Method for co-producing fiber sugar, pulp fiber and lignin compound fertilizer using wood fiber biomass

Abstract

The present invention provides a method for co-producing fiber sugars, pulp fibers and powdered lignin using wood fiber biomass, comprising the following steps: pre-treatment, cooking pretreatment, solid-liquid separation, solid utilization and mixed liquid utilization. In the pretreatment reaction reagents of the cooking pretreatment step, the addition of an oxidant helps ammonia to react with lignin, thereby improving the fertilizer efficiency of the lignin powder; ferrous ions help to further improve the utilization efficiency of the oxidant, and they themselves can also be applied as fertilizers; if a large amount of oxidant is added, ferrous ions may not be added. The addition of sodium sulfite can simultaneously improve the delignification efficiency of the cooking treatment and improve the enzymatic hydrolysis efficiency of fine fibers. The present application also provides a method for preparing lignin compound fertilizer using the aforementioned powdered lignin. The method of the present invention for co-producing fiber sugars, pulp fibers and lignin using wood fiber biomass not only realizes the utilization of all components of lignocellulose, but also has low raw material costs, is environmentally friendly, and has good prospects for industrial application.

Description

Technical Field

[0001] The present invention belongs to the field of biochemical engineering and specifically relates to a method for co-producing cellulose sugar, pulp, and lignin compound fertilizer using lignocellulosic biomass. The method, based on pretreatment, modifies, separates, and utilizes lignocellulosic biomass components for high-value production, achieving comprehensive and economically feasible utilization of lignocellulosic biomass. Background Art

[0002] Wood fiber biomass resources are the carriers of natural plants that convert solar energy into chemical energy through photosynthesis. They are an important component of renewable resources. Biomass is the only renewable carbon source and is also a theoretically "zero carbon emission" resource. my country has abundant biomass resources. The total amount of wood fiber resources such as corn, rice, and wheat can exceed 900 million tons per year, which is a rich and cheap renewable resource (Bioprocessing, 2022, 20(5): 507-520). Utilizing these waste biomass resources is an important strategy to solve the bottleneck constraints of resources and energy and ensure the sustainable development of the circular economy. At present, the problem of straw burning is still serious. A large amount of wood fiber agricultural waste is burned or directly discarded, and the resource utilization and commercialization of the biomass industry are low. How to achieve the effective utilization of biomass remains a global problem.

[0003] Lignocellulosic biomass is mainly composed of cellulose, hemicellulose and lignin. At present, researchers have conducted in-depth research on its utilization and have achieved many results; however, these utilization methods mainly focus on the efficient utilization of a single component of lignocellulosic. Regarding the preparation of ethanol from cellulose, the pretreatment methods that have been reported include steam explosion pretreatment (Journal of Tianjin University of Science and Technology, 2021, 36(2): 1-7), acid pretreatment (China Papermaking, 2020, 39(3): 35-43) and twin-screw extrusion pretreatment of lignocellulosic (Journal of Jiangxi Agricultural Sciences, 2022, 34(2): 27-35). These pretreatment technologies can improve the enzymatic hydrolysis efficiency of cellulose and obtain a large amount of fermentable sugars, but there is no record of the utilization of lignin or residual substances. Therefore, the problems existing in the utilization of lignocellulosic biomass in existing technologies are mainly as follows: (1) the components are not effectively utilized, and lignin is mainly used as a low-value combustion product; (2) the product is single, only fermentable sugar is produced, and the industrial chain cannot be effectively extended; (3) the technical route is not designed according to the structural characteristics of lignocellulosic biomass, and the existing utilization technology is difficult to achieve effective integration and poor economic efficiency. Therefore, breaking through the existing lignocellulosic biomass utilization model, combining pretreatment technology to analyze the potential utilization value of each component, and realizing the comprehensive utilization of all components is of great significance to the high-value utilization of lignocellulose. Summary of the Invention

[0004] In view of the current situation that it is difficult to effectively utilize lignocellulose in the existing technology, the present invention provides a biomass comprehensive utilization technology solution for the co-production of fiber sugar, pulp fiber and lignin compound fertilizer using lignocellulose biomass. It not only solves the problem that large-scale production in biomass-related industries is difficult to implement, but also realizes the high-value utilization of lignocellulose and has broad application prospects.

[0005] The technical solution of the present invention is a method for co-producing cellulose sugar, pulp fiber and lignin using wood fiber biomass, comprising the following steps:

[0006] (1) Pretreatment: Cut the lignocellulosic biomass into pieces of 3-10 cm, wash it, and set it aside for later use. The lignocellulosic biomass is straw, corn cobs, wheat straw, or waste branches. The washing method uses a water film dust removal method, specifically, spraying water to wash the lignocellulosic biomass. During the water film dust removal process, the spray water washes out the biomass debris on the upper layer of the suspension, which can be separated and used as organic fertilizer. The suspension after removing sand and dust is further recycled.

