CN115414689A - Narrow-granularity-distribution and granularity-controllable magnesium hydroxide reaction crystallization device and process - Google Patents
Narrow-granularity-distribution and granularity-controllable magnesium hydroxide reaction crystallization device and process Download PDFInfo
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- CN115414689A CN115414689A CN202210613954.4A CN202210613954A CN115414689A CN 115414689 A CN115414689 A CN 115414689A CN 202210613954 A CN202210613954 A CN 202210613954A CN 115414689 A CN115414689 A CN 115414689A
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- 238000006243 chemical reaction Methods 0.000 title claims abstract description 231
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 title claims abstract description 140
- 239000000347 magnesium hydroxide Substances 0.000 title claims abstract description 140
- 229910001862 magnesium hydroxide Inorganic materials 0.000 title claims abstract description 140
- 238000002425 crystallisation Methods 0.000 title claims abstract description 79
- 230000008025 crystallization Effects 0.000 title claims abstract description 77
- 238000000034 method Methods 0.000 title claims abstract description 60
- 238000009826 distribution Methods 0.000 title claims abstract description 32
- 239000002245 particle Substances 0.000 claims abstract description 50
- 238000005485 electric heating Methods 0.000 claims abstract description 16
- 239000007921 spray Substances 0.000 claims abstract description 16
- 238000004519 manufacturing process Methods 0.000 claims abstract description 8
- 238000007599 discharging Methods 0.000 claims abstract description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 105
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 claims description 60
- 239000000725 suspension Substances 0.000 claims description 37
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 36
- 239000007788 liquid Substances 0.000 claims description 30
- 229910001629 magnesium chloride Inorganic materials 0.000 claims description 30
- 239000013078 crystal Substances 0.000 claims description 23
- 239000002994 raw material Substances 0.000 claims description 18
- 239000011780 sodium chloride Substances 0.000 claims description 18
- 229910001220 stainless steel Inorganic materials 0.000 claims description 8
- 239000010935 stainless steel Substances 0.000 claims description 8
- 230000014759 maintenance of location Effects 0.000 claims description 7
- 238000010899 nucleation Methods 0.000 claims description 5
- 230000006911 nucleation Effects 0.000 claims description 5
- 230000003247 decreasing effect Effects 0.000 claims description 2
- 238000012423 maintenance Methods 0.000 claims description 2
- 239000012295 chemical reaction liquid Substances 0.000 claims 2
- 239000000243 solution Substances 0.000 description 46
- 239000000047 product Substances 0.000 description 17
- 235000019580 granularity Nutrition 0.000 description 12
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 6
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 3
- 235000011941 Tilia x europaea Nutrition 0.000 description 3
- 229910021529 ammonia Inorganic materials 0.000 description 3
- 239000004571 lime Substances 0.000 description 3
- 239000008267 milk Substances 0.000 description 3
- 210000004080 milk Anatomy 0.000 description 3
- 235000013336 milk Nutrition 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000003786 synthesis reaction Methods 0.000 description 3
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 238000000053 physical method Methods 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000012267 brine Substances 0.000 description 1
- 229910052599 brucite Inorganic materials 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000012065 filter cake Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000003063 flame retardant Substances 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 235000013305 food Nutrition 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 238000010335 hydrothermal treatment Methods 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 239000012716 precipitator Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000036632 reaction speed Effects 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D9/00—Crystallisation
- B01D9/02—Crystallisation from solutions
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F5/00—Compounds of magnesium
- C01F5/14—Magnesium hydroxide
- C01F5/22—Magnesium hydroxide from magnesium compounds with alkali hydroxides or alkaline- earth oxides or hydroxides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The invention discloses a reaction crystallization device and a reaction crystallization process for magnesium hydroxide with narrow particle size distribution and controllable particle size. The reaction crystallization device consists of a reaction crystallizer (1), a delivery pump (2) and a pipeline (3). The reaction crystallizer (1) comprises a tower body (4), a guide shell (5), a longitudinal support plate (6), an air inlet pipe (7), a gas distributor (8), a feeding pipe (1) (9), a feeding pipe (2) (10), a spray head (11), a magnesium hydroxide discharging pipe (12) and an electric heating sleeve (13). The invention also provides a magnesium hydroxide reaction crystallization process. The device and the process provided by the invention can realize the controllable production of the magnesium hydroxide granularity, and the magnesium hydroxide with narrow particle size distribution can be prepared, thereby meeting the requirements of different industries on the granularity of magnesium hydroxide products. Has the advantages of flexible and controllable product granularity and narrow granularity distribution.
Description
Technical Field
The invention belongs to the technical field of inorganic chemical industry, relates to a magnesium hydroxide reaction crystallization device with narrow particle size distribution and controllable particle size and a process thereof, and particularly relates to a reaction crystallization device and a process for synthesizing magnesium hydroxide with different particle sizes by taking magnesium chloride and sodium hydroxide as raw materials.
Background
The magnesium hydroxide serving as an environment-friendly inorganic chemical product has the advantages of high thermal decomposition temperature, good adsorption capacity, high activity and the like, and can be applied to the fields of spaceflight, environmental protection, flame retardants, rubber and plastic fillers, medical foods and the like.
