CN113817001B

CN113817001B - Production process of lactitol crystal

Info

Publication number: CN113817001B
Application number: CN202111133935.3A
Authority: CN
Inventors: 何定兵
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-10-28
Filing date: 2020-10-28
Publication date: 2023-11-07
Anticipated expiration: 2040-10-28
Also published as: CN113817001A; CN112250722A; CN112250722B

Abstract

The invention discloses a production process of lactitol crystal, which comprises the following steps: (1) Carrying out hydrogenation reaction on lactose aqueous solution under the action of a catalyst to obtain lactose hydrogenated liquid; (2) Removing the catalyst in the lactose hydrogenated liquid to obtain a lactitol solution; then carrying out ion exchange, concentration and crystallization to obtain anhydrous lactitol crystal or lactitol monohydrate crystal. The process of the invention has the advantages that the yield of lactitol for the first crystallization of lactose raw material reaches 50.0% -65%, and meanwhile, the process is simplified, the production operation is easy, and the production cost is lower.

Description

Production process of lactitol crystal

Technical Field

The invention belongs to the field of chemical industry, and particularly relates to a lactitol production process crystal.

Background

Lactitol α (actitol), also known as lactitol, chemical name 4-0- β -D-galactopyranose-D-sorbitol. Crystalline lactitol is mainly in three forms: anhydrous lactitol, lactitol monohydrate, and lactitol dihydrate. The main uses of lactitol are as follows: (1) superior healthy sweeteners and prebiotics. The lactitol is mainly produced by taking lactose in milk as a raw material, is natural and healthy, has sweet taste similar to sucrose, has sweetness of 30% -40% of that of sucrose, is fresh and clear, has no peculiar smell, has non-caries property, and can be used for aspects of candy, chocolate, jam, jelly, table sweetening and the like. In addition, the lactitol can efficiently proliferate intestinal probiotics, has the effect of regulating intestinal health, and can be used for health products, medical auxiliary materials and the like. And the food does not increase hyperglycemia after being eaten, and can be used as a sweetener for diabetics. (2) Lactitol has low hygroscopicity, high water retention and good processing applicability of baked products. (3) The lactitol has good emulsifying property and thickening property, and can be used for dairy products, drinks, daily chemicals and the like.

Currently, there are related processes for preparing lactitol, but there are still certain problems. For example, chinese patent application CN103980329a discloses a process for preparing lactitol crystals, which comprises preparing lactose into solution, adjusting ph 7.0-8.0, adding raney nickel catalyst with solid mass of 5-10%, hydrogenation reaction for 2.0-3.0 h to obtain hydrogenation solution, decolorizing with activated carbon at the maximum temperature of 125-140 ℃, ion-exchanging with full bed to obtain purified solution, concentrating, crystallizing, centrifuging and oven drying to obtain crystalline lactitol. The crystallization mother liquor is purified by sequential simulated moving bed chromatography and then is crystallized continuously. The primary crystallization yield of lactitol is 42.5-48%, and secondary crystallization is required to be purified by simulated moving bed chromatography, so that the process is complex. The Chinese patent application CN 110818752A discloses a production process of lactitol, which comprises the steps of adding lactose into deionized water to prepare a lactose solution, adjusting pH, adding a quantitative catalyst, carrying out hydrogenation reaction at high temperature and high pressure to obtain a lactose hydrogenated liquid, removing the catalyst to obtain a lactitol solution, purifying, concentrating, crystallizing and drying the lactitol solution to obtain lactitol crystals, wherein the process has the following problems: (1) The crystallization operation modes of each mother solution of lactitol hydrogenation solution, primary mother solution, secondary mother solution, tertiary mother solution and quaternary mother solution are different, the operation is not uniform, and certain trouble is brought to operators; (2) The lactitol content is required to be low, and the yield is difficult to improve; (3) The crystallization process is mainly a cooling single-factor crystallization process, and is relatively backward compared with a multi-factor crystallization process.

Disclosure of Invention

The invention aims to: the invention aims to solve the technical problem of providing a production process of lactitol crystals aiming at the defects of the prior art.

In order to solve the technical problems, the invention discloses a production process of lactitol crystals, which comprises the following steps:

(1) Carrying out hydrogenation reaction on the aqueous solution of lactose under the action of high temperature, high pressure and a catalyst to obtain lactose hydrogenated liquid;

(2) Removing a catalyst in the lactose hydrogenated liquid after the lactose hydrogenated liquid is cooled to obtain a lactitol solution; and then carrying out ion exchange (purification), concentration, crystallization and drying to obtain anhydrous lactitol crystal or lactitol monohydrate crystal.

In the step (2), the crystallization is evaporation crystallization under the negative pressure of not higher than-0.08 MPa at the temperature of 78-98 ℃ and at the speed of 60-90 rpm.

In the step (1), the mass percentage of lactose in the lactose aqueous solution is 35% -60%, the purity of lactose is more than 98%, the purity refers to the mass percentage content of solid matters, and the pH of the lactose aqueous solution is 7.5-8.0.

Preferably, the substances for adjusting the pH include, but are not limited to, sodium hydroxide, sodium carbonate, sodium bicarbonate, calcium bicarbonate and the like, and the hydrogenation reaction is facilitated after the pH is adjusted; further preferably, the pH adjusting substance is sodium carbonate to further stabilize the pH.

In the step (1), the catalyst is a hydrogenation catalyst, and the dosage of the catalyst is 2.0-6.0% w/w of lactose.

Wherein the hydrogenation catalyst comprises, but is not limited to, ruthenium carbon catalyst and Raney nickel catalyst.

In the step (1), the hydrogenation reaction is carried out at 100-120 ℃ and at 8.0-12.0 MPa.

In the step (1), the time of the hydrogenation reaction is 1.0-3.0 h.

In the step (1), preferably, after the hydrogenation reaction is finished, the lactose hydrogenated liquid is cooled by a pure water (RO water) tank (the inside is in a coil pipe structure), and the RO water is heated to more than 70 ℃, so that the heated RO water can be directly used as a solvent for the sugar in the next reaction kettle to carry out the hydrogenation reaction; meanwhile, RO water is added into the purified water tank to be filled. By the method, cooling of lactose hydrogenated liquid can be accelerated, and meanwhile, heat is supplied to the water for heating, so that energy is saved, lactose can be converted, the lactose conversion speed and the refraction degree are improved, namely, the mass percentage of lactose in the solution is improved, and energy is effectively utilized.

In the step (2), the method for removing the catalyst in the lactose hydrogenated liquid comprises, but is not limited to, sedimentation and filtration; preferably, after the catalyst in the lactose hydrogenated liquid is settled, the temperature is reduced to 75-79 ℃, activated carbon is added, and then a plate-and-frame filter press is used for removing the catalyst in the lactose hydrogenated liquid; wherein the dosage of the activated carbon is 0.2-1.0 kg/m ³ Lactose hydrogenated liquid.

In the step (2), the conductivity of the lactitol solution is less than or equal to 200 mu s/cm, and the transmittance is more than or equal to 95%; in the lactitol solution, the mass percentage of lactitol is more than or equal to 98.0 percent, and the residual lactose content is less than or equal to 0.02 percent w/w.

In the step (2), the process of ion exchange (purification) is to sequentially pass the lactitol solution through the functions of cation exchange resin-anion exchange resin-cation exchange resin-anion exchange resin to obtain the lactitol solution after ion exchange purification.

Wherein the cation exchange resin is D001-F macroporous cation resin, and the anion exchange resin is D304-F macroporous cation resin.

Wherein the flow rate of the lactitol solution is 2-5 BV/h.

Preferably, a pleated membrane filter is installed 10 μm before the ion exchange column.

Further preferably, the lactitol solution is subjected to activated carbon incubation and then filtered to obtain a decolorized lactitol solution prior to the ion exchange.

Wherein the purity of lactitol in the purified lactitol solution is more than or equal to 98%, the conductivity is less than or equal to 20 mu s/cm, and the transmittance is more than or equal to 99%.

In the step (2), the concentration is to concentrate the lactitol solution after the ion exchange to 68-72% of the lactitol by mass percent.

Preferably, the concentration is performed by using a four-effect evaporator or a three-effect evaporator.

