CN119572327A - LNG cold energy cascade utilization power generation system and method combining air separation units - Google Patents
LNG cold energy cascade utilization power generation system and method combining air separation units Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K13/00—General layout or general methods of operation of complete plants
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K13/00—General layout or general methods of operation of complete plants
- F01K13/003—Arrangements for measuring or testing
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K13/00—General layout or general methods of operation of complete plants
- F01K13/006—Auxiliaries or details not otherwise provided for
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K13/00—General layout or general methods of operation of complete plants
- F01K13/02—Controlling, e.g. stopping or starting
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K17/00—Using steam or condensate extracted or exhausted from steam engine plant
- F01K17/02—Using steam or condensate extracted or exhausted from steam engine plant for heating purposes, e.g. industrial, domestic
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
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Abstract
本发明提供了一种结合空分单元的LNG冷能梯级利用发电系统及方法，该系统包括：LNG供气路，包括依次连接的第一增压泵、空分单元以及LNG蒸发器；乙二醇水循环单元，包括依次循环连接的空分单元、第二增压泵以及第一加热器；动力发电循环单元，循环流通有循环工质进行做功发电，包括第一加热器、第一透平膨胀机、LNG蒸发器和第三增压泵。本发明通过乙二醇水吸收空分单元内部余热后供给动力发电循环单元，LNG供气路提供的天然液化气在空分单元释放高品位冷能后进入动力发电循环单元进一步释放剩余冷能，实现了LNG冷能以及余热的梯级使用，可有效减少空分单元电耗，并可以显著动力发电循环单元的工作效率，实现能源的清洁高效利用。
The present invention provides a LNG cold energy cascade utilization power generation system and method combined with an air separation unit, the system comprising: an LNG gas supply line, comprising a first booster pump, an air separation unit and an LNG evaporator connected in sequence; an ethylene glycol water circulation unit, comprising an air separation unit, a second booster pump and a first heater connected in sequence; a power generation circulation unit, in which a circulating working medium circulates to generate power, comprising a first heater, a first turbine expander, an LNG evaporator and a third booster pump. The present invention supplies the power generation circulation unit with ethylene glycol water after absorbing the waste heat inside the air separation unit, and the natural liquefied gas provided by the LNG gas supply line enters the power generation circulation unit after releasing high-grade cold energy in the air separation unit to further release the remaining cold energy, thereby realizing the cascade use of LNG cold energy and waste heat, effectively reducing the power consumption of the air separation unit, and significantly improving the working efficiency of the power generation circulation unit, thereby realizing clean and efficient utilization of energy.
Description
Technical Field
The invention relates to the technical field of power generation systems, in particular to an LNG cold energy cascade utilization power generation system and method combining air separation units.
Background
The LNG cold energy air separation system is an efficient, energy-saving and environment-friendly technology for air separation by utilizing the cold energy of LNG (liquefied natural gas). In the air separation process, air enters an oxygen-nitrogen-argon rectification system after being filtered, compressed and purified, and is separated into components such as oxygen, nitrogen, argon and the like. The heat exchange system is used for cooling air and nitrogen by the cold energy of the LNG, and the air separation process is carried out at extremely low temperature, so that compared with a traditional air separation system, the external supply of cold energy can be realized after the LNG cold energy is introduced, the energy consumption of a refrigerating unit is reduced, the power consumption is greatly reduced, and the system operation efficiency is improved. In addition, due to the reduction of energy consumption, the heat generated by the system is correspondingly reduced, so that the water consumption for heat dissipation and cooling is reduced, and in general, an LNG cold energy air separation system uses glycol as a circulating cooling medium, is cooled by LNG in an LNG-glycol heat exchanger, and is used as a cold source of a compressor stage-to-stage cooler, a final-stage cooler, a motor system, a lubricating oil system and the like, so that the water consumption is further reduced. The comprehensive LNG cold energy air separation technology has wide application prospect, and can be applied to the fields of gas separation, gas purification, gas liquefaction and the like in the industries of petrochemical industry, chemical industry, medicine, electronics, food and the like.