[0007] (2) Steaming pretreatment: adding a pretreatment reaction reagent to the lignocellulosic biomass obtained in step (1) at a solid-liquid ratio of 1:4-1:10, and steaming the mixture at a temperature of 100-140°C for 40-120 minutes to obtain a reactant; wherein the pretreatment reaction reagent comprises an ammonia concentration of 10-25wt%, a ferrous ion concentration of 0-0.01wt%, an appropriate amount of sodium sulfite, and an oxidant; wherein the sodium sulfite is 2-10wt% of the weight of the biomass raw material. The pretreatment reaction reagent is specifically added as follows: first, adding ammonia, ferrous ions, and sodium sulfite to perform a steaming reaction; after the reaction proceeds for 20-40 minutes, introducing an oxidant into the system to continue the reaction until the reaction is complete. Among the pretreatment reaction reagents, the addition of an oxidant facilitates the reaction of ammonia with lignin, increasing the fertilizer efficiency of the lignin powder. Ferrous ions further promote the sulfonation reaction and improve the utilization efficiency of the oxidant, and can also be applied as a fertilizer. If a large amount of oxidant is added, ferrous ions can be omitted. The addition of sodium sulfite can simultaneously enhance the delignification efficiency of the cooking process and improve the enzymatic hydrolysis efficiency of fine fibers. It is important to emphasize that adding the oxidant after 20-40 minutes of the sulfonation reaction can, on the one hand, reduce its excess consumption caused by reaction with sodium sulfite, and on the other hand, the initial reaction of sodium sulfite with the biomass helps to improve the efficiency of the subsequent oxidation reaction.

[0008] The oxidant is oxygen or hydrogen peroxide. When oxygen is used as the oxidant, the specific operation is as follows: oxygen is introduced into a sealed reaction apparatus until the pressure reaches 0.6-1.5 MPa, and then a steaming pretreatment is performed. When hydrogen peroxide is used as the oxidant, the concentration of hydrogen peroxide in the pretreatment reaction reagent is 0.5-2 wt%, the steaming temperature is not higher than 120°C, and the treatment time is less than 90 minutes.

[0009] (3) The reactant obtained in step (2) is subjected to solid-liquid separation to obtain black liquor containing lignin and solid mainly composed of cellulose; the solid is washed and neutralized for standby use, and the washed water is mixed with the black liquor to obtain a mixed liquid for standby use.

[0010] (4) The solid obtained in step (3) is subjected to pulping and graded screening to obtain long fibers and fine fibers; the material concentration of the pulping is 4-10%, and the aperture of the graded screening is 16-60 mesh. Among them, the length of the long fibers is 0.5-5 mm and is used as pulp. The length of the fine fibers is less than 0.5 mm and is subjected to enzymatic hydrolysis to produce sugar; the specific steps are: preparing a fine fiber slurry with a concentration of 5-25%, adding 2-10 FPU / g of cellulase, enzymatically hydrolyzing and saccharifying at 40-50°C for 24-48 hours, and separating the solid and liquid after the reaction to obtain sugar solution and enzymatic hydrolysis residue. The enzymatic hydrolysis residue can be used as organic fertilizer, or mixed with lignin powder fertilizer to prepare compound fertilizer.

[0011] (5) The mixed solution obtained in step (3) is heated and concentrated to a solid content of 25-40 wt%, and then dried to obtain a nitrogen-containing powdered lignin. Ammonia can be recovered simultaneously during the heating and concentration of the mixed solution. The main component of the powdered lignin is ammoniated lignin, accompanied by a small amount of cellulose, hemicellulose, inorganic ash, and small molecular degradation products of lignin and hemicellulose.

[0012] The powdered lignin prepared using the aforementioned method is used in the preparation of lignin compound fertilizer. Lignin, as a protective agent, can improve the fertilizer's efficacy and utilization efficiency, thus possessing high application value. Specifically, 40-80 parts of powdered lignin, 25-35 parts of phosphate fertilizer, 25-35 parts of potassium fertilizer, and 0-15 parts of nitrogen fertilizer are weighed and uniformly mixed. The mixture is then granulated, dried, and cooled to produce the lignin compound fertilizer. Lignin alone can be used as the nitrogen fertilizer, or a small amount of other nitrogen fertilizers can be added as needed.

[0013] Among them, the phosphate fertilizer is any one of monoammonium phosphate, diammonium phosphate, calcium phosphate, double superphosphate, calcium dihydrogen phosphate, calcium magnesium phosphate, and phosphate rock powder, or a mixture of several of them; the potash fertilizer is any one of potassium sulfate, potassium chloride, potassium dihydrogen phosphate, and sylvite, or a mixture of several of them; the nitrogen fertilizer is any one of ammonium sulfate, urea, ammonium bicarbonate, sodium nitrate, ammonium nitrate, and a mixture of several of them.

[0014] Preferably, the lignin compound fertilizer further comprises an appropriate amount of enzymatic hydrolysis residue obtained in step (4), and the amount of the enzymatic hydrolysis residue is 0-30 wt% of the weight of the fertilizer.

[0015] Beneficial effects of the present invention:

[0016] (1) The method of the present invention for co-producing cellulose sugar, pulp fiber and lignin from lignocellulosic biomass not only realizes the utilization of all components of lignocellulose, but also the ammonia produced in the process can be recycled, without wastewater discharge, and is environmentally friendly.

