System and process for producing green methanol from biogas based on fermentation of urban organic solid waste

Abstract

The present application provides a kind of system and process for producing green methanol based on town organic solid waste fermentation, including biogas purification and impurity removal unit, biogas mixing reforming unit, methanol synthesis unit, methanol rectification refining unit, methanol storage unit and supply unit;Biogas purification and impurity removal unit is used to remove sulfur-containing gas in biogas;Biogas mixing reforming unit includes raw material heater, reforming reactor, steam generator and gas-liquid separator, for biogas mixing reforming;Methanol synthesis unit includes first synthesis reactor, first high-pressure gas-liquid separation tank, second synthesis reactor, second high-pressure gas-liquid separation tank and low-pressure gas-liquid separation tank, for generating crude methanol;Methanol rectification refining unit uses rectification column and heat pump rectification technology to rectify and refine crude methanol.Compared with the traditional process that needs to remove CO2, the present application avoids CO2 emission or loss, realizes full carbon conversion, improves carbon utilization efficiency and improves the overall economy of the system.

Description

Technical Field

[0001] This invention relates to the technical field of green fuel synthesis, and in particular to a system and process for producing green methanol from biogas produced by fermentation of urban organic solid waste. Background Technology

[0002] Biogas, a renewable gaseous resource produced through the anaerobic fermentation of organic waste, is mainly composed of CH4 (approximately 50%–70% by volume) and CO2 (approximately 30%–50% by volume), possessing both energy and carbon resource attributes. The efficient conversion of biogas into green methanol has become an important development direction for resource utilization.

[0003] In existing technologies, the production of green methanol from biogas typically employs the following process route: first, the biogas is separated and purified to remove CO2 and obtain biomethane; then, syngas is produced through high-temperature steam reforming; and finally, methanol is synthesized. However, this process route has at least the following shortcomings:

[0004] (1) Low carbon utilization rate: About 30% to 50% of the CO2 in biogas is separated and emitted or only used for low value-added purposes during the pretreatment process, resulting in an overall carbon resource utilization rate that is usually less than 60%;

[0005] (2) High energy consumption and cost: The CO2 separation process consumes a lot of energy, usually accounting for 20% to 30% of the total energy consumption. It also increases the complexity of the equipment and investment, thereby weakening the economic efficiency of the product.

[0006] Therefore, it is necessary to design a system and process for producing green methanol from biogas based on the fermentation of urban organic solid waste. This system should not require the pre-removal of CO2 and should enable the synergistic conversion of CH4 and CO2 in biogas to produce green methanol, thereby improving carbon resource utilization efficiency, reducing energy consumption and production costs, and overcoming the shortcomings of existing technologies. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a system and process for producing green methanol from biogas based on the fermentation of urban organic solid waste, in order to solve the problems of low overall carbon resource utilization, high energy consumption and production costs caused by the prior separation and purification of biogas in the prior art.

[0008] To achieve the above and other related objectives, the present invention provides a system for producing green methanol from biogas based on the fermentation of urban organic solid waste, including a biogas purification and impurity removal unit, a biogas mixing and reforming unit, a methanol synthesis unit, a methanol distillation and refining unit, a methanol storage unit, and a hydrogen supply unit.

[0009] The biogas purification and impurity removal unit includes a first desulfurization reactor, a biogas preheater, and a second desulfurization reactor, used to remove sulfur-containing gases from biogas.

[0010] The biogas mixing and reforming unit includes a feedstock heater, a reforming reactor, a steam generator, and a gas-liquid separator, which are used to mix and reform biogas to generate syngas for methanol production.

[0011] The methanol synthesis unit includes a first synthesis reactor, a first high-pressure gas-liquid separator, a second synthesis reactor, a second high-pressure gas-liquid separator, and a low-pressure gas-liquid separator, used to generate crude methanol;

[0012] The methanol distillation and refining unit distills and refines crude methanol and stores it in the methanol storage unit.

[0013] The hydrogen supply unit is used to supply hydrogen to the biogas preheater and the methanol synthesis unit.

[0014] Preferably, the air inlet of the first desulfurization reactor is used to introduce biogas, the exhaust outlet of the first desulfurization reactor is connected to the air inlet of the biogas preheater, and the exhaust outlet of the biogas preheater is connected to the air inlet of the second desulfurization reactor.

[0015] The exhaust port of the second desulfurization reactor is connected to the inlet of the raw material heater, the exhaust port of the raw material heater is connected to the inlet of the reforming reactor, the exhaust port of the reforming reactor is connected to the inlet of the gas-liquid separator, and a steam generator is installed between the exhaust port of the reforming reactor and the inlet of the gas-liquid separator; demineralized water is introduced into the steam generator, the demineralized water absorbs the heat of the synthesis gas in the reforming reactor to generate water vapor, and the water vapor enters the inlet of the raw material heater;

[0016] The exhaust port of the gas-liquid separator is connected to the inlet of the first synthesis reactor; the discharge port of the first synthesis reactor is connected to the inlet of the first high-pressure gas-liquid separator; the exhaust port of the first high-pressure gas-liquid separator is connected to the inlet of the second synthesis reactor; the discharge port of the second synthesis reactor is connected to the inlet of the second high-pressure gas-liquid separator; the discharge ports of the first and second high-pressure gas-liquid separators are connected to the inlet of the low-pressure gas-liquid separator; and the discharge port of the low-pressure gas-liquid separator is connected to the methanol distillation and refining unit.

[0017] The exhaust port of the first high-pressure gas-liquid separator is connected to the feed port of the first synthesis reactor through a first valve; the exhaust port of the second high-pressure gas-liquid separator is connected to the feed port of the first synthesis reactor through a second valve; the exhaust port of the second high-pressure gas-liquid separator is connected to the feed port of the second synthesis reactor through a third valve; the first valve, the second valve, and the third valve are respectively used to control the opening and closing of the gas path.

