CN114177644A - Crystallization device for producing large-particle crystals and application thereof - Google Patents
Crystallization device for producing large-particle crystals and application thereof Download PDFInfo
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- CN114177644A CN114177644A CN202111538578.9A CN202111538578A CN114177644A CN 114177644 A CN114177644 A CN 114177644A CN 202111538578 A CN202111538578 A CN 202111538578A CN 114177644 A CN114177644 A CN 114177644A
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Abstract
The crystallization device for producing large-particle crystals comprises a cylindrical outer cylinder with a closed bottom, a cylindrical guide cylinder, a stirrer and a motor, wherein the cylindrical guide cylinder is positioned in the outer cylinder, two ends of the cylindrical guide cylinder are not closed, a main body part of the stirrer is positioned in the guide cylinder, the motor drives the stirrer to rotate, the bottom surface of the outer cylinder is a W-shaped curved surface, the upper end of the outer cylinder is provided with a cover plate, and the ratio of the effective height H1 of the outer cylinder to the inner diameter D1 of the outer cylinder is 1.9-2.2; the ratio of the inner diameter D2 of the guide cylinder to the inner diameter D1 of the outer cylinder is 0.38-0.40, the ring surface of the lower end of the guide cylinder is tangent to the top of the upper convex arc surface of the central part of the bottom of the outer cylinder, a connecting piece is arranged on the ring surface of the upper end of the guide cylinder, the length of the connecting piece is equal to the total height of the outer cylinder-the height H2 of the guide cylinder, and the guide cylinder is fixed by connecting the connecting piece with the cover plate; the stirrer consists of a stirring rod and an impeller, and the distance H4 between the bottom surface of the impeller and the lower end of the guide shell is equal to the diameter d of the impeller. The crystallization device can obtain crystals with large average grain diameter and uniform grain size, simplify the structure, reduce the use power and further reduce the cost.
Description
Technical Field
The invention belongs to the technical field of crystallization, and relates to a crystallization device (crystallizer) for producing large-particle crystals and application thereof.
Background
Crystallization refers to an operation process in which a solute is precipitated from a raw material solution by cooling, evaporation, a chemical reaction, or the like to form crystal particles. For the consideration of post-processing, transportation, etc., many chemical products take crystal particles as the final product form, and it is desirable that the crystal particles of the final product are large. The crystallization operation unit gradually becomes one of the main production means of chemical solid products by virtue of the advantages of strong operability, excellent purification capability, low energy consumption, environmental friendliness and the like.
As crystallization devices (crystallizers) for producing large-particle crystals, draft tube baffle crystallizers (DTB crystallizers), Oslo crystallizers (OSLO crystallizers) and the like are mainly used. The DTB crystallizer is suitable for a plurality of crystallization processes such as a cooling crystallization method, a reaction crystallization method, an evaporation crystallization method and the like, so that the DTB crystallizer is more and more widely applied to industrial production of food, feed, pharmacy, bulk chemicals and the like, but the yield of the DTB crystallizer is influenced by the size of the stirring paddle due to the structural characteristic that the sectional area of a guide cylinder of the DTB crystallizer is equal to the sectional area of an annular channel, and the larger the yield of the DTB crystallizer is, the larger the required size of the stirring paddle is. The manufacturing size of the stirring paddle is greatly limited in industrial upsizing of the DTB crystallizer because the amplification cost is sharply increased after reaching a certain size due to problems such as design difficulty, operation stability, power consumption, and the like, and further amplification is difficult. In addition, DTB crystallizers also exist: because no particle size grading is carried out, the stirring paddle rotating at a high speed frequently collides with crystals to cause a remarkable secondary nucleation phenomenon, so that the uniformity of the particle size of the product is poor; the industrial production of phosphate has small particle size, high energy consumption for filtration and drying, and the industrial production of nitrate has small particle size and is easy to agglomerate. The OSLO crystallizer has the main flow field characteristic of crystal particle fluidization, and although the coarse and uniform crystal particles can be produced by the OSLO crystallizer due to the particle size grading effect, the space utilization rate in the OSLO crystallizer is low, the production intensity is low, and the large-flow external circulation pump causes high equipment cost investment and limits the production scale.
