Natural gas heating system and boiler system

Abstract

The utility model discloses a natural gas heating system and boiler system.The natural gas heating system comprises a first heat exchanger, a second heat exchanger and a gas turbine generator set, the first heat exchanger is suitable for being communicated with a medium-pressure economizer so that hot water in the medium-pressure economizer can flow into the first heat exchanger, and the first heat exchanger is suitable for introducing natural gas; the second heat exchanger is suitable for being communicated with the high-pressure economizer so that hot water in the high-pressure economizer can flow into the second heat exchanger, and the second heat exchanger is communicated with the first heat exchanger so that the natural gas can be heated to the first preset temperature. The hot water in the high-pressure coal economizer passes through the second heat exchanger to secondarily heat the natural gas to a second preset temperature, and the gas turbine generator set is communicated with the second heat exchanger. The natural gas heating system has the advantages of being simple in structure, high in heating efficiency and the like.

Description

TECHNICAL FIELD

[0001] The utility model relates to a boiler energy -conserving and efficiency increasing technical field, specifically, relate to a natural gas heating system and boiler system. BACKGROUND

[0002] With the wide application of clean energy technology, the proportion of the unit installation of the gas-steam combined cycle participated by the heavy-duty gas turbine is also more and more in China. For the heavy-duty gas turbine, it has three components: air compressor 33, combustion chamber and turbine. The air compressor 33 compresses air into high-temperature and high-pressure gas, mixes with the pretreated natural gas in the combustion chamber, burns, and drives the turbine to work, and then drives the generator to generate electricity. The exhaust gas of the gas turbine is introduced into the waste heat boiler, and then high-temperature and high-pressure steam is generated, and the steam is used to drive the steam turbine to generate electricity. The exhaust steam of the steam turbine is input into the condenser to release heat, and the condensed water is transported to the waste heat boiler to drive the steam power cycle. In this way, not only the total output power is improved, but also the characteristics of the gas turbine and the steam turbine are utilized to increase the heat efficiency of the cycle.

[0003] In the related art, the performance heating scheme of the gas-steam combined cycle has low natural gas heating efficiency and does not meet the natural gas heating temperature standard. CONTENT OF THE UTILITY MODEL

[0004] The utility model is made based on the discovery and understanding of the inventor to the following facts and problems:

[0005] In the related art, in the process of gas-steam combined cycle, the natural gas can only be heated to 100-200 DEG C, which cannot meet the requirement of higher natural gas temperature, which will cause unstable natural gas combustion and cause the gas turbine to extinguish, and even cause the damage of the combustion part.

[0006] The utility model aims at solving at least one of the technical problems in the related art to some extent.

[0007] Therefore, the embodiment of the utility model provides a natural gas heating system with high heating efficiency and standard heating temperature.

[0008] The embodiment of the utility model provides a boiler system with low cost and high heat energy utilization rate.

[0009] The natural gas heating system according to the embodiment of the utility model includes: first heat exchanger, the first heat exchanger is suitable for communicating with the medium pressure economizer, so that the hot water in the medium pressure economizer flows into the first heat exchanger, the first heat exchanger is suitable for the natural gas, so that the hot water in the medium pressure economizer is heated to the first preset temperature through the first heat exchanger, second heat exchanger, the second heat exchanger is suitable for communicating with the high pressure economizer, so that the hot water in the high pressure economizer flows into the second heat exchanger, the second heat exchanger is communicated with the first heat exchanger, so that the natural gas after heating flows into the second heat exchanger, so that the hot water in the high pressure economizer is heated to the second preset temperature through the second heat exchanger, gas turbine generator set, the gas turbine generator set is communicated with the second heat exchanger, so that the natural gas after heating through the second heat exchanger flows into the gas turbine generator set to drive the gas turbine generator set to generate electricity.

[0010] The natural gas heating system according to the embodiment of the utility model sets up first heat exchanger, second heat exchanger and gas turbine generator set, and the temperature of natural gas is raised to the second preset temperature through the hot water in the medium pressure economizer and the hot water in the high pressure economizer through the first heat exchanger and the second heat exchanger respectively, the internal waste heat of waste heat boiler is fully utilized, the step utilization of energy is realized, the natural gas consumption is reduced, the unit performance is greatly improved, and the combustion stability of the gas turbine unit is improved.

