Scattered gas recycling and liquefying system

Abstract

The utility model discloses a scattered gas recycling and liquefying system, and belongs to the field of liquefying equipment. The system comprises a natural gas input pipeline, a first cold box, a second cold box, a first refrigeration compressor, a second refrigeration compressor, a third refrigeration compressor, a first JT throttle valve, a second JT throttle valve, a third JT throttle valve and a fourth JT throttle valve. The first refrigeration compressor, a third channel of the first cold box, a third channel of the second cold box, a third JT throttle valve, a second channel of the second cold box and a second channel of the first cold box are sequentially connected to form a loop; the second refrigeration compressor, a fifth channel of the first cold box, the second JT throttle valve and a fourth channel of the first cold box are sequentially connected to form a loop; a third refrigeration compressor, a seventh channel of the first cold box, a first JT throttle valve and a sixth channel of the first cold box are sequentially connected to form a loop; the natural gas input pipeline is sequentially connected with a first pipeline of the first cold box, a first pipeline of the second cold box and the fourth JT throttling valve. According to the utility model, the cost is reduced.

Description

Technical Field

[0001] The utility model belongs to the field of liquefaction equipment, in particular to a scattered gas recovery and liquefaction system. Background Art

[0002] In recent years, domestic LNG recovery facilities for bulk gas and pilot gas production have primarily relied on liquefaction systems with screw compressors and plate-fin heat exchangers as their core equipment. Due to the processing capacity of a single screw compressor and its compression efficiency factor, screw compressors are typically used for smaller-scale liquefaction systems. A key characteristic of bulk gas recovery is unstable feed gas volumes, short production cycles, and large fluctuations in feed gas volumes. To address this, the current approach is to connect several liquefaction systems in parallel, adjusting the number of liquefaction systems based on fluctuations in processing volume. This model cannot adapt well to fluctuations in feed gas volumes, extending construction cycles and investment costs. Because it cannot quickly adapt to feed gas fluctuations, the liquefaction system operates below full capacity, resulting in relatively high liquefaction unit consumption. Utility Model Content

[0003] The purpose of the utility model is to overcome the deficiencies of the prior art and provide a scattered gas recovery and liquefaction system.

[0004] The purpose of the utility model is achieved through the following technical solutions: a scattered gas recovery and liquefaction system, including a natural gas input pipeline, a first cold box, a second cold box, a first refrigeration compressor, a second refrigeration compressor, a third refrigeration compressor, a first J_T throttle valve, a second J_T throttle valve, a third J_T throttle valve and a fourth J_T throttle valve;

[0005] The first cold box is provided with a first channel, a second channel, a third channel, a fourth channel, a fifth channel, a sixth channel and a seventh channel;

[0006] The second cold box is provided with a first channel, a second channel and a third channel;

[0007] The first refrigeration compressor, the third channel of the first cold box, the third channel of the second cold box, the third J_T throttle valve, the second channel of the second cold box, and the second channel of the first cold box are connected in sequence to form a loop;

[0008] The second refrigeration compressor, the fifth channel of the first cold box, the second J_T throttle valve, and the fourth channel of the first cold box are connected in sequence to form a loop;

[0009] The third refrigeration compressor, the seventh channel of the first cold box, the first J_T throttle valve, and the sixth channel of the first cold box are connected in sequence to form a loop;

[0010] The natural gas input pipeline is connected to the first pipeline of the first cold box, the first pipeline of the second cold box and the fourth J_T throttle valve in sequence.

[0011] Furthermore, the first cold box is a pre-cooling liquefaction heat exchanger.

[0012] Furthermore, the second cold box is a liquefaction subcooling heat exchanger.

[0013] Furthermore, the first refrigeration compressor, the second refrigeration compressor and the third refrigeration compressor are all screw refrigeration compressors.

[0014] Furthermore, the first J_T throttle valve, the second J_T throttle valve, the third J_T throttle valve and the fourth J_T throttle valve are all program-controlled valves.

