Energy system for synthesizing green methanol based on biomass gasification and oxygen-enriched combustion

Abstract

The invention provides an energy system for synthesizing green methanol based on biomass gasification and oxygen-enriched combustion, and belongs to the technical field of new energy. The energy system comprises an electrolysis system, an oxygen-enriched combustion system, a methanol synthesis system, a biomass gasification system and an ammonia-process carbon capture unit, an oxygen outlet of the electrolysis system is communicated with the oxygen-enriched combustion system, and a hydrogen outlet of the electrolysis system is communicated with the methanol synthesis system; oxygen generated by the electrolysis system is supplied to the biomass oxygen-enriched combustion system for supporting combustion, and hydrogen is supplied to the methanol synthesis system; a hydrogen outlet of the biomass gasification system is communicated with the methanol synthesis system; a carbon dioxide outlet of the oxygen-enriched combustion system is communicated with the methanol synthesis system through the ammonia-process carbon capture unit; the material energy flow of the energy system is adjusted through hydrogen generated by the biomass gasification system, and the adjusting flexibility of the energy system is improved; the concentration of carbon dioxide output by the oxygen-enriched combustion system is concentrated through the ammonia-process carbon capture unit, and the pretreatment requirement of methanol synthesis is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy, and relates to an energy system for synthesizing green methanol based on biomass gasification and oxy-fuel combustion. Background Art

[0002] Existing methanol synthesis technologies mostly use CO2 / CO and H2 as raw materials, and are synthesized through pressurized catalysis. A small part is prepared by pressurized conversion / high-temperature cracking of crude oil. All of them rely on fossil fuels or their processed products to provide a carbon source, resulting in high economic costs and carbon emissions. Moreover, since the catalyst is easily poisoned and deactivated by sulfides, a large amount of energy consumption cost is required for gas desulfurization treatment.

[0003] Based on this, Chinese Patent CN 114320490A discloses a green energy chemical system based on renewable energy hydrogen production. It considers using renewable energy electrolysis water technology to provide a hydrogen source. However, the oxygen generated by electrolyzing water lacks a good consumption path, and there is also a lack of a low-carbon emission carbon source supply method. Furthermore, Chinese Patent CN113944544A discloses an energy system and an energy utilization method based on renewable energy and hydrogen methanolization. It proposes to combine renewable energy electrolysis water with biomass oxy-fuel combustion, rely on oxy-fuel combustion to consume the oxygen of electrolyzed water, and produce CO2 through oxy-fuel combustion to provide a carbon source. The advantages are that it solves the problem of oxygen consumption, reduces the carbon emissions of the system by using the carbon sink effect of biomass, and the cost is also controlled to a certain extent. However, this technical route still has two main deficiencies. One is that renewable energy electrolysis water is used as both the hydrogen source and the oxygen source of oxy-fuel combustion at the same time. Limited by the hydrogen-oxygen atom ratio in water molecules, the flexible regulation ability of the system material flow needs to be strengthened. The other is that the CO2 concentration obtained after biomass oxy-fuel combustion is difficult to reach more than 70% due to the actual process conditions of the power plant, which cannot meet the pretreatment conditions for synthesizing methanol. Summary of the Invention

[0004] In view of the above problems, the present invention provides an energy system for synthesizing green methanol based on biomass gasification and oxy-fuel combustion. The present invention adjusts the material energy flow of the energy system through a biomass gasification system to increase the flexibility of the energy system; and improves the carbon dioxide concentration through an ammonia-based carbon capture unit to meet the needs of methanol synthesis.

[0005] The object of the present invention is to provide an energy system for synthesizing green methanol based on biomass gasification and oxy-fuel combustion, including an electrolysis system, an oxy-fuel combustion system, a methanol synthesis system, a biomass gasification system, and an ammonia-based carbon capture unit.

[0006] The oxygen outlet of the electrolysis system is connected to the oxy-fuel combustion system, and the hydrogen outlet of the electrolysis system is connected to the methanol synthesis system; the oxygen generated by the electrolysis system is supplied to the oxy-fuel combustion system to support combustion, and the hydrogen is supplied to the methanol synthesis system.

