Crystallizer and crystallization method for carnallite decomposition

Abstract

The crystallizer comprises a shell with a discharge port, an outer cylinder is fixedly arranged in the shell, an inner cylinder is fixedly arranged in the outer cylinder, a stirring paddle driven by a driving device is arranged in the inner cylinder, and an overflow weir with an overflow port is further arranged on the upper portion of the shell. And a coarse-fraction crystal mush feeding hole, a diluted mother liquor inlet and a fine-fraction crystal mush feeding hole are sequentially connected to the inner cylinder from top to bottom. The invention also discloses a decomposition and crystallization method for carnallite. According to the crystallizer provided by the invention, through respective feeding of coarse and fine particle fractions, reverse convection of coarse particle materials and light mother liquor, and involute feeding of fine particle fractions and light mother liquor, the decomposition time of coarse particle fractions carnallite is prolonged, the decomposition speed of fine particle fractions carnallite is reduced, and the stirring power is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of inorganic salt chemical industry, and particularly relates to a crystallizer for carnallite decomposition. BACKGROUND

[0002] Potash is a general term for potassium-containing minerals, which can be divided into soluble potassium salt minerals and insoluble potassium-containing aluminosilicate minerals according to their solubility. The former is a natural accumulation of soluble potassium salt minerals that can be utilized as mineral resources, including soluble solid potassium salt deposits (such as sylvite, carnallite, and polyhalite) and potassium-containing brine formed by evaporation and concentration of potassium-containing water. Aluminosilicate rocks are insoluble potassium-containing rocks or potassium-rich rocks (such as alunite, nepheline, potassium feldspar, and potassium-rich shale, sandstone, and potassium-rich mudstone). Potash is divided into soluble potassium salt minerals and insoluble potassium-containing aluminosilicate minerals, and currently the main development and utilization is of soluble potassium salt resources. Carnallite is mainly obtained by solar evaporation of liquid ore (brine) in a salt pan, and the process for processing and producing potassium chloride from carnallite mainly includes carnallite crushing, cold decomposition crystallization, flotation purification, dehalogenation and demagnesium, washing and desodium, and drying and cooling. The quality of the final potassium chloride product is related to the control of the cold decomposition crystallization process, which consists of cold crystallization and fine crystal dissolution. The dissolution of carnallite includes two processes in series, dissolution and crystallization. After the dissolution of carnallite, the concentration of potassium chloride exceeds the saturation concentration, and the potassium chloride is precipitated from the solution. To obtain potassium chloride crystals with larger particle size, the dissolution rate of carnallite needs to be controlled to avoid excessive dissolution leading to supersaturation and the generation of a large amount of fine crystals, which affects the subsequent solid-liquid separation, drying process, and crystallization yield.

[0003] Chinese patent document CN 103073030A discloses a crystallizer for hydrolyzing carnallite. The outer cylinder significantly differentiates the velocity distribution in the crystallizer, dividing it into two regions with different operations, namely, a circulation zone with a larger velocity inside the outer cylinder and a settling zone with a smaller velocity outside the outer cylinder. Compared with the traditional DTB-type crystallizer, the crystallizer has a higher decomposition efficiency and potassium recovery rate for carnallite, but its structure still cannot meet the requirements of high-efficiency hydrolysis of carnallite with a larger particle size. Carnallite with a larger particle size quickly settles to the bottom of the crystallizer due to insufficient space residence time, which cannot achieve complete hydrolysis. Therefore, in actual production, a large amount of water greater than the theoretical amount is added to obtain the decomposition of most of the carnallite at the expense of potassium recovery rate. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art and provide a crystallizer for carnallite decomposition suitable for a wider particle size distribution of carnallite, higher production efficiency, and higher potassium recovery rate.

[0005] Another object of the present application is to provide a method for performing the foregoing crystallizer to decompose and crystallize the carnallite.

[0006] The present application is a crystallizer for decomposing carnallite, which comprises a shell with a discharge port, an outer cylinder fixedly arranged in the shell, an inner cylinder fixedly arranged in the outer cylinder, a stirring paddle driven by a driving device arranged in the inner cylinder, and an overflow weir with an overflow port arranged at the upper portion of the shell.

