A process and system for preparing green methanol and co-producing carbon dioxide

Abstract

The present invention discloses a process and system for preparing green methanol and co-producing carbon dioxide. The process of the present invention includes the steps of new energy power generation, water electrolysis, biomass power generation, carbon dioxide purification, biomass gasification, methanol synthesis and methanol distillation. By setting up the coupling of biomass power generation and biomass gasification, a part of the primary CO2 product obtained after the purification operation of CO2 generated by biomass combustion power generation is sent to biomass gasification, and the other part can be obtained after the CO2 distillation operation to obtain food-grade CO2 product for external delivery, which has extremely high carbon source utilization and single-pass conversion rate. By setting up the combined power supply of new energy power generation and biomass power generation, the volatility and instability of wind and solar new energy power generation can be compensated, and the power reliability of the chemical plant is more stable than the process scheme of simple new energy power generation for hydrogen production and chemicals, which can overcome the problem of the stability of new energy power generation affected by weather, climate, etc.

Description

Technical Field

[0001] The present invention relates to the field of new energy power generation technology, and specifically to a process and system for producing green hydrogen by utilizing renewable energy, coupled with biomass gasification and biomass power generation to produce green methanol and co-produce carbon dioxide. Background Art

[0002] Currently, fossil fuels such as coal and oil dominate the power industry in both the global and domestic energy mixes. Coal and natural gas consumption is high, and thermal power generation has become a major source of harmful emissions, posing a threat to energy development and the ecological environment. Furthermore, fossil energy sources are facing the risk of depletion within the foreseeable future. Against the backdrop of current energy challenges, the development of clean and renewable energy sources is gaining increasing attention. Clean and renewable energy sources offer sufficient energy supply. Replacing fossil fuel power generation with clean and renewable energy sources can reduce environmental pollution from fossil fuels, alleviate the imbalance between energy supply and demand, and effectively address the issue of energy depletion.

[0003] Hydrogen is a high-quality, clean, large-scale energy storage carrier, and methanol is considered an ideal hydrogen carrier. Using renewable green electricity to produce green methanol (hereinafter referred to as green methanol) eliminates complex process steps such as coal gasification and purification and reduces fixed asset investment. Water is directly electrolyzed into high-purity hydrogen and oxygen. Hydrogen reacts with carbon dioxide and carbon monoxide formed from biomass combustion to produce green methanol in a single step. The high-purity oxygen generated by electrolysis can be used for steelmaking and coal chemical processes, greatly reducing the energy consumption of traditional air separation oxygen production. The green methanol product can be used for zero-carbon ocean shipping or downstream chemicals such as zero-carbon olefins and zero-carbon aromatics. Producing green hydrogen from renewable green electricity is driving the chemical industry's zero-carbon transformation and upgrading.

[0004] It cannot be ignored that the large-scale development of renewable energy is subject to two limitations: on the one hand, it is difficult to transmit green electricity from remote areas with abundant renewable energy, and the cost of large-scale ultra-high voltage transmission is high. This problem can be solved by adopting suitable energy storage carriers (such as methanol); on the other hand, the volatility and imbalance of renewable power production will lead to increasing difficulties in grid balancing and absorption. Although electrochemical energy storage can provide system balancing capacity, this will lead to continued increases in system costs. Summary of the Invention

[0005] In response to the above problems, the present invention provides a process and system for producing green hydrogen using renewable energy, coupled with biomass gasification and biomass power generation to produce green methanol and co-produce carbon dioxide. By coupling biomass gasification and biomass power generation, the CO content in the green alcohol synthesis feed gas is increased, thereby further improving the carbon source conversion rate; renewable energy power generation is combined with biomass power generation to ensure the power stability and reliability of the overall process and system; and carbon dioxide is co-produced to achieve carbon emission reduction.

[0006] Specifically, on the one hand, the process for preparing green methanol and co-producing carbon dioxide of the present invention includes new energy power generation, water electrolysis, biomass power generation, carbon dioxide purification, biomass gasification, methanol synthesis and methanol distillation, wherein:

[0007] The renewable energy power generation: using wind energy and / or solar energy to generate green electricity, which is first supplied to the water electrolysis process, and the remaining electricity is transmitted to the power grid;

[0008] The electrolysis of water: electrolysis of water generates green hydrogen and oxygen;

[0009] Biomass power generation: biomass is burned under the action of a combustion aid to generate electricity, which is then fed to the power grid. Part of the oxygen generated in the water electrolysis process is mixed with air as a combustion aid and fed into the biomass power generation process. The first flue gas generated by the combustion is desulfurized and denitrified to generate a second flue gas, which is then fed into the carbon dioxide purification process.

