阅读说明：本技术 一种液化天然气动力船液化天然气冷能梯级利用系统 (Liquefied natural gas cold energy cascade utilization system of liquefied natural gas power ship ) 是由 姚寿广 张旭 沈晓宇 肖民 杨宗明 于 2019-11-08 设计创作，主要内容包括：本发明公开了一种液化天然气动力船液化天然气冷能梯级利用系统,该系统首先利用冷媒将-162℃至-140℃的LNG冷能用于氮气制备；之后利用两级朗肯循环将高压低温的LNG冷能转换为电能；随后将汽化后的天然气送入膨胀机直接膨胀发电；再利用单级朗肯循环将低压低温的LNG冷能转换为电能；最后利用冷媒将中冷部分的LNG冷能梯次回收用于船舶低温冷库循环系统、高温冷库循环系统和第二级空调循环系统供冷,该系统将LNG冷能进行合理梯级利用,提高冷能和冷<Image he="58" wi="54" file="DDA0002266577470000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>的综合利用效率,降低了船舶的营运成本。(The invention discloses a liquefied natural gas cold energy cascade utilization system of a liquefied natural gas power ship, which firstly utilizes a refrigerant to use LNG cold energy at-162 ℃ to-140 ℃ for nitrogen preparation; then, the high-pressure low-temperature LNG cold energy is converted into electric energy by utilizing a two-stage Rankine cycle; then the vaporized natural gas is sent into an expander to be directly expanded to generate power; the low-pressure and low-temperature LNG cold energy is converted into electric energy by using a single-stage Rankine cycle; and finally, the LNG cold energy of the intercooling part is recycled in steps by utilizing the refrigerant and is used for cooling the ship low-temperature refrigeration house circulating system, the high-temperature refrigeration house circulating system and the second-stage air-conditioning circulating system, and the system reasonably and stepwisely utilizes the LNG cold energy to improve the cold energy and cold energy The comprehensive utilization efficiency of the ship is improved, and the operating cost of the ship is reduced.)

1. The liquefied natural gas cold energy cascade utilization system of the liquefied natural gas power ship is characterized by comprising the following implementation steps of: firstly, LNG cold energy at-162 ℃ to-140 ℃ is used for preparing nitrogen by using a refrigerant; then, the high-pressure low-temperature LNG cold energy is converted into electric energy by utilizing a two-stage Rankine cycle; then the vaporized natural gas is sent into an expander to be directly expanded to generate power; the low-pressure and low-temperature LNG cold energy is converted into electric energy by using a single-stage Rankine cycle; and then the LNG cold energy of the intercooling part is recycled in steps by utilizing the refrigerant and is used for cooling the ship low-temperature refrigeration house circulating system, the high-temperature refrigeration house circulating system and the second-stage air conditioner circulating system.

2. The liquefied natural gas cold energy cascade utilization system of the liquefied natural gas power ship according to claim 1, comprising the following steps:

the method comprises the following steps: LNG cold energy is first used in the nitrogen production cycle

Pressurizing the liquefied natural gas at normal pressure to 4-5 MPa, wherein the temperature is-161 ℃ to-160 ℃, and then sending the liquefied natural gas into an LNG heat exchanger (3) of the nitrogen preparation cycle to exchange heat with a nitrogen preparation cycle working medium;

step two: the two-stage Rankine cycle power generation system is arranged at the tail end of the nitrogen preparation cycle

The LNG primarily utilized by the nitrogen preparation cycle is at-140 ℃ to-135 ℃, and is sent to a condenser (4) of a primary Rankine cycle in a two-stage Rankine cycle power generation system, the primary Rankine cycle working medium firstly absorbs part of heat of a seawater desalination system, then absorbs heat of a secondary Rankine cycle working medium to generate vaporization, the liquefied natural gas is cooled and liquefied after acting through an expander (18), the secondary Rankine cycle working medium firstly absorbs heat of a primary air conditioning system, then absorbs part of waste heat of cylinder liner water of a main engine to generate vaporization, and the liquefied working medium is cooled and liquefied by the primary Rankine cycle working medium after acting through the expander (23);

step three: LNG expander is arranged at tail end of two-stage Rankine cycle power generation system

The natural gas after passing through the nitrogen preparation system and the two-stage Rankine cycle power generation system is sent to an expander (5) for direct expansion work at the temperature of-57 to-55 ℃;

step four: the single-stage Rankine cycle power generation system is arranged at the tail end of the LNG expander