[0007] The crystallizer for decomposing carnallite according to the present application has the following preferred technical solutions. 1. The coarse-grained crystal slurry inlet, the dilute mother liquor inlet, and the fine-grained crystal slurry inlet are respectively arranged at the upper portion, the middle portion, and the lower portion of the inner cylinder.

[0008] 2. The region between the shell and the outer cylinder is a settling zone, the region between the outer cylinder and the inner cylinder is a nucleation zone, the upper portion of the inner cylinder is a decomposition zone, and the lower portion of the inner cylinder is a crystal slurry circulation zone.

[0009] 3. The upper portion of the shell is in a cylindrical shape, the lower portion of the shell is in a conical shape, the included angle a between the side wall and the bottom of the shell is 45-70°, and the ratio of the height of the shell to the outer diameter of the crystallizer is 1.2:1-1:1.8.

[0010] 4. The upper portion of the inner cylinder is in a circular table structure, the lower portion of the inner cylinder is in a cylindrical structure, and the included angle β between the side wall of the upper portion of the inner cylinder and the side wall of the lower portion of the inner cylinder is 30-60°.

[0011] 5. The upper portion of the outer cylinder is in a circular table structure, the lower portion of the outer cylinder is in a cylindrical structure, the included angle γ between the side wall of the upper portion of the outer cylinder and the side wall of the lower portion of the outer cylinder is 30-60°, the top of the outer cylinder is 500-1000 mm higher than the top of the inner cylinder, and the bottom of the outer cylinder is 600-2000 mm higher than the bottom of the inner cylinder.

[0012] 6. The coarse-grained crystal slurry inlet is tangentially arranged in the inner cylinder, and the distance between the coarse-grained crystal slurry inlet and the top of the inner cylinder is 400-1000 mm.

[0013] 7. The fine-grained crystal slurry inlet is arranged at an angle δ of 30-90° with the side wall of the lower portion of the shell, is 100-300 mm away from the stirring paddle, and is tangentially arranged in the inner cylinder.

[0014] 8. The discharge port is located at the bottom of the shell and is 150-300mm away from the bottom of the crystallizer. The overflow weir is arranged in a ring on the upper inner wall of the shell, with a width of 300-600mm. An overflow port is set at the lowest point of the overflow weir, and the overflow port is 600-900mm away from the top of the crystallizer. A cleaning port is also provided at the bottom of the shell. The stirring paddle adopts an upward-propelling propeller blade, which is powered by a drive device installed at the top of the crystallizer. The stirring paddle is located in the crystal slurry circulation zone. The distance between the stirring paddle and the bottom of the crystallizer is 200~1600mm.

[0015] This invention also discloses a method for the decomposition and crystallization of carnallite, characterized in that the method uses the crystallizer for carnallite decomposition described in any of the preceding claims, and: the method controls the particle size of the slurry entering the crystallizer; the coarse particles are fed horizontally and tangentially from the upper part of the inner cylinder of the crystallizer, and the unsaturated dilute mother liquor or water is fed tangentially from the middle; the mother liquor or water decomposes countercurrently with the coarse particles during the rising process, thereby prolonging the contact time between the unsaturated mother liquor or water and the coarse particles; the fine particles are fed from the bottom of the crystallizer and fed obliquely upward into the stirring zone, thereby reducing the decomposition rate of the fine particles by mixing with the circulating high-magnesium mother liquor.

