阅读说明：本技术 一种制备木糖的电渗析及层析联合工艺 (Electrodialysis and chromatography combined process for preparing xylose ) 是由 吴限智 陈德水 徐小荣 莫世清 王战龙 于 2019-08-06 设计创作，主要内容包括：本发明公开一种制备木糖的电渗析及层析联合工艺,属于木糖生产技术领域。首先,对半纤维素水解液进行三级电渗析,最终得到第一级高盐液、第三级高盐液和第三级高糖液；其次,将第三级高盐液经浓缩及脱盐后,与第三级高糖液一并进入离子交换柱层析工序；最后,将离子交换柱再生后得到的再生液(含碱和含糖)进行脱碱,得到碱液和糖液,将碱液回用于离子交换柱再生,而糖液与第三级高盐液一并浓缩、脱盐,再次进行层析。一方面增加木糖溶液中杂质的去除率,提高产品质量；另一方面将第三级高盐液和再生液进行回收利用,减少跑糖量,提高经济效益,且在提高木糖溶液质量及生产效率的前提下,减少污水中COD含量,降低环保压力。(The invention discloses an electrodialysis and chromatography combined process for preparing xylose, and belongs to the technical field of xylose production. Firstly, performing three-stage electrodialysis on hemicellulose hydrolysate to finally obtain a first-stage high-salt solution, a third-stage high-salt solution and a third-stage high-sugar solution; secondly, concentrating and desalting the third-level high-salt solution, and then performing ion exchange column chromatography with the third-level high-sugar solution; and finally, dealkalizing the regenerated liquid (containing alkali and sugar) obtained after the regeneration of the ion exchange column to obtain alkali liquor and sugar liquid, reusing the alkali liquor for the regeneration of the ion exchange column, concentrating and desalting the sugar liquid and the third-stage high-salt liquid together, and performing chromatography again. On one hand, the removal rate of impurities in the xylose solution is increased, and the product quality is improved; on the other hand carries out recycle with third level high salt solution and regeneration liquid, reduces the race sugar volume, improves economic benefits, and under the prerequisite that improves xylose solution quality and production efficiency, reduces COD content in the sewage, reduces the environmental protection pressure.)

1. an electrodialysis and chromatography combined process for preparing xylose is characterized by comprising the following steps:

1) first-stage electrodialysis: introducing the hemicellulose hydrolysate into a first-stage electrodialysis system, introducing a second-stage high-salt solution, and performing the action of an electrodialysis membrane to obtain a first-stage high-sugar solution and a first-stage high-salt solution;

2) Second-stage electrodialysis: introducing the first-stage high-sugar solution obtained in the step 1) into a second-stage electrodialysis system, introducing desalted water, and performing the action of an electrodialysis membrane to obtain a second-stage high-sugar solution and a second-stage high-salt solution;

3) Third-stage electrodialysis: introducing the second-stage high-sugar solution obtained in the step 2) into a third-stage electrodialysis system, introducing desalted water, and performing the action of an electrodialysis membrane to obtain a third-stage high-sugar solution and a third-stage high-salt solution;

4) Temporary storage: concentrating and desalting the third-stage high-salt solution obtained in the step 3), and storing the concentrated and desalted third-stage high-salt solution and the third-stage high-sugar solution obtained in the step 3) in a temporary storage tank for later use;

5) Chromatography: injecting the temporary storage solution obtained in the step 4) into an ion exchange column, and carrying out chromatography to obtain a xylose solution;

6) Regeneration: introducing alkali liquor into the ion exchange column used in the step 5), and regenerating to obtain regenerated liquid containing sugar and alkali;

7) Recycling: carrying out electrodialysis dealkalization on the regenerated solution obtained in the step 6) to obtain regenerated alkali liquor and alkaline regenerated sugar liquor, and introducing the regenerated alkali liquor into the ion exchange column used in the step 5) for recycling; concentrating and desalting the alkaline regenerated sugar solution and the third-stage high-salt solution obtained in the step 3) for recycling.

2. The electrodialysis and chromatography combined process for preparing xylose according to claim 1, wherein in step 1), the hemicellulose hydrolysate comprises xylose with a concentration of 70-90 g/L, sodium sulfate with a concentration of 20-22 g/L and sulfuric acid with a concentration of 20-25 g/L.

3. the integrated electrodialysis and chromatography process for preparing xylose according to claim 1, wherein in steps 6) and 7), the ion exchange column used in step 5) comprises an ion exchange column with discharge conductance > 0.5ms/cm or discharge pH < 3.

