Waste heat recycling system and method for natural gas booster station

Abstract

The invention discloses a waste heat recycling system and method for a natural gas booster station. The waste heat recycling system is mainly composed of a combustion-driven compressor, a flue gas heat exchanger, a working medium storage tank, a working medium pump, a steam turbine, a power generator, a high-temperature electrolytic cell and a natural gas-hydrogen mixing device. High-temperature flue gas of a combustion-driven compressor is connected into a flue gas heat exchanger to exchange heat with water, superheated steam is prepared, and the steam enters a steam turbine to act to become high-temperature saturated water; most high-temperature saturated water enters an air cooler to be cooled and then enters a heat preservation water tank, and part of the high-temperature saturated water enters a high-temperature electrolytic bath; water in the heat preservation water tank is fed into the flue gas heat exchanger for heat exchange through the water feeding pump; the system has the advantages that the flue gas waste heat recovery rate is high, zero power consumption of the booster station is realized, and the fuel gas consumption of the fuel-driven compressor is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste heat utilization of natural gas boosting stations, relates to a waste heat recycling system for natural gas boosting stations, and also relates to a waste heat recycling method for natural gas boosting stations. Background Art

[0002] Changqing Gas Field has put into operation more than 100 natural gas booster stations, most of which use natural gas engine-driven compression technology, generating a large amount of high-temperature flue gas of about 450°C directly discharged into the atmosphere every year. The natural gas booster station has a large number of fuel-driven compressors and abundant flue gas waste heat resources. The main process of the natural gas booster station is consistent and the heat load is stable, providing good objective conditions for waste heat recovery and utilization.

[0003] At present, the waste heat of high-temperature flue gas in natural gas booster stations is generally used for waste heat power generation technology. The power load of booster stations is small, and the waste heat power generation capacity in the station is much greater than the power load in the station. In addition, natural gas booster stations are located in remote areas and generally do not have the conditions for power transmission, so there is a problem of power consumption. Summary of the invention

[0004] The purpose of the present invention is to provide a waste heat recycling system for a natural gas boosting station, which utilizes the waste heat of the flue gas in the boosting station to generate electricity and produce hydrogen, thereby effectively utilizing the waste heat of the flue gas from the fuel-driven compressor of the boosting station, effectively improving the energy utilization level of the boosting station, and reducing the carbon emissions of the boosting station.

[0005] The technical solution adopted by the present invention is a waste heat recycling system for a natural gas booster station, including a flue gas heat exchanger, which is respectively connected to a steam turbine, an air cooler, and a high-temperature electrolyzer; the steam turbine is connected to a generator, and the air cooler is connected to an insulated water tank; the insulated water tank is connected to the flue gas heat exchanger to form a circulation loop, and a water feed pump is also provided on the connecting pipeline between the insulated water tank and the flue gas heat exchanger.

[0006] The present invention is also characterized in that:

[0007] The gas outlet of the high-temperature electrolyzer is connected to the natural gas-hydrogen mixing device, the natural gas-hydrogen mixing device is connected to the natural gas pipeline and the gas inlet of the fuel-driven compressor, and the hydrogen outlet of the high-temperature electrolyzer is connected to the natural gas-hydrogen mixing device.

[0008] The generator is connected to the site electricity user, and a power controller is also arranged on the connection line. The power supply end of the generator is connected to the power controller, and the power supply end of the power controller is connected to the high-temperature electrolytic cell.

[0009] The flue gas outlet of the fuel-driven compressor is connected to the flue gas inlet of the flue gas heat exchanger, the flue gas outlet of the flue gas heat exchanger is connected to the chimney, and the outlet of the feed water pump is connected to the flue gas heat exchanger.

[0010] The steam outlet of the flue gas heat exchanger is connected to the steam turbine, and the steam turbine and the generator are connected by a shaft.