[0010] The carbon dioxide purification includes purification and refining operations. The second flue gas is purified to obtain a primary CO2 product. The primary CO2 product is divided into two streams. One stream is mixed with another part of the oxygen generated in the water electrolysis process and input into the biomass gasification process as a gasifying agent. The other stream is refined to obtain a food-grade CO2 product.

[0011] The biomass gasification: biomass is gasified under the action of a gasifying agent to generate a first synthesis gas;

[0012] Methanol synthesis: The hydrogen obtained in the water electrolysis process is compressed and mixed with the compressed first synthesis gas to obtain a raw gas, and the raw gas reacts to generate crude methanol;

[0013] The methanol distillation: the crude methanol is separated and purified to obtain a high-quality green methanol product;

[0014] The method further includes inputting saturated steam produced as a by-product of the biomass gasification process and the methanol synthesis process into the biomass power generation process to generate electricity after the first flue gas is superheated.

[0015] In the above technical solution, biomass power generation and biomass gasification are coupled, and this coupling is manifested in the following aspects:

[0016] First, part of the biomass used in the present invention is used for combustion in the biomass power generation process to generate electricity, and the other part of the biomass is used in the biomass gasification process to produce the first synthesis gas for green alcohol synthesis.

[0017] Optionally, in the process of the present invention, the mass ratio of the biomass input to the biomass power generation step and the biomass gasification step is 1:(0.2-3). In actual production, the carbon source proportion of the gasifying agent input to the biomass gasification step can be controlled by adjusting the distribution ratio of the biomass in the biomass power generation step and the biomass gasification step, and further controlling the CO content in the first synthesis gas to meet the process requirements and carbon source demand in the subsequent methanol synthesis step.

[0018] Optionally, the biomass used in the present invention includes various organisms produced by photosynthesis using the atmosphere, water, land, etc., and can further be biomass straw.

[0019] Secondly, the primary CO2 product obtained after the biomass undergoes purification operations in the biomass power generation process and the carbon dioxide purification process has a CO2 purity of over 99.5%, with the remainder being N2 and H2O. The purification process includes absorption and desorption. The primary CO2 product is divided into two streams:

[0020] One stream is mixed with a portion of the oxygen produced in the water electrolysis process to form a gasifying agent, which is then fed into the biomass gasification process. The gasifying agent comprises high-purity CO2, oxygen, and water vapor. In the biomass gasification process, the biomass generates CO and hydrogen under the action of the gasifying agent, while the CO2 in the gasifying agent is also partially reduced. The resulting first synthesis gas from the biomass gasification process is a CO2-rich mixed gas comprising CO2, CO, and hydrogen. The first synthesis gas is compressed and fed into the methanol synthesis process.

[0021] Another stream of primary CO2 product is refined to produce a food-grade CO2 product that meets the food-grade CO2 requirements of GB1886.228-2016, with a CO2 purity of ≥99.9%. The refining operation includes adsorption and distillation. Optionally, the food-grade CO2 is stored in a liquid form in a storage tank after supercooling to facilitate product storage and output. Optionally, the food-grade CO2 product can be used as feed gas for subsequent dry ice production. In actual production, the production of green alcohol and dry ice can be flexibly adjusted according to market demand.

[0022] The present invention uses a mixture of the primary CO2 product and oxygen as the gasifying agent, avoiding the introduction of nitrogen oxide impurities into the first syngas by using air as the gasifying agent, further simplifying the process. Furthermore, the first syngas is a CO2-rich mixture containing CO, so the methanol synthesis process utilizes a CO2-rich methanol synthesis process. Compared to the 25% to 30% per-pass conversion rate of pure CO2-based methanol production processes, the present invention significantly improves the methanol per-pass conversion rate to nearly 50%.

[0023] Optionally, the molar ratio of CO in the first synthesis gas is 1% to 70%. In the actual production process, the proportion of the primary CO2 product stream input into the biomass gasification process can be determined according to the demand for carbon source in the methanol synthesis process, and the proportion of CO in the first synthesis gas and the output of the food-grade CO2 product of the present invention can be further regulated.