The preparation method of magnesium hydroxide can be largely divided into a physical method and a chemical synthesis method, and the physical method mainly comprises the following steps: crushing brucite, namely crushing magnesium hydroxide naturally formed in the nature; the chemical method comprises the following steps: calcium process, alkaline process and ammonia process.
The calcium method, namely the lime milk neutralization method, takes a soluble magnesium source and lime milk as raw materials, the method has simpler process flow and low production cost, but the lime milk has low purity and is easy to contain heavy metal impurities, and the obtained magnesium hydroxide product is easy to adsorb and wrap a large amount of impurity ions so as to have low purity; the biggest defect of preparing high-purity magnesium hydroxide by using an ammonia synthesis method is that the obtained magnesium hydroxide product has wider particle size distribution, lower yield and poorer product application effect, and in addition, the production operation environment is poorer due to the strong volatility of ammonia; the alkaline method is a sodium hydroxide method, sodium hydroxide is adopted as a precipitator to prepare magnesium hydroxide from concentrated seawater and brine, and in the conventional research and industrial production, the high-purity magnesium hydroxide is prepared, the process flow is simple, the product purity is high, but the sodium hydroxide is strong in alkalinity and high in reaction speed, the explosion nucleation is easy to occur to obtain colloid, the product granularity is fine, the granularity distribution is wide, the slurry obtained by the reaction is difficult to filter, wash and dry, and the requirement on the corrosion resistance of production equipment is high.
Patent CN105813979A applied by United states of Russian Kaussideke in China firstly synthesizes magnesium hydroxide particles with particle size below 1 μm at a certain temperature, and then carries out hydrothermal treatment under the fluid impact of superheated steam to improve and homogenize the particle size of the product and reduce the specific surface area. Chinese patent CN101234769A reports a process for preparing high-purity superfine magnesium hydroxide by a sodium hydroxide method, and a crystal product of magnesium hydroxide with the granularity of 50nm to 83nm is prepared by a crystal seed decomposition method. The invention optimizes the position and contact mode of sodium hydroxide and magnesium chloride raw materials added into a reaction system by optimizing the structure of a magnesium hydroxide synthesis reaction crystallizer, the synthesis process flow and process conditions, establishes reasonable material concentration and temperature distribution in the reaction crystallizer by an air stirring and heating device, and controls the generation and consumption rate of the supersaturation degree of the solution, so that the generation of magnesium hydroxide, the formation of magnesium hydroxide crystal nucleus and the growth process can be controlled to be completed in different areas, and finally the magnesium hydroxide product with narrow particle size distribution and flexible and controllable particle size is obtained, thereby solving the problems of difficult filtration, washing and drying of the magnesium hydroxide filter cake produced by the original sodium hydroxide method and the limitation of product application.
Disclosure of Invention
The invention aims to solve the technical problem of providing a reaction crystallization device and a process for synthesizing magnesium hydroxide by taking magnesium chloride and sodium hydroxide as raw materials, realizing controllable production of magnesium hydroxide granularity, preparing magnesium hydroxide with different granularities and meeting the requirements of different users on the granularity of magnesium hydroxide products. Has the advantages of flexible and adjustable product granularity and narrow granularity distribution.
In order to achieve the above object, the present invention is implemented by the following technical solutions.
According to one aspect of the invention, the reactive crystallization device for magnesium hydroxide with narrow particle size distribution and controllable particle size is characterized by comprising a reactive crystallizer (1), a delivery pump (2) and a pipeline (3), wherein the number of the reactive crystallizers (1) is 1 to 3 grades; the reaction crystallizer (1) comprises a tower body (4), a guide shell (5), a longitudinal support plate (6), an air inlet pipe (7), a gas distributor (8), a feeding pipe (1) (9), a feeding pipe (2) (10), a spray head (11), a magnesium hydroxide discharging pipe (12) and an electric heating sleeve (13).
The diameter of the guide cylinder (5) of the reaction crystallizer (1) is 0.5 to 0.7 time of the inner diameter of the tower body (4), the lower edge of the guide cylinder (5) is 2 to 40cm away from the bottom of the tower body (4), and the upper edge of the guide cylinder (5) is 40 to 120cm away from the top of the tower body (4).
A longitudinal support plate (6) is arranged between the tower body (4) of the reaction crystallizer (1) and the guide shell (5).
The outer wall of the tower body (4) of the reaction crystallizer (1) is provided with an electric heating jacket (13).
The air inlet pipe (7), the feeding pipe 1 (9) and the feeding pipe 2 (10) of the reactive crystallizer (1) are arranged in the following mode.
(1) The opening of the feeding pipe 1 (9) is positioned in the guide cylinder (5), the height of the pipe opening is 2 to 30cm, the opening of the feeding pipe 2 (10) is positioned in the center of the tower body (4) and is connected with the spray head (11), and the lower edge of the spray head (11) is 10 to 80cm away from the upper edge of the guide cylinder (5).
(2) Magnesium chloride raw material is added into a reaction crystallizer (1) through a feeding pipe 1 (9), and sodium hydroxide raw material is added into the reaction crystallizer (1) through a feeding pipe 2 (10); alternatively, the magnesium chloride raw material is fed into the reaction crystallizer (1) through the feeding pipe 2 (10), and the sodium hydroxide raw material is fed into the reaction crystallizer (1) through the feeding pipe 1 (9).
