CN116003484A - Method for extracting xylose from papermaking waste liquid - Google Patents

Abstract

The invention discloses a method for extracting xylose from papermaking waste liquid, which comprises the steps of adding a flocculant into the papermaking waste liquid according to a certain proportion, filtering and collecting filtrate, then physically decoloring the filtrate to obtain decolored filtrate, and then sequentially carrying out ion exchange, nanofiltration, evaporative concentration, cooling crystallization, centrifugation and drying on the decolored filtrate to obtain the finished xylose. The method can remove lignin in the papermaking waste liquid, improve the purification degree of the papermaking waste liquid, and improve the purity of xylose in the papermaking waste liquid at the same time so as to obtain crystalline xylose, and has no other harmful byproducts in the production process.

Description

Method for extracting xylose from papermaking waste liquid

Technical Field

The invention relates to the technical field of xylose processing, in particular to a method for extracting xylose from papermaking waste liquid.

Background

Xylose belongs to five-carbon sugar, and natural D-xylose exists in plants in the form of polysaccharide. Most commonly, xylose, which is called feedstock grade xylose, is reduced to xylitol by hydrogenation over a catalyst. The xylose is easy to generate Maillard reaction at higher temperature, endows food with attractive color tone and special flavor, and can be applied to the fields of food, medicines, pet foods and the like.

Wood is an important papermaking raw material, and most hemicellulose in the process of producing dissolving pulp enters pulping waste liquid through prehydrolysis, and the discharge of the pulping waste liquid can cause environmental pollution and resource waste. Xylose is the main component of hemicellulose in wood, and papermaking wastewater generated in the wood prehydrolysis process is utilized to prepare xylose, so that the xylose production cost is reduced, waste materials can be changed into valuable materials, and pollution of the papermaking wastewater is reduced. Because the xylose content in the papermaking waste liquid can not achieve the crystallization effect, the papermaking waste liquid needs to be further treated so as to improve the purity of the xylose in the papermaking waste liquid.

Such as Chinese patent: CN112877273a, a saccharomycete for decomposing miscellaneous sugars such as galactose and mannose, uses saccharomycete to remove miscellaneous sugars in waste paper-making liquid, but when xylose is obtained from waste paper-making liquid by this method, fermentation byproducts such as organic acid harmful to the environment are produced during fermentation, and can not be directly discharged.

Therefore, how to improve the method for extracting xylose from papermaking waste liquid to avoid the generation of harmful fermentation byproducts such as organic acid is a technical problem to be solved by the person skilled in the art.

Disclosure of Invention

The invention aims to provide a method for extracting xylose from papermaking waste liquid, which is used for removing lignin in the papermaking waste liquid, improving the purification degree of the papermaking waste liquid, and improving the purity of xylose in the papermaking waste liquid so as to obtain crystalline xylose, and has no other harmful byproducts in the production process.

In order to achieve the above object, the present invention provides a method for extracting xylose from papermaking waste liquid, comprising the following steps:

step 1, adding water into papermaking waste liquid to dilute the papermaking waste liquid to 18-20% of refraction, regulating the temperature of the papermaking waste liquid to 45-55 ℃ and regulating the PH value to 5.5-6.0, and then adding 0.5-1% of flocculating agent according to the volume ratio;

step 2, standing the feed liquid prepared in the step 1 for 30-60min, and filtering to collect filtrate;

step 3, performing physical decolorization treatment on the filtrate in the step 2 to obtain decolorized filtrate;

step 4, filtering the decolored filtrate in the step 3 by using a nanofiltration membrane to obtain nanofiltration permeate;

step 5, carrying out cation exchange and anion exchange on the nanofiltration permeate in the step 4 to obtain ion exchange filtrate with the PH of more than 4.0 and the light transmittance of more than 90 percent;

step 6, carrying out vacuum evaporation concentration on the ion exchange filtrate in the step 5 to obtain concentrated solution, wherein the refraction of the concentrated solution is controlled to be 78-82%, and the evaporation temperature is controlled to be 80-90 ℃;

step 7, cooling the concentrated solution in the step 6 to room temperature at a speed of 0.5-1 ℃/h to obtain massecuite;

step 8, centrifuging the massecuite obtained in the step 7 to obtain semi-finished xylose;

and 9, drying the semi-finished xylose in the step 8 to obtain the finished xylose.

Further, in step 1, sodium carbonate is added to the papermaking waste liquid diluted by adding water to adjust the pH value.

Further, in step 2, the filtering after standing the feed liquid prepared in step 1 for 30-60min includes:

standing the feed liquid prepared in the step 1 for 30-60min, and filtering under 0.2-0.4Mpa.

