Methanol fuel ship energy recovery system

Abstract

The invention discloses a methanol fuel ship energy recovery system which comprises a waste gas energy recovery unit, a condensate water treatment unit and a control unit, an inlet of the waste gas energy recovery unit is connected to an exhaust pipe of a main engine, and an outlet of the waste gas energy recovery unit is connected with the condensate water treatment unit; the waste gas energy recovery unit comprises a first-stage plate heat exchanger and a second-stage power generation module, a liquid outlet of the first-stage plate heat exchanger is connected to a fresh water making system and an outboard drainage channel, the second-stage power generation module generates power through waste heat of a waste gas medium-temperature section, and the output end of the second-stage power generation module is connected to a ship power grid. The condensate water treatment unit comprises a gas-liquid separator and a purification module, the gas-liquid separator is connected with a waste gas outlet of the secondary power generation module, the purification module is connected with a liquid outlet of the gas-liquid separator, and a liquid outlet of the purification module is connected to a technical water tank or an outboard drainage emergency channel. Reasonable utilization and recovery of waste heat of waste gas of the methanol fuel ship are achieved, and emission pollution is reduced.

Description

Technical Field

[0001] This application relates to the technical field of methanol-fueled ships, and more particularly to an energy recovery system for methanol-fueled ships. Background Technology

[0002] With the continued booming development of the global shipping industry and the ever-expanding scale of trade, ships, as key logistics carriers in international trade, are facing increasingly severe energy consumption and the resulting environmental problems, becoming a critical bottleneck restricting the sustainable development of the industry. Against this backdrop, methanol-fueled ships, with their advantages of clean, readily available, and renewable methanol fuel, as well as low emissions of sulfur oxides and particulate matter during combustion, are gradually emerging in the field of marine power, attracting widespread attention and active exploration from the industry.

[0003] However, in actual operation, methanol-fueled ships currently release exhaust gases from the main engine combustion directly into the atmosphere without any energy recovery treatment. A deeper analysis from an energy utilization perspective reveals that the conversion of methanol fuel into mechanical energy during combustion within the main engine cylinders is not entirely efficient; the high-temperature exhaust gases produced contain a considerable amount of energy. Related research and actual measurements indicate that this portion of exhaust gas carries 30%-40% of the total energy input from the fuel. This significant energy loss directly leads to low overall energy efficiency for the ship, making it difficult to meet the industry's increasingly stringent energy-saving standards. This not only significantly increases fuel costs during ship operation but may also result in additional penalties for failing to meet energy efficiency standards, weakening the ship's competitiveness in the market.

[0004] From an environmental protection perspective, the waste of energy from exhaust gases means that more methanol fuel needs to be consumed to meet the power demands of ships. This further consumption of methanol fuel inevitably leads to increased emissions of greenhouse gases such as carbon dioxide. In the context of a global trend of jointly addressing climate change and actively advocating for green and low-carbon development, these additional carbon emissions caused by energy waste undoubtedly exacerbate the deterioration of the Earth's ecological environment, accelerate global warming, and run counter to the concept of sustainable development. Summary of the Invention

[0005] The purpose of this application is to provide a methanol-fueled ship energy recovery system that can solve the above-mentioned problems existing in the prior art.

[0006] To achieve the above objectives, this application adopts the following technical solution: On the one hand, a methanol fuel ship energy recovery system is provided, including: an exhaust gas energy recovery unit, a condensate treatment unit and a control unit. The inlet of the exhaust gas energy recovery unit is connected to the exhaust pipe of the main engine through a flange, the outlet of the exhaust gas energy recovery unit is connected to the condensate treatment unit, and the control unit is electrically connected to the exhaust gas energy recovery unit and the condensate treatment unit respectively. The exhaust gas energy recovery unit includes a primary plate heat exchanger and a secondary power generation module arranged in series. The primary plate heat exchanger uses seawater as a cooling medium to recover waste heat from the high-temperature section of the exhaust gas. The liquid outlet of the primary plate heat exchanger is connected to the desalination system and the outboard drainage channel, respectively. The secondary power generation module generates electricity using waste heat from the medium-temperature section of the exhaust gas, and the output end of the secondary power generation module is connected to the ship's electrical grid. The condensate treatment unit includes a gas-liquid separator and a purification module arranged in sequence. The gas-liquid separator is connected to the exhaust gas outlet of the secondary power generation module, and the purification module is connected to the liquid outlet of the gas-liquid separator. The liquid outlet of the purification module is connected to a technical water tank or an external drainage emergency channel.