(3) The opening of the air inlet pipe (7) is positioned in the center of the tower body (4), the height of the opening of the air inlet pipe is 1 to 10cm lower than that of the opening of the feed pipe 1 (9), the upper end of the air inlet pipe (7) is connected with a gas distributor (8), the gas distributor is a round stainless steel plate, and holes are uniformly formed in the stainless steel plate; the opening of the air inlet pipe (7) can also be positioned in an annular gap between the tower body (4) and the guide cylinder (5), the height of the opening of the pipe is 2 to 30cm above the lower edge of the guide cylinder (5), the upper end of the air inlet pipe (7) is connected with a gas distributor (8), the gas distributor is an annular stainless steel plate, and holes are uniformly formed in the stainless steel plate.
The number of the reaction crystallizers (1) can be increased or decreased from 1 to 3 according to different product granularity requirements, magnesium chloride is added into each reaction crystallizer (1) through a feeding pipe 1 (9) or a feeding pipe 2 (10), sodium hydroxide is added into each reaction crystallizer (1) through a feeding pipe 2 (10) or a feeding pipe 1 (9), and the requirement of uniform particle size distribution is met.
According to another aspect of the invention, the magnesium hydroxide reaction crystallization process of the magnesium hydroxide reaction crystallization device with narrow particle size distribution and controllable particle size is characterized in that the generated magnesium hydroxide suspension flows through the reaction crystallizers (1) in series and in sequence.
The magnesium hydroxide reaction crystallization process is characterized in that magnesium hydroxide products can be conveyed out of a magnesium hydroxide pipeline of each stage of reaction crystallizer (1).
The operation method of the magnesium hydroxide reaction crystallization process of the magnesium hydroxide reaction crystallization device with narrow particle size distribution and controllable particle size is characterized by comprising the following steps.
(1) Adding 1-27 mass percent sodium chloride solution into each reaction crystallizer (1) as reaction crystallization base solution, introducing air at a set flow rate, and maintaining the height of the liquid level of the aerated sodium chloride solution to be 10-80 cm higher than the upper edge of the guide cylinder (5); and controlling the electric heating sleeves to heat the reaction crystallizers (1) at all levels by using the control module, so that the temperatures of the sodium chloride solutions in the reaction crystallizers (1) at all levels respectively reach the set operating temperature values.
(2) Adding a magnesium chloride solution and a sodium hydroxide solution into the 1 st-stage reaction crystallizer (1) according to a set proportion, simultaneously opening a magnesium hydroxide discharge pipe (12) below the 1 st-stage reaction crystallizer (1), and conveying magnesium hydroxide suspension generated by reaction out of a reaction crystallization device through the magnesium hydroxide discharge pipe (12).
(3) After the 1 st-stage reaction crystallization process is stable, a valve behind the 1 st-stage reaction crystallizer (1) is opened, the suspension containing magnesium hydroxide crystals generated by the reaction is sent to the 2 nd-stage reaction crystallizer (1), a magnesium chloride solution and a sodium hydroxide solution are added into the 2 nd-stage reaction crystallizer (1) according to a set proportion, a magnesium hydroxide discharge pipe (12) below the 2 nd-stage reaction crystallizer (1) is opened at the same time, and the magnesium hydroxide suspension generated by the reaction is conveyed out of the reaction crystallization device through the magnesium hydroxide discharge pipe (12).
(4) After the 2 nd-stage reaction crystallization process is stable, a valve behind the 2 nd-stage reaction crystallizer (1) is opened, the suspension containing magnesium hydroxide crystals generated by the reaction is sent to the 3 rd-stage reaction crystallizer (1), a magnesium chloride solution and a sodium hydroxide solution are added into the 3 rd-stage reaction crystallizer (1) according to a set proportion, a magnesium hydroxide discharge pipe (12) below the 3 rd-stage reaction crystallizer (1) is opened at the same time, the magnesium hydroxide suspension generated by the reaction is conveyed out of the reaction crystallization device through the magnesium hydroxide discharge pipe (12), and the reaction crystallization process enters a continuous and stable operation state.
(5) Under the continuous and stable operation state, the magnesium chloride solution and the sodium hydroxide solution are added into each reaction crystallizer (1) in parallel according to the set proportion and the set flow; the magnesium hydroxide suspension liquid flows out of each stage of reactive crystallizer (1) at a set flow rate, the magnesium hydroxide suspension liquid flowing out of each stage of reactive crystallizer (1) can enter the next stage of reactive crystallizer (1), can also be conveyed out of the reactive crystallizer for preparing magnesium hydroxide products with different particle sizes, and one part of the magnesium hydroxide suspension liquid can enter the next stage of reactive crystallizer (1) and the other part of the magnesium hydroxide suspension liquid can be conveyed out of the reactive crystallizer.
The magnesium hydroxide reactive crystallization operation method is characterized in that the set temperature shown in the step (1) is 75-80 ℃, and the set gas flow rate is 0.022-0.044 ms.