[0024] Through the coupling of biomass power generation and biomass gasification, it can be seen that no matter whether the biomass power generation process or the biomass gasification process is input, the carbon source in the biomass used in the process flow of the present invention is not directly discharged into the atmosphere, but all the carbon source in the biomass is used to prepare green alcohol products and co-produced CO2 products. Therefore, the process of the present invention has an extremely high carbon source utilization rate.

[0025] Optionally, the biomass gasification process adopts a circulating fluidized bed gasification process, with a gasification temperature of 560-1400° C. and a gasification pressure of 0-6500 KPaG.

[0026] In the above technical solution, a technical feature of combining new energy power generation and biomass power generation is set up.

[0027] The reaction equations for preparing methanol using CO2 and CO as raw materials are shown in (1) and (2) respectively:

[0028]

[0029]

[0030] As can be seen from reaction formulas (1) and (2), the amount of hydrogen required for the subsequent green alcohol synthesis is relatively large. Therefore, the green electricity obtained from the new energy power generation process will be supplied to the water electrolysis process first for electrolysis to produce hydrogen and oxygen, and the remaining electricity will be delivered to the power grid to supply the electricity needs of other processes in the process flow of the present invention. Further considering the volatility and imbalance of wind and solar power generation and the continuous electricity demand of the subsequent green alcohol synthesis process, a biomass power generation process coupled with new energy power generation is provided in the process of the present invention. The electricity obtained from this process is delivered to the power grid to compensate for the volatility of the electricity used by the new energy power generation to supply the water electrolysis process, the methanol synthesis process and other processes, thereby ensuring that the electricity consumption of the process of the present invention is continuous and stable, making the process electricity consumption more stable and safe.

[0031] Furthermore, the combustion aid used in the biomass power generation process is formed by mixing a portion of the oxygen generated in the water electrolysis process with air. Optionally, the molar ratio of oxygen in the combustion-supporting gas is 5% to 99%. Compared to biomass power generation processes that directly use air as a combustion aid, the use of an oxygen-enriched combustion aid in the biomass power generation process of the present invention can reduce the content of nitrogen oxide impurities in the first flue gas, reduce the difficulty of subsequent desulfurization and denitrification operations, and simplify the process flow.

[0032] Optionally, part of the oxygen generated in the water electrolysis process is delivered as a product. In actual production, the distribution of the oxygen generated by the water electrolysis can be controlled in combination with the oxygen content in the combustion-supporting gas and the CO content in the first synthesis gas, and the oxygen product can be delivered.

[0033] Optionally, the water electrolysis process is carried out in an alkaline electrolytic cell; the operating temperature of the alkaline electrolytic cell is 85-95° C., and the operating pressure is 1.6-1.8 MPaG.

[0034] Optionally, a hydrogen storage process is further included to store the hydrogen generated in the water electrolysis process and to input hydrogen into the methanol synthesis process. The storage capacity of the hydrogen storage device will be calculated and matched according to the load curve of the local wind power generator set and / or photovoltaic generator set and the allowable load of the downstream chemical device to ensure that in actual production, when the output of the new energy power generation process is small and the hydrogen production is reduced, the process of the present invention can also be guaranteed to operate at high load, thereby reducing the risk of device shutdown, improving the operating load and annual operating hours of the overall process, and increasing the production of green alcohol.

[0035] In the above technical solution, the biomass power generation process utilizes an extraction-condensing steam turbine generator set, and the extracted steam generated by power generation is fed into the methanol synthesis process, the methanol distillation process, and the carbon dioxide purification process. The present invention process feeds the saturated steam produced as a by-product of biomass gasification and methanol synthesis into the biomass fuel power generation process, where it is superheated to generate electricity. The steam extracted and condensed by the extraction-condensing steam turbine generator set is then fed into the methanol synthesis process, the methanol distillation process, and the carbon dioxide purification process via pipelines. This eliminates the need for a separate steam generation system, reduces equipment investment and floor space, and achieves cascaded energy utilization.

[0036] It should be noted that the first flue gas in the present invention includes nitrogen, CO2, part of water vapor and unreacted O2, as well as trace amounts of nitrogen oxides and SO2; the second flue gas after desulfurization and denitrification treatment removes nitrogen oxides and SO2.

