Biogas purification device and method based on electrochemical iron production

Abstract

The invention belongs to the technical field of biogas purification, and particularly relates to a biogas purification device and method based on electrochemical iron production. According to the method, an iron electrode is adopted as an anode, a biogas purification device based on an electrochemical system is constructed, a pH value regulation and control system is arranged, the pH value in an electrolytic tank of the biogas purification device is regulated and controlled, an electrochemical method is utilized, Fe < 2 + > is generated on the iron anode in situ, H2 and OH <-> are synchronously generated on a cathode in situ, CO2 and H2S in the biogas are synchronously removed, and the biogas is purified. The purification of the marsh gas is realized. The method disclosed by the invention is simple, convenient, efficient, short in process, less in equipment, low in investment and operation cost and convenient to operate and maintain, CO2 and H2S in the biogas can be efficiently removed at the same time in one step, the aim of purifying the biogas is fulfilled, and the method has a good application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of biogas purification, and in particular relates to a biogas purification device and method based on electrochemical iron production. Background Art

[0002] Biogas is an important, efficient and renewable energy source, and its green, low-carbon and high-value utilization is an important direction for achieving carbon neutrality and green and low-carbon transformation.

[0003] However, in addition to methane (CH4), biogas usually contains a large amount of impurities such as carbon dioxide (CO2), hydrogen sulfide (H2S), etc. The CO2 content in biogas is generally very high (20-50%), which significantly reduces the calorific value of biogas and makes it difficult to compress it, while the H2S in biogas causes odor and safety issues as well as equipment corrosion risks.

[0004] At present, most of the biogas in my country has not been utilized or utilized in a green, low-carbon and high-value manner. Large enterprises usually use on-site combustion for heating or power generation, while small and medium-sized enterprises generally use direct air combustion of biogas. Because the unpurified biogas has poor combustion effect and low utilization rate, it leads to incomplete combustion. On the one hand, a large amount of sulfide and carbon-containing compound pollution is generated, which poses a safety risk. On the other hand, the energy in the biogas is not utilized or utilized to the maximum extent, resulting in huge waste and carbon emissions, which cannot meet the requirements of green and low-carbon.

[0005] The high content of CO2 and H2S in biogas has become the main obstacle to the green, low-carbon and high-value utilization of biogas. After the biogas is purified to remove CO2 and H2S, its combustion characteristics are greatly improved and it can be directly used as vehicle fuel or natural gas to achieve high-value utilization.

[0006] At present, the biogas purification processes that have been researched and developed at home and abroad all have desulfurization (removal of H2S) and decarbonization (removal of CO2) as their main goals. They generally have problems such as high operating costs, serious secondary pollution, and large carbon emissions. It is urgent to develop new green, low-carbon and efficient biogas purification technologies.

[0007] The prior art discloses that ferrous ions can be used to desulfurize biogas, such as Chinese patent application CN116392962 A. However, the existing technology of removing hydrogen sulfide using ferrous ions has the defects of significantly reducing the desulfurization effect due to the decrease in system pH caused by the addition of ferrous ions, or greatly increasing the amount of ferrous ions and further reducing the pH caused by them; on the other hand, the prior art does not have a method for decarbonizing biogas using ferrous ions, and the decarbonization of biogas using ferrous ions is also highly dependent on pH and is significantly negatively affected by lower pH. Summary of the invention

[0008] In order to solve the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a biogas purification device based on electrochemical iron production. The device can simultaneously and efficiently remove carbon dioxide and hydrogen sulfide in biogas to achieve biogas purification.

[0009] The present invention also provides a biogas purification method based on the above device. The present invention constructs a biogas purification device based on an electrochemical system, sets a pH value control system, controls the pH value inside the biogas purification device, and generates Fe in situ at the iron anode using an electrochemical method. 2+ , and H2 and OH are simultaneously generated in situ at the cathode - , CO2 and H2S in biogas are removed simultaneously and efficiently, achieving biogas purification. This method can be applied to purify biogas produced by anaerobic treatment of wastewater containing organic matter, biogas produced by anaerobic digestion of solid waste such as sludge and biomass containing organic matter, and biogas containing CO2 and H2S from other sources.

