LNG cold energy cascade power generation system and power generation method

Abstract

The application discloses an LNG cold energy cascade power generation system and a power generation method. The LNG cold energy cascade power generation system comprises an evaporation device, an expander, a power generation device, a plurality of condensing devices and a plurality of pressure regulating components. The evaporation device is used for forming working medium steam. The expander is used for driving the power generation device to generate power. The expander comprises an expander inlet and a plurality of expander outlets. The working medium steam from the evaporation device can enter the expander to form working medium steam with different pressures. The working medium steam with different pressures is discharged from the plurality of expander outlets respectively. The working medium steam with different pressures is exchanged with LNG in the plurality of condensing devices respectively to form organic working medium with different pressures. The plurality of pressure regulating components are used for adjusting the pressures of the organic working medium with different pressures to be consistent. According to the LNG cold energy cascade power generation system, the utilization rate of LNG cold energy can be improved, and cold and heat loss in the heat exchange process can be reduced, so that the power generation power of the LNG cold energy cascade power generation system is further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy and environmental protection, in particular to an LNG cold energy cascade power generation system and a power generation method. BACKGROUND

[0002] Natural gas is a low-carbon energy source with the characteristics of cleanliness, high efficiency and high quality. The main transportation method of natural gas is to reduce the temperature of natural gas to about -162℃ to become liquefied natural gas (LNG), and the volume becomes 1 / 600 of the gaseous state, and then transported by sea liquefied natural gas (LNG) ship. Before LNG is supplied to users for use, it must be gasified. The temperature of the gasification process of liquefied natural gas is constantly changing, and the gasification process of liquefied natural gas carries a large amount of cold energy, which has very high utilization value.

[0003] Therefore, it is necessary to provide an LNG cold energy cascade power generation system and a power generation method to at least partially solve the above problems. SUMMARY

[0004] A series of simplified concepts are introduced in the summary section, which will be further described in detail in the specific embodiment section. The summary section of the present application does not mean to attempt to limit the key features and essential technical features of the claimed technical solution, nor to attempt to determine the protection scope of the claimed technical solution.

[0005] In order to at least partially solve the above problems, according to a first aspect of the present application, an LNG cold energy cascade power generation system is provided, which comprises:

[0006] An evaporation device, the evaporation device comprising a working medium pipeline, the evaporation device being used for heat exchange between a heat source and an organic working medium in the working medium pipeline to form working medium steam;

[0007] An expander, the expander comprising an expander inlet and a plurality of expander outlets, the expander inlet being in communication with the working medium pipeline of the evaporation device, so that the working medium steam from the evaporation device can enter the expander to form working medium exhaust steam of different pressures, the working medium exhaust steam of different pressures being discharged from the plurality of expander outlets respectively;

[0008] A power generation device, the power generation device being in driving connection with the expander to convert mechanical energy into electrical energy;

[0009] a plurality of condensing devices corresponding to the plurality of expander outlets, the plurality of condensing devices being connected in parallel between the expander and the evaporating device via pipelines, and the plurality of condensing devices being connected in series via LNG pipelines, so that the organic working medium at different pressures is formed by heat exchange between the working medium steam at different pressures and the LNG in the plurality of condensing devices; and

[0010] a plurality of pressure regulating members respectively arranged on the pipelines between the evaporating device and the plurality of condensing devices, for adjusting the pressure of the organic working medium at different pressures to be consistent.

[0011] The LNG cold energy cascade power generation system according to the present application comprises an evaporating device, an expander, a power generation device, a plurality of condensing devices and a plurality of pressure regulating members. The evaporating device comprises a working medium pipeline, and is used for heat exchange between a heat source and an organic working medium in the working medium pipeline to form working medium steam. The expander comprises an expander inlet and a plurality of expander outlets. The expander inlet is communicated with the working medium pipeline of the evaporating device, so that the working medium steam from the evaporating device can enter the expander to form working medium steam at different pressures. The working medium steam at different pressures is discharged from the plurality of expander outlets respectively. The power generation device is drivingly connected with the expander, so as to convert mechanical energy into electrical energy. The plurality of condensing devices are arranged corresponding to the plurality of expander outlets. The plurality of condensing devices are connected in parallel between the expander and the evaporating device via pipelines, and the plurality of condensing devices are connected in series via LNG pipelines, so that the organic working medium at different pressures is formed by heat exchange between the working medium steam at different pressures and the LNG in the plurality of condensing devices. The plurality of pressure regulating members are respectively arranged on the pipelines between the evaporating device and the plurality of condensing devices, for adjusting the pressure of the organic working medium at different pressures to be consistent. In this way, the LNG cold energy cascade power generation system can effectively utilize the changing gasification temperature in the gasification process of LNG, and match the condensation curve of the working medium steam and the gasification curve of the LNG by increasing the temperature of the LNG at the outlet of the LNG pipeline, so as to improve the utilization rate of the LNG cold energy, reduce the cold and heat loss in the heat exchange process, and further improve the power generation power of the LNG cold energy cascade power generation system.

[0012] Optionally, the expander further comprises a plurality of rotating members, and the working medium steam enters the plurality of rotating members in sequence to expand and work to form the working medium steam at different pressures. The working medium steam from the plurality of rotating members is discharged through the plurality of expander outlets respectively. In this way, the working medium steam can expand and work in the expander respectively, so as to generate electricity respectively.

[0013] Optionally, the mass flow of the working medium steam at the expander inlet is equal to the sum of the mass flow of the working medium steam at the plurality of expander outlets. According to the present scheme, the energy loss is reduced when the expander works.

