Ammonia fuel BOG reliquefaction system for ships
By using an absorption-ejector type marine ammonia fuel BOG reliquefaction system, the ammonia vapor is absorbed and pressurized by an absorber and an evaporator, which solves the problems of high compressor cost and noise, achieves efficient and energy-saving ammonia vapor reliquefaction, and reduces equipment and operating costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SUNRUI MARINE ENVIRONMENT ENG
- Filing Date
- 2023-10-25
- Publication Date
- 2026-06-19
Smart Images
Figure CN117366905B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of marine technology, and in particular to an absorber-ejector type marine ammonia fuel BOG reliquefaction system. Background Technology
[0002] With the intensification of global warming, reducing greenhouse gas emissions has become one of the most important tasks facing the world today. Increasing the proportion of zero-carbon or low-carbon energy in the world's energy consumption structure helps reduce greenhouse gas emissions and promotes the realization of "carbon neutrality" in the global carbon cycle system. In the shipping industry, ammonia, as a zero-carbon fuel, has attracted widespread attention. As a fuel for ship engines, ammonia is usually stored in fuel tanks as liquid ammonia at -33°C. During storage, due to heat leakage from the environment, the liquid ammonia in the fuel tanks inevitably absorbs heat and evaporates. The ammonia vapor produced by evaporation (BOG) accumulates and can cause the tank pressure to rise, easily leading to safety accidents. Therefore, it is necessary to treat the ammonia vapor in the fuel tanks.
[0003] Currently, most existing ammonia vapor reliquefaction systems are similar in structure and principle to the marine ammonia vapor reliquefaction system disclosed in patent CN115468379A. They all compress and pressurize ammonia vapor through a compressor, then condense the ammonia vapor into liquid ammonia using a condenser, and then cool and depressurize the liquid ammonia through a throttling valve before returning it to the storage tank to achieve ammonia vapor reliquefaction.
[0004] However, the high cost and energy consumption of compressors increase the equipment and operating costs of the ammonia vapor reliquefaction system. Furthermore, the noise generated by the compressors during operation can disrupt the work of the crew. Therefore, it is necessary to design a highly efficient, energy-saving, and low-cost marine ammonia fuel BOG reliquefaction system. Summary of the Invention
[0005] The purpose of this invention is to provide an absorption-ejector type marine ammonia fuel BOG reliquefaction system that eliminates the need for a compressor, thereby reducing equipment and operating costs, reducing noise during operation, and controlling the temperature of the reflux ammonia liquid.
[0006] This invention provides an absorption-ejector type marine ammonia fuel BOG reliquefaction system, comprising a liquid ammonia storage tank, a pressurization assembly, a condenser, a first regulating valve, a gas-liquid separator, a liquid ammonia pump, and an ejector; the pressurization assembly includes an absorber, an evaporator, and a solution pump; the BOG outlet of the liquid ammonia storage tank is connected to the ammonia inlet of the absorber, the concentrated ammonia water outlet of the absorber is connected to the inlet of the solution pump, and the outlet of the solution pump is connected to the concentrated ammonia water inlet of the evaporator;
[0007] The evaporator is used to heat ammonia water, causing the ammonia in the ammonia water to evaporate into ammonia vapor; the dilute ammonia water outlet of the evaporator is connected to the dilute ammonia water inlet of the absorber through an ammonia water pipeline; the ammonia vapor outlet of the evaporator is divided into two paths, one of which is connected to the inlet of the condenser, the outlet of the condenser is connected to the inlet of the first regulating valve, and the outlet of the first regulating valve is connected to the inlet of the gas-liquid separator; the other path of the ammonia vapor outlet is connected to the working fluid inlet of the ejector.
[0008] The liquid ammonia outlet of the gas-liquid separator is connected to the inlet of the liquid ammonia pump, and the outlet of the liquid ammonia pump is connected to the liquid ammonia storage tank; the ammonia outlet of the gas-liquid separator is connected to the ejector fluid inlet of the ejector, and the mixed fluid outlet of the ejector is connected to the ammonia inlet of the absorber.
[0009] Furthermore, the ammonia vapor outlet of the evaporator is located at the top of the evaporator, and a distillation device is provided inside the evaporator. The distillation device is located below the ammonia vapor outlet of the evaporator and is used to remove water vapor from the ammonia vapor.
[0010] Furthermore, the distillation apparatus is a packed gland distillation apparatus, and the concentrated ammonia inlet of the evaporator is located above the distillation apparatus.
[0011] Furthermore, a cooling device for cooling the ammonia water is provided at the bottom of the absorber.
[0012] Furthermore, the dilute ammonia water inlet of the absorber is located at the top of the absorber, and the ammonia gas inlet of the absorber is located at the bottom of the absorber; a spray device is provided at the top of the absorber, and the ammonia water pipeline is connected to the spray device through the dilute ammonia water inlet of the absorber, and the spray device is located above the ammonia gas inlet of the absorber.
[0013] Furthermore, a throttling valve is installed on the ammonia water pipeline.
[0014] Furthermore, the internal space of the gas-liquid separator is divided into a gas phase space and a liquid phase space. The gas phase space is located above the liquid phase space. The ammonia outlet of the gas-liquid separator is connected to the gas phase space, and the liquid ammonia outlet of the gas-liquid separator is connected to the liquid phase space. The gas-liquid separator is equipped with a vertically arranged heat transfer plate. The top end of the heat transfer plate is located in the gas phase space, and the bottom end of the heat transfer plate is located in the liquid phase space.
