阅读说明：本技术 一种回收bog气体的lng快速卸车系统及方法 (LNG rapid unloading system and method for recycling BOG gas ) 是由 杨萍 喻维 高艳英 杨立伟 周穆军 霍红伟 蒋景彬 谢海莹 陈佳源 王玉成 于 2018-07-26 设计创作，主要内容包括：本发明公开一种回收BOG气体的LNG快速卸车系统及方法,其包括通过输气管道依次连接的LNG储罐、BOG加热器、常温天然气压缩机和BOG调压计量装置,BOG调压计量装置的天然气出口与天然气外输管道连接。本发明通过在BOG加热器后设置一台常温的天然气压缩机,压缩机可将储罐内的BOG气体快速压缩到下游用气点,使储罐内的压力迅速下降,加大LNG槽车与储罐之间的压力差,从而加快卸车速度。同时天然气压缩机还可以回收槽车内的BOG气体,将其快速压缩到下游用气点,既增加了供气量实现部分收入,又可以降低LNG槽车内的气相压力,保证安全。(The invention discloses an LNG (liquefied natural gas) rapid unloading system and method for recycling BOG (boil off gas), which comprises an LNG storage tank, a BOG heater, a normal-temperature natural gas compressor and a BOG pressure-regulating metering device which are sequentially connected through a gas transmission pipeline, wherein a natural gas outlet of the BOG pressure-regulating metering device is connected with a natural gas external transmission pipeline. According to the invention, the natural gas compressor at normal temperature is arranged behind the BOG heater, and the compressor can rapidly compress BOG gas in the storage tank to a downstream gas point, so that the pressure in the storage tank is rapidly reduced, the pressure difference between the LNG tank car and the storage tank is increased, and the unloading speed is accelerated. Meanwhile, the natural gas compressor can also recover BOG gas in the tank car and rapidly compress the BOG gas to a downstream gas consumption point, so that the gas supply amount is increased to realize partial income, the gas phase pressure in the LNG tank car can be reduced, and the safety is ensured.)

1. An LNG rapid unloading system for recovering BOG gas is characterized by comprising an LNG storage tank, a BOG heater, a normal temperature natural gas compressor and a BOG pressure regulating metering device which are sequentially connected through a gas transmission pipeline, wherein a natural gas outlet of the BOG pressure regulating metering device is connected with a natural gas external transmission pipeline, wherein the BOG heater is provided with two gas inlet pipelines, the first gas inlet pipeline is connected with the LNG tank wagon and is used for introducing the BOG of the LNG tank wagon, the second gas inlet pipeline is connected with the LNG storage tank and is used for introducing the BOG of the LNG storage tank, the BOG heater also comprises a storage tank internal pressure detector for detecting the pressure in the LNG storage tank and an LNG tank wagon pressure detector for detecting the pressure in the LNG tank, the temperature detector is used for detecting the temperature of gas on the gas inlet pipeline of the compressor, and the control unit is in communication connection with the pressure detector in the storage tank, the pressure detector in the LNG tank car and the temperature detector and controls the start and stop of the normal-temperature natural gas compressor.

2. The LNG rapid unloading system of claim 1, wherein the BOG outlet of the transport LNG tank wagon and the BOG outlet of the LNG storage tank are respectively connected to the natural gas inlet of the BOG heater through pipelines.

3. The LNG rapid unloading system of claim 1, wherein the pressure detector in the storage tank is arranged on the second air inlet pipeline, the LNG tank car pressure detector is arranged on the first air inlet pipeline, and the temperature detector is arranged on a pipeline between the BOG heater and the normal temperature natural gas compressor.

4. The LNG rapid unloading system of claim 1, wherein the inlet pipeline of the normal temperature natural gas compressor is provided with a temperature alarm and a pressure alarm, and an audible and visual alarm is given when the temperature is lower than a set value; and/or the air outlet pipeline of the normal-temperature natural gas compressor is provided with a pressure alarm linkage, an audible and visual alarm is given out when overpressure occurs, and the compressor is closed in an interlocking manner when the overpressure exceeds a set value.

5. The LNG rapid unloading system of claim 1, wherein the control unit is one of a programmable controller or a distributed control system.

6. A method for rapid LNG unloading for BOG gas recovery, the method comprising:

before the LNG tank car is unloaded, the pressure in the storage tank is obtained through a storage tank pressure detector, the pressure value in the tank is obtained, when the pressure value in the tank reaches the inlet pressure range of the BOG compressor, the compressor is started, the gas in the storage tank is rapidly compressed to a downstream gas point, the pressure in the storage tank begins to drop after the compressor is started, the LNG tank car begins to unload, and when the pressure value in the tank is reduced to a compressor inlet low-pressure alarm value, the compressor is closed;

after the LNG tank wagon is unloaded, a large amount of BOG gas has been gathered in the tank wagon, detect tank wagon internal pressure through LNG tank wagon pressure measurement appearance, obtain the tank wagon internal pressure value, when the tank wagon internal pressure value reaches BOG compressor entry pressure scope, start the compressor, compress the gas fast in the tank wagon to low reaches gas point, the tank wagon internal pressure begins to descend after the compressor starts, when the pressure value reduces compressor entry low pressure alarm value in the tank wagon, close the compressor.

