CN114317618A - Cascade Utilization Process of Lignocellulosic Raw Materials Based on Alkali Pretreatment - Google Patents

Abstract

The invention discloses a cascade utilization process of lignocellulosic raw materials based on alkali pretreatment. The process includes: (1) pulverizing the lignocellulose raw materials and then adding alkali liquid to perform alkali pretreatment; (2) performing solid-liquid pretreatment on the pretreated materials (3) Perform anaerobic fermentation treatment on solid A to obtain biogas; (4) After stirring liquid B, pour it into an inorganic acid solution quickly, adjust the pH value to 4.1-4.5, and carry out solid-liquid separation after fully stirring; ( 5) After washing, freezing and drying the solid C to obtain lignin particles; (6) adding ethanol to the liquid D for sedimentation treatment, adjusting the pH value to 4.1 to 4.5, and then vacuum filtration after standing, and the filter residue is hemicellulose, The filtrate was dried to obtain sodium dihydrogen phosphate. The present invention processes the pretreatment liquid to prepare lignin particles, hemicellulose and sodium dihydrogen phosphate, and finally realizes the efficient conversion and utilization of lignocellulose raw materials.

Description

Cascade Utilization Process of Lignocellulosic Raw Materials Based on Alkali Pretreatment

technical field

The invention relates to the technical field of energy utilization of lignocellulosic raw materials, in particular to a cascade utilization process of lignocellulosic raw materials based on alkali pretreatment.

Background technique

Due to the shortage of fossil energy and the need for environmental protection, people's demand for biofuels is increasing, and anaerobic fermentation is the most energy-saving production process among all biofuel production technologies. Lignocellulosic biomass is widely used in anaerobic fermentation to produce methane, and its methane production is closely related to the biodegradability of the feedstock. Although lignocellulosic feedstocks have good anaerobic fermentation potential, their refractory structural properties prevent them from being directly converted into high methane yields. Therefore, it is extremely important to destroy the lignocellulose structure through pretreatment and improve the anaerobic fermentation performance of the raw material.

Traditional pretreatment techniques can be divided into physical, chemical and biological pretreatment. Among them, alkali pretreatment is one of the most commonly used pretreatment technologies with the best lignin removal effect. Compared with other chemical pretreatments, the reaction conditions of alkali treatment are milder and do not require conditions such as high temperature and high pressure. Compared with other alkali pretreatments, sodium hydroxide pretreatment has lower delignification levels, ammonium hydroxide requires high temperature and high pressure to achieve the effect of sodium hydroxide pretreatment, and the cycle of quicklime is too long. Sodium hydroxide stands out as a commonly used alkali reagent for the treatment of lignocellulose. However, sodium hydroxide pretreatment also has some disadvantages, that is, a large amount of pretreatment liquid will be produced, which will cause harm to the environment. Treating the pretreatment liquid and producing products with added value can improve the anaerobic fermentation performance of lignocellulosic raw materials while improving economic efficiency and realizing environmental protection.

Usually, after pretreatment of lignocellulosic feedstock, only the solid fraction whose internal structure has been destroyed is used for anaerobic fermentation, while the liquid fraction containing the removed lignin and carbohydrates is often discarded. The large amount of lignin contained in the pretreatment solution can be used to prepare lignin nanoparticles. Lignin nanoparticles have high utilization value and can be used in the preparation of concrete, plastics and nanomedicine. The hemifibers in the pretreatment solution can be separated and precipitated for industrial development and biotechnology. The current general-purpose acid-precipitated black liquor to make lignin will introduce salts that cannot be used, resulting in resource loss. Therefore, it is necessary to provide a comprehensive alkali pretreatment and acid precipitation process to further improve the energy conversion efficiency and economy of the entire process.

SUMMARY OF THE INVENTION

In order to solve the problems in the prior art, in view of the complex internal structure of lignocellulosic raw materials, the present invention proposes a cascade utilization process of lignocellulosic raw materials based on alkali pretreatment, which can improve the anaerobic fermentation performance of lignocellulose raw materials. At the same time, the pretreatment liquid is treated to prepare lignin particles, hemicellulose and sodium dihydrogen phosphate, so that the full components of lignocellulosic raw materials can be comprehensively and efficiently utilized, and the cost in the pretreatment process of lignocellulosic raw materials is solved. The problem is that the pretreatment liquid cannot be effectively used, and finally the efficient conversion and utilization of lignocellulose raw materials is realized.

