Device and method for purifying biogas by using ferrous salt and / or ferric salt
By using ferrous salt and/or ferrous salt in the biogas purification system to react with CO2 and H2S, the precipitated product is generated and the pH value is adjusted in real time, the high cost and pH drop of CO2 and H2S removal in the prior art is solved, and the problem of high cost and pH drop in CO2 and H2S removal in the prior art is achieved. Efficient purification and resource recovery of biogas.
Patent Information
- Application Number
- CN202411307622.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-19
- Publication Date
- 2024-12-13
AI Technical Summary
The prior art has problems such as high operating costs, large carbon emissions and serious secondary pollution when removing CO2 and H2S in biogas. In addition, ferrous ions/ferrous ions are used to remove hydrogen sulfide and can easily lead to a decrease in the pH of the system, affecting the desulfurization effect. No synchronous desulfurization and decarbonization method has been seen.
Using a biogas purification system based on ferrous salt and/or iron salt, the precipitated product is generated by reacting ferrous salt solution and/or iron salt solution with CO2 and H2S in the biogas, and the pH control system is used to maintain the internal biogas purification device. The pH value is within the range of 8.5±0.2, achieving synchronous and efficient removal of CO2 and H2S.
It has achieved efficient purification of biogas, reduced operating costs and carbon emissions, avoided the side effects caused by the decline in pH, and has good application prospects and resource recycling value.
Smart Images
Figure CN119120078A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of biogas purification, and in particular relates to a device and method for purifying biogas by utilizing ferrous salt and / or ferric salt. 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 / ferric ions can be used to remove hydrogen sulfide, such as Chinese patent application CN103723823A. However, the existing technology of removing hydrogen sulfide using ferrous ions / ferric ions has the defects of significantly reducing the desulfurization effect by causing the pH of the system to drop due to the addition of ferrous ions / ferric ions, or greatly increasing the amount of ferrous ions / ferric ions and further reducing the pH caused by them; on the other hand, there is no method of using ferrous ions / ferric ions to simultaneously desulfurize and decarbonize biogas in the prior art, and the use of ferrous ions / ferric ions to decarbonize biogas 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 device for purifying biogas using ferrous salts and / or ferric salts. The device can simultaneously and efficiently remove carbon dioxide and hydrogen sulfide in biogas to achieve biogas purification.
[0009] Another object of the present invention is to provide a method for purifying biogas using ferrous salts and / or ferric salts. The method comprises constructing a biogas purification system based on ferrous salts and / or ferric salts, setting a ferrous salt solution and / or ferric salt solution supply system and a pH value control system, and utilizing CO2 and H2S in the biogas to react with Fe in the ferrous salt solution. 2+ and / or Fe in iron salt solution 3+ The precipitate product generated by the reaction is removed, and the pH value inside the biogas purification system is adjusted by the pH control system, so that CO2 and H2S in the biogas can be removed simultaneously and efficiently, achieving the purpose of biogas purification.
[0010] The purpose of the present invention is achieved through the following technical solutions: A device for purifying biogas using ferrous salt and / or ferric salt, the device comprising a biogas purification device, a biogas diffuser, an agitator, a ferrous salt solution and / or ferric salt solution supply system and a pH value control system; The ferrous salt solution and / or ferric salt solution supply system comprises a ferrous salt solution and / or ferric salt solution preparation device and a reagent pump, and the biogas purification device is connected to the ferrous salt solution and / or ferric salt solution preparation device via the reagent pump; The pH value control system includes a pH detector, an alkali solution preparation device and an alkali solution pump; the biogas purification device is connected to the alkali solution preparation device through the alkali solution pump; the pH detector is connected to the biogas purification device; The biogas diffuser and the stirrer are arranged at the bottom of the biogas purification device, and the biogas diffuser is connected to the biogas inlet pipeline; the biogas purification device is provided with a precipitation product outlet at the bottom, and an overflow liquid outlet and a biogas outlet at the top.
