CN115638038A - Natural gas pressure energy comprehensive utilization system - Google Patents
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- 238000010248 power generation Methods 0.000 claims abstract description 71
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Abstract
The invention discloses a natural gas pressure energy comprehensive utilization system, which is characterized by comprising the following components: natural gas pressure difference power generation electronic system and gas-supercritical CO 2 A combined cycle subsystem; the natural pressure difference power generation subsystem is used for converting the pressure energy of the high-pressure natural gas into electric energy and cold energy and outputting low-pressure natural gas; gas-supercritical CO 2 The combined cycle subsystem is used for recovering cold energy and low-pressure natural gas and converting the chemical energy of the cold energy and the low-pressure natural gas into electric energy; the method can efficiently utilize the pressure energy of the natural gas under complex scenes such as high pressure, high pressure ratio, high flow and the like to improveHigh natural gas pressure energy utilization efficiency.
Description
Technical Field
The invention belongs to the technical field of natural gas pressure energy utilization, and particularly relates to a comprehensive utilization system of natural gas pressure energy.
Background
The natural gas output of China is gradually increased year by year, and the natural gas consumption of China is estimated to reach 5500 hundred million to 6000 hundred million cubic meters by 2030 years; the pressure of natural gas on the west-east gas transmission pipeline reaches 10MPa, while the pressure of natural gas of residential users is not more than 0.2MPa, and the natural gas is depressurized before being transmitted to the users. According to the measurement and calculation of related research, when 1kg of natural gas is pressed from 10MPa to 0.8MPa, the released pressure can reach 359.12kJ and is about 0.1 kW.h, so that the recovery potential of the natural gas pressure energy is huge. Natural gas can release pressure energy at the step-down in-process, and conventional pressure regulating station, gas storage storehouse etc. station adopt the choke valve step-down, can waste a large amount of pressure energy undoubtedly at the pressure regulating in-process.
At present, the natural gas pressure can be utilized by a plurality of technical types, but most of the natural gas pressure can be in a theoretical stage, and the natural gas pressure utilization method is not suitable for complex scenes such as high pressure, high pressure ratio, large flow and the like of a gas storage. For complex scenes, a measure of throttling and reducing pressure is still generally adopted at present. On the one hand, the larger the natural gas pressure drop is, the larger the temperature drop generated by the Joule-Thomson effect is, the lower the temperature inside the equipment is, the cold energy in the middle process cannot be timely absorbed, the solution can only be realized by improving the preheating temperature, therefore, the demand of the head end on the heat energy is larger, the requirement on the taste of the heat source is higher, and the system is
The efficiency is low; on the other hand, with the rise of head end pressure, the requirements on equipment strength and sealing are higher; therefore, the prior art is difficult to utilize the natural gas pressure energy of a complex scene.
For the problem that the natural gas pressure can be difficultly utilized in a complex scene, the problem can be solved by improving the performance and the applicability of key equipment, but the problem of cost and material is limited at present; the other method is to improve the existing pressure energy utilization process, and the key links are connected in series, in parallel and the like, so that the application range of the pressure energy utilization system is enlarged. The method has feasibility at present, and has the defects that the scenes are considered to be single mostly in the method provided at present, the method is difficult to be simultaneously suitable for the scenes of comprehensive large flow and high pressure, and the utilization efficiency of the pressure energy of the natural gas is low.
At present, supercritical CO 2 The use of the Brayton cycle in nuclear reactor systems has been widely studied because of the CO 2 Has good thermal stability and physical property, and is supercritical CO 2 The density is high near the critical point, the compression work can be reduced, and the cycle thermal efficiency is high; in addition, due to supercritical CO 2 High density, simple cycle, and therefore supercritical CO 2 The power system equipment such as a compressor, a turbine and the like for working media has compact structure and can reduce the equipment cost. The main reason of low utilization efficiency of natural gas pressure energy is the waste of cold energy if supercritical CO is used 2 The Brayton cycle is combined with the pressure energy of the natural gas, so that the cold energy obtained by the natural gas due to depressurization can be efficiently utilized, and the efficient utilization of energy is realized. At present, research on the utilization technology of the pressure energy of natural gas applying Brayton cycle is less, and the existing differential pressure power generation technology has insufficient applicability to high-pressure, high-pressure-ratio and high-flow scenes. In addition, the problem of low utilization efficiency of natural gas pressure energy also exists.
Therefore, how to efficiently utilize the natural gas pressure energy under complex scenes such as high pressure, high pressure ratio, large flow and the like, improve the utilization efficiency of the natural gas pressure energy, and assist in realizing the aim of double carbon is a key problem of current research.
