Exhaust system and control method for liquefied natural gas low-temperature pump well

Abstract

The invention discloses an exhaust system and a control method for a liquefied natural gas low-temperature pump well. The exhaust system comprises a liquid level detector arranged in a low-temperature storage tank, an exhaust pipeline connected to the pump well in the low-temperature storage tank, and an outputting pipeline connected to the pump well in the low-temperature storage tank; a low-temperature tank inner pump is arranged at the bottom of the pump well; an exhaust control valve is arranged in the exhaust pipeline; a liquid discharge control valve is arranged in the outputting pipeline; the liquid level detector, the exhaust control valve, the liquid discharge control valve and the low-temperature tank inner pump are connected to a control unit; and the control unit can control the on-off states of the exhaust control valve so as to control the exhaust time. According to the exhaust system and the control method for the liquefied natural gas low-temperature pump well, the liquid level in the storage tank is detected by the liquid level detector in real time, the volume of the gas phase space is calculated through a formula, the reasonable exhaust time at the headspace of the pump well is calculated according to the efficiency curve of the pump, and therefore the possibility that exhaust gas is too much or not enough can be effectively avoided, and the occurrence of accidents can be reduced.

Description

technical field [0001] The invention belongs to the field of LNG, and in particular relates to a liquefied natural gas cryogenic pump well exhaust system and a control method. Background technique [0002] As a high-quality clean energy, natural gas is more and more widely used in production and life. Atmospheric liquefied natural gas (LNG) is a common form of natural gas due to its small size and ease of transportation and storage. However, due to the large amount of flash steam (Boil Off Gas, BOG) that will appear during the storage of LNG, for example, during the use of LNG storage tanks, after the pump stops running, the liquid in the pump well will flow back to the storage tank with its own weight, resulting in the liquid in the pump well The space from the surface to the top of the storage tank is filled with BOG gas, and this part of the gas needs to be evacuated during each start-up of the pump. [0003] The previous method of exhausting is to control the time of t...

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Problems solved by technology

[0003] The previous method of exhausting is to control the time of the exhaust control valve and set a fixed time for exhausting, which will lead to incomplete exhausting or incomplete exhausting. In severe cases, LNG liquid will directly enter the exhausting pipeline , causing severe vibration of the exhaust pipeline, bringing danger to equipment and personnel

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