Full-liquid air separation device using cold energy of liquefied natural gas (LNG)

Abstract

The invention disclose a full-liquid air separation device using the cold energy of the liquefied natural gas (LNG), comprising an air compressing and pre-cooling system, an air purifying system, an air separating system and a nitrogen circulating system capable of recycling the cold energy of the LNG which has the pressure of 8.0MPa or higher. The nitrogen circulating system capable of recycling the cold energy of the LNG comprises a nitrogen compressor, a wound tube heat exchanger and a gas-liquid separator; the gaseous nitrogen coming out of the gas separating system is made to enter the wound tube heat exchanger to exchange heat with the LNG and then is compressed by the nitrogen compressor to have higher pressure; the liquid nitrogen coming out of the wound tube heat exchanger is separated into gaseous nitrogen and liquid hydrogen; the liquid nitrogen coming out of the gas-liquid separator is separated into two branches, wherein one branch of the liquid nitrogen is fed in the air separating system to be used as the return liquid of a lower tower to involve in the rectification of the lower tower and to be made to carry the cold energy in the air separating system, and the other branch of the liquid nitrogen is discharged as the liquid nitrogen product; the gaseous nitrogen coming out of the gas-liquid separator is made to enter the wound tube heat exchanger and reheated to the temperature of the inlet of the nitrogen compressor and then made to enter the nitrogen compressor to circulate. Compared with the prior air separation device of the same scale, the full-liquid air separation device can save the electric energy of more than 50 percent and the consumed water of more than 90 percent.

Description

technical field [0001] The invention relates to an air separation device, in particular to an all-liquid air separation device utilizing LNG cold energy. Background technique [0002] Natural gas is a high-quality energy source with high calorific value, cleanliness, and low combustion pollution. Its main component is methane, which is liquefied for ease of transportation. The liquefaction temperature is generally -150°C to -161°C, and it becomes liquefied natural gas (LNG). After being transported to the destination, it needs to be vaporized in order to utilize it. A large amount of cold energy will be generated during vaporization. The cold energy released when LNG under 0.1Mpa is reheated from -161°C to 27°C is about 950KJ / kg, 8.0Mpa The cold energy released when the NG is reheated from -161°C to 27°C under low temperature is about 830KJ / kg. LNG contains huge high-quality cold energy. If it is not recycled, it will be a great waste. At present, LNG cold energy utilizatio...

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Problems solved by technology

The compression of gas requires a lot of power and cooling water, so the unit power consumption of liquid air separa

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