[0011] A device for purifying biogas using ferrous salt and / or ferric salt, the device comprising a biogas purification device, a stirrer, a water distributor, a ferrous salt solution and / or ferric salt solution supply system and a pH value control system; The biogas purification device is also provided with a reagent 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 biogas purification device; the ejector is provided with an inlet for biogas to be purified; The ferrous salt solution and / or ferric salt solution supply system comprises a ferrous salt solution and / or ferric salt solution preparation device and a medicine pump, and the ferrous salt solution and / or ferric salt solution preparation device is connected to the first pipeline mixer through the medicine pump; The pH value control system includes a pH detector, an alkali solution preparation device and an alkali 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 biogas purification device; The lower part of the biogas purification device is provided with a circulating agent inlet and a precipitation product outlet, and the upper part of the biogas purification device is provided with an overflow liquid outlet and a biogas outlet.
[0012] Based on the device described in the present invention, the present invention also provides a method for purifying biogas using ferrous salts and / or ferric salts, comprising the following steps: (1) A certain amount of water medium is set in the biogas purification device to transport the biogas to be purified into the biogas purification device; (2) According to the flow rate of the biogas to be purified and the content of CO2 and H2S in the biogas, the ferrous salt solution and / or ferric salt solution supply system supplies a certain amount of ferrous salt solution and / or ferric salt solution to the biogas purification device to maintain a certain ferrous ion / ferric ion concentration in the biogas purification device; the agitator provides a stirring effect to uniformly mix the ferrous salt solution and / or ferric salt solution and the biogas to be purified in the biogas purification device; (3) The pH value control system detects the pH value inside the biogas purification device through a pH detector and controls the alkali solution pump to supply a certain amount of alkali solution to the biogas purification device; under the action of the agitator, the alkali solution is evenly mixed with the ferrous salt solution and / or the ferric salt solution, so that the pH value inside the biogas purification device is maintained at 8.5±0.2; (4) CO2, H2S in the biogas to be purified and Fe in the ferrous salt solution 2+ and / or Fe in iron salt solution 3+ The precipitated products generated during the reaction are removed, and the purified biogas is discharged from the biogas purification device. The precipitated products (FeCO3, FeS) generated during the biogas purification process are regularly discharged from the biogas purification device, and the overflow liquid is continuously discharged from the biogas purification device and transported to the ferrous salt solution and / or ferric salt solution supply system for the preparation of ferrous salt solution and / or ferric salt solution to complete the biogas purification process.
[0013] As another embodiment of the present invention, the method for purifying biogas using ferrous salts and / or ferric salts comprises the following steps: The ferrous salt solution and / or ferric salt solution provided in the biogas purification device is transported by a circulation pump and circulates in the biogas purification device; The first pipeline mixer is connected to the ferrous salt solution and / or ferric salt solution preparation device through a reagent pump, and mixes the ferrous salt solution and / or ferric salt solution delivered by the reagent pump with the circulating ferrous salt solution and / or ferric salt solution, and then enters the biogas purification device through a water distributor; The second pipeline mixer is connected to the alkali preparation device through an alkali pump, and mixes the alkali delivered by the alkali pump with the circulating ferrous salt solution and / or ferric salt solution, and then enters the biogas purification device through a water distributor; At the same time, the biogas to be purified is mixed with the circulating ferrous salt solution and / or ferric salt solution through the ejector, and then enters the biogas purification device through the water distributor, and is evenly mixed with the ferrous salt solution and / or ferric salt solution in the biogas purification device under the action of the agitator; the ferrous salt solution and / or ferric salt solution supply system supplies the ferrous salt solution and / or ferric salt solution to the biogas purification device through the agent pump to maintain a certain ferrous ion / ferric ion concentration in the biogas purification device; The pH value control system supplies a certain amount of alkali solution to the biogas purification device by regulating the alkali solution pump, so that the pH value inside the biogas purification device is maintained at 8.5±0.2, and performs the process of purifying biogas using ferrous salt and / or ferric salt; CO2, H2S in the biogas to be purified and Fe in the ferrous salt solution 2+ and / or Fe in iron salt solution 3+ The precipitated products generated during the reaction are removed, and the purified biogas is discharged from the biogas purification device. The precipitated products (FeCO3, FeS) generated during the biogas purification process are regularly discharged from the biogas purification device, and the overflow liquid is continuously discharged from the biogas purification device and transported to the ferrous salt solution and / or ferric salt solution supply system for the preparation of ferrous salt solution and / or ferric salt solution to complete the biogas purification process.
