CN110925042A

CN110925042A - Multistage LNG cold energy power generation and comprehensive utilization system and method

Info

Publication number: CN110925042A
Application number: CN201911345624.6A
Authority: CN
Inventors: 杨天亮; 张勇; 甄晓伟; 田欢
Original assignee: Qingdao Zhongji Longyuan Energy Technology Co Ltd
Current assignee: Qingdao Zhongji Longyuan Energy Technology Co Ltd
Priority date: 2019-12-24
Filing date: 2019-12-24
Publication date: 2020-03-27

Abstract

The invention provides a multistage LNG cold energy power generation and comprehensive utilization system and a method, wherein the system comprises at least two stages of circulating power generation units; the circulating power generation unit comprises an electric energy conversion device, an LNG heat exchange device and a secondary refrigerant heat exchange device which are sequentially and circularly connected along the flow direction of a circulating working medium; LNG heat transfer devices in each stage of circulating power generation unit are sequentially connected along the LNG flow direction to form an LNG heat transfer channel. The invention provides a multi-working-medium multi-cycle LNG cold energy utilization power generation system capable of adopting an ultralow temperature heat source. The system can effectively recover LNG cold energy, adopts multi-working-medium multi-cycle to perform multi-stage 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 and social benefits.

Description

Multistage LNG cold energy power generation and comprehensive utilization system and method

Technical Field

The invention belongs to the technical field of LNG comprehensive utilization, relates to a multi-stage LNG cold energy power generation and comprehensive utilization system and method, and particularly relates to a multi-working-medium multi-cycle LNG cold energy power generation and comprehensive utilization system and method adopting an ultralow temperature heat source.

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

Aiming at the defects in the prior art, the invention aims to provide a multi-stage LNG cold energy power generation and comprehensive utilization system and method. The system can effectively recover LNG cold energy, adopts multi-working-medium multi-cycle to perform multi-stage 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.

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

in a first aspect, the present invention provides a multi-stage LNG cold energy power generation and integrated utilization system, which includes at least two stages of cyclic power generation units.

The circulating power generation unit comprises an electric energy conversion device, an LNG heat exchange device and a secondary refrigerant heat exchange device which are sequentially and circularly connected along the flow direction of a circulating working medium; LNG heat transfer devices in each stage of circulating power generation unit are sequentially connected along the LNG flow direction to form an LNG heat transfer channel.

The invention provides a multi-working-medium multi-cycle LNG cold energy utilization power generation system capable of adopting an ultralow temperature heat source. The system can effectively recover LNG cold energy, adopts multi-working-medium multi-cycle to perform multi-stage 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 preferred technical scheme of the present invention, a pressurization device is disposed on a connection pipeline between the LNG heat exchange device and the secondary refrigerant heat exchange device.

Preferably, the supercharging device is a booster pump.

Preferably, the electric energy conversion device is a turbine.

As a preferable technical scheme, the circulating power generation unit further comprises a circulating working medium heat exchange device positioned between the LNG heat exchange device and the secondary refrigerant heat exchange device.

Preferably, a supercharging device is arranged on a connecting pipeline between the LNG heat exchange device and the circulating working medium heat exchange device.

Preferably, the LNG heat exchange device in the last stage of circulating power generation unit is further connected with a final stage heat exchange device along the LNG flow direction, and the LNG exchanges heat with the secondary refrigerant in the final stage heat exchange device.

According to a preferred technical scheme, the last stage of circulating power generation unit comprises an electric energy conversion device, an LNG heat exchange device, a supercharging device and a secondary refrigerant heat exchange device which are sequentially and circularly connected along the flow direction of the LNG in the LNG heat exchange channel, and the rest of the circulating power generation units at all stages comprise the electric energy conversion device, the LNG heat exchange device, the circulating working medium heat exchange device, the supercharging device and the secondary refrigerant heat exchange device which are sequentially and circularly connected along the flow direction of the circulating working medium.

Preferably, along the LNG flow direction in the LNG heat exchange channel, the outlet of the electric energy conversion device of the cyclic power generation unit is divided into two paths, one path is connected to the hot-side inlet of the LNG heat exchange device of the current-stage cyclic power generation unit, and the other path is connected to the hot-side inlet of the cyclic working medium heat exchange device of the previous-stage cyclic power generation unit.

Preferably, a hot side outlet of the LNG heat exchange device of the current-stage circulating power generation unit and a hot side outlet of the circulating working medium heat exchange device of the previous-stage circulating power generation unit are combined into one path and then connected with a supercharging device of the current-stage circulating power generation unit.

As a preferable technical scheme of the invention, the comprehensive utilization system comprises a primary circulation power generation unit and a secondary circulation power generation unit.

Preferably, the first-stage circulating power generation unit comprises a first electric energy conversion device, a first heat exchange device, a second heat exchange device and a third heat exchange device which are sequentially and circularly connected along the flow direction of the circulating working medium.

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

Preferably, the secondary circulation power generation unit comprises a second electric energy conversion device, a fourth heat exchange device and a sixth heat exchange device which are sequentially and circularly connected along the flow direction of the circulation working medium.

Preferably, a second pressure boosting device is arranged on a connecting pipeline between the fourth heat exchange device and the sixth heat exchange device.

Preferably, the first heat exchange device and the fourth heat exchange device are sequentially connected along the flow direction of the LNG to form an LNG channel, the LNG is introduced into the first heat exchange device to exchange heat with the circulating medium flowing out of the first electric energy conversion device, and the heat-exchanged LNG enters the fourth heat exchange device to exchange heat with the circulating medium flowing out of the second electric energy conversion device.

Preferably, the outlet of the second electric energy conversion device is divided into two paths, one path is connected with the hot side inlet of the second heat exchange device, the other path is connected with the hot side inlet of the fourth heat exchange device, the circulating working medium flowing out of the second electric energy conversion device is divided into two parts, one part enters the second heat exchange device to exchange heat with the circulating working medium flowing out of the first heat exchange device, and the other part enters the fourth heat exchange device to exchange heat with the LNG flowing out of the first heat exchange device.

Preferably, a hot side outlet of the second heat exchange device and a hot side outlet of the fourth heat exchange device are combined into one path and then connected with the second supercharging device, circulating working media discharged after heat exchange in the second heat exchange device and the fourth heat exchange device respectively converge and then are sent to the sixth heat exchange device through the second supercharging device, and heat exchange is carried out between the circulating working media and secondary refrigerant in the sixth heat exchange device.

Preferably, the comprehensive utilization system further comprises a final-stage heat exchange device connected with a cold-side outlet of the fourth heat exchange device, and the LNG flows out of the fourth heat exchange device and enters the final-stage heat exchange device to exchange heat with the coolant.

In a second aspect, the invention provides a multistage LNG cold energy power generation and comprehensive utilization method, and the comprehensive utilization system of the first aspect is adopted to comprehensively utilize the LNG cold energy.