In the step (2), the crystallization comprises the following steps:

(i) Placing the concentrated lactitol solution in a crystallization kettle, evaporating water under the stirring condition at 75-78 ℃ and negative pressure not higher than-0.08 MPa, generating crystal nucleus, and immediately adding crystal seeds; wherein, when seed crystal is added, the temperature is more than or equal to 78 ℃; preferably 78-98 ℃;

(ii) Controlling the temperature of the crystallization kettle to be 78-98 ℃, adding the concentrated lactitol solution into the crystallization kettle, and stopping adding until the total volume of the mixed solution in the crystallization kettle reaches 75-80% of the volume of the crystallization kettle;

(iii) Placing the material obtained in the step (ii) into a crystallization tank with the temperature of 78-98 ℃, and directly centrifuging under the stirring condition, or preserving heat at the temperature of 78-98 ℃ and centrifuging, or cooling the crystallization tank to the temperature of more than 78 ℃ and centrifuging again; and collecting the centrifuged crystals, and drying to obtain the anhydrous lactitol crystals.

In step (i), the crystallization kettle comprises, but is not limited to, a vertical crystallization kettle.

In the step (i), the seed crystal is anhydrous lactitol powder with 200 meshes, and the dosage of the seed crystal is 0.002% -0.004% of the solid mass of the whole solution.

Wherein the solid is dry matter after the water content of the solid-liquid mixture in the crystallization kettle is removed after the crystallization kettle is finished. The calculation method is as follows: the total material volume in the crystallization kettle is multiplied by the density of the evaporated material and the refraction of the evaporated material.

In the step (ii), the adding rate of the concentrated lactitol solution is 0.02-0.05 BV/h; wherein V is the meaning of doubling the total volume B of the crystallization kettle.

In the step (ii), the temperature is 78-98 ℃ and means that the temperature is raised from the initial temperature (the temperature when the seed crystal is added) to the final temperature, namely the temperature is controlled from 78 ℃ to 98 ℃ in the whole crystallization process, or the temperature is raised for evaporative crystallization, or the temperature is lowered for evaporative crystallization, and the temperature in a crystallization kettle and a crystallization tank is not lower than 78 ℃.

In the step (iii), the cooling rate is 0.5-3 ℃/h.

In step (2), the crystallization preferably includes the following steps:

(i) Placing the concentrated lactitol solution in a crystallization kettle, starting a steam valve and stirring, stirring at a rotating speed of 60-90 rpm, and heating to above 75 ℃; then, starting a vacuum valve and a vacuum pump, evaporating water under negative pressure not higher than-0.08 MPa, and immediately adding seed crystal after generating crystal nucleus; preferably, when evaporating until the refraction of the material is 85% -87%, observing the inside of the crystallization kettle by using a sugar boiling microscope, and immediately adding seed crystal after generating crystal nucleus; wherein, when seed crystal is added, the temperature is more than or equal to 78 ℃; preferably 78-98 ℃;

(ii) Continuing negative pressure and vacuum evaporation, the grains are more and bigger; meanwhile, controlling the temperature of the crystallization kettle to be 78-98 ℃, adding concentrated lactitol solution to the crystallization kettle in batches after adding seed crystals for 0.5h, and stopping adding until the total volume of mixed solution in the crystallization kettle reaches 75-80% of the volume of the crystallization kettle (within 8-12 h); simultaneously, stopping the vacuum pump, closing the steam valve, closing the vacuum valve, breaking vacuum, opening the discharge valve, and stopping stirring after all materials are taken out;

(iii) Preheating a crystallization tank to 78-98 ℃ (the temperature is consistent with that of the vertical crystallization kettle at the moment), discharging the material obtained in the step (ii) into the crystallization tank, and stirring at 2-6 rpm; directly centrifuging, or centrifuging after heat preservation, or opening a cooling water valve to start cooling, controlling the cooling speed to be 0.5-3 ℃/h, cooling to be more than 78 ℃, and centrifuging after cooling down water when the temperature is at the lowest 78 ℃; obtaining a first crystallization mother liquor and crystals; collecting the first crystallization mother liquor to a mother liquor collecting tank, collecting crystals, and drying to obtain anhydrous lactitol crystals; in the step, the temperature in the crystallization tank is not lower than 80 ℃ from the beginning of centrifugation to the end of centrifugation.

Wherein step (iii) is replaced with: placing the material obtained in the step (ii) into a crystallization tank at 78-98 ℃, cooling the crystallization tank to more than 45 ℃ under the stirring condition, centrifuging at the temperature of less than 78 ℃, collecting the centrifuged crystal, and drying the crystal to obtain the lactitol monohydrate crystal.

Wherein the cooling rate is 0.5-3 ℃/h.

Preferably, step (iii) is replaced by: placing the material obtained in the step (ii) into a horizontal crystallization tank, opening a cooling water valve at the rotating speed of 2-6 rpm, cooling at the speed of 0.5-3 ℃/h, wherein the final temperature after cooling is more than 45 ℃ and less than 78 ℃, and centrifuging to obtain a first crystallization mother liquor and crystals; the first mother solution flows into a mother solution tank, the crystals are collected and dried, and then the lactitol monohydrate crystals are obtained; if the final temperature after cooling is lower than 45 ℃, the lactose dihydrate is obtained.

In the step (2), when the product is anhydrous lactitol, drying the product at 80-100 ℃; when the product is lactitol monohydrate, the drying is carried out at 50-90 DEG C

The water content of the anhydrous lactitol prepared by the process is 0.01-0.3%, and the melting point is 146-147 ℃; the water content of the lactitol monohydrate crystal is 0.301-10.5%, and the melting point is 94-97 ℃.

Preferably, the primary crystallization mother liquor obtained in the above process is subjected to the same processes of ion exchange (purification), concentration, crystallization and drying again to obtain anhydrous or lactitol monohydrate crystals.

The beneficial effects are that: compared with the prior art, the invention has the following advantages:

(1) The primary crystallization yield of lactitol relative to lactose raw material reaches 50.0% -65%, the total yield of anhydrous lactitol relative to lactose raw material dry basis mass reaches more than 90%, and meanwhile, the process is simplified, the production operation is easy, the production cost is lower, and the same operation is carried out, so that the lactitol monohydrate can be obtained by only changing the temperature.

(2) In the hydrogenation process, lactose is hydrolyzed by RO water (70-90 ℃) after heat exchange with lactose hydrogenation liquid discharge, the highest concentration of the lactose aqueous solution is improved to 60%, the pH value (7.5-8) of the solution is improved and stabilized in a small extent, thereby ensuring and improving the activity of the catalyst, further reducing the control temperature of hydrogenation reaction and reducing lactose decomposition and side reaction.

(3) The invention selects more efficient catalyst types and improves hydrogenation efficiency; and the catalyst dosage and the hydrogen pressure are optimized, so that the hydrogenation efficiency and the yield are improved.

(4) On the basis of high-efficiency hydrogenation to obtain high-purity lactitol solution, the invention adopts a multi-factor crystallization process to crystallize the stock solution and mother solution for multiple times, thereby facilitating the precise control operation and improving the crystallization yield; the mother liquor is not decolorized, is directly treated by adopting an ion exchange process with lower cost, does not need simulated moving bed chromatography purification, reduces the production cost, and ensures higher yield and higher yield than single factors by later feeding and recrystallization.

Drawings

The foregoing and/or other advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings and detailed description.

FIG. 1 shows a process flow for lactitol production.

Fig. 2 is a photograph and an electron microscope of anhydrous lactose crystals.

FIG. 3 is a photograph and an electron microscope of a lactose monohydrate crystal.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to specific embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

The experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials, unless otherwise specified, are commercially available.

The method for detecting the lactitol content refers to GBGB1886.98 high performance liquid chromatography.

The method for detecting the lactitol moisture in the invention refers to GB5009.3 Karl Fischer method.

Other physical and chemical index detection methods refer to GB1886.98 2016.

In the invention, the squares are m ³ 。

In the following examples, the cation resin and anion resin used in the ion exchange process were D001-F macroporous weak acid cation exchange resin and D301-F macroporous weak base anion exchange resin (both supplied by Jiangsu Su Qing Water treatment group Co., ltd.).

