High-efficiency low-energy-consumption carbon capture system and method used before ship combustion

Abstract

The invention provides a high-efficiency and low-energy-consumption carbon capture system used before combustion of an LNG (Liquefied Natural Gas) or methanol fuel ship, which comprises an air separation device, a gas generator, a shift reactor, an on-board boiler, an absorption tower, a heat exchange system, a desorption tower, a CO2 storage tank, a hydrogen fuel cell, a waste heat recovery device, a steam turbine and a condenser, a membrane separation module is arranged at the top or the upper half part of the absorption tower, is connected with the absorption tower body through a pipeline and is used for realizing separation and purification of hydrogen. According to the system, on one hand, energy consumption can be reduced through effective waste heat management, and on the other hand, CO2 and H2 are effectively separated through a separation and purification technology, so that high-purity CO2 and H2 are obtained and are conveniently stored and supplied to a hydrogen fuel cell.

Description

Technical Field

[0001] The present invention relates to the technical field of ship power and environmental governance, and particularly relates to an efficient low-energy-consumption carbon capture system for ships before combustion. Background Art

[0002] In recent years, the International Maritime Organization (IMO) has imposed strict restrictions on greenhouse gas emissions from ships and required ships to gradually achieve the goal of zero carbon emissions. The traditional ship combustion method will continue to emit CO2 and other pollutants, and it is difficult to meet the future requirements for environmental protection and energy efficiency due to low fuel utilization efficiency. To address these challenges, liquefied natural gas (LNG) and methanol have gradually become the mainstream choices in the new shipbuilding market, and more than 60% of ships have adopted these fuels. Compared with traditional heavy fuel oil, LNG and methanol can effectively reduce CO2 emissions. However, although these fuels are relatively environmentally friendly, they still cannot achieve zero carbon emissions, so carbon capture technology must be used to further reduce emissions.

[0003] Carbon capture technology is divided into pre-combustion capture and post-combustion capture. Post-combustion carbon capture technology usually captures CO2 after a large amount of CO2 is generated by combustion, and the capture process requires complex separation of diluted gas containing a large amount of nitrogen and water vapor. This method wastes a large amount of energy, while pre-combustion carbon capture effectively reduces the concentration of CO2, improves the capture efficiency, and reduces the energy consumption of the system by capturing and separating CO2 before the fuel gas is burned. Post-combustion capture technology is usually interfered by impurities (such as sulfur oxides SOx, nitrogen oxides NOx, particulate matter PM, etc.) in the flue gas, and these pollutants need additional pretreatment processes to remove, increasing the operation complexity and energy consumption.

[0004] Different from post-combustion capture, pre-combustion carbon capture technology can effectively reduce the concentration of CO2, improve the capture efficiency, and reduce the energy consumption of the system by capturing CO2 before the fuel gas is burned. Compared with post-combustion capture, the greatest advantages of pre-combustion capture technology are: 1. Improve capture efficiency: Pre-combustion capture can effectively avoid the interference of impurities on the capture process and simplify the treatment process; 2. Reduce energy consumption: By processing gas at lower temperature and pressure, pre-combustion capture technology can significantly reduce energy consumption; 3. Improve flexibility and environmental friendliness: Since it does not rely on high-temperature flue gas, the pre-combustion capture system can operate in a smaller space and under lower operating conditions, improving the flexibility of the system and reducing the dependence on external energy.

[0005] There are currently two main problems that hinder the large-scale application of pre-combustion capture technology. First, the application scenario of ships has relatively high energy consumption requirements. Although pre-combustion carbon capture reduces energy consumption compared to post-combustion carbon capture, the thermocatalytic reforming technology needs to react at high temperatures (usually between 700°C and 900°C), which will lead to low system energy efficiency and consume a large amount of energy. As the requirements for low energy consumption and high energy efficiency of ships are getting higher and higher, reducing energy consumption and optimizing energy recovery have become a key direction for technological development. On the other hand, a large amount of hydrogen is generated in pre-combustion capture and is used in new energy hydrogen fuel cells to provide power for ships. During the thermocatalytic reforming process, the purity of hydrogen is usually relatively low, perhaps only reaching 90% to 95%. Since impurities (such as carbon monoxide, carbon dioxide, etc.) will react with the catalyst in the hydrogen fuel cell and reduce the efficiency of the battery, it is crucial to improve the purity. In addition, the CO2 capture technology also faces the problem of low purity, which affects subsequent storage and utilization. Summary of the Invention

[0006] The purpose of the present invention is to provide a high-efficiency and low-energy-consumption carbon capture system for pre-combustion of LNG or methanol fuel ships. On the one hand, through effective waste heat management, energy consumption can be reduced. On the other hand, through separation and purification technology, the effective separation of CO2 and H2 can be achieved to obtain high-purity CO2 and H2, which is convenient for storage and supply to hydrogen fuel cells.

[0007] To solve the above technical problems, the present invention provides a high-efficiency and low-energy-consumption carbon capture system for pre-combustion of LNG or methanol fuel ships, which includes: an air separation device, a gas generator, a shift reactor, a ship boiler, an absorption tower, a heat exchange system, a stripping tower, a CO2 storage tank, a hydrogen fuel cell, a waste heat recovery device, a steam turbine, and a condenser. A membrane separation module is provided at the top or upper half of the absorption tower and is connected to the absorption tower body through a pipeline for realizing the separation and purification of hydrogen.