4. the integrated electrodialysis and chromatography process for preparing xylose according to claim 1, wherein the feed flow rate of hemicellulose hydrolysate in the first-stage electrodialysis system is 40-50 m³the feed flow of the second-stage high-salt liquid is 15-17 m³h; the voltage is 150V, the current is 100A, and the temperature is 40-45 ℃; the discharge flow of the first-stage high-salt liquid is 15-17 m³The discharge flow of the first-stage high-sugar liquid is 40-50 m³/h；

In the second-stage electrodialysis system, the feeding flow of the first-stage high-sugar liquid is 40-50 m³The feed flow of the desalted water is 15-17 m³H; the voltage is 150V, the current is 100A, and the temperature is 40-45 ℃; the discharge flow of the second-stage high-salt liquid is 15-17 m³The discharge flow of the second-stage high-sugar liquid is 40-50 m³/h；

In the third-stage electrodialysis system, the feeding flow rate of the second-stage high-sugar liquid is 40-50 m³The feed flow of the desalted water is 15-17 m³H; the voltage is 150V, the current is 75-100A, and the temperature is 40-45 ℃; the discharge flow of the third-stage high-salt solution is 15-17 m³the third-stage high sugar liquid discharge flow is 40-50 m³/h；

in the ion exchange column in the step 5), the feeding flow of the temporary storage liquid is 40-50 m³h, the temperature is 35-45 ℃, and the pressure is 0.1 MPa; the discharge flow of the xylose solution is 40-50 m³/h；

in the regeneration step 6), the alkali liquor feeding flow is 10-15 m³h, the temperature is 35-45 ℃, and the pressure is 0.1 MPa;

In the step 7), the discharge flow of the regenerated alkali liquor is 10-15 m³the discharge flow of the alkaline regenerated sugar liquid is 10-15 m³/h。

5. The electrodialysis and chromatography combined process for preparing xylose according to claim 1 or 3, wherein in step 1), the first-stage high-salt solution comprises reducing sugar with concentration of 17-20 g/L, sulfuric acid with concentration of 35-45 g/L and sodium sulfate with concentration of 15-18 g/L; the first-stage high-sugar solution comprises reducing sugar with the concentration of 75-90 g/L, sulfuric acid with the concentration of 12-14 g/L and sodium sulfate with the concentration of 5-10 g/L;

In the step 2), the second-stage high-salt solution comprises reducing sugar with the concentration of 15-18 g/L, sulfuric acid with the concentration of 20-35 g/L and sodium sulfate with the concentration of 15-18 g/L; the second-stage high-sugar solution comprises reducing sugar with the concentration of 75-90 g/L, sulfuric acid with the concentration of 5-10 g/L and sodium sulfate with the concentration of 5-10 g/L;

in the step 3), the third-stage high-salt solution comprises reducing sugar with the concentration of 13-15 g/L, sulfuric acid with the concentration of 5-8 g/L and sodium sulfate with the concentration of 5-8 g/L; the third-stage high-sugar solution comprises reducing sugar with the concentration of 75-90 g/L, sulfuric acid with the concentration of 1-2 g/L and sodium sulfate with the concentration of 1-2 g/L;

in the step 5), the xylose solution comprises 75-85 g/L xylose;

in the step 6), the regeneration liquid comprises 20-30 g/L reducing sugar and 30-40/L sodium hydroxide;

In the step 7), the regenerated alkali solution comprises 60-70 g/L of sodium hydroxide, and the alkaline regenerated sugar solution comprises 20-30 g/L of reducing sugar, 5-10 g/L of sodium sulfate and 0.2-0.5 g/L of sodium hydroxide.

6. The integrated electrodialysis and chromatography process for preparing xylose according to claim 4, wherein in step 1), the conductance of the first-stage high-salt solution is 150-180 ms/cm, the pH is 0.5-1.0, and the refraction is 5.5-6.5; the conductance of the first-level high-sugar liquid is 40-50 ms/cm, the pH is 1.0-1.3, and the refraction is 8.0-9.0;

In the step 2), the conductance of the second-stage high-salt solution is 70-80 ms/cm, the pH is 1.0-1.2, and the refraction is 3-4; the conductance of the second-level high-sugar liquid is 18-20 ms/cm, the pH is 1.8-2.1, and the refraction is 8.0-9.0;

In the step 3), the conductivity of the third-stage high-salt solution is 20-30 ms/cm, the pH value is 2-2.2, and the refraction is 1-2; the conductance of the third-level high-sugar liquid is 3-4 ms/cm, the pH is 2.2-2.8, and the refraction is 8.0-9.0;

In the step 5), the conductivity of the xylose solution is 0.05-0.5 ms/cm, the pH is 2.5-3.5, and the refraction is 8-9;

In the step 6), the conductivity of the regeneration liquid is 40-60 ms/cm, the pH value is 13-14, and the refraction is 4-5;

in the step 7), the conductivity of the regenerated alkali liquor is 70-80 ms/cm, the pH value is 13-14, and the refraction is 4-5; the conductance of the alkaline regenerated sugar liquid is 15-25 ms/cm, the pH is 9-11, and the refraction is 4-5.

