High-efficiency Surplus Pressure Power Generation System for Natural Gas

Abstract

The present invention belongs to the technical field of energy-saving utilization of natural gas residual pressure, and discloses a high-efficiency natural gas residual pressure power generation system, which is arranged in a natural gas transmission and distribution station. The natural gas transmission and distribution station includes a first gas supply pipeline, a second gas supply pipeline and a third gas supply pipeline. The second gas supply pipeline is connected between the first gas supply pipeline and the third gas supply pipeline. The second gas supply pipeline includes a first branch and a second branch arranged in parallel. A pressure regulator is arranged on the first branch, and an expansion generator, a heat exchanger, a first flow valve and a first temperature sensor are arranged on the second branch. The first temperature sensor detects the temperature of the natural gas flowing through the heat exchanger. The first flow valve adjusts the flow rate of the natural gas flowing from the first gas supply pipeline to the expansion generator. When the temperature of the natural gas flowing through the heat exchanger is still too low, the flow rate of the natural gas flowing to the expansion generator is reduced to ensure that the heat exchanger can fully heat the natural gas, so as to reach the required temperature of the urban natural gas pipeline network.

Description

Technical Field

[0001] The present invention relates to the technical field of energy-saving utilization of natural gas residual pressure, and particularly to a high-efficiency natural gas residual pressure power generation system. Background Art

[0002] In a natural gas transportation system, high-pressure gaseous transportation is usually adopted to improve transportation efficiency. When gaseous natural gas is transported to a city gate station, it needs to be depressurized to the pressure required by the city pipeline network. Traditional processes mostly use pressure regulators for depressurization. Specifically, upstream natural gas is sent to the pressure regulator through a supply pipeline, the natural gas is depressurized by the pressure regulator, and then sent to the city pipeline network.

[0003] In recent years, to improve energy utilization efficiency, the prior art has proposed integrating an expansion generator in the depressurization link. Specifically, for the natural gas transported from upstream, part of the natural gas is sent to the expansion generator, and the other part is still sent to the pressure regulator for depressurization. The expansion generator converts the pressure energy into electrical energy through mechanical work, thereby on the one hand recovering and utilizing the pressure energy, and on the other hand realizing green and environmental protection power generation. Subsequently, the natural gas sent to the expansion generator and the pressure regulator can be merged and sent to the city pipeline network together.

[0004] As described above, the temperature of the natural gas depressurized by the expansion generator will drop sharply, and the temperature of the natural gas sent to the city pipeline network cannot be too low. Exemplarily, the temperature of the natural gas depressurized by the expansion generator will drop below -20°C, but the required temperature of the natural gas sent to the city pipeline network is greater than or equal to 0°C. Even if the temperature of the natural gas depressurized by the pressure regulator meets the requirements of the city pipeline network, and the natural gas sent to the city pipeline network is obtained by the merger of the natural gas sent to the pressure regulator and the natural gas sent to the expansion generator, in order to strictly ensure that the temperature of the subsequent merged natural gas sent to the city pipeline network meets the requirements, the prior art usually sets a heat exchanger on the downstream side of the expansion generator. The heat exchanger heats the natural gas flowing through the expansion generator to ensure that the temperature of the natural gas sent to the expansion generator has reached the required temperature of the city pipeline network before it merges with the natural gas sent to the pressure regulator, thereby strictly ensuring that the temperature of the subsequent merged natural gas sent to the city pipeline network meets the requirements.

[0005] However, the heat exchanger may experience a decrease in heating efficiency due to external environmental factors or its own factors. When extreme cold weather occurs in winter or the heating efficiency of the heat exchanger decreases, the heat exchanger cannot sufficiently heat the natural gas flowing through the expansion generator, resulting in a very low temperature of the natural gas flowing from the expansion generator to the city pipeline network, and further resulting in the temperature of the subsequent merged natural gas sent to the city pipeline network not meeting the safety requirements. Summary of the Invention

