Three-stage coupling continuous enhanced hydrogen production method

Abstract

The invention discloses a three-stage coupling continuous enhanced hydrogen production method. The method comprises the following steps: step 1, preparing an oxygen-free environment; step 2, enrichment and propagation of hydrogenogens; step 3, enrichment and propagation of photosynthetic bacteria; step 4, performing enzymolysis saccharification on the kitchen garbage; 5, carrying out anaerobic dark fermentation to produce hydrogen; step 6, carrying out anaerobic light fermentation to produce hydrogen; and 7, continuously culturing to produce hydrogen. According to the continuous culture principle, hydrogen is continuously and efficiently produced through the dark fermentation tank, the light fermentation tank and the microbial electrolysis cell at the same time, and the method has the advantages of low cost, short fermentation time, complete process and high yield. And when the hydrogen production rate of dark fermentation begins to decrease, the substrate is continuously circulated, and the volatile organic acid generated by terminal metabolism of dark fermentation is consumed by light fermentation, so that the feedback inhibition effect of the volatile organic acid on hydrogenogens is effectively solved. The utilization range of the substrate of the microbial electrolysis cell is wide, thorough oxidation of residual organic matters is realized under the assistance of electricity-producing microorganisms, and the problem of incomplete dark-light coupling anaerobic fermentation can be effectively solved.

Description

Technical Field

[0001] The invention relates to a three-stage coupled continuous enhanced hydrogen production method, belonging to the technical field of hydrogen production. Background Art

[0002] Against the backdrop of increasingly depleted global energy and increasingly severe environmental problems, hydrogen energy, as a clean, efficient and sustainable form of energy, is gradually becoming a strategic direction for countries around the world to compete for development. At present, the main methods of hydrogen production are fossil fuel hydrogen production, water electrolysis hydrogen production, biological hydrogen production, and thermochemical water cracking hydrogen production. For fossil fuel hydrogen production, it will cause large system energy consumption and a large number of waste pollutants, and there are environmental problems such as serious pollution; for water electrolysis hydrogen production, it requires more electricity, the cost is high, and it is difficult to carry out large-scale production; for thermochemical water cracking hydrogen production, the reaction process is relatively complicated, the construction cost is high, and the current technology is not mature enough. Compared with the above hydrogen production methods, biohydrogen production uses microorganisms to decompose organic waste to produce hydrogen, and consumes organic waste while producing energy. It has the advantages of low energy consumption, high yield, high stability, and large-scale production.

[0003] The biological hydrogen production process is divided into two categories: anaerobic photofermentation and anaerobic dark fermentation. Anaerobic dark fermentation can utilize a wide variety of organic matter and has a high hydrogen production rate, but the terminal metabolites of dark fermentation contain a large number of low-molecular organic acids. Volatile organic acids have a feedback inhibitory effect on hydrogen-producing bacteria, which to a certain extent limits the dark fermentation hydrogen production rate and amount. Photosynthetic hydrogen-producing bacteria in anaerobic photofermentation can further produce hydrogen using low-molecular organic volatile acids, but the disadvantage is that the fermentation cycle is too long and the fermentation is incomplete.

[0004] At the same time, as a country with a large population in the world, China faces a huge problem in the harmless treatment and resource utilization of kitchen waste. Kitchen waste has a high moisture content, is easy to rot and rancid, and is prone to mosquitoes and flies. At present, the domestic treatment method is still mainly landfill and incineration, which has caused great pollution to the environment. Kitchen waste contains a large amount of organic matter, which is suitable as a substrate for microbial fermentation. However, most of the organic matter in kitchen waste is macromolecular organic matter such as starch and protein, which will reduce the utilization rate of microorganisms for substrates. Summary of the invention

[0005] Purpose of the invention: In view of the deficiencies in the prior art, the present invention provides a three-stage coupled continuous enhanced hydrogen production method. The present invention adopts the principle of continuous culture to simultaneously and continuously and efficiently produce hydrogen through a dark fermentation tank, a light fermentation tank, and a microbial electrolysis cell, fundamentally changing the batch and periodic fermentation of traditional anaerobic fermentation. It has the advantages of low cost, short fermentation time, complete process, and high yield.

