BOG compressor system and control method thereof

Abstract

The invention discloses a BOG compressor system and a control method thereof, and relates to the technical field of BOG compression. Comprising a gas heat exchanger, a temperature transmitter, a temperature controller, a filter screen, a BOG compressor, a temperature regulating valve and a gas mixer, a first gas inlet of the gas heat exchanger is communicated with a BOG buffer tank, a gas outlet of the gas mixer is communicated with an after-condenser, and a first gas outlet of the gas heat exchanger, the BOG compressor and a first gas inlet of the gas mixer are sequentially communicated; the filter screen is arranged between a first gas outlet of the gas heat exchanger and the BOG compressor, one end of the temperature regulating valve is connected between the BOG compressor and a first gas inlet of the gas mixer, and the other end of the temperature regulating valve is communicated with a second gas inlet of the gas heat exchanger; and a second gas outlet of the gas heat exchanger is communicated with a second gas inlet of the gas mixer. According to the invention, the blockage of a condensed liquid film of the filter screen can be effectively prevented, and a guarantee is provided for the lasting and reliable operation of the BOG compressor.

Description

Technical Field

[0001] This invention belongs to the field of BOG compression technology, specifically relating to a BOG compressor system and its control method. Background Technology

[0002] Natural gas, as a clean and efficient energy source, is widely used in national production and daily life. To meet demand, the fundamentals of the domestic natural gas market will further improve, and the import volume of liquefied natural gas (LNG) is expected to rebound strongly.

[0003] LNG typically needs to be unloaded and stored at LNG receiving terminals, and then vaporized and transported or transferred by tanker trucks. Boil-off gas (BOG) is generated throughout the process, and the BOG gas is usually compressed by a BOG compressor and then condensed back into LNG by a recondenser for recovery.

[0004] To protect the BOG compressor, a filter screen is usually installed at its inlet. Under normal circumstances, BOG gas is composed of methane with very little heavy components. The BOG gas temperature at the compressor inlet is higher than its dew point temperature, so a liquid film will not condense on the filter screen, causing blockage.

[0005] During the loading and unloading of LNG vessels and the purging and replacement of equipment and pipelines at LNG receiving terminals, the content of heavy components in BOG gas increases, causing the BOG gas dew point temperature to be much higher than the BOG gas temperature. When BOG gas with a higher content of heavy components passes through the BOG compressor inlet filter, it will condense into a liquid film on the filter, causing blockage.

[0006] Especially during periods of high LNG receiving terminal throughput and frequent LNG vessel unloading, the frequency of BOG compressor inlet filter clogging increases, reducing BOG compressor availability and even leading to situations where BOG cannot be recovered in time and ultimately has to be disposed of by the flare system.

[0007] Therefore, how to provide an effective solution to prevent clogging of the BOG compressor inlet filter has become a pressing problem to be solved in the existing technology. Summary of the Invention

[0008] The purpose of this invention is to provide a BOG compressor system and its control method to solve the above-mentioned problems existing in the prior art.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a BOG compressor system, comprising: a gas heat exchanger, a temperature transmitter, a temperature controller, a filter, a BOG compressor, a temperature regulating valve, and a gas mixer. The first inlet of the gas heat exchanger is connected to a BOG buffer tank, and the outlet of the gas mixer is connected to a re-condenser. The first outlet of the gas heat exchanger, the BOG compressor, and the first inlet of the gas mixer are sequentially connected. The filter is disposed between the first outlet of the gas heat exchanger and the BOG compressor. One end of the temperature regulating valve is connected between the BOG compressor and the first inlet of the gas mixer, and the other end of the temperature regulating valve is connected to the second inlet of the gas heat exchanger. The second outlet of the gas heat exchanger is connected to the second inlet of the gas mixer.

