CN109289235B - Device for evaporative crystallization and crystallization method of vitamin C - Google Patents
Device for evaporative crystallization and crystallization method of vitamin C Download PDFInfo
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- CN109289235B CN109289235B CN201811291596.XA CN201811291596A CN109289235B CN 109289235 B CN109289235 B CN 109289235B CN 201811291596 A CN201811291596 A CN 201811291596A CN 109289235 B CN109289235 B CN 109289235B
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- C07D307/02—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings
- C07D307/34—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members
- C07D307/56—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
- C07D307/62—Three oxygen atoms, e.g. ascorbic acid
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Abstract
The invention provides a device for evaporative crystallization, which comprises an evaporation container and a crystallization container, and further comprises a first circulation unit and a second circulation unit, wherein the first circulation unit comprises a first branch pipe, a first circulation pump and a first circulation inlet pipe which are sequentially connected; the second circulation unit comprises a second branch pipe, a second circulation pump, a heater and a second circulation inlet pipe which are sequentially connected, and the first circulation inlet pipe and the second circulation inlet pipe are connected to the evaporation container. The invention also provides a crystallization method of the vitamin C. The method provides an additional first circulation loop to reintroduce the first fine crystals into the vaporization vessel as nuclei for growing larger second particles and inducing more and more uniform second particles.
Description
Technical Field
The invention relates to the field of chemical process improvement, in particular to a device for evaporative crystallization and a vitamin C crystallization method.
Background
Vitamin C is one of essential vitamins for human bodies, is mainly used for vitamin C deficiency in clinic, is also widely used as food and feed additives, and has large market demand.
Chinese patent CN101397286B discloses a continuous crystallization method of vitamin C, which is characterized in that an ion-exchanged vitamin C aqueous solution is pumped into a primary crystallizer for vacuum evaporation crystallization, then an evaporation concentrated solution of vitamin C generated in the primary crystallizer is continuously introduced into a secondary crystallizer for vacuum cooling crystallization, and after liquid-solid separation, crystal washing and centrifugation are carried out, and then a crude vitamin C crystal is obtained after continuous discharging; and dissolving the crude vitamin C product in purified water, filtering and pumping the solution into a third-stage crystallizer to realize continuous crystallization of the refined vitamin C product, and after liquid-solid separation, washing crystals and centrifuging the crystals to continuously discharge the materials to obtain the refined vitamin C product crystals. The method has a complex process, and although coarse, uniform and regular crystal grains can be obtained, the size of the crystal grains cannot be controlled.
Disclosure of Invention
In view of the above problems, the present invention provides a crystallization method capable of directly obtaining vitamin C with high purity, uniform and regular crystal grains and controllable size, and an apparatus for evaporative crystallization.
The present invention provides an apparatus for evaporative crystallization, comprising:
the evaporation container is used for evaporating the solvent, a flow guide pipe is arranged at the bottom of the evaporation container, and an evaporation gas outlet is also arranged at the top of the evaporation container;
the crystallization container is used for crystallization, the crystallization container is positioned below the evaporation container, the flow guide pipe extends into the crystallization container and is communicated with the crystallization container, and a crystal slurry discharge port is arranged at the bottom of the crystallization container; wherein the content of the first and second substances,
a circulating material outlet pipe is connected to the side wall of the crystallization container and is branched into a first branch pipe and a second branch pipe;
the device for evaporative crystallization further comprises a first circulating unit and a second circulating unit, wherein the first circulating unit comprises a first branch pipe, a first circulating pump and a first circulating inlet pipe, and the first branch pipe is connected with the first circulating pump; the first circulation inlet pipe is provided with a first end and a second end, the first end of the first circulation inlet pipe is connected with the first circulation pump, and the second end of the first circulation inlet pipe is connected with the evaporation container;
the second circulation unit comprises a second branch pipe, a second circulation pump, a heater and a second circulation inlet pipe, the second branch pipe is sequentially connected with the second circulation pump and the heater, the second circulation inlet pipe is provided with a third end and a fourth end, the third end of the second circulation inlet pipe is connected with the heater, and the fourth end of the second circulation inlet pipe is connected with the evaporation container;
the device for evaporative crystallization further comprises a raw material liquid inlet pipe, wherein the raw material liquid inlet pipe is connected to the second branch pipe and is used for pumping the raw material liquid to the heater through a second circulating pump.
The invention also provides a crystallization method of vitamin C, which comprises the following steps:
(1) providing the above apparatus for evaporative crystallization;
(2) continuously injecting a raw material liquid into the raw material liquid inlet pipe, wherein the mass fraction of vitamin C in the raw material liquid is 10-45%, and the temperature of the raw material liquid is 25-80 ℃;
(3) and (3) evaporation: the raw material liquid enters the evaporation container through a second branch pipe, a second circulating pump, a heater and a second circulating inlet pipe, the vacuum degree of the evaporation container is controlled to be 0.09 MPa-0.097 MPa, and a solvent in the raw material liquid is evaporated to obtain an evaporation treatment liquid;
(4) and (3) crystallization: the evaporation treatment liquid enters a crystallization container through the flow guide pipe, and crystallization is carried out in the crystallization container to obtain crystallization particles and mother liquid, wherein the crystallization particles comprise first particles with larger particle size and fine crystal particles with smaller particle size;
(5) shunting: when the overall height of the crystallization particles and the mother liquor reaches or exceeds the circulating material outlet pipe, the fine crystal particles and the mother liquor enter the circulating material outlet pipe and are branched, wherein the mother liquor is branched into a first mother liquor and a second mother liquor, the fine crystal particles are branched into a first fine crystal and a second fine crystal, the first fine crystal and the first mother liquor flow into a first branch pipe, the second fine crystal and the second mother liquor flow into a second branch pipe, and the first particles are settled at the bottom of a crystallization container;
(6) the second fine crystals and the second mother liquor flowing into the second branch pipe continue to carry out crystallization in the next period, namely evaporation in the step (3), crystallization in the step (4) and flow division in the step (5);
(7) the first fine crystals and the first mother liquor flowing into the first branch pipe enter the evaporation container through the first circulating pump and the first circulating inlet pipe, and the next period of crystallization, namely the evaporation in the step (3), the crystallization in the step (4) and the diversion in the step (5) are carried out continuously, wherein the first fine crystals are used as crystal nuclei for inducing to obtain second particles with larger particle sizes and are settled to the bottom of the crystallization container;
(8) and (3) leading out the crystal mush containing the first particles and the second particles through a crystal mush discharge port to obtain a vitamin C finished product.
