Natural gas liquefying system for carbon dioxide precooling double-stage nitrogen expansion

Abstract

The invention discloses a natural gas liquefying system for carbon dioxide precooling double-stage nitrogen expansion. The natural gas liquefying system comprises a natural gas conveying pipe, a carbon dioxide precooling circulating device, a heavy hydrocarbon removing device, a double-stage nitrogen cooling circulating device, a BOG heat exchanger, a first throttling valve, a second throttling valve, a LNG throttling valve, a gas-liquid separation device, a LNG pump and a LNG tank. The natural gas liquefying system realizes precooling through carbon dioxide and deep cooling through nitrogen, optimally designs the technological process of a carbon dioxide precooling double-stage nitrogen expansion liquefying system, improves the process flexibility, reduces the energy consumption of the liquefying system, improves the safety, and can realize stable, efficient and continuous production demands of offshore liquefied natural gas under the conditions of different sea areas and different gas properties.

Description

technical field [0001] The invention relates to the field of natural gas liquefaction, in particular to a carbon dioxide precooling two-stage nitrogen expansion natural gas liquefaction system. Background technique [0002] Natural gas resources are widely distributed on land and oceans around the world. From land to ocean is an inevitable trend of oil and gas exploration and development in the world. FLNG (Floating Liquefied Natural Gas) is a new type of offshore device proposed by the marine engineering community in recent years, which integrates the production, storage and loading and unloading of liquefied natural gas. It has low investment costs, short construction periods, and low development risks for the exploitation of offshore gas fields. Ease of migration and other features. [0003] Unfavorable factors such as typhoons, waves, and space constraints need to be considered in offshore operations, making the technical difficulty of floating liquefaction process high...

AI Technical Summary

Problems solved by technology

In the prior art, the pressure of the high-temperature nitrogen cycle and the low-temperature nitrogen cycle are the same, and the process design cannot adjust the heat transfer temperature difference in different temperature zones, and the adjustability is poor, which reduces the environmental adaptability and feed gas adaptability of the FLNG device, which is not conducive to stable and efficient production

[0007] After being pressurized by the expander booster and compressor, the nitrogen pressure is as high as 5MPa or more, the pressure level of equipment and pipelines is high, the wall thickness increases, and the weight of process equipment increases, resulting in an increase in the load of supporting structures such as pipe racks, and damage The strength of the hull structure puts forward higher requirements, and the cost of the upper process module and the hull rises sharply, which increases the investment and reduces the economy of the floating natural gas liquefaction device

[0008] In summary, the existing floating natural gas liquefaction technology has the disadvantages of low safety, poor adjustability, high energy consumption, and poor economy

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