Process and system for producing green methanol from biomass

Abstract

The invention relates to a process and system for producing green methanol from biomass, and relates to the technical field of biomass energy, the process comprises the following steps: S1, biomass gasification; s2, carrying out first heat exchange, and cooling the decoked cracking gas; s3, second heat exchange: cooling the pyrolysis gas subjected to the first heat exchange to a dust removal purification temperature; s4, dust removal and purification; s5, desulfurization, wherein pyrolysis gas in the step is used as a cooling medium in the step S3 for heat exchange; s6, methane reforming: the desulfurized pyrolysis gas and water vapor are subjected to a reforming reaction to generate raw material gas, and the synthesis gas in the step S2 serves as a cooling medium in the step S2 to exchange heat with the pyrolysis gas, so that the heat of the reforming reaction comes from the pyrolysis gas in the step S2; and S7, methanol generation. Through heat coupling in methanol production, the heat loss of the methanol production system is reduced, the heat utilization rate of the methanol production system is increased, the proportion of fuel gas in pyrolysis gas is reduced, the proportion of methanol synthesized by pyrolysis gas is increased, and the yield of methanol is increased.

Description

Technical Field

[0001] This application relates to the field of biomass energy technology, and in particular to a process and system for producing green methanol from biomass. Background Technology

[0002] Biomass energy is an ideal renewable energy source. It is widely available, renewable, and my country has abundant biomass resources. Therefore, the utilization of biomass energy has become an increasingly important research topic. Producing methanol from biomass materials allows for the use of renewable resources to replace fossil fuels in the production of a clean energy carrier, reducing carbon emissions and waste pollution.

[0003] Existing patent document CN118240597A discloses a biochar slurry and a system for producing sustainable fuel methanol using it. In this patent document, the crude syngas produced by the gasification of biochar slurry is cooled and purified, and then subjected to water-gas shift conversion, methane dry reforming, and acid gas removal before being used to produce methanol. In the prior art, when the syngas enters the methane dry reforming process after water-gas shift conversion, the syngas needs to be additionally heated to reach the temperature required for methane dry reforming. However, the heat from the crude syngas is insufficient to heat the syngas, increasing the heat loss of the methanol production system and resulting in a decrease in the heat utilization rate of the methanol production system. Summary of the Invention

[0004] To address the problem that the heat from crude syngas is insufficient to heat the syngas, thereby increasing heat loss in the methanol production system and reducing its heat utilization rate, this application provides a process and system for producing green methanol from biomass.

[0005] The process and system for producing green methanol from biomass provided in this application adopt the following technical solution: A process for producing green methanol from biomass includes the following steps: S1 Biomass gasification: Biomass is gasified into cracked gas containing CO, CO2, CH4, and H2, and the cracked gas is decoked; S2 First heat exchange: The decoked cracked gas undergoes heat exchange with a cooling medium to lower its temperature; S3 Second heat exchange: The cracked gas after the first heat exchange undergoes another heat exchange with the cooling medium, further reducing its temperature to the dust removal and purification temperature; S4 Dust removal and purification: The cracked gas is purified and dust is removed; S5 Desulfurization: The cracked gas undergoes desulfurization, and the cracked gas in this step is used as the cooling medium in step S3 for heat exchange to heat the cracked gas to the temperature required for desulfurization; S6 Methane reforming: The desulfurized cracked gas is mixed with water vapor to form syngas, and a reforming reaction occurs to generate feed gas. The syngas in this step is used as the cooling medium in step S2 to exchange heat with the cracked gas, providing heat for the methane reforming reaction; S7 Methanol generation: Methanol is synthesized from the reformed feed gas.

[0006] By adopting the above technical solution, during the cooling process of the cracked gas before dust removal and purification, the cracked gas provides heat for methane reforming, causing the temperature of the cracked gas to drop and achieving the first heat exchange. After the first heat exchange, the cracked gas heats the cracked gas that needs desulfurization. Through the first and second heat exchanges, the heat in methanol production is coupled, so that the cracked gas provides heat for subsequent desulfurization and methane reforming while cooling, reducing the amount of additional heat provided by the external system for desulfurization and methane reforming of the cracked gas, making full use of the heat of the cracked gas, reducing the heat loss of the methanol production system, and improving the heat utilization rate of the methanol production system.

[0007] Preferably, step S7 includes the following steps: S71 heat recovery, where the reformed feed gas is cooled by exchanging heat with water, and the water is heated to generate steam, providing steam for the methane reforming in step S6, and then exchanged heat with the cooling medium for further cooling; S72 decarbonization, where the heat-recovered feed gas is decarbonized; S73 methanol synthesis, where the decarbonized feed gas undergoes a synthesis reaction to generate crude methanol, the crude methanol containing 3%-10% (by mass) water; S74 methanol distillation, where the crude methanol is distilled to produce industrial methanol, the crude methanol serving as the cooling medium in step S71, allowing the feed gas to heat the crude methanol and provide heat for the methanol distillation.