7. the electrodialysis and chromatography combined process for preparing xylose according to claim 1, wherein in step 4), the conductance of the concentrated solution is 200-250 ms/cm; the conductivity of the desalted solution is 3-5 ms/cm.

8. The integrated electrodialysis and chromatography process for preparing xylose according to claim 1, wherein the system used in the integrated electrodialysis and chromatography process for preparing xylose comprises a desalted water storage tank (1), electrodialysis devices, an ion exchange column (13) and an alkali liquor storage tank (5), the number of electrodialysis devices is three, namely a first electrodialysis device (2), a second electrodialysis device (3) and a third electrodialysis device (4), the first electrodialysis device (2) is connected with the second electrodialysis device (3), and a first electrodialysis system is formed between the first electrodialysis device (2) and the second electrodialysis device (3); the second-stage electrodialysis device (3) is connected with the desalted water storage tank (1), and a second-stage electrodialysis system is formed between the desalted water storage tank (1) and the second-stage electrodialysis device (3); the second electrodialysis device (3) is connected with the third electrodialysis device (4), the third electrodialysis device (4) is connected with the desalted water storage tank (1), and a third electrodialysis system is formed between the desalted water storage tank (1) and the third electrodialysis device (4);

The ion exchange column (13) is connected with the third-stage electrodialysis system, the ion exchange column (13) is connected with the alkali liquor storage tank (5), and an ion exchange column regeneration system is formed between the ion exchange column (13) and the alkali liquor storage tank (5); the ion exchange column (13) is connected with a dealkalization device (6).

9. The integrated electrodialysis and chromatography process for preparing xylose according to claim 8, wherein the feed inlet of the first electrodialysis unit (2) is connected with a conveying pipe (7) for conveying hemicellulose hydrolysate, the high-sugar solution outlet of the first electrodialysis unit (2) is connected with the feed inlet of the second electrodialysis unit (3) through the conveying pipe (7), the high-salt solution outlet of the second electrodialysis unit (3) is connected with the first electrodialysis unit (2) through the conveying pipe (7), and the high-sugar solution outlet of the second electrodialysis unit (3) is connected with the feed inlet of the third electrodialysis unit (4) through the conveying pipe (7); a high-sugar liquid outlet of the third electrodialysis device (4) is connected with a temporary storage tank (8) through a conveying pipe (7), and a high-salt liquid outlet of the third electrodialysis device (4) is connected with the temporary storage tank (8) through the conveying pipe (7); the temporary storage tank (8) is connected with a feed inlet of the ion exchange column (13); still be equipped with between third electrodialysis device (4) high salt liquid export and the jar (8) of keeping in concentration device (9) and desalination device (10), third electrodialysis device (4) high salt liquid export is connected with concentration device (9), and concentration device (9) are connected with desalination device (10), and desalination device (10) are connected with jar (8) of keeping in.

10. the integrated electrodialysis and chromatography process for preparing xylose according to claim 8 or 9, wherein the alkali outlet of the dealkalization device (6) is connected with the regeneration port of the ion exchange column (13) through a delivery pipe (7), or the alkali outlet of the dealkalization device (6) is connected with the lye storage tank (5) through the delivery pipe (7); the sugar outlet of the dealkalization device (6) is connected with a concentration device (9) through a conveying pipe (7).

Technical Field

the invention relates to an electrodialysis and chromatography combined process for preparing xylose, in particular to an electrodialysis and chromatography combined process for preparing xylose from hemicellulose hydrolysate, and belongs to the technical field of xylose production.

Background

The hemicellulose is a main raw material for producing xylose, wherein the main procedures comprise hydrolysis, decoloration, desalting, deacidification, evaporation, centrifugation, drying and the like in the process of preparing the xylose by taking the hemicellulose as the raw material. The specific process for producing xylose comprises the following steps: taking hemicellulose as a raw material, adding sulfuric acid into the hemicellulose under a heating condition, hydrolyzing the hemicellulose into xylose and other miscellaneous sugars by the sulfuric acid, and simultaneously, impurities such as sodium sulfate, sulfuric acid and the like exist in a hydrolysate; since the xylose produced before the centrifugation step is present in a solution state, impurities such as sodium sulfate and sulfuric acid in the hemicellulose hydrolysate need to be removed efficiently in order to improve the quality of the xylose.

at present, in the existing separation method, salt (such as calcium oxide and barium carbonate) and acid (such as sulfuric acid) are generally added into hemicellulose hydrolysate to generate precipitate (calcium sulfate or barium sulfate) so as to remove impurities such as sodium sulfate, sulfuric acid and the like in the hemicellulose hydrolysate, but the separation process is complex, large in regulation and control difficulty, low in efficiency and high in cost, and electrolyte in the hydrolysate still has more residues and cannot meet the actual process requirements.

