CN102996378B - Generating method utilizing hydrocarbon mixture as working medium to recover liquefied natural gas cold energy - Google Patents

Abstract

The invention relates to a method for generating electricity by recovering cold energy of liquefied natural gas by using hydrocarbon mixture as working medium. The method comprises the following steps: allowing the mixed working fluid and the boosted liquefied natural gas to enter the heat exchanger for heat exchange; the heat-exchanged mixed working fluid is boosted, and then returned to the heat exchanger for another heat exchange, and the heat exchange is performed again Afterwards, the mixed working medium enters the turbo expander to expand to do work and drive the generator to generate electricity; the mixed working medium passing through the turbo expander returns to the heat exchanger for the next cycle; the heat-exchanged liquefied natural gas is output for outward transportation or air supply. The present invention also provides a system for recovering cold energy of liquefied natural gas and generating electricity by using hydrocarbon mixture as a working medium, which is used in the above method. The method provided by the invention is a power cycle process flow that can be used to generate electricity. LNG is used as a low-temperature heat source, and the surrounding environment and industrial waste heat are used as high-temperature heat sources. The cold energy of LNG is recovered to generate mechanical energy and drive the generator to generate electricity.

Description

Method for generating electricity by recovering liquefied natural gas cold energy by using hydrocarbon mixture as working medium

technical field

The invention relates to a method for generating electricity by recovering cold energy of liquefied natural gas by using a hydrocarbon mixture as a working medium, and belongs to the technical field of natural gas liquefaction.

Background technique

Generally, the cold energy utilization technology of liquefied natural gas (LNG) includes LNG power generation, air separation, cold storage cold source, seawater desalination, light hydrocarbon separation, low temperature drying, etc. As one of the main ways of LNG cold energy utilization, cold energy power generation technology plays an important role. The basic principle of using LNG cold energy to generate electricity is generally through a low-temperature power cycle process, using LNG as a low-temperature cold source, and using the mechanical work generated by the low-temperature power cycle to drive the generator set to generate electricity. How to obtain higher utilization efficiency of cold energy is an important technical problem, and various methods have been disclosed in this technical field.

Utility model patent No. 201120294959.2 discloses a four-stage recycling system for LNG cold energy. The system uses a two-stage cascaded Rankine cycle to generate electricity, which is composed of two independent low-temperature Rankine cycles connected in series, and the process flow is relatively complicated.

Invention patent application No. 200910047533.4 discloses a thermoelectric power generation module utilizing cold energy of LNG and its preparation method. The technical solution adopted in this patent application is based on a completely different principle from the power cycle, and uses thermoelectric temperature difference power generation technology. Since it is not feasible to directly use the latent or sensible heat of LNG to exchange heat with air or water in low-temperature centralized air-conditioning systems and cold storage, the technical solution disclosed in this patent application requires an intermediate cold storage medium to reduce the heat exchange temperature. Temperature difference power generation. The thermoelectric power generation module for low temperature is installed on the temperature difference pipeline of the system, such as between the inlet and outlet pipelines of the heat exchanger. The thermoelectric power generation module adopts a fully static thermoelectric material thermoelectric power generation method, which has the advantages of simplicity, no moving parts, and convenient series and parallel combinations.

No. 200720007870.7 utility model patent discloses a cascade integrated utilization system of LNG cold energy. The system is a gradient and integrated utilization system of LNG cold energy, including four parts: cold energy service company, cold storage company, indoor skating rink and cold water air-conditioning control area, which can realize cascaded and full utilization of cold energy. This system is a cascaded cold energy utilization scheme of LNG cold energy. Only part of the LNG cold energy is used to generate electricity. This part of the electricity uses butane as the working medium. A butane Rankine cycle is used to convert the cold energy of LNG into electrical energy.

No. 201210112919.0 invention patent application discloses a fuel cell and organic Rankine cycle combined power generation system based on LNG cold energy utilization. The technical solution disclosed in this patent application is also a cascaded cold energy utilization scheme for LNG cold energy. Only part of the LNG cold energy is used to generate electricity. This part of the electricity uses a certain organic substance as a working medium, and uses a Rankine cycle to recover LNG. The cold energy of the flue gas and the waste heat of the flue gas are converted into electrical energy.