[0011] The temperature controller is electrically connected to the temperature transmitter and the temperature regulating valve respectively. The temperature transmitter is used to detect the temperature of BOG gas entering the filter screen from the first outlet of the gas heat exchanger. When the BOG gas temperature is lower than the dew point temperature, the temperature controller controls the temperature regulating valve to increase the opening degree to adjust the amount of BOG gas from the BOG compressor entering the second inlet of the gas heat exchanger, so as to maintain the temperature of BOG gas entering the filter screen from the first outlet of the gas heat exchanger above the dew point temperature.

[0012] Based on the above disclosure, the BOG compressor system provided by this invention comprises a gas heat exchanger, a temperature transmitter, a temperature controller, a filter, a BOG compressor, a temperature regulating valve, and a gas mixer. The first inlet of the gas heat exchanger is connected to the BOG buffer tank, and the outlet of the gas mixer is connected to the re-condenser. The first outlet of the gas heat exchanger, the first inlet of the BOG compressor, and the first outlet of the gas mixer are sequentially connected. The filter is positioned between the first outlet of the gas heat exchanger and the BOG compressor. One end of the temperature regulating valve is connected between the BOG compressor and the first inlet of the gas mixer. One end is connected to the second inlet of the gas heat exchanger, and the second outlet of the gas heat exchanger is connected to the second inlet of the gas mixer. A temperature controller is electrically connected to a temperature transmitter and a temperature regulating valve. The temperature transmitter detects the temperature of the BOG gas entering the filter from the first outlet of the gas heat exchanger. The temperature controller controls the temperature regulating valve to increase its opening when the BOG gas temperature is lower than the dew point temperature, thereby regulating the amount of BOG gas from the BOG compressor entering the second inlet of the gas heat exchanger. This ensures that the temperature of the BOG gas entering the filter from the first outlet of the gas heat exchanger remains above the dew point temperature. In this way, the high-temperature BOG gas at the outlet of the BOG compressor can be used to heat the low-temperature BOG gas at its inlet, saving energy and ensuring that the temperature of the BOG gas entering the filter remains above the dew point temperature. This effectively prevents the condensate film from clogging the filter, ensuring the long-term and reliable operation of the BOG compressor.

[0013] In one possible design, the temperature controller is also used to control the temperature regulating valve to reduce its opening when the BOG gas temperature is higher than the first preset temperature, so as to regulate the amount of BOG gas from the BOG compressor and entering the second inlet of the gas heat exchanger, so that the temperature of the BOG gas entering the filter from the first outlet of the gas heat exchanger is maintained between the dew point temperature and the second preset temperature.

[0014] Wherein, the first preset temperature is higher than the second preset temperature, and the second preset temperature is higher than the dew point temperature.

[0015] In one possible design, the BOG compressor system further includes a filter inlet pressure gauge and a filter outlet pressure gauge. The filter inlet pressure gauge is located between the first outlet of the gas heat exchanger and the filter, and the filter outlet pressure gauge is located between the filter and the BOG compressor. The filter inlet pressure gauge is used to detect the first BOG gas pressure entering the filter, and the filter outlet pressure gauge is used to detect the second BOG gas pressure entering the BOG compressor from the filter.

[0016] In one possible design, the temperature controller is also electrically connected to the filter inlet pressure gauge and the filter outlet pressure gauge, respectively. The temperature controller is also used to adjust the opening of the temperature regulating valve so that the difference between the first BOG gas pressure and the second BOG gas pressure is less than or equal to the preset threshold when the first BOG gas pressure is higher than the second BOG gas pressure, the difference between the first BOG gas pressure and the second BOG gas pressure is higher than a preset threshold, and the temperature transmitter data is abnormal.

[0017] In one possible design, the BOG compressor system also includes a shut-off valve connected between the BOG compressor and the first inlet of the gas mixer.

[0018] In one possible design, the BOG compressor system also includes a pressure regulating valve connected between the BOG compressor and the first inlet of the gas mixer.

[0019] In a second aspect, the present invention provides a control method for a BOG compressor system, applied to the BOG compressor system described in the first aspect or any possible design of the first aspect, comprising:

[0020] The temperature of BOG gas entering the filter screen from the first outlet of the gas heat exchanger is detected by the temperature transmitter.

