A lng subcooled filling system

Abstract

The invention provides an LNG subcooling filling system, which includes an LNG tanker, a liquid nitrogen tanker, and a liquid nitrogen-natural gas subcooler. The liquid nitrogen-natural gas subcooler includes a liquid nitrogen heat exchange pipeline and an LNG heat exchange pipeline , the inlet of the LNG heat exchange pipeline is connected to the liquid discharge port of the LNG tanker, and the outlet of the LNG heat exchange pipeline is provided with a subcooled LNG filling pipe connected to the filling port of the membrane type liquid tank; the liquid nitrogen heat exchange pipeline The inlet is connected to the discharge port of the liquid nitrogen tanker through the liquid nitrogen discharge pipe, and the outlet of the liquid nitrogen heat exchange pipe is connected to the atmosphere; the liquid nitrogen discharge pipe is provided with a flow regulating valve; the subcooled LNG filling pipe is provided with There is a temperature sensor; the invention transports the LNG in the LNG tanker to the liquid nitrogen-natural gas subcooler, makes it exchange heat with the liquid nitrogen for cooling to obtain subcooled LNG, and fills the subcooled LNG into the film type liquid tank, Ensure that the natural gas entering the membrane-type liquid tank is liquid natural gas in a saturated state or supercooled state, so as to prevent the membrane-type liquid tank from discharging gaseous natural gas due to excessive pressure caused by overheating and evaporation of LNG in the tank, resulting in waste of natural gas resources and potential safety hazards and environmental pollution.

Description

technical field [0001] The invention belongs to the technical field of LNG filling, and in particular relates to an LNG subcooling filling system for a ship's membrane-type liquid tank. Background technique [0002] At present, the membrane-type liquid tank is one of the main large-scale storage containers for LNG on ships. It is a low-temperature atmospheric container and has been widely used due to its low construction cost, short construction period, large storage volume and good thermal insulation performance. [0003] Natural gas, the main component is methane, which is boil-off gas (BOG) at normal temperature and pressure. Under normal pressure, the liquefaction temperature of natural gas is -162°C, and the boil-off gas (BOG) will be cooled and liquefied into liquefied natural gas at this temperature. (LNG), when LNG is loaded, unloaded and transported, in order to ensure the maximum transportation volume of natural gas, it is necessary to always keep it below the liqu...

AI Technical Summary

Problems solved by technology

[0004] However, during the LNG filling process, due to the influence of the external environment temperature (such as pipeline heat leakage and liquid tank temperature being too high, etc.), part of the LNG in the filling pipeline evaporates into gas, and these BOG vapors and the gas produced in the tanker The gaseous natural gas will eventually accumulate in the membrane liquid tank, which will increase the pressure of the membrane liquid tank

In order to avoid the expansion and cracking of the film type liquid tank, part of the BOG needs to be discharged into the atmosphere through the safety valve or the vent pipe of the liquid tank to achieve the purpose of pressure relief, which not only causes waste of natural gas, but also brings safety hazards and emits a large amount of greenhouse gases

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