System and method for producing high quality xylitol crystals

Abstract

The present invention relates to a system and method for producing high-quality xylitol crystals. The system includes a conditioning tank, a heat exchanger, a decolorization tank, an ion exchange system, a microporous filter, a first evaporator, a first crystallization tank, a first centrifuge, a fluidized drying tank, a xylitol dissolving tank, a second evaporator, a second crystallization tank, a second centrifuge, a hot air drying tank, and a cold air fluidized bed, which are connected in sequence through a pipe, the first centrifuge is further connected to the conditioning tank through a pipe, the second centrifuge is further connected to the xylitol dissolving tank through a pipe, the conditioning tank is provided with a supply port for xylitol hydrogenation liquid, the xylitol dissolving tank is further provided with a water supply port for purified water, and the material from the cold air fluidized bed is the xylitol crystal product. The present invention adds water to the initially produced xylitol crystals at a certain ratio to dissolve them to obtain a higher purity xylitol solution, and recrystallizes the xylitol solution to produce xylitol crystals with a higher pH and better flavor.

Description

[Technical field]

[0001] The present invention relates to the technical field of xylitol production, and more particularly to a system and method for producing high quality xylitol crystals. [Background technology]

[0002] At present, the industrial production of xylitol mainly uses chemical hydrogenation, which involves hydrolyzing agricultural textile waste containing hemicellulose with dilute acid, neutralizing, decolorizing, concentrating and crystallizing the hydrolysis liquid to obtain xylose crystals, dissolving the xylose crystals to obtain a certain concentration of xylose solution, hydrogenating the xylitol to reduce it, and finally obtaining xylitol crystals through steps such as ion exchange, vacuum concentration, cooling crystallization and centrifugal drying. In order to improve the yield of xylitol products, the centrifuged mother liquor is often blended with the hydrogenation solution, resulting in the presence of 4-6% miscellaneous sugars and sugar alcohols in the blended liquid. Although these miscellaneous sugars and sugar alcohols have little effect on the xylitol crystallization process, they will reduce the pH value of the product, ultimately resulting in a significant difference in the flavor of the product.

[0003] In the xylitol production process, there are two main factors that affect the pH of the product. One is the ion exchange process, which is the process in which the H in the resin is released in the cation exchange column and the anion exchange column of the xylitol solution. + and OH - are exchanged, and the pH of the xylitol crystals finally produced differs depending on the difference in the amount of exchange between the cation exchange column and the anion exchange column. Secondly, the pH of the xylitol crystals greatly differs depending on the components of the xylitol concentrate. The acidity coefficient (pKa) of miscellaneous sugars such as glucose and xylose is smaller than that of xylitol, as shown in Table 1 below. Therefore, if a certain amount of miscellaneous sugars is present in the xylitol concentrate, the pH of the produced xylitol crystals will be lower and the difference in flavor will be greater, as shown in Table 2 below.

[0004] [Table 1]

[0005] [Table 2]

[0006] At present, there are mainly two ways to increase the pH of xylitol crystals. One is to add strong alkaline resin or mixed layer resin after the ion exchange process, for example, Patent Publication No. CN109438184A and Patent Publication No. CN110894180A. The other is to add a small amount of alkaline liquid to the ion exchange liquid, for example, Patent Publication No. CN112661796A. Both methods aim to increase the pH of xylitol crystals by increasing the pH of the xylitol concentrate. Although the route of this process is simple and clear, and has a corresponding technical effect, it does not essentially solve the problem of low pH and large difference in flavor of xylitol produced by traditional processes.

[0007] Therefore, considering this problem existing in the conventional production process of xylitol, it is very important to find a way to increase the pH of xylitol crystals and improve their flavor, due to their inherent properties that affect their low pH and great differences in flavor. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a system and method for producing high-quality xylitol crystals, which can add water to the initially produced xylitol crystals at a certain ratio to dissolve them, obtain a higher purity xylitol solution, and recrystallize this xylitol solution to produce xylitol crystals with a higher pH and better flavor. This system can significantly increase the pH of the xylitol crystals, stably maintain the pH for a long period of time, and effectively improve the flavor of the xylitol crystals.