[0017] (2) The method described in the present invention has a simple process, and sulfonation coupling followed by oxidation are achieved in one reactor, which can further improve the pretreatment effect, is simple to control, and has good industrial application prospects.

[0018] (3) The lignin obtained by the method described in the present invention contains beneficial nitrogen elements, hemicellulose and small molecular products of degradation, and can be directly used as the core material of compound fertilizer without further modification, which helps to obtain fertilizers with excellent performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Attachment Figure 1 These are photos of plants grown using the compound fertilizers prepared in Example 1 and Comparative Example 1;

[0020] Attachment Figure 2 This is a comparison of the length and width of leaves of plants using the compound fertilizers prepared in Example 1 and Comparative Example 1;

[0021] Attachment Figure 3 This is a comparison chart of plant biomass using the compound fertilizer prepared using Example 1 and Comparative Example 1;

[0022] Attachment Figure 4 This is a comparison of the length and width of leaves of plants using the compound fertilizers prepared in Example 1 and Comparative Example 2;

[0023] Attachment Figure 5 It is a comparison chart of plant biomass using the compound fertilizer prepared using Example 1 and Comparative Example 2. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to specific examples. It will be readily understood by those skilled in the art that the contents described in the examples are only for illustrating the present invention and should not and will not limit the present invention described in detail in the claims.

[0025] Example 1: Co-production of cellulose sugars, pulp fiber and powdered lignin using lignocellulosic biomass

[0026] The corn cobs were broken and cut into approximately 4 cm pieces, then washed and dusted. The dust-removed material was then steamed for pretreatment. The steaming pretreatment process involved adding a pretreatment reagent to the dust-removed material at a solid-to-liquid ratio of 1:5, and steaming at 110°C for 90 minutes to obtain a reaction product. The pretreatment reaction product contained 15 wt% ammonia, 0.0025 wt% ferrous ions, an appropriate amount of sodium sulfite, and an oxidizing agent. The sodium sulfite concentration was 10 wt% of the biomass feedstock. Hydrogen peroxide was used as the oxidizing agent, with a hydrogen peroxide concentration of 0.5 wt%. The pretreatment process involved first adding ammonia, ferrous ions, and sodium sulfite for a pretreatment steaming reaction. After 30 minutes of steaming, hydrogen peroxide was pumped into the reactor. After steaming, solid-liquid separation was performed to produce black liquor and fiber solids. The product then entered a three-stage countercurrent displacement washing unit, where the washing liquid and black liquor were combined to produce a mixed liquor with a solids concentration of approximately 80 g / L.

[0027] The solids in the above-mentioned mixed liquid are sent to a high-concentration refiner for refining at a pulp concentration of 8%. The refined material is diluted to 50g / L in proportion and sent to a fiber screening device with a screen aperture of 30 mesh to obtain a suspension of long fibers and fine fibers; the suspension containing fine fibers is then separated from the solid and liquid to obtain fine fibers and filtrate. Among them, the filtrate is used as dilution water to dilute the refined material for recycling; the long fibers are sent to the fiber concentration equipment for dehydration and used as pulp; the pulping, fine fibers and long fiber filtrates can all be used as return water; the fine fibers are sent to the enzymatic hydrolysis tank for saccharification. The fine fibers are prepared into a slurry with a concentration of 12wt%, and cellulase 10FPU / g cellulose is added. Enzymatic hydrolysis and saccharification are carried out in the enzymatic hydrolysis tank. The enzymatic hydrolysis temperature is 50℃, the enzymatic hydrolysis time is 48h, and the total sugar yield is 93%. After the reaction, the material liquid is separated from the solid and liquid to obtain sugar solution and enzymatic hydrolysis residue; the enzymatic hydrolysis residue is directly applied as organic fertilizer.

[0028] After the cooking reaction, the mixed liquid is heated and concentrated to obtain a liquid with a solid content of 30% (ammonia is recovered simultaneously); it is then spray-dried to obtain powdered nitrogen-containing lignin. Elemental analysis shows that the nitrogen content in the lignin is approximately 10%. The powdered nitrogen-containing lignin, potassium sulfate, and calcium dihydrogen phosphate are mixed and granulated in proportion to prepare a lignin compound fertilizer. In parts by weight, the prepared lignin compound fertilizer contains 80 parts of nitrogen-containing lignin, 30 parts of potassium sulfate, and 35 parts of calcium dihydrogen phosphate, with no additional nitrogen fertilizer added. The production of lignin compound fertilizer follows the conventional compound fertilizer production process, namely, batching, stirring, granulation, particle drying, cooling, and packaging.