[0011] In some embodiments, the first heat exchanger has a first channel and a second channel capable of heat exchange, the first channel is suitable for communicating with the medium pressure economizer, so that the hot water in the medium pressure economizer flows into the first channel, and the second channel is suitable for the natural gas, so that the hot water in the first channel heats the natural gas in the second channel to the first preset temperature.

[0012] In some embodiments, the first channel is suitable for communicating with the condenser, so that the hot water flowing out of the first channel flows into the condenser.

[0013] In some embodiments, the second heat exchanger has a third channel and a fourth channel capable of heat exchange, the third channel is suitable for communicating with the high pressure economizer, so that the hot water in the high pressure economizer flows into the third channel, and the fourth channel is communicated with the first heat exchanger, so that the natural gas after heating of the first heat exchanger flows into the fourth channel, so that the hot water in the third channel heats the natural gas in the fourth channel to the second preset temperature.

[0014] In some embodiments, the third channel is suitable for communicating with the medium pressure economizer, so that the hot water flowing out of the third channel flows into the medium pressure economizer.

[0015] In some embodiments, the gas turbine generator set further comprises an air compressor adapted to generate compressed air and in communication with the gas turbine, such that the compressed air generated by the air compressor flows into the gas turbine to mix with the natural gas.

[0016] In some embodiments, the gas turbine generator set further comprises an air compressor adapted to generate compressed air and in communication with the gas turbine, such that the compressed air generated by the air compressor flows into the gas turbine to mix with the natural gas.

[0017] In some embodiments, the first heat exchanger is a double-pipe heat exchanger, and the second heat exchanger is a single-pipe shell-and-tube heat exchanger.

[0018] In some embodiments, the first preset temperature is 200℃, and the second preset temperature is 300℃.

[0019] The boiler system of the embodiment of the present application comprises: a boiler, wherein a medium-pressure economizer and a high-pressure economizer are arranged in the boiler; and a natural gas heating system, wherein the natural gas heating system is the natural gas heating system of any one of the above embodiments, and the medium-pressure economizer and the high-pressure economizer are both in communication with the natural gas heating system. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a structural schematic view of the natural gas heating system of the embodiment of the present application.

[0021] The natural gas heating system 100;

[0022] The first heat exchanger 1;

[0023] The second heat exchanger 2;

[0024] The gas turbine generator set 3; the gas turbine 31; the generator 32; and the air compressor 33. DETAILED DESCRIPTION

[0025] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the drawings. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0026] The natural gas heating system 100 according to the embodiment of the present application is described below with reference to the drawings.

[0027] As Figure 1As shown, the natural gas heating system 100 according to the embodiment of the present application comprises a first heat exchanger 1, a second heat exchanger 2 and a gas turbine generator set 3.

[0028] The first heat exchanger 1 is adapted to communicate with the medium-pressure economizer, so that the hot water in the medium-pressure economizer flows into the first heat exchanger 1, and the first heat exchanger 1 is adapted to pass in natural gas, so that the hot water in the medium-pressure economizer is heated by the first heat exchanger 1 to heat the natural gas, so as to heat the natural gas to a first preset temperature. Specifically, as shown in Figure 1 As shown, the inlet of the first heat exchanger 1 can communicate with the outlet of the medium-pressure economizer, so that the hot water generated by the medium-pressure economizer flows into the first heat exchanger 1, and the inlet of the first heat exchanger 1 can also communicate with the natural gas pipe, so that the natural gas passes into the first heat exchanger 1, and the natural gas and the hot water exchange heat through the first heat exchanger 1, so that the temperature of the natural gas increases to the first preset temperature, and the temperature of the hot water decreases.