[0018] Preferably, the methanol distillation and refining unit includes a distillation column, a top condenser, and a top separator. The inlet of the distillation column is connected to the outlet of the low-pressure gas-liquid separator. The top condenser is located at the top of the distillation column and is connected to the top separator. The distillation column is used to remove light and heavy component impurities from crude methanol. The top condenser is used to condense methanol vapor and recover methanol. The top separator is used to recover buffered methanol and adjust the methanol reflux ratio.

[0019] Preferably, the methanol distillation and refining unit further includes a distillation heat pump assembly and a reboiler. The reboiler is located at the bottom of the distillation column and is used to heat the crude methanol in the distillation column. The distillation heat pump assembly is located between the reboiler and the overhead condenser and is used to recover the latent heat of methanol condensation in the overhead condenser and supply the latent heat to the reboiler.

[0020] Preferably, the system further includes a decarbonization separation reactor for separating CO2 from biogas; the inlet of the decarbonization separation reactor is connected to the outlet of the second desulfurization reactor, one outlet of the decarbonization separation reactor is connected to the inlet of the raw material heater, and the other outlet of the decarbonization separation reactor is connected to the inlet of the second synthesis reactor; all the gas in the second desulfurization reactor enters the biogas preheater after passing through the decarbonization separation reactor; or part of the gas in the second desulfurization reactor enters the biogas preheater after passing through the decarbonization separation reactor; or the gas in the second desulfurization reactor enters the biogas preheater directly without passing through the decarbonization separation reactor.

[0021] To achieve the above or other objectives, this invention also discloses a process for producing green methanol from biogas generated by fermentation of urban organic solid waste. The process utilizes the aforementioned system for producing green methanol from biogas generated by fermentation of urban organic solid waste, and the steps are as follows:

[0022] S1: The biogas purification and impurity removal unit removes sulfur-containing gases from the biogas to form raw material gas;

[0023] S2: The biogas mixing and reforming unit is used to mix and reform the feed gas to generate synthesis gas for methanol production;

[0024] S3: The synthesis gas generated in step S2 enters the methanol synthesis unit to produce crude methanol;

[0025] S4: The crude methanol obtained in step S3 is purified by distillation in a methanol distillation unit and stored in a methanol storage unit to obtain green methanol.

[0026] Preferably, step S1 includes the following steps:

[0027] S1.1: Biogas enters the first desulfurization reactor, which removes sulfur-containing gases from the biogas, reducing the sulfur content to below 20 ppm;

[0028] S1.2: The biogas after passing through the first desulfurization reactor is mixed with the hydrogen supplied by the hydrogen supply unit and then enters the biogas preheater. After the biogas preheater heats the mixture to 250-350℃, the mixture of biogas and hydrogen enters the second desulfurization reactor.

[0029] S1.3: The mixture of biogas and hydrogen enters the second desulfurization reactor, which removes sulfur-containing gases from the mixture, reducing the sulfur content to below 0.1 ppm.

[0030] Preferably, step S2 includes the following steps:

[0031] S2.1: The raw material gas generated in step S1 is mixed with the water vapor generated in the steam generator and enters the raw material heater, where the raw material heater heats the mixed gas to 500-700℃;

[0032] S2.2: The heated feed gas and water vapor mixture enter the reforming reactor, where a mixed reforming reaction occurs to generate syngas;

[0033] S2.3: The synthesis gas generated in step S2.2 enters the gas-liquid separator through the steam generator. The steam generator absorbs the heat of the synthesis gas to produce water vapor. The synthesis gas enters the gas-liquid separator for gas-liquid separation. The gas phase substance enters the methanol synthesis unit, and the liquid phase substance is recycled back to the steam generator to produce water vapor.

[0034] Preferably, step S3 includes the following steps:

[0035] S3.1: The synthesis gas generated in step S2 is mixed with the hydrogen supplied by the hydrogen supply unit and then enters the first synthesis reactor to carry out the methanol synthesis reaction under the action of the catalyst; the gaseous and liquid phases in the first synthesis reactor enter the first high-pressure gas-liquid separator for separation, the gaseous phase enters the second synthesis reactor, and the liquid phase enters the low-pressure gas-liquid separator.

[0036] S3.2: The gaseous substances separated in the first high-pressure gas-liquid separator enter the second synthesis reactor and undergo methanol synthesis reaction under the action of a catalyst; the gaseous and liquid substances in the second synthesis reactor enter the second high-pressure gas-liquid separator for separation, and the gaseous substances are used as circulating gas to enter the feed inlet of the first synthesis reactor or the feed inlet of the second synthesis reactor.

[0037] S3.3: After the low-pressure gas-liquid separator depressurizes the liquid phase material in the first high-pressure gas-liquid separator and the liquid phase material in the second high-pressure gas-liquid separator, the liquid phase material enters the methanol distillation and refining unit.

[0038] Preferably, step S4 includes the following steps:

[0039] S4.1: The crude methanol generated in step S3 enters the distillation column in the methanol distillation and refining unit. The distillation column is heated to remove light component impurities and heavy component impurities from the crude methanol.

[0040] S4.2: The top condenser at the top of the distillation column condenses the methanol vapor and recovers it to the top separator in the methanol distillation and refining unit; the green methanol in the top separator is stored in the methanol storage unit.

[0041] In steps S4.1 and S4.2, the distillation heat pump assembly in the methanol distillation and refining unit recovers the latent heat of methanol vapor condensation in the top condenser of the column and transfers the latent heat to the reboiler at the bottom of the distillation column for the distillation of crude methanol.

[0042] As described above, the system and process for producing green methanol from biogas based on the fermentation of urban organic solid waste, as disclosed in this invention, have the following beneficial effects:

[0043] 1. This invention relates to a system and process for producing green methanol from biogas produced through the fermentation of urban organic solid waste. Using biogas as raw material, it fully utilizes the CH4 and CO2 within it. Through reforming and subsequent methanol synthesis reactions, green carbon elements are converted into methanol products, achieving efficient utilization of carbon resources and a complete carbon utilization process route, avoiding green carbon loss. Compared to traditional processes that require CO2 removal, this process avoids CO2 emissions or loss, achieving "complete carbon conversion." It improves carbon utilization efficiency, reduces carbon emissions, and enhances the overall economic and environmental performance of the system.