[0006] Technical solution: A three-stage coupled continuous enhanced hydrogen production method, comprising the following steps: Step 1: Prepare an anaerobic environment: introduce nitrogen N2 into the current preparation environment for 10-15 minutes to complete the preparation of the anaerobic environment; Step 2: Enrichment and expansion of hydrogen-producing bacteria: The anaerobic activated sludge is subjected to heat treatment and acid treatment to screen and enrich hydrogen-producing bacteria, and the bacteria are expanded at 35-37°C and pH 3.5-7.0; Step 3: enrichment and expansion of photosynthetic bacteria: 100-110 g of anaerobic activated sludge was added to a 1000 mL anaerobic container, filled with enrichment medium, stirred evenly, and cultured under light to screen and enrich photosynthetic bacteria. The photosynthetic bacteria were expanded at 30-35 °C, pH 7-7.5, and light intensity of 2500-2600 lux. Step 4: Enzymatic saccharification of kitchen waste: pre-treat the kitchen waste, then add α-amylase and glucoamylase to the kitchen waste, adjust the pH to 5.5-6, the temperature to 50-55°C, stir for 20-24 hours, and obtain enzymatic saccharified kitchen waste; adjust the pH of the enzymatic saccharified kitchen waste to 7.0-7.5, add water to dilute the enzymatic saccharified kitchen waste, obtain diluted enzymatic saccharified kitchen waste, and store it as a substrate for later use; Step 5: anaerobic dark fermentation hydrogen production: inoculate hydrogen-producing bacteria into a dark fermentation tank at an inoculation rate of 10-15%, introduce 85%-90% diluted enzymatic saccharification kitchen waste, and perform anaerobic dark fermentation hydrogen production at 35-37°C and pH 7.0-7.5; Step 6: Anaerobic photofermentation hydrogen production: Inoculate photosynthetic bacteria at an inoculation rate of 5%-10% into a photofermentation tank filled with 90%-95% photosynthetic hydrogen production medium, and perform photofermentation hydrogen production at 30-35°C, pH 7.0-7.5, and light intensity 2500-3000 lux; Step 7, continuous cultivation and hydrogen production: real-time monitoring of dark fermentation hydrogen production rate, when the dark fermentation hydrogen production rate begins to decline, the enzymatic saccharification kitchen waste in step 3 is flowed into the dark fermentation tank, the dark fermentation liquid in the dark fermentation tank is flowed into the light fermentation tank, and the light fermentation liquid is flowed into the microbial electrolysis cell, the flow rate is 50-100 mL / h, and hydrogen is continuously produced through dark fermentation, light fermentation, and microbial electrolysis cell. The microbial electrolysis cell MEC has a starting voltage of 0.3~0.8 V and a starting temperature of 33 ℃. It starts to operate after the voltage remains stable; the MEC operating voltage is 0.7~0.9 V and the operating temperature is 4~9 ℃, which is much lower than the electrolysis method 1.8~2.0 V.

[0007] Preferably, the method for preparing the anaerobic activated sludge in step 2 and step 3 is: stir the sludge and water evenly, let it stand for 2-4 hours, remove the impurities floating on the water surface, repeat the above operation three times, drain the water, and place the sludge in an anaerobic environment for 25-30 days to obtain anaerobic activated sludge.

[0008] Preferably, the heat treatment temperature in step 2 is 120-125°C, and the time is 8-10 min; the acid treatment pH is 3.5-4.0, and the time is 20-24 h.

[0009] Preferably, the expansion culture medium for the hydrogen-producing bacteria in step 2 contains 5-8 g glucose, 8-10 g tryptone, 3-5 g yeast extract, and 3-5 g NaCl per liter.

[0010] Preferably, the enrichment method of photosynthetic bacteria in step 3 is: S1. Take 100-110 g of anaerobic activated sludge and enrichment medium, mix them evenly, seal them and isolate them from air, and culture them in an incubator at 30-35 °C and 5000-6000 lux until the liquid culture turns reddish brown, i.e. R: 100-165, G: 20-90, B: 20-70; S2. Take 100-110 ml of photosynthetic bacteria liquid and the enrichment medium, mix them evenly, seal them and isolate them from air, and culture them in an incubator at 30-35°C and 5000-6000 lux until the photosynthetic bacteria density of the liquid culture reaches 90-95%; According to the step of S2, the enrichment medium is transferred for 3-5 times for cultivation until the density of photosynthetic bacteria in the liquid culture reaches 90-95%, and the enrichment of photosynthetic bacteria is completed.