In an electric power generation cycle, the calculation of cycle efficiency follows the carnot theorem, and the improvement of efficiency is subject to the cycle maximum temperature and condensation temperature. In the existing power cycle, for example, the highest temperature of the steam Rankine cycle is the gaseous temperature of the steam, the lowest temperature is about the ambient temperature of the condensed steam in the condenser, and the two temperature limits limit the working range of the working medium, so that the efficiency cannot be further improved. The LNG cold energy power generation system is a high-efficiency energy utilization mode, and the technical principle is mainly based on a large amount of cold energy released by LNG (liquefied natural gas) in the gasification process, so that working media are cooled to be far lower than normal temperature, and the temperature difference of the hot end and the cold end of the working media can be increased, thereby improving the power generation and the operation efficiency. In the process, LNG absorbs heat, evaporates and gasifies, energy is obtained at the same time, the temperature rises to more than 0 ℃, and then natural gas pipe network is introduced.
In the conventional LNG cold energy air separation system, however, part of cold energy is not fully utilized after the LNG is supplied with cold energy, meanwhile, a certain scale of cooling water is required to be configured for cooling waste heat at the positions of a compressor stage, a motor system, a lubricating oil system and the like in the air separation system, so that energy waste is caused, meanwhile, in the conventional LNG cold energy power generation system, a hot end is heated by using seawater or air generally, the heating temperature is normal temperature, heat source input with higher temperature is lacked, and further improvement of power circulation efficiency is limited.
Disclosure of Invention
Aiming at the problems, the invention provides an LNG cold energy cascade utilization power generation system and method combining air separation units.
The invention provides an LNG cold energy cascade utilization power generation system combined with a space division unit, which comprises the following components:
The LNG supply path comprises a first booster pump, an air separation unit and an LNG evaporator which are connected in sequence;
the glycol water circulation unit comprises a space division unit, a second booster pump and a first heater which are sequentially and circularly connected;
A power generation circulation unit which circulates and circulates a circulation working medium to do work and generate electricity and comprises a first heater, a first turbine expander, an LNG evaporator and a third booster pump,
Wherein the LNG supply pipeline is communicated with liquefied natural gas input from outside, the liquefied natural gas absorbs heat in the air separation unit and the LNG evaporator in sequence,
Glycol water circulates in the glycol water circulation unit, the glycol water absorbs heat in the air separation unit, releases heat in the first heater,
The circulating working medium in the power generation circulating unit exchanges heat with glycol water in the first heater, and exchanges heat with liquefied natural gas in the LNG evaporator.
According to the technical scheme, the air separation unit can realize the high-efficiency air separation function by receiving the low-temperature circulating glycol water indirectly supplied by the glycol water circulation unit and the high-grade cold energy of the liquefied natural gas supplied by the LNG gas supply pipeline, and meanwhile, the power generation circulation unit can carry out power generation circulation and realize high-efficiency power production by receiving the high-temperature circulating glycol water indirectly supplied by the glycol water circulation unit and the low-grade cold energy of the liquefied natural gas supplied by the LNG gas supply pipeline.
Furthermore, the invention forms an ethylene glycol water circulation loop by constructing the ethylene glycol water circulation unit, the ethylene glycol water can absorb waste heat of a compressor stage chamber, a motor system and a lubricating oil system in the air separation unit and exchange heat in the first heater to supply the waste heat to the power generation circulation unit, meanwhile, LNG cold energy which is not completely utilized in the air separation unit is also collected by the LNG evaporator to supply the waste heat to the power generation circulation unit, thereby realizing the efficient utilization of the LNG cold energy and the waste heat, effectively reducing the power consumption and the water consumption of the air separation unit, remarkably improving the working efficiency of the power generation circulation unit and realizing the clean and efficient utilization of energy.
Optionally, the power generation circulation unit is formed by nesting a plurality of power generation circulation loops in a cascading arrangement.
