System and method for producing methanol from waste incineration flue gas

Abstract

The application discloses a kind of garbage incineration flue gas system and method for preparing methanol, the system includes preprocessing unit, carbon capture unit, wind light preparation unit, buffer unit, methanol synthesis unit and control unit, preprocessing unit is used to carry out purification treatment, carbon capture unit includes the absorption tower and regeneration tower connected in sequence, absorption tower is connected with preprocessing unit, regeneration tower returns absorption tower by absorbent circulation path, and is provided with electric dialysis desalination module, wind light preparation unit is used to drive electrolytic water hydrogen production, buffer unit is used to store hydrogen and carbon dioxide and store electric energy, methanol synthesis unit is used to receive hydrogen and carbon dioxide and carry out catalytic synthesis methanol, control unit is used to adjust operating load according to the storage state of buffer unit, to solve the problem that it is difficult to realize the stable capture of carbon dioxide in garbage incineration flue gas and its continuous use for methanol synthesis.

Description

Technical Field

[0001] This invention relates to the field of carbon emission reduction and resource utilization technology, specifically to a system and method for producing methanol from waste incineration flue gas. Background Technology

[0002] The flue gas produced during the incineration of municipal solid waste contains a certain concentration of carbon dioxide. This carbon dioxide has high potential for resource utilization and can be used to prepare basic chemical products such as methanol. It is one of the important pathways to achieve carbon reduction and resource utilization through waste incineration.

[0003] In existing technologies, calcium-based cyclic absorption or amine absorption processes are commonly used to capture carbon dioxide from flue gas, and high-purity carbon dioxide is obtained through regeneration for subsequent chemical synthesis. However, under the operating conditions of waste incineration flue gas, the flue gas contains various impurities such as SOx, NOx, HCl, and heavy metals, which can easily lead to the degradation or even deactivation of the absorbent, thus affecting the long-term stable operation of the carbon dioxide capture process. Simultaneously, some processes have high requirements for operating temperature and energy input conditions, resulting in poor matching with the actual operating conditions of waste incineration flue gas, further increasing the instability of system operation. Furthermore, in combined wind-solar-hydrogen co-generation systems that couple carbon dioxide to methanol, wind power generation and photovoltaic power generation exhibit significant intermittency and volatility, while the methanol synthesis process requires a continuous and stable supply of hydrogen and carbon dioxide. When the output of wind and solar power generation declines rapidly, existing technologies typically use independent regulation or sequential control to adjust the operating status of the water electrolysis hydrogen production unit and the methanol synthesis unit separately. This makes it difficult to coordinate and control the energy consumption and raw material supply between the units, which can easily lead to competition for electricity and raw materials between the hydrogen production process and the methanol synthesis process. This can cause large fluctuations in the system's operating load and even trigger interlock protection, resulting in the shutdown of the entire system.

[0004] Therefore, existing technologies cannot achieve stable capture of carbon dioxide from waste incineration flue gas and its continuous use in methanol synthesis. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a system and method for producing methanol from waste incineration flue gas, thereby solving the technical problem in the prior art of stably capturing carbon dioxide from waste incineration flue gas and continuously using it for methanol synthesis.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a system for producing methanol from waste incineration flue gas, comprising: a pretreatment unit for purifying waste incineration flue gas; a carbon capture unit including an absorption tower and a regeneration tower, the absorption tower having a flue gas inlet and a rich liquid outlet, the flue gas inlet being connected to the outlet of the pretreatment unit, the rich liquid outlet being connected to the regeneration tower, the regeneration tower having a lean liquid outlet and a carbon dioxide outlet, the lean liquid outlet returning to the absorption tower through an absorbent circulation path, and an electrodialysis desalination module being provided on the absorbent circulation path; a wind and solar hydrogen production unit including a wind power generation device, a photovoltaic power generation device, and a water electrolysis hydrogen production device, the wind power generation device and the photovoltaic power generation device being electrically connected to the water electrolysis hydrogen production device for driving the water electrolysis hydrogen production; and a buffer unit including a raw material buffer and an electrical energy buffer. The system comprises a raw material buffer unit connected to the carbon dioxide output ports of the water electrolysis hydrogen production unit and the regeneration tower, respectively, for storing hydrogen and carbon dioxide. The input end of the power buffer unit is electrically connected to the wind power generation unit and the photovoltaic power generation unit, and the output end of the power buffer unit is electrically connected to the water electrolysis hydrogen production unit, for storing and releasing electrical energy to regulate the input power of the water electrolysis hydrogen production unit. A methanol synthesis unit, connected to the raw material buffer unit, receives hydrogen and carbon dioxide and performs catalytic synthesis of methanol. A control unit, connected to the wind and solar hydrogen production unit, the buffer unit, and the methanol synthesis unit, acquires the electrical energy status of the power buffer unit, the storage status of the raw material buffer unit, and the output status of the wind power generation unit and the photovoltaic power generation unit, and regulates the operating load of the water electrolysis hydrogen production unit and the methanol synthesis unit.

[0007] In some embodiments, the pretreatment unit includes a quench cooling tower, a wet scrubbing tower, and a flue gas fine filter connected in sequence. The quench cooling tower is used to receive and cool the waste incineration flue gas, the wet scrubbing tower is used to scrub the cooled flue gas, and the flue gas fine filter is used to filter the scrubbed flue gas.

[0008] In some embodiments, the absorber uses a binary mixed phase change absorbent, which includes N-methyldiethanolamine and diethylenetriamine, wherein the mass ratio of the absorbent is: N-methyldiethanolamine 33% to 35%, diethylenetriamine 6.5% to 7.5%, water content 28% to 30%, and the remainder is a supplementary solvent.

[0009] In some embodiments, the supplemental solvent includes at least one of water, alcohol solvents, or alkanolamine stabilizers.

[0010] In some embodiments, the waste incineration flue gas to methanol system further includes a heat reuse unit, which includes a heat exchange loop that recovers the reaction heat generated by the methanol synthesis unit and the waste heat from the pretreatment unit.