The natural gas directly expanded and acted by a nitrogen preparation system, a two-stage Rankine cycle power generation system and an LNG expander is sent into a condenser (6) of a single-stage Rankine cycle at the pressure of 0.7 Mpa-1 Mpa and the temperature of-115 ℃ to-120 ℃, the single-stage Rankine cycle working medium firstly absorbs part of heat of a seawater desalination system, then absorbs part of waste heat of cylinder liner water of a main engine to be vaporized, and is cooled and liquefied by the natural gas after being acted by an expander (28);

step five: the seawater desalination system is nested in the two-stage Rankine cycle power generation system and the single-stage Rankine cycle system

The temperature of the refrigerant of the seawater desalination system is-15 to-10 ℃ after heat exchange by a seawater desalination device (32), a part of the refrigerant after passing through a flow divider (33) is sent to a first-stage Rankine cycle heat regenerator (16) in a two-stage Rankine cycle power generation system to exchange heat with a first-stage Rankine cycle working medium, the temperature is reduced to-90 to-85 ℃, the other part of the refrigerant is sent to a heat regenerator (27) of a single-stage Rankine cycle power generation system to exchange heat with the single-stage Rankine cycle working medium, the temperature is reduced to-75 to-70 ℃, the two streams of refrigerant are mixed through a mixer (29) after being cooled, the temperature of the mixed refrigerant is-83 to-80 ℃, and the refrigerant is pushed into the seawater desalination device (32) through a refrigerant pump (30) of the;

step six: the first-stage air conditioning system is nested in the two-stage Rankine cycle power generation system

The temperature of the refrigerant of the air conditioning system is 10-20 ℃ after exchanging heat with the external environment, the refrigerant is sent into a secondary Rankine cycle heat regenerator (21) in the two-stage Rankine cycle power generation system to exchange heat with a secondary Rankine cycle working medium, the temperature is reduced to-10 ℃ to-8 ℃, and the refrigerant is pushed by a refrigerant pump (43) of the first-stage air conditioning system to exchange heat with the external environment;

step seven: the low-temperature refrigeration house system is arranged at the tail end of the single-stage Rankine cycle power generation system

The natural gas which is directly expanded to work through a nitrogen preparation system, a two-stage Rankine cycle power generation system and an LNG expander (5) and utilized by the single-stage Rankine cycle power generation system is delivered to a low-temperature refrigeration house system for cooling, the temperature of the refrigerant cooled by the natural gas is-37 ℃ to-35 ℃, the refrigerant is pushed by a refrigerant pump (34) of the low-temperature refrigeration house to exchange heat with the external environment, the temperature is raised to-20 ℃ to-15 ℃, and then cold energy is absorbed for next cycle refrigeration;

step eight: the high-temperature refrigeration house system is arranged at the tail end of the low-temperature refrigeration house system

The natural gas after being utilized by the low-temperature refrigeration house system is at-24 ℃ to-20 ℃, is sent into the high-temperature refrigeration house system for cooling, is pushed by a refrigerant pump (37) of the high-temperature refrigeration house to exchange heat with the external environment, and is raised to-9 ℃ to absorb cold energy for next cycle refrigeration;

step nine: the second-stage air conditioning system is arranged at the tail end of the high-temperature refrigeration house system

The natural gas which is directly expanded to work through a nitrogen preparation system, a two-stage Rankine cycle power generation system and an LNG expander (5) and is utilized by a single-stage Rankine cycle power generation system, a low-temperature refrigeration house system and a high-temperature refrigeration house system is at the temperature of-14 ℃ to-10 ℃, the natural gas is sent to a second-stage air conditioning system for cooling, the temperature of a refrigerant which is cooled and liquefied by the natural gas is at the temperature of-9 ℃ to-5 ℃, the refrigerant is pushed by a refrigerant pump (40) of the second-stage air conditioning system to exchange heat with the external environment for vaporization, the temperature is raised to 20 ℃ to 22 ℃, and then cold energy;

step ten: the natural gas temperature regulating heat exchanger is arranged at the tail end of the second-stage air conditioning system

The natural gas which is directly expanded to work through a nitrogen preparation system, a two-stage Rankine cycle power generation system and an LNG expander (5) is sent to a cylinder liner water heat exchanger (10) to exchange heat with part of main engine cylinder liner water, the temperature of the natural gas after heat exchange is raised to 25-28 ℃, and the natural gas is sent to a main engine to be combusted, wherein the temperature of the natural gas is 12-15 ℃.