[0037] Specifically, on the other hand, the system for preparing green methanol and co-producing carbon dioxide of the present invention includes a new energy power generation device, a water electrolysis device, a biomass power generation device, a carbon dioxide purification device, a biomass gasification device, a methanol synthesis device and a methanol distillation device, wherein:

[0038] The new energy power generation device includes a wind turbine and / or a photovoltaic generator, which uses wind energy and / or solar energy to generate electricity. The electricity generated by the device is first supplied to the water electrolysis device, and the remaining part is transmitted to the power grid.

[0039] The water electrolysis device comprises an electrolytic cell, in which water is electrolyzed to produce hydrogen and oxygen;

[0040] The biomass power generation device includes a circulating fluidized bed boiler, an extraction-condensing steam turbine generator set, a desulfurization unit, and a denitrification unit. The biomass is burned under the action of a combustion-supporting agent to generate steam that drives the extraction-condensing steam turbine generator set to generate electricity, which is then transmitted to the power grid. Part of the oxygen generated by the water electrolysis device is mixed with air and fed into the circulating fluidized bed boiler as a combustion-supporting agent. The first flue gas generated by combustion in the circulating fluidized bed boiler passes through the desulfurization unit and the denitrification unit to generate a second flue gas. The second flue gas is fed into the carbon dioxide purification device through a pipeline.

[0041] The carbon dioxide purification device comprises a purification unit and a refining unit. The second flue gas is purified by the purification unit to obtain a primary CO2 product. The primary CO2 product is divided into two streams. One stream is mixed with a portion of the oxygen generated by the water electrolysis device and then input into the biomass gasification device as a gasifying agent; the other stream is refined by the refining unit to obtain a CO2 product.

[0042] The biomass gasification device comprises a circulating fluidized bed gasifier, a high-temperature gasification furnace and a waste heat boiler connected in sequence, wherein the biomass is gasified under the action of a gasifying agent to obtain a first synthesis gas;

[0043] The methanol synthesis device comprises a methanol synthesis tower, wherein the hydrogen generated by the electrohydrolysis device is compressed by a first compressor and then mixed with the first synthesis gas compressed by a second compressor, and crude methanol is generated in the methanol synthesis tower;

[0044] The methanol distillation device is used to purify and separate the crude methanol to obtain high-quality green methanol products;

[0045] The saturated steam produced as by-products of the biomass gasification unit and the methanol synthesis unit is respectively connected to the extraction-condensing steam turbine generator set after heat exchange with the first flue gas through pipelines.

[0046] Optionally, the system for preparing green methanol and co-producing carbon dioxide of the present invention further includes a hydrogen storage device for storing the hydrogen produced by the water electrolysis device and inputting the hydrogen into the methanol synthesis device.

[0047] Further optionally, the hydrogen storage device is a high-pressure gaseous hydrogen storage device or a liquid hydrogen storage device; further optionally, it is a high-pressure gaseous hydrogen storage device.

[0048] Optionally, the steam after extraction and condensation is connected to the methanol synthesis device, the methanol distillation device and the carbon dioxide purification device through pipelines.

[0049] Optionally, the extraction-condensing steam turbine generator set is a double extraction-condensing steam turbine generator set.

[0050] Optionally, in addition to the two branches for inputting the gasifying agent and the combustion-supporting gas, the oxygen output pipeline of the water electrolysis device is also provided with a third branch for externally delivering the oxygen product.

[0051] Optionally, there are multiple electrolytic cells; further, 4-5 electrolytic cells may be arranged as a group, and the electrolytic cells may be controlled in groups, so that the operation and start and stop of the water electrolysis device are more flexible, thereby improving the green hydrogen production efficiency.

[0052] Optionally, the electrolytic cell is an alkaline electrolytic cell.

[0053] Optionally, the carbon dioxide purification device further includes a supercooler for condensing the refined food-grade CO2 product to obtain a liquid food-grade liquid CO2 product.

[0054] Compared with the existing technology, the green methanol co-production carbon dioxide production process and system of the present invention has the following beneficial effects:

[0055] The present invention couples biomass power generation with biomass gasification. The CO2 generated by biomass combustion for power generation is not directly released into the atmosphere. Instead, it undergoes purification to produce a primary CO2 product. A portion of this primary CO2 product is fed to the biomass gasification process. The CO2-rich syngas, reduced by the gasification process, is mixed with high-pressure hydrogen produced by electrolytic hydrogen production and fed into a methanol synthesis unit to ultimately produce the green alcohol product. The remaining portion undergoes CO2 refining to produce a food-grade CO2 product for external delivery. Throughout the entire process, no carbon source from the biomass is directly released into the atmosphere, resulting in extremely high carbon source utilization. The present invention utilizes a CO2-rich methanol production process to significantly improve single-pass conversion rates.

