Air separation method utilizing liquefied natural gas cold energy

Abstract

The invention discloses an air separation method utilizing liquefied natural gas cold energy, comprising an air separation unit, an LNG cold energy utilization unit providing refrigeration energy for the LNG cold energy utilization unit and a glycol water solution circulation unit utilizing NG high temperature cold energy. In the invention, low temperature cold energy of the LNG is applied to the air separation system, thus unit power consumption of a liquid air separation product can be reduced to about 0.30kwh/m, which is one third of the unit power consumption of a liquid air separation product in conventional process production; and unit power consumption of the internal compressed gas product also can be greatly reduced, and meanwhile a large number of cooling water can be saved, thus being in accordance with the trend of energy saving, consumption reduction and circular economy developing and having obvious social benefit and economic benefit.

Description

technical field [0001] The invention relates to an air separation method, in particular to an air separation method utilizing the cold energy of liquefied natural gas. Background technique [0002] LNG (liquefied natural gas) is a high-quality clean energy. In order to meet the requirements of pipeline transportation, LNG needs to be pressurized to a specified pressure. During pressurization, part of the cold energy of LNG is converted into pressure energy. The pressurized LNG still has high-grade low-temperature cold energy. The usual way is to use seawater heating to gasify and heat up and send it to the gas pipeline. This wastes precious low-temperature cold energy. [0003] Air separation method, especially the air separation method for producing liquid air separation products such as liquid oxygen, liquid nitrogen and liquid argon, and the air separation method for producing part of pressurized gas oxygen, gas nitrogen (internal compressed gas product) and part of l...

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Problems solved by technology

[0004] Chinese patent application specification CN 1873357A discloses an air separation method for recovering the cold energy of liquefied natural gas. The low-temperature nitrogen compressor of the patent application only has one stage of compression, the inlet temperature is -110°C to -120°C, and the outlet pressure is 3.0 to 3.5MPa; There is a booster turbo expander in the cycle; the intake air is cooled by cold nitrogen; because the cold energy of LNG is not fully utilized, and the product extraction rate of the patented rectification system is low, the unit energy consumption of the product is relatively high

[0006] Chinese patent application specification CN 101050913A discloses an air separation method for producing liquid oxygen and liquid nitrogen by using the cold extracted from liquefied natural gas. Temperature and exhaust pressure; the extraction rate of oxygen and argon in the rectification tissue of the patent application is low; the patent application does not have an ethylene glycol aqueous solution cooling system, not only the shaft power of the raw material air compressor is high, but the high-temperature cooling energy of NG is not sufficient Utilization, resulting in high unit energy consumption of the product, and the NG exiting the air separation system is still at low temperature, which cannot meet the pipeline transportation requirements

[0007] Chinese patent application specification CN 1407303A discloses an air separation device using the cooling capacity of liquefied natural gas. The patent application does not specify what kind of nitrogen compressor is used, and there is no ethylene glycol aqueous solution cooling system, which is only suitable for small air separation equipment

[0008] None of the above-mentioned patent application descriptions involves measures to detect possible LNG leakage in time, which is more likely to cause some problems and accidents

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