[0044] 2. The system and process for producing green methanol from biogas based on the fermentation of urban organic solid waste involved in this invention still retain the decarbonization separation reactor in the prior art. Since the composition of biogas fluctuates with the seasons, this application can be flexibly adjusted according to the actual situation, so that biogas partially, completely, or not pass through the decarbonization separation reactor. The CO2 that partially or completely passes through the decarbonization separation reactor is combined with green hydrogen to synthesize green methanol, which has a wide range of applications.

[0045] 3. The system and process for producing green methanol from biogas based on the fermentation of urban organic solid waste involved in this invention adopt a hydrogen supply unit that couples renewable energy hydrogen production and biomass hydrogen production to achieve green hydrogen source replenishment and reaction regulation, thereby realizing the greening of the hydrogen source.

[0046] 4. The system and process for producing green methanol from biogas based on the fermentation of urban organic solid waste involved in this invention use electric heating to provide the heat source for the reforming reactor, replacing the traditional fuel combustion heating method in the prior art. It can be directly coupled with renewable energy sources such as wind power and photovoltaics to achieve near-zero carbon heating, improve temperature control accuracy, and facilitate the stable operation of the reforming reaction.

[0047] 5. The system and process for producing green methanol from biogas based on the fermentation of urban organic solid waste involved in this invention are provided with a first synthesis reactor and a second synthesis reactor. The two-stage methanol synthesis reactors are arranged in series, and a gas-liquid separation unit is set after each stage to return unreacted gas to the inlet of the front reactor. This realizes the function of two-stage methanol synthesis reactors in series and flexible return of circulating gas, which improves the single-pass conversion rate and the total conversion rate. At the same time, the unreacted CO and CO2 are gradually consumed through circulation to achieve full carbon conversion. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the process flow for the green methanol production system based on biogas from urban organic solid waste fermentation, as per the present invention; (excluding the decarbonization separation reactor).

[0049] Figure 2 This is a schematic diagram of the process flow for the green methanol production system based on biogas from urban organic solid waste fermentation, as per the present invention. (Including a decarbonization and separation reactor)

[0050] Explanation of reference numerals in the attached figures:

[0051] 11. First desulfurization reactor; 12. Biogas preheater; 13. Second desulfurization reactor; 21. Decarbonization separation reactor; 31. Feed heater; 32. Reforming reactor; 33. Steam generator; 34. Gas-liquid separator; 41. First synthesis reactor; 42. First high-pressure gas-liquid separator; 43. Second synthesis reactor; 44. Second high-pressure gas-liquid separator; 45. Low-pressure gas-liquid separator; 51. Distillation column; 52. Top condenser; 53. Top separator; 54. Distillation heat pump assembly; 55. Reboiler; 61. Methanol storage unit; 71. Hydrogen production module; 72. Hydrogen storage module. Detailed Implementation

[0052] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0053] It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art and are not intended to limit the scope of the invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0054] like Figure 1 As shown, the present invention provides a system for producing green methanol from biogas based on the fermentation of urban organic solid waste, including a biogas purification and impurity removal unit, a biogas mixing and reforming unit, a methanol synthesis unit, a methanol distillation and refining unit, a methanol storage unit 61, and a hydrogen supply unit.

[0055] The biogas purification and impurity removal unit includes a first desulfurization reactor 11, a biogas preheater 12 and a second desulfurization reactor 13, which are used to remove sulfur-containing gases from biogas.

[0056] The biogas mixing and reforming unit includes a feedstock heater 31, a reforming reactor 32, a steam generator 33, and a gas-liquid separator 34, which are used to mix and reform biogas to generate syngas for methanol production.

[0057] The methanol synthesis unit includes a first synthesis reactor 41, a first high-pressure gas-liquid separator 42, a second synthesis reactor 43, a second high-pressure gas-liquid separator 44, and a low-pressure gas-liquid separator 45, for producing crude methanol.

[0058] The methanol distillation and refining unit distills and refines crude methanol and stores it in the methanol storage unit 61.

[0059] The hydrogen supply unit is used to supply hydrogen to the biogas preheater 12 and the methanol synthesis unit.

[0060] Furthermore, such as Figure 1 As shown, the air inlet of the first desulfurization reactor 11 is used to introduce biogas, the exhaust outlet of the first desulfurization reactor 11 is connected to the air inlet of the biogas preheater 12, and the exhaust outlet of the biogas preheater 12 is connected to the air inlet of the second desulfurization reactor 13.

[0061] The exhaust port of the second desulfurization reactor 13 is connected to the inlet of the raw material heater 31, the exhaust port of the raw material heater 31 is connected to the inlet of the reforming reactor 32, the exhaust port of the reforming reactor 32 is connected to the inlet of the gas-liquid separator 34, and the steam generator 33 is located between the exhaust port of the reforming reactor 32 and the inlet of the gas-liquid separator 34; demineralized water is introduced into the steam generator 33, and the demineralized water absorbs the heat of the synthesis gas in the reforming reactor 32 to generate water vapor, and the water vapor enters the inlet of the raw material heater 31;

[0062] The exhaust port of the gas-liquid separator 34 is connected to the feed port of the first synthesis reactor 41, the discharge port of the first synthesis reactor 41 is connected to the feed port of the first high-pressure gas-liquid separator 42, the exhaust port of the first high-pressure gas-liquid separator 42 is connected to the feed port of the second synthesis reactor 43, and the discharge port of the second synthesis reactor 43 is connected to the feed port of the second high-pressure gas-liquid separator 44; the liquid discharge ports of the first high-pressure gas-liquid separator 42 and the second high-pressure gas-liquid separator 44 are connected to the liquid discharge port of the low-pressure gas-liquid separator 45; the discharge port of the low-pressure gas-liquid separator 45 is connected to the methanol distillation and refining unit.