Utility model patent No. 201120294858.5 discloses a multi-stage recycling system for LNG cold energy suitable for ships. The system is a multi-stage LNG cold energy utilization system suitable for ships. The power generation part of the system adopts a combination of a two-stage cascaded Rankine cycle and a natural gas expansion cycle. The Rankine cycle is composed of two independent low-temperature Rankine cycles in series, and the process flow is relatively complicated.

Invention patent application No. 201010123728.5 discloses an integrated optimization method for improving the efficiency of liquefied natural gas cold energy power generation. This method is also a cascaded cold energy utilization scheme of LNG cold energy, in which the cold energy power generation part consists of a basic single-stage Rankine cycle and a natural gas expansion cycle.

Contents of the invention

In order to solve the above-mentioned technical problems, the object of the present invention is to provide a method for recovering cold energy of liquefied natural gas to generate electricity by using hydrocarbon mixture as a working medium. Ken cycle can get high power generation efficiency.

The purpose of the present invention is also to provide a system for recovering cold energy of liquefied natural gas to generate electricity by using hydrocarbon mixture as working medium.

In order to achieve the above object, the present invention firstly provides a method for reclaiming LNG cold energy power generation with a hydrocarbon mixture as a working medium, which includes the following steps:

(1) Make the mixed working fluid and the boosted liquefied natural gas enter the heat exchanger for heat exchange (or the first heat exchange);

(2) The mixed working fluid after the heat exchange is boosted, and then returns to the heat exchanger for another heat exchange (or called the second heat exchange). Drive the generator to generate electricity;

(3) The mixed working fluid passing through the turbo expander returns to the heat exchanger for the next cycle;

(4) Export the heat-exchanged liquefied natural gas for external transportation or gas supply.

The method for recovering LNG cold energy power generation by using hydrocarbon mixture as the working medium provided by the present invention is carried out in a continuous cycle, wherein the mixed working medium has been continuously circulated, and the LNG is also continuously input into the heat exchanger for heat exchange . The above method can also be referred to as a recycling method for cold energy of liquefied natural gas.

According to a specific embodiment of the present invention, preferably, in the above method, the mixed working medium used comprises the following composition in terms of molar percentage: methane 20%-40%, ethane or ethylene 35%-55%, propane 20-35%, the sum of each component meets 100%; more preferably, in terms of molar percentage, the mixed working fluid includes the following components: methane 23%-30%, ethane or ethylene 40%-50%, propane 23- 32%, the sum of each component satisfies 100%. By adjusting the composition of the mixed working fluid, it can adapt to the requirements of different liquefied natural gas components, pressure, natural gas export or gas supply pressure, etc., so as to minimize the heat exchange loss of the heat exchanger and improve the efficiency of the entire process , generating more electricity.

According to a specific embodiment of the present invention, preferably, in step (2), the pressure of the boosted liquefied natural gas is 8-15 MPa or the pressure required for transportation or gas supply. The pressure required for transportation or gas supply depends on the requirements of the receiving station, and generally matches the pressure of the pipe network outside the station.

According to a specific embodiment of the present invention, preferably, in the above step (2), the pressure of the mixed working fluid after heat exchange (first heat exchange) before boosting is 105-300kPa, preferably 120-150kPa.

According to a specific embodiment of the present invention, preferably, in the above step (2), the pressure of the mixed working medium after heat exchange (the first heat exchange) after boosting is 800-3000kPa, preferably 1000-1800kPa.

According to a specific embodiment of the present invention, preferably, in the above step (2), the temperature of the liquefied natural gas after heat exchange (first heat exchange) is -80°C to 30°C, preferably -60°C to -15°C ℃.

According to a specific embodiment of the present invention, preferably, in the above step (2), the temperature of the mixed working fluid after heat exchange (the first heat exchange) is -160°C to -100°C, preferably -150°C to -100°C -110°C.

According to a specific embodiment of the present invention, preferably, in the above step (2), the temperature of the mixed working fluid after reheat exchange (second heat exchange) is -90°C to -30°C, preferably -60°C to -35°C.

In the above method provided by the present invention, higher efficiency can be obtained by controlling the temperature, generally by controlling the temperature and flow rate of the medium with which heat exchange is performed, such as the flow rate of air, the temperature and flow rate of refrigerant, etc., the specific control The method can be carried out with reference to the existing method.