[0029] Example 2: Co-production of cellulose sugars, pulp fiber and powdered lignin using lignocellulosic biomass

[0030] Unlike Example 1, the wheat straw is cut to approximately 6 cm, then washed and dusted. The dust-removed material is then subjected to a steaming pretreatment. The specific conditions for the steaming pretreatment are: a liquid-to-solid ratio of 1:10, a processing temperature of 140°C, and a processing time of 40 minutes. The pretreatment reagents include a 25% ammonia concentration, no ferrous ions, and a sodium sulfite dosage of 2% by weight of the biomass raw material. Oxygen is used as the oxidant. The specific operation is as follows: ammonia, ferrous ions, and sodium sulfite are first added to perform a pretreatment steaming reaction. After 20 minutes of steaming, oxygen is introduced into the closed reaction vessel until the pressure reaches 1.5 MPa. After steaming, solid-liquid separation is performed to obtain black liquor and fiber solids. The mixture then enters a three-stage countercurrent displacement washing apparatus, where the washing liquid and black liquor are mixed to obtain a mixed liquor with a solids concentration of approximately 70 g / L.

[0031] The solids in the above-mentioned mixed liquid are sent to a high-concentration refiner for refining at a pulp concentration of 8%. After refining, the material is diluted to 50g / L in proportion and sent to a fiber screening device with a screen aperture of 30 mesh to obtain a suspension of long fibers and fine fibers; the suspension containing fine fibers is then separated from the solid and liquid to obtain fine fibers and filtrate. Among them, the filtrate is used as dilution water to dilute the refined material for recycling; the long fibers are sent to the fiber concentration equipment for dehydration and used as pulp; the pulping, fine fibers and long fiber filtrates can all be used as return water; the fine fibers are sent to the enzymatic hydrolysis tank for saccharification. The fine fibers are prepared into a slurry with a concentration of 10wt%, and cellulase 10FPU / g cellulose is added. Enzymatic hydrolysis and saccharification are carried out in the enzymatic hydrolysis tank. The enzymatic hydrolysis temperature is 50℃, the enzymatic hydrolysis time is 48h, and the total sugar yield is 89%. After the reaction, the material liquid is separated from the solid and liquid to obtain sugar solution and enzymatic hydrolysis residue; the enzymatic hydrolysis residue is directly applied as organic fertilizer.

[0032] After the cooking reaction, the mixed liquid is heated and concentrated to obtain a liquid with a solid content of 30% (ammonia is recovered simultaneously). It is then spray-dried to obtain powdered nitrogen-containing lignin. Elemental analysis shows that the nitrogen content of the lignin is approximately 12%. The powdered nitrogen-containing lignin, potassium sulfate, monocalcium phosphate, and urea are mixed and granulated in appropriate proportions to produce a lignin compound fertilizer. In parts by weight, the prepared lignin compound fertilizer comprises 50 parts nitrogen-containing lignin, 35 parts potassium sulfate, 30 parts monocalcium phosphate, and 10 parts urea.

[0033] Example 3: Co-production of cellulose sugars, pulp fiber and powdered lignin using lignocellulosic biomass

[0034] Unlike Example 1, the bagasse was broken up and cut into approximately 3 cm pieces, then washed and dusted. The dust-removed material was then subjected to a steaming pretreatment. The specific conditions for the steaming pretreatment were: a liquid-to-solid ratio of 1:5, a processing temperature of 100°C, and a processing time of 120 minutes. The pretreatment reagents included a 15% ammonia concentration, a 0.01% ferrous ion concentration, and a sodium sulfite dosage of 4% by weight of the biomass raw material. Hydrogen peroxide was used as the oxidant at a concentration of 2% by weight. The specific operation was to first add ammonia, ferrous ions, and sodium sulfite to initiate a pretreatment steaming reaction. After 40 minutes of steaming, hydrogen peroxide was pumped into the reactor. After steaming, solid-liquid separation was performed to obtain black liquor and fiber solids. The resulting mixture then entered a three-stage countercurrent displacement washing apparatus. The washing liquid and black liquor were mixed to obtain a mixed liquor with a solids concentration of approximately 80 g / L.

[0035] The solids in the above-mentioned mixed liquid are sent to a high-concentration refiner for refining at a pulp concentration of 10%. After refining, the material is diluted to 40g / L in proportion and sent to a fiber screening device with a screen aperture of 30 mesh to obtain a suspension of long fibers and fine fibers; the suspension containing fine fibers is then separated from the solid and liquid to obtain fine fibers and filtrate. Among them, the filtrate is used as dilution water to dilute the refined material for recycling; the long fibers are sent to the fiber concentration equipment for dehydration and used as pulp; the pulping, fine fibers and long fiber filtrates can all be used as return water; the fine fibers are sent to the enzymatic hydrolysis tank for saccharification. The fine fibers are prepared into a slurry with a concentration of 9wt%, and cellulase 8FPU / g cellulose is added. Enzymatic hydrolysis and saccharification are carried out in the enzymatic hydrolysis tank. The enzymatic hydrolysis temperature is 45℃, the enzymatic hydrolysis time is 48h, and the total sugar yield is 88%. After the reaction, the material liquid is separated from the solid and liquid to obtain sugar solution and enzymatic hydrolysis residue; the enzymatic hydrolysis residue is directly applied as organic fertilizer.