[0007] Furthermore, the control unit includes a dynamic flow distributor and a multi-objective optimization controller. The dynamic flow distributor adjusts the flow rate of the cooling medium entering the exhaust gas energy recovery unit according to the main engine load and seawater temperature. The multi-objective optimization controller controls the power generation of the secondary power generation module and the freshwater output of the primary plate heat exchanger based on ship energy efficiency.

[0008] Furthermore, the condensate treatment unit also includes a water quality sensor, which is used to monitor the pH value, conductivity, and methanol residue of the condensate.

[0009] Furthermore, the secondary power generation module is an organic Rankine cycle power generation module, which includes an evaporator, an expansion generator, and a condenser connected in sequence via pipelines. The output end of the expansion generator is connected to the ship's power grid, and the condenser shares a seawater cooling pipeline with the primary plate heat exchanger.

[0010] Furthermore, the purification module includes a membrane electrode assembly, an ion exchange resin layer, and an ultraviolet photocatalytic assembly arranged sequentially. The membrane electrode assembly is used to apply a pulse voltage to achieve electrochemical separation of carbon dioxide, the ion exchange resin layer is used to adsorb heavy metal ions, and the ultraviolet photocatalytic assembly is used to degrade residual methanol.

[0011] Furthermore, the multi-objective optimization controller is configured to prioritize the full-power operation of the secondary power generation module when the ship is in a high-load operating state.

[0012] Furthermore, a cooling water bypass pipeline is provided between the desalination system and the primary plate heat exchanger. The multi-objective optimization controller is also configured to: when the seawater temperature is greater than 30°C, control the cooling water bypass pipeline to open and the seawater cooling pipeline to close.

[0013] Furthermore, the technical water tank is connected to the ship's sanitation system, and the output end of the technical water tank is equipped with a mineral addition module, which is used to adjust the mineralization of the purified water to drinking water standards.

[0014] Furthermore, the evaporator uses a mixed working fluid of R245fa and R1233zd.

[0015] Furthermore, the mass ratio of the mixed working fluid is R245fa:R1233zd=7:3, and the evaporation temperature of the evaporator is set to 85℃-95℃.

[0016] The beneficial effects of this application are as follows: Seawater is heated by a primary plate heat exchanger and supplied to the desalination system as a raw material for desalination, fully utilizing waste heat from exhaust gases to produce the freshwater needed by the ship, reducing dependence on external energy sources for freshwater production, and simultaneously lowering energy consumption. If the seawater does not need to enter the desalination system, direct discharge overboard avoids unnecessary heat loss. The secondary power generation module utilizes the waste heat from the mid-temperature section of the exhaust gas, further converting it into electricity and integrating it into the ship's power grid to power ship equipment. This achieves graded and efficient recovery and utilization of waste heat from exhaust gases, significantly improving the ship's energy efficiency, substantially increasing the ship's energy efficiency coefficient, and effectively reducing operating costs. This system reduces the amount of methanol fuel consumed due to wasted exhaust gas energy, thereby reducing emissions of greenhouse gases such as carbon dioxide, which is of positive significance in mitigating global warming. Simultaneously, the condensate treatment unit performs gas-liquid separation and purification of the exhaust gas condensate, enabling the purified water to be rationally utilized or safely discharged, avoiding pollution of the ship's and marine environments by untreated condensate, aligning with the concepts of green, low-carbon, and sustainable development. Attached Figure Description

[0017] The present application will now be described in further detail with reference to the accompanying drawings and embodiments.

[0018] Figure 1 This is a schematic diagram of the methanol fuel ship energy recovery system described in the embodiments of this application; Figure 2 This is a schematic diagram of the principle of the methanol fuel ship energy recovery system described in the embodiments of this application.

