阅读说明：本技术 一种混合工质的lng冷能发电和综合利用系统及方法 (LNG cold energy power generation and comprehensive utilization system and method of mixed working medium ) 是由 杨天亮 张勇 甄晓伟 田欢 于 2019-12-24 设计创作，主要内容包括：本发明提供了一种混合工质的LNG冷能发电和综合利用系统及方法,所述系统包括LNG气化单元、冷能输送单元和循环发电单元；沿LNG流向,LNG气化单元包括依次连接的第一换热装置和第二换热装置；冷能输送单元包括第四换热装置和第五换热装置,第五换热装置连接第二换热装置；循环发电单元包括电能转换装置和气液分离装置；沿混合工质流向,电能转换装置依次循环连接第二换热装置、气液分离装置和第四换热装置,气液分离装置还连接第一换热装置。该系统能够有效回收LNG冷能,采用混合工质在换热装置内进行多级换热,降低冷能回收过程中的传热温差,实现高效电能转换,具有显著的经济效益和社会效益。(The invention provides a mixed working medium LNG cold energy power generation and comprehensive utilization system and a method, wherein the system comprises an LNG gasification unit, a cold energy transmission unit and a circulating power generation unit; along the LNG flow direction, the LNG gasification unit comprises a first heat exchange device and a second heat exchange device which are connected in sequence; the cold energy conveying unit comprises a fourth heat exchange device and a fifth heat exchange device, and the fifth heat exchange device is connected with the second heat exchange device; the circulating power generation unit comprises an electric energy conversion device and a gas-liquid separation device; and the electric energy conversion device is sequentially and circularly connected with the second heat exchange device, the gas-liquid separation device and the fourth heat exchange device along the flow direction of the mixed working medium, and the gas-liquid separation device is also connected with the first heat exchange device. The system can effectively recover LNG cold energy, adopts mixed working media to carry out multistage heat exchange in the heat exchange device, reduces heat transfer temperature difference in the cold energy recovery process, realizes high-efficiency electric energy conversion, and has remarkable economic benefit and social benefit.)

1. The LNG cold energy power generation and comprehensive utilization system of the mixed working medium is characterized by comprising an LNG gasification unit, a cold energy conveying unit and a circulating power generation unit;

along the flow direction of the LNG, the LNG gasification unit comprises a first heat exchange device and a second heat exchange device which are connected in sequence;

the cold energy conveying unit comprises a fourth heat exchange device and a fifth heat exchange device, the fifth heat exchange device is connected with the second heat exchange device, and LNG enters the fifth heat exchange device to exchange heat with secondary refrigerant after sequentially passing through the first heat exchange device and the second heat exchange device for heat;

the circulating power generation unit comprises an electric energy conversion device and a gas-liquid separation device;

the electric energy conversion device is sequentially connected with the second heat exchange device, the gas-liquid separation device and the fourth heat exchange device in a circulating manner along the flow direction of the mixed working medium, and the gas-liquid separation device is also connected with the first heat exchange device; the mixed working medium is subjected to power generation by the electric energy conversion device and then enters the second heat exchange device to exchange heat with the LNG, the mixed working medium subjected to heat exchange enters the gas-liquid separation device, the gas-phase working medium obtained by gas-liquid separation enters the first heat exchange device to exchange heat with the LNG, and the liquid-phase working medium obtained by gas-liquid separation enters the electric energy conversion device through the fourth heat exchange device to realize cycle power generation.

2. The comprehensive utilization system of claim 1, wherein the mixed working fluid comprises at least two organic working fluids;

preferably, the boiling points of the organic working mediums are different;

preferably, the mixed working fluid comprises a combination of at least two of methane, ethane or propane;

preferably, the mixed working medium is a mixture of methane, ethane and propane;

preferably, the volume ratio of methane, ethane and propane in the mixed working medium is (0.3-0.5): (0.3-0.5): (0.1 to 0.2);

preferably, the coolant comprises a solution of ethylene glycol and/or calcium chloride.

3. The integrated utilization system according to claim 1 or 2, further comprising a third heat exchange means;

the outlet of the electric energy conversion device is divided into two paths, one path is connected with a hot side inlet of the second heat exchange device, the other path is connected with a hot side inlet of the third heat exchange device, the hot side outlet of the second heat exchange device and the hot side outlet of the third heat exchange device are combined into one path and then connected with a liquid inlet of the gas-liquid separation device, a gas phase outlet of the gas-liquid separation device is connected with the hot side inlet of the first heat exchange device, the hot side outlet of the first heat exchange device is connected with a cold side inlet of the third heat exchange device, and a cold side outlet of the third heat exchange device and a liquid phase outlet of the gas-liquid separation device are combined into one path and then connected with a cold side;

the mixed working medium is divided into two parts after being worked by the electric energy conversion device to generate electricity, one part of the mixed working medium enters the second heat exchange device to exchange heat with the LNG flowing out of the first heat exchange device, and the other part of the mixed working medium enters the third heat exchange device to exchange heat with the gas-phase working medium flowing out of the first heat exchange device; and the mixed working media which are subjected to heat exchange and temperature reduction in the second heat exchange device and the third heat exchange device respectively converge and then enter the gas-liquid separation device.

