Natural gas distributed energy system and method adapting to large thermal load fluctuation

Abstract

The invention discloses a natural gas distributed energy system and method adapting to large thermal load fluctuation, and relates to the technical field of natural gas energy. The waste heat boiler is communicated with an output port of the gas turbine and outputs steam; a steam turbine; a second generator; a heat accumulator; a steam header; and a feed pump. According to the natural gas distributed energy system and method adapting to the large heat load fluctuation, steam is stored through the heat accumulator, storage in the heat supply valley and release in the heat supply peak are achieved, the heat supply pressure in the central heat supply peak is relieved, gradient utilization of the steam is achieved through the steam turbine, and the heat supply efficiency is improved. The generator can be driven to generate electricity to relieve electricity pressure, steam can be decompressed, and decompressing units are reduced. A series of problems of low-efficiency operation of a unit under a low-load working condition, redundant configuration of the unit, high labor intensity of workers, influence on the service life of the unit and the like caused by large steam load fluctuation in regional centralized heating are comprehensively solved.

Description

Technical Field

[0001] The present invention relates to the field of natural gas energy technology, and in particular to a natural gas distributed energy system and method that can adapt to large thermal load fluctuations. Background Art

[0002] The natural gas distributed energy system realizes the cascade utilization of energy through the trigeneration of cooling, heating and electricity. It has the advantages of local supply, energy saving and high efficiency, clean and environmental protection, and has broad development prospects. However, the heat load of the centralized heating or cogeneration industry is affected by the different types of heat users and different seasonal time periods in the heating area, and has the characteristics of large and frequent changes throughout the year. In this way, the conventional natural gas distributed energy system will bring the following problems: First, the system load fluctuation adaptability is poor, the energy utilization efficiency is low, and the workers need to frequently adjust the unit operation, which is labor-intensive; second, the frequent fluctuation of the unit will shorten the service life of the unit, especially the core equipment gas turbine is not allowed to start and stop frequently or operate at a load below 70% (the efficiency is greatly affected after it is lower than this working condition); third, the configuration of the unit according to the maximum heat load causes redundant investment waste (especially the core equipment gas turbine is generally imported and the cost is very expensive), which is not economical. Therefore, how to adjust the peak and valley of heating and save energy while meeting the continuous fluctuation of heat load has become an important issue.

[0003] Natural gas distributed energy systems that adapt to large fluctuations in heat load can balance the mismatch between energy supply and demand by utilizing thermal energy storage technology. The system can store excess thermal energy during periods of low energy demand and release the thermal energy during peak demand periods.

[0004] In conjunction with publication number CN103256754B, published on March 11, 2015, a composite energy supply system coupling a natural gas-based distributed energy system and a ground-source heat pump is disclosed.

[0005] However, in the above-mentioned technology and the existing technology, there is a mismatch in energy quality between the medium-pressure steam released by the steam energy storage accumulator of the energy station and the low-pressure steam required for external heating. The thermal energy needs to be decompressed before it can be delivered to the heating end, resulting in energy waste in the process. Summary of the invention

[0006] The purpose of the present invention is to provide a natural gas distributed energy system and method that can adapt to large fluctuations in heat load, in order to solve the above-mentioned problems.

[0007] In order to achieve the above-mentioned object, the present invention provides the following technical solutions: a natural gas distributed energy system adaptable to large fluctuations in heat load, comprising a gas turbine for burning natural gas to generate high-temperature gas and perform work; A waste heat boiler is connected to the output port of the gas turbine and outputs steam; A steam turbine, the steam inlet of which is connected to the waste heat boiler, and the steam outlet of which is connected to the steam cylinder; a second generator, which is driven by the steam turbine and connected to the power supply end through the power grid; Regenerators, which are used to store excess steam; The steam sub-cylinder is used to receive the steam discharged from the steam turbine and the waste heat boiler and evenly distribute it, and the steam sub-cylinder is connected to the heating end through the urban heating pipeline network; A feed water pump is driven by the second generator to supply water to the waste heat boiler.

[0008] Preferably, it further comprises a first pipeline for connecting the waste heat boiler and the sub-cylinder, on which a first valve is arranged; a second pipeline for connecting the waste heat boiler and the heat accumulator, on which a second valve is arranged; A third pipeline for connecting the heat accumulator and the steam turbine, on which a third valve is provided; The fourth pipeline is used to connect the waste heat boiler and the steam turbine.

[0009] Preferably, the first valve, the second valve and the third valve are all stop valves of model J961.