Example 1: (constant temperature evaporation crystallization above 78 ℃ C. Without cooling)

(1) As shown in figure 1, 1800.0kg of lactose is added into deionized water to prepare lactose aqueous solution with the mass percent concentration of 50.0 percent (namely lactose refraction), the lactose content is 99.0 percent, food-grade sodium carbonate is used for adjusting the pH value to 7.55, raney nickel catalyst with the mass percent of lactose of 2 percent is added, the hydrogenation temperature is set to 110 ℃, the hydrogen pressure is 8.0-10 MPa, the reaction is carried out for 3.0h, and the lactose aqueous solution is discharged into a primary sedimentation tank to obtain lactose hydrogenated solution; the discharge pipeline passes through a tank (the inside of which is a coil pipe structure) filled with RO water to about 5 sides, namely, the temperature of the hydrogenated liquid is reduced, the RO water is also heated to above 70 ℃, the lactose is hydrated by the RO after heating when the sugar is gasified in the next kettle, and then the tank filled with the RO water is fully filled.

(2) Settling lactitol hydrogenated liquid in a primary settling tank for 2 hours, putting the upper hydrogenated liquid in a secondary settling tank, and continuing to settle for 2 hours to obtain lactitol solution; the lactitol solution is indicated as follows: purity 98.6%, lactitol refraction 49.8%, conductivity 150.0 μs/cm, transmittance 96.0%, lactose residue 0.01% w/w, indicating complete hydroconversion ratio.

(3) Ion exchange purification: adding active carbon (1 kg/square) into the lactitol solution, heating to 75 ℃, preserving heat for 30 minutes, filtering through a plate frame, and obtaining a decolorized lactitol solution, wherein the transmittance reaches more than 96 percent, and the decolorized lactitol solution is free of ground color after suction filtration; then the lactose purified solution is subjected to cation-anion-cation-anion exchange resin at the rate of 2.5BV/h, and the lactitol purified solution is obtained after ion exchange, wherein the indexes are as follows: lactitol purity is 98.7%, conductivity is 13.5 μs/cm, and light transmittance is 99.9%.

(4) Concentrating: the lactitol hydrogenated solution after multiple productions was collected, and concentrated to a refractive index of 68.2% using a four-effect evaporator.

(5) And (3) crystallization:

(i) The concentrated material is added into a vertical crystallization kettle (the total volume is 15 square), and the initial liquid volume is 10m ³ Starting a stirring switch and a steam valve, stirring at 72rpm, heating to 76 ℃, starting a vacuum valve and a vacuum pump, starting evaporating water at high temperature and negative pressure vacuum (-0.081 MPa), when the refraction of the material is 85.2%, observing with a microscope at 80 ℃, starting to generate crystal nucleus, and adding 3kg (0.0021%) of crystal seeds (200 meshes of anhydrous lactitol crushed fine powder);

(ii) Stirring at 72rpm and negative pressure of-0.081 MPa, continuing to evaporate, and simultaneously, keeping the temperature range of the whole process at 79+/-0.5 ℃; after seeding for 0.5h, at 0.5m ³ The concentrated lactitol solution (refractive index 68.2%) was fed to the crystallization kettle at a rate of/h (0.043 BV/h) for about 8 hours, the total volume of the mixture in the crystallization kettle being 11.5m ³ Left and right (76.67% of total volume of crystallization kettle); at this time, the temperature was 79℃and the vacuum pump was stopped, and the valve was closedClosing the steam valve, closing the vacuum valve, breaking vacuum, opening the discharge valve, and stopping stirring after all materials are discharged;

(iii) Placing the materials into a horizontal crystallization tank with the preheating temperature of 79 ℃ and stirring at the speed of 3rpm; discharging and centrifuging, wherein mother liquor flows out from a liquid outlet on the outer layer of the centrifuge, collecting a primary mother liquor tank, collecting lactitol after centrifuging, drying by using a vibrating fluidized bed, and obtaining 9.42 tons of anhydrous lactitol at a hot air temperature of 90 ℃, wherein an electron microscopic chart is shown in fig. 2, and the indexes are as follows: lactitol content is 99.1%, melting point is 146.5 ℃, moisture content is 0.016%, and yield is 62.8%.

(6) And (3) after the obtained primary crystallization mother liquor is treated by ion exchange resin, evaporating the primary mother liquor to the concentration of 69% by using a four-effect evaporator.

(7) And (3) crystallization:

(i) Adding concentrated primary mother liquor into a vertical crystallization kettle (total volume is 15 square), and the initial liquid volume is 10m ³ Starting a stirring switch and a steam valve, stirring at 90rpm, heating to 78 ℃, starting a vacuum valve and a vacuum pump, starting evaporating water at high temperature and negative pressure vacuum (-0.081 MPa), when the refraction of the material is 86.3%, observing with a microscope at 79 ℃, starting to generate crystal nucleus, and adding 3kg (0.0021%) of crystal seeds (200 meshes of anhydrous lactitol crushed fine powder);

(ii) Stirring at 90rpm, and continuously evaporating under negative pressure of-0.081 MPa, wherein the temperature range of the whole process is 79+/-0.5 ℃; after seeding for 0.5h, at 0.4m ³ The concentrated lactitol solution (refractive index 69%) was fed to a crystallization kettle at a rate of/h (0.0348 BV/h) for about 8 hours, the total volume of the mixture in the crystallization kettle being 11.5m ³ Left and right (76.67% of total volume of crystallization kettle); at the moment, the temperature is 79 ℃, the vacuum pump is stopped, the steam valve is closed, the vacuum is broken, the discharge valve is opened, and stirring is stopped after all materials are discharged;

(iii) Placing the materials into a horizontal crystallization tank with the preheating temperature of 79 ℃ and stirring at the speed of 3rpm; discharging and centrifuging, wherein mother liquor flows out from a liquid outlet on the outer layer of the centrifuge, and is collected into a secondary mother liquor tank, then lactitol is collected and centrifuged, crystals are dried by a vibrating fluidized bed, the temperature of hot air is 95 ℃, and 7.8 tons of anhydrous lactitol is obtained, wherein the indexes are as follows: lactitol content is 99.2%, melting point is 146.1 ℃, moisture content is 0.019%, and current yield is 52%. The total yield was 62.8% + (1-62.8%) x 52% = 82.19% ≡82.2%

And (3) introducing the secondary mother liquor into the same operation of the steps (6) and (7), and obtaining 5.05 tons of anhydrous lactitol, wherein the indexes are as follows: lactitol content is 99.0%, melting point is 146.1 ℃, moisture content is 0.019%, and current yield is 33.67%. The total yield was 82.2% + (1-82.2%) x 33.67% = 88.19%.

Example 2 (Evaporation crystallization at 77 ℃ C., crystallization tank 79 ℃ C.)

1) 1800.0kg of lactose is added into RO water (the temperature is 78 ℃ after heat exchange with lactulose hydrogenation liquid) to prepare lactose water solution with the mass percentage concentration of 56.0 percent (namely lactose refraction and concentration), the lactose content is 98.5 percent, sodium carbonate water solution (30 percent) is used for adjusting pH7.8, raney nickel catalyst with the mass of 3.2 percent of lactose is added, the hydrogenation temperature is set at 115 ℃, the hydrogen pressure is 8.8MPa, the reaction time is 2.5 hours, and the lactose water solution is discharged into a settling tank to obtain lactose hydrogenation liquid;

(2) Settling lactitol hydrogenated liquid in a primary settling tank for 2 hours, putting the upper hydrogenated liquid in a secondary settling tank, and settling again for 1.5 hours to obtain lactitol hydrogenated liquid solution; the lactitol solution is indicated as follows: lactitol purity 98.15%, lactitol refraction 55.8%, lactose residue 0.01% (w/w), conductivity 147 μs/cm, and transmittance 96.0%.

(3) Purifying: adding active carbon (1 kg/square) into a lactitol solution, heating to 78.5 ℃, preserving heat for 30 minutes, filtering through a plate frame, enabling transmittance to reach 97%, carrying out suction filtration, enabling the decolorized lactitol solution to have no ground color, and carrying out cation-anion-cation-anion exchange resin at a rate of 3.5BV/h, thereby obtaining a lactitol purifying solution after ion exchange, wherein the indexes are as follows: the concentration of the mass percent is 55.5%, the purity of lactitol is 98.2%, the conductivity is 12 mu s/cm, and the light transmission is 99.9%.

(4) Concentrating: the lactitol hydrogenated solutions after multiple productions were pooled and concentrated to a refractive index of 70.1% using a four-effect evaporator.