[0011] Preferably, the components of the photosynthetic bacteria enrichment and expansion culture medium in step 3 include yeast extract 1-1.5 g, NH4Cl 1-1.5 g, CH3COONa 4-4.5 g, NaCl 4.5-5 g, NaHCO3 2-2.5 g, MgCl2 0.1-0.2 g, K2HPO4 0.2-0.3 g, and pH 7.0-7.5 per liter.

[0012] Preferably, the kitchen waste pretreatment in step 4 is as follows: pick out impurities in the kitchen waste, let it stand for 5-7 hours, separate the oil layer, grind it into a paste with a grinder with a filter hole of 3 mm, sterilize it at 120-125°C for 15-20 min, and cool it to room temperature 25-28°C.

[0013] Preferably, in step 4, the amount of α-amylase added is 200-250 U / g, the amount of glucoamylase added is 200-250 U / g, and the enzymatic saccharification time is 20-24 h.

[0014] Preferably, in step 4, the enzymatically saccharified kitchen waste is diluted with water to a glucose content of 10-15 g / L.

[0015] Preferably, the components of the photosynthetic hydrogen production medium in step six are: yeast extract 0.1-0.2 g, NH4Cl 0.2-0.3 g, sodium glutamate 3.5-4.0 g, NaCl 4-5 g, MgCl2 0.1-0.2 g, K2HPO4 0.4-0.5 g, pH 7.0-7.5.

[0016] Since the substrate used contains solid particulate inorganic matter and is not liquid, it does not participate in the fermentation process and will be deposited at the bottom or in the pipe. Therefore, in order to prevent pipe blockage and reduce the effective area of ​​the container to hold the fermented material, hydrogen is produced continuously for one month each time, and the enzymatic saccharification kitchen waste tank, dark fermentation tank, light fermentation tank, and microbial electrolysis cell are cleaned of deposited solids. The solid residue is distilled at 600°C in anoxic distillation to produce biochar in order to save energy and reduce emissions.

[0017] Beneficial effects: The present invention uses the continuous culture principle to simultaneously and continuously produce hydrogen efficiently through dark fermentation tanks, light fermentation tanks, and microbial electrolysis cells, which fundamentally changes the batch and periodic fermentation conditions of traditional anaerobic fermentation, and has the advantages of low cost, short fermentation time, complete process, and high yield; The microbial electrolysis cell has a wide range of substrate utilization. With the assistance of power-producing microorganisms, the residual organic matter can be completely oxidized, which can effectively solve the problem of incomplete dark-light coupled anaerobic fermentation. With the assistance of the microbial electrolysis cell, the residual organic matter can be completely oxidized, driving the anaerobic metabolic process while increasing the hydrogen production rate; Enzymatic saccharification treatment promotes the hydrolysis of kitchen waste, degrading macromolecular organic matter into easily usable small molecular organic matter, thus improving the utilization rate of kitchen waste substrate; When the dark fermentation hydrogen production rate begins to decline, the substrate is continuously circulated, and the light fermentation consumes the volatile organic acids produced by the terminal metabolism of the dark fermentation, effectively solving the feedback inhibition of the volatile organic acids on the hydrogen-producing bacteria; The hydrogen-producing bacteria and photosynthetic bacteria used are obtained by enrichment culture from sludge, which saves costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0019] Figure 1 It is the principle diagram of the method of the present invention; Figure 2 The present invention is a diagram of a device for implementing the method. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] In the description of the present invention, it is necessary to understand that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0022] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0023] like Figure 1 As shown, a three-stage coupled continuous enhanced hydrogen production method comprises the following steps: Step 1: Prepare an anaerobic environment: introduce nitrogen N2 into the current preparation environment for 10 minutes to complete the preparation of the anaerobic environment; Step 2: Enrichment and expansion of hydrogen-producing bacteria: Heat treatment was performed on the anaerobic activated sludge. After cooling to room temperature, hydrogen-producing bacteria were screened and enriched by acid treatment. The heat treatment temperature was 121 °C for 8 min. The acid treatment pH was 4.0 for 24 h. The pH value was then adjusted to 7.0 with 0.1 mol / L NaOH solution to obtain a hydrogen-producing bacteria enrichment solution. The expansion culture medium of hydrogen-producing bacteria was added at an inoculation rate of 5%. The components of the expansion culture medium of hydrogen-producing bacteria were 5 g glucose, 10 g tryptone, 5 g yeast extract, and 5 g NaCl per liter. The culture was expanded at 37 °C for 20-30 h to obtain a hydrogen-producing bacteria inoculum.