[0056] This invention combines renewable energy and biomass power generation, utilizing wind and solar power generation for electrolytic hydrogen production, and biomass gasification to generate syngas rich in CO and hydrogen for green methanol synthesis. The electricity generated by biomass power generation is used to power chemical plants such as electrohydrolysis and methanol synthesis, compensating for the volatility and instability of wind and solar power generation. The power reliability of these chemical plants is more stable than a pure renewable energy power generation process for hydrogen and chemical production, overcoming the impact of weather and climate on the stability of renewable energy power generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0058] Figure 1 This is a schematic structural diagram of the green methanol co-production carbon dioxide system of the present invention.

[0059] The above drawings include the following reference numerals:

[0060] 1- New energy power generation device, 2- Water electrolysis device, 3- Biomass power generation device, 4- Carbon dioxide purification device, 41- Purification unit, 42- Refining unit, 5- Biomass gasification device, 6- Methanol synthesis device, 61- First compressor, 62- Second compressor, 7- Methanol distillation device, 8- Hydrogen storage device, 9- Power grid. DETAILED DESCRIPTION

[0061] The present invention will be further described below through specific embodiments and in conjunction with the accompanying drawings. It should be noted that in this embodiment, relational terms such as "first," "second," and the like are used solely to distinguish one component from another with the same name, and do not necessarily require or imply any actual relationship or order between these components. Features defined as "first," "second," and the like may explicitly or implicitly include one or more of these features.

[0062] In the description of the present invention, unless otherwise specified or limited, the term "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be internal communication between two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood based on specific circumstances.

[0063] Example 1

[0064] A system for preparing green methanol and co-producing carbon dioxide, the system comprises a new energy power generation device 1, a water electrolysis device, a biomass power generation device 3, a carbon dioxide purification device 4, a biomass gasification device 5, a methanol synthesis device and a methanol distillation device 7, wherein:

[0065] New energy power generation device 1: including a wind turbine generator set and / or a photovoltaic generator set, which uses wind energy and / or solar energy to generate electricity; the electricity generated by this device is first supplied to the water electrolysis device 2, and the remaining part is transmitted to the power grid 9;

[0066] Water electrolysis device 2: including an electrolytic cell, in which water is electrolyzed to produce hydrogen and oxygen;

[0067] Biomass power generation device 3: includes a circulating fluidized bed boiler, an extraction-condensing steam turbine generator set, a desulfurization unit, and a denitrification unit. Biomass combustion under the action of a combustion-supporting agent generates steam that drives the extraction-condensing steam turbine generator set to generate electricity, which is transmitted to the power grid 9. A portion of the oxygen generated by the water electrolysis device 2 is mixed with air and fed into the circulating fluidized bed boiler as a combustion-supporting agent. First flue gas generated by combustion in the circulating fluidized bed boiler passes through the desulfurization unit and the denitrification unit in sequence to produce second flue gas. The second flue gas is then fed into the carbon dioxide purification device 4 via a pipeline.

[0068] The carbon dioxide purification device 4 includes a purification unit 41 and a refining unit 42. The second flue gas is purified by the purification unit 41 to obtain a first CO2 product. The first CO2 product is divided into two streams. One stream is mixed with a portion of the oxygen generated by the water electrolysis device 2 and then input into the biomass gasification device 5 as a gasifying agent; the other stream is refined by the refining unit 42 to obtain a second CO2 product.

[0069] Optionally, the purification unit includes an absorption tower and a regeneration tower, and the refining unit includes an adsorption bed and a distillation tower.

[0070] Biomass gasification device 5: includes a circulating fluidized bed gasifier, a high-temperature gasification furnace and a waste heat boiler connected in sequence, and the biomass is gasified under the action of a gasifying agent to obtain a first synthesis gas;

[0071] Methanol synthesis unit 6: includes a methanol synthesis tower. The hydrogen generated by the electrohydrolysis unit is compressed by the first compressor 61 and then mixed with the first synthesis gas compressed by the second compressor 62 to produce crude methanol in the methanol synthesis tower.