[0009] The present invention is achieved as follows: A system for producing high-quality xylitol crystals is provided, comprising a conditioning tank, a heat exchanger, a decolorization tank, an ion exchange system, a microporous filter, a first evaporator, a first crystallization tank, a first centrifuge, a fluidized drying tank, a xylitol dissolving tank, a second evaporator, a second crystallization tank, a second centrifuge, a hot air drying tank, and a cold air fluidized bed, which are sequentially connected through piping, the first centrifuge and the second centrifuge are each provided with a liquid outlet, the liquid outlet of the first centrifuge is connected through piping to one supply port of the conditioning tank, the liquid outlet of the second centrifuge is connected through piping to one supply port of the xylitol dissolving tank, the conditioning tank is provided with a supply port for a material to be treated, the xylitol dissolving tank is further provided with a water inlet for purified water, the cold air fluidized bed is provided with an outlet, the material to be treated is a xylitol hydrogenated liquid, and the material discharged from the outlet of the cold air fluidized bed is a xylitol crystal product.

[0010] The technical problem to be solved by the present invention is further Production of xylitol concentrate: Step 1: The xylitol hydrogenated liquid and the first centrifuged mother liquor sent from the first centrifuge are mixed uniformly at a certain ratio to obtain a mixed liquid material, which is then subjected to heat exchange in a heat exchanger, decolorization in a decolorization tank, ion exchange in an ion exchange system, filtration in a microporous filter, and evaporation in a first evaporator to obtain a xylitol concentrate with a concentration of 1200-1400g / L and a purity of 94-96%; Step 2: crystallization of xylitol concentrate: the xylitol concentrate is crystallized by lowering the temperature in the first crystallization tank for 8-12 hours, and the resulting xylitol paste is separated by a first centrifuge and dried in a fluidized drying bed to obtain crude xylitol crystals; the first centrifugal mother liquor obtained by separation by the first centrifuge is recycled to a balancing tank via piping and is harmonized with the xylitol hydrogenated liquid for reuse; in this step, the purity of the crude xylitol crystals is 98.5-99.8%, pH<5.0, and the purity of the first centrifugal mother liquor is 88-92%; and step 3: dissolving and recrystallizing the crude xylitol crystals: sending the crude xylitol crystals to a xylitol dissolving tank, dissolving them in purified water added to the xylitol dissolving tank, and then mixing them uniformly with the second centrifuged mother liquor sent from the second centrifuge at a certain ratio to obtain a xylitol dissolved mixture, which is then concentrated by a second evaporator, crystallized by a second crystallizer, centrifuged by a second centrifuge, hot air dried by a hot air drying tank, and cold air dried by a cold air fluidized bed to obtain a high-quality xylitol crystal product. The second centrifuged mother liquor obtained by separation by the second centrifuge is recycled to the xylitol dissolving tank via a pipe and mixed with the crude xylitol crystal dissolved solution for reuse, in which the purity of the high-quality xylitol crystal product is >99.8% and the pH is >6.0.

[0011] Compared with the prior art, the system and method for producing high-quality xylitol crystals of the present invention includes: uniformly mixing hydrogenation liquid with first centrifugal mother liquor to obtain mixed liquid material; purifying and concentrating the mixed liquid material through heat exchanger, decolorization tank, ion exchange system, microporous filter and first evaporator to obtain xylitol concentrate; crystallizing the xylitol concentrate through a specific process in the first crystallization vessel to obtain xylitol paste; separating the xylitol paste through the first high-speed centrifuge to obtain the first centrifugal mother liquor, recycling it to the blending vessel; drying the obtained xylitol crude crystals in the first fluidized bed, adding purified water to dissolve in the xylitol dissolving tank, uniformly mixing with the second centrifugal mother liquor through the second centrifuge, and sending it to the second evaporator for concentration; concentrating the xylitol dissolving liquid in the second evaporator, recrystallizing the xylitol liquid in the second crystallization vessel, and then separating it through the second centrifuge to obtain crystalline xylitol and second centrifugal mother liquor. The second centrifuged mother liquor is recycled to the xylitol dissolving tank, and the crystalline xylitol is dried in a hot air drying tank and a cold air fluidized bed to obtain a high-quality xylitol crystalline product. The purity of the xylitol product produced by the present invention is further increased, and the pH stability of the xylitol crystals is more excellent, and even after being left for one month, the pH remains at 6.0 or higher. In addition, the sweetness of the xylitol product produced by this method is improved, the aftertaste is sweet, the erosion and numbness of teeth are reduced, and the flavor of the product is obviously improved. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing the principle of the system for producing high-quality xylitol crystals of the present invention. [Diagram 2] FIG. 1 is a schematic diagram for evaluating the flavor of xylitol crystals produced in each of the examples and comparative examples of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] In order to clarify the technical problems, technical solutions and advantageous effects of the present invention, the present invention will be described in more detail below with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to illustrate the present invention and are not intended to limit the present invention.

