阅读说明：本技术 木质纤维素类原料电芬顿预处理厌氧发酵循环制备燃气的方法 (Method for circularly preparing fuel gas by electro-Fenton pretreatment anaerobic fermentation of lignocellulose raw material ) 是由 李连华 吴佩雯 何林松 孙永明 李颖 邢涛 于 2020-05-06 设计创作，主要内容包括：本发明公开了一种木质纤维素类原料电芬顿预处理厌氧发酵循环制备燃气的方法,木质纤维素原料经过青贮或黄贮,直接满足了传统电芬顿反应所需的pH条件,通过微生物燃料电池装置MFC产生的电势驱动电芬顿反应进行,破坏了木质纤维素类原料的内部结构,提高了厌氧产气性能；通过将厌氧发酵剩余物固液分离,沼液回流到微生物燃料电池装置MFC,避免了沼液的处理问题,使液体中的残留的有机质成分重新进入到微生物燃料电池装置MFC,提高了反应器的稳定性；通过将厌氧发酵剩余物固液分离,沼渣资源化利用,实现了资源的合理化利用,避免了二次污染,降低了运行成本。(The invention discloses a method for circularly preparing fuel gas by performing electro-Fenton pretreatment and anaerobic fermentation on a lignocellulose raw material, wherein the lignocellulose raw material is subjected to ensiling or yellow storage, so that the pH condition required by the traditional electro-Fenton reaction is directly met, and the potential generated by a Microbial Fuel Cell (MFC) drives the electro-Fenton reaction to be performed, so that the internal structure of the lignocellulose raw material is damaged, and the anaerobic gas production performance is improved; by performing solid-liquid separation on the anaerobic fermentation residues and refluxing the biogas slurry to the microbial fuel cell device MFC, the problem of biogas slurry treatment is solved, residual organic matter components in the liquid enter the microbial fuel cell device MFC again, and the stability of the reactor is improved; by solid-liquid separation of the anaerobic fermentation residues and resource utilization of biogas residues, reasonable utilization of resources is realized, secondary pollution is avoided, and the operation cost is reduced.)

1. The method for circularly preparing the fuel gas by the electro-Fenton pretreatment anaerobic fermentation of the lignocellulose raw material is characterized by comprising the following steps of:

(1) collecting and crushing the lignocellulose raw material, and storing by adopting an ensiling or yellow storage process; wherein the ensiling process is suitable for fresh green lignocellulose raw materials with the water content of 60-80 wt%, the ensiling time is 30-90 days, and the pH value of the ensiled raw materials is 3.0-4.5; the yellow storage process is suitable for semi-dry lignocellulose raw materials with the water content of 40-60 wt%, the yellow storage time is 30-90 days, and the pH value of the raw materials after yellow storage can reach 3.5-4.2;

(2) mixing the lignocellulose raw material subjected to ensiling or yellow storage in the step (1) with water according to a solid-to-liquid ratio of 1 (10-20), and feeding the mixture into an electro-Fenton reactor for electro-Fenton pretreatment for 12-24 hours; the anode of the electro-Fenton reactor takes iron as an electrode, the cathode of the electro-Fenton reactor is introduced with air, and the required power supply is supplied by a microbial fuel cell device;

(3) feeding the raw materials pretreated by Fenton in the step (2) into an anaerobic reactor for anaerobic fermentation; the fermentation temperature is 30-37 deg.C or 50-55 deg.C, and the organic loading of the feed is 1.0-4.0kg VS/(m)³D) a hydraulic retention time of 30 to 45 d;

(4) and (4) allowing gas generated after anaerobic fermentation in the step (3) to enter a gas storage device, allowing fermentation residues to enter a solid-liquid separation device for solid-liquid separation, allowing part of biogas slurry to enter a microbial fuel cell device, and allowing part of biogas slurry to flow back to an anaerobic reactor, so as to recycle biogas residues.

