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LIN Subcooling Method for a Nitrogen Liquefier

IP.com Disclosure Number: IPCOM000019398D
Publication Date: 2003-Sep-12
Document File: 1 page(s) / 32K

Publishing Venue

The IP.com Prior Art Database

Abstract

It is generally desired that liquid nitrogen (LIN) leaving a nitrogen liquefier should be deeply subcooled. This is generally achieved by cooling it in a dedicated plate fin exchanger, against LIN boiling at close to atmospheric pressure. Typically the low pressure LIN is provided by flashing part of the product LIN into an LP separator and then thermosyphoning it through the subcooler. The subcooler can be either inside or external to the separator. A level controller is used to control the LIN flow supplied to the separator. The vaporized GAN can either be sent directly to the main liquefier exchanger, or it can first be superheated against the subcooling product LIN.

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LIN Subcooling Method for a Nitrogen Liquefier

It is generally desired that liquid nitrogen (LIN) leaving a nitrogen liquefier should be deeply subcooled. This is generally achieved by cooling it in a dedicated plate fin exchanger, against LIN boiling at close to atmospheric pressure. Typically the low pressure LIN is provided by flashing part of the product LIN into an LP separator and then thermosyphoning it through the subcooler. The subcooler can be either inside or external to the separator. A level controller is used to control the LIN flow supplied to the separator. The vaporized GAN can either be sent directly to the main liquefier exchanger, or it can first be superheated against the subcooling product LIN.

It is suggested that the boiling LIN separator be deleted. The boiling LIN supply would then be flashed directly into the subcooler and would be vaporized and superheated in a single pass through the exchanger. The flow of flashed LIN to the subcooler would be modulated to control the temperature of the superheated GAN leaving the exchanger.

In order for this scheme to work, special attention needs to be paid to the boiling LIN heat exchanger passage design.

One design would be to use hardway fin throughout the boiling passages or at least for a part of those passages. Such a design would prevent LIN being easily entrained up into the superheat section of the exchange. The use of a hardway fin design would require additional boiling passages in order to minimize...