CN106755125B - Treatment method for mixed fermentation of cellulosic ethanol waste liquid and agricultural wastes - Google Patents

Treatment method for mixed fermentation of cellulosic ethanol waste liquid and agricultural wastes Download PDF

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CN106755125B
CN106755125B CN201611237533.7A CN201611237533A CN106755125B CN 106755125 B CN106755125 B CN 106755125B CN 201611237533 A CN201611237533 A CN 201611237533A CN 106755125 B CN106755125 B CN 106755125B
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fermentation
alkali
liquid
straw
pig manure
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CN106755125A (en
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艾平
张济韬
沈子赢
杨志浩
陆逸
胡钗
田启欢
彭靖靖
晏水平
王媛媛
王明
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Huazhong Agricultural University
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    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
    • C12P5/00—Preparation of hydrocarbons or halogenated hydrocarbons
    • C12P5/02—Preparation of hydrocarbons or halogenated hydrocarbons acyclic
    • C12P5/023—Methane
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/02—Biological treatment
    • C02F11/04—Anaerobic treatment; Production of methane by such processes
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
    • C12P2201/00—Pretreatment of cellulosic or lignocellulosic material for subsequent enzymatic treatment or hydrolysis
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
    • Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel

Abstract

The invention discloses a treatment method for mixed fermentation of cellulosic ethanol waste liquid and agricultural wastes, belonging to the technical field of biological energy. The processing method comprises the following steps: adding a first alkali liquor into the waste cellulosic ethanol solution for neutralization to prepare mixed wastewater, wherein the pH value of the mixed wastewater is 6.5-8; mixing the mixed wastewater with the pig manure and/or the alkali-treated straws to prepare a fermentation stock solution, and controlling the TS concentration range of the fermentation stock solution to be 3-9%; and (4) carrying out anaerobic fermentation on the fermentation stock solution, and collecting methane generated by fermentation. The pH value of the waste cellulosic ethanol liquid is adjusted by using the first alkali liquor, then the mixed wastewater is mixed with the pig manure and/or the alkali-treated straws to prepare a fermentation stock solution, and the fermentation stock solution is subjected to anaerobic fermentation to produce the biogas.

Description

Treatment method for mixed fermentation of cellulosic ethanol waste liquid and agricultural wastes
Technical Field
The invention relates to the technical field of biological energy, in particular to a treatment method for mixed fermentation of cellulosic ethanol waste liquid and agricultural wastes.
Background
The ethanol is clean, environment-friendly and renewable, and is a very promising energy source which can replace petroleum as fuel. In the traditional ethanol industry, grains are used as raw materials to produce ethanol, if corn with rich starch is used as the raw material, fermentation can be carried out to produce ethanol without too complicated process, the ethanol yield is high, but the disadvantage of competing for grains with people is not beneficial to large-scale popularization, so that the production of ethanol by using fiber raw materials to replace grains as the raw materials becomes a future development trend. At present, the cellulosic ethanol production line of the Henan Tian Guang group in China realizes the aim of annual production of 3000t of ethanol, and the ethanol is produced by using agricultural wastes such as straws and the like as raw materials, wherein the saccharification rate is 43 percent, and the conversion rate of sugar alcohol is 91 percent. However, in the process of cellulosic ethanol fermentation, a large amount of byproducts are produced, the residual liquid of cellulosic ethanol fermentation mash after distillation and the supernatant obtained after solid-liquid separation are cellulosic ethanol waste liquid, the production amount of the cellulosic ethanol waste liquid is large, and the produced waste liquid is 11-15t per 1t of ethanol. Wherein, the pH value of the waste liquid is 4-5, the waste liquid contains a large amount of organic matters, more than 50 kinds of the detected waste liquid comprise micromolecule volatile acid, furan derivatives, aldehydes and a large amount of inorganic matters, and finally the COD value of the waste liquid is up to 30000-50000mg/L, wherein the acetic acid content can reach 20000mg/L, the chroma of the waste liquid is high, the process required by the treatment of the waste liquid is complex and difficult, and the resource utilization and the energy utilization of the waste liquid after the cellulosic ethanol fermentation are very significant work.