The device for evaporative crystallization has the following advantages:
because of the action of multi-strand acting force (fluid acting force from the evaporation container, acting force brought by discharging, acting force brought by the first circulating pump and the second circulating pump), the crystallization liquid in the crystallization container is in a turbulent flow state, the occurrence of crystal agglomeration can be effectively avoided, and the size of precipitated crystal particles can be controlled; meanwhile, the turbulent flow state further promotes the separation of large and small crystals, and the fine crystal grains in the crystals are circularly led into the heater and the evaporation container under the action of the first circulating pump and the second circulating pump. The first fine crystals circulated directly into the evaporation vessel serve as nuclei for recrystallization in the next cycle, so that the second particles are precipitated more rapidly and are formed into second particles of more uniform size.
The second branch pipe is internally provided with a heater which can give heat to the raw material liquid or the second mother liquid conveyed by the second circulation unit so as to promote the raw material liquid or the second mother liquid to evaporate part of the solvent in the evaporation container, and the crystallization of the raw material liquid or the second mother liquid in the crystallization container is more facilitated. The device can realize continuous formation of vitamin C finished products, has high crystallization efficiency and is suitable for industrial production.
Further, when the crystallization container is internally provided with the rectification classifier, the rectification classifier can comb disordered flow field distribution in the crystallization container (without the rectification classifier), so that the flow path lengths of liquid flows below the rectification classifier tend to be consistent, the flow velocities of all liquid flows tend to be consistent, the flow field distribution is regular and ordered, and more uniform precipitation of crystal particles is promoted. Meanwhile, a flow speed difference is formed between the inside of the passage of the rectifying classifier and the lower part of the rectifying classifier, and because the lower flow speed below the rectifying classifier is powerless to continuously entrain the larger first particles, the larger first particles are precipitated in the entrainment process of the low-flow-speed fluid below the rectifying classifier, and the fine particles entrained to the vicinity of the passage of the rectifying classifier by the liquid flow below the rectifying classifier are entrained by the high-flow-speed liquid flow in the passage of the rectifying classifier, are circularly guided into the heater to be reheated and dissolved, and are circularly guided into the evaporation container to be used as crystal nuclei. The whole process can achieve the effects of screening and separating crystallized particles by adjusting the aperture ratio of the channel and the size ratio of the channel, so that the first particles and the second particles with more uniform and controllable particle sizes are finally obtained.
The crystallization method of vitamin C has the following advantages:
crystallizing the raw material liquid to obtain vitamin C crystal particles, shunting fine crystal particles contained in the vitamin C crystal particles, directly reintroducing first fine crystals into the evaporation container and allowing the first fine crystals to enter the crystallization container along with the evaporation treatment liquid to serve as crystal nuclei for crystallization in the next period, and finally slowly growing the crystal nuclei to obtain second particles with target sizes and inducing more second particles to be separated out more quickly. That is, the method provides an additional first circulation loop to reintroduce the first fine crystals into the evaporation vessel as crystal nuclei, and finally obtains more second particles having a more uniform particle size distribution. The crystallization yield of the method reaches more than 90 percent, the HPLC purity is more than 99 percent, the obtained product has smooth crystal face, good fluidity and uniform particle size, and the particle size of more than 90 percent of crystal grains is distributed between 40 meshes and 100 meshes.
Furthermore, when the rectifying classifier is arranged in the crystallization container, the rectifying classifier can comb out disordered flow field distribution in the crystallization container (without the rectifying classifier), so that the flow path lengths of liquid flows below the rectifying classifier tend to be consistent, the flow velocities of all liquid flows tend to be consistent, the flow field distribution is regular and ordered, and more uniform precipitation of crystal particles is promoted. Meanwhile, a flow speed difference is formed between the inside of the passage of the rectifying classifier and the lower part of the rectifying classifier, and because the lower flow speed below the rectifying classifier is powerless to continuously entrain the larger first particles, the larger first particles are precipitated in the entrainment process of the low-flow-speed fluid below the rectifying classifier, and the fine particles entrained to the vicinity of the passage of the rectifying classifier by the liquid flow below the rectifying classifier are entrained by the high-flow-speed liquid flow in the passage of the rectifying classifier, are circularly guided into the heater to be reheated and dissolved, and are circularly guided into the evaporation container to be used as crystal nuclei. The whole process can achieve the functions of screening and separating crystallized particles by adjusting the aperture ratio of the channel and the size ratio of the channel, so that a product with more uniform and controllable particle size is finally obtained.
Further, the ratio of the evaporation speed of the solvent in the raw material liquid to the feeding speed of the raw material liquid is set to be 0.4-0.8, and the ratio of the discharging speed of the crystal slurry to the feeding speed of the raw material liquid is set to be 0.1-0.9, so that the supersaturation degree of the mother liquid is maintained, and the crystallization process can be continuous.
Further, by setting the ratio of the flow rate of the first stream to the flow rate of the second stream to 1: 100-10: 1, products with uniform particle size can be obtained, and the method can also be used for large-scale industrial production.
Drawings
FIG. 1 is a schematic diagram showing the structure and flow of an apparatus for evaporative crystallization according to embodiment 1 of the present invention.