2. The method for cyclic production of fuel gas by electro-fenton pre-treatment anaerobic fermentation of lignocellulosic feedstocks according to claim 1, wherein said lignocellulosic feedstocks comprise one or more of corn stover, sorghum stover, switchgrass, and hybrid pennisetum.

3. The method for preparing fuel gas by electro-fenton pre-treatment anaerobic fermentation circulation of lignocellulosic raw material as claimed in claim 1 or 2, wherein the microbial fuel cell is a single chamber or a double chamber, the microbial fuel cell body is composed of an anode chamber and a cathode chamber, and the anode chamber and the cathode chamber are separated by a cation exchange membrane or a salt bridge; the anode chamber electrode material is one or more of graphite, carbon felt and carbon paper; the cathode catalyst is carbon cloth or active carbon; the carbon source of the microbial fuel cell device is from biogas slurry obtained after solid-liquid separation of the anaerobic reactor, the pH value of the biogas slurry is about 7.0-8.0, and the temperature of the biogas slurry is 30-35 ℃.

4. The method for preparing fuel gas by performing electro-fenton pretreatment anaerobic fermentation circulation on the lignocellulose raw material according to claim 1 or 2, wherein the electro-fenton reactor is a sequencing batch pretreatment device and comprises a main structure, a feed pipe, a water outlet pipe, a stirring device, a water decanter, a collecting hopper and a discharge pipe, wherein the stirring device comprises a rotating shaft and a stirring blade connected below the rotating shaft, the upper end of the rotating shaft penetrates through the top of the main structure and is connected with a stirring motor arranged at the top of the main structure, the water decanter floats on the liquid level and is controlled by a PLC (programmable logic controller), the water outlet pipe is connected with the water decanter, the bottom of the main structure is connected with the collecting hopper, and the discharge pipe is arranged at the bottom of the collecting hopper.

The technical field is as follows:

the invention relates to the technical field of energy utilization of lignocellulose raw materials, in particular to a method for circularly preparing fuel gas by performing electro-Fenton pretreatment and anaerobic fermentation on the lignocellulose raw materials.

Background art:

most of the lignocellulose raw materials have the characteristics of easy planting, high yield, short growth period and the like, are widely applied to the industries of papermaking and construction, and are also used as animal feeds in some cases. Nevertheless, a large amount of lignocellulosic raw materials or residues resulting from processing are not utilized. The traditional treatment techniques are incineration, landfill and composting, but the methods all cause different damage to the environment. Compared with the traditional technologies, the anaerobic fermentation technology can realize the combination of the reduction treatment of the lignocellulose raw materials and the production of clean energy.

The lignocellulose consists of cellulose, hemicellulose and lignin, contains rich organic matter content and carbon content, and has good anaerobic fermentation potential. However, the components are tightly connected to form a refractory biological structure, so that the lignocellulose raw material cannot obtain good gas production performance if directly subjected to anaerobic fermentation. Lignocellulosic feedstocks therefore require pretreatment to destroy their complex internal structure prior to anaerobic fermentation to improve the anaerobic digestion properties of the feedstock. Common pretreatment processes include acid/alkali pretreatment, hydrothermal pretreatment, steam explosion pretreatment and the like, but the traditional pretreatment methods have higher required cost and energy consumption, so that the pretreatment cost of the lignocellulose raw material is reduced, and the energy conversion in the whole process is improved.

Compared with the traditional Fenton method, the electro-Fenton technology has the advantages of high utilization rate of the Fenton reagent, saving the cost required in the process of storing and transferring electrons, and having stronger oxidation capacity and lower energy consumption. The electro-Fenton technology utilizes electrochemical action to generate hydrogen peroxide, O, by cathodic reduction in an acidic environment with a pH value of 2-4₂+2H⁺+2e^-→H₂O₂In the presence of anodic oxidation to form Fe²⁺Generating strong oxidizing hydroxyl radical, Fe under the combined action of hydrogen peroxide and ferrous ion²⁺+H₂O₂→Fe³⁺+OH^-OH, thereby achieving the effect of oxidative degradation. However, implementation of electro-fenton technology requires meeting the feed pH requirements and requires an external power source, which increases the cost of operation.