[0015] Furthermore, the absorption-ejector marine ammonia fuel BOG reliquefaction system also includes a control module, which is electrically connected to the first regulating valve. The control module is used to control the opening degree of the first regulating valve to control the temperature of the liquid ammonia entering the liquid ammonia storage tank from the gas-liquid separator.
[0016] Furthermore, a second regulating valve is provided on the pipeline between the BOG outlet of the liquid ammonia storage tank and the ammonia inlet of the absorber.
[0017] Furthermore, the absorption-ejector marine ammonia fuel BOG reliquefaction system also includes a control module, which is electrically connected to the second regulating valve and the liquid ammonia pump respectively. The control module is used to control the pumping flow rate of the liquid ammonia pump and the opening degree of the second regulating valve, so that the mass of ammonia vapor entering the absorber from the liquid ammonia storage tank can compensate for the mass of liquid ammonia entering the liquid ammonia storage tank from the gas-liquid separator.
[0018] The absorption-ejector type marine ammonia fuel BOG reliquefaction system provided by this invention adopts the absorption-ejector composite refrigeration principle, rather than the commonly used compression refrigeration. It utilizes dilute ammonia water in the absorber to absorb ammonia vapor from the liquid ammonia storage tank to form concentrated ammonia water. This concentrated ammonia water is pumped to the evaporator via a solution pump. The evaporator heats the concentrated ammonia water to saturation, causing the ammonia in the concentrated ammonia water to evaporate into ammonia vapor. Simultaneously, the concentration of the concentrated ammonia water decreases, becoming dilute ammonia water. The ammonia vapor exiting the evaporator splits into two paths. One path of ammonia vapor is condensed by the condenser to form liquid ammonia. Then, the liquid ammonia is depressurized by the first regulating valve to form supersaturated liquid ammonia or saturated liquid ammonia (specifically, the depressurization process forms supersaturated liquid ammonia). Whether the ammonia is in a saturated or supersaturated state depends on the set opening of the first regulating valve. After entering the gas-liquid separator, some of the supersaturated or saturated liquid ammonia evaporates into ammonia vapor and absorbs heat, cooling the remaining liquid ammonia to a subcooled state. This subcooled ammonia is then pumped back to the liquid ammonia storage tank, achieving the reliquefaction and recovery of ammonia vapor. Another stream of ammonia vapor from the evaporator acts as the working fluid and enters the ejector. The ammonia vapor in the gas-liquid separator acts as the ejector fluid, drawing the ammonia vapor into the ejector for mixing before being absorbed again by the absorber. Simultaneously, the pressure in the gas-liquid separator decreases, lowering the temperature of the liquid ammonia injected into the storage tank. Furthermore, by adjusting the opening of the first regulating valve, the temperature of the liquid ammonia injected into the storage tank can be regulated. This absorption-ejector type marine ammonia fuel BOG reliquefaction system utilizes an absorber and evaporator to absorb and pressurize ammonia vapor, eliminating the need for a compressor. This reduces equipment and operating costs, as well as noise levels (the system has no moving parts other than pumps and valves, resulting in low noise). Simultaneously, the ejector reduces the pressure within the gas-liquid separator, yielding cooler liquid ammonia and lowering the pressurization ratio of the pressurization components. This enhances the absorption capacity of water in the absorber for ammonia, improving efficiency and reducing operating costs and system design complexity. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the absorption-ejector type marine ammonia fuel BOG reliquefaction system in an embodiment of the present invention.
[0020] Figure 2 for Figure 1 A schematic diagram of the structure of a gas-liquid separator.
[0021] Figure 3 for Figure 1 A schematic diagram of the ejector.
[0022] Figure 4 This is a schematic diagram of the control logic of the control module in an embodiment of the present invention.
[0023] Figure 5 This is a schematic diagram of the structure of an absorption-ejector type marine ammonia fuel BOG reliquefaction system in another embodiment of the present invention. Detailed Implementation
[0024] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.
[0025] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification and claims of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.
[0026] The directional terms such as "up," "down," "left," "right," "front," "back," "top," and "bottom" (if present) used in the specification and claims of this invention are defined by the position of the structures in the drawings and the relative positions of the structures, and are only for the clarity and convenience of expressing the technical solution. It should be understood that the use of directional terms should not limit the scope of protection claimed in this application.
[0027] like Figures 1 to 3 As shown in the embodiment of the present invention, the absorption-ejector type marine ammonia fuel BOG reliquefaction system includes a liquid ammonia storage tank 1, a pressurization assembly, a condenser 5, a first regulating valve 6, a gas-liquid separator 7, a liquid ammonia pump 8, and an ejector 10. The pressurization assembly includes an absorber 2, an evaporator 3, and a solution pump 4. The BOG outlet of the liquid ammonia storage tank 1 is connected to the ammonia inlet 21 of the absorber 2. The absorber 2 is used to absorb ammonia vapor to form concentrated ammonia water. The concentrated ammonia water outlet 22 of the absorber 2 is connected to the inlet of the solution pump 4, and the outlet of the solution pump 4 is connected to the concentrated ammonia water inlet 31 of the evaporator 3.