[0016] Principle: Carnallite decomposition involves two sequential processes: dissolution and crystallization. Carnallite dissolves very quickly; even in mother liquor near its cosaturation point (E25), the decomposition rate can reach over 95% within 1-2 minutes. In contrast, potassium chloride crystallizes more slowly and nucleates more rapidly in high-magnesium mother liquor. Therefore, the potassium chloride particles obtained in typical cold decomposition processes are very fine. Thus, rate-controlled decomposition of carnallite at room temperature is achieved by controlling the decomposition conditions and reducing the dissolution rate of carnallite to control the supersaturation of potassium chloride in the solution, thereby reducing the number of potassium chloride crystals and achieving the goal of growing potassium chloride crystals at room temperature. Currently, crystallizers use a wide-grade feed for carnallite, resulting in extremely rapid decomposition of fine particles, which can be completed instantaneously. This leads to excessively high supersaturation of the crystal slurry, producing a large number of fine crystals. Meanwhile, coarse particles enter the outer cylinder of the crystallizer before being effectively decomposed, resulting in incomplete decomposition of coarse particles and affecting Kc. + Recovery rate.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention's crystallizer rationally controls the particle size entering the crystallizer. Coarse particles are fed horizontally and tangentially from the upper part of the crystallizer's inner cylinder. The radial velocity ensures more uniform feeding and slows down the settling speed of coarse particles. Unsaturated dilute mother liquor enters tangentially from the middle. During its ascent, the mother liquor decomposes countercurrently with the coarse particles, extending the contact time between the unsaturated mother liquor and the coarse particles and improving the decomposition rate of coarse carnallite. Fine particles are fed from the bottom of the crystallizer and obliquely upwards into the stirring zone. By mixing with the circulating high-magnesium mother liquor, the decomposition rate of fine particles is reduced. The crystallizer design fully considers the slow decomposition rate and low decomposition rate of coarse particles, and the fast decomposition rate and high supersaturation of fine particles.

[0018] This invention further optimizes the bottom of the crystallizer and the structure of the inner and outer cylinders. The bottom design of the crystallizer reduces the dead zone at the bottom, avoiding the accumulation of coarse particles. The design of the inner cylinder of the crystallizer reduces the velocity of the rising water flow in the inner cylinder, prolonging the decomposition time of carnallite. The design of the outer cylinder of the crystallizer reduces the space between the lower part of the outer cylinder and the lower part of the inner cylinder and extends the lower part of the outer cylinder, reducing the velocity of the fluid inside the outer cylinder, prolonging the crystallization time of fine particles and accelerating the discharge rate of coarse particles. Attached Figure Description

[0019] Figure 1 This is a schematic cross-sectional view of the crystallizer of the present invention; The reference numerals in the attached figures are explained as follows: 1. Shell; 2. Outer cylinder; 3. Inner cylinder; 4. Agitator; 5. Coarse-grained crystal slurry inlet; 6. Fine-grained crystal slurry inlet; 7. Overflow port; 8. Dilute mother liquor inlet; 9. Discharge port; 10. Drive unit; 11. Overflow weir; 12. Cleaning port. Detailed Implementation

[0020] The invention will be better understood through the following examples.

[0021] Example 1, referring to Figure 1 A crystallizer for the decomposition of carnallite includes a shell 1 with a discharge port 9, an outer cylinder 2 fixedly disposed inside the shell 1, an inner cylinder 3 fixedly disposed inside the outer cylinder 2, an agitator 4 driven by a drive device 10 disposed in the inner cylinder 3, and an overflow weir 11 with an overflow port 7 disposed on the upper part of the shell 1. The crystallizer is characterized in that a coarse-grained crystal slurry inlet 5, a dilute mother liquor inlet 8, and a fine-grained crystal slurry inlet 6 are connected sequentially from top to bottom on the inner cylinder 3.

[0022] The coarse-grained crystal slurry inlet 5, the dilute mother liquor inlet 8, and the fine-grained crystal slurry inlet 6 are respectively connected to the upper, middle, and lower parts of the inner cylinder 3.

[0023] The area between the shell 1 and the outer cylinder 2 is a settling zone, the area between the outer cylinder 2 and the inner cylinder 3 is a crystal growing zone, the upper part of the inner cylinder 1 is a decomposition zone, and the lower part is a crystal slurry circulation zone.

[0024] The upper part of the shell 1 is cylindrical, and the lower part is conical, the included angle α between the side wall and the bottom of the shell 1 is 45°, and the ratio of the height of the shell 1 to the outer diameter of the crystallizer is 1.2:1.

[0025] The upper part of the inner cylinder 3 is a circular table structure, and the lower part of the crystal slurry circulation zone is a cylindrical structure, the included angle β between the side wall of the upper part and the side wall of the lower part of the inner cylinder 3 is 30°.