[0007] The hydrogen outlet of the biomass gasification system is connected to the methanol synthesis system; the material energy flow of the energy system is adjusted by the hydrogen generated by the biomass gasification system to increase the adjustment flexibility of the energy system;

[0008] The carbon dioxide outlet of the oxygen-enriched combustion system is connected to the methanol synthesis system through the ammonia carbon capture unit; the carbon dioxide concentration output by the oxygen-enriched combustion system is concentrated by the ammonia carbon capture unit to meet the pretreatment requirements of methanol synthesis.

[0009] In a preferred embodiment of the present invention, the electrolysis system comprises an electrolytic cell, an oxygen storage device and a hydrogen storage device, and the electrolytic cell is connected to the oxygen storage device and the hydrogen storage device, respectively.

[0010] In a preferred embodiment of the present invention, it also includes biomass raw materials. The biomass raw materials enter the biomass gasification system and undergo a gasification reaction to generate carbon products and hydrogen. The hydrogen is stored in the hydrogen storage device and is used to supply the methanol synthesis system. The remaining hydrogen is output as fuel.

[0011] In a preferred embodiment of the present invention, the CO2 concentration output by the oxygen-enriched combustion system is concentrated and enriched by the ammonia carbon capture unit to be greater than 80%.

[0012] In a preferred embodiment of the present invention, carbon dioxide is absorbed by the ammonia carbon capture unit, and after the carbon dioxide is introduced into ammonia water to precipitate ammonium bicarbonate crystals, the carbon dioxide is released to achieve carbon enrichment.

[0013] In a preferred embodiment of the present invention, the heating temperature is 60°C to 70°C when releasing carbon dioxide.

[0014] In a preferred embodiment of the present invention, it also includes renewable energy, which enters the electrolysis system to electrolyze water to produce hydrogen and oxygen, and the remaining renewable energy generates electricity and is integrated into the power grid.

[0015] In a preferred embodiment of the present invention, the methanol generated by the methanol synthesis system is output as methanol, chemical raw material and methanol reforming system raw material respectively.

[0016] In a preferred embodiment of the present invention, calcium oxide is sprayed into the oxygen-enriched combustion system, and the calcium oxide reacts with sulfur dioxide generated during the combustion process to generate calcium sulfate for desulfurization.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention uses the hydrogen generated by the biomass gasification system to enhance the flexible adjustment ability of the system material flow and increase the overall output of the system; and through the ammonia-based carbon capture unit, it ensures that the CO2 concentration in the output of oxy-fuel combustion is further enriched to meet the conditions for synthesizing methanol, thereby improving the system stability; the CO2 concentration output by the combination of oxy-fuel combustion and the ammonia-based carbon capture unit is >80%, which can be directly compressed to synthesize methanol, and the synthesized methanol meets the usage requirements.

[0019] In addition, the present invention also enhances the negative carbon emission ability of the methanol synthesis system and reduces the production cost; the overall desulfurization cost of the system is reduced through the desulfurization technology in the oxy-fuel combustion furnace. Brief Description of the Drawings

[0020] Figure 1 It is a schematic structural diagram of the energy system for synthesizing green methanol based on biomass gasification and oxy-fuel combustion provided by the present invention.

[0021] Reference Numerals: 1-renewable energy, 2-electrolytic cell, 3-power grid, 4-oxygen storage device, 5-biomass raw material, 6-biomass gasification system, 7-hydrogen storage device, 8-fuel, 9-carbon product, 10-oxy-fuel combustion system, 11-ammonia-based carbon capture unit, 12-methanol synthesis system, 13-methanol, 14-chemical raw material, 15-raw material for methanol reforming system. Detailed Embodiments

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the protection scope of the present invention.

[0023] As described in the background art, the current deficiencies in the prior art are mainly in two aspects: one is that while using renewable energy electrolyzed water as the hydrogen source and the oxygen source for oxy-fuel combustion, limited by the hydrogen-oxygen atom ratio in water molecules, the flexible regulation ability of the system material flow needs to be strengthened; the other is that the CO2 concentration obtained after biomass oxy-fuel combustion is difficult to reach more than 70% due to the actual process conditions of the power plant, and it cannot meet the pretreatment conditions for synthesizing methanol.