[0010] The purpose of the present invention is achieved through the following technical solutions: The present invention provides a biogas purification device based on electrochemical iron production, comprising an electrolytic cell, an anode, a cathode, a power supply, an electrolyte solution, a biogas diffuser, an agitator and a pH value control system; the electrolyte solution, the anode and the cathode are arranged in the electrolytic cell, and the anode, the cathode, the power supply, the electrolytic cell and the electrolyte solution constitute an electrochemical system, and the two ends of the power supply are respectively connected to the anode and the cathode through a power line to provide voltage and current to the electrochemical system; the anode is an iron electrode; The pH value control system includes a pH detector, an alkali solution supply system, an acid solution supply system and a control system. The alkali solution supply system includes an alkali solution preparation device and an alkali solution pump. The acid solution supply system includes an acid solution preparation device and an acid solution pump. The alkali solution preparation device is connected to the electrolytic cell through the alkali solution pump. The acid solution preparation device is connected to the electrolytic cell through the acid solution pump. The pH detector is connected to the electrolytic cell. The biogas diffuser and the stirrer are arranged at the bottom of the electrolytic cell, and the biogas diffuser is connected to the biogas inlet pipeline; the lower part of the electrolytic cell is also provided with an iron precipitation product outlet, and the upper part of the electrolytic cell is provided with a biogas outlet.

[0011] As another embodiment of the present invention, the biogas purification device based on electrochemical iron production comprises an electrolytic cell, an anode, a cathode, a power supply, an electrolyte solution, a stirrer, a water distributor and a pH value control system; the anode, the cathode and the electrolyte solution are arranged in the electrolytic cell, and the electrolytic cell, the anode, the cathode, the power supply and the electrolyte solution constitute an electrochemical system, and the two ends of the power supply are respectively connected to the anode and the cathode through a power line to provide voltage and current to the electrochemical system; the anode is an iron electrode; The electrolytic cell is also provided with an electrolyte solution circulation pipeline, on which a circulation pump, a first pipeline mixer, a second pipeline mixer and an ejector are sequentially arranged, the ejector is connected to the water distributor, and the water distributor and the agitator are arranged at the bottom of the electrolytic cell; the ejector is provided with an inlet for biogas to be purified; The pH value control system includes a pH detector, an alkali solution supply system, an acid solution supply system and a control system. The alkali solution supply system includes an alkali solution preparation device and an alkali solution pump. The acid solution supply system includes an acid solution preparation device and an acid solution pump. The acid solution preparation device is connected to the first pipeline mixer through the acid solution pump. The alkali solution preparation device is connected to the second pipeline mixer through the alkali solution pump. The pH detector is connected to the electrolytic cell. The lower part of the electrolytic cell is provided with an inlet for mixed gas-liquid flow of electrolyte solution and biogas and an outlet for iron precipitation products, and the upper part of the electrolytic cell is provided with an electrolyte solution outlet and a biogas outlet.

[0012] Preferably, in the above device, the iron electrode includes but is not limited to iron plate, carbon steel, stainless steel, scrap iron or iron-containing composite electrode.

[0013] Preferably, in the above device, the cathode is a metal electrode, a carbon-based material electrode or a composite electrode; the metal electrode includes an iron electrode or a non-ferrous metal electrode.