[0008] By adopting the above technical solutions, the heat recovery step can use the heat of the reformed feed gas to heat water to generate steam for methane reforming, thereby realizing heat recovery and utilization; the decarbonization step can adjust the composition of the feed gas, which is beneficial to subsequent methanol synthesis; the methanol distillation step uses the heat of the feed gas to provide heat for distillation, thereby realizing heat coupling utilization, improving heat utilization rate, reducing the amount of external heat supply, and reducing heat loss.

[0009] Preferably, step S1 includes: S11 pulverization, pulverizing the biomass, wherein the particle diameter of the pulverized biomass is ≤1cm; S12 drying, drying the pulverized biomass, wherein the moisture content of the dried biomass is ≤18% (by mass); S13 pyrolysis, wherein the pulverized biomass is pyrolyzed to generate pyrolysis gas; and S14 tar removal, removing tar from the pyrolysis gas.

[0010] By adopting the above technical solution, biomass is crushed to a particle diameter of ≤1cm and dried to a moisture content of ≤18% (by mass) before being pyrolyzed to generate pyrolysis gas. The tar in the pyrolysis gas is then removed, which is beneficial to the subsequent biomass gasification process, making the pyrolysis more complete. Furthermore, the removal of tar can avoid the impact of tar on subsequent process equipment, ensuring the stable operation of the entire biomass-to-green methanol production process.

[0011] Preferably, after step S4, a step S401 is added for the storage and diversion of cracked gas. In step S401, the cracked gas after dust removal and purification is stored and divided into two parts. One part of the cracked gas is sent to step S5 for desulfurization and participates in methanol synthesis; the other part of the cracked gas is used as fuel gas to provide heat for biomass cracking in step S13, biomass decoking in step S14, and methane reforming in step S6. The ratio of cracked gas participating in methanol synthesis to cracked gas participating in combustion is ≥5:1 (volume).

[0012] By adopting the above technical solution, the pyrolysis gas after dust removal and purification is stored and diverted. One part is used for methanol synthesis, and the other part is used as fuel gas to provide heat for biomass pyrolysis, coke removal, and methane reforming. The ratio of pyrolysis gas participating in methanol synthesis to that participating in combustion is determined to be ≥5:1 (by volume). This allows for the rational allocation of the pyrolysis gas. While ensuring sufficient feedstock gas for methanol synthesis, it also provides the necessary heat for key steps in the production process, improving the comprehensive utilization rate of the pyrolysis gas and reducing the additional input of external energy. Through the first heat exchange, the second heat exchange, the heating of water with feedstock gas to generate steam, and the use of feedstock gas heat to provide heat for distillation, heat coupling is achieved. This reduces the heat generated by fuel gas for desulfurization of pyrolysis gas, methane reforming, steam production, and methanol distillation, thereby reducing the proportion of pyrolysis gas used as fuel gas, increasing the proportion of pyrolysis gas used for methanol synthesis, and increasing methanol production.

[0013] Preferably, the hot air generated during the biomass pyrolysis in step S13, the decoking of biomass in step S14, and the methane reforming in step S6 is conveyed to step S12 to provide heat for the drying of biomass.

[0014] By adopting the above technical solution, the fuel gas from the biomass pyrolysis in step S13, the biomass decoking in step S14, and the methane reforming heat exchange in step S6 is used to provide heat for the drying of biomass in step S12, thereby realizing further utilization of heat, improving the heat utilization rate of the entire biomass-to-green methanol production process, and reducing heat loss.

[0015] Preferably, in step S13, the biomass is pyrolyzed in the absence of air to produce pyrolysis gas containing CO, CO2, CH4, and H2, as well as solid carbon, and the fixed carbon is cleaned up. The discharge temperature of the pyrolysis gas is 700-800℃.

[0016] By adopting the above technical solution, biomass is pyrolyzed in the absence of air to produce pyrolyzed gas containing CO, CO2, CH4, and H2, as well as solid carbon. Cleaning the solid carbon can avoid affecting subsequent processes. The pyrolyzed gas with an outlet temperature of 700-800℃ can provide feedstock in a suitable state for subsequent processes.

[0017] Preferably, in step S14, the cracked gas is decoked by photocatalytic decoking, and the outlet temperature of the cracked gas after decoking is ≤850℃, the CH4 content is 22%-25% (volume), and the tar content is <0.1% (mass).

[0018] By adopting the above technical solution, photocatalytic decoking can effectively remove tar from the cracked gas, resulting in a cracked gas discharge temperature ≤850℃, CH4 content of 22%-25% (by volume), and tar content <0.1%, providing relatively pure cracked gas for subsequent methanol synthesis, which is beneficial to improving the efficiency and quality of methanol synthesis.