[0015] Furthermore, the scattered gas recovery and liquefaction system also includes a controller and a flow meter. The controller is respectively connected to the first refrigeration compressor, the second refrigeration compressor, the third refrigeration compressor, the first J_T throttle valve, the second J_T throttle valve, the third J_T throttle valve, the fourth J_T throttle valve and the flow meter, and the flow meter is arranged at the natural gas input pipeline.

[0016] The beneficial effects of the present invention are as follows: in the present invention, the first refrigeration compressor, the second refrigeration compressor and the third refrigeration compressor form a refrigeration cycle to provide the cooling capacity required for pre-cooling, supercooling and liquefaction of natural gas. When the system load is high, three refrigeration compressors are used for refrigeration, and when the system load is low, two refrigeration compressors are used for refrigeration, thereby maintaining a high liquefaction efficiency while reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the composition of the scattered gas recovery and liquefaction system in the utility model;

[0018] In the figure, E1 is the first cold box, E2 is the second cold box, C1 is the first refrigeration compressor, C2 is the second refrigeration compressor, C3 is the third refrigeration compressor, V1 is the first J_T throttle valve, V2 is the second J_T throttle valve, V3 is the third J_T throttle valve, and V4 is the fourth J_T throttle valve. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work shall fall within the scope of protection of the present invention.

[0020] See Figure 1 This embodiment provides a scattered gas recovery and liquefaction system:

[0021] like Figure 1 As shown, a scattered gas recovery and liquefaction system includes a natural gas input pipeline, a first cold box E1, a second cold box E2, a first refrigeration compressor C1, a second refrigeration compressor C2, a third refrigeration compressor C3, a first J_T throttle valve V1, a second J_T throttle valve V2, a third J_T throttle valve V3 and a fourth J_T throttle valve V4.

[0022] The first cold box E1 is provided with a first channel, a second channel, a third channel, a fourth channel, a fifth channel, a sixth channel and a seventh channel; the second cold box E2 is provided with a first channel, a second channel and a third channel.

[0023] The first refrigeration compressor C1, the third channel of the first cold box E1, the third channel of the second cold box E2, the third J_T throttle valve V3, the second channel of the second cold box E2, and the second channel of the first cold box E1 are connected in sequence to form a loop. Specifically, the outlet of the first refrigeration compressor C1 is connected to the inlet of the third channel of the first cold box E1, the outlet of the third channel of the first cold box E1 is connected to the inlet of the third channel of the second cold box E2, the outlet of the third channel of the second cold box E2 is connected to one end of the third J_T throttle valve V3, the other end of the third J_T throttle valve V3 is connected to the inlet of the second channel of the second cold box E2, the outlet of the second channel of the second cold box E2 is connected to the inlet of the second channel of the first cold box E1, and the outlet of the second channel of the first cold box E1 is connected to the inlet of the first refrigeration compressor C1.

[0024] The second refrigeration compressor C2, the fifth channel of the first cold box E1, the second J_T throttle valve V2, and the fourth channel of the first cold box E1 are connected in sequence to form a loop. Specifically, the outlet of the second refrigeration compressor C2 is connected to the inlet of the fifth channel of the first cold box E1, the outlet of the fifth channel of the first cold box E1 is connected to one end of the second J_T throttle valve V2, the other end of the second J_T throttle valve V2 is connected to the inlet of the fourth channel of the first cold box E1, and the outlet of the fourth channel of the first cold box E1 is connected to the inlet of the second refrigeration compressor C2.

[0025] The third refrigeration compressor C3, the seventh channel of the first cold box E1, the first J_T throttle valve V1, and the sixth channel of the first cold box E1 are sequentially connected to form a loop. Specifically, the outlet of the third refrigeration compressor C3 is connected to the inlet of the seventh channel of the first cold box E1, the outlet of the seventh channel of the first cold box E1 is connected to one end of the first J_T throttle valve V1, the other end of the first J_T throttle valve V1 is connected to the inlet of the sixth channel of the first cold box E1, and the outlet of the sixth channel of the first cold box E1 is connected to the inlet of the third refrigeration compressor C3.