Disclosure of Invention
The present invention is directed to overcome the disadvantages of the prior art, and to provide a crystallization apparatus for producing large-grained crystals and the use thereof, so as to obtain crystals having a large average grain size and a uniform grain size, and to provide a simple structure, a reduced power consumption, and a reduced cost.
The purpose of the invention is mainly realized by the following technical scheme:
1. increase the height-diameter ratio of the outer cylinder of the crystallization device
The ratio of the height of the outer cylinder to the inner diameter of the traditional DTB crystallizer is H1/D1, which is usually about 1.1. The invention adopts the technical scheme that the ratio of the height to the inner diameter of the outer cylinder H1/D1 is increased to 1.9-2.2.
2. Reducing the diameter of the draft tube of a crystallization device
Power P ═ KN for stirring paddle3d5Rho, wherein N is the rotating speed of the stirring paddle; d is the diameter of the stirring paddle, rho is the liquid density, and K is a constant; i.e. the paddle power is proportional to the paddle diameter to the power of 5. The gap between the propelling type stirring paddle and the inner wall of the guide shell is smaller and better under the condition of no contact, so the diameter of the stirring paddle limits the size of the guide shell, and the smaller the diameter of the stirring paddle, the smaller the inner diameter of the guide shell. The inner diameter of a guide shell of an industrially used DTB crystallizer is 0.71D1 or 0.55D1, the technical scheme of the invention is to reduce the inner diameter of the guide shell to (0.38-0.4) D1, and D1 is the inner diameter of an outer cylinder.
3. Optimizing the structural parameters of the W-shaped bottom surface of the outer cylinder of the crystallizer
The invention has the technical scheme that the W-shaped curved surface is selected as the bottom surface of the outer cylinder of the crystallizer, structural parameters R1 and R2 for forming the W-shaped curved surface are optimized, the crystalline particle deposition is avoided at a relatively low rotating speed, and suspension discharged from a guide cylinder is guided to change the flow direction on the bottom surface of the outer cylinder of the crystallizer.
The crystallization device for producing large-particle crystals comprises a cylindrical outer cylinder with a closed bottom, a cylindrical guide cylinder, a stirrer and a motor, wherein the cylindrical guide cylinder is positioned in the outer cylinder, two ends of the cylindrical guide cylinder are not closed, a main body part of the stirrer is positioned in the guide cylinder, the motor drives the stirrer to rotate, the bottom surface of the outer cylinder is a W-shaped curved surface, the upper end of the outer cylinder is provided with a cover plate, the ratio of the effective height H1 of the outer cylinder to the inner diameter D1 of the outer cylinder is 1.9-2.2, and the total height of the outer cylinder is equal to the effective height H1 plus the process height H3; the ratio of the inner diameter D2 of the guide cylinder to the inner diameter D1 of the outer cylinder is 0.38-0.40, the height H2 of the guide cylinder is smaller than the effective height H1 of the outer cylinder, the ring surface of the lower end of the guide cylinder is tangent to the top of the upper convex cambered surface at the central part of the bottom of the outer cylinder, a connecting piece is arranged on the ring surface of the upper end of the guide cylinder, the length of the connecting piece is equal to the total height of the outer cylinder-the height H2 of the guide cylinder, and the guide cylinder is fixed by connecting the connecting piece with the cover plate; the stirrer consists of a stirring rod and an impeller fixed at the lower end of the stirring rod, and the distance H4 between the bottom surface of the impeller and the lower end of the guide shell is equal to the diameter d of the impeller.
In the crystallization device for producing large-particle crystals, the difference between the effective height H1 of the outer cylinder and the height H2 of the guide cylinder is 10-15 mm.
In the crystallization device for producing large-particle crystals, the bottom of the outer cylinder with the W-shaped curved surface is composed of an upper convex circular arc surface with the radius of R2 and lower convex circular arc surfaces which are positioned at two sides of the upper convex circular arc surface and have the radius of R1, wherein R2 is 0.187D2, and R1 is 0.160D 1.
