阅读说明：本技术 用于低品味热源的能量自给型二氧化碳冷热电联产系统 (Energy self-sufficient carbon dioxide combined cooling heating and power system for low-grade heat source ) 是由 张强 骆泽威 曹锐 赵永杰 于 2019-11-05 设计创作，主要内容包括：本发明公开了一种用于低品味热源的能量自给型二氧化碳冷热电联产系统,包括跨临界二氧化碳回热朗肯动力循环系统和跨临界二氧化碳喷射制冷循环系统,所述系统集成回热朗肯循环和喷射制冷循环,采用二氧化碳作为单一工质,通过跨临界二氧化碳回热朗肯循环系统的抽气透平将低品味热能转换为有用功,并利用热水器向用户提供热能。跨临界二氧化碳喷射制冷循环系统利用抽气透平的高压排气余热驱动喷射器向用户输出冷能,通过合理布置系统,使系统输出更多的电能。本发明采用工质泵和低压比的压气机,有效减少系统运行时的压缩功,提高系统的净发电量和低品位热能的转换效率。(The invention discloses an energy self-sufficient carbon dioxide combined cooling heating and power system for a low-grade heat source, which comprises a trans-critical carbon dioxide regenerative Rankine power cycle system and a trans-critical carbon dioxide jet refrigeration cycle system, wherein the system integrates regenerative Rankine cycle and jet refrigeration cycle, carbon dioxide is used as a single working medium, low-grade heat energy is converted into useful work through an air exhaust turbine of the trans-critical carbon dioxide regenerative Rankine cycle system, and a water heater is used for providing heat energy for a user. The transcritical carbon dioxide jet refrigeration cycle system utilizes the high-pressure exhaust waste heat of the air exhaust turbine to drive the ejector to output cold energy to users, and the system outputs more electric energy through reasonable arrangement. The invention adopts the working medium pump and the air compressor with low pressure ratio, effectively reduces the compression work during the operation of the system, and improves the conversion efficiency of the net power generation quantity and the low-grade heat energy of the system.)

1. An energy self-sufficient carbon dioxide combined cooling heating and power system for a low-grade heat source is characterized in that: the system comprises a transcritical carbon dioxide regenerative Rankine power cycle system and a transcritical carbon dioxide jet refrigeration cycle machine system; the transcritical carbon dioxide regenerative Rankine power cycle system comprises a heat source heat exchanger (1), an air exhaust turbine (2), a generator (3), a water heater (4), a three-way valve (5), a condenser (6), a working medium pump (7) and a heat regenerator (8), wherein a low-grade heat source carrier sequentially passes through an inlet and an outlet of the high-temperature side of the heat source heat exchanger (1), a low-temperature side inlet of the heat source heat exchanger (1) is communicated with a low-temperature side outlet of the heat regenerator (8), an inlet of the air exhaust turbine (2) is communicated with a low-temperature side outlet of the heat source heat exchanger (1), a high-pressure outlet of the air exhaust turbine (2) is communicated with a high-temperature side inlet of the heat regenerator (8), a low-pressure outlet of the air exhaust turbine (2) is communicated with a high-temperature side inlet of the water heater (4), a high-temperature side outlet of the, the outlet of the high-temperature side of the condenser (6) is communicated with the inlet of the working medium pump (7), and the inlet of the low-temperature side of the heat regenerator (8) is communicated with the outlet of the working medium pump (7); the transcritical carbon dioxide refrigeration cycle system comprises a gas cooler (9), an ejector (10), a gas-liquid separator (11), a gas compressor (12), a throttle valve (13) and an evaporator (14), wherein a high-temperature side inlet of the gas cooler (9) is communicated with a high-temperature side outlet of a heat regenerator (8), a working flow inlet of the ejector (10) is communicated with the high-temperature side outlet of the gas cooler (9), an injection flow inlet of the ejector (10) is communicated with a low-temperature side outlet of the evaporator (14), an outlet of the ejector (10) is communicated with an inlet of the gas-liquid separator (11), a gas outlet of the gas-liquid separator (11) is communicated with an inlet of the gas compressor (12), a liquid outlet of the gas-liquid separator (11) is communicated with an inlet of the throttle valve (13), and an inlet of an outlet evaporator (14) of the throttle valve.