The comprehensive utilization method comprises the following steps:

the circulating working medium enters the electric energy conversion device to do work for power generation and then enters the LNG heat exchange device, the LNG heat exchange device exchanges heat with LNG to cool the LNG and then is introduced into the secondary refrigerant heat exchange device to exchange heat with the secondary refrigerant, and the circulating working medium after heat exchange and temperature rise circularly flows back to the electric energy conversion device to realize circulating power generation; LNG flows through the LNG heat exchange devices of the circulating power generation units at all levels in sequence to complete multi-level heat exchange.

As a preferred technical scheme of the invention, the comprehensive utilization method specifically comprises the following steps:

the method comprises the following steps that (I) a first circulating working medium enters a first electric energy conversion device to do work and generate power, then is introduced into a first heat exchange device to exchange heat with LNG (liquefied natural gas) for cooling, the first circulating working medium after heat exchange is sent into a second heat exchange device through a first supercharging device, exchanges heat with part of second circulating working medium discharged by the second electric energy conversion device to heat, and the first circulating working medium after heat exchange enters a third heat exchange device to exchange heat with secondary refrigerant conveyed by a user needing cooling;

(II) the second circulating working medium enters a second electric energy conversion device to do work and generate power and then is divided into a first working medium and a second working medium, the first working medium enters a fourth heat exchange device to exchange heat with LNG flowing out of the first heat exchange device, the second working medium enters a second heat exchange device to exchange heat with the first circulating working medium entering the second heat exchange device in the step (I), the first working medium and the second working medium converge after being respectively subjected to heat exchange and enter a second supercharging device, and the first working medium and the second working medium are sent into a sixth heat exchange device through the second supercharging device to exchange heat with secondary refrigerant conveyed by a user needing cooling;

and (III) allowing the LNG to enter a first heat exchange device to exchange heat with the circulating medium flowing out of the first electric energy conversion device in the step (I), allowing the LNG after heat exchange to enter a fourth heat exchange device to exchange heat with a second working medium flowing out of the second electric energy conversion device in the step (II), and allowing the LNG after heat exchange to enter a final-stage heat exchange device to exchange heat with a secondary refrigerant conveyed by a user needing cooling.

As a preferable technical scheme of the invention, in the step (I), the first cycle working medium is an organic working medium.

Preferably, the first cycle fluid is methane, ethane, trifluoromethane or liquid ammonia.

Preferably, the input temperature of the first cycle fluid is 0 to 10 ℃, 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 range of values are also applicable.

Preferably, the input pressure of the first cycle fluid is 2 to 3MPa, and may be, for example, 2.0MPa, 2.1MPa, 2.2MPa, 2.3MPa, 2.4MPa, 2.5MPa, 2.6MPa, 2.7MPa, 2.8MPa, 2.9MPa or 3.0MPa, but is not limited to the recited values, and other values not recited in this range are equally applicable.

Preferably, the temperature of the first cycle fluid after work and power generation in the first electric energy conversion device is reduced to-80 to-60 ℃, for example, the temperature can be-80 ℃, 79 ℃, 78 ℃, 77 ℃, 76 ℃, 75 ℃, 74 ℃, 73 ℃, 72 ℃, 71 ℃, 70 ℃, 69 ℃, 68 ℃, 67 ℃, 66 ℃, 65 ℃, 64 ℃, 63 ℃, 62 ℃, 61 ℃ or-60 ℃, but the temperature 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 first cycle fluid after power generation in the first electric energy conversion device is reduced to 0.1-0.2 MPa, such as 0.10MPa, 0.11MPa, 0.12MPa, 0.13MPa, 0.14MPa, 0.15MPa, 0.16MPa, 0.17MPa, 0.18MPa, 0.19MPa or 0.20MPa, but not limited to the recited values, and other values in the range are also applicable.

Preferably, the first circulating medium is cooled to be liquefied through heat exchange in the first heat exchange device.

Preferably, said first circulating medium is cooled in the first heat exchange means to-90 to-70 ℃ by heat exchange, and may be, for example, -90 ℃, -89 ℃, -88 ℃, -87 ℃, -86 ℃, -85 ℃, -84 ℃, -83 ℃, -82 ℃, -81 ℃, -80 ℃, -79 ℃, -78 ℃, -77 ℃, -76 ℃, -75 ℃, -74 ℃, -73 ℃, -72 ℃, -71 ℃ or-70 ℃, but is not limited to the values recited, and other values not recited in this range of values are equally applicable.

Preferably, the first circulating medium is pressurized by the first pressurizing means to 2 to 3MPa, for example, 2.0MPa, 2.1MPa, 2.2MPa, 2.3MPa, 2.4MPa, 2.5MPa, 2.6MPa, 2.7MPa, 2.8MPa, 2.9MPa or 3.0MPa, but not limited to the values listed, and other values not listed in the range of values are also applicable.

Preferably, said first circulating medium is warmed to-60 to-40 ℃ in the second heat exchange means by heat exchange, 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 recited, and other values not recited in this range of values are equally applicable.

Preferably, the temperature of the first circulating medium is raised to 0 to 10 ℃ by heat exchange in the third heat exchange device, 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 secondary refrigerant is ethylene glycol or calcium chloride.

Preferably, the coolant is delivered to the user in a temperature range of 5 to 15 deg.C, such as 5 deg.C, 6 deg.C, 7 deg.C, 8 deg.C, 9 deg.C, 10 deg.C, 11 deg.C, 12 deg.C, 13 deg.C, 14 deg.C or 15 deg.C, but not limited to the values recited, and other values not recited in this range are equally applicable.

Preferably, the coolant is cooled to-50 to-30 ℃ in the third heat exchange device by heat exchange, for example, the coolant may be-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 listed, and other values not listed in the range of values are equally applicable.

As a preferable technical scheme of the invention, in the step (II), the second cycle working medium is an organic working medium.

Preferably, the temperature of the second cycle fluid after working and power generation in the second electric energy conversion device is not higher than the temperature of the first cycle fluid after working and power generation in the first electric energy conversion device.

Preferably, the temperature of the second cycle fluid after work and power generation is reduced to-50 to-40 ℃, 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 the range of values are equally applicable.

Preferably, the second cycle fluid is ethane, ethylene, propane, difluoromethane or liquid nitrogen.

Preferably, the input temperature of the second cycle fluid is 0 to 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 values are also applicable.

Preferably, the input pressure of the second cycle fluid is 0.5 to 1MPa, for example 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa, 0.9MPa or 1.0MPa, but not limited to the values listed, and other values not listed in this range are equally applicable.

Preferably, the second cycle working medium is divided into a first working medium and a second working medium according to volume after acting to generate power.