4. The integrated utilization system according to any one of claims 1 to 3, further comprising at least one pressure boosting device;

preferably, the comprehensive utilization system comprises a first supercharging device and a second supercharging device;

preferably, the first supercharging device is arranged on a connecting pipeline between the first heat exchange device and the third heat exchange device;

preferably, the second pressure boosting device is arranged on a connecting pipeline between the gas-liquid separation device and the fourth heat exchange device, and an outlet of the second pressure boosting device and a cold side outlet of the third heat exchange device are combined into one path and then connected with a cold side inlet of the fourth heat exchange device.

5. The integrated utilization system according to any one of claims 1 to 4, wherein said pressurizing means is a pressurizing pump;

preferably, the electric energy conversion device is a turbine.

6. A method for generating power and comprehensively utilizing LNG cold energy of mixed working media is characterized in that the comprehensive utilization system of any one of claims 1-5 is adopted to generate power by utilizing the LNG cold energy;

the comprehensive utilization method comprises the following steps:

LNG sequentially passes through the first heat exchange device and the second heat exchange device to exchange heat, and then enters the fifth heat exchange device to exchange heat with secondary refrigerant conveyed by a user needing cooling;

(II) the mixed working medium is subjected to power generation by the electric energy conversion device and then enters a second heat exchange device to exchange heat with the LNG entering the second heat exchange device in the step (I), and the mixed working medium after heat exchange enters a gas-liquid separation device to be separated to obtain a gas-phase working medium and a liquid-phase working medium;

(III) introducing the gas-phase working medium into a first heat exchange device to exchange heat with the LNG entering the first heat exchange device in the step (I);

and (IV) the liquid-phase working medium enters a fourth heat exchange device to exchange heat with the secondary refrigerant conveyed by a user needing cooling, and the liquid-phase working medium after heat exchange enters an electric energy conversion device to repeat the step (II) to realize cyclic working power generation.

7. The comprehensive utilization method according to claim 6, wherein the LNG delivery pressure in step (I) is 8-12 MPa;

preferably, the temperature of the LNG is-160 to-120 ℃;

preferably, the LNG is subjected to heat exchange through a first heat exchange device and is heated to-130 to-100 ℃;

preferably, the LNG is subjected to heat exchange in a second heat exchange device to be heated and gasified into natural gas;

preferably, the LNG is subjected to heat exchange through a second heat exchange device and is heated to-50 to-30 ℃;

preferably, the natural gas is subjected to heat exchange with the secondary refrigerant in a fifth heat exchange device and then is heated to 0-10 ℃;

preferably, the natural gas enters a natural gas pipe network after being subjected to heat exchange and temperature rise by a fifth heat exchange device;

preferably, the temperature of the secondary refrigerant conveyed by the user needing cooling is 5-15 ℃;

preferably, the secondary refrigerant exchanges heat in the fifth heat exchange device and is cooled to-40 to-20 ℃.

8. The comprehensive utilization method according to claim 6 or 7, wherein the step (II) specifically comprises:

the mixed working medium is divided into a first mixed working medium and a second mixed working medium after the electric energy conversion device does work to generate electricity, the first mixed working medium enters the second heat exchange device to exchange heat with the LNG entering the second heat exchange device in the step (I), and the second mixed working medium enters the third heat exchange device to exchange heat with the liquefied gas-phase working medium flowing out of the first heat exchange device in the step (III); the first mixed working medium and the second mixed working medium respectively exchange heat and reduce temperature, then converge and enter a gas-liquid separation device, and are separated to obtain a gas-phase working medium and a liquid-phase working medium;

preferably, the mixed working medium comprises at least two organic working media;

preferably, the boiling points of the organic working mediums are different;

preferably, the mixed working fluid comprises a combination of at least two of methane, ethane or propane;

preferably, the mixed working medium is a mixture of methane, ethane and propane;

preferably, the volume ratio of methane, ethane and propane in the mixed working medium is (0.3-0.5): (0.3-0.5): (0.1 to 0.2);

preferably, the conveying pressure of the mixed working medium is 3-5 MPa;

preferably, the temperature of the mixed working medium entering the electric energy conversion device is 0-10 ℃;

preferably, the temperature of the mixed working medium is reduced to minus 60 to minus 20 ℃ after the mixed working medium works and generates electricity in the electric energy conversion device;

preferably, the pressure of the mixed working medium is reduced to 0.5-2 MPa after the mixed working medium works and generates electricity in the electric energy conversion device;

preferably, the first mixed working medium accounts for 50-80% of the total volume flow of the mixed working medium;

preferably, the first mixed working medium exchanges heat with LNG in a second heat exchange device and is cooled to-100 to-80 ℃;

preferably, the second mixed working medium exchanges heat with the gas-phase working medium in the third heat exchange device and is cooled to-100 to-80 ℃.