2. The energy-self-contained carbon dioxide combined cooling, heating and power system for a low-grade heat source of claim 1, wherein: one inlet of the three-way valve (5) is communicated with the high-temperature side outlet of the water heater (4), and the other inlet of the three-way valve (5) is communicated with the outlet of the compressor (12); the outlet of the three-way valve (5) is communicated with the high-temperature side inlet of the condenser (6).

3. The energy-self-contained carbon dioxide combined cooling, heating and power system for a low-grade heat source of claim 1, wherein: part of the electric energy output by the air exhaust turbine (2) is used for driving the air compressor (12) and the working medium pump (7).

4. The energy-self-contained carbon dioxide combined cooling, heating and power system for a low-grade heat source of claim 1, wherein: the air extraction turbine (2) is coaxially connected with the generator (3).

5. The energy-self-contained carbon dioxide combined cooling, heating and power system for a low-grade heat source of claim 1, wherein: the system changes the carbon dioxide flow of the high-pressure outlet and the low-pressure outlet of the air extraction turbine (2) by adjusting the air extraction ratio of the air extraction turbine (2), thereby changing the output cold and heat of the system.

Technical Field

The invention belongs to the technology of energy conversion and utilization, and particularly relates to an energy self-sufficient carbon dioxide combined cooling, heating and power generation system for a low-grade heat source.

Background

In the face of the excessive use of traditional petrochemical fuels and the increasingly serious environmental pollution problems caused thereby, the development and utilization of sustainable energy sources become a hot research direction. Heat sources such as solar energy, geothermal energy, biomass energy, industrial low-temperature waste heat energy, and internal combustion engine exhaust waste heat energy are considered as alternative energy sources that satisfy the currently growing energy demand and reduce greenhouse gas emissions. Although the amount of the low-grade heat energy is large, the energy flow density is low, and the heat energy conversion efficiency is not high in the utilization process. Therefore, it is of great significance to design the structure of the thermodynamic system to efficiently utilize the low-grade heat energy.

The natural carbon dioxide has the characteristics of stable thermophysical property and environmental friendliness. When carbon dioxide is used as a thermodynamic cycle working medium, the system has the characteristics of high thermal efficiency and compact structure. Because carbon dioxide has a lower critical temperature, a supercritical brayton cycle can be adopted in a thermodynamic system utilizing low-grade heat energy, namely the carbon dioxide is in a supercritical state in the processes of heat absorption and heat release. The compressor in the supercritical brayton cycle consumes a relatively high compression work when compressing gaseous carbon dioxide, thereby reducing the net work output of the system. Particularly, when the temperature of the heat source is not high, the power converted by the low-grade heat source of the system cannot meet the requirement of the power required by the gas compressor, and the system cannot work normally at the moment. In order to maintain the normal operation of the system, extra high-quality energy (electric energy or mechanical energy) must be input into the thermodynamic system from the outside to meet the power required by the compressor.

In addition, in the utilization process of the low-grade heat source, the system can output heat energy or cold energy simultaneously besides outputting net work to the outside so as to improve the utilization efficiency of the low-grade heat source. Transcritical jet refrigeration cycle using carbon dioxide as working medium has also received wide attention. Compared with the traditional compression refrigeration cycle, the transcritical carbon dioxide jet refrigeration cycle has the advantages of simple structure, few moving parts, easiness in maintenance and the like. However, the compressor in the current ejector refrigeration cycle also consumes a large amount of compression work when compressing gaseous carbon dioxide, thereby degrading the coefficient of performance of the refrigeration cycle.

In order to solve the problems, the existing low-grade heat source utilization system needs to be improved, and a combined cycle scheme which can meet the power consumption requirement of system components by utilizing the output energy of the system and can output net electric energy, heat energy and cold energy to the outside is provided.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the problems of the prior art that the utilization system of the low-grade heat source is insufficient and the utilization efficiency is low, the invention provides an energy self-sufficient carbon dioxide combined cooling, heating and power generation system for the low-grade heat source.