The waste liquid has several treatment and utilization methods, and the physical method includes waste liquid concentration and burning, membrane technology, plate-frame press filtering, centrifugal separation, natural settling, etc.; the chemical method mainly comprises a method of adding an oxidant for oxidation and a method of utilizing anaerobic biological treatment. The physical method alone can not completely degrade the waste liquid, but the method of adding oxidant for oxidation has the disadvantages of high cost, large investment and insufficient environmental protection, but the problem can be well solved by utilizing anaerobic biological treatment. The anaerobic fermentation has wide substrate utilization range and mild treatment process, can convert organic substances in the waste liquid into methane, improves energy conversion, and simultaneously reduces the organic concentration of the wastewater.
When the cellulosic ethanol waste residue liquid is used as a single substrate to directly perform anaerobic fermentation, the direct anaerobic fermentation is easy to fail under the condition of not adjusting the carbon-nitrogen ratio and the pH value of the waste residue liquid due to the characteristics of low carbon-nitrogen ratio, low pH value, high organic acid content, high suspended matter content and the like of the waste residue liquid.
Disclosure of Invention
In order to solve the problem that the direct anaerobic fermentation by taking the waste cellulosic ethanol liquid as a single substrate is easy to fail, the embodiment of the invention provides a treatment method for mixed fermentation of the waste cellulosic ethanol liquid and agricultural wastes. The technical scheme is as follows:
the embodiment of the invention provides a treatment method for mixed fermentation of cellulosic ethanol waste liquid and agricultural wastes, which comprises the following steps:
(1) adding a first alkali liquor into the waste cellulosic ethanol solution for neutralization to prepare mixed wastewater, wherein the pH value of the mixed wastewater is 6.5-8;
(2) mixing the mixed wastewater with the pig manure and/or the alkali-treated straws to prepare a fermentation stock solution, and controlling the TS concentration range of the fermentation stock solution to be 3-9%; and (4) carrying out anaerobic fermentation on the fermentation stock solution, and collecting methane generated by fermentation.
Alkali treatment of straw is a well-known technique in the art, and specifically, in the step (2) above, the alkali-treated straw is obtained by the following method:
and (3) pretreating the straw raw material by using a second alkali liquor, carrying out solid-liquid separation on the pretreated mixture after pretreatment, and drying the obtained solid to obtain the straw subjected to alkali treatment.
Wherein, the solid-liquid separation is realized by adopting a simple screening method, such as a filter screen, and the obtained solid is dried after the separation to obtain the straw after the alkali treatment.
Further, in the above method, the pretreatment of the straw raw material with the second alkali solution comprises:
soaking the straw raw material in a second alkali liquor, and stirring at regular time to ensure that the second alkali liquor fully soaks the straw raw material.
Preferably, in the method for pretreating straws, the second alkali solution is a NaOH solution with the mass fraction of 1% -3%, the pretreatment temperature is 40-60 ℃, the time is 12-36h, and the solid-to-liquid ratio is 7.5% -10%. It should be noted that the solid-liquid ratio is a concentration unit, and in the present invention, specifically refers to the mass ratio of the straw mass to the water in the solvent.
Preferably, the grain diameter of the used straw raw material is less than or equal to 3 mm.
In one possible implementation manner of the invention, in the step (2), when the mixed wastewater and the pig manure are adopted for mixing, the TS concentration is controlled to be less than or equal to 6 percent.
In another possible implementation manner of the invention, in the step (2), when the mixed wastewater is mixed with the pig manure and the alkali-treated straw, the mass ratio of the alkali-treated straw to the pig manure in the fermentation stock solution is 1: 2-2: 1, wherein the mass ratio is preferably about 1: 1.
Wherein TS mass is the total solids content in the sample, and TS concentration refers to the percentage of the total solids content in the sample to the total mass of the sample, i.e., TS concentration is the mass of solids in the sample/total mass of the sample.
In the step (2), the anaerobic fermentation is carried out under the conventional fermentation conditions of straw and pig manure, and specifically, the fermentation conditions can be as follows:
anaerobic fermentation is carried out at a temperature of 35-55 ℃.