9. The comprehensive utilization method according to any one of claims 6 to 8, wherein the step (III) specifically comprises:

introducing the gas-phase working medium obtained by separation of the gas-liquid separation device into a first heat exchange device to exchange heat with the LNG entering the first heat exchange device in the step (I), pressurizing the gas-phase working medium subjected to heat exchange by a first pressurizing device and then entering a third heat exchange device, and exchanging heat between the gas-phase working medium and a second mixed working medium flowing out of the electric energy conversion device in the third heat exchange device;

preferably, the gas-phase working medium is subjected to heat exchange, temperature reduction and condensation in the first heat exchange device to form liquid;

preferably, the gas-phase working medium is pressurized to 4-5 MPa by a first pressurizing device;

preferably, the gas-phase working medium exchanges heat in the third heat exchange device and is heated to-50 to-40 ℃.

10. The integrated utilization system according to any one of claims 6 to 9, wherein the step (iv) specifically comprises:

the liquid phase working medium obtained by the separation of the gas-liquid separation device is mixed with the gas phase working medium flowing out of the third heat exchange device to form a mixed working medium, the mixed working medium enters the fourth heat exchange device to exchange heat with the secondary refrigerant conveyed by a user needing cooling, and the mixed working medium after heat exchange enters the electric energy conversion device to repeat the step (II) to realize cyclic working power generation;

preferably, the liquid phase working medium obtained by the separation of the gas-liquid separation device is pressurized to 4-5 MPa by the second pressurizing device and then is mixed with the gas phase working medium flowing out of the third heat exchange device;

preferably, the temperature of the mixed working medium obtained after the liquid-phase working medium and the gas-phase working medium are mixed is-60 to-40 ℃;

preferably, the mixed working medium exchanges heat in a fourth heat exchange device and is heated to 0-10 ℃;

preferably, the pressure of the mixed working medium after heat exchange in the fourth heat exchange device is changed to 4-5 MPa;

preferably, the temperature of the secondary refrigerant conveyed by the user needing cooling is 5-15 ℃;

preferably, the secondary refrigerant exchanges heat in the fourth heat exchange device and is cooled to-40 to-20 ℃.

Technical Field

The invention belongs to the technical field of LNG cold energy utilization, relates to a system and a method for generating and comprehensively utilizing LNG cold energy, and particularly relates to a system and a method for generating and comprehensively utilizing LNG cold energy of a mixed working medium.

Background

The natural gas is a mixture of different components according to a certain proportion, and the main component of the natural gas is hydrocarbon, including methane, ethane, propane, butane and the like, wherein the methane accounts for more than 90 percent. LNG, i.e., Liquefied natural gas (Liquefied natural gas), is a natural gas that is liquid at normal pressure obtained by purifying natural gas produced in a gas field and then liquefying the natural gas at a series of ultra-low temperatures, and is known as the cleanest fossil energy on earth. Typically, liquefied natural gas is liquefied at normal atmospheric pressure by reducing the temperature to about-162 c.

To facilitate natural gas transportation, natural gas is typically liquefied. The currently common storage temperature of the LNG is-162 ℃, the temperature used by a user is about 5 ℃, the cold energy released in the gasification process from the storage temperature to the use temperature is about 830kJ/kg, and if the cold energy possessed by the LNG is converted into electric energy with 100% efficiency, the cold energy per ton of LNG can be converted into electric energy of 240 kWh.

It follows that the LNG cold energy available is considerable. The cold energy has higher utilization value from the aspect of energy quality, and if the LNG cold energy is utilized through a specific process, the purposes of saving energy and improving economic benefit can be achieved.

The LNG cold energy can be utilized in a direct or indirect manner. The direct utilization method of LNG comprises cold energy power generation, seawater desalination, liquefaction and separation of air (liquid oxygen and liquid nitrogen), light hydrocarbon separation, freezing warehouse, liquefied carbonic acid, dry ice preparation and air conditioning; indirectly utilizing frozen food, pulverizing waste at low temperature, freezing and storing, treating at low temperature, and storing food.