FIG. 2 is a schematic diagram showing the structure and flow of an apparatus for evaporative crystallization according to embodiment 2 of the present invention.
FIG. 3 is a schematic view of a rectifying classifier in the apparatus for evaporative crystallization of FIG. 2.
Wherein, 1, raw material liquid enters a pipe; 2a, a first branch pipe; 2b, second branch pipes; 3. a second circulation pump; 4. a heater; 5. a second circulation inlet pipe; 6. an evaporation vessel; 7. a flow guide pipe; 8. a crystallization vessel; 9. a defoaming and defoaming device; 10. an evaporation gas outlet; 11. a balance tube; 12. a circulating material outlet pipe; 13. a first circulation pump; 14. a first circulation inlet pipe; 15. discharging the crystal slurry; 16. a centrifuge; 17. a rectification classifier; 18. a channel.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it should be apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.
Referring to fig. 1, an apparatus for evaporative crystallization is provided in embodiment 1 of the present invention. The device for evaporative crystallization comprises an evaporation container 6, a crystallization container 8, the crystallization container 8 is located below the evaporation container 6, the evaporation container 6 is used for evaporating a solvent, the crystallization container 8 is used for crystallization, an evaporation gas outlet 10 is arranged at the top of the evaporation container 6, a flow guide pipe 7 is arranged at the bottom of the evaporation container 6, the flow guide pipe 7 extends into the crystallization container 8 and is communicated with the crystallization container 8, a circulating material outlet pipe 12 is connected to the side wall of the crystallization container 8, and the circulating material outlet pipe 12 is branched into a first branch pipe 2a and a second branch pipe 2 b.
The evaporator for evaporative crystallization further comprises a first circulation unit and a second circulation unit, wherein the first circulation unit comprises a first branch pipe 2a, a first circulation pump 13 and a first circulation inlet pipe 14, the first branch pipe 2a is connected with the first circulation pump 13, the first circulation inlet pipe 14 is provided with a first end and a second end, the first end of the first circulation inlet pipe 14 is connected with the first circulation pump 13, and the second end of the first circulation inlet pipe 14 is connected with the evaporation container 6.
The second circulation unit includes that the second divides pipe 2b, second circulating pump 3, heater 4 and second circulation to advance pipe 5, and second divides pipe 2b to be connected with second circulating pump 3, heater 4 in proper order, and the second circulation advances pipe 5 and has third end and fourth end, the second circulation advance the third end of pipe 5 with heater 4 links to each other, and the fourth end that the pipe 5 was advanced in the second circulation is connected to evaporating vessel 6.
The apparatus for evaporative crystallization further comprises a raw material liquid inlet pipe 1, and the raw material liquid inlet pipe 1 is connected to the second branch pipe 2b and is used for sending the raw material liquid to the heater 4 by the second circulation pump 3.
There are two circulation loops outside the crystallization vessel 8 and the evaporation vessel 6. The first circulation loop (corresponding to the first circulation unit) is: a crystallization container 8, a circulating material outlet pipe 12, a first branch pipe 2a, a first circulating pump 13, a first circulating inlet pipe 14 and an evaporation container 6; the second circulation loop (corresponding to the second circulation unit) is: crystallization container 8, circulating material outlet pipe 12, second branch pipe 2b, second circulating pump 3, heater 4, second circulation inlet pipe 5 and evaporation container 6. The second branch pipe 2b also serves to continuously introduce the raw material liquid into the second circulation circuit by being connected to the raw material liquid inlet pipe 1.
The first circulation loop is used to introduce part of the mother liquor (defined as the first mother liquor) in the crystallization vessel 8 and part of the fine crystal grains obtained by crystallization (defined as the first fine crystals) directly to the evaporation vessel 6, which serve as crystallization nuclei for the next cycle, thereby inducing more uniform crystallization grains. It should be noted that the first fine crystals continue to grow to produce larger and more uniform second grains, and that the re-entry of the first fine crystals into the crystallization vessel 8 also induces the formation of more second grains in an orderly manner, i.e. the effect of the first circulation loop is divided into two aspects: one is to allow a greater number of second particles to form; secondly, the fine crystal grains are grown into uniform second grains.
The second circulation loop is used for feeding another part of mother liquor (defined as second mother liquor) in the crystallization vessel 8 and another part of fine crystal grains (defined as second fine crystals) obtained by crystallization into the evaporation vessel 6 by the action of the heater 4, and the solvent is evaporated and then fed into the crystallization vessel 8 for crystallization in the next cycle.
The evaporation vessel 6 usually needs no additional heating, and the temperature of the raw material liquid or the second mother liquid flowing in from the second circulation inlet pipe 5 rises after being heated by the heater 4, so that the raw material liquid or the second mother liquid can evaporate part of the solvent in the evaporation vessel 6. In order to avoid the yield loss caused by the entrainment of part of the product by the foam generated in the solvent evaporation process, a defoaming and defoaming device 9 is arranged in the evaporation container 6 near the evaporation gas outlet 10, and the defoaming and defoaming device 9 can be a screen structure or other types of defoaming and defoaming devices.
The side wall of the evaporation container 6 and the side wall of the crystallization container 8 are also provided with balance pipes 11, and the balance pipes 11 are communicated with the evaporation container 6 and the crystallization container 8.
And a crystal slurry discharge port 15 is arranged at the bottom of the crystallization container 8.
Referring to fig. 2, an apparatus for evaporative crystallization is provided in embodiment 2 of the present invention. The apparatus for evaporative crystallization has substantially the same structure as that of the apparatus for evaporative crystallization of example 1 except that: a rectifying and classifying device 17 is provided in the crystallization vessel 8. Referring to fig. 3, the rectifier classifier 17 includes a plurality of channels 18. The role of the rectifying classifier 17 is to obtain more uniform crystalline particles.