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

an energy self-sufficient carbon dioxide combined cooling heating and power system for a low-grade heat source comprises a trans-critical carbon dioxide regenerative Rankine power cycle system and a trans-critical carbon dioxide jet refrigeration cycle system;

the transcritical carbon dioxide regenerative Rankine power cycle system comprises a heat source heat exchanger, an air exhaust turbine, a water heater, a three-way valve, a condenser, a working medium pump, a heat regenerator and a generator; a low-grade heat source carrier sequentially passes through an inlet and an outlet on the high-temperature side of a heat source heat exchanger, a low-temperature side inlet of the heat source heat exchanger is communicated with a low-temperature side outlet of a heat regenerator, an inlet of an air exhaust turbine is communicated with a low-temperature side outlet of the high-temperature heat source heat exchanger, a high-pressure outlet of the air exhaust turbine is communicated with a high-temperature side inlet of the heat regenerator, a low-pressure outlet of the air exhaust turbine is communicated with a high-temperature side inlet of a water heater, a high-temperature side outlet of the water heater is communicated with one inlet of a three-way valve, an outlet of the three-;

the transcritical carbon dioxide refrigeration cycle system comprises a gas cooler, an ejector, a gas-liquid separator, a gas compressor, an evaporator and a throttle valve;

the inlet of the high-temperature side of the gas cooler is communicated with the outlet of the high-temperature side of the heat regenerator, the working flow inlet of the ejector is communicated with the outlet of the high-temperature side of the gas cooler, the ejector flow inlet of the ejector is communicated with the outlet of the low-temperature side of the evaporator, the outlet of the ejector is communicated with the inlet of the gas-liquid separator, the gas outlet of the gas-liquid separator is communicated with the inlet of the gas compressor, the liquid outlet of the gas-liquid separator is communicated with the inlet of the throttle valve, and the outlet of the throttle.

Furthermore, one inlet of the three-way valve is communicated with the high-temperature side outlet of the water heater, and the other inlet of the three-way valve is communicated with the outlet of the compressor; the outlet of the three-way valve is communicated with the inlet of the high-temperature side of the condenser.

Furthermore, a part of the electric energy output by the air exhaust turbine is used for driving the air compressor and the working medium pump.

Further, the air exhaust turbine is coaxially connected with the generator.

Furthermore, the invention can change the carbon dioxide flow at the high-pressure outlet and the low-pressure outlet of the air extraction turbine by adjusting the air extraction ratio of the air extraction turbine, thereby changing the output cold quantity and the heat quantity of the system.

Compared with the prior art, the system has the following remarkable beneficial effects:

(1) the working medium pump of the transcritical carbon dioxide regenerative Rankine power cycle system is used for compressing liquid saturated carbon dioxide, and compared with a gas compressor for compressing gaseous carbon dioxide, the working medium pump can effectively reduce the consumed compression work, so that the net output electric energy of the system is improved;

(2) the electric energy generated by the system can be used for driving the working medium pump and the air compressor to ensure the normal operation of the system, and the rest electric energy can be provided for users to use, so that the energy utilization rate is improved.

(3) In the invention, the outlet of the compressor of the transcritical carbon dioxide jet refrigeration system is communicated with the three-way valve, and the pressure of the carbon dioxide at the outlet of the compressor does not need to be increased to the maximum pressure required by the traditional jet refrigeration cycle, so that the compressor has smaller pressure ratio when working, the consumed electric energy is correspondingly reduced, and the generated energy of the system is increased;

(4) the system of the invention brings possibility for selecting the compressor with high efficiency and low cost by reducing the pressure ratio of the compressor, thereby ensuring the working reliability of the system;

(5) the system can control the flow of the carbon dioxide entering the cooler of the jet refrigeration cycle system and the regenerative Rankine power cycle system water heater from the outlet of the air exhaust turbine by adjusting the air exhaust ratio of the air exhaust turbine, thereby changing the proportion of the heat and the cold output by the system, meeting the requirements of users on the heat and the cold in different seasons and improving the flexibility of the operation of the system.

(6) The system provided by the invention utilizes the carbon dioxide waste heat at the high-pressure outlet of the air exhaust turbine to drive the jet refrigeration cycle, realizes the gradient utilization of heat energy, and can effectively improve the utilization efficiency of low-grade heat sources.

Drawings

FIG. 1 is a schematic structural diagram of the present invention.

Detailed Description

For the purpose of explaining the technical solution disclosed in the present invention in detail, the following description is further described with reference to the accompanying drawings and specific embodiments.