Disclosure of Invention
In view of the above problems, the present invention provides a system for comprehensively utilizing natural gas pressure energy, which at least solves some of the above technical problems, and the method can efficiently utilize natural gas pressure energy under complex scenes such as high pressure, large pressure ratio, large flow rate, etc., and improve the utilization efficiency of natural gas pressure energy.
The embodiment of the invention provides a system for comprehensively utilizing pressure energy of natural gas, which comprises: natural gas pressure difference power generation subsystem (100) and gas-supercritical CO 2 Combined cycle sub-system (200)；
The natural pressure difference power generation subsystem (100) is used for converting the pressure energy of the high-pressure natural gas into electric energy and cold energy and outputting low-pressure natural gas;
the gas-supercritical CO 2 A combined cycle subsystem (200) for recovering the cold energy and the low pressure natural gas and converting chemical energy of the cold energy and the low pressure natural gas into electrical energy.
Furthermore, the natural gas differential pressure power generation subsystem (100) comprises a single-path two-stage differential pressure power generation subsystem, a multi-path single-stage differential pressure power generation subsystem and a multi-path two-stage differential pressure power generation subsystem.
Furthermore, the single-path two-stage differential pressure power generation subsystem comprises a high-pressure turbine expansion machine (1), a low-pressure turbine expansion machine (2), a first pressure regulating generator (3), a second pressure regulating generator (4), a high-pressure heat exchanger (5) and a low-pressure heat exchanger (6);
the high-pressure turbo expander (1), the high-pressure heat exchanger (5), the low-pressure turbo expander (2) and the low-pressure heat exchanger (6) are sequentially connected through pipelines; the inlet end of the high-pressure turboexpander (1) is used for introducing high-pressure natural gas; an outlet of a heat absorption end of the low-pressure heat exchanger (6) is used for leading out low-pressure natural gas;
the high-pressure turboexpander (1) is coaxially connected with the first pressure regulating generator (3);
the low-pressure turbine expander (2) is coaxially connected with the second pressure regulating generator (4).
Furthermore, the high-pressure heat exchanger (5) and the low-pressure heat exchanger (6) are connected through a pipeline to form a heat exchange branch.
Furthermore, the multi-path single-stage differential pressure power generation subsystem comprises a turboexpander (17), a pressure regulating power generator (18), a heat exchanger (19) and a natural gas branch valve (20);
the natural gas branch valve (20), the turboexpander (17) and the heat exchanger (19) are sequentially connected through pipelines to form a pressure reduction branch;
the multi-path single-stage differential pressure power generation subsystem is formed by connecting a plurality of pressure reduction branches in parallel; wherein the inlet end of the natural gas branch valve (20) on each pressure reduction branch is used for introducing high-pressure natural gas; an outlet at the end of the heat exchanger (19) on each pressure reduction branch is used for leading out low-pressure natural gas;
the turbine expander (17) is coaxially connected with the pressure regulating generator (18).
Furthermore, the multi-path single-stage differential pressure power generation subsystem also comprises a refrigerant branch valve (21);
the refrigerant branch valve (21) is connected with the heat exchanger (19) through a pipeline to form a refrigerant branch; and the refrigerant branches are connected in parallel to form a heat exchange branch.
Furthermore, the multi-path two-stage differential pressure power generation subsystem comprises a high-pressure turbine expansion machine (1), a low-pressure turbine expansion machine (2), a first pressure regulating power generator (3), a second pressure regulating power generator (4), a high-pressure heat exchanger (5), a low-pressure heat exchanger (6) and a natural gas branch valve (20);
the natural gas branch valve (20), the high-pressure turbo expander (1), the high-pressure heat exchanger (5), the low-pressure turbo expander (2) and the low-pressure heat exchanger (6) are sequentially connected through pipelines to form a pressure reduction branch;
the multi-path two-stage differential pressure power generation subsystem is formed by connecting a plurality of voltage reduction branches in parallel; wherein the inlet end of the high-pressure turboexpander (1) on each pressure reduction branch is used for introducing high-pressure natural gas; the outlet of the heat absorption end of the low-pressure heat exchanger (6) on each pressure reduction branch is used for leading out low-pressure natural gas;
the high-pressure turboexpander (1) is coaxially connected with the first pressure regulating generator (3);
the low-pressure turbine expander (2) is coaxially connected with the second pressure regulating generator (4).