[0014] Preferably, the ferrous salt is ferrous chloride and / or ferrous sulfate, and the ferric salt is ferric chloride and / or ferric sulfate.
[0015] 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.
[0016] 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 biogas purification device through the diffuser or ejector and the water distributor, the biogas to be purified is evenly mixed with the ferrous salt solution and / or ferric salt solution provided in the biogas purification device under the action of the agitator; thus, the CO2 and H2S in the biogas are mixed with the Fe 2+ and / or Fe in iron salt solution3+ The reaction occurs and forms a precipitate which is removed, thus achieving the purpose of biogas purification.
[0017] First, using the Fe in the ferrous salt solution 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.
[0018] ① ② At the same time, using the Fe in the ferrous salt solution 2+ It reacts with H2S in biogas to generate FeS precipitate, and simultaneously achieves efficient removal of H2S in biogas (Formula ③).
[0019] ③ If an iron salt solution is provided in the biogas purification device, the Fe 3+ First, it reacts with H2S in the biogas to be purified, and the sulfide is oxidized to generate elemental S. At the same time, Fe 3+ Reduced to Fe 2+ (Formula ④). Then, Fe 2+ Through reactions ①, ② and ③, efficient removal of CO2 and H2S in the biogas to be purified is achieved.
[0020] ④ In the case where a mixed solution of ferrous salt solution and ferric salt solution is set in the biogas purification device, CO2 and H2S in the biogas are reacted with Fe in the ferrous salt solution. 2+ and / or Fe in iron salt solution 3+ Reactions (Formulas ①, ②, ③ and ④) occur, achieving the simultaneous and efficient removal of CO2 and H2S in biogas, thereby achieving the purpose of biogas purification.
[0021] In the case of adding ferrous / ferric ions for wet desulfurization of biogas, the addition of ferrous / ferric ions to the water medium actually has an important impact on the pH value of the system. This is because iron salts are strongly acidic compounds, and the commonly used iron salt dosage will reduce the pH value of the water medium. At the same time, the precipitation reaction of ferrous / ferric ions with H2S is highly dependent on pH and is significantly negatively affected by lower pH values, especially under neutral or near-neutral pH conditions (i.e., 6-8). For example, a decrease from pH 7.0 to 6.5 results in an increase of more than 200% in iron salt dosage requirements 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.
[0022] The present invention provides a pH value control system to control the pH value inside the biogas purification device in real time, so that the pH value inside the biogas purification device is always maintained within the range of 8.5±0.2, which can effectively overcome the above defects and achieve the purpose of synchronously, stably and efficiently removing CO2 and H2S in biogas.
[0023] 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.
[0024] Furthermore, the iron content in the 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 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
[0025] Figure 1 is a schematic diagram of embodiment 1 of the present invention; Figure 2 is a schematic diagram of Embodiment 2 of the present invention; Among them, 1-biogas purification device, 2-ferrous salt solution / ferric salt solution, 3-agitator, 4-biogas diffuser, 5-ferrous salt solution / ferric salt solution preparation device, 6-medicine pump, 7-alkali solution preparation device, 8-alkali solution pump, 9-pH detector, 10-circulation pump, 11-first pipeline mixer, 12-second pipeline mixer, 13-ejector, 14-water distributor. DETAILED DESCRIPTION
[0026] 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.
[0027] Example 1 like Figure 1 As shown, this embodiment provides a device for purifying biogas using ferrous salts and / or ferric salts, comprising a biogas purification device 1, a biogas diffuser 4, an agitator 3, a ferrous salt solution and / or ferric salt solution supply system and a pH value control system; the ferrous salt solution and / or ferric salt solution supply system comprises a ferrous salt solution and / or ferric salt solution preparation device 5 and a reagent pump 6, and the biogas purification device 1 is connected to the ferrous salt solution and / or ferric salt solution preparation device 5 through the reagent pump 6; the pH value control system comprises a pH detector 9, an alkali solution preparation device 7 and an alkali solution pump 8; the biogas purification device 1 is connected to the alkali solution preparation device 7 through the alkali solution pump 8; the pH detector 9 is connected to the biogas purification device 1; the biogas diffuser 4 and the agitator 3 are arranged at the bottom of the biogas purification device 1, and the biogas diffuser 4 is connected to the biogas inlet pipeline; the biogas purification device is provided with a precipitation product outlet at the bottom, and the biogas purification device is provided with an overflow liquid outlet and a biogas outlet at the top.