[0011] The high-temperature saturated water outlet of the steam turbine is connected to the air cooler and the high-temperature electrolytic cell, and the condensate water outlet of the air cooler is connected to the insulation water tank.

[0012] The second technical solution adopted by the present invention is: a method for recycling waste heat in a natural gas booster station, and the specific operation steps are as follows:

[0013] First, the fuel-driven compressor generates high-temperature flue gas which enters the flue gas heat exchanger. After heat exchange in the flue gas heat exchanger, the high-temperature flue gas enters the chimney and is discharged into the atmosphere. The insulated water tank contains 95°C hot water, and the water supply pump sends the hot water into the flue gas heat exchanger to heat it into superheated steam. The superheated steam enters the steam turbine to do work, driving the generator to generate electricity. The current enters the power controller for distribution, and after meeting the electricity consumption of the booster station, the remaining power is distributed to the high-temperature electrolyzer by the power controller. After doing work, the superheated steam becomes high-temperature saturated water, part of which enters the air cooler for cooling and then enters the insulated water tank, and part of which enters the high-temperature electrolyzer for electrolysis to produce hydrogen. Hydrogen and natural gas are fully mixed in the natural gas-hydrogen mixing device and then enter the fuel-driven compressor for combustion and work.

[0014] The beneficial effects of the present invention are:

[0015] The waste heat recycling system for a natural gas booster station provided by the present invention has the advantages of high flue gas waste heat recovery rate, achieving zero electricity consumption in the booster station, and reducing the gas consumption of the fuel-driven compressor, which specifically includes:

[0016] 1. The present invention solves the problem of on-site consumption of surplus electricity from the power generation part by combining flue gas waste heat power generation and electrolytic hydrogen production process.

[0017] 2. The present invention monitors the power load in the station through the power controller, adjusts the power load of the high-temperature electrolytic cell in real time, matches the power load with the power generated by the generator, and the power generated can be fully and effectively utilized.

[0018] 3. The present invention uses high-temperature saturated water generated by a steam turbine to electrolyze hydrogen, which effectively improves the efficiency of water electrolysis, which is more than 10% higher than that of hydrogen production by electrolysis at room temperature.

[0019] 4. The hydrogen produced by the present invention is mixed with natural gas and used in the fuel-driven compressor, thereby avoiding the hydrogen storage process and reducing the risk points of the overall process.

[0020] 5. The present invention realizes the diversification of the flue gas waste heat utilization products of the boosting station by forming a waste heat recycling process in the boosting station through the flue gas waste heat power generation part, water electrolysis to produce hydrogen and natural gas-hydrogen mixed combustion. The produced electricity and hydrogen are consumed in the station, which solves the energy consumption problem of remote boosting stations and has no impact on the main process of the boosting station. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a schematic diagram of a waste heat recycling process for a natural gas boosting station.

[0022] In the figure: 1-fuel-driven compressor; 2-flue gas heat exchanger; 3-chimney; 4-insulated water tank; 5-feedwater pump; 6-steam turbine; 7-generator; 8-air cooler; 9-power controller; 10-high-temperature electrolyzer; 11-natural gas-hydrogen mixing device; 12-natural gas pipeline; 13-site electricity users. DETAILED DESCRIPTION

[0023] The following is a detailed description of an embodiment of the present invention in conjunction with the accompanying drawings. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0024] Example 1

[0025] The waste heat recycling system for a natural gas booster station of the present invention is as follows: Figure 1 As shown, it includes a flue gas heat exchanger 2, which is respectively connected to a steam turbine 6, an air cooler 8, and a high-temperature electrolytic cell 10; the steam turbine 6 is connected to a generator 7, and the air cooler 8 is connected to a thermal insulation water tank 4; the thermal insulation water tank 4 is connected to the flue gas heat exchanger 2 to form a circulation loop, and a water feed pump 5 is also provided on the connecting pipeline between the thermal insulation water tank 4 and the flue gas heat exchanger 2.