(5) And (3) crystallization:

(i) Adding the concentrated material into a vertical knotCrystal kettle (total volume 15 square), initial liquid volume about 10m ³ Starting a stirring switch and a steam valve, stirring at 90rpm, heating to above 79 ℃, starting a vacuum pump, starting evaporating water under negative pressure vacuum (-0.081 MPa), evaporating until the refraction of the material is 85.9%, observing at 77 ℃ by a microscope, starting to generate crystal nucleus, and adding 3.5kg of crystal seeds (200-mesh anhydrous lactitol crushed fine powder);

(ii) Stirring at 90rpm, negative pressure-0.081 MPa, adding seed crystal at 77+ -0.5deg.C for 0.5 hr, and stirring at 0.4m ³ The concentrated lactitol solution (70.1% refractive index) was fed to the crystallization kettle at a rate of/h (0.0348 BV/h) for about 8 hours, the total volume of the mixture in the crystallization kettle being 11.5m ³ Left and right (76.67% of total volume of crystallization kettle); at the moment, the temperature is 79 ℃, the vacuum pump of the vertical crystallization kettle is stopped, the vacuum is broken, the discharge valve is opened, and stirring is stopped after all materials are discharged;

(iii) Placing the materials into a horizontal crystallization tank with a preheating temperature of 82 ℃, starting the horizontal crystallization tank to stir at a rotating speed of 3rpm, at the moment, increasing the temperature of the material liquid to 79 ℃, starting a blanking valve of the horizontal crystallization tank, slowly adding the materials into a centrifugal machine, centrifuging, and introducing the mother liquor into a primary mother liquor collecting tank, and drying the crystals by hot air at 90 ℃ to obtain 8.8 tons of lactitol, wherein the water content is 4.9%, the melting point is 95 ℃, the purity of the lactitol is 99.6%, and the yield is 58.67%, as shown in an electron microscopic diagram of FIG. 3.

In this example, although the temperature of the latter crystallization tank was increased, the former crystallization stage was lower than 78 ℃, and no lactitol was obtained, but lactitol monohydrate was obtained.

Example 3 (evaporative crystallization above 78 ℃ C.)

(1) 1800.0kg of lactose is added into RO water (the temperature is 75 ℃ after heat exchange with lactulose hydrogenation liquid) to prepare lactose water solution with the mass percent concentration of 57.5 percent (namely lactose refraction), the lactose content is 99.0 percent, sodium carbonate water solution (30 percent) is used for adjusting pH7.9, raney nickel catalyst with the mass of 3.5 percent of lactose is added, the hydrogenation temperature is set at 110 ℃, the hydrogen pressure is 8.0MPa, the reaction is carried out for 2.5 hours, and the lactose water solution is discharged into a primary sedimentation tank to obtain lactose hydrogenation liquid.

(2) Settling lactitol hydrogenated liquid in a primary settling tank for 2 hours, putting the upper hydrogenated liquid in a secondary settling tank, and settling again for 1.5 hours to obtain lactitol hydrogenated liquid solution; the lactitol solution is indicated as follows: lactitol purity 98.6%, lactitol refraction 57.0%, lactose residue 0.01% (w/w), conductivity 132 μs/cm, and transmittance 96.1%.

(3) Ion exchange purification: adding active carbon (1 kg/square) into a lactitol solution, heating to 76 ℃, preserving heat for 30 minutes, filtering by a plate frame, enabling the transmittance to reach more than 96%, carrying out suction filtration, enabling the decolorized lactitol solution to have no ground color, and carrying out cation-anion-cation-anion exchange resin at the rate of 4BV/h, thereby obtaining a lactitol purifying solution after ion exchange, wherein the indexes are as follows: the concentration of the mass percent is 57%, the purity of lactitol is 98.5%, the conductivity is 11 mu s/cm, and the light transmission is 99.9%.

(4) Concentrating: the lactitol hydrogenated solutions after multiple productions were pooled and concentrated to a refractive index of 70.8% using a four-effect evaporator.

(5) And (3) crystallization:

(i) The concentrated material is added into a vertical crystallization kettle (total volume is 15 square), and the initial liquid volume is 12m ³ Starting a stirring switch and a steam valve, stirring at 90rpm, heating to 78 ℃, starting a vacuum valve and a vacuum pump, starting evaporating water at high temperature and negative pressure vacuum (-0.081 MPa), when the material refractive index is 85.7%, observing with a microscope at 79 ℃, starting to generate crystal nucleus, and adding 3kg of crystal seed (200 mesh anhydrous lactitol crushed fine powder);

(ii) Stirring at 90rpm, and continuously evaporating under negative pressure of-0.081 MPa, wherein the temperature range of the whole process is 79+/-0.5 ℃; stopping the vacuum pump of the vertical crystallization kettle after 0.5h of seed crystal is added, closing a steam valve, closing a vacuum valve, breaking vacuum, opening a discharge valve, and stopping stirring after all materials are discharged;

(iii) Placing the materials into a horizontal crystallization tank with the preheating temperature of 79 ℃, starting the horizontal crystallization tank to stir at the rotating speed of 3rpm, starting a blanking valve of the horizontal crystallization tank, slowly adding the materials into a centrifugal machine, centrifuging, enabling mother liquor to enter a primary mother liquor tank to obtain anhydrous lactitol, enabling the hot air temperature to be 92 ℃, and obtaining 6.88 tons of anhydrous lactitol and moisture after drying is finished: 0.013%, melting point of 146.1 ℃, purity of anhydrous lactitol of 99.9%, yield of 57.33%.

Example 4 (Evaporation at 79 ℃ C. For 5 hours)

(1) 1800.0kg of lactose is added into deionized water to prepare lactose aqueous solution with the mass percent concentration of 50.0 percent (namely lactose refraction) and the lactose content of 99.0 percent, food-grade sodium carbonate is used for adjusting the pH value to 7.55, raney nickel catalyst with the mass percent of lactose is added, the hydrogenation temperature is set to 110 ℃, the hydrogen pressure is 8.0-10 MPa, the reaction is carried out for 3.0h, and the lactose aqueous solution is discharged into a primary sedimentation tank to obtain lactose hydrogenated liquid; the discharge pipeline passes through a tank (the inside of which is a coil pipe structure) filled with RO water to about 5 sides, namely, the temperature of the hydrogenated liquid is reduced, the RO water is also heated to above 70 ℃, the lactose is hydrated by the RO after heating when the sugar is gasified in the next kettle, and then the tank filled with the RO water is fully filled.

(5) And (3) crystallization:

(i) The concentrated material is added into a vertical crystallization kettle (the total volume is 15 square), and the initial liquid volume is 10m ³ Starting stirring switch and steam valve, stirring at 72rpm, heating to 76deg.C, starting vacuum valve and vacuum pump, evaporating water at high temperature under negative pressure (-0.081 MPa), and evaporating to obtain the final productWhen the refraction of the material is 85.2%, the temperature is 80 ℃, the crystal nucleus starts to appear after microscopic observation, and 3kg (0.0021%) of seed crystal (200 meshes of anhydrous lactitol crushed fine powder) is added;

(ii) Stirring at 72rpm under negative pressure of-0.081 MPa at 0.5m ³ The concentrated lactitol solution (refractive index 68.2%) was fed to the crystallization kettle at a rate of/h (0.0435 BV/h) for about 8 hours, the total volume of the mixture in the crystallization kettle being 11.5m ³ Left and right (76.67% of total volume of crystallization kettle); the evaporation crystallization temperature is guaranteed to be 79 ℃ after the whole seed crystal is added, the vacuum pump is stopped, the steam valve is closed, the vacuum is broken, the discharge valve is opened, and stirring is stopped after all materials are discharged;

(iii) Placing the materials into a horizontal crystallization tank with the preheating temperature of 79 ℃ and stirring at the speed of 3rpm; preserving heat for 5 hours, discharging and centrifuging, collecting mother liquor from a liquid outlet on the outer layer of the centrifuge, collecting primary mother liquor tank, collecting lactitol after centrifuging, drying by a vibrating fluidized bed, and obtaining 8.96 tons of anhydrous lactitol at the hot air temperature of 91 ℃ according to the following indexes: lactitol content is 99.1%, melting point is 146.7 ℃, moisture content is 0.011%, and yield is 59.7%.

Example 5 (evaporative crystallization at above 78 ℃ C. 80 ℃ C. Reduced to 78.0 ℃ C.)

