A system and method for co-producing xylose crystals and caramel pigment using xylose massecuite

Abstract

The present invention relates to a system and method for co-producing xylose crystals and caramel pigments by using xylose massecuite. The system comprises a raw material storage tank, a coagulation tank, a flocculation tank, a neutralization tank, a first filter, a nanofiltration membrane separator, an electrodialysis membrane separator, a chromatographic separation device, an evaporation concentration tank, a crystallization tank, a centrifugal separator, a dryer, a sugar solution mixing tank, a browning reaction kettle, a second filter and a scraped film evaporator; the extract outlet of the chromatographic separation device is connected to the evaporation concentration tank, the raffinate outlet is connected to the sugar solution mixing tank, the solid matter outlet of the centrifugal separator is connected to the dryer, the liquid matter outlet is connected to the sugar solution mixing tank, the raw material storage tank stores the xylose massecuite raw material to be processed, the material output by the dryer is xylose crystals, and the material obtained by the scraped film evaporator is a high red index caramel pigment. The present invention makes full use of the xylose massecuite that cannot be used and affects the environmental ecology, and also produces high value-added xylose crystals and high red index caramel pigments.

Description

Technical Field

[0001] The invention belongs to the technical field of sugar alcohol preparation, and particularly relates to a system and method for co-producing xylose crystals and caramel pigment by utilizing xylose massecuite. Background Art

[0002] Xylose is mainly concentrated into sugar paste after hydrolysis of plants such as corn cobs, straws, and rice husks, and then refined. A foreign company uses bagasse as raw material for papermaking, and produces more than 30,000 tons / year of xylose sugar paste as a byproduct. Due to raw material problems, the sugar paste is mixed with fine silicides, which are difficult to remove and cause clogging of the filtering equipment, thereby affecting the overall production efficiency, and ultimately leading to the inability to effectively utilize the xylose sugar paste. In addition, the xylose sugar paste is rich in 80wt% of sugar resources, of which pentose accounts for 45wt% and hexose accounts for about 30wt%. Using xylose sugar paste as raw material, after removing the impurities that affect the use, the pentose in the xylose sugar paste raw material is prepared into xylose crystals, hexose and residual pentose are prepared into high red caramel pigments, which can not only make full use of the xylose sugar paste that cannot be used and affects the environmental ecology, but also can produce high value-added xylose crystals and high red caramel pigments. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a system and method for co-producing xylose crystals and caramel pigments by using xylose massecuite, wherein the impurity silicification in the xylose massecuite is removed by a coagulation-flocculation process, and then the pentoses in the xylose massecuite are prepared into xylose crystals, and the hexoses and residual pentoses are prepared into high red index caramel pigments. The present invention not only makes full use of the xylose massecuite that cannot be used and affects the environment and ecology, but also produces high value-added xylose crystals and high red index caramel pigments, and effectively utilizes the xylose massecuite produced as a by-product of the papermaking industry.

[0004] The present invention is implemented in this way, providing a system for co-producing xylose crystals and caramel pigments by using xylose massecuite, comprising a xylose preparation subsystem and a caramel pigment preparation subsystem connected to each other through pipelines, the xylose preparation subsystem comprising a raw material storage tank, a coagulation tank, a flocculation tank, a neutralization tank, a first filter, a nanofiltration membrane separator, an electrodialysis membrane separator, a chromatographic separation device, an evaporation concentration tank, a crystallization tank, a centrifugal separator and a dryer connected in sequence through pipelines, and the caramel pigment preparation subsystem comprising a sugar solution mixing tank, a browning reactor, a second filter and a scraper membrane connected in sequence through pipelines Evaporator; the chromatographic separation device is respectively provided with an extract outlet and a raffinate outlet, the extract outlet is connected with the feed port of the evaporation concentration tank through a pipeline, the raffinate outlet is connected with the feed port of the sugar solution mixing tank through a pipeline, the centrifugal separator is respectively provided with a solid outlet and a liquid outlet, the solid outlet is connected with the feed port of the dryer through a pipeline, the liquid outlet is connected with a feed port of the sugar solution mixing tank, the raw material storage tank stores the xylose massecuite raw material to be processed, the material output from the discharge port of the dryer is xylose crystals, and the material finally obtained from the discharge port of the scraped film evaporator is high red index caramel pigment.

[0005] Furthermore, what is outputted from the extracting liquid outlet of the chromatographic separation device is a chromatographic extracting liquid, and what is outputted from the raffinate liquid outlet of the chromatographic separation device is a chromatographic raffinate liquid.