Furthermore, the multi-path two-stage differential pressure power generation subsystem also comprises a refrigerant branch valve (21);
the refrigerant branch valve (21), the high-pressure heat exchanger (5) and the low-pressure heat exchanger (6) are connected through pipelines to form a refrigerant branch; and the plurality of refrigerant branches are connected in parallel to form a heat exchange branch.
Further, the fuel gas-supercritical CO 2 The combined cycle sub-system (200) includes CO 2 Expander (7), CO 2 Generator (8), supercritical CO 2 A heat exchanger (9) andCO 2 a compressor (10);
end of the heat exchange branch, CO 2 Compressor (10), supercritical CO 2 Heat exchanger (9), CO 2 The expander (7) and the head end of the heat exchange branch are sequentially connected through a pipeline to form a Brayton cycle;
the CO is 2 Generator (8), CO 2 Expander (7) and CO 2 The compressors (10) are coaxially connected.
Further, the gas-supercritical CO 2 The combined cycle subsystem (200) also comprises a fuel control valve (11), a flue gas heat exchanger (12), a combustion chamber (13), a compressor (14), a gas turbine (15) and a gas generator (16);
the fuel control valve (11) is used for introducing low-pressure natural gas; the fuel control valve (11), the flue gas heat exchanger (12) and the combustion chamber (13) are connected in sequence through pipelines,
the compressor (14) is used for introducing air; the compressor (14), the combustion chamber (13), the gas turbine (15) and the supercritical CO 2 The heat exchanger (9) and the flue gas heat exchanger (12) are sequentially connected through a pipeline, and the heat release end outlet of the flue gas heat exchanger (12) leads out smoke;
the compressor (14), the gas turbine (15) and the gas generator (16) are coaxially connected.
Compared with the prior art, the system for comprehensively utilizing the pressure energy of the natural gas, which is disclosed by the invention, has the following beneficial effects:
1. the method has high scene applicability, solves the problem of difficult utilization of natural gas pressure energy in complex scenes such as high pressure, high pressure ratio, large flow and the like, and avoids the waste of clean energy.
2. The method utilizes gas-supercritical CO 2 The combined cycle subsystem makes full use of the cold energy carried by the downstream natural gas after the natural gas is depressurized, and has high energy utilization efficiency and low operation cost.
3. The method is applied to stations with high pressure, high pressure ratio and large flow, the required fuel natural gas is taken from the downstream on site, and the use cost is further reduced.
4. In the differential pressure power generation subsystem of the method, the special structure ensures that the method has low requirements on the manufacturing process of single equipment and low investment cost.
5. The generated power can be used for self-use in the factory, the residual power can be connected to the internet, and can be consumed nearby, and the economic benefit is high.
6. The method fully utilizes the pressure energy of the natural gas, reduces the specific gravity of gas power generation, has lower carbon emission factor, has extremely low contents of sulfide and nitrogen oxide in the flue gas generated by fully mixing and burning the natural gas and the air, and accords with the environmental protection concept.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
fig. 1 is a schematic structural diagram of a single-circuit two-stage differential pressure power generation subsystem provided in an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of a multi-path single-stage differential pressure power generation subsystem provided by an embodiment of the invention.
Fig. 3 is a schematic structural diagram of a multi-path two-stage differential pressure power generation subsystem provided by an embodiment of the invention.
Fig. 4 is a schematic structural diagram of a system for comprehensively utilizing pressure energy of natural gas according to an embodiment of the present invention.
In the figure: 100-a natural pressure differential power generation subsystem; 200-gas-supercritical CO 2 A combined cycle subsystem; 1-a high pressure turboexpander; 2-a low pressure turboexpander; 3-a first voltage regulating generator; 4-a second voltage regulated generator; 5-a high pressure heat exchanger; 6-low pressure heat exchanger; 7-CO 2 An expander; 8-CO 2 A generator; 9-supercritical CO 2 A heat exchanger; 10-CO 2 A compressor; 11-a fuel control valve; 12-flue gas heat exchanger; 13-a combustion chamber; 14-a compressor; 15-a gas turbine; 16-a gas generator; 17-a turboexpander; 18-voltage regulated generators; 19-a heat exchanger; 20-a natural gas bypass valve; 21-refrigerant branch valve.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
Referring to fig. 1, an embodiment of the present invention provides a natural gas pressure energy comprehensive utilization system suitable for complex scenes, including a natural gas pressure difference power generation subsystem 100 and a gas-supercritical CO 2 A combined cycle subsystem 200; the natural pressure difference power generation subsystem 100 converts pressure energy of high-pressure natural gas into electric energy and cold energy by using an expander and a generator, and outputs low-pressure natural gas; the cold energy is transferred to the gas-supercritical CO through the heat exchanger 2 In the combined cycle subsystem 200; gas-supercritical CO 2 The combined cycle subsystem 200 takes low-pressure natural gas as fuel, and finally converts the cold energy and the chemical energy of the natural gas pressure difference power generation subsystem 100 into electric energy after internal conversion.