The magnesium hydroxide reaction crystallization operation method is characterized in that the set proportion of the steps (2), (3), (4) and (5) is that the molar ratio of magnesium chloride to sodium hydroxide is kept to be 1:1.5 to 3.0; the set flow rates of the magnesium chloride solution and the sodium hydroxide solution in the step (5) are to maintain the retention time of the feed liquid in the reaction crystallizer (1) to be 0.5-3 h; the set flow rate of the magnesium hydroxide suspension liquid in the step (5) is based on the maintenance of the liquid level in the reaction crystallizer (1) of the stage.
The production process of the narrow-granularity-distribution and granularity-controllable magnesium hydroxide reaction crystallization device, the magnesium hydroxide reaction crystallization process and the magnesium hydroxide reaction crystallization operation method is characterized in that reaction crystallization nucleation and crystal growth processes are carried out in different crystallizers, the average granularity of the obtained magnesium hydroxide product can be flexibly adjusted within 5-50 mu m according to needs, and the granularity distribution is narrow.
Compared with the existing magnesium hydroxide reaction crystallization equipment and process, the invention has the beneficial effects that.
The magnesium hydroxide reaction crystallization process is optimized, crystallization nucleation and crystal growth processes are carried out in different reaction crystallizers (1), the 1 st-stage reaction crystallizer (1) is mainly used for crystallization nucleation, and the subsequent reaction crystallizers (1) at all stages are used for crystal growth. In addition, the structure of the reaction crystallizer, the gas flow rate and the position of a raw material feeding port are optimized, the flow state in the reaction crystallizer (1), the concentration distribution and the retention time of the two raw materials are optimized, and the reasonable reaction rate and the crystallization supersaturation degree are controlled to obtain a product with expected granularity.
Drawings
The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention.
Fig. 1 shows a magnesium hydroxide reaction crystallizing device according to a preferred embodiment of the present invention.
Figure 2 shows a magnesium hydroxide reactive crystallizer (1) according to a preferred embodiment of the present invention.
Figure 3 shows a magnesium hydroxide reactive crystallizer (1) according to a preferred embodiment of the present invention.
Wherein: a reaction crystallizer (1), a delivery pump (2) and a pipeline (3). The reaction crystallizer (1) comprises a tower body (4), a guide shell (5), a longitudinal support plate (6), an air inlet pipe (7), an air distributor (8), a feeding pipe (1) (9), a feeding pipe (2) (10), a spray head (11), a magnesium hydroxide discharging pipe (12) and an electric heating sleeve (13).
Detailed Description
The following examples illustrate the invention in detail.
Example 1.
A reaction crystallizer (1) of the magnesium hydroxide reaction crystallizer (1) of grade 1 is adopted to form a reaction crystallizing device. Air is introduced at a set flow rate, and the height of the liquid level of the aerated sodium chloride solution is maintained to be 80cm higher than the upper edge of the guide cylinder (5). A longitudinal support plate (6) is arranged between the tower body (4) and the guide cylinder (5); the tower body (4) is wrapped by an electric heating jacket (13); the opening of the feeding pipe 1 (9) is positioned in the center of the guide shell (5), the height of the pipe opening is 30cm, the opening of the feeding pipe 2 (10) is positioned in the center of the guide shell (5) and is connected with the spray head (11), and the lower edge of the spray head (11) is 80cm away from the upper edge of the guide shell (5); the diameter of the guide shell (5) is 0.7 times of the inner diameter of the tower body (4), the lower edge of the guide shell (5) is 2cm away from the bottom of the tower body (4), the upper edge of the guide shell (5) is 120cm away from the top of the tower body (4), the opening of the air inlet pipe (7) is positioned in the center of the tower body (4), the height of the opening of the air inlet pipe is 10cm lower than that of the opening of the inlet pipe 1 (9), and the upper end of the air inlet pipe (7) is connected with the gas distributor (8).
Sodium chloride solution with the mass concentration of 10 percent is added into the reaction crystallizer (1) as reaction crystallization base liquid, and the air speed is 0.044m/s. Electrifying the electric heating sleeve (13) of the 1 st-stage reaction crystallizer (1) to ensure that the temperature of the sodium chloride solution in the reaction crystallizer (1) reaches 80 ℃. Adding a 14% magnesium chloride solution and a 10% sodium hydroxide solution into the 1 st-stage reaction crystallizer (1), starting a magnesium hydroxide discharge pipe (12) of the 1 st-stage reaction crystallizer (1), conveying magnesium hydroxide suspension generated by reaction out of a reaction crystallization device, and enabling the reaction crystallization process to enter a continuous stable operation state. Under the continuous and stable operation state, the adding proportion of the two raw materials in each stage of reaction crystallizer (1) is kept to be 1:2, the adding speed is to maintain the retention time of the feed liquid in the reaction crystallizer (1) to be 1.5h, and the conveying flow of the conveying pump is based on the standard of maintaining the liquid level in the reaction crystallizer (1) of the stage to be stable.
Through the reaction crystallization process, the magnesium hydroxide crystal with the average particle size of 9 mu m and uniform particle size distribution can be prepared.
Example 2.