[0006] Furthermore, the liquid transported from the liquid outlet of the centrifugal separator is xylose centrifuge mother liquor.

[0007] The present invention is implemented by providing a method for co-producing xylose crystals and caramel pigment by using xylose massecuite, wherein the method uses the system for co-producing xylose crystals and caramel pigment by using xylose massecuite as described above, and the method comprises the following steps:

[0008] Step 1: The xylose massecuite in the raw material storage tank is transported to a coagulation tank through a pipeline for silicide aggregation treatment, and then is sequentially transported to a flocculation tank and a neutralization tank through a pipeline for flocculation treatment and neutralization treatment, respectively.

[0009] Step 2: The neutralized liquid is transported to the first filter through a pipeline for filtration treatment, and then sent to the nanofiltration membrane separator and the electrodialysis membrane separator through a pipeline in sequence for decolorization treatment and desalination treatment respectively.

[0010] Step 3, the chromatographic separation feed liquid after desalting treatment is sent to the chromatographic separation device for chromatographic separation treatment, and the chromatographic separation extract with high xylose content obtained after the chromatographic separation treatment is sequentially transported to the evaporation concentration tank for evaporation concentration treatment, the crystallization tank for crystallization treatment, and the centrifugal separator for centrifugal separation treatment through a pipeline; the chromatographic separation raffinate with low xylose content obtained after the chromatographic separation treatment is transported to the sugar solution mixing tank through a pipeline to be mixed with the xylose centrifuge mother liquor.

[0011] Step 4: Send the xylose solids separated by centrifugation to a dryer for drying to obtain finished xylose crystals.

[0012] Step 5, the mixed sugar liquid of the chromatographic separation raffinate and the xylose centrifuge mother liquor in the sugar liquid mixing tank is transported to the browning reactor through a pipeline for browning reaction, and then filtered through a second filter and evaporated in a scraped film evaporator through a pipeline to prepare a high red index caramel pigment.

[0013] Compared with the prior art, the system and method of the present invention for co-producing xylose crystals and caramel pigment by using xylose massecuite has the following characteristics:

[0014] 1. The silicide impurities that affect filtration are removed through the coagulation-flocculation process, and the filtration rate of xylose massecuite is increased by nearly 3 times, making it possible to industrialize the preparation of xylose massecuite into xylose crystals.

[0015] 2. By preparing the pentoses in xylose massecuite into xylose crystals, and hexoses and residual pentoses into high red index caramel pigment, the resource utilization rate is improved while a high red index caramel pigment product with a red index of up to 7 is prepared, which greatly improves the comprehensive utilization value of sugar resources in xylose massecuite.

[0016] 3. Through the improvement and optimization of the entire process system, the pentoses in xylose massecuite are prepared into xylose crystals, and the hexoses and residual pentoses are prepared into high red index caramel pigment. The xylose massecuite with a selling price of RMB 200-500 / ton is transformed into xylose crystals with a selling price of RMB 20,000-25,000 / ton and high red index caramel pigment with a selling price of RMB 4,000-5,000 / ton, which greatly improves the economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the principle of a preferred embodiment of a system for co-producing xylose crystals and caramel pigment by using xylose massecuite of the present invention;

[0018] Figure 2 The present invention is a schematic diagram of the flow direction of various materials in a method for co-producing xylose crystals and caramel pigment by utilizing xylose massecuite. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0020] Please also refer to Figure 1 as well as Figure 2As shown, a preferred embodiment of the system for co-producing xylose crystals and caramel pigment from xylose massecuite of the present invention comprises a xylose preparation subsystem I and a caramel pigment preparation subsystem II interconnected by pipelines. The arrow direction in the figure is a schematic diagram of the flow direction of materials in the system.

[0021] The xylose preparation subsystem I includes a raw material storage tank 1, a coagulation tank 2, a flocculation tank 3, a neutralization tank 4, a first filter 5, a nanofiltration membrane separator 6, an electrodialysis membrane separator 7, a chromatographic separation device 8, an evaporation concentration tank 9, a crystallization tank 10, a centrifugal separator 11 and a dryer 12, which are connected in sequence through pipelines. The caramel pigment preparation subsystem II includes a sugar solution mixing tank 13, a browning reactor 14, a second filter 15 and a scraped film evaporator 16, which are connected in sequence through pipelines.