The dimensions of the lower end of the channel 18 are greater than the dimensions of the upper end of the channel 18, which is a design goal in two respects: (1) the occurrence of the phenomenon of particle back mixing is prevented; (2) the possibility of clogging the channels 18 is avoided. The axial cross-section of the channel 18 may be, but is not limited to, trapezoidal, bowl-shaped, drop-shaped.
The ratio of the size of the lower end of the channel 18 to the size of the upper end of the channel 18 is 1.1:1 to 10:1, and preferably, the ratio of the size of the lower end of the channel 18 to the size of the upper end of the channel 18 is 1.5:1 to 5: 1.
The upper end of the channel 18 has a dimension of 3 mm to 100 mm, preferably 5 mm to 50 mm.
The open area ratio (i.e., the sum of the areas of the upper ends of the channels as a percentage of the area of the upper surface of the rectifying classifier) of the plurality of channels 18 is 5% to 50%, preferably 10% to 30%.
The device for evaporative crystallization has the following advantages:
the evaporation container 6 is used for evaporating the solvent in the raw material liquid, the crystallization container 8 is used for crystallization, and the circulating material outlet pipe 12 is branched into the first branch pipe 2a and the second branch pipe 2b, the first branch pipe 2a is used for guiding first fine grains formed by crystallization of the raw material liquid into the evaporation container 6 again, the first fine grains can be used as crystal nuclei for crystallization in the next period, so that second grains are grown, and more uniform second grains are induced to be formed; the second branch pipe 2b is provided with a heater 4 for giving heat to the raw material liquid or the second mother liquid to partially evaporate the solvent in the evaporation vessel 6, which is more advantageous for the crystallization of the raw material liquid or the second mother liquid in the crystallization vessel 8.
The invention also provides a crystallization method of the vitamin C. The crystallization method comprises the following steps:
(1) providing a device for evaporative crystallization;
(2) continuously injecting a raw material liquid into the raw material liquid inlet pipe 1, wherein the mass fraction of vitamin C in the raw material liquid is 10-45%, and the temperature of the raw material liquid is 25-80 ℃;
(3) and (3) evaporation: the raw material liquid enters the evaporation container 6 through a second branch pipe 2b, a second circulating pump 3, a heater 4 and a second circulating inlet pipe 5, the vacuum degree of the evaporation container is controlled to be 0.09 MPa-0.097 MPa, and a solvent in the raw material liquid is evaporated to obtain an evaporation treatment liquid;
(4) and (3) crystallization: the evaporation treatment liquid enters a crystallization container 8 through the draft tube 7, and crystallization is carried out in the crystallization container 8 to obtain crystallization particles and mother liquid, wherein the crystallization particles comprise first particles with larger particle size and fine crystal particles with smaller particle size;
(5) shunting: when the overall height of the crystallization particles and the mother liquor reaches or exceeds the circulating material outlet pipe 12, the fine crystal particles and the mother liquor enter the circulating material outlet pipe 12 and are branched, wherein the mother liquor is branched into a first mother liquor and a second mother liquor, the fine crystal particles are branched into a first fine crystal and a second fine crystal, the first fine crystal and the first mother liquor flow into a first branch pipe 2a, the second fine crystal and the second mother liquor flow into a second branch pipe 2b, and the first particles are settled at the bottom of the crystallization container;
(6) the second fine crystals and the second mother liquor flowing into the second branch pipe 2b continue to be crystallized in the next period, namely, the evaporation in the step (3), the crystallization in the step (4) and the diversion in the step (5);
(7) the first fine crystals and the first mother liquor flowing into the first branch pipe 2a enter the evaporation container 6 through the first circulating pump 13 and the first circulating inlet pipe 14, and continue to perform the next period of crystallization, namely evaporation in step (3), crystallization in step (4) and diversion in step (5), wherein the first fine crystals are used as crystal nuclei to induce second particles with larger particle size to settle to the bottom of the crystallization container;
(8) and (3) leading out the crystal mush containing the first particles and the second particles through a crystal mush discharge port 15 to obtain a vitamin C finished product.
Wherein, the mass fraction of the vitamin C in the raw material liquid in the step (2) is preferably 15 to 30 percent, and the temperature of the raw material liquid is preferably 30 to 70 ℃.
And (2) injecting the raw material liquid from the raw material liquid inlet pipe 1 to the step (8) of leading out the crystal slurry from the crystal slurry discharge hole 15 for the first time for 0.5-6 hours. The ratio of the evaporation rate of the solvent in the raw material liquid to the feeding rate of the raw material liquid is 0.4-0.8, preferably 0.5-0.7. This is because the first crystallization is performed by injecting more feed solution so that there is enough vitamin C in the crystallization vessel 8 to achieve the proper supersaturation and residence time. The timing of discharging the crystal slurry may be determined based on the solid content of the crystal particles (including the first particles and the second particles) in the crystallization vessel 8. For example, when the solid content is greater than 42%, the discharge port 15 of the slurry may be opened to discharge the slurry. Of course, in the subsequent flow, the raw material liquid is continuously injected from the raw material liquid inlet pipe 1, and the slurry can be continuously obtained at the slurry outlet 15.
Defining the sum of the first fine crystals and the first mother liquor as a first stream and the sum of the second fine crystals and the second mother liquor as a second stream. In the case that the total amount of the mother liquor and the fine crystal grains is constant and the fine crystal grains are uniformly distributed, it can be considered that the ratio of the first fine crystal to the second fine crystal is equal to the ratio of the flow rate of the first stream to the flow rate of the second stream. In the invention, the ratio of the flow rate of the first stream to the flow rate of the second stream is controlled to be 1: 100-10: 1, so that the ratio of the first fine crystals can be controlled, and the ratio of the crystal nuclei circulating back to the evaporation container 6 can be controlled. Preferably, the ratio of the flow rate of the first stream to the flow rate of the second stream is 1: 10-4: 5.
