Natural gas differential pressure power generation system based on composite heating of solar energy and geothermal energy and working method of natural gas differential pressure power generation system

Abstract

The invention belongs to the field of natural gas power generation, discloses a natural gas differential pressure power generation system based on solar energy and geothermal energy composite heating and a working method thereof, and aims to overcome the defects that in the prior art, a differential pressure power generation system is poor in stability, the temperature of depressurized natural gas is too low, and the power generation efficiency is low. High-pressure natural gas is heated through solar energy and geothermal energy, and the power generation efficiency is improved. By coupling a solar energy and geothermal energy composite heating system and a natural gas pressure difference power generation system, the two systems heat upstream natural gas in a composite mode through solar energy and geothermal energy by sharing a heat exchanger, and the upstream natural gas does work to generate power through a natural gas pressure difference power generation unit after absorbing heat. And the circulating fluid after heat loss enters the solar energy and geothermal energy composite heating system again for circulating energy absorption and heat supply. The problems that downstream natural gas transportation is blocked by ice, the use temperature is low, and conventional reheating energy dependence is high are solved, and full utilization of solar energy and geothermal energy is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of natural gas power generation, and particularly relates to a natural gas pressure difference power generation system based on solar energy and geothermal energy composite heating and a working method thereof. BACKGROUND

[0002] Natural gas has a very high pressure after being mined from the ground, usually between several MPa to tens of MPa, and long-distance transportation of natural gas is carried out by using high-pressure pipeline transportation at 5MPa-8MPa, and when reaching the city gate station, the pressure needs to be reduced to 1.6MPa-4MPa for transportation into the city pipe network, and then in the high and medium pressure regulating station, the pressure of the natural gas is reduced to about 0.4MPa for medium pressure transportation into the medium pressure pipe network, and in the medium and low pressure regulating station, the medium pressure natural gas is again reduced to about 0.1MPa for low pressure transportation to the end user. At present, the pressure reduction method used in the natural gas pressure regulating station in China is generally to reduce the pressure by the throttling effect generated by the pressure regulator, but the pressure difference energy is not well utilized. The natural gas pressure difference power generation system can well utilize the pressure energy generated by the original pressure regulation for power generation, and is a promising green power generation mode with zero carbon, no emission and no consumption.

[0003] As a clean energy with abundant reserves, geothermal energy plays a key role in promoting energy transformation in China and meeting the national carbon emission reduction strategy. Geothermal energy heating has the advantages of high energy efficiency, low heating cost, and clean and low carbon, but the traditional ground source heat pump system has problems such as unbalanced cold and heat load and deteriorating heat extraction conditions year by year.

[0004] The temperature of the natural gas upstream of the natural gas pressure difference power generation unit affects the power generation efficiency, and the process of expansion and pressure reduction in the power generation process is accompanied by a temperature drop of dozens of degrees, and the downstream low-temperature natural gas may be blocked by ice, which affects the transportation and use of the downstream natural gas, so it is imperative to reheat the upstream or downstream natural gas. The conventional reheating method usually uses air source heat pumps and circulating water heat pumps, which are highly dependent on external heat sources, and the heat pumps consume a lot of electric energy, which affects the power generation efficiency. Therefore, it is an urgent problem for those skilled in the art to develop a method for heating high-pressure natural gas using green energy for power generation. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application provides a natural gas pressure difference power generation system based on solar energy and geothermal energy composite heating and a working method thereof, which aims to solve the defects of poor stability of the pressure difference power generation system in the prior art, too low temperature of the natural gas after pressure reduction, and low power generation efficiency, and to realize comprehensive utilization of various green energies such as pressure difference energy, solar energy and geothermal energy of upstream and downstream natural gas.

[0006] To achieve the purpose of the present application, the technical scheme adopted is: The application discloses a natural gas pressure difference power generation system based on solar-geothermal energy composite heating, which comprises a solar-geothermal energy composite heating system and a natural gas pressure difference power generation system; wherein the solar-geothermal energy composite heating system comprises a geothermal well, a solar heat collector, a phase change heat storage tank, a circulating pump and a heat exchanger; wherein the natural gas pressure difference power generation system comprises a natural gas pressure difference power generation unit and the heat exchanger; wherein the natural gas pressure difference power generation unit comprises a turbine expander, a speed reducer and a generator; and wherein the heat exchanger is a common equipment of the solar-geothermal energy composite heating system and the natural gas pressure difference power generation system.

[0007] Further, the geothermal well, the solar heat collector, the phase change heat storage tank, the heat exchanger and the circulating pump are connected to form a circulating loop.

[0008] Further, the geothermal well, the phase change heat storage tank, the heat exchanger and the circulating pump are connected to form a circulating loop.