[0028] Evaporator 3 is used to heat ammonia water, causing the ammonia in the ammonia water to evaporate into ammonia vapor. The dilute ammonia water outlet 30 of evaporator 3 is connected to the dilute ammonia water inlet 23 of absorber 2 via ammonia water pipeline 9. The ammonia vapor outlet 32 of evaporator 3 is divided into two paths. One path of ammonia vapor outlet 32 is connected to the inlet of condenser 5, which is used to condense ammonia vapor into liquid ammonia. The outlet of condenser 5 is connected to the inlet of first regulating valve 6, which is used to regulate the flow rate and pressure in the pipeline. The outlet of first regulating valve 6 is connected to the inlet of gas-liquid separator 7 (specifically, to the liquid ammonia inlet 73 of gas-liquid separator 7). The other path of ammonia vapor outlet 32 is connected to the working fluid inlet 101 of ejector 10.
[0029] The liquid ammonia outlet 72 of the gas-liquid separator 7 is connected to the inlet of the liquid ammonia pump 8, and the outlet of the liquid ammonia pump 8 is connected to the liquid ammonia storage tank 1; the ammonia outlet 71 of the gas-liquid separator 7 is connected to the ejector fluid inlet 102 of the ejector 10, and the mixed fluid outlet 103 of the ejector 10 is connected to the ammonia inlet 21 of the absorber 2.
[0030] Specifically, during operation, the liquid ammonia in the liquid ammonia storage tank 1 evaporates to produce ammonia vapor (BOG, Boil-Off Gas). This ammonia vapor enters the absorber 2 and is absorbed by the dilute ammonia solution there, producing concentrated ammonia solution. The concentrated ammonia solution is then pressurized and pumped to the evaporator 3 by the solution pump 4. The evaporator 3 heats the concentrated ammonia solution to saturation, causing the ammonia in the solution to evaporate into ammonia vapor (at this point, the pressure of the ammonia vapor is relatively high, allowing it to be condensed into liquid ammonia upon entering the condenser 5). Simultaneously, the concentration of the concentrated ammonia solution decreases, becoming dilute ammonia solution. The dilute ammonia solution in the evaporator 3 flows back to the absorber 2 via the ammonia solution pipeline 9 for reuse in absorbing ammonia vapor.
[0031] The ammonia vapor exiting from the ammonia vapor outlet 32 of the evaporator 3 splits into two streams. One stream is condensed by the condenser 5 to form liquid ammonia (the condenser 5 condenses the ammonia vapor into liquid ammonia). The liquid ammonia then undergoes a pressure reduction via the first regulating valve 6 to form either supersaturated or saturated liquid ammonia (the specific pressure reduction determines whether it results in a supersaturated or saturated state; the smaller the opening, the greater the pressure drop, and the easier it is for the liquid ammonia to become supersaturated). After entering the gas-liquid separator 7, a portion of the liquid ammonia evaporates into ammonia vapor and absorbs heat, cooling the remaining liquid ammonia to a subcooled state (the condenser 5 can only perform preliminary condensation of ammonia and cannot cool it to a low temperature). Thus, the supersaturated or saturated liquid ammonia enters the gas-liquid separator 7 in two states: ammonia vapor and subcooled liquid ammonia. The subcooled liquid ammonia in the gas-liquid separator 7 is pumped back to the liquid ammonia storage tank 1 by the liquid ammonia pump 8, achieving the reliquefaction and recovery of ammonia vapor. Another stream of ammonia vapor from evaporator 3 enters ejector 10 as the working fluid. Ammonia vapor from gas-liquid separator 7 serves as the ejector fluid, drawing the ammonia vapor from gas-liquid separator 7 into ejector 10 (the ammonia vapor from evaporator 3 flows at a high velocity, creating a negative pressure within ejector 10, thus drawing the ammonia vapor from gas-liquid separator 7 into ejector 10). The two streams of ammonia vapor mix in ejector 10 and then re-enter absorber 2, where they are absorbed by dilute ammonia water. Because the ammonia vapor in gas-liquid separator 7 is drawn away, the pressure within gas-liquid separator 7 decreases, thereby lowering the evaporation temperature of the liquid ammonia within gas-liquid separator 7. This results in an even lower temperature for the subcooled liquid ammonia generated within gas-liquid separator 7, ultimately reducing the temperature of the liquid ammonia injected into liquid ammonia storage tank 1.
[0032] Meanwhile, because the working fluid and the ejector fluid are mixed in the ejector 10, the pressure of the ammonia gas entering the absorber 2 is increased, which in turn increases the pressure inside the absorber 2, thereby improving the absorption capacity of the dilute ammonia water in the absorber 2 for ammonia gas (the higher the pressure, the higher the absorption capacity of the water for ammonia gas), and improving the working efficiency.
[0033] Meanwhile, although using some ammonia vapor from evaporator 3 as the working fluid to eject ammonia vapor from gas-liquid separator 7 requires increasing the evaporation rate of evaporator 3 for the same liquefaction rate, the pressure ratio of the booster assembly is reduced because the booster assembly inputs ammonia gas at a higher pressure. In other words, the pressure ratio is reduced by increasing the evaporation rate, thus simplifying the system design. Furthermore, the reduced pressure ratio decreases the pressure ratio of solution pump 4, thereby saving on equipment and operating costs.
