CN116549999A - Continuous crystallization method of water-soluble fertilizer - Google Patents
Continuous crystallization method of water-soluble fertilizer Download PDFInfo
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- CN116549999A CN116549999A CN202310745353.3A CN202310745353A CN116549999A CN 116549999 A CN116549999 A CN 116549999A CN 202310745353 A CN202310745353 A CN 202310745353A CN 116549999 A CN116549999 A CN 116549999A
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- crystallizer
- crystallization
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- water
- soluble fertilizer
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- 238000002425 crystallisation Methods 0.000 title claims abstract description 96
- 239000003337 fertilizer Substances 0.000 title claims abstract description 35
- 230000008025 crystallization Effects 0.000 claims abstract description 73
- 239000007788 liquid Substances 0.000 claims abstract description 40
- 239000011550 stock solution Substances 0.000 claims abstract description 34
- 239000012452 mother liquor Substances 0.000 claims abstract description 26
- 239000013078 crystal Substances 0.000 claims abstract description 21
- 239000010413 mother solution Substances 0.000 claims abstract description 20
- 239000002002 slurry Substances 0.000 claims abstract description 13
- 239000011259 mixed solution Substances 0.000 claims abstract description 11
- 238000003756 stirring Methods 0.000 claims abstract description 9
- 238000002156 mixing Methods 0.000 claims abstract description 8
- 238000001816 cooling Methods 0.000 claims description 35
- 239000000523 sample Substances 0.000 claims description 21
- 238000000034 method Methods 0.000 claims description 10
- 230000001276 controlling effect Effects 0.000 claims description 8
- 230000001105 regulatory effect Effects 0.000 claims description 6
- 238000001704 evaporation Methods 0.000 claims description 4
- 230000008020 evaporation Effects 0.000 claims description 4
- 230000001376 precipitating effect Effects 0.000 claims 1
- 238000009826 distribution Methods 0.000 abstract description 6
- 230000006911 nucleation Effects 0.000 abstract description 4
- 238000010899 nucleation Methods 0.000 abstract description 4
- 230000003068 static effect Effects 0.000 abstract description 3
- 239000000463 material Substances 0.000 description 18
- ZCCIPPOKBCJFDN-UHFFFAOYSA-N calcium nitrate Chemical compound [Ca+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ZCCIPPOKBCJFDN-UHFFFAOYSA-N 0.000 description 15
- 238000004519 manufacturing process Methods 0.000 description 7
- 238000000926 separation method Methods 0.000 description 7
- 238000007599 discharging Methods 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 239000000243 solution Substances 0.000 description 4
- 238000005265 energy consumption Methods 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 description 2
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 2
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- YIXJRHPUWRPCBB-UHFFFAOYSA-N magnesium nitrate Chemical compound [Mg+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O YIXJRHPUWRPCBB-UHFFFAOYSA-N 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- FGIUAXJPYTZDNR-UHFFFAOYSA-N potassium nitrate Chemical compound [K+].[O-][N+]([O-])=O FGIUAXJPYTZDNR-UHFFFAOYSA-N 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 description 1
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 description 1
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 1
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 1
- 235000011130 ammonium sulphate Nutrition 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- NGLMYMJASOJOJY-UHFFFAOYSA-O azanium;calcium;nitrate Chemical compound [NH4+].[Ca].[O-][N+]([O-])=O NGLMYMJASOJOJY-UHFFFAOYSA-O 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- ICSSIKVYVJQJND-UHFFFAOYSA-N calcium nitrate tetrahydrate Chemical compound O.O.O.O.[Ca+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ICSSIKVYVJQJND-UHFFFAOYSA-N 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 239000011549 crystallization solution Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000009422 external insulation Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 229910001629 magnesium chloride Inorganic materials 0.000 description 1
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 1
- 235000019341 magnesium sulphate Nutrition 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 235000019837 monoammonium phosphate Nutrition 0.000 description 1
- 239000006012 monoammonium phosphate Substances 0.000 description 1
- 229910000402 monopotassium phosphate Inorganic materials 0.000 description 1
- 235000019796 monopotassium phosphate Nutrition 0.000 description 1
- 239000001103 potassium chloride Substances 0.000 description 1
- 235000011164 potassium chloride Nutrition 0.000 description 1
- GNSKLFRGEWLPPA-UHFFFAOYSA-M potassium dihydrogen phosphate Chemical compound [K+].OP(O)([O-])=O GNSKLFRGEWLPPA-UHFFFAOYSA-M 0.000 description 1
- 235000010333 potassium nitrate Nutrition 0.000 description 1
- 239000004323 potassium nitrate Substances 0.000 description 1
- LWIHDJKSTIGBAC-UHFFFAOYSA-K potassium phosphate Substances [K+].[K+].[K+].[O-]P([O-])([O-])=O LWIHDJKSTIGBAC-UHFFFAOYSA-K 0.000 description 1