[0024] Step 3: enrichment and expansion of photosynthetic bacteria: 100 g of anaerobic activated sludge was added to a 1000 mL anaerobic container, 900 mL of enrichment medium was added, the mixture was stirred evenly, light culture was performed, photosynthetic bacteria were screened and enriched, 5% of the inoculum was added to the expansion medium of photosynthetic bacteria, and photosynthetic bacteria were expanded at 30 °C, pH 7.5, and a light intensity of 2500 lux. The enrichment method of photosynthetic bacteria is: S1. Take 100 g of anaerobic activated sludge and 900 mL of enrichment medium, mix them evenly, seal them and isolate them from air, and culture them in an incubator at 30 °C and 40 W incandescent lamp, i.e., 5000-6000 lux, until the liquid culture turns reddish brown, i.e., R: 100-165, G: 20-90, B: 20-70; S2. Take 100 ml of photosynthetic bacteria liquid and 900 ml of enrichment medium, mix them evenly, seal them and isolate them from air, and culture them in an incubator at 30°C and 40 W incandescent lamp, i.e., 5000-6000 lux, until the photosynthetic bacteria in the liquid culture reach 90-95%; According to the step of S2, the enrichment medium is transferred for 3-5 times for cultivation until the density of photosynthetic bacteria in the liquid culture reaches 90-95%, and the enrichment of photosynthetic bacteria is completed.

[0025] The components of the photosynthetic bacteria enrichment and expansion culture medium are yeast extract 1 g, NH4Cl 1 g, CH3COONa4 g, NaCl 5 g, NaHCO32 g, MgCl20.1 g, K2HPO40.2 g, and pH 7.5 per liter.

[0026] The method for preparing the anaerobic activated sludge in step 2 and step 3 is as follows: the sludge and water are mixed evenly, and after standing for 2-4 hours, impurities floating on the water surface are removed, and after repeating the above operation three times, the water is discharged, and the sludge is placed in an oxygen-free environment for 25-30 days to obtain the anaerobic activated sludge.

[0027] Step 4: Enzymatic saccharification of kitchen waste: pick out impurities in the kitchen waste, i.e. bones, fish bones, metals, wood products, and plastics, let stand for 5 hours, separate the oil layer, grind it into a paste with a grinder with a filter hole of 3 mm, sterilize it at 121°C for 15 minutes, cool it to room temperature 25-28°C, then add α-amylase and glucoamylase to the kitchen waste, the amount of α-amylase added is 200 U / g, the amount of glucoamylase added is 200 U / g, the enzymatic saccharification time is 24 hours, adjust the pH to 5.5, the temperature is 50°C, stir for 24 hours, and obtain enzymatic saccharified kitchen waste; adjust the pH of the enzymatic saccharified kitchen waste to 7.0, the glucose content after enzymatic hydrolysis is 216.6 g / L, dilute the enzymatic saccharified kitchen waste with water to a glucose content of 10 g / L, obtain the diluted enzymatic saccharified kitchen waste, and store it in a 10 L tank as a substrate for standby use; Step 5: anaerobic dark fermentation to produce hydrogen: inoculate hydrogen-producing bacteria into a dark fermentation tank at a 10% inoculation rate, introduce 9 L of diluted enzymatically saccharified kitchen waste, and perform anaerobic dark fermentation to produce hydrogen at 37 °C and pH 7.0; Step 6: Anaerobic photofermentation for hydrogen production: Inoculate photosynthetic bacteria at a 5% inoculation rate into a photofermentation tank filled with 9.5 L photosynthetic hydrogen production medium, and perform photofermentation for hydrogen production at 30 °C, pH 7.5, and a light intensity of 2500 lux; The components of photosynthetic hydrogen production medium are: yeast extract 0.1 g, NH4Cl 0.3 g, sodium glutamate 4.0 g, NaCl 5 g, MgCl2 0.1 g, K2HPO4 0.5 g, pH 7.5.