[0019] Preferably, in step S5, the pyrolysis gas is desulfurized using a dry method at a desulfurization temperature of 320°C, and the sulfur content in the desulfurized pyrolysis gas is ≤0.1ppm.

[0020] By adopting the above technical solution and using dry desulfurization, the sulfur content in the cracked gas can be reduced to 0.1 ppm at a desulfurization temperature of 320℃. This reduces the impact of sulfur on the subsequent methane reforming and methanol synthesis processes, ensures stable process operation, and improves the production quality of green methanol.

[0021] Preferably, in step S72, the decarbonization method of the raw gas is PSA partial decarbonization, and the CO2 content in the decarbonized raw gas is 2%-3% (by volume).

[0022] By adopting the above technical solution, the CO2 content in the feed gas is controlled at 2%-3% (by volume) through PSA partial decarbonization, which optimizes the composition of the feed gas, improves the efficiency and quality of subsequent methanol synthesis reactions, reduces the occurrence of side reactions, and enhances the purity and yield of industrial methanol.

[0023] A system for producing green methanol from biomass using the aforementioned process includes a pulverizing module, a drying module, a dry distillation and cracking furnace, a photoelectric coke removal furnace, a CH4 converter, a heat exchange module, a purification and dust removal module, a gas holder, a desulfurization module, a heat recovery module, a decarbonization module, a methanol synthesis module, a methanol distillation column, and a cracked gas power supply module; biomass is processed through the pulverizing module, the drying module, and the dry distillation and cracking furnace to generate cracked gas; The pyrolysis gas is stored in a gas holder after passing through a photoelectric coking furnace for coking removal, a CH4 converter for cooling, a heat exchange module for cooling, and a purification and dust removal module for dust removal. The cracked gas in the gas holder is used to heat the dry distillation cracking furnace, the photoelectric coke removal furnace, and the CH4 conversion furnace through the cracked gas power supply module. The pyrolysis gas in the gas holder is heated by the heat exchange module, desulfurized by the desulfurization module, and generated as feed gas in the reactor of the CH4 conversion furnace; The raw gas is heated to steam by the heat recovery module, crude methanol is heated by the methanol distillation column, and decarbonized by the decarbonization module before entering the methanol synthesis module to synthesize crude methanol. Crude methanol is converted into industrial methanol and stored in a methanol distillation column.

[0024] By adopting the above technical solution, the system can realize the complete process of biomass-to-green methanol production. Biomass is sequentially subjected to crushing, drying, gasification, coking removal, heat exchange, dust removal and purification, desulfurization, and reforming before methanol is synthesized. Specifically, the cracked gas is cooled in the CH4 converter and heat exchange module, achieving the first and second heat exchanges, providing heat for subsequent desulfurization and methane reforming, reducing the need for external heat input, fully utilizing the heat from the cracked gas, minimizing heat loss in the methanol production system, and improving heat utilization efficiency. The feed gas passes through a heat recovery module where water is heated and vaporized into steam, providing steam for methane reforming. This steam then flows through a methanol distillation column to heat the crude methanol distillation, providing heat for methanol distillation and further improving heat utilization efficiency. The combustion of the cracked gas supplies heat to the dry distillation cracking furnace, the photoelectric coking removal furnace, and the first heat exchange module, achieving energy recycling and reducing energy consumption.

[0025] In summary, this application includes at least one of the following beneficial technical effects: 1. By exchanging heat with syngas and desulfurized cracked gas during the first and second heat exchange processes, respectively, the heat in methanol production is coupled, reducing the amount of additional heat provided by the external system for desulfurization and methane reforming of cracked gas, reducing heat loss in the methanol production system, making full use of the heat of cracked gas, and improving the heat utilization rate of the methanol production system. 2. By using the first heat exchange, the second heat exchange, the heating of water with feed gas to generate steam, and the heat from the feed gas to provide heat for distillation, heat coupling is achieved. This reduces the heat generated by the fuel gas for desulfurization of cracked gas, methane reforming, steam production, and methanol distillation, thereby reducing the proportion of cracked gas used as fuel gas, increasing the proportion of cracked gas used to synthesize methanol, and increasing methanol production. 3. The heat recovery step can use the heat of the reformed feed gas to heat water to generate steam for methane reforming, and the methanol distillation step can use the heat of the feed gas to provide heat for distillation, thus realizing the coupled use of heat, improving the heat utilization rate, reducing the amount of external heat supply, and reducing heat loss. 4. The heat exchanged fuel gas is used to provide heat for the drying of biomass, which realizes further utilization of heat, improves the heat utilization rate of the entire biomass production process of green methanol, and reduces heat loss. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a system for producing green methanol from biomass according to an embodiment of this application.

[0027] Figure 2 This is a flowchart of a process for producing green methanol from biomass according to an embodiment of this application.