3. The lng cold energy cascade utilization system of claim 2, wherein: and sixthly, the required refrigerating capacity of the air conditioning system in the step nine is matched with the LNG flow of the specific ship type.

4. The LNG cold energy cascade utilization system of claim 3, wherein: the refrigerating capacity of the air conditioning system is realized by adjusting the opening degree or closing of a valve (44).

5. The lng cold energy cascade utilization system of claim 1, wherein: and step five, the required refrigerating capacity of the seawater desalination system corresponds to the LNG flow of the specific ship type.

6. The lng cold energy cascade utilization system of claim 1, wherein: when the cold energy brought out by the heat regenerator (26) meets the refrigerating capacity required by seawater desalination, the valve C (48) and the valve D (49) are partially opened, the valve A (46) and the valve B (47) are completely closed, and the refrigerating capacity required by a seawater desalination system is controlled by adjusting the opening degrees of the valve C (48) and the valve D (49);

when the cold energy brought out by the heat regenerator (26) can not meet the refrigerating capacity required by seawater desalination, the valve C (48) and the valve D (49) are completely opened, the valve A (46) and the valve B (47) are partially opened, and the refrigerating capacity required by a seawater desalination system is met by adjusting the opening degrees of the valve A (46) and the valve B (47).

7. The lng cold energy cascade utilization system of claim 1 or 2, wherein: the one-level Rankine cycle working medium in the two-level Rankine power generation circulating system is a mixed working medium of R1150 and methane, and the mass ratio is 43: 57; the two-stage Rankine cycle working medium in the two-stage Rankine power generation cycle system is a mixed working medium of R1150 and ethane, and the mass ratio is 60: 40; the Rankine cycle working medium in the single-stage Rankine power generation circulating system is a mixed working medium of R1150 and R1270, and the mass ratio is 52: 48.

8. The lng cold energy cascade utilization system of claim 1 or 2, wherein: the refrigerant of the nitrogen preparation system is R1150; the refrigerant of the second-stage air conditioning system is R410 a.

9. The lng cold energy cascade utilization system of claim 1 or 2, wherein: and refrigerants of the seawater desalination system, the primary air conditioning system, the low-temperature refrigeration house system and the high-temperature refrigeration house system are all R600.

10. The lng cold energy cascade utilization system of claim 1, wherein: the primary Rankine cycle working medium cold energy and the single-stage Rankine cycle working medium cold energy leading-out part in the two-stage Rankine cycle are used for cooling of the ship seawater desalination circulation system through a refrigerant by using the heat regenerator (16), and the secondary Rankine cycle working medium cold energy leading-out part in the two-stage Rankine cycle is used for cooling of the ship first-stage air conditioning circulation system through the refrigerant by using the heat regenerator (21).

Technical Field

The invention relates to the technical field of ships, in particular to a liquefied natural gas cold energy cascade utilization system of a liquefied natural gas power ship.

Background

In recent years, the yield and the import quantity of Liquefied Natural Gas (LNG) in China are greatly increased, the annual yield of the LNG in a factory in China in 2017 is increased by 187.45% before five years, the import quantity of the LNG is increased by 116% before five years, the total supply quantity of the LNG is increased by 122% before five years, the consumption quantity of the Natural Gas in China 2017 is only increased by 39.2% before five years, and the occupation ratio of the LNG in the total consumption quantity of the Natural Gas in 2017 is increased by 59.3%, so that the increase is still ongoing.

The LNG is characterized in that the main component of the LNG is methane, the LNG is colorless, tasteless, nontoxic and noncorrosive, huge cold energy is 830-860 kJ/kg < 6 > in liquid LNG with the temperature of minus 163 ℃ at normal pressure, and in the process of LNG ocean transportation, a part of LNG is usually used by an LNG ship host machine, but the LNG is not directly connected into the host machine for combustion, and the LNG is usually heated and vaporized into normal-temperature Natural Gas (NG) with the temperature of 25 ℃ and then is introduced into the host machine for combustion.

For the treatment of the LNG fuel sent into the main engine, the conventional LNG power ship mostly adopts a forced vaporization mode, for example, a mode of heat exchange with seawater, so that the liquid low-temperature LNG is vaporized and heated to the temperature required by the air intake of the main engine, and therefore, the cold energy of the LNG is not reasonably utilized, energy waste is caused, and the ecological environment is also polluted.

In addition, the ships have more cold energy demand places, such as ship cold storages, air conditioners, seawater desalination systems and the like, and the refrigeration mainly depends on the compressor to consume more electric energy, so that the LNG cold energy is adopted to replace the traditional refrigeration mode, a large amount of electric energy can be saved, and the operation cost is reduced.