According to the technical scheme, the cascade arrangement of the power generation sub-circulation loops further realizes cascade utilization of heat and cold energy, can effectively increase the operation efficiency of the whole circulation system, and improves the generated energy.
Optionally, the power generation circulation unit comprises a first power generation sub-circulation loop and a second power generation sub-circulation loop which are arranged in cascade,
The first power generation sub-circulation loop comprises a first heater, a first turbo expander, a second heater and a third booster pump which are sequentially and circularly connected,
The second power generation sub-circulation loop comprises a second heater, a second turbo expander, an LNG evaporator and a fourth booster pump which are sequentially and circularly connected.
Optionally, in the LNG supply path, the LNG input to the air separation unit is less than-150 ℃ and the LNG input to the LNG vaporizer is less than 0 ℃.
According to the technical scheme, the LNG gas supply pipeline can provide high-grade cold energy for the air separation unit to perform air separation, and meanwhile, the power generation circulation unit can provide residual low-grade cold energy to perform cooling liquefaction of the circulation working medium, so that the efficient utilization of the LNG cold energy is realized.
Optionally, in the glycol water circulation unit, the glycol water input to the air separation unit is lower than an ambient temperature, and the glycol water input to the first heater is higher than the ambient temperature.
According to the technical scheme, the glycol water circulation unit can provide cold energy for the air separation unit, and after the waste heat of the air separation unit is absorbed, the power generation circulation unit is provided with heat energy to perform heating evaporation of the circulation working medium, so that the waste heat in the air separation unit is efficiently utilized.
Optionally, in the power generation circulation unit, the temperature of the circulating working medium after flowing through the first heater is higher than the ambient temperature, and the temperature of the circulating working medium after flowing through the LNG evaporator is lower than the ambient temperature.
According to the technical scheme, the circulating working medium in the power generation circulating unit can be heated by the glycol water absorbing the waste heat of the air separation unit in the first heater, and meanwhile, the residual cold energy of the natural liquefied gas passing through the LNG evaporator can be cooled, so that the circulating working medium can circulate to do work and generate power, and clean and efficient utilization of energy is realized.
Optionally, a natural gas expander is also connected to the LNG vaporizer.
According to the technical scheme, the liquefied natural gas which is sequentially subjected to heat absorption by the air unit and the LNG evaporator is input into the natural gas expander to perform expansion work, so that heat absorbed by the liquefied natural gas in the LNG gas supply circuit can be converted into electric energy and output, and the generated energy is further improved.
The invention also provides a power generation method, which is applied to the LNG cold energy cascade utilization power generation system combined with the air separation unit, and comprises the following steps:
The power generation circulation unit comprises:
a working medium pressurizing step, namely pressurizing the low-temperature circulating working medium in a liquid form through a third booster pump;
A working medium heat exchange step, namely absorbing heat of the glycol water circulation unit at the first heater by the pressurized low-temperature circulation working medium, and heating and evaporating the working medium;
Working medium working step, namely the heated circulating working medium expands outwards in the first turbine expander to do work, and the self temperature and pressure are reduced;
A working medium cooling step, namely absorbing low-temperature cold energy of liquefied natural gas at an LNG evaporator through a working cycle working medium, cooling and liquefying the working cycle working medium to form a low-temperature cycle working medium, and then repeating a working medium pressurizing step, a working medium heat exchanging step and a working medium working step to perform power generation circulation;
The glycol water circulation unit comprises:
the heat absorption step is that the glycol water flows through the inside of the air separation unit to absorb waste heat, and the temperature of the glycol water rises;
the step of pressurizing, namely, the glycol water flows through a second pressurizing pump, the self pressure is increased, and the flow stability of the glycol water circulation unit is maintained;
The cooling step, namely heating low-temperature circulating working medium in the power generation circulating unit by glycol water at the first heater, reducing the temperature of the glycol water, and then repeating the heat absorption step and the pressurizing step to circulate the glycol water;
The LNG supply line comprises:
The LNG pressurizing step is to pressurize the liquefied natural gas supplied from the outside through a first booster pump, and maintain the stable flow of the LNG supply path;
the heating step, namely, the pressurized liquefied natural gas enters the air separation unit to cool the air, and the temperature of the air separation unit is increased;
And a reheating step, namely cooling the circulating working medium in the power generation circulating unit by the liquefied natural gas output from the air separation unit at the LNG evaporator, and further raising the temperature of the liquefied natural gas and gasifying the liquefied natural gas.