(1) Adding 1800.0. 1800.0k g of lactose into RO water (the temperature is 75 ℃ after heat exchange with lactulose hydrogenated liquid) to prepare lactose aqueous solution with the mass percent concentration of 58.0 percent (namely lactose refraction), adjusting pH7.9 by using sodium carbonate aqueous solution (30%), adding Raney nickel catalyst with the mass percent of 3.5 percent of lactose, setting the hydrogenation temperature of 110 ℃, the hydrogen pressure of 8.0MPa, reacting for 2.5 hours, discharging to a settling tank, and obtaining lactose hydrogenated liquid.

(2) Settling lactitol hydrogenated liquid in a primary settling tank for 2 hours, putting the upper hydrogenated liquid in a secondary settling tank, and settling again for 1.5 hours to obtain lactitol hydrogenated liquid solution; the lactitol solution is indicated as follows: lactitol purity 98.7%, lactitol refraction 57.5%, lactose residue 0.01% (w/w), conductivity 135 μs/cm, and transmittance 96.5%.

(3) Ion exchange purification: adding active carbon (1 kg/square) into a lactitol solution, heating to 75 ℃, preserving heat for 30 minutes, filtering by a plate frame, enabling the transmittance to reach more than 96%, carrying out suction filtration, enabling the decolorized lactitol solution to have no ground color, and carrying out cation-anion-cation-anion exchange resin at the rate of 4BV/h, thereby obtaining a lactitol purifying solution after ion exchange, wherein the indexes are as follows: the concentration of the mass percent is 56%, the purity of lactitol is 98.7%, the conductivity is 12 mu s/cm, and the light transmission is 99.9%.

(4) Concentrating: the lactitol hydrogenated solutions after multiple productions were pooled and concentrated to a refractive index of 71.5% using a four-effect evaporator.

(5) And (3) crystallization:

(i) The concentrated material is added into a vertical crystallization kettle (total volume is 15 square), and the initial liquid volume is 10.5m ³ Starting a stirring switch and a steam valve, stirring at 90rpm, heating to 78 ℃, starting a vacuum valve and a vacuum pump, starting evaporating water at high temperature and negative pressure vacuum (-0.081 MPa), when the material refractive index is 85.7%, observing with a microscope at 80 ℃, starting to generate crystal nucleus, and adding 3kg of crystal seed (200 mesh anhydrous lactitol crushed fine powder);

(ii) Stirring at 90rpm, and continuously evaporating under negative pressure of-0.081 MPa, wherein the temperature range of the whole process is 80+/-0.5 ℃; after seeding for 0.5h, at 0.45m ³ The concentrated lactose hydrogenated liquid (concentration: 71.5%) was fed into the crystallization kettle at a rate of/hr (0.0375 BV/h), and the total volume of the mixed liquid in the final crystallization kettle was 12m ³ Left and right (accounting for 80 percent of the total volume of the crystallization kettle); stopping the vacuum pump of the vertical crystallization kettle, closing the steam valve, closing the vacuum valve, breaking vacuum, opening the discharge valve, and stopping stirring after all the materials are discharged;

(iii) Placing the materials into a horizontal crystallization tank with a preheating temperature of 80 ℃, starting the horizontal crystallization tank to stir, starting cooling water to cool the materials at a rotating speed of 2rpm, cooling at a cooling speed of 2 ℃/hour, cooling and crystallizing, wherein the temperature is 80.0 ℃ after 40 minutes, starting a blanking valve of the horizontal crystallization tank, slowly adding the materials into a centrifugal machine, centrifuging, enabling mother liquor to enter a primary mother liquor tank to obtain anhydrous lactitol, enabling hot air temperature to be 96 ℃, and drying to obtain 9 tons of anhydrous lactitol and moisture: 0.015%, melting point of 146.7 ℃, purity of anhydrous lactitol of 99.9%, and yield of 60%.

Example 6: (temperature of evaporation crystallization is reduced to 46 ℃ C. Above 78 ℃ C.)

(1) 1800.0kg of lactose is added into RO water (the temperature is 70 ℃ after heat exchange with lactulose hydrogenation liquid) to prepare lactose water solution with the mass percent concentration of 57.0 percent (namely lactose refraction), the lactose content is 99.0 percent, sodium carbonate water solution (30 percent) is used for adjusting pH7.8, raney nickel catalyst with the mass percent of lactose is added, the hydrogenation temperature is set at 110 ℃, the hydrogen pressure is 8.0MPa, the reaction is carried out for 3.0 hours, and the lactose water solution is discharged into a primary sedimentation tank to obtain lactose hydrogenation liquid; the discharging pipeline passes through a tank (the inside of which is a coil pipe structure) filled with RO water to about 5 sides, namely, the temperature of the hydrogenated liquid is reduced, the RO water is also heated to above 70 ℃, the lactose is hydrated by the RO after heating when the sugar is boiled in the next kettle, and then the tank filled with the RO water is filled.

(2) Settling lactitol hydrogenated liquid in a primary settling tank for 2 hours, and putting the upper hydrogenated liquid into a secondary settling tank for 1 hour to obtain lactitol hydrogenated liquid solution; the lactitol solution is indicated as follows: lactitol purity 98.3%, lactitol refraction 56.5%, lactose residue 0.01% w/w, conductivity 135 μs/cm, and transmittance 96.0%.

(3) Ion exchange purification: adding active carbon (1 kg/square) into a lactitol solution, heating to 75 ℃, preserving heat for 30 minutes, filtering through a plate frame, enabling transmittance to reach 96.4%, carrying out suction filtration, enabling the decolorized lactitol solution to pass through a cation-anion-cation-anion exchange resin at a rate of 3.5BV/h, and obtaining a lactitol purifying solution after ion exchange, wherein the indexes are as follows: the concentration of the mass percent is 56%, the purity of lactitol is 98.7%, the conductivity is 12 mu s/cm, and the light transmission is 99.9%.

(4) Concentrating: the lactitol hydrogenated liquid after multiple times of production is summarized, and concentrated to refractive index 72% by using a four-effect evaporator,

(5) And (3) crystallization:

(i) The concentrated material is added into a vertical crystallization kettle (the total volume is 15 square), and the initial liquid volume is 10m ³ Starting stirring switch and steam valve, stirring at 90rpm, heating to 80deg.C, starting vacuum valve and vacuum pump, and steaming under high temperature and negative pressure (-0.081 MPa) Evaporating water until the refraction of the material is 85.7%, observing with a microscope at 83 ℃, adding 3kg of seed crystal (200 mesh anhydrous lactitol crushed fine powder) to start to appear crystal nucleus;

(ii) Stirring at 90rpm, and continuously evaporating under negative pressure of-0.081 MPa, wherein the temperature range of the whole process is 79+/-0.5 ℃; after seeding for 0.5h, at 0.35m ³ The concentrated lactose hydrogenated liquid (refractive index 72%) was fed into the crystallization kettle at a rate of 0.03BV/h for about 8 hours, and the total volume of the mixed liquid in the final crystallization kettle was 11.5m ³ Left and right (accounting for 80 percent of the total volume of the crystallization kettle); stopping the vacuum pump of the vertical crystallization kettle at 78.5 ℃, closing a steam valve, closing a vacuum valve, breaking vacuum, opening a discharge valve, and stopping stirring after all materials are discharged;

(iii) Placing the material into a horizontal crystallization tank with a preheating temperature of 78.5 ℃, starting the horizontal crystallization tank to stir, rotating at 2rpm, starting cooling water to cool the material, cooling at a cooling speed of 3 ℃/h, cooling and crystallizing, wherein the temperature is 46 ℃ after 14 hours, starting a blanking valve of the horizontal crystallization tank, slowly feeding the material into a centrifugal machine, centrifuging, feeding mother liquor into a primary mother liquor collecting tank to obtain lactitol, heating at 75 ℃ to obtain lactitol, drying at 10.05 tons of lactitol, water content of 5.0%, melting point of 96.5 ℃, purity of 99.9% and yield of 67%.

Example 7 (not evaporating but only reducing the temperature above 78 ℃ C.)