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 description 1
- 229910052939 potassium sulfate Inorganic materials 0.000 description 1
- 235000011151 potassium sulphates Nutrition 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D9/00—Crystallisation
- B01D9/0004—Crystallisation cooling by heat exchange
- B01D9/0013—Crystallisation cooling by heat exchange by indirect heat exchange
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D9/00—Crystallisation
- B01D9/02—Crystallisation from solutions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D9/00—Crystallisation
- B01D2009/0086—Processes or apparatus therefor
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
Abstract
The invention provides a continuous crystallization method of a water-soluble fertilizer, which belongs to the technical field of crystallization reaction and comprises the following steps: continuously conveying the crystallization stock solution into a mixer through a feeding pipeline; continuously conveying part of mother liquor in the mother liquor tank to a mixer through a circulating pipeline; mixing the mother solution and the crystallization stock solution in a mixer, and adjusting the supersaturation degree of the crystallization stock solution; conveying the mixed crystallization stock solution and mother solution into a crystallizer, and separating out crystals in the crystallizer by stirring; delivering the slurry produced after crystallization into a centrifugal machine, separating liquid in the slurry through the centrifugal machine, and delivering the liquid to a mother liquor tank; according to the continuous crystallization method of the water-soluble fertilizer, the crystallization stock solution and the mother solution are subjected to static mixing through the mixer, and the supersaturation degree of the mixed solution after the crystallization stock solution and the mother solution are mixed is reduced in the mixer, so that the nucleation quantity is reduced, crystals are more likely to grow in the crystallizer, and the crystallization granularity distribution is more uniform.
Description
Technical Field
The invention relates to the technical field of crystallization reaction, in particular to a continuous crystallization method of a water-soluble fertilizer.
Background
Crystallization is a typical product separation technology in chemical industry production, and purification, crystallization and separation of products are realized through cooling. The common process method is intermittent, and specific operations comprise feeding, cooling, discharging and the like, specifically, hot crystallization stock solution is added into a special crystallizer at one time, then crystallization is realized by adopting heat exchange modes such as natural cooling, forced cooling and the like, and after the crystallization operation is finished, materials are completely discharged and solid-liquid separation is carried out.
The production mode has a plurality of operation procedures, the product quality difference among different batches is large, and the quality difference among the batches is obvious. The two auxiliary links of feeding and discharging occupy quite long time in the whole operation period, so that the crystallization equipment is low in utilization rate, low in productivity, high in energy consumption and long in operation period.
Chinese patent document CN110870984a discloses a continuous crystallizer, which comprises a buffer tank and a crystallization tank, wherein the crystallization stock solution enters the crystallization tank through the buffer tank, and after continuous crystallization in the crystallization tank, the finished product crystallization solution is discharged through a second liquid outlet. The crystallizer used in this scheme can be fed continuously and discharged continuously.
However, in the above-mentioned scheme, the non-uniformity of the crystal grain size distribution is easily caused during the production process by controlling only the reaction temperature.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to overcome the defect that the continuous crystallizer in the prior art cannot ensure uniform grain size distribution, thereby providing a continuous crystallization method of water-soluble fertilizer.
In order to solve the technical problems, the invention provides a continuous crystallization method of a water-soluble fertilizer, which comprises the following steps:
continuously conveying the crystallization stock solution into a mixer through a feeding pipeline;
continuously conveying part of mother liquor in the mother liquor tank to a mixer through a circulating pipeline;
mixing the mother solution and the crystallization stock solution in a mixer, and adjusting the supersaturation degree of the crystallization stock solution;
conveying the mixed crystallization stock solution and mother solution into a crystallizer, and separating out crystals in the crystallizer by stirring;
and (3) delivering the slurry produced after crystallization into a centrifugal machine, separating liquid in the slurry through the centrifugal machine, and delivering the liquid to a mother liquid tank.