[0063] The exhaust port of the first high-pressure gas-liquid separator 42 is connected to the inlet of the first synthesis reactor 41 through a first valve; the exhaust port of the second high-pressure gas-liquid separator 44 is connected to the inlet of the first synthesis reactor 41 through a second valve; the exhaust port of the second high-pressure gas-liquid separator 44 is connected to the inlet of the second synthesis reactor 43 through a third valve; the first valve, the second valve and the third valve are used to control the opening and closing of the gas path.

[0064] In this embodiment, the first synthesis reactor 41, the first high-pressure gas-liquid separator 42, the second synthesis reactor 43, and the second high-pressure gas-liquid separator 44 constitute a synthesis method with two towers connected in series. The gaseous substances in the first high-pressure gas-liquid separator 42 and the second high-pressure gas-liquid separator 44 form circulating gas. The circulating gas, together with fresh synthesis gas and supplementary hydrogen, adjusts the composition of the mixed gas, thereby improving the utilization rate of raw materials and the overall conversion rate of the system.

[0065] When the second valve is opened and the first and third valves are closed, the gaseous substances in the first high-pressure gas-liquid separator 42 enter the second synthesis reactor 43, and the gaseous substances in the second high-pressure gas-liquid separator 44 are recycled to the first synthesis reactor 41 for another reaction, consuming the remaining CO and CO2. The path of the circulating gas is: first synthesis reactor 41 → first high-pressure gas-liquid separator 42 → second synthesis reactor 43 → second high-pressure gas-liquid separator 44 → first synthesis reactor 41. That is, the gaseous substances in the second high-pressure gas-liquid separator 44 are recycled through the first synthesis reactor 41 and the second synthesis reactor 43, which is a large loop process.

[0066] When the third valve is opened and the first and second valves are closed, the gaseous substances in the first high-pressure gas-liquid separator 42 enter the second synthesis reactor 43, and the gaseous substances in the second high-pressure gas-liquid separator 44 are recycled to the second synthesis reactor 43 for another reaction, consuming the remaining CO and CO2. The path of the recycled gas is: first synthesis reactor 41 → first high-pressure gas-liquid separator 42 → second synthesis reactor 43 → second high-pressure gas-liquid separator 44 → second synthesis reactor 43 → second high-pressure gas-liquid separator 44. That is, the gaseous substances in the second high-pressure gas-liquid separator 44 are recycled through the second synthesis reactor 43, which is a small loop process.

[0067] When the first and third valves are open and the second valve is closed, the gaseous substances in the first high-pressure gas-liquid separator 42 simultaneously enter the first synthesis reactor 41 and the second synthesis reactor 43. The gaseous substances in the second high-pressure gas-liquid separator 44 are recycled to the second synthesis reactor 43 for further reaction, consuming the remaining CO and CO2. The path of the circulating gas is: first synthesis reactor 41 → first high-pressure gas-liquid separator 42 → first synthesis reactor 41 and second synthesis reactor 43 → second high-pressure gas-liquid separator 44 → second synthesis reactor 43 → second high-pressure gas-liquid separator 44. That is, the gaseous substances in the first synthesis reactor 41 pass through both the first synthesis reactor 41 and the second synthesis reactor 43, and the gaseous substances in the second high-pressure gas-liquid separator 44 are recycled through the second synthesis reactor 43, forming two small cycles to achieve a double-cycle process.

[0068] In summary, the first synthesis reactor 41 in this application mainly produces methanol from CO and hydrogen, while the second synthesis reactor 43 mainly produces methanol from CO2 and hydrogen. Therefore, operators can open appropriate valves according to the proportion of CO2 in the biogas to achieve different circulating gas paths. By gradually consuming unreacted CO and CO2 through circulation, the single-pass conversion rate and the total conversion rate can be improved, thus achieving full carbon conversion.

[0069] Preferred, such as Figure 1 As shown, the methanol distillation and refining unit includes a distillation column 51, a top condenser 52, and a top separator 53. The feed inlet of the distillation column 51 is connected to the discharge outlet of the low-pressure gas-liquid separator 45. The top condenser 52 is located at the top of the distillation column 51 and is connected to the top separator 53. The distillation column 51 is used to remove light and heavy component impurities from crude methanol. The top condenser 52 is used to condense methanol vapor and recover methanol. The top separator 53 is used to recover buffered methanol and adjust the methanol reflux ratio.

[0070] Preferred, such as Figure 1As shown, the methanol distillation and refining unit also includes a distillation heat pump assembly 54 and a reboiler 55. The reboiler 55 is located at the bottom of the distillation column 51 and is used to heat the crude methanol in the distillation column 51. The distillation heat pump assembly 54 is located between the reboiler 55 and the overhead condenser 52 and is used to recover the latent heat of methanol condensation in the overhead condenser 52 and supply the latent heat to the reboiler 55. In this embodiment, the distillation column 51 includes, but is not limited to, single-column, double-column, triple-column, quadruple-column, and five-column distillation processes, which can be determined according to capacity and quality requirements. The reboiler 55 is used to heat the crude methanol in the distillation column 51, and the capacity of the distillation column 51 can be controlled by controlling the heat of the reboiler 55. The methanol distillation and refining unit uses the distillation column 51 and heat pump distillation technology to refine crude methanol.

[0071] Preferred, such as Figure 1 , Figure 2 As shown, the hydrogen supply unit in this application includes a hydrogen production module 71 and a hydrogen storage module 72. The hydrogen production module 71 is used to produce green hydrogen for biogas purification and to adjust the hydrogen-to-carbon ratio of syngas. Hydrogen production can be achieved through renewable energy water electrolysis or biomass. The hydrogen storage module 72 is used to buffer excess hydrogen from the hydrogen production module 71 and to release hydrogen to adjust the hydrogen-to-carbon ratio of syngas. It can be a gaseous hydrogen storage system, a solid-state hydrogen storage system, or a liquid hydrogen storage system.