In the crystallization device for producing large-particle crystals, the diameter D of an impeller in a stirrer is equal to the inner diameter D2-10 mm of a guide shell.
In the crystallization device for producing large-particle crystals, the wall thickness of the guide shell is less than 3 mm. The wall thickness of the outer cylinder is designed according to the relation of product density, chemical property, yield and the like.
The invention also provides the application of the crystallization device in the production of potassium nitrate crystals and calcium hydrophosphate crystals.
Compared with the prior art, the invention has the following beneficial effects:
1. because the crystallization device reduces the inner diameter of the guide shell and uses a smaller stirring paddle, the use power of the motor is reduced; meanwhile, the produced crystal particles are large, so that the filtering resistance can be reduced, the filtering power consumption is reduced, and the production energy consumption is further reduced.
2. Because the crystallization device increases the height-diameter ratio of the outer cylinder, the separation of a crystal growth area similar to an OSLO crystallizer and a stirring power area is realized, and the diameter of crystal particles is larger; moreover, the large height-diameter ratio outer cylinder increases the crystallization capacity in the longitudinal direction and is matched with the small guide cylinder, so that a smaller stirring paddle can be used for a larger output, the manufacturing difficulty of the stirring paddle is reduced, and the large-scale production is easier to realize in industry; in addition, the large height-diameter ratio of the outer cylinder increases the heat exchange area and enhances the heat exchange, thereby reducing the energy consumption during the constant temperature operation.
3. As the bottom surface of the outer cylinder of the crystallizing device is a W-shaped curved surface and the structural parameters R1 and R2 are optimized, the crystallizing device can avoid the deposition of crystallized particles, guide the suspension discharged from the guide cylinder to change the flow direction on the bottom surface of the outer cylinder of the crystallizer, and is beneficial to improving the uniformity of the particle size of large-particle crystals (see application examples and comparative examples).
4. The crystallizing device has few components, and the guide shell can be fixed by connecting the guide shell with the cover plate through the connecting piece due to the reduction of the inner diameter of the guide shell, so the crystallizing device has a simple structure and reduces the manufacturing cost.
Drawings
FIG. 1 is a schematic view of the structure of a crystallization apparatus for producing large-grained crystals according to the present invention.
Fig. 2 is a sectional view a-B of fig. 1.
FIG. 3 is a schematic diagram of a conventional DTB crystallizer.
Fig. 4 is a sectional view a '-B' of fig. 3.
Fig. 5 is a schematic view of a system for producing potassium nitrate crystal granules using the crystallization apparatus according to the present invention.
Fig. 6 is a graph comparing the grain size distribution of potassium nitrate crystal grains obtained using the crystallization apparatus of the present invention with that obtained using a conventional DTB crystallizer.
Fig. 7 is a schematic diagram of a system for producing granules of crystals of calcium hydrogen phosphate using the crystallization apparatus according to the present invention.
FIG. 8 is a graph comparing the particle size distribution of calcium hydrogen phosphate crystal particles obtained using the crystallization apparatus of the present invention and using a conventional type DTB crystallizer.
FIG. 9 is a graph comparing the average particle size of calcium hydrogen phosphate crystal grains obtained using the crystallization apparatus of the present invention with that obtained using a conventional type DTB crystallizer.
In the figure, 1-outer cylinder, 2-guide cylinder, 3-stirring paddle, 4-outer cylinder bottom surface, 5-cover plate, 6-connecting piece, 7-motor, 8-crystallizing device for producing large granular crystal, 9-water bath, 10-circulating water thermostat, 11-circulating pump, 12-sampling bottle, 13-vacuum pump, 14-feeding pump, 15-slurry mixing tank.
Detailed Description
The crystallization apparatus for producing large-grained crystals and the use thereof according to the present invention will be further described by way of examples and application examples.
Example 1
In this embodiment, a crystallization apparatus for producing large-particle crystals is shown in fig. 1, and includes an outer cylinder 1, a cover plate 5, a draft tube 2, a connecting member 6, a stirrer 3, and a motor 7.