[0014] Optionally, the mass flow of the working medium steam from the multiple expander outlets is equal or unequal. Thus, the utilization rate of cold energy is improved.

[0015] Optionally, the energy absorbed by the LNG is equal to the sum of the energy released by the working medium steam from the multiple expander outlets. Thus, the utilization rate of the cold energy of the LNG is improved.

[0016] Optionally, the pressure and / or temperature of the working medium steam from the multiple condensing devices increases in turn along the flow direction of the LNG. Thus, the heat exchange efficiency and the utilization rate of the cold energy of the LNG are improved.

[0017] Optionally, the heat source is seawater, air, solar energy, geothermal energy, hot water, steam, flue gas, circulating water, or process fluid. Thus, the energy of existing substances can be effectively utilized to achieve the effects of energy saving and environmental protection.

[0018] Optionally, the organic working medium is a mixture composed of one or more of methane, ethane, propane, ethylene, propylene, tetrafluoroethane, ammonia, etc. Thus, the energy of existing substances can be effectively utilized to achieve the effects of energy saving and environmental protection, and the organic working medium liquefaction temperature and the LNG gasification temperature can be well matched to improve the power generation efficiency.

[0019] Optionally, the expander is one or more of an axial flow turbine expander, a centrifugal turbine expander, a radial flow turbine expander, or a screw expander. Thus, various expanders can be applied to expand the application range.

[0020] The application also provides a power generation method for the LNG cold energy cascade power generation system.

[0021] According to the gasification temperature of the LNG and the temperature of the heat source, the composition of the organic working medium is selected;

[0022] According to the temperature of the heat source, the pressure of the working medium steam is matched;

[0023] According to the gasification temperature of the LNG, the pressure of the organic working medium preset by the multiple condensing devices is matched respectively, so that the temperature of the organic working medium matches the gasification temperature of the LNG;

[0024] According to the pressure of the working medium steam and the pressure of the organic working medium preset, the expander is selected.

[0025] According to the power generation method of the application, for the LNG cold energy cascade power generation system, the power generation method comprises selecting the composition of the organic working medium according to the gasification temperature of the LNG and the temperature of the heat source, matching the pressure of the working medium vapor according to the temperature of the heat source, matching the pressure of the organic working medium preset by the plurality of condensing devices according to the gasification temperature of the LNG respectively, so that the temperature of the organic working medium matches the gasification temperature of the LNG, and selecting the expander according to the pressure of the working medium vapor and the preset pressure of the organic working medium. In this way, the changing gasification temperature in the gasification process of the LNG can be effectively utilized, the utilization rate of the LNG cold energy can be improved, and the cold and heat loss in the heat exchange process can be reduced, so that the appropriate expander can be selected. BRIEF DESCRIPTION OF DRAWINGS

[0026] The following drawings of the application are hereby incorporated as part of the application for the purpose of understanding the application. The embodiments of the application and their description shown in the drawings are used to explain the devices and principles of the application. In the drawings,

[0027] Figure 1 A schematic diagram of the LNG cold energy cascade power generation system according to a preferred embodiment of the application;

[0028] Figure 2 A schematic diagram of the LNG cold energy cascade power generation system according to a preferred embodiment of the application; Figure 1 A schematic diagram of the condensing curve of the working medium vapor and the gasification temperature curve of the LNG; and

[0029] Figure 3 A flowchart of the power generation method according to a preferred embodiment of the application.

[0030] BRIEF DESCRIPTION OF DRAWINGS

[0031] 100: LNG cold energy cascade power generation system 110: Evaporating device

[0032] 111: Heat source pipeline 112: Evaporation pipeline

[0033] 120: Expander 121: First expander outlet

[0034] 122: Second expander outlet 123: Third expander outlet

[0035] 124: Expander inlet 130: Power generation device

[0036] 141: First condensing device 142: Second condensing device

[0037] 143: Third condensing device 151: First expansion pipeline

[0038] 152: Second expansion pipeline 153: Third expansion pipeline

[0039] 171: First pressure regulating member 172: Second pressure regulating member

[0040] 173: Third pressure regulating component; 191: LNG pipeline inlet.

[0041] 192: LNG pipeline outlet Detailed Implementation

[0042] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0043] To fully understand the present invention, detailed structures will be presented in the following description to illustrate it. Obviously, the implementation of the present invention is not limited to the specific details familiar to those skilled in the art. Preferred embodiments of the present invention are described in detail below; however, the present invention may have other embodiments besides these detailed descriptions and should not be construed as being limited to the embodiments set forth herein.

[0044] It should be understood that the terminology used herein is intended only to describe particular embodiments and is not intended to limit the invention. The singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. When the terms “comprising” and / or “including” are used in this specification, they indicate the presence of the stated feature, integral, step, operation, element, and / or component, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or combinations thereof. The terms “upper,” “lower,” “front,” “rear,” “left,” “right,” and similar expressions used in this invention are for illustrative purposes only and are not intended to be limiting.

[0045] The ordinal numbers such as "first" and "second" used in this invention are merely identifiers and do not have any other meaning, such as a specific order. Moreover, for example, the term "first component" does not imply the existence of "second component," and the term "second component" does not imply the existence of "first component."

[0046] Hereinafter, specific embodiments of the present invention will be described in more detail with reference to the accompanying drawings, which illustrate representative embodiments of the present invention and are not intended to limit the present invention.

[0047] like Figure 1 As shown, the present invention provides an LNG cold energy cascade power generation system 100, which can effectively utilize the cold energy carried by LNG to generate electricity, improve utilization rate, and reduce energy waste.