[0072] Preferred, such as Figure 2 As shown, the system for producing green methanol from biogas based on the fermentation of urban organic solid waste also includes a decarbonization separation reactor 21, which is used to separate CO2 from biogas. The inlet of the decarbonization separation reactor 21 is connected to the outlet of the second desulfurization reactor 13, one outlet of the decarbonization separation reactor 21 is connected to the inlet of the raw material heater 31, and the other outlet of the decarbonization separation reactor 21 is connected to the inlet of the second synthesis reactor 43. All the gas in the second desulfurization reactor 13 enters the biogas preheater 12 after passing through the decarbonization separation reactor 21; or part of the gas in the second desulfurization reactor 13 enters the biogas preheater 12 after passing through the decarbonization separation reactor 21; or the gas in the second desulfurization reactor 13 enters the biogas preheater 12 directly without passing through the decarbonization separation reactor 21.

[0073] In this embodiment, the decarbonization reactor 21 is used to separate CO2 from biogas, and the separated CO2 is mainly used in the second synthesis reactor 43. Biogas is produced by the anaerobic fermentation of organic matter, and thus the composition of biogas fluctuates seasonally. To achieve full carbon content from biogas and low-energy production of green methanol, the decarbonization reactor 21 is mainly determined based on the CO2 content in the biogas feedstock and the performance of the catalyst in the second synthesis reactor 43. The decarbonization reactor 21 in this application uses pressure swing adsorption (PSA) to separate CO2 from biogas.

[0074] To achieve the above or other objectives, the present invention also discloses a process for producing green methanol from biogas generated by fermentation of urban organic solid waste. Using the aforementioned system for producing green methanol from biogas generated by fermentation of urban organic solid waste, the steps are as follows:

[0075] S1: The biogas purification and impurity removal unit removes sulfur-containing gases from the biogas to form raw material gas;

[0076] S1.1: Biogas enters the first desulfurization reactor 11, which removes sulfur-containing gases from the biogas, reducing the sulfur content to below 20 ppm. The sulfur-containing gases are mainly composed of H2S. Desulfurization methods can include dry desulfurization, wet desulfurization, biological desulfurization, and low-temperature methanol washing desulfurization. In this embodiment, iron oxide dry desulfurization is selected, which can reduce the sulfur content to 10 ppm.

[0077] S1.2: The biogas after passing through the first desulfurization reactor 11 is mixed with the hydrogen provided by the hydrogen production module 71 and then enters the biogas preheater 12. The biogas preheater 12 heats the biogas to 250-350℃, which meets the temperature required for the reaction in the second desulfurization reactor 13. The mixture of biogas and hydrogen enters the second desulfurization reactor 13 for deep purification of biogas.

[0078] S1.3: The mixture of biogas and hydrogen enters the second desulfurization reactor 13, which further removes sulfur-containing gases from the mixture, reducing the sulfur content to below 0.1 ppm. In this embodiment, the biogas preheater 12 heats the mixture of biogas and hydrogen to the reaction temperature of the second desulfurization reactor 13, where it undergoes deep purification under the action of catalysts and adsorbents, ensuring the requirements for the catalysts used in the reforming reactor 32 and the first synthesis reactor 41 are met. In this embodiment, the catalysts and adsorbents in the second desulfurization reactor 13 are compounds of cobalt, molybdenum, and ZnO; ZnO also removes chlorine-containing gases from the biogas during the desulfurization process.

[0079] At this time, the raw gas discharged from the exhaust port of the second desulfurization reactor 13 contains CH4, CO, CO2, and H2.

[0080] S2: The biogas mixing and reforming unit is used to mix and reform the feed gas to generate synthesis gas for methanol production;

[0081] S2.1: The raw material gas generated in step S1 mixes with the water vapor generated in the steam generator 33 and enters the raw material heater 31, which heats the mixture to 500-700℃. Biogas reforming is a strongly endothermic reaction, requiring preheating of the mixture of raw material gas and water vapor to reach the activation temperature of the catalyst in the reforming reactor 32, while avoiding condensation of water vapor mixed with the raw material gas.

[0082] S2.2: The heated feed gas and water vapor mixture enters the reforming reactor 32, where a mixed reforming reaction occurs to generate syngas. The catalyst in the reforming reactor 32 is a Ni-based catalyst, the reforming temperature is 800-1000℃, and the reforming pressure is 5-30 bar. The reforming reactor 32 is an electrically driven reactor, enabling directional and precise energy supply and accurate control of the reforming reaction temperature.

[0083] The main reactions occurring in reforming reactor 32 are CH4 + H2O → CO + 3H2 and CH4 + CO2 → 2H2 + 2CO. Thus, the main components of the syngas are CO, CO2, and H2. Reforming reactor 32 is selected from reforming furnaces of square or circular shapes, and electric heating is preferred to provide the heat required for the reforming reaction.

[0084] S2.3: The syngas generated in step S2.2 enters the gas-liquid separator 34 through the steam generator 33. The steam generator 33 absorbs the heat from the syngas to produce steam. The syngas then undergoes gas-liquid separation in the gas-liquid separator 34. The gaseous phase enters the methanol synthesis unit, while the liquid phase is recycled back to the steam generator 33 to produce steam. The steam generator 33 is an energy recovery device used to introduce deionized and demineralized water to remove impurities. The demineralized water absorbs the heat from the syngas to produce steam. The steam mixes with the feed gas and enters the reforming reactor 32 to adjust the water-to-carbon ratio in the feed gas. A suitable water-to-carbon ratio helps eliminate carbon buildup on the catalyst in the reforming reactor 32. The steam flow rate is adjusted according to the water-to-carbon ratio required by the catalyst in the reforming reactor 32.