Preferably, the first working fluid accounts for 60-80% of the total volume of the second working fluid, for example, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79% or 80%, but not limited to the recited values, and other values not recited in the range of values are also applicable.

Preferably, said first working fluid is cooled in the fourth heat exchange means to-55 to-45 ℃ by heat exchange, for example-55 ℃, -54 ℃, -53 ℃, -52 ℃, -51 ℃, -50 ℃, -49 ℃, -48 ℃, -47 ℃, -46 ℃ or-45 ℃, but is not limited to the values listed, and other values not listed in this range are equally applicable.

Preferably, said second working fluid is cooled in the second heat exchange means to-55 to-45 ℃ by heat exchange, for example-55 ℃, -54 ℃, -53 ℃, -52 ℃, -51 ℃, -50 ℃, -49 ℃, -48 ℃, -47 ℃, -46 ℃ or-45 ℃, but is not limited to the values listed, and other values not listed in this range are equally applicable.

Preferably, the first working medium and the second working medium are merged and then pressurized to 0.8 to 1.5MPa, for example, 0.8MPa, 0.9MPa, 1.0MPa, 1.1MPa, 1.2MPa, 1.3MPa, 1.4MPa or 1.5MPa by the second pressurizing device, but the values are not limited to the values listed, and other values not listed in the range of the values are also applicable.

Preferably, the first working medium and the second working medium are converged and then sent to the sixth heat exchange device through the second supercharging device to exchange heat with the coolant conveyed by the user needing cooling to 0-10 ℃, for example, 0 ℃, 1 ℃, 2 ℃, 3 ℃, 4 ℃, 5 ℃, 6 ℃, 7 ℃, 8 ℃, 9 ℃ or 10 ℃, but not limited to the enumerated values, and other non-enumerated values in the numerical range are also applicable.

Preferably, the pressure of the converged first working medium and second working medium after the converged first working medium and second working medium are sent to the sixth heat exchange device through the second supercharging device to exchange heat with the coolant conveyed by the user needing cooling is 0.5 to 1MPa, for example, 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa, 0.9MPa or 1.0MPa, but the pressure is not limited to the values listed, and other values not listed in the range of the values are also applicable.

Preferably, the secondary refrigerant is ethylene glycol or calcium chloride.

Preferably, the coolant is cooled to-50 to-30 ℃ in the sixth heat exchange device by heat exchange, for example, the coolant may be-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 listed, and other values not listed in the range of values are equally applicable.

In a preferred embodiment of the present invention, in the step (iii), the LNG feed pressure is 5 to 10MPa, for example, 5MPa, 6MPa, 7MPa, 8MPa, 9MPa or 10MPa, but the LNG feed pressure is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.

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

Preferably, the LNG is warmed to-90 to-80 ℃ by heat exchange in the first heat exchange means, and may be, for example, -90 ℃, -89 ℃, -88 ℃, -87 ℃, -86 ℃, -85 ℃, -84 ℃, -83 ℃, -82 ℃, -81 ℃ or-80 ℃, but is not limited to the recited values, and other values not recited in this range are equally applicable.

Preferably, the LNG is warmed to-60 to-50 ℃ in the fourth heat exchange means by heat exchange, and may be, for example, -60 ℃, -59 ℃, -58 ℃, -57 ℃, -56 ℃, -55 ℃, -54 ℃, -53 ℃, -52 ℃, -51 ℃ or-50 ℃, but is not limited to the recited values, and other values not recited in this range are equally applicable.

Preferably, the LNG is gasified to obtain natural gas after heat exchange in the final heat exchange device.

Preferably, the LNG is heated to 0 to 10 ℃ by heat exchange in the final heat exchanger, and may be, for example, 0 ℃, 1 ℃, 2 ℃, 3 ℃, 4 ℃, 5 ℃, 6 ℃, 7 ℃, 8 ℃, 9 ℃ or 10 ℃, but not limited to the values listed, and other values not listed in the range of the values are also applicable.

Preferably, the LNG is discharged into a natural gas pipe network after heat exchange in the final heat exchange device.

Preferably, the secondary refrigerant is ethylene glycol or calcium chloride.

Preferably, the coolant is cooled to-50 to-30 ℃ in the final heat exchanger, such as-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 listed, and other values not listed in the range of values are equally suitable.

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 the secondary refrigerant.

(2) The invention fully utilizes the cold energy utilization under different temperature gradients and has high energy utilization efficiency. Simultaneously this application chooses for use multiple independent working medium circulation power generation system, and the circulation working medium adopts different temperature utilization scope, with LNG intensification process phase-match, has great advantage on cold energy generating efficiency.

(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. The system provided by the invention adopts independent circulation of various circulating working media, and simultaneously considers different temperature gradients for heat exchange, so that the temperature difference is proper, the irreversible loss in the heat exchange process is small, and the energy utilization rate is high.

Drawings

Fig. 1 is a schematic structural diagram of a two-stage 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 a two-stage LNG cold energy power generation and comprehensive utilization system according to embodiment 2 of the present invention;

fig. 3 is a schematic structural diagram of a two-stage LNG cold energy power generation and comprehensive utilization system according to embodiment 3 of the present invention;

fig. 4 is a schematic structural diagram of a three-stage LNG cold energy power generation and comprehensive utilization system according to embodiment 4 of the present invention;

fig. 5 is a schematic structural diagram of a three-stage LNG cold energy power generation and comprehensive utilization system according to embodiment 5 of the present invention;

fig. 6 is a schematic structural diagram of a three-stage LNG cold energy power generation and comprehensive utilization system according to embodiment 6 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-sixth heat exchange device; 7-a seventh heat exchange device; 8-an eighth heat exchange device; 9-a ninth heat exchange device; 10-a first electrical energy conversion device; 11-a second electrical energy conversion device; 12-a third electrical energy conversion device; 13-a first supercharging device; 14-a second supercharging device; 15-a third supercharging device; 16-final stage heat exchange 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.

Example 1

The present embodiment provides an integrated utilization system as described in fig. 1, which includes a primary circulating power generation unit and a secondary circulating power generation unit.

The first-stage circulating power generation unit comprises a first electric energy conversion device 10, a first heat exchange device 1, a first supercharging device 13 and a third heat exchange device 3 which are sequentially and circularly connected along the flow direction of a circulating working medium. The circulating working medium performs work to generate power in the first electric energy conversion device 10, then enters the first heat exchange device 1 to exchange heat with LNG, the circulating working medium after heat exchange is pumped into the third heat exchange device 3 through the first supercharging device 13 to exchange heat with the secondary refrigerant conveyed by a user needing cooling, and the circulating working medium after heat exchange enters the first electric energy conversion device 10 to realize circulating work to generate power.