The reaction crystallizer (1) of the magnesium hydroxide of 3 grades is adopted to form a reaction crystallization device. Air is introduced at a set flow rate, and the height of the liquid level of the aerated sodium chloride solution is maintained to be 50cm higher than the upper edge of the guide cylinder (5). A longitudinal support plate (6) is arranged between the tower body (4) and the guide cylinder (5); the tower body (4) is wrapped by an electric heating jacket (13); the opening of the feeding pipe 1 (9) is positioned in the center of the guide shell (5), the height of the pipe opening is 2cm, the opening of the feeding pipe 2 (10) is positioned in the center of the guide shell (5) and is connected with the spray head (11), and the distance from the lower edge of the spray head (11) to the upper edge of the guide shell (5) is 60cm; the diameter of the guide shell (5) is 0.6 times of the inner diameter of the tower body (4), the lower edge of the guide shell (5) is 40cm away from the bottom of the tower body (4), the upper edge of the guide shell (5) is 80cm away from the top of the tower body (4), the air inlet pipe (7) is positioned in an annular gap between the tower body (4) and the guide shell (5), the height of the pipe opening is 30cm above the lower edge of the guide shell (5), and the upper end of the air inlet pipe (7) is connected with the gas distributor (8).
Sodium chloride solution with the mass concentration of 27 percent is added into each reaction crystallizer (1) as reaction crystallization base liquid, and the air speed is 0.035m/s. Electrifying the electric heating sleeves (13) of the 1 st to 3 rd reaction crystallizers (1) to ensure that the temperature of the sodium chloride solution in the three reaction crystallizers (1) reaches 70 ℃, 75 ℃ and 80 ℃ respectively. Adding a magnesium chloride solution with the mass concentration of 23% and a sodium hydroxide solution with the mass concentration of 17% into the 1 st-stage reaction crystallizer (1), starting a magnesium hydroxide discharge pipe (12) of the 1 st-stage reaction crystallizer (1), and conveying a magnesium hydroxide suspension generated by the reaction out of a reaction crystallization device. After 0.5h, closing a magnesium hydroxide discharge pipe (12) of the 1 st-stage reaction crystallizer (1), opening a pipe valve for communicating the 1 st-stage reaction crystallizer (1) with the 2 nd-stage reaction crystallizer (1), conveying the crystal-containing suspension generated by the reaction to the 2 nd-stage reaction crystallizer (1), adding a magnesium chloride solution with the mass concentration of 18% and a sodium hydroxide solution with the mass concentration of 12% into the 2 nd-stage reaction crystallizer (1), opening the magnesium hydroxide discharge pipe (12) of the 2 nd-stage reaction crystallizer (1), and conveying the magnesium hydroxide suspension generated by the reaction out of the reaction crystallization device. After 0.5h, closing a magnesium hydroxide discharge pipe (12) of the 2 nd-stage reaction crystallizer (1), opening a pipe valve for communicating the 2 nd-stage reaction crystallizer (1) with the 3 rd-stage reaction crystallizer (1), conveying the crystal-containing suspension generated by the reaction to the 3 rd-stage reaction crystallizer (1), adding a magnesium chloride solution with the mass concentration of 13% and a sodium hydroxide solution with the mass concentration of 7% into the 3 rd-stage reaction crystallizer (1), opening the magnesium hydroxide discharge pipe (12) of the 3 rd-stage reaction crystallizer (1), conveying the magnesium hydroxide suspension generated by the reaction out of a reaction crystallization device, and enabling the reaction crystallization process to enter a continuous and stable operation state. Under the continuous and stable operation state, the adding proportion of the two raw materials in each stage of reaction crystallizer (1) is kept to be 1: and 3, keeping the retention time of the feed liquid in the reaction crystallizer (1) for 3 hours at the adding speed, and keeping the liquid level in the reaction crystallizer (1) of the stage as the standard by the conveying flow of the conveying pump.
Through the reaction crystallization process, the magnesium hydroxide crystal with the average particle size of 30 mu m and uniform particle size distribution is prepared.
And parts of magnesium hydroxide suspension are respectively taken out from outlet pipelines behind the 1 st, 2 nd and 3 rd stage reaction crystallizers (1), and the average particle sizes of magnesium hydroxide crystals are respectively determined to be 7 mu m, 23 mu m and 50 mu m, and the particle size distribution is uniform.
Example 3.
The magnesium hydroxide reactive crystallizer (1) of the 2-level is adopted to form a reactive crystallization device. Air is introduced at a set flow rate, and the liquid level height of the aerated sodium chloride solution is maintained to be 10cm higher than the upper edge of the guide shell (5). A longitudinal support plate (6) is arranged between the tower body (4) and the guide cylinder (5); the tower body (4) is wrapped by an electric heating jacket (13); the opening of the feeding pipe 1 (9) is positioned in the center of the guide shell (5), the height of the pipe opening is 10cm higher than the lower edge of the guide shell (5), the opening of the feeding pipe 2 (10) is positioned in the center of the guide shell (5) and is connected with the spray head (11), and the lower edge of the spray head (11) is 10cm away from the upper edge of the guide shell (5); the diameter of the guide shell (5) is 0.6 times of the inner diameter of the tower body (4), the lower edge of the guide shell (5) is 10cm away from the bottom of the tower body (4), the upper edge of the guide shell (5) is 40cm away from the top of the tower body (4), the opening of the air inlet pipe (7) is positioned in the center of the tower body (4), the height of the opening of the pipe is 1cm lower than that of the opening of the inlet pipe 1 (9), and the upper end of the air inlet pipe (7) is connected with the gas distributor (8).