[0036] After the cooking reaction, the mixed liquid is heated and concentrated to obtain a liquid with a solid content of 30% (ammonia is recovered simultaneously). It is then spray-dried to obtain powdered nitrogen-containing lignin. Elemental analysis shows that the nitrogen content of the lignin is approximately 9%. The powdered nitrogen-containing lignin, potassium chloride, and phosphate rock are mixed and granulated in appropriate proportions to produce a lignin compound fertilizer. The prepared lignin compound fertilizer comprises 80 parts nitrogen-containing lignin, 28 parts potassium chloride, and 30 parts phosphate rock, with no additional nitrogen fertilizer added.

[0037] Example 4: Co-production of cellulose sugars, pulp fiber and powdered lignin using lignocellulosic biomass

[0038] Unlike Example 1, the corn stalks were cut to approximately 10 cm in thickness and then washed and dusted. The dust-removed material was then subjected to a steaming pretreatment. The specific conditions for the steaming pretreatment were: a liquid-to-solid ratio of 1:5, a processing temperature of 120°C, and a processing time of 100 minutes. The pretreatment reagents included a 10% ammonia concentration, a 0.003% ferrous ion concentration, and a sodium sulfite dosage of 3% by weight of the biomass raw material. Oxygen was used as the oxidant. The specific operation was as follows: ammonia, ferrous ions, and sodium sulfite were first added to initiate a pretreatment steaming reaction. After 30 minutes of steaming, oxygen was introduced into the closed device to a pressure of 0.6 MPa. After steaming, solid-liquid separation was performed to produce black liquor and fiber solids. The resulting mixture then entered a three-stage countercurrent displacement washing apparatus. The washing liquid and black liquor were mixed to produce a mixed liquor with a solids concentration of approximately 70 g / L.

[0039] The solids in the above-mentioned mixed liquid are sent to a high-concentration refiner for refining at a pulp concentration of 4%. After refining, the material is diluted to 50g / L in proportion and sent to a fiber screening device with a screen aperture of 30 mesh to obtain a suspension of long fibers and fine fibers; the suspension containing fine fibers is then separated from the solid and liquid to obtain fine fibers and filtrate. Among them, the filtrate is used as dilution water to dilute the refined material for recycling; the long fibers are sent to the fiber concentration equipment for dehydration and used as pulp; the pulping, fine fibers and long fiber filtrates can all be used as return water; the fine fibers are sent to the enzymatic hydrolysis tank for saccharification. The fine fibers are prepared into a slurry with a concentration of 8wt%, and cellulase 5FPU / g cellulose is added. Enzymatic hydrolysis and saccharification are carried out in the enzymatic hydrolysis tank. The enzymatic hydrolysis temperature is 50℃, the enzymatic hydrolysis time is 48h, and the total sugar yield is 87%. After the reaction, the material liquid is separated from the solid and liquid to obtain sugar solution and enzymatic hydrolysis residue; the enzymatic hydrolysis residue is directly applied as organic fertilizer.

[0040] After the cooking reaction, the mixed liquid is heated and concentrated to obtain a liquid with a solid content of 30% (ammonia is recovered simultaneously). It is then spray-dried to obtain powdered nitrogen-containing lignin. Elemental analysis shows that the nitrogen content of the lignin is approximately 9%. The powdered nitrogen-containing lignin, potassium sulfate, calcium magnesium phosphate fertilizer, and ammonium sulfate are mixed and granulated in appropriate proportions to produce a lignin compound fertilizer. In parts by weight, the prepared lignin compound fertilizer comprises 40 parts nitrogen-containing lignin, 28 parts potassium sulfate, 32 parts calcium magnesium phosphate fertilizer, and 15 parts ammonium sulfate.

[0041] Example 5: Co-production of cellulose sugars, pulp fiber and powdered lignin using lignocellulosic biomass

[0042] Unlike Example 1, the waste branches were cut to approximately 2 cm in thickness, then washed and dusted. The dust-removed material was then subjected to a steaming pretreatment. The specific conditions for the steaming pretreatment were: a liquid-to-solid ratio of 1:6, a processing temperature of 120°C, and a processing time of 100 minutes. The pretreatment reagents included a 20% ammonia concentration, a 0.001% ferrous ion concentration, and a sodium sulfite dosage of 5% by weight of the biomass feedstock. Hydrogen peroxide was used as the oxidant at a concentration of 1% by weight. The specific operation involved first adding ammonia, ferrous ions, and sodium sulfite to initiate a pretreatment steaming reaction. After 35 minutes of steaming, hydrogen peroxide was pumped into the reactor. After steaming, solid-liquid separation was performed to produce black liquor and fiber solids. The resulting mixture then entered a three-stage countercurrent displacement washing apparatus. The washing liquid and black liquor were mixed to produce a mixed liquor with a solids concentration of approximately 80 g / L.