CN204238992U discloses a system for generating power by utilizing liquefied natural gas cooling energy, which comprises a first LNG pump, a second LNG pump, a third LNG pump, a low-pressure natural gas condenser, a medium-pressure natural gas condenser, a low-pressure refrigerant condenser, a first liquid refrigerant pump, a second liquid refrigerant pump, a third liquid refrigerant pump, a refrigerant gasifier, a high-pressure natural gas heater, a high-pressure natural gas superheater, a refrigerant expander, a natural gas expander, a secondary medium-pressure refrigerant condenser and a medium-pressure refrigerant condenser. However, the technical scheme provided by the application is complex in system and high in investment and operation cost, and meanwhile, low-temperature waste heat must be utilized when the system operates; secondly, the cold energy after heat exchange of the system cannot be provided for users needing cold, and the efficient utilization of low-grade cold energy cannot be realized; thirdly, the natural gas output by the system is low-pressure natural gas, and the system cannot be applied to a high-pressure conveying pipe network of an LNG receiving station.

CN105569752A discloses a process and a device for generating electricity by using LNG cold energy. A large amount of cold energy is released in the process of supplying natural gas to a downstream pipe network through LNG vaporization, the process utilizes two independent cycles to recover the cold energy for power generation, the loss of the cold energy is avoided, the economic benefit of enterprises is improved, the pollution problem caused by power plant power generation is avoided during power generation, and the requirements of energy conservation and environmental protection are met. However, the system adopts two sets of circulation to complete LNG cold energy utilization, the system is complex, the unit LNG cold energy generating capacity is low, a high-temperature heat source is needed, and comprehensive utilization of the LNG cold energy cannot be realized.

CN208168940U discloses a large-scale LNG receiving station utilizes liquefied natural gas cold energy power generation system, three groups of independent heat exchange channels are arranged in a main heat exchanger, the inlet and outlet ends of a first heat exchange channel are respectively connected with a liquefied natural gas pipe and a natural gas pipe, the outlet end of a second heat exchange channel is connected with a mixed working medium buffer tank, the outlet end of the mixed working medium buffer tank is connected with a mixed working medium booster pump, the outlet end of the mixed working medium booster pump is connected with the inlet end of a third heat exchange channel, the outlet end of the third heat exchange channel is connected with a mixed working medium heater, the outlet end of the mixed working medium heater is connected with the inlet end of an expander, the outlet end of the expander is connected with the inlet end of the second heat exchange channel, the expander is connected with a generator, LNG cold energy is converted into electric energy by adopting low-temperature Rankine cycle of the mixed working medium, the system has good adjustability and working. The system adopts a heat exchanger to directly exchange heat and liquefy the mixed working medium with the LNG, the heat exchanger is large, heat exchange is not carried out according to temperature gradient, heat exchange efficiency is low, and finally total heat transfer efficiency and energy utilization rate are low. In addition, comprehensive utilization of the cold energy of the LNG cannot be realized. Meanwhile, the kind of the mixed working medium provided by the patent is different from the proportion of the working medium.

Although some patents and technologies can realize LNG cold energy power generation, most systems have the problems of complex power generation system, low cold energy utilization rate, high temperature of required waste heat source, low unit cold energy power generation amount and the like.

Disclosure of Invention

The invention aims to provide a mixed working medium LNG cold energy power generation and comprehensive utilization system and a method, provides possibility for comprehensive utilization of cold energy of an LNG receiving station, can realize LNG cold energy power generation on the premise of ensuring gasification of LNG receiving station liquid natural gas, improves energy utilization rate, and can meet the use requirements of users needing cooling by adopting secondary refrigerant to transport the cold energy.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the invention provides a mixed working medium LNG cold energy power generation and comprehensive utilization system, which comprises an LNG gasification unit, a cold energy transmission unit and a circulating power generation unit.

Along the LNG flow direction, LNG vaporizing unit including first heat transfer device and the second heat transfer device that connects gradually.

The cold energy conveying unit comprises a fourth heat exchange device and a fifth heat exchange device, the fifth heat exchange device is connected with the second heat exchange device, and LNG enters the fifth heat exchange device to exchange heat with secondary refrigerant after sequentially passing through the first heat exchange device and the second heat exchange device for heat.

The circulating power generation unit comprises an electric energy conversion device and a gas-liquid separation device.

The electric energy conversion device is sequentially connected with the second heat exchange device, the gas-liquid separation device and the fourth heat exchange device in a circulating manner along the flow direction of the mixed working medium, and the gas-liquid separation device is also connected with the first heat exchange device; the mixed working medium is subjected to power generation by the electric energy conversion device and then enters the second heat exchange device to exchange heat with the LNG, the mixed working medium subjected to heat exchange enters the gas-liquid separation device, the gas-phase working medium obtained by gas-liquid separation enters the first heat exchange device to exchange heat with the LNG, and the liquid-phase working medium obtained by gas-liquid separation enters the electric energy conversion device through the fourth heat exchange device to realize cycle power generation.