The invention provides an energy self-sufficient carbon dioxide combined cooling heating and power system for a low-grade heat source, which comprises a trans-critical carbon dioxide regenerative Rankine power cycle system and a trans-critical carbon dioxide jet refrigeration cycle system. The system integrates regenerative Rankine cycle and jet refrigeration cycle, and carbon dioxide is used as a single working medium. An air exhaust turbine of the transcritical carbon dioxide regenerative Rankine power cycle system converts low grade heat energy into useful work. In addition, the water heater of the transcritical carbon dioxide regenerative rankine power cycle system can also provide thermal energy (e.g., hot water) to the user. Meanwhile, the transcritical carbon dioxide jet refrigeration system utilizes the exhaust waste heat of the air exhaust turbine to drive the ejector to output cold energy to users. And the system outputs more electric energy by reasonably arranging the system. By adopting the working medium pump and the air compressor with low pressure ratio, the compression work during the operation of the system is effectively reduced, and the net power generation quantity and the low-grade heat energy conversion efficiency of the system are improved.

As shown in fig. 1, in the system of the present invention, the transcritical carbon dioxide regenerative rankine cycle power system includes a heat source heat exchanger 1, an air exhaust turbine 2, a generator 3, a water heater 4, a three-way valve 5, a condenser 6, a working medium pump 7 and a heat regenerator 8; the transcritical carbon dioxide refrigeration cycle system comprises a gas cooler 9, an ejector 10, a gas-liquid separator 11, a compressor 12, a throttle valve 13 and an evaporator 14.

Specifically, a low-grade heat source carrier sequentially passes through a high-temperature side inlet and an outlet of a heat source heat exchanger 1, a low-temperature side inlet of the heat source heat exchanger 1 is communicated with a low-temperature side outlet of a heat regenerator 8, an inlet of an air exhaust turbine 2 is communicated with a low-temperature side outlet of the heat source heat exchanger 1, a high-pressure outlet of the air exhaust turbine 2 is communicated with a high-temperature side inlet of the heat regenerator 8, a low-pressure outlet of the air exhaust turbine 2 is communicated with a high-temperature side inlet of a water heater 4, a high-temperature side outlet of the water heater 4 is communicated with one inlet of a three-way valve 5, an outlet of the three-way valve 5 is communicated with a high-temperature side inlet of a condenser 6, a high-temperature side outlet of the condenser 6 is communicated with an inlet of a working medium pump 7, a low-temperature side inlet of the heat regenerator; the outlet of the three-way valve 5 is communicated with the high-temperature side inlet of the condenser 6. Further, the air exhaust turbine 2 is coaxially connected to the generator 3.

The inlet of the high-temperature side of the gas cooler 9 is communicated with the outlet of the high-temperature side of the regenerator 8, the outlet of the high-temperature side of the gas cooler 9 is communicated with the working flow inlet of the ejector 10, the injection flow inlet of the ejector 10 is communicated with the outlet of the low-temperature side of the evaporator 14, the outlet of the ejector 10 is communicated with the inlet of the gas-liquid separator 11, the gas outlet of the gas-liquid separator 11 is communicated with the inlet of the compressor 12, the liquid outlet of the gas-liquid separator 11 is communicated with the inlet of the throttle valve 13, and the outlet of the throttle valve 13 is communicated with the inlet of the.

In the implementation of the system according to the invention, a part of the electrical energy output by the extraction turbine 2 is used to drive the compressor 12 and the working medium pump 7. And the system can change the carbon dioxide flow of the high-pressure outlet and the low-pressure outlet of the air extracting turbine 2 by adjusting the air extracting ratio of the air extracting turbine 2, thereby changing the output cold quantity and the heat quantity of the system.

The specific working process of the invention is as follows:

the carrier of the low-grade heat source (such as solar energy, geothermal energy, industrial waste heat or exhaust waste heat of an internal combustion engine) with the temperature of 250 ℃ sequentially flows through the inlet and the outlet at the low-temperature side of the heat source heat exchanger 1 to be used as energy for driving a combined cooling heating and power system.