In the power generation method, the LNG supply pipeline optionally further comprises a working step of enabling the liquefied natural gas obtained through the reheating step to enter a natural gas turbine expander to do work for external expansion, wherein the liquefied natural gas is reduced in temperature and pressure and then is introduced into an external natural gas supply pipe network.
Drawings
Fig. 1 is a schematic diagram of an LNG cold energy cascade utilization power generation system incorporating an air separation unit in a first embodiment of the present invention;
Fig. 2 is a schematic diagram of a LNG cold energy cascade utilization power generation system incorporating an air separation unit in a second embodiment of the present invention;
Fig. 3 is a schematic diagram of an LNG cold energy cascade utilization power generation system incorporating a space division unit in a third embodiment of the present invention.
Reference numerals are a first booster pump 1, an air separation unit 2, a second booster pump 3, a first heater 4, a first turbo expander 5, an LNG vaporizer 6, a third booster pump 7, a second heater 41, a second turbo expander 51, a fourth booster pump 71, and a natural gas expander 8.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, are intended to fall within the scope of the present invention.
< First embodiment >
Fig. 1 is a schematic diagram of an LNG cold energy cascade utilization power generation system incorporating a space division unit in a first embodiment of the present invention.
As shown in fig. 1, the LNG cold energy cascade power generation system including the air separation unit in the present embodiment includes a first booster pump 1, an air separation unit 2, a second booster pump 3, a first heater 4, a first turbo expander 5, an LNG vaporizer 6, and a third booster pump 7.
In this embodiment, the air separation unit is an LNG cold energy air separation system, and the air separation unit separates air by a rectification method, receives cold energy indirectly supplied by the LNG gas supply path and the glycol water circulation unit, and is used for cooling the air before rectification and cooling the motor, the lubricating oil system, and the compressor system in the air separation unit, respectively. The space division unit is a prior art and is not described in detail herein.
The LNG supply line includes a first booster pump 1, an air separation unit 2, and an LNG vaporizer 6, which are sequentially connected.
The glycol water circulation unit comprises a space division unit 2, a second booster pump 3 and a first heater 4 which are sequentially and circularly connected.
The power generation circulation unit comprises a first heater 4, a first turboexpander 5, an LNG evaporator 6 and a third booster pump 7 which are sequentially and circularly connected.
The LNG supplied from the LNG supply line is supplied with an externally supplied LNG, and the LNG absorbs heat in the air separation unit 2 and the LNG vaporizer 6 in this order.
The glycol water circulation unit circulates glycol water, and the glycol water absorbs heat in the air separation unit 2 and releases heat in the first heater 4.
The circulation flow in the power generation circulation unit is provided with a circulation working medium, the circulation working medium exchanges heat with glycol water in the first heater 4, and the circulation working medium exchanges heat with liquefied natural gas in the LNG evaporator 6.
Specifically, the liquefied natural gas input into the air separation unit 2 is ultralow-temperature liquid at a temperature lower than-150 ℃ and absorbs heat in the air separation unit 2, the ethylene glycol water input into the air separation unit 2 is lower than the ambient temperature and absorbs heat in the air separation unit 2, and the air separation unit 2 receives the low-temperature circulating ethylene glycol water indirectly supplied by the ethylene glycol water circulating unit and the LNG high-grade cold energy provided by the LNG air supply pipeline, so that high-efficiency air separation can be realized.