[0048] The LNG cold energy cascade power generation system 100 comprises an evaporation device 110, an expander 120, a power generation device 130, a plurality of condensing devices and a plurality of pressure regulating members, and is provided with an organic working medium, which can exchange heat with LNG and thus absorb a large amount of cold energy carried by LNG. The power generation device is in driving connection with the expander to convert mechanical energy into electric energy and thus generate power.

[0049] Specifically, the evaporation device 110 comprises a working medium pipeline, which is provided with the organic working medium, and a heat source can exchange heat with the organic working medium in the working medium pipeline. The temperature of the organic working medium is lower than that of the heat source, and the organic working medium can absorb the energy of the heat source to form working medium vapor.

[0050] Preferably, the heat source can be free natural resources such as seawater and air, and can also be waste heat resources such as hot water, steam, flue gas, circulating water or process fluid. The process fluid can be a fluid generated by process processing, including gas and liquid. Alternatively, the process fluid can be process wastewater. The evaporation device can comprise a heat source pipeline 111 provided with a fluid or the like as the heat source. The heat source in the heat source pipeline 111 can exchange heat with the organic working medium in the working medium pipeline. Of course, the heat source can also be solar energy or geothermal energy to directly exchange heat with the organic working medium. Thus, the energy of the existing substance can be effectively utilized to achieve the effect of energy saving and environmental protection. Preferably, the organic working medium is a mixture of one or more of methane, ethane, propane, ethylene, propylene, tetrafluoroethane and ammonia. Thus, the energy carried by the heat source can be effectively absorbed, the energy loss in the heat exchange process can be reduced, and the efficiency can be improved.

[0051] The expander 120 can comprise an expander inlet 124 and a plurality of expander outlets. The expander inlet 124 can be connected to the working medium pipeline of the evaporation device 110 through an evaporation pipeline 112, so that the working medium vapor from the evaporation device 110 can enter the expander 120 to form working medium vapor with different pressures. The plurality of expander outlets can correspond to a plurality of pressure levels of the working medium vapor respectively. The expander 120 can also be in driving connection with the power generation device 130 to drive the power generation device 130 to generate power. Preferably, the expander 120 can be one or more of an axial flow turbine expander, a centrifugal turbine expander, a radial flow turbine expander or a screw expander. Thus, the LNG cold energy cascade power generation system 100 can apply a variety of expanders 120 to expand the application range.

[0052] The working fluid vapor enters the expander 120 via the expander inlet 124 to expand and do work, and expands to a certain pressure. A portion of the working fluid vapor is discharged from one of the plurality of expander outlets, and another portion of the working fluid vapor continues to expand and do work, so that the expander 120 can drive the power generator 130 to realize multi-stage power generation, and generate working fluid exhausts of different pressures.

[0053] The working fluid exhausts of different pressures can be discharged from the plurality of expander outlets, respectively. The plurality of expander outlets are arranged in correspondence with the plurality of condensing devices, and the plurality of condensing devices are connected in parallel via the pipelines between the expander 120 and the evaporating device 110. The plurality of condensing devices are connected in series via the LNG pipelines, and the LNG pipelines are provided with LNG. In this way, the working fluid exhausts from the expander 120 can exchange heat with the LNG via the condensing devices to form organic working fluid, and the organic working fluid returns to the evaporating device 110 to exchange heat with the heat source.

[0054] Preferably, the expander 120 further comprises a plurality of rotating members, and the working fluid vapor can sequentially enter the plurality of rotating members to expand and do work to form working fluid exhausts of different pressures. The rotating members can be configured as impellers or screws capable of expanding and doing work. The impellers or screws are rotatable. For example, the expander 120 comprises a first expander outlet 121, a second expander outlet 122, and a third expander outlet 123, the plurality of condensing devices comprises a first condensing device 141, a second condensing device 142, and a third condensing device 143, and the pipelines can comprise a first expansion pipeline 151, a second expansion pipeline 152, and a third expansion pipeline 153. The first expander outlet 121, the second expander outlet 122, and the third expander outlet 123 can simultaneously discharge working fluid exhausts. The plurality of rotating members comprise a first-stage rotating member, a second-stage rotating member, and a third-stage rotating member. Of course, the expander 120 can comprise a larger number of expander outlets and a larger number of rotating members to form a larger number of working fluid exhausts of different pressures. In order to make the page concise, Figure 1 Only three expander outlets, three condensing devices, and three expansion pipelines are shown in the figure.

[0055] The working fluid vapor in the expander 120 can enter the first-stage rotating member to expand and do work, and expand to a certain pressure to form working fluid exhausts. A portion of the working fluid exhausts is discharged from the first expander outlet 121. The pressure of the working fluid exhausts discharged from the first expander outlet 121 is P1. Another portion of the working fluid vapor continues to enter the second-stage rotating member to expand and do work, and expand to another certain pressure. Another portion of the working fluid exhausts is discharged from the second expander outlet 122. The pressure of the working fluid exhausts discharged from the second expander outlet 122 is P2. Still another portion of the working fluid vapor continues to enter the third-stage rotating member to expand and do work, and expand to still another certain pressure. Still another portion of the working fluid exhausts is discharged from the third expander outlet 123. The pressure of the working fluid exhausts discharged from the third expander outlet 123 is P3.

[0056] The first expansion pipeline 151 is in communication with the first expander outlet 121. The working medium exhaust steam from the first expander outlet 121 can enter the first condenser 141 through the first expansion pipeline 151.