Preferably, after the straw raw material is pretreated by the second alkaline solution, the treatment method further comprises the following steps:
and (3) performing solid-liquid separation on a mixture consisting of the straw raw material and the second alkali liquor to obtain residual alkali liquor serving as the first alkali liquor, and adding the residual alkali liquor into the fiber ethanol waste liquor in the step (1).
Preferably, after the step (2), the processing method further comprises:
and performing solid-liquid separation on the fermented stock solution to obtain solid biogas residues and liquid biogas slurry, wherein the biogas slurry is reused for preparing a second alkali solution for pretreating the straw raw material.
The technical scheme provided by the embodiment of the invention has the following beneficial effects: adjusting the pH value of the waste cellulosic ethanol liquid by using residual alkali liquor after the alkali treatment of the straw raw material, then mixing the pig manure and/or the alkali treated straw with the waste cellulosic ethanol liquid to prepare a fermentation raw material, carrying out anaerobic fermentation on the fermentation raw material to produce methane, enhancing the degradation and conversion of the waste cellulosic ethanol liquid while enhancing the methane production capability of the straw and the pig manure fermentation, mixing the alkali treated straw and the waste cellulosic ethanol liquid to prepare a fermentation stock solution independently, mixing the pig manure and the waste cellulosic ethanol liquid to prepare the fermentation stock solution simultaneously, wherein the pig manure and the alkali treated straw are used for providing necessary nutrition in the fermentation process to prevent the waste cellulosic ethanol liquid from being fermented independently and easily failing due to lack of necessary nutrition, the raw materials have wide sources and low cost, not only improves the biogas output of agricultural waste fermentation, but also solves the problem that the cellulosic ethanol waste liquid is difficult to ferment and degrade.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only one embodiment of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a flow chart of a treatment method for mixing and fermenting cellulosic ethanol waste liquid and agricultural wastes according to an embodiment of the present invention;
FIG. 2 is a graph showing fermentation time-gas production in examples 1, 2 and 3 of the present invention and comparative example 2;
FIG. 3 is a graph showing fermentation time-gas production in examples 4, 5 and 6 of the present invention and comparative example 3;
FIG. 4 is a graph showing the comparison of fermentation time and gas production in examples 7, 8 and 9 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a flow chart of a treatment method for mixed fermentation of waste cellulosic ethanol liquid and agricultural wastes provided by an embodiment of the invention, referring to FIG. 1, in examples 1-9 and comparative examples 1-3 under the laboratory conditions described later, straws and first alkali liquid after alkali treatment are obtained by the following methods:
using NaOH solution with the mass fraction of 2% as second alkali liquor, pretreating the straw raw material, mixing the straw raw material and the second alkali liquor, wherein the solid-to-liquid ratio of the straw raw material to the second alkali liquor is 10%, and treating for 12 hours at the temperature of 60 ℃. And after pretreatment, carrying out solid-liquid separation on a mixture consisting of the straw raw material and the second alkali liquor, drying the solid obtained after separation to obtain the straw subjected to alkali treatment, and taking the obtained residual alkali liquor as the first alkali liquor. Wherein, the TS concentration of the straw subjected to alkali treatment is about 92 percent.
In other embodiments of the present invention, the second alkaline solution may be pretreated with a 1% -3% by mass NaOH solution (or an alkaline solution such as a calcium hydroxide solution), the solid-to-liquid ratio of the straw raw material to the second alkaline solution ranges from 7.5% to 10%, the temperature is 40-60 ℃, and the pretreatment time is 12-36 hours.
Example 1
50mL of waste cellulosic ethanol liquid is treated under laboratory conditions, and the treatment method is as follows:
(1) mixing 50mL of waste cellulosic ethanol liquid with 100mL of first alkali liquor to prepare mixed wastewater, wherein the pH value of the mixed wastewater is 7.09, and in the invention, neutralizing the waste cellulosic ethanol liquid to make the pH value of the mixed wastewater be 6.5-8.
