System and method for producing methanol using off-peak electricity and steam turbine extraction

Abstract

This invention discloses a system and method for producing methanol using off-peak electricity and steam extraction from a steam turbine. The system comprises a feedstock pressurization unit, a methanol synthesis unit, a water electrolysis hydrogen production unit, a carbon dioxide capture and supply unit, and a coal-fired boiler unit. The feedstock pressurization unit includes a steam turbine and a compressor coaxially connected to the steam turbine. The methanol synthesis unit includes a heat exchanger with a first heat exchange channel and a second heat exchange channel. One end of the second heat exchange channel is connected to the compressor outlet, and the other end is connected to the synthesis reactor. The coal-fired boiler unit includes a high-pressure cylinder and a medium-pressure cylinder. The high-pressure cylinder is connected to the steam inlet of the steam turbine via a first extraction pipe, and the medium-pressure cylinder is connected to one end of the first heat exchange channel via a second extraction pipe. According to this embodiment of the invention, the system for producing methanol using off-peak electricity and steam extraction from a steam turbine reduces carbon emissions and costs.

Description

Technical Field

[0001] This invention relates to the fields of energy, chemical industry and low carbon, and in particular to a system and method for producing methanol by combining off-peak electricity at night and steam extraction from a steam turbine. Background Technology

[0002] With the introduction of the "dual carbon" target, the installed capacity of renewable energy (such as wind and solar power) has grown rapidly. However, renewable energy power generation is intermittent and fluctuates, leading to serious "wind curtailment" and "solar curtailment," especially during off-peak hours at night when a large amount of wind power cannot be connected to the grid, resulting in energy waste. How to effectively absorb this off-peak electricity (valley electricity) is a major challenge currently facing the power system.

[0003] Meanwhile, carbon dioxide (CO2) capture, utilization, and storage (CCUS) technology is considered one of the key technologies for mitigating climate change. Reacting captured CO2 with "green hydrogen" produced from renewable energy sources to produce methanol (CO2 + 3H2 → CH3OH + H2O) is an effective way to achieve carbon resource recycling and store intermittent renewable energy, also known as "liquid sunlight" or "electricity-to-fuel" technology.

[0004] However, current CO2 hydrogenation to methanol processes still face several technical bottlenecks. First, the water electrolysis process for hydrogen production is energy-intensive; if grid electricity is used, costs are heavily influenced by electricity prices, resulting in poor economic viability. Second, the methanol synthesis reaction itself (typically requiring 5-10 MPa pressure and 200-300°C temperature) consumes a significant amount of energy. Traditional processes often rely on burning fossil fuels separately to power the process, which undoubtedly increases overall energy consumption and carbon emissions, diminishing its "green" attributes. Therefore, further reducing the overall energy consumption and cost of this process is crucial for its industrial application. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, one objective of this invention is to propose a system for producing methanol using off-peak electricity and steam extraction from a steam turbine. By using off-peak electricity from the grid to electrolyze water and produce hydrogen in a water electrolysis unit, the unstable electrical energy in the grid is converted into chemical energy for storage, which not only solves the problem of renewable energy consumption but also reduces the cost of hydrogen production. Steam is extracted from the high-pressure cylinder of a coal-fired boiler unit to drive a steam turbine and compressor, and steam is extracted from the medium-pressure cylinder to provide a heat source for methanol synthesis. This fully utilizes the waste heat in the coal-fired boiler, integrating the methanol production process with the coal-fired boiler's thermal power generation system. This fully utilizes the waste heat resources of the coal-fired boiler to produce methanol, achieving cascaded energy utilization, reducing carbon emissions and costs, and facilitating the large-scale production of green hydrogen and green methanol.

[0006] The present invention also proposes a method for producing methanol using the above-mentioned system that utilizes off-peak electricity at night and steam extraction from a steam turbine.

[0007] A system for producing methanol using off-peak electricity and steam extraction from a steam turbine, according to a first aspect of the present invention, comprises: a feedstock pressurization unit, including a steam turbine and a compressor coaxially connected to the steam turbine; the steam turbine includes a steam inlet and a steam outlet; the compressor includes a first inlet, a second inlet, and an outlet; the compressor mixes and pressurizes hydrogen and carbon dioxide and discharges the mixture through the outlet; and a methanol synthesis unit, including a heat exchanger, a synthesis reactor, and a distillation column; the heat exchanger includes a first heat exchange channel and a second heat exchange channel that are isolated from each other but exchange heat with each other; one end of the second heat exchange channel is connected to the outlet, and the other end of the second heat exchange channel is connected to the synthesis reactor; the product outlet of the synthesis reactor is connected to the distillation column; hydrogen and carbon dioxide react in the synthesis reactor to produce methanol; and the methanol is purified by distillation in the distillation column. The system includes: a water electrolysis hydrogen production unit, which uses off-peak electricity from the power grid to electrolyze water and produce hydrogen; a carbon dioxide capture and supply unit, which is connected to a second air inlet and supplies carbon dioxide to the second air inlet; and a coal-fired boiler unit, comprising a coal-fired boiler, a high-pressure cylinder, and a medium-pressure cylinder. The high-pressure cylinder is connected to the steam inlet via a first extraction steam pipe to supply high-pressure steam to the steam inlet, and the medium-pressure cylinder is connected to one end of the first heat exchange channel via a second extraction steam pipe to supply medium-pressure steam to the first heat exchange channel.