[0008] A preferred technical solution is that the air separation device is connected to the gas generator through a pipeline, the gas generator is connected to the shift reactor through a pipeline. On the one hand, the shift reactor is connected to the ship boiler through a pipeline to receive steam from the ship boiler. On the other hand, it is connected to the bottom of the absorption tower through a pipeline. The top of the absorption tower is connected to the hydrogen fuel cell through a pipeline to transport purified hydrogen. The bottom of the absorption tower is connected to the heat exchange system through a pipeline. The heat exchange system is connected to the stripping tower through a pipeline to realize the heat exchange between the absorption tower and the stripping tower. The stripping tower is connected to the CO2 storage tank through a pipeline. The hydrogen fuel cell is connected to the waste heat recovery device through a pipeline. The waste heat recovery device is connected to the steam turbine through a pipeline. The steam turbine is connected to the condenser through a pipeline.

[0009] A preferred technical solution is that the separation membrane used in the membrane separation module is a polyether block amine membrane, and the thickness of the membrane is set to be from 50 microns to 100 microns.

[0010] A preferred technical solution is that the membrane separation module includes a plurality of separation components, each separation component is composed of a plurality of thin film units, and each separation component and thin film unit are formed in parallel or in series to form a larger gas separation area.

[0011] A preferred technical solution is to control the waste heat distribution of the hydrogen fuel cell through a temperature sensor and a PLC control system. The waste heat in the high-temperature part (400 - 600K) is used for power generation by a steam turbine: when the ship's power demand is high, the waste heat recovery device will preferentially utilize the waste heat in the high-temperature part of the hydrogen fuel cell to supply the steam turbine. This part of the waste heat is directly converted into steam through the waste heat recovery device and supplied to the steam turbine for power generation; the waste heat in the medium and low-temperature part (300 - 400K) is used for the regeneration heating of the stripping column: the medium and low-temperature waste heat (about 300 - 400K) generated by the hydrogen fuel cell will be transported to the stripping column through the adjustment system of the waste heat recovery device.

[0012] A preferred technical solution is that the waste heat recovery device automatically adjusts the heat output according to the feedback data of the real-time temperature sensor and the PLC control system. When the ship's load is high, more heat is supplied to the steam turbine; when the regeneration demand of the stripping column increases, the waste heat is preferentially supplied to the stripping column.

[0013] The present invention also provides a method for pre-combustion carbon capture using the above system, which includes:

[0014] The first step is the purification of the raw material before carbon capture. An air separation device is used to remove impurities in the raw material gas to ensure that high-purity methane or methanol enters the gas generator.

[0015] The second step is the thermal catalytic preparation of syngas. In the gasification reactor, methane or methanol is decomposed into syngas composed of CO and H2 through an electrochemical reaction.

[0016] The third step is the reforming reaction. The syngas obtained in the second step is introduced into the shift reactor, and CO is converted into CO2 and H2 through the water gas shift reaction.

[0017] The fourth step is the separation and storage of CO2. The absorption tower uses the absorbent to separate CO2 from the mixed gas and sends it to the stripping column. The absorbent rich in CO2 desorbs CO2 through heating, and the purified CO2 is stored in the CO2 storage tank for easy transportation or sequestration.

[0018] The fifth step is that the obtained high-purity H2 directly enters the hydrogen fuel cell for power generation.

[0019] A preferred technical solution is that in the fourth step, the temperature of the absorption tower is controlled between 40°C and 60°C, the pressure is controlled between 1 and 5 bar, and the liquid-gas ratio is controlled between 1:1 and 1:3.

[0020] A preferred technical solution is that in the fourth step, the working pressure of the membrane separation module of the absorption tower is 0.5 - 2 bar, and the temperature is between 30°C and 50°C.

[0021] Advantages of the present invention

[0022] The high-efficiency and low-energy-consumption pre-combustion carbon capture system provided by the present invention enables the purity of hydrogen to reach 99% through optimized hydrogen separation technology, fully meeting the requirements of hydrogen fuel cells. The system optimizes the energy flow through a waste heat recovery device, maximizes the energy utilization efficiency, and reduces the fuel consumption of the ship. Description of the drawings

[0023] Figure 1 Schematic structural diagram of the high-efficiency and low-energy-consumption pre-combustion carbon capture system for LNG or methanol fuel ships of the present invention. Detailed implementation manners

[0024] The present invention provides a high-efficiency and low-energy-consumption pre-combustion carbon capture system for ships, which includes:

[0025] Air separation unit: Remove impurities such as nitrogen (N2), carbon dioxide (CO2), and sulfide (H2S) from the input raw material gas to ensure that high-purity methane (CH4) or methanol (CH3OH) enters the system. The purified gas is transported to the gas generator through a pipeline;

[0026] Gas generator: The raw material gas filtered by the air separation unit undergoes a thermal catalytic cracking reaction of methane or methanol in the gas generator to decompose methane or methanol into carbon monoxide (CO) and hydrogen (H2), which is transported to the shift reactor through a pipeline. If methane is decomposed, this process is usually carried out at a high temperature of 700°C to 900°C. If methanol is decomposed, it is usually carried out at a temperature of 250°C to 450°C. Since this reaction depends on the action of a catalyst, common catalysts include metals such as nickel, platinum, and palladium;

