Boil-off gas treatment system
By designing an evaporative gas treatment system using cold energy utilization system in the liquefied natural gas receiving station, the problem of high energy consumption in the existing system is solved, and the energy consumption is significantly reduced and cost optimization is achieved.
Patent Information
- Application Number
- CN202510147234.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-10
- Publication Date
- 2025-05-06
AI Technical Summary
In the existing liquefied natural gas receiving stations, the energy consumption of the low-temperature evaporation gas treatment system is high, resulting in high power consumption of the compressor, high maintenance frequency and high energy consumption of the air thermostat.
An evaporation gas treatment system is designed to utilize the low-temperature evaporation gas through a cold energy utilization system, reduce the manufacturing cost and energy consumption of the compressor, and optimize the compressor load through the controller and data acquisition module.
It has achieved the reduction of energy consumption of evaporation gas treatment, avoided high-energy and high-cost low-temperature compressors, reduced the cost of evaporation gas treatment, and reduced the energy consumption by about 70%.
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Abstract
Description
Technical Field
[0001] The present application relates to the technical field of liquefied natural gas, and in particular to a boil-off gas processing system. Background Art
[0002] LNG will be continuously gasified in the LNG storage tanks in the LNG receiving station to produce low-temperature boil-off gas (BOG). The temperature range of the low-temperature boil-off gas is -155℃~-130℃. The current BOG treatment scheme for LNG receiving stations is as follows: 1. After the low-temperature BOG is pressurized by the low-temperature BOG compressor in two stages, it will be heat exchanged and decompressed in the air temperature controller before entering the medium- and low-pressure natural gas regional pipeline network; 2. After the low-temperature BOG is pressurized by the low-temperature BOG compressor, it will be condensed in the recondenser and returned to the LNG storage tank; 3. After the low-temperature BOG is pressurized by the low-temperature BOG compressor, it will continue to be pressurized and sent to the high-pressure pipeline network.
[0003] LNG peak-shaving stations and some newly added LNG receiving stations with medium and low pressure natural gas regional pipeline supply functions (gas supply pressure: 1-4 barg, temperature not less than 2°C). Currently, LNG receiving stations use the first solution mentioned above to supply medium and low pressure natural gas municipal pipelines.
[0004] The low-temperature BOG compressor (2-stage reciprocating compressor) of the LNG receiving station is designed to match the operating pressure of the recondenser with a discharge pressure of 7.5 barg, which is much higher than the pressure of the medium and low-pressure natural gas regional pipeline network. If the low-temperature BOG compressor is directly reduced to the pressure of the regional gas pipeline network for long-term operation, it will face the following problems: 1. The first and second stage exhaust pressures of the compressor are low and the exhaust temperature is very low; 2. The compressor operates far away from the design working conditions for a long time, and cannot guarantee stable operation, and the maintenance frequency is high; 3. The power consumption of the compressor is high; 4. Since the exhaust temperature of the compressor is very low, the air temperature controller needs to run continuously, which consumes a lot of energy. Therefore, a low-energy low-temperature evaporation gas treatment system is urgently needed. Summary of the invention
[0005] The purpose of the present application is to provide a boil-off gas treatment system, which can reduce the energy consumption of boil-off gas treatment.
[0006] To achieve the above objectives, this application provides the following solutions:
[0007] In a first aspect, the present application provides a boil-off gas processing system, comprising: a liquefied natural gas storage tank, a boil-off gas heat exchanger, a compressor, a metered external transmission, a cold energy utilization system, a controller and a data acquisition module, wherein the gas phase outlet of the liquefied natural gas storage tank is connected to the boil-off gas inlet of the boil-off gas heat exchanger, the boil-off gas outlet pipeline of the boil-off gas heat exchanger is sequentially connected to the compressor and the metered external transmission, the refrigerant outlet of the boil-off gas heat exchanger is connected to the refrigerant inlet of the cold energy utilization system, the hot refrigerant outlet of the cold energy utilization system is connected to the hot refrigerant inlet of the boil-off gas heat exchanger, and the controller is respectively connected to the data acquisition module and the compressor; the refrigerant output by the boil-off gas heat exchanger enters the cold energy utilization system for heat exchange and then returns to the boil-off gas heat exchanger;
[0008] The data acquisition module is used to acquire the first pressure of the liquefied natural gas storage tank, and the controller is used to control the load of the compressor according to the first pressure; the metering output is used to output the boil-off gas after metering.