[0010] Preferably, it also includes a heating end monitoring and control unit for monitoring the heat consumption of the heating end and adjusting it in real time, and the monitoring and control unit is signal-connected to the first valve, the second valve and the third valve.

[0011] Preferably, a coupling is provided between the steam turbine and the second generator.

[0012] Preferably, the waste heat boiler is a double-pressure waste heat boiler of model NG-LM6000-R or the same type.

[0013] Preferably, the waste heat boiler is provided with a steam pressure detection unit.

[0014] Preferably, it also includes a first generator driven by a gas turbine to generate electricity, and the first generator is connected to the power supply end through a town power supply network.

[0015] Preferably, the water supply pump is an electric water supply pump of model HGC4 / 12 or the same type.

[0016] A natural gas distributed energy method adapted to large fluctuations in heat load comprises the following steps: Step 1: The high-temperature flue gas from the gas turbine enters the waste heat boiler and exchanges heat with the water supplied by the feed pump, converting the water into high-pressure and low-pressure steam; Step 2: The waste heat boiler outputs high-pressure and low-pressure steam, and the output steam is divided into two paths: The first route, low-pressure steam, directly enters the steam cylinder through the first pipeline; After the second high-pressure steam enters the steam turbine, it first drives the second generator to generate electricity, and supplies power to the feedwater pump through the second generator. The low-pressure steam discharged from the steam turbine enters the sub-cylinder again. When the heating supply is low (heat demand is low), part of the steam enters the heat accumulator through the second pipeline and is stored. When the heating supply is at a peak (heat demand peak), the steam enters the steam turbine through the fifth pipeline through the exhaust port of the heat accumulator, and is combined with the high-pressure steam in the waste heat boiler to drive the steam turbine cascade to generate electricity, and discharge the low-pressure steam. Step 3: The steam cylinders evenly distribute the low-pressure steam from the waste heat boiler and the steam turbine and then transport it to the heating end. In the above technical scheme, the natural gas distributed energy system and method provided by the present invention that is adaptable to large fluctuations in heat load has the following beneficial effects: by storing steam in the heat accumulator, it is stored during the low heat supply period and released during the peak heat supply period, thereby alleviating the heating pressure during the peak heat supply period of the centralized heating system, and the cascade utilization of steam is realized through the steam turbine, which can not only drive the generator to generate electricity to alleviate the power supply pressure, but also reduce the pressure of the steam and reduce the number of pressure reducing units. It comprehensively solves a series of problems in regional centralized heating, such as inefficient operation of the unit under low load conditions, redundant unit configuration, high labor intensity of workers, and affected unit life, caused by large fluctuations in steam load. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0018] Figure 1 The present invention provides a structure of a natural gas distributed energy system that is adaptable to large fluctuations in heat load. Description of reference numerals: 1. Gas turbine; 2. Waste heat boiler; 3. Cylinder; 4. Regenerator; 5. Steam turbine; 6. Speed ​​reducer; 7. Generator; 8. Feed water pump; 9. Deaerator; 10. Third valve; 11. First valve; 12. Second valve; a, first pipeline; b, second pipeline; c, third pipeline; d, fourth pipeline. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0020] like Figure 1 As shown, a natural gas distributed energy system adapted to large fluctuations in heat load comprises: A gas turbine 1, which is used to burn natural gas to generate high-temperature gas and perform work; A waste heat boiler 2, which is connected to the output port of the gas turbine 1 and outputs steam; The steam turbine 5 has a steam inlet connected to the waste heat boiler 2 and a steam outlet connected to the steam cylinder 3; A second generator 7, which is driven by the steam turbine 5 and connected to the power supply end through the power grid; A heat accumulator 4 for storing excess steam; The steam sub-cylinder 3 is used to receive low-pressure steam and evenly distribute it, and the steam sub-cylinder 3 is connected to the heating end through the town heating network; A feed water pump 8 is driven by the second generator 7 to supply water to the waste heat boiler 2 .

[0021] Specifically, while the gas turbine 1 generates high-temperature and high-pressure flue gas, it drives the turbine to expand and perform work, so as to convert the chemical energy of the natural gas into mechanical energy, and then generate electricity through the mechanical energy, and the excess electric energy is transmitted to the power supply end. The waste heat boiler 2 is connected with the sub-cylinder 3, the heat accumulator 4 and the steam turbine 5 through pipelines, and the heat accumulator 4 is provided with an input port and an exhaust port for receiving steam. High-pressure steam and low-pressure steam are simultaneously generated in the waste heat boiler 2, and the high-pressure steam preferentially drives the steam turbine 5 to perform work. By driving the steam turbine 5, part of the pressure and thermal energy of the high-pressure steam is converted into the mechanical energy of the steam turbine 5. In this process, the high-pressure steam is converted into low-pressure steam, and then the low-pressure steam also enters the sub-cylinder 3 and after being evenly divided, the low-pressure steam is output to the heating end through the urban heating pipeline network.

