Turbine expansion unit for reducing pressure of high-pressure gas and starting and stopping control method of turbine expansion unit

Abstract

The invention relates to a turbo expander unit for high-pressure gas pressure reduction, in particular to a turbo expander unit for high-pressure gas pressure reduction and a starting and stopping control method thereof, and aims to solve the problems that an existing turbo expander unit for high-pressure gas pressure reduction is high in control requirement and complex in operation, meanwhile, many fault points are introduced, and the working efficiency is high. And the reliability of the turbine expansion unit is reduced. The unit comprises an upstream pipeline, an expansion machine branch, a bypass regulating valve branch and a downstream pipeline, and the expansion machine branch and the bypass regulating valve branch are connected between the air outlet end of the upstream pipeline and the air inlet end of the downstream pipeline in parallel. An air inlet quick cut-off valve, an air inlet adjusting valve, an expansion machine, an exhaust pressure detection instrument and an exhaust cut-off valve are sequentially arranged on the expansion machine branch in the airflow direction, a bypass adjusting valve is arranged on the bypass adjusting valve branch, and a downstream pipeline pressure detection instrument is arranged on the downstream pipeline.

Description

Technical Field

[0001] This invention relates to a turbine expander unit for high-pressure gas depressurization, and more specifically to a turbine expander unit for high-pressure gas depressurization and its start-up and shutdown control methods. Background Technology

[0002] In fields such as natural gas transportation, there are situations where the upstream gas pressure is higher than the user's gas pressure. In such cases, certain measures are needed to reduce the gas pressure to meet the user's gas pressure requirements. For example, after receiving natural gas transported through pipelines, the relevant units at the city gas gate station will use valves to reduce the pressure of the natural gas.

[0003] To save energy and reduce emissions, some manufacturers are developing turbine expanders to replace valves for depressurizing natural gas. However, during the start-up process of the turbine expander, downstream gas is prone to backflow, causing the unit to reverse and endangering its safe operation.

[0004] Chinese invention patent application CN115788612A discloses a piping system and start-up / shutdown method for a differential pressure turbine expander unit. The system includes a process gas pipeline, an expander branch, and a pressure-reducing bypass. The expander branch and the pressure-reducing bypass are connected in parallel at both ends of the process gas pipeline. The process gas pipeline is equipped with a pressure-reducing valve. The expander branch is equipped with a turbine expander. The turbine expander inlet is equipped with a series-connected inlet quick-closing protection valve and an inlet regulating valve, and the turbine expander outlet is equipped with an outlet regulating valve. The pressure-reducing bypass is equipped with a series-connected bypass quick-closing protection valve and a pressure-reducing regulating valve. The newly added parallel pressure-reducing bypass avoids the influence of the original pipeline pressure-reducing valve's adjustment speed and accuracy on the expander unit's start-up and shutdown control process, reducing uncertainties during unit start-up and shutdown. The inlet regulating valve of the expander branch works in conjunction with the pressure-reducing regulating valve of the pressure-reducing bypass to ensure smooth downstream gas supply, stable flow, and constant upstream and downstream pressure throughout the unit's start-up and shutdown operation. Although the invention can prevent downstream gas backflow during the start-up of the expander and ensure the safe operation of the unit, it has multiple valves in the downstream pipeline and branch pipeline at the outlet of the turbine expander unit, including outlet check valve, outlet regulating valve, bypass quick-closing protection valve, pressure reducing regulating valve, etc. Setting too many valves means that the control requirements of the unit are higher and the operation is more complicated. It also introduces more failure points and reduces the reliability of the turbine expander unit. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problems of existing turbine expanders used for high-pressure gas depressurization, which have high control requirements, complex operation, and introduce many failure points, thus reducing the reliability of the turbine expander. The invention provides a turbine expander for high-pressure gas depressurization and its start-up and shutdown control method.

[0006] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0007] A turbine expander unit for high-pressure gas depressurization is characterized by the following features:

[0008] It includes an upstream pipeline, an expander branch, a bypass regulating valve branch, and a downstream pipeline. The expander branch and the bypass regulating valve branch are connected in parallel between the outlet end of the upstream pipeline and the inlet end of the downstream pipeline.

[0009] Along the airflow direction, the expander branch is equipped with an intake quick-cut-off valve, an intake regulating valve, an expander, an exhaust pressure detection instrument, and an exhaust cut-off valve in sequence.