In the evaporation process of the step (3), the temperature of the raw material liquid or the second mother liquid flowing into the second branch pipe 2b is increased to 30 to 90 ℃ after passing through the heater 4. Preferably, the temperature of the raw material liquid or the second mother liquid flowing into the second branch pipe 2b is increased to 40 to 70 ℃ after passing through the heater 4.
During the diversion in the step (5), a rectification classifier 17 can be arranged in the crystallization vessel 8. When the total height of the crystallization particles and the mother liquor reaches or exceeds the position where the circulating material outlet pipe 12 is connected to the crystallization vessel 8, fine crystal particles among the crystallization particles and the mother liquor enter the circulating material outlet pipe 12 through the rectification classifier 17. The role of the rectifying classifier 17 is to make fine-grained particles enter the recycled material outlet pipe 12, while the first larger-grained particles remain in the crystallization vessel 8, and finally to achieve a uniform product grain size. It will be appreciated that the bottom of the crystallization vessel 8 may be provided with a tapered region to facilitate classification of the crystal particles and more convenient discharge.
And (3) the time from the step (2) of injecting the raw material liquid into the raw material liquid inlet pipe to the step (8) of leading out the material of the crystal slurry from the crystal slurry discharge hole for the first time is 1-8 hours. After the first time of discharging the crystal slurry from the crystal slurry discharging port 15, the ratio of the evaporation rate of the solvent in the raw material liquid to the feeding rate of the raw material liquid is adjusted to be small. And (3) adjusting the ratio of the discharging speed of the crystal slurry in the step (8) to the feeding speed of the raw material liquid in the step (2) to be 0.1-0.9. The material residence time can be calculated by dividing the total amount of material in steady state operation of the evaporative crystallization apparatus of the present invention by the discharge rate. Preferably, in order to maintain a proper supersaturation degree and residence time and thus ensure uniform particle size distribution of final crystal particles, the ratio of the discharge speed of the crystal slurry in the step (8) to the feed speed of the raw material liquid in the step (2) is 0.3-0.6.
After the step (8), the slurry containing the first particles and the second particles is discharged through the slurry discharge port 15, centrifuged by the centrifuge 16 to obtain a cake and a mother liquor obtained by centrifugation, and the mother liquor obtained by centrifugation is recovered and circulated to the raw material liquid inlet pipe 1.
The crystallization method of vitamin C has the following advantages:
crystallizing the raw material liquid to obtain vitamin C crystal particles, and by shunting fine crystal particles contained in the vitamin C crystal particles, directly reintroducing the first fine crystals into the evaporation container 6 and introducing the first fine crystals into the crystallization container 8 along with the evaporation treatment liquid to serve as crystal nuclei for crystallization in the next period, and finally slowly growing the crystal nuclei to obtain more second particles with more uniform crystal grains.
The process for the crystallization of vitamin C according to the invention will be further illustrated by the following examples.
The purity range of the crude vitamin C product in the embodiment is selected to be between 90% and 95%.
The data and effects in the embodiments of the present invention do not limit the practical application range of the technology of the present invention.
Example 1
In this example, the crystallization operation was carried out using the apparatus for evaporative crystallization shown in FIG. 1, and specifically, the following steps were carried out:
(1) dissolving a vitamin C crude product with the HPLC purity of 94 percent by using water, decoloring and filtering to obtain a raw material solution of the vitamin C with the mass percentage concentration of 20 percent, wherein the temperature is 40 ℃.
(2) The heater 4 is started, raw material liquid of vitamin C is pumped from the raw material liquid inlet pipe 1 and is conveyed to the heater 4 through the second circulating pump 3, and the temperature of the raw material liquid is raised to 55 ℃. The heated raw material liquid was continuously fed into the evaporation vessel 6 at a rate of 200 kg/h.
(3) Controlling the vacuum degree of the evaporation container 6 to be 0.095MPa, so that the raw material liquid can quickly reach a boiling state after entering the evaporation container 6, the evaporation speed of water is maintained at 140kg/h, a large amount of solvent is volatilized, and the concentrated solution enters the crystallization container 8 through the draft tube 7. When the liquid level in the crystallization container 8 reaches the circulating material outlet pipe 12 and can realize circulating flow, the feeding speed of the raw material liquid is reduced to 140kg/h, the flow rate of the second circulating pump 3 is controlled at 1000kg/h, the flow rate of the first circulating pump 13 is controlled at 258kg/h, the ratio of the flow rate of the first stream to the flow rate of the second stream is controlled at 0.3, and the stability is maintained for 3 hours.
(4) When the solid content of the conical settling zone at the bottom of the crystallization container 8 reaches 57%, a valve of a crystal slurry discharge port 15 at the bottom of the crystallization container 8 is opened, the crystal slurry in the crystallization container 8 enters a continuous centrifuge 16 at a flow rate of 60kg/h for filtration, a filter cake is washed by process water and then continuously discharged, and filtered mother liquor can be circulated to a raw material liquor inlet pipe 1 after concentration and decoloration treatment.
(5) After the discharge of the crystal slurry in the crystallization vessel 8 is started, the feed rate of the raw material liquid is adjusted to 200kg/h, the flow rate of the first circulating pump 13 is controlled to 240kg/h, and the ratio of the flow rate of the first stream to the flow rate of the second stream is controlled to 0.3.
(6) And drying the obtained filter cake to obtain white vitamin C crystal particles, wherein the HPLC purity is 99.6 percent based on the feed amount, the crystallization yield is 91 percent, the 40-mesh passing rate of the vitamin C crystal particles is 100 percent, the 60-mesh passing rate is 59 percent, and the 100-mesh passing rate is 8 percent, and the requirements of CP2015, EP8.0 and USP33 are met.
Example 2
The apparatus for evaporative crystallization used in the method for crystallizing vitamin C used in this example was the apparatus for evaporative crystallization shown in FIG. 2.
