Waste heat driven marine methanol engine source carbon capture device and method

Abstract

The invention discloses a waste heat driven marine methanol engine source carbon capture device and method. The waste heat driven marine methanol engine source carbon capture device comprises a methanol hydrothermal reforming system and a CO2 membrane separation system. The methanol hydrothermal reforming system comprises an evaporation vaporizer and a hydrothermal reforming reactor; the evaporation vaporizer is used for heating the mixed solution to prepare methanol steam; the hydrothermal reforming reactor is used for realizing methanol steam reforming, methanol decomposition and water-gas conversion; the CO2 membrane separation system is used for separating high-purity hydrogen and CO2 through a gas separation membrane; high-temperature tail gas is used for providing reaction temperature for three devices step by step, and a phase change material is used for storing heat. According to the invention, hydrogen is prepared through methanol hydrothermal reforming and CO2 membrane separation technologies in a marine methanol engine, hydrogen is used for replacing part of methanol to be introduced into a cylinder for combustion, engine tail gas waste heat is recycled in a stepped manner, and a phase change material is used instead of tail gas for direct heating, so that the reaction temperature can be accurately and stably controlled; and the goal of zero carbon emission of the ship engine can be achieved.

Description

Technical Field

[0001] The present invention relates to the field of marine methanol engines, and particularly to a waste heat-driven marine methanol engine source carbon capture device and method. Background Art

[0002] With the increasing attention to the climate crisis and environmental protection, the International Maritime Organization (IMO) has continuously tightened the carbon emission standards for ships, requiring zero carbon emissions for ships by 2050. Ship carbon reduction is mainly achieved by adopting low-carbon / zero-carbon alternative fuels, such as green fuels like ammonia, hydrogen, methanol, etc. Among them, green methanol is synthesized from by-product hydrogen in coke oven gas and carbon dioxide captured from industrial tail gas, and its production uses renewable energy (such as wind energy, solar energy, etc.), realizing the resource utilization of carbon dioxide and carbon neutrality. In addition, methanol has good combustion performance, a high calorific value of the equivalent mixture, good anti-knock performance, a fast flame propagation speed, and the infrastructure for storage, transportation, and refueling can be transformed on the original gasoline and diesel facilities, with low construction costs and broad application prospects.

[0003] However, as a carbon-containing carbon-neutral fuel, methanol still inevitably produces carbon emissions. To achieve zero carbon emissions, carbon capture technology must be relied on. At present, direct ship exhaust carbon capture mainly faces development bottlenecks such as low capture efficiency, large space volume, and high capture energy consumption. In contrast, source carbon capture technology based on fuel reforming and purification technology is structurally compact, has high capture efficiency and good effects, and has great potential. The most representative methanol steam reforming and CO 2 separation technology has been relatively mature in the field of industrial hydrogen production. The generated hydrogen can replace part of the methanol and be introduced into the cylinder for combustion, reducing the carbon content of the mixed fuel. Combining with exhaust carbon capture can effectively achieve zero carbon emissions. However, in the environment of marine engines, the current reforming and separation equipment has problems such as the need for external heat supply and the need to strictly control the catalytic reaction temperature to ensure a high methanol conversion efficiency and CO 2 selectivity, and cannot be directly applied.

[0004] In view of the above analysis, the design and development of an efficient and energy-saving source carbon capture technology for marine methanol engines is of great significance in ship carbon reduction. Summary of the Invention

[0005] In view of the problems of high carbon emissions in current marine engines and the deficiencies of carbon capture technology, the present invention proposes a waste heat-driven source carbon capture device and method for marine methanol engines. This device hierarchically recovers the waste heat of the engine exhaust gas for methanol steam reforming and CO 2 membrane separation, and introduces the reformed and separated gas into the cylinder for combustion, realizing source decarbonization of the methanol engine.

[0006] The object of the present invention is achieved by the following technical solutions: A waste heat-driven marine methanol engine source carbon capture device, comprising: a methanol aqueous reforming system and a CO2 membrane separation system;

[0007] The methanol aqueous reforming system includes an evaporation vaporizer and a hydrothermal reforming reactor: The evaporation vaporizer uses high-temperature tail gas as a heat exchange medium to heat the mixed solution to prepare methanol water vapor, completing the first-stage recovery of the tail gas waste heat.

[0008] The hydrothermal reforming reactor includes a methanol water vapor passage and a secondary tail gas waste heat recovery passage. Methanol water vapor is input into the methanol water vapor passage and undergoes methanol water vapor reforming, methanol decomposition, and water gas shift through a reforming catalyst and then outputs; In the secondary tail gas waste heat recovery, the tail gas that has passed through the evaporation vaporizer is input, and the phase change material is heated through a heat exchange pipeline to provide the reaction temperature for the methanol water vapor passage.