The secondary circulation power generation unit comprises a second electric energy conversion device 11, a fourth heat exchange device 4, a second supercharging device 14 and a sixth heat exchange device 6 which are sequentially and circularly connected along the flow direction of the circulation working medium. The circulating working medium performs work in the second electric energy conversion device 11 to generate power, then enters the fourth heat exchange device 4 to exchange heat with LNG, the circulating working medium after heat exchange is pumped into the sixth heat exchange device 6 through the second supercharging device 14 to exchange heat with the secondary refrigerant conveyed by the user needing cooling, and the circulating working medium after heat exchange enters the second electric energy conversion device 11 to realize the power generation by performing the circulating work

A cold side outlet of the first heat exchange device 1 is connected with a cold side inlet of the fourth heat exchange device 4, the LNG is introduced into the first heat exchange device 1 to exchange heat with the circulating medium flowing out of the first electric energy conversion device 10, and the heat-exchanged LNG enters the fourth heat exchange device 4 to exchange heat with the circulating medium flowing out of the second electric energy conversion device 11.

The comprehensive utilization system also comprises a final-stage heat exchange device 16 connected with a cold side outlet of the fourth heat exchange device 4, and LNG flows out of the fourth heat exchange device 4 and then enters the final-stage heat exchange device 16 to exchange heat with the secondary refrigerant.

In the present embodiment, the first and second boosting

devices

13 and 14 are booster pumps, and the first and second electric

energy conversion devices

10 and 11 are turbines.

Example 2

The present embodiment provides an integrated utilization system as shown in fig. 2, which includes a primary circulating power generation unit and a secondary circulating power generation unit.

The primary circulating power generation unit comprises a first electric energy conversion device 10, a first heat exchange device 1, a first supercharging device 13, a second heat exchange device 2 and a third heat exchange device 3 which are sequentially and circularly connected along the flow direction of a circulating working medium. The circulating working medium performs work power generation in the first electric energy conversion device 10, then enters the first heat exchange device 1 to exchange heat with LNG, the circulating working medium after heat exchange is pumped into the second heat exchange device 2 through the first supercharging device 13, the circulating working medium performs secondary heat exchange in the second heat exchange device 2, then enters the third heat exchange device 3, performs heat exchange with coolant conveyed by a user needing cooling in the third heat exchange device 3, and the circulating working medium after heat exchange enters the first electric energy conversion device 10 to realize circulating work power generation.

The secondary circulation power generation unit comprises a second electric energy conversion device 11, a fourth heat exchange device 4, a second supercharging device 14, a fifth heat exchange device 5 and a sixth heat exchange device 6 which are sequentially and circularly connected along the flow direction of the circulation working medium. The circulating working medium performs work in the second electric energy conversion device 11 to generate power, then enters the fourth heat exchange device 4 to exchange heat with LNG, the circulating working medium after heat exchange is pumped into the fifth heat exchange device 5 through the second supercharging device 14, the circulating working medium performs secondary heat exchange in the fifth heat exchange device 5 and then enters the sixth heat exchange device 6, the circulating working medium after heat exchange exchanges heat with the secondary refrigerant conveyed by the user needing cooling in the sixth heat exchange device 6, and the circulating working medium after heat exchange enters the second electric energy conversion device 11 to realize circulating work and power generation.

In the present embodiment, the first and second boosting

devices

13 and 14 are booster pumps, and the first and second electric

energy conversion devices

10 and 11 are turbines.

Example 3

The present embodiment provides an integrated utilization system as shown in fig. 3, which includes a primary circulating power generation unit and a secondary circulating power generation unit.

The primary circulating power generation unit comprises a first electric energy conversion device 10, a first heat exchange device 1, a first supercharging device 13, a second heat exchange device 2 and a third heat exchange device 3 which are sequentially and circularly connected along the flow direction of a circulating working medium. The circulating working medium performs work in the first electric energy conversion device 10 to generate power, then enters the first heat exchange device 1 to exchange heat with LNG to cool, the circulating working medium after heat exchange is sent into the second heat exchange device 2 through the first supercharging device 13, exchanges heat with part of the circulating working medium discharged by the second electric energy conversion device 11 in the second heat exchange device 2, and the circulating working medium after heat exchange enters the third heat exchange device 3 to exchange heat with the secondary refrigerant conveyed by the user needing cooling.

The secondary circulation power generation unit comprises a second electric energy conversion device 11, a fourth heat exchange device 4, a second supercharging device 14 and a sixth heat exchange device 6 which are sequentially and circularly connected along the flow direction of the circulation working medium. The outlet of the second electric energy conversion device 11 is divided into two paths, one path is connected with the hot side inlet of the second heat exchange device 2, and the other path is connected with the hot side inlet of the fourth heat exchange device 4. The circulating working medium is divided into two parts after acting to generate power in the second electric energy conversion device 11, one part enters the second heat exchange device 2 to exchange heat with the circulating working medium flowing out of the first heat exchange device 1, and the other part enters the fourth heat exchange device 4 to exchange heat with the LNG flowing out of the first heat exchange device 1. And a hot side outlet of the second heat exchange device 2 and a hot side outlet of the fourth heat exchange device 4 are combined into a path and then connected with a second supercharging device 14, circulating working media discharged after heat exchange in the second heat exchange device 2 and the fourth heat exchange device 4 respectively converge and then are sent into a sixth heat exchange device 6 through the second supercharging device 14, and heat exchange with secondary refrigerant is carried out in the sixth heat exchange device 6.

A cold side outlet of the first heat exchange device 1 is connected with a cold side inlet of the fourth heat exchange device 4, the LNG is introduced into the first heat exchange device 1 to exchange heat with the circulating medium flowing out of the first electric energy conversion device 10, and the heat-exchanged LNG enters the fourth heat exchange device 4 to exchange heat with part of the circulating medium flowing out of the second electric energy conversion device 11.

In the present embodiment, the first and second boosting

devices

13 and 14 are booster pumps, and the first and second electric

energy conversion devices

10 and 11 are turbines.

Example 4

The embodiment provides a comprehensive utilization system as shown in fig. 4, and the comprehensive utilization system comprises a primary circulating power generation unit, a secondary circulating power generation unit and a tertiary circulating power generation unit.

The secondary circulation power generation unit comprises a second electric energy conversion device 11, a fourth heat exchange device 4, a second supercharging device 14 and a sixth heat exchange device 6 which are sequentially and circularly connected along the flow direction of the circulation working medium. The circulating working medium performs work in the second electric energy conversion device 11 to generate power, then enters the fourth heat exchange device 4 to exchange heat with LNG, the circulating working medium after heat exchange is pumped into the sixth heat exchange device 6 through the second supercharging device 14 to exchange heat with the secondary refrigerant conveyed by the user needing cooling, and the circulating working medium after heat exchange enters the second electric energy conversion device 11 to realize circulating work and power generation.