[0027] Shift reactor: Convert CO in the syngas into CO2 and H2 through steam methane reforming (SMR) technology, and the reacted gas is transported to the absorption tower through a pipeline;

[0028] Onboard boiler: Provide the waste heat required by the shift reactor to reduce additional energy demand;

[0029] Absorption Tower: It uses the absorbent to separate CO2 and H2 in the mixed gas. H2 is sent through a pipeline to a hydrogen fuel cell to provide kinetic energy for the ship. The CO2 dissolved in the absorbent is sent through a pipeline to the desorption tower for desorption. In the traditional absorption tower, after the absorbent absorbs CO2, the obtained H2 purity is insufficient, usually between 90% and 95%. There is still CO2 and other impurity gases that have not been completely absorbed by the absorbent. In the present invention, the membrane separation technology is adopted for the absorption tower to separate and purify H2 to ensure that the hydrogen purity reaches more than 99.9%.

[0030] Heat Exchange System: It is connected to the absorption tower and the desorption tower through pipelines respectively. On the one hand, it adjusts the gas temperature in the absorption tower, reduces the temperature of the high-temperature product obtained from the steam reforming of the shift reactor, and increases the solubility of CO2 in the absorbent, thereby enhancing the CO2 capture efficiency. On the other hand, it provides heating energy for the desorption tower to desorb CO2 from the absorbent rich in CO2 into the gas phase.

[0031] Desorption Tower: It purifies and desorbs the CO2 separated by the absorption tower and finally sends it to the CO2 storage tank.

[0032] CO2 Storage Tank: It stores the purified CO2 for subsequent sequestration or transportation.

[0033] Hydrogen Fuel Cell: It reacts the separated high-purity H2 with oxygen to generate electric energy to supply energy for the ship's power system, and the generated heat is reused through the waste heat recovery device.

[0034] Waste Heat Recovery Device: It recovers the excess steam and the waste heat of the hydrogen fuel cell to provide energy for the steam turbine.

[0035] Steam Turbine: It uses the heat and steam provided by the waste heat recovery device to generate electricity to supplement the ship's power demand.

[0036] Condenser: It is connected to the steam turbine and the waste heat recovery device through pipelines. It cools the steam transmitted from the waste heat recovery device and the steam turbine, causing it to release heat and condense into liquid water.

[0037] The absorption tower adopts a multi-layer absorption tower structure design, which is composed of a tower body, an absorbent spraying system, a mixed gas inlet, an absorbent liquid outlet, a purified H2 gas outlet, and a membrane separation module, etc. The tower body is composed of multiple spray bed layers. Each spray bed layer includes a spray head, a gas flow channel, and a liquid flow channel, which can ensure the full contact between the liquid absorbent and the gas.

[0038] Tower Body: It adopts a tower body with a circular or square structure. The height of the tower body is divided into several sections according to needs, and each section has one or more spray layers. The absorption tower can be made of corrosion-resistant materials such as carbon steel, stainless steel, or synthetic plastics to ensure long-term stable operation.

[0039] Spray system: The spray device in the tower adopts an efficient spraying device, such as an atomizing nozzle or a rotating nozzle, and sprays the liquid absorbent (such as liquid amine) into the gas stream to ensure the maximum contact area between the gas and the liquid. The nozzle design should ensure uniform distribution to prevent excessive or insufficient absorbent.

[0040] Gas flow channel and liquid flow channel: The gas in the absorption tower enters from the bottom and flows through multiple spray layers. The absorbent in the absorption tower is sprayed layer by layer, so that CO2 in the gas is efficiently absorbed.

[0041] The absorbent in the absorption tower circulates from the top of the tower into the nozzle through a pipeline. After CO2 in the gas is absorbed by the absorbent, the liquid flows out through the bottom of the tower and enters the next-stage stripping tower with the dissolved CO2.

[0042] The absorption tower adopts a multi-layer segmented design based on the contact area and absorption time between the mixed gas and the absorbent. In the present invention, the absorption tower is divided into 3 layers, and each layer includes at least one nozzle and one absorbent bed layer. During the absorption process, the temperature of the absorption tower is controlled between 40°C and 60°C. This temperature range helps the stability of the liquid amine absorbent and can reduce the volatilization or decomposition of the absorbent caused by too high temperature. The pressure of the absorption tower is controlled between 1 and 5 bar. A higher pressure helps to increase the solubility of CO2 and enhance the absorption efficiency. The ratio of the liquid flow rate of the absorbent to the gas flow rate of the mixed gas (liquid-gas ratio) is crucial for the contact area between the gas and the absorbent, thus affecting the absorption efficiency of CO2. In different layers, it is adjusted according to the gas flow rate and CO2 concentration, and the preferred ratio should be between 1:1 and 1:3.

[0043] The absorbent used in the absorption tower should have strong CO2 adsorption capacity and operating conditions suitable for the capture of high-flow CO2 on ships. Preferred absorbents are liquid amines (MEA or DEA), triethanolamine (TEA), or dimethylethanolamine (DMEA).