[0034] Simultaneously, by adjusting the opening degree of the first regulating valve 6, the temperature of the liquid ammonia injected into the liquid ammonia storage tank 1 can be adjusted. Specifically, when the opening degree of the first regulating valve 6 is reduced, on the one hand, the amount of ammonia vapor entering the condenser 5 decreases, and the temperature of the liquid ammonia condensed in the condenser 5 will decrease; on the other hand, the pressure drop after the first regulating valve 6 is greater due to the reduced opening degree, resulting in a lower temperature of the subcooled liquid ammonia generated in the gas-liquid separator 7; furthermore, the amount of high-pressure ammonia vapor entering the ejector 10 increases due to the reduced opening degree of the first regulating valve 6, resulting in a lower negative pressure in the ejector 10, which in turn lowers the pressure in the gas-liquid separator 7, and further lowers the temperature of the subcooled liquid ammonia generated in the gas-liquid separator 7. Through the combination of these three factors, the temperature of the liquid ammonia injected into the liquid ammonia storage tank 1 decreases, but the liquid ammonia return flow rate decreases. Conversely, when the opening degree of the first regulating valve 6 is increased, the temperature of the liquid ammonia injected into the liquid ammonia storage tank 1 increases, but the liquid ammonia return flow rate increases.
[0035] The absorption-ejection type marine ammonia fuel BOG reliquefaction system provided in this embodiment of the invention adopts the absorption-ejection composite refrigeration principle, rather than the commonly used compression refrigeration. It utilizes dilute ammonia water in absorber 2 to absorb ammonia vapor in liquid ammonia storage tank 1 to form concentrated ammonia water. The concentrated ammonia water is pumped to evaporator 3 by solution pump 4. Evaporator 3 heats the concentrated ammonia water to saturation, causing the ammonia in the concentrated ammonia water to evaporate into ammonia vapor. Simultaneously, the concentration of the concentrated ammonia water decreases, becoming dilute ammonia water. The ammonia vapor exiting evaporator 3 is divided into two paths. One path of ammonia vapor is condensed by condenser 5 to form liquid ammonia. Then, the liquid ammonia is depressurized by the first regulating valve 6 to form supersaturated ammonia. Liquid ammonia, whether saturated or supersaturated, enters the gas-liquid separator 7. Part of the liquid ammonia evaporates into ammonia vapor, absorbing heat, while the remaining liquid ammonia is cooled to a subcooled state. It is then pumped back to the liquid ammonia storage tank 1 by the liquid ammonia pump 8, achieving the reliquefaction and recovery of ammonia vapor. Another stream of ammonia vapor from the evaporator 3 enters the ejector 10 as the working fluid. The ammonia vapor in the gas-liquid separator 7 serves as the ejector fluid, drawing it into the ejector 10 for mixing before being absorbed again by the absorber 2. Simultaneously, the pressure within the gas-liquid separator 7 decreases, lowering the temperature of the liquid ammonia injected into the liquid ammonia storage tank 1. Furthermore, the temperature of the liquid ammonia injected into the liquid ammonia storage tank 1 can be adjusted by regulating the opening of the first regulating valve 6. This absorption-ejector type marine ammonia fuel BOG reliquefaction system utilizes absorber 2 and evaporator 3 to absorb and pressurize ammonia vapor, eliminating the need for a compressor and thus reducing equipment and operating costs, as well as noise levels (the system has no moving parts other than pumps and valves, resulting in low noise). Simultaneously, ejector 10 reduces the pressure within gas-liquid separator 7, obtaining cooler liquid ammonia and lowering the pressurization ratio of the pressurization components. This increases the ammonia absorption capacity of water in absorber 2, improving efficiency and reducing operating costs and system design complexity. Furthermore, ejector 10 is less expensive than other types of pressurization equipment.
[0036] Furthermore, such as Figure 1 As shown, in this embodiment, the ammonia vapor outlet 32 of the evaporator 3 is located at the top of the evaporator 3, and the dilute ammonia water outlet 30 of the evaporator 3 is located at the bottom of the evaporator 3. The evaporator 3 is equipped with a distillation device 33, which is located below the ammonia vapor outlet 32 and above the dilute ammonia water outlet 30. The distillation device 33 is used to remove water vapor from the ammonia vapor.
[0037] Specifically, when the evaporator 3 heats the concentrated ammonia solution, in addition to ammonia evaporating into ammonia vapor, some water also evaporates into water vapor. If the water vapor mixes with the ammonia vapor and condenses together, it will reduce the purity of the recovered liquid ammonia. Therefore, this embodiment uses a distillation device 33 to remove water vapor from the ammonia vapor, thereby reducing the water vapor content in the evaporated components and reducing impurities in the reliquefied liquid ammonia.
[0038] Furthermore, such as Figure 1 As shown, in this embodiment, the distillation unit 33 is a packed-slot distillation unit, and the concentrated ammonia inlet 31 of the evaporator 3 is located above the distillation unit 33. Therefore, when the concentrated ammonia pumped in by the solution pump 4 enters the evaporator 3, the concentrated ammonia can come into countercurrent contact with water vapor within the packed-slot distillation unit, thereby absorbing the water vapor (since the concentrated ammonia has a high concentration, it will not absorb ammonia vapor), further improving the water vapor removal efficiency.