[0024] Based on this, the present invention provides an energy system for synthesizing green methanol based on biomass gasification and oxy-fuel combustion, including an electrolysis system, an oxy-fuel combustion system 10, a methanol synthesis system 12, a biomass gasification system 6, and an ammonia-based carbon capture unit 11. By adjusting the material energy flow of the energy system through the biomass gasification system 6, the flexibility of the new energy-oxy-fuel combustion-methanol synthesis system is improved. Specifically, when the amount of H2 produced by electrolyzing water in the electrolysis system is lower than the amount required for chemical synthesis of methanol, the H2 output by the biomass gasification system 6 can be used to make up for it, realizing the efficient conversion of the enriched CO2 in the oxy-fuel combustion system 10 and improving the flexibility of system adjustment. The main purpose of the energy system provided by the present invention is to convert CO2 into green energy. Therefore, the adjustment trend of the present invention is to capture and convert all CO2 in the system. If the amount of CO2 is lower than the amount required for methanol synthesis, the excess H2 can be stored and transported to the market. Therefore, the excess of H2 has basically no negative impact as long as the complete conversion of CO2 can be ensured. This is where the adjustment function of the biomass gasification system 6 lies. Second, based on the ammonia-based carbon capture unit 11, CO2 is stored in ammonium bicarbonate crystals and released under mild reaction conditions to increase the CO2 concentration to meet the needs of methanol synthesis.

[0025] The following is illustrated by specific examples.

[0026] Example 1

[0027] An energy system for synthesizing green methanol based on biomass gasification and oxy-fuel combustion, including an electrolysis system, an oxy-fuel combustion system 10, a methanol synthesis system 12, a biomass gasification system 6, and an ammonia-based carbon capture unit 11;

[0028] The oxygen outlet of the electrolysis system is connected to the oxy-fuel combustion system 10, and the hydrogen outlet of the electrolysis system is connected to the methanol synthesis system 12. The oxygen generated by the electrolysis system is supplied to the oxy-fuel combustion system 10 to support combustion, and the hydrogen is supplied to the methanol synthesis system 12. Specifically, the electrolysis system includes an electrolytic cell 2, an oxygen storage device 4, and a hydrogen storage device 7. The electrolytic cell 2 is respectively connected to the oxygen storage device 4 and the hydrogen storage device 7. The oxygen storage device 4 is an oxygen tank, and the hydrogen storage device 7 is a hydrogen tank.

[0029] Renewable energy 1 enters the electrolytic cell 2 to electrolyze water to produce hydrogen and oxygen. The remaining renewable energy generated is incorporated into the power grid 3. The oxygen produced by the electrolytic cell 2 is supplied to the oxy-fuel combustion system 10 via the oxygen storage device 4 to support combustion. The hydrogen produced by the electrolytic cell 2 is supplied to the methanol synthesis system 12 via the hydrogen storage device 7, and the remaining hydrogen is input into the market as fuel 8. The renewable energy 1 is wind energy / solar energy, etc., and wind energy and / or solar energy are used for power generation, including wind turbine generators and / or photovoltaic generator sets. The heat generated by the oxy-fuel combustion system 10 can be converted into electrical energy and incorporated into the power grid 3.

[0030] The hydrogen outlet of the biomass gasification system 6 is connected to the methanol synthesis system 12; the hydrogen generated by the biomass gasification system 6 is used to adjust the material energy flow of the energy system and increase the flexibility of system regulation; specifically, the biomass raw material 5 enters the biomass gasification system 6 and undergoes a directed catalytic gasification reaction to generate high-quality carbon products 9 such as carbon nanotubes and hydrogen, achieving carbon-hydrogen co-production. The prepared carbon products 9 can be used in multiple fields such as material strengthening, electronic devices, drug delivery, and catalytic reactions. That is to say, the carbon products 9 can be applied to different fields according to their own properties, and the present invention does not limit this. The hydrogen is supplied to the methanol synthesis system 12 via the hydrogen storage device 7.

[0031] Specifically, when methane synthesis is carried out in the methanol synthesis system 12, hydrogen and carbon dioxide are synthesized into green methanol through a catalytic hydrogenation reaction with a molar ratio of 3:1. It can be understood that the hydrogen refers to the hydrogen jointly produced by the biomass gasification system 6 and the electrolysis system. The remaining hydrogen is output as the fuel 8.