[0011] In some embodiments, the heat exchange circuit includes a primary heat exchange branch, a secondary heat exchange branch, and a tertiary heat exchange branch. The primary heat exchange branch is used to transport the reaction heat generated by the methanol synthesis unit to the regeneration tower. The secondary heat exchange branch is used to transport the reaction heat generated by the methanol synthesis unit to the wind and solar hydrogen production unit. The tertiary heat exchange branch is used to transport the waste heat of the pretreatment unit to the absorption tower.

[0012] In some embodiments, the heat exchange circuit is provided with a control valve, which is used to switch the heat exchange circuit to an external heat source heating channel when the reaction heat generated by the methanol synthesis unit is lower than the heating demand.

[0013] In some embodiments, the raw material buffer includes a hydrogen buffer tank and a carbon dioxide buffer tank, which are used for independent storage and buffering regulation of hydrogen and carbon dioxide.

[0014] In some embodiments, the control unit is configured to: preferentially adjust the operating power of the water electrolysis hydrogen production unit based on the state of charge of the power buffer and the predicted output state of the wind power generation unit and the photovoltaic power generation unit, so as to absorb the output fluctuations of the wind power generation unit and the photovoltaic power generation unit; and reduce the operating load of the methanol synthesis unit when the storage state of the raw material buffer is insufficient, so as to maintain the continuous and stable operation of the methanol synthesis unit.

[0015] Secondly, the present invention also provides a method for producing methanol from waste incineration flue gas, comprising the following steps: pretreating the waste incineration flue gas to remove particulate matter and acidic impurities; passing the pretreated flue gas into a carbon capture unit, using an absorbent to absorb carbon dioxide in the flue gas to form a rich liquid, transporting the rich liquid to a regeneration tower for regeneration treatment to obtain carbon dioxide gas, and returning the regenerated lean liquid to the absorbent tower through an absorbent circulation path to continue participating in carbon dioxide absorption, and performing online electrodialysis desalination treatment on the absorbent in the absorbent circulation path; using a wind power generation device and a photovoltaic power generation device to drive an electrolytic water hydrogen production device to produce hydrogen, and using a buffer unit to separately process hydrogen, carbon dioxide, and the hydrogen from the wind power generation device and the photovoltaic power generation device. The system stores and regulates the electrical energy generated by the photovoltaic power generation unit; it introduces hydrogen and carbon dioxide into the methanol synthesis unit for a catalytic reaction to produce methanol, and transfers the reaction heat generated by the methanol synthesis unit to the regeneration tower of the carbon capture unit for heat recovery and utilization; it obtains the state of charge of the electrical energy buffer in the buffer unit, the storage status of the raw material buffer, and the predicted output status of the wind power generation unit and the photovoltaic power generation unit; based on the predicted output status and state of charge, it adjusts the operating power of the water electrolysis hydrogen production unit to regulate the energy storage status of the electrical energy buffer; based on the storage status of the raw material buffer, it adjusts the production load of the methanol synthesis unit to match the raw material consumption of the methanol synthesis unit with the supply capacity of the raw material buffer, maintaining the continuous and stable operation of the system.

[0016] Compared with existing technologies, the waste-to-methanol system and method provided by this invention, through the pretreatment unit set at the front end of the carbon capture unit, cools, washes, and filters the waste-to-incineration flue gas, reducing the adverse effects of acidic gases, particulate matter, and organic pollutants on the absorbent. Simultaneously, an electrodialysis desalination module is installed in the absorbent circulation path to purify the circulating absorbent online, reducing the accumulation of impurities such as thermally stable salts, minimizing the need for frequent absorbent replacement, and improving the stability and economy of the carbon dioxide capture process. Furthermore, this application incorporates a heat reuse unit to recover and utilize waste heat during system operation in stages, and coordinates and regulates the wind-solar hydrogen production, carbon dioxide supply, and methanol synthesis processes through buffer and control units, reducing the impact of wind and solar fluctuations on system operation. This achieves continuous operation between carbon dioxide capture, wind-solar hydrogen production, and methanol synthesis, improving the stability of continuous system operation. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a waste incineration flue gas to methanol system provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the path of the hot reuse unit provided in an embodiment of the present invention; Figure 3 This is a schematic flowchart of the method for producing methanol from waste incineration flue gas provided in an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures: 10. Pretreatment unit; 11. Quenching tower; 12. Wet scrubbing tower; 13. Flue gas fine filter; 20. Carbon capture unit; 21. Absorption tower; 22. Regeneration tower; 23. Absorbent circulation path; 24. Electrodialysis desalination module; 30. Wind and solar hydrogen production unit; 31. Wind power generation device; 32. Photovoltaic power generation device; 33. Water electrolysis hydrogen production device; 40. Buffer unit; 41. Raw material buffer; 411. Hydrogen buffer tank; 412. Carbon dioxide buffer tank; 42. Electrical energy buffer; 50. Methanol synthesis unit; 60. Control unit; 71. Primary heat exchange branch; 72. Secondary heat exchange branch; 73. Tertiary heat exchange branch; 74. Control valve. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] To address the technical challenge of achieving stable capture of carbon dioxide from waste incineration flue gas and its continuous use in methanol synthesis in existing technologies, this invention provides a system and method for producing methanol from waste incineration flue gas. This system enables stable capture of carbon dioxide from waste incineration flue gas, continuous integration with wind and solar hydrogen production processes, and stable operation of the methanol synthesis process.

[0021] It should be noted that the waste incineration flue gas to methanol system and method described in this invention are used for, but not limited to, carbon emission reduction and resource utilization. For ease of explanation, this invention only uses the application of the waste incineration flue gas to methanol system and method to carbon emission reduction and resource utilization equipment as an example. The principle of the waste incineration flue gas to methanol system and method applied to other types of equipment is essentially the same as that applied to carbon emission reduction and resource utilization equipment, and will not be elaborated here.