In 2019, 04/05, a patent document with publication number CN109575088A entitled "a method for refining xylose in hemicellulose hydrolysate" specifically discloses: relates to the technical field of chemical production, and the method comprises the following steps: 1) removing impurities from the hemicellulose hydrolysate, and then feeding the hemicellulose hydrolysate into an ultrafiltration membrane to obtain a permeate; 2) separating the permeate with nanofiltration membrane, and leaving sulfuric acid in the concentrated solution, wherein the permeate contains acetic acid and xylose; 3) performing electrodialysis separation on the acetic acid and xylose aqueous solution; 4) the xylose aqueous solution is directly used for producing furfural; 5) the acetic acid is extracted and separated by solvent extraction and rectification to obtain the acetic acid with the concentration of 98.5 percent. The method is simple to operate, the obtained xylose aqueous solution is directly used for producing furfural, the obtained acetic acid with the mass concentration of about 20% is extracted and separated by a solvent extraction and rectification device, and the acetic acid with the mass concentration of 98.5% can be obtained. In the process, the separated sulfuric acid is returned to the hydrolysis process for continuous use, and the effective components are recycled, so that the production cost is saved.

a patent document with publication number CN101792822A entitled "method for separating and purifying xylose and arabinose from hemicellulose acid hydrolysate" was disclosed at 04.08.2010, and specifically disclosed therein: the steps of separation and purification are as follows: (1) performing electrodialysis and membrane filtration concentration pretreatment on hemicellulose hydrolysate obtained by direct acid hydrolysis, and deoxidizing and filtering high-purity water for later use; (2) the pretreated hemicellulose hydrolysate enters a simulated moving bed chromatographic separation device for separation, and two discharge liquids are obtained after separation; (3) and concentrating the two discharge liquids by using a multi-effect falling film evaporator, and cooling and crystallizing to obtain xylose and arabinose products. The invention adopts a simulated moving bed chromatographic separation device (SSMB) system to extract monosaccharide, connects a plurality of adsorption columns in series to form a closed loop, changes the inlet and outlet positions of each strand of material by continuously switching valves, realizes the relative movement of solid and liquid phases, and separates and extracts different components.

although separation and purification treatment of hemicellulose hydrolysate by electrodialysis, membrane filtration, simulated moving bed chromatographic separation apparatus, multiple-effect falling-film evaporator, ion exchange column, etc. is disclosed in the above prior art documents, there are also technical problems as follows: firstly, after separation treatment, the generated wastewater (high COD) seriously pollutes the environment and causes environmental pressure; secondly, the sugar leakage amount is large, and the resource waste is caused.

disclosure of Invention

the invention aims to overcome the defects of the prior art and provides an electrodialysis and chromatography combined process for preparing xylose. Performing three-stage electrodialysis on the hemicellulose hydrolysate to obtain a first-stage high-salt solution, a third-stage high-salt solution and a third-stage high-sugar solution, concentrating and desalting the third-stage high-salt solution (comprising reducing sugar with the concentration of 13-15 g/L and the conductivity of 20-30 ms/cm), injecting the concentrated and desalted third-stage high-salt solution and the third-stage high-sugar solution into an ion exchange column, and performing a chromatography process;

In the chromatography process, based on the exchange capacity of the resin in the ion exchange column, switching the ion exchange column meeting the requirement (the discharge conductance is less than or equal to 0.5ms/cm or the pH is more than or equal to 3); when the adsorption capacity of the ion exchange column is saturated, introducing alkali liquor to regenerate the ion exchange column to obtain regenerated liquid containing alkali and sugar, dealkalizing the regenerated liquid to obtain regenerated alkali liquor and regenerated alkaline sugar liquid, reusing the regenerated alkali liquor for regenerating the ion exchange column, concentrating the regenerated alkaline sugar liquid and the third-stage high-salt liquid, desalting, and performing chromatography in the ion exchange column.

In the combined process, limitation is performed through electrodialysis, ion exchange column chromatography, specific control conditions and the like, so that on one hand, the removal rate of impurities in the xylose solution is increased, and the product quality is improved; on the other hand carries out recycle with third level high salt solution and regeneration liquid, reduces the race sugar volume (80 ~ 90%), improves economic benefits, simultaneously, under the prerequisite that improves xylose solution quality and production efficiency, reduces COD content in the sewage, reduces environmental protection pressure.

