Carbon dioxide liquefaction method, device for a ship and ship

Abstract

The application provides a carbon dioxide liquefaction method, device and ship for a ship, the carbon dioxide liquefaction method for the ship comprising the following steps: compressing carbon dioxide gas to increase the pressure and temperature of the carbon dioxide gas; compressing and expanding air to obtain a heat exchange medium with a temperature lower than that of the carbon dioxide gas; and exchanging heat between the heat exchange medium and the carbon dioxide gas to obtain carbon dioxide liquid. The carbon dioxide liquefaction method for the ship solves the problem of high global warming potential and global warming potential of the commonly used low-temperature liquefied refrigerant of the carbon dioxide gas for the ship by using environmentally friendly air as a refrigerant. Meanwhile, the mechanical energy generated by the air expansion can be output to the first compressor in the process of air expansion, so that the system working efficiency is improved and the system energy consumption is reduced while refrigeration is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ships, in particular to a carbon dioxide liquefaction method and device for a ship and the ship. BACKGROUND

[0002] With the acceleration of the global process of the greenhouse effect, the control of greenhouse gases has become the focus of international attention. The shipping industry is one of the important sources of greenhouse gas emissions. With the implementation of the International Maritime Organization's greenhouse gas emission reduction strategy and the implementation of the domestic "carbon neutralization" initiative, carbon emission reduction will become an important direction for ship emission treatment in the future.

[0003] Carbon dioxide capture and storage technology is an effective way to achieve large-scale carbon emission reduction of ships. It reduces the carbon dioxide content in flue gas by capturing, separating, liquefying and storing carbon dioxide in flue gas. Among them, the carbon dioxide liquefaction and storage unit is an important part of the whole capture and storage technology, but there are few studies on carbon dioxide liquefaction technology under the use environment of ships, and a mature process route has not yet been formed.

[0004] At present, the traditional land-based carbon dioxide liquefaction technology mainly adopts two ways:

[0005] 1. High pressure liquefaction process, mainly pressurize the normal temperature carbon dioxide gas to the critical pressure state, the pressure is about 78bar after pressurization, and then cooled to 30℃ to realize the liquefaction of the gas. This method has large compressor power consumption, but the cold energy used in the cooling process is small, so the total energy consumption is low. However, due to the high final temperature, the liquid density is small, which leads to large volume of liquefied carbon dioxide, which is difficult to meet the compactness requirement of the whole liquefaction and storage system for practical ship application. In addition, due to the high final pressure, the material requirement of the system is high, and the overall cost is high.

[0006] 2. Low temperature cooling process, mainly introduces a compressor and a refrigeration system, compresses the normal temperature and pressure gas to about 20bar, and then cools the gas to-20℃ through the cold energy released by the refrigeration system to realize the liquefaction of the gas. Although the liquid carbon dioxide formed by this method has small volume, the cold energy required by the refrigeration system is large, which is difficult to meet the low energy consumption requirement of the whole liquefaction and storage system for practical ship application, and with the increasing strictness of environmental protection regulations, the selection range of ship low temperature refrigerant is becoming smaller and smaller. SUMMARY

[0007] The present application provides a carbon dioxide liquefaction method and device for a ship, which realizes the liquefaction of carbon dioxide under the condition of reducing pollution.

[0008] The application provides a carbon dioxide liquefaction method for a ship, comprising the following steps: compressing carbon dioxide gas to increase the pressure and temperature of the carbon dioxide gas; compressing air and expanding the air to obtain a heat exchange medium with a temperature lower than that of the carbon dioxide gas; and exchanging heat between the heat exchange medium and the carbon dioxide gas to obtain carbon dioxide liquid.

[0009] In some embodiments, at least part of the mechanical work generated by the expansion of the air is used to compress the air.

[0010] In some embodiments, before the carbon dioxide gas is compressed, the carbon dioxide gas is subjected to pressure stabilization by a pressure stabilizing tank.

[0011] In some embodiments, the power for compressing the carbon dioxide gas is adjusted according to the pressure in the pressure stabilizing tank; and / or the power for compressing the air is adjusted according to the temperature at the outlet of the heat exchanger.