[0009] Optionally, the controller includes a compressor control unit, which is used to: shut down the compressor when the first pressure is lower than a set value, start the compressor when the first pressure is higher than the set value, and control the load of the compressor to increase with the increase of the first pressure and decrease with the decrease of the first pressure.
[0010] Optionally, the data acquisition module includes a first pressure transmitter; the first pressure transmitter is used to detect the first pressure of the liquefied natural gas storage tank.
[0011] Optionally, the data acquisition module includes a second pressure transmitter and a temperature transmitter; the second pressure transmitter and the temperature transmitter are both arranged on the pipeline between the evaporating gas outlet of the evaporating gas heat exchanger and the compressor, the second pressure transmitter is used to detect the intake pressure of the compressor, and the temperature transmitter is used to detect the intake temperature of the compressor.
[0012] Optionally, the boil-off gas processing system further includes a first control valve, which is connected to the controller and is arranged between the gas phase outlet of the liquefied natural gas storage tank and the boil-off gas inlet of the boil-off gas heat exchanger, and the controller is used to control the opening of the first control valve according to the intake pressure and load of the compressor.
[0013] Optionally, the evaporative gas processing system also includes a second control valve, which is connected to the controller and is arranged between the refrigerant outlet of the evaporative gas heat exchanger and the refrigerant inlet of the cold energy utilization system. The controller controls the load of the cold energy utilization system according to the evaporative gas temperature.
[0014] Optionally, the cold energy utilization system includes an ice maker and a cold water heat exchanger, the refrigerant output by the evaporative gas heat exchanger enters the cold water heat exchanger or returns to the evaporative gas heat exchanger after heat exchange in the ice maker, and the cold water heat exchanger is used to connect to an air conditioning system.
[0015] Optionally, the evaporative gas heat exchanger is a siphon type gas heat exchanger, and the temperature difference range of the siphon type gas heat exchanger is 80°C to 115°C.
[0016] Optionally, the compressor is a single-stage compressor.
[0017] Optionally, the adjustment range of the compressor load is 50% to 100% of the rated load.
[0018] According to the specific embodiments provided in this application, this application discloses the following technical effects:
[0019] The present application provides a boil-off gas processing system suitable for medium and low pressure natural gas regional pipeline networks, which utilizes the energy of low-temperature boil-off gas through a cold energy utilization system, reduces the manufacturing cost and energy consumption of the compressor, and makes full use of the cold energy of the low-temperature boil-off gas, thereby reducing the energy consumption of boil-off gas processing. At the same time, it can avoid the use of high-energy consumption and high-cost low-temperature compressors, thereby reducing the cost of boil-off gas processing. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0021] Figure 1 A schematic structural diagram of an evaporation gas treatment system provided in one embodiment of the present application.
[0022] Reference numerals:
[0023] 1-first pressure transmitter, 2-first control valve, 3-evaporating gas heat exchanger, 4-temperature transmitter, 5-second pressure transmitter, 6-controller, 7-compressor, 8-metering transmission, 9-second control valve, 10-cold energy utilization system, 11-liquefied natural gas storage tank. DETAILED DESCRIPTION
[0024] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0025] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.
[0026] The present application provides a boil-off gas treatment system, such as Figure 1 As shown, the boil-off gas processing system includes: a liquefied natural gas storage tank 11, a boil-off gas heat exchanger 3, a compressor 7, a metered external transmission 8, a cold energy utilization system 10, a controller 6 and a data acquisition module. The gas phase outlet of the liquefied natural gas storage tank 11 is connected to the boil-off gas inlet of the boil-off gas heat exchanger 3, the boil-off gas outlet pipeline of the boil-off gas heat exchanger 3 is sequentially connected to the compressor 7 and the metered external transmission 8, the refrigerant outlet of the boil-off gas heat exchanger 3 is connected to the refrigerant inlet of the cold energy utilization system 10, the hot refrigerant outlet of the cold energy utilization system 10 is connected to the hot refrigerant inlet of the boil-off gas heat exchanger 3, and the controller 6 is respectively connected to the data acquisition module and the compressor 7; the refrigerant output by the boil-off gas heat exchanger 3 enters the cold energy utilization system 10 for heat exchange and then returns to the boil-off gas heat exchanger 3.