[0019] In the diagram: 1. Main engine; 2. Exhaust gas energy recovery unit; 201. Primary plate heat exchanger; 202. Secondary power generation module; 3. Condensate treatment unit; 301. Gas-liquid separator; 302. Purification module; 4. Control unit; 401. Dynamic flow distributor; 402. Multi-objective optimization controller; 5. Seawater cooling pipeline; 6. Desalination system; 7. Outboard drainage channel; 8. Technical water tank; 9. Outboard drainage emergency channel. Detailed Implementation

[0020] To make the technical problems solved by this application, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the embodiments of this application are further described in detail below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] In the description of this application, unless otherwise expressly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0023] like Figure 1 and Figure 2 As shown, this embodiment provides a methanol fuel ship energy recovery system, including: an exhaust gas energy recovery unit 2, a condensate treatment unit 3, and a control unit 4. The inlet of the exhaust gas energy recovery unit 2 is connected to the exhaust pipe of the main engine 1 through a flange, and the outlet of the exhaust gas energy recovery unit 2 is connected to the condensate treatment unit 3. The control unit 4 is electrically connected to the exhaust gas energy recovery unit 2 and the condensate treatment unit 3 respectively. The exhaust gas energy recovery unit 2 includes a primary plate heat exchanger 201 and a secondary power generation module 202 arranged in series. The primary plate heat exchanger 201 uses seawater as a cooling medium to recover waste heat from the high-temperature section of the exhaust gas. The liquid outlet of the primary plate heat exchanger 201 is connected to the desalination system 6 and the external drainage channel 7, respectively. The secondary power generation module 202 uses waste heat from the medium-temperature section of the exhaust gas to generate electricity, and the output end of the secondary power generation module 202 is connected to the ship's electrical grid. The condensate treatment unit 3 includes a gas-liquid separator 301 and a purification module 302 arranged in sequence. The gas-liquid separator 301 is connected to the exhaust gas outlet of the secondary power generation module 202, and the purification module 302 is connected to the liquid outlet of the gas-liquid separator 301. The liquid outlet of the purification module 302 is connected to the technical water tank 8 or the external drainage emergency channel 9.

[0024] Based on the above scheme, in the waste gas energy recovery stage, waste gas enters the waste gas energy recovery unit 2 from the exhaust pipe of the main engine 1 through a flange. The primary plate heat exchanger 201 in this unit uses seawater as the cooling medium. When the high-temperature waste gas flows through the primary plate heat exchanger 201, the seawater exchanges heat with the waste gas, absorbing the waste heat from the high-temperature section of the waste gas, thus raising the seawater temperature. The heated seawater can be treated in two ways: first, it can be used as raw material for the desalination system 6 to produce fresh water, achieving secondary utilization of thermal energy; second, if the desalination system 6 does not require additional seawater raw material or encounters special circumstances such as malfunction, the heated seawater can be directly discharged to the outside through the external drainage channel 7. After being processed by the primary plate heat exchanger 201, the waste gas temperature decreases, and then it enters the secondary power generation module 202. The secondary power generation module 202 utilizes the waste heat from the medium-temperature section of the waste gas to generate electricity. The generated electricity is connected to the ship's electrical grid through the output terminal to power various electrical equipment on the ship, further exploring the value of the waste heat from the waste gas.

[0025] Regarding condensate treatment, the exhaust gas after passing through the secondary power generation module 202 enters the condensate treatment unit 3. The gas-liquid separator 301 first separates the gas-liquid mixture in the exhaust gas, separating the liquid. The separated liquid enters the purification module 302 for purification. The purified liquid can be connected to the technical water tank 8 for specific technical applications, or discharged through the external drainage emergency channel 9 in emergency situations, depending on the ship's actual needs. The control unit 4 is electrically connected to both the exhaust gas energy recovery unit 2 and the condensate treatment unit 3, enabling real-time monitoring of the operating parameters of these two units, such as temperature, pressure, and flow rate. It also precisely regulates the operating status of each unit according to preset programs and algorithms, ensuring the stable and efficient operation of the entire system.