[0026] The upper part of the outer cylinder 2 is a circular table structure, and the lower part is a cylindrical structure, the included angle γ between the side wall of the upper part and the side wall of the lower part of the outer cylinder 2 is 30°, the top of the outer cylinder 2 is 500mm higher than the top of the inner cylinder 1, and the bottom of the outer cylinder 2 is 600mm higher than the bottom of the inner cylinder 1.

[0027] The coarse-grained crystal slurry inlet 5 is tangentially fed into the inner cylinder 3, and the distance between the coarse-grained crystal slurry inlet 5 and the top of the inner cylinder 3 is 400mm.

[0028] The fine-grained crystal slurry inlet 6 is connected to the inner cylinder 3 at an angle δ of 30° to the side wall of the lower part of the shell 1, and the height is 100mm away from the stirring paddle, the dilute mother liquor inlet 8 is located between the coarse-grained crystal slurry inlet 5 and the fine-grained crystal slurry inlet 6, and is tangentially fed into the inner cylinder 3.

[0029] The discharge port 9 is arranged at the bottom of the shell 1, and the distance from the bottom end of the crystallizer is 150mm, the overflow weir 11 is arranged in a circle on the inner wall of the upper part of the shell 1, the width of the overflow weir 11 is 300mm, an overflow port 7 is arranged at the lowest part of the overflow weir 11, the height of the overflow port 7 from the top of the crystallizer is 600mm, and a cleaning port 12 is further arranged at the bottom of the shell 1. The stirring paddle 4 adopts an upward thrust type propeller blade, and is powered by a driving device 10 installed at the top of the crystallizer, and the stirring paddle 4 is located in the crystal slurry circulation zone; the distance between the stirring paddle 4 and the bottom of the crystallizer is 200mm.

[0030] Example 2, refer to Figure 1 A crystallizer for carnallite decomposition, The angle a between the side wall and the bottom of the shell 1 is 70°, and the ratio of the height of the shell 1 to the outer diameter of the crystallizer is 1:1.8. The angle β between the side wall of the upper zone and the side wall of the lower zone of the inner cylinder 3 is 60°. The angle γ between the side wall of the upper zone and the side wall of the lower zone of the outer cylinder 2 is 60°, the top of the outer cylinder 2 is 1000 mm higher than the top of the inner cylinder 1, and the bottom of the outer cylinder 2 is 2000 mm higher than the bottom of the inner cylinder 1. The distance between the coarse-grained crystal slurry feeding port 5 and the top of the inner cylinder 3 is 1000 mm. The fine-grained crystal slurry feeding port 6 is connected to the inner cylinder 3 at an angle δ of 90° with the lower side wall of the shell 1, and the height is 300 mm away from the stirring paddle.

[0031] The discharge port 9 is arranged at the bottom of the shell 1, and the distance from the bottom end of the crystallizer is 300 mm. The overflow weir 11 is arranged in a circle on the inner wall of the upper part of the shell 1, and the width of the overflow weir 11 is 600 mm. An overflow port 7 is arranged at the lowest part of the overflow weir 11, and the height of the overflow port 7 from the top of the crystallizer is 900 mm. A cleaning port 12 is also arranged at the bottom of the shell 1. The distance between the stirring paddle 4 and the bottom of the crystallizer is 1600 mm.

[0032] The rest is the same as in Example 1.

[0033] Example 3, with reference to Figure 1 A crystallizer for carnallite decomposition, The angle a between the side wall and the bottom of the shell 1 is 55°, and the ratio of the height of the shell 1 to the outer diameter of the crystallizer is 1:1.3. The angle β between the side wall of the upper zone and the side wall of the lower zone of the inner cylinder 3 is 45°. The angle γ between the side wall of the upper zone and the side wall of the lower zone of the outer cylinder 2 is 45°, the top of the outer cylinder 2 is 800 mm higher than the top of the inner cylinder 1, and the bottom of the outer cylinder 2 is 1000 mm higher than the bottom of the inner cylinder 1. The distance between the coarse-grained crystal slurry feeding port 5 and the top of the inner cylinder 3 is 800 mm. The fine-grained crystal slurry feeding port 6 is connected to the inner cylinder 3 at an angle δ of 60° with the lower side wall of the shell 1, and the height is 200 mm away from the stirring paddle.