[0008] The system for producing methanol using off-peak electricity and steam extraction from a steam turbine, as described in this embodiment of the invention, utilizes off-peak electricity from the power grid to electrolyze water and produce hydrogen. This converts unstable electrical energy from the power grid into chemical energy for storage, solving the problem of renewable energy consumption and reducing hydrogen production costs. Furthermore, steam is extracted from the high-pressure cylinder of the coal-fired boiler unit to drive the steam turbine and compressor, and steam is extracted from the medium-pressure cylinder to provide a heat source for methanol synthesis. This fully utilizes the waste heat from the coal-fired boiler, integrating the methanol production process with the coal-fired boiler's thermal power generation system. This fully utilizes the waste heat resources of the coal-fired boiler to produce methanol, achieving cascaded energy utilization, reducing carbon emissions and costs, and facilitating the large-scale production of green hydrogen and green methanol.

[0009] According to some embodiments of the present invention, a third steam extraction pipe is further included, one end of which is connected to the steam exhaust port, and the other end of which is connected to the second steam extraction pipe.

[0010] According to some embodiments of the present invention, the third extraction steam pipeline is provided with a flow valve; and / or, the second extraction steam pipeline includes an extraction steam pipe section and a manifold pipe section, one end of the extraction steam pipe section is connected to the intermediate pressure cylinder, the other end of the extraction steam pipe section is connected to both the manifold pipe section and the third extraction steam pipeline, the end of the manifold pipe section away from the extraction steam pipe section is connected to one end of the first heat exchange channel, and the extraction steam pipe section is provided with a flow valve.

[0011] According to some embodiments of the present invention, a condensate recovery device is further included, which is connected to the other end of the first heat exchange channel to condense and recover the steam discharged from the other end of the first heat exchange channel.

[0012] According to some embodiments of the present invention, a flue gas extraction pipe is further included, one end of which is connected to the coal-fired boiler and extracts flue gas from the coal-fired boiler, and the other end of which is connected to the carbon dioxide capture and supply.

[0013] According to some embodiments of the present invention, a hydrogen storage unit is also included, which is connected between the water electrolysis hydrogen production unit and the methanol synthesis unit.

[0014] According to some embodiments of the present invention, a carbon dioxide storage unit is also included, which is connected between the carbon dioxide capture and supply unit and the methanol synthesis unit.

[0015] According to a second aspect of the present invention, a method for producing methanol using off-peak electricity and steam extraction from a steam turbine is used to produce methanol using a system according to a first aspect of the present invention, wherein the method for producing methanol using off-peak electricity and steam extraction from a steam turbine includes: S1: During the off-peak period of the power grid load at night, the water electrolysis hydrogen production unit uses off-peak electricity to electrolyze water to produce hydrogen, and then introduces the hydrogen into the first air inlet. S2: The carbon dioxide capture and supply unit captures and purifies carbon dioxide, and introduces carbon dioxide into the second air inlet. S3: The first extraction pipe extracts the high-pressure steam from the high-pressure cylinder and introduces it into the steam inlet 311. The high-pressure steam drives the steam turbine to rotate, thereby driving the compressor to operate. The compressor compresses carbon dioxide and hydrogen to 5~8 MPa and introduces the compressed mixed gas into the second heat exchange channel. S4: The second extraction pipe extracts the medium-pressure steam from the medium-pressure cylinder and introduces it into the first heat exchange channel. The medium-pressure steam is a mixture of hydrogen and carbon dioxide heated together. The heated mixture is then introduced into the synthesis reactor. S5: Hydrogen and carbon dioxide react in the synthesis reactor to produce crude methanol, which is then sent to a distillation column for purification to obtain a refined methanol product that meets the standards. S6: Collect the steam discharged from the other end of the first heat exchange channel, condense the steam to form cooling water, and send the cooling water into the coal-fired boiler unit.