[0022] Furthermore, the steam turbine 5 drives the second generator 7 to generate electricity, thereby supplying power to the feed water pump 8, which pumps water into the waste heat boiler 2, so that the water is converted into high-pressure and low-pressure steam under the high-temperature flue gas output by the gas turbine 1.

[0023] like Figure 1 As shown, a natural gas distributed energy method adapted to large thermal load fluctuations is applied to the above-mentioned natural gas distributed energy system adapted to large thermal load fluctuations, comprising the following steps: Step 1: The high-temperature flue gas from the gas turbine 1 enters the waste heat boiler 2 and exchanges heat with the water supplied by the feed water pump 8 so that the water is converted into high-pressure and low-pressure steam; Step 2: Waste heat boiler 2 outputs high-pressure and low-pressure steam, and the output steam is divided into two paths: The first low-pressure steam directly enters the steam cylinder 3 through the first pipeline a; After the second high-pressure steam enters the steam turbine 5, it first drives the second generator 7 to generate electricity, and supplies power to the feedwater pump 8 through the second generator 7. The low-pressure steam discharged from the steam turbine 5 enters the sub-cylinder 3 again. When the heating supply is low (heat demand is low), part of the steam enters the heat accumulator 4 through the second pipeline b to be stored. When the heating supply is at a peak (heat demand peak), the steam enters the steam turbine 5 through the fifth pipeline e through the exhaust port of the heat accumulator 4, and is combined with the high-pressure steam in the waste heat boiler 2 to drive the steam turbine 5 for cascade utilization to generate electricity, and discharge the low-pressure steam. Step 3: The steam cylinder 3 evenly distributes the low-pressure steam from the waste heat boiler 2 and the steam turbine 5 and transmits it to the heating end.

[0024] Specifically, when the heating supply is low, the low-pressure steam in the waste heat boiler 2 is directly transported to the heating end through the steam cylinder 3, and the high-pressure steam enters the steam turbine 5 and is used to drive the second generator 7 to generate electricity, and the second generator 7 is used to power the water supply pump 8, and the excess electricity enters the power supply end through the town power supply network to relieve the power supply pressure, and at the same time, the excess steam output by the waste heat boiler 2 is stored in the heat accumulator 4; During the peak heating period, the high-pressure steam stored in the waste heat boiler 2 and the heat accumulator 4 is jointly fed into the steam turbine 5 for cascade utilization to generate electricity, and the high-pressure steam is converted into low-pressure steam and fed into the steam sub-cylinder 3, which is evenly distributed by the sub-cylinder 3 and transported to the heating end through the urban heating network.

[0025] In the above technology, the storage of steam by the heat accumulator 4 is realized in the low-heating valley and released in the peak-heating peak, which relieves the heating pressure of the centralized heating peak. The cascade utilization of steam is realized by the steam turbine 5, which can not only drive the second generator 7 to generate electricity to relieve the power pressure, but also reduce the pressure of the steam to reduce the pressure reducing unit. A series of problems in regional centralized heating, such as low-load condition inefficient operation of the unit, redundant unit configuration, high labor intensity of workers, and affected unit life, are comprehensively solved due to large fluctuations in steam load.

[0026] As an embodiment further provided by the present invention, it also includes a first pipeline a for connecting the waste heat boiler 2 and the sub-cylinder 3, on which a first valve 11 is arranged; A second pipeline b for connecting the waste heat boiler 2 and the heat accumulator 4, on which a second valve 12 is provided; For communicating the third pipe c of the heat accumulator 4 and the turbine 5, on which a third valve 10 is provided; A fourth pipeline d is used to connect the waste heat boiler 2 and the steam turbine 5 .