[0072] Methanol distillation unit 7: used to purify and separate crude methanol to obtain high-quality green methanol products;

[0073] The saturated steam produced as by-products of the biomass gasification unit 5 and the methanol synthesis unit 6 is respectively connected to the extraction-condensing steam turbine generator set after heat exchange with the first flue gas through pipelines.

[0074] In the system for preparing green methanol and co-producing carbon dioxide of the present invention, steam from three sources, namely the biomass gasification unit 5, the methanol synthesis unit 6 and the circulating fluidized bed boiler, is superheated by the flue gas output by the circulating fluidized bed boiler and then enters the extraction-condensing steam turbine generator set to generate electricity.

[0075] Please note that Figure 1The figure shows a connection mode in which the saturated steam output pipelines of the biomass gasification device 5 and the methanol synthesis device 6 are merged, exchanged with the flue gas, and then input into the biomass power generation device 3. A person skilled in the art can, through non-creative labor, set up a connection mode in which the saturated steam output pipelines of the biomass gasification device 5 and the methanol synthesis device 6 are respectively exchanged with the flue gas, and then input into the biomass power generation device 3 for power generation. The technical solution thus formed falls within the scope of protection of the present invention.

[0076] Optionally, the system for preparing green methanol and co-producing carbon dioxide of the present invention further includes a hydrogen storage device 8 for storing hydrogen produced by the water electrolysis device 2 and inputting the hydrogen into the methanol synthesis device 6.

[0077] Optionally, the steam after extraction and condensation is connected to the methanol synthesis device 6, the methanol distillation device 7 and the carbon dioxide purification device 4 through pipelines.

[0078] Optionally, the water electrolysis device 2 is further provided with a third branch for delivering oxygen products.

[0079] Optionally, the extraction-condensing steam turbine generator set is a double-extraction-condensing steam turbine generator set.

[0080] Example 2

[0081] This example demonstrates a process flow for producing green methanol and co-producing carbon dioxide under specific working conditions using the system for producing green methanol and co-producing carbon dioxide as shown in Example 1. It should be noted that this process flow is merely a demonstration of a preferred process and does not limit the scope of protection of the present invention.

[0082] New energy power generation: wind turbines and photovoltaic generators are used to generate electricity.

[0083] Electrohydrolysis: The electricity generated by the renewable energy power generation process is used for electrolysis of water. The electricity generated by the biomass power generation process can also be used through the power grid 9. This process is carried out in an alkaline electrolytic cell. The optimal operating temperature of the alkaline solution in the electrolytic cell is about 85-95°C, and the operating pressure of the electrolytic cell is 1.6-1.8MPaG. The amount of pure hydrogen produced by water electrolysis is 122,000-162,000Nm 3 / h.

[0084] Biomass Power Generation: This process utilizes a circulating fluidized bed boiler and a double-extraction condensing steam turbine generator set. The biomass input to this process has a low-grade calorific value of approximately 14.68 MJ / kg, and the biomass boiler consumes 35,000-45,000 kg / h of steam. Steam generated through direct biomass combustion is 80-100 t / h, while 5.0 MPaG steam byproduct from the biomass gasification process accounts for approximately 60-90 t / h, and 5.0 MPaG steam byproduct from the methanol synthesis process accounts for approximately 60-90 t / h. Steam from these three sources is superheated by the flue gas output of the circulating fluidized bed boiler and then fed into the double-extraction condensing steam turbine generator set to generate 30-50 MW of power.

[0085] The first-stage extraction steam of the double-extraction condensing steam turbine generator set is 1.1MPaG, 50-60t / h, and the second-stage extraction steam is 0.5MPaG, 63-83t / h. These two parts of extraction steam will be used for methanol distillation, methanol synthesis and carbon dioxide purification processes. The steam reuse process has been fully coupled through calculation.

[0086] A portion of the oxygen generated in the water electrolysis process is mixed with air as a combustion aid and fed into the biomass power generation process. The molar ratio of oxygen in the combustion aid is 5% to 99%. The first flue gas generated by combustion is desulfurized and denitrified to produce a second flue gas, which is fed into the carbon dioxide purification process.

[0087] Under normal operating conditions of the process of this embodiment, the electricity consumption of methanol synthesis, methanol distillation and other processes is about 40-55Mw, and the power generation capacity of the circulating fluidized bed boiler can meet the normal load electricity consumption of these processes.