[0016] According to embodiments of the present invention, a method for producing methanol using off-peak electricity and steam extraction from a steam turbine is proposed. This method utilizes a water electrolysis unit to produce hydrogen during off-peak electricity grid periods, converting unstable electrical energy into chemical energy for storage. This not only solves the problem of renewable energy consumption but also reduces hydrogen production costs. Furthermore, steam is extracted from the high-pressure cylinder of a coal-fired boiler unit, driving a steam turbine to operate a compressor. Steam is also extracted from the medium-pressure cylinder to heat a mixture of hydrogen and carbon dioxide, providing a heat source for methanol synthesis. This fully utilizes the waste heat from the coal-fired boiler, integrating the methanol production process with the coal-fired boiler's thermal power generation system. This fully leverages the waste heat resources of the coal-fired boiler to produce methanol, achieving cascaded energy utilization, reducing carbon emissions and costs, and facilitating the large-scale production of green hydrogen and green methanol.

[0017] According to some embodiments of the present invention, in step S3, the molar ratio of hydrogen to carbon dioxide is 2.5:1 to 3.5:1.

[0018] According to some embodiments of the present invention, in step S3, the pressure of the steam extracted from the high-pressure cylinder is 2.5 MPa to 5 MPa, and the temperature is 250°C to 350°C; and / or, in step S4, the pressure of the steam extracted from the intermediate-pressure cylinder is 0.6 MPa to 1 MPa, and the temperature is 250°C to 350°C.

[0019] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a simplified schematic diagram of a system for producing methanol using off-peak electricity at night and steam extracted from a steam turbine, according to some embodiments of the present invention.

[0021] Figure label: 100. A system for producing methanol using off-peak electricity at night and steam extracted from a steam turbine; 1. Electrolysis of water to produce hydrogen; 11. Hydrogen storage unit; 2. Carbon dioxide capture and supply unit; 21. Carbon dioxide storage unit; 3. Raw material pressurization unit; 31. Steam turbine; 311. Steam inlet; 312. Steam outlet; 32. Compressor; 321. First inlet; 322. Second inlet; 323. Outlet; 4. Methanol synthesis unit; 41. Heat exchanger; 42. Synthesis reactor; 421. Distillation column; 5. Coal-fired boiler unit; 51. Coal-fired boiler; 511. Flue gas extraction pipe; 52. High-pressure cylinder; 53. Medium-pressure cylinder; 541. First extraction pipe; 542. Second extraction pipe; 543. Extraction pipe section; 544. Manifold section; 545. Third extraction pipe; 546. Flow valve; 6. Condensate recovery device; 7. Methanol storage tank. Detailed Implementation

[0022] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0023] The following is for reference. Figure 1 A system for producing methanol using off-peak electricity at night and steam extracted from a steam turbine, according to an embodiment of the present invention, is described.

[0024] According to a first aspect of the present invention, a system 100 for producing methanol by combining off-peak electricity at night and steam extraction from a steam turbine includes: a raw material pressurization unit 3, a methanol synthesis unit 4, a water electrolysis hydrogen production unit 1, a carbon dioxide capture and supply unit 2, and a coal-fired boiler unit 5.

[0025] Reference Figure 1 The raw material pressurization unit 3 includes a steam turbine and a compressor 32 coaxially connected to the steam turbine. The steam turbine includes a steam inlet 311 and a steam outlet 312. The compressor 32 includes a first inlet 321, a second inlet 322 and an outlet 323. The compressor 32 mixes hydrogen and carbon dioxide, pressurizes them, and discharges them through the outlet 323.

[0026] The methanol synthesis unit 4 includes a heat exchanger 41, a synthesis reactor 42, and a distillation column 421. The heat exchanger 41 includes a first heat exchange channel and a second heat exchange channel that are isolated from each other but exchange heat with each other. One end of the second heat exchange channel is connected to the gas outlet 323, and the other end of the second heat exchange channel is connected to the synthesis reactor 42. The product outlet of the synthesis reactor 42 is connected to the distillation column 421. Hydrogen and carbon dioxide react in the synthesis reactor 42 to produce methanol, and the methanol is purified by distillation in the distillation column 421.

[0027] The water electrolysis hydrogen production unit 1 uses off-peak electricity from the power grid to electrolyze water and produce hydrogen. The water electrolysis hydrogen production unit 1 is connected to the first air inlet 321 and hydrogen is introduced into the first air inlet 321.

[0028] The carbon dioxide capture and supply unit 2 is connected to the second air inlet 322 and introduces carbon dioxide into the second air inlet 322.

[0029] The coal-fired boiler unit 5 includes a coal-fired boiler 51, a high-pressure cylinder 52 and a medium-pressure cylinder 53. The high-pressure cylinder 52 is connected to the steam inlet 311 through a first steam extraction pipe 541 to introduce high-pressure steam into the steam inlet 311. The medium-pressure cylinder 53 is connected to one end of the first heat exchange channel through a second steam extraction pipe 542 to introduce medium-pressure steam into the first heat exchange channel.