The purpose of this invention is to provide a kind of lignocellulosic raw material cascade utilization technology based on alkali pretreatment, and this technology comprises the steps:

(1) adding lye to carry out alkali pretreatment after pulverizing the lignocellulose raw material;

(2) solid-liquid separation is carried out to the pretreated material in step (1) to obtain solid A and liquid B;

(3) subjecting the solid A obtained in step (2) to anaerobic fermentation treatment to obtain biogas rich in methane; after the anaerobic fermentation treatment is completed, the anaerobic fermentation residue is refluxed to participate in the next anaerobic fermentation treatment ;

(4) fully stirring the liquid B obtained in the step (2) and rapidly transferring it to the mineral acid solution, adjusting the pH value to be 4.1 to 4.5, and performing solid-liquid separation after fully stirring to obtain solid C and liquid D;

(5) the solid C obtained in the step (4) is washed, frozen and dried to obtain lignin particles;

(6) adding ethanol to the liquid D obtained in step (4) to carry out sedimentation treatment, adjusting the pH value to be 4.1 to 4.5, vacuum filtration after standing, the obtained filter residue is hemicellulose, and the obtained filtrate is vacuum-dried Obtain sodium dihydrogen phosphate.

Preferably, the alkali solution in step (1) is sodium hydroxide solution.

Preferably, in step (1), the solid-to-liquid ratio of the lignocellulosic raw material and the lye is 1kg: (10-20)L.

Preferably, in step (1), the mass concentration of the alkali solution is 2.5% to 5% (w/v).

Preferably, the alkali pretreatment conditions in step (1) are: the pretreatment temperature is 30-37°C, and the pretreatment time is 12-24h.

Preferably, the anaerobic fermentation treatment conditions in step (3) are: the fermentation temperature is 30-37°C or 50-55°C, the organic load of the feed is 1.0-4.0 kg VS/(m ³ ·d), and the hydraulic retention time is 30～45d.

Preferably, the inorganic acid solution in the step (4) is a phosphoric acid solution, and the mass concentration of the inorganic acid solution is 10%-15% (w/v).

Preferably, in the step (4), high-speed centrifugation is used for solid-liquid separation, and the centrifugation conditions are: centrifugation speed of 8000-10000 rpm and centrifugation time of 5-10 minutes.

Preferably, in the step (6), the volume ratio of the liquid D to ethanol is 1:2-3.

Compared with the prior art, the present invention has the following advantages:

1. The advantage of the present invention is that the use of sodium hydroxide pretreatment reduces the lignin content in the raw material, destroys the internal structure of the lignocellulose raw material, and improves the anaerobic fermentation performance;

2. The fermentation temperature of anaerobic fermentation treatment is medium temperature (30~37℃) or high temperature (50~55℃), because methanogens are relatively active in these two temperature ranges, which can improve the gas production rate of raw materials .

3. By refluxing the anaerobic fermentation residue to participate in the next anaerobic fermentation treatment, the processing problem of biogas residue and biogas slurry is avoided, and the stable operation of the anaerobic reactor is also ensured.

4. The pretreatment liquid obtained after the pretreatment of lignocellulose raw materials is first poured into the mineral acid solution and then solid-liquid separation is carried out. The obtained solid is washed, frozen and dried to obtain lignin particles, and the obtained liquid is added with ethanol for After the sedimentation treatment is filtered, the obtained filter residue is hemicellulose, and the obtained filtrate is vacuum-dried to obtain sodium dihydrogen phosphate, so that the yield of the obtained substances is improved, and the energy conversion efficiency, the comprehensive utilization rate of raw materials, and the process are improved. diversity, resource recovery and economic benefits.

5. The morphology of the obtained lignin particles is a spherical particle size of 60-360 nm, the lignin particles are different from the traditional lignin particles used as fuel, and the lignin particles can be used for coatings, glues and composite materials.

6. In step (4), the pH value is controlled at 4.1-4.5, because when the pH is too high, it is difficult to obtain spherical lignin particles; in step (6), the pH is controlled at 4.1-4.5 in an environment This is because when the pH is too high or too low, other forms of sodium salt will be formed, and it will be difficult to obtain potassium dihydrogen phosphate.

Description of drawings

Fig. 1 is the process flow schematic diagram of the present invention.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Unless otherwise specified, the equipment and reagents used in the present invention are conventional commercially available products in the technical field.