Sodium chloride solution with the mass concentration of 1 percent is added into the reaction crystallizer (1) as reaction crystallization base liquid, and the air speed is 0.022m/s. Electrifying the electric heating sleeves (13) of the 1 st to 2 nd-stage reaction crystallizers (1) to ensure that the temperature of the sodium chloride solution in the two reaction crystallizers (1) reaches 70 ℃ and 80 ℃ respectively. Adding 9 percent magnesium chloride solution and 7 percent sodium hydroxide solution into the 1 st-stage reaction crystallizer (1), starting a magnesium hydroxide discharge pipe (12) of the 1 st-stage reaction crystallizer (1), and conveying magnesium hydroxide suspension generated by reaction out of a reaction crystallization device. After 0.5h, closing a magnesium hydroxide discharge pipe (12) of the 1 st-stage reaction crystallizer (1), opening a communicating pipe between the 1 st-stage reaction crystallizer (1) and the 2 nd-stage reaction crystallizer (1), conveying the crystal-containing suspension generated by the reaction to the 2 nd-stage reaction crystallizer (1), adding a magnesium chloride solution with the mass concentration of 5% and a sodium hydroxide solution with the mass concentration of 4% into the 2 nd-stage reaction crystallizer (1), opening a magnesium hydroxide discharge pipe (12) of the 2 nd-stage reaction crystallizer (1), conveying the magnesium hydroxide suspension generated by the reaction out of a reaction crystallization device, and enabling the reaction crystallization process to enter a continuous and stable operation state. Under the continuous and stable operation state, the adding proportion of the two raw materials in each stage of reaction crystallizer (1) is kept to be 1:1.5, the adding speed is to maintain the retention time of the feed liquid in the reaction crystallizer (1) for 0.5h, and the conveying flow of the conveying pump is based on the standard of maintaining the liquid level in the reaction crystallizer (1) at the current stage to be stable.
Through the reaction crystallization process, the magnesium hydroxide crystal with the average particle size of 15 mu m and uniform particle size distribution is prepared.
Partial magnesium hydroxide suspension liquid is respectively extracted from outlet pipelines behind the 1 st and 2 nd stage reaction crystallizers (1), the average particle size of magnesium hydroxide crystals is respectively measured to be 10 mu m and 15 mu m, and the particle size distribution is uniform.
Example 4.
The reaction crystallizer (1) of the magnesium hydroxide of 3 grades is adopted to form a reaction crystallizing device. Air is introduced at a set flow rate, and the height of the liquid level of the aerated sodium chloride solution is maintained to be 50cm higher than the upper edge of the guide cylinder (5). A longitudinal support plate (6) is arranged between the tower body (4) and the guide cylinder (5); the tower body (4) is wrapped by an electric heating jacket (13); the opening of the feeding pipe 1 (9) is positioned in the center of the guide shell (5), the height of the pipe opening is 20cm, the opening of the feeding pipe 2 (10) is positioned in the center of the guide shell (5) and is connected with the spray head (11), and the distance from the lower edge of the spray head (11) to the upper edge of the guide shell (5) is 60cm; the diameter of the guide cylinder (5) is 0.7 times of the inner diameter of the tower body (4), the lower edge of the guide cylinder (5) is 10cm away from the bottom of the tower body (4), the upper edge of the guide cylinder (5) is 70cm away from the top of the tower body (4), the air inlet pipe (7) is positioned in an annular gap between the tower body (4) and the guide cylinder (5), the height of the pipe opening is 2cm above the lower edge of the guide cylinder (5), and the upper end of the air inlet pipe (7) is connected with the gas distributor (8).
The following examples illustrate the invention in detail.
