Photovoltaic and photo-thermal coupled natural gas pressure energy and cold energy power generation, hydrogen production and hydrogen doping system

Abstract

The invention discloses a photovoltaic and photo-thermal coupled natural gas pressure energy and cold energy power generation, hydrogen production and hydrogen doping system, and belongs to the field of energy recovery. The system comprises a traditional pressure regulating branch and an expansion power generation hydrogen production branch. The traditional pressure regulating branch consists of a pressure regulating valve and a heater; the pressure regulating valve is arranged on the pipeline and is used for regulating flow and controlling a switch; the heater is used for heating natural gas in the traditional pressure regulating branch. The expansion power generation hydrogen production branch is used for generating power by recycling pressure energy of the high-pressure natural gas and cold energy generated by expansion; and meanwhile, the purpose of heating natural gas is achieved. The expansion power generation hydrogen production branch comprises a natural gas expansion machine, a condenser, a secondary heater, a pump, an organic Rankine cycle expansion machine, an evaporator, a heat storage water tank, a photovoltaic photo-thermal assembly, a battery, an ORC power generator, a gas-fired boiler, a natural gas expansion power generator and a water electrolysis hydrogen production device. Low-temperature natural gas flowing out of the natural gas expansion machine is subjected to cold energy recovery through a condenser, and organic Rankine cycle is used for achieving cold energy recovery. The problems of natural gas pressure energy waste, cold energy recovery after natural gas expansion, electrolytic hydrogen production and natural gas hydrogen doping can be solved.

Description

Technical Field

[0001] The invention relates to a natural gas pressure energy cooling power generation hydrogen production and blending system coupled with photovoltaic and thermal energy, belonging to the field of energy recovery. Background Art

[0002] Nowadays, most of the natural gas transportation in my country is based on pipeline transportation, and the pressure of natural gas transported in pipelines is getting higher and higher. After the natural gas is extracted from the large gas fields, it is transported to cities or users through long-distance pipelines. In order to adapt to the operation of gas transmission networks at all levels in the city and the needs of users, it is necessary to reduce the natural gas from high pressure (such as the design pressure of long-distance pipelines is 10MPa) to a lower pressure (the pressure of urban gas pipelines in my country is mostly 1.6-4.0MPa) at pressure regulating stations at all levels in the city.

[0003] According to the survey, the pressure regulation of natural gas mostly adopts the throttling method, and the pressure energy is not reasonably utilized. In the process of pressure regulation, the pressure energy of natural gas is all used to overcome the flow resistance of the throttle valve and the pressure regulating valve, resulting in a large amount of pressure energy not being reasonably utilized, resulting in energy waste. There is a very rich pressure energy in the process of natural gas pressure reduction. The West-East Gas Transmission Line I and Line II are adjusted from 8.0MPa to 0.4MPa. If this part of the pressure energy is recycled, then the expander can be used to drive the generator to generate electricity through expansion, and 6 billion kWh can be recycled each year, which is equivalent to 1.2 times the annual power generation of Xiaolangdi. Due to the remote distribution of the pipeline network, in order to ensure the supply of urban natural gas, most urban pressure regulating stations are distributed in remote places, such as lighting, cooling, heating, monitoring equipment, etc. Although the electricity consumption is small, it is difficult to use electricity due to geographical reasons. This is also some of the problems faced by gas companies. Compared with the complicated process and expensive price of the city power grid.

[0004] The existing differential pressure power generation system is based on the original pressure regulating line, and a pressure regulating branch consisting of an expander and a generator is connected in parallel. In this branch, the high-pressure natural gas drives the generator to generate electricity and turns into low-pressure natural gas through expansion work. The cold energy consumption problem caused by the low-temperature natural gas after expansion is mostly heated by gas boilers, which not only causes energy waste but also affects the production of natural gas, consuming a lot of precious gas energy.