[0012] Correspondingly, the application also provides a carbon dioxide liquefaction device for a ship, comprising a cooling unit and a carbon dioxide gas compression unit, wherein the cooling unit comprises a first compressor, a first expander and a heat exchanger, which are sequentially connected end to end to form a cooling loop; the carbon dioxide gas compression unit comprises a second compressor and a storage tank which are sequentially connected, and the heat exchanger is arranged between the second compressor and the storage tank; the cooling unit uses air as a heat exchange medium for cooling the carbon dioxide gas at the heat exchanger.

[0013] In some embodiments, the first compressor and the first expander are connected to transmit the power recovered by the first expander to the first compressor.

[0014] In some embodiments, a pressure stabilizing tank is further arranged upstream of the second compressor.

[0015] In some embodiments, the carbon dioxide liquefaction device for a ship further comprises a controller, and a temperature sensor is arranged at the outlet of the heat exchanger, the controller is connected to the temperature sensor and the first compressor, and the controller adjusts the power of the first compressor according to the sensing parameter of the temperature sensor; and / or a pressure sensor is arranged at the pressure stabilizing tank, the controller is connected to the pressure sensor and the second compressor, and the controller adjusts the power of the second compressor according to the sensing parameter of the pressure sensor.

[0016] In some embodiments, the first compressor is a multi-stage compressor, and the multi-stage compressor has an inter-stage cooler.

[0017] In some embodiments, the second compressor is a multi-stage compressor having an inter-stage cooler.

[0018] In some embodiments, a filter is arranged before the second compressor.

[0019] Correspondingly, the application further provides a ship comprising the aforementioned carbon dioxide liquefaction device for a ship and an exhaust pipe connected to the inlet of the carbon dioxide gas compression unit.

[0020] The application has the following beneficial effects: the application provides a carbon dioxide liquefaction method, device and ship for a ship, which solves the problem of high global warming potential and global warming potential of the low-temperature liquefied refrigerant of the commonly used carbon dioxide gas for a ship by using environmentally friendly air as a refrigerant. Meanwhile, the mechanical energy generated by air expansion is output to the first compressor in the process of air expansion, so that the system working efficiency is improved and the system energy consumption is reduced while refrigeration is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort.

[0022] Figure 1 An exemplary flowchart of the carbon dioxide liquefaction method for a ship in the application is shown.

[0023] Figure 2 An exemplary flowchart of the control of the compression parameters in the carbon dioxide liquefaction method for a ship in the application is shown.

[0024] Figure 3 An exemplary structural diagram of the carbon dioxide liquefaction device for a ship in the application is shown.

[0025] Figure 4 An exemplary meridian section view of the first expander is shown.

[0026] Main element marks in the embodiments of the application:

[0027] Cooling unit 10 First compressor 11

[0028] First expander 12 Scroll 121

[0029] Nozzle 122 Impeller 123

[0030] diffuser 124 heat exchanger 13

[0031] temperature sensor 14 carbon dioxide gas compression 20

[0032] unit

[0033] pressure stabilizing tank 21 second compressor 22

[0034] storage tank 23 pressure sensor 24 DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person skilled in the art without creative work fall within the scope of protection of the present application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application. In the present application, the orientation words such as "upper", "lower", "left", "right" generally refer to the upper, lower, left and right in the actual use or working state of the device, and specifically refer to the drawing surface direction in the drawings.

[0036] In addition, the terms "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" can explicitly or implicitly include at least one of the features.

[0037] The present application provides a carbon dioxide liquefaction method and device for a ship and a ship, which are described in detail below. It should be noted that the description order of the following embodiments is not limited as the preferred order of the embodiments of the present application. In the following embodiments, the description of each embodiment has its own emphasis, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0038] Please refer to Figure 1 The embodiments of the present application provide a carbon dioxide liquefaction method for a ship, which includes the following steps S100-S300.

[0039] In step S100, the carbon dioxide gas is compressed to increase the pressure and temperature of the carbon dioxide gas.

[0040] Here, please refer to Figure 3 The carbon dioxide gas can be compressed by the second compressor 22 in the carbon dioxide gas compression unit 20 to compress the carbon dioxide gas into high-temperature and high-pressure gas.

[0041] Please refer back to Figure 1 In step S200, air is compressed and expanded to obtain a heat exchange medium having a temperature lower than that of the carbon dioxide gas.

[0042] Here, please combine Figure 3 The air can be compressed by a first compressor 11 of a cooling unit 10, and expanded by a first expander 12 of the cooling unit 10, so that the air can be used as a heat exchange medium and used to cool the carbon dioxide gas. Here, the first compressor 11 can be a multi-stage compressor provided with an inter-stage cooler for inter-stage cooling of the air.