[0028] In the device, the pH value control system detects the pH value inside the biogas purification device in real time through the pH detector installed on the biogas purification device, and controls the alkali solution pump through the control system to maintain the pH value inside the biogas purification device 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 solution pump is controlled by the control system to reduce the amount of alkali solution added, so that the pH value inside the biogas purification device 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 solution pump is controlled by the control system to increase the amount of alkali solution added, so that the pH value inside the biogas purification device increases and is maintained within the range of 8.5±0.2.
[0029] The biogas to be purified is transported into the biogas purification device through a biogas diffuser and is evenly mixed with the ferrous salt solution and / or ferric salt solution to perform a process of purifying the biogas using ferrous salt and / or ferric salt; the ferrous salt solution and / or ferric salt solution supply system includes a ferrous salt solution / ferric salt solution preparation device and a reagent pump, and the ferrous salt solution and / or ferric salt solution is supplied to the biogas purification device through the reagent pump to maintain a certain ferrous ion / ferric ion concentration in the biogas purification device.
[0030] The device described in this embodiment is used to purify biogas produced in the anaerobic treatment process of wastewater. Under room temperature conditions, the biogas to be purified is transported into the biogas purification device at a flow rate of 0.5 L / (L•h). The ferrous salt solution and / or ferric salt solution supply system supplies a certain amount of ferrous salt solution to the biogas purification device, so that the ferrous ion concentration in the biogas purification device is maintained within the range of 200±10 mg / L. The pH value control system detects the pH value inside the biogas purification device through a pH detector, and controls the alkali solution pump to supply a certain amount of alkali solution to the biogas purification device, so that the pH value inside the biogas purification device is maintained within the range of 8.5±0.2.
[0031] The biogas to be purified is transported into the biogas purification device 1 through the biogas diffuser 4 and is evenly mixed with the ferrous salt solution in the biogas purification device 1; thus, CO2, H2S in the biogas to be purified and Fe in the ferrous salt solution are mixed together. 2+ Reaction occurs and is removed; First, using the Fe in the ferrous salt solution 2+ It reacts with CO2 in biogas to generate FeCO3 precipitation, removes CO2 in biogas, and forms a CO2 sink (Formula ①, ②), achieving efficient removal of CO2 in biogas. 2+ It reacts with H2S in biogas to generate FeS precipitate, and simultaneously achieves efficient removal of H2S in biogas (Formula ③).
[0032] Then the purified biogas is discharged from the biogas purification device 1, and the iron precipitation products (FeCO3, FeS) generated during the biogas purification process are regularly discharged from the biogas purification device 1, completing the purification process of the biogas to be purified.
[0033] After purification, the CO2 content in the biogas to be purified dropped from about 27% (volume ratio) before purification to below 5.0% (volume ratio), and the H2S concentration dropped from 17000 mg / m 3 Decreased to around 90 mg / m 3 the following.
[0034] In addition, the iron content in the 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 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 95 ml / g, and the specific filtration resistance (SRF) is reduced from 2.73×10 13 Down to 1.95×10 13 This indicates that the iron precipitate obtained by the present invention has significant resource recovery and utilization value.
[0035] Example 2 like Figure 2 As shown, this embodiment provides a device for purifying biogas using ferrous salts and / or ferric salts, comprising a biogas purification device 1, an agitator 3, a water distributor 14, a ferrous salt solution and / or ferric salt solution supply system and a pH value control system; the biogas purification device 1 is also provided with a reagent circulation pipeline, on which a circulation pump 10, a first pipeline mixer 11, a second pipeline mixer 12 and an ejector 13 are sequentially arranged; the ejector 13 is connected to the water distributor 14, and the water distributor 14 and the agitator 3 are arranged at the bottom of the biogas purification device 1; the ejector 13 is provided with an inlet for biogas to be purified; the ferrous salt The solution and / or iron salt solution supply system includes a ferrous salt solution and / or iron salt solution preparation device 5 and a reagent pump 6, and the ferrous salt solution and / or iron salt solution preparation device 5 is connected to the first pipeline mixer 11 through the reagent pump 6; the pH value control system includes a pH detector 9, an alkali solution preparation device 7 and an alkali solution pump 8; the alkali solution preparation device 7 is connected to the second pipeline mixer 12 through the alkali solution pump 8; the pH detector 9 is connected to the biogas purification device 1; the biogas purification device 1 is provided with a circulating reagent inlet and a precipitation product outlet at the lower part, and the biogas purification device 1 is provided with an overflow liquid outlet and a biogas outlet at the upper part.