[0029] The second heat exchanger 2 is adapted to communicate with the high-pressure economizer, so that the hot water in the high-pressure economizer flows into the second heat exchanger 2, and the second heat exchanger 2 communicates with the first heat exchanger 1, so that the heated natural gas flows into the second heat exchanger 2, so that the hot water in the high-pressure economizer is heated by the second heat exchanger 2 to heat the natural gas to a second preset temperature. Specifically, as shown in Figure 1 As shown, the inlet of the second heat exchanger 2 communicates with the outlet of the high-pressure economizer, so that the hot water generated by the high-pressure economizer flows into the second heat exchanger 2, and the inlet of the second heat exchanger 2 can also communicate with the outlet of the first heat exchanger 1, so that the natural gas heated by the first heat exchanger 1 flows into the second heat exchanger 2, and the hot water is heated by the second heat exchanger 2 to heat the natural gas to a second preset temperature.

[0030] The gas turbine generator set 3 communicates with the second heat exchanger 2, so that the natural gas heated by the second heat exchanger 2 flows into the gas turbine generator set 3 to drive the gas turbine generator set 3 to generate electricity. Specifically, as shown in Figure 1 As shown, the inlet of the gas turbine generator set 3 communicates with the outlet of the second heat exchanger 2, so that the heated natural gas flows into the gas turbine generator set 3, thereby driving the gas turbine generator set 3 to generate electricity.

[0031] The natural gas heating system 100 of this embodiment includes a first heat exchanger 1, a second heat exchanger 2, and a gas turbine generator set 3. Hot water from the medium-pressure economizer and the high-pressure economizer respectively passes through the first heat exchanger 1 and the second heat exchanger 2 to raise the temperature of the natural gas to a second preset temperature. This fully utilizes the waste heat from the waste heat boiler, converting it into the heat energy required to raise the natural gas temperature, achieving efficient cascade utilization of energy. It significantly reduces the consumption of natural gas as the primary fuel, lowers operating costs, improves the overall performance of the gas turbine generator set 3, and enhances the combustion stability of the gas turbine 31 unit. Furthermore, because the natural gas is preheated to the second preset temperature before entering the gas turbine 31, the combustion efficiency and stability inside the gas turbine are enhanced. This achieves complete and uniform combustion of natural gas, thereby reducing energy loss due to incomplete combustion and also reducing the generation of harmful emissions.

[0032] In some embodiments, the first heat exchanger 1 has a first channel (not shown) and a second channel (not shown) for heat exchange. The first channel is adapted to communicate with a medium-pressure economizer so that hot water in the medium-pressure economizer flows into the first channel. The second channel is adapted to be circulated with natural gas so that the hot water in the first channel heats the natural gas in the second channel to a first preset temperature. Specifically, as shown... Figure 1 As shown, the inlet of the first channel is connected to the outlet of the medium-pressure economizer, so that the hot water of the medium-pressure economizer flows into the first channel. The inlet of the second channel is connected to the natural gas pipeline, so that the natural gas exchanges heat with the hot water in the first channel and the natural gas in the second channel, causing the natural gas temperature to rise to the first preset value.

[0033] In some embodiments, the first channel is adapted to communicate with a condenser so that hot water flowing out of the first channel flows into the condenser. Specifically, as Figure 1 As shown, the outlet of the first channel is connected to the inlet of the condenser to cool the steam inside the condenser, which helps maintain the vacuum state of the condenser, improves energy utilization efficiency, and also promotes the environmental protection and energy-saving performance of the system.

[0034] In some embodiments, the second heat exchanger 2 has a heat-exchangeable third channel (not shown) and a fourth channel (not shown). The third channel is adapted to communicate with a high-pressure economizer so that hot water in the high-pressure economizer flows into the third channel. The fourth channel is communicated with the first heat exchanger 1 so that natural gas heated by the first heat exchanger 1 flows into the fourth channel, thereby heating the natural gas in the fourth channel to a second preset temperature with the hot water in the third channel. Specifically, as shown... Figure 1As shown, the inlet of the third channel is communicated with the outlet of the high-pressure economizer, and the hot water in the high-pressure economizer flows into the third channel, the inlet of the fourth channel is communicated with the outlet of the second channel of the first heat exchanger 1, and the natural gas heated by the first heat exchanger 1 flows into the fourth channel, so that the hot water in the third channel exchanges heat with the heat exchanger in the fourth channel, and the temperature of the natural gas continues to rise until it reaches the second preset temperature, thereby providing strong support for the subsequent power generation process.