The natural gas pressure difference power generation subsystem 100 and the gas-supercritical CO are then performed 2 The specific construction and associated operating principles of the combined cycle subsystem 200 are described in detail.
1. The natural gas pressure difference power generation subsystem 100:
the natural gas differential pressure power generation subsystem 100 comprises a single-path two-stage differential pressure power generation subsystem, a multi-path single-stage differential pressure power generation subsystem and a multi-path two-stage differential pressure power generation subsystem; the specific structure and operation principle of these three subsystems will be described in detail below:
A. the single-path two-stage differential pressure power generation subsystem comprises:
the single-path two-stage differential pressure power generation subsystem is suitable for being applied to working environments with high pressure, high pressure ratio and small flow; referring to fig. 2, the subsystem specifically includes a high-pressure turboexpander 1, a low-pressure turboexpander 2, a first pressure regulating generator 3, a second pressure regulating generator 4, a high-pressure heat exchanger 5, and a low-pressure heat exchanger 6; wherein, the high-pressure turbine expander 1, the high-pressure heat exchanger 5, the low-pressure turbine expander 2 and the low-pressure heat exchanger 6 are connected in sequence through pipelines; the inlet end of the high-pressure turboexpander 1 is used for introducing high-pressure natural gas; an outlet of a heat absorption end of the low-pressure heat exchanger 6 is used for leading out low-pressure natural gas; the high-pressure turbo expander 1 is coaxially connected with the first pressure regulating generator 3; the low-pressure turbo expander 2 is coaxially connected with the second pressure regulating generator 4; the high-pressure heat exchanger 5 and the low-pressure heat exchanger 6 are connected through a pipeline to form a heat exchange branch; in this subsystem, the expanded natural gas absorbs heat from the gas-supercritical CO2 combined cycle subsystem 200 through the high pressure heat exchanger 5 and the low pressure heat exchanger 6 in sequence.
The working principle of the single-path two-stage differential pressure power generation subsystem is as follows: the high-pressure natural gas is directly introduced into a high-pressure turbine expander 1 for expansion and depressurization treatment; the high-pressure natural gas pushes a rotor in the high-pressure turboexpander 1 to rotate in the pressure reduction process, and the rotor drives a coaxial first pressure regulating generator 3 to generate electricity; the outlet end of the high-pressure turboexpander 1 is connected with the cold flow strand inlet of the high-pressure heat exchanger 5, and the depressurized natural gas passes through the high-pressure heat exchanger 5; in the high-pressure heat exchanger 5, the cold flow stream of natural gas and the hot flow stream of CO 2 Heat exchange is carried out; because the temperature of the natural gas is lower after the pressure reduction, the natural gas absorbs CO 2 Heat rising temperature, CO 2 Carrying out medium-pressure cooling in a high-pressure heat exchanger 5; the cold flow strand outlet of the high-pressure heat exchanger 5 is connected with a low-pressure turboexpander 2, and the low-pressure turboexpander 2 has the same principle of expansion and pressure reduction power generation aiming at natural gas; the outlet end of the low-pressure turboexpander 2 is connected with the cold flow strand inlet of the low-pressure heat exchanger 6, the natural gas is heated in the low-pressure heat exchanger 6 and led out to a low-pressure pipe network, and CO is introduced into the low-pressure pipe network 2 Further isobaric cooling is carried out in the low-pressure heat exchanger 6.