[0009] Further, the solar heat collector, the heat exchanger, the circulating pump and the geothermal well are connected to form a circulating loop.

[0010] Further, the phase change heat storage tank is connected in parallel with the solar heat collector.

[0011] Further, the heat exchanger is connected with the turbine expander, the speed reducer and the generator.

[0012] Further, the natural gas pressure difference power generation unit is one or several groups; each group of the natural gas pressure difference power generation unit comprises one turbine expander, one speed reducer and one generator.

[0013] Further, the solar-geothermal energy composite heating system and the natural gas pressure difference power generation system are coupled through the heat exchanger.

[0014] The application provides two working methods of the natural gas pressure difference power generation system based on solar-geothermal energy composite heating according to different conditions of solar energy supply.

[0015] 1. When the solar energy supply is sufficient, the method comprises the following steps: (1) when the light is sufficient, the circulating fluid is pressurized and circulated by the circulating pump, the circulating fluid first enters the geothermal well, the geothermal well absorbs the geothermal energy of the underground rock layer to heat the circulating fluid, the circulating fluid heated by the geothermal energy enters the solar heat collector, the solar heat collector absorbs the solar load to convert the light energy into heat energy, and further heats the circulating fluid, the circulating fluid heated by the solar heat collector enters the heat exchanger, the circulating fluid exchanges heat with the upstream natural gas in the heat exchanger, and then the circulating fluid reenters the circulating pump to be pressurized and complete the circulation; when the heat load of the natural gas pressure difference power generation system is met, the surplus heat is conducted to the phase change heat storage tank through the circulating fluid and then enters the heat exchanger to heat the upstream natural gas; (2) After the upstream natural gas absorbs heat in the heat exchanger, it enters the turbine expander through the turbine inlet, the heated natural gas does work in the turbine expander, and generates electricity through the reducer and the generator, and the worked natural gas enters the downstream natural gas from the turbine outlet.

[0016] 2. When solar energy supply is insufficient or the solar energy collector does not work, the following steps are included: (1) When the light is insufficient or the solar energy collector does not work, the circulating fluid is pressurized by the circulating pump to circulate, the circulating fluid first enters the geothermal well, the geothermal well absorbs the geothermal energy of the underground rock stratum to heat the circulating fluid, the circulating fluid enters the phase change heat storage tank to absorb heat after storing enough heat, and then enters the heat exchanger to exchange heat with the upstream natural gas, and then the circulating fluid reenters the circulating pump to be pressurized to complete the circulation; the surplus heat stored in the phase change heat storage tank is conducted to the phase change heat storage tank by the circulating fluid under the condition that the heat load of the natural gas pressure difference power generation system is met. (2) After the upstream natural gas absorbs heat in the heat exchanger, it enters the turbine expander through the turbine inlet, the heated natural gas does work in the turbine expander, and generates electricity through the reducer and the generator, and the worked natural gas enters the downstream natural gas from the turbine outlet.

[0017] The above technical scheme has the following beneficial effects: 1. The present application relates to natural gas power generation, solar energy heating and geothermal heating and other fields, and uses solar energy and geothermal energy to heat high-pressure natural gas, which then enters the natural gas pressure difference unit to work and generate electricity, thereby realizing the full utilization of solar energy and geothermal energy.

[0018] 2. The solar-geothermal energy composite heating system and the natural gas pressure difference power generation system are coupled systems, in order to make the natural gas pressure difference power generation system better utilize the heat energy of the solar-geothermal energy composite heating system, the present application increases a heat exchanger before the upstream natural gas enters each natural gas pressure difference power generation unit to heat the upstream natural gas, thereby raising the temperature of the upstream natural gas entering the turbine inlet of the turbine expander of the natural gas pressure difference power generation unit, improving the working efficiency of the turbine expander, and raising the temperature of the natural gas after the expansion and pressure reduction process in the turbine expander, thereby improving the temperature of the downstream natural gas and solving the problems of ice blocking and low temperature of the downstream natural gas.

[0019] 3. The solar-geothermal energy combined heating will play the complementary advantages of multiple energies, thereby effectively solving the problem of annual performance degradation of the system. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The present application provides a natural gas pressure difference power generation system based on solar-geothermal energy composite heating. DETAILED DESCRIPTION

[0021] In order to make the above objectives, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are further described in detail below with reference to the drawings.

[0022] Embodiment 1 The natural gas pressure difference power generation system based on solar and geothermal energy composite heating provided by the present application is provided with a solar and geothermal energy composite heating system and a natural gas pressure difference power generation system.