[0026] The natural gas input pipeline is sequentially connected to the first pipeline of the first cold box E1, the first pipeline of the second cold box E2, and the fourth J_T throttle valve V4. Specifically, the inlet of the natural gas input pipeline is connected to a gas source, the outlet of the natural gas input pipeline is connected to the inlet of the first pipeline of the first cold box E1, the outlet of the first pipeline of the first cold box E1 is connected to the inlet of the first pipeline of the second cold box E2, the outlet of the first pipeline of the first cold box E1 is connected to one end of the fourth J_T throttle valve V4, and the other end of the fourth J_T throttle valve V4 is connected to a storage tank.

[0027] When the first refrigeration compressor C1 is working, the third J_T throttle valve V3 is opened, and the refrigerant in the first refrigeration compressor C1 flows through the first cold box E1 and the second cold box E2 in sequence. The refrigerant is in a cooled state before flowing through the third J_T throttle valve. After flowing through the third J_T throttle valve, the refrigerant is used to provide cooling capacity, and the cooling capacity comes from the throttling expansion of the third J_T throttle valve (the third J_T throttle valve can produce throttling expansion because of the first refrigeration compressor C1); when the second refrigeration compressor C2 is working, the second J_T throttle valve V2 is opened, and the refrigerant in the second refrigeration compressor C2 flows through the first cold box E1. The refrigerant is in a cooled state before flowing through the second J_T throttle valve. In the cooling state, the refrigerant is used to provide cooling after flowing through the second J_T throttle valve, and the cooling energy comes from the throttling expansion of the second J_T throttle valve (the second J_T throttle valve can produce throttling expansion because of the second refrigeration compressor C2); when the third refrigeration compressor C3 is working, the first J_T throttle valve V1 is opened, and the refrigerant in the third refrigeration compressor C3 flows through the first cold box E1. The refrigerant is in a cooled state before flowing through the first J_T throttle valve, and the refrigerant is used to provide cooling after flowing through the first J_T throttle valve, and the cooling energy comes from the throttling expansion of the first J_T throttle valve (the first J_T throttle valve can produce throttling expansion because of the third refrigeration compressor C3).

[0028] When cooling and liquefying natural gas, the fourth J_T throttle valve V4 is opened and the corresponding refrigeration compressors (the first refrigeration compressor C1, the second refrigeration compressor C2, and the third refrigeration compressor C3) are started. The refrigerant in the refrigeration compressors provides the cooling capacity required to cool the liquefied natural gas. After the natural gas is liquefied and cooled to form the LGN product, it flows out through the fourth J_T throttle valve V4.

[0029] In this embodiment, when the system load is large (such as a load greater than 70%), the first refrigeration compressor C1, the second refrigeration compressor C2 and the third refrigeration compressor C3 operate simultaneously to maintain a high liquefaction efficiency; when the system load is small (such as less than or equal to 70%), the third refrigeration compressor C3 is turned off, and the first refrigeration compressor C1 and the second refrigeration compressor C2 operate, which can reduce costs while maintaining a high liquefaction efficiency.

[0030] In this embodiment, each circuit is provided with a J_T throttle valve, which generates low temperature by throttling isenthalpic expansion; at the same time, the pressure ratio of the refrigeration compressor and the refrigerant circulation volume of the refrigeration compressor can be adjusted within an appropriate range.

[0031] In some embodiments, the first cold box E1 is a pre-cooling liquefaction heat exchanger.

[0032] In some embodiments, the second cold box E2 is a liquefaction subcooling heat exchanger.

[0033] The first cold box E1 is used for pre-cooling and liquefaction, and the second cold box E2 is used for liquefaction and supercooling.