[0022] The chromatographic separation device 8 is provided with an extract outlet and a raffinate outlet respectively, the extract outlet is connected to the feed port of the evaporation concentration tank 9 through a pipeline, and the raffinate outlet is connected to the feed port of the sugar solution mixing tank 13 through a pipeline. The centrifugal separator 11 is provided with a solid outlet and a liquid outlet respectively, the solid outlet is connected to the feed port of the dryer 12 through a pipeline, and the liquid outlet is connected to one feed port of the sugar solution mixing tank 13. The other feed port of the sugar solution mixing tank 13 is connected to the raffinate outlet of the chromatographic separation device 8 through a pipeline. The raw material storage tank 1 stores the raw material xylose massecuite A to be processed, the material output from the discharge port of the dryer 12 is xylose crystals B, and the material finally obtained from the discharge port of the scraped film evaporator 16 is high red index caramel pigment C.

[0023] The chromatographic extract D is output from the extract outlet of the chromatographic separation device 8, and the chromatographic raffinate E is output from the raffinate outlet of the chromatographic separation device 8.

[0024] The liquid delivered from the liquid outlet of the centrifugal separator 11 is xylose centrifugal mother liquor F.

[0025] The coagulation tank 2 is used to gather fine silicides together, the flocculation tank 3 is used to precipitate the gathered fine silicides, the neutralization tank 4 is used to neutralize the pH of the xylose massecuite liquid, and the first filter 5 is used to filter the floccules. The nanofiltration membrane separator 6 is used for decolorization of the xylose liquid, the retentate is the pigment liquid, and the permeate is the decolorization liquid. The electrodialysis membrane separator 7 is used for desalination of the xylose liquid, the retentate is the concentrated salt liquid, and the permeate is the desalted liquid. The chromatographic separation device 8 is used to separate the chromatographic separation feed liquid G flowing through into a chromatographic separation extract with a high xylose content and a chromatographic separation raffinate with a low xylose content. The evaporation concentration tank 9 and the crystallization tank 10 are used for evaporation concentration and xylose crystallization, and the centrifugal separator 11 is used to separate crystalline xylose and xylose centrifuge mother liquor. The dryer 12 is used to dry the crystalline xylose to obtain the xylose crystal B product.

[0026] The sugar solution mixing tank 13 is used to mix the chromatographic separation raffinate and the xylose centrifuge mother liquor, and the browning reactor 14 is used to brown the mixed sugar solution to obtain a high red index caramel pigment crude product. The second filter 15 is used to remove solid impurities in the caramel pigment, and the scraped film evaporator 16 is used to concentrate the caramel pigment at low temperature to obtain a high red index caramel pigment C.

[0027] The present invention is implemented by providing a method for co-producing xylose crystals and caramel pigment by using xylose massecuite, wherein the method uses the system for co-producing xylose crystals and caramel pigment by using xylose massecuite as described above, and the method comprises the following steps:

[0028] Step 1: transport the xylose massecuite A in the raw material storage tank 1 to the coagulation tank 2 through a pipeline for silicide aggregation treatment, and then sequentially transport it to the flocculation tank 3 and the neutralization tank 4 through a pipeline for flocculation treatment and neutralization treatment respectively.

[0029] Step 2: The neutralized liquid is transported to the first filter 5 through a pipeline for filtration, and then sent to the nanofiltration membrane separator 6 and the electrodialysis membrane separator 7 through a pipeline in sequence for decolorization and desalination, respectively.

[0030] Step 3, the chromatographic separation feed liquid G after desalting treatment is sent to the chromatographic separation device 8 for chromatographic separation treatment, and the chromatographic separation extract D with high xylose content obtained after the chromatographic separation treatment is sequentially transported to the evaporation concentration tank 9 through a pipeline for evaporation concentration treatment, the crystallization tank 10 for crystallization treatment, and the centrifugal separator 11 for centrifugal separation treatment; the chromatographic separation raffinate E with low xylose content obtained after the chromatographic separation treatment is transported to the sugar liquid mixing tank 13 through a pipeline to mix with the xylose centrifuge mother liquor F to prepare a high red finger caramel pigment.

[0031] Step 4: Send the xylose solids separated by centrifugation to the dryer 12 for drying to obtain the finished xylose crystals B.