[0023] The solar and geothermal energy composite heating system is provided with a geothermal well, a solar heat collector, a phase change heat storage tank, a heat exchanger and a circulating pump; the geothermal well, the solar heat collector, the phase change heat storage tank, the heat exchanger and the circulating pump are connected in sequence to form a circulating loop; the geothermal well, the phase change heat storage tank, the heat exchanger and the circulating pump are connected in sequence to form a circulating loop; the solar heat collector, the heat exchanger, the circulating pump and the geothermal well are connected in sequence to form a circulating loop; and the phase change heat storage tank and the solar heat collector are connected in parallel.

[0024] The natural gas pressure difference power generation system is provided with a natural gas pressure difference power generation unit and a heat exchanger; the natural gas pressure difference power generation unit includes a turbine expander, a speed reducer and a generator; and the heat exchanger is connected with the turbine expander, the speed reducer and the generator in sequence. In this embodiment, the natural gas pressure difference power generation unit is provided with two groups; each group of the natural gas pressure difference power generation unit includes one turbine expander, one speed reducer and one generator, as shown in FIG. 2. Figure 1

[0025] The heat exchanger is arranged between the solar and geothermal energy composite heating system and the natural gas pressure difference power generation system, and is a common equipment of the two systems.

[0026] The solar and geothermal energy composite heating system and the natural gas pressure difference power generation system are coupled through the heat exchanger.

[0027] Embodiment 2 The working method of the natural gas pressure difference power generation system based on solar and geothermal energy composite heating provided by this embodiment is provided when the solar energy supply is sufficient, and includes the following steps: (1) When the light is sufficient, the circulating fluid is pressurized and circulated by the circulating pump, the circulating fluid first enters the geothermal well, the geothermal well absorbs the geothermal energy of the underground rock layer to heat the circulating fluid, the circulating fluid heated by the geothermal energy enters the solar heat collector, the solar heat collector absorbs the solar load to convert the light energy into heat energy, further heats the circulating fluid, the circulating fluid heated by the solar heat collector enters the heat exchanger, the circulating fluid exchanges heat with the upstream natural gas in the heat exchanger, and then the circulating fluid reenters the circulating pump for pressurization and the next cycle; in this embodiment, when the light is sufficient, the surplus heat is conducted to the phase change heat storage tank for energy storage under the condition of meeting the heat load of the natural gas pressure difference power generation system; ​(2) After the upstream natural gas absorbs heat in the heat exchanger, it is divided into two streams and enters the two turbine expanders through the two turbine inlets. The heated natural gas does work in the two turbine expanders and generates electricity through their respective reducers and generators. The two streams of natural gas after doing work enter the downstream natural gas through their respective turbine outlets.

[0028] Taking a turbine expander depressurized from 8MPa to 4MPa, with an inlet temperature of 25℃ and a power output of 200,000 standard cubic meters per hour as an example, the working method of the natural gas pressure differential power generation system based on solar and geothermal combined heating provided in this embodiment, with the turbine expander inlet temperature increased to 90℃, resulted in an actual power generation of 2934kW, which is 33.4% higher than the conventional power generation, thus improving the power generation efficiency.

[0029] Example 3 This embodiment describes the operating method of a natural gas differential pressure power generation system based on solar and geothermal combined heating when the solar collector is not in operation, including the following steps: (1) When the solar collector is not working, the circulating fluid is pressurized by the circulating pump and circulated. The circulating fluid first enters the geothermal well, where it absorbs geothermal energy from the underground rock layer to heat the circulating fluid. After the circulating fluid enters the phase change heat storage tank that stores enough heat to absorb heat, it enters the heat exchanger. In the heat exchanger, the circulating fluid exchanges heat with the upstream natural gas. Then the circulating fluid re-enters the circulating pump for pressurization and enters the next cycle. The heat stored in the phase change heat storage tank is the heat energy that is transferred to the phase change heat storage tank through the circulating fluid when the heat load of the natural gas pressure difference power generation system is met. (2) After the upstream natural gas absorbs heat in the heat exchanger, it is divided into two streams and enters the two turbine expanders through the two turbine inlets. The heated natural gas does work in the two turbine expanders and generates electricity through their respective reducers and generators. The two streams of natural gas after doing work enter the downstream natural gas through their respective turbine outlets.

[0030] Taking a turbine expander depressurized from 8MPa to 4MPa, with an inlet temperature of 25℃ and a power output of 200,000 standard cubic meters per hour as an example, the working method of the natural gas pressure differential power generation system based on solar and geothermal combined heating provided in this embodiment, with the turbine expander inlet temperature increased to 50℃, resulted in an actual power generation of 2492kW, which is 13.3% higher than the conventional power generation, thus improving the power generation efficiency.