[0030] For example, at night, when the grid load is low, the water electrolysis hydrogen production unit 1 uses off-peak electricity from the grid to electrolyze water and produce hydrogen. This converts unstable electrical energy from the grid into chemical energy for storage, which not only solves the problem of renewable energy consumption but also reduces the cost of hydrogen production.

[0031] Methanol synthesis requires sufficient pressure from the raw materials. The raw material pressurization unit 3 pressurizes hydrogen and carbon dioxide to facilitate the reaction. Steam is extracted from the high-pressure cylinder 52 in the coal-fired boiler unit 5, driving the steam turbine to rotate, which in turn drives the compressor 32 to pressurize the hydrogen and carbon dioxide. This fully utilizes the waste heat in the coal-fired boiler 51, eliminating the need for additional energy for the methanol production process, reducing carbon emissions and costs, and facilitating the large-scale production of green hydrogen and green methanol.

[0032] While the coal-fired boiler unit 5 is generating electricity, high-pressure steam extracted from the high-pressure cylinder 52 of the coal-fired boiler unit 5 enters the steam inlet 311 of the steam turbine through the first extraction pipe 541. The thermal energy of the high-pressure steam expands and does work in the turbine, directly converting into mechanical energy to drive the steam turbine to rotate. The steam turbine is coaxially connected to the compressor 32, which can drive the compressor 32 to operate, mixing and pressurizing the hydrogen and carbon dioxide entering the compressor 32. The steam after doing work becomes exhaust steam and is discharged from the steam exhaust port 312, completing the energy-saving process of replacing the electric motor to drive the compressor 32 with steam extraction from the steam turbine.

[0033] Methanol synthesis also requires heat to raise the temperature of hydrogen and carbon dioxide to the necessary reaction temperature. In related technologies, fossil fuels are typically burned separately for methanol synthesis, increasing energy consumption and carbon emissions. By extracting steam from the intermediate-pressure cylinder 53 of the coal-fired boiler unit 5 to provide a heat source for methanol synthesis, the waste heat in the coal-fired boiler 51 is fully utilized. This integrates the methanol production process with the thermal power generation system of the coal-fired boiler 51, making full use of the waste heat resources of the boiler 51 to produce methanol, reducing carbon emissions and costs, and facilitating the large-scale production of green hydrogen and green methanol.

[0034] While the coal-fired boiler unit 5 is generating electricity, medium-pressure steam extracted from the medium-pressure cylinder 53 enters the first heat exchange channel of the heat exchanger 41 in the methanol synthesis unit 4 through the second extraction steam pipe 542. This medium-pressure steam serves as a heat source, indirectly exchanging heat with the low-temperature hydrogen and carbon dioxide mixed feedstock gas from the compressor 32 in the second heat exchange channel. The mixed gas is preheated to the temperature required for the synthesis reaction before entering the synthesis reactor 42. This process not only recovers and utilizes the waste heat from the medium-pressure extraction steam of the coal-fired unit but also meets the initial heat requirements of the methanol synthesis reaction, achieving cascaded energy utilization.

[0035] During methanol synthesis, the water electrolysis hydrogen production unit 1 uses off-peak electricity from the power grid to electrolyze water and produce hydrogen, which is then introduced into the first inlet 321. The carbon dioxide capture and supply unit 2 introduces carbon dioxide into the second inlet 322. After the hydrogen and carbon dioxide enter the compressor 32 together, the high-pressure steam drawn from the high-pressure cylinder 52 drives the steam turbine to rotate, which in turn drives the compressor 32 to pressurize the hydrogen and carbon dioxide to the pressure required for the reaction. The pressurized hydrogen and carbon dioxide are then discharged from the outlet 323 and enter the second heat exchange channel of the heat exchanger 41. The medium-pressure gas drawn from the medium-pressure cylinder 53 enters the first heat exchange channel and heats the hydrogen and carbon dioxide mixture in the second heat exchange channel, raising the temperature of the hydrogen and carbon dioxide mixture to the temperature required for the reaction.

[0036] The hydrogen and carbon dioxide mixture discharged from the second heat exchange channel enters the synthesis reactor 42, where it reacts under the action of a catalyst to produce crude methanol and release heat. The product then enters the distillation column 421 from the outlet. In the distillation column 421, the components are separated and purified based on their boiling point differences to obtain high-purity methanol. The entire process utilizes green hydrogen produced from off-peak electricity and captured carbon dioxide as raw materials, with power and heat provided by steam extraction from the coal-fired boiler unit 5, achieving the co-production of low-carbon methanol.