[0005] Among the methods of utilizing low-temperature natural gas cold energy, cold energy power generation is widely used and the technology is mature. Compared with other processes such as air separation and low-temperature cold storage where cold energy is applied, it occupies a smaller area, and the generated electricity can be connected to the power grid without being controlled by downstream. The methods of cold energy power generation mainly include direct expansion of natural gas, low-temperature organic Rankine cycle, low-temperature Brayton cycle, multi-stage combined cycle and compound cycle. The direct expansion method cannot fully utilize the low-temperature cold energy of low-temperature natural gas, and the cold energy utilization rate is low; the Brayton cycle method, multi-stage cycle and compound cycle are more complicated in equipment operation or system, and are less used in practice; the low-temperature organic Rankine cycle method has a simple process and good flexibility, so most cold energy power generation devices use this process.

[0006] Considering that there is ample space on the roof of a plant to utilize solar energy, if the low-temperature organic Rankine cycle can be used to recover cold energy and combined with solar photovoltaic thermal technology, it can not only generate heat to meet the heat source required by the organic Rankine cycle and ensure the stable operation of the cold energy recovery process, but also generate photovoltaic power to create huge economic and energy-saving value for the enterprise.

[0007] Therefore, it is urgent to develop a comprehensive energy system that adds organic Rankine cycle cold energy recovery technology and photovoltaic thermal technology on the basis of the expansion power generation and pressure regulating branch to solve the waste of natural gas pressure energy and the problem of cold energy recovery after natural gas expansion. Reasonable use of the obtained electric energy to complete the supply of heat and electricity loads, and use electric energy for electrolysis to produce hydrogen to complete the function of natural gas hydrogen blending, so that the pressure regulating station can sell hydrogen-blended natural gas and excess electricity for profit, and promote the development of hydrogen energy and green energy. Summary of the invention

[0008] In order to solve the problem of waste of natural gas pressure energy and cold energy recovery after natural gas expansion, the purpose of the present invention is to provide a natural gas pressure energy cold energy power generation hydrogen production and blending system coupled with photovoltaic and thermal energy. Aiming at the disadvantage that the low-temperature natural gas cold energy of existing pressure regulating facilities is difficult to absorb and process, the system connects a new pressure regulating branch in parallel to the traditional pressure regulating device, combines natural gas pressure regulation, organic Rankine cycle, photovoltaic and thermal energy, pressure energy recovery and utilization, and cold energy absorption and processing, and can realize natural gas pressure difference power generation to recover pressure energy, and uses the hot water supplied by the photovoltaic and thermal subsystem as the organic Rankine cycle heat source, and the expanded low-temperature natural gas as the organic Rankine cycle cold source, which can realize the complementary utilization of solar energy and natural gas cold energy to recover cold energy, which can not only solve the problem of cold energy absorption, but also meet the thermal power load demand of the pressure regulating plant, and complete the process of hydrogen production by electrolysis and natural gas hydrogen blending, and improve economic and environmental benefits.

[0009] The objective of the present invention is achieved through the following technical solutions:

[0010] The invention discloses a natural gas pressure energy cooling power generation hydrogen production and blending system coupled with photovoltaic and thermal energy, comprising a traditional pressure regulating branch and an expansion power generation hydrogen production branch.

[0011] The traditional pressure regulating branch is composed of a pressure regulating valve and a heater; the pressure regulating valve arranged on the pipeline is used to adjust the flow and control the switch; the heater is used to heat the natural gas in the traditional pressure regulating branch.

[0012] The expansion power generation and hydrogen production branch generates electricity by recovering the pressure energy of high-pressure natural gas and the cold energy generated by expansion; at the same time, it achieves the purpose of heating the natural gas, allowing the natural gas at a suitable temperature to flow into the low-pressure natural gas pipeline, and uses the obtained electricity to complete electrolytic hydrogen production, and mixes the hydrogen into the low-pressure natural gas pipeline.

[0013] The expansion power generation hydrogen production branch includes a natural gas expander, a condenser, a secondary heater, a pump, an organic Rankine cycle expander, an evaporator, a hot water storage tank, a photovoltaic thermal component, a battery, an ORC generator, a gas boiler, a natural gas expansion generator and an electrolytic hydrogen production device.