[0006] The object of the present invention is to provide a natural gas high-efficiency residual pressure power generation system to solve the problem that the heat exchange efficiency of the heat exchanger decreases due to external environmental factors or its own factors, resulting in the temperature of the natural gas flowing from the expansion generator to the urban gas network still being extremely low, and further resulting in the temperature of the natural gas subsequently converged and sent to the urban gas network not meeting the safety requirements.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] A natural gas high-efficiency residual pressure power generation system is arranged in a natural gas transmission and distribution station. The natural gas transmission and distribution station includes a first gas supply pipeline, a second gas supply pipeline, and a third gas supply pipeline. The upstream end of the first gas supply pipeline is connected to the gas source supply pipeline. The second gas supply pipeline is connected between the downstream end of the first gas supply pipeline and the upstream end of the third gas supply pipeline. The downstream end of the third gas supply pipeline is connected to the urban natural gas network. The second gas supply pipeline includes a first branch and a second branch arranged in parallel. A pressure regulator for regulating the gas pressure of natural gas is arranged on the first branch. The natural gas high-efficiency residual pressure power generation system includes an expansion generator, and the expansion generator is arranged on the second branch. The natural gas high-efficiency residual pressure power generation system further includes a natural gas heat exchange unit, and the natural gas heat exchange unit includes:

[0009] A heat exchanger is arranged on the second branch and is located on the downstream side of the expansion generator. The heat exchanger is configured to exchange heat between the natural gas flowing out of the expansion generator and a heat exchange medium;

[0010] A first flow valve is arranged on the second branch and is located on the upstream side of the expansion generator. The first flow valve is configured to regulate the flow rate of the natural gas flowing from the first gas supply pipeline to the expansion generator;

[0011] A first temperature sensor is arranged on the second branch and is located on the downstream side of the heat exchanger. The first temperature sensor is configured to detect the temperature of the natural gas flowing through the heat exchanger, and the first temperature sensor is electrically connected to the first flow valve.

[0012] Preferably, the natural gas heat exchange unit further includes:

[0013] The fourth gas supply pipeline and the shell-and-tube heat exchanger, the upstream end of the fourth gas supply pipeline is communicated with the first branch, and the communication position between the fourth gas supply pipeline and the first branch is located on the upstream side of the pressure regulator. The shell-and-tube heat exchanger is arranged on the second branch and is located on the downstream side of the heat exchanger. The downstream end of the fourth gas supply pipeline is communicated with the intake end of the shell-and-tube heat exchanger. The shell-and-tube heat exchanger is configured to heat the natural gas transported along the second branch. A control valve is arranged on the fourth gas supply pipeline, and the control valve is electrically connected with the first flow valve;

[0014] The fifth gas supply pipeline, the upstream end is communicated with the outlet end of the shell-and-tube heat exchanger, the downstream end of the fifth gas supply pipeline is communicated with the first branch, and the communication position between the fifth gas supply pipeline and the first branch is located on the downstream side of the communication position between the fourth gas supply pipeline and the first branch and is located on the upstream side of the pressure regulator.

[0015] Preferably, a second flow valve is arranged on the fourth gas supply pipeline. The second flow valve is configured to control the flow rate of the natural gas flowing from the first branch to the shell-and-tube heat exchanger. The first temperature sensor, the first flow valve, the control valve, and the second flow valve are electrically connected.

[0016] Preferably, the natural gas heat exchange unit further includes a second temperature sensor arranged on the first branch. The second temperature sensor is located on the downstream side of the pressure regulator and is configured to detect the temperature of the natural gas flowing from the first branch to the third gas supply pipeline.

[0017] Preferably, the natural gas heat exchange unit further includes a third temperature sensor arranged on the third gas supply pipeline. The third temperature sensor is configured to detect the temperature of the natural gas flowing from the third gas supply pipeline to the urban natural gas pipeline network.

[0018] Preferably, the natural gas heat exchange unit further includes a first heater arranged on the third gas supply pipeline. The first heater is arranged on the upstream side of the third temperature sensor and is configured to heat the natural gas flowing from the third gas supply pipeline to the urban natural gas pipeline network. The third temperature sensor is electrically connected with the first heater.

[0019] Preferably, the heat exchanger is an air heat exchanger.

[0020] Preferably, the natural gas heat exchange unit further includes a second heater. The second heater is arranged adjacent to the heat exchanger and is configured to heat the heat exchanger.

[0021] Preferably, the natural gas heat exchange unit further includes a third heater disposed on the second branch. The third heater is disposed upstream of the first temperature sensor and is configured to heat the natural gas conveyed along the second branch. The first flow valve is electrically connected to the third heater.

[0022] Preferably, the natural gas heat exchange unit includes two or more of the heat exchangers. The two or more heat exchangers are connected in series and / or in parallel on the second branch. The first temperature sensor can detect the temperature of the natural gas flowing through all the heat exchangers and then converging.

