Energy-saving BOG gas recovery device

Abstract

The utility model belongs to the technical field of LNG (Liquefied Natural Gas) production and storage, and particularly relates to an energy-saving BOG (Boil Off Gas) recovery device. In order to solve the problems of resource waste, environmental pollution, high energy consumption, limited application scene and the like caused by the existing BOG gas utilization mode, the BOG gas generated by the LNG storage tank is subjected to pressure control by a pressure regulating valve, then is sent to an air bath type vaporizer for reheating and pressurized by a compressor, and is divided into three paths, one path is sent to an incinerator device to be used as combustion accompanying gas, and the other path is sent to an LNG storage tank to be used as combustion accompanying gas. One path is recycled from a raw material gas pipe network to improve the resource utilization efficiency, and the other path is used as emergency vent gas from a torch system.

Description

TECHNICAL FIELD

[0001] The utility model belongs to LNG production and storage technical field, concretely relates to an energy-saving BOG gas recovery device. BACKGROUND

[0002] BOG (Boil-Off Gas) refers to the gas produced by evaporation and flashing during the storage of liquefied natural gas (LNG) due to pressure reduction and absorption of external heat. BOG gas is mainly composed of methane and contains a small amount of ethane, nitrogen and other trace components. The proportion of these components depends on the composition and production process of the raw LNG. In the industrial production process, in order to reduce the generation and emission of BOG, high-performance thermal insulation materials and advanced insulation technology are usually used to slow down the heat exchange between LNG and the external environment. However, LNG storage devices will inevitably produce BOG gas.

[0003] Currently, there are three main ways to utilize this gas: 1) direct emission into the atmosphere, which causes resource waste and environmental pollution; 2) recovery into the inlet of a cryogenic separation device, which requires the use of low-temperature high-pressure ratio compressors, increasing device investment and energy consumption; 3) as tail gas for incineration, which causes resource waste and environmental pollution; 4) direct recovery into the raw gas pipeline network, which has the disadvantages of high energy consumption and large equipment investment; 5) pressurized delivery to the gas pipeline network, which is limited in use and only suitable for enterprises with stable downstream users and high and stable fuel gas demand.

[0004] To address the above problems, the present invention proposes a new type of BOG gas recovery device to save energy, reduce environmental pollution and improve enterprise economic efficiency. SUMMARY

[0005] The utility model provides a kind of energy-saving BOG gas recovery device for the above problems, from the BOG gas generated by LNG storage tank, after pressure regulating valve control pressure, send to air bath type vaporizer reheat, compressor pressurization, divide into three ways, one way to incinerator device as accompanying combustion gas use, one way to raw gas pipeline network recovery, improve resource utilization efficiency, one way to flare system as emergency vent gas.

[0006] To achieve the above purpose, the utility model adopts the following technical scheme:

[0007] The utility model provides an energy -conserving BOG gas recovery device, including LNG storage tank, air bath type gasifier and compressor, the outlet of LNG storage tank is connected with the import pipeline of air bath type gasifier, the outlet of air bath type gasifier is connected with the import pipeline of compressor, and the outlet of compressor is connected with the import pipeline of incinerator device, raw material gas pipe network, torch system respectively.

[0008] Further, a pressure regulating valve is arranged on the pipeline between the outlet of the LNG storage tank and the inlet of the air bath type gasifier.

[0009] Further, a nitrogen regulating valve is also included, and the outlet of the nitrogen regulating valve is connected with the import pipeline of the air bath type gasifier.

[0010] Further, two air bath type gasifiers are arranged in parallel.

[0011] Further, a temperature instrument switch is arranged on the pipeline between the outlet of the air bath type gasifier and the inlet of the compressor.

[0012] Further, the compressor is a screw compressor.

[0013] Compared with the prior art, the utility model has the following advantages:

[0014] 1. The problem of BOG gas not being recycled, directly polluting the environment, and wasting resources is solved.

[0015] 2. The problem of the BOG gas compressor being large in investment and harsh in production operation conditions is solved.

[0016] 3. The problem of the BOG gas being sent to the fuel gas pipe network and being high in technical requirements for downstream users and being limited in use scenarios is solved.

[0017] 4. The utilization process of the BOG gas can be flexibly adjusted according to the actual production conditions, and the resource utilization efficiency and enterprise economic benefits are improved. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a structure schematic view of an energy -conserving BOG gas recovery device. DETAILED DESCRIPTION

[0019] In order to further illustrate the technical scheme of the utility model, the utility model will be further described through examples.