Disclosure of Invention

The purpose of the invention is as follows: in order to solve the defects of the prior art, the invention provides a liquefied natural gas cold energy cascade utilization system of a liquefied natural gas power ship, which reasonably utilizes the LNG cold energy in a cascade manner to improve the cold energy and the cold

The comprehensive utilization efficiency of the ship is improved, and the operating cost of the ship is reduced.

As a further preferred aspect of the present invention, the lng cold energy cascade utilization system of the lng-powered ship according to the present invention comprises the following implementation steps: firstly, LNG cold energy at-162 ℃ to-140 ℃ is used for preparing nitrogen by using a refrigerant; then, the high-pressure low-temperature LNG cold energy is converted into electric energy by utilizing a two-stage Rankine cycle; then the vaporized natural gas is sent into an expander to be directly expanded to generate power; the low-pressure and low-temperature LNG cold energy is converted into electric energy by using a single-stage Rankine cycle; and then the LNG cold energy of the intercooling part is recycled in steps by utilizing the refrigerant and is used for cooling the ship low-temperature refrigeration house circulating system, the high-temperature refrigeration house circulating system and the second-stage air conditioner circulating system.

As a further preferred embodiment of the present invention, the lng cold energy cascade utilization system of the lng-powered ship comprises the following steps:

the method comprises the following steps: LNG cold energy is first used in the nitrogen production cycle

Pressurizing the liquefied natural gas at normal pressure to 4-5 MPa, wherein the temperature is-161 ℃ to-160 ℃, and then sending the liquefied natural gas into an LNG heat exchanger of the nitrogen preparation cycle to exchange heat with a nitrogen preparation cycle working medium;

step two: the two-stage Rankine cycle power generation system is arranged at the tail end of the nitrogen preparation cycle

The LNG primarily utilized by the nitrogen preparation cycle is at-140 ℃ to-135 ℃, and is sent to a condenser of a first Rankine cycle in a two-stage Rankine cycle power generation system, the first Rankine cycle working medium absorbs part of heat of a seawater desalination system firstly, then absorbs heat of a second Rankine cycle working medium to generate vaporization, and is cooled and liquefied by liquefied natural gas after being acted by an expander, the second Rankine cycle working medium absorbs heat of a first-stage air conditioning system firstly, absorbs part of waste heat of cylinder liner water of a main engine to generate vaporization, and is cooled and liquefied by the first Rankine cycle working medium after being acted by the expander;

step three: LNG expander is arranged at tail end of two-stage Rankine cycle power generation system

The natural gas after passing through the nitrogen preparation system and the two-stage Rankine cycle power generation system is sent to an expander for direct expansion work at the temperature of-57 ℃;

step four: the single-stage Rankine cycle power generation system is arranged at the tail end of the LNG expander

Step four: the single-stage Rankine cycle power generation system is arranged at the tail end of the LNG expander

The natural gas directly expanded and acted by a nitrogen preparation system, a two-stage Rankine cycle power generation system and an LNG expander is sent into a condenser of a single-stage Rankine cycle at the pressure of 0.7-1 Mpa and the temperature of-115-120 ℃, the single-stage Rankine cycle working medium firstly absorbs part of heat of a seawater desalination system, then absorbs part of waste heat of cylinder liner water of a main engine to be vaporized, and the natural gas is cooled and liquefied after being acted by the expander;

step five: the seawater desalination system is nested in the two-stage Rankine cycle power generation system and the single-stage Rankine cycle system

The temperature of a refrigerant of the seawater desalination system is-15 ℃ to-10 ℃ after heat exchange by seawater desalination equipment, a part of the refrigerant after passing through a diverter valve is sent to a first-stage Rankine cycle heat regenerator in a two-stage Rankine cycle power generation system to exchange heat with a first-stage Rankine cycle working medium, the temperature is reduced to-90 ℃ to-85 ℃, the other part of the refrigerant is sent to a heat regenerator of a single-stage Rankine cycle power generation system to exchange heat with the single-stage Rankine cycle working medium, the temperature is reduced to-75 ℃ to-70 ℃, two streams of the refrigerant are mixed by a mixer after being cooled, the temperature of the mixed refrigerant is-83 ℃ to-80 ℃, and the refrigerant after seawater desalination is pushed by a refrigerant;

step six: the first-stage air conditioning system is nested in the two-stage Rankine cycle power generation system