[0043] The solids in the above-mentioned mixed liquid are sent to a high-concentration refiner for refining at a pulp concentration of 8%. After refining, the material is diluted to 50g / L in proportion and sent to a fiber screening device with a screen aperture of 30 mesh to obtain a suspension of long fibers and fine fibers; the suspension containing fine fibers is then separated from the solid and liquid to obtain fine fibers and filtrate. Among them, the filtrate is used as dilution water to dilute the refined material for recycling; the long fibers are sent to the fiber concentration equipment for dehydration and used as pulp; the pulping, fine fibers and long fiber filtrates can all be used as return water; the fine fibers are sent to the enzymatic hydrolysis tank for saccharification. The fine fibers are prepared into a slurry with a concentration of 8wt%, and cellulase 6FPU / g cellulose is added. Enzymatic hydrolysis and saccharification are carried out in the enzymatic hydrolysis tank. The enzymatic hydrolysis temperature is 50℃, the enzymatic hydrolysis time is 48h, and the total sugar yield is 87%. After the reaction, the material liquid is separated from the solid and liquid to obtain sugar solution and enzymatic hydrolysis residue; the enzymatic hydrolysis residue is directly applied as organic fertilizer.

[0044] After the cooking reaction, the mixed liquid is heated and concentrated to obtain a liquid with a solid content of 30% (ammonia is recovered simultaneously), which is then spray-dried to obtain powdered nitrogen-containing lignin. Elemental analysis shows that the nitrogen content of the lignin is approximately 11%. The powdered nitrogen-containing lignin, potassium sulfate, and calcium phosphate are mixed and granulated in appropriate proportions to produce a lignin compound fertilizer. The prepared lignin compound fertilizer comprises 70 parts nitrogen-containing lignin, 32 parts potassium sulfate, and 32 parts calcium phosphate by weight, with no additional nitrogen fertilizer added.

[0045] Comparative Example 1:

[0046] Without using any oxidizing agent and following the experimental steps and conditions of Example 1, the resulting powdered lignin had a nitrogen content of approximately 4%, while the nitrogen content of the powdered lignin in Example 1 was approximately 10%. The inventors have discovered that the amount of chemically bound nitrogen in lignin significantly impacts the subsequent preparation of compound fertilizers; the greater the amount of bound nitrogen, the better the nitrogen slow-release effect and higher the fertilizer efficiency. Therefore, the reduced bound nitrogen content in powdered lignin prepared without an oxidizing agent will affect the nitrogen slow-release effect of the compound fertilizer, thereby affecting its efficiency.

[0047] Comparative Example 2:

[0048] Without sodium sulfite, the experimental procedures and conditions described in Example 1 were followed. The delignification efficiency of the cooking pretreatment decreased, resulting in a lower amount of dissolved lignin in the black liquor. The solids concentration in the final mixture of wash liquor and black liquor dropped from 80 g / L to approximately 60 g / L. This reduced delignification also resulted in a decrease in the efficiency of enzymatic hydrolysis of fine fibers, with the total sugar yield falling from 93% to 78% under the same conditions.

[0049] Comparative Example 3:

[0050] Without adding ferrous ions, the powdered lignin obtained by following the experimental steps and conditions of Example 1 had a nitrogen content of approximately 6%, while the nitrogen content of the powdered lignin in Example 1 was approximately 10%. As shown above, the reduction in the bound nitrogen content in the powdered lignin affects the slow-release fertilizer effect of the lignin powder.

[0051] Comparative Example 4:

[0052] Hydrogen peroxide, ammonia, ferrous ions, and sodium sulfite were simultaneously added to the reactor and pretreatment reaction was carried out simultaneously. All other conditions were the same as in Example 1. Compared with Example 1, after the pretreatment cooking in Comparative Example 4, the lignin removal rate was only 60%, significantly lower than the 91% in Example 1. The nitrogen content of the resulting powdered lignin was only 2.4%, significantly lower than the 10% in Example 1. The delignification efficiency of the cooking pretreatment was reduced, resulting in a significant decrease in the amount of dissolved lignin in the black liquor. The solids concentration in the final mixture of the washing liquid and black liquor decreased from 80 g / L to 26 g / L. The significant reduction in delignification efficiency also resulted in a significant decrease in the enzymatic hydrolysis efficiency of fine fibers, with the total sugar yield decreasing from 93% to 53% under the same conditions. This is because when all components of the pretreatment reagent are added simultaneously, the majority of the hydrogen peroxide reacts first with the sodium sulfite, significantly reducing the degree of sulfonation and oxidation of the lignin in the raw material, ultimately significantly reducing the lignin removal rate and, in turn, the overall utilization efficiency of the raw material.

[0053] Comparative Example 5:

[0054] Ammonia, ferrous ions, and hydrogen peroxide were added before the pretreatment reaction began, and sodium sulfite was added after 30 minutes of reaction. All other conditions were the same as in Example 1. Compared with Example 1, after the pretreatment cooking in Comparative Example 5, the lignin removal rate was only 69%, significantly lower than the 91% in Example 1; the nitrogen content of the resulting powdered lignin was only 5.4%, significantly lower than the 10% in Example 1; the delignification efficiency of the cooking pretreatment was reduced, resulting in a significant decrease in the amount of dissolved lignin in the black liquor; the solids concentration in the final mixed liquor after the washing liquid and black liquor was reduced from 80 g / L to 61 g / L; the significant reduction in delignification efficiency also resulted in a significant decrease in the efficiency of enzymatic hydrolysis of fine fibers, with the total sugar yield decreasing from 93% to 72% under the same conditions. This is because, when ammonia, ferrous ions and hydrogen peroxide are added at the same time, most of the hydrogen peroxide reacts with the ferrous ions first, resulting in premature consumption of the ferrous ions, which cannot catalyze the subsequent sulfonation reaction, and ultimately significantly reduces the lignin removal rate, thereby reducing the comprehensive utilization efficiency of raw materials.