[0023] Advantages of the present invention:

[0024] The present invention controls the temperature of the natural gas sent to the urban natural gas pipeline network through the natural gas heat exchange unit. Specifically, the natural gas heat exchange unit detects the temperature of the natural gas flowing through the heat exchanger through the first temperature sensor, and adjusts the flow rate of the natural gas flowing from the first gas supply pipeline to the expansion generator through the first flow valve. Moreover, the first temperature sensor is electrically connected to the first flow valve. Thus, the natural gas heat exchange unit in the present invention can regulate the distribution amount of the natural gas conveyed along the first gas supply pipeline to the second branch according to the detection result of the first temperature sensor. Specifically, when the temperature of the natural gas flowing through the heat exchanger is still too low due to the low heating efficiency of the heat exchanger, the first flow valve controls to reduce the flow rate of the natural gas flowing from the first gas supply pipeline to the expansion generator, so as to reduce the distribution amount of the natural gas conveyed along the first gas supply pipeline to the second branch, ensuring that the heat exchanger can fully heat the natural gas flowing through it, so that the temperature of the natural gas sent to the expansion generator can reach the required temperature of the urban natural gas pipeline network before it converges with the natural gas sent to the pressure regulator, and further enabling the temperature of the natural gas converging in the third gas supply pipeline subsequently to reach the required temperature of the urban natural gas pipeline network. Description of the Drawings

[0025] Figure 1 is a schematic structural diagram of a natural gas high-efficiency residual pressure power generation system disposed in a natural gas transmission and distribution station in the first embodiment of the present invention;

[0026] Figure 2 is a schematic structural diagram of a natural gas high-efficiency residual pressure power generation system disposed in a natural gas transmission and distribution station in the second embodiment of the present invention.

[0027] In the figure:

[0028] 1. First air supply pipeline; 2. Second air supply pipeline; 21. First branch; 211. Pressure regulator; 212. Second temperature sensor; 22. Second branch; 221. Expansion generator; 222. Heat exchanger; 223. First flow valve; 224. First temperature sensor; 225. Third heater; 226. Shunt; 3. Third air supply pipeline; 31. Third temperature sensor; 32. First heater; 4. Fourth air supply pipeline; 41. Control valve; 42. Second flow valve; 5. Shell-and-tube heat exchanger; 6. Fifth air supply pipeline; 7. Second heater. Detailed implementation mode

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. In addition, it should be noted that for the convenience of description, only parts related to the present invention are shown in the drawings, rather than all structures.

[0030] In the description of the present invention, unless otherwise clearly defined and limited, the terms "connected", "connected", and "fixed" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0031] In the present invention, unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features therebetween. Moreover, the first feature being "above", "above", and "on" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "below", "below", and "under" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely indicates that the horizontal height of the first feature is lower than that of the second feature.

[0032] In the description of this embodiment, the orientation or positional relationship terms such as "above", "below", "right", and "left" are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of description and simplifying the operation, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for distinction in description and have no special meaning.

[0033] Embodiment 1

[0034] Please refer to Figure 1 , this embodiment provides a natural gas high-efficiency residual pressure power generation system. The natural gas high-efficiency residual pressure power generation system is arranged in a natural gas transmission and distribution station. The natural gas transmission and distribution station includes a first gas supply pipeline 1, a second gas supply pipeline 2, and a third gas supply pipeline 3. The upstream end of the first gas supply pipeline 1 is connected to a gas source supply pipeline (not shown in the figure). The second gas supply pipeline 2 is connected between the downstream end of the first gas supply pipeline 1 and the upstream end of the third gas supply pipeline 3. The downstream end of the third gas supply pipeline 3 is connected to the urban natural gas pipeline network (not shown in the figure). The second gas supply pipeline 2 includes a first branch 21 and a second branch 22 arranged in parallel. A pressure regulator 211 for adjusting the natural gas pressure is provided on the first branch 21. The natural gas high-efficiency residual pressure power generation system includes an expansion generator 221. The expansion generator 221 is arranged on the second branch 22. A part of the natural gas transported from the upstream flows into the first branch 21, and the other part flows into the second branch 22. Among them, the natural gas flowing into the first branch 21 is depressurized by the pressure regulator 211, and the depressurized natural gas flows into the third gas supply pipeline 3. The natural gas flowing into the second branch 22 flows through the expansion generator 221. Under the action of the natural gas, the expansion generator 221 converts the pressure energy into electrical energy through mechanical work, thereby reducing the pressure of the natural gas. The depressurized natural gas also flows into the third gas supply pipeline 3. After the two parts of natural gas converge in the third gas supply pipeline 3, they are sent to the urban natural gas pipeline network together.