[0010] A bypass regulating valve is installed on the bypass regulating valve branch;

[0011] Downstream pipeline pressure monitoring instruments are installed on the downstream pipeline.

[0012] Furthermore, the expander branch is also equipped with an intake pressure detection instrument, an intake temperature detection instrument, and a flow meter, all of which are located between the intake regulating valve and the expander.

[0013] Furthermore, exhaust temperature detection instruments are also installed on the downstream pipeline.

[0014] Meanwhile, the present invention also provides a start-up control method for the above-mentioned turbine expander unit for high-pressure gas depressurization, which is characterized by including the following steps:

[0015] A1. Ensure that the intake quick shut-off valve, intake regulating valve, and exhaust shut-off valve are all closed, and control the opening of the bypass regulating valve so that the pressure measured by the downstream pipeline pressure detection instrument is the downstream target pressure value.

[0016] A2. Open the intake quick-cut-off valve;

[0017] A3. Slowly open the intake regulating valve to make the expander rotate until the pressure value measured at the exhaust pressure detection instrument is equal to or greater than the pressure value measured at the downstream pipeline pressure detection instrument.

[0018] A4. Open the exhaust shut-off valve and then wait for the expander speed to stabilize;

[0019] A5. Gradually increase the opening of the intake regulating valve until the expander speed reaches the design speed to complete the start-up of the turbine expander unit used for high-pressure gas depressurization. While gradually increasing the opening of the intake regulating valve, gradually decrease the opening of the bypass regulating valve to keep the pressure value measured at the downstream pipeline pressure detection instrument at the downstream target pressure value.

[0020] Furthermore, in step A3, when slowly opening the intake regulating valve, the opening speed of the intake regulating valve should be such that the speed of the expander does not exceed the design speed.

[0021] Meanwhile, the present invention also provides a shutdown control method for the above-mentioned turbine expander unit for high-pressure gas depressurization, which is applicable during normal operation of the unit. Its special feature is that it includes the following steps:

[0022] B1. Gradually reduce the opening of the intake regulating valve while gradually increasing the opening of the bypass regulating valve, so that the pressure value measured at the downstream pipeline pressure detection instrument remains at the downstream target pressure value until the intake regulating valve is completely closed.

[0023] B2. Close the exhaust shut-off valve and the intake quick shut-off valve to complete the shutdown of the turbine expander unit used for high-pressure gas depressurization.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects:

[0025] 1. The turbo expander unit for high-pressure gas depressurization and its start-up and shutdown control method of the present invention reduce the number of valves in the unit, reduce the risk of unit failure, improve the reliability of the unit, and are simple to operate;

[0026] 2. The turbo expander unit for high-pressure gas depressurization and its start-up control method of the present invention open the exhaust shut-off valve only when the pressure value measured at the exhaust pressure detection instrument is equal to or greater than the pressure value measured at the downstream pipeline pressure detection instrument. This ensures the correct start-up of the unit, effectively prevents downstream gas backflow from causing unit reversal, and ensures the safe operation of the unit. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the gas path structure of an embodiment of a turbine expander unit for high-pressure gas decompression according to the present invention.

[0028] The annotations in the attached figures are explained as follows:

[0029] 1-Expander, 2-Bypass regulating valve, 3-Inlet quick shut-off valve, 4-Inlet pressure measuring instrument, 5-Inlet temperature measuring instrument, 6-Downstream pipeline pressure measuring instrument, 7-Exhaust temperature measuring instrument, 8-Flow meter, 9-Inlet regulating valve, 10-Exhaust shut-off valve, 11-Exhaust pressure measuring instrument, 12-Upstream pipeline, 13-Expander branch, 14-Bypass regulating valve branch, 15-Downstream pipeline. Detailed Implementation

[0030] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0031] like Figure 1 As shown in the embodiment of this application, a turbine expander unit for high-pressure gas depressurization is provided. The process flow has a high exhaust pressure, generally higher than 5 bara. The unit includes an upstream pipeline 12, an expander branch 13, a bypass regulating valve branch 14, and a downstream pipeline 15. High-pressure gas enters the upstream pipeline 12 from the inlet end of the upstream pipeline 12. The expander branch 13 and the bypass regulating valve branch 14 are connected in parallel between the outlet end of the upstream pipeline 12 and the inlet end of the downstream pipeline 15. The outlet end of the downstream pipeline 15 is connected to the downstream user.