[0085] S2.4: The heat in the synthesis gas is absorbed by the steam generator 33 and then enters the gas-liquid separator 34. The synthesis gas is separated into dry synthesis gas and condensate below 45°C. The dry synthesis gas is used for methanol synthesis. The condensate is recovered and combined with demineralized water before entering the steam generator 33 to form water vapor.

[0086] S3: The synthesis gas generated in step S2 enters the methanol synthesis unit to produce crude methanol;

[0087] S3.1: The synthesis gas generated in step S2 is mixed with the hydrogen supplied by the hydrogen supply unit and then enters the first synthesis reactor 41 to carry out the methanol synthesis reaction under the action of the catalyst; the gaseous and liquid phase substances in the first synthesis reactor 41 enter the first high-pressure gas-liquid separator 42 for separation, the gaseous substances enter the second synthesis reactor 43, and the liquid phase substances enter the low-pressure gas-liquid separator 45.

[0088] The hydrogen supply unit provides hydrogen to the synthesis gas (the hydrogen can be sourced from the hydrogen production module 71 and the hydrogen storage module 72) to adjust the hydrogen-to-carbon ratio ((H2-CO2) / (CO+CO2)) in the synthesis gas, ensuring that all the carbon in the synthesis gas participates in the methanol synthesis reaction. The catalyst in the first synthesis reactor 41 is a Cu-based catalyst, and the main reaction that occurs in the first synthesis reactor 41 is CO+2H2→CH3OH. The gaseous substances in the first synthesis reactor 41 include the remaining CO, the remaining H2, and most of the CO2, while the liquid substances are crude methanol.

[0089] S3.2: The gaseous substances separated in the first high-pressure gas-liquid separator 42 enter the second synthesis reactor 43, where they undergo further methanol synthesis under the action of a catalyst, thereby improving the overall conversion rate of the synthesis gas and increasing the methanol yield. The gaseous and liquid substances in the second synthesis reactor 43 enter the second high-pressure gas-liquid separator 44 for separation, and the gaseous substances are used as circulating gas to enter the inlet of the first synthesis reactor 41 or the inlet of the second synthesis reactor 43.

[0090] The catalyst in the second synthesis reactor 43 is a Ni-based catalyst. The main reaction that occurs in the second synthesis reactor 43 is CO2 + 3H2 → CH3OH + H2O. The gaseous substances in the second synthesis reactor 43 include the remaining CO, the remaining H2, the remaining CO2, and water vapor, while the liquid substances are crude methanol. The gaseous substances in the second synthesis reactor 43 are recycled as circulating gas.

[0091] S3.3: The low-pressure gas-liquid separator 45 depressurizes the liquid phase substances in the first high-pressure gas-liquid separator 42 and the second high-pressure gas-liquid separator 44, after which the liquid phase substances enter the methanol distillation and refining unit. The low-pressure gas-liquid separator 45 depressurizes the crude methanol to meet the pressure requirements for distillation in the distillation column 51.

[0092] S4: The crude methanol obtained in step S3 is refined by distillation in the methanol distillation unit and stored in the methanol storage unit 61 to obtain green methanol.

[0093] S4.1: The crude methanol generated in step S3 enters the distillation column 51 in the methanol distillation and refining unit. The distillation column 51 is heated to remove light and heavy component impurities from the crude methanol. Light component impurities include dimethyl ether and dissolved gases (e.g., CO2), while heavy component impurities include water and high-boiling-point heavy components. The crude methanol is heated to generate methanol vapor, yielding high-purity green methanol that meets various standards. The distillation column 51 is not limited to single-column, double-column, triple-column, quadruple-column, or five-column distillation processes; the specific configuration depends on capacity and quality requirements. For example, the first distillation column may be used to separate light component impurities, the second distillation column to separate heavy component impurities, and the third distillation column to heat the crude methanol to generate methanol vapor.

[0094] S4.2: The overhead condenser 52 at the top of the distillation column 51 condenses methanol vapor and recovers it to the overhead separator 53 in the methanol distillation and refining unit; the green methanol in the overhead separator 53 is stored in the methanol storage unit 61. The overhead condenser 52 is used to condense the methanol vapor at the top of the column, recover the methanol product, and control and adjust the reflux ratio and the green methanol production; the overhead separator 53 is used to recover the green methanol product buffered in the overhead condenser 52, adjust the reflux ratio, and store the buffered green methanol product in the methanol storage unit 61.

[0095] In steps S4.1 and S4.2, the distillation heat pump assembly 54 in the methanol distillation and refining unit recovers the latent heat of methanol vapor condensation in the top condenser 52 of the column, improves the heat source grade, and transfers the latent heat to the reboiler 55 at the bottom of the distillation column 51 for the distillation of crude methanol in the distillation column 51.

[0096] Other, such as Figure 2 As shown, when the system includes a decarbonization separation reactor 21, the decarbonization separation reactor 21 is used to separate CO2 from biogas; the process steps at this time are as follows:

[0097] A1: The biogas purification and impurity removal unit removes sulfur-containing and carbon-containing gases from the biogas to form raw material gas;

[0098] The steps A1.1-A1.3 are the same as those in S1.1-S1.3 above;

[0099] A1.4: The feed gas discharged from the exhaust port of the second desulfurization reactor 13 passes through the decarbonization separation reactor 21, either partially or entirely. The decarbonization separation reactor 21 uses pressure swing adsorption (PSA) to separate CO2 from the biogas. The separated CO2 enters the second synthesis reactor 43. The components of the feed gas after it has completely passed through the decarbonization separation reactor 21 include CH4, CO, and H2. The components of the feed gas after it has partially passed through the decarbonization separation reactor 21 include CH4, CO, H2, and a portion of CO2.