[0037] For example, the outlet of distillation column 421 is connected to methanol storage tank 7, and distillation column 421 delivers high-purity methanol product to methanol storage tank 7 for storage.

[0038] The system 100 for methanol production using off-peak electricity and steam extraction from a steam turbine, according to an embodiment of the present invention, uses off-peak electricity from the power grid in the water electrolysis hydrogen production unit 1 to electrolyze water and produce hydrogen, converting unstable electrical energy from the power grid into chemical energy for storage. This not only solves the problem of renewable energy consumption but also reduces the cost of hydrogen production. Steam is extracted from the high-pressure cylinder 52 of the coal-fired boiler unit 5 to drive the steam turbine and compressor 32, and steam is extracted from the medium-pressure cylinder 53 to provide a heat source for methanol synthesis. This fully utilizes the waste heat in the coal-fired boiler 51, integrating the methanol production process with the thermal power generation system of the coal-fired boiler 51. This fully utilizes the waste heat resources of the coal-fired boiler 51 to produce methanol, achieving cascaded energy utilization, reducing carbon emissions and costs of the process, and facilitating the large-scale production of green hydrogen and green methanol.

[0039] Reference Figure 1 According to some embodiments of the present invention, the system 100 for producing methanol by combining off-peak electricity at night and steam extraction from a steam turbine further includes a third steam extraction pipe 545, one end of which is connected to a steam exhaust port 312, and the other end of which is connected to a second steam extraction pipe 542.

[0040] The high-pressure steam extracted from the high-pressure cylinder 52 enters the steam turbine and performs work there. The gas still has some residual heat. By setting up a third extraction steam pipe 545 to connect the steam exhaust port 312 to the second extraction steam pipe 542, this part of the gas after performing work can be introduced into the second extraction steam pipe 542 and mixed with the medium-pressure steam extracted from the medium-pressure cylinder 53 to heat hydrogen and carbon dioxide together. This makes full use of the residual heat of the gas discharged from the steam exhaust port 312, resulting in higher energy utilization and making it more conducive to the large-scale production of green hydrogen and green methanol.

[0041] Reference Figure 1 According to some embodiments of the present invention, a flow valve 546 is provided on the third steam extraction pipe 545.

[0042] The high-pressure steam drawn from the high-pressure cylinder 52 enters the steam turbine and does work there. The pressure then decreases and the steam becomes exhaust steam. The medium-pressure steam drawn directly from the medium-pressure cylinder 53 enters the second extraction pipe 542. The exhaust steam and the medium-pressure steam mix together to heat hydrogen and carbon dioxide.

[0043] By installing a flow valve 546 on the third extraction steam pipe 545, the flow valve 546 can control the flow rate of the exhaust steam in the third extraction steam pipe 545. This can control the rate at which the gas in the third extraction steam pipe 545 enters the second extraction steam pipe 542, thereby changing the ratio of exhaust steam to medium-pressure steam entering the first heat exchange channel, and adjusting the temperature of the mixture of exhaust steam and medium-pressure steam to adjust the temperature of the mixture of hydrogen and carbon dioxide in the second heat exchange channel.

[0044] Reference Figure 1 According to some embodiments of the present invention, the second extraction steam pipe 542 includes an extraction steam pipe section 543 and a manifold pipe section 544. One end of the extraction steam pipe section 543 is connected to the intermediate pressure cylinder 53, and the other end of the extraction steam pipe section 543 is connected to both the manifold pipe section 544 and the third extraction steam pipe 545. The end of the manifold pipe section 544 away from the extraction steam pipe section 543 is connected to one end of the first heat exchange channel. A flow valve 546 is provided on the extraction steam pipe section 543.

[0045] High-pressure steam extracted from high-pressure cylinder 52 enters the steam turbine and performs work there, causing its pressure to decrease and become exhaust steam. This exhaust steam then enters the manifold section 544 within the second extraction pipe 542 via the third extraction pipe 545. Medium-pressure steam extracted from intermediate-pressure cylinder 53 flows into the manifold section 544 via the extraction pipe section 543, where it mixes with the exhaust steam.

[0046] By installing a flow valve 546 on the extraction pipe section 543, the flow valve 546 can control the rate at which the medium-pressure steam extracted from the medium-pressure cylinder 53 enters the manifold, thereby changing the ratio of exhaust steam to medium-pressure steam in the manifold section 544, and adjusting the temperature of the mixture of exhaust steam and medium-pressure steam to regulate the temperature of the mixture of hydrogen and carbon dioxide in the second heat exchange channel.

[0047] Reference Figure 1 According to some embodiments of the present invention, a condensate recovery device 6 is also included, which is connected to the other end of the first heat exchange channel to condense and recover the steam discharged from the other end of the first heat exchange channel.