[0044] The specific structure is as follows:

[0045] The first layer: In the first section of the absorption tower, the spray system is used in combination with an absorbent with a concentration of 5%-15% to treat CO2 in the mixed gas to ensure more efficient preliminary absorption. The temperature control is usually set at 40-50°C because the absorption performance of the absorbent is optimal in this temperature range and can avoid the volatilization or decomposition of the solution caused by too high temperature. The pressure control is at 1-3 bar. A lower pressure helps to maintain the gas flow rate and absorption efficiency, and at the same time ensures a higher solubility of the liquid. The liquid-gas ratio is set between 1:1 and 1:2.

[0046] Second layer: These layers are mainly used to further absorb the remaining CO2 in the gas. Since the CO2 concentration becomes lower, an absorbent solution with a concentration of 20%-30% is used to improve the CO2 absorption efficiency. The temperature control is usually set at 45-55°C. As the CO2 concentration decreases, the absorbent solution concentration increases accordingly. Keeping the temperature within the range of 45-55°C helps to improve the adsorption capacity of the liquid amine. Increasing the pressure to 2.5-4 bar further increases the solubility of CO2 in the absorbent solution, and the liquid-gas ratio is between 1:1.5 and 1:2.

[0047] Third layer: Increase the absorbent solution concentration to 30%-50%, adjust the temperature to 50-60°C, adjust the pressure to 3-5 bar, and adjust the liquid-gas ratio to 1:2 to 1:3 to ensure that as much CO2 as possible is completely absorbed.

[0048] Membrane separation technology is a technology that uses the principle of selective permeability of semi-permeable membrane materials to separate different gas components. Its working principle is based on the different permeation rates of gas molecules on the surfaces and pores of different membrane materials. Membrane materials usually have different pore structures and chemical properties, which determine the permeation rate and selectivity of gas molecules. In the process of hydrogen purification in the absorption tower, the role of membrane separation technology is to use the characteristics that hydrogen molecules are smaller and have a stronger ability to penetrate the membrane than carbon dioxide and other impurities to efficiently separate hydrogen from the mixed gas. The selective permeability of the membrane material is closely related to the size of its pores, the intermolecular interaction, and the chemical structure of the membrane. In the present invention, by screening from a variety of semi-permeable membrane materials and controlling and adjusting the pressure and temperature of the membrane separation module, high-purity H2 can be obtained. The membrane separation module is arranged at the top or the upper half of the absorption tower 5 and is connected to the tower body through a pipeline. It does not directly contact the absorbent solution but is located in the upper region of the gas flow in the absorption tower. The hydrogen in the gas is separated from CO2 through a highly selective membrane material. Hydrogen permeates through the membrane, and CO2 and other impurity gases are blocked, thus achieving the purification of hydrogen.

[0049] In the membrane separation module, the gas (a mixed gas containing hydrogen and CO2) enters the membrane separation area from the outlet of the absorption tower. At this time, the gas pressure in this area is usually relatively high, that is, the high-pressure side area, which may be in the range of 1-5 bar. In the membrane separation area, the gas is separated through a membrane with selective permeability. Hydrogen, as a gas with smaller molecules, will permeate through the membrane and enter the low-pressure side area with a pressure in the range of 0.5-2 bar, while CO2 and other larger molecules will be blocked and remain on the high-pressure side. Finally, the high-purity hydrogen that permeates through the membrane enters the low-pressure side and is transported to subsequent equipment (such as a hydrogen fuel cell) through a pipeline, while the remaining carbon dioxide and other gases continue to stay on the high-pressure side and are discharged.

[0050] Selection of membrane materials: To select the appropriate membrane materials, we comprehensively considered factors such as the durability, transmittance, and corrosion resistance of the membrane to ensure that the membrane materials can meet the requirements of the high-efficiency and low-energy-consumption carbon capture system before ship combustion and can operate stably for a long time.

[0051] Durability: The environmental conditions on ships are usually very harsh. Therefore, the membrane materials must have long-term stability and durability. Especially in an environment involving high-concentration CO2, the membrane materials need to be able to withstand corrosive gases for a long time.

[0052] Transmittance: The selective transmittance of hydrogen is the core requirement of membrane separation technology. The membrane needs to be able to efficiently transmit hydrogen while blocking CO2 and other impurity gases. The level of transmittance directly affects the efficiency of the system. We need to select membrane materials with excellent hydrogen transmission ability.

[0053] Corrosion resistance: Since the CO2 concentration on ships is relatively high and the operating environment of the absorption tower involves acidic or corrosive gases, the membrane materials must have strong corrosion resistance and be able to resist the influence of corrosive gases such as CO2 and H2S.

[0054] In addition, the membrane also needs to remain stable within a certain temperature and pressure range.

[0055] After a large number of screenings and tests, the present invention selects polyether block amine membrane (PEBAX membrane) as the most excellent separation membrane for purifying H2. The PEBAX membrane is a polymer membrane based on block copolymer and has high hydrogen selectivity, especially under operating conditions of low to medium pressure. It has strong corrosion resistance and is suitable for CO2 and hydrogen separation. However, its performance may decline in a high-temperature and high-pressure environment. Therefore, it is necessary to control the temperature and pressure during the gas membrane separation process. Further preferably, PEBAX 2533 provided by Arkema Company.