[0028] Explanation of reference numerals in the attached diagram: 1. Crushing module; 2. Drying module; 3. Pyrolysis furnace; 4. Photovoltaic coke removal furnace; 5. CH4 converter; 6. Heat exchange module; 7. Purification and dust removal module; 8. Gas holder; 9. Desulfurization module; 10. Heat recovery module; 11. Decarbonization module; 12. Methanol synthesis module; 13. Methanol distillation column; 14. Pyrolysis gas power supply module; 141. Third blower; 142. Pyrolysis kiln hot air furnace; 143. Catalytic kiln hot air furnace; 15. First blower; 16. Second blower; 17. Storage tank; 18. Compressor. Detailed Implementation

[0029] The following will be combined with the appendix Figure 1-2 The technical solutions in the embodiments of the present invention are further described in detail below. The described embodiments are only possible technical implementations of the present invention, but are not limited thereto. Those skilled in the art can certainly combine the embodiments of the present invention to obtain other embodiments without creative effort, which are also within the protection scope of the present invention.

[0030] This application mainly adopts the "multi-stage heat exchange coupling heat utilization of cracked gas" scheme, which achieves the effect of "realizing heat coupling in methanol production and improving heat utilization rate". The following is a further detailed description of this application.

[0031] Reference Figure 1 This application provides a system for producing green methanol from biomass, including a crushing module 1, a drying module 2, a dry distillation and cracking furnace 3, a photoelectric coke removal furnace 4, a heat exchange module 6, a purification and dust removal module 7, a gas holder 8, a desulfurization module 9, a CH4 conversion furnace 5, a heat recovery module 10, a decarbonization module 11, a methanol synthesis module 12, a methanol distillation column 13, and a cracked gas power supply module 14.

[0032] The crushing module 1 can use equipment such as crushers to pulverize and refine biomass. There are various types of crushers, such as hammer crushers and jaw crushers. Different types of crushers are suitable for different types of biomass and can pulverize biomass into suitable particle sizes to facilitate subsequent gasification reactions.

[0033] The crushed biomass pellets are conveyed to the drying module 2 by a conveying device, which includes, but is not limited to, a conveyor belt device or a propeller conveyor device. In this embodiment, the drying module 2 includes a rotary kiln dryer, where the pellets come into full contact with hot air and the moisture evaporates quickly.

[0034] The dried biomass pellets enter the dry distillation and pyrolysis furnace 3. The dry distillation and pyrolysis furnace 3 gasifies the pulverized biomass to produce pyrolysis gas and removes solid carbon. The pyrolysis gas produced by the dry distillation and pyrolysis furnace 3 is introduced into the photocatalytic coke removal furnace 4 through a pipeline. The photocatalytic coke removal furnace 4 combines the core principle of photocatalysis technology with reactor design optimization to achieve efficient tar decomposition.

[0035] Reference Figure 2 The high-temperature pyrolysis gas, after being decoked in the photoelectric decoking furnace 4, enters the heating system of the CH4 converter 5. The high-temperature pyrolysis gas in the heating system heats and reacts with the components in the reactor of the CH4 converter 5. This heating process between the high-temperature pyrolysis gas and the components in the reactor achieves the first heat exchange, resulting in a decrease in the temperature of the pyrolysis gas. After heat exchange in the heating system of the CH4 converter 5, the pyrolysis gas enters the heat exchanger in the heat exchange module 6 for a second heat exchange.

[0036] After secondary heat exchange, the pyrolysis gas enters the purification and dust removal module 7. In this embodiment, the purification and dust removal module 7 includes a spray scrubbing tower. The pyrolysis gas undergoes dust removal and cooling in the spray scrubbing tower. The scrubbing water, carrying ash, enters the circulating water system for concentration, cooling, and recycling. The pyrolysis gas exiting the scrubbing tower enters two sets of parallel filters for final filtration. The filters have a self-cleaning function and can be switched periodically.

[0037] The purified and dust-removed pyrolysis gas is transported to the gas holder 8 for storage via the first blower 15. In this embodiment, the first blower 15 is a vortex blower. The pyrolysis gas in the gas holder 8 is divided into two parts: A portion of the cracked gas is used as fuel gas and is introduced into the dry distillation cracking furnace 3 and the photocatalytic coke removal furnace 4 through the cracked gas power supply module 14. The cracked gas power supply module 14 includes a third blower 141, a dry distillation kiln hot air furnace 142, and a catalytic kiln hot air furnace 143. The third blower 141 delivers the cracked gas to the dry distillation kiln hot air furnace 142 and the catalytic kiln hot air furnace 143. The hot air generated by the dry distillation kiln hot air furnace 142 provides heat to the dry distillation cracking furnace 3 and then enters the rotary kiln dryer in the drying module 2 to dry the biomass. The hot air generated by the catalytic kiln hot air furnace 143 provides heat to the photocatalytic catalysis in the photocatalytic coke removal furnace 4 and then enters the rotary kiln dryer in the drying module 2 to dry the biomass. A portion of the fuel gas is also fed into the heating system within CH4 converter 5 to provide heat for the reaction within the reactor. The heat required for the reaction within CH4 converter 5 mainly consists of two parts: the heat released during the first heat exchange of the high-temperature cracked gas, and the heat from the combustion of the cracked gas. Of these two parts, the heat released by the high-temperature cracked gas accounts for the majority of the heat required within CH4 converter 5. The flue gas produced by combustion within CH4 converter 5 exits CH4 converter 5 and goes to the rotary kiln dryer in drying module 2 to dry the biomass.