B. The multi-path single-stage differential pressure power generation subsystem comprises:
the multi-path single-stage differential pressure power generation subsystem is suitable for being applied to working environments with medium and low pressure, small pressure ratio and small flow; referring to fig. 3, the subsystem includes a turboexpander 17, a pressure regulating generator 18, a heat exchanger 19, and a natural gas bypass valve 20; wherein, the natural gas branch valve 20, the turbo expander 17 and the heat exchanger 19 are connected in sequence through pipelines to form a pressure reduction branch; the multi-path single-stage differential pressure power generation subsystem is formed by connecting a plurality of voltage reduction branches in parallel; wherein, the inlet end of the natural gas branch valve 20 on each pressure reduction branch is used for introducing high-pressure natural gas; the outlet of the end of the heat exchanger 19 on each pressure reduction branch is used for leading out low-pressure natural gas; the turbine expander 17 is coaxially connected with the pressure regulating generator 18; the multi-path single-stage differential pressure power generation subsystem also comprises a refrigerant branch valve 21; the refrigerant branch valve 21 is connected with the heat exchanger 19 through a pipeline to form a refrigerant branch; a plurality of refrigerant branches are connected in parallel to form a heat exchange branch; in the subsystem, the expanded natural gas in each branch passes through a heat exchanger 19 to be converted from gas-supercritical CO 2 Heat absorption in the combined cycle subsystem 200; the natural gas branch valve 20 is used for shunting natural gas by adjusting the opening of the valve according to the flow of inlet natural gas; refrigerant bypass valve 20 for balanced CO distribution 2 Flow rate;
the working principle of the multi-path single-stage differential pressure power generation subsystem is as follows: the head end of the branch corresponds to natural gas shunting, m groups of natural gas pressure difference power generation units are arranged, the flow rate of each group is a, and the head end is connected to the flow rate Q; when the total flow Q satisfies: (n-1) when a is not less than Q and not more than na (wherein n is a positive integer not more than m), the natural gas branch valves 20 and the corresponding refrigerant branch valves 21 of the front n branches are opened, and the branch valves on the other branches are closed; for each branch, the pressure regulating principle refers to the serial pressure regulating method of the multi-path single-stage differential pressure power generation subsystem, and high-pressure natural gas is expanded and depressurized in the turbine expander 17 to drive the pressure regulating generator 18 to generate power; the outlet end of the turboexpander 17 is connected with the cold flow strand inlet of the heat exchanger 19, and the natural gas is heated in the heat exchanger 19, converged at the tail end of the branch and then introduced into a low-pressure pipe network; CO2 2 Cooling at medium pressure in a heat exchanger 19, merging the tail ends, and introducing fuel gas-supercritical CO 2 CO in combined cycle subsystem 200 2 In the compressor 10.
C. The multi-path two-stage differential pressure power generation subsystem comprises:
the multi-path two-stage differential pressure power generation subsystem is suitable for being applied to working environments with high pressure, high pressure ratio and large flow; referring to fig. 4, the subsystem includes a high pressure turboexpander 1, a low pressure turboexpander 2, a first pressure regulating generator 3, a second pressure regulating generator 4, a high pressure heat exchanger 5, a low pressure heat exchanger 6, and a natural gas bypass valve 20; wherein, the natural gas branch valve 20, the high-pressure turbine expander 1, the high-pressure heat exchanger 5, the low-pressure turbine expander 2 and the low-pressure heat exchanger 6 are connected in sequence through pipelines to form a pressure reduction branch; the multi-path two-stage differential pressure power generation subsystem is formed by connecting a plurality of voltage reduction branches in parallel; wherein, the inlet end of the high-pressure turbine expander 1 on each pressure reduction branch is used for introducing high-pressure natural gas; the heat absorption end outlet of the low-pressure heat exchanger 6 on each pressure reduction branch is used for leading out low-pressure natural gas; the high-pressure turbo expander 1 is coaxially connected with the first pressure regulating generator 3; the low-pressure turbine expander 2 is coaxially connected with the second pressure regulating generator 4; the multi-path two-stage differential pressure power generation subsystem further comprises a refrigerant branch valve 21; the refrigerant branch valve 21, the high-pressure heat exchanger 5 and the low-pressure heat exchanger 6 are connected through pipelines to form a refrigerant branch; a plurality of refrigerant branches are connected in parallel to form a heat exchange branch; the expanded natural gas on each branch passes through the high-pressure heat exchanger 5 and the low-pressure heat exchanger 6 to sequentially pass through the gas-supercritical CO 2 Heat absorption in the combined cycle subsystem 200; the natural gas branch valve 20 is used for shunting natural gas by adjusting the opening of the valve according to the flow of inlet natural gas; refrigerant bypass valve 20 for balanced CO distribution 2 Flow rate;
the working principle of the multi-path two-stage differential pressure power generation subsystem is as follows: the head end of each branch circuit is used for shunting natural gas, and the shunting method can refer to the parallel pressure regulating method of the multi-path single-stage differential pressure power generation subsystem, namely the opening number of valves is controlled, so that each branch circuit device works in a proper flow interval; each branch adopts a two-stage pressure regulating method, and the pressure regulating principle can refer to the serial pressure regulating method of the multi-path single-stage differential pressure power generation subsystem; natural gas expansion pressure reduction power generation and CO generation 2 After heat exchange, the heat exchange is converged at the tail ends of the branches and then led out to a low-pressure pipe network; CO2 2 Sequentially passes through the high-pressure heat exchanger 5 andthe low-pressure heat exchanger 6 is cooled in isobaric pressure, and the tail ends of the low-pressure heat exchanger are merged and then gas-supercritical CO is introduced 2 CO in the Combined cycle subsystem 200 2 In the compressor 10.
