Load adjusting device for preparing liquefied natural gas by using natural gas pressure energy

Abstract

The utility model relates to a load adjusting device for preparing liquefied natural gas by using natural gas pressure energy. A gaseous gas supply pipeline comprises a first branch pipe communicated with a natural gas conveying header pipe; a pressure stabilizing valve, a flow regulating valve A, a flow meter A, a pressure sensor A, a temperature sensor A, a natural gas expansion machine, a refrigerant compressor and a refrigerant precooler are sequentially arranged on the first branch pipe in a matched mode; the liquefied gas supply pipeline comprises a second branch pipe, a flow regulating valve B, a flow meter, a natural gas purification device and a cold box are sequentially arranged on the second branch pipe in a matched mode, and the cold box, the refrigerant compressor and the refrigerant precooler are communicated through equipped refrigerant circulating pipes; and a pressure sensor C, a temperature sensor C, a flow regulating valve C and a flow meter C are sequentially arranged on the refrigerant circulating pipe and between the refrigerant compressor and the refrigerant precooler. The device has the advantage of effectively solving the problem of stable operation of the natural gas pressure energy utilization device.

Description

Technical Field

[0001] The present application belongs to the technical field of natural gas regulation, and in particular, relates to a load regulating device for producing liquefied natural gas by utilizing natural gas pressure energy. Background Art

[0002] Natural gas is mainly transported to users at all levels through national pipelines, provincial pipelines and urban pipelines. Its pressure level is generally reduced from 10MPa in the national pipeline to 4.0MPa in the provincial pipeline, and then to 0.8MPa in each city pipeline for delivery to end users. In order to effectively utilize the pressure energy between natural gas pipelines, it is proposed to use a natural gas expander to directly drive the refrigerant compressor, use the cold energy after expansion to pre-cool the natural gas, and the refrigerant compressor provides cold energy to the liquefied cold box to produce liquefied natural gas. However, in the actual operation of the system, the pressure and gas volume of the natural gas in the pipeline fluctuate, which brings great challenges to the stable operation of the natural gas pressure energy utilization device, and also affects the stable operation of the pipeline network. Therefore, it is necessary to optimize the load regulation between the natural gas expander, the refrigerant compressor and the cold box. Utility Model Content

[0003] The technical problem to be solved by the utility model is to solve the insufficiency of the load regulation problem among the natural gas expander, the refrigerant compressor and the cold box in the prior art, thereby providing a load regulation device for producing liquefied natural gas by utilizing the natural gas pressure energy.

[0004] The physical principle of a load regulating device for producing liquefied natural gas using natural gas pressure energy is as follows:

[0005] The expansion power (Pe) of the natural gas expander is determined by the expansion machine's suction and exhaust pressure (Pes, Ped), suction and exhaust pressure (Tes, Ted) and the natural gas flow rate (Me) of the expander. The natural gas expander directly drives the refrigerant compressor. The expansion power (Pe) of the natural gas expander is equal to the input power (Pc) of the refrigerant compressor. The cold energy (Qe) of the natural gas expander precools the refrigerant of the refrigerant compressor, which is determined by the exhaust temperature (Ted) of the expander, the exhaust temperature (Tcd) of the refrigerant compressor, the natural gas flow rate (Me) of the expander and the flow rate (Mc) of the refrigerant compressor. The refrigerant compressor compresses the mixed refrigerant to provide cooling capacity (Qc) for the cold box. The cooling capacity (Qc) is determined by the suction and exhaust pressure (Pcs, Pcd) of the refrigerant compressor and the refrigerant flow rate (Mc). The liquefied amount of natural gas (Mlng) in the cold box is determined by the cooling capacity (Qc) output by the refrigerant compressor and the cooling energy (Qe) of the natural gas expander. The physical relationship between the liquefied natural gas volume (Mlng), natural gas flow (Me) and refrigerant flow (Mc) is as follows:

[0006] Pe=Pc

[0007] Pe=f (Pes, Ped, Tes, Ted, Me)

[0008] Pc=f (Pcs, Pcd, Tcs, Tcd, Mc)

[0009] Qlng = Qe + Qc

[0010] Qe= f(Ted,Tcd,Me,Mc)

[0011] Qc= f (Pcs, Pcd, Tcs, Tcd, Mc)

[0012] Qlng = f(Pes,Tes,Mlng)

[0013] The technical solution adopted by the utility model to solve its technical problems is:

[0014] A load regulating device for producing liquefied natural gas by utilizing natural gas pressure energy, comprising a natural gas transmission main pipe and a gaseous gas supply pipeline and a liquefied gas supply pipeline connected through a pipeline connector; the gaseous gas supply pipeline comprises a first branch pipe connected to the natural gas transmission main pipe through a pipeline connector, the first branch pipe is provided with a pressure stabilizing valve, a flow regulating valve A, a flow meter A, a pressure sensor A, a temperature sensor A, a natural gas expander, a refrigerant compressor, and a refrigerant precooler in sequence, and a speed sensor is provided on the connecting pipe between the natural gas expander and the refrigerant compressor;

[0015] The liquefied gas supply pipeline includes a second branch pipe, on which a flow regulating valve B, a flow meter, a natural gas purification device, and a cold box are provided in sequence. The cold box, the refrigerant compressor, and the refrigerant precooler are connected through a refrigerant circulation pipe. A pressure sensor C, a temperature sensor C, a flow regulating valve C, and a flow meter C are provided in sequence on the refrigerant circulation pipe and located between the refrigerant compressor and the refrigerant precooler.

[0016] There is also a central controller, which transmits signals with the pressure regulating valve, flow control valve A, flow meter A, pressure sensor A, temperature sensor A, speed sensor, flow control valve B, flow meter B, flow control valve C, flow meter C, pressure sensor C, and temperature sensor C through wireless or wired means.

[0017] Furthermore, the pressure stabilizing valve adopts a pneumatically controlled throttle valve structure to stabilize the pressure entering the natural gas expander and eliminate pressure fluctuations in the natural gas pipeline network.

[0018] Furthermore, the flow control valve A adopts a pneumatically controlled ball valve structure to adjust the flow of natural gas entering the natural gas expander and control the start, stop and speed of the natural gas expander.

[0019] Furthermore, the flow control valve B adopts a pneumatically controlled ball valve structure to adjust the flow of liquefied natural gas.

[0020] Furthermore, the flow control valve C adopts a pneumatically controlled ball valve structure to adjust the refrigerant flow.

[0021] Furthermore, flow meter A measures the flow of natural gas entering the natural gas expander.

[0022] Furthermore, the pressure sensor A measures the suction pressure and the exhaust pressure of the natural gas expander.

[0023] Furthermore, the temperature sensor A measures the suction temperature and the exhaust temperature of the natural gas expander.

[0024] Furthermore, the speed sensor measures the speed of the refrigerant compressor directly driven by the natural gas expander.

[0025] Furthermore, flow meter B measures the flow rate of liquefied natural gas.

[0026] Furthermore, the flow meter C measures the refrigerant flow rate.

[0027] Furthermore, the pressure sensor C measures the suction pressure and the discharge pressure of the refrigerant compressor.

[0028] Furthermore, the temperature sensor C measures the suction temperature and the discharge temperature of the refrigerant compressor.

[0029] Furthermore, the central controller uses PLC to monitor the flow, pressure and temperature of expanded natural gas, the flow, pressure and temperature of liquefied natural gas, and the flow, pressure and temperature of refrigerant.

[0030] The beneficial effects of the utility model are:

[0031] By adjusting the physical relationship among natural gas flow and pressure, expander speed, and refrigerant pressure and flow, load matching between high-pressure natural gas pressure energy and cold energy and liquefied natural gas production is achieved. It has the advantages of fast response speed, high control accuracy, safety and reliability, and can effectively solve the problem of stable operation of natural gas pressure energy utilization equipment. Therefore, it has great promoting significance for the recovery and utilization of natural gas pressure energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The technical solution of the present application is further described below in conjunction with the accompanying drawings and embodiments.

[0033] Figure 1 It is a schematic diagram of the main structure of an embodiment of the present application;

[0034] Figure 2 This is a schematic diagram of the control principle structure of the central controller of an embodiment of the present application;

[0035] The reference numerals in the figure are:

[0036] 01. Pressure regulating valve; 02. Flow regulating valve A; 03. Flow meter A; 04. Pressure sensor A; 05. Temperature sensor A; 06. Speed ​​sensor; 07. Flow regulating valve B; 08. Flow meter B; 09. Flow regulating valve C; 10. Flow meter C; 11. Pressure sensor C; 12. Temperature sensor C; 13. Central controller; 14. Natural gas transmission main; 15. Gaseous gas supply pipeline; 16. Liquefied gas supply pipeline; 17. First branch pipe; 18. Natural gas expander; 19. Refrigerant compressor; 20. Refrigerant precooler; 22. Second branch pipe, 23. Natural gas purification device; 24. Cold box; 25. Refrigerant circulation pipe. DETAILED DESCRIPTION

[0037] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0038] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, 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 cannot be understood as limiting the scope of protection of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention of the present utility model, unless otherwise specified, "multiple" means two or more.