[0055] Example 6: Effect of using compound fertilizer

[0056] The potted fertilizer effect of the lignin compound fertilizer prepared in Example 1 was verified. It was divided into 4 verification groups, specifically: blank control (no fertilizer), lignin compound granulated fertilizer, lignin compound powder fertilizer (lignin compound fertilizer is not granulated, and is used directly after mixing according to the formula), and conventional fertilizer; each verification group includes 6 potted plants as parallel samples. Among them, conventional fertilizer refers to the conventional fertilizer used here obtained by removing the nitrogen-containing lignin in the lignin compound fertilizer and replacing it with a fertilizer containing the same amount of nitrogen; the nitrogen content in the lignin compound fertilizer is 10%.

[0057] The pot size of the potted plant experiment was 19 cm high and 18 cm in diameter. The soil was collected from Pingdu, Qingdao. The specific steps of the potted plant experiment were as follows: Soak the seeds of 568 pakchoy in 45℃ water for 45 minutes, wrap them with moist toilet paper, and ℃ After overnight planting, the plants were planted (one seed per pot, with 10 pots planted per validation group). After the seeds germinated and grew for one week, five plants with good growth and relatively uniform traits were selected from the 10 pots in each validation group for use in the experiment. After 40 days of germination, data were harvested and averaged (specific data were summed and averaged). The fertilization plan was as follows: base fertilizer was combined with topdressing after 20 days of growth, with the application rate of base fertilizer and topdressing being the same. The single application rate of lignin compound fertilizer per pot was 2.06g, and the conventional fertilizer rate was fertilized according to the weight of nitrogen, phosphorus, and potassium in the lignin compound fertilizer.

[0058] Experimental results: Figure 2 and Figure 3It can be seen that the leaf length of the plants in the blank control group is 18.7 cm, the leaf width is 10.5 cm, and the biomass is 7 g; the leaf length of the plants in the lignin compound granulated fertilizer is 27.8 cm, the leaf width is 17.0 cm, and the biomass is 13.2 g; the leaf length of the plants in the lignin compound powder fertilizer is 27.5 cm, the leaf width is 16.5 cm, and the biomass is 11.7 g; the leaf length of the plants in the conventional chemical fertilizer is 27.3 cm, the leaf width is 16.3 cm, and the biomass is 9.99 g.

[0059] From this, we can see that the plants in the blank group without fertilizer are short in size, and the sizes of the plants in the other three groups are not much different. The order of the biomass of the four groups of plants is: lignin compound fertilizer granulation > lignin compound powder fertilizer > conventional chemical fertilizer > blank without fertilizer ( Figure 3 It is clear that compared with conventional chemical fertilizers, the leaf length and width of plants using lignin granulated fertilizer are not much different, but the biomass has a significant advantage, increasing by about 32.4%. The direct application of lignin powder fertilizer has a slightly smaller advantage, increasing by 16.8%.

[0060] Example 7: Comparative Example 2:

[0061] The potted plant fertilizer efficacy of the lignin compound fertilizers prepared in Examples 2-5 was verified, with Example 2 being used as an example. The nitrogen content of the lignin compound fertilizer prepared in Example 2 was 12%, and the single fertilizer application amount was 1.98 g. Other details of the potted plant experiment were carried out according to the "Compound Fertilizer Use Effect Comparison Example 1".

[0062] Experimental results: Figure 4 and Figure 5 It can be seen that the leaf length of the plants in the blank control group was 24.9 cm, the leaf width was 15.2 cm, and the biomass was 8.2 g; the leaf length of the plants in the lignin compound granulated fertilizer was 27.1 cm, the leaf width was 18.2 cm, and the biomass was 12.1 g; the leaf length of the plants in the lignin compound powder fertilizer was 27.0 cm, the leaf width was 18.7 cm, and the biomass was 11 g; the leaf length of the plants in the conventional chemical fertilizer was 26.6 cm, the leaf width was 17.6 cm, and the biomass was 9.44 g.

[0063] As can be seen, the size differences between the fertilized plants were not significant, and the size of the potted samples of lignin compound fertilizer was slightly larger. The biomass ranking of the four groups of plants was the same as the conclusion of Example 6: lignin compound fertilizer granulation > lignin compound fertilizer powder > conventional fertilizer > blank fertilizer; compared with conventional fertilizer, the leaf length and leaf width of the plants using lignin granulation fertilizer were not much different, but the biomass had a significant advantage, increasing by about 28.2%; direct application of lignin powder fertilizer had a slight advantage, increasing by 16.5%.