[0014] As shown in FIG. 1, a preferred embodiment of the system for producing high-quality xylitol crystals of the present invention includes a conditioning tank 1, a heat exchanger 2, a decolorization tank 3, an ion exchange system 4, a microporous filter 5, a first evaporator 6, a first crystallization tank 7, a first centrifuge 8, a fluidized drying layer 9, a xylitol dissolving tank 10, a second evaporator 11, a second crystallization tank 12, a second centrifuge 13, a hot air drying tank 14, and a cold air fluidized bed 15, which are connected in sequence via piping. Each of the first centrifuge 8 and the second centrifuge 13 is provided with a liquid outlet. The liquid discharge outlet of the first centrifuge 8 is connected to one supply port of the matching tank 1 via a pipe, and the liquid discharge outlet of the second centrifuge 13 is connected to one supply port of the xylitol dissolving tank 10 via a pipe. The matching tank 1 is provided with a supply port for the material to be treated, the xylitol dissolving tank 10 is further provided with a water supply port for purified water E, and the cold air fluidized bed 15 is provided with an outlet. The material to be treated is xylitol hydrogenated liquid A, and the material discharged from the outlet of the cold air fluidized bed 15 is the xylitol crystal B product.

[0015] The first centrifugal separator 8 discharges a first centrifugal mother liquor C from a liquid outlet, and the second centrifugal separator 13 discharges a second centrifugal mother liquor D from a liquid outlet. The blending tank 1 is used to uniformly mix the xylitol hydrogenated liquid A and the first centrifugal mother liquor C to obtain a mixed liquid material.

[0016] The present invention further discloses a method for producing high quality xylitol crystals, comprising the steps of:

[0017] Step 1: Making a xylitol concentrate The xylitol hydrogenated liquid A and the first centrifuged mother liquor C sent from the first centrifuge 8 are harmonized and mixed uniformly at a certain ratio to obtain a mixed liquid material, which is then subjected to heat exchange in the heat exchanger 2, decolorization in the decolorization tank 3, ion exchange in the ion exchange system 4, filtration in the microporous filter 5, and evaporation treatment in the first evaporator 6 in that order to obtain a xylitol concentrate having a concentration of 1200 to 1400 g / L and a purity of 94 to 96%.

[0018] Step 2: Crystallization of the xylitol concentrate The xylitol concentrate is crystallized by lowering the temperature in the first crystallization tank 7 for 8 to 12 hours, and the resulting xylitol paste is separated by the first centrifuge 8 and dried in the fluidized drying layer 9 to obtain crude xylitol crystals. The first centrifuged mother liquor C obtained by separation by the first centrifuge 8 is recycled to the harmony tank 1 via piping and is re-used together with the xylitol hydrogenated liquid A. In this step, the purity of the crude xylitol crystals is 98.5 to 99.8%, pH < 5.0, and the purity of the first centrifuged mother liquor C is 88 to 92%.