2. Gas-supercritical CO 2 Combined-cycle subsystem 200:
gas-supercritical CO 2 The combined cycle subsystem 200 includes CO 2 Expander 7, CO 2 Generator 8, supercritical CO 2 Heat exchanger 9, CO 2 The system comprises a compressor 10, a fuel control valve 11, a flue gas heat exchanger 12, a combustion chamber 13, a compressor 14, a gas turbine 15 and a gas generator 16;
the heat exchange branch structures corresponding to different pressure regulating methods are different, and for the natural gas differential pressure power generation subsystem 100, in a single-path two-stage differential pressure power generation subsystem, a high-pressure heat exchanger 5 and a low-pressure heat exchanger 6 are sequentially connected through a pipeline to form a heat exchange branch; in the multi-path single-stage differential pressure power generation subsystem, a refrigerant branch valve 21 and a heat exchanger 19 are sequentially connected through a pipeline to form a refrigerant branch, and the heat exchange branch is formed by connecting a plurality of refrigerant branches in parallel; in the multi-path two-stage differential pressure power generation subsystem, a refrigerant branch valve 21, a high-pressure heat exchanger 5 and a low-pressure heat exchanger 6 are sequentially connected through pipelines to form a refrigerant branch, and a heat exchange branch is formed by connecting a plurality of refrigerant branches in parallel;
in gas-supercritical CO 2 End of heat exchange leg, CO, in combined cycle subsystem 200 2 Compressor 10, supercritical CO 2 Heat exchanger 9, CO 2 The expander 7 and the head end of the heat exchange branch are sequentially connected through a pipeline to form a Brayton cycle; CO2 2 Generator 8, CO 2 Expander 7 and CO 2 The compressor 10 is coaxially connected; the fuel control valve 11 is used for introducing low-pressure natural gas; the fuel control valve 11, the flue gas heat exchanger 12 and the combustion chamber 13 are sequentially connected through a pipeline, and the air compressor 14 is used for introducing air; the compressor 14, the combustion chamber 13, the gas turbine 15 and the supercritical CO 2 The heat exchanger 9 and the flue gas heat exchanger 12 are sequentially connected through a pipeline, and the heat release end outlet of the flue gas heat exchanger 12 leads out smoke exhaust; the compressor 14, the gas turbine 15 and the gas generator 16 are coaxially connected; wherein critical CO 2 The heat exchanger 9 is formed by the outlet flue gas and CO of a gas turbine 15 2 Outlet CO of compressor 10 2 Carrying out heat exchange; outlet natural gas and supercritical CO of fuel control valve 11 2 The outlet flue gas of the heat exchanger 9 exchanges heat in a flue gas heat exchanger 12; the fuel control valve 11 is used for controlling the flow of low-pressure natural gas entering the combustion chamber 13;
gas-supercritical CO 2 The operating principle of the combined cycle subsystem 200 is: low temperature, low pressure CO in the Brayton cycle 2 In CO 2 Adiabatic compression, CO, in compressor 10 2 Low temperature high pressure CO exiting the outlet of compressor 10 2 Is fed as a cold stream into supercritical CO 2 In heat exchanger 9, CO 2 In supercritical CO 2 Medium-pressure heating in a heat exchanger; supercritical CO 2 High-temperature high-pressure CO led out from outlet of heat exchanger 9 2 Is fed into CO 2 In the expander 7, CO 2 In CO 2 Adiabatic expansion, CO, in the expander 7 2 High-temperature low-pressure CO led out from the outlet of the expander 7 2 The hot stream is sent into the high-pressure heat exchanger 5 or the heat exchanger 19 to realize heat supply to the natural gas pressure difference power generation subsystem 100; CO2 2 Cooling at a constant pressure in the high-pressure heat exchanger 5 or the heat exchanger 19; low-temperature and low-pressure CO led out from the outlet of the high-pressure heat exchanger 5 or the heat exchanger 19 2 Is finally sent back to CO 2 In the compressor 10.