[0048] High-temperature gas releases heat in the first heat exchange channel, and its temperature decreases to form low-temperature steam. By setting up a condensate recovery device 6 to condense the steam discharged from the other end of the first heat exchange channel into condensate, and then recover it, this part of the water resources can be saved and energy can be avoided.

[0049] For example, the condensate recovery device 6 is connected to the boiler feedwater tank in the coal-fired boiler unit 5 via a recovery water pipe, allowing condensate to circulate in the coal-fired boiler unit 5. This reduces steam loss during water circulation in the coal-fired boiler unit 5, thus saving energy.

[0050] Reference Figure 1According to some embodiments of the present invention, a flue gas extraction pipe 511 is also included. One end of the flue gas extraction pipe 511 is connected to a coal-fired boiler 51 and extracts the flue gas from the coal-fired boiler 51. The other end of the flue gas extraction pipe 511 is connected to a carbon dioxide capture and supply unit 2. By having one end of the flue gas extraction pipe 511 extract the flue gas from the coal-fired boiler 51 and the other end connected to the carbon dioxide capture and supply unit 2, the carbon dioxide capture and supply unit 2 can recover and capture carbon dioxide from the flue gas of the coal-fired boiler 51. The higher carbon dioxide content in the flue gas makes it easier for the carbon dioxide capture and supply unit 2 to capture carbon dioxide. On the other hand, it can also reduce the amount of carbon dioxide emitted from the flue gas of the coal-fired boiler unit 5, reduce the carbon emissions and cost of the process, and facilitate the large-scale production of green hydrogen and green methanol.

[0051] Reference Figure 1 According to some embodiments of the present invention, a hydrogen storage unit 11 is also included, which is connected between the water electrolysis hydrogen production unit 1 and the methanol synthesis unit 4. By setting up the hydrogen storage unit 11, the hydrogen produced in the water electrolysis hydrogen production module is passed into the hydrogen storage unit 11 for storage, and the hydrogen storage unit 11 then supplies hydrogen to the methanol synthesis unit 4. The flow rate of hydrogen supplied to the methanol synthesis unit 4 is more stable, reducing gas flow fluctuations and making the methanol synthesis reaction more stable.

[0052] According to some embodiments of the present invention, a carbon dioxide storage unit 21 is further included, which is connected between the carbon dioxide capture and supply unit 2 and the methanol synthesis unit 4. By setting up the carbon dioxide storage unit 21, the carbon dioxide produced in the carbon dioxide capture and supply unit 2 is passed into the carbon dioxide storage unit 21 for storage, and the carbon dioxide storage unit 21 then supplies carbon dioxide to the methanol synthesis unit 4. The flow rate of carbon dioxide supplied to the methanol synthesis unit 4 is more stable, reducing gas flow fluctuations and making the methanol synthesis reaction more stable.

[0053] According to a second aspect of the present invention, a method for producing methanol using off-peak electricity and steam extraction from a steam turbine is described. The method utilizes a system 100 according to a first aspect of the present invention to produce methanol using off-peak electricity and steam extraction from a steam turbine. The method includes: S1: During the off-peak period of the power grid load at night, the water electrolysis hydrogen production unit 1 uses off-peak electricity to electrolyze water to produce hydrogen, and then introduces the hydrogen into the first air inlet 321. S2: Carbon dioxide capture and supply unit 2 captures carbon dioxide and purifies it, and introduces the carbon dioxide into the second air inlet 322. S3: The first extraction pipe 541 extracts the high-pressure steam in the high-pressure cylinder 52 and introduces it into the steam inlet 311. The high-pressure steam drives the steam turbine to rotate, thereby driving the compressor 32 to operate. The compressor 32 compresses carbon dioxide and hydrogen to 5~8 MPa and introduces the compressed mixed gas into the second heat exchange channel. S4: The second extraction pipe 542 extracts the medium-pressure steam in the medium-pressure cylinder 53 and introduces it into the first heat exchange channel. The medium-pressure steam is a mixture of hydrogen and carbon dioxide for heating. The heated mixture is then introduced into the synthesis reactor 42. S5: Hydrogen and carbon dioxide react in synthesis reactor 42 to produce crude methanol, which is then sent to distillation column 421 for purification to obtain a refined methanol product that meets the standards. S6: Collect the steam discharged from the other end of the first heat exchange channel, condense the steam to form cooling water, and send the cooling water into the coal-fired boiler unit 5.

[0054] By using the water electrolysis hydrogen production unit 1 to electrolyze water and produce hydrogen during the off-peak hours of the power grid in step S1, the unstable electrical energy in the power grid is converted into chemical energy for storage, which not only solves the problem of renewable energy consumption, but also reduces the cost of hydrogen production.