Optionally, the flow ratio of the crystallization stock solution to the circulating mother solution is adjusted through the supersaturation intelligent controller so as to control the temperature of the mixed solution in the mixer, thereby adjusting and controlling the supersaturation degree of the mixed solution in the mixer.
Optionally, the supersaturation degree intelligent controller monitors the flow rate of the crystallization stock solution in the feeding pipeline through a first flow meter on the feeding pipeline, and monitors the flow rate of the mother solution in the circulating pipeline through a second flow meter on the circulating pipeline.
Optionally, the supersaturation degree intelligent controller monitors the temperature of the mixed liquid in the mixer through a first temperature probe on the mixer.
Optionally, the mixed liquor in the crystallizer is cooled by circulating heat exchange of the cooling circulating liquor of the inner heat exchanger and the outer crystallizer.
Optionally, the cooling circulation liquid between the internal heat exchanger and the external crystallizer is driven by a cooling circulation pump, and the cooling circulation pump is controlled by the intelligent controller connected with a frequency converter.
Optionally, a liquid level gauge is arranged on the crystallizer, and the liquid level height in the crystallizer is monitored through the liquid level gauge.
Optionally, part of mother liquor separated by the centrifugal machine is returned to a previous working procedure for evaporation concentration.
Optionally, a second temperature probe is arranged in the middle area of the crystallizer, and the temperature of the liquid in the crystallizer is monitored through the second temperature probe.
Optionally, an ultrasonic probe is connected to the bottom region of the crystallizer, and the real-time characteristic parameter information of the crystal state in the crystallizer is monitored through the ultrasonic probe.
The technical scheme of the invention has the following advantages:
according to the continuous crystallization method for the water-soluble fertilizer, provided by the invention, the crystallization stock solution and the mother solution are subjected to static mixing through the mixer, and the supersaturation degree of the mixed solution after the crystallization stock solution and the mother solution are mixed is reduced in the mixer, so that the nucleation quantity is reduced, crystals are more likely to grow in the crystallizer, and the crystallization granularity distribution is more uniform.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic front view of one embodiment of a continuous crystallization system for water-soluble fertilizers provided in the examples of the present invention;
FIG. 2 is a schematic front view of another embodiment of a continuous crystallization system for water-soluble fertilizers provided in the examples of the present invention;
fig. 3 is a specific embodiment of a continuous crystallization method of a water-soluble fertilizer provided in examples of the present invention.
Reference numerals illustrate:
1. a mixer; 2. a crystallizer; 3. a centrifuge; 4. a mother liquor tank; 5. a motor; 6. a speed reducer; 7. a stirrer; 8. an external insulation layer; 9. a first electrically controlled valve; 10. a second electrically controlled valve; 11. a first flowmeter; 12. a second flowmeter; 13. a third flowmeter; 14. a first temperature probe; 15. a second temperature probe; 16. an internal heat exchanger; 17. an external heat exchanger; 18. a cooling circulation pump; 19. a liquid level gauge; 20. an ultrasonic probe.
Detailed Description
The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In addition, the technical features of the different embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
The continuous crystallization method of the water-soluble fertilizer provided by the embodiment can be used for producing the water-soluble fertilizer, and particularly, large-scale crystallization production of the water-soluble fertilizer is carried out.
As shown in fig. 1, in the continuous crystallization method of a water-soluble fertilizer provided in this embodiment, a specific embodiment of a continuous crystallization system of a water-soluble fertilizer is used, which includes: a mixer 1, a crystallizer 2, a centrifuge 3 and a mother liquor tank 4. The crystallizer 2 is provided with a feed inlet and a discharge outlet, the mixer 1 is communicated with the feed inlet of the crystallizer 2, and the product solution enters the mixer 1 through a feed pipeline. The inlet of the centrifugal machine 3 is communicated with the discharge port of the crystallizer 2, and slurry discharged from the discharge port at the bottom of the crystallizer 2 is subjected to solid-liquid separation through centrifugal rotation of the centrifugal machine 3. The mother liquor tank 4 is communicated with a liquid outlet of the centrifugal machine 3, and the mother liquor tank 4 is communicated with the mixer 1 through a circulating pipeline.