In order to achieve the technical purpose, the following technical scheme is proposed:

an electrodialysis and chromatography combined process for preparing xylose comprises the following steps:

1) first-stage electrodialysis: introducing the hemicellulose hydrolysate into a first-stage electrodialysis system, introducing a second-stage high-salt solution (when the electrodialysis system is used for the first time, introducing desalted water, stopping introducing the desalted water when the electrodialysis system is in normal operation, namely the second-stage electrodialysis system generates the second-stage high-salt solution, and converting the introduction of the second-stage high-salt solution), and obtaining a first-stage high-sugar solution and the first-stage high-salt solution under the action of an electrodialysis membrane;

2) Second-stage electrodialysis: introducing the first-stage high-sugar solution obtained in the step 1) into a second-stage electrodialysis system, introducing desalted water, and performing the action of an electrodialysis membrane to obtain a second-stage high-sugar solution and a second-stage high-salt solution;

3) Third-stage electrodialysis: introducing the second-stage high-sugar solution obtained in the step 2) into a third-stage electrodialysis system, introducing desalted water, and performing the action of an electrodialysis membrane to obtain a third-stage high-sugar solution and a third-stage high-salt solution;

4) Temporary storage: concentrating and desalting the third-stage high-salt solution obtained in the step 3), and storing the concentrated and desalted third-stage high-salt solution and the third-stage high-sugar solution obtained in the step 3) in a temporary storage tank for later use;

5) chromatography: injecting the temporary storage solution obtained in the step 4) into an ion exchange column, and carrying out chromatography to obtain a xylose solution;

6) Regeneration: introducing alkali liquor into the ion exchange column used in the step 5), and regenerating to obtain regenerated liquid containing sugar and alkali;

7) Recycling: carrying out electrodialysis dealkalization on the regenerated solution obtained in the step 6) to obtain regenerated alkali liquor and alkaline regenerated sugar liquor, and introducing the regenerated alkali liquor into the ion exchange column used in the step 5) for recycling; concentrating and desalting the alkaline regenerated sugar solution and the third-stage high-salt solution obtained in the step 3) for recycling.

further, in the step 1), the hemicellulose hydrolysate comprises xylose with the concentration of 70-90 g/L, sodium sulfate with the concentration of 20-22 g/L and sulfuric acid with the concentration of 20-25 g/L.

Further, in the steps 6) and 7), the ion exchange column used in the step 5) comprises an ion exchange column with discharge conductivity of more than 0.5ms/cm or discharge pH of less than 3.

furthermore, in the first-stage electrodialysis system, the feed flow of the hemicellulose hydrolysate is 40-50 m³The feed flow of the second-stage high-salt liquid is 15-17 m³H; the voltage is 150V, the current is 100A, and the temperature is 40-45 ℃; the discharge flow of the first-stage high-salt liquid is 15-17 m³The discharge flow of the first-stage high-sugar liquid is 40-50 m³/h；

in the second-stage electrodialysis system, the feeding flow of the first-stage high-sugar liquid is 40-50 m³the feed flow of the desalted water is 15-17 m³H; voltage 150V, current 100A, temperature 40-45 ℃ of temperature; the discharge flow of the second-stage high-salt liquid is 15-17 m³The discharge flow of the second-stage high-sugar liquid is 40-50 m³/h；

In the third-stage electrodialysis system, the feeding flow rate of the second-stage high-sugar liquid is 40-50 m³the feed flow of the desalted water is 15-17 m³H; the voltage is 150V, the current is 75-100A, and the temperature is 40-45 ℃; the discharge flow of the third-stage high-salt solution is 15-17 m³The third-stage high sugar liquid discharge flow is 40-50 m³/h；

in the ion exchange column in the step 5), the feeding flow of the temporary storage liquid is 40-50 m³H, the temperature is 35-45 ℃, and the pressure is 0.1 MPa; the discharge flow of the xylose solution is 40-50 m³/h；

In the regeneration step 6), the alkali liquor feeding flow is 10-15 m³H, the temperature is 35-45 ℃, and the pressure is 0.1 MPa;

In the step 7), the discharge flow of the regenerated alkali liquor is 10-15 m³the discharge flow of the alkaline regenerated sugar liquid is 10-15 m³/h。