[0032] The carbon dioxide outlet of the oxy-fuel combustion system 10 is connected to the methanol synthesis system 12 via the ammonia-based carbon capture unit 11; the enriched CO2 generated by the oxy-fuel combustion system 10 is supplied to the methanol synthesis system 12 as a carbon source via the ammonia-based carbon capture unit 11, and the concentration of the CO2 output by the oxy-fuel combustion system 10 is concentrated by the ammonia-based carbon capture unit 11 to meet the pretreatment requirements for methanol synthesis. Specifically, in the ammonia-based carbon capture unit 11, the existing ammonia-based carbon capture method is used to absorb CO2 at room temperature. The CO2 is introduced into ammonia water with a concentration of 28%, and ammonium bicarbonate crystals are precipitated and then heated at 60 °C to release CO2, realizing carbon enrichment. It should be noted that as long as the heating condition ≥ 60 °C can achieve the release of CO2, such as the heating temperature is 60 °C - 70 °C, and the heating temperature can be set according to the actual situation during the preparation process. It can be understood that a lower heating temperature can save energy.

[0033] This process uses biomass raw materials to replace traditional fossil fuels to provide a carbon source, reduce costs, and play the role of biomass carbon sinks to ensure the negative carbon quota of the system, ensuring the greenness of methanol preparation. At the same time, the ammonia-based carbon capture unit 11 further concentrates and enriches the CO2 concentration output by the oxy-fuel combustion system 10, making it easier to meet the pretreatment requirements of methanol synthesis and improving the system stability. In addition, in the oxy-fuel combustion system 10, in-furnace desulfurization treatment is adopted. During desulfurization treatment, CaO is sprayed into the furnace nozzle to convert SO2 into CaSO4 to achieve in-furnace desulfurization. It should be noted that the CaO dosage is calculated according to the calcium-sulfur molar ratio of 2:1, that is, the CaO dosage is added twice the SO2 emission amount, so that the sulfur content of the gas output from biomass with a relatively low natural sulfur content is controlled at an ideal level, omitting the traditional dry / wet desulfurization link and reducing the system desulfurization cost. The green methanol produced in the methanol synthesis system is respectively input into the corresponding markets as methanol 13, chemical raw materials 14, and methanol reforming system raw materials 15.

[0034] Example 2

[0035] In this example, the above energy system is used for methanol synthesis.

[0036] Taking wind energy or photovoltaic as renewable energy, the electrolyzer 2 electrolyzes water to produce hydrogen and oxygen, and the remaining renewable energy power generation is incorporated into the power grid 3. The oxygen generated by the electrolyzer 2 is supplied to the oxy-fuel combustion unit through the oxygen storage device 4 to support combustion, and the hydrogen is supplied to the methanol synthesis system 12, and the remaining hydrogen is input into the market as fuel 8.

[0037] Taking straw as the biomass raw material, it enters the biomass gasification system 5, and a carbon-based supported metal is used as the catalyst. The addition amount of the catalyst is 5% - 20% of the straw mass. It can be understood that the addition amount of the catalyst can be adjusted according to specific reaction conditions. Under the action of the catalyst, a continuous gasification reaction is carried out at 800 °C to generate carbon products 9 and hydrogen. The hydrogen is supplied to the methanol synthesis system 12 through the hydrogen tank, and the remaining hydrogen is output as the fuel 8. In the methane synthesis system, the molar ratio of hydrogen to carbon dioxide is 3:1.

[0038] The CO2 generated by the oxy-fuel combustion system 10 is supplied to the methanol synthesis system 12 as a carbon source through the ammonia-based carbon capture unit 11, and the ammonia-based carbon capture unit 11 concentrates the CO2 concentration output by the oxy-fuel combustion system 10 to meet the pretreatment requirements of methanol synthesis.