[0057] The second expansion pipeline 152 is in communication with the second expander outlet 122. The working medium exhaust steam from the second expander outlet 122 can enter the second condenser 142 through the second expansion pipeline 152. The third expansion pipeline 153 is in communication with the third expander outlet 123. The working medium exhaust steam from the third expander outlet 123 can enter the third condenser 143 through the third expansion pipeline 153.

[0058] Further, the plurality of condensers are connected in series via the LNG pipeline, and the LNG is arranged in the LNG pipeline and can enter the plurality of condensers respectively and exchange heat with different working medium exhaust steam in different condensers. The working medium exhaust steam at different pressures can exchange heat with the LNG in the plurality of condensers to form organic working medium at different pressures. Different condensers can receive cold energy at different temperature stages in the gasification process of the LNG, and the working medium exhaust steam entering the condenser is condensed into organic working medium at a corresponding pressure.

[0059] Specifically, the LNG pipeline includes an inlet 191 and an outlet 192. The inlet 191 of the LNG pipeline can be close to the third condenser 143, and the outlet 192 of the LNG pipeline can be close to the first condenser 141. The LNG can first enter the third condenser 143, and the LNG absorbs the energy of the working medium exhaust steam in the third expansion pipeline 153 to be gasified. The working medium exhaust steam in the third expansion pipeline 153 is condensed to form organic working medium. The LNG can in turn enter the second condenser 142, and the LNG absorbs the energy of the working medium exhaust steam in the second expansion pipeline 152 to be gasified. The working medium exhaust steam in the second expansion pipeline 152 is condensed to form organic working medium. The LNG can in turn enter the first condenser 141, and the LNG absorbs the energy of the working medium exhaust steam in the first expansion pipeline 151 to be gasified.

[0060] The temperature of the LNG at the outlet 192 of the LNG pipeline is higher than the temperature of the LNG at the inlet 191 of the LNG pipeline, that is, the LNG cold energy cascade power generation system increases the outlet temperature of the LNG. The working medium exhaust steam in each expansion pipeline is condensed to form organic working medium. The pressures of the organic working medium formed by the first condenser 141, the organic working medium formed by the second condenser 142, and the organic working medium formed by the third condenser 143 are different.

[0061] The organic working fluids of different pressures can enter the evaporating device 110 through the multiple pressure regulating members. The multiple pressure regulating members are arranged on the pipelines between the evaporating device 110 and the multiple condensing devices, respectively, for adjusting the pressures of the organic working fluids of different pressures to be consistent. The pressure regulating members can be configured as working fluid pumps. For example, the pressure regulating members can pressurize the organic working fluids discharged from the condensing devices.

[0062] The organic working fluids from the different expansion pipelines can be pressurized through the different pressure regulating members, and the pressures of the organic working fluids pressurized by the multiple pressure regulating members are consistent. The organic working fluids after pressure regulation are returned to the evaporating device 110 to continue heat exchange with the heat source, thereby ensuring the normal operation of the organic working fluid flow path. The multiple pressure regulating members can pressurize the organic working fluids of different pressures discharged from the multiple condensing devices, respectively, so that the pressures of the organic working fluids discharged from the multiple pressure regulating members are consistent. The organic working fluids of consistent pressures are converged and then flow into the evaporating device 110.

[0063] Preferably, the multiple pressure regulating members include a first pressure regulating member 171, a second pressure regulating member 172, and a third pressure regulating member 173. The first pressure regulating member 171 is arranged between the first condensing device 141 and the evaporating device 110, the organic working fluid from the first condensing device 141 can enter the first pressure regulating member 171, and the first pressure regulating member 171 adjusts the pressure of the organic working fluid from the first condensing device 141. The second pressure regulating member 172 is arranged between the second condensing device 142 and the evaporating device 110, the organic working fluid from the second condensing device 142 can enter the second pressure regulating member 172, and the second pressure regulating member 172 adjusts the pressure of the organic working fluid from the second condensing device 142. The third pressure regulating member 173 is arranged between the third condensing device 143 and the evaporating device 110, the organic working fluid from the third condensing device 143 can enter the third pressure regulating member 173, and the third pressure regulating member 173 adjusts the pressure of the organic working fluid from the third condensing device 143.

[0064] The pressure of the organic working fluid adjusted by the first pressure regulating member 171, the pressure of the organic working fluid adjusted by the second pressure regulating member 172, and the pressure of the organic working fluid adjusted by the third pressure regulating member 173 are consistent. The organic working fluids after pressure regulation are returned to the evaporating device 110 to perform heat exchange with the heat source.

[0065] The pressure of the organic working fluid at the inlet of each pressure regulating member can correspond to the pressure of the working fluid vapor in the corresponding condensing device. The pressures of the organic working fluids at the outlets of the multiple pressure regulating members are consistent, and the outlets of the multiple pressure regulating members can be connected to the evaporating device 110 respectively or connected to the evaporating device 110 after being converged.

[0066] According to the LNG cold energy cascade power generation system of the present invention, the LNG cold energy cascade power generation system includes an evaporator, an expander, a power generation unit, multiple condensing units, and multiple pressure regulating components. The evaporator includes a heat source pipeline and a working fluid pipeline. The evaporator is used to exchange heat between the heat source in the heat source pipeline and the organic working fluid in the working fluid pipeline to form working fluid vapor. The expander is driven by the power generation unit to drive the power generation unit to generate electricity. The expander includes an expander inlet and multiple expander outlets. The expander inlet is connected to the working fluid pipeline of the evaporator so that the working fluid vapor from the evaporator can... The LNG-cooled cascade power generation system effectively utilizes the constantly changing vaporization temperature of LNG during vaporization. By increasing the LNG outlet temperature, the system matches the condensation curve of the working fluid with the vaporization curve of the LNG, improving the utilization rate of LNG cold energy and reducing heat loss during heat exchange, thereby further increasing the power generation capacity of the LNG-cooled cascade power generation system. Multiple condensing units are installed corresponding to the multiple expander outlets and are connected in parallel between the expander and evaporator via pipelines. These condensing units are also connected in series via LNG pipelines, allowing the working fluid at different pressures to exchange heat with the LNG in the condensing units to form organic working fluids at different pressures.