[0035] As described above, in this embodiment, the natural gas high-efficiency residual pressure power generation system further includes a natural gas heat exchange unit. The natural gas heat exchange unit includes a heat exchanger 222. The heat exchanger 222 is arranged on the second branch 22 and is located on the downstream side of the expansion generator 221. The heat exchanger 222 is configured to exchange heat between the natural gas flowing out of the expansion generator 221 and the heat exchange medium, so that the temperature of the natural gas sent to the expansion generator 221 reaches the required temperature of the urban natural gas pipeline network before converging with the natural gas sent to the pressure regulator 211, thereby strictly ensuring that the temperature of the natural gas flowing into the third gas supply pipeline 3 can reach the required temperature of the urban natural gas pipeline network.

[0036] Based on the content described above, the heat exchanger 222 is generally an air heat exchanger or an electric heating water bath heat exchanger, etc. Exemplarily, in this embodiment, an air heat exchanger is taken as an example. The air heat exchanger uses the outside air as the heat exchange medium. Specifically, the air heat exchanger heats the natural gas flowing out of the expansion generator 221 by exchanging heat between the natural gas transported along the second branch 22 and the outside air. However, when the temperature of the outside air is relatively low due to seasonal influence, the heating efficiency of the heat exchanger 222 will be significantly reduced, so that the natural gas flowing through the expansion generator 221 cannot be heated sufficiently, and then the temperature of the natural gas flowing from the expansion generator 221 to the third gas supply pipeline 3 is still extremely low. Therefore, the natural gas converging in the third gas supply pipeline 3 subsequently is likely to have the problem that the temperature does not meet the safety requirements of the urban natural gas pipeline network.

[0037] To solve the above problems, in this embodiment, the natural gas heat exchange unit further includes a first flow valve 223 and a first temperature sensor 224. Both the first flow valve 223 and the first temperature sensor 224 are arranged on the second branch 22. Among them, the first flow valve 223 is located on the upstream side of the expansion generator 221 and is configured to adjust the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221, while the first temperature sensor 224 is located on the downstream side of the heat exchanger 222 and is configured to detect the temperature of the natural gas flowing through the heat exchanger 222. The first temperature sensor 224 is electrically connected to the first flow valve 223.

[0038] Based on the above, in this embodiment, the natural gas heat exchange unit controls the temperature of the natural gas sent to the urban natural gas pipeline network. Specifically, the natural gas heat exchange unit detects the temperature of the natural gas flowing through the heat exchanger 222 through the first temperature sensor 224, and adjusts the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221 through the first flow valve 223. Moreover, the first temperature sensor 224 is electrically connected to the first flow valve 223. Thus, the natural gas heat exchange unit can control the distribution amount of the natural gas transported along the first gas supply pipeline 1 to the second branch 22 according to the detection result of the first temperature sensor 224. Specifically, when the temperature of the natural gas flowing through the heat exchanger 222 is still relatively low due to the low heating efficiency of the heat exchanger 222, the first flow valve 223 controls to reduce the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221, so as to reduce the distribution amount of the natural gas transported along the first gas supply pipeline 1 to the second branch 22. Correspondingly, the distribution amount of the natural gas transported along the first gas supply pipeline 1 to the first branch 21 increases, so as to ensure that the heat exchanger 222 can fully heat the natural gas flowing through it, so that the temperature of the natural gas sent to the expansion generator 221 can reach the required temperature of the urban natural gas pipeline network before it converges with the natural gas sent to the pressure regulator 211, and then the temperature of the natural gas converging in the third gas supply pipeline 3 subsequently reaches the required temperature of the urban natural gas pipeline network.

[0039] In addition, based on the content described above, the heat exchanger 222 in this embodiment is an air heat exchanger. Therefore, the process of heating the natural gas flowing out of the expansion generator 221 by the heat exchanger 222 does not require additional energy consumption, thereby being more environmentally friendly.

[0040] Furthermore, it is worth noting that as the first flow valve 223 controls the reduction of the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221, the power generation of the expansion generator 221 will also decrease, resulting in a reduction in energy utilization efficiency.