[0039] The constructed system is simulated and balanced calculated. In the oxy-fuel combustion unit, the boiler design capacity is 150 t / h, the matching unit power is 38 MW, the consumption of biomass raw material 5 is 47000 kg / h, and the corresponding output of CO2 is 56955.3 m 3 / h, with a concentration of 65%. After being processed by the ammonia-based carbon capture unit 11, the CO2 concentration can be increased to 86.5%, and the O2 generated by electrolyzing water for matching is 30033 m 3 / h, and the H2 is 60066 m 3 / h, synthesizing 7730.9 kg / h of methanol, with a conversion rate of 37% and a selectivity of 73%. Through simulation calculations, the power generation efficiency of the oxy-fuel combustion unit is 45%, and the overall negative carbon capacity of the system is approximately 26.2 t / h.

[0040] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0041] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. An energy system for synthesizing green methanol based on biomass gasification and oxygen-enriched combustion, characterized in that: It includes an electrolysis system, an oxygen-enriched combustion system (10), a methanol synthesis system (12), a biomass gasification system (6), and an ammonia carbon capture unit (11); The oxygen outlet of the electrolysis system is in communication with the oxygen-enriched combustion system (10), and the hydrogen outlet of the electrolysis system is in communication with the methanol synthesis system (12); the oxygen generated by the electrolysis system is supplied to the oxygen-enriched combustion system (10) to support combustion, and the hydrogen is supplied to the methanol synthesis system (12); The hydrogen outlet of the biomass gasification system (6) is connected to the methanol synthesis system (12); the material energy flow of the energy system is adjusted by the hydrogen generated by the biomass gasification system (6), thereby increasing the adjustment flexibility of the energy system; The carbon dioxide outlet of the oxygen-enriched combustion system (10) is connected to the methanol synthesis system (12) through the ammonia carbon capture unit (11); the carbon dioxide concentration output by the oxygen-enriched combustion system (10) is concentrated by the ammonia carbon capture unit (11) to meet the pretreatment requirements of methanol synthesis.

2. The energy system for synthesizing green methanol based on biomass gasification and oxygen-enriched combustion according to claim 1 is characterized in that: The electrolysis system comprises an electrolytic cell (2), an oxygen storage device (4) and a hydrogen storage device (7), wherein the electrolytic cell (2) is connected to the oxygen storage device (4) and the hydrogen storage device (7) respectively.

3. The energy system for synthesizing green methanol based on biomass gasification and oxygen-enriched combustion according to claim 1 is characterized in that: It also includes a biomass raw material (5), which enters the biomass gasification system (6) and undergoes a gasification reaction to generate a carbon product (9) and hydrogen. The hydrogen is stored in the hydrogen storage device (7) and is used to supply the methanol synthesis system (12). The remaining hydrogen is output as fuel (8).

4. The energy system for synthesizing green methanol based on biomass gasification and oxygen-enriched combustion according to claim 1 is characterized in that: The carbon dioxide concentration output by the oxygen-enriched combustion system (10) is concentrated and enriched by the ammonia carbon capture unit (11) to be greater than 80%.

5. The energy system for synthesizing green methanol based on biomass gasification and oxygen-enriched combustion according to claim 4 is characterized in that: Carbon dioxide is absorbed by the ammonia carbon capture unit (11), and after the carbon dioxide is introduced into ammonia water to precipitate ammonium bicarbonate crystals, the carbon dioxide is released to achieve carbon enrichment.

6. The energy system for synthesizing green methanol based on biomass gasification and oxygen-enriched combustion according to claim 5 is characterized in that: When releasing carbon dioxide, the heating temperature is 60°C to 70°C.

7. The energy system for synthesizing green methanol based on biomass gasification and oxygen-enriched combustion according to claim 1 is characterized in that: It also includes renewable energy (1), which enters the electrolysis system to electrolyze water to produce hydrogen and oxygen, and the remaining renewable energy generates electricity and is integrated into the power grid (3).

8. The energy system for synthesizing green methanol based on biomass gasification and oxygen-enriched combustion according to claim 1 is characterized in that: The methanol generated by the methanol synthesis system (12) is output as methanol (13), chemical raw material (14) and methanol reforming system raw material (15).

9. The energy system for synthesizing green methanol based on biomass gasification and oxygen-enriched combustion according to claim 8 is characterized in that: Calcium oxide is sprayed into the oxygen-enriched combustion system (10), and the calcium oxide reacts with sulfur dioxide generated during the combustion process to generate calcium sulfate for desulfurization.

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