3-grade magnesium hydroxide reaction crystallization is adopted, sodium chloride solution with the mass concentration of 18% is added into each reaction crystallizer (1) to serve as reaction crystallization base liquid, and the air speed is 0.044m/s. Electrifying the electric heating sleeves (13) of the 1 st to 3 rd reaction crystallizers (1) to ensure that the temperature of the sodium chloride solution in the three reaction crystallizers (1) reaches 70 ℃, 75 ℃ and 80 ℃ respectively. Adding a magnesium chloride solution with the mass concentration of 30% and a sodium hydroxide solution with the mass concentration of 24% into the 1 st-stage reaction crystallizer (1), starting a magnesium hydroxide discharge pipe (12) of the 1 st-stage reaction crystallizer (1), and conveying a magnesium hydroxide suspension generated by the reaction out of a reaction crystallization device. After 0.5h, closing a magnesium hydroxide discharge pipe (12) of the 1 st-stage reaction crystallizer (1), opening a pipe valve for communicating the 1 st-stage reaction crystallizer (1) with the 2 nd-stage reaction crystallizer (1), conveying the crystal-containing suspension generated by the reaction to the 2 nd-stage reaction crystallizer (1), adding a magnesium chloride solution with the mass concentration of 25% and a sodium hydroxide solution with the mass concentration of 18% into the 2 nd-stage reaction crystallizer (1), opening the magnesium hydroxide discharge pipe (12) of the 2 nd-stage reaction crystallizer (1), and conveying the magnesium hydroxide suspension generated by the reaction out of a reaction crystallization device. After 0.5h, closing a magnesium hydroxide discharge pipe (12) of the 2 nd-stage reaction crystallizer (1), opening a pipe valve for communicating the 2 nd-stage reaction crystallizer (1) with the 3 rd-stage reaction crystallizer (1), conveying the crystal-containing suspension generated by the reaction to the 3 rd-stage reaction crystallizer (1), adding a magnesium chloride solution with the mass concentration of 16% and a sodium hydroxide solution with the mass concentration of 10% into the 3 rd-stage reaction crystallizer (1), opening the magnesium hydroxide discharge pipe (12) of the 3 rd-stage reaction crystallizer (1), conveying the magnesium hydroxide suspension generated by the reaction out of a reaction crystallization device, and enabling the reaction crystallization process to enter a continuous and stable operation state. Under the continuous and stable operation state, the adding proportion of the two raw materials in each stage of reaction crystallizer (1) is kept to be 1:2, the adding speed is to maintain the retention time of the feed liquid in the reaction crystallizer (1) for 3h, and the conveying flow of the conveying pump is based on the standard of maintaining the liquid level in the reaction crystallizer (1) of the stage to be stable.
Through the reaction crystallization process, the magnesium hydroxide crystal with the average particle size of 32 mu m and uniform particle size distribution is prepared.
And parts of magnesium hydroxide suspension are respectively taken out from outlet pipelines behind the 1 st, 2 nd and 3 rd stage reaction crystallizers (1), and the average particle sizes of magnesium hydroxide crystals are respectively measured to be 9 microns, 24 microns and 32 microns, and the particle size distribution is uniform.
Claims (9)
1. A reaction crystallization device for magnesium hydroxide with narrow particle size distribution and controllable particle size is characterized by consisting of reaction crystallizers (1), a delivery pump (2) and pipelines (3), wherein the number of the reaction crystallizers (1) is 1 to 3 grades; the reaction crystallizer (1) comprises a tower body (4), a guide cylinder (5), a longitudinal support plate (6), an air inlet pipe (7), a gas distributor (8), a feeding pipe (1) (9), a feeding pipe (2) (10), a spray head (11), a magnesium hydroxide discharging pipe (12) and an electric heating sleeve (13); the diameter of a guide cylinder (5) of the reaction crystallizer (1) is 0.5 to 0.7 time of the inner diameter of the tower body (4), the lower edge of the guide cylinder (5) is 2 to 40cm away from the bottom of the tower body (4), and the upper edge of the guide cylinder (5) is 40 to 120cm away from the top of the tower body (4); a longitudinal support plate (6) is arranged between the tower body (4) of the reaction crystallizer (1) and the guide shell (5); the outer wall of the tower body (4) of the reaction crystallizer (1) is provided with an electric heating jacket (13).
2. A reactive crystallization apparatus for magnesium hydroxide with narrow particle size distribution and controllable particle size according to claim 1, characterized in that the air inlet pipe (7), the feeding pipe 1 (9) and the feeding pipe 2 (10) of the reactive crystallizer (1) are arranged in the following way:
(1) the opening of the feeding pipe 1 (9) is positioned in the guide shell (5), and the height of the opening is 2-30cm beyond the lower edge of the guide shell (5);
(2) the opening of the feeding pipe 2 (10) is positioned in the center of the tower body (4) and is connected with a spray head (11), and the lower edge of the spray head (11) is 10 to 80cm away from the upper edge of the guide shell (5);
(3) magnesium chloride raw material is added into a reaction crystallizer (1) through a feeding pipe 1 (9), and sodium hydroxide raw material is added into the reaction crystallizer (1) through a feeding pipe 2 (10); or magnesium chloride raw material is added into the reaction crystallizer (1) through the feeding pipe 2 (10), and sodium hydroxide raw material is added into the reaction crystallizer (1) through the feeding pipe 1 (9);
(4) the opening of the air inlet pipe (7) is positioned in the center of the tower body (4), the height of the opening of the air inlet pipe is 1-10cm lower than that of the opening of the feed pipe 1 (9), the upper end of the air inlet pipe (7) is connected with a gas distributor (8), the gas distributor is a round stainless steel plate, and holes are uniformly formed in the stainless steel plate; the opening of the air inlet pipe (7) can also be positioned in an annular gap between the tower body (4) and the guide cylinder (5), the height of the opening of the pipe is 2 to 30cm above the lower edge of the guide cylinder (5), the upper end of the air inlet pipe (7) is connected with a gas distributor (8), the gas distributor is an annular stainless steel plate, and holes are uniformly formed in the stainless steel plate.
3. The reactive crystallization apparatus for magnesium hydroxide with narrow particle size distribution and controllable particle size according to claim 1, wherein the number of the reactive crystallizers (1) can be increased or decreased between 1 to 3 levels according to different particle size requirements of the product, magnesium chloride is fed into each reactive crystallizer (1) through the feeding tube 1 (9) or the feeding tube 2 (10), and sodium hydroxide is fed into each reactive crystallizer (1) through the feeding tube 2 (10) or the feeding tube 1 (9), so as to achieve the requirement of uniform particle size distribution.