[0034] In some embodiments, the first refrigeration compressor C1 , the second refrigeration compressor C2 and the third refrigeration compressor C3 are all screw refrigeration compressors.

[0035] In some embodiments, the first J_T throttle valve V1 , the second J_T throttle valve V2 , the third J_T throttle valve V3 and the fourth J_T throttle valve V4 are all programmable valves.

[0036] In some embodiments, the scattered gas recovery and liquefaction system also includes a controller and a flow meter. The controller is respectively connected to the first refrigeration compressor C1, the second refrigeration compressor C2, the third refrigeration compressor C3, the first J_T throttle valve V1, the second J_T throttle valve V2, the third J_T throttle valve V3, the fourth J_T throttle valve V4 and the flow meter. The flow meter is arranged at the natural gas input pipeline. The flow meter is used to detect the intake volume of natural gas. The greater the intake volume, the greater the load of the system. When the intake volume of natural gas is greater than the set value, the controller turns on the three refrigeration compressors and the corresponding throttle valves. When the intake volume of natural gas is less than or equal to the set value, the controller turns on the first refrigeration compressor C1, the second refrigeration compressor C2 and the corresponding throttle valve, and turns off the third refrigeration compressor C3 and the corresponding throttle valve, thereby realizing automatic adjustment of the scattered gas recovery and liquefaction system.

[0037] In addition, the system load can be determined based on the operating parameters of the refrigeration compressor (such as discharge pressure, current, etc.), and then the controller can be used to automatically control the switching of the corresponding refrigeration compressor and throttle valve.

[0038] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Instead, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the concept described herein through the above teachings or techniques or knowledge in the relevant fields. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be protected by the claims appended hereto.

Claims

1. A scattered gas recovery liquefaction system, characterized in that: It includes a natural gas input pipeline, a first cold box, a second cold box, a first refrigeration compressor, a second refrigeration compressor, a third refrigeration compressor, a first J_T throttle valve, a second J_T throttle valve, a third J_T throttle valve and a fourth J_T throttle valve; The first cold box is provided with a first channel, a second channel, a third channel, a fourth channel, a fifth channel, a sixth channel and a seventh channel; The second cold box is provided with a first channel, a second channel and a third channel; The first refrigeration compressor, the third channel of the first cold box, the third channel of the second cold box, the third J_T throttle valve, the second channel of the second cold box, and the second channel of the first cold box are connected in sequence to form a loop; The second refrigeration compressor, the fifth channel of the first cold box, the second J_T throttle valve, and the fourth channel of the first cold box are connected in sequence to form a loop; The third refrigeration compressor, the seventh channel of the first cold box, the first J_T throttle valve, and the sixth channel of the first cold box are connected in sequence to form a loop; The natural gas input pipeline is connected to the first pipeline of the first cold box, the first pipeline of the second cold box and the fourth J_T throttle valve in sequence.

2. A scattered gas recovery liquefaction system according to claim 1, characterized in that: The first cold box is a pre-cooling liquefaction heat exchanger.

3. The scattered gas recovery and liquefaction system according to claim 1, characterized in that: The second cold box is a liquefaction subcooling heat exchanger.

4. The scattered gas recovery and liquefaction system according to claim 1, characterized in that: The first refrigeration compressor, the second refrigeration compressor and the third refrigeration compressor are all screw refrigeration compressors.

5. The scattered gas recovery and liquefaction system according to claim 1, characterized in that: The first J_T throttle valve, the second J_T throttle valve, the third J_T throttle valve and the fourth J_T throttle valve are all program-controlled valves.

6. The scattered gas recovery and liquefaction system according to claim 1, characterized in that: The scattered gas recovery and liquefaction system also includes a controller and a flow meter. The controller is respectively connected to the first refrigeration compressor, the second refrigeration compressor, the third refrigeration compressor, the first J_T throttle valve, the second J_T throttle valve, the third J_T throttle valve, the fourth J_T throttle valve and the flow meter. The flow meter is arranged at the natural gas input pipeline.

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