When in use, as shown in fig. 3, the method specifically comprises the following steps:
continuously conveying the crystallization stock solution into the mixer 1 through a feeding pipeline;
continuously conveying part of the mother liquor in the mother liquor tank 4 into the mixer 1 through a circulating pipeline;
mixing the mother solution and the crystallization stock solution in a mixer 1, and adjusting the supersaturation degree of the crystallization stock solution;
the mixed crystallization stock solution and mother solution are conveyed into a crystallizer 2, and crystallization is precipitated in the crystallizer 2 by stirring;
the slurry produced after crystallization is sent to a centrifuge 3, and the liquid in the slurry is separated by the centrifuge 3 and sent to a mother liquor tank 4.
According to the continuous crystallization method for the water-soluble fertilizer, provided by the embodiment, the crystallization stock solution and the mother solution are subjected to static mixing through the mixer 1, and the supersaturation degree of the mixed solution after the crystallization stock solution and the mother solution are mixed is reduced in the mixer 1, so that the nucleation quantity is reduced, crystals are easier to grow in the crystallizer 2, and the crystallization granularity distribution is more uniform.
As shown in FIGS. 1 and 2, the volume of the crystallizer 2 used in this example was 120m 3 . In addition, the present invention is not limited to a specific volume of the mold 2, and in some embodiments, the volume of the optional mold 2 may be in the range of 100.+ -. 50m 3 。
As shown in fig. 1, the crystallizer 2 in this embodiment includes: crystallizer body, top cap, motor 5, reduction gear 6, agitator 7, feed inlet, discharge gate and outside heat preservation 8. Wherein, the crystallizer body is made of stainless steel material, and the motor 5, the speed reducer 6 and the stirrer 7 are connected in sequence and are arranged on the top cover of the crystallizer 2; the electromagnetic valve is additionally arranged at the feed inlet and the discharge outlet. In addition, it should be noted that the specific structure of the crystallizer 2 is not limited by the present invention, and in some embodiments, other conventional structures may be adopted for the specific structure of the crystallizer 2.
In this embodiment, as shown in fig. 1, the stirrer 7 in the crystallizer 2 is a multi-layer axial-flow stirrer 7, the number of stirring paddles is at least two, and the multi-layer axial-flow stirrer 7 is used for strengthening material dispersion, so as to effectively regulate and control the crystal granularity. In addition, the specific structure of the stirrer 7 is not limited in the present invention, and in some embodiments, the stirrer 7 may have other conventional structures.
In this embodiment, the rotation speed of the stirrer 7 is controlled by a frequency converter, specifically, the rotation speed of the stirrer 7 is controlled by the frequency converter according to the crystal growth size, and the power consumption is controlled to the minimum level on the premise of ensuring that crystals do not settle during the crystallization production process, that is, the minimum rotation speed at which no crystal settlement occurs.
In the present embodiment, the crystal stock solution introduced into the mixer 1 is a mixture of water and one or more water-soluble fertilizers such as potassium sulfate, magnesium sulfate, ammonium sulfate, monopotassium phosphate, monoammonium phosphate, potassium nitrate, calcium ammonium nitrate, calcium nitrate, magnesium nitrate, potassium chloride, and magnesium chloride.
As shown in fig. 1, in the continuous crystallization system of water-soluble fertilizer, the mixer 1 is connected with an intelligent supersaturation degree controller, a first electric control valve 9 is arranged on the feeding pipeline, a second electric control valve 10 is arranged on the circulating pipeline, and the intelligent supersaturation degree controller is respectively electrically connected with the first electric control valve 9 and the second electric control valve 10.
When the device is used, the supersaturation degree intelligent controller is used for adjusting the flow ratio of the crystallization stock solution and the circulating mother solution and controlling the temperature of the mixed solution in the mixer 1, so that the supersaturation degree of the mixed solution in the mixer 1 is regulated and controlled. Specifically, the supersaturation degree intelligent controller respectively controls the first electric control valve 9 and the second electric control valve 10 according to the supersaturation degree of the mixed liquid in the mixer 1 so as to adjust the ratio of the product solution to the mother liquid. Through on-line measurement and automatic control technical means, the material temperature, flow and heat exchange rate are accurately controlled, and the material dispersion is enhanced by utilizing the efficient axial flow stirrer 7, so that the problems of complex structure, inconvenient maintenance, high energy consumption and low production efficiency of the intermittent crystallizer 2 and the universal continuous crystallization system are solved.