[0026] Furthermore, the control unit 4 includes a dynamic flow distributor 401 and a multi-objective optimization controller 402. The dynamic flow distributor 401 adjusts the flow rate of the cooling medium entering the exhaust gas energy recovery unit 2 according to the load of the main engine 1 and the seawater temperature. The multi-objective optimization controller 402 controls the power generation of the secondary power generation module 202 and the freshwater output of the primary plate heat exchanger 201 based on ship energy efficiency coordination. The dynamic flow distributor 401 constantly monitors the load of the main engine 1 and the seawater temperature. The load of the main engine 1 reflects the amount of heat generated by the exhaust gas, while the seawater temperature affects the efficiency of heat exchange between the main engine 1 and the exhaust gas. When the load of the main engine 1 increases, it means that the heat generated by the exhaust gas increases. At this time, the dynamic flow distributor 401 will appropriately increase the flow rate of the cooling medium (seawater) entering the exhaust gas energy recovery unit 2 according to the seawater temperature. This is because more seawater can more fully absorb the heat in the exhaust gas, ensuring that efficient heat exchange can still be achieved even when the heat of the exhaust gas increases. Conversely, when the load on host 1 decreases, the dynamic flow distributor 401 will correspondingly reduce the seawater flow to avoid excessive heat exchange and energy waste caused by too much seawater. At the same time, changes in seawater temperature will also affect the flow distribution. If the seawater temperature is low, its heat absorption capacity is strong, and the flow can be appropriately reduced; if the seawater temperature is high, its heat absorption capacity is weakened, and the flow needs to be increased to ensure the heat exchange effect.

[0027] The multi-objective optimization controller 402 aims to improve ship energy efficiency, comprehensively considering two key parameters: the power generation of the secondary power generation module 202 and the freshwater output of the primary plate heat exchanger 201. It collects various data during system operation, such as exhaust gas temperature and flow rate, seawater temperature and flow rate, and the ship's electrical grid demand. Based on this data, it performs real-time analysis and calculation using complex intelligent algorithms to find the optimal balance between the power generation of the secondary power generation module 202 and the freshwater output of the primary plate heat exchanger 201, while meeting the ship's various operational requirements. For example, when the ship's electrical grid demand is low, the multi-objective optimization controller 402 will appropriately reduce the power generation of the secondary power generation module 202 while increasing the freshwater output of the primary plate heat exchanger 201 to fully utilize waste heat from the exhaust gas to produce more freshwater; conversely, when the electrical demand is high, it prioritizes ensuring power generation and appropriately reduces the freshwater output.

[0028] Generally, the condensate treatment unit 3 also includes a water quality sensor, which monitors the pH value, conductivity, and methanol residue of the condensate. The newly added water quality sensor in the condensate treatment unit 3 is an intelligent monitoring device capable of accurately sensing various key water quality indicators of the condensate. When the condensate flows out of the gas-liquid separator 301 and enters the purification module 302, the water quality sensor starts working simultaneously. It utilizes advanced sensing technology to measure the pH value, conductivity, and methanol residue of the condensate in real time and with precision. For pH monitoring, the water quality sensor is equipped with a dedicated pH-sensitive electrode, which reacts with hydrogen ions in the condensate to generate an electrical signal related to the pH value. By converting this electrical signal into a digital signal and processing it through a built-in calibration and calculation program, the pH value of the condensate can be accurately determined. The conductivity measurement is based on the principle of ionic conductivity in the condensate. The conductivity measurement module in the water quality sensor applies a weak alternating electric field to the condensate, measures the resistance change as current flows through the condensate, and then calculates its conductivity. The conductivity reflects the concentration of ions in condensate and is a crucial indicator of water purity. Methanol residue detection employs a specific chemical sensing technology. The methanol sensor in the water quality sensor is coated with a highly selective material for methanol. When condensate comes into contact with the sensor, methanol molecules are adsorbed by the sensitive material, causing changes in the sensor's electrical properties (such as resistance and capacitance). By detecting these changes in electrical properties and combining them with a pre-established calibration curve, the residual methanol content in the condensate can be accurately determined. The water quality sensor transmits real-time data on pH, conductivity, and methanol residue to control unit 4 via wired or wireless means. Upon receiving this data, control unit 4 analyzes and judges it according to preset water quality standards and safety thresholds.