[0038] Another portion of the cracked gas is used as methanol synthesis gas. After being compressed by compressor 18, it is sent to the heat exchanger of heat exchange module 6. After heat exchange, it enters desulfurization module 9 for methanol synthesis. Most of the cracked gas in gas tank 8 is used as methanol synthesis gas.

[0039] The exhaust ports of the dry distillation pyrolysis furnace 3, the photoluminescent coke removal furnace 4, and the CH4 converter 5 are all connected to the air inlet of the rotary kiln dryer through pipes. This allows the hot air discharged from the dry distillation pyrolysis furnace 3 and the photoluminescent coke removal furnace 4, along with the flue gas discharged from the CH4 converter 5, to be introduced into the rotary kiln dryer in the drying module 2 through pipes to heat and dry the biomass. The air outlet of the rotary kiln dryer in the drying module 2 is connected to a second fan 16 through a pipe. The second fan 16 discharges the flue gas after drying. In this embodiment, the second fan 16 is an induced draft fan.

[0040] In this embodiment, the desulfurization module 9 is a dry desulfurization tower. The dry desulfurization tower utilizes solid desulfurizing agents (such as activated carbon, iron oxide, zinc oxide, etc.) to adsorb or chemically react with hydrogen sulfide (H2S) and other sulfides in the gas, fixing the sulfides on the desulfurizing agent and realizing the gas desulfurization process.

[0041] After desulfurization, the cracked gas is mixed with water vapor and then enters the reactor of CH4 converter 5. The high-temperature cracked gas in the heating system heats the cracked gas, water vapor and other components entering CH4 converter 5. The cracked gas undergoes a methane reforming reaction in CH4 converter 5 to generate feed gas. The photoluminescent coke removal furnace 4 is connected to CH4 converter 5, so that the high-temperature cracked gas from photoluminescent coke removal furnace 4 provides high-temperature heat to CH4 converter 5.

[0042] The raw gas enters the heat recovery module 10. In this embodiment, the heat recovery module 10 is a waste heat boiler. The raw gas is fed into the boiler water preheater of the waste heat boiler to heat the boiler water in the evaporator to generate steam, which then heats the steam in the superheater. The steam then enters the boiler water preheater for further cooling. The steam is then piped into the desulfurized cracked gas to provide steam for the methane reforming reaction. The raw gas is piped into the pre-column of the methanol distillation column 13 to heat the reboiler of the methanol distillation column 13 and the crude methanol, providing heat for the distillation of crude methanol. After heat exchange, the temperature of the raw gas decreases, and it returns to the demineralized water preheater of the heat recovery module 10 for further heat exchange and cooling. The cooled gas undergoes gas-liquid separation. During the cooling process, gas-liquid separation is performed stage by stage to separate the condensate from the raw gas. The raw gas then goes to the decarbonization module 11 to partially remove CO2.

[0043] In this embodiment, the decarbonization module 11 is a decarbonization adsorption tower. Multiple towers are connected in parallel and selected adsorbents such as activated carbon, activated alumina, and molecular sieves to achieve a PSA (pressure swing adsorption) partial decarbonization process for CO2. PSA partial decarbonization technology utilizes the difference in adsorption capacity of adsorbents for CO2 and other components (such as CH4, H2, etc.) in the feed gas, and achieves selective removal of CO2 through pressure changes.

[0044] The decarbonized feed gas enters the methanol synthesis module 12, which includes a low-pressure tubular methanol synthesis tower. The feed gas reacts under the action of a catalyst to produce crude methanol. The crude methanol then enters the methanol distillation tower 13, where it is purified by distillation to produce industrial methanol, which is then stored in the storage tank 17.

[0045] Reference Figure 2 This application also provides a process for producing green methanol from biomass, including the following steps: S1 biomass gasification involves gasifying biomass into pyrolysis gas containing CO, CO2, CH4, and H2, followed by char removal from the pyrolysis gas, including: S11 crushing involves feeding biomass raw materials into a crusher, which then crushes the biomass raw materials into particles with a diameter of ≤1cm. This crushing process does not require granulation of the biomass; it only requires crushing.