According to the specific embodiment of the present invention, preferably, in the above step (4), the heat-exchanged liquefied natural gas leaving the heat exchanger first exchanges heat with the refrigerant, and then outputs; or, the heat-exchanged liquefied natural gas leaving the heat exchanger The hot liquefied natural gas first exchanges heat with the refrigerant, and then exchanges heat with the external environment or industrial waste heat, and then enters the turbo expander to expand to do work and drive the generator to generate electricity, and then output. In the above-mentioned method provided by the present invention, the flow process of LNG can be: after the LNG is raised to the pressure required for outward transportation or gas supply (the pressure can be boosted by the LNG pump), it enters the heat exchanger to exchange heat with the mixed working medium and is Heating, and then exchanging heat with conventional refrigerants and providing cold energy to the air conditioner and then transporting or supplying air to the outside, or directly transporting or supplying air to the outside after coming out of the heat exchanger; the above process can also be: LNG first increases to one Very high pressure, generally 8MPa to 15MPa, then enter the heat exchanger to vaporize and heat up, then exchange heat with conventional refrigerants and provide cooling capacity to the air conditioner, then exchange heat with the environment or industrial waste heat, and then enter the natural gas expander to expand and do work , the natural gas is decompressed to the required pressure for external transportation or gas supply, and then it is exported or supplied. The mechanical work generated by the natural gas expander can also be used for power generation.

In the above method, the gaseous mixed working fluid enters the heat exchanger and undergoes heat exchange (the first heat exchange) to absorb the cold energy of LNG and condenses into a liquid, and then enters the heat exchanger for heat exchange after being pressurized (the second heat exchange). heat) and be heated (after heating, it can be liquid, gas or gas-liquid two-phase, generally gas-liquid two-phase), and then enter the turbo expander to expand and do work (it can also enter another heat exchanger for further heating (or called After the third heat exchange), it enters the turbo expander to expand and do work), drives the generator to generate electricity, and the gaseous mixed working medium from the expander returns to the heat exchanger to complete the cycle. In step (2), preferably, the mixed working fluid after heat exchange is first exchanged with one or more of the external environment, refrigerant and industrial waste heat (the third heat exchange), and then enters the turbine The expander expands to do work and drives the generator to generate electricity. The third heat exchange can be done in the following way: the mixed working fluid that has undergone heat exchange again from the heat exchanger exchanges heat with the surrounding environment in another heat exchanger, where the heat exchange with the surrounding environment can also exchange heat with the air , water can also be used as an intermediary, so that the mixed working fluid and water are first exchanged for heat, and then the water is exchanged with air or discharged outside the factory; Heat exchange (where the refrigerant can be water, brine, ethylene glycol, propylene glycol, glycerol, etc. commonly used in air conditioning systems), the mixed working fluid is heated, and the released cold is transferred to the refrigerant, and through the refrigerant to the air conditioning system Transfer the cold.

According to the specific embodiment of the present invention, preferably, the third heat exchange of the mixed working fluid can be carried out according to the following steps: the heat exchanged mixed working medium coming out of the heat exchanger first exchanges heat with the refrigerant to -10°C to 10°C, then exchange heat with the external environment, and then use industrial waste heat to heat to 40°C to 150°C, and then enter the turbo expander; among them, preferably use industrial waste heat to heat to 40°C to 90°C, more preferably 50°C to 80°C.

In the above-mentioned method provided by the present invention, the heat exchanger that realizes the heat exchange (first heat exchange, second heat exchange) of the mixed working fluid and LNG can be any form of low-temperature heat exchanger, as long as it can realize three streams of fluid It is enough to exchange heat and make them reach the required temperature, such as plate-fin low-temperature heat exchangers, etc. The heat exchanger used for the heat exchange between the mixed working fluid and the external environment, refrigerant, and industrial waste heat (the third heat exchange) can also be any form of heat exchanger that can realize the above-mentioned heat exchange.