[0032] Step 5: The mixed sugar liquid of the chromatographic separation raffinate and the xylose centrifuge mother liquor in the sugar liquid mixing tank 13 is transported to the browning reactor 14 through a pipeline for browning reaction, and then filtered through the second filter 15 and evaporated in the scraped film evaporator 16 through a pipeline to prepare a high red index caramel pigment.

[0033] In step 1, the dry matter concentration of sugar resources in xylose massecuite A is 80-90 wt%. Among them, hexose contains 30-35 wt% and pentose contains 45-50 wt%. During the coagulation treatment, 1.0 g / L-10.0 g / L of iron-magnesium compounding agent is added to the xylose massecuite liquid as a coagulant. The iron-magnesium compounding agent is a compound of magnesium chloride and ferrous sulfate, and the compounding ratio is m 氯化镁 :m 硫酸亚铁The ratio of the mixture to the aqueous solution is 1:1 to 9:1, and the mixture is stirred thoroughly to make it uniform. The pH value of the xylose massecuite liquid is adjusted to 9 to 10 with sodium hydroxide. During the flocculation treatment, 1.0 to 10.0 g / L diatomaceous earth is added for adsorption. The mixture is stirred slowly for 30 minutes and then separated by sedimentation. The supernatant is transported to the neutralization tank 4 and hydrochloric acid is added to adjust the pH value to neutral.

[0034] In step 2, during the nanofiltration decolorization treatment, the operating temperature of the nanofiltration membrane separator 6 is 40-60°C and the operating pressure is 15-35 bar; during the electrodialysis desalination treatment, the operating current of the electrodialysis membrane separator 7 is 60-120A, the voltage is 200-250V, and the operating pressure is 15-35 bar.

[0035] In step five, during the browning reaction treatment, the reaction aid used is a compound of food-grade succinic acid and citric acid, and the compound ratio is 7:3~5:5. The reaction process is controlled as follows: first adjust the pH to 2.0~4.0, then raise the temperature to 80~90°C for reaction for 30~50min, then raise the temperature to 150~170°C for reaction for 2~4h and continuously add food-grade defoaming agent. After the reaction is completed, add water to the refractive index of about 40%; during the scraped film evaporation treatment, the evaporation pressure of the scraped film evaporator 16 is 4~5bar, and the vacuum degree is 80~90kpa.

[0036] The system and method for co-producing xylose crystals and caramel pigment using xylose massecuite of the present invention are further described below by means of specific examples.

[0037] The present invention is the first system and method for co-producing xylose crystals and caramel pigment using xylose massecuite, which uses xylose massecuite as a raw material to prepare finished xylose crystals and then uses chromatographic separation raffinate to mix with xylose centrifuge mother liquor to prepare high red index caramel pigment. The method comprises the following steps:

[0038] Step 1: transport the xylose massecuite A in the raw material storage tank 1 to the coagulation tank 2 through a pipeline for silicide aggregation treatment. During the coagulation treatment, 10.0 g / L of an iron-magnesium compounding agent is added to the xylose massecuite liquid as a coagulant. The iron-magnesium compounding agent is a compound of magnesium chloride and ferrous sulfate, and the compounding ratio is m 氯化镁 :m 硫酸亚铁 The ratio of the sugar solution to the flocculation tank is 1:1, and the mixture is stirred thoroughly to make it uniform. The pH value of the sugar solution is adjusted to 9 with sodium hydroxide, and then the mixture is sent to the flocculation tank for flocculation. During the flocculation treatment, 10.0 g / L diatomaceous earth is added for adsorption, and the mixture is slowly stirred for 30 minutes and then separated by sedimentation. The supernatant is sent to the neutralization tank 4, and hydrochloric acid is added to adjust the pH value to 7.

[0039] Step 2: The neutralized liquid is transported to the first filter 5 through a pipeline for filtration. After filtration, it is then sent to the nanofiltration membrane separator 6 and the electrodialysis membrane separator 7 through a pipeline in sequence for decolorization and desalination. The filtration rate through the 0.8 μm filter membrane is 1.13 m / s.3 / (m 2 * h), in line with daily production efficiency requirements. During nanofiltration decolorization, the nanofiltration membrane separator operates at a temperature of 60°C and a pressure of 15 bar; during electrodialysis desalination, the electrodialysis membrane separator operates at a current of 120A, a voltage of 200V, and a pressure of 15 bar.