[0022] Please see Figure 1 , Figure 1 This is a schematic diagram of a waste incineration flue gas to methanol system according to an embodiment of the present invention. The system includes a pretreatment unit 10, a carbon capture unit 20, a wind-solar hydrogen production unit 30, a buffer unit 40, a methanol synthesis unit 50, and a control unit 60. In this embodiment, the pretreatment unit 10 performs front-end purification of the waste incineration flue gas, the carbon capture unit 20 captures carbon dioxide from the purified flue gas, and the buffer unit 40 and control unit 60 coordinate the supply process of carbon dioxide and hydrogen, enabling the captured carbon dioxide to be continuously used for methanol synthesis. This solves the technical problem in the prior art of stably capturing carbon dioxide from waste incineration flue gas and continuously using it for methanol synthesis.

[0023] The pretreatment unit 10 is located upstream of the carbon capture unit 20 and is used to purify the waste incineration flue gas before it enters the carbon capture unit 20. Since waste incineration flue gas typically contains impurities such as acidic gases, particulate matter, heavy metals, and organic pollutants, direct entry into the carbon capture unit 20 can easily lead to absorbent degradation, salt accumulation, or decreased absorption performance, thus affecting the long-term stable operation of the carbon dioxide capture process. Therefore, in this embodiment, the pretreatment unit 10 first reduces the impurity content in the flue gas, making the flue gas entering the carbon capture unit 20 more suitable for the subsequent absorbent capture process, thereby reducing the adverse effects of impurities on the carbon capture process from the source.

[0024] The carbon capture unit 20 includes an absorption tower 21 and a regeneration tower 22. The absorption tower 21 has a flue gas inlet and a rich liquid outlet. The flue gas inlet is connected to the outlet of the pretreatment unit 10, allowing the pretreated waste incineration flue gas to enter the absorption tower 21 and contact the absorbent, where the absorbent absorbs carbon dioxide. The absorbent, after absorbing carbon dioxide, forms a rich liquid, which is transported to the regeneration tower 22 through the rich liquid outlet. The regeneration tower 22 has a lean liquid outlet and a carbon dioxide outlet. The rich liquid releases carbon dioxide within the regeneration tower 22, and the released carbon dioxide is output through the carbon dioxide outlet. The desorbed lean liquid returns to the absorption tower 21 through the absorbent circulation path 23 via the lean liquid outlet, thus forming a cycle of absorbent use between the absorption tower 21 and the regeneration tower 22.

[0025] Furthermore, an electrodialysis desalination module 24 is installed on the absorbent circulation path 23. The electrodialysis desalination module 24 is used for online purification of the circulating absorbent, particularly to reduce the accumulation of thermally stable salts and other impurities during absorbent circulation. During multiple cycles of absorbent use, it can promptly remove salt components that affect absorbent performance, reduce absorbent performance degradation, and avoid frequent absorbent replacements due to absorbent failure. This allows the carbon capture unit 20 to maintain stable operation for a longer period under waste incineration flue gas conditions. Therefore, this embodiment does not achieve conventional carbon dioxide capture solely through the absorption tower 21 and regeneration tower 22, but rather improves the stability and economy of the carbon dioxide capture process by introducing the electrodialysis desalination module 24 into the absorbent circulation path 23, enabling continuous purification of the absorbent during circulation.

[0026] The wind-solar hydrogen production unit 30 includes a wind power generation device 31, a photovoltaic power generation device 32, and a water electrolysis hydrogen production device 33. The wind power generation device 31 and the photovoltaic power generation device 32 are electrically connected to the water electrolysis hydrogen production device 33 to provide electrical energy, enabling the device to produce hydrogen. This embodiment uses renewable energy to produce hydrogen required for methanol synthesis, reducing carbon emissions from traditional fossil fuel-based hydrogen production and making the subsequent methanol synthesis process more suitable for forming a low-carbon or green methanol production pathway.

[0027] The buffer unit 40 includes a raw material buffer 41 and an electrical energy buffer 42. The raw material buffer 41 is connected to the carbon dioxide output ports of the water electrolysis hydrogen production unit 33 and the regeneration tower 22, respectively, and is used to receive and store the hydrogen produced by the water electrolysis hydrogen production unit 33 and the carbon dioxide output by the regeneration tower 22. Due to the fluctuations in wind power and photovoltaic power generation, the hydrogen production of the water electrolysis hydrogen production unit 33 will also vary accordingly; at the same time, the carbon dioxide output by the carbon capture unit 20 may also fluctuate with the flue gas operating conditions or regeneration status. If hydrogen and carbon dioxide are directly supplied to the methanol synthesis unit 50, it is easy to cause instability in the feed of the methanol synthesis unit 50, affecting the continuous operation of the catalytic reaction. Therefore, in this embodiment, the raw material buffer 41 is used to temporarily store and regulate hydrogen and carbon dioxide, so that hydrogen and carbon dioxide can be supplied to the methanol synthesis unit 50 in a relatively stable state. The electrical energy buffer 42 is electrically connected to the wind power generation unit 31 and the photovoltaic power generation unit 32, and is used to store the electrical energy generated by the wind power generation unit 31 and the photovoltaic power generation unit 32. When the wind and solar power output is high, the power buffer 42 can store excess power.

[0028] The methanol synthesis unit 50 is connected to the feedstock buffer 41 to receive hydrogen and carbon dioxide from the feedstock buffer 41 and to produce methanol through hydrogenation under the action of a catalyst. Because the feedstock buffer 41 can buffer and regulate the hydrogen and carbon dioxide, the supply of feedstock gas into the methanol synthesis unit 50 is more stable, which helps to reduce frequent changes in reaction load caused by feedstock fluctuations, thereby improving the continuity and stability of the methanol synthesis process.