The present invention also provides a system for recovering cold energy of LNG to generate electricity by using hydrocarbon mixture as a working medium, which includes: a first heat exchanger, a mixed working medium pump, a liquefied natural gas pump, a turbo expander, a generator, and natural gas input Pipelines, natural gas output pipelines; of which:

The first heat exchanger has a first flow channel, a second flow channel, and a third flow channel. The inlet of the first flow channel communicates with the natural gas input pipeline, and the outlet of the first flow channel communicates with the natural gas output pipeline, and the liquefied natural gas input pipeline is provided with There are LNG pumps;

The outlet of the turbo expander is connected with the inlet of the third flow channel, the outlet of the third flow channel is connected with the inlet of the mixed working medium pump, the outlet of the mixed working medium pump is connected with the inlet of the second flow channel, and the outlet of the second flow channel is connected with the inlet of the mixed working medium pump. The outlet communicates with the inlet of the turbo expander;

The generator is connected with the turbo expander and is used to generate electricity driven by the turbo expander.

In the above system, preferably, at least one heat exchanger is provided on the pipeline between the outlet of the second flow channel and the inlet of the turbo expander and/or at least one heat exchanger is provided on the natural gas output pipeline. That is, in the above-mentioned system, at least one heat exchanger may be provided on the pipeline between the outlet of the second channel and the inlet of the turbo expander to realize the exchange between the mixed working medium and the external environment, refrigerant, industrial waste heat, etc. The third heat exchange; at least one heat exchanger may also be provided on the natural gas output pipeline to realize the heat exchange between natural gas and refrigerant. In the same system, either one of the above two heat exchangers can be installed separately, or both heat exchangers can be installed at the same time.

In the above system, the first heat exchanger that realizes the heat exchange between the mixed working fluid and LNG (first heat exchange, second heat exchange) can be any form of low-temperature heat exchanger, as long as it can realize the exchange of three fluids heat and make them reach the required temperature. Preferably, the above-mentioned first heat exchanger is a plate-fin low-temperature heat exchanger.

The heat exchanger used for the heat exchange between the mixed working fluid and the external environment, refrigerant, and industrial waste heat (the third heat exchange) can also be any form of heat exchanger that can realize the above-mentioned heat exchange.

In the above system, preferably, two heat exchangers are arranged on the pipeline between the outlet of the second flow channel and the inlet of the turbo expander. One is used to exchange heat between the mixed working fluid and the refrigerant, and the other is used to exchange heat between the mixed working fluid and the external environment or industrial waste heat. Or industrial waste heat heat exchange.

In the above system, preferably, two heat exchangers are arranged on the natural gas output pipeline. One heat exchanger is used to exchange heat between natural gas and refrigerant, and the other heat exchanger is used to exchange heat between natural gas and external environment or industrial waste heat. Among them, natural gas generally first exchanges heat with refrigerant to raise its temperature, and then exchanges heat with external environment or industrial waste heat heat up.

In the above system, the third flow channel of the first heat exchanger, the mixed working medium pump, the second flow channel, the second heat exchanger, and the turbo expander form a circulation loop of the mixed working medium. The natural gas input pipeline, the first The first flow channel of the heat exchanger and the natural gas output pipeline form a natural gas channel.

The method for recovering liquefied natural gas cold energy power generation by using hydrocarbon mixture as working medium provided by the present invention is a process flow for generating electricity by recovering waste heat and LNG cold energy by using hydrocarbon mixture as working medium, which can only use one-stage refrigeration cycle It can be realized, and has the characteristics of simple process and high energy efficiency. This method is a power cycle process that can be used for power generation. It uses low-temperature LNG as a low-temperature heat source, uses the surrounding environment and industrial waste heat as a high-temperature heat source, and generates energy by recovering cold energy of LNG and low-grade heat energy of industrial waste heat. Mechanical energy drives a generator to generate electricity. In this method, a high cold energy utilization efficiency can be obtained by rationally adjusting the ratio of the mixed working fluid, and this method can be used alone for power generation, or can be used in conjunction with the LNG direct expansion power generation process.

Description of drawings

Fig. 1 is the schematic structural diagram of the system for recovering cold energy of liquefied natural gas to generate electricity by using hydrocarbon mixture as working medium provided in Example 1;

Fig. 2 is the schematic structural diagram of the system for recovering liquefied natural gas cold energy power generation using hydrocarbon mixture as the working medium provided in Example 2;

Fig. 3 is a schematic structural diagram of a system for recovering cold energy of liquefied natural gas for power generation provided by Example 4 using a hydrocarbon mixture as a working medium.