[0034] The discharge port 9 is arranged at the bottom of the shell 1, and the distance from the bottom end of the crystallizer is 200 mm. The overflow weir 11 is arranged in a circle on the inner wall of the upper part of the shell 1, and the width of the overflow weir 11 is 450 mm. An overflow port 7 is arranged at the lowest part of the overflow weir 11, and the height of the overflow port 7 from the top of the crystallizer is 750 mm. A cleaning port 12 is also arranged at the bottom of the shell 1. The distance between the stirring paddle 4 and the bottom of the crystallizer is 1000 mm.

[0035] The rest is the same as in Example 1.

[0036] Example 4, a method for sylvite decomposition crystallization, which uses the crystallizer for sylvite decomposition as claimed in any one of Examples 1 or 2 or 3, and: the method controls the particle size of the slurry entering the crystallizer, the coarse particle level uses horizontal tangential feeding at the upper part of the inner cylinder, unsaturated light mother liquor or water uses tangential feeding at the middle part, the light mother liquor or water and the coarse particle slurry are countercurrently decomposed during the rising process, and the contact time of the unsaturated mother liquor or water and the coarse particle slurry is prolonged; the fine particle slurry uses feeding at the bottom of the crystallizer and is given into the stirring zone obliquely upward, and the decomposition rate of the fine particle slurry is reduced by mixing with the circulating high-magnesium mother liquor.

[0037] Example 5, the structure of the crystallizer is shown in Figure 1 The area between the shell 1 and the outer cylinder 2 is the settling zone, the area between the outer cylinder 2 and the inner cylinder 3 is the crystal growth zone, the upper part of the inner cylinder 1 is the decomposition zone, and the lower part is the slurry circulation zone. The stirring paddle 4 uses an upward thrust propeller blade, is powered by the driving device 10, is installed at the top of the crystallizer, and is located in the slurry circulation zone. The crystallizer is provided with two feeding ports for coarse and fine raw materials and one light mother liquor feeding port. The coarse particle feeding port 5 is tangentially fed into the inner cylinder 3, the fine particle feeding port is inserted into the vicinity of the impeller of the inner cylinder 3 obliquely upward, and the light mother liquor inlet 8 is tangentially fed into the inner cylinder 3 between the coarse and fine particle ports. The discharge port 9 is located at the bottom of the crystallizer, an overflow weir 11 is made on the inner wall of the upper part of the crystallizer shell 1, an overflow port is provided at the lowest part of the overflow weir, and the cleaning port 12 is located at the bottom of the crystallizer.

[0038] In this embodiment: the distance of the stirring paddle from the bottom of the crystallizer is 1000 mm, the distance of the coarse particle feeding port 5 from the top of the inner cylinder 3 is 1200 mm, the fine particle feeding port is inserted into the vicinity of the impeller of the inner cylinder 3 obliquely upward at an angle of 30° from the shell wall 1, the height is 100 mm from the stirring paddle, and the light mother liquor inlet 8 is located between the coarse and fine particle ports at a height of 1000 mm from the coarse particle inlet.

[0039] The discharge port 9 is located at the bottom of the crystallizer at a height of about 200 mm from the bottom of the crystallizer, the width of the overflow weir is 500 mm, an overflow port is provided at the lowest part of the overflow weir, and the cleaning port 7 is located at a height of 600 mm from the top of the crystallizer.