As shown in fig. 1, in the continuous crystallization system of water-soluble fertilizer, a first flowmeter 11 is arranged on the feeding pipeline, a second flowmeter 12 is arranged on the circulating pipeline, and a third flowmeter 13 is arranged at the discharge port of the crystallizer 2. The flowmeter is concretely an electromagnetic flowmeter. The feeding and discharging flow rates of the crystallizer 2 are monitored by a flowmeter, so that the total feeding speed and the discharging speed are ensured to be equal. When the intelligent supersaturation degree controller is used, the intelligent supersaturation degree controller monitors the flow rate of the crystallization stock solution in the feeding pipeline through the first flow meter 11 on the feeding pipeline; the supersaturation degree intelligent controller monitors the flow rate of the mother liquor in the circulation pipeline through a second flowmeter 12 on the circulation pipeline.
As shown in fig. 1, the mixer 1 is connected with a first temperature probe 14, and the first temperature probe 14 is electrically connected with the intelligent supersaturation degree controller. The temperature probe 14 is used for monitoring the temperature in the mixer 1 and sending the monitored temperature information to the supersaturation degree intelligent controller so as to accurately control the supersaturation degree of the mixed liquor in the mixer 1 through the supersaturation degree intelligent controller. When the intelligent supersaturation degree controller is used, the temperature of mixed liquid in the mixer 1 is monitored through the first temperature probe 14 on the mixer 1.
As shown in fig. 2, in the continuous crystallization system of water-soluble fertilizer, further comprising: the cooling circulation liquid between the inner heat exchanger 16 and the outer crystallizer 2 is driven by a cooling circulation pump 18, and the cooling circulation pump 18 is connected with a frequency converter through the intelligent controller for control. Specifically, the intelligent controller is electrically connected with the cooling circulation pump 18 through a frequency converter, and the rotation speed of the cooling circulation pump 18 can be controlled through the setting of the frequency converter, so that the cooling strength is adjusted. The inner heat exchanger 16 is arranged inside the crystallizer 2, the outer heat exchanger 17 is arranged outside the crystallizer 2, and the outer heat exchanger 17 is communicated with the inner heat exchanger 16The heat exchange pipeline is communicated, a cooling circulation pump 18 is arranged on the heat exchange pipeline, and the cooling circulation pump 18 is used for forcedly flowing cooling circulation liquid between the inner heat exchanger 16 and the outer heat exchanger 17. Specifically, the internal heat exchanger 16 is a stainless steel tube type heat exchanger, the installation position of the internal heat exchange tube is the inner periphery of the stirrer 7, the minimum distance from the inner wall of the crystallizer 2 is not less than 5cm, and the heat exchange area of each cubic material is not less than 2m 2 . In use, the mixed liquor in the crystallizer 2 is cooled by circulating heat exchange of the cooling circulation liquor of the inner heat exchanger 16 and the outer crystallizer 2. Specifically, the heat brought by the mixed solution and the heat released by crystallization are taken away by the cooling circulating liquid in the internal heat exchanger 16, and the constant temperature of the materials in the crystallizer 2 is realized by automatically controlling the inlet temperature and flow of the cooling circulating liquid.
As shown in fig. 2, in the continuous crystallization system of a water-soluble fertilizer, a level gauge 19 is provided on the crystallizer 2. The real-time liquid level of the materials in the crystallizer 2 is measured on line through a liquid level meter 19, and the feeding and discharging speeds are controlled through an electromagnetic valve, so that the dynamic balance of the flow of the feeding and discharging materials is realized. When in use, the liquid level in the crystallizer 2 is controlled to exceed the height of the upper stirring blade of the stirrer 7, then the stirrer 7 and the cooling circulation pump 18 are started, the flow rate of the cooling circulation liquid is regulated through the frequency converter, the cooling speed of the materials is controlled to be not more than 5 ℃ per hour, and the temperature of the materials in the crystallizer 2 is controlled to be within the range of 20-35 ℃ so as to separate out a large amount of crystals. During the continuous operation of the crystallizer 2, the difference between the temperature of the cooling circulation liquid and the average temperature of the materials in the crystallizer 2 is controlled to be not more than 3 ℃ so as to ensure the uniformity of the crystallization granularity distribution.