7. The method as claimed in claim 6, wherein the inlet of the natural gas compressor at normal temperature is provided with a temperature alarm in addition to a pressure alarm, when the temperature of BOG gas after being reheated by the BOG heater is lower than the allowable temperature range of the inlet of the compressor, an audible and visual alarm is given to prompt the compressor to be closed, and a standby bypass pipeline is opened so as not to damage the compressor equipment.

8. The method of claim 6 or 7, wherein the BOG compressor inlet pressure ranges from 0.1 to 0.35MPa and the compressor inlet low pressure alarm value is 0.1 MPa.

Technical Field

The invention belongs to the field of LNG (liquefied natural gas), and particularly relates to an LNG rapid unloading system and method for recycling BOG (boil off gas).

Background

Natural gas is used as high-quality clean energy and is more and more widely applied in production and life. Atmospheric Liquefied Natural Gas (LNG) is small in size, convenient to transport and store, and a common form of natural gas. However, due to the large amount of Boil Off Gas (BOG) in the LNG storage process, for example, during the use of the LNG storage tank and the tanker, the BOG Gas continuously increases the pressure in the LNG storage tank and the tanker, which is not only beneficial to the safe storage and transportation of the containers, but also prolongs the unloading time of the LNG tanker.

At present, after the unloading of the LNG gasification station tank car is finished, the pressure in the LNG tank car is generally 0.6MPa, and when the LNG tank car is returned to the LNG gas source station for filling, the pressure of the LNG tank car is generally required to be not more than 0.2MPa, the BOG gas in a single tank car is about 300-400 Kg, and the BOG gas can be directly emptied or returned to the LNG gas source station for reliquefaction, wherein the direct emptying can pollute the atmospheric environment, the reliquefaction increases the energy consumption, and the oil consumption of the vehicle is increased. Based on the above two points, a technology is needed to accelerate the unloading time of the LNG tanker and to recover and utilize the BOG gas in the LNG tanker.

Disclosure of Invention

The LNG rapid unloading system for recovering the BOG gas is provided for solving the problems in the prior art, achieves the functions of rapid unloading and BOG gas recovery, can avoid the BOG gas in a tank car from being directly discharged due to overhigh pressure, recycles the gas, and can reduce the residence time of the LNG tank car in a station.

The invention relates to an LNG rapid unloading system for recovering BOG gas, which comprises an LNG storage tank, a BOG heater, a normal temperature natural gas compressor and a BOG pressure regulating and metering device which are sequentially connected through a gas transmission pipeline, wherein a natural gas outlet of the BOG pressure regulating and metering device is connected with a natural gas external transmission pipeline, wherein the BOG heater is provided with two gas inlet pipelines, the first gas inlet pipeline is connected with the LNG tank wagon and is used for introducing the BOG of the LNG tank wagon, the second gas inlet pipeline is connected with the LNG storage tank and is used for introducing the BOG of the LNG storage tank, the BOG heater also comprises a storage tank internal pressure detector for detecting the pressure in the LNG storage tank and an LNG tank wagon pressure detector for detecting the pressure in the LNG tank, the temperature detector is used for detecting the temperature of gas on the gas inlet pipeline of the compressor, and the control unit is in communication connection with the pressure detector in the storage tank, the pressure detector in the LNG tank car and the temperature detector and controls the start and stop of the normal-temperature natural gas compressor.

Further, a BOG outlet of the LNG transporting tank wagon and a BOG outlet of the LNG storage tank are respectively connected to a natural gas inlet of the BOG heater through pipelines.

Further, pressure detector sets up on the second admission line in the storage tank, and LNG tank wagon pressure detector sets up on first admission line, and temperature-detecting appearance sets up on the pipeline between BOG heater and normal atmospheric temperature natural gas compressor.

Furthermore, a temperature alarm and a pressure alarm are arranged on an air inlet pipeline of the normal-temperature natural gas compressor, and when the temperature is lower than a set value, a sound-light alarm is given out. The air outlet pipeline of the normal-temperature natural gas compressor is provided with a pressure alarm linkage, an audible and visual alarm is given out when overpressure occurs, and the compressor is closed in a linkage mode when the overpressure exceeds a set value.

Further, the control unit is one of a Programmable Logic Controller (PLC) or a Distributed Control System (DCS).