[0040] The crystallizer in this example is cylindrical in the upper part and conical in the lower part, the angle a between the side wall and the bottom of the shell 1 is 60°, and the ratio of the height of the shell 1 to the outer diameter of the crystallizer is 1:1. The upper part of the inner cylinder 3 of the crystallizer is in the form of a circular table structure, and the lower part of the inner cylinder 3 of the crystallizer is in the form of a circular cylinder structure, and the angle β between the side wall of the upper part of the inner cylinder 3 and the side wall of the lower part is 60°. The upper part of the outer cylinder 2 of the crystallizer is in the form of a circular table structure, and the lower part of the outer cylinder 2 is in the form of a circular cylinder structure, and the angle γ between the side wall of the upper part of the outer cylinder 2 and the side wall of the lower part is 57°, and the top of the outer cylinder 2 is about 800 mm higher than the top of the inner cylinder 1, and the bottom of the outer cylinder 2 is about 1000 mm higher than the bottom of the inner cylinder 1.

[0041] Example 6, the implementation of this example is basically the same as the structure of example 1, only affected by the particle size composition of the raw ore, the local structure of the crystallizer is optimized, the distance between the stirring paddle and the bottom of the crystallizer is adjusted to 1200 mm, the distance between the coarse particle level feed port 5 and the top of the inner cylinder 3 is 400 mm, the fine particle level feed port is inserted near the impeller of the inner cylinder 3 at an angle δ of 55° with the shell wall 1, and the height is 100 mm away from the stirring paddle, the dilute mother liquor inlet 8 is located between the coarse particle level and the fine particle level, and the height is 1200 mm away from the coarse particle level inlet.

[0042] The discharge port 9 is located at the bottom of the crystallizer, about 200 mm away from the bottom of the crystallizer, the width of the overflow weir is 600 mm, an overflow port is arranged at the lowest part of the overflow weir, and the cleaning port 7 is 800 mm away from the top of the crystallizer.

[0043] The crystallizer in this example is cylindrical in the upper part and conical in the lower part, the angle a between the side wall and the bottom of the shell 1 is 60°, and the ratio of the height of the shell 1 to the outer diameter of the crystallizer is 1:1. The upper part of the inner cylinder 3 of the crystallizer is in the form of a circular table structure, and the lower part of the inner cylinder 3 of the crystallizer is in the form of a circular cylinder structure, and the angle β between the side wall of the upper part of the inner cylinder 3 and the side wall of the lower part is 60°. The upper part of the outer cylinder 2 of the crystallizer is in the form of a circular table structure, and the lower part of the outer cylinder 2 is in the form of a circular cylinder structure, and the angle γ between the side wall of the upper part of the outer cylinder 2 and the side wall of the lower part is 57°, and the top of the outer cylinder 2 is about 800 mm higher than the top of the inner cylinder 1, and the bottom of the outer cylinder 2 is about 1000 mm higher than the bottom of the inner cylinder 1.

[0044] Example 7, comparative test The crystallizer shown in the Chinese public patent document CN 103073030A discloses a crystallizer for hydrolyzing carnallite, under the conditions of temperature 25℃, carnallite processing capacity 200t / h, underflow flow rate controlled at 220m 3 / h, underflow concentration 30% (weight concentration), and feed particle size P80-2mm, the carnallite cold decomposition can obtain potassium chloride particles with particle size of 0.16mm (average particle size), and the decomposition rate is about 80%.

[0045] Experimental Example, using the crystallizer described in Example 6, under the conditions of temperature 25°C, carnallite treatment capacity 200 t / h, underflow flow rate controlled at 220 m 3 / h, underflow concentration 30% (weight concentration), feed particle size P80 -2 mm, the carnallite cold decomposition according to Example 1 can obtain potassium chloride particles with a particle size of 0.20 mm (average particle size), and a decomposition rate of about 90%.

[0046] As can be very obviously seen from the above examples, the use of the crystallizer of the present application to produce potassium chloride can increase the carnallite decomposition rate by 10%, and the potassium chloride particles are also significantly increased.

Claims

1. A crystallizer for sylvite decomposition, comprising a shell with a discharge port, a fixed outer cylinder arranged in the shell, a fixed inner cylinder arranged in the outer cylinder, a stirring paddle driven by a driving device arranged in the inner cylinder, and an overflow weir with an overflow port arranged at the upper part of the shell, characterized in that: The coarse particle grade crystal slurry feeding port, the light mother liquor inlet and the fine particle grade crystal slurry feeding port are sequentially connected on the inner cylinder from top to bottom.