The guide cylinder 2 is in a cylindrical shape with both ends not closed, the inner diameter D2 of the guide cylinder is 6cm, the wall thickness is 2.5mm, and the height H2 is 30 cm.
The outer cylinder 1 is a cylinder with a closed bottom, the inner diameter D1 of the outer cylinder is 15cm, the wall thickness is 2.5mm, the effective height H1 of the outer cylinder is 2.1D1 of the outer cylinder is 31cm, the process height H3 of the outer cylinder is 15cm, the bottom surface of the closed bottom is a W-shaped curved surface, the W-shaped curved surface is composed of an upper convex arc surface with the radius of R2 and lower convex arc surfaces which are positioned at two sides of the upper convex arc surface and have the radius of R1, the R1 of the outer cylinder is 0.160D1 of the outer cylinder is 2.4cm, and the R2 of the outer cylinder is 0.187D2 of the outer cylinder is 2.8 cm.
The ratio of the effective height H1 of the outer cylinder to the inner diameter D1 of the outer cylinder is 31cm/15cm which is 2.1, the ratio of the inner diameter D2 of the guide cylinder to the inner diameter D1 of the outer cylinder is 6cm/15cm which is 0.40, the difference between the effective height H1 of the outer cylinder and the height H2 of the guide cylinder is 31 cm-30 cm which is 10mm,
the connecting piece 6 is three arc-shaped pieces extending along the annular surface of the guide cylinder 2, as shown in fig. 2, the included angle between the center lines of the three arc-shaped pieces is 120 degrees, the included angle between the two side surfaces of each arc-shaped piece is 30 degrees, the three arc-shaped pieces are identical in length, and the total height of the outer cylinder and the height of the guide cylinder are H1+ H3-H2 which is 31cm +15 cm-30 cm which is 16 cm.
The stirrer 3 consists of a stirring rod and an impeller fixed at the lower end of the stirring rod, wherein the diameter D of the impeller is 6 cm-10 cm-5 cm, and the diameter D of the impeller is 2-10 mm.
The combination mode of the above components: the guide cylinder 2 is positioned in the outer cylinder 1, the ring surface of the lower end of the guide cylinder is tangent to the top of the upper convex arc surface at the central part of the bottom of the outer cylinder, and three arc-shaped sheet connecting pieces extending from the ring surface of the upper end of the guide cylinder are connected with a cover plate 5 arranged at the upper end of the outer cylinder 1, so that the guide cylinder is fixed; the main part of the stirrer 3 is positioned in the guide shell 2, the distance H4 between the bottom surface of the impeller and the lower end of the guide shell is equal to the diameter d of the impeller equal to 5cm, the upper end of the stirring rod penetrates through the cover plate 5 to extend out to be connected with the motor 7, and the motor 7 is fixedly installed through a support.
Application example 1
In this application example, the crystallization apparatus and the supporting equipment for producing large granular crystals described in example 1 were used to produce potassium nitrate crystal granules, and a system for producing potassium nitrate crystal granules, which is composed of the crystallization apparatus 8 and the supporting equipment for producing large granular crystals described in example 1, a water bath 9, a circulating water incubator 10, a circulating pump 11, a sampling bottle 12, and a vacuum pump 13, is shown in fig. 5.
The operation of producing potassium nitrate crystal granules is as follows:
4800mL of deionized water and 3100g of potassium nitrate were placed in the crystallization apparatus 8 described in example 1, a 52 ℃ potassium nitrate solution was prepared in a 52 ℃ water bath environment, then cooled and crystallized at a constant rate of 5 ℃/h with the aid of a circulating water incubator 10 and a circulating pump 11, crystals began to precipitate when the temperature of the potassium nitrate solution decreased to about 42 ℃, 4g of seed crystals were added while stirring, and crystallization was continued to be cooled at a constant rate of 5 ℃/h while stirring, the temperature was stopped when the temperature of the potassium nitrate crystallization system decreased to 25 ℃, the temperature was maintained and stirred for another 30min for particle aging, and after the particle aging was completed, the potassium nitrate crystal particle product was obtained by filtration through a 300 mesh filter cloth.