[0035] In some embodiments, the third channel is adapted to be communicated with the medium-pressure economizer, so that the hot water flowing out of the third channel flows into the medium-pressure economizer. Specifically, as shown in Figure 1 As shown, the outlet of the third channel is communicated with the inlet of the medium-pressure economizer, and the hot water cooled in the third channel flows into the medium-pressure economizer, so that the cooled hot water is heated by the medium-pressure economizer, and the system realizes efficient recovery and reuse of heat, thereby improving the overall energy utilization efficiency.

[0036] In some embodiments, the gas turbine generator set 3 includes a gas turbine 31 and a generator 32, the gas turbine 31 is communicated with the second heat exchanger 2, so that the heated natural gas flows into the gas turbine 31 to drive the gas turbine 31 to rotate, and the generator 32 is connected with the gas turbine 31, so that the gas turbine 31 drives the generator 32 to rotate to make the generator 32 generate electricity. Specifically, as shown in Figure 1 As shown, the combustion chamber of the gas turbine 31 is communicated with the outlet of the fourth channel of the second heat exchanger 2, so that the heated natural gas flows into the gas turbine 31 and burns in the gas turbine 31 to drive the gas turbine 31 to rotate, and the generator 32 is connected with the gas turbine 31, so that the gas turbine 31 drives the generator 32 to generate electricity, so that the internal energy of the natural gas is converted into electrical energy.

[0037] In some embodiments, the gas turbine generator set 3 further includes an air compressor 33, the air compressor 33 is adapted to generate compressed air and is communicated with the gas turbine 31, so that the compressed air generated by the air compressor 33 flows into the gas turbine 31 to mix with the natural gas. Specifically, as shown in Figure 1 As shown, the outlet of the air compressor 33 is communicated with the combustion chamber of the gas turbine 31, so that the compressed air flows into the combustion chamber of the gas turbine 31, and the compressed air mixes with the natural gas to provide combustion-supporting gas for the natural gas, and also increases the output of the gas turbine 31 and improves the unit efficiency.

[0038] In some embodiments, the first heat exchanger 1 is a double-pipe heat exchanger. Specifically, the first heat exchanger 1 is a double-pipe heat exchanger, and the hot water from the medium-pressure economizer flows through the shell side of the double-pipe heat exchanger, and the natural gas flows through the tube side of the double-pipe heat exchanger. Since the natural gas has good heat conduction performance when flowing through the tube side, it can more effectively transfer heat to the tube wall. Although the hot water has relatively poor heat conduction performance when flowing through the shell side, the shell side design usually has a large heat exchange area, which helps to make up for the lack of heat conduction performance, thereby achieving efficient heat exchange. In addition, the fluid flow between the tube side and the shell side can form a certain velocity difference and pressure difference, which helps to enhance the convective heat transfer effect and further improve the heat exchange efficiency. Finally, natural gas is a flammable and explosive gas, so safety needs to be ensured during the heat exchange process. Placing the natural gas on the tube side can make it easier to monitor and control, and once an abnormal situation such as leakage occurs, measures can be taken to handle it quickly. At the same time, the tube side design usually has higher pressure-bearing capacity, which helps to ensure the safe transmission of natural gas under high pressure.

[0039] In some embodiments, the second heat exchanger 2 is a single-pipe shell-and-tube heat exchanger. Specifically, the second heat exchanger 2 is a single-pipe shell-and-tube heat exchanger, and the hot water from the high-pressure economizer flows through the tube side of the single-pipe shell-and-tube heat exchanger, and the natural gas flows through the shell side of the single-pipe shell-and-tube heat exchanger. Since the natural gas has good flowability when flowing through the shell side, it can form a more uniform flow state, which helps to reduce flow resistance and improve heat exchange efficiency. At the same time, the shell side design usually has a large space that can accommodate more heat exchange tubes, thereby further increasing the heat exchange area. The hot water flows through the tube side, which can make full use of the heat conduction performance of the tube wall to efficiently transfer heat to the gas. In addition, the water flow rate in the tube can be controlled by adjusting the pump flow rate, thereby achieving more accurate temperature regulation and heat exchange control. Placing the natural gas on the shell side can reduce the direct contact area between the gas and the heat exchange tube wall, reducing the risk of damage to the equipment due to gas leakage or explosion and other abnormal situations. At the same time, the shell side design usually has higher strength and pressure-bearing capacity, which can better cope with the high pressure and high temperature environment of the gas. Since the tube system is closed and controllable, it can more effectively prevent water leakage and other safety problems when the hot water flows through the tube side. Finally, natural gas has lower density and higher compressibility, while hot water has higher density and incompressibility. Placing the natural gas on the shell side can better adapt to its flow characteristics and reduce energy loss during the flow process. At the same time, the hot water flowing through the tube side can utilize the shape and layout of the tube system to optimize its flow state, improving flow efficiency and heat exchange efficiency.