Example 1

(1) Select hybrid Pennisetum as lignocellulose raw material, pulverize the hybrid Pennisetum raw material and send it to an alkali pretreatment device, then add a sodium hydroxide solution with a mass concentration of 5% (w/v) for alkali pretreatment , the solid-liquid ratio of hybrid Pennisetum raw material and sodium hydroxide solution was 1:10, the pretreatment temperature was 37℃, and the pretreatment time was 24h.

(2) The pretreated material in step (1) is subjected to solid-liquid separation through a high-speed centrifuge to obtain solid A and liquid B.

(3) the solid A obtained in the step (2) is entered into the anaerobic fermentation system to carry out anaerobic fermentation treatment, and the anaerobic fermentation treatment conditions are: the fermentation temperature is 37 ° C, and the feed organic load is 2.0kg VS/(m ³ · d), the hydraulic retention time is 40d, and the biogas rich in methane is obtained. The biogas is sent to the gas storage device, and the biogas can be used for co-generation, purification and quality reuse; 85% of the anaerobic fermentation residue is returned to the anaerobic reactor for the next anaerobic fermentation treatment, and 15% of the anaerobic fermentation residue is returned to the anaerobic reactor. The anaerobic fermentation residue is prepared into solid or liquid organic fertilizer by the existing technology.

(4) The liquid B obtained in the step (2) was fully stirred at room temperature and then poured into a phosphoric acid solution with a mass concentration of 10%, and the pH value was adjusted to 4.3. Separation, centrifugation speed 8000rpm, centrifugation time 8min; solid C and liquid D are obtained.

(5) After washing, freezing and drying the solid C obtained in step (4), lignin particles are obtained.

(6) in the liquid D that obtains in step (4), add ethanol and carry out sedimentation treatment, the volume ratio of liquid D and ethanol is 1: 2, and adjusting pH value is 4.3, vacuum filtration after standing for 5min, the filter residue of gained is carried out The hemicellulose is obtained by drying, and the obtained filtrate is vacuum-dried to obtain sodium dihydrogen phosphate.

After testing, using the process of the present Example 1 to treat the hybrid Pennisetum, the pH of the discharge in step (3) can be maintained at 7.2-7.5, indicating that the operation of the anaerobic fermentation system is relatively stable; the lignin removal of the Hybrid Pennisetum The lignin particle has a spherical shape and a particle size of 60-360 nm. The lignin particle is different from being used as a fuel. The traditional lignin particles can be used in coatings, glues and composite materials; the recovery rate of hemicellulose is 82%, and the recovery rate of sodium dihydrogen phosphate is 27%.

Example 2

(1) Select straw as lignocellulose raw material, crush the straw raw material and send it to the alkali pretreatment device, and then add sodium hydroxide solution with a mass concentration of 2.5% (w/v) for alkali pretreatment, the straw raw material and hydrogen peroxide The solid-liquid ratio of the sodium solution was 1:10, the pretreatment temperature was 30°C, and the pretreatment time was 12h.

(2) The pretreated material in step (1) is subjected to solid-liquid separation through a high-speed centrifuge to obtain solid A and liquid B.

(3) the solid A obtained in the step (2) is entered into the anaerobic fermentation system to carry out anaerobic fermentation treatment, and the anaerobic fermentation treatment conditions are: the fermentation temperature is 37 ° C, and the feed organic load is 2.0kg VS/(m ³ · d), the hydraulic retention time is 40d, and the biogas rich in methane is obtained. The biogas is sent to the gas storage device, and the biogas can be used for co-generation, purification and quality reuse; 85% of the anaerobic fermentation residue is returned to the anaerobic reactor for the next anaerobic fermentation treatment, and 15% of the anaerobic fermentation residue is returned to the anaerobic reactor. The anaerobic fermentation residue is prepared into solid or liquid organic fertilizer by the existing technology.

(4) The liquid B obtained in the step (2) was fully stirred at room temperature and then poured into a phosphoric acid solution with a mass concentration of 10%, and the pH value was adjusted to 4.1. Separation, centrifugation speed 10000rpm, centrifugation time 10min; solid C and liquid D are obtained.

(5) After washing, freezing and drying the solid C obtained in step (4), lignin particles are obtained.

(6) in the liquid D that obtains in step (4), add ethanol and carry out sedimentation treatment, the volume ratio of liquid D and ethanol is 1: 2, the pH value of adjustment is 4.1, and vacuum filtration after standing for 10min, the filter residue of gained is carried out The hemicellulose is obtained by drying, and the obtained filtrate is vacuum-dried to obtain sodium dihydrogen phosphate.