[0032] Along the airflow direction, the expander branch 13 is sequentially equipped with an intake quick-cut-off valve 3, an intake regulating valve 9, an intake pressure measuring instrument 4, a flow meter 8, an intake temperature measuring instrument 5, an expander 1, an exhaust pressure measuring instrument 11, and an exhaust cut-off valve 10. The intake pressure measuring instrument 4 uses a pressure transmitter, the intake temperature measuring instrument 5 uses a temperature transmitter, and the exhaust pressure measuring instrument 11 uses a pressure transmitter.

[0033] A bypass regulating valve 2 is provided on the bypass regulating valve branch 14. The bypass regulating valve 2 has a quick shut-off function.

[0034] Downstream pipeline 15 is equipped with a downstream pipeline pressure detection instrument 6 and an exhaust temperature detection instrument 7, which are installed sequentially along the airflow direction. The downstream pipeline pressure detection instrument 6 is a pressure transmitter, and the exhaust temperature detection instrument 7 is a temperature transmitter.

[0035] In this embodiment, the intake quick-cut-off valve 3, intake regulating valve 9, exhaust cut-off valve 10, and bypass regulating valve 2 are all manual valves. In other embodiments, the intake quick-cut-off valve 3, intake regulating valve 9, exhaust cut-off valve 10, and bypass regulating valve 2 can all be electric valves and electrically connected to the controller.

[0036] During normal operation of expander 1, both the inlet quick-cut-off valve 3 and the exhaust cut-off valve 10 are open, the bypass regulating valve 2 is closed, and the inlet regulating valve 9 is at the opening required by the downstream target pressure value. High-pressure gas passes sequentially through the inlet quick-cut-off valve 3, the inlet regulating valve 9, the inlet pressure measuring instrument 4, the flow meter 8, and the inlet temperature measuring instrument 5 before entering expander 1 for expansion and decompression. The expanded and decompressed gas then passes sequentially through the exhaust pressure measuring instrument 11, the exhaust cut-off valve 10, the downstream pipeline pressure measuring instrument 6, and the exhaust temperature measuring instrument 7 before being sent to the downstream user. The inlet pressure measuring instrument 4, the flow meter 8, and the inlet temperature measuring instrument 5 measure the pressure, flow rate, and temperature of the gas entering expander 1, respectively. The exhaust pressure measuring instrument 11 measures the pressure of the gas discharged from the outlet of expander 1, and the downstream pipeline pressure measuring instrument 6 and the exhaust temperature measuring instrument 7 measure the pressure and temperature of the gas sent to the downstream user, respectively.

[0037] When expander 1 stops running, the high-pressure gas is reduced in pressure by bypass regulating valve 2, and then sent to the downstream user after passing through downstream pipeline pressure detection instrument 6 and exhaust temperature detection instrument 7 in sequence.

[0038] When an emergency occurs in expander 1 and an emergency shutdown is required, the intake quick-cut-off valve 3 closes quickly, and at the same time, the bypass regulating valve 2 opens quickly.

[0039] This application embodiment also provides a start-up control method for the above-mentioned turbine expander unit for high-pressure gas depressurization, including the following steps:

[0040] A1. Ensure that the intake quick shut-off valve 3, intake regulating valve 9 and exhaust shut-off valve 10 are all closed, and control the opening of the bypass regulating valve 2 so that the pressure measured by the downstream pipeline pressure detection instrument 6 is the downstream target pressure value.

[0041] A2. Open the intake quick-cut-off valve 3, and keep the intake regulating valve 9 and exhaust cut-off valve 10 closed.

[0042] A3. Slowly open the intake regulating valve 9 to make the expander 1 rotate until the pressure value measured at the exhaust pressure detection instrument 11 is equal to the pressure value measured at the downstream pipeline pressure detection instrument 6.

[0043] When slowly opening the intake regulating valve 9, the opening speed of the intake regulating valve 9 should be such that the speed of the expander 1 does not exceed the design speed.

[0044] In other embodiments, step A3 may also be: slowly open the intake regulating valve 9 to make the expander 1 rotate until the pressure value measured at the exhaust pressure detection instrument 11 is greater than the pressure value measured at the downstream pipeline pressure detection instrument 6.

[0045] A4. Open the exhaust shut-off valve 10 to connect the expander 1 to the process pipeline network, and then wait for the speed of the expander 1 to stabilize.