[0029] The control unit 60 is connected to the wind and solar hydrogen production unit 30, the buffer unit 40, and the methanol synthesis unit 50. It is used to acquire the output status of the wind power generation device 31 and the photovoltaic power generation device 32, the power status of the power buffer 42, and the storage status of hydrogen and carbon dioxide in the raw material buffer 41. Based on the above status, it coordinates and controls the operation status of the water electrolysis hydrogen production device 33 and the methanol synthesis unit 50.

[0030] Specifically, the control unit 60 can obtain the predicted output information corresponding to the wind power generation device 31 and the photovoltaic power generation device 32 through the communication interface, and combine the current state of charge of the power buffer 42 and the actual output power of the wind power generation device 31 and the photovoltaic power generation device 32 to determine the power supply status of the system in the future preset time period.

[0031] Under normal operating conditions, when the charge state of the power buffer 42 is within the preset range and the pressure in the hydrogen buffer tank 411 and the carbon dioxide buffer tank 412 meets the requirements for methanol synthesis, the control unit 60 controls the water electrolysis hydrogen production device 33 to operate at the preset operating power and controls the methanol synthesis unit 50 to maintain normal production load, so as to improve the utilization efficiency of the power generated by the wind power generation device 31 and the photovoltaic power generation device 32.

[0032] In the event of a warning of reduced wind and solar power output, when the control unit 60 determines, based on predicted output information, that the output power of the wind power generation device 31 and the photovoltaic power generation device 32 will decrease within a preset time period, the control unit 60 adjusts the operating power of the water electrolysis hydrogen production device 33 according to the state of charge of the energy buffer 42. When the energy storage state of the energy buffer 42 is high, the current operating state of the water electrolysis hydrogen production device 33 can be maintained, and the stored energy can be used to compensate for short-term energy shortages. When the energy storage state of the energy buffer 42 decreases, the operating power of the water electrolysis hydrogen production device 33 is reduced, gradually adjusting it towards a stable operating state to reduce energy consumption and slow down the rate of energy storage decline.

[0033] In the event of insufficient power supply, when the state of charge of the power buffer 42 falls below a preset safe level, and the real-time wind and solar power output is insufficient to maintain the normal operation of the water electrolysis hydrogen production unit 33, the control unit 60 executes a control strategy that prioritizes methanol synthesis operation. Specifically, the control unit 60 prioritizes reducing the operating power of the water electrolysis hydrogen production unit 33 to reduce power consumption and prioritizes power supply to the methanol synthesis unit 50; simultaneously, the control unit 60 adjusts the operating load of the methanol synthesis unit 50 according to the hydrogen storage level in the hydrogen buffer tank 411, enabling the methanol synthesis unit 50 to maintain operation using the hydrogen and carbon dioxide stored in the raw material buffer 41. When the hydrogen storage level in the hydrogen buffer tank 411 further decreases to a preset level, the control unit 60 further reduces the operating load of the methanol synthesis unit 50 or puts it into a low-load operation state.

[0034] Through the above control method, this embodiment prioritizes adjusting the fluctuations of wind and solar power generation to the water electrolysis hydrogen production stage, and uses the power buffer 42 and the raw material buffer 41 to coordinate and adjust the energy and raw material supply, so that the methanol synthesis unit 50 can maintain continuous and stable operation as much as possible, and reduce the adverse effects of the intermittent nature of wind and solar power generation on the methanol synthesis process.

[0035] In this embodiment, the pretreatment unit 10 reduces the adverse effects of flue gas impurities on the absorbent, the carbon capture unit 20 and the electrodialysis desalination module 24 achieve the cyclic purification and stable capture of the absorbent, the buffer unit 40 buffers the fluctuations of hydrogen, carbon dioxide and electricity, and the control unit 60 coordinates the control based on the wind and solar forecast status, the electricity storage status and the raw material storage status, prioritizes the adjustment of the hydrogen production process and ensures the stable operation of the methanol synthesis process, thus achieving the stable capture of carbon dioxide in the waste incineration flue gas, the continuous connection with the wind and solar hydrogen production process, and the stable operation of the methanol synthesis process.

[0036] In one embodiment, the pretreatment unit 10 includes a quench cooling tower 11, a wet scrubbing tower 12 and a flue gas fine filter 13 connected in sequence. After the waste incineration flue gas flows through the quench cooling tower 11, the wet scrubbing tower 12 and the flue gas fine filter 13 in sequence, it enters the absorption tower 21 of the carbon capture unit 20.

[0037] The quench cooling tower 11 is used to receive and cool the flue gas from waste incineration. Since the flue gas exiting the incineration system is at a high temperature, directly entering subsequent scrubbing or carbon capture processes could easily affect the scrubbing efficiency and the stability of the absorbent. Therefore, the quench cooling tower 11 lowers the flue gas temperature through contact with or heat exchange with the cooling medium, making the flue gas temperature suitable for subsequent wet scrubbing and carbon dioxide absorption processes. Rapidly cooling the flue gas using the quench cooling tower 11 also reduces the generation of some secondary pollutants under high-temperature conditions, which is beneficial to improving the stability of subsequent purification treatment.

[0038] The wet scrubbing tower 12 is connected to the outlet of the quench cooling tower 11 and is used to scrub the cooled flue gas. A spray assembly can be installed inside the wet scrubbing tower 12 to spray scrubbing liquid into the tower, ensuring full contact between the flue gas and the scrubbing liquid, thereby removing acidic gases and soluble impurities from the flue gas. For example, the wet scrubbing tower 12 can reduce the content of residual acidic components such as sulfur dioxide, nitrogen oxides, and hydrogen chloride in the flue gas, and can capture some heavy metal vapors and aerosols. This reduces the risk of degradation, salt accumulation, or performance degradation of the absorbent caused by these impurities entering the carbon capture unit 20.

[0039] The flue gas fine filter 13 is connected to the outlet of the wet scrubbing tower 12 for further filtration of the scrubbed flue gas. The flue gas fine filter 13 can use activated carbon fiber, filter media, or other adsorption filter materials to remove residual fine particulate matter, aerosols, organic pollutants, and trace amounts of dioxins from the scrubbed flue gas. The impurity content of the flue gas treated by the flue gas fine filter 13 is further reduced, meeting the requirements for long-term recycling of the absorbent in the carbon capture unit 20.