[0067] Preferably, the mass flow rate of the working fluid steam at the expander inlet 124 is equal to the sum of the mass flow rates of the working fluid exhaust steam at the outlets of the multiple expanders. According to this scheme, energy loss is reduced when the expander 120 performs work. Figure 2 The condensation curve of the working fluid exhaust gas and the vaporization curve of LNG in this embodiment are shown, wherein the condensation curve of the working fluid exhaust gas is P1 to P2. n The lines shown in the diagram are arranged in a stepped manner, and the vaporization curve of LNG is a smooth transition curve shown between L1 and L2.

[0068] Specifically, as described above, the working fluid steam in the expander 120 can enter the first stage rotating component to expand and do work, expanding to a certain pressure to form working fluid exhaust steam. Part of the working fluid exhaust steam is discharged from the first expander outlet 121, another part of the working fluid steam continues to enter the second stage rotating component to expand and do work, another part of the working fluid exhaust steam is discharged from the second expander outlet 122, another part of the working fluid steam continues to enter the third stage rotating component to expand and do work, another part of the working fluid exhaust steam is discharged from the third expander outlet 123, and so on up to the nth stage rotating component.

[0069] The mass flow rate of the working fluid steam entering expander 120 through expander inlet 124 is V. The pressure of the working fluid exhaust steam discharged through first expander outlet 121 is P1, and the mass flow rate of the working fluid exhaust steam discharged through first expander outlet 121 is V1. The pressure of the working fluid exhaust steam discharged through second expander outlet 122 is P2, and the mass flow rate of the working fluid exhaust steam discharged through second expander outlet 122 is V2. The pressure of the working fluid exhaust steam discharged through third expander outlet 123 is P3, and the mass flow rate of the working fluid exhaust steam discharged through third expander outlet 123 is V3. The pressure of the working fluid exhaust steam discharged through the nth expander outlet is P. n The mass flow rate of the working fluid exhaust steam discharged through the outlet of the nth expander is V. n .

[0070] Since the working fluid steam performs work sequentially in expander 120 and is discharged through different expander outlets, the pressure values ​​of the working fluid exhaust steam discharged from multiple expander outlets are P1>P2>P3>……>P n The mass flow rate of the working fluid exhaust steam discharged from multiple expander outlets is V1+V2+V3+……+V n =V. After the working fluid steam does work in the first-stage rotating component, a portion of the exhaust steam is discharged. It then enters the second-stage rotating component to continue doing work. The mass flow rate of the working fluid steam entering the second-stage rotating component can be V1'. Similarly, the mass flow rate of the working fluid steam entering the third-stage rotating component is V2', and the mass flow rate of the working fluid steam entering the nth-stage rotating component is V. n-1 'Then the mass flow rate V of the working fluid steam entering the multiple rotating components' n-1 '=V n +V n Therefore, the working fluid steam can enter the expander to do work separately, thereby generating electricity and improving power generation efficiency.

[0071] The LNG cold energy cascade power generation system 100 of this embodiment can match the condensation curve of the working fluid exhaust gas with the LNG vaporization temperature curve, reducing heat loss during the heat exchange process, improving the utilization rate of LNG cold energy, and further improving the power generation efficiency of the LNG cold energy cascade power generation system 100. Furthermore, the LNG cold energy cascade power generation system can form n pressure stages P1 to P2. n Compared to working fluid exhaust gas under a single pressure, the working fluid exhaust gas increases the output power of the expander 120, improves power generation efficiency, and also improves the cold energy utilization efficiency of LNG. This avoids the situation where the condensation curve of the working fluid exhaust gas and the LNG vaporization temperature curve cross over, which would prevent heat exchange from being achieved.

[0072] Preferably, the mass flow rates of the working fluid exhaust steam at the outlets of multiple expanders can be equal or unequal. In an optional embodiment, the mass flow rates of the working fluid exhaust steam at the outlets of multiple expanders can be equal. This allows for balanced work and stable power generation. The mass flow rate of the working fluid exhaust steam at the outlet 121 of the first expander can be V1, the mass flow rate of the working fluid exhaust steam at the outlet 122 of the second expander can be V2, the mass flow rate of the working fluid exhaust steam at the outlet 123 of the third expander can be V3, and the mass flow rate of the working fluid exhaust steam at the outlet of the nth expander can be V... n V1 = V2 = V3 = ... = V n .

[0073] In another alternative implementation, the mass flow rates of the working fluid exhaust gas at the outlets of the multiple expanders can be unequal. The mass flow rates of the working fluid exhaust gas at the outlets of the multiple expanders can vary according to the different heat exchange rates of each stage of the LNG, so as to effectively improve the utilization rate of the LNG's cold energy and increase power generation efficiency.