[0019] Step 3: Dissolution and recrystallization of crude xylitol crystals The crude xylitol crystals are sent to the xylitol dissolving tank 10, dissolved in purified water added to the xylitol dissolving tank 10, and then mixed uniformly with the second centrifuged mother liquor D sent from the second centrifuge 13 at a certain ratio to obtain a xylitol dissolved mixture. The xylitol dissolved mixture is concentrated by the second evaporator 11, crystallized by the second crystallizing pot 12, centrifuged by the second centrifuge 13, dried with hot air by the hot air drying tank 14, and dried with cold air by the cold air fluidized bed 15 to obtain a high-quality xylitol crystal B product. The second centrifuged mother liquor D obtained by separation by the second centrifuge 13 is recycled to the xylitol dissolving tank 10 via piping, mixed with the crude xylitol crystal dissolved liquid, and reused. In this step, the purity of the high-quality xylitol crystal B product is >99.8% and pH>6.0.

[0020] Specifically, in step 1, the temperature of the xylitol concentrate is 90 to 100°C.

[0021] Specifically, in step 2, in the cooling crystallization in the first crystallization vessel 7, xylitol seed crystals are added, the addition ratio of the xylitol seed crystals is 0.001 to 0.002%, the mesh of the xylitol seed crystals is 60 to 120 mesh, and the temperature of the system when the xylitol seed crystals are added is 64 to 66°C.

[0022] Specifically, in step 3, in the crystallization in the second crystallization vessel 12, xylitol seed crystals are added, the addition ratio of the xylitol seed crystals is 0.001 to 0.002%, the mesh of the xylitol seed crystals is 60 to 120 mesh, and the temperature of the system when the xylitol seed crystals are added is 64 to 66°C.

[0023] The system and method for producing high quality xylitol crystals of the present invention are further described below with reference to specific examples. <Example 1>

[0024] A first embodiment of the method for producing high quality xylitol crystals of the present invention comprises the following steps.

[0025] Step 11: The xylitol hydrogenated liquid A and the first centrifuged mother liquor C are blended in a certain ratio, and the blended liquid is sequentially purified and concentrated in the heat exchanger 2, the decolorization tank 3, the ion exchange system 4, the microporous filter 5, and the first evaporator 6 to obtain a xylitol concentrate having a temperature of 100°C, a concentration of 1200g / L, and a purity of 94%.

[0026] Step 12: The vacuum degree of the first crystallization vessel 7 was maintained at -0.095 MPa, and the xylitol concentrate was further evaporated. When the temperature of the first crystallization vessel 7 dropped to 65°C, 0.001% xylitol seed crystals (80-100 mesh) were added, and the system was maintained at 65°C for 8 hours to evaporate and crystallize. Finally, the mixture was centrifuged by the first centrifuge 8 and fluidized drying by the fluidized drying layer 9 to obtain crude xylitol crystals with a purity of 99.5% and a pH of 4.87, and centrifuged by the first centrifuge 8 to obtain the first centrifuged mother liquor C with a purity of 90%, which was recycled to the harmony tank 1.

[0027] Step 13: The above-mentioned xylitol crude crystals with a purity of 99.5% were dissolved by adding purified water, and then blended with the second centrifuged mother liquor D to obtain a second blended liquid with a xylitol content of 98.2%. The second blended liquid was further concentrated to a concentration of 1350 g / L in the second evaporator 11 and placed in the second crystallization tank 12. The vacuum degree of the second crystallization tank 12 was maintained at -0.095 MPa, the temperature was maintained at 65 ° C, 0.001% xylitol seed crystals (80-100 mesh) were added, and the mixture was evaporated for 8 h to crystallize. Finally, the mixture was centrifuged by the second centrifuge 13, hot air drying by the hot air drying tank 14, and cold air drying by the cold air fluidized bed 15 to obtain a xylitol crystal B product with a purity of 99.97%. The second centrifuged mother liquor D obtained by centrifuging the second centrifuge 13 was recycled to the xylitol dissolving tank 10.

[0028] According to the method described in the Chinese Pharmacopoeia, the acidity of the produced xylitol crystal B was measured, and a xylitol solution was produced using new ultrapure water at a ratio of 10g crystals to 20ml water, and the pH of the xylitol solution in this example was measured to be 6.06. The obtained xylitol crystal B was left at room temperature for one week, and then measured using the same method to find that the pH of the xylitol solution was 6.03. The xylitol crystal was left at room temperature for one month, and then measured using the same method to find that the pH of the xylitol solution was 6.01.