In this embodiment, according to the capacity requirement, the flow rate of the slurry discharged from the discharge port at the bottom of the crystallizer 2 is automatically adjusted by the control system, and the discharged slurry is directly sent to the centrifuge 3 for solid-liquid separation, and part of the separated mother liquor is returned to the crystallizer 2 for circulation, and the rest of the mother liquor is returned to the previous process for evaporation concentration.
As shown in fig. 2, in the continuous crystallization system of water-soluble fertilizer, the middle area of the crystallizer 2 is provided with a second temperature probe 15, and the second temperature probe 15 is used for monitoring the temperature in the crystallizer 2 so as to control the crystallization reaction.
As shown in fig. 2, in the continuous crystallization system of water-soluble fertilizer, an ultrasonic probe 20 is connected to the bottom region of the crystallizer 2, and the ultrasonic probe 20 is used for detecting real-time characteristic parameter information of the crystal state in the crystallizer 2.
A specific continuous crystallization method of the water-soluble fertilizer is provided below.
Step one, the density is higher than 1.50g/cm 3 The calcium nitrate concentrate, i.e. the high temperature crystallization stock solution, is placed in a mixer 1.
Step two, mother liquor generated after centrifugal separation of the crystal calcium nitrate product is conveyed into a mixer 1 through a mother liquor circulating pump and is continuously mixed with high-temperature crystallization stock solution, and the flow ratio of the high-temperature crystallization stock solution to the mother liquor is controlled to be 4:1. specifically, the ratio of the height Wen Yuanye of the mother liquor entering the mixer 1 to the mother liquor is regulated by an electromagnetic valve arranged on a pipeline, and the temperature and the supersaturation degree of the mixed liquor at the outlet of the mixer 1 are controlled at constant levels through intelligent control.
And thirdly, adding the mixed materials into the crystallizer 2 from a feed inlet at the top of the crystallizer 2, starting a feed pump, simultaneously opening a discharge valve at the bottom of the crystallizer 2, controlling the flow through the opening of an electromagnetic valve, and ensuring that the liquid level in the crystallizer 2 is kept at a constant level. Specifically, the level of the feed liquid in the crystallizer 2 is controlled to exceed the height of the upper stirring blade of the stirrer 7.
Step four, starting the stirrer 7 and the cooling circulating pump 18, and setting the frequency of the motor 5 of the stirrer 7 to 35Hz. The flow rate of the cooling circulating water is regulated by a frequency converter, the cooling speed of the materials is controlled to be not more than 5 ℃ per hour, the temperature of the materials in the crystallizer 2 is reduced to be lower than 35 ℃ after 30 hours, and a large amount of crystals are separated out.
During the continuous operation of the crystallizer 2, the difference between the temperature of the cooling circulation liquid and the average temperature of the materials in the crystallizer 2 is controlled to be not more than 3 ℃.
Step five, according to the capacity requirement, automatically regulating and controlling the flow of slurry discharged from a discharge port at the bottom of the crystallizer 2, directly delivering the discharged slurry into a centrifugal machine 3 for solid-liquid separation, returning part of separated mother liquor to the crystallizer 2 for circulation, and returning the rest mother liquor to the previous working procedure for evaporation concentration.
With the above method, when the frequency converter used for the stirrer 7 was set to 35Hz, the particle size range of the prepared calcium nitrate product was: 15% for the 0.1-0.5mm portion, 43.5% for the 0.5-1.0mm portion, and 41.5% for the 1.0-2.0mm portion.
When the frequency converter used for the stirrer 7 was set to 40Hz, the particle size range of the calcium nitrate product prepared was: the 0.1-0.5mm portion accounts for 16.2%, the 0.5-1.0mm portion accounts for 42.9%, and the 1.0-2.0mm portion accounts for 40.9%.
By adopting the method, 5 tons of tetrahydrate calcium nitrate products are produced per hour, daily yield reaches 120 tons, the maximum output power of the stirring system is 37kW, and the steam consumption of each ton of products is 0.3-0.4 ton.
Comparative example
30 volumes of 2m are adopted 3 The intermittent crystallizer 2 is treated and the crystallization operation of the calcium nitrate solution is carried out, the intermittent crystallizer 2 is cooled by introducing cooling circulating water into a jacket, the structure of a stirrer 7 is a blade type, and the hot concentrated material is cooled from 100 ℃ to 25 ℃ for more than 36 hours. The inner wall is provided with crystal scale, and each batch needs to be cleaned.