[0014] The low-temperature natural gas flowing out of the natural gas expander is recovered through the condenser by the organic Rankine cycle. The organic Rankine cycle includes an evaporator, an organic Rankine cycle expander, a pump, a condenser and an ORC generator; after the working fluid is pressurized by the pump, it enters the evaporator to exchange heat with the hot water in the hot water storage tank to form a high-temperature and high-pressure gas, and then enters the organic Rankine cycle expander to expand, driving the ORC generator to generate electricity. The expanded gas enters the condenser and transfers heat to the expanded low-temperature natural gas, recovering the cold energy of the natural gas, completing the first heating of the natural gas, forming a liquid working fluid, and then continuing the organic Rankine cycle. During the cycle, the electricity produced by the ORC generator driven by the expander is incorporated into the battery for storage and utilization.

[0015] Photovoltaic thermal components absorb solar energy and generate electricity and heat energy at the same time; the electricity flows into the battery for storage and utilization; the heat energy is absorbed by the water in the heat storage tank and enters the water tank for storage and utilization.

[0016] The hot water storage tank is connected to the heat source side of the evaporator and the secondary heater respectively to form a heat exchange cycle.

[0017] When the heat in the hot water storage tank is not sufficient, the gas boiler provides heat to the secondary heater to complete the natural gas secondary heating process.

[0018] The water electrolysis hydrogen production device uses the electricity in the battery to perform the electrolysis hydrogen production process, and transports the hydrogen to a low-pressure natural gas pipeline for hydrogen blending treatment to form hydrogen-blended natural gas.

[0019] The invention discloses a natural gas pressure energy cold energy power generation hydrogen production and blending system coupled with photovoltaic and solar thermal energy, which also includes a boiler heating valve and a water tank heating valve; the boiler heating valve is used to open the boiler heating valve when solar energy is scarce and the heat of the hot water storage tank is insufficient, so that the natural gas is secondary heated by the gas boiler; the water tank heating valve is placed on the connecting pipeline between the hot water storage tank and the secondary heater, and provides heat to the secondary heater when the heat of the hot water storage tank is sufficient.

[0020] Beneficial effects:

[0021] 1. The invention discloses a natural gas pressure energy cold energy power generation hydrogen production and blending system coupled with photovoltaic and solar thermal energy, which adopts ORC cycle instead of traditional heater. Compared with the method of consuming primary energy to heat low-temperature natural gas, it realizes the cold energy recovery power generation of low-temperature natural gas after expansion, thereby saving energy and improving energy utilization.

[0022] 2. The present invention discloses a natural gas pressure energy cold energy power generation hydrogen production and blending system coupled with photovoltaic thermal energy. Since PVT photovoltaic thermal components are added to the system, the properties of organic Rankine cycle temperature difference power generation are utilized, and solar energy is used as a heat source to complete the heating of low-temperature natural gas. Compared with heating the low-temperature natural gas with a heater alone, it saves energy, utilizes renewable energy, is more green and environmentally friendly, and can also meet the heat load requirements of the voltage regulating plant.

[0023] 3. The natural gas pressure regulation process in the existing pressure regulating stations is mostly throttling valve pressure reduction, which wastes a lot of pressure energy, and the cost of power supply from the remote city grid is high. The natural gas pressure energy and cold energy power generation and hydrogen blending system coupled with photovoltaic and solar thermal energy disclosed in the present invention uses a natural gas expander to generate electricity using natural gas pressure energy, and uses PVT and ORC to complement the use of solar energy and cold energy to generate electricity. Compared with traditional devices, the pressure energy is recovered, the output electric energy is of high quality, the power consumption problem of the pressure regulating station is solved, and it can be supplied for electrolytic hydrogen production, obtaining hydrogen blending natural gas income and electricity sales income.

[0024] 4. The invention discloses a natural gas pressure energy cold energy power generation hydrogen production and blending system coupled with photovoltaic and thermal energy. The heat converted by photovoltaic and thermal energy is stored in a heat storage tank. It not only provides a heat source for the evaporator of the organic Rankine cycle to realize cold energy recovery and power generation, but also provides domestic hot water for the factory area and secondary heating of natural gas. In the photovoltaic and thermal energy assembly, the water in the heat storage tank acts as a medium to absorb the heat of the photovoltaic panel, improve the working life of the photovoltaic cell and the solar energy conversion efficiency, and thus increase the output of photovoltaic power generation.