[0014] Based on the device described in the present invention, the present invention also provides a biogas purification method based on electrochemical iron production, comprising the following steps: (1) An electrolyte solution is set in the electrolytic cell of the biogas purification device. According to the flow rate of the biogas to be purified and the content of CO2 and H2S in the biogas, the voltage / current of the electrochemical system is adjusted to generate Fe2+ in the electrolytic cell through the anode reaction. 2+ , cathode reaction generates H2 and OH - and is uniformly mixed with the electrolyte solution by the action of a stirrer; (2) The pH value control system detects the pH value of the electrolyte solution in the electrolytic cell through a pH detector, and controls the alkali solution pump or the acid solution pump to supply a certain amount of alkali solution or acid solution to the electrolyte solution, so that the pH value of the electrolyte solution is maintained at 8.5±0.2; (3) The biogas to be purified is transported into the electrolytic cell of the biogas purification device through the biogas diffuser, and reacts with the electrochemical reaction product Fe under the action of the agitator. 2+ , and the electrolyte solution provided in the electrolytic cell are mixed uniformly; (4) CO2, H2S in the biogas to be purified and Fe in the electrolyte solution 2+The precipitated product generated by the reaction is removed, and the purified biogas is discharged from the electrolytic cell after purification. The iron precipitated product generated during the biogas purification process is regularly discharged from the electrolytic cell, and the H2 generated by the electrochemical reaction at the cathode is also discharged together with the purified biogas, completing the biogas purification process.

[0015] In the above method, under the action of the current of the electrochemical system, the anode generates Fe 2 + At the same time, the cathode generates H2 and OH through electrochemical reaction. - The electrochemical reaction generates a product Fe 2+ , H2 and OH - The biogas to be purified is transported into the electrolyte solution through a biogas diffuser, and the product of the electrochemical reaction at the anode and cathode of the electrochemical system is mixed with the biogas and the electrolyte solution by the agitator to perform a biogas purification process based on electrochemical iron production. Then, the purified biogas is discharged from the electrolytic cell, and the H2 generated by the electrochemical reaction at the cathode is also discharged together with the purified biogas, completing the biogas purification process.

[0016] As another embodiment of the present invention, the biogas purification method based on electrochemical iron production comprises the following steps: (1) An electrolyte solution is set in the electrolytic cell of the biogas purification device. According to the flow rate of the biogas to be purified and the content of CO2 and H2S in the biogas, the voltage / current of the electrochemical system is adjusted to generate Fe2+ in the electrolytic cell through the anode reaction. 2+ , cathode reaction generates H2 and OH - and is mixed evenly with the electrolyte solution by the action of the stirrer; mixed with the electrochemical reaction product Fe 2 + The electrolyte solution is transported by a circulation pump and circulated in the electrolytic cell; (2) The pH value control system detects the pH value of the electrolyte solution in the electrolytic cell through a pH detector, and controls the alkali solution pump or acid solution pump to supply a certain amount of alkali solution or acid solution to the circulating electrolyte solution, which enters the electrolytic cell through a water distributor, so that the pH value of the electrolyte solution is maintained at 8.5±0.2; (3) The biogas to be purified is mixed with the circulating electrolyte solution through the ejector, and then enters the electrolytic cell through the water distributor, where it reacts with the electrochemical reaction product Fe 2+ , the electrolyte solution is mixed evenly; (4) CO2, H2S in the biogas to be purified and Fe in the electrolyte solution 2+The precipitated product generated by the reaction is removed, and the purified biogas is discharged from the electrolytic cell after purification. The iron precipitated product generated during the biogas purification process is regularly discharged from the electrolytic cell, and the H2 generated by the electrochemical reaction at the cathode is also discharged together with the purified biogas, completing the biogas purification process.

[0017] Preferably, the biogas to be treated includes biogas produced by anaerobic treatment of wastewater containing organic matter, biogas produced by anaerobic digestion of sludge and solid waste containing organic matter, and biogas containing CO2 and H2S from other sources.

[0018] Compared with the prior art, the principles, advantages and beneficial effects of the present invention are described as follows: When the biogas to be purified enters the electrolytic cell through the diffuser or ejector and water distributor, the biogas to be purified is evenly mixed with the electrolyte solution set in the electrolytic cell under the action of the agitator; at the same time, the Fe generated by the iron anode of the electrochemical system 2+ , and H2 and OH generated at the cathode - The solution is mixed into an electrolyte solution containing the biogas to be purified.

[0019] Therefore, CO2 and H2S in biogas react with the electrochemical product Fe 2+ The reactants are removed, thus achieving the purpose of biogas purification.