(2) Mixing 5g of alkali-treated straw with mixed wastewater to prepare a fermentation raw material, adding 200mL of sludge into the fermentation raw material, finally adding biogas slurry to form 400mL of fermentation stock solution, performing anaerobic fermentation at the fermentation temperature of 35 ℃ for 30 days (the fermentation is finished at 30 days), collecting gas by adopting a drainage method, and monitoring the methane content in the gas and the COD value in the fermentation stock solution after the fermentation (the recorded experiment results are shown in Table 1).
Specifically, the TS concentration calculation formula of the straw in the fermentation raw material is mStraw and stalk*92％/(mStraw and stalk+mLees liquid+mFirst alkali solution) 0.03 in terms of 5 × 0.92/(5+50+ 100). Therefore, the TS concentration of 5g of the alkali-treated straw in the fermentation feedstock was about 3%.
As the original COD value of the waste cellulosic ethanol liquid is higher, the COD values of the added first alkali liquor, sludge and the like which can be used for fermentation are relatively lower and can be ignored, the initial COD values of the fermentation stock solutions in each experimental group are close, and the initial COD values of the prepared fermentation stock solutions in each group are about 5500 mg/L.
The sludge and the biogas slurry are obtained from the anaerobic fermentation tank after the anaerobic fermentation gas production is finished, the sludge is bottom sludge in the anaerobic fermentation tank, and the biogas slurry is upper liquid in the anaerobic fermentation tank. The sludge is rich in anaerobic fermentation microorganisms and serves as an anaerobic fermentation inoculum, the TS mass of the added sludge is 50-60% of that of the straw TS mass, and the biogas slurry is used for adjusting the total fermentation volume.
Example 2
5g of the alkali-treated straw obtained in step (2) of example 1 was replaced with 10g of the alkali-treated straw, and the rest of the procedure was the same as in example 1, and the results of the experiment were recorded in Table 1.
In this example, it can be calculated that the TS concentration of 10g of the alkali-treated straw in the fermentation feedstock is about 6%.
Example 3
The same procedure as in example 1 was repeated except that 5g of the alkali-treated straw in step (2) of example 1 was replaced with 15g of the alkali-treated straw, and the results of the experiment were recorded in Table 1.
In this example, it can be calculated that the TS concentration of 15g of alkali-treated straw in the fermentation feedstock is about 9%.
Example 4
5g of the alkali-treated straw obtained in the step (2) of example 1 was replaced with 20g of pig manure, and the rest of the steps were the same as in example 1, and the results of the experiment were recorded in Table 1.
The adopted pig manure is fresh pig manure, wherein the TS concentration of the pig manure is about 23.29%, and the calculation formula of the TS concentration of 20g of the pig manure in the fermentation raw material is mPig manure*23.29％/(mPig manure+mLees liquid+mFirst alkali solution) 20 × 0.2329/(20+50+100) ═ 0.03, so 20g of pig manure had a TS concentration of about 3% in the fermentation feedstock.
Example 5
5g of the alkali-treated straw obtained in the step (2) of example 1 was replaced with 40g of pig manure, and the rest of the steps were the same as in example 1, and the results of the experiment were recorded in Table 1.
In this example, it can be calculated that the TS concentration of 40g of pig manure in the fermentation feedstock is about 6%.
Example 6
The 5g of alkali-treated straw in step (2) of example 1 was replaced with 60g of pig manure, and the rest of the procedure was the same as in example 1, and the results of the test were recorded in Table 1.
In this example, it can be calculated that 60g of pig manure has a TS concentration of about 9% in the fermentation feedstock.
Example 7
5g of the alkali-treated straw obtained in the step (2) of example 1 was replaced with 10g of alkali-treated straw and 20g of pig manure, and the rest of the steps were the same as those of example 1, and the results of the tests were recorded in Table 1.
Wherein the TS concentration of 10g of the alkali-treated straws and 20g of the pig manure in the fermentation raw material is about 9 percent, and the TS concentration ratio of the alkali-treated straws to the pig manure is 2: 1.
Example 8
5g of the alkali-treated straw obtained in the step (2) of example 1 was replaced with 7.5g of the alkali-treated straw and 30g of pig manure, and the rest of the steps were the same as those of example 1, and the results of the tests were recorded in Table 1.