[0055] In step S2, the carbon dioxide capture and supply unit 2 can capture carbon dioxide from the air or from the flue gas of the coal-fired boiler unit 5.

[0056] In step S3, steam is extracted from the high-pressure cylinder 52 of the coal-fired boiler unit 5, driving the steam turbine to operate the compressor 32. This fully utilizes the waste heat in the coal-fired boiler 51, integrating the methanol production process with the thermal power generation system of the coal-fired boiler 51, thus making full use of the waste heat resources of the coal-fired boiler 51 to produce methanol. In step S4, steam is extracted from the medium-pressure cylinder 53. The medium-pressure steam is used to heat a mixture of hydrogen and carbon dioxide, providing a heat source for methanol synthesis. This fully utilizes the waste heat in the coal-fired boiler 51, integrating the methanol production process with the thermal power generation system of the coal-fired boiler 51, thus making full use of the waste heat resources of the coal-fired boiler 51 to produce methanol, achieving cascaded energy utilization.

[0057] According to an embodiment of the present invention, a method for producing methanol using off-peak electricity and steam extraction from a steam turbine is proposed. This method utilizes a water electrolysis unit 1 to produce hydrogen during off-peak hours, converting unstable electrical energy from the grid into chemical energy for storage. This not only solves the problem of renewable energy consumption but also reduces hydrogen production costs. Steam is extracted from the high-pressure cylinder 52 of the coal-fired boiler unit 5, driving a steam turbine to operate the compressor 32. Steam is also extracted from the intermediate-pressure cylinder 53, heating a mixture of hydrogen and carbon dioxide to provide a heat source for methanol synthesis. This fully utilizes the waste heat in the coal-fired boiler 51, integrating the methanol production process with the thermal power generation system of the coal-fired boiler 51. This fully utilizes the waste heat resources of the coal-fired boiler 51 to produce methanol, achieving cascaded energy utilization, reducing carbon emissions and costs, and facilitating the large-scale production of green hydrogen and green methanol.

[0058] According to some embodiments of the present invention, in step S3, the molar ratio of hydrogen to carbon dioxide is 2.5:1 to 3.5:1. By setting the molar ratio of hydrogen to carbon dioxide to 2.5:1 to 3.5:1, the hydrogen and carbon dioxide can react sufficiently, avoiding an excess of any one reactant.

[0059] According to some embodiments of the present invention, in step S3, the pressure of the steam extracted by the high-pressure cylinder 52 is 2.5 MPa to 5 MPa, and the temperature is 250°C to 350°C. This ensures that the high-pressure steam extracted by the high-pressure cylinder 52 has sufficient energy, which can fully drive the steam turbine 31 to rotate, thereby driving the operation of the compressor 32.

[0060] According to some embodiments of the present invention, in step S4, the pressure of the steam extracted by the intermediate-pressure cylinder 53 is 0.6 MPa to 1 MPa, and the temperature is 250°C to 350°C. This ensures that the intermediate-pressure steam extracted by the intermediate-pressure cylinder 53 has sufficient heat, allowing it to be introduced into the first heat exchange channel. This heats the hydrogen and carbon dioxide in the second heat exchange channel, raising their temperatures to facilitate the reaction and preparation of methanol.

[0061] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0062] In the description of this invention, "first feature" and "second feature" may include one or more of the features.

[0063] In the description of this invention, "a plurality of" means two or more.

[0064] In the description of this invention, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or it may include the first and second features not being in direct contact but being in contact through another feature between them.

[0065] In the description of this invention, the terms "above," "over," and "on top" for the first feature and the second feature include the first feature being directly above or diagonally above the second feature, or simply indicating that the first feature is at a higher horizontal level than the second feature.

[0066] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0067] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A system for producing methanol using off-peak electricity at night and steam extracted from a steam turbine, characterized in that, include: The raw material pressurization unit includes a steam turbine and a compressor coaxially connected to the steam turbine. The steam turbine includes a steam inlet and a steam outlet. The compressor includes a first inlet, a second inlet, and an outlet. The compressor mixes hydrogen and carbon dioxide, pressurizes the mixture, and discharges it through the outlet. A methanol synthesis unit includes a heat exchanger, a synthesis reactor, and a distillation column. The heat exchanger includes a first heat exchange channel and a second heat exchange channel that are isolated from each other but exchange heat with each other. One end of the second heat exchange channel is connected to the gas outlet, and the other end of the second heat exchange channel is connected to the synthesis reactor. The product outlet of the synthesis reactor is connected to the distillation column. Hydrogen and carbon dioxide react in the synthesis reactor to produce methanol, and the methanol is purified by distillation in the distillation column. An electrolysis water hydrogen production unit, wherein the electrolysis water hydrogen production unit uses off-peak electricity from the power grid to electrolyze water to produce hydrogen, and the electrolysis water hydrogen production unit is connected to the first air inlet and introduces hydrogen into the first air inlet. A carbon dioxide capture and supply unit is connected to the second air inlet and introduces carbon dioxide into the second air inlet; A coal-fired boiler unit includes a coal-fired boiler, a high-pressure cylinder, and a medium-pressure cylinder. The high-pressure cylinder is connected to the steam inlet through a first steam extraction pipe to introduce high-pressure steam into the steam inlet. The medium-pressure cylinder is connected to one end of the first heat exchange channel through a second steam extraction pipe to introduce medium-pressure steam into the first heat exchange channel.