[0025] 5. The invention discloses a natural gas pressure energy cooling power generation hydrogen production and blending system coupled with photovoltaic and solar thermal energy, which uses photovoltaic and solar thermal components as the main heating part and gas boilers as auxiliary heating, thereby reducing the use of gas boilers, significantly reducing carbon emissions, reducing gas resource consumption, and complying with the low-carbon development trend. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of a natural gas pressure energy cooling power generation hydrogen production and hydrogen blending system coupled with photovoltaic and thermal energy of the present invention;

[0027] Figure 2 This is a schematic diagram of the energy flow of a natural gas pressure energy cold energy power generation hydrogen production and blending system coupled with photovoltaic and thermal energy of the present invention: wherein, 1—pressure regulating valve, 2—natural gas expander, 3—condenser, 4—secondary heater, 5—pump, 6—organic Rankine cycle expander, 7—evaporator, 8—heat storage tank, 9—photovoltaic and thermal components, 10—boiler heating valve, 11—water tank heating valve, 12—battery, 13—ORC generator, 14—gas boiler, 15—natural gas expansion generator, 16—heater, 17—water electrolysis hydrogen production device. DETAILED DESCRIPTION

[0028] In order to better illustrate the purpose and advantages of the present invention, the invention is further described below with reference to the accompanying drawings and examples.

[0029] Embodiment 1:

[0030] like Figure 1 As shown, this embodiment discloses a natural gas pressure energy cooling power generation hydrogen production and blending system coupled with photovoltaic and thermal energy, including a traditional pressure regulating branch and an expansion power generation hydrogen production branch.

[0031] The conventional pressure regulating branch is composed of a pressure regulating valve 1 and a heater 16; the pressure regulating valve 1 is arranged on the pipeline, and the pressure regulating valve 1 is used to adjust the flow and control the switch; the heater 16 is used to heat the natural gas in the conventional pressure regulating branch;

[0032] The expansion power generation and hydrogen production branch generates electricity by recovering the pressure energy of high-pressure natural gas and the cold energy generated by expansion; at the same time, it achieves the purpose of heating the natural gas, allowing the natural gas at a suitable temperature to flow into the low-pressure natural gas pipeline, and uses the obtained electricity to complete electrolytic hydrogen production, and mixes the hydrogen into the low-pressure natural gas pipeline.

[0033] The expansion power generation hydrogen production branch includes a natural gas expander 2, a condenser 3, a secondary heater 4, a pump 5, an organic Rankine cycle expander 6, an evaporator 7, a hot water storage tank 8, a photovoltaic thermal component 9, a battery 12, an ORC generator 13, a gas boiler 14, a natural gas expansion generator 15 and an electrolytic hydrogen production device 17;

[0034] Figure 1The low-temperature natural gas in the heat exchanger is recovered through the condenser 3 by an organic Rankine cycle, which includes an evaporator 7, an organic Rankine cycle expander 6, a pump 5, a condenser 3 and an ORC generator 13. After the working fluid is pressurized by the pump 5, it enters the evaporator 7 to exchange heat with the hot water in the hot water storage tank 8 to increase the temperature to form a high-temperature and high-pressure gas, and then enters the organic Rankine cycle expander 6 to expand, driving the ORC generator 13 to generate electricity. The expanded gas enters the condenser 3, transfers heat to the expanded low-temperature natural gas, recovers the cold energy of the natural gas, completes the first heating of the natural gas, forms a liquid working fluid, and then continues the organic Rankine cycle. During the cycle, the power generated by the ORC generator 13 driven by the expander 6 is incorporated into the battery 12 for storage and utilization.

[0035] Figure 1 The hot water storage tank 8 is connected to the heat source side of the evaporator 7 and the secondary heater 4 respectively to form a heat exchange cycle;

[0036] Figure 1 The photovoltaic thermal component 9 absorbs solar energy and generates electricity and heat energy at the same time. The photovoltaic thermal component 9 is provided with a hot water outlet and a cold water inlet; the hot water storage tank 8 contains a water flow pipeline, which is connected with the hot water outlet and the cold water inlet of the photovoltaic thermal component 9 to form a heat exchange cycle; the heat energy is absorbed by a heat carrier, such as water, from the photovoltaic cell 9 to transfer the heat to the hot water storage tank 8 for storage and utilization. The hot water storage tank 8 is provided with a high-temperature water outlet and a low-temperature water inlet, which are connected to the heat source side of the evaporator 7 and the secondary heater 4 to form a heat exchange cycle; similarly, the electricity produced by the photovoltaic thermal component 9 is incorporated into the battery 12 through the inverter for storage and utilization.