The ethylene glycol water input into the first heater 4 is higher than the ambient temperature and exchanges heat with the circulating working medium, so that the low-temperature circulating working medium is heated and evaporated and then enters the first turbine expander 5 to do work and generate electricity, the liquefied natural gas input into the LNG evaporator 6 is low-temperature liquid lower than 0 ℃ and exchanges heat with the circulating working medium, so that the circulating working medium after doing work is cooled and liquefied and enters the third booster pump 7 to boost pressure, the circulating circulation of the circulating working medium can be realized, the repeated work and power generation cycle can be realized, and the efficient electric power production can be realized.
In this embodiment, after the waste heat of the compressor stage, the motor system, and the lubricating oil system in the air separation unit 2 is absorbed by the glycol water, heat exchange is performed between the first heater 4 and the circulating working medium, and the waste heat is supplied to the power generation circulation unit, so that the waste heat in the air separation unit 2 is fully utilized.
Meanwhile, the externally input Liquefied Natural Gas (LNG) enters the LNG evaporator 6 to exchange heat with the circulating working medium in the power generation circulating unit after the air separation unit 2 releases high-grade cold energy, so that the residual cold energy is further released, and the full utilization of the LNG cold energy is realized.
Therefore, the LNG cold energy cascade utilization power generation system combined with the air separation unit fully utilizes the waste heat and the LNG cold energy in the air separation unit, can effectively reduce the power consumption and the water consumption of the air separation unit, can remarkably improve the working efficiency of the power generation circulation unit, and realizes clean and efficient utilization of energy.
Further, the power generation method of the LNG cold energy cascade power generation system combined with the air separation unit applied to the present embodiment includes the steps of:
The power generation circulation unit comprises:
and the working medium pressurizing step is to pressurize the low-temperature circulating working medium in a liquid form through a third booster pump 7.
And a working medium heat exchange step, namely absorbing the heat of the glycol water circulation unit at the first heater 4 by the pressurized low-temperature circulation working medium, and heating and evaporating the working medium.
And working medium working step, namely the heated circulating working medium is expanded and worked in the first turbine expander 5, and the self temperature and pressure are reduced.
And a working medium cooling step, namely absorbing low-temperature cold energy of liquefied natural gas at the LNG evaporator 6 by the working circulation working medium, cooling and liquefying the working circulation working medium to form a low-temperature circulation working medium, and then repeating the working medium pressurizing step, the working medium heat exchanging step and the working medium working step to perform power generation circulation.
The glycol water circulation unit comprises:
and in the heat absorption step, the glycol water flows through the air separation unit 2 to absorb the waste heat among a motor system, a lubricating oil system and a compressor stage, and the temperature of the glycol water rises.
And in the pressurizing step, glycol water flows through the second booster pump 3, the self pressure is increased, and the flow stability of the glycol water circulation unit is maintained.
And a cooling step, namely heating low-temperature circulating working media in the power generation circulating unit by glycol water at the first heater 4, reducing the temperature of the glycol water, and then repeating the heat absorption step and the pressurizing step to circulate the glycol water.
The LNG supply line comprises:
And in the LNG pressurizing step, the liquefied natural gas supplied from the outside is pressurized by the first booster pump 1, so that the flow of the LNG supply path is maintained stable.
And a heating step, namely, the pressurized liquefied natural gas enters the air separation unit 2 to cool air, and the temperature of the liquefied natural gas is increased.
And in the reheating step, the liquefied natural gas output from the air separation unit 2 cools the circulating working medium in the power generation circulating unit at the LNG evaporator 6, the temperature of the liquefied natural gas is further increased and gasified, and then the liquefied natural gas is introduced into an external natural gas supply pipe network.
< Second embodiment >
In this embodiment, the LNG supply line and the glycol water circulation unit are the same as those in the first embodiment.
