Air separation method utilizing cold energy of liquefied natural gas

Abstract

The invention discloses an air separation method utilizing cold energy of liquefied natural gas (LNG), which comprises three parts of an air separation unit, an LNG cold energy utilization unit for providing the cold energy for the air separation unit and a circulating coolant circulation unit utilizing NG high-temperature cold energy. The air separation method can greatly reduce the unit power consumption of a liquid air separation product or an internal compressed gas product after utilizing low-temperature cold energy of the LNG for the air separation unit, obtain a large number of liquid nitrogen products, lead the extraction rate of argon to be high, simultaneously save a large amount of cooling water, be in line with the big trend of energy conservation, consumption reduction and development of cyclic economy and have obvious social benefits and economic benefits.

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] The air separation system is especially the air separation system that produces liquid air separation products such as liquid oxygen, liquid nitrogen and liquid argon, and the air separation system that produces part of pressurized gas oxygen, gas nitrogen (internal compressed gas products) and pa...

AI Technical Summary

Problems solved by technology

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

[0006] Chinese patent application specification CN 101050913A discloses an air separation system 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] Chinese patent application specification CN 101571340A discloses an air separation system that utilizes the cold energy of liquefied natural gas. The patent uses a three-stage low-temperature air intake cycle nitrogen compressor and an ethylene glycol cooling system, but the liquid oxygen product is mainly obtained by relying on The high-pressure subcooled liquid nitrogen in the low-pressure oxygen and LNG-nitrogen heat exchanger is throttled to the low pressure to exchange heat with it, and one of the cold sources of the supercooled circulating high-pressure liquid nitrogen is the throttled low-pressure liquid nitrogen, that is, circulating low-temperature nitrogen compression The inlet flow of a section of the machine is relatively large, resulting in high shaft power of the low-temperature nitrogen compressor

[0009] 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

Images