(1) Dissolving a vitamin C crude product with the HPLC purity of 94 percent by using water, decoloring and filtering to obtain a raw material solution of the vitamin C with the mass percentage concentration of 20 percent, wherein the temperature is 40 ℃.
(2) The heater 4 is started, raw material liquid of vitamin C is pumped from the raw material liquid inlet pipe 1 and is conveyed to the heater 4 through the second circulating pump 3, and the temperature of the raw material liquid is raised to 55 ℃. The heated raw material liquid was continuously fed into the evaporation vessel 6 at a rate of 200 kg/h. The diameter of the upper end of the channel 18 was 10 mm, the ratio of the diameter of the lower end of the channel 18 to the diameter of the upper end of the channel 18 was 2.7:1, and the open porosity of the channel was 20%.
(3) Controlling the vacuum degree of the evaporation container 6 to be 0.095MPa, so that the raw material liquid can quickly reach a boiling state after entering the evaporation container 6, the evaporation speed of water is maintained at 140kg/h, a large amount of solvent is volatilized, and the concentrated solution enters the crystallization container 8 through the draft tube 7. When the liquid level in the crystallization container 8 reaches the circulating material outlet pipe 12 and can realize circulating flow, the feeding speed of the raw material liquid is reduced to 140kg/h, the flow rate of the second circulating pump 3 is controlled at 1000kg/h, the flow rate of the first circulating pump 13 is controlled at 258kg/h, the ratio of the flow rate of the first stream to the flow rate of the second stream is controlled at 0.3, and the stability is maintained for 3 hours.
(4) When the solid content of the conical settling zone at the bottom of the crystallization container 8 reaches 57%, a valve of a crystal slurry discharge port 15 at the bottom is opened, the crystal slurry in the crystallization container 8 enters a continuous centrifuge 16 at the flow rate of 60kg/h for filtration, a filter cake is washed by process water and then continuously discharged, and filtered mother liquor can be circulated to a raw material liquid inlet pipe 1 after concentration and decoloration treatment.
(5) After the crystal slurry in the crystallizer starts to be discharged, the feeding speed of the raw material liquid is adjusted to 200kg/h, the flow rate of the first circulating pump 13 is controlled to 240kg/h, and the ratio of the flow rate of the first stream to the flow rate of the second stream is controlled to 0.3.
(6) And drying the obtained filter cake to obtain white vitamin C crystal particles, wherein the HPLC purity is 99.5%, and the crystallization yield is 91% in terms of the feed amount, wherein the 40-mesh passing rate of the vitamin C crystal particles is 99%, the 60-mesh passing rate is 44%, and the 100-mesh passing rate is 0.2%, and the requirements of CP2015, EP8.0 and USP33 are met.
Example 3
On the basis of example 2, the ratio of the flow rate of the first stream to the flow rate of the second stream in step (3) was controlled to 344kg/h, the ratio of the flow rate of the first stream to the flow rate of the second stream was controlled to 0.4, and the flow rate of the first circulating pump 13 in step (5) was controlled to 320kg/h, the ratio of the flow rate of the first stream to the flow rate of the second stream was controlled to 0.4; the other conditions were the same as in example 2. And drying the obtained filter cake to obtain white vitamin C crystal particles, wherein the HPLC purity is 99.3%, and the crystal yield is 90.5% in terms of the feed amount, wherein the 40-mesh passing rate, the 60-mesh passing rate and the 100-mesh passing rate of the vitamin C crystal particles are 100%, 81% and 10%.
Example 4
On the basis of example 2, the ratio of the flow rate of the first stream to the flow rate of the second stream in step (3) was controlled to be 172kg/h, the ratio of the flow rate of the first stream to the flow rate of the second stream was controlled to be 0.2, and the flow rate of the first circulating pump 13 in step (5) was controlled to be 160kg/h, and the ratio of the flow rate of the first stream to the flow rate of the second stream was controlled to be 0.2; the other conditions were the same as in example 2. And drying the obtained filter cake to obtain white vitamin C crystal particles, wherein the HPLC purity is 99.7%, and the crystal yield is 91.5% in terms of the feed amount, and the 40-mesh passing rate, the 60-mesh passing rate and the 100-mesh passing rate of the vitamin C crystal particles are respectively 99.5%, 48% and 2%.
Example 5
On the basis of example 2, the ratio of the flow rate of the first stream to the flow rate of the second stream in step (3) was controlled to be 43kg/h, the ratio of the flow rate of the first stream to the flow rate of the second stream was controlled to be 0.05, and the flow rate of the first circulating pump 13 in step (5) was controlled to be 40kg/h, and the ratio of the flow rate of the first stream to the flow rate of the second stream was controlled to be 0.05; the other conditions were the same as in example 2. And drying the obtained filter cake to obtain white vitamin C crystal particles, wherein the HPLC purity is 99.8%, and the crystal yield is 90.9% in terms of the feed amount, wherein the 40-mesh passing rate, the 60-mesh passing rate and the 100-mesh passing rate of the vitamin C crystal particles are 100%, 82% and 16%.
Example 6
On the basis of the example 2, the ratio of the flow rate of the first stream to the flow rate of the second stream in the step (3) of controlling the first circulating pump 13 at 860kg/h, the ratio of the flow rate of the first stream to the flow rate of the second stream in the step (5) of controlling the flow rate of the first circulating pump 13 at 800kg/h, and the ratio of the flow rate of the first stream to the flow rate of the second stream in the step (3) of controlling the flow rate of the first stream to the flow rate of the second stream at 1; the other conditions were the same as in example 2. And drying the obtained filter cake to obtain white vitamin C crystal particles, wherein the HPLC purity is 99.4%, and the crystal yield is 91% in terms of the feed amount, and the 40-mesh passing rate, the 60-mesh passing rate and the 100-mesh passing rate of the vitamin C crystal particles are 100%, 84% and 17%.
Example 7
The apparatus for evaporative crystallization used in the method for crystallizing vitamin C used in this example was the apparatus for evaporative crystallization shown in FIG. 2.