[0040] In this embodiment, the pretreatment unit 10 forms a multi-stage purification path of cooling, washing and fine filtration before the carbon capture unit 20, so that the waste incineration flue gas is fully adapted and treated before entering the absorption tower 21, reducing the adverse effects of complex impurities on the absorbent, thereby improving the stability of the carbon dioxide capture process and providing a more stable source of raw materials for the subsequent continuous use of carbon dioxide in methanol synthesis.

[0041] In one embodiment, the absorption tower 21 uses a binary mixed phase change absorbent, which includes N-methyldiethanolamine and diethylenetriamine. The mass ratio of the absorbent is: N-methyldiethanolamine 33% to 35%, diethylenetriamine 6.5% to 7.5%, water content 28% to 30%, and the remaining components are supplementary solvents.

[0042] N-Methyldiethanolamine, as the main component of the absorbent, can absorb carbon dioxide in flue gas and maintain good circulation stability during the absorption process. Diethylenetriamine, as an enhanced absorption component, can improve the absorption rate of carbon dioxide by the absorbent, so that the carbon dioxide in the pretreated waste incineration flue gas can be absorbed by the absorbent more quickly after entering the absorption tower 21. Water, as a solvent component, is used to adjust the flowability and mass transfer performance of the absorbent system, so that the absorbent can circulate stably between the absorption tower 21 and the regeneration tower 22.

[0043] Within the aforementioned ratio range, N-methyldiethanolamine, diethylenetriamine, and water can form an absorbent system suitable for capturing carbon dioxide from waste incineration flue gas. On one hand, this absorbent system ensures high carbon dioxide absorption efficiency; on the other hand, the absorbent after absorbing carbon dioxide maintains significant phase change separation characteristics, which is beneficial for the separation of the carbon dioxide-rich phase and the carbon dioxide-poor phase, as well as subsequent regeneration. This binary mixed phase change absorbent can reduce absorbent regeneration energy consumption while ensuring effective carbon dioxide capture. Furthermore, by adjusting the composition of the absorbent system by adding solvent, the stability of the absorbent during the circulation process can be further improved, making it suitable for long-term continuous capture of waste incineration flue gas.

[0044] In one embodiment, the waste incineration flue gas to methanol system further includes a heat reuse unit. This unit recovers and redistributes usable heat generated during system operation to reduce the external energy requirements of the carbon capture unit 20 regeneration process and the auxiliary heating process of the wind-solar-hydrogen production unit 30. The heat reuse unit includes a heat exchange loop connected to the methanol synthesis unit 50, the carbon capture unit 20, the wind-solar-hydrogen production unit 30, and the pretreatment unit 10. This loop recovers the reaction heat generated by the methanol synthesis unit 50 and the waste heat generated by the pretreatment unit 10, and transfers the recovered heat to the corresponding heat-using components.

[0045] Further, please refer to Figure 2 , Figure 2 This is a schematic diagram of the heat reuse unit provided in this embodiment of the invention. The heat exchange loop includes a primary heat exchange branch 71, a secondary heat exchange branch 72, and a tertiary heat exchange branch 73, to classify and utilize heat within the system according to different heat grades. The primary heat exchange branch 71 is connected to the methanol synthesis unit 50 and the regeneration tower 22, and is used to transport the higher-temperature reaction heat generated by the methanol synthesis unit 50 to the regeneration tower 22. Since the regeneration tower 22 needs to reduce the binding capacity between the absorbent and carbon dioxide through heating, causing the absorbent to release the absorbed carbon dioxide and obtain a higher concentration of carbon dioxide gas, the high-temperature reaction heat from the methanol synthesis unit 50 is preferentially supplied to the regeneration tower 22, which can match the high-grade heat with the high-temperature heat demand and improve heat utilization efficiency.

[0046] The secondary heat exchange branch 72 is connected to the methanol synthesis unit 50 and the wind-solar hydrogen production unit 30, and is used to transfer the medium- and low-temperature waste heat generated by the methanol synthesis unit 50 to the wind-solar hydrogen production unit 30. The secondary heat exchange branch 72 can be connected to the electrolyte preheating structure of the water electrolysis hydrogen production unit 33, and is used to preheat the electrolyte entering the water electrolysis hydrogen production unit 33. By preheating the electrolyte, the operating conditions of the water electrolysis hydrogen production unit 33 can be improved, the energy consumption during the start-up of the electrolysis process or during low-temperature operation can be reduced, and the wind-solar hydrogen production unit 30 can maintain a relatively stable hydrogen production state under the condition of fluctuating wind and solar power output.

[0047] The tertiary heat exchange branch 73 is connected to the pretreatment unit 10 and the absorption tower 21, and is used to transfer the waste heat in the pretreatment unit 10 to the absorption tower 21. The pretreatment unit 10 generates a certain amount of low-temperature waste heat during the cooling, washing, or filtering process of the waste incineration flue gas. This low-temperature waste heat can be transferred to the makeup liquid or absorbent makeup liquid side of the absorption tower 21 through the tertiary heat exchange branch 73, for preheating or temperature regulation of the liquid entering the absorption tower 21. This improves the temperature conditions of the gas-liquid contact process within the absorption tower 21, reduces the adverse effects of flue gas temperature fluctuations on the absorption process, and enhances the operational stability of the absorption tower 21.