[0088] Carbon dioxide purification: The second flue gas is purified to obtain a primary CO2 product. The primary CO2 product is divided into two streams. One stream is mixed with another part of the oxygen generated in the water electrolysis process and input into the biomass gasification process as a gasifying agent. The other stream is distilled to obtain a food-grade CO2 product.

[0089] Biomass gasification: The equipment used in this process includes a circulating fluidized bed gasifier, a high-temperature gasification section furnace, and a waste heat boiler. The operating pressure of the circulating fluidized bed gasifier is approximately 0-6500KPaG, the operating temperature of the circulating fluidized bed gasifier is 560-1400℃, and the operating temperature of the high-temperature gasification section is 560-1400℃. The biomass mass required for biomass gasification is 45,000-57,000kg / h, and the biomass gasification gas production is approximately 108,000-128,000Nm 3 / h, the first synthesis gas is mainly composed of hydrogen, CO and CO2, wherein the molar ratio of CO is 1%-70%.

[0090] Methanol synthesis and methanol distillation: The compressed first synthesis gas is mixed with green hydrogen produced by compressed electrolyzed water. The reaction proceeds in a methanol synthesis tower to produce crude methanol. This crude methanol is separated and purified through methanol distillation to produce high-quality green methanol. The methanol synthesis and methanol distillation processes can be configured into multiple production lines based on production requirements. Each line can produce 20,000-33,000 kg / h of green methanol, bringing the combined production capacity of methanol synthesis and methanol distillation to 60,000-99,000 kg / h of green methanol.

[0091] The above is a further detailed description of the present invention in conjunction with specific embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, simple improvements and modifications can be made without departing from the concept of the present invention, and all of these should be considered to fall within the scope of protection of the present invention.

Claims

1. A process for preparing green methanol and co-producing carbon dioxide, characterized in that: Including new energy power generation, water electrolysis, biomass power generation, carbon dioxide purification, biomass gasification, methanol synthesis and methanol distillation, among which, The renewable energy power generation: uses wind energy and / or solar energy to generate green electricity, which is first supplied to the water electrolysis process, and the remaining electricity is transmitted to the power grid; The electrolysis of water: electrolysis of water to generate hydrogen and oxygen; Biomass power generation: biomass is burned under the action of a combustion aid to generate electricity, which is then fed to the power grid. Part of the oxygen generated in the water electrolysis process is mixed with air as a combustion aid and fed into the biomass power generation process. The first flue gas generated by the combustion is desulfurized and denitrified to generate a second flue gas, which is then fed into the carbon dioxide purification process. The carbon dioxide purification includes purification and refining operations. The second flue gas is purified to obtain a primary CO2 product. The primary CO2 product is divided into two streams. One stream is mixed with another part of the oxygen generated in the water electrolysis process and input into the biomass gasification process as a gasifying agent. The other stream is refined to obtain a food-grade CO2 product. The biomass gasification: biomass is gasified under the action of a gasifying agent to generate a first synthesis gas; Methanol synthesis: The hydrogen obtained in the water electrolysis process is compressed and mixed with the compressed first synthesis gas to obtain a raw gas, and the raw gas reacts to generate crude methanol; The methanol distillation: the crude methanol is separated and purified to obtain a high-quality green methanol product; The method further includes inputting saturated steam produced as a by-product of the biomass gasification process and the methanol synthesis process into the biomass power generation process to generate electricity after the first flue gas is superheated.

2. The process for preparing green methanol and co-producing carbon dioxide according to claim 1, characterized in that: The molar ratio of CO in the first synthesis gas is 1% to 70%.

3. The process for preparing green methanol and co-producing carbon dioxide according to claim 1, characterized in that: The molar ratio of oxygen in the combustion-supporting gas is 5% to 99%.

4. The process for preparing green methanol and co-producing carbon dioxide according to claim 1, characterized in that: In the preparation process, the mass ratio of the biomass input to the biomass power generation process and the biomass gasification process is 1: (0.2-3)。 5. The process for preparing green methanol and co-producing carbon dioxide according to claim 1, characterized in that: The biomass gasification process adopts a circulating fluidized bed gasification process, with a gasification temperature of 560-1400° C. and a gasification pressure of 0-6500 KPaG.

6. The process for preparing green methanol and co-producing carbon dioxide according to claim 1, characterized in that: The biomass power generation process adopts an extraction-condensing steam turbine generator set, and the extraction steam generated by power generation is respectively input into the methanol synthesis process, the methanol distillation process and the carbon dioxide purification process.