After testing, using the process of Example 2 to treat the straw, the pH of the discharge in step (3) can be maintained at 7.2-7.5, the lignin removal rate of the straw can reach 70%, the gas production rate of the raw material is greater than 300mL/gVS, and the spherical particle size is obtained. For lignin particles of 90-480nm, the recovery rate of hemicellulose is 75%, and the recovery rate of sodium dihydrogen phosphate is 23%.

Example 3

The difference between Example 3 and Example 1 is only that the pH value is adjusted to 4.5 in step (4) and the pH value is adjusted to 4.5 in step (6).

After testing, using the process of this Example 3 to treat the hybrid Pennisetum, the pH of the discharge in step (3) can be maintained at 7.2-7.5, the lignin removal rate of the hybrid Pennisetum reaches 75%, and the gas yield of the raw material is greater than 280mL/ gVS, lignin particles with spherical particle size of 60-240 nm were obtained; the recovery rate of hemicellulose was 85%, and the recovery rate of sodium dihydrogen phosphate was 21%.

Example 4

The difference between the present embodiment 4 and the embodiment 1 is only: the mass concentration of the sodium hydroxide solution in the step (1) is 3.75% (w/v) and the solid-liquid ratio of the hybrid pennisetum raw material and the sodium hydroxide solution is 1 : 20.

After testing, using the process of this example 4 to treat the hybrid pennisetum, the pH of the discharge in step (3) can be maintained at 7.2-7.5, the lignin removal rate of the hybrid pennisetum reaches 64%, and the gas production rate of the raw material is greater than 265mL/ gVS, the lignin particles with spherical particle size of 120-240 nm were obtained, the recovery rate of hemicellulose was 76%, and the recovery rate of sodium dihydrogen phosphate was 32%.

Example 5

The difference between Example 5 and Example 1 is only that the mass concentration of the phosphoric acid solution in step (4) is 15% (w/v).

After testing, using the process of the present Example 5 to treat the hybrid Pennisetum, the pH of the discharge in step (3) can be maintained at 7.2-7.5, the lignin removal rate of the hybrid Pennisetum reaches 75%, and the gas yield of the raw material is greater than 280mL/ gVS, the lignin particles with spherical particle size of 210-420 nm were obtained, the recovery rate of hemicellulose was 73%, and the recovery rate of sodium dihydrogen phosphate was 36%.

Example 6

The difference between Example 6 and Example 1 is only that the mass concentration of the phosphoric acid solution in step (4) is 12.5% (w/v).

After testing, using the process of the present Example 6 to treat the hybrid Pennisetum, the pH of the discharge in step (3) can be maintained at 7.2-7.5, the lignin removal rate of the hybrid Pennisetum reaches 75%, and the gas production rate of the raw material is greater than 280mL/ gVS, the lignin particles with spherical particle size of 190-390 nm were obtained, the recovery rate of hemicellulose was 76%, and the recovery rate of sodium dihydrogen phosphate was 30%.

Example 7

The difference between Example 7 and Example 1 is only that the volume ratio of liquid D to ethanol in step (6) is 1:3.

After testing, using the process of this example 7 to treat the hybrid pennisetum, the pH of the discharge in step (3) can be maintained at 7.2-7.5, the lignin removal rate of the hybrid pennisetum reaches 75%, and the gas production rate of the raw material is greater than 280mL/ gVS, the lignin particles with spherical particle size of 60-360 nm were obtained, the recovery rate of hemicellulose was 86%, and the recovery rate of sodium dihydrogen phosphate was 27%.

Example 8

The only difference between Example 8 and Example 1 is that the fermentation temperature in step (3) is 53°C.

After testing, using the process of this example 8 to treat the hybrid pennisetum, the pH of the discharge in step (3) can be maintained at 7.2-7.5, the lignin removal rate of the hybrid pennisetum reaches 75%, and the raw material gas production rate is greater than 320mL/ gVS, the lignin particles with spherical particle size of 60-360 nm were obtained, the recovery rate of hemicellulose was 82%, and the recovery rate of sodium dihydrogen phosphate was 27%.

Comparative Example 1

The difference between this comparative example 1 and Example 1 is only that the pH value is adjusted to 2.0 in step (4) and the pH value is adjusted to 2.0 in step (6).

After testing, using the process of Comparative Example 1 to treat the hybrid Pennisetum, the pH of the discharge in step (3) can be maintained at 7.2-7.5, the lignin removal rate of the hybrid Pennisetum reaches 75%, and the gas production rate of the raw material is greater than 320mL/gVS , the lignin particles with spherical particle size of 120-240 nm were obtained, the recovery rate of hemicellulose was 89%, and no sodium dihydrogen phosphate was recovered.