[0036] In the device, the pH value control system detects the pH value inside the biogas purification device in real time through the pH detector installed on the biogas purification device, and controls the alkali solution pump through the control system to maintain the pH value inside the biogas purification device 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 solution pump is controlled by the control system to reduce the amount of alkali solution added, so that the pH value inside the biogas purification device 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 solution pump is controlled by the control system to increase the amount of alkali solution added, so that the pH value inside the biogas purification device increases and is maintained within the range of 8.5±0.2.
[0037] The device described in this embodiment is used to purify biogas produced by anaerobic digestion of sludge. The added reagents are ferrous salt solution and ferric salt solution, and the biogas flow rate is 0.7 L / (L•h). The ferrous salt solution and ferric salt solution provided in the biogas purification device 1 are transported by the circulation pump 10 and circulate in the biogas purification device 1; at the same time, the biogas to be purified is mixed with the circulating ferrous salt solution and ferric salt solution through the ejector 13, and then enters the biogas purification device 1 through the water distributor 14, and is evenly mixed with the ferrous salt solution and ferric salt solution in the biogas purification device 1 under the action of the agitator 3; thus, the CO2 and H2S in the biogas to be purified and the Fe in the ferrous salt solution are mixed evenly. 2+ and Fe in iron salt solution 3+The reaction generates precipitates (Formulas ①, ②, ③ and ④) and is removed, thereby achieving the simultaneous and efficient removal of CO2 and H2S in the biogas, and achieving the purpose of biogas purification. Then, the purified biogas is discharged from the biogas purification device 1, and the precipitated products (FeCO3, FeS, etc.) generated during the biogas purification process are regularly discharged from the biogas purification device 1, completing the purification process of the biogas to be purified.
[0038] In Fe 2+ and Fe 3+ Under the condition of 100 mg / L addition, the CO2 content in the biogas to be purified decreased from about 32% (volume ratio) before purification to below 8.0% (volume ratio), and the H2S concentration decreased from 2580 mg / m 3 Decreased to around 95 mg / m 3 the following.
[0039] 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 device for purifying biogas using ferrous salts and / or ferric salts, characterized in that: The device comprises a biogas purification device, a biogas diffuser, an agitator, a ferrous salt solution and / or ferric salt solution supply system and a pH value control system; The ferrous salt solution and / or ferric salt solution supply system comprises a ferrous salt solution and / or ferric salt solution preparation device and a reagent pump, and the biogas purification device is connected to the ferrous salt solution and / or ferric salt solution preparation device via the reagent pump; The pH value control system includes a pH detector, an alkali solution preparation device and an alkali solution pump; the biogas purification device is connected to the alkali solution preparation device through the alkali solution pump; the pH detector is connected to the biogas purification device; The biogas diffuser and the stirrer are arranged at the bottom of the biogas purification device, and the biogas diffuser is connected to the biogas inlet pipeline; the biogas purification device is provided with a precipitation product outlet at the bottom, and an overflow liquid outlet and a biogas outlet at the top.
2. A device for purifying biogas using ferrous salts and / or ferric salts, characterized in that: The device comprises a biogas purification device, a stirrer, a water distributor, a ferrous salt solution and / or ferric salt solution supply system and a pH value control system; The biogas purification device is also provided with a reagent 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 biogas purification device; the ejector is provided with an inlet for biogas to be purified; The ferrous salt solution and / or ferric salt solution supply system comprises a ferrous salt solution and / or ferric salt solution preparation device and a medicine pump, and the ferrous salt solution and / or ferric salt solution preparation device is connected to the first pipeline mixer through the medicine pump; The pH value control system includes a pH detector, an alkali solution preparation device and an alkali 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 biogas purification device; The lower part of the biogas purification device is provided with a circulating agent inlet and a precipitation product outlet, and the upper part of the biogas purification device is provided with an overflow liquid outlet and a biogas outlet.