[0041] To improve energy utilization efficiency, it is necessary to ensure that the pressure energy can be fully recovered and utilized. Therefore, the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221 should not be too low. At the same time, the temperature of the natural gas after flowing through the heat exchanger 222 also needs to meet the required temperature of the urban natural gas pipeline network. For this purpose, the natural gas heat exchange unit in this embodiment further includes a fourth gas supply pipeline 4 and a shell-and-tube heat exchanger 5. The upstream end of the fourth gas supply pipeline 4 is connected to the first branch 21, and the connection position of the fourth gas supply pipeline 4 and the first branch 21 is located upstream of the pressure regulator 211. The shell-and-tube heat exchanger 5 is arranged on the second branch 22 and is located downstream of the heat exchanger 222. The downstream end of the fourth gas supply pipeline 4 is connected to the intake end of the shell-and-tube heat exchanger 5. The shell-and-tube heat exchanger 5 is configured to exchange heat with the natural gas transported along the second branch 22.

[0042] Based on the above, in this embodiment, as the first flow valve 223 controls the gradual reduction of the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221, when the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221 is reduced to the first preset value, the first flow valve 223 stops controlling the reduction of the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221. At the same time, the fourth gas supply pipeline 4 transfers the natural gas transported along the first branch 21 to the shell-and-tube heat exchanger 5. Since the connection position of the fourth gas supply pipeline 4 and the first branch 21 is located upstream of the pressure regulator 211, the natural gas sent to the shell-and-tube heat exchanger 5 through the fourth gas supply pipeline 4 is at a higher temperature, so that heat exchange can be carried out through the shell-and-tube heat exchanger 5, and then the natural gas flowing through the expansion generator 221 can be heated to make the temperature of the natural gas flowing through the expansion generator 221 rise to meet the required temperature of the urban natural gas pipeline network.

[0043] As described above, in this embodiment, during the process of the first flow valve 223 controlling the gradually decreasing flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221, if the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221 decreases to a first preset value, this embodiment then uses the natural gas in the first branch 21 to heat the natural gas transported along the second branch 22. Thus, without the need to further decrease the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221, it is still possible to ensure that the temperature of the natural gas sent from the expansion generator 221 to the third gas supply pipeline 3 reaches the required temperature of the urban natural gas pipeline network.

[0044] It should be noted that based on the content described above, as the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221 decreases, the distribution amount of the natural gas transported along the first gas supply pipeline 1 to the second branch 22 will decrease. Correspondingly, the distribution amount of the natural gas transported along the first gas supply pipeline 1 to the first branch 21 will increase. And only when the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221 decreases to the first preset value, and correspondingly, when the flow rate of the natural gas flowing from the first gas supply pipeline 1 into the first branch 21 rises to the second preset value, the natural gas transferred from the first branch 21 into the shell-and-tube heat exchanger 5 can sufficiently heat the natural gas sent from the expansion generator 221 to the third gas supply pipeline 3.

[0045] It can be understood that a control valve 41 is provided on the fourth gas supply pipeline 4. The control valve 41 is electrically connected to the first flow valve 223. The control valve 41 will only open when the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221 decreases to the first preset value. When the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221 is higher than the first preset value, the natural gas heat exchange unit only regulates the temperature of the natural gas sent from the expansion generator 221 to the third gas supply pipeline 3 through the heat exchanger 222, the first temperature sensor 224, and the first flow valve 223.

[0046] Based on the above, this embodiment can use the fourth gas supply pipeline 4 and the shell-and-tube heat exchanger 5 to assist in heating the natural gas sent from the expansion generator 221 to the third gas supply pipeline 3 after the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221 decreases to the first preset value. Thus, while ensuring that the temperature of the natural gas flowing through the heat exchanger 222 can reach the required temperature of the urban natural gas pipeline network, it also ensures that the power generation of the expansion generator 221 remains at a relatively high level.

[0047] It can be understood that the natural gas heat exchange unit further includes a fifth gas supply pipeline 6. The upstream end of the fifth gas supply pipeline 6 is communicated with the gas outlet end of the shell-and-tube heat exchanger 5, and the downstream end of the fifth gas supply pipeline 6 is communicated with the first branch 21. Moreover, the connection position of the fifth gas supply pipeline 6 and the first branch 21 is located on the downstream side of the connection position of the fourth gas supply pipeline 4 and the first branch 21 and on the upstream side of the pressure regulator 211, so that the natural gas transferred to the shell-and-tube heat exchanger 5 can return to the first branch 21 and then be depressurized subsequently.

[0048] It is worth noting that after the natural gas returned from the shell-and-tube heat exchanger 5 to the first branch 21 is depressurized by the pressure regulator 211, its temperature can be compensated by the heat tracing module in the pressure regulator 211 to reach the required temperature of the urban natural gas pipeline network without subsequent mixing.