[0009] The CO2 membrane separation system includes a reformed gas passage and a tertiary tail gas waste heat recovery passage; The reformed gas output from the hydrothermal reforming reactor is input into the reformed gas passage and separated into high-purity hydrogen and CO through a gas separation membrane. 2 The tertiary tail gas waste heat recovery passage provides the reaction temperature for CO2 membrane separation through a heat exchange pipeline and a phase change material.

[0010] Further, a water tank, two metering pumps, and a mixing tank are further included before the methanol aqueous reforming system. The water tank enters the mixing tank through the first metering pump, and methanol enters the mixing tank through the second metering pump, and is fully mixed in the mixing tank to form a methanol aqueous solution.

[0011] Further, the outputs after methanol water vapor reforming, methanol decomposition, and water gas shift are respectively:

[0012]

[0013] Further, the phase change material is adjusted according to the temperature required by different catalysts.

[0014] Further, a condenser and a gas-liquid separator are also installed after the hydrothermal reforming reactor to remove the moisture in the reformed gas and return the unreacted methanol water mixture to the mixing tank.

[0015] Further, the hydrogen obtained by the CO2 membrane separation system enters the engine high-pressure fuel injection system as fuel, and the CO 2 is stored after being pressurized.

[0016] On the other hand, the specification also provides a waste heat-driven marine methanol engine source carbon capture method based on the above device, and this method includes:

[0017] S1. Input methanol and water into a mixing tank through metering pumps to obtain a methanol-water mixture;

[0018] S2. Use the tail gas as the heat exchange medium of an evaporative vaporizer to heat the methanol-water mixture to obtain methanol steam;

[0019] S3. The methanol steam enters a hydrothermal reforming reactor for methanol steam reforming, methanol decomposition, and water-gas shift to obtain reformed gas; the tail gas is input into the hydrothermal reforming reactor as the heat exchange medium of the phase change material; heat is stored through the phase change material, and the reaction temperature of the hydrothermal reforming reactor is controlled;

[0020] S4. Remove the water in the reformed gas to obtain dry gas, return the unreacted methanol-water mixture to the mixing tank, and pass the dry gas into a CO 2 membrane separation reactor for carbon capture.

[0021] Advantages of the present invention:

[0022] 1. In the field of marine methanol engines, hydrogen is prepared through methanol hydrothermal reforming and CO 2 membrane separation technology, and part of the methanol is replaced by hydrogen and introduced into the cylinder for combustion. The present invention can achieve carbon capture at the source of methanol engines, which helps to achieve the goal of zero carbon emissions for ship engines.

[0023] 2. Recover the waste heat of the engine exhaust gas in a cascaded manner, which is used for vaporization of methanol aqueous solution, methanol hydrothermal reforming reaction, and CO 2 membrane separation in sequence, solving the problem that the carbon capture system requires external energy supply, reducing energy consumption, and at the same time improving the comprehensive energy utilization rate of marine methanol engines.

[0024] 3. Aiming at the problems that methanol hydrothermal reforming and CO2 membrane separation are sensitive to temperature, and the current mainstream waste heat recovery methods all use the exhaust gas for direct heating, it is proposed to use a phase change material for heat storage, so as to stabilize the heat source and accurately control the temperature. Using a phase change material instead of direct exhaust gas heating can more accurately and stably control the reaction temperature, avoid fluctuations in the heat source, and the phase change material can be changed according to the characteristics of the reforming catalyst and CO 2 separation membrane to regulate the temperature, which is beneficial to improving the methanol conversion efficiency, CO 2 selectivity, and membrane separation efficiency. Description of the Drawings

[0025] Figure 1 It is the working principle diagram of a waste heat-driven marine methanol engine carbon capture device at the source;

[0026] Figure 2 It is the structural schematic diagram of the carbon capture device at the source. Detailed Embodiments

[0027] The following further elaborates on the specific implementation manners of the present invention in conjunction with the accompanying drawings.

[0028] As Figure 1 shown, a

[0029] The waste heat-driven marine methanol engine source carbon capture device of the present invention mainly includes a methanol-water steam reforming system and a CO2 membrane separation system, as well as additional components such as a water tank, a mixing tank, a condenser, a gas-liquid separator, a metering pump, a pressurizing pump, and a CO 2 gas tank.