2. The system for producing methanol using off-peak electricity and steam extraction from a steam turbine according to claim 1, characterized in that, It also includes a third steam extraction pipe, one end of which is connected to the steam exhaust port, and the other end of which is connected to the second steam extraction pipe.

3. The system for producing methanol using off-peak electricity and steam extraction from a steam turbine according to claim 2, characterized in that, The third extraction steam pipeline is equipped with a flow valve; and / or, the second extraction steam pipeline includes an extraction steam pipe section and a manifold pipe section, one end of the extraction steam pipe section is connected to the intermediate pressure cylinder, the other end of the extraction steam pipe section is connected to both the manifold pipe section and the third extraction steam pipeline, the end of the manifold pipe section away from the extraction steam pipe section is connected to one end of the first heat exchange channel, and the extraction steam pipe section is equipped with a flow valve.

4. The system for producing methanol using off-peak electricity and steam extraction from a steam turbine according to claim 1, characterized in that, It also includes a condensate recovery device, which is connected to the other end of the first heat exchange channel to condense and recover the steam discharged from the other end of the first heat exchange channel.

5. The system for producing methanol using off-peak electricity and steam extraction from a steam turbine according to claim 1, characterized in that, It also includes a flue gas extraction pipe, one end of which is connected to the coal-fired boiler and extracts the flue gas from the coal-fired boiler, and the other end of which is connected to the carbon dioxide capture and supply unit.

6. The system for producing methanol using off-peak electricity and steam extraction from a steam turbine according to claim 1, characterized in that, It also includes a hydrogen storage unit connected between the water electrolysis hydrogen production unit and the methanol synthesis unit.

7. The system for producing methanol using off-peak electricity and steam extraction from a steam turbine according to claim 1, characterized in that, It also includes a carbon dioxide storage unit connected between the carbon dioxide capture and supply unit and the methanol synthesis unit.

8. A method for producing methanol using off-peak electricity at night and steam extraction from a steam turbine, characterized in that, Methanol is produced using the system for producing methanol from off-peak electricity and steam extraction from a steam turbine as described in any one of claims 1-7, wherein the method for producing methanol from methanol from off-peak electricity and steam extraction from a steam turbine comprises: S1: During the off-peak period of the power grid load at night, the water electrolysis hydrogen production unit uses off-peak electricity to electrolyze water to produce hydrogen, and then introduces the hydrogen into the first air inlet. S2: The carbon dioxide capture and supply unit captures and purifies carbon dioxide, and introduces carbon dioxide into the second air inlet. S3: The first extraction pipe extracts the high-pressure steam from the high-pressure cylinder and introduces it into the steam inlet 311. The high-pressure steam drives the steam turbine to rotate, thereby driving the compressor to operate. The compressor compresses carbon dioxide and hydrogen to 5~8 MPa and introduces the compressed mixed gas into the second heat exchange channel. S4: The second extraction pipe extracts the medium-pressure steam from the medium-pressure cylinder and introduces it into the first heat exchange channel. The medium-pressure steam is a mixture of hydrogen and carbon dioxide heated together. The heated mixture is then introduced into the synthesis reactor. S5: Hydrogen and carbon dioxide react in the synthesis reactor to produce crude methanol, which is then sent to a distillation column for purification to obtain a refined methanol product that meets the standards. S6: Collect the steam discharged from the other end of the first heat exchange channel, condense the steam to form cooling water, and send the cooling water into the coal-fired boiler unit.

9. The method for producing methanol using off-peak electricity and steam extraction from a steam turbine according to claim 8, characterized in that, In step S3, the molar ratio of hydrogen to carbon dioxide is 2.5:1 to 3.5:

1.

10. The method for producing methanol using off-peak electricity at night and steam extraction from a steam turbine according to claim 8, characterized in that, In step S3, the pressure of the steam extracted from the high-pressure cylinder is 2.5 MPa to 5 MPa, and the temperature is 250°C to 350°C; and / or, in step S4, the pressure of the steam extracted from the intermediate-pressure cylinder is 0.6 MPa to 1 MPa, and the temperature is 250°C to 350°C.

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