[0028] Step 7, continuous cultivation for hydrogen production: real-time monitoring of dark fermentation hydrogen production rate, when the dark fermentation hydrogen production rate begins to decrease, the enzymatic saccharification kitchen waste in step 3 is flowed into the dark fermentation tank, the dark fermentation liquid in the dark fermentation tank is flowed into the light fermentation tank, and the light fermentation liquid is flowed into the microbial electrolysis cell, the flow rate is 50 mL / h, the microbial electrolysis cell MEC is started and operated until stable, the applied voltage is controlled to be 0.7~0.9 V, and the operating temperature is 4~9 ℃. Dark fermentation, light fermentation, and microbial electrolysis cells continue to produce hydrogen, and hydrogen is produced continuously and efficiently for one month. The hydrogen production operation is stopped and the deposited solids are cleaned. The experiment was repeated three times, and the average hydrogen yield of the experiment was 66.64 mL H2 / g substrate dry weight, and the organic matter content in the remaining substrate was 3%.

[0029] Control experiment 1: using kitchen waste without enzymatic saccharification: The glucose content of the kitchen waste after the removal of impurities and sterilization was directly tested, and the average glucose content was 46.28 g / L; after the operation in step 4, the glucose content of the undiluted enzymatic saccharified kitchen waste was tested, and the average glucose content was 216.6 g / L. The average glucose content after enzymatic hydrolysis was 4.68 times higher than that without enzymatic hydrolysis.

[0030] Control experiment 2: using only dark fermentation and microbial electrolysis cells to continuously produce hydrogen: According to step 2, hydrogen-producing bacteria inoculum was obtained. According to step 4, enzymatic saccharification of kitchen waste was obtained. The hydrogen-producing bacteria were inoculated into the dark fermentation tank at an inoculum of 10%, and 9 L of diluted enzymatic saccharification of kitchen waste was introduced to produce hydrogen by anaerobic dark fermentation at 37 °C; no light fermentation tank was set. When the hydrogen production rate of the dark fermentation tank began to decrease, the enzymatic saccharification of kitchen waste was allowed to flow into the anaerobic dark fermentation tank, and the dark fermentation liquid was directly flowed into the microbial electrolysis cell, and the flow rate was controlled to be 50 mL / h; the MEC was started and operated until stable, and the applied voltage was controlled to be 0.7~0.9 V, and the operating temperature was 4~9 °C. Dark fermentation and microbial electrolysis cell continued to produce hydrogen, and hydrogen production continued for one month, and the hydrogen production operation was stopped, and the deposited solids were cleaned. The experiment was repeated three times, and the average hydrogen yield was 54.46 mL H2 / g substrate dry weight.

[0031] Control experiment 3: continuous hydrogen production using only dark fermentation and light fermentation: According to step 2, hydrogen-producing bacteria inoculum was obtained. According to step 4, enzymatic saccharification of kitchen waste was obtained. The hydrogen-producing bacteria were inoculated into the dark fermentation tank at an inoculation rate of 10%, and 9 L of diluted enzymatic saccharification of kitchen waste was introduced to produce hydrogen by anaerobic dark fermentation at 37 °C; the photosynthetic bacteria were inoculated into the photo-fermentation tank containing 9.5 L of photosynthetic hydrogen production medium at an inoculation rate of 5%, and photo-fermentation was carried out to produce hydrogen at 30 °C and a light intensity of 2500 lux. No microbial electrolysis cell was set. When the hydrogen production rate of the dark fermentation tank began to decrease, the enzymatic saccharification of kitchen waste was allowed to flow into the anaerobic dark fermentation tank, the dark fermentation liquid flowed into the photo-fermentation tank, and the photo-fermentation liquid flowed into the photo-fermentation liquid storage tank, and the flow rate was controlled to be 50 mL / h. Dark fermentation and photo-fermentation continued to produce hydrogen. After one month of continuous hydrogen production, the hydrogen production operation was stopped, all valves were closed, and the deposited solids were cleaned. The experiment was repeated three times, and the average hydrogen yield was 51.09 mL H2 / g substrate dry weight. The organic matter content in the photofermentation liquid storage tank was 20%.