Explanation of main figures and symbols:

First heat exchanger 1 mixed working medium pump 2 second heat exchanger 3 first turbo expander 4 generator 5 liquefied natural gas pump 6 natural gas input pipeline 7 natural gas output pipeline 8 third heat exchanger 9 fourth heat exchanger 10 fifth heat exchanger 11 second turbo expander 12

Detailed ways

In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

Example 1

This embodiment provides a system for recovering cold energy of liquefied natural gas to generate electricity by using hydrocarbon mixture as a working medium, and its structure is shown in FIG. 1 . The system includes a first heat exchanger 1, a mixed working medium pump 2, a second heat exchanger 3, a first turbo expander 4, a generator 5, a liquefied natural gas pump 6, a natural gas input pipeline 7, and a natural gas output pipeline 8, in:

The first heat exchanger 1 is a plate-fin low-temperature heat exchanger, which has three flow channels, which are the first flow channel, the second flow channel, and the third flow channel from right to left in FIG. The inlet is communicated with the natural gas input pipeline 7, the outlet of the first flow channel is communicated with the natural gas output pipeline 8, and the natural gas input pipeline 7 is provided with a liquefied natural gas pump 6;

The outlet of the first turboexpander 4 communicates with the inlet of the third flow channel, the outlet of the third flow channel communicates with the inlet of the mixed working medium pump 2, and the outlet of the mixed working medium pump 2 communicates with the inlet of the second flow channel, The outlet of the second flow channel communicates with the inlet of the first turboexpander 4;

The generator 5 is connected with the first turbo expander 4 and is used to generate electricity driven by the turbo expander 4 .

In the above cycle recovery system, the third flow channel of the first heat exchanger 1, the mixed working medium pump 2, the second flow channel, the second heat exchanger 3, and the first turbo expander 4 constitute the circulation of the mixed working medium In the loop, the natural gas input pipeline 7, the first flow channel of the first heat exchanger 1, and the natural gas output pipeline 8 form a natural gas channel.

This embodiment also provides a method for recovering liquefied natural gas cold energy to generate electricity by using hydrocarbon mixture as a working medium, which is carried out by using the above-mentioned system, and specifically includes the following steps:

After the LNG input from the natural gas input pipeline 7 is raised to the pressure required for external transportation or gas supply by the liquefied natural gas pump 6, it enters the first flow channel of the first heat exchanger 1 for heat exchange and is heated, and then passes through the natural gas output pipeline 8 Conveying or supplying air to the outside;

The gaseous mixed working fluid enters the third channel of the first heat exchanger 1 to absorb the cold energy of LNG and condenses into a liquid. After being pressurized by the mixed working medium pump 2, it enters the second channel of the first heat exchanger 1 for heating (heating Finally, it can be in liquid state, gas or gas-liquid two-phase, generally gas-liquid two-phase), and then enters the second heat exchanger to exchange heat with air (that is, the external environment), and the temperature of the mixed working medium rises and then enters the first turbo expander 4 Expansion works, drives the generator 5 to generate electricity, and the gaseous mixed working medium from the first turboexpander 4 returns to the third channel of the first heat exchanger 1 to complete a cycle and enter the next cycle.

Example 2

This embodiment provides a system for recovering cold energy of liquefied natural gas to generate electricity by using hydrocarbon mixture as a working medium, and its structure is shown in FIG. 2 . This system is based on the system provided in Example 1, which uses hydrocarbon mixture as the working medium to recover the cold energy of liquefied natural gas for power generation. A third heat exchanger 9 is added on the pipeline between them, and a fourth heat exchanger 10 is added on the natural gas output pipeline 8, and the others are the same as in Embodiment 1.

This embodiment also provides a method for recovering liquefied natural gas cold energy to generate electricity using a hydrocarbon mixture as a working medium, which is carried out by using the above-mentioned system provided by this embodiment, and specifically includes the following steps:

After the LNG input from the natural gas input pipeline 7 is raised to the pressure required for external transportation or gas supply through the liquefied natural gas pump 6, it enters the first flow channel of the first heat exchanger 1 for heat exchange and is heated, and then passes through the fourth exchange. Heat exchange with ethylene glycol (refrigerant) in the heater 10, transfer the cold energy to ethylene glycol, and then ethylene glycol provides cold energy to the air conditioner, and then transport or supply gas through the natural gas output pipeline 8;