The three-stage circulation power generation unit comprises a third electric energy conversion device 12, a seventh heat exchange device 7, a third supercharging device 15 and a ninth heat exchange device 9 which are sequentially and circularly connected along the flow direction of the circulation working medium. The circulating working medium performs work in the third electric energy conversion device 12 to generate power, then enters the seventh heat exchange device 7 to exchange heat with LNG, the circulating working medium after heat exchange is pumped into the ninth heat exchange device 9 through the third supercharging device 15 to exchange heat with the secondary refrigerant conveyed by the user needing cooling, and the circulating working medium after heat exchange enters the third electric energy conversion device 12 to realize circulating work and power generation.

A cold side outlet of the first heat exchange device 1 is connected with a cold side inlet of the fourth heat exchange device 4, a cold side outlet of the fourth heat exchange device 4 is connected with a cold side inlet of the seventh heat exchange device 7, the LNG is introduced into the first heat exchange device 1 to exchange heat with the circulating medium flowing out of the first electric energy conversion device 10, the heat-exchanged LNG enters the fourth heat exchange device 4 to exchange heat with the circulating medium flowing out of the second electric energy conversion device 11, and the heat-exchanged LNG enters the seventh heat exchange device 7 to exchange heat with the circulating medium flowing out of the third electric energy conversion device 12.

The comprehensive utilization system also comprises a final-stage heat exchange device 16 connected with a cold side outlet of the seventh heat exchange device 7, and LNG flows out of the seventh heat exchange device 7 and enters the final-stage heat exchange device 16 to exchange heat with the secondary refrigerant.

In the present embodiment, the first to third

pressure boosting devices

13, 14, and 15 are booster pumps, and the first to third electric

energy conversion devices

10, 11, and 12 are turbines.

Example 5

The present embodiment provides an integrated utilization system as shown in fig. 5, which includes a primary circulating power generation unit and a secondary circulating power generation unit.

The three-stage circulation power generation unit comprises a third electric energy conversion device 12, a seventh heat exchange device 7, a third supercharging device 15, an eighth heat exchange device 8 and a ninth heat exchange device 9 which are sequentially and circularly connected along the flow direction of a circulation working medium. The circulating working medium performs work in the third electric energy conversion device 12 to generate power, then enters the seventh heat exchange device 7 to exchange heat with LNG, the circulating working medium after heat exchange is pumped into the eighth heat exchange device 8 through the third supercharging device 15, the circulating working medium performs secondary heat exchange in the eighth heat exchange device 8, then enters the ninth heat exchange device 9, performs heat exchange with the secondary refrigerant conveyed by the user needing cooling in the ninth heat exchange device 9, and the circulating working medium after heat exchange enters the third electric energy conversion device 12 to realize circulating work and power generation.

In the present embodiment, the first to third

pressure boosting devices

13, 14, and 15 are booster pumps, and the first to third electric

energy conversion devices

10, 11, and 12 are turbines.

Example 6

The present embodiment provides an integrated utilization system as shown in fig. 6, which includes a primary circulating power generation unit and a secondary circulating power generation unit.

The secondary circulation power generation unit comprises a second electric energy conversion device 11, a fourth heat exchange device 4, a second supercharging device 14, a fifth heat exchange device 5 and a sixth heat exchange device 6 which are sequentially and circularly connected along the flow direction of the circulation working medium. The outlet of the second electric energy conversion device 11 is divided into two paths, one path is connected with the hot side inlet of the second heat exchange device 2, and the other path is connected with the hot side inlet of the fourth heat exchange device 4. The circulating working medium is divided into two parts after acting to generate power in the second electric energy conversion device 11, one part enters the second heat exchange device 2 to exchange heat with the circulating working medium flowing out of the first heat exchange device 1, and the other part enters the fourth heat exchange device 4 to exchange heat with the LNG flowing out of the first heat exchange device 1. And a hot side outlet of the second heat exchange device 2 and a hot side outlet of the fourth heat exchange device 4 are combined into a whole and then connected with a second supercharging device 14, circulating working media discharged after heat exchange in the second heat exchange device 2 and the fourth heat exchange device 4 respectively converge and then are sent into a fifth heat exchange device 5 through the second supercharging device 14, and enter a sixth heat exchange device 6 after exchanging heat with a circulating medium in the fifth heat exchange device 5, and exchange heat with secondary refrigerant in the sixth heat exchange device 6.

The three-stage circulation power generation unit comprises a third electric energy conversion device 12, a seventh heat exchange device 7, a third supercharging device 15 and a ninth heat exchange device 9 which are sequentially and circularly connected along the flow direction of the circulation working medium. The outlet of the third electric energy conversion device 12 is divided into two paths, one path is connected with the hot side inlet of the fifth heat exchange device 5, and the other path is connected with the hot side inlet of the seventh heat exchange device 7. The circulating working medium is divided into two parts after acting to generate power in the third electric energy conversion device 12, one part enters the fifth heat exchange device 5 to exchange heat with the converged circulating working medium discharged by the second heat exchange device 2 and the fourth heat exchange device 4, and the other part enters the seventh heat exchange device 7 to exchange heat with the LNG flowing out of the fourth heat exchange device 4. And a hot side outlet of the fifth heat exchange device 5 and a hot side outlet of the seventh heat exchange device 7 are combined into a path and then connected with a third supercharging device 15, circulating working media discharged after heat exchange in the fifth heat exchange device 5 and the seventh heat exchange device 7 respectively converge and then are sent into a ninth heat exchange device 9 through the third supercharging device 15, and heat exchange with secondary refrigerant is carried out in the ninth heat exchange device 9.

A cold side outlet of the first heat exchange device 1 is connected with a cold side inlet of the fourth heat exchange device 4, a cold side outlet of the fourth heat exchange device 4 is connected with a cold side inlet of the seventh heat exchange device 7, the LNG is introduced into the first heat exchange device 1 to exchange heat with the circulating medium flowing out of the first electric energy conversion device 10, the heat-exchanged LNG enters the fourth heat exchange device 4 to exchange heat with a part of the circulating medium flowing out of the second electric energy conversion device 11, and the heat-exchanged LNG enters the seventh heat exchange device 7 to exchange heat with a part of the circulating medium flowing out of the third electric energy conversion device 12.

In the present embodiment, the first to third

pressure boosting devices

13, 14, and 15 are booster pumps, and the first to third electric

energy conversion devices

10, 11, and 12 are turbines.