[0030] As Figure 1 shown, the present invention designs a waste heat-driven source carbon capture device and method for a marine methanol engine. Its working principle is to produce hydrogen by steam reforming methanol and CO 2 membrane separation, mix it with the main fuel methanol for combustion, reduce the overall carbon content of the fuel, and thus reduce the original carbon emission content of the engine. Among them, the heat required for reforming and separation is provided by the engine exhaust gas, solving the problem of its need for external energy supply. At the same time, phase change materials are used for heat storage and temperature control, enabling the methanol hydrogen production technology to be applied to marine methanol engines.

[0031] As Figure 2 shown, the source carbon capture device mainly includes a methanol-water steam reforming system and a CO 2 membrane separation system 9, as well as additional components such as a water tank 1, a mixing tank 4, a condenser 7, a gas-liquid separator 8, a first metering pump 2, a second metering pump 3, a pressurizing pump 10, and a CO 2 gas tank 11. The methanol-water steam reforming system includes an evaporation vaporizer 5 and a steam reforming reactor 6.

[0032] The evaporation vaporizer 5 is used to heat the methanol aqueous solution to obtain methanol water vapor. Its structure includes a first heat exchange pipeline, a heat preservation outer shell, and two inlets and two outlets, namely a first tail gas inlet, a methanol aqueous solution inlet, a methanol water vapor outlet, and a first tail gas outlet.

[0033] The steam reforming reactor 6 structure includes a reaction chamber, a second heat exchange pipeline 605, a heat preservation outer shell, and two inlets and two outlets, namely a second tail gas inlet 602, a methanol water vapor inlet 601, a reformed gas outlet 606, and a second tail gas outlet 607. The reaction chamber is filled with a reforming catalyst 604, and the first phase change material 603 is filled between the reaction chamber and the outer shell.

[0034] The CO 2 membrane separation reactor structure includes a membrane separation gas tank, a third heat exchange pipeline, a heat preservation outer shell, and two inlets and three outlets, namely a third tail gas inlet 902, a reformed gas inlet 901, a separated gas outlet 905, and a CO 2Outlet 908, the third exhaust gas outlet 907, and the second phase change material 906 is filled between the gas tank and the outer shell.

[0035] During operation, a certain flow rate of liquid water and methanol enter the mixing tank 4 under the action of the first metering pump 2 and the second metering pump 3 respectively, and are fully mixed to form an aqueous methanol solution. The evaporator vaporizer 5 uses high-temperature exhaust gas as the heat exchange medium to heat the mixed solution to prepare methanol water vapor, completing the first-stage recovery of the exhaust gas waste heat. The methanol water vapor enters from the methanol water vapor inlet 601 of the reforming reactor, and mainly undergoes three reactions of methanol steam reforming, methanol decomposition, and water gas shift under the action of the reforming catalyst 604, as shown in equations (1), (2), and (3). After the reaction, the reformed gas flows out from the reformed gas outlet 606 of the reforming reactor.

[0036]

[0037] The exhaust gas is introduced from the second exhaust gas inlet 602 of the reforming reactor, and flows out from the second exhaust gas outlet 607 after passing through the second heat exchange pipe 605, which is used to heat the first phase change material 603 to complete the second-stage waste heat recovery. The operating conditions of the engine will affect the temperature and flow rate of the exhaust gas, that is, the exhaust gas is an unstable heat source. Using phase change materials can, on the one hand, give play to its heat storage performance and continuously and stably supply heat for the reforming reaction, and on the other hand, effectively control the reaction temperature within the optimal working range of the catalyst to obtain a higher methanol conversion rate and CO 2 selectivity. The first phase change material 603 can be adjusted according to different catalysts. Taking the commonly used CuO / ZnO / Al 2 O 3 catalyst as an example, its optimal working temperature is generally 200°C to 300°C, and polymer phase change materials such as polyethylene terephthalate, polyimide, and polyamide can be used.

[0038] The condenser 7 and the gas-liquid separator 8 are used to remove water from the reformed gas to obtain dry gas. In addition, the unreacted methanol is also condensed into a liquid state. The gas-liquid separator 8 circulates the methanol-water mixture through the return pipeline to the mixing tank 4 for recycling, and the dry gas is introduced into the CO 2 membrane separation system 9. Gas membrane separation mainly relies on the selective permeability of specific polymer membrane materials to different gas molecules to selectively separate a certain gas from the gas mixture. Commonly used CO 2 separation membranes include polyethersulfone membranes, polyimide thin films, etc.