[0039] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0040] The technical solution of the present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments. Example

[0041] The present embodiment provides a load regulating device for producing liquefied natural gas by utilizing natural gas pressure energy, comprising a natural gas transmission main pipe 14 and a gaseous gas supply pipeline 15 and a liquefied gas supply pipeline 16 connected through a pipeline connector; the gaseous gas supply pipeline 15 comprises a first branch pipe 17 connected to the natural gas transmission main pipe 14 through a pipeline connector, and the first branch pipe 17 is provided with a pressure regulating valve A01, a flow regulating valve A02, a flow meter A03, a pressure sensor A04, a temperature sensor A05, a natural gas expander 18, a refrigerant compressor 19, and a refrigerant precooler 20 in sequence, and a speed sensor 06 is provided on the connecting pipe between the natural gas expander 18 and the refrigerant compressor 19;

[0042] The liquefied gas supply line 16 includes a second branch pipe 22, on which a flow regulating valve B07, a flow meter B08, a natural gas purification device 23, and a cold box 24 are provided in sequence. The cold box 24, the refrigerant compressor 19, and the refrigerant precooler 20 are connected through a refrigerant circulation pipe 25. The refrigerant circulation pipe 25 and located between the refrigerant compressor 19 and the refrigerant precooler 20 are provided with a pressure sensor C11, a temperature sensor C12, a flow regulating valve C09, and a flow meter C10 in sequence.

[0043] There is also a central controller 13, which transmits signals with the pressure regulating valve 01, the flow regulating valve A02, the flow meter A03, the pressure sensor A04, the temperature sensor A05, the speed sensor 06, the flow regulating valve B07, the flow meter B08, the flow regulating valve C09, the flow meter C10, the pressure sensor C11, and the temperature sensor C12 through wireless or wired means.

[0044] The invention also includes a temperature sensor and a pressure sensor installed on the first branch pipe to measure the output fluid temperature and pressure of the natural gas expander and the refrigerant compressor.

[0045] The invention also includes a temperature sensor and a pressure sensor installed on the second branch pipe to measure the output fluid temperature and pressure of the natural gas expander and the refrigerant compressor.

[0046] The pressure regulating valve 01 adopts a pneumatically controlled throttle valve structure to stabilize the pressure entering the natural gas expander D and eliminate the pressure fluctuation of the natural gas PNG in the pipeline network.

[0047] The flow control valve A02 adopts a pneumatic control ball valve structure to adjust the natural gas flow entering the natural gas expander D and control the start, stop and speed of the natural gas expander D.

[0048] Flow meter A03 adopts electromagnetic structure to measure the natural gas flow entering the natural gas expander D.

[0049] Pressure sensor A04 adopts explosion-proof structure and measures the suction pressure and exhaust pressure of natural gas expander D.

[0050] The temperature sensor A05 adopts an explosion-proof structure and measures the suction temperature and exhaust temperature of the natural gas expander D.

[0051] The speed sensor 06 adopts a Hall effect structure to measure the speed of the refrigerant compressor 19 directly driven by the natural gas expander D.

[0052] The flow control valve B07 adopts a pneumatically controlled ball valve structure to adjust the flow of liquefied natural gas.

[0053] Flow meter B08 adopts electromagnetic structure to measure the flow of liquefied natural gas.

[0054] The flow control valve C09 adopts a pneumatically controlled ball valve structure to adjust the refrigerant flow.

[0055] Flow meter C10 adopts electromagnetic structure to measure refrigerant flow.

[0056] The pressure sensor C11 adopts an explosion-proof structure and measures the suction pressure and exhaust pressure of the refrigerant compressor 19.

[0057] The temperature sensor C12 adopts an explosion-proof structure and measures the suction temperature and exhaust temperature of the refrigerant compressor 19.

[0058] Wireless or wired signal transmission with the pressure regulating valve, flow control valve A, flow meter A, pressure sensor A, temperature sensor A, speed sensor, flow control valve B, flow meter B, flow control valve C, flow meter C, pressure sensor C, temperature sensor C means that the central controller 13 uses PLC to monitor parameters such as the flow, pressure and temperature of expanded natural gas, parameters such as the flow, pressure and temperature of liquefied natural gas, and parameters such as the flow, pressure and temperature of refrigerant.