[0027] Specifically, the first valve 11, the second valve 12 and the third valve 10 are all stop valves of model J961. When the heating supply is low, the first valve 11 is lowered and the third valve 10 is closed, so that the second valve 12 operates normally. At this time, the second pipeline b and the fourth pipeline d are both unblocked, so that the steam in the waste heat boiler 2 preferentially enters the steam turbine 5 through the fourth pipeline d and drives the steam turbine 5. The excess steam enters the heat accumulator 4 for storage, and drives the second generator 7 to generate electricity through the steam turbine 5. The electricity generated is used to supply the water pump 8. At the same time, the excess electricity is transmitted to the power supply end through the urban power supply network. During the peak heating period, the second valve 12 is lowered or closed to allow the first valve 11 and the third valve 10 to operate normally, so that the first pipeline a and the third pipeline c are unobstructed, and the fourth pipeline d is not affected by the valve. At this time, the low-pressure steam directly enters the sub-cylinder 3 through the waste heat boiler 2, and the high-pressure steam in the heat accumulator 4 is also converted into low-pressure steam through the turbine 5 and enters the sub-cylinder 3, thereby alleviating the peak pressure.

[0028] As another embodiment further provided by the present invention, it also includes a heating end monitoring and control unit for monitoring the heat consumption of the heating end and regulating it in real time, and the monitoring and control unit is signal-connected to the first valve 11 , the second valve 12 and the third valve 10 .

[0029] Specifically, a control program is provided in the heating end monitoring and control unit, including a metering unit for detecting external heating demand, which can adopt a pressure detector arranged on the heating pipe network on the surface, or a flow meter for detecting the flow at the output end of the sub-cylinder 3, or a metering unit known to technical personnel in this field.

[0030] When the temperature detector detects that the pressure of the heating network is low (lower than the design pressure value), or the flow meter detects that the flow rate at the output end of the cylinder 3 is lower than the average value, that is, the current heating peak period, the second valve 12 is lowered or closed through signal control, and the first valve 11 and the third valve 10 are kept open; conversely, when the pressure of the heating network is high (higher than the design pressure value), or the flow rate at the output end is higher than the average value, it is the heating trough period, the first valve 11 and the third valve 10 are lowered or closed through signal control, and the second valve 12 is opened.

[0031] As another embodiment further provided by the present invention, a coupling is provided between the steam turbine 5 and the second generator 7 .

[0032] Specifically, the coupling can make the transmission between the steam turbine 5 and the second generator 7 more stable, reducing energy loss in the process.

[0033] As another embodiment further provided by the present invention, the waste heat boiler 2 is a double-pressure waste heat boiler of model NG-LM6000-R or the same type.

[0034] Specifically, the dual-pressure waste heat boiler has the ability to provide high-pressure and low-pressure steam at the same time. Under normal operating conditions, the low-pressure steam enters the sub-cylinder 3, while the high-pressure steam preferentially enters the turbine 5 stage for power generation, and then is converted into low-pressure steam and enters the sub-cylinder 3. This is a gas turbine combined cycle system, which can greatly improve the power generation efficiency of the entire system (the combined cycle system can convert more electrical energy, which is a high-quality energy, and the power generation efficiency is 20% higher than that of the traditional coal-fired thermal power generation system, and can reach up to 64%). After calculation, the high-pressure steam pressure is between 7.0-9.8MPa, and the system investment and operation economy are the highest.

[0035] Furthermore, the accumulator 4 is a high-pressure accumulator. The cost of a steam accumulator is generally proportional to its volume. Affected by manufacturing and transportation conditions, the volume of a single accumulator should not be greater than 150m3. 3 The higher the steam pressure entering the heat accumulator, the higher the heat storage per unit volume of saturated water, that is, the heat accumulator of the same volume can store more heat. When the heating supply is low, part of the high-pressure steam is stored in the heat accumulator 4; when the heating supply is high, the high-pressure steam is released through the heat accumulator 4, and combined with the high-pressure steam generated by the waste heat boiler 2, it enters the steam turbine 5 for cascade utilization and power generation, and generates low-pressure steam for external heating, which reduces a module for reducing pressure. On this basis, the waste heat boiler 2 is provided with a steam pressure detection unit to detect whether the current pressure is consistent with the preset pressure.

[0036] As another embodiment further provided by the present invention, it also includes a first generator 6 driven by the gas turbine 1 to generate electricity, and the first generator 6 is connected to the power supply end through the urban power supply network.

[0037] Specifically, the gas turbine 1 generates a large amount of high-temperature and high-pressure gas when burning natural gas, and then drives the first generator 6 to generate electricity by working on the first generator 6, and transmits the electricity to the power supply end, reducing dependence on municipal electricity and alleviating power supply pressure.

[0038] As another embodiment further provided by the present invention, the water supply pump 8 is an electric water supply pump of model HGC4 / 12 or the same type.