[0029] Specifically, the secondary power generation module 202 is an organic Rankine cycle power generation module, which includes an evaporator, an expander generator, and a condenser connected in sequence via pipelines. The output of the expander generator is connected to the ship's electrical grid, and the condenser shares a seawater cooling pipeline 5 with the primary plate heat exchanger 201. In the evaporator stage, the exhaust gas, after initial cooling by the primary plate heat exchanger 201, enters the evaporator. At this time, the low-temperature, low-pressure organic working fluid also flows into the evaporator. The exhaust gas and the organic working fluid exchange heat within the evaporator, with the exhaust gas transferring its own medium-temperature residual heat to the organic working fluid. After absorbing heat, the organic working fluid's temperature rises and it gradually vaporizes, eventually becoming high-temperature, high-pressure steam. This process fully utilizes the remaining heat in the exhaust gas, providing a power source for subsequent power generation.

[0030] The high-temperature, high-pressure organic working fluid vapor then flows into the expander generator. Inside the expander generator, the organic working fluid vapor expands and does work, driving the generator rotor to rotate. The rotation of the rotor causes relative motion between the magnetic field and the coils inside the generator, generating electrical energy according to the principle of electromagnetic induction. The generated electrical energy is connected to the ship's electrical grid through the output terminal of the expander generator, providing power to various electrical equipment on board and realizing the conversion of waste heat from exhaust gas into electrical energy.

[0031] After completing its work, the organic working fluid vapor becomes low-temperature and low-pressure, and enters the condenser. The condenser and the first-stage plate heat exchanger 201 share a seawater cooling pipe 5, with low-temperature seawater flowing into the condenser through the pipe. In the condenser, the low-temperature and low-pressure organic working fluid vapor exchanges heat with the low-temperature seawater, transferring its own heat to the seawater and gradually condensing into liquid organic working fluid. The cooled liquid organic working fluid flows back to the evaporator through the pipe, forming a complete organic Rankine cycle that continuously converts waste heat from the exhaust gas into electrical energy.

[0032] Meanwhile, the purification module 302 includes a membrane electrode assembly, an ion exchange resin layer, and an ultraviolet photocatalytic component arranged sequentially. The membrane electrode assembly is used to apply a pulsed voltage to achieve electrochemical separation of carbon dioxide, the ion exchange resin layer is used to adsorb heavy metal ions, and the ultraviolet photocatalytic component is used to degrade residual methanol. When the membrane electrode assembly is working, a pulsed voltage is applied to both sides of it. Under the action of the pulsed voltage, a specific electric field environment is formed inside the membrane electrode assembly. After condensate flows into the membrane electrode assembly, the carbon dioxide molecules therein undergo directional movement under the action of the electric field force. Due to the special structure and material properties of the membrane electrode assembly, it can selectively allow carbon dioxide molecules to pass through while blocking the passage of other components, thereby achieving electrochemical separation of carbon dioxide. This process is based on the principles of electrochemistry and ion migration. By precisely controlling the parameters of the pulsed voltage, such as voltage magnitude and frequency, the separation effect of carbon dioxide can be optimized.

[0033] The condensate, after being treated by the membrane electrode assembly, enters the ion exchange resin layer. Ion exchange resin is a high-molecular polymer with a three-dimensional network structure, on which a large number of exchangeable ion groups are attached. When the condensate passes through the ion exchange resin layer, heavy metal ions in the water (such as lead, mercury, cadmium, etc.) undergo a displacement reaction with the exchangeable ions on the resin. For example, hydrogen ions or sodium ions on the cation exchange resin will exchange with heavy metal cations, causing the heavy metal ions to be adsorbed onto the resin, thereby achieving the purpose of removing heavy metal ions from the condensate. Different types of ion exchange resins can selectively adsorb different ions; by rationally selecting the type and combination of resins, multiple heavy metal ions in the condensate can be efficiently removed.