[0056] The thickness of the membrane is set to be 50 to 100 microns, which can achieve a relatively high transmittance, ensure high purity of hydrogen, and at the same time ensure that the membrane has sufficient mechanical strength and stability in the high-flow CO2 gas environment of the ship.

[0057] The membrane separation module includes multiple separation components. Each separation component is composed of multiple thin film units. Each separation component and thin film unit are connected in parallel or in series to form a relatively large gas separation area to improve the separation efficiency. The gas passes through the thin film unit, hydrogen is efficiently separated and enters the low-pressure side of the membrane, while impurities such as CO2 are retained on the high-pressure side of the membrane.

[0058] Membrane operating pressure: The working pressure of the membrane separation module is usually set at 0.5 - 2 bar to ensure that hydrogen can pass through the membrane smoothly while CO2 is blocked. A pressure control device is installed between the absorption tower and the membrane separation module to ensure that the pressure of the membrane separation module is controlled within 0.5 - 2 bar by adjusting the flow rate and the pressure at the gas outlet inside the tower. This device ensures that the internal pressure of the absorption tower adapts to the high-pressure requirements during the absorption process, while the membrane separation module can operate at a low pressure to achieve the purification of hydrogen.

[0059] The membrane separation module should be operated between 30 °C and 50 °C to ensure the stable performance of the membrane and prevent it from being damaged by high temperatures, which may affect the durability of the membrane material.

[0060] The present invention also provides a method for pre-combustion carbon capture using the above system, which includes:

[0061] The first step is the purification of the raw material before carbon capture. An air separation unit (1) is used to remove impurities from the raw material gas to ensure that high-purity methane or methanol enters the gas generator (2);

[0062] The second step is the thermal catalytic preparation of syngas. In the gasification reactor, methane or methanol is decomposed into syngas composed of CO and H2 through an electrochemical reaction;

[0063] The third step is the reforming reaction. The syngas obtained in the second step is introduced into the shift reactor (3), and CO is converted into CO2 and H2 through the water-gas shift reaction;

[0064] The fourth step is the separation and storage of CO2. The absorption tower uses the absorbent to separate CO2 from the mixed gas and sends it to the stripping tower. The absorbent rich in CO2 desorbs CO2 by heating, and the purified CO2 is stored in the CO2 storage tank for easy transportation or sequestration;

[0065] The fifth step is that the obtained high-purity H2 directly enters the hydrogen fuel cell for power generation.

[0066] Waste heat utilization is a key link in optimizing energy recovery and improving the overall efficiency of the pre-combustion high-efficiency and low-energy-consumption carbon capture system of the present invention for ships. Through effective waste heat management, not only can energy consumption be reduced, but also the recycling of various energy sources can be achieved.

[0067] A large amount of waste heat is generated during the power generation process of the hydrogen fuel cell, with a temperature range between 300 - 600 K. To improve the energy utilization efficiency of the system, the present invention adopts a hierarchical waste heat recovery method, and controls the waste heat distribution of the hydrogen fuel cell through a temperature sensor and a PLC control system to make full use of the waste heat.

[0068] The waste heat in the high-temperature part (400 - 600 K) is used for power generation by a steam turbine:

[0069] When the power demand of the ship is relatively high, the waste heat recovery device will preferentially utilize the waste heat from the high-temperature part of the hydrogen fuel cell to supply the steam turbine. This part of the waste heat is directly converted into steam through the waste heat recovery device and supplied to the steam turbine for power generation.

[0070] The operating temperature range of the steam turbine is 473 - 523K. Therefore, the high-temperature waste heat can effectively meet the steam turbine's demand for high-temperature steam. In this way, the waste heat is fully utilized, and at the same time, it provides necessary power support for the ship.

[0071] The waste heat in the medium and low temperature part (300 - 400K) is used for the regeneration heating of the desorption tower:

[0072] The medium and low temperature waste heat (about 300 - 400K) generated by the hydrogen fuel cell will be transported to the desorption tower through the adjustment system of the waste heat recovery device. The desorption tower requires a certain amount of heat for the CO2 desorption process, and this moderately warm waste heat will be used as the regeneration heating source to improve the thermal energy efficiency of the desorption tower.

[0073] The desorption temperature of the desorption tower needs to be maintained at 423K. With the auxiliary heating of the medium and low temperature waste heat, the external heat source demand of the desorption tower can be reduced, further improving the overall energy efficiency of the system.

[0074] The heat dynamic allocation of the waste heat recovery device is controlled by temperature sensors and the PLC control system. According to the demand, the heat is dynamically distributed to each part to optimize the system operation.

[0075] Priority demand of the steam turbine: When the ship's power demand increases, the waste heat recovery device preferentially transports heat to the steam turbine. The steam turbine generates electricity through high-temperature steam to provide power support. At this time, the waste heat recovery device will adjust the distribution of the waste heat quantity and direct more heat to the steam turbine to ensure its stable operation.

[0076] Priority demand of the desorption tower: When the desorption tower enters the CO2 desorption stage, the waste heat recovery device will supply the remaining waste heat to the desorption tower according to the heat demand of the desorption tower. The desorption tower requires a certain amount of heat to maintain its desorption temperature (423K). Therefore, the waste heat recovery device will dynamically adjust its heat supply quantity according to the temperature data real-time feedback by the desorption tower to ensure the operation efficiency of the desorption tower.