(1) Dissolving a vitamin C crude product with the HPLC purity of 94 percent by using water, decoloring and filtering to obtain a raw material solution of the vitamin C with the mass percentage concentration of 20 percent, wherein the temperature is 60 ℃.
(2) The heater 4 is started, the raw material liquid of the vitamin C is pumped from the raw material liquid inlet pipe 1 and is conveyed to the heater 4 through the second circulating pump 3, and the temperature of the raw material liquid is increased to 66 ℃. The heated raw material liquid was continuously fed into the evaporation vessel 6 at a rate of 250 kg/h. The diameter of the upper end of the channel 18 was 10 mm, the ratio of the diameter of the lower end of the channel 18 to the diameter of the upper end of the channel 18 was 2.7:1, and the open porosity of the channel was 20%.
(3) Controlling the vacuum degree of the evaporation container 6 to be 0.09MPa, so that the raw material liquid is quickly brought to a boiling state after entering the evaporation container 6, the evaporation speed of water is maintained at 150kg/h, a large amount of solvent is volatilized, and the concentrated solution enters the crystallization container 8 through the draft tube 7. When the liquid level in the crystallization container 8 reaches the circulating material outlet pipe 12 and can realize circulating flow, the feeding speed of the raw material liquid is reduced to 150kg/h, the flow rate of the second circulating pump 3 is controlled at 1300kg/h, the flow rate of the first circulating pump 13 is controlled at 230kg/h, the ratio of the flow rate of the first stream to the flow rate of the second stream is controlled at 0.2, and the stability is maintained for 3 hours.
(4) When the solid content of the conical settling zone at the bottom of the crystallization container 8 reaches 42%, a valve of a crystal slurry discharge port 15 at the bottom is opened, the crystal slurry in the crystallization container 8 enters a continuous centrifuge 16 at the flow rate of 100kg/h for filtration, a filter cake is washed by process water and then continuously discharged, and filtered mother liquor can be circulated to a raw material liquid inlet pipe 1 after concentration and decoloration treatment.
(5) After the crystal slurry in the crystallizer starts to be discharged, the feeding speed of the raw material liquid is adjusted to 250kg/h, the flow rate of the first circulating pump 13 is controlled to 210kg/h, and the ratio of the flow rate of the first stream to the flow rate of the second stream is controlled to 0.2.
(6) And drying the obtained filter cake to obtain white vitamin C crystal particles, wherein the HPLC purity is 99.8%, and the crystallization yield is 90.8% in terms of the feed amount, wherein the 40-mesh passing rate of the vitamin C crystal particles is 100%, the 60-mesh passing rate is 40%, and the 100-mesh passing rate is 0.3%, and the requirements of CP2015, EP8.0 and USP33 are met.
Example 8
On the basis of example 7, the diameter of the upper end of the channel 18 in the step (2) is 50 mm, the ratio of the diameter of the lower end of the channel 18 to the diameter of the upper end of the channel 18 is 1.5:1, and the opening rate of the channel is 20%; the other conditions were the same as in example 7. And drying the obtained filter cake to obtain white vitamin C crystal particles, wherein the HPLC purity is 99.3%, and the crystal yield is 90.3% in terms of the feed amount, wherein the 40-mesh passing rate, the 60-mesh passing rate and the 100-mesh passing rate of the vitamin C crystal particles are 100%, 52% and 6%.
Example 9
On the basis of example 7, the diameter of the upper end of the channel 18 in the step (2) is 5 mm, the ratio of the diameter of the lower end of the channel 18 to the diameter of the upper end of the channel 18 is 5:1, and the opening rate of the channel is 20%; the other conditions were the same as in example 7. And drying the obtained filter cake to obtain white vitamin C crystal particles, wherein the HPLC purity is 99.1%, and the crystal yield is 90.1% in terms of the feed amount, wherein the 40-mesh passing rate, the 60-mesh passing rate and the 100-mesh passing rate of the vitamin C crystal particles are 100%, 50% and 5%.
Example 10
On the basis of example 7, the diameter of the upper end of the channel 18 in the step (2) is 50 mm, the ratio of the diameter of the lower end of the channel 18 to the diameter of the upper end of the channel 18 is 1.5:1, and the opening rate of the channel is 40%; the other conditions were the same as in example 7. And drying the obtained filter cake to obtain white vitamin C crystal particles, wherein the HPLC purity is 99.4%, and the crystal yield is 90.4% in terms of the feed amount, wherein the 40-mesh passing rate, the 60-mesh passing rate and the 100-mesh passing rate of the vitamin C crystal particles are 100%, 51% and 8%.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (11)
1. A method for crystallizing vitamin C, comprising the steps of:
(1) there is provided an apparatus for evaporative crystallization, wherein the apparatus for evaporative crystallization comprises:
the evaporation container is used for evaporating the solvent, a flow guide pipe is arranged at the bottom of the evaporation container, and an evaporation gas outlet is also arranged at the top of the evaporation container;
the crystallization container is used for crystallization, the crystallization container is positioned below the evaporation container, the flow guide pipe extends into the crystallization container and is communicated with the crystallization container, and a crystal slurry discharge port is arranged at the bottom of the crystallization container; wherein the content of the first and second substances,
a circulating material outlet pipe is connected to the side wall of the crystallization container and is branched into a first branch pipe and a second branch pipe;
the device for evaporative crystallization further comprises a first circulating unit and a second circulating unit, wherein the first circulating unit comprises a first circulating pump, a first circulating inlet pipe and a first branch pipe, and the first branch pipe is connected with the first circulating pump; the first circulation inlet pipe is provided with a first end and a second end, the first end of the first circulation inlet pipe is connected with the first circulation pump, and the second end of the first circulation inlet pipe is connected with the evaporation container;
the second circulation unit comprises a second circulation pump, a heater, a second circulation inlet pipe and a second branch pipe, the second branch pipe is sequentially connected with the second circulation pump and the heater, the second circulation inlet pipe is provided with a third end and a fourth end, the third end of the second circulation inlet pipe is connected with the heater, and the fourth end of the second circulation inlet pipe is connected with the evaporation container;