Further, in the step 1), the first-stage high-salt solution comprises reducing sugar with the concentration of 17-20 g/L, sulfuric acid with the concentration of 35-45 g/L and sodium sulfate with the concentration of 15-18 g/L; the first-stage high-sugar solution comprises reducing sugar with the concentration of 75-90 g/L, sulfuric acid with the concentration of 12-14 g/L and sodium sulfate with the concentration of 5-10 g/L;

In the step 2), the second-stage high-salt solution comprises reducing sugar with the concentration of 15-18 g/L, sulfuric acid with the concentration of 20-35 g/L and sodium sulfate with the concentration of 15-18 g/L; the second-stage high-sugar solution comprises reducing sugar with the concentration of 75-90 g/L, sulfuric acid with the concentration of 5-10 g/L and sodium sulfate with the concentration of 5-10 g/L;

in the step 3), the third-stage high-salt solution comprises reducing sugar with the concentration of 13-15 g/L, sulfuric acid with the concentration of 5-8 g/L and sodium sulfate with the concentration of 5-8 g/L; the third-stage high-sugar solution comprises reducing sugar with the concentration of 75-90 g/L, sulfuric acid with the concentration of 1-2 g/L and sodium sulfate with the concentration of 1-2 g/L;

in the step 5), the xylose solution comprises 75-85 g/L xylose;

In the step 6), the regeneration liquid comprises 20-30 g/L reducing sugar and 30-40/L sodium hydroxide;

In the step 7), the regenerated alkali solution comprises 60-70 g/L of sodium hydroxide, and the alkaline regenerated sugar solution comprises 20-30 g/L of reducing sugar, 5-10 g/L of sodium sulfate and 0.2-0.5 g/L of sodium hydroxide.

further, in the step 1), the conductance of the first-stage high-salt solution is 150-180 ms/cm, the pH value is 0.5-1.0, and the refraction is 5.5-6.5; the conductance of the first-level high-sugar liquid is 40-50 ms/cm, the pH is 1.0-1.3, and the refraction is 8.0-9.0;

In the step 2), the conductance of the second-stage high-salt solution is 70-80 ms/cm, the pH is 1.0-1.2, and the refraction is 3-4; the conductance of the second-level high-sugar liquid is 18-20 ms/cm, the pH is 1.8-2.1, and the refraction is 8.0-9.0;

In the step 3), the conductivity of the third-stage high-salt solution is 20-30 ms/cm, the pH value is 2-2.2, and the refraction is 1-2; the conductance of the third-level high-sugar liquid is 3-4 ms/cm, the pH is 2.2-2.8, and the refraction is 8.0-9.0;

In the step 5), the conductivity of the xylose solution is 0.05-0.5 ms/cm, the pH is 2.5-3.5, and the refraction is 8-9;

In the step 6), the conductivity of the regeneration liquid is 40-60 ms/cm, the pH value is 13-14, and the refraction is 4-5;

In the step 7), the conductivity of the regenerated alkali liquor is 70-80 ms/cm, the pH value is 13-14, and the refraction is 4-5; the conductance of the alkaline regenerated sugar liquid is 15-25 ms/cm, the pH is 9-11, and the refraction is 4-5.

further, in the steps 1), 2) and 3), the electrodialysis membrane is an alloy membrane.

Further, in the concentration step of the step 4), a homogeneous electrodialysis membrane or an alloy membrane is adopted for concentration, and the conductance of the concentrated solution is 200-250 ms/cm.

further, in the desalting step of the step 4), an alloy membrane is adopted for desalting, and the conductivity of the desalted solution is 3-5 ms/cm.

further, in step 5), the ion exchange column comprises a cation exchange column and an anion exchange column, wherein the cation exchange column adopts 001 × 7 type of cation resin, and the anion exchange column adopts D301 type of anion resin.

Further, in the electrodialysis dealkalization step of step 7), dealkalization is performed using an alloy membrane.

Further, the alkali liquor comprises a sodium hydroxide aqueous solution.

According to the standard GB/T23532-2009 xylose, after detection, the hemicellulose hydrolysate is subjected to electrodialysis separation: the electric conductivity is less than or equal to 4ms/cm, the light transmittance is more than or equal to 98.0 percent, the refraction is more than or equal to 7.0, the specific rotation is 18.5-19.5 degrees, and the pH value is 2.2-2.8; the content of reducing sugar is more than or equal to 70g/L, the content of xylose is more than or equal to 55g/L, and the purity of xylose is more than or equal to 80 percent; less than or equal to 0.3 percent of inorganic acid, less than or equal to 0.4 percent of total acid, less than or equal to 0.005 percent of sulfate, less than or equal to 0.05 percent of ash, less than or equal to 0.3 percent of water and less than or equal to 0.005 percent of chloride;

after ion exchange column chromatography, the conductivity of the xylose solution is 0.05-0.5 ms/cm, the pH is 2.5-3.5, and the refraction is 8-9.