And 2, standing the feed liquid prepared in the step one for 30-60min, and filtering through a plate-frame filter.

Further, in the step 4, the filtration pressure of the nanofiltration membrane is not more than 30Bar.

Further, in step 8, the centrifuging the massecuite in step eight includes:

and D, centrifuging the massecuite obtained in the step eight by using a centrifugal machine, wherein the rotating speed of the centrifugal machine is 1000-1200 r/min.

Further, in step 3, the decolorizing treatment of the filtrate in step 2 includes:

primary decolorization; heating the filtrate in the step 2 to 60-70 ℃, adding five thousandths of active carbon according to the volume ratio, and then sequentially stirring and filtering to obtain intermediate filtrate;

secondary decolorization; the primary decolorized filtrate is passed through a granular carbon column to obtain a decolorized filtrate having a light transmission of > 40%.

Further, the subjecting the nanofiltration permeate in step 4 to cation exchange and anion exchange comprises:

and (3) sequentially carrying out primary cation exchange, primary anion exchange, secondary cation exchange and secondary anion exchange on the nanofiltration permeate in the step (4).

By adopting the method for extracting xylose from the papermaking waste liquid, a certain proportion of flocculating agent is added into the papermaking waste liquid, the filtrate is filtered and collected, then the filtrate is subjected to physical decolorization to obtain decolorized filtrate, and then the decolorized filtrate is subjected to ion exchange, nanofiltration, evaporation concentration, cooling crystallization, centrifugation and drying in sequence, so that the finished xylose is finally obtained;

the method can remove the impurities in the papermaking waste liquid to obtain purified papermaking waste liquid, so that crystalline xylose is obtained through a subsequent process, wherein the method can effectively remove the impurities in the papermaking waste liquid by adding the efficient decolorizing flocculant to obtain purified papermaking waste liquid, and then the purity of xylose in the purified papermaking waste liquid can be improved through a nanofiltration membrane filtration process, so that most other miscellaneous sugars can be filtered, the content of other miscellaneous sugars is reduced, and the method is beneficial to obtaining crystalline xylose; in addition, the flocculated lignin can be sold as a byproduct, so that the pollution to the environment is reduced, and the economic benefit is increased.

Detailed Description

The following embodiments are described in further detail in order to enable those skilled in the art to better understand the technical aspects of the present invention.

The invention discloses a method for extracting xylose from papermaking waste liquid, which comprises the following steps:

step 1, diluting and flocculating; diluting papermaking waste liquid with water to 18-20% of refraction, regulating the temperature to 45-55 ℃ and the PH value to 5.5-6.0, and then adding 0.5-1% of flocculant according to the volume ratio; this step 1 may be performed in a stirred tank to allow faster mixing by stirring; wherein, heating to 45-55 ℃ can fully stir the papermaking waste liquid; wherein:

if the refraction is lower than the 18-20%, the addition amount of the flocculant is large, and the cost is increased; if the refraction is higher than the 18-20%, the flocculation effect is poor;

if the temperature is lower than the range of 45-55 ℃, the flocculation effect is poor; if the temperature is higher than the range of 45-55 ℃, the advantage of flocculation effect is not obvious;

if the pH value is lower than the range of 5.5-6.0, the flocculation effect is poor; if the PH value is higher than the range of 5.5-6.0, partial xylose isomerism exists, and the yield of xylose is affected;

and if the addition amount of the flocculant is less than 0.5-1%, the flocculation effect is poor; above 0.5-1%, the flocculant effect advantage is not obvious; the impurities in the papermaking waste liquid can be more flocculated and separated out according to the refraction, temperature and PH ranges, and then the filtration is obtained

Step 2, filtering; standing the feed liquid prepared in the step 1 for 30-60min, and filtering to collect filtrate;

step 3, decoloring; performing physical decolorization treatment on the filtrate in the step 2 to obtain decolorized filtrate;

step 4, nanofiltration; filtering the decolored filtrate in the step 3 by using a nanofiltration membrane to obtain nanofiltration permeate;

step 5, cation and anion exchange; carrying out cation exchange and anion exchange on the nanofiltration permeate in the step 4 to obtain ion exchange filtrate with the pH of more than 4.0 and the light transmittance of more than 90 percent; specifically, the nanofiltration permeate is subjected to ion exchange resin to realize cation and anion exchange, and how to use the ion exchange resin is common knowledge in the field is not described in detail; the ion exchange filtrate with the PH of more than 4.0 and the light transmittance of more than 90 percent is arranged, so that the purity of the ion exchange solution can be improved, pigment groups can be removed, and the crystallized finished xylose can meet the taste requirement;