The power generation circulation unit is formed by nesting a plurality of power generation sub-circulation loops. In this embodiment, the nesting manner is in a cascade arrangement, and the number of the plurality of power generation sub-circulation loops is specifically two, and the plurality of power generation sub-circulation loops are respectively a first power generation sub-circulation loop and a second power generation sub-circulation loop.
Fig. 2 is a schematic diagram of an LNG cold energy cascade utilization power generation system incorporating a space division unit in a second embodiment of the present invention.
As shown in fig. 2, the LNG cold energy cascade power generation system including the air separation unit in the present embodiment includes a first booster pump 1, an air separation unit 2, a second booster pump 3, a first heater 4, a first turbo expander 5, an LNG evaporator 6, a third booster pump 7, a second heater 41, a second turbo expander 51, and a fourth booster pump 71.
The LNG supply line includes a first booster pump 1, an air separation unit 2, and an LNG vaporizer 6, which are sequentially connected.
The glycol water circulation unit comprises a space division unit 2, a second booster pump 3 and a first heater 4 which are sequentially and circularly connected.
The power generation circulation unit comprises a first power generation sub-circulation loop and a second power generation sub-circulation loop which are arranged in a cascading way.
The first power generation sub-cycle includes a first heater 4, a first turbo expander 5, a second heater 41, and a third booster pump 7, which are sequentially and cyclically connected.
The second power generation sub-circulation circuit includes a second heater 41, a second turbo expander 51, an LNG vaporizer 6, and a fourth booster pump 71, which are sequentially and circularly connected.
In this embodiment, the first power generation sub-cycle and the second power generation sub-cycle circulate a first cycle fluid and a second cycle fluid respectively. The first heater 4 of the glycol water circulation circuit is used as a first heat source, and the heat from the first heater 4 is transferred to the second power generation sub-circulation circuit through the first power generation sub-circulation circuit. The LNG evaporator 6 is arranged in the second power generation sub-circulation loop, cold energy is transmitted to the first power generation sub-circulation loop through the second power generation sub-circulation loop, and gradient utilization of LNG cold energy and waste heat in the air separation unit is achieved.
In this embodiment, the first circulating working medium and the ethylene glycol water in the first power generation sub-circulation loop exchange heat in the first heater 4, the first circulating working medium and the second circulating working medium exchange heat in the second heater 41, and the second circulating working medium and the natural liquefied gas exchange heat in the LNG evaporator 6.
Further, in the power generation method of the LNG cold energy cascade power generation system combined with the air separation unit applied to the present embodiment, steps in the ethylene glycol water circulation unit and in the LNG gas supply path are the same as those of the first embodiment, and the power generation circulation unit includes a first power generation sub-cycle and a second power generation sub-cycle, specifically including the following steps:
in the first power generation sub-cycle:
And the pressurizing step is to pressurize the low-temperature first circulating working medium in a liquid form through a third booster pump 6.
And the heat exchange step is that the pressurized low-temperature first circulating working medium absorbs the heat of the glycol water circulating unit at the first heater 4 and heats up and evaporates itself.
The working step is that the first circulating working medium after temperature rise expands outwards in the first turbine expander 5 to do work, and the temperature and pressure of the working medium are reduced.
And a cooling step, namely performing heat exchange on the first circulating working medium subjected to work doing with the second low-temperature circulating working medium at the second heater 41, cooling and liquefying the first circulating working medium to form the low-temperature circulating working medium, and then repeating the pressurizing step, the heat exchange step and the work doing step to perform first power generation sub-circulation.
In the second power generation sub-cycle:
And in the pressurizing step, the low-temperature second circulating working medium is pressurized in a liquid form through a fourth booster pump 71.
The heat exchange step is that the low-temperature second circulating working medium after pressurization absorbs the heat of the first circulating working medium at the second heater 41, and the self-heating evaporation is carried out.
The working step is that the heated second circulating working medium expands outwards in the second turbine expander 51 to do work, and the temperature and pressure of the working medium are reduced.