[0020] First, the Fe generated by the iron anode 2+ It reacts with CO2 in biogas to generate FeCO3 precipitate, removes CO2 in biogas, and forms a CO2 sink (Formula ①, ②), achieving efficient removal of CO2 in biogas.

[0021] ① ② At the same time, the Fe generated by the iron anode of the electrochemical system 2+ It reacts with H2S in biogas to generate FeS precipitate, and simultaneously achieves efficient removal of H2S in biogas (Formula ③).

[0022] ③ In the case of adding ferrous ions for wet desulfurization of biogas, the addition of ferrous ions to the water medium actually has an important impact on the pH value of the system. This is because ferrous salts are strongly acidic compounds, and the commonly used ferrous salt dosage will reduce the pH value of the wastewater. And because the precipitation reaction of ferrous ions with H2S is highly dependent on pH, it is significantly negatively affected by lower pH values, especially under conditions where the pH is neutral or close to neutral levels (i.e. 6-8). For example, a decrease from pH 7.0 to 6.5 results in an increase of more than 200% in the iron salt dosage requirement to achieve the same sulfide concentration. In addition, the decrease in pH also shifts the reaction equilibrium from HS - Transfer to volatile H2S, resulting in the release of more H2S, causing problems such as reduced H2S removal effect, reduced biogas methane purity, equipment corrosion and safety risks. In addition, the decrease in pH also leads to a significant decrease in biogas decarbonization effect, reduced biogas methane purity and a significant increase in carbon emissions.

[0023] The present invention utilizes OH generated at the cathode of the electrochemical system - , which can effectively maintain the alkaline environment of the electrolyte solution. By regulating the current value of the electrochemical system, the pH can be maintained between 7.5-9.0. In an alkaline environment of pH 7.5-9.0, H2S is mainly in the form of HS - and S 2- The ionic state exists in the electrolyte solution, which is conducive to the reaction of H2S with Fe 2+ FeS precipitation is formed (Formula ③), which effectively improves the removal effect of H2S in biogas. Similarly, an alkaline environment with a pH of 7.5-9.0 is also conducive to the generation of Fe at the iron anode. 2+ It reacts with CO2 in biogas to generate FeCO3 precipitate (Formula ②), thus improving the removal efficiency of CO2 in biogas.

[0024] At the same time, the present invention sets a pH value control system to fine-tune the pH value inside the biogas purification device, so that the pH value inside the biogas purification device is stably maintained within the range of 8.5±0.2, thereby achieving the purpose of synchronously, stably and efficiently removing CO2 and H2S in biogas.

[0025] The method of the present invention is simple and efficient, has a short process, requires less equipment, has low investment and operating costs, is easy to operate and maintain, and can simultaneously and efficiently remove CO2 and H2S from biogas in one step, achieving the purpose of biogas purification, and has good application prospects.

[0026] Furthermore, the iron content in the electrochemical iron precipitation product obtained by the present invention can reach about 57%, and it has the potential to be used as an iron ore raw material; at the same time, the electrochemical iron precipitation product obtained by the present invention can be applied to wastewater and sludge treatment processes, effectively improving the dehydration and precipitation performance of the sludge, and has significant resource recovery and utilization value. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of a device according to Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of a device according to Embodiment 2 of the present invention; Among them, 1-electrolytic cell, 2-anode, 3-cathode, 4-power supply, 5-electrolyte solution, 6-agitator, 7-biogas diffuser, 8-acid preparation device, 9-acid pump, 10-alkali preparation device, 11-alkali pump, 12-pH detector, 13-circulation pump, 14-first pipeline mixer, 15-second pipeline mixer, 16-ejector, 17-water distributor. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with the examples and drawings, but the embodiments of the present invention are not limited thereto. The raw materials involved in the present invention can be purchased directly from the market. For process parameters not particularly noted, conventional techniques can be used.