4. Process for the reactive crystallization of magnesium hydroxide using a reactive crystallization apparatus for magnesium hydroxide with a narrow particle size distribution and a controlled particle size according to claims 1 and 2, characterized in that the resulting magnesium hydroxide suspension flows in series through the reactive crystallizers (1) in succession.
5. A reactive magnesium hydroxide crystallisation process according to claim 4, wherein the magnesium hydroxide product is transported in the magnesium hydroxide line of each reactive crystalliser stage (1).
6. An operation method using the narrow particle size distribution and controllable particle size magnesium hydroxide reaction crystallization apparatus according to claims 1 to 3 and the magnesium hydroxide reaction crystallization process according to claims 4 to 5, characterized by comprising the steps of:
(1) adding 1-27 mass percent sodium chloride solution into each reaction crystallizer (1) as reaction crystallization base solution, introducing air at a set flow rate, and maintaining the height of the liquid level of the aerated sodium chloride solution to be 10-80 cm higher than the upper edge of the guide cylinder (5); the control module is used for controlling the electric heating sleeve to heat each stage of reaction crystallizer (1) so as to enable the temperature of the sodium chloride solution in each stage of reaction crystallizer (1) to reach the set operating temperature value respectively;
(2) adding a magnesium chloride solution and a sodium hydroxide solution into the 1 st-stage reaction crystallizer (1) according to a set proportion, simultaneously opening a magnesium hydroxide discharge pipe (12) below the 1 st-stage reaction crystallizer (1), and conveying a magnesium hydroxide suspension generated by reaction out of a reaction crystallization device through the magnesium hydroxide discharge pipe (12);
(3) after the 1 st-stage reaction crystallization process is stable, opening a valve behind the 1 st-stage reaction crystallizer (1), sending the suspension containing magnesium hydroxide crystals generated by the reaction to the 2 nd-stage reaction crystallizer (1), adding a magnesium chloride solution and a sodium hydroxide solution into the 2 nd-stage reaction crystallizer (1) according to a set proportion, simultaneously opening a magnesium hydroxide discharge pipe (12) below the 2 nd-stage reaction crystallizer (1), and conveying the magnesium hydroxide suspension generated by the reaction out of the reaction crystallization device through the magnesium hydroxide discharge pipe (12);
(4) after the 2 nd-stage reaction crystallization process is stable, opening a valve behind the 2 nd-stage reaction crystallizer (1), sending suspension containing magnesium hydroxide crystals generated by reaction to the 3 rd-stage reaction crystallizer (1), adding a magnesium chloride solution and a sodium hydroxide solution into the 3 rd-stage reaction crystallizer (1) according to a set proportion, simultaneously opening a magnesium hydroxide discharge pipe (12) below the 3 rd-stage reaction crystallizer (1), conveying the magnesium hydroxide suspension generated by reaction out of a reaction crystallization device through the magnesium hydroxide discharge pipe (12), and enabling the reaction crystallization process to enter a continuous and stable operation state;
(5) under the continuous and stable operation state, the magnesium chloride solution and the sodium hydroxide solution are added into each reaction crystallizer (1) in parallel according to the set proportion and the set flow; the magnesium hydroxide suspension liquid flows out of each stage of reactive crystallizer (1) at a set flow rate, and the magnesium hydroxide suspension liquid flowing out of each stage of reactive crystallizer (1) can enter the next stage of reactive crystallizer (1) and can also be conveyed out of the reactive crystallization device to prepare magnesium hydroxide products with different particle sizes; or one part of the reaction liquid enters the next stage of the reaction crystallizer (1) and the other part of the reaction liquid is conveyed out of the reaction crystallizer.
7. The reactive crystallization method of magnesium hydroxide according to claim 6, wherein the set temperature in step (1) is 70 to 80 ℃, and the set gas flow rate is 0.022 to 0.044m/s.
8. A reactive crystallization process for magnesium hydroxide according to claim 6, wherein said steps (2), (3), (4) and (5) are carried out in such proportions as to maintain the molar ratio of magnesium chloride to sodium hydroxide in the range of 1:1.5 to 3.0; the set flow rates of the magnesium chloride solution and the sodium hydroxide solution in the step (5) are to maintain the retention time of the feed liquid in the reaction crystallizer (1) to be 0.5-3 h; the set flow rate of the magnesium hydroxide suspension in the step (5) is based on the maintenance of the liquid level in the reaction crystallizer (1) of the stage.
9. The production process adopting any one of the magnesium hydroxide reaction crystallization device with controllable particle size according to claims 1 to 3, any one of the magnesium hydroxide reaction crystallization processes according to claims 4 to 5 and any one of the magnesium hydroxide reaction crystallization operation methods according to claims 6 to 8 is characterized in that the reaction crystallization nucleation and the crystal growth process are carried out in different crystallizers, the average particle size of the obtained magnesium hydroxide product can be flexibly adjusted within the range of 5 to 50 μm according to the requirement, and the particle size distribution is narrow.
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