7. The process for preparing green methanol and co-producing carbon dioxide according to claim 1, characterized in that: The water electrolysis process is carried out in an alkaline electrolytic cell; the operating temperature of the alkaline electrolytic cell is 85-95° C., and the operating pressure is 1.6-1.8 MPaG.

8. The process for preparing green methanol and co-producing carbon dioxide according to claim 1, characterized in that: The method further includes a hydrogen storage process for storing the hydrogen generated by the water electrolysis process and for inputting hydrogen into the methanol synthesis process.

9. The process for preparing green methanol and co-producing carbon dioxide according to claim 1, characterized in that: The method also includes delivering part of the oxygen generated in the water electrolysis process as a product.

10. A system for producing green methanol and co-producing carbon dioxide, characterized in that: It includes new energy power generation equipment, water electrolysis equipment, biomass power generation equipment, carbon dioxide purification equipment, biomass gasification equipment, methanol synthesis equipment and methanol distillation equipment, among which, The new energy power generation device includes a wind turbine generator set and / or a photovoltaic generator set, which uses wind energy and / or solar energy to generate electricity. The electricity generated by the device is first supplied to the water electrolysis device, and the remaining part is transmitted to the power grid. The water electrolysis device comprises an electrolytic cell, in which water is electrolyzed to produce hydrogen and oxygen; The biomass power generation device includes a circulating fluidized bed boiler, an extraction-condensing steam turbine generator set, a desulfurization unit and a denitrification unit; biomass burns under the action of a combustion-supporting agent to generate steam that drives the extraction-condensing steam turbine generator set to generate electricity, which is transmitted to the power grid; wherein, a portion of the oxygen generated by the electrolytic water device is mixed with air and input into the circulating fluidized bed boiler as a combustion-supporting agent; the first flue gas generated by the combustion of the circulating fluidized bed boiler is passed through the desulfurization unit and the denitrification unit to obtain a second flue gas; the second flue gas is input into the carbon dioxide purification device through a pipeline; the carbon dioxide purification device includes a purification unit and a refining unit, the second flue gas is purified by the purification unit to obtain a primary CO2 product, the primary CO2 product is divided into two streams, one stream is mixed with a portion of the oxygen generated by the electrolytic water device and input into the biomass gasification device as a gasifying agent; the other stream is refined by the refining unit to obtain a CO2 product; The biomass gasification device comprises a circulating fluidized bed gasifier, a high-temperature gasification furnace and a waste heat boiler connected in sequence, wherein the biomass is gasified under the action of a gasifying agent to obtain a first synthesis gas; The methanol synthesis device comprises a methanol synthesis tower, wherein the hydrogen generated by the electrohydrolysis device is compressed by a first compressor and then mixed with the first synthesis gas compressed by a second compressor, and crude methanol is generated in the methanol synthesis tower; The methanol distillation device is used to purify and separate the crude methanol to obtain high-quality green methanol products; The saturated steam produced as by-products of the biomass gasification unit and the methanol synthesis unit is respectively connected to the extraction-condensing steam turbine generator set after heat exchange with the first flue gas through pipelines.

11. The system for preparing green methanol and co-producing carbon dioxide according to claim 10, characterized in that: It also includes a hydrogen storage device for storing hydrogen produced by the water electrolysis device and inputting hydrogen into the methanol synthesis device.

12. The system for preparing green methanol and co-producing carbon dioxide according to claim 11, characterized in that: The hydrogen storage device is a high-pressure gaseous hydrogen storage device or a liquid hydrogen storage device.

13. The system for preparing green methanol and co-producing carbon dioxide according to claim 10, characterized in that: The condensed steam is respectively connected to the methanol synthesis device, the methanol distillation device and the carbon dioxide purification device through pipelines.

14. The system for preparing green methanol and co-producing carbon dioxide according to claim 10, characterized in that: The extraction-condensing steam turbine generator set is a double-extraction-condensing steam turbine generator set.

15. The system for preparing green methanol and co-producing carbon dioxide according to claim 10, characterized in that: The water electrolysis device is also provided with a third branch for delivering oxygen products.

16. The system for preparing green methanol and co-producing carbon dioxide according to claim 10, characterized in that: There are multiple electrolytic cells.

17. The system for preparing green methanol and co-producing carbon dioxide according to claim 10, characterized in that: The electrolytic cell is an alkaline electrolytic cell.

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