Example 7

The comprehensive utilization system provided by the embodiment 3 is adopted to comprehensively utilize the cold energy of the LNG, and the comprehensive utilization method specifically comprises the following steps:

the method comprises the following steps that (I) first cycle working medium trifluoromethane with the input temperature of 5 ℃ and the input pressure of 2.4MPa enters a first electric energy conversion device 10 to do work and generate electricity, the temperature is reduced to-75 ℃, and the pressure is reduced to 0.15 MPa;

the first circulating working medium after acting and generating power enters a first heat exchange device 1 to exchange heat with LNG, cool to-83 ℃ and liquefy;

the heat-exchanged first circulating working medium is pressurized to 2.5MPa by the first pressurizing device 13 and then sent into the second heat exchange device 2, and exchanges heat with part of the second circulating working medium discharged by the second electric energy conversion device 11 and is heated to-48 ℃;

the first circulating working medium after heat exchange enters a third heat exchange device 3 to exchange heat with the secondary refrigerant glycol with the temperature of 10 ℃ conveyed by a user needing cooling, the temperature of the first circulating medium after heat exchange is raised to 5 ℃, and the temperature of the secondary refrigerant is lowered to minus 36 ℃;

(II) the temperature of the second cycle working medium difluoromethane with the input temperature of 5 ℃ and the input pressure of 0.95MPa is reduced to minus 45 ℃ after entering a second electric energy conversion device 11 to do work and generate electricity;

the second circulating medium after acting and generating power is divided into a first working medium and a second working medium according to the volume, wherein the first working medium accounts for 70% of the total volume of the second circulating working medium;

the first working medium enters the fourth heat exchange device 4 to exchange heat with LNG flowing out of the first heat exchange device 1 and is cooled to-48 ℃;

the second working medium enters the second heat exchange device 2 to exchange heat with the first circulating working medium entering the second heat exchange device 2 in the step (I) and cool to-48 ℃;

the first working medium and the second working medium respectively exchange heat and then converge to form a mixed working medium, the mixed working medium enters the second supercharging device 14, the mixed working medium is supercharged to 1MPa by the second supercharging device 14 and then is sent into the sixth heat exchange device 6 to exchange heat with the secondary refrigerant glycol with the temperature of 10 ℃ conveyed by a user needing cooling, the temperature of the mixed working medium after heat exchange is raised to 5 ℃, and the temperature of the secondary refrigerant after heat exchange is lowered to-36 ℃.

(III) LNG which is delivered from an LNG receiving station and has the pressure of 10MPa and the temperature of-150 ℃ enters a first heat exchange device 1 to exchange heat with the circulating medium flowing out of the first electric energy conversion device 10 in the step (I), and the LNG is heated to-83 ℃ through heat exchange;

the LNG subjected to heat exchange and temperature rise enters a fourth heat exchange device 4 to exchange heat with a second working medium flowing out of the second electric energy conversion device 11 in the step (II), and the LNG is subjected to heat exchange and temperature rise to-53 ℃;

the LNG after heat exchange enters a final-stage heat exchange device 16 to exchange heat with the coolant glycol with the temperature of 10 ℃ conveyed by a user needing cooling, the LNG after heat exchange is heated to 5 ℃, and the coolant after heat exchange is cooled to-36 ℃.

Example 8

The difference between the embodiment and embodiment 7 is that the secondary refrigerant is replaced by seawater, the seawater is used for exchanging heat with the first cycle working medium in the third heat exchange device, and the seawater is used for exchanging heat with the second cycle working medium in the sixth heat exchange device, so that the power generation requirement of the cycle working medium is met after heat exchange; and exchanging heat with the LNG in the final-stage heat exchange device, so that the LNG after heat exchange meets the gasification requirement.

The other operation steps and process parameters were exactly the same as in example 7.

Example 9

the method comprises the following steps that (I) first cycle working medium methane with the input temperature of 0 ℃ and the input pressure of 3MPa enters a first electric energy conversion device 10 to do work and generate electricity, the temperature is reduced to-80 ℃, and the pressure is reduced to 0.2 MPa;

the first circulating working medium after acting and generating power enters a first heat exchange device 1 to exchange heat with LNG, cool to-90 ℃ and liquefy;

the first circulating working medium after heat exchange is pressurized to 3MPa by the first pressurizing device 13 and then sent to the second heat exchange device 2, and exchanges heat with part of the second circulating working medium discharged by the second electric energy conversion device 11 and heats up to-60 ℃;

the first circulating working medium after heat exchange enters a third heat exchange device 3 to exchange heat with the secondary refrigerant calcium chloride at 5 ℃ conveyed by a user needing cooling, the temperature of the first circulating medium after heat exchange is raised to 0 ℃, and the temperature of the secondary refrigerant is lowered to-50 ℃;

(II) feeding a second cycle working medium ethane with the input temperature of 0 ℃ and the input pressure of 1MPa into a second electric energy conversion device 11 to do work and generate electricity, and then reducing the temperature to-50 ℃;

the second circulating medium after acting and generating power is divided into a first working medium and a second working medium according to the volume, wherein the first working medium accounts for 60% of the total volume of the second circulating working medium;

the first working medium enters the fourth heat exchange device 4 to exchange heat with LNG flowing out of the first heat exchange device 1 and is cooled to-55 ℃;

the second working medium enters the second heat exchange device 2 to exchange heat with the first circulating working medium entering the second heat exchange device 2 in the step (I) and cool to-55 ℃;

the first working medium and the second working medium respectively exchange heat and then converge to form a mixed working medium to enter the second supercharging device 14, the mixed working medium is supercharged to 1.5MPa by the second supercharging device 14 and then is sent into the sixth heat exchange device 6 to exchange heat with the secondary refrigerant calcium chloride at 5 ℃ conveyed by a user needing cooling, the temperature of the mixed working medium after heat exchange is raised to 0 ℃, and the temperature of the secondary refrigerant after heat exchange is lowered to-50 ℃.

(III) LNG which is delivered from an LNG receiving station and has the pressure of 5MPa and the temperature of-160 ℃ enters a first heat exchange device 1 to exchange heat with the circulating medium flowing out from the first electric energy conversion device 10 in the step (I), and the LNG is heated to-90 ℃ through heat exchange;

the LNG subjected to heat exchange and temperature rise enters a fourth heat exchange device 4 to exchange heat with a second working medium flowing out of the second electric energy conversion device 11 in the step (II), and the LNG is subjected to heat exchange and temperature rise to-60 ℃;

the LNG after heat exchange enters a final-stage heat exchange device 16 to exchange heat with the secondary refrigerant calcium chloride at 5 ℃ conveyed by a user needing cooling, the LNG after heat exchange is heated to 0 ℃, and the secondary refrigerant after heat exchange is cooled to-50 ℃.