The invention also provides a method for rapidly unloading LNG (liquefied natural gas) for recovering BOG (boil off gas), which comprises the following steps:

before the LNG tank wagon is unloaded, the pressure in the storage tank is obtained through a storage tank pressure detector, an in-tank pressure value is obtained, when the in-tank pressure value reaches the inlet pressure range (0.1-0.35 MPa) of a BOG compressor, the compressor is started, gas in the storage tank is quickly compressed to a downstream gas using point, the pressure in the storage tank starts to drop after the compressor is started, the LNG tank wagon starts to be unloaded, when the in-tank pressure value is reduced to a compressor inlet low-pressure alarm value (0.1MPa), the compressor is closed, the in-tank pressure value can be quickly reduced in the process, the pressure difference between the LNG tank wagon and the LNG storage tank is increased, and the unloading time of the LNG tank;

after LNG tank wagon is unloaded, it is gaseous to have accumulated a large amount of BOG in the tank wagon, detect tank wagon internal pressure through LNG tank wagon pressure measurement appearance, obtain the pressure value in the tank wagon, when the pressure value reaches BOG compressor entry pressure scope (0.1 ~ 0.35MPa) in the tank wagon, start the compressor, compress the gas fast in the tank wagon to low reaches gas point, the tank wagon internal pressure begins to descend after the compressor starts, when the pressure value reduces compressor entry low pressure alarm value (0.1MPa) in the tank wagon, close the compressor, this process can reduce the pressure value in the tank wagon rapidly, it is gaseous to retrieve the BOG in the tank wagon, reach the condition of step-down safe transportation.

Furthermore, the inlet of the normal-temperature natural gas compressor is provided with a pressure alarm and a temperature alarm, when the temperature of BOG gas after being reheated by the BOG heater is lower than the allowable temperature range of the inlet of the compressor, a sound and light alarm is given out to prompt the closing of the compressor and the opening of a standby bypass pipeline so as to avoid damaging compressor equipment.

The invention has the beneficial effects that:

(1) the system and the control method have high automation degree and strong adaptability, can realize the quick unloading of the LNG tank car, and reduce the stay time of the tank car in the station and the field working time of operators.

(2) The invention can effectively recover the BOG gas in the LNG tank wagon, is beneficial to the safe transportation of the tank wagon, reduces the overpressure discharge or direct emptying of a certain amount of BOG gas, realizes reasonable benefit and improves the safety and reliability of the transportation of the tank wagon.

Drawings

Fig. 1 is a schematic diagram of an LNG rapid unloading system for recovering BOG gas according to the present invention.

Detailed Description

The invention is further illustrated by the following examples in connection with the accompanying drawings.

As shown in fig. 1, an LNG rapid unloading system for recovering BOG gas comprises an LNG storage tank 1, a BOG heater 3, a normal temperature natural gas compressor 4 and a BOG pressure regulating and metering device 5 which are connected in sequence through a gas transmission pipeline, wherein a natural gas outlet of the BOG pressure regulating and metering device 5 is connected with a natural gas external transmission pipeline, wherein the BOG heater 3 is provided with two gas inlet pipelines, the first gas inlet pipeline is connected with the LNG tank wagon 2 and is used for introducing BOG of the LNG tank wagon, the second gas inlet pipeline is connected with the LNG storage tank 1 and is used for introducing BOG of the LNG storage tank 1, the BOG heater also comprises a storage tank internal pressure detector P1 for detecting the pressure in the LNG storage tank, an LNG tank wagon pressure detector P2 for detecting the pressure of the LNG tank wagon, the temperature detector T1 is used for detecting the gas temperature on the air inlet pipeline of the compressor, and the control unit 6 is in communication connection with the storage tank internal pressure detector P1, the LNG tank car internal pressure detector P2 and the temperature detector T1 and controls the start and stop of the normal-temperature natural gas compressor.

The BOG outlet of the LNG tank wagon 2 and the BOG outlet of the LNG storage tank are respectively connected with the natural gas inlet of the BOG heater 3 through pipelines.

The pressure detector P1 in the storage tank is arranged on the second air inlet pipeline, the LNG tank wagon pressure detector P2 is arranged on the first air inlet pipeline, and the temperature detector T1 is arranged on the pipeline between the BOG heater 3 and the normal-temperature natural gas compressor 4.

The air inlet pipeline of the normal temperature natural gas compressor 4 can be provided with a temperature alarm and a pressure alarm, and sound and light alarm is given out when the air inlet pipeline is lower than a set value. The air outlet pipeline of the normal-temperature natural gas compressor is provided with a pressure alarm linkage, an audible and visual alarm is given out when overpressure occurs, and the compressor is closed in a linkage mode when the overpressure exceeds a set value.

The control unit may be one of a Programmable Logic Controller (PLC) or a Distributed Control System (DCS).