[0074] For example, when the mass flow rate of LNG is V lng The mass flow rate of the working fluid exhaust steam at the outlet 121 of the first expander can be V1, the mass flow rate of the working fluid exhaust steam at the outlet 122 of the second expander can be V2, the mass flow rate of the working fluid exhaust steam at the outlet 123 of the third expander can be V3, and the mass flow rate of the working fluid exhaust steam at the outlet of the nth expander can be V... n V1, V2, V3, ..., V n The different flow rates of the working fluid exhaust gas from each expander are designed to allow the LNG to enter different condensation units for heat exchange with varying flow rates, thus maximizing power generation efficiency. Of course, the flow rates of the working fluid exhaust gas discharged from different expander outlets can be partially the same to accommodate the different heat exchange requirements of the LNG; this embodiment is not intended to limit this.

[0075] Furthermore, Figure 2 The vaporization curve of LNG is shown, where L1 represents the vaporization rate of LNG entering the nth condensation unit (e.g., LNG vaporization curve). Figure 1 L1 represents the coordinate point of the LNG in the third condensing unit 143, and L2 represents the coordinate point of the LNG discharged from the first condensing unit 141. The temperature of the LNG entering the nth condensing unit is lower than the temperature of the LNG discharged from the first condensing unit 141. The temperature of the LNG entering the nth condensing unit is the lowest, and the temperature of the LNG discharged from the first condensing unit 141 is the highest. In this embodiment of the LNG cold energy cascade power generation system 100, the temperature of the LNG increases during the release of cold energy, and a smooth vaporization temperature curve can be formed between L1 and L2. The vaporization temperature of LNG refers to the temperature of LNG during the vaporization process, which varies during the vaporization process.

[0076] The working medium exhaust steam of different pressures enters different condensing devices through different pipelines. The working medium exhaust steam of the first pressure P1 discharged by the first expander outlet 121 enters the first condensing device 141 through the first expansion pipeline 151. The working medium exhaust steam of the second pressure P2 discharged by the second expander outlet 122 enters the second condensing device 142 through the second expansion pipeline 152. The working medium exhaust steam of the third pressure P3 discharged by the third expander outlet 123 enters the third condensing device 143 through the third expansion pipeline 153. The working medium exhaust steam of the nth pressure Pn discharged by the nth expander outlet enters the nth condensing device through the nth expansion pipeline. n

[0077] The first condensing device 141 is located downstream of the second condensing device 142 in the flow direction of the LNG, the second condensing device 142 is located downstream of the third condensing device 143 in the flow direction of the LNG, and so on to the nth condensing device. The LNG flows from the nth condensing device to the first condensing device 141. The pressure of the working medium exhaust steam in the first condensing device 141 is greater than that in the second condensing device 142, the pressure of the working medium exhaust steam in the second condensing device 142 is greater than that in the third condensing device 143, and so on to the pressure of the working medium exhaust steam in the nth condensing device. That is, the pressure of the working medium exhaust steam in the first condensing device 141 is the highest, and the pressure of the working medium exhaust steam in the nth condensing device is the lowest. The pressures of the working medium exhaust steam of the plurality of condensing devices can be sequentially increased in the flow direction of the LNG. The LNG can flow from the condensing device with low-pressure working medium exhaust steam into the condensing device with high-pressure working medium exhaust steam. The pressure of the LNG remains basically unchanged during the gasification process. Thus, the different gasification temperatures of the LNG at different stages can be effectively utilized, the energy utilization rate is improved, and energy waste is reduced.

[0078] Similarly, the temperatures of the working medium exhaust steam of different pressures are also different. The working medium exhaust steam of the first temperature T1 discharged by the first expander outlet 121 enters the first condensing device 141 through the first expansion pipeline 151. The working medium exhaust steam of the second temperature T2 discharged by the second expander outlet 122 enters the second condensing device 142 through the second expansion pipeline 152. The working medium exhaust steam of the third temperature T3 discharged by the third expander outlet 123 enters the third condensing device 143 through the third expansion pipeline 153. The working medium exhaust steam of the nth temperature Tn discharged by the nth expander outlet enters the nth condensing device through the nth expansion pipeline. n

[0079] ​​The temperature of the working medium steam in the first condensing device 141 is greater than the temperature of the working medium steam in the second condensing device 142, the temperature of the working medium steam in the second condensing device 142 is greater than the temperature of the working medium steam in the third condensing device 143, and so on to the temperature of the working medium steam in the nth condensing device. That is, the temperature of the working medium steam in the first condensing device 141 is the highest, and the temperature of the working medium steam in the nth condensing device is the lowest. The temperature of the working medium steam of the plurality of condensing devices can be sequentially increased along the flow direction of the LNG. The LNG can flow from the condensing device where the low-temperature working medium steam is located to the condensing device where the high-temperature working medium steam is located. Thus, the different gasification temperatures of the LNG at each stage can be effectively utilized, the energy utilization rate is improved, and energy waste is reduced.

[0080] The gasification temperature curve of the LNG matches the condensation curve of the working medium steam. Referring to the condensation curve of the working medium steam shown in FIG. 1, P1-Pn, the condensation temperature of the working medium steam gradually decreases. Figure 2 n The corresponding condensation temperature gradually decreases. Referring to the gasification temperature curve of the LNG shown in FIG. 1, L1-L2, the temperature gradually increases between L1 and L2. The energy absorbed by the LNG is equal to the sum of the energy released by the working medium steam discharged from the plurality of expander outlets. In this way, there is no heat loss in the process of releasing cold energy by the LNG, and the energy utilization rate is improved. Figure 2

[0081] The present application also provides a power generation method for the LNG cold energy cascade power generation system 100 described above. As shown in FIG. 2, the power generation method comprises the following steps: Figure 3

[0082] The composition of the organic working medium is selected according to the gasification temperature of the LNG and the temperature of the heat source.