[0020] For example, Figure 1As shown, the energy-saving BOG gas recovery device of the embodiment comprises an LNG storage tank 1, an air bath vaporizer 3 and a compressor 6. The outlet of the LNG storage tank 1 is connected with the inlet pipeline of the air bath vaporizer 3. The outlet of the air bath vaporizer 3 is connected with the inlet pipeline of the compressor 6. The outlet of the compressor 6 is connected with the inlet pipeline of a burning furnace device 7, a raw gas pipeline network 8 and a flare system 9 respectively.

[0021] A pressure regulating valve 2 is arranged on the pipeline between the outlet of the LNG storage tank 1 and the inlet of the air bath vaporizer 3 for controlling pressure. The air bath vaporizer 3 is arranged in parallel with two air bath vaporizers, one for normal operation and the other for ice melting and temperature recovery. A temperature instrument switch 5 is arranged on the pipeline between the outlet of the air bath vaporizer 3 and the inlet of the compressor 6.

[0022] The compressor 6 of the embodiment is a screw compressor.

[0023] The device further comprises a nitrogen regulating valve 4, the outlet of which is connected with the inlet pipeline of the air bath vaporizer 3. When the inlet pressure of the air bath vaporizer 3 is lower than 5 KPa, nitrogen is supplemented to maintain stable pressure.

[0024] In addition, various valves are arranged on the corresponding pipelines of the device for controlling pressure, flow and the like.

[0025] The use process of the device is as follows:

[0026] The low-temperature BOG gas from the LNG storage tank 1, with a temperature of -162℃ and a pressure of 20 KPa, is sent to the inlet of the air bath vaporizer 3 after the pressure is controlled by the pressure regulating valve 2, and is heated to 0-30℃ by the air bath vaporizer 3 and then enters the inlet of the compressor 6. The air bath vaporizer 3 is arranged with two air bath vaporizers, one for normal operation and the other for ice melting and temperature recovery, and the two air bath vaporizers are switched over once every 12 hours on average. In order to protect the safe and stable operation of the device, a nitrogen supplement regulating valve is arranged at the inlet of the air bath vaporizer 3. When the inlet pressure of the air bath vaporizer 3 is lower than 5 KPa, the nitrogen supplement regulating valve is automatically opened to supplement nitrogen and maintain stable pressure. A temperature instrument switch 5 and a low-temperature interlock are arranged at the inlet of the compressor 6. When the temperature at the inlet of the compressor 6 is lower than -5℃, the interlock stops the compressor 6. The BOG gas after being pressurized by the compressor 6 reaches a pressure of 0.2 MPa and is divided into three paths. One path is sent to the burning furnace device 7 after the flow is controlled by a BOG to burning furnace regulating valve, and is used as a waste gas accompanying gas under abnormal conditions of start-up and shut-down and production to ensure the compliant disposal of the waste gas. Another path is sent to the raw gas pipeline network 8 after the flow is controlled by a BOG to raw gas pipeline network regulating valve, and is used as raw gas for further use. The third path is sent to the flare system 9 for burning after the pressure is controlled by a BOG to flare system regulating valve, and is disposed of in the flare system under the conditions of overall device shut-down or abnormal production.

[0027] The above device realizes efficient recycling of BOG gas, improves the economic benefits of enterprises and creates good environmental protection benefits.

[0028] The main features and advantages of the present application are shown and described above, for those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and can be realized in other specific forms without departing from the spirit or basic characteristics of the present application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, the scope of the present application is defined by the appended claims rather than the above description, therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application.

[0029] In addition, it should be understood that although the present application is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be properly combined to form other embodiments that those skilled in the art can understand.

Claims

1. An energy-saving BOG gas recovery device, characterized in that, It includes an LNG storage tank (1), an air bath vaporizer (3) and a compressor (6). The outlet of the LNG storage tank (1) is connected to the inlet pipeline of the air bath vaporizer (3), the outlet of the air bath vaporizer (3) is connected to the inlet pipeline of the compressor (6), and the outlet of the compressor (6) is connected to the inlet pipeline of the incinerator unit (7), the raw gas pipeline network (8), and the flare system (9).

2. The energy-saving BOG gas recovery device according to claim 1, characterized in that, A pressure regulating valve (2) is installed on the pipeline between the outlet of the LNG storage tank (1) and the inlet of the air bath vaporizer (3).

3. The energy-saving BOG gas recovery device according to claim 1, characterized in that, It also includes a nitrogen regulating valve (4), the outlet of which is connected to the inlet pipe of the air bath vaporizer (3).

4. The energy-saving BOG gas recovery device according to claim 1, characterized in that, Two air-bath vaporizers (3) are connected in parallel.

5. The energy-saving BOG gas recovery device according to claim 1, characterized in that, A temperature instrument switch (5) is installed on the pipeline between the outlet of the air bath vaporizer (3) and the inlet of the compressor (6).

6. The energy-saving BOG gas recovery device according to claim 1, characterized in that, The compressor (6) is a screw compressor.

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