The gaseous mixed working fluid enters the third channel of the first heat exchanger to absorb the cold energy of LNG and condenses into a liquid. After being pressurized by the mixed working medium pump 2, it enters the second channel of the first heat exchanger 1 for heating (after heating It can be liquid, gas or gas-liquid two-phase, generally gas-liquid two-phase), and then enter the third heat exchanger 9 to exchange heat with ethylene glycol (refrigerant), transfer the cold to ethylene glycol and then transfer it to ethylene glycol Provide cooling capacity to the air conditioner, and then the mixed working fluid enters the second heat exchanger 3 to exchange heat with the air. After the temperature of the mixed working fluid rises to 3-5°C lower than the ambient temperature, it enters the first turbo expander 4 to expand and perform work, driving The generator 5 generates electricity, and the gaseous mixed working medium from the first turboexpander 4 returns to the third flow channel of the first heat exchanger 1 to complete a cycle and enter the next cycle.

In this embodiment, the mixed working fluid used is a mixture of methane, ethylene and propane, wherein, based on the molar percentage of the mixed working fluid, the content of methane is 34%, the content of ethylene is 24%, and the content of propane The content is 42%. In this embodiment, about 47-51 kilowatt-hours of electricity can be generated per ton of liquefied natural gas.

Example 3

This embodiment also provides a method for recovering LNG cold energy power generation using hydrocarbon mixture as a working medium, which is carried out by using the system for recovering LNG cold energy power generation using hydrocarbon mixture as a working medium provided in Example 2. Specifically include the following steps:

After the LNG input from the natural gas input pipeline 7 is raised to the pressure required for external transportation or gas supply through the liquefied natural gas pump 6, it enters the first flow channel of the first heat exchanger 1 for heat exchange and is heated, and then passes through the fourth exchange. Heat exchange with ethylene glycol (refrigerant) in the heater 10, transfer the cold energy to ethylene glycol, and then ethylene glycol provides cold energy to the air conditioner, and then transport or supply gas through the natural gas output pipeline 8;

The gaseous mixed working fluid enters the third channel of the first heat exchanger to absorb the cold energy of LNG and condenses into a liquid. After being pressurized by the mixed working medium pump 2, it enters the second channel of the first heat exchanger 1 for heating (after heating It can be liquid, gas or gas-liquid two-phase, generally gas-liquid two-phase), and then enter the third heat exchanger 9 to exchange heat with ethylene glycol (refrigerant), transfer the cold to ethylene glycol and then transfer it to ethylene glycol Provide cooling capacity to the air conditioner, and then the mixed working medium enters the second heat exchanger 3 to recover industrial waste heat. After the temperature of the mixed working medium rises to 50-80°C, it enters the first turbo expander 4 to expand and perform work, driving the generator 5 to generate electricity , the gaseous mixed working fluid coming out of the first turboexpander 4 returns to the third flow channel of the first heat exchanger 1 to complete a cycle and enter the next cycle.

In this embodiment, the mixed working fluid used is a mixture of methane, ethylene and propane, wherein, based on the molar percentage of the mixed working fluid, the content of methane is 28%, the content of ethylene is 38%, and the content of propane The content is 34%. In this embodiment, about 58-63 kilowatt-hours of electricity can be generated per ton of liquefied natural gas.

Example 4

This embodiment provides a system for recovering cold energy of liquefied natural gas to generate electricity by using hydrocarbon mixture as a working medium, and its structure is shown in FIG. 3 . This system is based on the system provided in Example 2, which uses hydrocarbon mixture as the working fluid to recover the cold energy of liquefied natural gas to generate electricity. In addition to the fourth heat exchanger 10 on the natural gas output pipeline 8, a fifth heat exchanger is added. Device 11 and second turboexpander 12, others are the same as in Embodiment 2.

This embodiment also provides a method for recovering liquefied natural gas cold energy to generate electricity using a hydrocarbon mixture as a working medium, which is carried out by using the above-mentioned system provided by this embodiment, and specifically includes the following steps:

After the LNG input from the natural gas input pipeline 7 is boosted to 10MPa by the liquefied natural gas pump 6, it enters the first flow channel of the first heat exchanger 1 for heat exchange and is heated, and then passes through the fourth heat exchanger 10 and the second Alcohol (refrigerant) performs heat exchange, transfers the cooling capacity to ethylene glycol, and then ethylene glycol provides cooling capacity to the air conditioner, and then the natural gas exchanges heat with the air in the fifth heat exchanger 11 to raise the temperature 3-5 degrees below the ambient temperature. °C, enter the second natural gas turbo expander 12 to expand to the pressure required for external transportation or gas supply, and then transport or supply gas through the natural gas output pipeline 8;