[0049] It can be understood that since the specific structure and working principle of the pressure regulator 211 are both prior arts, they will not be elaborated in this embodiment.

[0050] It is also worth noting that although the heat tracing module in the pressure regulator 211 can compensate the temperature of the natural gas transported along the first branch 21, in order to ensure that the temperature of the natural gas sent from the pressure regulator 211 to the third gas supply pipeline 3 can reach the required temperature of the urban natural gas pipeline network, in this embodiment, a second flow valve 42 is further provided on the fourth gas supply pipeline 4. The second flow valve 42 is configured to control the flow rate of the natural gas flowing from the first branch 21 to the shell-and-tube heat exchanger 5. The first temperature sensor 224, the first flow valve 223, the control valve 41, and the second flow valve 42 are electrically connected. That is, in this embodiment, the natural gas transferred to the shell-and-tube heat exchanger 5 through the fourth gas supply pipeline 4 is not all the natural gas transported along the first branch 21, but only a part of the natural gas is diverted to the shell-and-tube heat exchanger 5 to heat the natural gas flowing through the expansion generator 221, so as to ensure that the temperature of the natural gas flowing to the pressure regulator 211 is not too low.

[0051] Specifically, when the control valve 41 is not opened, the natural gas transported along the first branch 21 is not sufficient to fully heat the natural gas flowing through the expansion generator 221. Only when the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221 is reduced to the first preset value, the flow rate of the natural gas transported along the first branch 21 can meet the requirement of fully heating the natural gas flowing through the expansion generator 221. At this time, the control valve 41 will be opened. After the control valve 41 is opened, the second flow valve 42 can control the natural gas transported along the first branch 21 to flow to the shell-and-tube heat exchanger 5 at a preset flow rate, so as to meet the requirement of fully heating the natural gas flowing through the expansion generator 221 while not affecting the temperature of the natural gas sent from the pressure regulator 211 to the third gas supply pipeline 3.

[0052] In addition, the natural gas heat exchange unit further includes a second temperature sensor 212 disposed on the first branch 21. The second temperature sensor 212 is located on the downstream side of the pressure regulator 211 and is configured to detect the temperature of the natural gas flowing from the first branch 21 to the third gas supply pipeline 3, so as to ensure that the temperature of the natural gas sent from the pressure regulator 211 to the third gas supply pipeline 3 can reach the required temperature of the urban natural gas pipeline network.

[0053] It can be understood that the second temperature sensor 212 is electrically connected to the first flow valve 223. When the temperature of the natural gas sent from the pressure regulator 211 to the third gas supply pipeline 3 fails to reach the required temperature of the urban natural gas pipeline network due to an accident such as a malfunction of the heat tracing module of the pressure regulator 211, the second temperature sensor 212 can control the first flow valve 223 to further reduce the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221, so as to preferentially ensure that the temperature of the natural gas sent to the third gas supply pipeline 3 reaches the required temperature of the urban natural gas pipeline network.

[0054] Furthermore, the natural gas heat exchange unit further includes a third temperature sensor 31 disposed on the third gas supply pipeline 3. The third temperature sensor 31 is configured to detect the temperature of the natural gas flowing from the third gas supply pipeline 3 to the urban natural gas pipeline network, so as to ensure that the temperature of the natural gas flowing from the third gas supply pipeline 3 to the urban natural gas pipeline network reaches the required temperature of the urban natural gas pipeline network.

[0055] Moreover, the natural gas heat exchange unit further includes a first heater 32 disposed on the third gas supply pipeline 3. The first heater 32 is disposed on the upstream side of the third temperature sensor 31 and is configured to heat the natural gas flowing from the third gas supply pipeline 3 to the urban natural gas pipeline network. The third temperature sensor 31 is electrically connected to the first heater 32. When an accident occurs and the third temperature sensor 31 detects that the temperature of the natural gas flowing from the third gas supply pipeline 3 to the urban natural gas pipeline network fails to reach the required temperature of the urban natural gas pipeline network, the first heater 32 compensates for the temperature of the natural gas transported along the third gas supply pipeline 3, so as to ensure that the temperature of the natural gas flowing into the urban natural gas pipeline network reaches the required temperature of the urban natural gas pipeline network.

[0056] It can be understood that the first heater 32 can be selected as an electric heater or a steam heat exchanger, etc., and the present embodiment does not make specific restrictions on this.