[0037] Figure 1 The water electrolysis hydrogen production device 17 utilizes the electricity in the battery 12 to perform an electrolysis hydrogen production process, and transports the hydrogen to a low-pressure natural gas pipeline for hydrogen blending treatment to form hydrogen-blended natural gas.

[0038] Under normal working conditions, the hot water in the heat storage tank 8 is preferentially supplied to the evaporator 7 in the organic Rankine cycle to provide a heat source. When the solar energy is sufficient, the water tank heating valve 11 is opened. The hot water in the heat storage tank 8 can provide heat for the organic Rankine cycle and also provide heat for the secondary heater 4, thereby increasing the temperature of the natural gas and meeting the heat load required for domestic water use in the plant area. When the solar energy is scarce, considering that the heating capacity of the photovoltaic thermal component is small, a gas boiler 14 is added. When the heat in the heat storage tank 8 is not sufficient, the hot water in the heat storage tank 8 is preferentially supplied to the organic Rankine cycle heat source, the water tank heating valve 11 is closed, and the boiler heating valve 10 is opened. The gas boiler 14 provides heat for the secondary heater 4 and meets the heat load required for domestic water use in the plant area.

[0039] This embodiment discloses a natural gas pressure energy cooling power generation hydrogen production and hydrogen blending system coupled with photovoltaic and thermal energy. The working process is as follows: when the inlet pressure of a certain pressure regulating skid in the pressure regulating station is 1.6MPA, the outlet pressure is 0.3MPA, the natural gas flow is 60,000 cubic meters per day, and the natural gas inlet temperature is 30 degrees Celsius, Figure 1 After the natural gas expander 2 expands, the outlet temperature reaches -53.09 degrees Celsius, the output mechanical work is calculated to be 83.56kW, and the power generation is calculated to be 68.74kW. At this time, the low-temperature natural gas contains a large amount of cold energy for use. The temperature requirement of the downstream low-pressure natural gas is 5 degrees Celsius. When the outlet temperature is raised to the required temperature, the cold energy generated is 57.97kW. The low-temperature natural gas flows through the condenser in the ORC cycle for heat exchange. The cold energy absorbed and utilized by the organic Rankine cycle is 50.07kW, and the ORC power generation is 4.31kW. At this time, the heat provided by the PVT photovoltaic thermal component to the ORC cycle is 54.38kW, and the power generation of the PVT component is 10.38kW. The total power generation is 83.43kW. The temperature of the low-temperature natural gas after recovery through the ORC cycle has not yet reached the required temperature, so the heat required for secondary heating of the natural gas is 7.9kW. Assuming that the system runs for 7000 hours a year and the PVT components run for 1600 hours, it is calculated that the annual power generation potential is about 527958kWh, and the total power load of the voltage regulating station is 164437kWh a year. The power generation is much greater than the power load, and can be sold online to obtain economic benefits. In the system of the present invention, an evaluation index is selected to evaluate it.

[0040] This indicator mainly reflects the energy consumption or primary energy consumption rate of the system, and can directly evaluate the operating effect of the system. The primary energy saving rate refers to the ratio of the primary energy saved by the present invention to the primary energy consumed by the traditional pressure regulation process. The traditional pressure regulation system is composed of a traditional pressure regulating valve 1 and a heater 16. In the present invention, the energy input is mainly natural gas, so the consumption of natural gas is selected for calculation. The calculation formula is as follows:

[0041]

[0042] Where: V SYS The natural gas consumption in the system of the present invention includes: the gas consumption of the heat provided by the gas boiler and the gas consumption converted from the power consumption of the pump in the system;

[0043] V CT The natural gas consumption in the traditional pressure regulating device includes: the gas consumption converted from the power consumption in the system and the gas consumption of the heater.