[0046] S12 drying involves conveying the pulverized biomass to a rotary kiln dryer for drying. The high-temperature gas required for drying comes from the hot air discharged from the dry distillation pyrolysis furnace 3 and the photoelectric coke removal furnace 4, as well as the hot flue gas discharged from the CH4 conversion furnace 5, achieving the coupled utilization of hot air heat. The moisture content of the dried biomass is ≤18% (by mass).

[0047] S13 pyrolysis: The dried biomass enters the pyrolysis furnace 3 for pyrolysis and gasification to form pyrolysis gas. The pyrolysis gas contains components such as CO, CO2, CH4, and H2. The outlet temperature of the pyrolysis gas is 700℃-800℃. Incompletely pyrolyzed residual carbon and ash are discharged from the pyrolysis furnace 3 together and stored as by-products. The hot air generated by the pyrolysis furnace 3 is introduced into the rotary kiln dryer as hot air for drying the biomass.

[0048] S14 decoking involves passing the pyrolysis gas generated in the dry distillation pyrolysis furnace 3 into the photoelectric decoking furnace 4 for decoking. The outlet temperature of the decoking gas is ≤850℃, the methane content is 22%-25% (volume), and the tar content is <0.1% (mass). The hot air generated in the photoelectric decoking furnace 4 is passed into the rotary kiln dryer as hot air for drying biomass.

[0049] In the first heat exchange (S2), the high-temperature pyrolysis gas from the photoluminescent coke oven 4 is introduced into the heating system of the CH4 converter 5, where it undergoes its first heat exchange with the components within the CH4 converter 5 reactor. The components in the CH4 converter 5 reaction zone act as a cooling medium to cool the pyrolysis gas, while the pyrolysis gas, in turn, heats the components in the CH4 converter 5 reaction zone. The high-temperature pyrolysis gas cools down after the first heat exchange. The flue gas discharged from the CH4 converter 5 is then introduced into the drying module 2 as hot air for biomass drying.

[0050] The second heat exchange in S3 involves the pyrolysis gas, after the first heat exchange, entering the heat exchanger and exchanging heat with the cooling medium in the heat exchanger's heat exchange coil. The medium in the heat exchange coil heats up, while the temperature of the pyrolysis gas further decreases to the dust removal and purification temperature.

[0051] S4 dust removal and purification involves passing the pyrolysis gas after the second heat exchange into a bag filter for purification and dust removal.

[0052] The storage and diversion of S401 cracked gas: The cracked gas after dust removal and purification is transported to the gas holder 8 for storage by the first fan 15. Part of the cracked gas stored in the gas holder 8 is used as fuel gas, and the other part is used as raw material for methanol synthesis. The ratio of cracked gas participating in methanol synthesis to cracked gas participating in combustion is ≥5:1 (volume). This allows for the rational allocation of cracked gas usage. While ensuring sufficient raw material gas for methanol synthesis, it also provides the required heat for key steps in the production process, improving the comprehensive utilization rate of cracked gas and reducing the additional input of external energy. This embodiment takes a cracked gas to combustion ratio of 5:1 as an example.

[0053] Fuel gas is introduced into the hot blast stove 142 of the dry distillation kiln and the hot blast stove 143 of the catalytic kiln via a third blower for combustion to produce high-temperature gas. The hot air generated by the hot blast stove 142 of the dry distillation kiln provides heat to the dry distillation cracking furnace 3, and then enters the rotary kiln dryer in the drying module 2 to dry the biomass. The hot air generated by the hot blast stove 143 of the catalytic kiln provides heat to the photocatalytic process in the photocatalytic decoking furnace 4, and then also enters the rotary kiln dryer in the drying module 2 to dry the biomass, thus meeting the operational needs of the dry distillation cracking furnace 3 and the photocatalytic decoking furnace 4. A portion of the fuel gas is also directly introduced into the heating system of the CH4 converter 5 and used as fuel for the CH4 converter 5.

[0054] By using the flue gas generated from biomass pyrolysis, biomass decoking, and methane reforming to provide heat for biomass drying, flue gas heat coupling is achieved, enabling further utilization of heat and improving the heat utilization rate of the entire biomass-to-green methanol production process while reducing heat loss.

[0055] By using the first heat exchange, the second heat exchange, the heating of water with feed gas to generate steam, and the heat from the feed gas to provide heat for distillation, heat coupling is achieved. This reduces the heat generated by the fuel gas for desulfurization of cracked gas, methane reforming, steam production, and methanol distillation, thereby reducing the proportion of cracked gas used as fuel gas, increasing the proportion of cracked gas used to synthesize methanol, and increasing methanol production.

[0056] S5 desulfurization involves desulfurizing the cracked gas. The cracked gas, which is separated from the gas holder 8 and participates in methanol synthesis, is compressed by the compressor 18 and then introduced into the heat exchange coil in the heat exchanger as the cooling medium for the second heat exchange. Through the second heat exchange, the cracked gas reaches the temperature required for desulfurization. The cracked gas is then introduced into the dry desulfurization tower for dry desulfurization. The temperature of dry desulfurization is 320℃, and the sulfur content in the desulfurized cracked gas is ≤0.1ppm.

