Method for air separation production on liquid oxygen and liquid nitrogen through LNG (Liquefied Natural Gas) cold energy

Abstract

The invention provides a method for air separation production on the liquid oxygen and the liquid nitrogen through the LNG (Liquefied Natural Gas) cold energy. According to the all-liquid air separation method, the investment is less, the energy-saving rate is high, the energy consumption is low, the cold loss is small, the output of the liquid nitrogen and the liquid oxygen is large, and the production cost can be greatly reduced. According to the technical scheme, the implementation steps of the method includes that the raw nitrogen from an air separation tower cold box is reheated through a main heat exchanger cold box to join the medium-pressure and low-temperature nitrogen separated through a gas and liquid separation tank to be reheated through a circulating heat exchanger cold box, the reheated low-pressure and low-temperature nitrogen is reheated through the circulating heat exchanger cold box, and the medium-pressure and normal-temperature nitrogen boosted through a nitrogen booster enters a circulating nitrogen booster to be boosted into the high-pressure nitrogen; the high-pressure nitrogen is precooled through the circulating heat exchanger cold box; the precooled high-pressure nitrogen is fed into the air separation tower cold box to serve as an air separation cold source, the high-purity and high-pressure liquid nitrogen is obtained at the bottom of an upper tower of an LNG cold energy recovery tower cold box, the high-pressure liquid nitrogen is throttled through a throttling valve to obtain the medium-pressure liquid nitrogen and the medium-pressure nitrogen, and the medium-pressure liquid nitrogen and the medium-pressure nitrogen are throttled through the throttling valve to obtain a low-pressure liquid nitrogen product and the low-pressure nitrogen.

Description

technical field [0001] The invention relates to a separation method of full-liquid air separation for producing industrial gas products such as liquid oxygen and liquid nitrogen by using LNG cold energy and a small amount of electric energy to liquefy and separate air at low temperature, and a system for utilizing LNG cold energy. Background technique [0002] Liquefied natural gas (LNG) not only contains huge cooling capacity, but more importantly, its cooling capacity is of high quality. As the amount of LNG continues to grow, the amount of cooling produced by gasification also increases. During the gasification process of LNG, the cold energy released by it can be utilized directly or indirectly. Direct utilization methods include cold energy power generation, air liquefaction separation, refrigerated warehouses, manufacture of liquefied carbon dioxide, seawater desalination, air conditioning, and low-temperature cultivation; indirect utilization methods include liquid o...

AI Technical Summary

Problems solved by technology

The disadvantages of the current air separation plant process using LNG cold energy to produce liquid oxygen and liquid nitrogen are: ① The temperature required for oxygen liquefaction and nitrogen liquefaction, which consume a large amount of cooling capacity, is lower than the LNG vaporization temperature -161°C, and must be actively liquefied. Refrigeration Supplement

②Simple compressed air refrigeration cannot balance the cooling capacity required by liquid oxygen and liquid nitrogen, and consumes a lot of energy

③The physical properties of LNG with different components are different. The lower the methane content, the higher the cooling temperature of LNG gasification, the lower the available cooling capacity and the lower the quality

⑤ LNG cold energy utilization efficiency is low

For the all-liquid air separation process, the main energy consumption in the air separation unit is the air compressor, the circulating nitrogen compressor, and the expander, so a large amount of cooling capacity is required, and the energy consumption is very high

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