[0044] The calculated primary energy saving rate is about 78%, indicating that compared with the voltage regulating branch, the system of this embodiment significantly reduces the problem of consuming a large amount of natural gas when absorbing cold energy, greatly reduces the primary energy consumption in the voltage regulating process, and brings environmental benefits to the voltage regulating plant; and through natural gas expansion power generation and cold energy recovery and utilization to generate sufficient electricity, it can sell electricity to the grid when meeting daily electricity load, bringing economic benefits to the voltage regulating plant.

[0045] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A natural gas pressure energy cooling power generation hydrogen production and blending system coupled with photovoltaic and thermal energy, characterized by: It includes the traditional voltage regulating branch and the expansion power generation and hydrogen production branch; The conventional pressure regulating branch is composed of a pressure regulating valve (1) and a heater (16); the pressure regulating valve (1) arranged on the pipeline is used to adjust the flow and control the switch; the heater (16) is used to heat the natural gas in the conventional pressure regulating branch; The expansion power generation and hydrogen production branch generates electricity by recovering the pressure energy of high-pressure natural gas and the cold energy generated by expansion; at the same time, it achieves the purpose of heating the natural gas, allowing the natural gas at a suitable temperature to flow into the low-pressure natural gas pipeline, and uses the obtained electricity to complete electrolytic hydrogen production, and mixes the hydrogen into the low-pressure natural gas pipeline.

2. A natural gas pressure energy cold energy power generation hydrogen production and blending system coupled with photovoltaic and thermal energy as claimed in claim 1, characterized in that: The expansion power generation hydrogen production branch comprises a natural gas expander (2), a condenser (3), a secondary heater (4), a pump (5), an organic Rankine cycle expander (6), an evaporator (7), a hot water storage tank (8), a photovoltaic thermal component (9), a battery (12), an ORC generator (13), a gas boiler (14), a natural gas expansion generator (15) and an electrolytic hydrogen production device (17); The low-temperature natural gas flowing out of the natural gas expander (2) is subjected to cold energy recovery through the condenser (3), which is realized by an organic Rankine cycle; the organic Rankine cycle includes an evaporator (7), an organic Rankine cycle expander (6), a pump (5), a condenser (3) and an ORC generator (13); after the working fluid is pressurized by the pump (5), it enters the evaporator (7) to exchange heat with the hot water in the hot water storage tank (8) to increase the temperature to form a high-temperature and high-pressure gas, and then enters the organic Rankine cycle expander (6) to expand, driving the ORC generator (13) to generate electricity, and the expanded gas enters the condenser (3) to transfer heat to the expanded low-temperature natural gas, recover the cold energy of the natural gas, complete the first heating of the natural gas, form a liquid working fluid, and then continue the organic Rankine cycle, and the organic Rankine cycle expander (6) drives the ORC generator (13) to generate electricity and is incorporated into the battery (12) for storage and utilization; The photovoltaic thermal component (9) absorbs solar energy and generates electric energy and thermal energy at the same time; the electric energy flows into the battery (12) for storage and utilization; the thermal energy is absorbed by the water in the hot water storage tank (8) and enters the water tank for storage and utilization; The hot water storage tank (8) is respectively connected to the heat source side of the evaporator (7) and the secondary heater (4) to form a heat exchange cycle; When the heat in the hot water storage tank (8) is insufficient, the gas boiler (14) provides heat to the secondary heater (4) to complete the secondary heating of the natural gas; The water electrolysis hydrogen production device (17) utilizes the electricity in the battery (12) to perform electrolysis to produce hydrogen, and transports the hydrogen to a low-pressure natural gas pipeline for hydrogen blending treatment to form hydrogen-blended natural gas.

3. A natural gas pressure energy cooling power generation hydrogen production and blending system coupled with photovoltaic and thermal energy as claimed in claim 1 or 2, characterized in that: The invention also comprises a boiler heating valve (10) and a water tank heating valve (11); the boiler heating valve (10) is used to open the boiler heating valve (10) when solar energy is scarce and the heat of the heat storage tank (8) is insufficient, so that the gas boiler performs secondary heating on the natural gas; the water tank heating valve (11) is placed on the connecting pipeline between the heat storage tank (8) and the secondary heater (4), and provides heat to the secondary heater when the heat of the heat storage tank (8) is sufficient.

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