[0077] Dynamic adjustment of heat allocation:

[0078] The waste heat recovery device automatically adjusts the heat output according to the feedback data of the real-time temperature sensors and the control system. When the ship's load is high, more heat is supplied to the steam turbine; when the regeneration demand of the desorption tower increases, the waste heat is preferentially supplied to the desorption tower.

[0079] This dynamic adjustment function can be achieved through a PLC control system. When the system detects an increase in power demand or a low temperature in the analytical tower, it automatically adjusts the heat output to ensure the maximization of system energy efficiency.

[0080] Through precise control of heat energy distribution and recovery, the overall energy recovery efficiency of the system will reach over 60%. This not only significantly reduces fuel consumption but also decreases dependence on external energy sources by reasonably distributing heat sources.

[0081] The recovery and utilization of boiler exhaust gas and waste heat from hydrogen fuel cells significantly reduce the overall energy consumption of the system, ensuring the maximization of waste heat utilization, thus optimizing energy flow and reducing carbon dioxide emissions.

[0082] The following uses examples and drawings to elaborate in detail on the implementation mode of the present invention, so as to fully understand how the present invention applies technical means to solve technical problems and the implementation process of achieving technical effects, and to implement accordingly.

[0083] As Figure 1 shown, the present invention provides an efficient low-energy-consumption carbon capture system for pre-combustion on ships, which includes:

[0084] Air separation unit 1: Remove impurities such as nitrogen (N2), carbon dioxide (CO2), and sulfide (H2S) from the input raw gas to ensure high-purity methane (CH4) enters the system. The purified gas is transported through a pipeline to gas generator 2;

[0085] Gas generator 2: The raw gas filtered by air separation undergoes a thermal catalytic cracking reaction of methane in gas generator 2, decomposing methane into carbon monoxide (CO) and hydrogen (H2), which is transported through a pipeline to shift reactor 3. This process usually occurs at a high temperature of 700°C to 900°C, and the catalyst used is CreaPure TM Ni / Al2O3 provided by Clariant;

[0086] Shift reactor 3: Convert CO in the syngas obtained from the reaction of gas generator 2 into CO2 and H2 through steam methane reforming (SMR) technology. The reacted gas is transported through a pipeline to absorption tower 5;

[0087] Onboard boiler 4: Connected to shift reactor 3 through a pipeline, and provides the required waste heat for shift reactor 3 through boiler steam to reduce additional energy demand;

[0088] Absorption tower 5: Use the absorbent to separate CO2 and H2 in the mixed gas. H2 is sent through a pipeline to hydrogen fuel cell 10 to provide kinetic energy for the ship, and the CO2 dissolved in the absorbent is sent through a pipeline to stripping tower 8 for stripping;

[0089] Heat exchange system 6: It is connected to the absorption tower 5 and the desorption tower 8 through pipelines respectively. On the one hand, it adjusts the gas temperature in the absorption tower, reduces the temperature of the high-temperature product obtained from the steam reforming in the shift reactor 3, and increases the solubility of CO2 in the absorbent liquid, thereby enhancing the CO2 capture efficiency. On the other hand, it provides heating energy for the desorption tower 8 to desorb CO2 from the absorbent liquid rich in CO2 into the gas phase;

[0090] Desorption tower 8: Purifies and desorbs the CO2 separated by the absorption tower 5, and finally sends it into the CO2 storage tank 9 through a pipeline;

[0091] CO2 storage tank 9: Stores the purified CO2 for subsequent sequestration or transportation;

[0092] Hydrogen fuel cell 10: Reacts the separated high-purity H2 with oxygen to generate electric energy to supply energy for the ship's power system, and the heat generated is reused through the waste heat recovery device 11;

[0093] Waste heat recovery device 11: Recovers the excess steam and the waste heat of the hydrogen fuel cell 10 to provide energy for the steam turbine 12;

[0094] Steam turbine 12: Utilizes the heat steam provided by the waste heat recovery device 11 to generate electricity to supplement the ship's power demand;

[0095] Condenser 13: It is connected to the steam turbine 12 and the waste heat recovery device 11 through pipelines. By cooling the steam transmitted from the waste heat recovery device 11 to the steam turbine 12, it releases heat and condenses into liquid water.

[0096] The absorption tower 5 adopts a multi-layer absorption tower structure design and is composed of a tower body, an absorbent liquid spraying system, a mixed gas inlet, an absorbent liquid outlet, a purified H2 gas outlet, and a membrane separation module 15, etc. The tower body is composed of multiple spraying bed layers. Each spraying bed layer includes a nozzle, a gas flow channel, and a liquid flow channel, which can ensure the full contact between the liquid absorbent and the gas. The tower body adopts a tower body with a circular or square structure. The height of the tower body is divided into several sections according to needs, and each section has one or more spraying layers. The absorption tower can be made of corrosion-resistant materials such as carbon steel, stainless steel, or synthetic plastics to ensure long-term stable operation. The spraying device in the tower adopts an efficient spraying device, such as an atomizing nozzle or a rotating nozzle, and sprays the liquid absorbent MEA into the gas stream to ensure the maximum contact area between the gas and the liquid. The nozzle design should ensure uniform distribution to prevent excessive or insufficient absorbent liquid. The absorbent liquid of the absorption tower circulates from the top of the tower through a pipeline into the nozzle. After the CO2 in the gas is absorbed by the absorbent liquid, the liquid flows out from the bottom of the tower and enters the next-stage desorption tower with the dissolved CO2.