[0032] Control experiment 4: Control the flow rate during continuous culture to 100 mL / h: According to step 2, hydrogen-producing bacteria inoculum was obtained. According to step 4, enzymatic saccharification of kitchen waste was obtained. The hydrogen-producing bacteria were inoculated into the dark fermentation tank at an inoculum of 10%, and 9 L of diluted enzymatic saccharification of kitchen waste was introduced to produce hydrogen by anaerobic dark fermentation at 37 °C; the photosynthetic bacteria were inoculated into the photo-fermentation tank containing 9.5 L of photosynthetic hydrogen production medium at an inoculum of 5%, and photo-fermentation of hydrogen was carried out at 30 °C and a light intensity of 2500 lux. When the hydrogen production rate of the dark fermentation tank began to decrease, the enzymatic saccharification of kitchen waste was allowed to flow into the anaerobic dark fermentation tank, the dark fermentation liquid flowed into the photo-fermentation tank, and the photo-fermentation liquid flowed into the microbial electrolysis cell, and the flow rate was controlled to be 100 mL / h; the MEC was started and operated until it was stable, and the applied voltage was controlled to be 0.7~0.9 V and the operating temperature was 4~9 °C. The dark fermentation, photo-fermentation, and microbial electrolysis cell continued to produce hydrogen, and hydrogen was produced continuously and efficiently for one month. The hydrogen production operation was stopped, all valves were closed, and the deposited solids were cleaned. The experiment was repeated three times, and the average hydrogen yield was 52.28 mL H2 / g substrate dry weight.

[0033] Control experiment 5: Traditional batch periodic fermentation, that is, dark fermentation to produce hydrogen until no hydrogen is produced, followed by light fermentation to produce hydrogen, and then light fermentation to produce hydrogen until no hydrogen is produced, followed by microbial electrolysis to produce hydrogen until no hydrogen is produced in the microbial electrolysis cell: According to step 2, hydrogen-producing bacteria inoculation liquid is obtained. According to step 4, enzymatic saccharification of kitchen waste is obtained. Inoculate hydrogen-producing bacteria into the dark fermentation tank at an inoculation rate of 10%, and pass 9 L of diluted enzymatic saccharification of kitchen waste to produce hydrogen by anaerobic dark fermentation at 37 °C. After the dark fermentation is completed, solid-liquid separation is performed, and the dark fermentation liquid is centrifuged, sterilized, i.e., sterilized by high-pressure steam at 121 °C for 30 minutes, and cooled to prepare a light fermentation substrate culture medium. Inoculate photosynthetic bacteria at an inoculation rate of 5%, and perform light fermentation in the light fermentation tank, and control the light fermentation reaction to proceed at a temperature of 30 °C and 2500 lux. After the light fermentation is completed, the light fermentation liquid is centrifuged, sterilized, i.e., sterilized by high-pressure steam at 121 °C for 30 minutes, and cooled. After the MEC runs stably, pass it into the microbial electrolysis cell, apply a voltage of 0.7~0.9 V, and operate at a temperature of 4~9 °C until the microbial electrolysis cell no longer produces hydrogen, and the hydrogen production process ends. The experiment was repeated three times, and the average hydrogen yield was 55.05 mL H2 / g substrate dry weight.

[0034] By comparing the continuous hydrogen production in this embodiment with the results of control tests one to five, it can be seen that: under the same other conditions, the average hydrogen production rate when there is a microbial electrolysis cell is 66.64 mL H2 / g substrate dry weight, and the organic content in the remaining substrate is 3%. The average hydrogen production rate when there is no microbial electrolysis cell is 51.09 mL H2 / g substrate dry weight, and the organic content in the remaining substrate is 20%. The average yield of the microbial electrolysis cell is 30% higher than that of the microbial electrolysis cell, and the substrate utilization rate is high. It can be seen that with the assistance of MEC, the complete oxidation of residual organic matter can be achieved, driving the anaerobic metabolic process while increasing the hydrogen production rate.

[0035] When other conditions were the same, the average hydrogen production rate with the light fermentation device was 66.64 mL H2 / g substrate dry weight, and the average hydrogen production rate without the light fermentation device was 54.46 mL H2 / g substrate dry weight. The average hydrogen production rate with the light fermentation device was 22% higher than that without the light fermentation device. The light fermentation device can improve the overall hydrogen production rate.

[0036] Under the same other conditions, the average glucose content of the enzymatic saccharification treatment was 4.68 times higher than that of the non-enzymatic treatment. It can be seen that the enzymatic saccharification treatment can provide sufficient and easily usable small molecule organic matter - glucose for subsequent fermentation and hydrogen production.