[0021] When the BOG gas temperature is lower than the dew point temperature, the temperature controller controls the temperature regulating valve to increase its opening to adjust the amount of BOG gas from the BOG compressor entering the second inlet of the gas heat exchanger, so that the temperature of the BOG gas entering the filter from the first outlet of the gas heat exchanger is maintained above the dew point temperature.

[0022] In one possible design, the method further includes:

[0023] When the BOG gas temperature is higher than the first preset temperature, the temperature controller controls the temperature regulating valve to reduce the opening to adjust the amount of BOG gas from the BOG compressor that enters the second inlet of the gas heat exchanger, so that the temperature of the BOG gas entering the filter screen from the first outlet of the gas heat exchanger is maintained between the dew point temperature and the second preset temperature.

[0024] Wherein, the first preset temperature is higher than the second preset temperature, and the second preset temperature is higher than the dew point temperature.

[0025] Beneficial effects:

[0026] This invention utilizes the high-temperature BOG gas at the outlet of the BOG compressor to heat the low-temperature BOG gas at the inlet, which not only saves energy but also ensures that the temperature of the BOG gas entering the filter is maintained above the dew point temperature, effectively preventing the condensate film from clogging the filter. This provides a guarantee for the long-term and reliable operation of the BOG compressor and facilitates practical application and promotion. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the BOG compressor system provided in an embodiment of this application;

[0028] Figure 2 A flowchart of the control method for the BOG compressor system provided in the embodiments of this application.

[0029] icon:

[0030] 2-Gas heat exchanger; 4-Temperature transmitter; 5-Temperature controller; 6-Filter inlet pressure gauge; 7-Filter; 8-Filter outlet pressure gauge; 9-BOG compressor; 11-Temperature regulating valve; 14-Shut-off valve; 15-Pressure regulating valve; 17-Gas mixer. Detailed Implementation

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be briefly introduced below in conjunction with the accompanying drawings and descriptions of the embodiments or the prior art. Obviously, the following description of the structure of the accompanying drawings is only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.

[0032] It should be understood that although the terms first, second, etc., may be used herein to describe various units, these units should not be limited by these terms. These terms are only used to distinguish one unit from another. For example, a first unit may be referred to as a second unit, and similarly, a second unit may be referred to as a first unit, without departing from the scope of the exemplary embodiments of the invention.

[0033] It should be understood that the term "and / or" that may appear in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. The term " / and" that may appear in this document describes another relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " that may appear in this document generally indicates that the related objects before and after it are in an "or" relationship.

[0034] To prevent clogging of the BOG compressor inlet filter, this application provides a BOG compressor system and its control method, which can effectively prevent condensate film clogging of the filter.

[0035] like Figure 1 As shown, the first aspect of this embodiment provides a BOG compressor system, which includes a gas heat exchanger 2, a temperature transmitter 4, a temperature controller 5, a filter 7, a BOG compressor 9, a temperature regulating valve 11, and a gas mixer 17.

[0036] The gas heat exchanger 2 has a first inlet connected to the BOG buffer tank, and the gas mixer 17 has an outlet connected to the recondenser. The gas heat exchanger 2, the BOG compressor 9, and the gas mixer 17 are connected in sequence. The filter screen 7 is located between the gas heat exchanger 2 and the BOG compressor 9. One end of the temperature regulating valve 11 is connected between the BOG compressor 9 and the gas mixer 17, and the other end of the temperature regulating valve 11 is connected to the gas heat exchanger 2's second inlet. The gas heat exchanger 2's second outlet is connected to the gas mixer 17's second inlet.

[0037] The temperature controller 5 is electrically connected to the temperature transmitter 4 and the temperature regulating valve 11 respectively. The temperature transmitter 4 is used to detect the temperature of BOG gas entering the filter screen 7 from the first outlet of the gas heat exchanger 2. The temperature controller 5 is used to control the temperature regulating valve 11 to increase the opening degree when the BOG gas temperature is lower than the dew point temperature, so as to regulate the amount of BOG gas from the BOG compressor 9 entering the second inlet of the gas heat exchanger 2, so as to maintain the temperature of BOG gas entering the filter screen 7 from the first outlet of the gas heat exchanger 2 above the dew point temperature.

