Backward flow type air separation system and method based on cold energy utilization of LNG (Liquefied Natural Gas) satellite station

Abstract

The invention discloses backward flow type air separation system and method based on the cold energy utilization of an LNG (Liquefied Natural Gas) satellite station. The invention adapts to the fluctuation of LNG dosage by adjusting the amount of cycled nitrogen, and complements the refrigerating output requirements required by the system simultaneously during the deficiency of the refrigerating output of the LNG by utilizing the method of flowing liquid nitrogen backwards. A nitrogen external circulation system is eliminated after the LNG cold energy is introduced in the air separation process, and the equipment of a nitrogen turbo-expander and a Freon refrigeration unit is omitted so that the process is simplified. The temperature of the circulation nitrogen at the outlet of a main heat exchanger is increased to 253 to 263 K from traditional 100 k around, and the problem of low temperature compression of the circulation nitrogen in the traditional system is avoided. The temperature of other flows of fluid of the main heat exchanger for cooling feeding air is reduced due to the increased temperature of the outlet of the circulation nitrogen, and the rest cold energy exchanges heat with the feeding air in front of a compressor and is exhausted after the temperature recovers to the room temperature, therefore, the temperature of the feeding air is further reduced to 273 to 280 K, and the energy consumption of the air compressor is saved.

Description

technical field [0001] The invention relates to a cryogenic air separation method and system, in particular to an inverted air separation system and method based on cold energy utilization of LNG satellite stations. Background technique [0002] Liquefied natural gas (LNG) is a low-temperature liquid mixture made through a low-temperature liquefaction process. It is a very clean fuel, and its main component is methane (due to differences in production areas, the methane content varies from 80% to 90%). In recent years, LNG receiving stations have been built or planned to be built in many coastal areas of my country. Before the LNG in the station is delivered to users, it usually needs to be heated and vaporized by seawater or air. In this process, there is no effect on the latent heat of vaporization and sensible heat of rewarming ( The cold energy released when vaporized from 112K to 300K natural gas at 0.1MPa is about 950kJ / kg), which is well utilized, resulting in a great ...

AI Technical Summary

Problems solved by technology

However, the LNG satellite stations that are mainly responsible for the natural gas supply of individual cities are very different. Their LNG consumption fluctuates with seasons, day and night, and even gas consumption at different times. Therefore, the cold energy they can provide will also change over time. Fluctuate according to a certain rule

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