The invention provides an LNG cold energy power generation system capable of adopting an ultralow temperature heat source mixed working medium. The system can effectively recover LNG cold energy, adopts mixed working media to carry out multistage heat exchange in the heat exchange device, reduces heat transfer temperature difference in the cold energy recovery process, realizes high-efficiency thermoelectric conversion, and has remarkable economic and social benefits.

As a preferable technical scheme of the invention, the mixed working medium comprises at least two organic working media.

Preferably, the boiling points of the organic working fluids are different.

Preferably, the mixed working fluid comprises a combination of at least two of methane, ethane or propane.

Preferably, the mixed working fluid is a mixture of methane, ethane and propane.

Preferably, the volume ratio of methane, ethane and propane in the mixed working fluid is (0.3-0.5): (0.1-0.2), and may be, for example, 0.3:0.3:0.1, 0.4:0.3:0.1, 0.5:0.3:0.1, 0.3:0.4:0.1, 0.3:0.5:0.1 or 0.3:0.3:0.2, but not limited to the enumerated values, and other non-enumerated values within the range of values are equally applicable.

Preferably, the coolant comprises a solution of ethylene glycol and/or calcium chloride.

As a preferable technical scheme of the invention, the comprehensive utilization system also comprises a third heat exchange device.

The outlet of the electric energy conversion device is divided into two paths, one path is connected with a hot side inlet of the second heat exchange device, the other path is connected with a hot side inlet of the third heat exchange device, the hot side outlet of the second heat exchange device and the hot side outlet of the third heat exchange device are combined into one path and then connected with a liquid inlet of the gas-liquid separation device, a gas phase outlet of the gas-liquid separation device is connected with the hot side inlet of the first heat exchange device, the hot side outlet of the first heat exchange device is connected with a cold side inlet of the third heat exchange device, and a cold side outlet of the third heat exchange device and a liquid phase outlet of the gas-liquid separation device are combined into one path and then connected with a cold side;

the mixed working medium is divided into two parts after being worked by the electric energy conversion device to generate electricity, one part of the mixed working medium enters the second heat exchange device to exchange heat with the LNG flowing out of the first heat exchange device, and the other part of the mixed working medium enters the third heat exchange device to exchange heat with the gas-phase working medium flowing out of the first heat exchange device; and the mixed working media which are subjected to heat exchange and temperature reduction in the second heat exchange device and the third heat exchange device respectively converge and then enter the gas-liquid separation device.

As a preferred technical solution of the present invention, the comprehensive utilization system further includes at least one pressure boosting device.

Preferably, the integrated utilization system includes a first pressure boosting device and a second pressure boosting device.

Preferably, the first pressure boosting device is arranged on a connecting pipeline between the first heat exchange device and the third heat exchange device.

Preferably, the second pressure boosting device is arranged on a connecting pipeline between the gas-liquid separation device and the fourth heat exchange device, and an outlet of the second pressure boosting device and a cold side outlet of the third heat exchange device are combined into one path and then connected with a cold side inlet of the fourth heat exchange device.

As a preferable technical scheme of the invention, the supercharging device is a booster pump.

Preferably, the electric energy conversion device is a turbine.

In a second aspect, the invention provides a method for generating power by using LNG cold energy of a mixed working medium and comprehensively utilizing the LNG cold energy, and the comprehensive utilization system of the first aspect is adopted to generate power by using the LNG cold energy.

The comprehensive utilization method comprises the following steps:

LNG sequentially passes through the first heat exchange device and the second heat exchange device to exchange heat, and then enters the fifth heat exchange device to exchange heat with secondary refrigerant conveyed by a user needing cooling;

(II) the mixed working medium is subjected to power generation by the electric energy conversion device and then enters a second heat exchange device to exchange heat with the LNG entering the second heat exchange device in the step (I), and the mixed working medium after heat exchange enters a gas-liquid separation device to be separated to obtain a gas-phase working medium and a liquid-phase working medium;

(III) introducing the gas-phase working medium into a first heat exchange device to exchange heat with the LNG entering the first heat exchange device in the step (I);

and (IV) the liquid-phase working medium enters a fourth heat exchange device to exchange heat with the secondary refrigerant conveyed by a user needing cooling, and the liquid-phase working medium after heat exchange enters an electric energy conversion device to repeat the step (II) to realize cyclic working power generation.

In a preferred embodiment of the present invention, the transfer pressure of LNG in step (i) is 8 to 12MPa, and may be, for example, 8.0MPa, 8.2MPa, 8.4MPa, 8.6MPa, 8.8MPa, 9.0MPa, 9.2MPa, 9.4MPa, 9.6MPa, 9.8MPa, 10.2MPa, 10.4MPa, 10.6MPa, 10.8MPa, 11.2MPa, 11.4MPa, 11.6MPa, 11.8MPa or 12.0 MPa.