The total heat exchange area of the 30 crystallizers 2 is 240m 3 The power consumption of the stirring system is 72kW, and the daily production of the tetra-water calcium nitrate product is only 24 tons, and the steam consumption of each ton of the product is 0.6-0.7 ton. The productivity is 20% of that of the continuous system, the power consumption is about 2 times of that of the continuous crystallization system, and the steam consumption is about 2 times of that of the continuous crystallization system.
The traditional batch crystallizer 2 has long crystallization time, occupies a very large space, takes more than 36 hours, and can not realize continuous production. In addition, the jacket type cooling mode, the water wall causes the phenomenon of material wall hanging, influences the heat transfer efficiency, prolongs the crystallization time and influences the nitrate calcium yield.
According to the comparison analysis, the continuous crystallization system can effectively adjust the size of crystal particles, conveniently adjust the productivity by controlling the cooling water amount or the cooled liquid amount, effectively control the supersaturation degree of the feed by automatically mixing the mother solution and the high-temperature feed, has less nucleation, is beneficial to crystal growth, does not form a wall, greatly improves the productivity and obviously reduces the energy consumption.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.
Claims (10)
1. A continuous crystallization method of a water-soluble fertilizer, which is characterized by comprising the following steps:
continuously conveying the crystallization stock solution into a mixer (1) through a feed pipeline;
continuously conveying part of the mother liquor in the mother liquor tank (4) into the mixer (1) through a circulating pipeline;
mixing the mother solution and the crystallization stock solution in a mixer (1), and adjusting the supersaturation degree of the crystallization stock solution;
delivering the mixed crystallization stock solution and mother solution into a crystallizer (2), and precipitating crystals in the crystallizer (2) by stirring;
the slurry produced after crystallization is conveyed into a centrifuge (3), and the liquid in the slurry is separated out through the centrifuge (3) and conveyed into a mother liquid tank (4).
2. The continuous crystallization method of a water-soluble fertilizer according to claim 1, wherein the supersaturation degree of the mixed solution in the mixer (1) is regulated by controlling the temperature of the mixed solution in the mixer (1) by adjusting the flow ratio of the crystallization stock solution and the circulating mother solution through the supersaturation degree intelligent controller.
3. The continuous crystallization method of a water-soluble fertilizer according to claim 2, wherein the supersaturation degree intelligent controller monitors the flow rate of the crystallization stock solution in the feeding pipeline through a first flow meter (11) on the feeding pipeline and monitors the flow rate of the mother solution in the circulating pipeline through a second flow meter (12) on the circulating pipeline.
4. The continuous crystallization method of a water-soluble fertilizer according to claim 2, wherein the supersaturation degree intelligent controller monitors the temperature of the mixed solution in the mixer (1) through a first temperature probe (14) on the mixer (1).
5. Continuous crystallization method of water-soluble fertilizer according to any one of claims 1-4, characterized in that the mixed liquor in the crystallizer (2) is cooled by circulating heat exchange of the cooling circulation liquor of the inner heat exchanger (16) and the outer crystallizer (2).
6. The continuous crystallization method of water-soluble fertilizer according to claim 5, characterized in that the cooling circulation liquid between the inner heat exchanger (16) and the outer crystallizer (2) is driven by a cooling circulation pump (18), and the cooling circulation pump (18) is controlled by the intelligent controller connected with a frequency converter.
7. Continuous crystallization method of water-soluble fertilizer according to any one of claims 1-4, characterized in that the crystallizer (2) is provided with a level gauge (19), by means of which level gauge (19) the level of the liquid in the crystallizer (2) is monitored.
8. The continuous crystallization method for water-soluble fertilizer according to any one of claims 1-4, wherein a part of mother liquor separated by the centrifuge (3) is returned to a preceding process for evaporation concentration.
9. Continuous crystallization method of water-soluble fertilizer according to any one of claims 1-4, characterized in that the middle area of the crystallizer (2) is provided with a second temperature probe (15), by means of which second temperature probe (15) the liquid temperature inside the crystallizer (2) is monitored.
10. Continuous crystallization method of water-soluble fertilizer according to any one of claims 1-4, characterized in that the bottom area of the crystallizer (2) is connected with an ultrasonic probe (20), and that the real-time characteristic parameter information of the crystal state in the crystallizer (2) is monitored by the ultrasonic probe (20).
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