[0097] The absorption tower 5 is divided into three layers, and each layer includes at least one spray head and a layer of absorbent liquid bed layer 14. By monitoring the sensors on the absorption tower and the PLC control system, the process of the absorption tower 5 absorbing and separating CO2 and H2 is controlled. The first layer: It is used in combination with the absorbent liquid MEA with a mass percentage concentration of 10%. The temperature control is usually set at 45°C, the pressure control is at 2 bar, and the liquid-gas ratio is set at 1:1;

[0098] The second layer: It uses the absorbent liquid MEA with a mass percentage concentration of 25%. The temperature control is at 50°C. As the CO2 pressure is set to 3 bar, the liquid-gas ratio is 1:1.5;

[0099] The third layer: The concentration of the absorbent liquid is increased to 40%, the temperature is adjusted to 60°C, the pressure is adjusted to 5 bar, and the liquid-gas ratio is adjusted to 1:3.

[0100] The membrane separation module is arranged at the top of the absorption tower 5 and is connected to the tower body through a pipeline. The PEBAX 2533 material provided by Arkema Company is selected as the membrane separation material, with a thickness of 100 microns. It does not directly contact the absorbent liquid but is located in the upper area of the gas flow in the absorption tower. The hydrogen in the gas is separated from CO2 through the highly selective membrane material. The hydrogen permeates through the membrane, and CO2 and other impurity gases are blocked, thus realizing the purification of hydrogen.

[0101] The membrane separation module includes a plurality of separation components. Each separation component is composed of a plurality of thin film units. Each separation component and thin film unit are formed in a parallel or series manner to form a larger gas separation area to improve the separation efficiency. The gas passes through the thin film unit, and hydrogen is efficiently separated and enters the low-pressure side of the membrane, while impurities such as CO2 are retained on the high-pressure side of the membrane. The working pressure of the membrane separation module is set at 2 bar, and the temperature is set at 40°C during the separation process. Through the separation of the membrane separation module of the present invention, the concentration of purified H2 can exceed 99%.

[0102] Waste heat utilization is a key link in optimizing energy recovery and improving the overall efficiency of the high-efficiency and low-energy-consumption pre-combustion carbon capture system of the present invention for ships. Through effective waste heat management, not only can energy consumption be reduced, but also the recycling of various energy sources can be realized.

[0103] The present invention adopts a hierarchical waste heat recovery method, and controls the waste heat distribution of the hydrogen fuel cell through a temperature sensor and a PLC control system to make full use of the waste heat.

[0104] The waste heat in the high-temperature part (400 - 600K) is used for the steam turbine 12 to generate electricity:

[0105] When the power demand of the ship is high, the waste heat recovery device 11 will preferentially utilize the waste heat from the high-temperature part of the hydrogen fuel cell 10 to supply it to the steam turbine 12. This part of the waste heat is directly converted into steam through the waste heat recovery device and supplied to the steam turbine 12 for power generation.

[0106] The waste heat in the medium and low temperature part (300 - 400K) is used for the regeneration heating of the stripping column 8:

[0107] The medium and low temperature waste heat generated by the hydrogen fuel cell 10 will be transported to the stripping column 8 through the adjustment system of the waste heat recovery device.

[0108] The heat dynamic allocation of the waste heat recovery device 11 is controlled by a temperature sensor and a PLC control system. The heat is dynamically distributed to each part according to the demand to optimize the system operation.

[0109] Priority demand of the steam turbine 12: When the power demand of the ship increases, the waste heat recovery device 11 preferentially transports the heat to the steam turbine 12. The steam turbine generates electricity through high-temperature steam to provide power support. At this time, the waste heat recovery device will adjust the distribution of the waste heat quantity and direct more heat to the steam turbine 12 to ensure its stable operation.

[0110] Priority demand of the stripping column 8: When the stripping column 8 enters the CO2 desorption stage, the waste heat recovery device will supply the remaining waste heat to the stripping column 8 according to the heat demand of the stripping column. The stripping column needs a certain amount of heat to maintain its desorption temperature (423K). Therefore, the waste heat recovery device 11 will dynamically adjust its heat supply quantity according to the temperature data real-time feedback by the stripping column 8 to ensure the operation efficiency of the stripping column.

[0111] Dynamic adjustment of heat allocation:

[0112] The waste heat recovery device 11 automatically adjusts the heat output according to the feedback data of the real-time temperature sensor and the control system. When the ship load is high, more heat is supplied to the steam turbine; while when the regeneration demand of the stripping column increases, the waste heat is preferentially supplied to the stripping column 8.

[0113] Through precise control of heat energy distribution and recovery, the overall energy recovery efficiency of the system will reach more than 80%, which not only greatly reduces the fuel consumption, but also reduces the dependence on external energy by reasonably distributing the heat source.

[0114] The recovery and utilization of boiler exhaust gas and hydrogen fuel cell waste heat significantly reduce the overall energy consumption of the system, ensure the maximization of waste heat utilization, thus optimizing the energy flow and reducing carbon dioxide emissions.