[0057] Furthermore, in this embodiment, the natural gas heat exchange unit includes two heat exchangers 222, and the two heat exchangers 222 are connected in parallel to the second branch 22. That is, two shunt paths 226 are connected in series on the second branch 22, and the two shunt paths 226 are connected in parallel with each other. The two heat exchangers 222 are respectively arranged on the two shunt paths 226, so that the natural gas flowing out of the expansion generator 221 can be heated by the two heat exchangers 222 together, and further ensure that the temperature of the natural gas sent to the expansion generator 221 reaches the required temperature of the urban natural gas pipeline network before it converges with the natural gas sent to the pressure regulator 211.

[0058] It can be understood that in this embodiment, the first temperature sensor 224 can detect the temperature of the natural gas flowing through all the heat exchangers 222 and then converging.

[0059] Of course, in other alternative embodiments, the natural gas heat exchange unit may also include three or more than four heat exchangers 222, and all the heat exchangers 222 are connected in parallel to the second branch 22. This embodiment does not make specific restrictions on this.

[0060] In addition, it can be understood that in other alternative embodiments, all the heat exchangers 222 included in the natural gas heat exchange unit may also be arranged in series on the second branch 22, or all the heat exchangers 222 included in the natural gas heat exchange unit may also be arranged on the second branch 22 in a combination of series and parallel. This embodiment does not make specific restrictions on this.

[0061] It should also be noted that based on the content described above, the heat exchanger 222 in this embodiment is an air heat exchanger. In addition, the natural gas heat exchange unit further includes a second heater 7, and the second heater 7 is arranged adjacent to the heat exchanger 222. The second heater 7 is configured to heat the heat exchanger 222, so as to prevent the service life of the heat exchanger 222 from being affected by external condensation during its operation.

[0062] It can be understood that the second heater 7 can be selected as a hot air blower or an electric heater, etc. This embodiment does not make specific restrictions on this.

[0063] Embodiment Two

[0064] As Figure 2As shown, compared with the first embodiment, the difference in this embodiment is that the natural gas heat exchange unit further includes a third heater 225 disposed on the second branch 22. The third heater 225 is disposed upstream of the first temperature sensor 224 and is configured to heat the natural gas transported along the second branch 22. The first flow valve 223 is electrically connected to the third heater 225. That is, in this embodiment, when the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221 decreases to a first preset value, the third heater 225 is activated to heat the natural gas flowing through the heat exchanger 222.

[0065] It can be understood that the third heater 225 can be selected as an electric heater, a steam heat exchanger, etc., and this embodiment does not make specific restrictions on this.

[0066] Moreover, the first temperature sensor 224 can detect the temperature of the natural gas heated by the third heater 225, so as to ensure that the temperature of the natural gas sent to the expansion generator 221 can reach the required temperature of the urban natural gas pipeline network before it converges with the natural gas sent to the pressure regulator 211.

[0067] Thus, in this embodiment, after the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221 decreases to the first preset value, the third heater 225 heats the natural gas flowing through the heat exchanger 222. Among them, the third heater 225 is only activated after the flow rate of the natural gas flowing from the first gas supply pipeline 1 to the expansion generator 221 decreases to the first preset value, so as to be able to take into account environmental protection while ensuring that the temperature of the natural gas sent to the expansion generator 221 can reach the required temperature of the urban natural gas pipeline network before it converges with the natural gas sent to the pressure regulator 211.