[0059] In the implementation scheme of the utility model, the pressure regulating valve stabilizes the pressure of the natural gas pipeline network to a set value, the flow regulating valve A is gradually opened from a closed state, the refrigerant compressor directly driven by the natural gas expander starts to operate, the speed sensor measures the speed of the refrigerant compressor directly driven by the natural gas expander, and when the flow regulating valve A is fully opened, the refrigerant compressor directly driven by the natural gas expander operates at full load, and the expanded low-temperature natural gas precools the high-pressure refrigerant of the refrigerant compressor to the rated temperature. The flow regulating valve C is gradually closed from a fully open state, and the exhaust pressure of the refrigerant compressor is adjusted to the set pressure, and the high-pressure refrigerant enters the cold box for precooling of the cold box. The flow regulating valve B is gradually opened from a closed state to a set load, and the liquefied natural gas enters the cold box after purification and heat exchange with the high-pressure refrigerant to cool to below -162°C, and becomes liquefied natural gas output. The central controller monitors the flow, pressure and temperature of the expanded natural gas, the flow, pressure and temperature of the liquefied natural gas, and the flow, pressure and temperature of the refrigerant in real time online.

[0060] When the natural gas flow in the pipeline network decreases, the power delivered by the natural gas expander to the refrigerant compressor decreases. After the central controller calculates the real-time online monitoring data, it sends the valve opening signal to the flow control valve B and the flow control valve C in real time. The opening of the flow control valve B decreases to the target value, the liquefied natural gas decreases, the opening of the flow control valve C decreases to the target value, the refrigerant flow decreases, and the flow of the liquefied natural gas is matched in real time with the cooling capacity output by the refrigerant compressor and the cooling energy of the natural gas expander.

[0061] When the natural gas flow in the pipeline increases, the power delivered by the natural gas expander to the refrigerant compressor increases. After the central controller calculates the real-time online monitoring data, it sends the valve opening signal to the flow control valve B and the flow control valve C in real time. The opening of the flow control valve B increases to the target value, the liquefied natural gas increases, the opening of the flow control valve C increases to the target value, the refrigerant flow increases, and the flow of liquefied natural gas is matched in real time with the cooling capacity output by the refrigerant compressor and the cooling energy of the natural gas expander.

[0062] Based on the above ideal embodiments of this application, the relevant staff can make various changes and modifications without departing from the technical concept of this application through the above description. The technical scope of this application is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A load regulating device for producing liquefied natural gas using natural gas pressure energy, characterized in that: It includes a natural gas transmission main pipe and a gaseous gas supply pipeline and a liquefied gas supply pipeline connected by pipeline connectors; the gaseous gas supply pipeline includes a first branch pipe connected to the natural gas transmission main pipe by a pipeline connector, the first branch pipe is provided with a pressure stabilizing valve, a flow regulating valve A, a flow meter A, a pressure sensor A, a temperature sensor A, a natural gas expander, a refrigerant compressor, and a refrigerant precooler in sequence, and a speed sensor is provided on the connecting pipe between the natural gas expander and the refrigerant compressor; the liquefied gas supply pipeline includes a second branch pipe, the second branch pipe is provided with a flow regulating valve B, a flow meter, a natural gas purification device, and a cold box in sequence, the cold box, the refrigerant compressor, and the refrigerant precooler are connected by a refrigerant circulation pipe, and the refrigerant circulation pipe and located between the refrigerant compressor and the refrigerant precooler are provided with a pressure sensor C, a temperature sensor C, a flow regulating valve C, and a flow meter C in sequence.

2. The load regulating device for producing liquefied natural gas by utilizing natural gas pressure energy according to claim 1, characterized in that: The invention also includes a temperature sensor and a pressure sensor installed on the first branch pipe to measure the output fluid temperature and pressure of the natural gas expander and the refrigerant compressor.

3. The load regulating device for producing liquefied natural gas by utilizing natural gas pressure energy according to claim 1, characterized in that: The invention also includes a temperature sensor and a pressure sensor installed on the second branch pipe to measure the output fluid temperature and pressure of the natural gas expander and the refrigerant compressor.

4. A load regulating device for producing liquefied natural gas using natural gas pressure energy according to any one of claims 1 to 3, characterized in that: It also includes a central controller, which transmits signals with the pressure regulating valve, flow control valve A, flow meter A, pressure sensor A, temperature sensor A, speed sensor, flow control valve B, flow meter B, flow control valve C, flow meter C, pressure sensor C, and temperature sensor C through wireless or wired means.

5. The load regulating device for producing liquefied natural gas by utilizing natural gas pressure energy according to claim 1, characterized in that: The pressure stabilizing valve is a pneumatically controlled throttle valve.

6. The load regulating device for producing liquefied natural gas by utilizing natural gas pressure energy according to claim 1, characterized in that: The flow regulating valve A is a pneumatically controlled ball valve.

7. The load regulating device for producing liquefied natural gas by utilizing natural gas pressure energy according to claim 1, characterized in that: The flow regulating valve B is a pneumatically controlled ball valve.

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