[0027] The data acquisition module is used to acquire the first pressure of the liquefied natural gas storage tank 11, and the controller 6 is used to control the load of the compressor 7 according to the first pressure; the metering output 8 is used to output the boil-off gas after metering.
[0028] In an exemplary embodiment, the controller 6 includes a compressor 7 control unit, which is used to: shut down the compressor 7 when the first pressure is lower than a set value, start the compressor 7 when the first pressure is higher than the set value, and control the load of the compressor 7 to increase with the increase of the first pressure and decrease with the decrease of the first pressure; to ensure that the pressure of the liquefied natural gas storage tank 11 is within a safe range, the boil-off gas processing system is at positive pressure, and the safe operation of the system is ensured.
[0029] In an exemplary embodiment, the cold energy utilization system 10 includes an ice maker and a cold water heat exchanger. The refrigerant output by the evaporative gas heat exchanger 3 enters the cold water heat exchanger or the ice maker returns to the evaporative gas heat exchanger 3 after heat exchange. The cold water heat exchanger is used to connect to an air conditioning system. The refrigerant output by the evaporative gas heat exchanger 3 enters the heat exchanger or the ice maker to produce cold water or ice. The cold water can be introduced into the air conditioning system for use.
[0030] The liquefied natural gas storage tank 11 outputs low-temperature boil-off gas. The present application utilizes the cold energy of the low-temperature boil-off gas first, which can not only utilize the cold energy, but also avoid the use of expensive, high-energy-consuming low-temperature compressor 7. While reducing system costs, it also reduces power consumption, and the exchanged cold energy can also be directly used for the air conditioning of the control room of the LNG receiving station.
[0031] In an exemplary embodiment, the data acquisition module includes a first pressure transmitter 1 ; the first pressure transmitter 1 is used to detect the first pressure of the liquefied natural gas storage tank 11 .
[0032] In an exemplary embodiment, the data acquisition module includes a second pressure transmitter 5 and a temperature transmitter 4; the second pressure transmitter 5 and the temperature transmitter 4 are both arranged on the pipeline between the evaporating gas outlet of the evaporating gas heat exchanger 3 and the compressor 7, the second pressure transmitter 5 is used to detect the intake pressure of the compressor 7 to ensure that the suction pressure of the compressor 7 is a positive pressure, and the temperature transmitter 4 is used to detect the intake temperature of the compressor 7 to ensure that the suction temperature is not lower than the minimum design temperature of the compressor 7.
[0033] In an exemplary embodiment, the boil-off gas processing system further includes a first control valve 2, which is connected to the controller 6. The first control valve 2 is arranged between the gas phase outlet of the liquefied natural gas storage tank 11 and the boil-off gas inlet of the boil-off gas heat exchanger 3. The controller 6 is used to control the opening of the first control valve 2 according to the load of the compressor 7. When the load of the compressor 7 increases, the opening of the first control valve 2 increases accordingly. When the load of the compressor 7 decreases, the opening of the first control valve 2 decreases accordingly, thereby ensuring safe operation of the system.
[0034] In an exemplary embodiment, the boil-off gas processing system further includes a second control valve 9, which is connected to the controller 6 and is disposed between the refrigerant outlet of the boil-off gas heat exchanger 3 and the refrigerant inlet of the cold energy utilization system 10. The controller 6 is used to control the boil-off gas temperature to ensure the safe operation of the compressor 7.
[0035] In an exemplary embodiment, the evaporation gas heat exchanger 3 is a siphon gas heat exchanger, and the temperature difference range of the siphon gas heat exchanger is 80° C. to 115° C. The lowest inlet temperature of the evaporation gas heat exchanger 3 is -155° C.