[0043] It can be understood that here, the order of steps S100 and S200 is not limited, either of them can be performed first, or both can be performed simultaneously. Of course, in actual use, both are basically in a state of simultaneous performance.

[0044] Please refer back to Figure 1 In step S300, the heat exchange medium exchanges heat with the carbon dioxide gas to obtain carbon dioxide liquid.

[0045] Thus, the method for liquefying carbon dioxide for ships uses air as a heat exchange medium, and liquefies carbon dioxide gas into liquid by compression, cooling, and expansion. Here, the heat exchange medium is air, which does not damage the environment, and can be taken from the environment without the need to additionally set up storage equipment for storing other heat exchange media such as propylene and ammonia, which is very convenient, safe, and pollution-free to use.

[0046] In some embodiments, at least part of the mechanical work generated by the expansion of the air is used to compress the air. Exemplarily, please combine Figure 3 The air is expanded by the first expander 12, and the air is compressed by the first compressor 11, the first expander 12 and the first compressor 11 are connected by a shaft (not shown in the figure), so that the shaft work generated by the expansion of the air can be transmitted to the first compressor 11 and used to assist in the compression of the air.

[0047] Thus, the method for liquefying carbon dioxide for ships has a large amount of shaft work output while refrigerating, which helps to improve the system efficiency and reduce the system energy consumption. Among them, since the motor and other driving equipment driving the compressor can use a smaller rated power model, it also helps to realize the miniaturization of the overall structure.

[0048] Exemplarily, the air is compressed by the first compressor 11 in multiple stages, and then is cooled by inter-stage cooling to become a normal-temperature high-pressure gas (6 MPa, 30 DEG C), and then the air enters the first expander 12 to be expanded, and the low-temperature low-pressure air is output after work is done by expansion, and the shaft power is output.

[0049] In some embodiments, before the carbon dioxide gas is compressed, the carbon dioxide gas is subjected to pressure stabilizing operation by the pressure stabilizing tank 21, so that the carbon dioxide gas has a relatively stable pressure.

[0050] Here, exemplarily, a controller can also be provided. The controller adjusts the power of the compressed carbon dioxide gas according to the pressure in the pressure stabilizing tank 21, and / or adjusts the power of the compressed air according to the temperature at the outlet of the heat exchanger 13.

[0051] Exemplarily, please refer to Figure 2 and please refer to Figure 3 The second compressor 22 is used to compress the carbon dioxide gas. Here, according to the sensing parameter of the pressure sensor 24 at the pressure stabilizing tank 21, the controller judges whether the pressure of the carbon dioxide gas in the pressure stabilizing tank 21 is stable, and adjusts the power of the second compressor 22 according to the pressure value, so as to compress the carbon dioxide gas to be within a preset pressure threshold range. Moreover, the controller adjusts the power of the first compressor 11 according to the sensing parameter of the temperature sensor 14 at the outlet of the heat exchanger 13, so as to ensure that the carbon dioxide can be cooled to be within a preset liquefaction temperature threshold range.

[0052] In order to better achieve the technical effects of the embodiments of the present application, the embodiments of the present application further provide a carbon dioxide liquefaction device for a ship, which can be used to implement the foregoing carbon dioxide liquefaction method for a ship.

[0053] Here, please refer to Figure 3 The carbon dioxide liquefaction device for a ship includes the cooling unit 10 and the carbon dioxide gas compression unit 20.

[0054] The cooling unit 10 includes the first compressor 11, the first expander 12 and the heat exchanger 13, which are sequentially and end-to-end connected to form a cooling loop. Here, the cooling unit 10 uses air as a heat exchange medium, so as to cool the carbon dioxide gas at the heat exchanger 13.

[0055] Therefore, the first compressor 11 is used for compressing air, the first expander 12 is used for isentropic expansion of air, and the heat exchanger 13 is used for heat exchange between air and carbon dioxide gas. Here, the heat exchange medium of the carbon dioxide liquefaction device for a ship adopts pure air, has no environmental impact, and is a completely environmentally friendly carbon dioxide liquefaction device.

[0056] In some embodiments, the first compressor 11 and the first expander 12 are connected to transmit the power recovered by the first expander 12 to the first compressor 11.