Preferably, the LNG is at a temperature of-160 ℃ to-120 ℃, and may be, for example, -160 ℃, 155 ℃, 150 ℃, 145 ℃, 140 ℃, 135 ℃, 130 ℃, 125 ℃ or-120 ℃, but is not limited to the recited values, and other values not recited within the range of values are equally applicable.

Preferably, the LNG is warmed to-130 to-100 c, for example, -130 c, -125 c, -120 c or-100 c, by heat exchange with the first heat exchange means, but not limited to the values recited, and other values not recited within this range are equally applicable.

Preferably, the LNG is subjected to heat exchange in the second heat exchange device to be heated and gasified into natural gas.

Preferably, the LNG is warmed to-50 to-30 ℃ by heat exchange with the second heat exchange means, and may be, for example, -50 ℃, -49 ℃, -48 ℃, -47 ℃, -46 ℃, -45 ℃, -44 ℃, -43 ℃, -42 ℃, -41 ℃, -40 ℃, -39 ℃, -38 ℃, -37 ℃, -36 ℃, -35 ℃, -34 ℃, -33 ℃, -32 ℃, -31 ℃ or-30 ℃, but is not limited to the values recited, and other values not recited in the range of values are equally applicable.

Preferably, the temperature of the natural gas is raised to 0 to 10 ℃ after heat exchange with the coolant in the fifth heat exchanger, and may be, for example, 0 ℃, 1 ℃, 2 ℃, 3 ℃, 4 ℃, 5 ℃, 6 ℃, 7 ℃, 8 ℃, 9 ℃ or 10 ℃, but is not limited to the values listed, and other values not listed in the range of the values are also applicable.

Preferably, the natural gas enters the natural gas pipe network after being subjected to heat exchange and temperature rise by the fifth heat exchange device.

Preferably, the coolant delivered by the user to be cooled has a temperature of 5 to 15 ℃, for example, 5 ℃, 6 ℃, 7 ℃, 8 ℃, 9 ℃, 10 ℃, 11 ℃, 12 ℃, 13 ℃, 14 ℃ or 15 ℃, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the coolant is cooled to-40 to-20 ℃ in the fifth heat exchange device, such as-40 ℃, -39 ℃, -38 ℃, -37 ℃, -36 ℃, -35 ℃, -34 ℃, -33 ℃, -32 ℃, -31 ℃, -30 ℃, -29 ℃, 28 ℃, 27 ℃, 26 ℃, 25 ℃, 24 ℃, 23 ℃, 22 ℃, 21 ℃ or 20 ℃, but is not limited to the values listed, and other values not listed in this range are equally suitable.

As a preferred technical solution of the present invention, the step (ii) specifically comprises:

the mixed working medium is divided into a first mixed working medium and a second mixed working medium after the electric energy conversion device does work to generate electricity, the first mixed working medium enters the second heat exchange device to exchange heat with the LNG entering the second heat exchange device in the step (I), and the second mixed working medium enters the third heat exchange device to exchange heat with the liquefied gas-phase working medium flowing out of the first heat exchange device in the step (III); and the first mixed working medium and the second mixed working medium respectively exchange heat, are cooled and then converge to enter a gas-liquid separation device, and are separated to obtain a gas-phase working medium and a liquid-phase working medium.

Preferably, the mixed working medium comprises at least two organic working media.

Preferably, the boiling points of the organic working fluids are different.

Preferably, the mixed working fluid comprises a combination of at least two of methane, ethane or propane.

Preferably, the mixed working fluid is a mixture of methane, ethane and propane.

Preferably, the volume ratio of methane, ethane and propane in the mixed working medium is (0.3-0.5): (0.3-0.5): (0.1 to 0.2) may be, for example, 0.3:0.3:0.1, 0.4:0.3:0.1, 0.5:0.3:0.1, 0.3:0.4:0.1, 0.3:0.5:0.1 or 0.3:0.3:0.2, but the numerical values are not limited to the enumerated values, and other numerical values not enumerated within the numerical range are also applicable.

Preferably, the mixed working fluid has a delivery pressure of 3 to 5MPa, and may be, for example, 3.0MPa, 3.1MPa, 3.2MPa, 3.3MPa, 3.4MPa, 3.5MPa, 3.6MPa, 3.7MPa, 3.8MPa, 3.9MPa, 4.0MPa, 4.1MPa, 4.2MPa, 4.3MPa, 4.4MPa, 4.5MPa, 4.6MPa, 4.7MPa, 4.8MPa, 4.9MPa or 5.0MPa, but not limited to the values listed, and other values not listed in the range of values are also applicable.