Example 10

the method comprises the following steps that (I) first cycle working medium ethane with the input temperature of 5 ℃ and the input pressure of 2.5MPa enters a first electric energy conversion device 10 to do work and generate electricity, the temperature is reduced to-70 ℃, and the pressure is reduced to 0.15 MPa;

the first circulating working medium after acting and generating power enters a first heat exchange device 1 to exchange heat with LNG, cool to-80 ℃ and liquefy;

the heat-exchanged first circulating working medium is pressurized to 2.5MPa by the first pressurizing device 13 and then sent into the second heat exchange device 2, and exchanges heat with part of the second circulating working medium discharged by the second electric energy conversion device 11 and is heated to-50 ℃;

the first circulating working medium after heat exchange enters a third heat exchange device 3 to exchange heat with the secondary refrigerant glycol with the temperature of 10 ℃ conveyed by a user needing cooling, the temperature of the first circulating medium after heat exchange is raised to 5 ℃, and the temperature of the secondary refrigerant is lowered to-40 ℃;

(II) feeding a second circulating working medium ethylene with the input temperature of 5 ℃ and the input pressure of 0.7MPa into a second electric energy conversion device 11 to do work and generate electricity, and then reducing the temperature to-45 ℃;

the first working medium enters the fourth heat exchange device 4 to exchange heat with LNG flowing out of the first heat exchange device 1 and is cooled to-50 ℃;

the second working medium enters the second heat exchange device 2 to exchange heat with the first circulating working medium entering the second heat exchange device 2 in the step (I) and cool to-50 ℃;

the first working medium and the second working medium respectively exchange heat and then converge to form a mixed working medium to enter the second supercharging device 14, the mixed working medium is supercharged to 1.2MPa by the second supercharging device 14 and then is sent into the sixth heat exchange device 6 to exchange heat with the secondary refrigerant glycol of 10 ℃ conveyed by a user needing cooling, the temperature of the mixed working medium after heat exchange is raised to 5 ℃, and the temperature of the secondary refrigerant after heat exchange is lowered to-40 ℃.

(III) LNG which is delivered from an LNG receiving station and has the pressure of 10MPa and the temperature of-150 ℃ enters a first heat exchange device 1 to exchange heat with the circulating medium flowing out of the first electric energy conversion device 10 in the step (I), and the LNG is heated to-85 ℃ through heat exchange;

the LNG subjected to heat exchange and temperature rise enters a fourth heat exchange device 4 to exchange heat with a second working medium flowing out of the second electric energy conversion device 11 in the step (II), and the LNG is subjected to heat exchange and temperature rise to-55 ℃;

the LNG after heat exchange enters a final-stage heat exchange device 16 to exchange heat with the coolant glycol with the temperature of 10 ℃ conveyed by a user needing cooling, the LNG after heat exchange is heated to 5 ℃, and the coolant after heat exchange is cooled to-40 ℃.

Example 11

the method comprises the following steps that (I) first cycle working medium liquid ammonia with the input temperature of 10 ℃ and the input pressure of 2MPa enters a first electric energy conversion device 10 to do work and generate electricity, the temperature is reduced to-60 ℃, and the pressure is reduced to 0.1 MPa;

the first circulating working medium after acting and generating power enters a first heat exchange device 1 to exchange heat with LNG, cool to-70 ℃ and liquefy;

the first circulating working medium after heat exchange is pressurized to 2MPa by the first pressurizing device 13 and then sent into the second heat exchange device 2, and exchanges heat with part of the second circulating working medium discharged by the second electric energy conversion device 11 and is heated to-40 ℃;

the first circulating working medium after heat exchange enters a third heat exchange device 3 to exchange heat with secondary refrigerant calcium chloride at 15 ℃ conveyed by a user needing cooling, the temperature of the first circulating medium after heat exchange is raised to 10 ℃, and the temperature of the secondary refrigerant is lowered to-30 ℃;

(II) the temperature of a second circulation working medium propane with the input temperature of 10 ℃ and the input pressure of 0.5MPa is reduced to-40 ℃ after the second circulation working medium propane enters a second electric energy conversion device 11 to do work and generate electricity;

the second circulating medium after acting and generating power is divided into a first working medium and a second working medium according to the volume, wherein the first working medium accounts for 80% of the total volume of the second circulating working medium;

the first working medium enters the fourth heat exchange device 4 to exchange heat with LNG flowing out of the first heat exchange device 1 and is cooled to-45 ℃;

the second working medium enters the second heat exchange device 2 to exchange heat with the first circulating working medium entering the second heat exchange device 2 in the step (I) and cool to-45 ℃;

the first working medium and the second working medium respectively exchange heat and then converge to form a mixed working medium to enter the second supercharging device 14, the mixed working medium is supercharged to 0.8MPa by the second supercharging device 14 and then is sent into the sixth heat exchange device 6 to exchange heat with the secondary refrigerant calcium chloride at 15 ℃ conveyed by a user needing cooling, the temperature of the mixed working medium after heat exchange is raised to 10 ℃, and the temperature of the secondary refrigerant after heat exchange is lowered to-30 ℃.

(III) LNG which is delivered from an LNG receiving station and has the pressure of 10MPa and the temperature of-140 ℃ enters a first heat exchange device 1 to exchange heat with the circulating medium flowing out of the first electric energy conversion device 10 in the step (I), and the LNG is heated to-80 ℃ through heat exchange;

the LNG subjected to heat exchange and temperature rise enters a fourth heat exchange device 4 to exchange heat with a second working medium flowing out of the second electric energy conversion device 11 in the step (II), and the LNG is subjected to heat exchange and temperature rise to-50 ℃;

the LNG after heat exchange enters a final-stage heat exchange device 16 to exchange heat with the secondary refrigerant calcium chloride at 15 ℃ conveyed by a user needing cooling, the LNG after heat exchange is heated to 10 ℃, and the secondary refrigerant after heat exchange is cooled to-30 ℃.

The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.

Claims

1. The multi-stage LNG cold energy power generation and comprehensive utilization system is characterized by comprising at least two stages of circulating power generation units;

2. The comprehensive utilization system of claim 1, wherein a pressure boosting device is disposed on the connecting pipeline between the LNG heat exchange device and the coolant heat exchange device;

preferably, the supercharging device is a booster pump;

preferably, the electric energy conversion device is a turbine.