[0100] A2: The biogas mixing and reforming unit is used to mix and reform the feed gas to generate syngas for methanol production;

[0101] The steps A2.1-A2.4 are the same as those in S2.1-S2.4 above;

[0102] A3: The synthesis gas generated in step A2 enters the methanol synthesis unit to produce crude methanol;

[0103] The steps in A3.1 are the same as those in S3.1 above;

[0104] A3.2: The gaseous substances separated in the first high-pressure gas-liquid separator 42 enter the second synthesis reactor 43, and the CO2 separated by decarbonization enters the second synthesis reactor 43 to carry out the methanol synthesis reaction under the action of a catalyst; the gaseous and liquid substances in the second synthesis reactor 43 enter the second high-pressure gas-liquid separator 44 for separation, and the gaseous substances enter the inlet of the first synthesis reactor 41 or the inlet of the second synthesis reactor 43 as circulating gas;

[0105] The catalyst in the second synthesis reactor 43 is a nickel-containing multi-element alloy catalyst. The main reaction that occurs in the second synthesis reactor 43 is CO2 + 3H2 → CH3OH + H2O. The gaseous substances in the second synthesis reactor 43 include the remaining CO, the remaining H2, the remaining CO2, and water vapor, while the liquid substances are crude methanol. The gaseous substances in the second synthesis reactor 43 are recycled as circulating gas.

[0106] The steps in A3.3 are the same as those in S3.3 above;

[0107] A4: The crude methanol obtained in step A3 is refined by distillation in the methanol distillation unit and stored in the methanol storage unit 61 to obtain green methanol;

[0108] The steps A4.1-A4.2 are the same as those in S4.1-S4.2 above.

[0109] This invention relates to a system and process for producing green methanol from biogas produced through the fermentation of urban organic solid waste. Using biogas as raw material, it fully utilizes the CH4 and CO2 within it. Through reforming and subsequent methanol synthesis reactions, green carbon elements are converted into methanol products, achieving efficient utilization of carbon resources and a complete carbon utilization process route, avoiding green carbon loss. Compared to traditional processes that require CO2 removal, this process avoids CO2 emissions or loss, achieving "complete carbon conversion," improving carbon utilization efficiency, reducing carbon emissions, and enhancing the overall economic and environmental performance of the system.

[0110] Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0111] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A system for producing green methanol from biogas produced by fermentation of urban organic solid waste, characterized in that: It includes a biogas purification and impurity removal unit, a biogas mixing and reforming unit, a methanol synthesis unit, a methanol distillation and refining unit, a methanol storage unit (61), and a hydrogen supply unit; The biogas purification and impurity removal unit includes a first desulfurization reactor (11), a biogas preheater (12), and a second desulfurization reactor (13), used to remove sulfur-containing gases from biogas; The biogas mixing and reforming unit includes a raw material heater (31), a reforming reactor (32), a steam generator (33), and a gas-liquid separator (34) connected in sequence, which are used to mix and reform biogas to generate syngas for methanol production. The gas-liquid separator (34) is adapted to perform gas-liquid separation on the flowing synthesis gas; The methanol synthesis unit includes a first synthesis reactor (41), a first high-pressure gas-liquid separator (42), a second synthesis reactor (43), a second high-pressure gas-liquid separator (44), and a low-pressure gas-liquid separator (45), for producing crude methanol; The exhaust port of the gas-liquid separator (34) is connected to the inlet of the first synthesis reactor (41), the discharge port of the first synthesis reactor (41) is connected to the inlet of the first high-pressure gas-liquid separator (42), the exhaust port of the first high-pressure gas-liquid separator (42) is connected to the inlet of the second synthesis reactor (43), and the discharge port of the second synthesis reactor (43) is connected to the inlet of the second high-pressure gas-liquid separator (44); the discharge ports of the first high-pressure gas-liquid separator (42) and the second high-pressure gas-liquid separator (44) are connected to the inlet of the low-pressure gas-liquid separator (45); the discharge port of the low-pressure gas-liquid separator (45) is connected to the methanol distillation and refining unit. The exhaust port of the first high-pressure gas-liquid separator (42) is connected to the inlet of the first synthesis reactor (41) through a first valve; the exhaust port of the second high-pressure gas-liquid separator (44) is connected to the inlet of the first synthesis reactor (41) through a second valve; the exhaust port of the second high-pressure gas-liquid separator (44) is connected to the inlet of the second synthesis reactor (43) through a third valve; the first valve, the second valve and the third valve are respectively used to control the opening and closing of the gas path; The methanol distillation and refining unit distills and refines crude methanol and stores it in the methanol storage unit (61); The hydrogen supply unit is used to supply hydrogen to the biogas preheater (12) and the methanol synthesis unit; It also includes a decarbonization separation reactor (21) for separating CO2 from biogas; The air inlet of the decarbonization separation reactor (21) is connected to the exhaust port of the second desulfurization reactor (13), one of the exhaust ports of the decarbonization separation reactor (21) is connected to the air inlet of the raw material heater (31), and the other exhaust port of the decarbonization separation reactor is connected to the feed port of the second synthesis reactor (43). All the gas in the second desulfurization reactor (13) enters the raw material heater (31) after passing through the decarbonization separation reactor (21); or part of the gas in the second desulfurization reactor (13) enters the raw material heater (31) after passing through the decarbonization separation reactor (21); or the gas in the second desulfurization reactor (13) enters the raw material heater (31) directly without passing through the decarbonization separation reactor (21).

2. The system for producing green methanol from biogas based on the fermentation of urban organic solid waste according to claim 1, characterized in that: The inlet of the first desulfurization reactor (11) is used to introduce biogas, the outlet of the first desulfurization reactor (11) is connected to the inlet of the biogas preheater (12), and the outlet of the biogas preheater (12) is connected to the inlet of the second desulfurization reactor (13). The exhaust port of the second desulfurization reactor (13) is connected to the inlet of the raw material heater (31), the exhaust port of the raw material heater (31) is connected to the inlet of the reforming reactor (32), the exhaust port of the reforming reactor (32) is connected to the inlet of the gas-liquid separator (34), and the steam generator (33) is located between the exhaust port of the reforming reactor (32) and the inlet of the gas-liquid separator (34); demineralized water is introduced into the steam generator (33), the demineralized water absorbs the heat of the synthesis gas in the reforming reactor (32) to generate water vapor, and the water vapor enters the inlet of the raw material heater (31).