[0039] During operation, the exhaust gas flows in from the third exhaust gas inlet 902 of the CO 2 membrane separation reactor 8, and also flows out from the exhaust gas outlet 907 after passing through the heat exchange pipe 904, completing the third-stage waste heat recovery. Although this part of the exhaust gas has undergone heat exchange twice, CO2 The temperature required for membrane separation is relatively low (for example, the optimal operating temperature of the polyimide membrane is about 80 °C), so the energy of the tail gas is still sufficient to heat the second phase change material 906 (such as polyvinyl alcohol, butyl acrylate, polylactic acid, etc.). The dry reformed gas flows in from the reformed gas inlet 901 of the membrane separation reactor, and is separated into high-purity hydrogen and CO after passing through the gas separation membrane 903 2 , where the high-purity hydrogen flows out from the separated gas outlet 905 and enters the engine high-pressure fuel injection system as fuel, and CO 2 flows out from the CO 2 outlet 908, and enters the CO 2 gas tank 11 for collection and storage after passing through the pressure pump 10.

[0040] Other embodiments of the present application will be readily apparent to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the present application that follow the general principles of the present application and include known common general knowledge or conventional technical means in the technical field not disclosed in the present application. The specification and examples are only illustrative, and the true scope and spirit of the present application are pointed out by the claims.

[0041] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and do not limit the present application. The present application is not limited to the precise structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present application is only limited by the appended claims.

Claims

1. A waste heat driven marine methanol engine source carbon capture device, characterized in that: include: Methanol hydrothermal reforming system and CO2 membrane separation system; The methanol hydrothermal reforming system comprises an evaporator and a hydrothermal reforming reactor: the evaporator uses the high-temperature exhaust gas output by the marine methanol engine as a heat exchange medium to heat the mixed solution to prepare methanol water vapor, thereby completing the first-stage recovery of the exhaust gas waste heat. The hydrothermal reforming reactor comprises a methanol water vapor passage and a secondary tail gas waste heat recovery passage. Methanol water vapor is input into the methanol water vapor passage and is subjected to methanol water vapor reforming, methanol decomposition and water-gas conversion by a reforming catalyst before being output; tail gas that has passed through an evaporator is input into the secondary tail gas waste heat recovery passage, and phase change materials are heated through a heat exchange pipe to provide a reaction temperature for the methanol water vapor passage. The CO2 membrane separation system includes a reforming gas passage and a three-stage exhaust gas waste heat recovery passage; the reforming gas output from the hydrothermal reforming reactor is input into the reforming gas passage and separated into high-purity hydrogen and CO2 through a gas separation membrane; the three-stage exhaust gas waste heat recovery passage provides reaction temperature for CO2 membrane separation through a heat exchange pipe and a phase change material.

2. The waste heat driven marine methanol engine source carbon capture device according to claim 1, characterized in that: The methanol hydrothermal reforming system also includes a water tank, two metering pumps and a mixing tank. The water tank allows water to enter the mixing tank through a first metering pump, and methanol to enter the mixing tank through a second metering pump, and the two are fully mixed in the mixing tank to form a methanol-water solution.

3. The waste heat driven marine methanol engine source carbon capture device according to claim 1, characterized in that: The outputs after methanol steam reforming, methanol decomposition and water gas shift are respectively:

4. The waste heat driven marine methanol engine source carbon capture device according to claim 1, characterized in that: The phase change material is adjusted according to the temperature required by different catalysts.

5. The waste heat driven marine methanol engine source carbon capture device according to claim 1, characterized in that: A condenser and a gas-liquid separator are installed after the hydrothermal reforming reactor to remove moisture from the reformed gas and return the incompletely reacted methanol-water mixture to the mixing box.

6. The waste heat driven marine methanol engine source carbon capture device according to claim 1, characterized in that: The hydrogen obtained by the CO2 membrane separation system enters the engine's high-pressure fuel injection system for use as fuel, and the CO2 is stored after being pressurized.

7. A method for capturing carbon from the source of a waste heat driven marine methanol engine based on the device according to any one of claims 1 to 6, characterized in that: The method includes: S1, inputting methanol and water into a mixing box through a metering pump to obtain a methanol-water mixture; S2, using the tail gas as a heat exchange medium of the evaporator to heat the methanol-water mixture to obtain methanol-water vapor; S3, the methanol water vapor enters the hydrothermal reforming reactor for methanol water vapor reforming, methanol decomposition and water gas conversion to obtain reformed gas; the tail gas is input into the hydrothermal reforming reactor as a heat exchange medium for the phase change material; heat is stored through the phase change material, and the reaction temperature of the hydrothermal reforming reactor is controlled; S4. Remove water from the reformed gas to obtain dry gas, return the incompletely reacted methanol-water mixture to the mixing box, and pass the dry gas into a CO2 membrane separation reactor for carbon capture.

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