step 6, evaporating and concentrating; carrying out vacuum evaporation concentration on the ion exchange filtrate in the step 5 to obtain concentrated solution, wherein the refraction of the concentrated solution is controlled to be 78-82%, the crystallization concentration of xylose can be achieved, and the evaporation temperature is controlled to be 80-90 ℃;

step 7, cooling and crystallizing; cooling the concentrated solution in the step 6 to room temperature at a speed of 0.5-1 ℃/h to obtain massecuite; cooling according to the range, so that crystals can fully grow, and the granularity of the crystals is ensured;

step 8, centrifuging; centrifuging the massecuite obtained in the step 7 to obtain semi-finished xylose;

step 9, drying; and (3) drying the semi-finished xylose in the step (8) to obtain finished xylose.

Example 1:

step 1, adding water into the papermaking waste liquid to dilute the papermaking waste liquid to 18% of refraction, adjusting the temperature of the papermaking waste liquid to 45 ℃, adjusting the PH value to 5.5, and then adding a flocculating agent with the volume ratio of 0.5%;

step 2, standing the feed liquid prepared in the step 1 for 30min, and filtering to collect filtrate;

step 3, performing physical decolorization treatment on the filtrate in the step 2 to obtain decolorized filtrate;

step 4, filtering the decolored filtrate in the step 3 by using a nanofiltration membrane to obtain nanofiltration permeate;

step 5, carrying out cation exchange and anion exchange on the nanofiltration permeate in the step 4 to obtain ion exchange filtrate with the PH of more than 4.0 and the light transmittance of more than 90 percent;

step 6, carrying out vacuum evaporation concentration on the ion exchange filtrate in the step 5 to obtain concentrated solution, wherein the refraction of the concentrated solution is controlled at 78%, and the evaporation temperature is controlled at 80 ℃;

step 7, cooling the concentrated solution in the step 6 to room temperature at a speed of 0.5 ℃/h to obtain massecuite;

step 8, centrifuging the massecuite obtained in the step 7 to obtain semi-finished xylose;

and 9, drying the semi-finished xylose in the step 8 to obtain the finished xylose.

Example 2:

step 1, adding water into the papermaking waste liquid to dilute the papermaking waste liquid to have a refraction of 19%, adjusting the temperature of the papermaking waste liquid to be 50 ℃, adjusting the PH value to be 5.8, and then adding a flocculating agent of 0.8% according to the volume ratio;

step 2, standing the feed liquid prepared in the step 1 for 45min, and filtering to collect filtrate;

step 3, performing physical decolorization treatment on the filtrate in the step 2 to obtain decolorized filtrate;

step 4, filtering the decolored filtrate in the step 3 by using a nanofiltration membrane to obtain nanofiltration permeate;

step 5, carrying out cation exchange and anion exchange on the nanofiltration permeate in the step 4 to obtain ion exchange filtrate with the PH of more than 4.0 and the light transmittance of more than 90 percent;

step 6, carrying out vacuum evaporation concentration on the ion exchange filtrate in the step 5 to obtain concentrated solution, wherein the refraction of the concentrated solution is controlled at 80%, and the evaporation temperature is controlled at 85 ℃;

step 7, cooling the concentrated solution in the step 6 to room temperature at a speed of 0.8 ℃/h to obtain massecuite;

step 8, centrifuging the massecuite obtained in the step 7 to obtain semi-finished xylose;

and 9, drying the semi-finished xylose in the step 8 to obtain the finished xylose.

Example 3:

step 1, adding water into the papermaking waste liquid to dilute the papermaking waste liquid to have 20% of refraction, adjusting the temperature of the papermaking waste liquid to be 55 ℃, adjusting the PH value to be 6.0, and then adding a 1% flocculant according to the volume ratio;

step 2, standing the feed liquid prepared in the step 1 for 60min, and filtering to collect filtrate;

step 3, performing physical decolorization treatment on the filtrate in the step 2 to obtain decolorized filtrate;

step 4, filtering the decolored filtrate in the step 3 by using a nanofiltration membrane to obtain nanofiltration permeate;

step 5, carrying out cation exchange and anion exchange on the nanofiltration permeate in the step 4 to obtain ion exchange filtrate with the PH of more than 4.0 and the light transmittance of more than 90 percent;

step 6, carrying out vacuum evaporation concentration on the ion exchange filtrate in the step 5 to obtain concentrated solution, wherein the refraction of the concentrated solution is controlled at 82%, and the evaporation temperature is controlled at 90 ℃;

step 7, cooling the concentrated solution in the step 6 to room temperature at a speed of 1 ℃/h to obtain massecuite;

step 8, centrifuging the massecuite obtained in the step 7 to obtain semi-finished xylose;

and 9, drying the semi-finished xylose in the step 8 to obtain the finished xylose.