The temperature of the refrigerant of the air conditioning system is 10-20 ℃ after exchanging heat with the external environment, the refrigerant is sent into a secondary Rankine cycle heat regenerator in a two-stage Rankine cycle power generation system to exchange heat with a secondary Rankine cycle working medium, the temperature is reduced to-10 ℃ to-8 ℃, and the refrigerant is pushed by a refrigerant pump of a first-stage air conditioning system to exchange heat with the external environment;

step seven: the low-temperature refrigeration house system is arranged at the tail end of the single-stage Rankine cycle power generation system

The temperature of the natural gas which is directly expanded to work through a nitrogen preparation system, a two-stage Rankine cycle power generation system and an LNG expander and is utilized by the single-stage Rankine cycle power generation system is about-40 ℃ to-38 ℃, the natural gas is sent into a low-temperature refrigeration house system for cooling, the temperature of a refrigerant cooled by the natural gas is-37 ℃ to-35 ℃, the refrigerant is pushed by a refrigerant pump of the low-temperature refrigeration house system to exchange heat with the external environment, the temperature is raised to-20 ℃ to-15 ℃, and then cold energy is absorbed for next cycle refrigeration;

step eight: the high-temperature refrigeration house system is arranged at the tail end of the low-temperature refrigeration house system

The temperature of the natural gas used by the low-temperature refrigeration house system is-24 ℃ to-20 ℃, the natural gas is sent into the high-temperature refrigeration house system for cooling, the temperature of a refrigerant cooled by the natural gas is-20 ℃ to-15 ℃, the refrigerant is pushed by a refrigerant pump of the high-temperature refrigeration house system to exchange heat with the external environment, the temperature is raised to-9 ℃ to absorb cold energy, and the next cycle of refrigeration is carried out;

step nine: the second-stage air conditioning system is arranged at the tail end of the high-temperature refrigeration house system

The natural gas which is directly expanded to work through a nitrogen preparation system, a two-stage Rankine cycle power generation system and an LNG expander and is utilized by a single-stage Rankine cycle power generation system, a low-temperature refrigeration house system and a high-temperature refrigeration house system is at a temperature of-14 ℃ to-10 ℃, the natural gas is sent to a second-stage air conditioning system for cooling, the temperature of a refrigerant which is cooled and liquefied through the natural gas is at a temperature of-9 ℃ to-5 ℃, the refrigerant is pushed by a refrigerant pump of the second-stage air conditioning system to exchange heat with the external environment for vaporization, the temperature is raised to 20 ℃ to 22 ℃, and then cold energy;

step ten: the natural gas temperature regulating heat exchanger is arranged at the tail end of the second-stage air conditioning system

The natural gas which is directly expanded to work through a nitrogen preparation system, a two-stage Rankine cycle power generation system and an LNG expander is fed into a cylinder liner water heat exchanger to exchange heat with part of main engine cylinder liner water at the temperature of 12-15 ℃, and the natural gas after heat exchange is raised to 25-28 ℃ and fed into a main engine to be combusted.

As a further preferred aspect of the present invention, the required cooling capacity of the air conditioning system in the sixth step and the ninth step is adapted to the LNG flow rate of a specific ship type.

As a further preferred embodiment of the present invention, the amount of cooling capacity of the air conditioning system is realized by adjusting the opening degree or closing of a valve.

As a further preferable aspect of the present invention, the amount of refrigeration required by the seawater desalination system in step five corresponds to the LNG flow rate of a specific ship type.

As a further optimization of the invention, when the cold energy brought out by the heat regenerator meets the refrigerating capacity required by seawater desalination, the valve C and the valve D are partially opened, the valve a and the valve B are completely closed, and the refrigerating capacity required by the seawater desalination system is controlled by adjusting the opening degrees of the valve C and the valve D;

when the cold energy brought out by the heat regenerator can not meet the refrigerating capacity required by the seawater desalination system, the valve C and the valve D are completely opened, the valve A and the valve B are partially opened, and the refrigerating capacity required by the seawater desalination system is met by adjusting the opening degrees of the valve A and the valve B.

In a further preferred embodiment of the present invention, the one-stage rankine cycle working medium in the two-stage rankine power generation cycle system is a mixed working medium of R1150 and methane.

As a further optimization of the invention, the mass ratio of the mixed working medium is 43: 57.

In a further preferred embodiment of the present invention, the two-stage rankine cycle working medium in the two-stage rankine power generation cycle system is a mixed working medium of R1150 and ethane.