Preferably, the temperature of the mixed working medium entering the electric energy conversion device is 0-10 ℃, for example, 0 ℃, 1 ℃, 2 ℃, 3 ℃, 4 ℃, 5 ℃, 6 ℃, 7 ℃, 8 ℃, 9 ℃ or 10 ℃, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the temperature of the mixed working medium is reduced to-60 to-20 ℃ after work is performed on the mixed working medium in the electric energy conversion device to generate electricity, and the temperature can be, for example, -60 ℃, 55 ℃, 50 ℃, 45 ℃, 40 ℃, 35 ℃, 30 ℃, 25 ℃ or-20 ℃, but the mixed working medium is not limited to the values listed, and other values not listed in the range of the values are also applicable.

Preferably, the pressure of the mixed working medium is reduced to 0.5-2 MPa after power generation in the electric energy conversion device, for example, 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa, 0.9MPa, 1.0MPa, 1.1MPa, 1.2MPa, 1.3MPa, 1.4MPa, 1.5MPa, 1.6MPa, 1.7MPa, 1.8MPa, 1.9MPa or 2.0MPa, but not limited to the recited values, and other values in the range of the recited values are also applicable.

Preferably, the first mixed working medium accounts for 50-80% of the total volume flow of the mixed working medium, for example, 50%, 55%, 60%, 65%, 70%, 75% or 80%, but not limited to the values listed, and other values not listed in the range of the values are also applicable.

Preferably, the first mixed working fluid is cooled to-100 to-80 ℃ in the second heat exchanger by heat exchange with LNG, and may be, for example, -100 ℃, -99 ℃, -98 ℃, -97 ℃, -96 ℃, -95 ℃, -94 ℃, -93 ℃, -92 ℃, -91 ℃, -90 ℃, -89 ℃, -88 ℃, -87 ℃, -86 ℃, -85 ℃, -84 ℃, -83 ℃, -82 ℃, -81 ℃ or-80 ℃, but is not limited to the values listed, and other values not listed in the range of values are equally applicable.

Preferably, the second mixed working fluid is cooled to-100 to-80 ℃ in the third heat exchange device through heat exchange with the gas-phase working fluid, and the temperature can be, for example, -100 ℃, -99 ℃, -98 ℃, -97 ℃, -96 ℃, -95 ℃, -94 ℃, -93 ℃, -92 ℃, -91 ℃, -90 ℃, -89 ℃, -88 ℃, -87 ℃, -86 ℃, -85 ℃, -84 ℃, -83 ℃, -82 ℃, -81 ℃ or-80 ℃, but the temperature is not limited to the enumerated values, and other non-enumerated values in the numerical value range are also applicable.

As a preferred technical solution of the present invention, the step (iii) specifically includes:

and (3) introducing the gas-phase working medium obtained by separation of the gas-liquid separation device into the first heat exchange device to exchange heat with the LNG entering the first heat exchange device in the step (I), pressurizing the gas-phase working medium subjected to heat exchange by the first pressurizing device and then entering the third heat exchange device, and exchanging heat between the gas-phase working medium and a second mixed working medium flowing out of the electric energy conversion device in the third heat exchange device.

Preferably, the gas-phase working medium exchanges heat in the first heat exchange device, is cooled and is condensed into liquid.

Preferably, the working fluid in the gaseous phase is pressurized by the first pressurizing device to 4 to 5MPa, for example, 4.0MPa, 4.1MPa, 4.2MPa, 4.3MPa, 4.4MPa, 4.5MPa, 4.6MPa, 4.7MPa, 4.8MPa, 4.9MPa or 5.0MPa, but not limited to the recited values, and other values not recited in the range of values are also applicable.

Preferably, said gaseous working fluid is heated in the third heat exchange means to-50 to-40 ℃ by heat exchange, for example-50 ℃, -49 ℃, -48 ℃, -47 ℃, -46 ℃, -45 ℃, -44 ℃, -43 ℃, -42 ℃, -41 ℃ or-40 ℃, but is not limited to the values listed, and other values not listed in this range of values are equally suitable.

As a preferred technical solution of the present invention, the step (iv) specifically includes:

and (3) mixing the liquid-phase working medium obtained by the separation of the gas-liquid separation device with the gas-phase working medium flowing out of the third heat exchange device to form a mixed working medium, allowing the mixed working medium to enter the fourth heat exchange device to exchange heat with the secondary refrigerant conveyed by the user needing cooling, and allowing the mixed working medium after heat exchange to enter the electric energy conversion device to repeat the step (II) to realize cyclic working power generation.