Wherein the TS concentration of 7.5g of the straws after the alkali treatment and 30g of the pig manure in the fermentation raw material is about 9 percent, and the TS concentration ratio of the straws after the alkali treatment to the pig manure is 1: 1.
Example 9
5g of the alkali-treated straw obtained in the step (2) of example 1 was replaced with 5g of the alkali-treated straw and 40g of pig manure, and the rest of the steps were the same as those of example 1, and the results of the tests were recorded in Table 1.
Wherein the TS concentration of 5g of the alkali-treated straws and 40g of the pig manure in the fermentation raw material is about 9 percent, and the TS concentration ratio of the alkali-treated straws to the pig manure is 1: 2.
Comparative example 1
5g of the alkali-treated straw was not added in step (2) of example 1, and the rest of the steps were the same as in example 1, and the results of the experiment were recorded in Table 1.
Comparative example 2
Mixing 10g of the alkali-treated straw with 50mL of first alkali liquor and 100mL of distilled water (distilled water is added instead of cellulosic ethanol waste liquor) to prepare a fermentation raw material, adding 200mL of sludge into the fermentation raw material, finally adding biogas slurry to form 400mL of fermentation stock solution, performing anaerobic fermentation at the fermentation temperature of 35 ℃ for 30 days, collecting gas by adopting a drainage method, and monitoring the methane content in the gas and the COD value in the fermentation stock solution after fermentation (the recorded experiment results are shown in Table 1).
Comparative example 3
Mixing 40g of pig manure with 50mL of first alkali liquor and 100mL of distilled water (the distilled water is added to replace the cellulosic ethanol waste liquor) to prepare a fermentation raw material, adding 200mL of sludge into the fermentation raw material, finally adding biogas slurry to form 400mL of fermentation stock solution, performing anaerobic fermentation for 30 days at the fermentation temperature of 35 ℃, collecting gas by adopting a drainage method, and monitoring the methane content in the gas and the COD value in the fermentation stock solution after fermentation (the recorded experiment results are shown in Table 1).
TABLE 1
Figure BDA0001195645030000071
Referring to table 1, in comparative example 1, the waste cellulosic ethanol solution was neutralized with the first alkali solution and then made into a fermentation stock solution, which failed to ferment normally.
Referring to table 1, in examples 1, 2 and 3, after mixing the straws with the waste cellulosic ethanol liquid, fermentation raw liquids with straw TS concentrations of 3%, 6% and 9% were prepared, and the fermentation raw liquids could be normally fermented to produce biogas, and as can be seen from examples 1, 2 and 3 and comparative example 1, the COD degradation rate in the waste cellulosic ethanol liquid was significantly improved.
Referring to fig. 2, the fermentation raw liquid of comparative example 2, in which the concentration of TS of straw is 6%, is not added with the spent cellulosic ethanol solution, and the fermentation raw liquid can be normally fermented to produce biogas, as shown in fig. 2, according to the experimental procedures of examples 1, 2, and 3, and comparative example 2, it can be seen from table 1 and fig. 2 that when the straw is mixed with the spent cellulosic ethanol solution and then fermented, the gas yield of fermentation is significantly improved compared with the case where the straw is fermented without the spent cellulosic ethanol solution.
Referring to table 1, in examples 4, 5 and 6, after mixing pig manure with waste cellulosic ethanol liquid, fermentation raw liquid with pig manure TS concentration of 3%, 6% and 9% was prepared, the fermentation raw liquid could be normally fermented to produce biogas, and the COD degradation rate in the waste cellulosic ethanol liquid was significantly improved as compared with example 4, 5 and 6 and comparative example 1. In addition, because the high concentration of pig manure can cause the generation of low C/N ammonia inhibition, the TS concentration of the pig manure is generally required to be controlled within 6% during production in order to ensure the normal fermentation.