[0034] Finally, the condensate flows into the ultraviolet photocatalytic module. The ultraviolet photocatalytic module contains an ultraviolet light source and a photocatalyst (such as titanium dioxide). When ultraviolet light irradiates the surface of the photocatalyst, the photocatalyst absorbs the energy of the ultraviolet light, generating electron-hole pairs. These electron-hole pairs have strong redox capabilities and can chemically react with residual methanol molecules in the condensate. During the reaction, the methanol molecules are oxidized and decomposed into harmless substances such as carbon dioxide and water, thus achieving the degradation of residual methanol. Simultaneously, ultraviolet light itself also has a certain bactericidal and disinfecting effect, which can further purify the condensate and improve water quality.

[0035] It is worth mentioning that the multi-objective optimization controller 402 is configured to prioritize the full-power operation of the secondary power generation module 202 when the ship is operating under high load. Under high load, the ship's engine power output reaches a high level, and the amount of exhaust gas produced also increases significantly, containing more waste heat energy. At this time, the secondary power generation module 202 (organic Rankine cycle power generation module) has greater power generation potential. The multi-objective optimization controller 402 dynamically coordinates and controls the various modules in the system based on preset optimization strategies and algorithm models. It prioritizes allocating more waste heat resources to the secondary power generation module 202, and ensures that the secondary power generation module 202 can operate at full power by adjusting the heat exchange efficiency between the organic working fluid and the exhaust gas in the evaporator and controlling the operating parameters of the expansion generator, thereby converting as much waste heat as possible into electrical energy.

[0036] Meanwhile, the multi-objective optimization controller 402 also comprehensively considers other factors, such as the heat exchange requirements of the primary plate heat exchanger 201, the processing capacity of the purification module 302, and the stability of the ship's power grid. Under the premise of ensuring the full-power operation of the secondary power generation module 202, it rationally allocates the remaining waste heat resources and other system resources to achieve an optimized balance between multiple objectives (such as power generation efficiency, waste heat recovery rate, water purification effect, and power grid stability) of the entire energy recovery system.

[0037] Specifically, a cooling water bypass pipe is provided between the desalination system 6 and the primary plate heat exchanger 201. The multi-objective optimization controller 402 is also configured to open the cooling water bypass pipe and close the seawater cooling pipe 5 when the seawater temperature is greater than 30°C. Under normal circumstances, seawater enters the primary plate heat exchanger 201 through the seawater cooling pipe 5, exchanges heat with the pre-treated waste gas, removes some of the heat from the waste gas, and lowers the waste gas temperature. At the same time, the seawater itself is discharged after its temperature rises. However, when the seawater temperature is too high (greater than 30°C), the cooling capacity of the seawater will decrease significantly. Because the cooling effect is closely related to the temperature difference between the seawater and the object being cooled, when the seawater temperature rises, the temperature difference between the seawater and the waste gas decreases, the heat exchange efficiency decreases, and it is unable to effectively remove the heat from the waste gas. This will affect the normal operation of the primary plate heat exchanger 201, and thus affect the performance of the entire energy recovery system. Once the cooling water bypass pipeline is opened, the seawater originally used to cool the primary plate heat exchanger 201 no longer enters the heat exchanger, but instead bypasses it directly through the bypass pipeline. At this time, the system can adopt other auxiliary cooling measures or adjust its operating mode to ensure stable system operation. For example, the circulation of other cooling media may be increased or the operating parameters of the desalination system 6 may be adjusted to avoid system failures or performance degradation due to insufficient seawater cooling capacity.

[0038] Optionally, the technical water tank 8 is connected to the ship's sanitation system, and the output end of the technical water tank 8 is equipped with a mineral addition module. The mineral addition module is used to adjust the mineralization of the purified water to drinking water standards. By precisely adjusting the mineralization of the recycled condensate through the mineral addition module, the originally low-mineralized condensate is transformed into high-quality freshwater that meets international drinking water standards and can be directly supplied to the ship's living system. This not only eliminates the risk of corrosion of the pipes by the weak acidity of traditional condensate, but also achieves freshwater self-sufficiency.