As a further optimization of the invention, the mass ratio of the mixed working medium is 60: 40.

As a further preferable aspect of the present invention, the rankine cycle working medium in the single-stage rankine power generation cycle system is a mixed working medium of R1150 and R1270.

As a further optimization of the invention, the mass ratio of the mixed working medium is 52: 48.

As a further preferred aspect of the present invention, the refrigerant of the nitrogen gas production system is R1150.

As a further preferred embodiment of the present invention, the refrigerants of the seawater desalination system, the primary air conditioning system, the low-temperature refrigerator system and the high-temperature refrigerator system are all R600.

In a further preferred embodiment of the present invention, the second-stage air conditioning system refrigerant is R410 a.

As a further preferable mode of the present invention, the heat regenerator is used for using the cold energy of the working medium in the first rankine cycle and the cold energy extraction part of the working medium in the single-stage rankine cycle in the two-stage rankine cycle for cooling of the seawater desalination system of the ship by the refrigerant, and the heat regenerator is used for using the cold energy extraction part of the working medium in the second rankine cycle in the two-stage rankine cycle for cooling of the first air conditioning system of the ship by the refrigerant.

Has the advantages that: the liquefied natural gas cold energy cascade utilization system of the liquefied natural gas power ship, disclosed by the invention, is characterized in that the cold energy of the fuel sent into the main engine is subjected to cascade utilization in a nitrogen preparation system, a ship power generation system, a seawater desalination system, a ship low-temperature cold storage circulating system, a ship high-temperature cold storage circulating system and a ship air-conditioning circulating system, the natural gas reaches the air inlet required temperature of the main engine by a natural gas temperature regulating heat exchanger and is sent into the main engine for combustion, the LNG cold energy is reasonably utilized in a cascade manner by the system, and the cold energy

The comprehensive utilization efficiency of the LNG cold energy is improved, the operation cost of the ship is reduced, and meanwhile, on the basis of utilizing the waste heat of the cylinder sleeve water of the main engine of the ship, the limited LNG cold energy can be reasonably distributed and utilized to a greater extent on different ship types by increasing and decreasing the load of each system and adjusting the valves of the nested systems according to the specific requirements of electric power, nitrogen, fresh water, a refrigeration house and an air conditioning module of different ship types and the specific working conditions under different space-time conditions.

Drawings

FIG. 1 is a schematic flow chart of the present invention;

wherein: 1-liquefied natural gas pump; 2-liquefied natural gas flow regulating valve; 3, 4, 6, 7, 8, 9-LNG heat exchangers; 10-natural gas temperature regulating heat exchanger; 11-a nitrogen preparation system refrigerant pump; 13-nitrogen preparation system heat exchanger; 14, 19, 24-power generation working medium pump; 16, 21, 26-regenerator; 17-a two-stage rankine cycle intermediate heat exchanger; 22, 27-power generation working medium evaporator; 5, 18, 23, 28-expander; 29-a refrigerant mixer of the seawater desalination system; 30-a refrigerant pump of a seawater desalination system; 32-a seawater desalination system heat exchanger; 33-refrigerant shunt valve of seawater desalination system; 34-a low-temperature refrigerator refrigerant pump; 36-low temperature freezer heat exchanger; 37-high temperature freezer coolant pump; 39-high temperature freezer heat exchanger; 40-a second stage air conditioning system refrigerant pump; 42-a second stage air conditioning system refrigerant evaporator; 43-refrigerant pump of first air-conditioning system; 45-first stage air conditioning system heat exchanger; 12,15,20,25,31,35,38,41, 44-valves; 46-valve A; 47-valve B; 48-valve C; 49-valve D.

Detailed Description

The invention is further elucidated with reference to the drawings and the embodiments.

As shown in fig. 1, the lng cold energy cascade utilization system of the lng-powered ship according to the present invention includes the following steps: firstly, LNG cold energy at-162 ℃ to-140 ℃ is used for preparing nitrogen by using a refrigerant; then, the high-pressure low-temperature LNG cold energy is converted into electric energy by utilizing a two-stage Rankine cycle; then the vaporized natural gas is sent into an expander to be directly expanded to generate power; the low-pressure and low-temperature LNG cold energy is converted into electric energy by using a single-stage Rankine cycle; and then the LNG cold energy of the intercooling part is recycled in steps by utilizing the refrigerant and is used for cooling the ship low-temperature refrigeration house circulating system, the high-temperature refrigeration house circulating system and the second-stage air conditioner circulating system.