Fig. 3 is drawn according to the experimental procedures of examples 4, 5, and 6 and comparative example 3, and referring to fig. 3, the fermentation raw liquid of the control example 3, in which the TS concentration of the pig manure is 6%, is not added with the waste cellulosic ethanol liquid, and the fermentation raw liquid can be normally fermented to produce biogas, and it can be seen from table 1 and fig. 3 that, when the pig manure is mixed with the waste cellulosic ethanol liquid and fermented, the fermentation yield is significantly improved compared with the fermentation of the pig manure without the waste cellulosic ethanol liquid, as compared with the fermentation of the example 5 and the comparative example 3.
Referring to table 1, in examples 7, 8 and 9, after the pig manure and the straw were mixed with the waste cellulosic ethanol liquid (the TS concentration ratio of the straw after the alkali treatment to the pig manure was 1:2, 1:1 and 2:1, respectively), fermentation raw liquids with TS concentrations of 9% were prepared, and the fermentation raw liquids could be normally fermented to produce biogas, and as can be seen from the comparison of examples 7, 8 and 9 with the comparative example 1, the COD degradation rate in the waste cellulosic ethanol liquid was significantly improved.
As can be seen from the results of the experiments of examples 7, 8 and 9, which show that FIG. 4 is plotted, and from the results of the comparative examples 7, 8 and 9, the fermentation gas yield of the fermentation stock solution is the highest when the concentration ratio of the straw to the pig manure TS in the fermentation stock solution is 1: 1.
In the treatment method provided by the invention, the straw subjected to alkali treatment and the cellulosic ethanol waste residue liquid can be independently mixed to prepare the fermentation stock solution, the pig manure and the cellulosic ethanol waste residue liquid can be independently mixed to prepare the fermentation stock solution, the straw subjected to alkali treatment and the pig manure and the cellulosic ethanol waste residue liquid can be simultaneously mixed to prepare the fermentation stock solution, and the pig manure and the straw subjected to alkali treatment are used for providing necessary nutrition in the fermentation process so as to prevent the problem that the cellulosic ethanol waste residue liquid is independently fermented and the fermentation is easy to fail due to the lack of the necessary nutrition.
Therefore, according to actual production, cheaper raw materials are selected to perform mixed fermentation of the waste cellulosic ethanol liquid, for example, local straw resources are rich, the price of the straw is cheaper, local materials can be used for saving cost, the straw is used for performing mixed fermentation of the waste cellulosic ethanol liquid, the concentration range of TS is controlled to be 3-9%, and the normal fermentation is ensured; if the local pig manure is rich in resources and the price of the pig manure is cheaper, the pig manure can be used for mixed fermentation of the cellulosic ethanol waste liquid, and it needs to be noted that when the pig manure and the waste liquid are used for mixed fermentation, the generation of low C/N ammonia inhibition is caused due to the overhigh concentration of the pig manure, so that the TS concentration of the pig manure needs to be controlled within 6%; if the local pig manure and the straws are cheap, the pig manure and the straws can be added simultaneously for improving the treatment efficiency of waste, the straws and the pig manure are mixed and then mixed into waste liquid, the TS concentration can be in the range of 3-9%, and preferably, when the dry weight ratio of the straws to the pig manure is controlled to be about 1:1, the gas yield of fermentation is high.
The invention has the beneficial effects that: mixing the residual alkali liquor after the alkali treatment of the straw raw material as a first alkali liquor with the waste cellulosic ethanol liquid to prepare mixed wastewater, adjusting the pH value of the waste cellulosic ethanol liquid, then mixing the pig manure and/or the alkali treated straw with the mixed wastewater to prepare a fermentation raw material, carrying out anaerobic fermentation on the fermentation raw liquid to produce methane, enhancing the capability of the straw and the pig manure for producing the methane by fermentation, simultaneously enhancing the degradation and conversion of the waste cellulosic ethanol liquid, mixing the alkali treated straw and the mixed wastewater separately to prepare the fermentation raw liquid, mixing the pig manure and the mixed wastewater separately to prepare the fermentation raw liquid, mixing the alkali treated straw and the pig manure with the mixed wastewater to prepare the fermentation raw liquid, mixing the pig manure and the alkali treated straw with the mixed wastewater to prepare the fermentation raw liquid, wherein the pig manure and the alkali treated straw are used for providing necessary nutrition in the fermentation process to prevent the waste cellulosic ethanol liquid from being fermented separately, the fermentation is easy to fail due to lack of necessary nutrition, the raw materials are wide in source and low in cost, the biogas yield of agricultural waste fermentation is increased, and the problem that the waste cellulosic ethanol liquid is difficult to ferment and degrade is solved.