[0026] The gas outlet of the high-temperature electrolyzer 10 is connected to the natural gas-hydrogen mixing device 11, and the natural gas-hydrogen mixing device 11 is connected to the natural gas pipeline 12 and connected to the gas inlet of the fuel-driven compressor 1, and the hydrogen outlet of the high-temperature electrolyzer 10 is connected to the natural gas-hydrogen mixing device 11.

[0027] The generator 7 is connected to the site electricity user 13 , and a power controller 9 is also provided on the connection line. The power supply end of the generator 7 is connected to the power controller 9 , and the power supply end of the power controller 9 is connected to the high-temperature electrolytic cell 10 .

[0028] The flue gas outlet of the fuel-driven compressor 1 is connected to the flue gas inlet of the flue gas heat exchanger 2 , and the flue gas outlet of the flue gas heat exchanger 2 is connected to the chimney 3 .

[0029] The outlet of the water feed pump 5 is connected to the flue gas heat exchanger 2 .

[0030] The steam outlet of the flue gas heat exchanger 2 is connected to the steam turbine 6, and the steam turbine 6 is connected to the generator 7 via a shaft.

[0031] The high-temperature saturated water outlet of the steam turbine 6 is connected to the air cooler 8 and the high-temperature electrolytic cell 10 , and the condensed water outlet of the air cooler 8 is connected to the thermal insulation water tank 4 .

[0032] Example 2

[0033] The present invention is used for the waste heat recycling system of the natural gas booster station, which innovates the traditional waste heat utilization process of a single product. The process mainly consists of a fuel-driven compressor, a flue gas heat exchanger, a working fluid storage tank, a working fluid pump, a steam turbine, a generator, a high-temperature electrolyzer and a natural gas-hydrogen mixing device. The high-temperature flue gas from the fuel-driven compressor is connected to the flue gas heat exchanger to exchange heat with water to produce superheated steam, and the steam enters the steam turbine to do work and becomes high-temperature saturated water; most of the high-temperature saturated water enters the air cooler for cooling and then enters the insulation water tank, and a part of the high-temperature saturated water enters the high-temperature electrolyzer; the water in the insulation water tank is sent to the flue gas heat exchanger by the water supply pump for heat exchange.

[0034] The power generated by the generator is used by the booster station, and the remaining power is used by the high-temperature electrolyzer. The hydrogen produced by the high-temperature electrolyzer enters the natural gas-hydrogen mixing device to mix with natural gas and enter the fuel-driven compressor.

[0035] Example 3

[0036] Reference Figure 1 , the waste heat recycling process of the natural gas booster station is as follows: first, the fuel-driven compressor 1 generates high-temperature flue gas that enters the flue gas heat exchanger 2. After heat exchange in the flue gas heat exchanger 2, the high-temperature flue gas enters the chimney 3 and is discharged into the atmosphere. The insulated water tank 4 contains 95°C hot water. The water supply pump 5 sends the hot water into the flue gas heat exchanger 2 to heat it into superheated steam. The superheated steam enters the steam turbine 6 to do work, driving the generator 7 to generate electricity. The current enters the power controller 9 for distribution. After meeting the power consumption of the booster station, the remaining power is distributed to the high-temperature electrolyzer 10 by the power controller 9. After doing work, the superheated steam becomes high-temperature saturated water. Part of it enters the air cooler 8 to cool and then enters the insulated water tank 4, and part of it enters the high-temperature electrolyzer 10 for electrolysis to produce hydrogen. Hydrogen and natural gas are fully mixed in the natural gas-hydrogen mixing device 11 and then enter the fuel-driven compressor 1 for combustion and work.

[0037] Example 4

[0038] Taking a booster station in Changqing as an example, the annual flue gas flow is 1.5x108Nm3 / a, and the average flue gas temperature is 450°C. The generator installed power is 100kW, the annual power generation is 73.6×104kWh, the power consumption in the station is 28×104kWh, and the remaining power is used to produce 10.13×104Nm3 of hydrogen, which can save 3.57×104Nm3 of natural gas as fuel.

