Method and system for realizing simultaneous ship loading and unloading of LNG receiving station

Abstract

The invention provides a method and system for realizing simultaneous ship loading and unloading of an LNG receiving station. The system comprises a barge pipeline used for being connected with an LNGship loading and unloading pipeline, a pneumatic control switching valve, a BOG compressor, an LNG storage tank, a torch control system and a corresponding LNG pressure control system. One part of LNG unloaded from a first LNG transport ship is unloaded to the LNG storage tank through a normal unloading pipeline, and one part of LNG passes through the barge pipeline and is unloaded to a second LNG transport ship by controlling the flow through an adjusting valve arranged on a ship loading pipeline. Meanwhile, the pressure of a cabin is matched with the pressure of the LNG storage tank at a fixed value. Under an emergency condition, the gas phase pressure of the top of the LNG storage tank realizes interlocking to shut down an XV valve on the barge pipeline to restore the single ship unloading process. In addition, on the one hand, the load of the BOG compressor is adjusted through pressure control, and on the other hand, a certain quantity of BOG is released to a torch through a PV control valve in front of the torch, so that the pressure of a whole BOG system remains stable. Interlocking of the whole control system is realized mainly through a pressure sensor, a transmitter and aPLC hard wire.

Description

Technical field [0001] The invention relates to the field of setting up loading and unloading docks in LNG receiving stations and realizing the functions of loading and unloading ships at the same time, and in particular to a method and system for realizing simultaneous loading and unloading of ships at LNG receiving stations. Background technique [0002] As a clean and efficient energy source, the share of liquefied natural gas (LNG) in the civil and industrial sectors has been increasing year by year. In particular, the “gas shortage” in the winter of 2017 has severely affected the domestic supply and demand of LNG. With the opening of transportation, the LNG transshipment market will not only be transported by LNG tankers, but the use of small boats for LNG transshipment will gradually come into the field of government and enterprises. [0003] In the field of LNG receiving stations, most receiving stations only have unloading docks, and few LNG receiving stations have loading ...

AI Technical Summary

Problems solved by technology

[0005] 1. The loading function is realized from the low-pressure LNG pipeline through the loading pipeline. Since the low-pressure LNG pipeline relies on the pump in the tank to provide power, and at the same time, it is necessary to ensure the normal operation of the loading and BOG recondenser. In order to ensure the pressure of the BOG recondenser, the tank Generally, the head of the internal pump is relatively high, about 270m. The pressure of the low-pressure LNG main pipe needs to be maintained at about 0.8MPag-1.0MPag, while the loading pressure only needs to be 0.2MPag-0.3MPag, and the ineffective energy consumption is large.

[0006] 2. The storage volume range of small LNG ships is relatively large, ranging from 3,000 to 150,000 square meters, and the measurement effect is difficult to be accurate

[0007] 3. The pressure control of the BOG system is complex and unstable, resulting in prolonged loading and unloading time

[0008] 4. Using low-pressure LNG main pipes for loading, the pressure loss is large, the BOG generation is large, and the pressure control of the BOG system is unstable

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