3. A method for purifying biogas using ferrous salts and / or ferric salts based on the device of claim 1, characterized in that: The following steps are involved: (1) A certain amount of water medium is set in the biogas purification device to transport the biogas to be purified into the biogas purification device; (2) According to the flow rate of the biogas to be purified and the content of CO2 and H2S in the biogas, the ferrous salt solution and / or ferric salt solution supply system supplies a certain amount of ferrous salt solution and / or ferric salt solution to the biogas purification device to maintain a certain ferrous ion / ferric ion concentration in the biogas purification device; the agitator provides a stirring effect to uniformly mix the ferrous salt solution and / or ferric salt solution and the biogas to be purified in the biogas purification device; (3) The pH value control system detects the pH value inside the biogas purification device through a pH detector and controls the alkali solution pump to supply a certain amount of alkali solution to the biogas purification device; under the action of the agitator, the alkali solution is evenly mixed with the ferrous salt solution and / or the ferric salt solution, so that the pH value inside the biogas purification device is maintained at 8.5±0.2; (4) CO2, H2S in the biogas to be purified and Fe in the ferrous salt solution 2+ and / or Fe in iron salt solution 3+ The precipitate product generated by the reaction is removed, and the purified biogas is discharged from the biogas purification device. The precipitate product generated during the biogas purification process is regularly discharged from the biogas purification device, and the overflow liquid is continuously discharged from the biogas purification device and transported to the ferrous salt solution and / or ferric salt solution supply system for preparing the ferrous salt solution and / or ferric salt solution to complete the biogas purification process.
4. A method for purifying biogas using ferrous salts and / or ferric salts based on the device of claim 2, characterized in that: The following steps are involved: The ferrous salt solution and / or ferric salt solution provided in the biogas purification device is transported by a circulation pump and circulates in the biogas purification device; The first pipeline mixer is connected to the ferrous salt solution and / or ferric salt solution preparation device through a reagent pump, and mixes the ferrous salt solution and / or ferric salt solution delivered by the reagent pump with the circulating ferrous salt solution and / or ferric salt solution, and then enters the biogas purification device through a water distributor; The second pipeline mixer is connected to the alkali preparation device through an alkali pump, and mixes the alkali delivered by the alkali pump with the circulating ferrous salt solution and / or ferric salt solution, and then enters the biogas purification device through a water distributor; At the same time, the biogas to be purified is mixed with the circulating ferrous salt solution and / or ferric salt solution through the ejector, and then enters the biogas purification device through the water distributor, and is evenly mixed with the ferrous salt solution and / or ferric salt solution in the biogas purification device under the action of the agitator; the ferrous salt solution and / or ferric salt solution supply system supplies the ferrous salt solution and / or ferric salt solution to the biogas purification device through the agent pump to maintain a certain ferrous ion / ferric ion concentration in the biogas purification device; The pH value control system supplies a certain amount of alkali solution to the biogas purification device by regulating the alkali solution pump, so that the pH value inside the biogas purification device is maintained at 8.5±0.2, and performs the process of purifying biogas using ferrous salt and / or ferric salt; CO2, H2S in the biogas to be purified and Fe in the ferrous salt solution 2+ and / or Fe in iron salt solution 3+ The precipitate product generated by the reaction is removed, and the purified biogas is discharged from the biogas purification device. The precipitate product generated during the biogas purification process is regularly discharged from the biogas purification device, and the overflow liquid is continuously discharged from the biogas purification device and transported to the ferrous salt solution and / or ferric salt solution supply system for preparing the ferrous salt solution and / or ferric salt solution to complete the biogas purification process.
5. The method according to claim 3 or 4, characterized in that: The ferrous salt is ferrous chloride and / or ferrous sulfate, and the ferric salt is ferric chloride and / or ferric sulfate.
6. The method according to claim 3 or 4, 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.