In the transcritical carbon dioxide regenerative Rankine power cycle system, a gaseous carbon dioxide working medium is cooled to a saturated liquid state by cooling water or an air cooling medium at the high-temperature side of a condenser 14, the pressure is increased to 12MPa after the gaseous carbon dioxide working medium enters a working medium pump 14, and then the gaseous carbon dioxide working medium enters the low-temperature side of a heat regenerator 8 to absorb the heat of the carbon dioxide at the high-temperature side. The carbon dioxide with the increased temperature enters the low-temperature side of the heat source heat exchanger 1 and is further heated to 220 ℃ by a low-grade heat source carrier fluid, the carbon dioxide with the high temperature and the high pressure enters the air exhaust turbine 2 to be expanded to generate mechanical power for driving the generator 2 to generate electricity, one part of the output electric energy is used for driving the working medium pump 7 and the air compressor 12, and the other part of the electric energy is output to a user. Part of the carbon dioxide passing through the air exhaust turbine 2 flows out of the high-pressure outlet, the pressure value of the carbon dioxide is 8.4MPa, the carbon dioxide enters the high-temperature side of the heat regenerator 8 to release heat, and then the carbon dioxide flows out of the high-temperature side outlet of the heat regenerator 8 to be used as working fluid of the jet refrigeration cycle; the other part of carbon dioxide flows out from a low-pressure outlet of the air extracting turbine 2, the pressure of the carbon dioxide is reduced to 5.73MPa of condensing pressure, the temperature of the carbon dioxide is changed to 156 ℃, the carbon dioxide enters a high-temperature side of the water heater 4 to release heat, and the heat is used for heating air or hot water to 50-90 ℃ and outputting heat energy to users. Then, the carbon dioxide gas with the reduced temperature flows through the three-way valve 5 and enters the condenser 14 to release heat, and the temperature is reduced to 20 ℃, so that the transcritical carbon dioxide regenerative Rankine power cycle is completed.

In the transcritical carbon dioxide jet refrigeration cycle system, high-pressure carbon dioxide from an outlet at the high-temperature side of a regenerator 8 releases heat to cooling water or an air cooling medium at the high-temperature side of a gas cooler 9, the temperature is reduced to 36 ℃, then the high-pressure carbon dioxide enters a working flow inlet of an ejector 10, low-pressure carbon dioxide from the low-temperature side of an evaporator 14 is sucked and enters an ejector flow inlet of the ejector 10, and the high-pressure carbon dioxide and the low-pressure carbon dioxide are mixed in the ejector 10 and then enter a gas-liquid separator 11. The liquid carbon dioxide in the gas-liquid separator 11 enters the throttle valve 13 from the liquid outlet, the pressure is reduced to the evaporation pressure of 3.97MPa, the corresponding temperature is 5 ℃, and then the liquid carbon dioxide enters the low-temperature side of the evaporator 14 to absorb heat, so that cold energy is provided for the outside; gaseous carbon dioxide in the gas-liquid separator 11 enters the compressor 12, the pressure is increased to the condensation pressure of 5.73MPa, then the gaseous carbon dioxide is merged with carbon dioxide from the outlet of the high-temperature side of the water heater 4, flows through the outlet of the three-way valve 5 and enters the condenser 6 to be cooled to 20 ℃, and the carbon dioxide jet refrigeration cycle is completed.

In the operation process of the system, the value of the air extraction ratio of the air extraction turbine 2 can be changed within the range of 0.1-0.9 by adjusting the air extraction ratio, so as to control the flow of the carbon dioxide at the high-pressure outlet and the low-pressure outlet of the air extraction turbine 2, thereby adjusting the proportion of the heat quantity and the cold quantity output by the system, and meeting different requirements of users on the heat quantity and the cold quantity in different seasons. For example, in winter, the demand of the user for heat is increased, the air extraction ratio of the air extraction turbine 2 is increased, the flow of the carbon dioxide passing through the low-pressure outlet of the air extraction turbine 2 is increased, and the heat output from the water heater 4 to the outside is increased; in summer, the demand of cold energy from the user increases, and the air extraction ratio of the air extraction turbine 2 is reduced to increase the flow rate of carbon dioxide passing through the high-pressure outlet of the air extraction turbine 2, thereby increasing the flow rate of carbon dioxide sucked by the ejector 10 and flowing through the low-temperature side of the evaporator 14 to increase the amount of cold output to the outside.