Example 10
According to the above experiment, the application of the present invention in industrial production is described below, taking the production of 1 ton of cellulosic ethanol as an example, the produced cellulosic ethanol waste liquid is about 11 tons, in this example, straw is used as raw material to be mixed with cellulosic ethanol for fermentation, and in this example, the TS concentration of straw used in the fermentation raw liquid is 3% in order to save raw material.
Firstly, the straw raw materials need to be pretreated by using a second alkali liquor, and a sodium hydroxide solution or a calcium hydroxide solution and the like can be used as the second alkali liquor to pretreat the straw raw materials, wherein the mass fraction of the second alkali liquor is in the range of 1% -3%, the lignin in the straw raw materials can be mainly degraded by using the alkali liquor for pretreatment, and the damage effect of the alkali liquor on cellulose and hemicellulose is insufficient, so that more organic matters can be reserved by using the alkali liquor for pretreatment, and a greater degree of energy conversion rate can be obtained.
In this embodiment, the second alkaline solution is a 2% by weight NaOH solution, and the 2% by weight NaOH solution can degrade lignin more sufficiently and is not prone to other side reactions.
Before the straw raw material is subjected to alkali treatment, the straw raw material can be crushed to the particle size of less than or equal to 3mm, so that the straw can be fully pretreated, and then the straw raw material and a NaOH solution with the mass fraction of 2% are mixed to prepare a mixture, wherein the solid-to-liquid ratio in the mixture is 7% -10%, and the pretreatment is carried out for 12-36 hours at the temperature of 60-85 ℃. In this example, the solid-to-liquid ratio was 7.5%, the temperature was 60 ℃ and the pretreatment time was 12 hours.
In the embodiment, the concentration of the TS in the prepared fermentation liquor is 3%, and considering the loss in the straw pretreatment process, about 11 tons of NaOH solution with the mass fraction of 2% is added for pretreatment when 0.7-1.0 ton of the straws are pretreated.
In order to save cost and improve benefit, the residual alkali liquor after the straw raw materials are treated can be used as the first alkali liquor for neutralizing the cellulosic ethanol waste liquid.
Therefore, in this embodiment, the processing method is:
crushing 0.7-1.0 ton of straw raw material into particles with the particle size of less than or equal to 3mm, sending the particles into a pretreatment tank, adding about 11 tons of NaOH solution with the mass fraction of 2% into the pretreatment tank, pretreating the straw raw material for 12 hours at the temperature of 60 ℃, stirring the mixture of the straw raw material and the NaOH solution in the pretreatment tank regularly in order to enable the NaOH solution to fully infiltrate the straw raw material, after the pretreatment is finished, carrying out solid-liquid separation on the pretreated mixture, wherein the solid obtained by the separation is the straw after alkali treatment, and the residual alkali liquor obtained by the separation is the first alkali liquor used for neutralizing the cellulosic ethanol waste liquid.
The first alkali liquor and the waste cellulosic ethanol liquid are mixed in the regulating tank, and after neutralization, mixed wastewater is obtained, the pH value of the mixed wastewater is slightly larger than 7, and fermentation stock solution is easy to acidify in the fermentation process, so that fermentation is difficult to carry out, and the regulation of the pH value of the mixed wastewater has important significance.
Mixing the obtained mixed wastewater and the straws after the alkali treatment in a fermentation tank to prepare a fermentation stock solution, carrying out anaerobic fermentation on the fermentation stock solution in the fermentation tank, and collecting the methane generated by the fermentation. After 30 days of anaerobic fermentation in a fermentation tank, the biogas which can be finally generated is about 24000m3Wherein the methane concentration is greater than 60%.