2. A crystalliser for sylvite decomposition according to claim 1, characterised in that: The coarse particle grade crystal slurry feeding port, the light mother liquor inlet and the fine particle grade crystal slurry feeding port are sequentially connected on the inner cylinder from top to bottom.

3. A crystallizer for sylvite decomposition according to claim 1, characterized in that: The area between the shell and the outer cylinder is a settling zone, the area between the outer cylinder and the inner cylinder is a crystal growing zone, the upper part of the inner cylinder is a decomposition zone, and the lower part of the inner cylinder is a crystal slurry circulation zone.

4. A crystallizer for sylvite decomposition according to claim 1, characterized in that: The upper part of the shell is in a cylindrical shape, the lower part of the shell is in a conical shape, the angle α between the side wall of the shell and the bottom is 45-70°, and the ratio of the height of the shell to the outer diameter of the crystallizer is 1.2:1-1:1.

8.

5. A crystallizer for sylvite decomposition according to claim 1, characterized in that: The upper part of the inner cylinder is in a circular table structure, the lower part of the inner cylinder is in a cylindrical structure, and the angle β between the side wall of the upper part of the inner cylinder and the side wall of the lower part of the inner cylinder is 30-60°.

6. A crystallizer for sylvite decomposition according to claim 1, characterized in that: The upper part of the outer cylinder is in a circular table structure, the lower part of the outer cylinder is in a cylindrical shape, the angle γ between the side wall of the upper part of the outer cylinder and the side wall of the lower part of the outer cylinder is 30-60°, the top of the outer cylinder is 500-1000 mm higher than the top of the inner cylinder, and the bottom of the outer cylinder is 600-2000 mm higher than the bottom of the inner cylinder.

7. A crystalliser for sylvite decomposition according to any one of claims 1 to 6, characterised in that: The coarse particle grade crystal slurry feeding port is tangentially fed to the inner cylinder, and the distance between the coarse particle grade crystal slurry feeding port and the top of the inner cylinder is 400-1000 mm.

8. A crystalliser for sylvite decomposition according to any one of claims 1 to 6, characterised in that: The fine particle grade crystal slurry feeding port is connected to the inner cylinder at a side of the impeller of the inner cylinder at an angle δ of 30-90° with the side wall of the lower part of the shell, and the height of the fine particle grade crystal slurry feeding port is 100-300 mm away from the stirring paddle, and the light mother liquor inlet is located between the coarse particle grade crystal slurry feeding port and the fine particle grade crystal slurry feeding port and is tangentially fed to the inner cylinder.

9. A crystalliser for sylvite decomposition according to any one of claims 1 to 6, characterised in that: The discharge port is located at the bottom of the shell and is 150-300 mm away from the bottom end of the crystallizer, the overflow weir is arranged in a circle on the inner wall of the upper part of the shell, the width of the overflow weir is 300-600 mm, an overflow port is arranged at the lowest part of the overflow weir, the height of the overflow port from the top of the crystallizer is 600-900 mm, and the bottom of the shell is further provided with a cleaning port. The stirring paddle is an up-thrust propeller blade, and the driving device is installed at the top of the crystallizer and provides power, and the stirring paddle is located in the crystal slurry circulation zone, and the distance between the stirring paddle and the bottom of the crystallizer is 200-1600 mm.

10. A method of sylvite decomposition crystallization, characterized by, The method uses the crystallizer for carnallite decomposition according to any one of claims 1-9, and the method controls the particle size of the slurry entering the crystallizer, the coarse particle grade is horizontally and tangentially fed to the upper part of the inner cylinder of the crystallizer, the unsaturated light mother liquor or water is tangentially fed to the middle part, the mother liquor or water is countercurrently decomposed with the coarse particle grade slurry in the rising process, the contact time of the unsaturated mother liquor or water with the coarse particle slurry is prolonged, the fine particle slurry is fed to the bottom of the crystallizer and is obliquely fed to the stirring zone, and the decomposition speed of the fine particle slurry is reduced by mixing with the circulating high-magnesium mother liquor.

Images