[0115] Implementing this intellectual property right for all of the above does not set limitations on other forms of implementing such new products and / or new methods. Those skilled in the art will utilize this important information to modify the above to achieve similar implementations. However, all modifications or adaptations based on the new products of the present invention are within the reserved rights.

[0116] As described above, it is only the preferred embodiment of the present invention, and it is not a limitation in other forms for the present invention. Any person skilled in the art may use the disclosed technical content above to make changes or modifications into equivalent embodiments with equivalent changes. However, as long as it does not depart from the technical solution content of the present invention, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. An efficient and low-energy carbon capture system for pre-combustion of LNG or methanol fuel ships, characterized in that, It includes: An air separation unit, a gas generator, a shift reactor, a ship boiler, an absorption tower, a heat exchange system, a stripping tower, a CO2 storage tank, a hydrogen fuel cell, a waste heat recovery device, a steam turbine and a condenser. A membrane separation module is provided at the top or the upper half of the absorption tower and is connected to the absorption tower body through a pipeline for separating and purifying hydrogen.

2. The high-efficiency and low-energy-consumption carbon capture system according to claim 1, wherein: The air separation unit is connected to the gas generator through a pipeline. The gas generator is connected to the shift reactor through a pipeline. On the one hand, the shift reactor is connected to the ship boiler through a pipeline to receive steam from the ship boiler. On the other hand, it is connected to the bottom of the absorption tower through a pipeline. The top of the absorption tower is connected to the hydrogen fuel cell through a pipeline to deliver purified hydrogen. The bottom of the absorption tower is connected to the heat exchange system through a pipeline. The heat exchange system is connected to the stripping tower through a pipeline to realize heat exchange between the absorption tower and the stripping tower. The stripping tower is connected to the CO2 storage tank through a pipeline. The hydrogen fuel cell is connected to the waste heat recovery device through a pipeline. The waste heat recovery device is connected to the steam turbine through a pipeline. The steam turbine is connected to the condenser through a pipeline.

3. The high-efficiency and low-energy-consumption carbon capture system according to claim 1 or 2, characterized in that: The separation membrane used in the membrane separation module is a polyether block amine membrane, and the thickness of the membrane is set to be 50 to 100 microns.

4. The high-efficiency and low-energy-consumption carbon capture system according to claim 1 or 2, characterized in that: The membrane separation module includes a plurality of separation components, and each separation component is composed of a plurality of thin film units. Each separation component and thin film unit are formed in a parallel or series manner to form a larger gas separation area.

5. The high-efficiency and low-energy-consumption carbon capture system according to claim 1 or 2, characterized in that: The waste heat distribution of the hydrogen fuel cell is controlled by a temperature sensor and a PLC control system. The high-temperature part of the waste heat (400 - 600K) is used for power generation by the steam turbine: when the ship's power demand is high, the waste heat recovery device will preferentially use the high-temperature part of the waste heat of the hydrogen fuel cell to supply the steam turbine. This part of the waste heat is directly converted into steam through the waste heat recovery device and supplied to the steam turbine for power generation. The medium and low-temperature part of the waste heat (300 - 400K) is used for the regeneration heating of the stripping tower: the medium and low-temperature waste heat (about 300 - 400K) generated by the hydrogen fuel cell will be transported to the stripping tower through the adjustment system of the waste heat recovery device.

6. The high-efficiency and low-energy-consumption carbon capture system according to claim 1 or 2, characterized in that: The waste heat recovery device automatically adjusts the heat output according to the feedback data of the real-time temperature sensor and the PLC control system. When the ship's load is high, more heat is supplied to the steam turbine; when the regeneration demand of the stripping tower increases, the waste heat is preferentially supplied to the stripping tower.

7. A method for pre-combustion carbon capture using the system according to any one of claims 1 to 6, characterized in that, It includes: The first step is the raw material purification before carbon capture. The air separation unit is used to remove impurities in the raw material gas to ensure that high-purity methane or methanol enters the gas generator. The second step is the thermal catalytic preparation of syngas. In the gasification reactor, methane or methanol is decomposed into syngas composed of CO and H2 through an electrochemical reaction. The third step is the reforming reaction. The syngas obtained in the second step is introduced into the shift reactor, and CO is converted into CO2 and H2 through the water gas shift reaction. The fourth step is the separation and storage of CO2. The absorption tower uses the absorbent to separate CO2 from the mixed gas and send it to the stripping tower. The absorbent rich in CO2 desorbs CO2 by heating, and the purified CO2 is stored in the CO2 storage tank for easy transportation or sequestration. In the fifth step, the obtained high-purity H2 directly enters a hydrogen fuel cell for power generation.

8. The method for pre-combustion carbon capture according to claim 7, characterized in that: In the fourth step described above, the temperature of the absorption tower is controlled between 40°C and 60°C, the pressure is controlled between 1 and 5 bar, and the liquid-gas ratio is controlled between 1:1 and 1:

3.

9. The method for pre-combustion carbon capture according to claim 7 or 8, characterized in that: In the fourth step described above, the working pressure of the membrane separation module of the absorption tower is 0.5 - 2 bar, and the temperature is between 30°C and 50°C.

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