[0029] Example 1 like Figure 1 As shown, this embodiment provides a biogas purification device based on electrochemical iron production, the biogas purification device includes an electrolytic cell 1, an anode 2, a cathode 3, a power supply 4, an electrolyte solution 5, a biogas diffuser 7, an agitator 6 and a pH value control system; the electrolyte solution 5, the anode 2, the cathode 3 and the agitator 6 are arranged in the electrolytic cell 1, and the anode 2, the cathode 3, the power supply 4, the electrolytic cell 1 and the electrolyte solution 5 constitute an electrochemical system, and the two ends of the power supply 4 are respectively connected to the anode 2 and the cathode 3 through a power line to provide voltage and current to the electrochemical system; the anode 2 and the cathode 3 are both made of low-carbon steel plates as electrode materials; the pH value control system includes A pH detector 12, an alkali solution supply system, an acid solution supply system and a control system, wherein the alkali solution supply system includes an alkali solution preparation device 10 and an alkali solution pump 11, and the acid solution supply system includes an acid solution preparation device 8 and an acid solution pump 9; the alkali solution preparation device 10 is connected to the electrolytic cell 1 through the alkali solution pump 11; the acid solution preparation device 8 is connected to the electrolytic cell 1 through the acid solution pump 9; the pH detector 12 is connected to the electrolytic cell 1; the biogas diffuser 7 and the agitator 6 are arranged at the bottom of the electrolytic cell 1, and the biogas diffuser 7 is connected to the biogas inlet pipeline; the lower part of the electrolytic cell is also provided with an iron precipitation product outlet, and the upper part of the electrolytic cell is provided with a biogas outlet.

[0030] The pH value control system of the present invention detects the pH value of the electrolyte solution inside the electrolytic cell in real time through the pH detector installed on the electrolytic cell, and controls the alkali pump or the acid pump through the control system to maintain the pH value inside the electrolytic cell within the range of 8.5±0.2. Specifically, when the pH value detected by the pH detector is greater than 8.7, the alkali pump is controlled by the control system to reduce the amount of alkali added, or the acid pump is controlled by the control system to increase the amount of acid added, so that the pH value inside the electrolytic cell decreases and is maintained within the range of 8.5±0.2; conversely, when the pH value detected by the pH detector is less than 8.3, the alkali pump is controlled by the control system to increase the amount of alkali added, or the acid pump is controlled by the control system to reduce the amount of acid added, so that the pH value inside the electrolytic cell increases and is maintained within the range of 8.5±0.2.

[0031] In this embodiment, the above device is applied to purify biogas produced in the anaerobic treatment process of wastewater. A 2 g / L NaCl solution is used as the electrolyte solution. Under the condition that the current of the electrochemical system is adjusted to 120 mA, the electrolyte solution of the electrolytic cell is Fe 2+ The dosage is 300 mg / L, the pH of the system is adjusted to 8.5±0.2, and the biogas to be purified is transported into the electrolytic cell at a flow rate of 0.5 L / (L•h) at room temperature. The specific steps include: (1) An electrolyte solution is set in the electrolytic cell of the biogas purification device. According to the flow rate of the biogas to be purified and the content of CO2 and H2S in the biogas, a certain amount of Fe is obtained in the electrolyte solution of the electrolytic cell by adjusting the voltage / current of the electrochemical system. 2+ ; (2) The pH value control system detects the pH value of the electrolyte solution in the electrolytic cell through a pH detector and controls the alkali solution pump or the acid solution pump to supply a certain amount of alkali solution or acid solution to the electrolyte solution, so that the pH value of the electrolyte solution is maintained within the range of 8.5±0.2; (3) The biogas to be purified is transported into the electrolytic cell of the biogas purification device and is evenly mixed with the electrolyte solution provided in the electrolytic cell; (4) CO2, H2S in the biogas to be purified and Fe in the electrolyte solution 2+ The precipitated product generated by the reaction is removed, and the purified biogas is discharged from the electrolytic cell after purification. The iron precipitated product generated during the biogas purification process is regularly discharged from the electrolytic cell, and the H2 generated by the electrochemical reaction at the cathode is also discharged together with the purified biogas, completing the biogas purification process.