[0039] Preferably, the evaporator uses a mixture of R245fa and R1233zd as the working fluid. Both R245fa and R1233zd are commonly used medium- and low-temperature organic working fluids in the Organic Rankine Cycle (ORC). The operation of the mixed working fluid within the evaporator is a complex thermodynamic process. When high-temperature exhaust gas from the ship's engine enters the evaporator, the heat in the exhaust gas is transferred to the mixed working fluid through heat exchange.

[0040] R245fa possesses high vapor pressure and good thermal stability, allowing it to vaporize rapidly at relatively low temperatures. It can quickly absorb heat from exhaust gases, transforming itself from a liquid to a gas, providing initial power for the entire cycle. R1233zd, on the other hand, has lower environmental impact and better thermodynamic properties. Its relatively low boiling point allows it to evaporate at relatively low temperatures, and it possesses a high latent heat of vaporization. This means that, with the same amount of heat absorbed, R1233zd can produce more vapor, thereby improving energy conversion efficiency.

[0041] When these two working fluids are mixed in a certain proportion, they complement each other. During the evaporation process, R245fa begins to vaporize first, and as the temperature rises, R1233zd gradually vaporizes as well. The vaporization process of the mixed working fluid is more stable and continuous, maintaining efficient heat exchange performance over a wider temperature range. This characteristic of the mixed working fluid allows the evaporator to make fuller use of the waste heat in the exhaust gas, converting more thermal energy into the internal energy of the working fluid, thereby driving the subsequent expansion and work process, achieving effective energy recovery and utilization.

[0042] The mass ratio of the mixed working fluid is R245fa:R1233zd = 7:3, and the evaporation temperature of the evaporator is set to 85℃-95℃. Regarding the mixed working fluid ratio, R245fa and R1233zd have different physicochemical properties. R245fa has a high vapor pressure and good thermal stability, allowing it to vaporize rapidly at lower temperatures, providing initial evaporation power for the mixed working fluid. R1233zd, on the other hand, has a lower environmental impact and a higher latent heat of vaporization, enabling it to absorb a large amount of heat and vaporize at relatively low temperatures. When the two are mixed in a 7:3 mass ratio, their respective advantages are fully utilized. The 70% proportion of R245fa allows the mixed working fluid to begin vaporizing at lower temperatures, quickly absorbing heat from the exhaust gas; the 30% proportion of R1233zd ensures that the mixed working fluid can continuously absorb a large amount of heat during subsequent heating processes, improving energy conversion efficiency.

[0043] The evaporation temperature is set at 85℃-95℃ based on several considerations. Within this temperature range, the working fluid mixture is in its optimal vaporization state. Firstly, this temperature range matches the temperature range of the exhaust gas from methanol-fueled ship engines. Engine exhaust gases typically have a high temperature, transferring heat to the working fluid mixture through heat exchange, allowing the working fluid to fully vaporize within this temperature range. If the evaporation temperature is too low, the working fluid will not vaporize sufficiently and cannot effectively absorb the heat from the exhaust gas; if the evaporation temperature is too high, it may cause excessive thermal stress on the evaporator material, affecting equipment lifespan, and may also cause some heat to be lost without being effectively utilized. Secondly, an evaporation temperature of 85℃-95℃ ensures that the working fluid mixture has suitable pressure and temperature during the subsequent expansion process, guaranteeing efficient operation of equipment such as the expander and achieving effective energy conversion.

[0044] In the description herein, it should be understood that the terms "upper," "lower," "left," "right," and other orientations or positional relationships are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used merely for descriptive distinction and have no special meaning.

[0045] In the description of this specification, references to terms such as "an embodiment," "example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0046] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0047] The technical principles of this application have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of this application without inventive effort, and these embodiments will all fall within the scope of protection of this application.