[0039] Furthermore, such as Figure 1 As shown, in this embodiment, a heat exchange device 34 for heating ammonia water is provided at the bottom of the evaporator 3. The heat exchange device 34 is heated by waste heat from the ship's main engine (i.e., the heat exchange device 34 exchanges heat with the waste heat from the ship's main engine, which can be main engine cylinder liner cooling water or main engine exhaust gas, etc.). Since the heat source for heating the concentrated ammonia water in the evaporator 3 comes from the waste heat from the ship's main engine, the energy utilization rate is improved, and the system's energy consumption and operating costs are reduced. In other embodiments, the heat exchange device 34 can also be an electric heating device, i.e., an electric heating device for heating ammonia water is provided at the bottom of the evaporator 3.
[0040] Furthermore, such as Figure 1 As shown, in this embodiment, a cooling device 24 for cooling ammonia water is provided at the bottom of the absorber 2. The cooling device 24 uses cooling water for cooling. Inside the absorber 2, since dilute ammonia water releases heat when absorbing ammonia vapor, and excessively high temperature will cause ammonia in the ammonia water to escape and reduce the solubility of ammonia, the cooling device 24 is provided to cool the ammonia water, thereby increasing the concentration of ammonia water and the ammonia absorption efficiency.
[0041] Furthermore, such as Figure 1As shown, in this embodiment, the dilute ammonia water inlet 23 of the absorber 2 is located at the top of the absorber 2, and the ammonia gas inlet 21 of the absorber 2 is located at the bottom of the absorber 2. After the ammonia vapor enters the absorber 2, it can come into countercurrent contact with the dilute ammonia water (the ammonia vapor flows from bottom to top, and the dilute ammonia water flows from top to bottom), thereby improving the absorption efficiency. At the same time, a spray device 25 (the spray device 25 specifically includes a spray pipe and nozzles installed on the spray pipe) is provided at the top of the absorber 2. The spray device 25 is located above the ammonia gas inlet 21 of the absorber 2. The ammonia water pipe 9 is connected to the spray device 25 through the dilute ammonia water inlet 23 of the absorber 2, so that the dilute ammonia water can be sprayed from top to bottom, thereby further improving the ammonia absorption efficiency.
[0042] Furthermore, such as Figure 5 As shown, in another embodiment, the absorber 2 is also provided with packing material 26, which is located between the spray device 25 and the ammonia inlet 21. The packing material 26 can increase the contact time between the dilute ammonia water and the ammonia vapor, thereby further improving the ammonia absorption efficiency.
[0043] Furthermore, such as Figure 1 As shown, in this embodiment, a throttling valve 91 is provided on the ammonia water pipeline 9. The throttling valve 91 is used to reduce the pressure of the dilute ammonia water (since the evaporator 3 is in a high-pressure state and the absorber 2 is in a low-pressure state, a throttling valve 91 needs to be installed on the ammonia water pipeline 9).
[0044] Furthermore, such as Figure 1 and Figure 2 As shown, in this embodiment, the ammonia outlet 71 and liquid ammonia inlet 73 of the gas-liquid separator 7 are located at the top of the gas-liquid separator 7, and the liquid ammonia outlet 72 of the gas-liquid separator 7 is located at the bottom of the gas-liquid separator 7. The internal space of the gas-liquid separator 7 is divided into a gas phase space 7A (i.e., the space where the gas is located) and a liquid phase space 7B (i.e., the space where the liquid is located). The gas phase space 7A is located above the liquid phase space 7B. The ammonia outlet 71 of the gas-liquid separator 7 is connected to the gas phase space 7A, and the liquid ammonia outlet 72 of the gas-liquid separator 7 is connected to the liquid phase space 7B. The gas-liquid separator 7 is provided with a vertically arranged heat transfer plate 74. The top end of the heat transfer plate 74 is located in the gas phase space 7A, and the bottom end of the heat transfer plate 74 is located in the liquid phase space 7B, that is, the heat transfer plate 74 extends from the gas phase space 7A to the liquid phase space 7B. The heat transfer plate 74 is used to improve the heat transfer efficiency between the gas phase and the liquid phase in the gas-liquid separator 7 (when some liquid ammonia in the gas-liquid separator 7 evaporates into ammonia vapor, it will absorb the heat of the unevaporated liquid ammonia, thereby reducing the temperature of the unevaporated liquid ammonia), thereby improving the cooling efficiency of liquid ammonia and increasing the reliquefaction efficiency.
[0045] Furthermore, such as Figure 2 As shown, in this embodiment, there are multiple heat transfer plates 74, which are spaced apart within the gas-liquid separator 7.
[0046] Furthermore, in this embodiment, the heat transfer plate 74 is a stainless steel plate, which not only has good heat transfer efficiency but also good corrosion resistance.
[0047] Furthermore, in this embodiment, the outer wall of the gas-liquid separator 7 is wrapped with a polyurethane insulation layer (not shown) to prevent the gas-liquid separator 7 from absorbing heat from the outside. The thickness of the polyurethane insulation layer can be 50 mm.