In a branch of the gas turbine, natural gas led out by throttling of a fuel control valve enters a combustion chamber 13, the natural gas and compressed air are mixed and combusted to generate high-temperature and high-pressure flue gas, and the fuel gas drives a gas turbine 15 to drive a gas generator 16 to generate electricity; the outlet flue gas is introduced into supercritical CO 2 The exhaust gas after heat exchange exchanges heat with the fuel natural gas at a heat flow strand inlet of the heat exchanger 9, and the exhaust gas is discharged to CO after the low-temperature fuel natural gas absorbs the final waste heat in the flue gas 2 In the expander 7, CO is passed 2 The expander 7 generates power; in the process, various taste heat sources are fully utilized, and the energy utilization efficiency is greatly improved.
In the above, the relationship between the work done by the turboexpander and the generator and the pressure energy of the natural gas can be expressed as:
in the formula, P EXP Jointly outputting power for the turbo expander and the generator; q is the natural gas flow; rho is the natural gas density; c. C p Is natural gas mass isobaric specific heat capacity; t is the inlet natural gas temperature; l is a radical of an alcohol 1 And L 2 Inlet/outlet natural gas pressure, respectively; f is the natural gas adiabatic index; eta E The turboexpander efficiency; eta g Is the generator efficiency.
Gas turbine and supercritical CO 2 The mathematical model of energy conversion in a heat exchanger can be expressed as:
P GT,t ＝AQ GT,t η GT,e /3600
H GT,t ＝AQ GT,t (1-η GT,e -η GT,loss )/3600
H HRB,t ＝H GT,t ·η HRB
in the formula, Q GT,t Is the natural gas flow entering the gas turbine; p is GT,t The electric output power of the gas turbine at the moment t; h GT,t The thermal power contained in the high-temperature flue gas discharged by the gas turbine at the time t; h HRB,t Supercritical CO at time t 2 Heat recovery power of the heat exchanger; a is the calorific value of the fuel gas; eta GT,e Generating efficiency for the gas turbine; eta GT,loss Is the heat loss rate of the gas turbine; eta HRB The heat energy recovery efficiency of the waste heat boiler is improved.
The mathematical model of energy conversion for a heat exchanger can be expressed as:
C cold ＝C hot ·η RU
in the formula, C hot The heat energy lost by the heat flow strand at the moment t; c cold Is the heat energy absorbed by the cold stream at time t; eta RU For heat exchange efficiency.
In the embodiment of the invention, because the power generation mode combining natural gas pressure energy and a conventional gas turbine is adopted, the pressure energy power generation is mainly used, and the gas power generation is assisted, the fuel consumption is less, the carbon emission factor is lower, and the emission of sulfides and nitrogen oxides is less.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A natural gas pressure energy comprehensive utilization system is characterized by comprising: natural gas pressure difference power generation subsystem (100) and gas-supercritical CO 2 A combined cycle subsystem (200);
the natural pressure difference power generation subsystem (100) is used for converting the pressure energy of the high-pressure natural gas into electric energy and cold energy and outputting low-pressure natural gas;
the gas-supercritical CO 2 A combined cycle subsystem (200) for recovering the cold energy and the low pressure natural gas and converting chemical energy of the cold energy and the low pressure natural gas into electrical energy.
2. The natural gas pressure energy comprehensive utilization system as claimed in claim 1, wherein the natural gas pressure difference power generation subsystem (100) comprises a single-path two-stage pressure difference power generation subsystem, a multi-path single-stage pressure difference power generation subsystem and a multi-path two-stage pressure difference power generation subsystem.
3. The system for comprehensively utilizing the pressure energy of the natural gas as claimed in claim 2, wherein the single-path two-stage differential pressure power generation subsystem comprises a high-pressure turbine expander (1), a low-pressure turbine expander (2), a first pressure regulating generator (3), a second pressure regulating generator (4), a high-pressure heat exchanger (5) and a low-pressure heat exchanger (6);
the high-pressure turbo expander (1), the high-pressure heat exchanger (5), the low-pressure turbo expander (2) and the low-pressure heat exchanger (6) are sequentially connected through pipelines; the inlet end of the high-pressure turboexpander (1) is used for introducing high-pressure natural gas; the outlet of the heat absorption end of the low-pressure heat exchanger (6) is used for leading out low-pressure natural gas;
the high-pressure turbo expander (1) is coaxially connected with the first pressure regulating generator (3);
the low-pressure turbine expander (2) is coaxially connected with the second pressure regulating generator (4).