(1) 1800.0kg of lactose is added into RO water (the temperature is 78 ℃ after heat exchange with lactulose hydrogenation liquid) to prepare lactose water solution with the mass percent concentration of 56.0 percent (namely lactose refraction), the lactose content is 98.5 percent, sodium carbonate water solution (30 percent) is used for adjusting pH7.9, raney nickel catalyst with the mass of 3.2 percent of lactose is added, the hydrogenation temperature is set at 110 ℃, the hydrogen pressure is 8.5MPa, the reaction time is 3.0 hours, and the lactose water solution is discharged into a primary sedimentation tank to obtain lactose hydrogenation liquid;

(2) Settling lactitol hydrogenated liquid in a primary settling tank for 2 hours, putting the upper hydrogenated liquid in a secondary settling tank, and settling again for 1.5 hours to obtain lactitol hydrogenated liquid solution; the lactitol solution is indicated as follows: lactitol purity 98.1%, lactitol refraction 55.5% lactose residue 0.01% (w/w), conductivity 145 μs/cm, and transmittance 96.0%.

(3) Purifying: adding active carbon (1 kg/square) into a lactitol solution, heating to 78 ℃, preserving heat for 30 minutes, filtering by a plate frame, enabling the transmittance to reach 97%, carrying out suction filtration, enabling the decolorized lactitol solution to have no ground color, and carrying out cation-anion-cation-anion exchange resin at the rate of 3BV/h, thereby obtaining a lactitol purifying liquid after ion exchange, wherein the indexes are as follows: the concentration of the mass percent is 55.6%, the purity of lactitol is 98.2%, the conductivity is 16 mu s/cm, and the light transmission is 99.9%.

(4) Concentrating: the lactitol hydrogenated liquid after multiple times of production is summarized, and concentrated to have the refraction of 70.6% by using a four-effect evaporator,

(5) And (3) crystallization:

(i) The concentrated material is added into a vertical crystallization kettle (total volume is 15 square), and the initial liquid volume is about 12m ³ Starting a stirring switch and a steam valve (the total dry basis mass is 9 tons), stirring at 90rpm, heating to more than 75 ℃, starting a vacuum pump, starting evaporating water at high temperature and negative pressure vacuum (-0.081 MPa), evaporating until the refraction of the material is 85.9%, observing at 90 ℃ by a microscope, starting to generate crystal nucleus, and adding 3.5kg of crystal seeds (200 meshes of anhydrous lactitol crushed fine powder);

(ii) Stirring at 90rpm, negative pressure of-0.081 MPa, and adding seed crystal at 90+ -0.5deg.C for 0.5 hr; stopping the vacuum pump of the vertical crystallization kettle, breaking vacuum, opening a discharge valve, and stopping stirring after all materials are discharged;

(iii) Placing the material into a horizontal crystallization tank with a preheating temperature of 90 ℃, starting the horizontal crystallization tank to stir, starting cooling water to cool the material at a speed of 2 ℃/h at a rotating speed of 3rpm, cooling and crystallizing for 6 hours, starting a blanking valve of the horizontal crystallization tank, slowly adding the material into a centrifuge, centrifuging, introducing mother liquor into a mother liquor collecting tank, allowing the mother liquor to pass through a hot air temperature of 93 ℃, drying to obtain 5.6 tons of anhydrous lactitol, wherein the water content is 0.011%, the melting point is 146.4 ℃, the purity of the anhydrous lactitol is 99.9%, and the quality of the lactitol crystal is 62.2%.

Example 8 (evaporation above 78 ℃ C., 90 ℃ C. Down to 78 ℃ C.)

(1) 1800.0kg of lactose is added into RO water (the temperature is 75 ℃ after heat exchange with lactulose hydrogenation liquid) to prepare lactose water solution with the mass percent concentration of 58.0 percent (namely lactose refraction), the lactose content is 99.0 percent, sodium carbonate water solution (30 percent) is used for adjusting pH7.9, raney nickel catalyst with the mass of 3.5 percent of lactose is added, the hydrogenation temperature is set at 110 ℃, the hydrogen pressure is 8.0MPa, the reaction is carried out for 2.5 hours, and the lactose water solution is discharged into a primary sedimentation tank to obtain lactose hydrogenation liquid;

(4) Concentrating: the lactitol hydrogenated liquid after the multi-kettle secondary production is summarized, and a four-effect evaporator is used for concentrating the lactitol hydrogenated liquid until the refraction is 71.5%,

(5) And (3) crystallization:

(i) The concentrated material is added into a vertical crystallization kettle (total volume is 15 square), and the initial liquid volume is 10.5m ³ Starting a stirring switch and a steam valve, stirring at 90rpm, heating to 80 ℃, starting a vacuum valve and a vacuum pump, starting evaporating water at high temperature and negative pressure vacuum (-0.081 MPa), when the material is evaporated to 85.7% of refraction, observing with a microscope at 92 ℃, starting to generate crystal nucleus, and adding 3kg of crystal seed (200-mesh anhydrous lactitol crushed fine powder);

(ii) Stirring at 90rpm, and continuously evaporating under negative pressure of-0.081 MPa, wherein the temperature range of the whole process is 90+/-0.5 ℃; after seeding for 0.5h, at 0.4m ³ The rate per hour (0.033 BV/h) to crystallizationThe lactose hydrogenated liquid (concentration 71.5%) after concentration treatment is supplemented in the kettle, and the total volume of the mixed liquid in the final crystallization kettle is 12m ³ Left and right (accounting for 80 percent of the total volume of the crystallization kettle); stopping the vacuum pump of the vertical crystallization kettle, closing the steam valve, closing the vacuum valve, breaking vacuum, opening the discharge valve, and stopping stirring after all the materials are discharged;

(iii) Placing the materials into a horizontal crystallization tank with a preheating temperature of 90 ℃, starting the horizontal crystallization tank to stir, starting cooling water to cool the materials at the rotating speed of 2rpm, cooling at the cooling speed of 2 ℃/hour, cooling and crystallizing, wherein the temperature after 6 hours is 78.0 ℃, starting a blanking valve of the horizontal crystallization tank, slowly adding the materials into a centrifugal machine, centrifuging, flowing mother liquor into a primary mother liquor tank to obtain anhydrous lactitol crystals, and drying at the hot air temperature of 96 ℃ to obtain 9.6 tons of anhydrous lactitol and water: 0.015%, melting point of 146.7 ℃, purity of anhydrous lactitol of 99.9%, and yield of 65%.

(6) And (3) after the obtained primary crystallization mother liquor is treated by ion exchange resin, evaporating the primary mother liquor to 70.2% by using a four-effect evaporator.

(7) And (3) crystallization:

(i) Adding concentrated primary mother liquor into a vertical crystallization kettle (total volume is 15 square), and the initial liquid volume is 10m ³ Starting a stirring switch and a steam valve, stirring at 90rpm, heating to 78 ℃, starting a vacuum valve and a vacuum pump, starting evaporating water at high temperature and negative pressure vacuum (-0.081 MPa), when the refraction of the material is 86.3%, observing with a microscope at 90 ℃, starting to generate crystal nucleus, and adding 3kg (0.0021%) of crystal seed (200 mesh anhydrous lactitol crushed fine powder);

(ii) Stirring at 90rpm, and continuously evaporating under negative pressure of-0.081 MPa, wherein the temperature range of the whole process is 90+/-0.5 ℃; after seeding for 0.5h, at 0.4m ³ The concentrated lactitol solution (70.2% refractive index) was fed to the crystallization kettle at a rate of/h (0.0348 BV/h) for about 8 hours, the total volume of the mixture in the crystallization kettle being 11.5m ³ Left and right (76.67% of total volume of crystallization kettle); at the moment, the temperature is 90 ℃, the vacuum pump is stopped, the steam valve is closed, the vacuum is broken, the discharge valve is opened, and the material is obtainedStopping stirring after all the materials are discharged;

(iii) Placing the materials into a horizontal crystallization tank with the preheating temperature of 90 ℃ and stirring at the speed of 3rpm; discharging and centrifuging, wherein mother liquor flows out from a liquid outlet on the outer layer of the centrifuge, and is collected into a secondary mother liquor tank, then lactitol is collected, crystals are centrifuged, and are dried by a vibrating fluidized bed, and the hot air temperature is 99 ℃ to obtain 8.1 tons of anhydrous lactitol, wherein the indexes are as follows: lactitol content is 99.2%, melting point is 146.1 ℃, moisture content is 0.019%, and current yield is 54%. Total yield 65% + (1-65%) x 54% = 83.9%;

the secondary mother liquor is subjected to the same operation as the operation of the steps (6) and (7) to obtain 5.67 tons of anhydrous lactitol, and the indexes are as follows: lactitol content is 99.3%, melting point is 146.1 ℃, moisture content is 0.013%, and current yield is 37.8%. The total yield was 83.9% + (1-83.9%) x 37.8% = 89.9858% ≡89.99%.