[0046] A5. Gradually increase the opening of the intake regulating valve 9 until the speed of the expander 1 reaches the design speed, thus completing the start-up of the turbine expander unit used for high-pressure gas decompression. While gradually increasing the opening of the intake regulating valve 9, gradually decrease the opening of the bypass regulating valve 2 so that the pressure value measured at the downstream pipeline pressure detection instrument 6 is maintained at the downstream target pressure value.

[0047] This application also provides a shutdown control method for the above-mentioned turbine expander unit used for high-pressure gas depressurization, applicable during normal operation of the unit, including the following steps:

[0048] B1. Gradually reduce the opening of the intake regulating valve 9, while gradually increasing the opening of the bypass regulating valve 2, so that the pressure value measured at the downstream pipeline pressure detection instrument 6 is maintained at the downstream target pressure value, until the intake regulating valve 9 is completely closed.

[0049] B2. Close the exhaust shut-off valve 10 and the intake quick shut-off valve 3 to complete the shutdown of the turbine expander unit used for high-pressure gas depressurization.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A turbine expander unit for high-pressure gas depressurization, characterized in that: It includes an upstream pipeline (12), an expander branch (13), a bypass regulating valve branch (14), and a downstream pipeline (15). The expander branch (13) and the bypass regulating valve branch (14) are connected in parallel between the outlet end of the upstream pipeline (12) and the inlet end of the downstream pipeline (15). The expander branch (13) is provided with an intake quick shut-off valve (3), an intake regulating valve (9), an expander (1), an exhaust pressure detection instrument (11) and an exhaust shut-off valve (10) in sequence along the airflow direction. A bypass regulating valve (2) is provided on the bypass regulating valve branch (14); The downstream pipeline (15) is equipped with a downstream pipeline pressure detection instrument (6).

2. The turbine expander unit for high-pressure gas depressurization according to claim 1, characterized in that: The expander branch (13) is also equipped with an intake pressure detection instrument (4), an intake temperature detection instrument (5) and a flow meter (8), which are all located between the intake regulating valve (9) and the expander (1).

3. The turbine expander unit for high-pressure gas depressurization according to claim 1, characterized in that: The downstream pipeline (15) is also equipped with an exhaust temperature detection instrument (7).

4. A start-up control method for a turbine expander unit for high-pressure gas depressurization as described in any one of claims 1-3, characterized in that, Includes the following steps: A1. Ensure that the intake quick shut-off valve (3), intake regulating valve (9) and exhaust shut-off valve (10) are all closed. By controlling the opening of the bypass regulating valve (2), ensure that the pressure measured by the downstream pipeline pressure detection instrument (6) is the downstream target pressure value. A2. Open the intake quick shut-off valve (3); A3. Slowly open the intake regulating valve (9) to make the expander (1) rotate until the pressure value measured at the exhaust pressure detection instrument (11) is equal to or greater than the pressure value measured at the downstream pipeline pressure detection instrument (6). A4. Open the exhaust shut-off valve (10), and then wait for the expander (1) speed to stabilize; A5. Gradually increase the opening of the intake regulating valve (9) until the speed of the expander (1) reaches the design speed, and complete the start-up of the turbine expander unit used for high pressure gas decompression. While gradually increasing the opening of the intake regulating valve (9), gradually decrease the opening of the bypass regulating valve (2) so that the pressure value measured at the downstream pipeline pressure detection instrument (6) is maintained at the downstream target pressure value.

5. The start-up control method for a turbine expander unit for high-pressure gas depressurization according to claim 4, characterized in that: In step A3, when the intake regulating valve (9) is opened slowly, the opening speed of the intake regulating valve (9) is such that the speed of the expander (1) does not exceed the design speed.

6. A shutdown control method for a turbine expander unit for high-pressure gas depressurization as described in any one of claims 1-3, applicable during normal operation of the unit, characterized in that, Includes the following steps: B1. Gradually reduce the opening of the intake regulating valve (9) while gradually increasing the opening of the bypass regulating valve (2) so that the pressure value measured at the downstream pipeline pressure detection instrument (6) remains at the downstream target pressure value until the intake regulating valve (9) is completely closed. B2. Close the exhaust shut-off valve (10) and the intake quick shut-off valve (3) to complete the shutdown of the turbine expander unit used for high-pressure gas decompression.

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