In the crystallization process, the stirring speed is adjusted according to the solid phase suspension condition, and the specific operation is as follows: and (3) adopting a stirring rotating speed of 300r/min at the initial stage of crystallization, and increasing the rotating speed by 20r/min on the basis of the original rotating speed every time when the particles are found to be settled so as to enable the crystals in the crystallization device 8 to be in an approximate critical off-bottom suspension state in the whole crystallization stage.
Comparative example 1
The comparative example produced potassium nitrate crystal pellets using a system consisting of a conventional DTB crystallizer and associated equipment. The structure of a conventional DTB crystallizer is shown in FIG. 3, and comprises an outer cylinder, a guide cylinder and a stirrer. The guide cylinder is in a cylindrical shape with two unsealed ends, the inner diameter D2 'is 14cm, the height H2' is 16cm, and the wall thickness is 2 mm; the outer cylinder is a cylinder with a closed bottom, the inner diameter D1 'of the outer cylinder is 20cm, the effective height H1' of the outer cylinder is 26cm, the wall thickness of the outer cylinder is 2.5mm, the bottom surface of the closed bottom is a W-shaped curved surface, the W-shaped curved surface is composed of an upper convex arc surface with the radius of R2 'and lower convex arc surfaces which are positioned at two sides of the upper convex arc surface and have the radius of R1', the R1 'is 0.150D1 of 3cm, and the R2' is 0.571D2 of 8 cm.
The ratio of the effective height H1 'of the outer cylinder to the inner diameter D1' of the outer cylinder is 26cm/20cm which is 1.3, the ratio of the inner diameter D2 'of the guide cylinder to the inner diameter D1' of the outer cylinder is 14cm/20cm which is 0.70, and the difference between the effective height H1 'of the outer cylinder and the height H2' of the guide cylinder is 26 cm-16 cm which is 10 cm.
The stirrer consists of a stirring rod and an impeller fixed at the lower end of the stirring rod, wherein the diameter D 'of the impeller is 14 cm-20 cm-12 cm, and the diameter D2' -20 mm of the guide shell is.
The combination mode of the above components: the guide cylinder is positioned in the outer cylinder, the guide cylinder is connected with the inner wall of the outer cylinder through four plate bodies distributed in 90 degrees to realize fixation (as shown in figure 4), and a distance is reserved between the ring surface of the lower end of the guide cylinder and the top of the convex cambered surface at the central part of the bottom of the outer cylinder; the impeller of agitator is located the draft tube, and the interval between the lower extreme of impeller bottom surface and draft tube is 6cm, and the upper end and the motor of puddler are connected, the motor passes through the support mounting and fixes.
The corollary equipment of the conventional DTB crystallizer also comprises a water bath 9, a circulating water thermostat 10, a circulating pump 11, a sampling bottle 12 and a vacuum pump 13.
The operation of the present comparative example for producing potassium nitrate crystal pellets was as follows:
4800mL of deionized water and 3100g of potassium nitrate are placed in the conventional DTB crystallizer, a potassium nitrate solution at 52 ℃ is prepared in a 52 ℃ water bath environment, then, with the assistance of a circulating water thermostat 10 and a circulating pump 11, cooling at a constant rate of 5 ℃/h is performed for crystallization, crystals begin to precipitate when the temperature of the potassium nitrate solution is reduced to about 42 ℃, 4g of seed crystals are added while stirring, the temperature is continuously reduced at a constant rate of 5 ℃/h while stirring for crystallization, the temperature is stopped when the temperature of a potassium nitrate crystallization system is reduced to 25 ℃, the temperature is maintained to be stirred for 30min again for particle aging, and after the particles are aged, the potassium nitrate crystal particle product is obtained by filtering through 300-mesh filter cloth.
In the crystallization process, the stirring speed is adjusted according to the solid phase suspension condition, and the specific operation is as follows: and (3) adopting a stirring rotating speed of 250r/min at the initial stage of crystallization, and increasing the rotating speed by 10r/min on the basis of the original rotating speed every time when the particles are found to sink to ensure that the crystals in the traditional DTB crystallizer are in an approximate critical off-bottom suspension state in the whole crystallization stage along with the gradual increase of crystal particles.