[0029] The xylitol crystals produced in Example 1 were evaluated by flavor testing, with the results shown in FIG. <Example 2>

[0030] A second embodiment of the method for producing high quality xylitol crystals of the present invention comprises the following steps.

[0031] Step 21: The xylitol hydrogenated liquid A and the first centrifuged mother liquor C are blended in a certain ratio, and the blended liquid is sequentially purified and concentrated in the heat exchanger 2, the decolorization tank 3, the ion exchange system 4, the microporous filter 5, and the first evaporator 6 to obtain a xylitol concentrate having a temperature of 90°C, a concentration of 1400g / L, and a purity of 94%.

[0032] Step 22: The vacuum degree of the first crystallization vessel 7 is maintained at -0.095MPa, and the xylitol concentrate is further evaporated. When the temperature of the first crystallization vessel 7 drops to 64°C, 0.001% xylitol seed crystals (100-120 mesh) are added, and the system is maintained at 64°C for 12 hours to evaporate and crystallize. Finally, the mixture is centrifuged by the first centrifuge 8 and fluidized drying by the fluidized drying layer 9 to obtain crude xylitol crystals with a purity of 99.6% and a pH of 4.90, and centrifuged by the first centrifuge 8 to obtain the first centrifuged mother liquor C with a purity of 89.5%, which is recycled to the harmony tank 1.

[0033] Step 23: The above xylitol crude crystals with a purity of 99.6% were dissolved by adding purified water, and then blended with the second centrifuged mother liquor D to obtain a second blended liquid with a xylitol content of 98.4%. The second blended liquid was further concentrated to a concentration of 1380 g / L in the second evaporator 11 and placed in the second crystallization tank 12. The vacuum degree of the second crystallization tank 12 was maintained at -0.095 MPa, the temperature was maintained at 65 ° C, 0.001% xylitol seed crystals (100-120 mesh) were added, and the mixture was evaporated for 10 h to crystallize. Finally, the mixture was centrifuged by the second centrifuge 13, hot air dried by the hot air drying tank 14, and cold air dried by the cold air fluidized bed 15 to obtain a xylitol crystal B product with a purity of 99.97%. The second centrifuged mother liquor D obtained by centrifuging the second centrifuge 13 was recycled to the xylitol dissolving tank 10.

[0034] According to the method described in the Chinese Pharmacopoeia, the acidity of the produced xylitol crystal B was measured, and a xylitol solution was produced using fresh ultrapure water at a ratio of 10 g crystals to 20 ml water. The pH of the xylitol solution in this example was measured to be 6.12. The obtained xylitol crystal B was left at room temperature for one week, and then measured using the same method to find that the pH of the xylitol solution was 6.08. The xylitol crystals were left at room temperature for one month, and then measured using the same method to find that the pH of the xylitol solution was 6.05.

[0035] The xylitol crystals produced in Example 2 were evaluated by flavor testing, with the results shown in FIG. <Example 3>

[0036] A third embodiment of the method for producing high quality xylitol crystals of the present invention comprises the following steps.

[0037] Step 31: The xylitol hydrogenation liquid A and the first centrifuged mother liquor C are blended in a certain ratio to obtain a blended liquid with a xylitol content of 96%. The blended liquid is sequentially purified and concentrated in the heat exchanger 2, the decolorization tank 3, the ion exchange system 4, the microporous filter 5, and the first evaporator 6 to obtain a xylitol concentrate with a temperature of 95°C and a concentration of 1350g / L.

[0038] Step 32: The vacuum degree of the first crystallization vessel 7 is maintained at -0.095MPa, and the xylitol concentrate is further evaporated. When the temperature of the first crystallization vessel 7 drops to 66°C, 0.002% xylitol seed crystals (60-80 mesh) are added, and the system is maintained at 66°C for 10 hours to evaporate and crystallize. Finally, the mixture is centrifuged by the first centrifuge 8 and fluidized drying by the fluidized drying layer 9 to obtain crude xylitol crystals with a purity of 99.7% and a pH of 4.99, and centrifuged by the first centrifuge 8 to obtain the first centrifuged mother liquor C with a purity of 92%, which is recycled to the harmony tank 1.