When the method for extracting xylose from the papermaking waste liquid provided by the invention is applied, the papermaking waste liquid is put into a stirring tank, the papermaking waste liquid is heated to be fully stirred, then a flocculant with a certain proportion is added, the filtrate is filtered and collected, then the filtrate is subjected to physical decolorization to obtain decolorized filtrate, and then the decolorized filtrate is subjected to ion exchange, nanofiltration, evaporative concentration, cooling crystallization, centrifugation and drying in sequence, so that the finished xylose is finally obtained;

the method can remove the impurities in the papermaking waste liquid to obtain purified papermaking waste liquid, so that crystalline xylose is obtained through a subsequent process, wherein the method can effectively remove the impurities in the papermaking waste liquid by adding the efficient decolorizing flocculant to obtain purified papermaking waste liquid, and then the purity of xylose in the purified papermaking waste liquid can be improved through a nanofiltration membrane filtration process, so that most other miscellaneous sugars can be filtered, the content of other miscellaneous sugars is reduced, and the method is beneficial to obtaining crystalline xylose; in addition, the flocculated lignin can be sold as a byproduct, so that the pollution to the environment is reduced, and the economic benefit is increased.

Based on the above examples, step 1, the PH was adjusted by adding sodium carbonate to the papermaking effluent diluted with water.

Based on the above embodiment, in step 2, the filtering after standing the feed liquid prepared in step 1 for 30-60min includes:

standing the feed liquid prepared in the step 1 for 30-60min, and filtering under 0.2-0.4Mpa.

If the pressure is lower than the filtering pressure range, the precoat is easy to fall off, so that the filtration phenomenon is caused; above this filtration pressure range, a smaller flow rate results.

Based on the embodiment, in the step 2, the feed liquid prepared in the step 1 is kept stand for 30-60min and then filtered by a plate-and-frame filter.

Based on the above embodiment, in step 4, the filtering pressure of the nanofiltration membrane is not greater than 30Bar due to the requirement of the material of the component of the nanofiltration membrane.

Based on the above embodiments, step 8, centrifuging the massecuite in step eight includes:

and D, centrifuging the massecuite obtained in the step eight by using a centrifugal machine, wherein the rotating speed of the centrifugal machine is 1000-1200 r/min.

Based on the above embodiment, the decolorizing treatment of the filtrate in step 3, step 2 includes:

primary decolorization; heating the filtrate in the step 2 to 60-70 ℃, adding five thousandths of active carbon according to the volume ratio, and then sequentially stirring and filtering to obtain intermediate filtrate;

secondary decolorization; the primary decolorized filtrate is passed through a granular carbon column to obtain a decolorized filtrate having a light transmission of > 40%.

On the basis of the above embodiment, the subjecting the nanofiltration permeate in step 4 to cation exchange and anion exchange includes:

and (3) sequentially carrying out primary cation exchange, primary anion exchange, secondary cation exchange and secondary anion exchange on the nanofiltration permeate in the step (4).

In addition, the present application performs the following comparative tests:

test one: three experimental groups with different concentrations of the papermaking waste liquid are arranged, each experimental group comprises an A group and a B group, the pH values of the papermaking waste liquid of the A group and the papermaking waste liquid of the B group are only different, so that the effect that the papermaking waste liquid of the different experimental groups is flocculated and then passes through a 0.45 mu m filter membrane is obtained, when the experimental groups are concretely implemented, the volume of each experimental group is 400ml, the temperature is 50 ℃, and the experimental results are shown in the following table 1:

TABLE 1

From the data in Table 1, it can be derived:

1) At the same pH value, the higher the concentration of the papermaking waste liquid is, the longer the filtering time of the filtrate after flocculation is, the more the weight of impurities on the filter membrane is, and the flocculation effect is lower than the flocculation effect of 18% when the concentration is 17%; at a concentration of 21%, the filtration time of the filtrate after flocculation is greatly increased. Therefore, the concentration is selected to be 18-20%, and the flocculation effect is good;

2) At the same concentration, the flocculation effect of pH3.0 and pH6.2 is poorer than that of pH5.5, and too high pH can cause xylose isomerization, so that pH 5.5-6.0 is selected as a flocculant to be added in a proper pH range.