The potassium nitrate crystal particle products produced in application example 1 and comparative example 1 were respectively detected according to the screening method (GB/T21524-. As can be seen from FIG. 6, with the use of the crystallization apparatus for producing large-grained crystals described in example 1, the major peak of the grain size distribution of potassium nitrate crystal grains appeared in the range of 1.43 to 1.60mm, and with the use of the conventional DTB crystallizer, the major peak of the grain size distribution of potassium nitrate crystal grains appeared in the range of 0.70 to 0.90 mm. Therefore, compared with the traditional DTB crystallizer, the crystallization device for producing large-particle crystals can produce the potassium nitrate crystals with larger particle size and better effect of producing the large-particle crystals under the condition of the same yield. The produced potassium nitrate crystal product has larger grain diameter, so the filtering resistance can be reduced, the filtering power consumption is reduced, and the production energy consumption is further reduced.
Application example 2
In this application example, the crystallization apparatus and the associated equipment for producing large granular crystals described in example 1 were used to produce calcium hydrogen phosphate crystal granules, and a system for producing calcium hydrogen phosphate crystal granules, which is composed of the crystallization apparatus 8 and the associated equipment water bath 9, circulating water thermostat 10, circulating pump 11, sampling bottle 12, vacuum pump 13, feed pump 14 and slurry mixing tank 15 for producing large granular crystals described in example 1, is shown in fig. 7.
The operation for producing calcium hydrogen phosphate crystal particles is as follows:
(1) 4.2L of dilute phosphoric acid solution with a mass concentration of 10.6% was prepared using technical grade 85% phosphoric acid and deionized water, and then 20% CaCO was added to the dilute phosphoric acid solution with stirring at a feed rate of 0.4kg/h3The solution forms a calcium hydrophosphate solution, and CaCO is stopped to be added when the pH value of the calcium hydrophosphate solution is 2.00-2.103Filtering the solution by using 300-mesh filter cloth to remove partial impurities containing elements such as sulfur, fluorine, silicon and the like in the calcium hydrophosphate solution, adding the calcium hydrophosphate solution after impurity removal into the crystallization device 8 of example 1, and controlling the temperature of the calcium hydrophosphate solution in the crystallization device 8 to be 55 ℃ through a water bath 9, a circulating water thermostat 10 and a circulating pump 11;
(2) the slurry is mixed with 20% CaCO by the feed pump 14 under stirring3Adding the solution into the crystallization device 8 at a feeding speed of 0.4kg/h, maintaining the temperature of a crystallization system in the crystallization device 8 at 55 ℃, controlling the stirring speed at 300r/min when calcium hydrophosphate crystals are precipitated, and increasing the rotating speed by 20r/min on the basis of the original rotating speed every time when the particles are found to sink as crystal particles gradually increase so as to enable the crystals in the crystallization device 8 to be in an approximate critical off-bottom suspension state in the whole crystallization stage; when the pH of the crystallization system was 4.20, the CaCO feed was stopped3And (3) after the crystallization production of the solution is finished, filtering the solution by a 300-mesh filter cloth, and drying crystal particles obtained by filtering at the constant temperature of 55 ℃ to obtain a calcium hydrophosphate product.
Comparative example 2
This comparative example used the conventional type DTB crystallizer described in comparative example 1 and the supporting equipment, water bath 9, circulating water thermostat 10, circulating pump 11, sampling bottle 12, vacuum pump 13, feed pump 14 and slurry mixing tank 15, which constituted a system for producing calcium hydrogen phosphate crystal grains (see fig. 7, i.e., the crystallization apparatus 8 in fig. 7 was replaced with the conventional type DTB crystallizer described in comparative example 1).