4. The comprehensive utilization system of natural gas pressure energy as claimed in claim 4, wherein the high-pressure heat exchanger (5) and the low-pressure heat exchanger (6) are connected through a pipeline to form a heat exchange branch.
5. The comprehensive utilization system of natural gas pressure energy according to claim 2, wherein the multi-path single-stage differential pressure power generation subsystem comprises a turbine expander (17), a pressure regulating generator (18), a heat exchanger (19) and a natural gas branch valve (20);
the natural gas branch valve (20), the turboexpander (17) and the heat exchanger (19) are sequentially connected through pipelines to form a pressure reduction branch;
the multi-path single-stage differential pressure power generation subsystem is formed by connecting a plurality of pressure reduction branches in parallel; wherein the inlet end of a natural gas branch valve (20) on each pressure reduction branch is used for introducing high-pressure natural gas; the outlet of the end of the heat exchanger (19) on each pressure reduction branch is used for leading out low-pressure natural gas;
the turboexpander (17) is coaxially connected with the pressure regulating generator (18).
6. The system for comprehensively utilizing the pressure energy of the natural gas as claimed in claim 5, wherein the multi-path single-stage differential pressure power generation subsystem further comprises a refrigerant branch valve (21);
the refrigerant branch valve (21) is connected with the heat exchanger (19) through a pipeline to form a refrigerant branch; and the refrigerant branches are connected in parallel to form a heat exchange branch.
7. The natural gas pressure energy comprehensive utilization system as claimed in claim 2, wherein the multi-path two-stage differential pressure power generation subsystem comprises a high-pressure turbine expander (1), a low-pressure turbine expander (2), a first pressure regulating generator (3), a second pressure regulating generator (4), a high-pressure heat exchanger (5), a low-pressure heat exchanger (6) and a natural gas branch valve (20);
the natural gas branch valve (20), the high-pressure turbo expander (1), the high-pressure heat exchanger (5), the low-pressure turbo expander (2) and the low-pressure heat exchanger (6) are sequentially connected through pipelines to form a pressure reduction branch;
the multi-path two-stage differential pressure power generation subsystem is formed by connecting a plurality of voltage reduction branches in parallel; wherein the inlet end of the high-pressure turboexpander (1) on each pressure reduction branch is used for introducing high-pressure natural gas; the outlet of the heat absorption end of the low-pressure heat exchanger (6) on each pressure reduction branch is used for leading out low-pressure natural gas;
the high-pressure turboexpander (1) is coaxially connected with the first pressure regulating generator (3);
the low-pressure turbine expander (2) is coaxially connected with the second pressure regulating generator (4).
8. The system for comprehensively utilizing the pressure energy of the natural gas as claimed in claim 7, wherein the multi-path two-stage differential pressure power generation subsystem further comprises a refrigerant branch valve (21);
the refrigerant branch valve (21), the high-pressure heat exchanger (5) and the low-pressure heat exchanger (6) are connected through pipelines to form a refrigerant branch; and the refrigerant branches are connected in parallel to form a heat exchange branch.
9. The comprehensive utilization system of natural gas pressure energy as claimed in any one of claims 4, 6 and 8, wherein the gas-supercritical CO is 2 The combined cycle sub-system (200) includes CO 2 Expander (7), CO 2 Generator (8), supercritical CO 2 Heat exchanger (9) and CO 2 A compressor (10);
end of the heat exchange branch, CO 2 Compressor (10), supercritical CO 2 Heat exchanger (9), CO 2 The expander (7) and the head end of the heat exchange branch are sequentially connected through a pipeline to form a Brayton cycle;
the CO is 2 Generator (8), CO 2 Expander (7) and CO 2 The compressor (10) is coaxially connected。
10. The system for comprehensively utilizing the pressure energy of natural gas as claimed in claim 9, wherein the gas-supercritical CO 2 The combined cycle subsystem (200) further comprises a fuel control valve (11), a flue gas heat exchanger (12), a combustion chamber (13), a compressor (14), a gas turbine (15) and a gas generator (16);
the fuel control valve (11) is used for introducing low-pressure natural gas; the fuel control valve (11), the flue gas heat exchanger (12) and the combustion chamber (13) are connected in sequence through pipelines,
the compressor (14) is used for introducing air; the compressor (14), the combustion chamber (13), the gas turbine (15) and the supercritical CO 2 The heat exchanger (9) and the flue gas heat exchanger (12) are sequentially connected through a pipeline, and the heat release end outlet of the flue gas heat exchanger (12) leads out smoke;
the compressor (14), the gas turbine (15) and the gas generator (16) are coaxially connected.
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