3. The system for producing green methanol from biogas based on the fermentation of urban organic solid waste according to claim 1, characterized in that: The methanol distillation and refining unit includes a distillation column (51), a top condenser (52), and a top separator (53). The feed inlet of the distillation column (51) is connected to the discharge outlet of the low-pressure gas-liquid separator (45). The top condenser (52) is located at the top of the distillation column (51) and is connected to the top separator (53). The distillation column (51) is used to remove light component impurities and heavy component impurities from crude methanol; the top condenser (52) is used to condense methanol vapor and recover methanol; the top separator (53) is used to recover buffered methanol and adjust the methanol reflux ratio.

4. The system for producing green methanol from biogas based on the fermentation of urban organic solid waste according to claim 3, characterized in that: The methanol distillation and refining unit also includes a distillation heat pump assembly (54) and a reboiler (55). The reboiler (55) is located at the bottom of the distillation column (51) and is used to heat the crude methanol in the distillation column (51). The distillation heat pump assembly (54) is located between the reboiler (55) and the overhead condenser (52) and is used to recover the latent heat of methanol condensation in the overhead condenser (52) and supply the latent heat to the reboiler (55).

5. A process for producing green methanol from biogas generated by fermentation of urban organic solid waste, using the system for producing green methanol from biogas generated by fermentation of urban organic solid waste as described in any one of claims 1-4, comprising the following steps: S1: The biogas purification and impurity removal unit removes sulfur-containing gases from the biogas to form raw material gas; S2: The biogas mixing and reforming unit is used to mix and reform the feed gas to generate synthesis gas for methanol production; S3: The synthesis gas generated in step S2 enters the methanol synthesis unit to produce crude methanol; S4: The crude methanol obtained in step S3 is refined by distillation in the methanol distillation unit and stored in the methanol storage unit (61) to obtain green methanol.

6. The process for producing green methanol from biogas based on the fermentation of urban organic solid waste according to claim 5, characterized in that: Step S1 includes the following steps: S1.1: Biogas enters the first desulfurization reactor (11), which removes sulfur-containing gases from the biogas and reduces the sulfur content to below 20 ppm; S1.2: After passing through the first desulfurization reactor (11), the biogas mixed with the hydrogen supplied by the hydrogen supply unit enters the biogas preheater (12). After the biogas preheater (12) heats the biogas to 250-350℃, the mixture of biogas and hydrogen enters the second desulfurization reactor (13). S1.3: The mixture of biogas and hydrogen enters the second desulfurization reactor (13), which removes sulfur-containing gases from the mixture and reduces the sulfur content to below 0.1 ppm.

7. The process for producing green methanol from biogas based on the fermentation of urban organic solid waste according to claim 5, characterized in that: Step S2 includes the following steps: S2.1: The raw material gas generated in step S1 is mixed with the water vapor generated in the steam generator (33) and enters the raw material heater (31). The raw material heater (31) heats the mixed gas to 500-700℃. S2.2: The mixture of heated raw material gas and water vapor enters the reforming reactor (32), where a mixed reforming reaction occurs to generate syngas; S2.3: The synthesis gas generated in step S2.2 enters the gas-liquid separator (34) through the steam generator (33). The steam generator (33) absorbs the heat of the synthesis gas to produce water vapor. The synthesis gas enters the gas-liquid separator (34) for gas-liquid separation. The gas phase material enters the methanol synthesis unit, and the liquid phase material is recycled back to the steam generator (33) to generate water vapor.

8. The process for producing green methanol from biogas based on the fermentation of urban organic solid waste according to claim 5, characterized in that: Step S3 includes the following steps: S3.1: The synthesis gas generated in step S2 is mixed with the hydrogen supplied by the hydrogen supply unit and then enters the first synthesis reactor (41) to carry out the methanol synthesis reaction under the action of the catalyst; the gaseous and liquid phase substances in the first synthesis reactor (41) enter the first high-pressure gas-liquid separator (42) for separation, the gaseous substances enter the second synthesis reactor (43) and the liquid phase substances enter the low-pressure gas-liquid separator (45); S3.2: The gaseous substances separated in the first high-pressure gas-liquid separator (42) enter the second synthesis reactor (43) and undergo methanol synthesis reaction under the action of a catalyst; the gaseous and liquid substances in the second synthesis reactor (43) enter the second high-pressure gas-liquid separator (44) for separation, and the gaseous substances enter the feed inlet of the first synthesis reactor (41) or the feed inlet of the second synthesis reactor (43) as circulating gas; S3.3: The low-pressure gas-liquid separator (45) depressurizes the liquid phase material in the first high-pressure gas-liquid separator (42) and the liquid phase material in the second high-pressure gas-liquid separator (44), and then the liquid phase material enters the methanol distillation and refining unit.

9. The process for producing green methanol from biogas based on the fermentation of urban organic solid waste according to claim 5, characterized in that: Step S4 includes the following steps: S4.1: The crude methanol generated in step S3 enters the distillation column (51) in the methanol distillation and refining unit. The distillation column (51) is heated to remove light component impurities and heavy component impurities from the crude methanol. S4.2: The top condenser (52) at the top of the distillation column (51) condenses the methanol vapor and recovers it to the top separator (53) in the methanol distillation and refining unit; the green methanol in the top separator (53) is stored in the methanol storage unit (61); In steps S4.1 and S4.2, the distillation heat pump assembly (54) in the methanol distillation and refining unit recovers the latent heat of methanol vapor condensation in the top condenser (52) and transfers the latent heat to the bottom reboiler (55) of the distillation column (51) for the distillation of crude methanol in the distillation column (51).

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