[0048] Furthermore, in this embodiment, since the system is applied to a waste incineration plant scenario, the waste heat generated by the pretreatment unit 10 originates from the waste incineration flue gas treatment process, which differs from the independent heat source heating method in traditional chemical systems. Specifically, the three-stage heat exchange branch 73 can recover the waste heat from the flue gas at the outlet of the quench cooling tower 11 to preheat the absorbent entering the absorption tower 21. The flue gas temperature at the outlet of the quench cooling tower 11 can be between 150°C and 200°C. By recovering this portion of the flue gas waste heat, the three-stage heat exchange branch 73 maintains the absorbent temperature entering the absorption tower 21 within the range of 40°C to 50°C. Since this embodiment uses a binary mixed phase change absorbent, the absorption performance and phase separation characteristics of the absorbent are related to the operating temperature. By adjusting the absorbent to a suitable temperature range, the viscosity of the absorbent can be reduced, and the mass transfer efficiency between the absorbent and the flue gas can be improved, thereby enhancing the carbon dioxide absorption effect. At the same time, by utilizing the waste heat of the waste incineration flue gas itself to regulate the temperature of the absorbent, no additional independent heat source is required, which helps to reduce the system's operating energy consumption.

[0049] The primary heat exchange branch 71, secondary heat exchange branch 72, and tertiary heat exchange branch 73 can be equipped with heat exchangers, circulating pumps, and flow regulators to adjust the flow rate of the heat exchange medium in each branch. The heat exchange medium can be heat transfer oil, water, or other heat transfer media suitable for the system temperature conditions. By setting up different heat exchange branches, the heat reuse unit can transfer the high-temperature reaction heat, medium-temperature waste heat, and low-temperature waste heat in the system to the corresponding heat-using parts, enabling the heat to be utilized in stages according to temperature grade, avoiding the inefficient use of high-grade heat and the direct discharge of low-grade waste heat.

[0050] Furthermore, in some embodiments, the heat exchange circuit is equipped with a control valve 74. The control valve 74 is used to switch the heat exchange circuit to an external heat source when the reaction heat generated by the methanol synthesis unit 50 is lower than the heating demand. The external heat source can be low-pressure steam provided by the waste incineration plant's waste heat boiler, the plant's waste heat network, or other available heat sources. Specifically, the external heat source is preferably low-pressure steam generated by the waste incineration boiler. When the methanol synthesis unit 50 is operating at low load, in the start-up phase, or when the reaction heat output is insufficient, the control valve 74 controls the opening of the external heat source heating channel, allowing the low-pressure steam to enter the heating circuit of the regeneration tower 22 to provide supplementary heat to the regeneration tower 22, preventing insufficient heat from affecting the absorbent regeneration process. By utilizing the low-pressure steam generated by the waste incineration boiler as a supplementary heat source, the waste heat generated within the waste incineration plant can be fully utilized, achieving energy synergy within the plant area.

[0051] In one embodiment, the raw material buffer unit 41 includes a hydrogen buffer tank 411 and a carbon dioxide buffer tank 412. The hydrogen buffer tank 411 is connected to the hydrogen output terminal of the wind-solar hydrogen production unit 30 to receive and store the hydrogen produced by the water electrolysis hydrogen production device 33. The carbon dioxide buffer tank 412 is connected to the carbon dioxide output port of the carbon capture unit 20 to receive and store the carbon dioxide released after the regeneration tower 22 regenerates the absorbent. The hydrogen buffer tank 411 and the carbon dioxide buffer tank 412 independently store and buffer the hydrogen and carbon dioxide, respectively, so that the two raw material gases can form a stable supply state before entering the methanol synthesis unit 50.

[0052] In one embodiment, the power buffer 42 is electrically connected to the water electrolysis hydrogen production device 33 for power regulation of the electrical energy output from the wind power generation device 31 and the photovoltaic power generation device 32. The power buffer 42 can be an electrochemical energy storage battery, an energy storage battery pack, or other energy storage device capable of charge and discharge regulation. Its input terminal is connected to the power output terminal of the wind power generation device 31 and the photovoltaic power generation device 32, and its output terminal is connected to the water electrolysis hydrogen production device 33.

[0053] In this embodiment, by setting up an energy buffer 42, the electrical energy output from the wind power generation device 31 and the photovoltaic power generation device 32 can be regulated by the energy buffer 42 before being supplied to the water electrolysis hydrogen production device 33. When the output power of the wind power generation device 31 and the photovoltaic power generation device 32 is higher than the current operating power required by the water electrolysis hydrogen production device 33, the energy buffer 42 can receive and store the surplus electrical energy; when the output power of the wind power generation device 31 and the photovoltaic power generation device 32 is lower than the current operating power required by the water electrolysis hydrogen production device 33, the energy buffer 42 can release electrical energy to the water electrolysis hydrogen production device 33 to supplement the power supply gap of the water electrolysis hydrogen production device 33.

[0054] In some embodiments, the power buffer 42 can also be used to maintain the minimum stable operating load of the water electrolysis hydrogen production device 33. That is, when the real-time output power of the wind power generation device 31 and the photovoltaic power generation device 32 is insufficient to maintain the stable operation of the water electrolysis hydrogen production device 33, the power buffer 42 can supplement the power supply to the water electrolysis hydrogen production device 33, so that the water electrolysis hydrogen production device 33 does not frequently shut down due to short-term reductions in wind and solar power output. As a result, the increased energy consumption and equipment wear caused by repeated start-ups and shutdowns of the water electrolysis hydrogen production device 33 can be reduced.

[0055] On the other hand, please see Figure 3 , Figure 3This is a schematic flowchart of a method for producing methanol from waste incineration flue gas provided in an embodiment of the present invention. This application also provides a method for producing methanol from waste incineration flue gas, which can be applied to the waste incineration flue gas methanol production system in any of the above embodiments. This method, through pretreatment of waste incineration flue gas, carbon dioxide capture, wind and solar hydrogen production, feedstock buffering, methanol synthesis, and heat energy recovery and utilization, enables the stable capture and continuous use of carbon dioxide from the waste incineration flue gas for methanol synthesis.

[0056] First, the waste incineration flue gas undergoes pretreatment to remove particulate matter and acidic impurities. The pretreatment process may include cooling, washing, and filtering the flue gas to reduce the levels of dust, acidic gases, soluble impurities, and some organic pollutants. This step minimizes the adverse effects of impurities in the flue gas on the subsequent absorbent, preventing performance degradation due to impurity accumulation and thus improving the stability of the subsequent carbon dioxide capture process.