[0036] The evaporation gas heat exchanger 3 is an evaporation gas heat exchanger 3 provided with a liquid level sensor, which is combined with a pressure sensor and a temperature controller 6 to improve the operation accuracy. The liquid level sensor is used to control the amount of refrigerant.
[0037] In an exemplary embodiment, the compressor 7 is a compressor.
[0038] In an exemplary embodiment, the load adjustment range of the compressor 7 is 50% to 100% of the rated load.
[0039] This application does not require the use of a low-temperature evaporation gas compressor, does not require air temperature controller heating, and the evaporation gas does not need to be decompressed and transported externally. The energy consumption is reduced by about 70%, and the long-term use can achieve energy-saving effects.
[0040] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0041] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.
Claims
1. A boil-off gas treatment system, characterized in that: The boil-off gas processing system comprises: a liquefied natural gas storage tank, a boil-off gas heat exchanger, a compressor, a metered external transmission, a cold energy utilization system, a controller and a data acquisition module. The gas phase outlet of the liquefied natural gas storage tank is connected to the boil-off gas inlet of the boil-off gas heat exchanger. The boil-off gas outlet pipeline of the boil-off gas heat exchanger is sequentially connected to the compressor and the metered external transmission. The refrigerant outlet of the boil-off gas heat exchanger is connected to the refrigerant inlet of the cold energy utilization system. The hot refrigerant outlet of the cold energy utilization system is connected to the hot refrigerant inlet of the boil-off gas heat exchanger. The controller is respectively connected to the data acquisition module and the compressor. The refrigerant output by the boil-off gas heat exchanger enters the cold energy utilization system for heat exchange and then returns to the boil-off gas heat exchanger. The data acquisition module is used to acquire the first pressure of the liquefied natural gas storage tank, and the controller is used to control the load of the compressor according to the first pressure; the metering output is used to output the boil-off gas after metering.
2. The boil-off gas treatment system according to claim 1, characterized in that: The controller includes a compressor control unit, which is used to: shut down the compressor when the first pressure is lower than a set value, start the compressor when the first pressure is higher than the set value, and control the load of the compressor to increase as the first pressure increases and decrease as the first pressure decreases.
3. The boil-off gas treatment system according to claim 1, characterized in that: The data acquisition module includes a first pressure transmitter; the first pressure transmitter is used to detect the first pressure of the liquefied natural gas storage tank.
4. The boil-off gas treatment system according to claim 1, characterized in that: The data acquisition module includes a second pressure transmitter and a temperature transmitter; the second pressure transmitter and the temperature transmitter are both arranged on the pipeline between the evaporating gas outlet of the evaporating gas heat exchanger and the compressor, the second pressure transmitter is used to detect the intake pressure of the compressor, and the temperature transmitter is used to detect the intake temperature of the compressor.
5. The boil-off gas treatment system according to claim 1, characterized in that: The boil-off gas processing system also includes a first control valve, which is connected to the controller and is arranged between the gas phase outlet of the liquefied natural gas storage tank and the boil-off gas inlet of the boil-off gas heat exchanger. The controller is used to control the opening of the first control valve according to the load of the compressor.
6. The boil-off gas treatment system according to claim 1, characterized in that: The evaporation gas processing system further includes a second control valve, which is connected to the controller and is disposed between a refrigerant outlet of the evaporation gas heat exchanger and a refrigerant inlet of the cold energy utilization system.
7. The boil-off gas treatment system according to claim 1, characterized in that: The cold energy utilization system includes an ice maker and a cold water heat exchanger. The refrigerant output by the evaporative gas heat exchanger enters the cold water heat exchanger or returns to the evaporative gas heat exchanger after heat exchange in the ice maker. The cold water heat exchanger is used to connect to an air conditioning system.
8. The boil-off gas treatment system according to claim 1, characterized in that: The evaporating gas heat exchanger is a siphon type gas heat exchanger, and the temperature difference range of the siphon type gas heat exchanger is 80°C to 115°C.
9. The boil-off gas treatment system according to claim 1, characterized in that: The compressor is a single-stage compressor.
10. The boil-off gas treatment system according to claim 1, wherein: The adjustment range of the compressor load is 50% to 100% of the rated load.