[0064] In summary, the method of the present invention for co-producing cellulose sugar, pulp fiber and lignin using wood fiber biomass realizes the utilization of all components of lignocellulose, and the ammonia produced in the process can be recycled and there is no wastewater discharge. The lignin obtained by the aforementioned method is used to prepare lignin compound fertilizer for plant planting (taking Chinese cabbage as an example). The leaf length and leaf width of the plant are slightly improved, but the biomass is significantly improved; wherein the improvement can reach 32.4% by using lignin granulation fertilizer, and the improvement can reach 16.8% by using lignin powder fertilizer. This shows that the aforementioned lignin compound fertilizer is not only low in cost but also has improved fertility and broad application prospects compared with conventional chemical fertilizers. It has important industrial application prospects and huge economic value.

Claims

1. A method for co-producing cellulose sugars, pulp fiber and lignin using lignocellulosic biomass, characterized by: The following steps are involved: (1) Pretreatment: Cut the lignocellulosic biomass into pieces of 3-10 cm, clean it and set aside; (2) Steaming pretreatment: adding a pretreatment reaction reagent to the wood fiber biomass obtained in step (1) at a solid-liquid ratio of 1:4-1:10, and steaming for 40-120 min at a temperature of 100-140°C to obtain a reactant; wherein the pretreatment reaction reagent comprises an ammonia concentration of 10-25wt%, a ferrous ion concentration of 0.001-0.01wt%, an appropriate amount of sodium sulfite and an oxidant; the specific operation is: adding ammonia, ferrous ions and sodium sulfite to carry out a steaming reaction for 20-40min, then adding an oxidant to the system to continue the reaction until the end; wherein the sodium sulfite is 2-10wt% of the weight of the biomass raw material; the oxidant is oxygen or hydrogen peroxide; when oxygen is used as the oxidant, the specific operation is: introducing oxygen into the closed reaction device until the pressure is 0.6-1.5 MPa, and then continue with the steaming pretreatment; when hydrogen peroxide is used as the oxidant, the concentration of hydrogen peroxide in the pretreatment reaction reagent is 0.5-2wt%, the steaming treatment temperature is not higher than 120°C, and the treatment time is less than 90min; (3) The reactants obtained in step (2) are subjected to solid-liquid separation to obtain black liquor containing lignin and solids mainly composed of cellulose; the solids are washed and neutralized for later use, and the washed water is mixed with the black liquor to obtain a mixed liquid for later use; (4) grinding and grading the solid obtained in step (3) to obtain long fibers and fine fibers; wherein the long fibers have a length of 0.5-5 mm and are used as pulp; the fine fibers have a length of less than 0.5 mm and are enzymatically hydrolyzed to produce sugar; (5) The mixed solution obtained in step (3) is heated and concentrated to a solid content of 25-40 wt%, and then dried to obtain powdered lignin containing nitrogen.

2. The method for co-producing cellulose sugars, pulp fiber and lignin from lignocellulosic biomass according to claim 1, characterized in that: In step (4), the concentration of the refined material is 4-10%, and the aperture of the sieve for graded screening is 16-60 mesh.

3. The method for co-producing cellulose sugars, pulp fiber and lignin from lignocellulosic biomass according to claim 1, characterized in that: In step (4), the specific steps of enzymatic hydrolysis of fine fibers to produce sugar are as follows: preparing a fine fiber slurry with a concentration of 5-25%, adding 2-10 FPU / g cellulose of cellulase, performing enzymatic hydrolysis and saccharification at 40-50°C for 24-48 hours, and separating the solid and liquid after the reaction to obtain a sugar solution and enzymatic hydrolysis residue.

4. The method for co-producing cellulose sugars, pulp fiber and lignin from lignocellulosic biomass according to claim 1, characterized in that: In step (5), while the mixed liquid is heated and concentrated, ammonia is recovered simultaneously.

5. The method for co-producing cellulose sugars, pulp fiber and lignin from lignocellulosic biomass according to claim 1, characterized in that: The wood fiber biomass is straw, corn cobs or waste branches; the cleaning adopts a water film dust removal method, specifically using spray water to clean the wood fiber biomass.

6. Use of the powdered lignin prepared by the method of claim 1 in the preparation of lignin compound fertilizer.

7. The use according to claim 6, characterized in that: Specifically, 40-80 parts of powdered lignin, 25-35 parts of phosphorus fertilizer, 25-35 parts of potassium fertilizer, and 0-15 parts of nitrogen fertilizer are weighed, mixed evenly, granulated, and dried to obtain the lignin compound fertilizer.

8. The use according to claim 7, characterized in that: The phosphate fertilizer is any one of monoammonium phosphate, diammonium phosphate, calcium phosphate, triple superphosphate, calcium dihydrogen phosphate, calcium magnesium phosphate, and phosphate rock powder, or a mixture of several of them; the potash fertilizer is any one of potassium sulfate, potassium chloride, potassium dihydrogen phosphate, and sylvite, or a mixture of several of them; the nitrogen fertilizer is any one of ammonium sulfate, urea, ammonium bicarbonate, sodium nitrate, and ammonium nitrate, or a mixture of several of them.

9. The use according to any one of claims 6 to 8, characterized in that: The lignin compound fertilizer further comprises an appropriate amount of enzymatic hydrolysis residue obtained in step (4), and the amount of the enzymatic hydrolysis residue is 0-30wt% of the weight of the fertilizer.

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