In the implementation, the anaerobic fermentation tank used for fermentation adopts a CSTR full-mixing stirring tank, the upper part of the fermentation tank is provided with a motor, a stirring paddle is arranged in the fermentation tank, and the motor controls the stirring paddle to regularly stir the fermentation stock solution in the fermentation tank.
In addition, the fermentation tank is also provided with a thermometer for monitoring the temperature of the fermentation environment, a pressure gauge for monitoring the pressure in the fermentation tank, a pH meter for monitoring the pH value of the fermentation stock solution, a liquid level meter for monitoring the liquid level height in the fermentation tank and a heating pipe for adjusting the temperature in the fermentation tank. The anaerobic fermentation adopts 35 ℃ medium temperature fermentation or 55 ℃ high temperature fermentation, and the temperature of the fermentation stock solution in the fermentation tank can be adjusted through a heating pipe; the gas production rate in the fermentation tank is observed through a pressure gauge, and when the gas production rate needs to be increased, the gas production rate can be increased by increasing the feeding concentration and the fermentation temperature; the pH value of the fermentation stock solution is monitored by a pH meter, and when the pH value of the system is slightly lower, the C/N ratio and the pH value are adjusted by using the raw materials of the fed mixed wastewater, the pig manure and the like so as to maintain stable gas production fermentation.
After the fermentation is finished, the fermented stock solution after the fermentation can be recycled, and the method specifically comprises the steps of carrying out solid-liquid separation on the fermented stock solution after the fermentation is finished, wherein the solid obtained after the separation can be used for manufacturing an organic fertilizer for utilization, and the biogas slurry obtained after the separation can be reused for preparing a second alkali liquor used for pretreating straws, can also be used for agricultural irrigation, and can also be reused for diluting the fermented stock solution so as to adjust the TS concentration of the fermented stock solution.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (7)

1. A treatment method for mixed fermentation of cellulosic ethanol waste liquid and agricultural wastes is characterized in that NaOH solution with the mass fraction of 1% -3% is used as second alkali liquid, and residual alkali liquid obtained by performing solid-liquid separation on a mixture obtained after straw raw materials are pretreated by the second alkali liquid is used as first alkali liquid, and the treatment method comprises the following steps:
(1) pretreating the straw raw material by using the second alkali liquor, performing solid-liquid separation on the pretreated mixture, drying the obtained solid to obtain the straw subjected to alkali treatment, wherein the pretreatment temperature is 40-60 ℃, the time is 12-36h, and the solid-liquid ratio is 7.5-10%;
(2) adding the first alkali liquor into the cellulosic ethanol waste residue liquid for neutralization to prepare mixed wastewater, wherein the pH value of the mixed wastewater is 6.5-8;
(3) mixing the mixed wastewater with the pig manure and/or the alkali-treated straws to prepare a fermentation raw material, and controlling the TS concentration range of the fermentation raw material to be 3-9%; anaerobic fermentation is carried out on the fermentation raw materials, and methane generated by fermentation is collected.
2. The process of claim 1, wherein pretreating the straw feedstock with the second alkaline solution comprises:
soaking the straw raw material in a second alkali liquor, and stirring at regular time to ensure that the second alkali liquor fully soaks the straw raw material.
3. The process of claim 1, wherein after step (2), the process further comprises:
and performing solid-liquid separation on the fermented stock solution to obtain solid biogas residues and liquid biogas slurry, wherein the biogas slurry is reused for preparing a second alkali solution for pretreating the straw raw material.
4. The process of claim 1, wherein the straw feedstock has a particle size of less than or equal to 3 mm.
5. The treatment method according to any one of claims 1 to 4, wherein in the step (3), when the mixed wastewater and the pig manure are used for mixing, the TS concentration is controlled to be 6% or less.
6. The treatment method according to any one of claims 1 to 4, wherein in the step (3), when the mixed wastewater is mixed with the pig manure and the alkali-treated straw, the TS concentration ratio of the alkali-treated straw to the pig manure in the fermentation stock solution is 1:2 to 2: 1.
7. The process according to any one of claims 1 to 4, wherein in step (3), the temperature of the anaerobic fermentation is 35 to 55 ℃.
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