Example 9 (77 ℃ C. Evaporative crystallization Cooling to 46 ℃ C.)

(1) 1800.0kg of lactose is added into RO water (the temperature is 77 ℃ after heat exchange with lactulose hydrogenation liquid) to prepare lactose water solution with the mass percent concentration of 60.0 percent (namely lactose refraction), the lactose content is 99.0 percent, sodium carbonate water solution (30 percent) is used for adjusting pH7.8, raney nickel catalyst with the mass of 3.5 percent of lactose is added, the hydrogenation temperature is set at 110 ℃, the hydrogen pressure is 8.0MPa, the reaction is carried out for 3.0 hours, and the lactose water solution is discharged into a primary sedimentation tank to obtain lactose hydrogenation liquid;

(2) Settling lactitol hydrogenated liquid in a primary settling tank for 2 hours, putting the upper hydrogenated liquid in a secondary settling tank, and settling again for 1.5 hours to obtain lactitol hydrogenated liquid solution; the lactitol solution is indicated as follows: lactitol purity 98.2%, lactitol refraction 58.5%, lactose residue 0.01% (w/w), conductivity 145 μs/cm, and transmittance 96.0%.

(3) Purifying: adding active carbon (1 kg/square) into a lactitol solution, heating to 77 ℃, preserving heat for 30 minutes, filtering by a plate frame, enabling the transmittance to reach 97%, carrying out suction filtration, enabling the decolorized lactitol solution to have no ground color, and carrying out cation-anion-cation-anion exchange resin at the rate of 3BV/h, thereby obtaining a lactitol purifying liquid after ion exchange, wherein the indexes are as follows: the concentration of the mass percent is 58%, the purity of lactitol is 98.7%, the conductivity is 13 mu s/cm, and the light transmission is 99.9%.

(4) Concentrating: the lactitol hydrogenated liquid after multiple times of production is summarized, and concentrated to have the refraction of 70.4% by using a four-effect evaporator,

(5) And (3) crystallization:

(i) The concentrated material is added into a vertical crystallization kettle (total volume is 15 square), and the initial liquid volume is 12m ³ Starting a stirring switch and a steam valve, stirring at 90rpm, heating to 77 ℃, starting a vacuum pump vacuum valve and evaporating water at high temperature and negative pressure vacuum (-0.081 MPa), when the material refractive index is 85.9%, observing with a microscope at 77 ℃, starting to generate crystal nucleus, and adding 3.5kg of crystal seed (200 mesh anhydrous lactitol crushed fine powder);

(ii) Stirring at 90rpm, negative pressure-0.081 MPa, temperature 77+ -0.5deg.C, seeding for 0.5 hr, stirring at 0.45m ³ The concentrated lactose hydrogenated liquid (refractive index 70.4%) was fed into the crystallization kettle at a rate of/h (0.039 BV/h) for about 10 hours, and the total volume of the mixed liquid in the final crystallization kettle was 11.5m ³ Left and right (accounting for 80 percent of the total volume of the crystallization kettle); at the moment, stopping a vacuum pump of the vertical crystallization kettle at the temperature of 77.5 ℃, breaking vacuum, opening a discharge valve, and stopping stirring after all materials are discharged; (total added liquid dry basis is 15 tons); stopping the vacuum pump of the vertical crystallization kettle, breaking vacuum, opening a discharge valve, and stopping stirring after all materials are discharged;

(iii) Placing the material into a horizontal crystallization tank with a preheating temperature of 77 ℃, starting the horizontal crystallization tank to stir, starting cooling water to cool the material at a rotating speed of 2rpm, cooling at a cooling speed of 3 ℃/h, cooling and crystallizing, starting a blanking valve of the horizontal crystallization tank after 10 hours at a temperature of 46 ℃, slowly adding the material into a centrifuge, centrifuging to obtain a lactitol crystal, and obtaining 7.2 tons of lactitol after drying at a hot air temperature of 88 ℃, wherein the moisture is as follows: the water of crystallization is 5.6%, the melting point is 96.5 ℃, the purity of lactitol is 99.1%, and the yield is 68%. (crystallization Water 5.6%)

Example 10 (evaporative crystallization at 79 ℃ C. Without cooling)

(1) 1800.0kg of lactose is added into RO water (the temperature is 70 ℃ after heat exchange with lactulose hydrogenation liquid) to prepare lactose water solution with the mass percent concentration of 55.0 percent (namely lactose refraction), the lactose content is 99.0 percent, (what substances are added to adjust the pH value is required to be added for adjusting the pH value), sodium carbonate water solution (30%) is used for adjusting the pH value to be 8, raney nickel catalyst with the mass percent of lactose is added, the hydrogenation temperature is set to 110 ℃, the hydrogen pressure is 8.0MPa, the reaction time is 3.0 hours, and the lactose water solution is discharged to a first sedimentation tank to obtain lactose hydrogenation liquid;

(2) And (3) settling the lactitol hydrogenated liquid in the primary settling tank for 2 hours, putting the upper hydrogenated liquid into the secondary settling tank, and settling again for 1 hour to obtain a lactitol hydrogenated liquid solution. The lactitol solution is indicated as follows: lactitol purity 98.6%, lactitol refraction 56.5%, lactose residue 0.01% (w/w), conductivity 145 μs/cm, and transmittance 96.0%.

(3) Purifying: adding active carbon (1 kg/square) into a lactitol solution, heating to 75 ℃, preserving heat for 30 minutes, filtering by a plate frame, enabling the transmittance to reach more than 96%, carrying out suction filtration, enabling the decolorized lactitol solution to have no ground color, and carrying out cation-anion-cation-anion exchange resin at the rate of 2.5V/h to obtain a lactitol purifying solution after ion exchange, wherein the indexes are as follows: the concentration of the mass percent is 56%, the purity of lactitol is 98.7%, the conductivity is 12 mu s/cm, and the light transmission is 99.9%.

(4) Concentrating: the lactitol hydrogenated liquid after the multi-kettle secondary production is summarized, and a four-effect evaporator is used for concentrating the lactitol hydrogenated liquid to refractive index 72%,

(5) And (3) crystallization:

(i) The concentrated material is added into a vertical crystallization kettle (total volume is 15 square), and the initial liquid volume is about 10m ³ Starting a stirring switch and a steam valve, stirring at 90rpm, heating to 78 ℃, starting a vacuum pump, starting evaporating water at high temperature and negative pressure vacuum (-0.081 MPa), when the refraction of the material is 85.8%, observing with a microscope at 77.5 ℃, starting to generate crystal nucleus, and adding 3kg of crystal seed (200 mesh anhydrous lactitol crushed fine powder);

(ii) Stirring at 85rpm, negative pressure-0.081 MPa, temperature 77+ -0.5, continuing to evaporate, adding seed crystal for 0.5 hr, and adding seed crystal at 0.38m ³ The concentrated lactose hydrogenated liquid (refractive index 72%) was fed into the crystallization kettle at a rate of/h (0.032 BV/h) for about 10 hours, and the total volume of the mixed liquid in the final crystallization kettle was 12m ³ Left and right (occupy)80% of the total volume of the crystallization kettle); at the moment, stopping a vacuum pump of the vertical crystallization kettle at the temperature of 77.5 ℃, breaking vacuum, opening a discharge valve, and stopping stirring after all materials are discharged; (total added liquid dry basis is 15 tons);

(iii) Placing the materials into a horizontal crystallization tank with a preheating temperature of 77.5 ℃, starting the horizontal crystallization tank for stirring, starting a blanking valve of the horizontal crystallization tank at a rotating speed of 2rpm, slowly adding the materials into a centrifugal machine for centrifugation, enabling mother liquor to enter a mother liquor collecting tank to obtain lactitol monohydrate crystals, enabling the temperature of hot air to be 88 ℃, and obtaining lactitol monohydrate of 8.9 tons and water after drying: the water content is 5.5%, the melting point is 96.5 ℃, the purity of lactitol monohydrate is 98.9%, and the yield is 65.9%. (moisture 5.5%)

Example 11 (No evaporation even if the temperature is reduced below 78 ℃ C.)