Claims

1. A methanol-fueled ship energy recovery system, characterized in that, include: The exhaust gas energy recovery unit (2), the condensate treatment unit (3), and the control unit (4) are provided. The inlet of the exhaust gas energy recovery unit (2) is connected to the exhaust pipe of the host (1) through a flange. The outlet of the exhaust gas energy recovery unit (2) is connected to the condensate treatment unit (3). The control unit (4) is electrically connected to the exhaust gas energy recovery unit (2) and the condensate treatment unit (3) respectively. The exhaust gas energy recovery unit (2) includes a primary plate heat exchanger (201) and a secondary power generation module (202) arranged in series. The primary plate heat exchanger (201) uses seawater as a cooling medium to recover the waste heat of the high-temperature section of the exhaust gas. The liquid outlet of the primary plate heat exchanger (201) is connected to the desalination system (6) and the external drainage channel (7) respectively. The secondary power generation module (202) generates electricity using the waste heat of the medium-temperature section of the exhaust gas, and the output end of the secondary power generation module (202) is connected to the ship's power grid. The condensate treatment unit (3) includes a gas-liquid separator (301) and a purification module (302) arranged in sequence. The gas-liquid separator (301) is connected to the exhaust gas outlet of the secondary power generation module (202). The purification module (302) is connected to the liquid outlet of the gas-liquid separator (301). The liquid outlet of the purification module (302) is connected to the technical water tank (8) or the external drainage emergency channel (9).

2. The methanol-fueled ship energy recovery system according to claim 1, characterized in that, The control unit (4) includes a dynamic flow distributor (401) and a multi-objective optimization controller (402). The dynamic flow distributor (401) adjusts the flow rate of the cooling medium entering the exhaust gas energy recovery unit (2) according to the load of the main engine (1) and the seawater temperature. The multi-objective optimization controller (402) controls the power generation of the secondary power generation module (202) and the freshwater output of the primary plate heat exchanger (201) based on the ship's energy efficiency.

3. The methanol-fueled ship energy recovery system according to claim 1, characterized in that, The condensate treatment unit (3) also includes a water quality sensor, which is used to monitor the pH value, conductivity and methanol residue of the condensate.

4. The methanol-fueled ship energy recovery system according to any one of claims 1-3, characterized in that, The secondary power generation module (202) is an organic Rankine cycle power generation module. The organic Rankine cycle power generation module includes an evaporator, an expansion generator and a condenser connected in sequence through pipelines. The output end of the expansion generator is connected to the ship's power grid. The condenser shares a seawater cooling pipeline (5) with the primary plate heat exchanger (201).

5. The methanol-fueled ship energy recovery system according to any one of claims 1-3, characterized in that, The purification module (302) includes a membrane electrode assembly, an ion exchange resin layer and an ultraviolet photocatalytic assembly arranged in sequence. The membrane electrode assembly is used to apply a pulse voltage to achieve electrochemical separation of carbon dioxide. The ion exchange resin layer is used to adsorb heavy metal ions. The ultraviolet photocatalytic assembly is used to degrade residual methanol.

6. The methanol-fueled ship energy recovery system according to claim 2, characterized in that, The multi-objective optimization controller (402) is configured to prioritize the full-power operation of the secondary power generation module (202) when the ship is in a high-load operation state.

7. The methanol-fueled ship energy recovery system according to claim 6, characterized in that, A cooling water bypass pipeline is provided between the desalination system (6) and the primary plate heat exchanger (201). The multi-objective optimization controller (402) is also configured to: when the seawater temperature is greater than 30°C, control the cooling water bypass pipeline to open and the seawater cooling pipeline (5) to close.

8. The methanol-fueled ship energy recovery system according to any one of claims 1-3, characterized in that, The technical water tank (8) is connected to the ship's sanitary system, and the output end of the technical water tank (8) is equipped with a mineral addition module, which is used to adjust the mineralization of the purified water to the drinking water standard.

9. The methanol-fueled ship energy recovery system according to claim 4, characterized in that, The evaporator uses a mixture of R245fa and R1233zd as the working fluid.

10. The methanol-fueled ship energy recovery system according to claim 9, characterized in that, The mass ratio of the mixed working fluid is R245fa:R1233zd=7:3, and the evaporation temperature of the evaporator is set to 85℃-95℃.

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