[0032] In the above method, under the action of the current of the electrochemical system, the anode 2 generates Fe 2+ At the same time, the cathode 3 generates H2 and OH through electrochemical reaction. -Therefore, the products of these electrochemical reactions, Fe 2+ , H2 and OH - The biogas to be purified is transported into the electrolytic cell 1 through the biogas diffuser 7; the stirrer 6 provides stirring to mix the electrochemical reaction product with the biogas to be purified and the electrolyte solution 5. 2+ The reactants are removed, thus achieving the purpose of biogas purification.

[0033] In this embodiment, the CO2 content in the biogas after purification treatment decreased from about 27% (volume ratio) before purification to less than 5.0% (volume ratio) after purification, and the H2S concentration decreased from 17500 mg / m 3 After purification, it dropped to about 80 mg / m 3 the following.

[0034] In addition, the iron content in the electrochemical iron precipitation product obtained by the present invention can reach about 57%, which has the potential to be used as an iron ore raw material; at the same time, the electrochemical iron precipitation product obtained by the present invention can be applied to wastewater and sludge treatment processes, effectively improving the dehydration and precipitation performance of sludge, and the sludge volume index (SVI) is reduced from 131 to 92 ml / g, and the specific filtration resistance (SRF) is reduced from 2.73×10 13 Down to 1.85×10 13 This indicates that the electrochemical iron precipitation product obtained by the present invention has significant resource recovery and utilization value.

[0035] Example 2 like Figure 2 As shown, this embodiment provides a biogas purification device based on electrochemical iron production, including an electrolytic cell 1, an anode 2, a cathode 3, a power supply 4, an electrolyte solution 5, a stirrer 6, a water distributor 17 and a pH value control system; the anode 2, the cathode 3, the electrolyte solution 5 and the stirrer 6 are arranged in the electrolytic cell 1, and the electrolytic cell 1, the anode 2, the cathode 3, the power supply 4 and the electrolyte solution 5 constitute an electrochemical system, and the two ends of the power supply 4 are respectively connected to the anode 2 and the cathode 3 through a power line to provide voltage and current to the electrochemical system; the anode 2 adopts a low-carbon steel plate as an electrode material, and the cathode 3 adopts a carbon-based material electrode; The electrolytic cell 1 is also provided with an electrolyte solution circulation pipeline, on which a circulation pump 13, a first pipeline mixer 14, a second pipeline mixer 15 and an ejector 16 are sequentially arranged, the ejector 16 is connected to the water distributor 17, and the water distributor 17 and the agitator 6 are arranged at the bottom of the electrolytic cell 1; the ejector is provided with an inlet for biogas to be purified; The pH value control system includes a pH detector 12, an alkali solution supply system, an acid solution supply system and a control system. The alkali solution supply system includes an alkali solution preparation device 10 and an alkali solution pump 11, and the acid solution supply system includes an acid solution preparation device 8 and an acid solution pump 9; the acid solution preparation device 8 is connected to the first pipeline mixer 14 through the acid solution pump 9; the alkali solution preparation device 10 is connected to the second pipeline mixer 15 through the alkali solution pump 11; the pH detector 12 is connected to the electrolytic cell 1; The lower part of the electrolytic cell is provided with an inlet for mixed gas-liquid flow of electrolyte solution and biogas and an outlet for iron precipitation products, and the upper part of the electrolytic cell is provided with an electrolyte solution outlet and a biogas outlet.