[0048] Furthermore, such as Figure 1 and Figure 3 As shown, in this embodiment, the ejector 10 includes an inlet section 105, a mixing section 106, and a diffusion section 107 connected in sequence. A nozzle 104 is provided at the inlet section 105, and the ammonia vapor outlet 32 of the evaporator 3 is connected to the nozzle 104 (i.e., the working fluid inlet 101 of the ejector 10 is the inlet of the nozzle 104); the ejector fluid inlet 102 is located on the inlet section 105. The mixing section 106 has a gradually decreasing diameter from top to bottom, and the diffusion section 107 has a gradually increasing diameter from top to bottom. The mixed fluid outlet 103 is located at the bottom of the diffusion section 107. Under the action of the nozzle 104, the working fluid converts potential energy into kinetic energy, forming a high-speed fluid. Due to turbulent diffusion, a low pressure is formed near the working fluid, drawing in the ejector fluid from the gas-liquid separator 7. The working fluid and the ejector fluid mix in the mixing section 106, the flow gradually becomes uniform, and the pressure increases. The mixed fluid then enters the diffusion section 107, where the flow velocity changes (the flow rate decreases), kinetic energy is converted into potential energy, and the pressure increases.
[0049] Furthermore, such as Figure 1 and Figure 4 As shown, in this embodiment, the absorption-ejector type marine ammonia fuel BOG reliquefaction system also includes a control module 200. The control module 200 is electrically connected to the first regulating valve 6. The control module 200 is used to control the opening degree of the first regulating valve 6 to control the temperature of the liquid ammonia entering the liquid ammonia storage tank 1 from the gas-liquid separator 7. Simultaneously, a temperature sensor (not shown) can also be installed on the gas-liquid separator 7 or on the pipeline between the gas-liquid separator 7 and the liquid ammonia storage tank 1. The temperature sensor is electrically connected to the control module 200, enabling the control module 200 to control the opening degree of the first regulating valve 6 based on the liquid ammonia temperature measured by the temperature sensor.
[0050] Furthermore, such as Figure 1 As shown, in this embodiment, a second regulating valve 11 is provided on the pipeline between the BOG outlet of the liquid ammonia storage tank 1 and the ammonia inlet 21 of the absorber 2. The second regulating valve 11 is used to regulate the discharge amount and discharge speed of ammonia vapor in the liquid ammonia storage tank 1.
[0051] Furthermore, such as Figure 1 and Figure 4As shown, in this embodiment, the control module 200 is also electrically connected to the second regulating valve 11 and the liquid ammonia pump 8, respectively. The control module 200 is used to control the opening and closing of the liquid ammonia pump 8 and / or the pumping flow rate and the opening degree of the second regulating valve 11, thereby maintaining the liquid ammonia level in the gas-liquid separator 7 stable (e.g., unchanged), and ensuring that the mass of ammonia vapor entering the absorber 2 from the liquid ammonia storage tank 1 can compensate for the mass of liquid ammonia entering the liquid ammonia storage tank 1 from the gas-liquid separator 7 (i.e., the mass of ammonia vapor entering the absorber 2 from the liquid ammonia storage tank 1 is equal to or close to the mass of liquid ammonia entering the liquid ammonia storage tank 1 from the gas-liquid separator 7), thereby ensuring the stable operation of the system.
[0052] Furthermore, in this embodiment, both the liquid ammonia pump 8 and the solution pump 4 are variable frequency pumps, and the liquid ammonia pump 8 and the solution pump 4 include, but are not limited to, centrifugal pumps, screw pumps, piston pumps, etc.
[0053] Furthermore, such as Figure 1 As shown, in this embodiment, the BOG outlet of the liquid ammonia storage tank 1 merges with the mixed fluid outlet 103 of the ejector 10 (specifically, through a three-way valve) and then connects together with the ammonia inlet 21 of the absorber 2.
[0054] Furthermore, in this embodiment, each pipeline is also equipped with a control valve (not shown in the figure).
[0055] Furthermore, such as Figure 1 As shown, in this embodiment, the condenser 5 is cooled by cooling water.
[0056] Furthermore, such as Figures 1 to 4 As shown in the figure, the absorption-ejector type marine ammonia fuel BOG reliquefaction system of this invention utilizes the absorption-ejector composite refrigeration principle to reliquefy ammonia fuel BOG. Its main working process is as follows:
[0057] 1. The concentrated ammonia in evaporator 3 is heated to saturation using waste heat from the ship's main engine (or by electric heating), causing the ammonia to evaporate into ammonia vapor. At the same time, the concentration of the concentrated ammonia decreases, becoming dilute ammonia. The waste heat from the ship's main engine can be the exhaust gas, with a temperature of approximately 190°C, which heats the concentrated ammonia to approximately 112°C.
[0058] Evaporator 3 is equipped with a distillation unit 33 to reduce the water vapor content in the evaporated components, thereby reducing impurities in the reliquefied liquid ammonia. The distillation unit 33 is a packed gland distillation unit.
[0059] The dilute ammonia water in evaporator 3 is throttled by throttling valve 91 to reduce pressure and is then injected into absorber 2 from top to bottom.
[0060] 2. The ammonia vapor exiting from the ammonia vapor outlet 32 of the evaporator 3 is divided into two streams. One stream of ammonia vapor enters the condenser 5, where it condenses into liquid ammonia under the action of cooling water. The temperature of the liquid ammonia is approximately 40°C. The condensed liquid ammonia is then throttled and depressurized by the first regulating valve 6 to form supersaturated liquid ammonia or saturated liquid ammonia. After entering the gas-liquid separator 7, a portion of the liquid ammonia evaporates into ammonia vapor and absorbs heat.