[0037] like Figure 2 As shown, the enzymatic saccharification kitchen waste storage tank 9 is used to store the enzymatically hydrolyzed kitchen waste and provide fermentation substrates to the dark fermentation tank, the light fermentation tank, and the microbial electrolysis cell after the first valve 1 is opened; Anaerobic dark fermentation tank 10: The hydrogen-producing bacteria in the tank will ferment and decompose the organic matter in the kitchen waste, such as glucose and starch, and convert the chemical energy therein into hydrogen H2.

[0038] Anaerobic photofermentation tank 11: Dark fermentation will produce a large amount of organic volatile acids, which contain a large amount of hydrogen, but dark fermentation itself cannot ferment and decompose them, and these volatile acids will inhibit the dark fermentation process. The photosynthetic bacteria in the photofermentation tank can use organic volatile acids as substrates to further produce hydrogen, which can increase the hydrogen production efficiency and alleviate the inhibitory effect of volatile acids on the dark fermentation process.

[0039] Microbial electrolysis cell 12: It is mainly used to ensure the complete decomposition and hydrogen production of residual substrates from light fermentation and dark fermentation, and to improve substrate utilization.

[0040] Principle: The first place that organic matter reaches is the anode of the microbial electrolysis cell, i.e., the carbon felt. It is rapidly oxidized and degraded, and produces electrons, protons, and CO2. The electrons are transferred to the anode directly or indirectly, and then the electrons reach the cathode through the external circuit. At the same time, the protons are transferred to the cathode through the proton exchange membrane inside the reactor. Under anaerobic conditions, the electrons and protons combine at the cathode to produce hydrogen.

[0041] The first liquid inlet pipe 4 and the second liquid inlet pipe 5 are responsible for adding inoculation liquid, the first gas flowmeter 6, the second gas flowmeter 7 and the third gas flowmeter 8 are responsible for monitoring the hydrogen production rate of each device and the overall hydrogen production rate. When the hydrogen production rate of the dark fermentation tank begins to decrease, the first valve 1, the second valve 2 and the third valve 3 are opened at the same time, and the pump 14 is started to allow the enzymatically saccharified kitchen waste to flow into the anaerobic dark fermentation tank. The flow rate is monitored by the liquid flowmeter 13, and the dark fermentation liquid flows into the light fermentation tank, and the light fermentation liquid flows into the microbial electrolysis cell for hydrogen production, and the produced hydrogen is stored in the hydrogen storage tank.

[0042] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0043] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A three-stage coupled continuous enhanced hydrogen production method, characterized in that: The following steps are involved: Step 1: Prepare an anaerobic environment: introduce nitrogen N2 into the current preparation environment for 10-15 minutes to complete the preparation of the anaerobic environment; Step 2: Enrichment and expansion of hydrogen-producing bacteria: heat treatment and acid treatment are performed on the anaerobic activated sludge to screen and enrich hydrogen-producing bacteria, and expansion is performed at 35-37°C and pH 3.5-7.0; Step 3: enrichment and expansion of photosynthetic bacteria: 100-110 g of anaerobic activated sludge was added to a 1000 mL anaerobic container, filled with enrichment medium, stirred evenly, and cultured under light to screen and enrich photosynthetic bacteria. The photosynthetic bacteria were expanded at 30-35 °C, pH 7-7.5, and light intensity of 2500-2600 lux. Step 4: Enzymatic saccharification of kitchen waste: pre-treat the kitchen waste, then add α-amylase and glucoamylase to the kitchen waste, adjust the pH to 5.5-6, the temperature to 50-55°C, stir for 20-24 hours, and obtain enzymatic saccharified kitchen waste; adjust the pH of the enzymatic saccharified kitchen waste to 7.0-7.5, add water to dilute the enzymatic saccharified kitchen waste, obtain diluted enzymatic saccharified kitchen waste, and store it as a substrate for later use; Step 5: anaerobic dark fermentation hydrogen production: inoculate hydrogen-producing bacteria into a dark fermentation tank at an inoculation rate of 10-15%, introduce 85%-90% diluted enzymatic saccharification kitchen waste, and perform anaerobic dark fermentation hydrogen production at 35-37°C and pH 7.0-7.5; Step 6: Anaerobic photofermentation hydrogen production: Inoculate photosynthetic bacteria at an inoculation rate of 5%-10% into a photofermentation tank filled with 90%-95% photosynthetic hydrogen production medium, and perform photofermentation hydrogen production at 30-35°C, pH 7.0-7.5, and light intensity 2500-3000 lux; Step 7. Continuous cultivation for hydrogen production: Monitor the dark fermentation hydrogen production rate in real time. When the dark fermentation hydrogen production rate begins to decrease, flow the enzymatically saccharified kitchen waste in step 3 into the dark fermentation tank, flow the dark fermentation liquid in the dark fermentation tank into the light fermentation tank, and flow the light fermentation liquid into the microbial electrolysis cell at a flow rate of 50-100 mL / h. At the same time, hydrogen is continuously produced through dark fermentation, light fermentation, and microbial electrolysis cell.