Comparative Example 2

The difference between this comparative example 2 and Example 1 is only that the pH value is adjusted to 7.0 in step (4) and the pH value is adjusted to 7.0 in step (6).

After testing, using the process of Comparative Example 2 to treat the hybrid Pennisetum, the pH of the discharge in step (3) can be maintained at 7.2-7.5, the lignin removal rate of the hybrid Pennisetum reaches 75%, and the gas production rate of the raw material is greater than 320mL/gVS , no spherical lignin particles were obtained, the recovery rate of hemicellulose was 76%, and no sodium dihydrogen phosphate was recovered.

The difference between Comparative Example 1, Comparative Example 2 and Example 1 is only in that the adjustment pH value in step (4) and step (6) is different, and its test data shows that when adjusting pH in step (4) is too high, no Spherical lignin particles are obtained, and when the pH is adjusted too high or too low in step (6), sodium dihydrogen phosphate is not recovered.

The descriptions of the above embodiments are only used to help understand the technical solutions of the present invention and the core idea thereof. It should be pointed out that for those skilled in the art, the present invention can be further improved without departing from the principles of the present invention. and modifications, these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims (9)

1. The alkali pretreatment-based lignocellulose raw material gradient utilization process is characterized by comprising the following steps of: the process comprises the following steps:

(1) crushing a lignocellulose raw material, and then adding alkali liquor to perform alkali pretreatment;

(2) carrying out solid-liquid separation on the pretreated material in the step (1) to obtain a solid A and a liquid B;

(3) carrying out anaerobic fermentation treatment on the solid A obtained in the step (2) to obtain biogas rich in methane; after the anaerobic fermentation treatment is finished, refluxing the anaerobic fermentation residues to participate in the next anaerobic fermentation treatment;

(4) fully stirring the liquid B obtained in the step (2), quickly transferring the liquid B into an inorganic acid solution, adjusting the pH value to 4.1-4.5, fully stirring, and performing solid-liquid separation to obtain a solid C and a liquid D;

(5) cleaning, freezing and drying the solid C obtained in the step (4) to obtain lignin particles;

(6) and (4) adding ethanol into the liquid D obtained in the step (4) for sedimentation treatment, adjusting the pH value to 4.1-4.5, standing, and then carrying out vacuum filtration, wherein the obtained filter residue is hemicellulose, and the obtained filtrate is subjected to vacuum drying to obtain sodium dihydrogen phosphate.

2. The alkali pretreatment-based lignocellulose feedstock cascade utilization process as claimed in claim 1, wherein the alkali solution in step (1) is sodium hydroxide solution.

3. The alkali pretreatment-based lignocellulose feedstock cascade utilization process as claimed in claim 2, wherein in step (1), the solid-to-liquid ratio of the lignocellulose feedstock and the alkali liquor is 1 kg: (10-20) L.

4. The alkali pretreatment-based lignocellulose raw material cascade utilization process as claimed in claim 3, wherein in the step (1), the mass concentration of the alkali liquor is 2.5-5% (w/v).

5. The alkali pretreatment-based lignocellulose feedstock cascade utilization process as claimed in claim 1, wherein the alkali pretreatment conditions in step (1) are as follows: the pretreatment temperature is 30-37 ℃, and the pretreatment time is 12-24 h.

6. The base-based primer of claim 1The gradient utilization process of the treated lignocellulose raw material is characterized in that the anaerobic fermentation treatment conditions in the step (3) are as follows: the fermentation temperature is 30-37 ℃ or 50-55 ℃, and the organic loading of the feed is 1.0-4.0 kg VS/(m)³D) the hydraulic retention time is 30-45 d.

7. The alkali pretreatment-based lignocellulosic feedstock cascade utilization process as claimed in claim 1, wherein the inorganic acid solution in the step (4) is phosphoric acid solution, and the mass concentration of the inorganic acid solution is 10% to 15% (w/v).

8. The alkali pretreatment-based lignocellulose raw material cascade utilization process as claimed in claim 1, wherein the solid-liquid separation is performed by high-speed centrifugation in the step (4), and the centrifugation conditions are as follows: the centrifugal speed is 8000-10000 rpm, and the centrifugal time is 5-10 min.

9. The alkali pretreatment based lignocellulosic feedstock cascade process of claim 1, wherein in step (6), the volume ratio of liquid D to ethanol is 1: 2 to 3.

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