Therefore, the problem to be solved is to find a suitable pretreatment technology to improve the anaerobic fermentation performance of the lignocellulose raw material to the maximum extent on the basis of reducing the treatment cost.

The invention content is as follows:

the invention aims to provide a method for circularly preparing fuel gas by performing electro-Fenton pretreatment and anaerobic fermentation on a lignocellulose raw material, which solves the problems of high cost in the pretreatment process of the lignocellulose raw material and low energy conversion efficiency in the anaerobic fermentation process.

The invention is realized by the following technical scheme:

a method for circularly preparing fuel gas by performing electro-Fenton pretreatment and anaerobic fermentation on a lignocellulose raw material comprises the following steps:

(1) collecting and crushing the lignocellulose raw material, and storing by adopting an ensiling or yellow storage process; wherein the ensiling process is suitable for fresh green lignocellulose raw materials with the water content of 60-80 wt%, the ensiling time is 30-90 days, and the pH value of the ensiled raw materials is 3.0-4.5; the yellow storage process is suitable for semi-dry lignocellulose raw materials with the water content of 40-60 wt%, the yellow storage time is 30-90 days, and the pH value of the raw materials after yellow storage can reach 3.5-4.2;

(2) mixing the lignocellulose raw material subjected to ensiling or yellow storage in the step (1) with water according to a solid-to-liquid ratio of 1 (10-20), and feeding the mixture into an electro-Fenton reactor for electro-Fenton pretreatment for 12-24 hours; the anode of the electro-Fenton reactor takes iron as an electrode, the cathode of the electro-Fenton reactor is introduced with air, and the required power supply is supplied by a microbial fuel cell device;

(3) and (3) the raw material pretreated by the Fenton in the step (2) enters an anaerobic reactorAnaerobic fermentation is carried out in the reactor; the fermentation temperature is 30-37 deg.C or 50-55 deg.C, and the organic loading of the feed is 1.0-4.0kg VS/(m)³D) a hydraulic retention time of 30 to 45 d;

(4) and (4) allowing gas generated after anaerobic fermentation in the step (3) to enter a gas storage device, allowing fermentation residues to enter a solid-liquid separation device for solid-liquid separation, allowing part of biogas slurry to enter a microbial fuel cell device, and allowing part of biogas slurry to flow back to an anaerobic reactor, so as to recycle biogas residues.

The lignocellulose raw materials include, but are not limited to, corn stalks, sorghum stalks, switchgrass, hybrid pennisetum and other raw materials.

The microbial fuel cell is a single chamber or double chambers, the microbial fuel cell main body consists of an anode chamber and a cathode chamber, and the anode chamber and the cathode chamber are separated by a cation exchange membrane or a salt bridge; the anode chamber electrode material is one or more of graphite, carbon felt and carbon paper; the cathode catalyst is catalyst carbon cloth or active carbon which is used conventionally; the carbon source of the microbial fuel cell device is from biogas slurry obtained after solid-liquid separation of the anaerobic reactor, the pH value of the biogas slurry is about 7.0-8.0, and the temperature of the biogas slurry is 30-35 ℃.

Particularly, the electro-Fenton reactor is a sequencing batch pretreatment device and comprises a main structure, a feeding pipe, a water outlet pipe, a stirring device, a water decanter, a collecting funnel and a discharging pipe, wherein the stirring device comprises a rotating shaft and a stirring blade connected below the rotating shaft, the upper end of the rotating shaft penetrates through the top of the main structure and is connected with a stirring motor arranged at the top of the main structure, the water decanter floats on the liquid level and is controlled by a PLC (programmable logic controller), the water outlet pipe is connected with the water decanter, the bottom of the main structure is connected with the collecting funnel, and the bottom of the collecting funnel is provided with the discharging pipe.