The operation for producing calcium hydrogen phosphate crystal particles is as follows:
(1) 4.2L of dilute phosphoric acid solution with the mass concentration of 10.6 percent is prepared by using industrial grade 85 percent phosphoric acid and deionized water, and then CaCO with the mass concentration of 20 percent is added into the dilute phosphoric acid solution at the feed rate of 0.4kg/h under stirring3The solution forms a calcium hydrophosphate solution, and CaCO is stopped to be added when the pH value of the calcium hydrophosphate solution is 2.00-2.103Filtering the solution by using 300-mesh filter cloth to remove partial impurities containing elements such as sulfur, fluorine, silicon and the like in the calcium hydrophosphate solution, adding the calcium hydrophosphate solution after impurity removal into the traditional DTB crystallizer in the comparative example 1, and controlling the temperature of the calcium hydrophosphate solution in the traditional DTB crystallizer to be 55 ℃ through a water bath 9, a circulating water thermostat 10 and a circulating pump 11;
(2) the slurry is mixed with 20% CaCO by the feed pump 14 under stirring3Adding the solution into a traditional DTB crystallizer at a feeding speed of 0.4kg/h, maintaining the temperature of a crystallization system in the traditional DTB crystallizer at 55 ℃, controlling the stirring speed at 250r/min when calcium hydrophosphate crystals are precipitated, and increasing the rotating speed by 10r/min on the basis of the original rotating speed every time when the particles are found to sink as crystal particles are gradually increased so as to enable the crystals in the traditional DTB crystallizer to be in an approximate critical off-bottom suspension state in the whole crystallization stage; when the pH of the crystallization system was 4.20, the CaCO feed was stopped3And (3) after the crystallization production of the solution is finished, filtering the solution by a 300-mesh filter cloth, and drying crystal particles obtained by filtering at the constant temperature of 55 ℃ to obtain a calcium hydrophosphate product.
The calcium hydrogen phosphate products produced in application example 2 and comparative example 2 were measured by a Malvern Mastersizer 3000 laser diffraction particle size analyzer, and the particle size distribution of the calcium hydrogen phosphate product was plotted in fig. 8 and 9. As can be seen from FIGS. 8 and 9, the calcium hydrogen phosphate product produced using the crystallization apparatus for producing large-particle crystals described in example 1 had an average particle size of 550.2 μm, and the calcium hydrogen phosphate product produced using the conventional DTB crystallizer had an average particle size of only 291.8. mu.m. Therefore, compared with the traditional DTB crystallizer, the crystallization device for producing large-particle crystals provided by the invention can produce calcium hydrophosphate with larger particle size, and has better effect of producing large-particle crystals. The produced calcium hydrophosphate product has larger grain size, so the filtration resistance can be reduced, the filtration power consumption is reduced, and the production energy consumption is further reduced.
The impeller diameter of the stirrer of the crystallization apparatus for producing large-grained crystals in application example 1 and application example 2 was 5cm, and the impeller diameter of the stirrer of the conventional DTB crystallizer in comparative example 1 and comparative example 2 was 12cm, since the stirrer power P ═ KN3d5Rho, compared with the traditional DTB crystallizer, the stirrer power of the crystallization device for producing large-particle crystals is far less than that of the traditional DTB crystallizer.
The practically used height-to-diameter ratio (ratio of the liquid level height to the inner diameter of the outer cylinder) of the crystallization apparatus for producing large-grained crystals in application examples 1 and 2 was 2.2, and therefore the heat exchange area was 3.14 × 15 × 15 × 2.2 (the bottom area was not taken into account), which was about 0.1554m2(ii) a The practical aspect ratio (ratio of the liquid level height to the inner diameter of the outer cylinder) of the conventional DTB crystallizer in comparative examples 1 and 2 was 0.95, and thus the heat exchange area was 3.14 × 20 × 20 × 0.95 (the base area was not taken into account), which was about 0.1193m2. Therefore, the heat exchange area of the crystallization device for producing large-particle crystals is increased by 36.26 percent compared with that of the traditional DTB crystallizer, the heat exchange is enhanced, and the energy consumption in constant temperature operation is reduced.