[0036] In this embodiment, the above device is applied to purify biogas produced in the anaerobic digestion process of sludge. When the current of the electrochemical system is adjusted to 80 mA, the electrolyte solution of the electrolytic cell has Fe 2+ The dosage is 200 mg / L, the pH of the system is adjusted to 8.5±0.2, and the biogas to be purified is transported into the electrolytic cell at a flow rate of 1.0 L / (L•h) at room temperature. The specific steps are as follows: (1) An electrolyte solution is set in the electrolytic cell of the biogas purification device. According to the flow rate of the biogas to be purified and the content of CO2 and H2S in the biogas, a certain amount of Fe is obtained in the electrolyte solution of the electrolytic cell by adjusting the voltage / current of the electrochemical system. 2+ ; mixed with electrochemical reaction product Fe 2+ The electrolyte solution is transported by a circulation pump and circulated in the electrolytic cell; (2) The pH value control system detects the pH value of the electrolyte solution in the electrolytic cell through a pH detector, and controls the alkali solution pump or acid solution pump to supply a certain amount of alkali solution or acid solution to the circulating electrolyte solution, which enters the electrolytic cell through a water distributor, so that the pH value of the electrolyte solution is maintained within the range of 8.5±0.2; (3) The biogas to be purified is mixed with the circulating electrolyte solution through the ejector, and then enters the electrolytic cell through the water distributor, where it reacts with the electrochemical reaction product Fe 2+ , the electrolyte solution is mixed evenly; (4) CO2, H2S in the biogas to be purified and Fe in the electrolyte solution 2+ The precipitated product generated by the reaction is removed, and the purified biogas is discharged from the electrolytic cell after purification. The iron precipitated product generated during the biogas purification process is regularly discharged from the electrolytic cell, and the H2 generated by the electrochemical reaction at the cathode is also discharged together with the purified biogas, completing the biogas purification process.

[0037] After purification, the CO2 content in the biogas dropped from about 32% (volume ratio) before purification to less than 6.3% (volume ratio) after purification, and the H2S concentration dropped from 2580 mg / m 3 After purification, it dropped to about 75 mg / m 3 the following.

[0038] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A biogas purification device based on electrochemical iron production, characterized in that: The biogas purification device comprises an electrolytic cell, an anode, a cathode, a power supply, an electrolyte solution, a biogas diffuser, an agitator and a pH value control system; the electrolyte solution, the anode and the cathode are arranged in the electrolytic cell; the anode, the cathode, the power supply, the electrolytic cell and the electrolyte solution constitute an electrochemical system, the two ends of the power supply are respectively connected to the anode and the cathode through a power line, and the anode is an iron electrode; The pH value control system includes a pH detector, an alkali solution supply system, an acid solution supply system and a control system. The alkali solution supply system includes an alkali solution preparation device and an alkali solution pump. The acid solution supply system includes an acid solution preparation device and an acid solution pump. The alkali solution preparation device is connected to the electrolytic cell through the alkali solution pump. The acid solution preparation device is connected to the electrolytic cell through the acid solution pump. The pH detector is connected to the electrolytic cell. The biogas diffuser and the stirrer are arranged at the bottom of the electrolytic cell, and the biogas diffuser is connected to the biogas inlet pipeline; the lower part of the electrolytic cell is also provided with an iron precipitation product outlet, and the upper part of the electrolytic cell is provided with a biogas outlet.

2. A biogas purification device based on electrochemical iron production, characterized in that: The biogas purification device comprises an electrolytic cell, an anode, a cathode, a power supply, an electrolyte solution, a stirrer, a water distributor and a pH value control system; the electrolyte solution, the anode and the cathode are arranged in the electrolytic cell; the electrolytic cell, the anode, the cathode, the power supply and the electrolyte solution constitute an electrochemical system, the two ends of the power supply are respectively connected to the anode and the cathode through a power line, and the anode is an iron electrode; The electrolytic cell is also provided with an electrolyte solution circulation pipeline, on which a circulation pump, a first pipeline mixer, a second pipeline mixer and an ejector are sequentially arranged, the ejector is connected to the water distributor, and the water distributor and the agitator are arranged at the bottom of the electrolytic cell; the ejector is provided with an inlet for biogas to be purified; The pH value control system includes a pH detector, an alkali solution supply system, an acid solution supply system and a control system. The alkali solution supply system includes an alkali solution preparation device and an alkali solution pump. The acid solution supply system includes an acid solution preparation device and an acid solution pump. The acid solution preparation device is connected to the first pipeline mixer through the acid solution pump. The alkali solution preparation device is connected to the second pipeline mixer through the alkali solution pump. The pH detector is connected to the electrolytic cell. The lower part of the electrolytic cell is provided with a mixed gas-liquid flow inlet of electrolyte solution and biogas and an outlet for iron precipitation products, and the upper part of the electrolytic cell is provided with an electrolyte solution outlet and a biogas outlet.