And a cooling step, namely performing heat exchange on the working second circulating working medium and the natural liquefied gas at the LNG evaporator 6, cooling and liquefying the working second circulating working medium to form a low-temperature second circulating working medium, and then repeating the pressurizing step, the heat exchange step and the working step to perform second power generation sub-circulation.
It will be appreciated that in some embodiments, the number of the cascade arrangement of the plurality of power generation sub-circuits exceeds two, heat from the first heater 4 can be transferred downward layer by layer through the plurality of power generation sub-circuits of the cascade arrangement, the LNG vaporizer 6 is arranged in the last power generation sub-circuit, and cold energy can be transferred upward layer by layer through the plurality of power generation sub-circuits of the cascade arrangement, thereby achieving a cascade utilization of LNG cold energy and waste heat in the air separation unit through the cascade arrangement of the plurality of power generation sub-circuits.
< Third embodiment >
Fig. 3 is a schematic diagram of an LNG cold energy cascade utilization power generation system incorporating a space division unit in a third embodiment of the present invention.
As shown in fig. 3, in the present embodiment, the glycol water circulation unit and the power generation circulation unit are the same as in the first embodiment. In the LNG supply path, the LNG vaporizer 6 is further connected with a natural gas expander 8.
The liquefied natural gas which is sequentially subjected to heat absorption by the air unit and the LNG evaporator 6 is input into the natural gas expander 8 to perform expansion work, so that heat absorbed by the liquefied natural gas in the LNG gas supply circuit can be converted into electric energy and output, the generated energy is further improved, and the high-efficiency utilization of energy is realized.
Further, the first booster pump 1 pressurizes the liquefied natural gas inputted from the outside to a pressure higher than the input pressure of the external natural gas supply pipe network, and after the liquefied natural gas sequentially flows through the air separation unit, the LNG vaporizer 6 and the natural gas expander 8, the pressure of the liquefied natural gas is the input pressure required by the external natural gas supply pipe network and is inputted to the natural gas supply pipe network.
In the power generation method applied to the LNG cold energy cascade power generation system combined with the air separation unit in the present embodiment, steps in the ethylene glycol water circulation unit and the power generation circulation unit are the same as those in the first embodiment, and the LNG supply path includes the following steps:
And in the LNG pressurizing step, the liquefied natural gas supplied from the outside is pressurized by the first booster pump 1, so that the flow of the LNG supply path is maintained stable.
And a heating step, namely, the pressurized liquefied natural gas enters the air separation unit 2 to cool air, and the temperature of the liquefied natural gas is increased.
And in the reheating step, the liquefied natural gas output from the air separation unit 2 cools the circulating working medium in the power generation circulating unit at the LNG evaporator 6, and the temperature of the liquefied natural gas is further increased and gasified.
And the working step is to input the liquefied natural gas which is heated and gasified in the reheating step into a natural gas turbine expander 8 to perform expansion working, and then the liquefied natural gas is led into an external natural gas supply pipe network after the temperature and pressure of the liquefied natural gas are reduced.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (9)
1. LNG cold energy cascade utilization power generation system that combines space division unit, characterized in that includes:
The LNG supply path comprises a first booster pump, an air separation unit and an LNG evaporator which are connected in sequence;
The glycol water circulation unit comprises the air separation unit, a second booster pump and a first heater which are sequentially and circularly connected;
A power generation circulation unit which circulates and circulates a circulation working medium to do work and generate electricity and comprises the first heater, a first turbine expander, the LNG evaporator and a third booster pump,
Wherein the LNG supply line is provided with liquefied natural gas inputted from outside, the liquefied natural gas absorbs heat in the air separation unit and the LNG vaporizer in sequence,
Glycol water circulates in the glycol water circulation unit, the glycol water absorbs heat in the air separation unit, releases heat in the first heater,
The circulating working medium in the power generation circulating unit exchanges heat with the glycol water in the first heater, and exchanges heat with the liquefied natural gas in the LNG evaporator.
2. The LNG cold energy cascade utilization power generation system in combination with a space division unit of claim 1, wherein the power generation cycle unit is formed of a plurality of power generation sub-cycle loops nested in a cascade arrangement.