[0057] Exemplarily, the first compressor 11 has a shaft, and a driving member such as a motor is connected to the shaft to drive the shaft to operate the first compressor 11. In addition, the first expander 12 is also connected to the shaft, and the power recovered from the expanded air is applied to the shaft to assist the driving of the shaft by the motor.

[0058] In some embodiments, the first compressor 11 is a multi-stage compressor having an inter-stage cooler. The exhaust gas of the previous stage of compression is cooled by inter-stage cooling, and the reduction of the suction temperature of the subsequent stage helps to prevent the temperature of the subsequent stage of compression from being too high and the cylinder from overheating.

[0059] In some embodiments, please refer to Figure 4 which shows a meridian plane schematic diagram of the radial flow first expander 12, and the meridian plane is the radial cross section of the whole first expander 12. The first expander 12 mainly includes a scroll 121, a nozzle 122, an impeller 123, etc., and the end of the impeller 123 is provided with a diffuser section 124, and the connection parts of various components can be provided with sealing structures. Here, the high-pressure air continuously reduces the pressure in the through-flow part of the first expander 12. The pressure energy of the air is converted into kinetic energy when flowing to the nozzle 122 ring, the speed increases, and finally the pressure energy of the air in the working wheel is converted into mechanical energy output shaft power to assist the operation of the first compressor 11.

[0060] Here, the high-pressure air becomes low-temperature and low-pressure gas through the first expander 12, and outputs power and cold energy, and the cold energy output after expansion liquefies the carbon dioxide gas into low-temperature carbon dioxide liquid through the heat exchanger 13.

[0061] In some embodiments, the carbon dioxide gas compression unit 20 includes a second compressor 22 and a storage tank 23 connected in sequence, and the heat exchanger 13 is arranged between the second compressor 22 and the storage tank 23.

[0062] Exemplarily, the second compressor 22 is a multi-stage compressor with an inter-stage cooler. The second compressor 22 is used to compress the carbon dioxide gas into high-temperature and high-pressure gas, and then the carbon dioxide gas is cooled by the inter-stage cooler into carbon dioxide gas at room temperature and high pressure. Then, the carbon dioxide gas is cooled into liquid by the heat exchanger 13, and finally enters the storage tank 23.

[0063] In some embodiments, a pressure stabilizing tank 21 is further provided upstream of the second compressor 22.

[0064] In some embodiments, a filter is provided in front of the second compressor 22. The filter is used to filter the input gas to remove impurities in the input gas, thereby preventing the second compressor 22 from surging, liquid knock, and the like.

[0065] In some embodiments, the carbon dioxide liquefying device for a ship further comprises a controller, and a temperature sensor 14 is provided at the outlet of the heat exchanger 13, the controller is connected to the temperature sensor 14 and the first compressor 11, and the controller adjusts the power of the first compressor 11 according to the sensing parameter of the temperature sensor 14. A pressure sensor 24 is provided at the pressure stabilizing tank 21, the controller is connected to the pressure sensor 24 and the second compressor 22, and the controller adjusts the power of the second compressor 22 according to the sensing parameter of the pressure sensor 24.

[0066] Here, the controller monitors the state of the device through the aforementioned temperature sensor 14 and pressure sensor 24 to control the first compressor 11 and the second compressor 22. Exemplarily, here, the carbon dioxide gas or the flue gas containing carbon dioxide enters the pressure stabilizing tank 21, and the pressure sensor 24 is provided at the pressure stabilizing tank 21. When the flow rate of the gas entering the pressure stabilizing tank 21 changes, the sensing parameter of the pressure sensor 24 changes, and the controller adjusts the frequency of the power of the second compressor 22 according to the sensing parameter of the pressure sensor 24 to compress the gas leaving the pressure stabilizing tank 21 to a set pressure threshold.

[0067] After the air is compressed by the first compressor 11 to high pressure, the air is expanded by the first expander 12 to become low-temperature and low-pressure heat exchange medium to liquefy the carbon dioxide gas leaving the second compressor 22 into liquid, and the carbon dioxide liquid then enters the storage tank 23. Here, the temperature sensor 14 is provided at the outlet of the heat exchanger 13, and the temperature value at the outlet of the heat exchanger 13 can be determined according to the sensing parameter of the temperature sensor 14, thereby determining whether the carbon dioxide is cooled to a preset temperature. According to the value of the sensing parameter, the controller adjusts the power of the first compressor 11 to cool the carbon dioxide to a preset temperature to liquefy into liquid.