the device for evaporative crystallization further comprises a raw material liquid inlet pipe, wherein the raw material liquid inlet pipe is connected to the second branch pipe and is used for pumping the raw material liquid to the heater through a second circulating pump;
(2) continuously injecting a raw material liquid into the raw material liquid inlet pipe, wherein the mass fraction of vitamin C in the raw material liquid is 10-45%, and the temperature of the raw material liquid is 25-80 ℃;
(3) and (3) evaporation: the raw material liquid enters the evaporation container through a second branch pipe, a second circulating pump, a heater and a second circulating inlet pipe, the vacuum degree of the evaporation container is controlled to be 0.09 MPa-0.097 MPa, and a solvent in the raw material liquid is evaporated to obtain an evaporation treatment liquid;
(4) and (3) crystallization: the evaporation treatment liquid enters a crystallization container through the flow guide pipe, and crystallization is carried out in the crystallization container to obtain crystallization particles and mother liquid, wherein the crystallization particles comprise first particles with larger particle size and fine crystal particles with smaller particle size;
(5) shunting: when the overall height of the crystallization particles and the mother liquor reaches or exceeds the circulating material outlet pipe, the fine crystal particles and the mother liquor enter the circulating material outlet pipe and are branched, wherein the mother liquor is branched into a first mother liquor and a second mother liquor, the fine crystal particles are branched into a first fine crystal and a second fine crystal, the first fine crystal and the first mother liquor flow into a first branch pipe, the second fine crystal and the second mother liquor flow into a second branch pipe, and the first particles are settled at the bottom of a crystallization container;
(6) the second fine crystals and the second mother liquor flowing into the second branch pipe continue to carry out crystallization in the next period, namely evaporation in the step (3), crystallization in the step (4) and flow division in the step (5);
(7) the first fine crystals and the first mother liquor flowing into the first branch pipe enter the evaporation container through the first circulating pump and the first circulating inlet pipe, and the next period of crystallization, namely the evaporation in the step (3), the crystallization in the step (4) and the diversion in the step (5) are carried out continuously, wherein the first fine crystals are used as crystal nuclei for inducing to obtain second particles with larger particle sizes and are settled to the bottom of the crystallization container;
(8) and (3) leading out the crystal mush containing the first particles and the second particles through a crystal mush discharge port to obtain a vitamin C finished product.
2. The crystallization method of vitamin C as claimed in claim 1, wherein a rectifying classifier is further provided in the crystallization vessel, the rectifying classifier comprises a plurality of channels, and the ratio of the size of the lower end of the channel to the size of the upper end of the channel is 1.1:1 to 10: 1.
3. The crystallization method of vitamin C according to claim 2, wherein the size of the upper end of the channel is 3 mm to 100 mm.
4. The crystallization method of vitamin C according to claim 2, wherein the open porosity of the channel is 5% to 50%.
5. The method for crystallizing vitamin C as claimed in claim 1, wherein a defoaming and defoaming device is provided inside the evaporation vessel near the evaporation gas outlet.
6. The crystallization method of vitamin C according to claim 1, wherein the side wall of the evaporation vessel and the side wall of the crystallization vessel are further provided with a balance pipe, and the balance pipe communicates the evaporation vessel and the crystallization vessel.
7. The process for crystallizing vitamin C according to claim 1, wherein in the step (2), the ratio of the evaporation rate of the solvent in the raw material liquid to the feed rate of the raw material liquid is 0.4 to 0.8,
the ratio of the discharging speed of the crystal slurry in the step (8) to the feeding speed of the raw material liquid in the step (2) is 0.1-0.9.
8. The method for crystallizing vitamin C as claimed in claim 1, wherein a rectifying classifier is further provided in said crystallization vessel during the diversion in step (5), and when the total height of the crystallized particles and the mother liquor reaches or exceeds the position where said circulating material outlet pipe is connected to said crystallization vessel, said fine-grained particles and the mother liquor are introduced into said circulating material outlet pipe through said rectifying classifier.
9. The crystallization method of vitamin C as claimed in claim 1, wherein the temperature of the raw material liquid or the second mother liquid flowing into the second branch pipe is increased to 30 to 90 ℃ after passing through the heater during the evaporation of the step (3).
10. The crystallization method of vitamin C according to claim 1, wherein the first fine crystals and the first mother liquor flowing into the first branch pipe in the step (5) are defined as a first stream, the second fine crystals and the second mother liquor flowing into the second branch pipe are defined as a second stream, and the ratio of the flow rate of the first stream to the flow rate of the second stream is 1: 100-10: 1.
11. The method for crystallizing vitamin C according to claim 1, wherein after the step (8), the slurry containing the first granules and the second granules is discharged through a slurry outlet, a cake is obtained by centrifugation, a mother liquor obtained by centrifugation is obtained, and the mother liquor obtained by centrifugation is recovered and circulated to a raw material liquid inlet pipe.
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| CN109289233B (en) * | 2018-10-31 | 2020-12-15 | 浙江新和成股份有限公司 | Device for evaporative crystallization and method for crystallizing methionine |
| CN109513232B (en) * | 2018-10-31 | 2020-12-15 | 浙江新和成股份有限公司 | Device for evaporative crystallization and crystallization method of ethyl maltol |
| CN109453539B (en) * | 2018-10-31 | 2020-12-15 | 浙江新和成股份有限公司 | Device for evaporative crystallization and method for crystallizing sucralose |
| CN109289234B (en) * | 2018-10-31 | 2020-12-15 | 浙江新和成股份有限公司 | Device for evaporative crystallization and crystallization method of vitamin B6 |
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