3. A biogas purification device based on electrochemical iron production according to claim 1 or 2, characterized in that: The iron electrode includes but is not limited to iron plate, carbon steel, stainless steel, scrap iron or iron-containing composite electrode.

4. A biogas purification device based on electrochemical iron production according to claim 1 or 2, characterized in that: The cathode is a metal electrode, a carbon-based material electrode or a composite electrode; the metal electrode includes an iron electrode or a non-ferrous metal electrode.

5. A biogas purification method for electrochemical iron production based on the device according to any one of claims 1, 3 or 4, characterized in that: The following steps are involved: (1) An electrolyte solution is set in the electrolytic cell of the biogas purification device. According to the flow rate of the biogas to be purified and the content of CO2 and H2S in the biogas, the voltage / current of the electrochemical system is adjusted to generate Fe2+ in the electrolytic cell through the anode reaction. 2+ , cathode reaction generates H2 and OH - and is uniformly mixed with the electrolyte solution by the action of a stirrer; (2) The pH value control system detects the pH value of the electrolyte solution in the electrolytic cell through a pH detector, and controls the alkali solution pump or the acid solution pump to supply a certain amount of alkali solution or acid solution to the electrolyte solution, so that the pH value of the electrolyte solution is maintained at 8.5±0.2; (3) The biogas to be purified is transported to the electrolytic cell of the biogas purification device and reacts with the electrochemical reaction product Fe under the action of the agitator. 2+ , the electrolyte solution provided in the electrolytic cell is mixed uniformly; (4) CO2, H2S in the biogas to be purified and Fe in the electrolyte solution 2+ The precipitated product generated by the reaction is removed, and the purified biogas is discharged from the electrolytic cell after purification. The iron precipitated product generated during the biogas purification process is regularly discharged from the electrolytic cell, and the H2 generated by the electrochemical reaction at the cathode is also discharged together with the purified biogas, completing the biogas purification process.

6. A biogas purification method for electrochemical iron production based on the device according to any one of claims 2, 3 or 4, characterized in that: The following steps are involved: (1) An electrolyte solution is set in the electrolytic cell of the biogas purification device. According to the flow rate of the biogas to be purified and the content of CO2 and H2S in the biogas, the voltage / current of the electrochemical system is adjusted to generate Fe2+ in the electrolytic cell through the anode reaction. 2+ , cathode reaction generates H2 and OH - and is mixed evenly with the electrolyte solution by the action of the stirrer; mixed with the electrochemical reaction product Fe 2+ The electrolyte solution is transported by a circulation pump and circulated in the electrolytic cell; (2) The pH value control system detects the pH value of the electrolyte solution in the electrolytic cell through a pH detector, and controls the alkali solution pump or acid solution pump to supply a certain amount of alkali solution or acid solution to the circulating electrolyte solution, which enters the electrolytic cell through a water distributor, so that the pH value of the electrolyte solution is maintained at 8.5±0.2; (3) The biogas to be purified is mixed with the circulating electrolyte solution through the ejector, and then enters the electrolytic cell through the water distributor, and is mixed with the electrochemical reaction product Fe under the action of the stirrer. 2+ , the electrolyte solution is mixed evenly; (4) CO2, H2S in the biogas to be purified and Fe in the electrolyte solution 2+ The precipitated product generated by the reaction is removed, and the purified biogas is discharged from the electrolytic cell after purification. The iron precipitated product generated during the biogas purification process is regularly discharged from the electrolytic cell, and the H2 generated by the electrochemical reaction at the cathode is also discharged together with the purified biogas, completing the biogas purification process.

7. The method according to claim 5 or 6, characterized in that: The biogas to be treated includes biogas produced by anaerobic treatment of wastewater containing organic matter, biogas produced by anaerobic digestion of sludge and solid waste containing organic matter, and biogas containing CO2 and H2S from other sources.

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