[0039] Step 33: After adding purified water to the above-mentioned xylitol crude crystals with a purity of 99.7% to dissolve them, it is blended with the second centrifuged mother liquor D to obtain a second blended liquid with a xylitol content of 98.4%. The second blended liquid is further concentrated to a concentration of 1400 g / L in the second evaporator 11 and placed in the second crystallization tank 12. The vacuum degree of the second crystallization tank 12 is maintained at -0.095 MPa, the temperature is maintained at 66 ° C, 0.002% xylitol seed crystals (60-80 mesh) are added, and the mixture is evaporated for 10 h to crystallize. Finally, the mixture is centrifuged by the second centrifuge 13, hot air dried by the hot air drying tank 14, and cold air dried by the cold air fluidized bed 15 to obtain a xylitol crystal B product with a purity of 100%. In addition, the second centrifuged mother liquor D is obtained by centrifuging the second centrifuge 13, and recycled to the xylitol dissolving tank 10.

[0040] According to the method described in the Chinese Pharmacopoeia, the acidity of the produced xylitol crystal B was measured, and a xylitol solution was produced using new ultrapure water at a ratio of 10g crystals to 20ml water, and the pH of the xylitol solution in this example was measured to be 6.09. The obtained xylitol crystal B was left at room temperature for one week, and then measured using the same method to find that the pH of the xylitol solution was 6.07. The xylitol crystal was left at room temperature for one month, and then measured using the same method to find that the pH of the xylitol solution was 6.05.

[0041] The xylitol crystals produced in Example 3 were evaluated for flavor testing, with the results shown in FIG.

[0042] To further illustrate the improvement effect of the present invention, the following comparative experiment was carried out. Comparative Example 1

[0043] A first comparative example of the method for producing xylitol crystals of the present invention includes the following steps.

[0044] Step D11: The xylitol hydrogenation liquid A and the first centrifuged mother liquor C are blended in a certain ratio to obtain a blended liquid with a xylitol content of 94%. The blended liquid is sequentially purified and concentrated in the heat exchanger 2, the decolorization tank 3, the ion exchange system 4, the microporous filter 5, and the first evaporator 6 to obtain a xylitol concentrate with a temperature of 95°C and a concentration of 1300g / L.

[0045] Step D12: The vacuum degree of the first crystallization vessel 7 was maintained at -0.095 MPa, and the xylitol concentrate was further evaporated. When the temperature of the first crystallization vessel 7 dropped to 64°C, 0.001% xylitol seed crystals (80-100 mesh) were added, and the system was maintained at 64°C for 10 hours to evaporate and crystallize. Finally, the mixture was centrifuged by the first centrifuge 8 and fluidized drying by the fluidized drying layer 9 to obtain xylitol crystals with a purity of 99.8%, and centrifuged by the first centrifuge 8 to obtain the first centrifuged mother liquor C with a purity of 90%, which was recycled to the harmony tank 1.

[0046] According to the method described in the Chinese Pharmacopoeia, the acidity of the produced xylitol crystals was measured, and a xylitol solution was produced using new ultrapure water at a ratio of 10g crystals to 20ml water, and the pH of the xylitol solution in this embodiment was measured to be 5.02. The obtained xylitol crystals were left at room temperature for one week, and then measured using the same method to find that the pH of the xylitol solution was 4.85. The xylitol crystals were left at room temperature for one month, and then measured using the same method to find that the pH of the xylitol solution was 4.64.

[0047] The xylitol crystals produced in Comparative Example 1 were tested and evaluated for flavor, and the results are shown in FIG. Comparative Example 2

[0048] The second comparative example of the method for producing xylitol crystals of the present invention includes the following steps. Step D21: The xylitol hydrogenation liquid A and the first centrifuged mother liquor C are blended in a certain ratio to obtain a blended liquid with a xylitol content of 94.5%. The blended liquid is sequentially purified and concentrated in the heat exchanger 2, the decolorization tank 3, the ion exchange system 4, the microporous filter 5, and the first evaporator 6 to obtain a xylitol concentrate with a temperature of 100°C and a concentration of 1200g / L.