Claims (7)
1. A crystallization device for producing large-particle crystals comprises a cylindrical outer cylinder (1) with a closed bottom, a cylindrical guide cylinder (2) which is positioned in the outer cylinder and has two unsealed ends, a stirrer (3) with a main body part positioned in the guide cylinder and a motor (7) for driving the stirrer to rotate, and is characterized in that the bottom surface of the outer cylinder is a W-shaped curved surface, a cover plate (5) is arranged at the upper end of the outer cylinder, the ratio of the effective height H1 of the outer cylinder (1) to the inner diameter D1 of the outer cylinder (1) is 1.9-2.2, and the total height of the outer cylinder is H1 plus the process height H3; the ratio of the inner diameter D2 of the guide cylinder to the inner diameter D1 of the outer cylinder is 0.38-0.40, the height H2 of the guide cylinder is smaller than the effective height H1 of the outer cylinder, the ring surface of the lower end of the guide cylinder is tangent to the top of the upper convex cambered surface at the central part of the bottom of the outer cylinder, a connecting piece (6) is arranged on the ring surface of the upper end of the guide cylinder, the length of the connecting piece (6) is equal to the total height of the outer cylinder-the height H2 of the guide cylinder, and the guide cylinder is fixed by connecting the connecting piece with a cover plate (5); the stirrer (3) consists of a stirring rod and an impeller fixed at the lower end of the stirring rod, and the distance H4 between the bottom surface of the impeller and the lower end of the guide shell is equal to the diameter d of the impeller.
2. The crystallization apparatus for producing large granular crystals as claimed in claim 1, wherein the difference between the effective height H1 of the outer cylinder and the height H2 of the guide cylinder is 10-15 mm.
3. The crystallization apparatus for producing large granular crystals according to claim 1 or 2, wherein the bottom of the outer cylinder of the W-shaped curved surface is composed of an upper convex circular arc surface with a radius of R2 and lower convex circular arc surfaces with a radius of R1 on both sides of the upper convex circular arc surface, wherein R2 is 0.187D2, and R1 is 0.160D 1.
4. The crystallization apparatus for producing large granular crystals according to claim 1 or 2, wherein the impeller diameter D in the stirrer (3) is equal to the inner diameter D2-10 mm of the draft tube.
5. The crystallization apparatus for producing large granular crystals according to claim 3, wherein the impeller diameter D in the stirrer (3) is equal to the inner diameter D2-10 mm of the draft tube.
6. Use of a crystallisation apparatus according to any one of claims 1 to 5 for the production of potassium nitrate crystals.
7. Use of a crystallisation apparatus as claimed in any one of claims 1 to 5 for the production of crystals of dibasic calcium phosphate.
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| GB835659A (en) * | 1958-05-21 | 1960-05-25 | Metallgesellschaft Ag | Crystallisation apparatus and method of operating the same |
| JP2013071097A (en) * | 2011-09-29 | 2013-04-22 | Yoichi Chiba | Crystallizer |
| CN104826357A (en) * | 2015-05-28 | 2015-08-12 | 化工部长沙设计研究院 | Crystallizer with rectifying hood |
| CN204637635U (en) * | 2015-05-12 | 2015-09-16 | 江苏揽山环境科技有限公司 | A kind of desulfurated plaster crystallization apparatus |
| CN105597362A (en) * | 2016-03-17 | 2016-05-25 | 化工部长沙设计研究院 | Mechanical crystallizer for sylvite industry |
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2021
- 2021-12-15 CN CN202111538578.9A patent/CN114177644B/en active Active
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| GB835659A (en) * | 1958-05-21 | 1960-05-25 | Metallgesellschaft Ag | Crystallisation apparatus and method of operating the same |
| JP2013071097A (en) * | 2011-09-29 | 2013-04-22 | Yoichi Chiba | Crystallizer |
| CN204637635U (en) * | 2015-05-12 | 2015-09-16 | 江苏揽山环境科技有限公司 | A kind of desulfurated plaster crystallization apparatus |
| CN104826357A (en) * | 2015-05-28 | 2015-08-12 | 化工部长沙设计研究院 | Crystallizer with rectifying hood |
| CN105597362A (en) * | 2016-03-17 | 2016-05-25 | 化工部长沙设计研究院 | Mechanical crystallizer for sylvite industry |
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