3. The LNG cold energy cascade utilization power generation system in combination with an air separation unit as defined in claim 2, wherein the power generation cycle unit comprises a first power generation sub-cycle and a second power generation sub-cycle in a cascade arrangement,
The first power generation sub-circulation loop comprises the first heater, the first turbo expander, the second heater and the third booster pump which are sequentially and circularly connected,
The second power generation sub-circulation loop comprises a second heater, a second turboexpander, the LNG evaporator and a fourth booster pump which are sequentially and circularly connected.
4. The LNG cold energy cascade power generation system incorporating an air separation unit of claim 1, wherein the LNG supply line is at a temperature of less than-150 ℃ and the LNG supplied to the air separation unit is at a temperature of less than 0 ℃ and the LNG supplied to the LNG vaporizer.
5. The LNG cold energy cascade power generation system combined with an air separation unit according to claim 1, wherein in the glycol water circulation unit, the glycol water inputted into the air separation unit is lower than an ambient temperature, and the glycol water inputted into the first heater is higher than an ambient temperature.
6. The LNG cold energy cascade power generation system with air separation unit according to claim 1, wherein in the power generation cycle unit, the temperature of the cycle fluid after flowing through the first heater is higher than the ambient temperature, and the temperature of the cycle fluid after flowing through the LNG vaporizer is lower than the ambient temperature.
7. The LNG cold energy cascade power generation system incorporating an air separation unit of claim 1 wherein the LNG vaporizer is further connected to a natural gas expander.
8. A power generation method applied to the LNG cold energy cascade utilization power generation system combined with the air separation unit according to any one of claims 1 to 7, comprising the steps of:
the power generation cycle unit comprises:
A working medium pressurizing step, namely pressurizing the low-temperature circulating working medium in a liquid form through the third booster pump;
A working medium heat exchange step, namely absorbing the heat of the glycol water circulation unit at the first heater by the pressurized low-temperature circulating working medium, and heating and evaporating the working medium;
working medium working step, namely the heated circulating working medium expands outwards in the first turbine expander to do work, and the self temperature and pressure are reduced;
a working medium cooling step, namely absorbing low-temperature cold energy of liquefied natural gas at the LNG evaporator through a working cycle working medium, cooling and liquefying the working cycle working medium to form a low-temperature cycle working medium, and then repeating the working medium pressurizing step, the working medium heat exchanging step and the working medium working step to perform power generation circulation;
The glycol water circulation unit comprises:
the heat absorption step is that glycol water flows through the inside of the air separation unit to absorb waste heat, and the temperature of the glycol water rises;
the step of pressurizing, namely enabling glycol water to flow through the second pressurizing pump, and increasing the self pressure to maintain the stable flow of the glycol water circulation unit;
A cooling step, namely heating low-temperature circulating working media in the power generation circulating unit by glycol water at the first heater, reducing the temperature of the glycol water, and then repeating the heat absorption step and the pressurizing step to circulate the glycol water;
the LNG supply line includes:
An LNG pressurizing step of pressurizing liquefied natural gas supplied from the outside by the first booster pump to maintain stable flow of the LNG supply path;
the pressurized liquefied natural gas enters the air separation unit to cool the air, and the temperature of the air separation unit is increased;
And a reheating step, namely cooling the circulating working medium in the power generation circulating unit at the LNG evaporator by the liquefied natural gas output from the air separation unit, further raising the temperature of the liquefied natural gas and gasifying the liquefied natural gas, and then introducing the liquefied natural gas into an external natural gas supply pipe network.
9. The method of generating power of claim 8, further comprising, at the LNG supply path:
and the working step is to input the liquefied natural gas heated and gasified in the reheating step into the natural gas turbine expander to do work on external expansion, the temperature and pressure of the liquefied natural gas are reduced, and then the liquefied natural gas is introduced into an external natural gas supply pipe network.
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