In the electrodialysis and chromatography combined process for preparing xylose, the adopted system comprises a desalted water storage tank, three electrodialysis devices, an ion exchange column and an alkali liquor storage tank, wherein the three electrodialysis devices are respectively a first electrodialysis device, a second electrodialysis device and a third electrodialysis device, the first electrodialysis device is connected with the second electrodialysis device, and a first electrodialysis system is formed between the first electrodialysis device and the second electrodialysis device; the second-stage electrodialysis device is connected with the desalted water storage tank, and a second-stage electrodialysis system is formed between the desalted water storage tank and the second-stage electrodialysis device; the second electrodialysis device is connected with the third electrodialysis device, the third electrodialysis device is connected with the desalted water storage tank, and a third electrodialysis system is formed between the desalted water storage tank and the third electrodialysis device;

The ion exchange column is connected with the third-stage electrodialysis system, the ion exchange column is connected with the alkali liquor storage tank, and an ion exchange column regeneration system is formed between the ion exchange column and the alkali liquor storage tank; the ion exchange column is connected with a dealkalizing device.

furthermore, a feed inlet of the first-stage electrodialysis device is connected with a conveying pipe for conveying hemicellulose hydrolysate, a high-sugar liquid outlet of the first-stage electrodialysis device is connected with a feed inlet of the second-stage electrodialysis device through the conveying pipe, a high-salt liquid outlet of the second-stage electrodialysis device is connected with the first-stage electrodialysis device through the conveying pipe, and a high-sugar liquid outlet of the second-stage electrodialysis device is connected with a feed inlet of the third-stage electrodialysis device through the conveying pipe; the high-sugar liquid outlet of the third electrodialysis device is connected with a temporary storage tank through a conveying pipe, and the high-salt liquid outlet of the third electrodialysis device is connected with the temporary storage tank through the conveying pipe; the temporary storage tank is connected with the feed inlet of the ion exchange column.

Further, still be equipped with enrichment facility and desalination device between third level electrodialysis device high salt liquid export and the jar of keeping in, third level electrodialysis device high salt liquid export is connected with enrichment facility, and enrichment facility is connected with desalination device, and desalination device is connected with the jar of keeping in.

Further, an alkali outlet of the dealkalization device is connected with a regeneration port of the ion exchange column through a conveying pipe, or the alkali outlet of the dealkalization device is connected with an alkali liquor storage tank through a conveying pipe; the sugar outlet of the dealkalization device is connected with the concentration device through a conveying pipe.

Furthermore, the number of the ion exchange columns is at least two, and the ion exchange columns are connected with each other through a conveying pipe.

Furthermore, the electrodialysis separation system also comprises a dilution tank and a neutralization tank, wherein a high-salt solution outlet of the first-stage electrodialysis device is connected with the dilution tank through a conveying pipe, and the dilution tank is connected with the neutralization tank; the neutralization tank is connected with a waste water discharge pipe, or the neutralization tank is connected with a recycling device through a conveying pipe.

Each conveying pipe is provided with a control valve according to actual requirements.

in the technical scheme, the related working principle is as follows:

In the electrodialysis system, positive and negative electrodes of a power supply are directly alternately and parallelly placed with a positive membrane and a negative membrane, the positive membrane and the negative membrane form a membrane group, and the membrane group is separated from the membrane group by a partition plate to form a fresh water chamber and a concentrated water chamber. Introducing hemicellulose hydrolysate materials into the fresh water chamber, introducing desalted water into the concentrated water chamber, and transferring cations (sodium ions and hydrogen ions) in the fresh water chamber to the negative electrode under the action of the direct-current electric field and only passing through a cation exchange membrane; anions (sulfate ions and hydroxyl ions) migrate to the positive electrode and only pass through an anion exchange membrane, so that sodium sulfate and sulfuric acid in the fresh water chamber are desalted; sodium sulfate and sulfuric acid are concentrated in the concentrated water chamber, and high-salt solution and high-sugar solution are respectively led out, so that the purposes of desalination and deacidification are achieved.

in order to fully ensure the electrodialysis effect, the first-stage electrodialysis, the second-stage electrodialysis and the third-stage electrodialysis are carried out; because the content of the reducing sugar in the third-stage high-salt solution is 13-15 g/L and the electrical conductivity is 20-30 ms/cm, the content of the reducing sugar in the first-stage high-salt solution is 75-90 g/L and the electrical conductivity is 40-50 ms/cm, and the sugar salt of the third-stage high-salt solution is lower based on the ratio of the reducing sugar to the electrical conductivity, the third-stage high-salt solution can be directly used as a raw material for preparing xylose after concentration and desalination (electrical conductivity removal), and therefore, the third-stage high-salt solution and the third-stage high-salt solution are used as intermediate feed liquid to enter an ion exchange column for chromatographic purification.