[0038] When BOG gas is pressurized and recovered through the BOG compressor system, the low-pressure, low-temperature BOG gas from the BOG buffer tank enters the gas heat exchanger 2 through the first inlet of the gas heat exchanger 2. The low-pressure, low-temperature BOG gas entering the gas heat exchanger 2 exchanges heat with a portion of the high-temperature BOG gas from the outlet of the BOG compressor 9. The temperature of the low-pressure, low-temperature BOG gas rises and becomes low-pressure, medium-temperature BOG gas. Then, it passes through the filter screen 7 and enters the BOG compressor 9.

[0039] Temperature transmitter 4 can be installed on the pipeline between the first outlet of gas heat exchanger 2 and filter screen 7. It is used to detect the temperature of BOG gas entering the filter screen 7 from the first outlet of gas heat exchanger 2 and feed it back to temperature controller 5. When the BOG gas temperature is lower than the dew point temperature, temperature controller 5 controls the temperature regulating valve 11 to increase the opening, thereby increasing the amount of high-temperature BOG gas from BOG compressor 9 entering the second inlet of gas heat exchanger 2. This increases the temperature of BOG gas in the tube side, keeping the temperature of BOG gas entering the filter screen 7 from the first outlet of gas heat exchanger 2 above the dew point temperature. This effectively prevents the condensate film of the filter screen from clogging and ensures the long-term and reliable operation of BOG compressor 9.

[0040] In one or more embodiments, the temperature controller 5 is further configured to control the temperature regulating valve 11 to reduce its opening when the BOG gas temperature is higher than a first preset temperature, thereby regulating the amount of BOG gas from the BOG compressor 9 entering the second inlet of the gas heat exchanger 2, so that the temperature of the BOG gas entering the filter 7 from the first outlet of the gas heat exchanger 2 is maintained between the dew point temperature and the second preset temperature. The first preset temperature is higher than the second preset temperature, and the second preset temperature is higher than the dew point temperature. This prevents the BOG gas entering the BOG compressor 9 from being too hot.

[0041] like Figure 1 As shown, to monitor for clogging of the filter 7 due to other reasons, the BOG compressor system provided in this embodiment of the application is further equipped with a filter inlet pressure gauge 6 and a filter outlet pressure gauge 8. The filter inlet pressure gauge 6 is located between the first outlet of the gas heat exchanger 2 and the filter 7, and the filter outlet pressure gauge 8 is located between the filter 7 and the BOG compressor 9. The filter inlet pressure gauge 6 is used to detect the first BOG gas pressure entering the filter 7, and the filter outlet pressure gauge 8 is used to detect the second BOG gas pressure entering the BOG compressor 9 from the filter 7. By detecting the first BOG gas pressure entering the filter 7 and the second BOG gas pressure entering the BOG compressor 9 from the filter 7, it is very convenient to determine whether the filter 7 is clogged due to other reasons.

[0042] In one or more embodiments, the temperature controller 5 is also electrically connected to the filter inlet pressure gauge 6 and the filter outlet pressure gauge 8, respectively. The temperature controller 5 is further configured to adjust the opening of the temperature regulating valve 11 so that the difference between the first BOG gas pressure and the second BOG gas pressure is less than or equal to the preset threshold when the first BOG gas pressure is higher than the second BOG gas pressure, the difference between the first BOG gas pressure and the second BOG gas pressure is higher than a preset threshold, and the temperature transmitter data is abnormal. Thus, when the temperature transmitter 4 fails to accurately measure the temperature of the BOG gas entering the filter 7 due to a malfunction, pressure measurement can be used to detect whether the filter 7 may be clogged with condensate film due to excessively low temperature, further ensuring the sustained and reliable operation of the BOG compressor.