The gaseous mixed working fluid enters the third channel of the first heat exchanger to absorb the cold energy of LNG and condenses into a liquid. After being pressurized by the mixed working medium pump 2, it enters the second channel of the first heat exchanger 1 for heating (after heating It can be liquid, gas or gas-liquid two-phase, generally gas-liquid two-phase), and then enter the third heat exchanger 9 to exchange heat with ethylene glycol (refrigerant), transfer the cold to ethylene glycol and then transfer it to ethylene glycol Provide cooling capacity to the air conditioner, then the mixed working medium enters the second heat exchanger 3 to exchange heat with the air, the temperature of the mixed working medium rises to 3-5°C lower than the ambient temperature, and then enters the turbo expander 4 to expand and do work, driving the generator 5 to generate electricity, and the gaseous mixed working medium from the turbo expander 4 returns to the third channel of the first heat exchanger 1 to complete a cycle and enter the next cycle.

In this embodiment, the mixed working fluid used is a mixture of methane, ethane and propane, wherein, based on the molar percentage of the mixed working fluid, the content of methane is 37.5%, and the content of ethylene is 13%. The propane content is 49.5%. In this embodiment, about 62-67 kilowatt-hours of electricity can be generated per ton of liquefied natural gas.

Example 5

This embodiment provides a method for recovering LNG cold energy power generation using hydrocarbon mixture as a working medium, which is carried out by using the system for recovering LNG cold energy power generation using hydrocarbon mixture as a working medium provided in Example 4, specifically Include the following steps:

After the LNG input from the natural gas input pipeline 7 is boosted to 10MPa by the liquefied natural gas pump 6, it enters the first flow channel of the first heat exchanger 1 for heat exchange and is heated, and then passes through the fourth heat exchanger 10 and the second Alcohol (refrigerant) conducts heat exchange, transfers the cooling capacity to ethylene glycol and then ethylene glycol provides cooling capacity to the air conditioner, and after the natural gas is heated up, it enters the fifth heat exchanger 11 and is heated to 60-70°C by using industrial waste heat. Then enter the second turbo expander 12 to expand to the pressure required for external transportation or gas supply, and then transport or supply gas through the natural gas output pipeline 8;

The gaseous mixed working fluid enters the third channel of the first heat exchanger to absorb the cold energy of LNG and condenses into a liquid. After being pressurized by the mixed working medium pump 2, it enters the second channel of the first heat exchanger 1 for heating (after heating It can be liquid, gas or gas-liquid two-phase, generally gas-liquid two-phase), and then enter the third heat exchanger 9 to exchange heat with ethylene glycol (refrigerant), transfer the cold to ethylene glycol and then transfer it to ethylene glycol Provide cooling capacity to the air conditioner, then the mixed working medium enters the second heat exchanger 3 to exchange heat with the air, the temperature of the mixed working medium rises to 3-5°C lower than the ambient temperature, and then enters the turbo expander 4 to expand and do work, driving the generator 5 to generate electricity, and the gaseous mixed working medium from the turbo expander 4 returns to the third channel of the first heat exchanger 1 to complete a cycle and enter the next cycle.

In this embodiment, the mixed working fluid used is a mixture of methane, ethane and propane, wherein, based on the molar percentage of the mixed working fluid, the content of methane is 36%, and the content of ethylene is 16%. The propane content is 48%. In this embodiment, about 85-90 kilowatt-hours of electricity can be generated per ton of liquefied natural gas.