[0061] Another stream of ammonia vapor from the evaporator 3 enters the ejector 10 as the working fluid, and the ammonia vapor in the gas-liquid separator 7 is used as the ejector fluid. The ammonia vapor in the gas-liquid separator 7 is drawn into the ejector 10.
[0062] 3. Due to the action of ejector 10, the pressure inside gas-liquid separator 7 is reduced to 0.04 MPa, and the saturated vapor pressure of ammonia is reduced to -50°C (wherein, gas-liquid separator 7 can withstand a negative pressure of -1 bar). The remaining liquid ammonia in gas-liquid separator 7 is cooled to a subcooled state (about -50°C), and then pumped back to liquid ammonia storage tank 1 by liquid ammonia pump 8, realizing the reliquefaction and recovery of ammonia vapor.
[0063] The gas-liquid separator 7 is equipped with a vertical heat transfer stainless steel plate to accelerate the heat transfer rate between the gas and liquid phases and increase the reliquefaction efficiency.
[0064] 4. The ammonia vapor exiting ejector 10 merges with the ammonia vapor discharged from liquid ammonia storage tank 1 and is injected into absorber 2 from bottom to top. In absorber 2, dilute ammonia water absorbs the ammonia vapor and becomes concentrated ammonia water again. The concentrated ammonia water in absorber 2 is cooled by cooling water and then pressurized by solution pump 4 before returning to evaporator 3 to participate in the next cycle.
[0065] 5. The control module 200 controls the temperature of the liquid ammonia entering the liquid ammonia storage tank 1 from the gas-liquid separator 7 and the flow rate of the liquid ammonia reflux by controlling the opening of the first regulating valve 6.
[0066] The control module 200 controls the liquid ammonia pump 8 to maintain a stable liquid ammonia level in the gas-liquid separator 7.
[0067] The control module 200 adjusts the mass of ammonia vapor entering the absorber 2 from the liquid ammonia storage tank 1 by controlling the opening of the second regulating valve 11, so that the mass of ammonia vapor entering the absorber 2 from the liquid ammonia storage tank 1 can just compensate for the mass of liquid ammonia entering the liquid ammonia storage tank 1 from the gas-liquid separator 7, thereby ensuring the stable operation of the system.
[0068] The absorption-ejection type marine ammonia fuel BOG reliquefaction system provided in this embodiment of the invention adopts the absorption-ejection composite refrigeration principle, rather than the commonly used compression refrigeration. It utilizes dilute ammonia water in absorber 2 to absorb ammonia vapor in liquid ammonia storage tank 1 to form concentrated ammonia water. The concentrated ammonia water is pumped to evaporator 3 by solution pump 4. Evaporator 3 heats the concentrated ammonia water to saturation, causing the ammonia in the concentrated ammonia water to evaporate into ammonia vapor. Simultaneously, the concentration of the concentrated ammonia water decreases, becoming dilute ammonia water. The ammonia vapor exiting evaporator 3 is divided into two paths. One path of ammonia vapor is condensed by condenser 5 to form liquid ammonia. Then, the liquid ammonia is depressurized by the first regulating valve 6 to form supersaturated ammonia. Liquid ammonia, whether saturated or supersaturated, enters the gas-liquid separator 7. Part of the liquid ammonia evaporates into ammonia vapor, absorbing heat, while the remaining liquid ammonia is cooled to a subcooled state. It is then pumped back to the liquid ammonia storage tank 1 by the liquid ammonia pump 8, achieving the reliquefaction and recovery of ammonia vapor. Another stream of ammonia vapor from the evaporator 3 enters the ejector 10 as the working fluid. The ammonia vapor in the gas-liquid separator 7 serves as the ejector fluid, drawing it into the ejector 10 for mixing before being absorbed again by the absorber 2. Simultaneously, the pressure within the gas-liquid separator 7 decreases, lowering the temperature of the liquid ammonia injected into the liquid ammonia storage tank 1. Furthermore, the temperature of the liquid ammonia injected into the liquid ammonia storage tank 1 can be adjusted by regulating the opening of the first regulating valve 6. This absorption-ejector type marine ammonia fuel BOG reliquefaction system utilizes absorber 2 and evaporator 3 to absorb and pressurize ammonia vapor, eliminating the need for a compressor and thus reducing equipment and operating costs, as well as noise levels (the system has no moving parts other than pumps and valves, resulting in low noise). Simultaneously, ejector 10 reduces the pressure within gas-liquid separator 7, obtaining cooler liquid ammonia and lowering the pressurization ratio of the pressurization components. This increases the absorption capacity of water in absorber 2 for ammonia, improving efficiency and reducing operating costs and system design complexity. Furthermore, ejector 10 is less expensive than other types of pressurization equipment. Moreover, the system uses ammonia as refrigerant, consistent with the reliquefied medium, allowing them to operate in the same circuit without requiring refrigerant replenishment.