[0049] Step D22: The vacuum degree of the first crystallization vessel 7 was maintained at -0.095 MPa, and the xylitol concentrate was further evaporated. When the temperature of the first crystallization vessel 7 dropped to 65°C, 0.002% xylitol seed crystals (100-120 mesh) were added, and the system was maintained at 65°C for 8 hours to evaporate and crystallize. Finally, the mixture was centrifuged by the first centrifuge 8 and fluidized drying by the fluidized drying layer 9 to obtain xylitol crystals with a purity of 99.75%, and centrifuged by the first centrifuge 8 to obtain the first centrifuged mother liquor C with a purity of 91%, which was recycled to the harmony tank 1.

[0050] According to the method described in the Chinese Pharmacopoeia, the acidity of the produced xylitol crystals was measured, and a xylitol solution was produced using fresh ultrapure water at a ratio of 10g crystals to 20ml water, and the pH of the xylitol solution in this embodiment was measured to be 5.04. The obtained xylitol crystals were left at room temperature for one week, and then measured using the same method to find that the pH of the xylitol solution was 4.81. The xylitol crystals were left at room temperature for one month, and then measured using the same method to find that the pH of the xylitol solution was 4.68.

[0051] The xylitol crystals produced in Comparative Example 2 were tested and evaluated for flavor, with the results shown in FIG. Comparative Example 3

[0052] The third comparative example of the method for producing xylitol crystals of the present invention includes the following steps.

[0053] Step D31: The xylitol hydrogenation liquid A and the first centrifuged mother liquor C are blended in a certain ratio to obtain a blended liquid with a xylitol content of 96%. The blended liquid is sequentially purified and concentrated in the heat exchanger 2, the decolorization tank 3, the ion exchange system 4, the microporous filter 5, and the first evaporator 6 to obtain a xylitol concentrate with a temperature of 92°C and a concentration of 1400g / L.

[0054] Step D32: The vacuum degree of the first crystallization vessel 7 was maintained at -0.095 MPa, and the xylitol concentrate was further evaporated. When the temperature of the first crystallization vessel 7 dropped to 66°C, 0.001% xylitol seed crystals (100-120 mesh) were added, and the system was maintained at 66°C for 12 hours to evaporate and crystallize. Finally, the mixture was centrifuged by the first centrifuge 8 and fluidized drying by the fluidized drying layer 9 to obtain xylitol crystals with a purity of 99.7%, and centrifuged by the first centrifuge 8 to obtain the first centrifuged mother liquor C with a purity of 92%, which was recycled to the harmony tank 1.

[0055] According to the method described in the Chinese Pharmacopoeia, the acidity of the produced xylitol crystals was measured, and a xylitol solution was produced using new ultrapure water at a ratio of 10g crystals to 20ml water, and the pH of the xylitol solution in this embodiment was measured to be 5.03. The obtained xylitol crystals were left at room temperature for one week, and then measured using the same method to find that the pH of the xylitol solution was 4.90. The xylitol crystals were left at room temperature for one month, and then measured using the same method to find that the pH of the xylitol solution was 4.73.

[0056] The xylitol crystals produced in Comparative Example 3 were tested and evaluated for flavor, and the results are shown in FIG.

[0057] The pH measurement results and flavor evaluation of the xylitol crystals produced in each of the above examples and comparative examples are summarized in Table 3 and Figure 2. As can be seen from Table 3, in all of Examples 1 to 3, the pH is 6.0 or more, and after leaving for one month, the pH of the xylitol crystals decreases by 0.1 or less. On the other hand, in Comparative Examples 1 to 3, the pH is only about 5.0, and after leaving for one month, the pH of the xylitol crystals decreases by 0.3 or more. From these data, the pH of the xylitol crystals can be clearly and stably lowered by the recrystallization method. In addition, as can be seen from the flavor radar chart in Figure 2, the characteristics preferred by consumers, such as sweetness and sweet aftertaste, of the xylitol crystal products produced in Examples 1 to 3 are all better than those of the comparative examples, and undesirable attributes such as tooth erosion and numbness are all lower than those of the comparative examples, which also shows that the flavor of the xylitol crystals produced using the method of the present invention is significantly improved.