Claims (12)

1. be the method that working medium reclaims cold energy of liquefied natural gas generating with hydrocarbon mixture, it comprises the following steps:

Make mixed working fluid enter heat exchanger with the LNG Liquefied natural gas through boosting and carry out heat exchange;

Mixed working fluid through heat exchange boosts, and then gets back to heat exchanger and carries out heat exchange again, and the mixed working fluid again after heat exchange enters turbo-expander expansion work and drive electrical generators generating;

Get back to heat exchanger through the mixed working fluid of turbo-expander and carry out next one circulation;

LNG Liquefied natural gas through heat exchange is exported, outwards to carry or air feed;

The described LNG Liquefied natural gas through heat exchange leaving heat exchanger first with refrigerant heat exchange, then with external environment or industrial exhaust heat heat exchange, enter turbo-expander expansion work more afterwards and drive electrical generators generating, and then export;

Wherein, with molar percent, described mixed working fluid comprises following one-tenth and is grouped into: methane 20%-40%, ethane or ethene 35%-55%, propane 20-35%, and each composition sum meets 100%;

The pressure of mixed working fluid before boosting through heat exchange is 105-300kPa; The pressure of mixed working fluid after boosting through heat exchange is 800-3000kPa;

Temperature through the LNG Liquefied natural gas of heat exchange is-80 DEG C to 30 DEG C; The temperature of the mixed working fluid again after heat exchange is-90 DEG C to-30 DEG C; The temperature of the described mixed working fluid through heat exchange is-160 DEG C to-100 DEG C.

2. method according to claim 1, wherein, with molar percent, described mixed working fluid has following one-tenth and is grouped into: methane 23%-30%, ethane or ethene 40%-50%, propane 23-32%, and each composition sum meets 100%.

3. method according to claim 1, wherein, the described pressure of LNG Liquefied natural gas through boosting be 8-15MPa or, conveying or the pressure needed for air feed.

4. the method according to claim 1 or 3, wherein, the pressure of mixed working fluid before boosting through heat exchange is 120-150kPa; The pressure of mixed working fluid after boosting through heat exchange is 1000-1800kPa.

5. method according to claim 1, wherein, the temperature through the LNG Liquefied natural gas of heat exchange is-60 DEG C to-15 DEG C; The temperature of the mixed working fluid again after heat exchange is-60 DEG C to-35 DEG C; The temperature of the described mixed working fluid through heat exchange is-150 DEG C to-110 DEG C.

6. method according to claim 1 or 5, wherein, the mixed working fluid after described heat exchange again first carries out heat exchange with one or more in external environment, refrigerant and industrial exhaust heat, and then enters turbo-expander expansion work and drive electrical generators generating.

7. method according to claim 1, wherein, the mixed working fluid after described heat exchange again first carries out heat exchange to-10 DEG C to 10 DEG C with refrigerant, then carries out heat exchange with external environment condition, recycling industrial exhaust heat is heated to 40 DEG C to 150 DEG C, then enters turbo-expander.

8. method according to claim 6, wherein, the mixed working fluid after described heat exchange again first carries out heat exchange to-10 DEG C to 10 DEG C with refrigerant, then carries out heat exchange with external environment condition, recycling industrial exhaust heat is heated to 40 DEG C to 150 DEG C, then enters turbo-expander.

9. the method according to claim 7 or 8, wherein, utilizes industrial exhaust heat to be heated to 40 DEG C to 90 DEG C.

10. method according to claim 9, wherein, utilizes industrial exhaust heat to be heated to 50 DEG C to 80 DEG C.

11. 1 kinds is the system that working medium reclaims LNG cold energy generation with hydrocarbon mixture, and it comprises: First Heat Exchanger, mixed working fluid pump, liquefied natural gas pump, turbo-expander, generator, rock gas input pipeline, rock gas output pipeline; Wherein:

Described First Heat Exchanger has first flow, the second runner, the 3rd runner, the entrance of described first flow is communicated with described rock gas input pipeline, the outlet of described first flow is communicated with described rock gas output pipeline, further, described LNG Liquefied natural gas input pipeline is provided with liquefied natural gas pump;

The outlet of described turbo-expander is communicated with the entrance of described 3rd runner, the outlet of described 3rd runner is communicated with the entrance of described mixed working fluid pump, described mixed working fluid delivery side of pump is communicated with the entrance of described second runner, and the outlet of described second runner is communicated with the entrance of described turbo-expander;

Described generator is connected with described turbo-expander, for generating electricity under the drive of described turbo-expander;

Rock gas output pipeline is provided with two heat exchangers, and a heat exchanger is used for making rock gas and refrigerant heat exchange, and another heat exchanger is used for making rock gas and external environment or industrial exhaust heat carry out heat exchange.

12. systems according to claim 11, wherein, the pipeline between the outlet of described second runner and the entrance of described turbo-expander is provided with at least one heat exchanger and/or described rock gas output pipeline is provided with at least one heat exchanger.