(1) 1800.0kg of lactose is added into RO water (the temperature is 79 ℃ after heat exchange with lactulose hydrogenation liquid) to prepare lactose water solution with the mass percent concentration of 56.0 percent (namely lactose refraction), the lactose content is 99.0 percent, sodium carbonate water solution (30 percent) is used for adjusting pH7.8, raney nickel catalyst with the mass of 3.2 percent of lactose is added, the hydrogenation temperature is set at 110 ℃, the hydrogen pressure is 8.0MPa, the reaction is carried out for 2.5 hours, and the lactose water solution is discharged into a primary sedimentation tank to obtain lactose hydrogenation liquid;

(2) Settling lactitol hydrogenated liquid in a primary settling tank for 2 hours, putting the upper hydrogenated liquid in a secondary settling tank, and settling again for 1 hour to obtain lactitol hydrogenated liquid solution; the lactitol solution is indicated as follows: lactitol purity 98.1%, lactitol refraction 55.5% lactose residue 0.01% (w/w), conductivity 145 μs/cm, and transmittance 96.0%.

(3) Purifying: adding active carbon (1 kg/square) into a lactitol solution, heating to 78 ℃, preserving heat for 30 minutes, filtering by a plate frame, enabling the transmittance to reach 97%, carrying out suction filtration, enabling the decolorized lactitol solution to have no ground color, and carrying out cation-anion-cation-anion exchange resin at the rate of 3BV/h, thereby obtaining a lactitol purifying liquid after ion exchange, wherein the indexes are as follows: the concentration of the mass percent is 56%, the purity of lactitol is 98.5%, the conductivity is 13 mu s/cm, and the light transmission is 99.9%.

(4) Concentrating: the lactitol hydrogenated liquid after multiple times of production is summarized, and concentrated to 70.5 percent of refraction by using a four-effect evaporator,

(5) And (3) crystallization:

(i) The concentrated material is added into a vertical crystallization kettle (total volume is 15 square), and the initial liquid volume is about 12m ³ Starting a stirring switch and a steam valve (the total dry basis weight is about 12 tons), stirring at 90rpm, heating to 77 ℃, starting a vacuum pump, starting evaporating water at high temperature and under negative pressure vacuum (-0.081 MPa), and starting to generate crystal nuclei after evaporation until the refraction of the materials is 85.9%, the temperature is 79 ℃ and microscopic observation, and adding 3.5kg of crystal seeds (200-mesh anhydrous lactitol crushed fine powder);

(ii) Stirring at 90rpm, negative pressure-0.081 MPa, adding seed crystal at 77+ -0.5deg.C for 0.5 hr, stopping vacuum pump of vertical crystallization kettle, breaking vacuum, opening discharge valve, and stopping stirring after all materials are discharged;

(iii) Placing the material into a horizontal crystallization tank with a preheating temperature of 79 ℃, starting the horizontal crystallization tank to stir, starting cooling water to cool the material at a speed of 3 ℃/h at a rotating speed of 2rpm, cooling and crystallizing, starting a blanking valve of the horizontal crystallization tank after 11 hours at a temperature of 45 ℃, slowly adding the material into a centrifuge, centrifuging to obtain lactitol, drying to obtain 6.72 tons of lactitol, wherein the water content is 6.4%, the melting point is 96.5 ℃, the purity of the lactitol is 99.3%, and the yield is 56%. (Water content 6.4%)

From examples 1 to 11, the following conclusions can be drawn:

1. the temperature of 78 ℃ is the key temperature for producing the anhydrous lactitol and the lactitol monohydrate;

2. as long as the crystallization-centrifugation temperature is maintained above 78 ℃ in the whole production process, anhydrous lactitol is obtained whether single-factor crystallization or multi-factor crystallization is carried out;

3. whenever the centrifugal temperature after crystallization is lower than 78 ℃ and higher than 45 ℃ in the whole production process, the lactose monohydrate is obtained whether the single-factor crystallization or the multi-factor crystallization is carried out; (Note: the crystallization of lactitol dihydrate below 45 ℃ C. Increases)

4. The yield of lactitol monohydrate is higher, and has a certain relationship with the water of crystallization contained in crystals;

5. the multi-factor (evaporation) crystallization is simpler to operate, less in key control points and higher in efficiency and yield than single-factor crystallization.

6. The method for improving the yield of the single-factor crystallization mainly comprises simulated moving bed chromatography purification, and the yield of the crystallization can be improved without the simulated moving bed chromatography purification by the multi-factor crystallization, so that the yield improvement level of the single-factor crystallization by using the simulated moving bed is achieved. The cost is reduced, the operation is simple and convenient, and the operation of staff is very facilitated.

7. Lactitol hydrogenated liquid, primary mother liquid, secondary mother liquid, tertiary mother liquid, quaternary mother liquid and even five-time centrifugal mother liquid, the crystallization operation mode, crystallization parameters and key control points of each mother liquid are different, the operation is unstable, a certain trouble is brought to the actual operation of operators, and thus the product quality is unstable; the key control points of a new crystallization process set are doubled, so that the actual operation of production staff is facilitated, and the quality is stable.

8. The centrifugal mother liquor needs to be crystallized after repeated chromatographic purification for 4-5 times and then evaporated and concentrated, the operation period is long, the cost is high, the crystallization times of the new crystallization process are reduced, the operation period is shorter, the yield can be improved by only three times of crystallization, the anhydrous lactitol can reach 90%, and the lactitol monohydrate can reach more than 96%

9. The traditional crystallization method generally comprises cooling crystallization, and the principle of cooling crystallization is that the supersaturation degree of a solution is increased by cooling, and crystals are separated out. The solution is enabled to keep a certain supersaturation degree from the beginning of adding the seed crystal to the end of negative pressure evaporation crystallization through the operation of negative pressure evaporation during multi-factor crystallization, crystal nucleus is separated out continuously, crystal grains grow continuously, and then the temperature is reduced continuously after the crystal grains enter a crystallization tank, and the crystal grains further grow. And thus the yield and efficiency will be higher.

Example 12

Based on example 1, only part of the parameters of the crystallization conditions in step (5) were modified on the basis of example 1, as specified in Table 1.

TABLE 1

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Claims

1. A process for producing lactitol crystals, comprising the steps of:

(1) Carrying out hydrogenation reaction on lactose aqueous solution under the action of a catalyst to obtain lactose hydrogenated liquid;

(2) Removing the catalyst in the lactose hydrogenated liquid to obtain a lactitol solution; then carrying out ion exchange, concentration and crystallization to obtain a lactitol monohydrate crystal; concentrating the lactitol solution after the ion exchange until the mass percentage concentration of lactitol is 68% -72%;

in the step (2), the crystallization comprises the following steps:

(i) Placing the concentrated lactitol solution in a crystallization kettle, evaporating water under the stirring condition and negative pressure of not higher than-0.08 MPa at the temperature of 75-78 ℃, and immediately adding seed crystals after evaporating until the refraction of the material is 85% -87% and generating crystal nuclei; wherein, when seed crystal is added, the temperature is more than or equal to 78 ℃;

(ii) Controlling the temperature of the crystallization kettle to be 78-98 ℃, adding the concentrated lactitol solution into the crystallization kettle at the rate of 0.02-0.05 BV/h, and stopping adding until the total volume of the mixed solution in the crystallization kettle reaches 75-80% of the volume of the crystallization kettle;

(iii) And (3) placing the material obtained in the step (ii) into a crystallization tank at 78-98 ℃, cooling the crystallization tank to 45-46 ℃ under the stirring condition, centrifuging, collecting centrifuged crystals, and drying the crystals to obtain the lactitol monohydrate crystals.

2. The production process according to claim 1, wherein in the step (1), the mass percentage of lactose in the lactose aqueous solution is 35% -60%, and the pH of the lactose aqueous solution is 7.5-8.0.

3. The process according to claim 1, wherein in step (1), the catalyst is a hydrogenation catalyst and the amount of catalyst is 2.0% -6.0% w/w of lactose.

4. The process according to claim 1, wherein in the step (1), the hydrogenation is carried out at 100 to 120 ℃ and at a pressure of 8.0 to 12.0 MPa.

5. The process according to claim 1, wherein in step (2), the conductivity of the lactitol solution is not more than 200 ms/cm and the transmittance is not less than 95%; in the lactitol solution, the mass percentage of lactitol is more than or equal to 98.0 percent, and the residual lactose content is less than or equal to 0.02 percent w/w.

6. The process according to claim 1, wherein in step (i), the seed crystal is a 200 mesh anhydrous lactitol powder; the dosage of the seed crystal is 0.002% -0.004% of the solid mass of the whole solution.