[0057] Subsequently, the pretreated flue gas is passed into the carbon capture unit 20 for carbon dioxide absorption. Specifically, after entering the absorption tower 21, the pretreated flue gas comes into contact with the absorbent, and the carbon dioxide in the flue gas is absorbed by the absorbent to form a rich liquid. The rich liquid enters the regeneration tower 22 for regeneration treatment to release carbon dioxide gas. The regenerated carbon dioxide gas can be further transported to the buffer unit 40 for temporary storage so as to ensure a stable supply to the methanol synthesis unit 50. The regenerated lean liquid is returned to the absorption tower 21 to continue participating in carbon dioxide absorption. Furthermore, during the absorbent circulation process, the absorbent can be purified online through the electrodialysis desalination module 24 to reduce the accumulation of salt impurities in the absorbent, enabling the absorbent to be used for a long time and reducing the frequency of absorbent replacement.

[0058] Simultaneously, wind and solar power generation drive a water electrolysis hydrogen production unit 33 to produce hydrogen. The electrical energy output from wind and solar power supplies the water electrolysis hydrogen production unit 33, enabling it to electrolyze water to generate hydrogen. Due to the fluctuations in wind and solar power generation, the produced hydrogen can first enter a buffer unit 40 for storage and regulation. By temporarily storing the hydrogen in the buffer unit 40, the impact of wind and solar power output fluctuations on the hydrogen supply can be reduced, allowing the hydrogen to be supplied to the methanol synthesis unit 50 in a relatively stable state.

[0059] After obtaining hydrogen and carbon dioxide, the hydrogen and carbon dioxide are introduced into the methanol synthesis unit 50 for a catalytic reaction to produce methanol. The buffer unit 40 can store and regulate the hydrogen and carbon dioxide separately, and supply feedstock gases to the methanol synthesis unit 50 according to its reaction requirements. This reduces the impact of fluctuations in the water electrolysis hydrogen production process and the carbon dioxide capture process on the methanol synthesis reaction, ensuring a more stable feedstock supply for the methanol synthesis unit 50 and guaranteeing the continuous operation of the catalytic synthesis process.

[0060] Furthermore, the reaction heat generated by the methanol synthesis unit 50 is transferred to the regeneration tower 22 of the carbon capture unit 20 for heat energy recovery and utilization. A certain amount of heat is released during the methanol synthesis reaction; this heat can be transferred to the regeneration tower 22 via a heat exchange loop to provide heat for the absorbent regeneration process. This reduces the waste of reaction heat from the methanol synthesis unit 50 and decreases the dependence of the regeneration tower 22 on external heat sources, thereby improving the overall energy utilization efficiency of the system. In some embodiments, when the reaction heat generated by the methanol synthesis unit 50 is insufficient to meet the heating requirements of the regeneration tower 22, an external heat source can be introduced to supplement the heating of the regeneration tower 22 to ensure the stable operation of the carbon dioxide regeneration process.

[0061] In addition, the charging state of the power buffer 42 in the buffer unit 40, the storage state of the raw material buffer 41, and the predicted output state of the wind power generation device 31 and the photovoltaic power generation device 32 are obtained, and the electrolysis water hydrogen production device 33 and the methanol synthesis unit 50 are coordinated and controlled according to the above states.

[0062] The control unit 60 can determine the energy supply trend of wind and solar power generation within a preset time period based on the predicted output status of the wind power generation device 31 and the photovoltaic power generation device 32, and adjust the operating power of the water electrolysis hydrogen production device 33 in conjunction with the current state of charge of the energy buffer 42. When the predicted wind and solar output is high and the energy buffer 42 has a large energy storage capacity, the operating power of the water electrolysis hydrogen production device 33 can be increased to fully utilize renewable energy to produce hydrogen; when the predicted wind and solar output decreases or the state of charge of the energy buffer 42 decreases, the operating power of the water electrolysis hydrogen production device 33 can be reduced to reduce energy consumption and maintain the energy buffer 42 in a stable energy storage state.

[0063] Furthermore, the production load of the methanol synthesis unit 50 is adjusted according to the hydrogen and carbon dioxide reserves in the raw material buffer 41. When the hydrogen and carbon dioxide reserves in the raw material buffer 41 meet the methanol synthesis requirements, the methanol synthesis unit 50 is controlled to maintain normal operating load; when the raw material reserves in the raw material buffer 41 decrease, the production load of the methanol synthesis unit 50 is reduced, so that the raw material consumption of the methanol synthesis unit 50 matches the supply capacity of the raw material buffer 41, avoiding system interruption due to insufficient raw material supply.

[0064] Through the above-mentioned coordinated control method, the fluctuations in the wind and solar power generation process can be preferentially adjusted to the water electrolysis hydrogen production stage, and the raw material buffer 41 can be used to buffer and regulate hydrogen and carbon dioxide, so that the methanol synthesis unit 50 can maintain a relatively stable operating state under the conditions of wind and solar fluctuations.

[0065] In this embodiment, the impact of flue gas impurities on the absorbent is reduced by pretreatment, carbon dioxide is stably captured by the carbon capture unit 20, green hydrogen source is obtained by wind and solar hydrogen production, and carbon dioxide and hydrogen are continuously supplied to the methanol synthesis unit 50 through buffer regulation, heat recovery and load regulation, thereby achieving the effect of stable capture of carbon dioxide in waste incineration flue gas and its continuous use for methanol synthesis.