[0039] The above describes the basic principles, main features and advantages of the present invention. Professionals and technicians in this industry should understand that the present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments only describe the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements will fall within the scope of the present invention to be protected.

Claims

1. A waste heat recycling system for a natural gas booster station, characterized in that: The invention comprises a flue gas heat exchanger (2), wherein the flue gas heat exchanger (2) is respectively connected to a steam turbine (6), an air cooler (8), and a high-temperature electrolytic cell (10); the steam turbine (6) is connected to a generator (7), and the air cooler (8) is connected to a heat-insulating water tank (4); the heat-insulating water tank (4) is connected to the flue gas heat exchanger (2) to form a circulation loop, and a water supply pump (5) is also provided on the connecting pipeline between the heat-insulating water tank (4) and the flue gas heat exchanger (2).

2. The waste heat recycling system for a natural gas boosting station according to claim 1, characterized in that: The gas outlet of the high-temperature electrolyzer (10) is connected to a natural gas-hydrogen mixing device (11), the natural gas-hydrogen mixing device (11) is connected to a natural gas pipeline (12) and is connected to a gas inlet of a fuel-driven compressor (1), and the hydrogen outlet of the high-temperature electrolyzer (10) is connected to the natural gas-hydrogen mixing device (11).

3. The waste heat recycling system for a natural gas boosting station according to claim 1, characterized in that: The generator (7) is connected to a site power user (13), and a power controller (9) is also provided on the connection line. The power supply end of the generator (7) is connected to the power controller (9), and the power supply end of the power controller (9) is connected to the high-temperature electrolytic cell (10).

4. The waste heat recycling system for a natural gas boosting station according to claim 1, characterized in that: The flue gas outlet of the fuel-driven compressor (1) is connected to the flue gas inlet of the flue gas heat exchanger (2), and the flue gas outlet of the flue gas heat exchanger (2) is connected to the chimney (3).

5. The waste heat recycling system for a natural gas boosting station according to claim 1, characterized in that: The outlet of the water supply pump (5) is connected to the flue gas heat exchanger (2).

6. The waste heat recycling system for a natural gas boosting station according to claim 1, characterized in that: The steam outlet of the flue gas heat exchanger (2) is connected to the steam turbine (6), and the steam turbine (6) and the generator (7) are connected by a shaft.

7. The waste heat recycling system for a natural gas boosting station according to claim 1, characterized in that: The high-temperature saturated water outlet of the steam turbine (6) is connected to the air cooler (8) and the high-temperature electrolytic cell (10), and the condensed water outlet of the air cooler (8) is connected to the heat-insulating water tank (4).

8. A method for recycling waste heat in a natural gas booster station, characterized in that: The specific steps are as follows: First, the fuel-driven compressor (1) generates high-temperature flue gas which enters the flue gas heat exchanger (2). After heat exchange in the flue gas heat exchanger (2), the high-temperature flue gas enters the chimney (3) and is discharged into the atmosphere. The insulated water tank (4) contains 95°C hot water. The water supply pump (5) sends the hot water into the flue gas heat exchanger (2) to heat it into superheated steam. The superheated steam enters the steam turbine (6) to perform work, driving the generator (7) to generate electricity. The current enters the power controller (9) for distribution. After meeting the power consumption of the boosting station, the remaining power is distributed by the power controller (9) to the high-temperature electrolyzer (10). After the superheated steam performs work, it becomes high-temperature saturated water. A part of it enters the air cooler (8) for cooling and then enters the insulated water tank (4), and a part of it enters the high-temperature electrolyzer (10) for electrolysis to produce hydrogen. The hydrogen and natural gas are fully mixed in the natural gas-hydrogen mixing device (11) and then enter the fuel-driven compressor (1) to burn and perform work.

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