[0043] Please see Figure 1 The BOG compressor system provided in this application embodiment also includes a shut-off valve 14 and a pressure regulating valve 15. The shut-off valve 14 is connected between the BOG compressor 9 and the first air inlet of the gas mixer 17, and the pressure regulating valve 15 is connected between the BOG compressor 9 and the first air inlet of the gas mixer 17.

[0044] The high-pressure, high-temperature BOG gas passing through the temperature regulating valve 11 and the gas heat exchanger 2 experiences a decrease in both temperature and pressure. Therefore, a pressure regulating valve 15 is installed between the BOG compressor 9 and the first inlet of the gas mixer 17 to ensure that the BOG gas pressure entering the second inlet of the gas mixer 17 meets the pressure requirements of the gas mixer 17. It is understandable that if the gas mixer 17 has an automatic pressure regulation function, or if the pressure drop of the high-temperature, high-pressure BOG gas passing through the temperature regulating valve 11 and the gas heat exchanger 2 is small and meets the pressure requirements of the gas mixer 17, the pressure regulating valve 15 may not be necessary.

[0045] In addition, if there is no high temperature limit on BOG gas at the inlet of BOG compressor 9, the temperature regulating valve 11 can be fully opened and the shut-off valve 14 can be closed to simplify the operation. If the temperature of BOG gas from the BOG buffer tank is higher than the dew point temperature, the temperature regulating valve 11 can be closed and the shut-off valve 14 can be opened to simplify the operation.

[0046] In summary, the BOG compressor system provided by this invention can use the high-temperature BOG gas at the outlet of the BOG compressor to heat the low-temperature BOG gas at the inlet, which not only saves energy, but also ensures that the temperature of the BOG gas entering the filter is maintained above the dew point temperature, effectively preventing the condensate film of the filter from clogging. This provides a guarantee for the long-term and reliable operation of the BOG compressor and facilitates practical application and promotion.

[0047] Please see Figure 2 The second aspect of this application provides a control method for a BOG compressor system, which is applied to the BOG compressor system described in the first aspect or any possible design of the first aspect. The control method for the BOG compressor system may include, but is not limited to, the following steps S201-S202.

[0048] Step S201. Detect the temperature of BOG gas entering the filter screen from the first outlet of the gas heat exchanger using a temperature transmitter.

[0049] Step S202. When the BOG gas temperature is lower than the dew point temperature, the temperature regulating valve is opened by controlling the temperature controller to adjust the amount of BOG gas from the BOG compressor that enters the second inlet of the gas heat exchanger, so that the temperature of the BOG gas entering the filter screen from the first outlet of the gas heat exchanger is maintained above the dew point temperature.

[0050] In one possible design, the method further includes:

[0051] When the BOG gas temperature is higher than the first preset temperature, the temperature controller controls the temperature regulating valve to reduce the opening to adjust the amount of BOG gas from the BOG compressor that enters the second inlet of the gas heat exchanger, so that the temperature of the BOG gas entering the filter screen from the first outlet of the gas heat exchanger is maintained between the dew point temperature and the second preset temperature.

[0052] Wherein, the first preset temperature is higher than the second preset temperature, and the second preset temperature is higher than the dew point temperature.

[0053] The working process, working details and technical effects of the control method for the BOG compressor system provided in the second aspect of this embodiment can be found in the first aspect of the embodiment, and will not be repeated here.

[0054] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A BOG compressor system, characterized in that, include: The gas heat exchanger (2), temperature transmitter (4), temperature controller (5), filter (7), BOG compressor (9), temperature regulating valve (11), and gas mixer (17) are connected. The first inlet of the gas heat exchanger (2) is connected to the BOG buffer tank, and the outlet of the gas mixer (17) is connected to the recondenser. The first outlet of the gas heat exchanger (2), the BOG compressor (9), and the first inlet of the gas mixer (17) are connected in sequence. The filter (7) is located between the first outlet of the gas heat exchanger (2) and the BOG compressor (9). One end of the temperature regulating valve (11) is connected between the BOG compressor (9) and the first inlet of the gas mixer (17), and the other end of the temperature regulating valve (11) is connected to the second inlet of the gas heat exchanger (2). The second outlet of the gas heat exchanger (2) is connected to the second inlet of the gas mixer (17). The temperature controller (5) is electrically connected to the temperature transmitter (4) and the temperature regulating valve (11) respectively. The temperature transmitter (4) is used to detect the temperature of BOG gas entering the filter screen (7) from the first outlet of the gas heat exchanger (2). The temperature controller (5) is used to control the temperature regulating valve (11) to increase the opening degree when the BOG gas temperature is lower than the dew point temperature, so as to regulate the amount of BOG gas from the BOG compressor (9) entering the second inlet of the gas heat exchanger (2) so that the temperature of BOG gas entering the filter screen (7) from the first outlet of the gas heat exchanger (2) is maintained above the dew point temperature.