[0057] In S6 methane reforming, the desulfurized cracked gas is mixed with water vapor to form syngas. The cracked gas and water vapor are then introduced into the reaction zone of CH4 reformer 5. The cracked gas entering the combustion zone of CH4 reformer 5 provides heat for the methane reforming reaction. Under the action of a catalyst, the cracked gas and water vapor undergo methane reforming to produce CO and H2, thereby increasing the H2 and CO content in the cracked gas and achieving a rough adjustment of the H2 / CO ratio in the cracked gas. After the reforming reaction, feed gas is generated. The CH4 content in the feed gas at the outlet of CH4 reformer 5 is <3% (by volume), and the pressure is 1.8-2.0 MPa.

[0058] S7 methanol is generated, and methanol is synthesized from the reformed feed gas, including the following steps: In heat recovery S71, the reformed feed gas is fed into the waste heat boiler, then into a steam superheater and waste boiler to produce steam. It then enters the boiler water preheater for further cooling. The steam is piped into the desulfurized cracked gas to provide steam for the methane reforming reaction. The feed gas then goes to the heat exchanger in methanol distillation column 13 for heat exchange and cooling, heating the crude methanol from step S74 to provide heat for its distillation. The heat-exchanged feed gas returns to the demineralized water preheater in heat recovery module 10 for further heat exchange and cooling. The cooled gas undergoes gas-liquid separation to remove condensate, and then the feed gas goes to decarbonization module 11.

[0059] S72 decarbonization: The heat-exchanged feed gas enters the decarbonization adsorption tower and undergoes partial decarbonization via PSA. The CO2 content in the decarbonized feed gas is 2%-3% (by volume), and the hydrogen-to-carbon ratio in the feed gas is adjusted.

[0060] In S73 methanol synthesis, the decarbonized feed gas enters the methanol synthesis tower. CO and H2 in the feed gas undergo a synthesis reaction under the action of a catalyst to produce crude methanol. The water content in the crude methanol is 3%-10% (by mass).

[0061] S74 Methanol distillation: The crude methanol generated in the methanol synthesis tower is fed into the methanol distillation tower 13 to distill the crude methanol into industrial methanol. The feed gas in step S71 heats the crude methanol to provide heat for methanol distillation.

[0062] S75 Methanol storage: The industrial methanol generated in step S74 is stored in methanol storage tank 17.

[0063] The heat recovery step can use the heat of the reformed feed gas to heat water to generate steam for methane reforming, thus realizing heat recovery and utilization; the decarbonization step can adjust the composition of the feed gas, which is beneficial to subsequent methanol synthesis; the methanol distillation step uses the heat of the feed gas to provide heat for distillation, realizing heat coupling utilization, improving heat utilization rate, reducing the amount of external heat supply, and reducing heat loss.

[0064] Taking biomass as wood chips and straw as an example, the relationship between the above process and methanol production is as follows: Biomass types Methanol quantity / ton Consumption / ton Wood chips with a moisture content of 36-40% 1 44-5 Straw with a moisture content of 20-30% 1 3-4 The implementation principle of a biomass-to-green methanol production process in this embodiment is as follows: This embodiment achieves the production of green methanol from biomass through a series of treatments, including gasification, multiple heat exchange, dust removal and purification, desulfurization, methane reforming, and methanol generation. In the heat exchange stage, the heat from the cracked gas is used to provide energy for subsequent desulfurization and methane reforming, reducing the need for external systems to provide additional heat to these stages. This ensures full utilization of the heat from the cracked gas, reduces heat loss in the methanol production system, and improves heat utilization efficiency. Compared with existing technologies, this represents a significant improvement, is more energy-efficient and environmentally friendly, and has good practicality and economic benefits.

[0065] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A process for producing green methanol from biomass, characterized in that: Includes the following steps: S1 biomass gasification involves gasifying biomass into pyrolysis gas containing CO, CO2, CH4, and H2, and then removing char from the pyrolysis gas. The first heat exchange in S2 involves heat exchange between the decoked pyrolysis gas and the cooling medium to reduce the temperature. S3 Second heat exchange: The cracked gas after the first heat exchange is exchanged with the cooling medium again, and the temperature of the cracked gas is further reduced to the dust removal and purification temperature. S4 dust removal and purification system purifies and removes dust from pyrolysis gas; S5 desulfurization involves desulfurizing the pyrolysis gas. In this step, the pyrolysis gas is used as the cooling medium in step S3 for heat exchange, so that the pyrolysis gas is heated to the temperature required for desulfurization. In S6 methane reforming, the desulfurized cracked gas is mixed with water vapor to form syngas, and a reforming reaction occurs to generate feed gas. The syngas in this step serves as the cooling medium in step S2 and exchanges heat with the cracked gas to provide heat for the methane reforming reaction. S7 methanol is generated, and methanol is synthesized from the reformed feed gas.