The pH value of the reaction condition of the electro-Fenton pretreatment is about 3.0-4.0, and the pH range required by the electro-Fenton pretreatment is realized by organic acid generated in the ensiling and yellow storage processes. Mixing lignocellulose raw material with water, introducing into an electro-Fenton reactor, introducing iron as an electrode into an anode of the electro-Fenton reactor, introducing air into a cathode of the electro-Fenton reactor, and generating H under acidic condition by electrochemical action₂O₂，O₂+2H⁺+2e^-→H₂O₂With Fe generated at the anode²⁺The reaction generates hydroxyl radicals (. OH) of strong oxidizing nature, which destroy the intrinsic structure of the lignocellulosic feedstock. And after the electro-Fenton pretreatment is finished, stirring is stopped, solid-liquid separation is carried out through standing precipitation, the PLC outputs an instruction to move the decanter below the liquid level, when the liquid level is reduced to the lowest value, the liquid in the decanter is lifted to the initial parking position and is discharged through a water outlet pipe, and the pretreated lignocellulose raw material is collected by a collection funnel and is discharged through a discharge pipe.

The invention has the following beneficial effects:

compared with the prior art, the method has the advantages that the lignocellulose raw material directly meets the pH condition required by the traditional electro-Fenton reaction through ensiling or yellow storage, and the pH is prevented from being reduced by adding acid; the potential generated by the microbial fuel cell device MFC drives the electro-Fenton reaction to proceed, so that the cost required by an external power supply is reduced; the internal structure of the lignocellulose raw material is destroyed through electro-Fenton pretreatment, and the anaerobic gas production performance is improved; by performing solid-liquid separation on the anaerobic fermentation residues and refluxing the biogas slurry to the microbial fuel cell device MFC, the problem of biogas slurry treatment is solved, residual organic matter components in the liquid enter the microbial fuel cell device MFC again, and the stability of the reactor is improved; by solid-liquid separation of the anaerobic fermentation residues and resource utilization of biogas residues, reasonable utilization of resources is realized, secondary pollution is avoided, and the operation cost is reduced.

Description of the drawings:

FIG. 1 is a schematic process flow diagram of the present invention;

FIG. 2 is a schematic diagram of the electro-Fenton reactor configuration of the present invention;

the device comprises a main structure 1, a main structure 2, a feeding pipe 3, a stirring motor 4, a rotating shaft 5, a stirring blade 6, a decanter 7, a water outlet pipe 8, a PLC (programmable logic controller) 9, a collecting funnel 10 and a discharging pipe.

The specific implementation mode is as follows:

the following is a further description of the invention and is not intended to be limiting.

The electro-fenton reactor shown in fig. 2 is a sequencing batch pretreatment device, and comprises a main body structure 1, a feed pipe 2, a water outlet pipe 7, a stirring device, a water decanter 6, a collecting funnel 9 and a discharging pipe 10, wherein the stirring device comprises a rotating shaft 4 and a stirring blade 5 connected below the rotating shaft 4, the upper end of the rotating shaft 4 penetrates through the top of the main body structure 1 and is connected with a stirring motor 3 arranged at the top of the main body structure 1, the water decanter 6 floats on the liquid surface and is controlled by a PLC controller 8, the water outlet pipe 7 is connected with the water decanter 6, the bottom of the main body structure 1 is connected with the collecting funnel 9, and the discharging pipe 10 is arranged at the bottom of the collecting funnel 9.