3. The comprehensive utilization system of claim 1 or 2, wherein the cyclic power generation unit further comprises a cycle fluid heat exchange device located between the LNG heat exchange device and the coolant heat exchange device;

preferably, a supercharging device is arranged on a connecting pipeline between the LNG heat exchange device and the circulating working medium heat exchange device;

4. The comprehensive utilization system according to any one of claims 1 to 3, wherein along the flow direction of LNG in the LNG heat exchange channel, the last stage of circulating power generation unit comprises an electric energy conversion device, an LNG heat exchange device, a supercharging device and a secondary refrigerant heat exchange device which are sequentially and circularly connected along the flow direction of a circulating working medium, and the rest of the stages of circulating power generation units comprise the electric energy conversion device, the LNG heat exchange device, the circulating working medium heat exchange device, the supercharging device and the secondary refrigerant heat exchange device which are sequentially and circularly connected along the flow direction of the circulating working medium;

preferably, along the flow direction of the LNG in the LNG heat exchange channel, an outlet of the electric energy conversion device of the cyclic power generation unit is divided into two paths, one path is connected with a hot-side inlet of the LNG heat exchange device of the current-stage cyclic power generation unit, and the other path is connected with a hot-side inlet of a cyclic working medium heat exchange device of a higher-stage cyclic power generation unit;

5. The integrated utilization system according to any one of claims 1 to 4, wherein the integrated utilization system comprises a primary cycle power generation unit and a secondary cycle power generation unit;

preferably, the primary circulating power generation unit comprises a first electric energy conversion device, a first heat exchange device, a second heat exchange device and a third heat exchange device which are sequentially and circularly connected along the flow direction of the circulating working medium;

preferably, a first pressure boosting device is arranged on a connecting pipeline between the first heat exchange device and the second heat exchange device;

preferably, the secondary circulating power generation unit comprises a second electric energy conversion device, a fourth heat exchange device and a sixth heat exchange device which are sequentially and circularly connected along the flow direction of the circulating working medium;

preferably, a second supercharging device is arranged on a connecting pipeline between the fourth heat exchange device and the sixth heat exchange device;

preferably, the first heat exchange device and the fourth heat exchange device are sequentially connected along the flow direction of the LNG to form an LNG channel, the LNG is introduced into the first heat exchange device to exchange heat with the circulating medium flowing out of the first electric energy conversion device, and the heat-exchanged LNG enters the fourth heat exchange device to exchange heat with the circulating medium flowing out of the second electric energy conversion device;

preferably, the outlet of the second electric energy conversion device is divided into two paths, one path is connected with the hot side inlet of the second heat exchange device, the other path is connected with the hot side inlet of the fourth heat exchange device, the circulating working medium flowing out of the second electric energy conversion device is divided into two parts, one part enters the second heat exchange device to exchange heat with the circulating working medium flowing out of the first heat exchange device, and the other part enters the fourth heat exchange device to exchange heat with the LNG flowing out of the first heat exchange device;

preferably, a hot side outlet of the second heat exchange device and a hot side outlet of the fourth heat exchange device are combined into one path and then connected with a second supercharging device, circulating working media discharged after heat exchange in the second heat exchange device and the fourth heat exchange device respectively converge and then are sent into a sixth heat exchange device through the second supercharging device, and heat exchange is carried out between the circulating working media and secondary refrigerant in the sixth heat exchange device;

6. A multistage LNG cold energy power generation and comprehensive utilization method is characterized in that the comprehensive utilization system of any one of claims 1-5 is adopted to comprehensively utilize the LNG cold energy;

the comprehensive utilization method comprises the following steps:

7. The comprehensive utilization method according to claim 6, specifically comprising the steps of:

8. The comprehensive utilization method according to claim 7, wherein in the step (I), the first cycle fluid is an organic fluid;

preferably, the first cycle fluid is methane, ethane, trifluoromethane or liquid ammonia;

preferably, the input temperature of the first cycle working medium is 0-10 ℃;

preferably, the input pressure of the first cycle working medium is 2-3 MPa;

preferably, the temperature of the first cycle working medium is reduced to-80 to-60 ℃ after the first cycle working medium works and generates electricity in the first electric energy conversion device;

preferably, the pressure of the first cycle working medium is reduced to 0.1-0.2 MPa after the first cycle working medium works and generates electricity in the first electric energy conversion device;

preferably, the first circulating medium is subjected to heat exchange in a first heat exchange device to reduce the temperature to be liquefied;

preferably, the first circulating medium is cooled to-90 to-70 ℃ in a first heat exchange device;

preferably, the first circulating medium is pressurized to 2-3 MPa by a first pressurizing device;

preferably, the first circulating medium is subjected to heat exchange in a second heat exchange device to raise the temperature to-60 to-40 ℃;

preferably, the first circulating medium exchanges heat in a third heat exchange device and is heated to 0-10 ℃;

preferably, the secondary refrigerant is ethylene glycol or calcium chloride;

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

preferably, the temperature of the secondary refrigerant is reduced to-50 to-30 ℃ in a heat exchange manner in the third heat exchange device.

9. The comprehensive utilization method according to claim 7 or 8, wherein in the step (II), the second cycle fluid is an organic fluid;

preferably, the temperature of the second cycle working medium after working and power generation in the second electric energy conversion device is not higher than the temperature of the first cycle working medium after working and power generation in the first electric energy conversion device;

preferably, the temperature of the second cycle working medium is reduced to-50 to-40 ℃ after the second cycle working medium does work and generates electricity;

preferably, the second cycle fluid is ethane, ethylene, propane, difluoromethane or liquid nitrogen;

preferably, the input temperature of the second cycle working medium is 0-10 ℃;

preferably, the input pressure of the second cycle working medium is 0.5-1 MPa;

preferably, the second cycle working medium is divided into a first working medium and a second working medium according to volume after doing work to generate power;

preferably, the first working medium accounts for 60-80% of the total volume of the second cycle working medium;

preferably, the first working medium exchanges heat in a fourth heat exchange device and is cooled to-55 to-45 ℃;

preferably, the second working medium exchanges heat in a second heat exchange device and is cooled to-55 to-45 ℃;

preferably, the first working medium and the second working medium are converged and then are pressurized to 0.8-1.5 MPa by a second pressurizing device;

preferably, the first working medium and the second working medium are converged and then sent into a sixth heat exchange device through a second supercharging device to exchange heat with secondary refrigerant conveyed by users needing cooling to 0-10 ℃;

preferably, the pressure of the converged first working medium and the converged second working medium is changed to 0.5-1 MPa after the converged first working medium and the converged second working medium are sent into a sixth heat exchange device through a second supercharging device to exchange heat with secondary refrigerant conveyed by a user needing cooling;

preferably, the secondary refrigerant is ethylene glycol or calcium chloride;

preferably, the secondary refrigerant exchanges heat in the sixth heat exchange device and is cooled to-50 to-30 ℃.

10. The comprehensive utilization method according to any one of claims 7 to 9, wherein in the step (III), the input pressure of the LNG is 5 to 10 MPa;

preferably, the input temperature of the LNG is-160 to-130 ℃;

preferably, the LNG is subjected to heat exchange in a first heat exchange device and is heated to-90 to-80 ℃;

preferably, the LNG is subjected to heat exchange in a fourth heat exchange device and is heated to-60 to-50 ℃;

preferably, the LNG is gasified after heat exchange in the final heat exchange device to obtain natural gas;

preferably, the LNG is subjected to heat exchange in an ultimate heat exchange device and is heated to 0-10 ℃;

preferably, the LNG is discharged into a natural gas pipe network after heat exchange in a final heat exchange device;

preferably, the secondary refrigerant is ethylene glycol or calcium chloride;

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