[0040] Step 3: The chromatographic separation feed liquid G after desalting treatment is sent to the chromatographic separation device 8 for chromatographic separation treatment. The chromatographic separation extract D with a xylose content of 85wt% obtained after the chromatographic separation treatment is sequentially transported to the evaporation concentration tank 9 through a pipeline for evaporation concentration treatment, the crystallization tank 10 for crystallization treatment, and the centrifugal separator 11 for centrifugal separation treatment. The chromatographic separation raffinate E with a xylose content of 10wt% obtained after the chromatographic separation treatment is transported to the sugar liquid mixing tank 13 through a pipeline and mixed with the xylose centrifuge mother liquor F (xylose content of 40wt%) to prepare a high red finger caramel pigment.

[0041] Step 4: Send the centrifugally separated xylose solids to the dryer 12 for drying to obtain the finished xylose crystals B. The xylose purity of the prepared xylose crystals reaches 98%.

[0042] Step six, the mixed sugar liquid of the chromatographic separation raffinate and the xylose centrifugal mother liquor in the sugar liquid mixing tank 13 is transported to the browning reactor 14 through a pipeline for browning reaction. During the browning reaction, the reaction aid used is a compound of food-grade succinic acid and citric acid, and the compounding ratio is 7:3. The reaction process is regulated as follows: first adjust the pH to 2.0, then heat to 90 ° C for reaction for 30 min, then heat to 170 ° C for reaction for 2 h and continuously drip food-grade defoamer, and then add water to the refraction of about 40% after the reaction. After that, the high red caramel pigment is prepared after the filtration treatment of the second filter 15 and the evaporation treatment of the scraped film evaporator 16 through the pipeline. During the scraped film evaporation treatment, the evaporation pressure of the scraped film evaporator 16 is 4 bar, and the vacuum degree is 90 kpa. The red index of the high red caramel pigment product finally prepared is as high as 7.5, and other indicators are all in accordance with national standards, and the utilization rate of carbohydrate resources is as high as 95%.

[0043] Comparative Example 1:

[0044] Xylose is directly extracted by using xylose massecuite A as raw material, and the specific steps include: xylose massecuite A in raw material storage tank 1 is transported to the first filter through a pipeline, and the filtration rate through a 0.8 μm filter membrane is 0.39 m 3 / (m 2 *h). After nanofiltration decolorization, electrodialysis desalination, chromatography separation, evaporation concentration, and crystallization centrifugation, the final xylose crystal product is obtained. Because the filtration is too low, the system is difficult to operate effectively, and the production efficiency drops by about 60%. The raffinate after chromatography separation is sold as syrup, and the xylose centrifuge mother liquor is recycled. The actual utilization rate of sugar resources is only 70%.

[0045] In summary, through the improvement of the entire system and method, the production efficiency is increased from 40% to 100%, the utilization rate of sugar resources in xylose massecuite A is increased from 70% to 95%, and the red index of caramel pigment is as high as 7.0. The present invention not only improves the possibility of preparing xylose using xylose massecuite A as a raw material, but also improves the comprehensive utilization value of sugar resources of xylose massecuite A.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A system for co-producing xylose crystals and caramel pigment using xylose massecuite, characterized in that: The invention comprises a xylose preparation subsystem and a caramel pigment preparation subsystem which are interconnected through pipelines. The xylose preparation subsystem comprises a raw material storage tank, a coagulation tank, a flocculation tank, a neutralization tank, a first filter, a nanofiltration membrane separator, an electrodialysis membrane separator, a chromatographic separation device, an evaporation concentration tank, a crystallization tank, a centrifugal separator and a dryer which are sequentially connected through pipelines. The caramel pigment preparation subsystem comprises a sugar solution mixing tank, a browning reaction kettle, a second filter and a scraped film evaporator which are sequentially connected through pipelines. The chromatographic separation device is provided with an extracting liquid, a mixing tank, a browning reaction kettle, a second filter and a scraped film evaporator respectively. The extract outlet is connected with the feed port of the evaporation concentration tank through a pipeline, the raffinate outlet is connected with the feed port of the sugar solution mixing tank through a pipeline, the centrifugal separator is respectively provided with a solid outlet and a liquid outlet, the solid outlet is connected with the feed port of the dryer through a pipeline, the liquid outlet is connected with a feed port of the sugar solution mixing tank, the raw material storage tank stores the xylose massecuite raw material to be processed, the material output from the discharge port of the dryer is xylose crystals, and the material finally obtained from the discharge port of the scraped film evaporator is high red index caramel pigment.