[0069] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. An absorption-ejector type marine ammonia fuel BOG reliquefaction system, characterized in that, The system includes a liquid ammonia storage tank (1), a pressurization assembly, a condenser (5), a first regulating valve (6), a gas-liquid separator (7), a liquid ammonia pump (8), and an ejector (10). The pressurization assembly includes an absorber (2), an evaporator (3), and a solution pump (4). The BOG outlet of the liquid ammonia storage tank (1) is connected to the ammonia inlet (21) of the absorber (2), the concentrated ammonia water outlet (22) of the absorber (2) is connected to the inlet of the solution pump (4), and the outlet of the solution pump (4) is connected to the concentrated ammonia water inlet (31) of the evaporator (3). The evaporator (3) is used to heat the ammonia water, so that the ammonia in the ammonia water evaporates into ammonia vapor; the dilute ammonia water outlet (30) of the evaporator (3) is connected to the dilute ammonia water inlet (23) of the absorber (2) through the ammonia water pipeline (9); the ammonia vapor outlet (32) of the evaporator (3) is divided into two paths, one path of the ammonia vapor outlet (32) is connected to the inlet of the condenser (5), the outlet of the condenser (5) is connected to the inlet of the first regulating valve (6), and the outlet of the first regulating valve (6) is connected to the inlet of the gas-liquid separator (7); the other path of the ammonia vapor outlet (32) is connected to the working fluid inlet (101) of the ejector (10); The liquid ammonia outlet (72) of the gas-liquid separator (7) is connected to the inlet of the liquid ammonia pump (8), and the outlet of the liquid ammonia pump (8) is connected to the liquid ammonia storage tank (1); the ammonia outlet (71) of the gas-liquid separator (7) is connected to the ejector fluid inlet (102) of the ejector (10), and the mixed fluid outlet (103) of the ejector (10) is connected to the ammonia inlet (21) of the absorber (2).
2. The absorption-ejection ammonia-fueled BOG reliquefaction system for marine use according to claim 1, characterized in that, The ammonia vapor outlet (32) of the evaporator (3) is located at the top of the evaporator (3). The evaporator (3) is equipped with a distillation device (33), which is located below the ammonia vapor outlet (32) of the evaporator (3). The distillation device (33) is used to remove water vapor from the ammonia vapor.
3. The absorption-ejection ammonia-fueled BOG reliquefaction system for marine use according to claim 2, characterized in that, The distillation apparatus (33) is a packed box distillation apparatus, and the concentrated ammonia water inlet (31) of the evaporator (3) is located above the distillation apparatus (33).
4. The absorption-ejection ammonia-fueled BOG reliquefaction system for marine use according to claim 1, characterized in that, The bottom of the absorber (2) is provided with a cooling device (24) for cooling the ammonia water.
5. The absorption-ejector type marine ammonia fuel BOG reliquefaction system as described in claim 1, characterized in that, The dilute ammonia water inlet (23) of the absorber (2) is located at the top of the absorber (2), and the ammonia gas inlet (21) of the absorber (2) is located at the bottom of the absorber (2); a spray device (25) is provided at the top of the absorber (2), and the ammonia water pipeline (9) is connected to the spray device (25) through the dilute ammonia water inlet (23) of the absorber (2), and the spray device (25) is located above the ammonia gas inlet (21) of the absorber (2).
6. The absorption-ejection ammonia-fueled BOG reliquefaction system for marine use according to claim 1, characterized in that, A throttle valve (91) is installed on the ammonia water pipeline (9).
7. The absorption-ejection ammonia-fueled BOG reliquefaction system for marine use according to claim 1, characterized in that, The internal space of the gas-liquid separator (7) is divided into a gas phase space (7A) and a liquid phase space (7B). The gas phase space (7A) is located above the liquid phase space (7B). The ammonia outlet (71) of the gas-liquid separator (7) is connected to the gas phase space (7A), and the liquid ammonia outlet (72) of the gas-liquid separator (7) is connected to the liquid phase space (7B). The gas-liquid separator (7) is provided with a vertically arranged heat transfer plate (74). The top end of the heat transfer plate (74) is located in the gas phase space (7A), and the bottom end of the heat transfer plate (74) is located in the liquid phase space (7B).
8. The absorption-ejection ammonia-fueled BOG reliquefaction system for marine use according to any one of claims 1 to 7, characterized in that, The absorption-ejector marine ammonia fuel BOG reliquefaction system also includes a control module (200), which is electrically connected to the first regulating valve (6). The control module (200) is used to control the opening degree of the first regulating valve (6) to control the temperature of the liquid ammonia entering the liquid ammonia storage tank (1) from the gas-liquid separator (7).
9. The absorption-ejection ammonia-fueled BOG reliquefaction system for marine use according to any one of claims 1 to 7, characterized in that, A second regulating valve (11) is provided on the pipeline between the BOG outlet of the liquid ammonia storage tank (1) and the ammonia inlet (21) of the absorber (2).
10. The absorption-ejection ammonia-fueled BOG reliquefaction system for marine use according to claim 9, characterized in that, The absorption-ejector marine ammonia fuel BOG reliquefaction system also includes a control module (200), which is electrically connected to the second regulating valve (11) and the liquid ammonia pump (8). The control module (200) is used to control the pumping flow rate of the liquid ammonia pump (8) and the opening degree of the second regulating valve (11) so that the mass of ammonia vapor entering the absorber (2) from the liquid ammonia storage tank (1) can compensate for the mass of liquid ammonia entering the liquid ammonia storage tank (1) from the gas-liquid separator (7).