阅读说明：本技术 一种温和湿热预处理玉米秸秆发酵生产沼气的方法 (Method for producing biogas by fermenting mild hydrothermal pretreatment corn straws ) 是由 曲威 董仁杰 杨守军 王禹霄飞 杨毅 于 2020-05-22 设计创作，主要内容包括：本发明公开了一种温和湿热预处理玉米秸秆发酵生产沼气的方法,包括如下步骤：(1)秸秆破碎：将秸秆干燥后进行破碎,得破碎秸秆；(2)预处理：将步骤(1)获得的破碎秸秆与CaO<Sub>2</Sub>溶液混合,75～85℃处理12～24h,过滤,得秸秆糊；(3)厌氧发酵：将步骤(2)获得的秸秆糊调节pH值至6.8～7.3,与沼液混合,密闭发酵10～30天,并收集发酵产生的沼气。本发明采用CaO<Sub>2</Sub>作为预处理剂,联合温和湿热条件处理玉米秸秆,获得了理想的产沼气效果。与现有的常规方法相比,该方法能够获得理想的处理效果、加快处理速度、减少化学品使用并且减少抑制物产生,且对底物的利用率高。本发明经济、高效、环保,适宜玉米秸秆的规模化发酵生产沼气。(The invention discloses a method for producing biogas by fermenting mild moist heat pretreated corn straws, which comprises the following steps: (1) crushing straws: drying and crushing the straws to obtain crushed straws; (2) pretreatment: mixing the crushed straws obtained in the step (1) with CaO 2 Mixing the solutions, treating at 75-85 ℃ for 12-24 h, and filtering to obtain straw paste; (3) anaerobic fermentation: adjusting the pH value of the straw paste obtained in the step (2) to 6.8-7.3, mixing the straw paste with biogas slurry, fermenting in a closed manner for 10-30 days, and collecting biogas generated by fermentation. The invention adopts CaO 2 As a pretreatment agent, the corn straw is treated under the mild damp and hot conditions, and an ideal methane generating effect is obtained. Compared with the conventional method, the method can obtain ideal treatment effect, increase treatment speed, reduce chemical use and generation of inhibitors, and has high utilization rate of the substrate. The invention is economic, efficient and environment-friendly, and is suitable for large-scale fermentation production of biogas by using the corn straws.)

1. A method for producing biogas by fermenting mild moist heat pretreatment corn straws is characterized by comprising the following steps:

(1) crushing straws: drying and crushing the straws to obtain crushed straws;

(2) pretreatment: mixing the crushed straws obtained in the step (1) with CaO₂Mixing the solutions, treating at 75-85 ℃ for 12-24 h, and filtering to obtain straw paste;

(3) anaerobic fermentation: adjusting the pH value of the straw paste obtained in the step (2) to 6.8-7.3, mixing the straw paste with biogas slurry, fermenting in a closed manner for 10-30 days, and collecting biogas generated by fermentation.

2. The method according to claim 1, wherein in step (2), CaO is added₂The concentration of the solution is 1.5-2.5 wt%.

3. The method according to claim 1 or 2, wherein in step (2), the straw and CaO are crushed₂The mass ratio of the solution is 1: (8-15).

4. The method according to claim 1 or 2, wherein in the step (3), before the closed fermentation, water is added into the mixed liquid of the straw paste and the biogas slurry; dry matter in the straw paste: biogas slurry: the dosage ratio of water is 1 g: (10-16) mL: (2-5) mL.

5. The method according to claim 1 or 2, wherein the temperature of the fermentation in the step (3) is 30 to 40 ℃.

6. The method according to claim 1 or 2, wherein in step (3), the pH adjustment is performed using a HCL solution.

7. The method according to claim 1 or 2, wherein in the step (1), the straws are crushed into 3-5 mm particles.

8. The method according to claim 1 or 2, wherein in step (1), the moisture content of the dried straw is below 0.5 wt%.

Technical Field

The invention belongs to the technical field of environmental protection, and particularly relates to a method for producing biogas by fermenting mild moist heat pretreatment corn straws.

Background

Corn belongs to crops with wide planting areas and high yield, and has an economic coefficient of about 0.35, so that a large amount of agricultural wastes are generated in the production process of the corn. About 2.15 million tons of straws are not reasonably utilized every year nationwide. The straw treatment modes are various, wherein the energy output input ratio of the biogas produced by anaerobic fermentation reaches 28/1, the efficiency is high, the cost is low, and the economic benefit reaches more than twice of that of the biogas produced by briquettes. In addition, anaerobic fermentation is based on microorganisms, neither substrate sterilization nor special culture inoculation measures are required, and the requirements on technology and equipment are low.

In the process of carrying out anaerobic fermentation by taking corn straws as raw materials, the decomposition of complex organic matters in the corn straws by hydrolysis is the rate-limiting step of the anaerobic fermentation. In order to improve the hydrolysis efficiency of the straws, proper pretreatment measures are necessary. The commonly used pretreatment modes mainly include biological pretreatment, chemical pretreatment, physical pretreatment, combined pretreatment and the like. From the composition characteristics of the corn straws, the cellulose is insoluble in water and has strong resistance to depolymerization, the hemicellulose is very sensitive to biological, thermal and chemical hydrolysis, and the lignin has strong resistance to biological and chemical degradation. Alkali treatment is a well-established and convenient chemical pretreatment method. The alkali chemical reagent can saponify and break the connecting bond between lignin and carbohydrate, promote the hydrolysis of enzyme and increase the methane yield and methane content in anaerobic fermentation. However, the problem of steric hindrance of materials due to the single pretreatment with an alkali solution is solved, and the environmental and material costs are high, which is not favorable for environmental protection and equipment maintenance. At present, a method for producing biogas by high-valued conversion and anaerobic fermentation of corn straws, which gives consideration to economic benefits and environmental benefits, is lacked in the field.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a method for producing biogas by fermenting mild moist heat pretreatment corn straws, which combines mild moist heat conditions with non-alkaline treatment agents and gives consideration to economic benefits and environmental benefits.

