Device and method for co-production of liquefied natural gas and liquid nitrogen

Abstract

The invention discloses a device and method for co-production of liquefied natural gas and liquid nitrogen. The method is characterized in that liquefied natural gas and liquid nitrogen are produced from natural gas containing nitrogen, low-temperature nitrogen-enriched gas flow obtained from the tower top of a denitrification tower is further purified in a nitrogen-methane fractionating tower, methane in the low-temperature nitrogen-enriched gas flow is recovered to prepare the LNG (Liquefied Natural Gas) product, and simultaneously purified nitrogen is prepared into a high-purified liquid nitrogen product. The device and method have the positive effects that on one hand, the quality of the LNG product is ensured, the tumbling accident of an LNG storage tank is avoided, and the source of raw materials of the LNG product is widened; and on the other hand, the low-temperature nitrogen-enriched gas flow is further purified, methane in the low-temperature nitrogen-enriched gas is recovered to prepare the LNG, and simultaneously purified nitrogen is prepared into the high-purified liquid nitrogen product, so that the better environment-friendly benefits and economic benefits are achieved, and the product yield is high.

Description

technical field [0001] The invention relates to a condensation and separation process for producing liquefied natural gas and liquid nitrogen from natural gas containing nitrogen, in particular to a device and method for co-producing liquid nitrogen from liquefied natural gas. Background technique [0002] Liquefied natural gas (LNG) is a hydrocarbon mixture with methane as the main component, which contains a small amount of ethane, propane, nitrogen, etc. that usually exist in natural gas. Its normal pressure boiling point is about -160 ° C. , Non-toxic and non-corrosive, the volume is about 1 / 600 of the same amount of gaseous natural gas, and has the advantages of flexible transportation, high storage efficiency, clean and environmental protection, and high combustion calorific value. As a high-quality fuel for vehicles and ships, LNG has the advantages of high octane number, good anti-knock performance, clean and environmental protection, long engine life, and low cost c...

AI Technical Summary

Problems solved by technology

However, since the loss of methane gas cannot be avoided in the process of removing nitrogen from LNG, since methane is the second greenhouse gas other than carbon dioxide, the greenhouse effect is 21 times that of carbon dioxide, and the venting of methane gas is not economically and environmentally friendly.

[0011] At the same time, these patents do not propose economical and effective utilization measures for the low-temperature nitrogen-enriched gas flow.

As an important gas product, high-purity liquid nitrogen is usually produced from air by cryogenic separation, which consumes a lot of energy

These patents do not further purify the low-temperature nitrogen-enriched gas stream, recover the methane in it to produce LNG or high-purity methane products, and at the same time prepare the purified nitrogen into high-purity liquid nitrogen products

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