by adopting the technical scheme, the beneficial technical effects brought are as follows:

firstly, in the invention, the hemicellulose hydrolysate which is pretreated by adopting the prior mature technology is subjected to three-stage electrodialysis to finally obtain a first-stage high-salt solution, a third-stage high-salt solution and a third-stage high-sugar solution, wherein the first-stage high-salt solution can be directly discharged after being diluted and neutralized, the environmental pressure is low, or the first-stage high-salt solution can be recycled, the waste is reduced, and the cost is saved; after the third-level high-salt solution is treated, the third-level high-salt solution and the third-level high-sugar solution are used as intermediate feed liquid meeting the indexes (the conductance is less than or equal to 4000us/cm, the refraction is more than or equal to 7.0, the inorganic acid is less than or equal to 0.3%, the total acid is less than or equal to 0.4%, the content of reducing sugar is more than or equal to 70g/L, the content of xylose is more than or equal to 55g/L, and the purity of xylose is more;

In the chromatography process, regenerating an ion exchange column with saturated adsorption capacity, and dealkalizing the regenerated liquid to obtain a reusable regenerated alkali liquid and an alkaline regenerated sugar liquid;

in the combined process, limitation is performed through electrodialysis, ion exchange column chromatography, specific control conditions and the like, so that on one hand, the removal rate of impurities in the xylose solution is increased, and the product quality is improved; on the other hand, the third-level high-salt solution and the regenerated solution are recycled, so that the sugar leakage amount is reduced (80-90%), the economic benefit is improved, and meanwhile, on the premise of improving the quality and the production efficiency of the xylose solution, the COD content in sewage is reduced, and the environmental protection pressure is reduced;

The method is applied to the xylose preparation process (desalting and deacidifying of hemicellulose hydrolysate), so that the purposes of impurity removal and purification of the xylose solution are achieved, the sugar leakage amount is reduced (by 80-90%) on the premise of improving the xylose quality and the production efficiency, and the economic benefit is improved. Simultaneously, reduce the emission of difficult processing sewage, increased substantially the environmental protection benefit, reduced environmental protection pressure, for example: the organic matter discharge is reduced by about 5.5 tons/day, the sewage treatment cost is saved by about 15 yuan/ton, the sewage treatment capacity is reduced by 400 cubic meters/day and the like;

the method adopts the electrodialysis method to remove the electrolyte, improves the operation efficiency and the effectiveness of removing the electrolyte, has higher controllability, effectively avoids introducing new impurities, reduces the cost, and increases the profit by about 2.5 ten thousand yuan/day;

Fourthly, after the third-level high-salt solution is concentrated and desalted, the third-level high-salt solution and the third-level high-sugar solution are used as final feed liquid meeting the index and enter the next procedure, the sugar leakage amount is reduced to 2-3% from 10%, and the yield of xylose is improved by about 2.8 tons/day;

Fifthly, in the invention, as most of the run sugar is recovered, the service life of the electrodialysis device is greatly prolonged (the service life of the membrane is prolonged by more than 30 percent), thus not only improving the stability of the xylose preparation process, but also improving the usability of the equipment and reducing the cost of equipment consumption;

in the process of ion exchange column chromatography, COD is mainly from regeneration of an anion column in the ion exchange column by alkali liquor, and the method carries out electrodialysis dealkalization on the regenerated liquid, so that not only can sugar in the regenerated liquid be recovered, but also the sugar leakage amount is reduced; and moreover, the alkali in the regeneration liquid is recovered and reused for regeneration of the ion exchange column to be regenerated, so that the COD content in the wastewater is greatly reduced, the economic value is improved, and the environment is protected.

drawings

FIG. 1 is a schematic diagram of a logic diagram of an integrated process system according to the present invention;

FIG. 2 is a block diagram of the work flow of the integrated process system of the present invention;

FIG. 3 is a schematic diagram of the electrodialysis operation in the present invention;

Wherein, in the figure: 1. desalting water storage tank, 2, first-stage electrodialysis device, 3, second-stage electrodialysis device, 4, third-stage electrodialysis device, 5, alkali liquor storage tank, 6, dealkalization device, 7, conveying pipe, 8, temporary storage tank, 9, concentration device, 10, desalination device, 11, dilution tank, 12, neutralization tank, 13, ion exchange column.

Detailed Description

In the following, the technical solutions in the embodiments of the present invention are clearly and completely described, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.