The specific technical scheme is as follows:

a method for producing biogas by fermenting mild moist heat pretreatment corn straws comprises the following steps:

(1) crushing straws: drying and crushing the straws to obtain crushed straws;

(2) pretreatment: mixing the crushed straws obtained in the step (1) with CaO₂Mixing the solutions, treating at 75-85 ℃ for 12-24 h, and filtering to obtain straw paste;

(3) anaerobic fermentation: adjusting the pH value of the straw paste obtained in the step (2) to 6.8-7.3, mixing the straw paste with biogas slurry, fermenting in a closed manner for 10-30 days, and collecting biogas generated by fermentation.

Corn stover is mainly composed of highly lignified cell walls, where cellulose, hemicellulose and lignin are very tightly bound to form very difficult to destroy lignocellulose. In the process of anaerobic fermentation by taking corn straws as raw materials, because lignin and hemicellulose protect the winding of cellulose and the crystal structure of the cellulose, the contact of microorganisms and organic matters is hindered, and the efficiency of producing methane by anaerobic fermentation is reduced. In order to improve the conversion efficiency of the corn straws, proper pretreatment measures are necessary.

The basic non-alkaline solution includes all solutions having a pH >7 at normal temperature other than the alkaline solution, such as alkaline salt solutions, alkaline oxide solutions, organic solutions, and the like. The alkaline non-alkali solution is used, so that the damage of strong alkaline substances to the environment and equipment can be reduced, in addition, the alkaline non-alkali solution contains rich ions, if the biogas slurry is returned to the field, various elements necessary for plant growth can be provided, special effects such as fungus growth inhibition and the like can be achieved, the utilization efficiency of fermentation products can be greatly improved, and the efficient harmless treatment of the corn straws is realized.

CaO₂Is a solid oxidant with low solubility, and can generate OH after slowly reacting with water^-Ions, making the solution alkaline. With CaO₂The solution has strong oxidability, and can destroy the crystal structure of crop straws to convert lignin into soluble aromatic compounds. Has no application in the field of the anaerobic fermentation production of methane by pretreating the corn straws.

Unexpectedly, the subject group discovered CaO₂The solution is used as a mild heat treatment combined with a treating agent, and the efficiency of generating the biogas by fermenting the straws can be obviously improved. The principle may be that the alkaline non-alkali solution is in mild, humid and hot environmentThe degradation and dissolution of hemicellulose and lignin can be promoted, and more hemicellulose and lignin can be promoted to be converted into volatile fatty acid, so that the anaerobic fermentation of methane bacteria is facilitated.

The mild moist heat is different from the conventional moist heat pretreatment in that the temperature is low and the pretreatment is carried out under normal pressure. Conventional wet heat treatment is generally carried out under high pressure at 120 ℃ or higher.

Further, in the step (2), CaO₂The concentration of the solution is 1.5-2.5 wt%. .

CaO₂The definition of the solution concentration is necessary, too high a concentration having a negative effect on the efficiency of the biogas production.

Further, in the step (2), the straws and CaO are crushed₂The mass ratio of the solution is 1: (8-15).

Further, in the step (3), before closed fermentation, adding water into the mixed liquid of the straw paste and the biogas slurry; dry matter in the straw paste: biogas slurry: the dosage ratio of water is 1 g: (10-16) mL: (2-5) mL.

Further, in the step (3), the pH adjustment is performed using an HCl solution. The HCL solution is preferably 0.3-0.5 mol/L dilute HCL solution "

Further, in the step (3), the fermentation temperature is 30-40 ℃.

Further, in the step (1), the straws are crushed into particles of 3-5 mm.

Further, in the step (1), the water content of the dried straw is below 0.5 wt%. The drying method is preferably hot air drying.

The invention has the following beneficial effects:

the invention adopts CaO₂As a pretreatment agent, the corn straw is treated under the mild damp and hot conditions, and an ideal methane generating effect is obtained. Compared with the conventional method, the method can obtain ideal treatment effect, increase treatment speed, reduce chemical use and generation of inhibitors, and has high utilization rate of the substrate. In addition, CaO₂The solution contains Ca²⁺If the biogas slurry is returned to the field, the ions can provide elements required by plant growth and can play a special role in inhibiting the growth of bacteria and the like, which will bring great importance to the fieldGreatly improves the utilization efficiency of fermentation products and realizes the high-efficiency harmless treatment of the straws. The COD value (chemical oxygen demand) and TVFA (total volatile fatty acid) content of the biogas residues obtained by the method are obviously lower than those of the conventional method, and ideal environmental benefits are obtained. The invention is economic, efficient and environment-friendly, and is suitable for large-scale fermentation production of biogas by using the corn straws.

Drawings

FIG. 1 is a schematic view showing the structure of a laboratory-made fermentation apparatus used in the present invention;

in the figure: 1. a sampling port; 2. a sealing cover; 3. a stirring motor; 4. a stirring paddle; 5. an air outlet; 6. an air collecting bag.

Detailed Description

The principles and features of this invention are described below in conjunction with examples, which are set forth to illustrate, but are not to be construed to limit the scope of the invention.