[0068] Obviously, the above embodiments of the present invention are merely examples for clearly explaining the present invention, rather than limiting the implementation manners of the present invention. For those of ordinary skill in the art, various obvious changes, re-adjustments, and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A natural gas high-efficiency excess pressure power generation system, arranged in a natural gas transmission and distribution station, the natural gas transmission and distribution station comprising a first gas supply pipeline (1), a second gas supply pipeline (2) and a third gas supply pipeline (3), the upstream end of the first gas supply pipeline (1) being connected to a gas source supplier's transmission pipeline, the second gas supply pipeline (2) being connected between the downstream end of the first gas supply pipeline (1) and the upstream end of the third gas supply pipeline (3), the downstream end of the third gas supply pipeline (3) being connected to a city natural gas pipeline network, the second gas supply pipeline (2) comprising a first branch (21) and a second branch (22) arranged in parallel, the first branch (21) being provided with a pressure regulator (211) for regulating the natural gas pressure, the natural gas high-efficiency excess pressure power generation system comprising an expansion generator (221), the expansion generator (221) being arranged on the second branch (22), and characterized in that: The natural gas high-efficiency residual pressure power generation system further includes a natural gas heat exchange unit, and the natural gas heat exchange unit includes: a heat exchanger (222), arranged on the second branch (22) and located at the downstream side of the expansion generator (221), the heat exchanger (222) being configured to exchange heat between the natural gas flowing out of the expansion generator (221) and a heat exchange medium; a first flow valve (223) disposed on the second branch (22) and located on the upstream side of the expansion generator (221), the first flow valve (223) being configured to adjust the flow of natural gas flowing from the first gas supply pipeline (1) to the expansion generator (221); a first temperature sensor (224), arranged on the second branch (22) and located at the downstream side of the heat exchanger (222), the first temperature sensor (224) being configured to detect the temperature of the natural gas after flowing through the heat exchanger (222), the first temperature sensor (224) being electrically connected to the first flow valve (223); a fourth air supply pipeline (4) and a shell and tube heat exchanger (5), wherein the upstream end of the fourth air supply pipeline (4) is in communication with the first branch (21), and the communication position between the fourth air supply pipeline (4) and the first branch (21) is located on the upstream side of the pressure regulator (211); the shell and tube heat exchanger (5) is arranged on the second branch (22) and is located on the downstream side of the heat exchanger (222); the downstream end of the fourth air supply pipeline (4) is in communication with the air inlet end of the shell and tube heat exchanger (5); the shell and tube heat exchanger (5) is configured to perform heat exchange on the natural gas transported along the second branch (22); a control valve (41) is arranged on the fourth air supply pipeline (4), and the control valve (41) is electrically connected to the first flow valve (223); a fifth air supply pipeline (6), the upstream end of which is in communication with the air outlet end of the shell and tube heat exchanger (5), the downstream end of which is in communication with the first branch (21), and the connection position between the fifth air supply pipeline (6) and the first branch (21) is located downstream of the connection position between the fourth air supply pipeline (4) and the first branch (21), and is located upstream of the pressure regulator (211); The natural gas heat exchange unit further comprises a first heater (32) arranged on the third gas supply pipeline (3), the first heater (32) being arranged on the upstream side of the third temperature sensor (31) and being configured to heat the natural gas flowing from the third gas supply pipeline (3) to the urban natural gas pipeline network, the third temperature sensor (31) being electrically connected to the first heater (32); The natural gas heat exchange unit further comprises a second heater (7), the second heater (7) being arranged adjacent to the heat exchanger (222), the second heater (7) being configured to heat the heat exchanger (222); The natural gas heat exchange unit comprises more than two heat exchangers (222), the more than two heat exchangers (222) are connected in series and / or in parallel to the second branch (22), and the first temperature sensor (224) is capable of detecting the temperature of the natural gas after flowing through all the heat exchangers (222) and merging.

2. The natural gas high-efficiency residual pressure power generation system according to claim 1 is characterized in that: The fourth gas supply pipeline (4) is provided with a second flow valve (42), the second flow valve (42) being configured to control the flow of natural gas flowing from the first branch (21) to the shell and tube heat exchanger (5), and the first temperature sensor (224), the first flow valve (223), the control valve (41), and the second flow valve (42) are electrically connected.

3. The natural gas high-efficiency residual pressure power generation system according to claim 2 is characterized in that: The natural gas heat exchange unit further comprises a second temperature sensor (212) arranged on the first branch (21), the second temperature sensor (212) being located on the downstream side of the pressure regulator (211) and being configured to detect the temperature of the natural gas flowing from the first branch (21) to the third gas supply pipeline (3).

4. The natural gas high-efficiency residual pressure power generation system according to claim 1, characterized in that: The natural gas heat exchange unit further comprises a third temperature sensor (31) arranged on the third gas supply pipeline (3), wherein the third temperature sensor (31) is configured to detect the temperature of the natural gas flowing from the third gas supply pipeline (3) to the urban natural gas pipeline network.

5. The natural gas high-efficiency residual pressure power generation system according to claim 1, characterized in that: The heat exchanger (222) is an air heat exchanger.

6. The natural gas high-efficiency residual pressure power generation system according to claim 1, characterized in that: The natural gas heat exchange unit further comprises a third heater (225) arranged on the second branch (22); the third heater (225) is arranged on the upstream side of the first temperature sensor (224) and is configured to heat the natural gas transported along the second branch (22); the first flow valve (223) is electrically connected to the third heater (225).

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