[0066] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A system for producing methanol from waste incineration flue gas, characterized in that, include: The pretreatment unit is used to purify the flue gas from waste incineration. The carbon capture unit includes an absorption tower and a regeneration tower. The absorption tower has a flue gas inlet and a rich liquid outlet. The flue gas inlet is connected to the outlet of the pretreatment unit. The rich liquid outlet is connected to the regeneration tower. The regeneration tower has a lean liquid outlet and a carbon dioxide outlet. The lean liquid outlet returns to the absorption tower through an absorbent circulation path, and an electrodialysis desalination module is provided on the absorbent circulation path. A wind-solar hydrogen production unit includes a wind power generation device, a photovoltaic power generation device, and a water electrolysis hydrogen production device. The wind power generation device and the photovoltaic power generation device are electrically connected to the water electrolysis hydrogen production device to drive the water electrolysis hydrogen production. The buffer unit includes a raw material buffer and an electrical energy buffer. The raw material buffer is connected to the carbon dioxide output port of the water electrolysis hydrogen production device and the regeneration tower, respectively, for storing hydrogen and carbon dioxide. The input end of the electrical energy buffer is electrically connected to the wind power generation device and the photovoltaic power generation device, and the output end of the electrical energy buffer is electrically connected to the water electrolysis hydrogen production device, for storing and releasing electrical energy to regulate the input power of the water electrolysis hydrogen production device. A methanol synthesis unit, connected to the raw material buffer, is used to receive hydrogen and carbon dioxide and perform catalytic synthesis of methanol; The control unit is connected to the wind and solar hydrogen production unit, the buffer unit, and the methanol synthesis unit. It is used to acquire the electrical energy status of the electrical energy buffer, the storage status of the raw material buffer, and the output status of the wind power generation device and the photovoltaic power generation device, and to adjust the operating load of the water electrolysis hydrogen production device and the methanol synthesis unit.

2. The waste incineration flue gas to methanol system according to claim 1, characterized in that, The pretreatment unit includes a quench cooling tower, a wet scrubbing tower, and a flue gas fine filter connected in sequence. The quench cooling tower is used to receive and cool the flue gas from waste incineration. The wet scrubbing tower is used to scrub the cooled flue gas. The flue gas fine filter is used to filter the scrubbed flue gas.

3. The waste incineration flue gas to methanol system according to claim 1, characterized in that, The absorption tower uses a binary mixed phase change absorbent, which includes N-methyldiethanolamine and diethylenetriamine. The mass ratio of the absorbent is: N-methyldiethanolamine 33% to 35%, diethylenetriamine 6.5% to 7.5%, water content 28% to 30%, and the remainder is a supplementary solvent.

4. The waste incineration flue gas to methanol system according to claim 3, characterized in that, The supplemental solvent includes at least one of water, alcohol solvents, or alkanolamine stabilizers.

5. The waste incineration flue gas to methanol system according to claim 1, characterized in that, The waste incineration flue gas to methanol system also includes a heat reuse unit, which includes a heat exchange circuit that recovers the reaction heat generated by the methanol synthesis unit and the waste heat from the pretreatment unit.

6. The waste incineration flue gas to methanol system according to claim 5, characterized in that, The heat exchange circuit includes a primary heat exchange branch, a secondary heat exchange branch, and a tertiary heat exchange branch. The primary heat exchange branch is used to transfer the reaction heat generated by the methanol synthesis unit to the regeneration tower. The secondary heat exchange branch is used to transfer the reaction heat generated by the methanol synthesis unit to the wind and solar hydrogen production unit. The tertiary heat exchange branch is used to transfer the waste heat of the pretreatment unit to the absorption tower.

7. The waste incineration flue gas to methanol system according to claim 6, characterized in that, The heat exchange circuit is equipped with a control valve, which is used to switch the heat exchange circuit to an external heat source heating channel when the reaction heat generated by the methanol synthesis unit is lower than the heating demand.

8. The waste incineration flue gas to methanol system according to claim 1, characterized in that, The raw material buffer includes a hydrogen buffer tank and a carbon dioxide buffer tank, which are used for independent storage and buffering regulation of hydrogen and carbon dioxide.

9. The waste incineration flue gas to methanol system according to claim 1, characterized in that, The control unit is configured as follows: Based on the state of charge of the power buffer and the predicted output state of the wind power generation device and the photovoltaic power generation device, the operating power of the water electrolysis hydrogen production device is preferentially adjusted to absorb the output fluctuations of the wind power generation device and the photovoltaic power generation device. And when the raw material buffer is insufficient, the operating load of the methanol synthesis unit is reduced to maintain the continuous and stable operation of the methanol synthesis unit.

10. A method for producing methanol from waste incineration flue gas, characterized in that, Includes the following steps: Pre-treatment of waste incineration flue gas is carried out to remove particulate matter and acidic impurities. The pretreated flue gas is fed into the carbon capture unit, where the absorbent absorbs the carbon dioxide in the flue gas to form a rich liquid. The rich liquid is then transported to the regeneration tower for regeneration to obtain carbon dioxide gas. The regenerated lean liquid is returned to the absorption tower through the absorbent circulation path to continue participating in carbon dioxide absorption. The absorbent in the absorbent circulation path is also subjected to online electrodialysis desalination treatment. Hydrogen is produced by using wind power generation and photovoltaic power generation devices to drive a water electrolysis hydrogen production device, and hydrogen, carbon dioxide, and electrical energy generated by the wind power generation and photovoltaic power generation devices are stored and regulated by a buffer unit. The hydrogen and carbon dioxide are introduced into the methanol synthesis unit to carry out a catalytic reaction to produce methanol, and the reaction heat generated by the methanol synthesis unit is transported to the regeneration tower of the carbon capture unit for heat energy recovery and utilization. The state of charge of the electrical energy buffer, the storage status of the raw material buffer, and the predicted output status of the wind power generation device and the photovoltaic power generation device are obtained in the buffer unit. Based on the predicted output state and the state of charge, the operating power of the water electrolysis hydrogen production device is adjusted to regulate the energy storage state of the energy buffer. Based on the storage status of the raw material buffer, the production load of the methanol synthesis unit is adjusted so that the raw material consumption of the methanol synthesis unit matches the supply capacity of the raw material buffer, thereby maintaining continuous and stable operation of the system.

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