[0040] In some embodiments, the first preset temperature is 200°C and the second preset temperature is 300°C. Since the feedwater temperature supplied to the first heat exchanger 1 by the medium-pressure economizer is generally 220°C-230°C, it can initially heat the natural gas to 200°C. The hot water temperature of the high-pressure economizer is generally 350°C, which heats the natural gas to 300°C. Because the combustion chamber of the gas turbine 31 requires a stable supply of natural gas, and the temperature of the natural gas needs to be within a certain range to ensure combustion stability and efficiency, the setting of the first preset temperature of 200°C and the second preset temperature of 300°C meets the requirements of the gas turbine 31 combustion chamber for natural gas temperature. Furthermore, the natural gas, after being heated in two stages, enters the combustion chamber and mixes with the air compressed by the air compressor 33 for combustion, which can increase the output of the gas turbine 31 and improve the unit efficiency.

[0041] The following is based on the appendix Figure 1 Specifically, the natural gas heating system 100 of this embodiment includes a gas turbine generator set 3 consisting of a gas turbine 31, a generator 32, an air compressor 33, and a combustion chamber. The combustion chamber of the gas turbine 31 is connected to a first heat exchanger 1 and a second heat exchanger 2. The first heat exchanger 1 is a double-tube safety type heat exchanger, with water flowing through the shell side and natural gas flowing through the tube side. The second heat exchanger 2 is a single-tube shell-and-tube heat exchanger; for process considerations, water flows through the tube side and gas flows through the shell side. The inlet side of the first heat exchanger 1 is connected to the medium-pressure economizer of the waste heat boiler, and the outlet side of the first heat exchanger 1 is connected to the condenser of the turbine generator set 32. The inlet side of the second heat exchanger 2 is connected to the high-pressure economizer, and the outlet side returns water to the medium-pressure economizer.

[0042] The feedwater temperature supplied to the first heat exchanger 1 by the medium-pressure economizer is generally 220-230℃, and the first heat exchanger 1 can heat the natural gas to a maximum of 200℃. The gas output from the first heat exchanger 1 is heated to 300℃ by the second heat exchanger 2 and sent to the combustion chamber of the gas turbine 31 to be mixed and burned with the air compressed by the air compressor 33, increasing the output of the gas turbine 31 and improving the unit efficiency. The heat source for the second heat exchanger 2 comes from the high-pressure economizer, where the hot water temperature is generally 350℃. After the hot water from the high-pressure economizer is fully heated by the natural gas in the second heat exchanger 2, it is returned to the medium-pressure economizer. Through this performance heating scheme, without introducing a new heat source into the gas turbine combustion chamber, the waste heat from the medium and high-pressure economizers is fully utilized, reducing natural gas consumption and heat consumption. By introducing hot water from the waste heat boiler high-pressure economizer and the second-stage performance heater, the temperature of the natural gas is greatly increased before entering the combustion chamber, improving the unit efficiency and solving the problem of high cost per kilowatt for existing gas turbine 31 units. Meanwhile, the increase in natural gas temperature helps to improve the Wahbe index, thereby improving the combustion stability of the gas turbine.

[0043] The boiler system of this utility model embodiment includes a boiler and a natural gas heating system 100.