2. The process for producing green methanol from biomass according to claim 1, characterized in that: Step S7 includes the following steps: S71 heat recovery involves exchanging heat between the reformed feed gas and water to cool it down, and heating the water to generate steam, which provides steam for the methane reforming in step S6, and then exchanging heat with the cooling medium to cool it down. S72 decarbonization is used to decarbonize the feed gas after heat recovery. S73 methanol synthesis involves the decarbonized feed gas undergoing a synthesis reaction to produce crude methanol, which contains 3%-10% (by mass) of water. S74 Methanol distillation: Crude methanol is distilled to produce industrial methanol. Crude methanol is used as the cooling medium in step S61, which heats the crude methanol with the feed gas, providing heat for methanol distillation.

3. The process for producing green methanol from biomass according to claim 1, characterized in that: Step S1 includes: S11 pulverization is used to pulverize biomass, and the particle diameter of the pulverized biomass is ≤1cm. S12 drying, drying and pulverizing biomass, the moisture content of the dried biomass is ≤18% (by mass). S13 pyrolysis: pulverized biomass is pyrolyzed to generate pyrolysis gas; S14 removes tar from the pyrolysis gas.

4. The process for producing green methanol from biomass according to claim 3, characterized in that: After step S4, step S401 is added for the storage and diversion of cracked gas. In step S401, the cracked gas after dust removal and purification is stored and divided into two parts. One part is cracked to remove sulfur in step S5 and participates in methanol synthesis. The other part of the cracked gas is used as fuel gas to provide heat for biomass cracking in step S13, biomass decoking in step S14, and methane reforming in step S6. The ratio of cracked gas participating in methanol synthesis to cracked gas participating in combustion is ≥5:1 (by volume).

5. The process for producing green methanol from biomass according to claim 3, characterized in that: The hot air generated during the biomass pyrolysis in step S13, the decoking of biomass in step S14, and the methane reforming in step S6 is transported to step S12 to provide heat for the drying of biomass.

6. The process for producing green methanol from biomass according to claim 3, characterized in that: In step S13, the biomass is pyrolyzed in the absence of air to produce pyrolysis gas containing CO, CO2, CH4, and H2, as well as solid carbon. The fixed carbon is then cleaned up, and the discharge temperature of the pyrolysis gas is 700-800℃.

7. The process for producing green methanol from biomass according to claim 3, characterized in that: In step S14, the cracked gas is decoked by photocatalytic decoking. After decoking, the outlet temperature of the cracked gas is ≤850℃, the CH4 content is 22%-25% (volume), and the tar content is <0.1% (mass).

8. The process for producing green methanol from biomass according to claim 1, characterized in that: In step S5, the pyrolysis gas is desulfurized using a dry method at a temperature of 320℃, and the sulfur content in the desulfurized pyrolysis gas is ≤0.1ppm.

9. The process for producing green methanol from biomass according to claim 2, characterized in that: In step S72, the decarbonization method of the raw gas is PSA partial decarbonization, and the CO2 content in the decarbonized raw gas is 2%-3% (by volume).

10. A system for producing green methanol from biomass using the aforementioned process, characterized in that: It includes a crushing module (1), a drying module (2), a dry distillation and cracking furnace (3), a photoelectric coke removal furnace (4), a CH4 converter (5), a heat exchange module (6), a purification and dust removal module (7), a gas holder (8), a desulfurization module (9), a heat recovery module (10), a decarbonization module (11), a methanol synthesis module (12), a methanol distillation tower (13), and a cracked gas power supply module (14); Biomass is processed through a pulverizing module (1), a drying module (2), and a dry distillation and pyrolysis furnace (3) to generate pyrolysis gas; The cracked gas is decoked by the photoluminescent coke decoking furnace (4), cooled by the heating system of the CH4 converter (5), cooled by the heat exchange module (6), and dusted by the purification and dust removal module (7) before being stored in the gas holder (8). The cracked gas in the gas holder (8) is heated by the cracked gas power supply module (14) for the dry distillation cracking furnace (3), the photoelectric coke removal furnace (4), and the CH4 converter (5); The cracked gas in the gas holder (8) is heated by the heat exchange module (6), desulfurized by the desulfurization module (9), and generated as raw material gas in the reactor of the CH4 converter (5); The raw gas is heated by steam in the heat recovery module (10), heated by crude methanol in the methanol distillation column (13), and decarbonized in the decarbonization module (11) before entering the methanol synthesis module (12) to synthesize crude methanol. Crude methanol is converted into industrial methanol and stored in a methanol distillation column (13).

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