[0083] The LNG cold energy cascade power generation system 100 comprises a heat source pipeline 111, a working medium pipeline, and an LNG pipeline. The heat source pipeline 111 is provided with a heat source, which can be seawater, solar energy, air, hot water, steam, flue gas, circulating water, or process wastewater. The working medium pipeline is provided with an organic working medium, which can be a mixture composed of one or more of methane, ethane, propane, ethylene, propylene, tetrafluoroethane, ammonia, etc. The LNG pipeline is provided with LNG.

[0084] The composition of the organic working medium can be selected first according to the gasification temperature of the LNG and the temperature of the heat source. The gasification temperature of the LNG refers to the temperature of the LNG in the gasification process, which is variable. For example, the organic working medium can be methane or a mixture of methane and ethane.

[0085] The pressure of the working medium steam is matched according to the temperature of the heat source.

[0086] ​​​The heat source in the heat source pipeline 111 and the organic working substance in the working substance pipeline can exchange heat in the evaporating device 110. The organic working substance can absorb the heat of the heat source to form working substance vapor. Thus, different pressures of working substance vapor can be matched according to different temperatures of the heat source.

[0087] The preset pressures of the organic working substance of the multiple condensing devices are matched according to the gasification temperature of the LNG, so that the temperature of the organic working substance generated by the condensing devices matches the gasification temperature of the LNG.

[0088] The LNG in the LNG pipeline can exchange heat with working substance exhaust vapor in the condensing device. The working substance exhaust vapor can form organic working substance after heat exchange. The working substance exhaust vapor can be formed by expansion work of the expander 120. In order to enable the expander 120 to perform appropriate expansion work and enable the working substance exhaust vapor formed after the expansion work of the expander 120 to have a suitable pressure. Therefore, the preset pressures of the organic working substance of the multiple condensing devices need to be matched according to the gasification temperature of the LNG, so as to ensure that the working substance exhaust vapor entering the condensing device can generate organic working substance with a preset pressure.

[0089] The LNG cold energy cascade system includes multiple condensing devices, and working substance exhaust vapors with different pressures enter different condensing devices to exchange heat with the LNG. The LNG pipeline connects the multiple condensing devices in series. The LNG can exchange heat with working substance exhaust vapors with different pressures in the multiple condensing devices in sequence, so that the working substance exhaust vapors absorb the cold energy of the LNG to form organic working substance. The temperature of the organic working substance can match the gasification temperature of the LNG. Thus, the utilization rate of the cold energy of the LNG can be improved.

[0090] The expander 120 is selected according to the pressure of the working substance vapor and the preset pressure of the organic working substance.

[0091] Different types of expanders 120 are selected according to the pressure of the working substance vapor and the preset pressure of the organic working substance, so as to ensure that the pressure value of the working substance exhaust vapor discharged from the expander outlet of the expander 120 meets the predetermined pressure, and thus the pressure of the organic working substance discharged from the condensing device meets the preset value.

[0092] According to the power generation method of the LNG cold energy cascade power generation system, the composition of the organic working substance is selected according to the gasification temperature of the LNG and the temperature of the heat source, the pressure of the working substance vapor is matched according to the temperature of the heat source, the preset pressures of the organic working substance of the multiple condensing devices are matched according to the gasification temperature of the LNG, so that the temperature of the organic working substance matches the gasification temperature of the LNG, and the expander is selected according to the pressure of the working substance vapor and the preset pressure of the organic working substance. In this way, the constantly changing gasification temperature in the gasification process of the LNG can be effectively utilized, the utilization rate of the cold energy of the LNG can be improved, the cold and heat loss in the heat exchange process can be reduced, and thus a suitable expander can be selected.

[0093] The evaporation device 110, the expander 120, the plurality of condensing devices and the plurality of pressure regulating components are connected together.

[0094] The evaporation device 110, the expander 120, the plurality of condensing devices and the plurality of pressure regulating components can be connected together through pipelines. In the evaporation device 110, the heat source of the heat source pipeline 111 exchanges heat with the organic working medium in the working medium pipeline, and the organic working medium absorbs heat to form working medium steam. The evaporation pipeline 112 communicates with the working medium pipeline of the evaporation device 110, and the working medium steam from the evaporation device 110 can enter the evaporation pipeline 112.

[0095] The expander 120 includes an expander inlet 124, and the working medium steam in the evaporation pipeline 112 enters the expander 120 through the expander inlet 124, and the working medium steam can expand and work in the expander 120 to drive the power generation device 130 to generate electricity.

[0096] The expander 120 can be an axial flow turbine expander, a centrifugal turbine expander, a radial flow turbine expander or a screw expander. Thus, the LNG cold energy cascade power generation system 100 can apply various expanders 120, expanding the application range.

[0097] The expander 120 includes a plurality of expander outlets, and the working medium steam working in the expander 120 can form working medium steam with different pressures, which can be discharged from the plurality of expander outlets corresponding to the pressure levels respectively.

[0098] The plurality of expander outlets enter the plurality of condensing devices through a plurality of pipelines respectively, and the plurality of condensing devices are also connected together through the LNG pipeline.

[0099] The condensing device is preset with a pressure level corresponding to the pressure of the working medium steam. The working medium steam with different pressures enters the plurality of condensing devices respectively. The LNG in the LNG pipeline can exchange heat with the working medium steam with different pressures in the different condensing devices in turn. The working medium steam absorbs the cold energy of the LNG at the corresponding pressure to be condensed into organic working medium.

[0100] The organic working medium with different pressures is adjusted in pressure through the plurality of pressure regulating components respectively, and the pressures of the organic working medium discharged from the plurality of pressure regulating components remain consistent. The organic working medium after pressure regulation enters the evaporation device 110 again for recycling.