2. The three-stage coupled continuous enhanced hydrogen production method according to claim 1, characterized in that: The method for preparing the anaerobic activated sludge in step 2 and step 3 is as follows: the sludge and water are mixed evenly, and after standing for 2-4 hours, impurities floating on the water surface are removed, and after repeating the above operation three times, the water is discharged, and the sludge is placed in an oxygen-free environment for 25-30 days to obtain the anaerobic activated sludge.

3. The three-stage coupled continuous enhanced hydrogen production method according to claim 1, characterized in that: The heat treatment temperature in step 2 is 120-125°C, and the time is 8-10 min; the acid treatment pH is 3.5-4.0, and the time is 20-24 h.

4. The three-stage coupled continuous enhanced hydrogen production method according to claim 1, characterized in that: The components of the culture medium for the hydrogen-producing bacteria in step 2 include 5-8 g of glucose, 8-10 g of tryptone, 3-5 g of yeast extract, and 3-5 g of NaCl per liter.

5. The three-stage coupled continuous enhanced hydrogen production method according to claim 1, characterized in that: The enrichment method of photosynthetic bacteria in step 3 is: S1. Take 100-110g of anaerobic activated sludge and enrichment medium, mix them evenly, seal them and isolate them from air, and culture them in an incubator at 30-35℃ and 5000-6000 lux until the liquid culture turns reddish brown, i.e. R: 100-165, G: 20-90, B: 20-70; S2. Take 100-110 ml of photosynthetic bacteria liquid and the enrichment medium, mix them evenly, seal them and isolate them from air, and culture them in an incubator at 30-35°C and 5000-6000 lux until the photosynthetic bacteria density of the liquid culture reaches 90-95%; According to the step of S2, the enrichment medium is transferred for 3-5 times for cultivation until the density of photosynthetic bacteria in the liquid culture reaches 90-95%, and the enrichment of photosynthetic bacteria is completed.

6. The three-stage coupled continuous enhanced hydrogen production method according to claim 1, characterized in that: The components of the photosynthetic bacteria enrichment and expansion culture medium in step 3 include yeast extract 1-1.5 g, NH4Cl 1-1.5 g, CH3COONa 4-4.5 g, NaCl 4.5-5 g, NaHCO3 2-2.5 g, MgCl2 0.1-0.2 g, K2HPO4 0.2-0.3 g, and pH 7.0-7.5 per liter.

7. The three-stage coupled continuous enhanced hydrogen production method according to claim 1, characterized in that: The kitchen waste pretreatment in step 4 is as follows: picking out impurities in the kitchen waste, standing for 5-7 hours, separating the oil layer, crushing it into a paste using a grinder with a filter hole of 3 mm, sterilizing it at 120-125°C for 15-20 minutes, and cooling it to room temperature 25-28°C.

8. The three-stage coupled continuous enhanced hydrogen production method according to claim 1, characterized in that: In the step 4, the amount of α-amylase added is 200-250 U / g, the amount of glucoamylase added is 200-250 U / g, and the enzymatic saccharification time is 20-24 h.

9. The three-stage coupled continuous enhanced hydrogen production method according to claim 1, characterized in that: In the step 4, the enzymatically saccharified kitchen waste is diluted with water to a glucose content of 10-15 g / L.

10. The three-stage coupled continuous enhanced hydrogen production method according to claim 1, characterized in that: The components of the photosynthetic hydrogen production medium in step 6 are: yeast extract 0.1-0.2 g, NH4Cl 0.2-0.3 g, sodium glutamate 3.5-4.0 g, NaCl 4-5 g, MgCl2 0.1-0.2 g, K2HPO4 0.4-0.5 g, pH 7.0-7.5.

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