Preferably, the liquid-phase working medium separated by the gas-liquid separation device is pressurized to 4 to 5MPa by the second pressurizing device and then mixed with the gas-phase working medium flowing out of the third heat exchange device, and may be, for example, 4.0MPa, 4.1MPa, 4.2MPa, 4.3MPa, 4.4MPa, 4.5MPa, 4.6MPa, 4.7MPa, 4.8MPa, 4.9MPa or 5.0MPa, but is not limited to the values listed, and other values not listed in the range of the values are also applicable.

Preferably, the temperature of the mixed working fluid obtained by mixing the liquid phase working fluid and the gas phase working fluid is-60 to-40 ℃, and may be, for example, -60 ℃, -59 ℃, -58 ℃, -57 ℃, -56 ℃, -55 ℃, -54 ℃, -53 ℃, -52 ℃, -51 ℃, -50 ℃, -49 ℃, -48 ℃, -47 ℃, -46 ℃, -45 ℃, -44 ℃, -43 ℃, -42 ℃, -41 ℃ or-40 ℃, but is not limited to the values listed, and other values not listed in the range of the values are also applicable.

Preferably, the temperature of the mixed working medium is raised to 0-10 ℃ in the fourth heat exchange device through heat exchange, for example, 0 ℃, 1 ℃, 2 ℃, 3 ℃, 4 ℃, 5 ℃, 6 ℃, 7 ℃, 8 ℃, 9 ℃ or 10 ℃, but is not limited to the recited values, and other values not recited in the numerical value range are also applicable.

Preferably, the pressure of the mixed working fluid after heat exchange in the fourth heat exchange device is 4 to 5MPa, for example, 4.0MPa, 4.1MPa, 4.2MPa, 4.3MPa, 4.4MPa, 4.5MPa, 4.6MPa, 4.7MPa, 4.8MPa, 4.9MPa or 5.0MPa, but not limited to the values listed, and other values not listed in the range of the values are also applicable.

Preferably, the coolant delivered by the user to be cooled has a temperature of 5 to 15 ℃, for example, 5 ℃, 6 ℃, 7 ℃, 8 ℃, 9 ℃, 10 ℃, 11 ℃, 12 ℃, 13 ℃, 14 ℃ or 15 ℃, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the coolant is cooled to-40 to-20 ℃ in the fourth heat exchange device by heat exchange, for example, the coolant may be-40 ℃, -39 ℃, -38 ℃, -37 ℃, -36 ℃, -35 ℃, -34 ℃, -33 ℃, -32 ℃, -31 ℃, -30 ℃, -29 ℃, -28 ℃, -27 ℃, -26 ℃, -25 ℃, -24 ℃, -23 ℃, -22 ℃, -21 ℃ or-20 ℃, but is not limited to the values listed, and other values not listed in the range of values are equally applicable.

The system refers to an equipment system, or a production equipment.

Compared with the prior art, the invention has the beneficial effects that:

(1) the LNG cold energy power generation system provides possibility for comprehensive utilization of cold energy of the LNG receiving station, can realize cold energy power generation of LNG on the premise of ensuring gasification of liquefied natural gas of the LNG receiving station, improves energy utilization rate, and can meet the use requirements of users needing cold by transporting the cold energy by using secondary refrigerant;

(2) most patents and technologies in the prior art have the defects of low cold energy utilization efficiency and no comprehensive utilization of cold energy, and meanwhile, most patents and technologies need to adopt a high-temperature heat source and need additional waste heat input. The invention fully utilizes the cold energy under different temperature gradients and has high energy utilization efficiency. Meanwhile, the mixed working medium of methane, ethane and propane which is prepared according to different proportions is selected, so that the invention has great advantages in both cold energy generation capacity and system heat exchange gradient.

(3) The LNG cold energy power generation technology and the cold energy comprehensive utilization technology are combined for the first time, the cold energy power generation is realized, and meanwhile, the utilized shallow cold resources are conveyed to the users needing cold for comprehensive utilization, so that the utilization efficiency of the cold energy is greatly improved, and the waste of cold energy is reduced.

Drawings

Fig. 1 is a schematic structural diagram of an LNG cold energy power generation and comprehensive utilization system provided in embodiment 1 of the present invention;

fig. 2 is a schematic structural diagram of an LNG cold energy power generation and comprehensive utilization system provided in embodiment 3 of the present invention;

wherein, 1-a first heat exchange device; 2-a second heat exchange device; 3-a third heat exchange device; 4-a fourth heat exchange device; 5-fifth heat exchange device; 6-gas-liquid separation device; 7-a second supercharging device; 8-a first supercharging device; 9-electric energy conversion device.

Detailed Description

It is to be understood that in the description of the present invention, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be taken as limiting the present invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

It should be noted that, in the description of the present invention, unless otherwise explicitly specified or limited, the terms "disposed," "connected" and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.

The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.