2. The BOG compressor system according to claim 1, characterized in that, The temperature controller (5) is also used to control the temperature regulating valve (11) to reduce the opening when the BOG gas temperature is higher than the first preset temperature, so as to regulate the amount of BOG gas from the BOG compressor (9) and entering the second inlet of the gas heat exchanger (2) so that the temperature of the BOG gas entering the filter screen (7) from the first outlet of the gas heat exchanger (2) is maintained between the dew point temperature and the second preset temperature. Wherein, the first preset temperature is higher than the second preset temperature, and the second preset temperature is higher than the dew point temperature.

3. The BOG compressor system according to claim 1, characterized in that, It also includes a filter inlet pressure gauge (6) and a filter outlet pressure gauge (8). The filter inlet pressure gauge (6) is located between the first outlet of the gas heat exchanger (2) and the filter (7). The filter outlet pressure gauge (8) is located between the filter (7) and the BOG compressor (9). The filter inlet pressure gauge (6) is used to detect the first BOG gas pressure entering the filter (7). The filter outlet pressure gauge (8) is used to detect the second BOG gas pressure entering the BOG compressor (9) from the filter (7).

4. The BOG compressor system according to claim 3, characterized in that, The temperature controller (5) is also electrically connected to the filter inlet pressure gauge (6) and the filter outlet pressure gauge (8), respectively. The temperature controller (5) is also used to adjust the opening of the temperature regulating valve (11) so that the difference between the first BOG gas pressure and the second BOG gas pressure is less than or equal to the preset threshold when the first BOG gas pressure is higher than the second BOG gas pressure, the difference between the first BOG gas pressure and the second BOG gas pressure is higher than a preset threshold, and the temperature transmitter data is abnormal.

5. The BOG compressor system according to claim 1, characterized in that, It also includes a shut-off valve (14) connected between the BOG compressor (9) and the first air inlet of the gas mixer (17).

6. The BOG compressor system according to claim 1, characterized in that, It also includes a pressure regulating valve (15) connected between the BOG compressor (9) and the first air inlet of the gas mixer (17).

7. A control method for a BOG compressor system, applied to the BOG compressor system according to any one of claims 1-6, characterized in that, include: The temperature of the BOG gas entering the filter screen (7) from the first outlet of the gas heat exchanger (2) is detected by the temperature transmitter (4); When the BOG gas temperature is lower than the dew point temperature, the temperature controller (5) controls the temperature regulating valve (11) to increase the opening degree, so as to regulate the amount of BOG gas from the BOG compressor (9) and entering the second inlet of the gas heat exchanger (2), so that the temperature of the BOG gas entering the filter screen (7) from the first outlet of the gas heat exchanger (2) is maintained above the dew point temperature.

8. The method according to claim 7, characterized in that, The method further includes: When the BOG gas temperature is higher than the first preset temperature, the temperature controller (5) controls the temperature regulating valve (11) to reduce the opening to adjust the amount of BOG gas from the BOG compressor (9) and entering the second inlet of the gas heat exchanger (2), so that the temperature of the BOG gas entering the filter screen (7) from the first outlet of the gas heat exchanger (2) is maintained between the dew point temperature and the second preset temperature. Wherein, the first preset temperature is higher than the second preset temperature, and the second preset temperature is higher than the dew point temperature.

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