A system and method for helium extraction and energy utilization from bog gas

Abstract

The invention relates to a system and method for extracting helium from BOG gas and utilizing energy, and the system for extracting helium from BOG gas and utilizing energy removes CH in BOG gas by using pure oxygen combustion 4 and H 2 ; and the mixed gas after pure oxygen combustion is processed by steam generating unit and air cooler to remove H 2 O, different from using the liquefaction temperature, the CO can be removed separately by means of step-by-step cooling 2 , O 2 , N 2 , and purified and liquefied to obtain high-purity liquid carbon dioxide, liquid oxygen and liquid nitrogen, wherein the liquid oxygen enters the pure oxygen combustion chamber for secondary use after being oxidized, and the liquid nitrogen is gasified and discharged into the atmosphere to remove CO 2 , O 2 , N 2 The final mixed gas enters the secondary cold box for cooling and purification to obtain pure helium. The heat energy generated by burning BOG gas with pure oxygen can meet the production heat of the LNG plant and the energy consumption demand of the system for helium extraction and the electricity consumption of the LNG plant. The overall structure of the system is simple and the energy consumption is small.

Description

technical field [0001] The invention relates to the technical field of BOG gas recovery in LNG plants, in particular to a system and method for extracting helium from BOG gas and utilizing energy. Background technique [0002] In the production process of LNG, the final throttle valve will produce a large amount of flash gas during the throttling process, and the liquefaction temperatures of helium, hydrogen, nitrogen and methane under normal pressure are -269°C, -253°C, -196°C respectively. ℃ and -162℃, under the pressure of the storage tank, helium, hydrogen and part of nitrogen will volatilize from LNG. At this time, compared with raw natural gas, because hydrocarbons and other gases are liquefied, non-condensable gases such as helium are obtained. One enrichment. Helium is an important strategic resource. It is found in some natural gas fields in my country that the helium content in natural gas is about 0.04% to 0.1%. The gas-liquid mixture at the outlet of the final ...

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Problems solved by technology

[0006] The helium extraction devices of the above two schemes are relatively independent, and are only for the purpose of extracting helium. Most of the combustible gases such as hydrogen and methane in the BOG gas are firstly removed by low-temperature separation, and the remaining hydrogen and methane are removed by catalytic oxidation, which consumes a lot of energy. , the device is relatively complex, there are many uncontrollable factors, and the energy balance and utilization of the LNG plant have not been well considered

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