyrolysis system 1 and is connected to the pyrolysis system 1.

[0058] In this embodiment, the heating system 2 is a circulating oil bath electric heating device. Its inner wall is made of high-temperature resistant stainless steel, and it uses electric heating. It has temperature control and a circulating pump to supply high-temperature hot oil to the pyrolysis system 1 to provide a heat source. The aforementioned apparatus for pyrolyzing heavy magnesium water also includes an oil bath tank 5, which mainly surrounds and heats the pyrolysis system 1.

[0059] The aforementioned pyrolysis system 1 is embedded in the oil bath tank 5, with the discharge port slightly higher than the bottom of the tank, providing a certain degree of sealing.

[0060] The aforementioned vacuum system 3 is a general vacuum mechanical pump, which can be a steam jet pump or a Roots pump. It is responsible for evacuating the pyrolysis tank to a vacuum level of 80kPa-90kPa in order to reduce the partial pressure of carbon dioxide during pyrolysis.

[0061] The aforementioned apparatus for pyrolyzing magnesium hydroxide also includes a stirrer 6, which is arc-shaped and can rotate close to the inner wall of the pyrolysis tank. While stirring, it scrapes off the basic magnesium carbonate adhering to the pyrolysis tank, preventing the adhering to the wall.

[0062] In some embodiments, the pyrolysis system 1 includes a discharge port 4, which is located at the bottom of the pyrolysis system 1 and is slightly higher than the bottom of the pyrolysis system 1.

[0063] In this embodiment, the discharge port 4 is slightly higher than the bottom of the pyrolysis system 1. When discharging, some material will be retained at the bottom as an inducer for the next pyrolysis, further controlling the product morphology.

[0064] The apparatus for pyrolyzing magnesium hydroxide is based on the above-described method for pyrolyzing magnesium hydroxide. The specific steps of the method for pyrolyzing magnesium hydroxide can be referred to in the above embodiments. Since the apparatus for pyrolyzing magnesium hydroxide adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0065] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0066] This application provides a method for pyrolyzing magnesium hydroxide, the method comprising:

[0067] S11. Heating the magnesium hydroxide solution; wherein...

[0068] Vacuum treatment is employed, and the vacuum level of the vacuum treatment is controlled, to carry out the first stage of pyrolysis;

[0069] The vacuum treatment is stopped at the first temperature of the magnesium hydroxide solution to proceed with the second stage of pyrolysis, yielding basic magnesium carbonate. For specific process steps, please refer to Examples 1-3 below.

[0070] Example 1

[0071] Before pyrolysis, turn on the electric heating device to heat the oil to 120℃ and maintain it. Then, open the feed port at the top of the pyrolysis tank, add an appropriate amount of heavy magnesium hydrate, and then close the feed port. Start the stirring device, turn on the vacuum system, and evacuate the vacuum degree in the pyrolysis tank to 90 kPa and maintain it. At this time, the temperature of the heavy magnesium hydrate is 20℃. Subsequently, control the heating rate to 1℃ / min. When the temperature of the heavy magnesium hydrate in the pyrolysis tank reaches 40℃, turn off the vacuum system. When the temperature of the heavy magnesium hydrate in the pyrolysis tank reaches 80℃, pyrolysis is completed after another 60 minutes. Then, open the discharge port at the bottom of the pyrolysis tank to discharge the material.

[0072] Example 2

[0073] Before pyrolysis, turn on the electric heating device to heat the oil to 150℃ and maintain it. Then, open the feed port at the top of the pyrolysis tank, add an appropriate amount of heavy magnesium hydrate, and then close the feed port. Start the stirring device, turn on the vacuum system, and evacuate the vacuum degree in the pyrolysis tank to 85kPa and maintain it. At this time, the temperature of the heavy magnesium hydrate is 25℃. Subsequently, control the heating rate to 1℃ / min. When the temperature in the pyrolysis tank reaches 50℃, turn off the vacuum system. When the temperature of the heavy magnesium hydrate in the pyrolysis tank reaches 90℃, pyrolyze for another 40 minutes to complete the pyrolysis. Then, open the discharge port at the bottom of the pyrolysis tank to discharge the material.

[0074] Example 3

[0075] Before pyrolysis, turn on the electric heating device to heat the oil to 200℃ and maintain it. Then, open the feed port at the top of the pyrolysis tank, add an appropriate amount of heavy magnesium hydrate, and then close the feed port. Start the stirring device, turn on the vacuum system, and evacuate the vacuum degree in the pyrolysis tank to 80kPa and maintain it. At this time, the temperature of the heavy magnesium hydrate is 30℃. Subsequently, control the heating rate to 1℃ / min. When the temperature in the pyrolysis tank reaches 60℃, turn off the vacuum system. When the temperature of the heavy magnesium hydrate in the pyrolysis tank reaches 90℃, pyrolyze for another 30 minutes to complete the pyrolysis. Then, open the discharge port at the bottom of the pyrolysis tank to discharge the material.

[0076] Comparative Example 1

[0077] The molten magnesium is heated directly to 95°C using a hot air furnace or other heating method, without a vacuum system. Once the solution reaches the temperature, it is kept at that temperature for 60–90 minutes before being discharged.

[0078] Table 1 evaluates the methods of pyrolysis of heavy magnesium water in Examples 1-3 and Comparative Example 1.

[0079] Table 1. Total pyrolysis time and particle size distribution of basic magnesium carbonate in pyrolyzed magnesium hydroxide.

[0080]

[0081]

[0082] The method described in this application improves the pyrolysis rate, shortens the total pyrolysis time, reduces energy consumption, and can obtain basic magnesium carbonate with a particle size greater than 300 μm.

[0083] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method of pyrolyzing heavy magnesium water, characterized by, The method comprises: The heavy magnesium water is heated; wherein, The vacuum treatment is adopted, and the vacuum degree of the vacuum treatment is controlled to be 80-90 kPa to carry out the first stage pyrolysis of the heavy magnesium water, in the first stage pyrolysis, the heavy magnesium water is rapidly heated to 20-30 DEG C in the process of reaching the above-mentioned vacuum degree; then the heating rate is controlled to be 1 DEG C / min, and the heavy magnesium water is slowly heated to a first temperature; When the temperature of the heavy magnesium water reaches the first temperature, the vacuum treatment is stopped to carry out the second stage pyrolysis of the heavy magnesium water, when the temperature of the above-mentioned heavy magnesium water reaches a second temperature, the time of being away from the end of pyrolysis is set to obtain basic magnesium carbonate; The first temperature is 40-60 DEG C; The second temperature is 80-90 DEG C; The time of being away from the end of pyrolysis is set to be 30-60 min; The heavy magnesium water after the above-mentioned second stage pyrolysis is filtered and calcined to obtain basic magnesium carbonate with a diameter greater than 300 μm.

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