[0039] Specifically, the water pump 8 is operated by the electricity supplied by the second generator 7 to relieve the power pressure. When the power output by the second generator 7 is insufficient, the water pump 8 can also be powered by the town power supply grid and the factory power grid.

[0040] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A natural gas distributed energy system that is adaptable to large fluctuations in heat load, characterized in that: include: A gas turbine (1) for burning natural gas to generate high-temperature gas and perform work; A waste heat boiler (2) which is connected to an output port of the gas turbine (1) and outputs steam; A steam turbine (5), wherein a steam inlet is connected to the waste heat boiler (2), and a steam outlet is connected to the steam cylinder (3); A second generator (7), which is driven by the steam turbine (5) and connected to the power supply end via a town power supply network; A heat accumulator (4) for storing excess steam; A steam distribution cylinder (3) is used to receive low-pressure steam and evenly distribute it, and the steam distribution cylinder (3) is connected to the heating end through a town heating pipe network; A feed water pump (8) is driven by the second generator (7) to supply water to the waste heat boiler (2).

2. A natural gas distributed energy system adapted to large fluctuations in heat load according to claim 1, characterized in that: It also includes a first pipeline (a) for connecting the waste heat boiler (2) and the sub-cylinder (3), on which a first valve (11) is arranged; a second pipeline (b) for connecting the waste heat boiler (2) and the heat accumulator (4), on which a second valve (12) is provided; A third pipeline (c) for connecting the heat accumulator (4) and the steam turbine (5), on which a third valve (10) is provided; A fourth pipeline (d) for connecting the waste heat boiler (2) and the steam turbine (5).

3. A natural gas distributed energy system adapted to large fluctuations in heat load according to claim 2, characterized in that: The first valve (11), the second valve (12) and the third valve (10) are all stop valves of model J961.

4. A natural gas distributed energy system adapted to large fluctuations in heat load according to claim 3, characterized in that: It also includes a heating end monitoring and control unit for monitoring the heat consumption of the heating end and regulating it in real time, and the monitoring and control unit is signal-connected to the first valve (11), the second valve (12) and the third valve (10).

5. A natural gas distributed energy system adapted to large fluctuations in heat load according to claim 1, characterized in that: A coupling is provided between the steam turbine (5) and the second generator (7).

6. A natural gas distributed energy system adapted to large fluctuations in heat load according to claim 1, characterized in that: The waste heat boiler (2) is a double-pressure waste heat boiler of model NG-LM6000-R or the same type.

7. A natural gas distributed energy system adapted to large fluctuations in heat load according to claim 1, characterized in that: The waste heat boiler (2) is provided with a steam pressure detection unit.

8. A natural gas distributed energy system adapted to large fluctuations in heat load according to claim 1, characterized in that: It also includes a first generator (6) driven by the gas turbine (1) to generate electricity, and connected to the power supply end via a power grid.

9. A natural gas distributed energy system adapted to large fluctuations in heat load according to claim 1, characterized in that: The water supply pump (8) is selected to be an electric water supply pump of model HGC4 / 12 or the same type.

10. A natural gas distributed energy method adapted to large fluctuations in heat load, characterized in that: The natural gas distributed energy system adapted to large fluctuations in heat load as described in any one of claims 1 to 9 comprises the following steps: Step 1: The high-temperature flue gas from the gas turbine (1) enters the waste heat boiler (2) and exchanges heat with the water supplied by the feed water pump (8) so that the water is converted into high-pressure and low-pressure steam; Step 2: The waste heat boiler (2) outputs high-pressure steam and low-pressure steam, and the output steam is divided into two paths: The first low-pressure steam directly enters the steam cylinder (3) through the first pipeline (a); After the second high-pressure steam enters the steam turbine (5), it preferentially drives the second generator (7) to generate electricity, and supplies power to the feedwater pump (8) through the second generator (7). The low-pressure steam discharged from the steam turbine (5) enters the sub-cylinder (3) again. When the heating supply is at a low point (heat consumption is at a low point), part of the steam enters the heat accumulator (4) through the second pipeline (b) to be stored. When the heating supply is at a peak point (heat consumption is at a peak point), the exhaust port of the heat accumulator 4 allows the steam to enter the steam turbine (5) through the fifth pipeline (e), and the steam is combined with the high-pressure steam in the waste heat boiler (2) to drive the steam turbine (5) for cascade utilization and generate electricity, and discharge the low-pressure steam. Step 3: The steam distributor (3) evenly distributes the low-pressure steam from the waste heat boiler (2) and the steam turbine (5) and transmits it to the heating end.

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