[0101] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the terms "comprises", "comprising", "includes", "including" and the like are specifically intended to be open-ended. Such terms recognize that, under some circumstances, a device, structure, process, etc. can include more than one component, and that the components can be interrelated. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. As used herein, the term "about" when used in connection with a numerical value throughout the present application means that the value of the specified numerical value is within 10% of the indicated value. As used herein, the term "consisting essentially of" means including, in addition to those ingredients recited, only those that do not materially affect the basic and novel characteristics of the composition and method claimed. As used herein, the term "consisting of means including, and limited to, whatever follows the term "consisting of." Thus, the term "consisting of" indicates that the listed compositions are the only active ingredients enunciated.

[0102] The present application has been described through the above embodiments, but it should be understood that the above embodiments are only for the purpose of example and illustration, and are not intended to limit the present application to the scope of the described embodiments. Furthermore, those skilled in the art can understand that the present application is not limited to the above embodiments, and that more various modifications and changes can be made according to the teachings of the present application, and that such modifications and changes fall within the scope of the present application claimed. The scope of protection of the present application is defined by the attached claims and their equivalent scope.

Claims

1. An LNG cold energy cascade power generation system, characterized in that, The LNG cold energy cascade power generation system includes: An evaporation device, comprising a working fluid pipeline, wherein the evaporation device is used to exchange heat between a heat source and an organic working fluid in the working fluid pipeline to form working fluid vapor, wherein the pressure of the working fluid vapor is matched according to the temperature of the heat source. An expander includes an expander inlet and multiple expander outlets. The expander inlet is connected to the working fluid pipeline of the evaporation device, so that the working fluid vapor from the evaporation device can enter the expander to form working fluid exhaust vapor at different pressures. The working fluid exhaust vapor at different pressures is discharged from the multiple expander outlets respectively. A power generation device, which is connected to the expander via a drive mechanism, to convert mechanical energy into electrical energy; Multiple condensing units are provided, each corresponding to one of the multiple expander outlets. These condensing units are connected in parallel between the expanders and the evaporators via pipelines, and are also connected in series via LNG pipelines. This allows waste gas at different pressures to exchange heat with LNG in the condensing units to form organic working fluids at different pressures. Multiple pressure regulating components are respectively disposed on the pipeline between the evaporator and the multiple condensers. The pressure of the organic working fluid at the inlet of each pressure regulating component corresponds to the pressure of the organic working fluid in the corresponding condenser. The multiple pressure regulating components are used to adjust the pressure of the organic working fluids with different pressures flowing out of the multiple condensers to be consistent. The composition of the organic working fluid is selected based on the vaporization temperature of the LNG and the temperature of the heat source. The plurality of condensation devices each have a preset pressure for the organic working fluid. The preset pressure of the organic working fluid is pre-matched according to the vaporization temperature of the LNG, so that the exhaust gas entering the condensation device can generate an organic working fluid with a preset pressure, and the temperature of the organic working fluid is matched with the vaporization temperature of the LNG. The expander is selected based on the pressure of the working fluid vapor and the preset pressure of the organic working fluid; and wherein... The outlets of the plurality of pressure regulating components are respectively connected to the evaporation device. The mass flow rate of the working fluid steam at the inlet of the expander is equal to the sum of the mass flow rates of the working fluid exhaust steam at the outlets of the plurality of expanders. The mass flow rate of the working fluid exhaust steam at the outlets of the plurality of expanders varies depending on the heat exchange rate of each section of the LNG.

2. The LNG cold energy cascade power generation system according to claim 1, characterized in that, The expander also includes a multi-stage rotating component. The working fluid steam enters the multi-stage rotating component in sequence to expand and do work to form the working fluid exhaust steam at different pressures. The working fluid exhaust steam from the multi-stage rotating component is discharged through the multiple expander outlets respectively.

3. The LNG cold energy cascade power generation system according to claim 1, characterized in that, The mass flow rates of the working fluid exhaust gas at the outlets of the multiple expanders may be equal or unequal.

4. The LNG cold energy cascade power generation system according to claim 1, characterized in that, The energy absorbed by the LNG is equal to the sum of the energy released by the exhaust gas from the outlets of the multiple expanders.

5. The LNG cold energy cascade power generation system according to claim 1, characterized in that, The pressure and / or temperature of the working fluid exhaust gas in the plurality of condensation units increase sequentially along the flow direction of the LNG.

6. The LNG cold energy cascade power generation system according to claim 1, characterized in that, The heat source is seawater, air, solar energy, geothermal energy, hot water, steam, flue gas, circulating water, or process fluid.

7. The LNG cold energy cascade power generation system according to claim 1, characterized in that, The organic working medium is a mixture of one or more of methane, ethane, propane, ethylene, propylene, tetrafluoroethane, and ammonia.

8. The LNG cold energy cascade power generation system according to claim 1, characterized in that, The expander is one or more of the following: axial flow turbine expander, centrifugal turbine expander, radial flow turbine expander, or screw expander.

9. A power generation method for use in an LNG cold energy cascade power generation system according to any one of claims 1-8, characterized in that, The power generation method includes: The composition of the organic working fluid is selected based on the vaporization temperature of the LNG and the temperature of the heat source; The pressure of the working fluid steam is matched according to the temperature of the heat source; The pressure of the organic working fluid is preset in the plurality of condensation devices according to the vaporization temperature of the LNG, so that the temperature of the organic working fluid matches the vaporization temperature of the LNG. The expander is selected based on the pressure of the working fluid vapor and the preset pressure of the organic working fluid.

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