[0044] The boiler is provided with a medium-pressure economizer and a high-pressure economizer. The natural gas heating system 100 is any one of the natural gas heating systems 100 in the above embodiments, and the medium-pressure economizer and the high-pressure economizer are both in communication with the natural gas heating system 100. Thus, the natural gas in the natural gas heating system 100 is heated by the hot water.

[0045] The boiler system has the advantages of simple structure and high thermal energy utilization rate.

[0046] In the description of the utility model, it is understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the utility model and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the utility model.

[0047] In addition, the terms "first" and "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first" and "second" can explicitly or implicitly include at least one of the features. In the description of the utility model, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0048] In the utility model, unless otherwise specifically defined and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected or in communication with each other; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the internal communication or interaction relationship of two elements, unless otherwise specifically limited. For ordinary skilled in the art, the specific meaning of the above terms in the utility model can be understood according to the specific circumstances.

[0049] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact through an intermediate medium. Moreover, the first feature "above", "above" and "above" the second feature can be directly above or obliquely above the first feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature can be directly below or obliquely below the first feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0050] In the present application, the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms is not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in the present application and the features of different embodiments or examples without contradiction.

[0051] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A natural gas heating system characterized by, The natural gas heating system comprises: a first heat exchanger adapted to communicate with the medium-pressure economizer so that hot water in the medium-pressure economizer flows into the first heat exchanger, the first heat exchanger being adapted to pass natural gas so that the hot water in the medium-pressure economizer heats the natural gas through the first heat exchanger to heat the natural gas to a first preset temperature; a second heat exchanger adapted to communicate with the high-pressure economizer so that hot water in the high-pressure economizer flows into the second heat exchanger, the second heat exchanger being in communication with the first heat exchanger so that the heated natural gas flows into the second heat exchanger to heat the hot water in the high-pressure economizer through the second heat exchanger to a second preset temperature; a gas turbine generator set in communication with the second heat exchanger so that the natural gas heated through the second heat exchanger flows into the gas turbine generator set to drive the gas turbine generator set to generate electricity.

2. The natural gas heating system of claim 1, wherein, The first heat exchanger has a first passage and a second passage capable of heat exchange, the first passage being adapted to communicate with the medium-pressure economizer so that hot water in the medium-pressure economizer flows into the first passage, the second passage being adapted to pass natural gas so that the hot water in the first passage heats the natural gas in the second passage to the first preset temperature.

3. The natural gas heating system of claim 2, wherein, The first passage is adapted to communicate with the condenser so that the hot water flowing out of the first passage flows into the condenser.

4. The natural gas heating system of claim 1, wherein, The second heat exchanger has a third passage and a fourth passage capable of heat exchange, the third passage being adapted to communicate with the high-pressure economizer so that hot water in the high-pressure economizer flows into the third passage, the fourth passage being in communication with the first heat exchanger so that the natural gas heated by the first heat exchanger flows into the fourth passage to heat the hot water in the third passage to the second preset temperature.

5. The natural gas heating system of claim 4, wherein, The third passage is adapted to communicate with the medium-pressure economizer so that the hot water flowing out of the third passage flows into the medium-pressure economizer.

6. The natural gas heating system of claim 1, wherein, The gas turbine generator set comprises a gas turbine and a generator, the gas turbine being in communication with the second heat exchanger so that the heated natural gas flows into the gas turbine to drive the gas turbine to rotate, the generator being connected with the gas turbine so that the gas turbine drives the generator to rotate to generate electricity.

7. The natural gas heating system of claim 6, wherein, The gas turbine generator set further comprises an air compressor adapted to generate compressed air and in communication with the gas turbine so that the compressed air generated by the air compressor flows into the gas turbine to mix with the natural gas.

8. The natural gas heating system of claim 1, wherein, The first heat exchanger is a double-pipe heat exchanger, and the second heat exchanger is a single-pipe shell-and-tube heat exchanger.

9. The natural gas heating system of claim 1, wherein, The first preset temperature is 200℃, and the second preset temperature is 300℃.

10. A boiler system characterized by, The natural gas heating system comprises: a boiler provided with a medium-pressure economizer and a high-pressure economizer; a natural gas heating system as claimed in any one of claims 1-9, the medium-pressure economizer and the high-pressure economizer both being in communication with the natural gas heating system.

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