2. The system for co-producing xylose crystals and caramel pigment by using xylose massecuite as claimed in claim 1, characterized in that: The liquid outputted from the extract outlet of the chromatographic separation device is a chromatographic extract liquid, and the liquid outputted from the raffinate outlet of the chromatographic separation device is a chromatographic raffinate liquid.

3. The system for co-producing xylose crystals and caramel pigment by using xylose massecuite as claimed in claim 1, characterized in that: The liquid delivered from the liquid outlet of the centrifugal separator is xylose centrifuge mother liquor.

4. A method for co-producing xylose crystals and caramel pigment using xylose massecuite, characterized in that: The method uses the system for co-producing xylose crystals and caramel pigment by using xylose massecuite as claimed in any one of claims 1 to 3, and the method comprises the following steps: Step 1, transporting the xylose massecuite in the raw material storage tank to a coagulation tank through a pipeline for silicide aggregation treatment, and then sequentially transporting it to a flocculation tank and a neutralization tank through a pipeline for flocculation treatment and neutralization treatment respectively; Step 2: The neutralized liquid is transported to the first filter through a pipeline for filtration, and then sent to the nanofiltration membrane separator and the electrodialysis membrane separator through a pipeline in sequence for decolorization and desalination, respectively; Step 3, the chromatographic separation feed liquid after desalting treatment is sent to the chromatographic separation device for chromatographic separation treatment, and the chromatographic separation extract with high xylose content obtained after the chromatographic separation treatment is sequentially transported to the evaporation concentration tank for evaporation concentration treatment, the crystallization tank for crystallization treatment, and the centrifugal separator for centrifugal separation treatment through a pipeline; the chromatographic separation raffinate with low xylose content obtained after the chromatographic separation treatment is transported to the sugar solution mixing tank through a pipeline to be mixed with the xylose centrifuge mother liquor; Step 4, sending the xylose solids separated by centrifugation to a dryer for drying to obtain finished xylose crystals; Step 5, the mixed sugar liquid of the chromatographic separation raffinate and the xylose centrifuge mother liquor in the sugar liquid mixing tank is transported to the browning reactor through a pipeline for browning reaction, and then filtered through a second filter and evaporated in a scraped film evaporator through a pipeline to prepare a high red index caramel pigment.

5. The method for co-producing xylose crystals and caramel pigment by using xylose massecuite as claimed in claim 4, characterized in that: In step 1, the dry matter mass percentage concentration of the sugar resources in the xylose massecuite is 80-90 wt%, wherein the hexose content in the sugar resources is 30-35 wt%, and the pentose content is 45-50 wt%. During the coagulation treatment, 1.0 g / L-10.0 g / L of an iron-magnesium compounding agent is added to the xylose massecuite liquid as a coagulant, and the iron-magnesium compounding agent is a compound of magnesium chloride and ferrous sulfate, and the compounding ratio is m 氯化镁 :m 硫酸亚铁 The ratio of the mixture is 1:1 to 9:1, and it is stirred thoroughly to make it uniform. The pH value of the xylose massecuite liquid is adjusted to 9 to 10 with sodium hydroxide. During the flocculation treatment, 1.0 to 10.0 g / L diatomaceous earth is added for adsorption. After slow stirring for 30 minutes, the mixture is separated by sedimentation. The supernatant is transported to the neutralization tank and hydrochloric acid is added to adjust the pH value to neutral.

6. The method for co-producing xylose crystals and caramel pigment by using xylose massecuite as claimed in claim 4, characterized in that: In step 2, during the nanofiltration decolorization treatment, the operating temperature of the nanofiltration membrane separator is 40~60°C and the operating pressure is 15~35 bar; during the electrodialysis desalination treatment, the operating current of the electrodialysis membrane separator is 60~120A, the voltage is 200~250V, and the operating pressure is 15~35 bar.

7. The method for co-producing xylose crystals and caramel pigment by using xylose massecuite as claimed in claim 4, characterized in that: In step five, during the browning reaction treatment, the reaction aid used is a compound of food-grade succinic acid and citric acid, and the compound ratio is 7:3~5:

5. The reaction process is controlled as follows: first adjust the pH to 2.0~4.0, then raise the temperature to 80~90°C for reaction for 30~50min, then raise the temperature to 150~170°C for reaction for 2~4h and continuously add food-grade defoaming agent. After the reaction, add water to the refractive index of 40%; during the scraped film evaporation treatment, the evaporation pressure of the scraped film evaporator is 4~5bar, and the vacuum degree is 80~90kpa.

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