And (2) testing II: the various components in the paper-making waste liquid before and after nanofiltration are compared with chromatographic separation and fermentation methods, and the experimental results are shown in the following table 2:

TABLE 2

From the data in Table 2, it can be derived:

the paper-making waste liquid treated by the nanofiltration method has low content of miscellaneous sugar and high xylose content, namely the effect of removing the miscellaneous sugar by the nanofiltration method is superior to that of chromatographic separation and fermentation methods, and fermentation byproducts such as organic acid and the like which are harmful to the environment are not existed.

In summary, when the process for purifying xylose solution provided by the invention is applied, the process has the following advantages:

1. through the implementation of the invention, the impurities in the papermaking waste liquid can be effectively removed, and the pollution to the environment is reduced;

2. the invention improves the purity of xylose in the papermaking waste liquid, and xylose can be extracted from the papermaking waste liquid by utilizing the subsequent process;

3. the filtered lignin can be sold as a byproduct, so that the production cost is reduced;

4. the concentrated phase after nanofiltration can be sold as caramel pigment, so that the production cost is reduced.

Finally, it is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises an element.

In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (8)

1. A method for extracting xylose from papermaking waste liquid, which is characterized by comprising the following steps:

step 1, adding water into papermaking waste liquid to dilute the papermaking waste liquid to 18-20% of refraction, regulating the temperature of the papermaking waste liquid to 45-55 ℃ and regulating the PH value to 5.5-6.0, and then adding 0.5-1% of flocculating agent according to the volume ratio;

step 2, standing the feed liquid prepared in the step 1 for 30-60min, and filtering to collect filtrate;

step 3, performing physical decolorization treatment on the filtrate in the step 2 to obtain decolorized filtrate;

step 4, filtering the decolored filtrate in the step 3 by using a nanofiltration membrane to obtain nanofiltration permeate;

step 5, carrying out cation exchange and anion exchange on the nanofiltration permeate in the step 4 to obtain ion exchange filtrate with the PH of more than 4.0 and the light transmittance of more than 90 percent;

step 6, carrying out vacuum evaporation concentration on the ion exchange filtrate in the step 5 to obtain concentrated solution, wherein the refraction of the concentrated solution is controlled to be 78-82%, and the evaporation temperature is controlled to be 80-90 ℃;

step 7, cooling the concentrated solution in the step 6 to room temperature at a speed of 0.5-1 ℃/h to obtain massecuite;

step 8, centrifuging the massecuite obtained in the step 7 to obtain semi-finished xylose;

and 9, drying the semi-finished xylose in the step 8 to obtain the finished xylose.

2. The method for extracting xylose from waste paper liquor according to claim 1, wherein in step 1, sodium carbonate is added to the waste paper liquor diluted by adding water to adjust the PH.

3. The method for extracting xylose from waste paper-making liquid according to claim 1, wherein in step 2, the filtering after standing the feed liquid prepared in step 1 for 30-60min comprises:

standing the feed liquid prepared in the step 1 for 30-60min, and filtering under 0.2-0.4Mpa.

4. A method for extracting xylose from waste paper-making liquid as claimed in claim 1 or 3, characterized in that in step 2, the liquor prepared in step one is left to stand for 30-60min and then filtered through a plate-and-frame filter.

5. The method of extracting xylose from a paper mill effluent of claim 1, wherein the nanofiltration membrane has a filtration pressure of no more than 30Bar in step 4.

6. The method of extracting xylose from waste paper making liquid as claimed in claim 1, wherein in step 8, the centrifuging of the massecuite in step eight comprises:

and D, centrifuging the massecuite obtained in the step eight by using a centrifugal machine, wherein the rotating speed of the centrifugal machine is 1000-1200 r/min.

7. The method for extracting xylose from waste paper liquor according to claim 1, wherein in step 3, the decolorization treatment of the filtrate in step 2 comprises:

primary decolorization; heating the filtrate in the step 2 to 60-70 ℃, adding five thousandths of active carbon according to the volume ratio, and then sequentially stirring and filtering to obtain intermediate filtrate;

secondary decolorization; the primary decolorized filtrate is passed through a granular carbon column to obtain a decolorized filtrate having a light transmission of > 40%.

8. The method of extracting xylose from a paper mill effluent according to claim 1, wherein said subjecting the nanofiltration permeate of step 4 to cation exchange and anion exchange comprises:

and (3) sequentially carrying out primary cation exchange, primary anion exchange, secondary cation exchange and secondary anion exchange on the nanofiltration permeate in the step (4).