[0031] Table 1 provides the operating parameters of the natural gas differential pressure power generation system based on solar geothermal energy composite heating in Embodiments 2 and 3 of the present invention under two conditions: sufficient solar energy supply and no solar collector operation, as well as the operating parameters of the conventional power generation method.

[0032] Table 1 It should be noted that the above examples are only used to illustrate the technical solutions of the present application but not to limit the present application. Although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced, without departing from the spirit and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. A natural gas differential pressure power generation system based on solar and geothermal combined heating, characterized in that: It includes a solar-geothermal composite heating system and a natural gas differential pressure power generation system; the solar-geothermal composite heating system includes a geothermal well, a solar collector, a phase change heat storage tank, a circulating pump, and a heat exchanger; the natural gas differential pressure power generation system includes a natural gas differential pressure generator set and a heat exchanger; the natural gas differential pressure generator set includes a turbine expander, a reducer, and a generator; the heat exchanger is a shared device for the solar-geothermal composite heating system and the natural gas differential pressure power generation system.

2. The natural gas pressure differential power generation system based on solar and geothermal combined heating as described in claim 1, characterized in that: The geothermal well, solar collector, phase change heat storage tank, heat exchanger and circulating pump set are connected to form a circulation loop.

3. The natural gas pressure differential power generation system based on solar and geothermal combined heating as described in claim 1, characterized in that: The geothermal well, phase change heat storage tank, heat exchanger and circulating pump are connected to form a circulation loop.

4. The natural gas pressure differential power generation system based on solar and geothermal combined heating as described in claim 1, characterized in that: The solar collector, heat exchanger, circulating pump, and geothermal well are connected to form a circulation loop.

5. The natural gas pressure differential power generation system based on solar and geothermal combined heating as described in claim 1, characterized in that: The phase change thermal storage tank is connected in parallel with the solar collector.

6. The natural gas pressure differential power generation system based on solar and geothermal combined heating as described in claim 1, characterized in that: The heat exchanger is connected to the turbine expander, the reducer, and the generator.

7. The natural gas pressure differential power generation system based on solar and geothermal combined heating as described in claim 1, characterized in that: The natural gas differential pressure generator set is one or more sets; each set of natural gas differential pressure generator set includes a turbine expander, a reducer and a generator.

8. The natural gas pressure differential power generation system based on solar and geothermal combined heating as described in claim 1, characterized in that: The solar-geothermal hybrid heating system and the natural gas differential pressure power generation system are coupled through a heat exchanger.

9. A method for operating a natural gas differential pressure power generation system based on solar-geothermal combined heating as described in any one of claims 1-8, characterized in that, The working method includes the following steps: (1) When there is sufficient sunlight, the circulating fluid is pressurized by the circulating pump and circulated. The circulating fluid first enters the geothermal well, which absorbs the geothermal energy of the underground rock layer to heat the circulating fluid. The circulating fluid heated by the geothermal energy enters the solar collector, which absorbs the solar load and converts the light energy into heat energy to further heat the circulating fluid. The circulating fluid heated by the solar collector enters the heat exchanger, where the circulating fluid exchanges heat with the upstream natural gas. Then the circulating fluid re-enters the circulating pump for pressurization to complete the circulation. When the heat load of the natural gas pressure differential power generation system is met, the surplus heat is conducted to the phase change heat storage tank through the circulating fluid and then enters the heat transfer device to heat the upstream natural gas. (2) After the upstream natural gas absorbs heat in the heat exchanger, it enters the turbine expander through the turbine inlet. The heated natural gas does work in the turbine expander and generates electricity through the reducer and generator. The natural gas that has done work enters the downstream natural gas through the turbine outlet.

10. A method for operating a natural gas differential pressure power generation system based on solar-geothermal combined heating as described in any one of claims 1-8, characterized in that, The working method includes the following steps: (1) When there is insufficient sunlight or the solar collector is not working, the circulating fluid is pressurized by the circulating pump and circulated. The circulating fluid first enters the geothermal well, where it absorbs the geothermal energy of the underground rock layer to heat the circulating fluid. After the circulating fluid enters the phase change heat storage tank that stores enough heat to absorb heat, it enters the heat exchanger. In the heat exchanger, the circulating fluid exchanges heat with the upstream natural gas. Then the circulating fluid re-enters the circulating pump for pressurization to complete the circulation. The heat stored in the phase change heat storage tank is the surplus heat that is transferred to the phase change heat storage tank through the circulating fluid when the heat load of the natural gas pressure difference power generation system is met. (2) After the upstream natural gas absorbs heat in the heat exchanger, it enters the turbine expander through the turbine inlet. The heated natural gas does work in the turbine expander and generates electricity through the reducer and generator. The natural gas that has done work enters the downstream natural gas through the turbine outlet.

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