[0068] Of course, it can be understood that in other embodiments, only one of the temperature sensor 14 and the pressure sensor 24 can be provided, and the above examples of the present embodiment do not constitute undue limitation on the present application.

[0069] Correspondingly, in order to better achieve the technical effects of the embodiments of the present application, the embodiments of the present application also provide a ship, which comprises the aforementioned carbon dioxide liquefaction device for a ship. Moreover, the ship is also provided with a flue gas pipeline, which is connected to the inlet of the carbon dioxide gas compression unit 20, and the carbon dioxide liquefaction device for a ship is used to cool and recover the carbon dioxide contained in the flue gas discharged from the flue gas pipeline.

[0070] It can be understood that the meanings of the terms in the embodiments of the present application are the same, and the specific implementation details of the contents not described in detail for a certain embodiment can be referred to the description in other embodiments. The example illustration and technical effects shown by the foregoing embodiments can be correspondingly realized, and for the repeated parts, the present embodiment will not make further description.

[0071] The carbon dioxide liquefaction method, device and ship for a ship provided by the present application are described in detail above, and the principles and implementation modes of the present application are described by applying specific examples. The above description of the embodiments is only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation modes and application ranges will be changed, and the above description should not be understood as limiting the present application.

Claims

1. A method for liquefying carbon dioxide in ships, characterized in that, Carbon dioxide liquefaction is performed using a carbon dioxide liquefaction device for ships, which includes a cooling unit, a carbon dioxide gas compression unit, and a controller. The cooling unit includes a first compressor, a first expander, and a heat exchanger, which are connected end-to-end to form a cooling circuit. A temperature sensor is installed at the outlet of the heat exchanger. The carbon dioxide gas compression unit includes a second compressor and a storage tank connected in sequence. The heat exchanger is positioned between the second compressor and the storage tank. A pressure stabilizing tank is also installed upstream of the second compressor, and a pressure sensor is installed at the pressure stabilizing tank. The cooling unit uses pure air as the heat exchange medium to cool the carbon dioxide gas at the heat exchanger. The method for liquefying carbon dioxide for ships includes the following steps: The pressure of carbon dioxide gas is stabilized using the pressure stabilizing tank. The carbon dioxide gas is compressed to increase its pressure and temperature; the power of the compression is adjusted according to the pressure inside the pressure stabilizing tank. Air is compressed and expanded to obtain a heat exchange medium with a temperature lower than that of the carbon dioxide gas; at least a portion of the mechanical work generated during the expansion of the air is used to compress the air. Carbon dioxide liquid is obtained by exchanging heat between the heat exchange medium and the carbon dioxide gas. The controller monitors the status of the temperature sensor and the pressure sensor to control the first compressor and the second compressor.

2. The carbon dioxide liquefaction method for ships as described in claim 1, characterized in that, The power of the compressed air is adjusted according to the temperature at the outlet of the heat exchanger.

3. The carbon dioxide liquefaction method for ships as described in claim 1, characterized in that, The first compressor is connected to the first expander to transmit the power recovered by the first expander to the first compressor.

4. The carbon dioxide liquefaction method for ships as described in claim 1, characterized in that, The controller is connected to the temperature sensor and the first compressor, and the controller adjusts the power of the first compressor according to the sensing parameters of the temperature sensor; the controller is also connected to the pressure sensor and the second compressor, and the controller adjusts the power of the second compressor according to the sensing parameters of the pressure sensor.

5. The carbon dioxide liquefaction method for ships as described in claim 1, characterized in that, The first compressor is a multi-stage compressor, and the multi-stage compressor has an interstage cooler.

6. The method for carbon dioxide liquefaction for ships as described in claim 1, characterized in that, The second compressor is a multi-stage compressor, and the multi-stage compressor has an interstage cooler.

7. The carbon dioxide liquefaction method for ships as described in claim 1, characterized in that, A filter is installed in front of the second compressor.

8. A ship, characterized in that, The vessel uses the carbon dioxide liquefaction method for vessels as described in any one of claims 1 to 7; The carbon dioxide liquefaction device for ships includes an exhaust pipe connected to the inlet of the carbon dioxide gas compression unit.

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