Example 1: method for circularly preparing fuel gas by electro-Fenton pretreatment anaerobic fermentation of silage hybrid pennisetum alopecuroides

The process flow diagram is shown in figure 1, and the method comprises the following steps:

(1) collecting and crushing the hybrid pennisetum alopecuroides, storing by adopting an ensiling process, and enabling the pH value to reach 3.0 after ensiling for 90 days;

(2) the hybrid pennisetum alopecuroides subjected to ensiling in the step (1) is mixed with water in a solid-to-liquid ratio of 1:15, and the mixture enters an electro-Fenton reactor shown in a figure 2 through a feeding pipe 2 for pretreatment, wherein the reaction time is 12 hours. The method comprises the following steps of (1) carrying out electrokinetic Fenton reaction by adopting a double-chamber microbial fuel cell device, wherein an electrode material of an anode chamber is graphite, an electrode material of a cathode chamber is activated carbon particles, and the two chambers are separated by a cation exchange membrane; after the electro-Fenton pretreatment is finished, stirring is stopped, solid-liquid separation is carried out through standing and precipitation, the PLC 8 outputs an instruction to move the water decanter 6 to be below the liquid level, when the liquid level is reduced to the lowest value, the liquid in the water decanter 6 is lifted to the initial parking position and is discharged through the water outlet pipe 7, and the pretreated lignocellulose raw material is collected by the collection funnel 9 and is discharged through the discharge pipe 10;

(3) discharging the lignocellulose raw material pretreated in the step (2) through a discharge pipe 10, allowing the lignocellulose raw material to enter an anaerobic reactor for medium-temperature anaerobic fermentation (37 ℃), wherein the organic loading of the reactor is 4.0kg VS/(m)³D) a hydraulic retention time of 30 d;

(4) gas generated after anaerobic fermentation in the step (3) enters a gas storage device, fermentation residues enter a solid-liquid separation device for solid-liquid separation, part of biogas slurry enters a microbial fuel cell, and part of biogas slurry flows back to an anaerobic reactor, so that biogas residues are recycled;

through detection, after the lignocellulose material raw material is pretreated by adopting the process, the lignin removal rate reaches 67 percent, the gas production rate of the raw material is more than 600mL/gVS, and the gas production rate of the tank volume reaches 2.0m³/(m³D) a 48% increase in the gas yield over the untreated feed.

Example 2: method for circularly preparing fuel gas by electro-Fenton pretreatment-anaerobic fermentation of yellow corn stalks

A process flow diagram is also shown in fig. 1, the method comprising the steps of:

(1) after the corn straws are collected and crushed, the corn straws are stored by adopting a yellow storage process, and the pH value reaches 3.5 after the corn straws are stored for 60 days;

(2) the corn straws after yellow storage in the step (1) are mixed with water according to the solid-liquid ratio of 1:20, and the mixture enters an electro-Fenton reactor shown in figure 2 through a feeding pipe 2 for pretreatment, wherein the reaction time is 24 hours. Adopting a single-chamber microbial fuel cell device to generate electric drive electro-Fenton reaction, taking a carbon felt as an anode and a carbon cloth as an air cathode; after the electro-Fenton pretreatment is finished, stirring is stopped, solid-liquid separation is carried out through standing and precipitation, the PLC 8 outputs an instruction to move the water decanter 6 to be below the liquid level, when the liquid level is reduced to the lowest value, the liquid in the water decanter 6 is lifted to the initial parking position and is discharged through the water outlet pipe 7, and the pretreated lignocellulose raw material is collected by the collection funnel 9 and is discharged through the discharge pipe 10;

(3) discharging the pretreated lignocellulose raw material in the step (2) through a discharge pipe 10, allowing the lignocellulose raw material to enter an anaerobic reactor for medium-high temperature anaerobic fermentation (55 ℃), wherein the organic loading of the reactor is 2.0kg VS/(m)³D) a hydraulic retention time of 45 d;

(4) gas generated after anaerobic fermentation in the step (3) enters a gas storage device, fermentation residues enter a solid-liquid separation device for solid-liquid separation, part of biogas slurry enters a microbial fuel cell, and part of biogas slurry flows back to an anaerobic reactor for recycling biogas residues;

through detection, after the lignocellulose material raw material is pretreated by the process, the lignin removal rate reaches 70%, the gas production rate of the raw material is more than 400mL/gVS, and the methane content is more than 70%.