[0058] [Table 3]

[0059] The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. 1. A system for producing high quality xylitol crystals, comprising: a conditioning tank, a heat exchanger, a decolorization tank, an ion exchange system, a microporous filter, a first evaporator, a first crystallization tank, a first centrifuge, a fluidized drying tank, a xylitol dissolving tank, a second evaporator, a second crystallization tank, a second centrifuge, a hot air drying tank, and a cold air fluidized bed, which are sequentially connected to each other via piping, wherein each of the first centrifuge and the second centrifuge is provided with a liquid outlet, the liquid outlet of the first centrifuge is connected to one supply port of the conditioning tank via piping, the liquid outlet of the second centrifuge is connected to one supply port of the xylitol dissolving tank via piping, the conditioning tank is provided with a supply port for a material to be treated, the xylitol dissolving tank is further provided with a water inlet for purified water, and the cold air fluidized bed is provided with an outlet, the material to be treated is a xylitol hydrogenated liquid, and the material discharged from the outlet of the cold air fluidized bed is a xylitol crystallized product.

2. 1. A method for producing high quality xylitol crystals, comprising: Step 1: preparing xylitol concentrate: the xylitol hydrogenated liquid and the first centrifuged mother liquor sent from the first centrifuge are mixed uniformly at a certain ratio to obtain a mixed liquid material, which is then heat exchanged in a heat exchanger, decolorized in a decolorizing tank, ion exchanged in an ion exchange system, filtered through a microporous filter, and evaporated in a first evaporator to obtain a xylitol concentrate with a concentration of 1200-1400g / L and a purity of 94-96%; Step 2: crystallization of xylitol concentrate: the xylitol concentrate is crystallized by lowering the temperature in the first crystallization vessel for 8-12 hours, the resulting xylitol paste is separated by the first centrifuge and dried in a fluidized drying bed to obtain crude xylitol crystals, and the first centrifuged mother liquor obtained by separation by the first centrifuge is recycled to the harmony tank via piping and harmonized with the xylitol hydrogenated liquid for reuse, in which the purity of the crude xylitol crystals is 98.5-99.8%, pH<5.0, and the purity of the first centrifuged mother liquor is 88-92%; and (3) dissolving and recrystallizing the crude xylitol crystals: sending the crude xylitol crystals to a xylitol dissolving tank, dissolving them in purified water added to the xylitol dissolving tank, and then mixing them uniformly with the second centrifuged mother liquor sent from the second centrifuge at a certain ratio to obtain a xylitol dissolved mixture, which is concentrated by a second evaporator, crystallized by a second crystallizing pot, centrifuged by a second centrifuge, hot air dried by a hot air drying tank, and cold air dried by a cold air fluidized bed to obtain a high-quality xylitol crystal product. The second centrifuged mother liquor obtained by separation by the second centrifuge is recycled to the xylitol dissolving tank through a pipe and mixed with the crude xylitol crystal dissolved solution for reuse, in which the purity of the high-quality xylitol crystal product is >99.8% and the pH is >6.

0.

3. The method for producing high quality xylitol crystals according to claim 2, characterized in that in step 1, the temperature of the xylitol concentrate is 90-100°C.

4. The method for producing high-quality xylitol crystals according to claim 2, characterized in that in step 2, xylitol seed crystals are added during cooling crystallization, the addition rate of xylitol seed crystals is 0.001-0.002%, the mesh of the xylitol seed crystals is 60-120 mesh, and the temperature of the system when the xylitol seed crystals are added is 64-66°C.

5. The method for producing high-quality xylitol crystals according to claim 1, characterized in that in step 3, in the crystallization in the second crystallization vessel, xylitol seed crystals are added, the addition rate of xylitol seed crystals is 0.001-0.002%, the mesh of the xylitol seed crystals is 60-120 mesh, and the temperature of the system when the xylitol seed crystals are added is 64-66°C.

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