Nitrogen production method and nitrogen production apparatus

Abstract

The present invention aims to provide a nitrogen production technology that can generate a large amount of product nitrogen gas during normal operation while simultaneously producing a small amount of product oxygen gas or product liquid oxygen. When liquid nitrogen is required, the operating mode can be switched to allow for the simultaneous production or increase of liquid nitrogen without increasing power consumption while maintaining the amount of product nitrogen gas. [Solution] A nitrogen production method comprising a first separation step, a first condensation step, a second separation step, a second condensation step, an oxygen separation step, an oxygen evaporation step, a product nitrogen output step, a product liquefied nitrogen output step, and a product oxygen output step, wherein in the first operating mode, at least the oxygen separation step, the oxygen evaporation step, and the product oxygen output step are performed, and in the second operating mode, the oxygen separation step, the oxygen evaporation step, and the product oxygen output step are not performed.

Claims

1. A first separation step involves cooling the raw material air to obtain low-temperature raw material air, which is then distilled to separate it into high-pressure nitrogen gas and high-pressure liquefied air. A first condensation step involves indirectly exchanging heat between the high-pressure nitrogen gas and the medium-pressure liquefied air obtained by reducing the pressure of the high-pressure liquefied air, thereby liquefying the high-pressure nitrogen gas to produce high-pressure liquefied nitrogen and vaporizing the medium-pressure liquefied air to produce medium-pressure air. A second separation step involves distilling the aforementioned medium-pressure air to separate it into medium-pressure nitrogen gas and medium-pressure liquefied air. A second condensation step involves indirectly exchanging heat between the aforementioned medium-pressure nitrogen gas and low-pressure liquefied air obtained by reducing the pressure of the aforementioned medium-pressure liquefied air, thereby liquefying the medium-pressure nitrogen gas to produce medium-pressure liquefied nitrogen and vaporizing the low-pressure liquefied air to produce low-pressure air. An oxygen separation step is performed by distilling a portion of the high-pressure liquefied air generated in the first rectification column, or a portion of the medium-pressure liquefied air generated in the second separation step, to separate it into waste air and liquid oxygen. An oxygen evaporation step is performed to vaporize the liquefied oxygen and generate an upward gas, A product nitrogen extraction process for extracting a portion of the aforementioned high-pressure nitrogen gas as a product, A product liquid nitrogen extraction step in which either or both of the high-pressure liquid nitrogen and the medium-pressure liquid nitrogen are extracted as product liquid nitrogen, The process includes a product oxygen extraction step in which the liquid oxygen or a portion of the oxygen gas obtained by vaporizing the liquid oxygen is extracted as a product, The system has at least a first operating mode and a second operating mode in which the amount of liquid nitrogen product discharged in the liquid nitrogen product discharge process is greater than that in the first operating mode. In the first operating mode, at least the oxygen separation step, the oxygen evaporation step, and the product oxygen extraction step are performed. In the second operating mode, the oxygen separation step, the oxygen evaporation step, and the product oxygen extraction step are not performed. A method for producing nitrogen characterized by the following features.

2. In the oxygen separation process described above, not only the waste air and the liquefied oxygen are separated, but also argon-enriched oxygen gas. The argon separation step involves distilling the argon-enriched oxygen gas to separate it into argon gas and argon-enriched liquefied oxygen. An argon condensation step is performed to liquefy the argon gas to produce liquefied argon, The process includes a product argon extraction step of extracting the argon gas or a portion of the liquefied argon as a product, The first operating mode further includes the argon separation step, the argon condensation step, and the product argon extraction step. The second operating mode further omits the argon separation step, the argon condensation step, and the product argon extraction step. The nitrogen production method according to feature 1.

3. In the first operating mode, a first adiabatic expansion step is performed in which a portion of the low-pressure air is heated and then adiabatically expanded to generate cold, The nitrogen production method according to claim 1 or 2, characterized in that, in the second operating mode, in addition to the first adiabatic expansion step, a second adiabatic expansion step is performed to generate cold by heating and then adiabatic expansion of the other part of the low-pressure air.

4. The nitrogen production method according to claim 3, characterized in that the temperatures of the low-pressure air to be adiabatically expanded in the first adiabatic expansion step and the second adiabatic expansion step are different.

5. In the first operating mode, a first adiabatic expansion step is performed in which a portion of the medium-pressure air is heated and then adiabatically expanded to generate the cold necessary for the device, The nitrogen production method according to claim 1 or 2, characterized in that, in the second operating mode, in addition to the first adiabatic expansion step, a second adiabatic expansion step is performed to generate cold by heating and then adiabatic expansion of the other part of the medium-pressure air.

6. The nitrogen production method according to claim 5, characterized in that the temperatures of the medium-pressure air to be adiabatically expanded in the first adiabatic expansion step and the second adiabatic expansion step are different.

7. A first rectification column separates low-temperature raw material air obtained by cooling raw material air into high-pressure nitrogen gas and high-pressure liquefied air by distillation, A first condenser indirectly exchanges heat between the high-pressure nitrogen gas and the medium-pressure liquefied air obtained by reducing the pressure of the high-pressure liquefied air, thereby liquefying the high-pressure nitrogen gas to produce high-pressure liquefied nitrogen and vaporizing the medium-pressure liquefied air to produce medium-pressure air. A second rectification column that distills the aforementioned medium-pressure air to separate it into medium-pressure nitrogen gas and medium-pressure liquefied air, A second condenser indirectly exchanges heat between the aforementioned medium-pressure nitrogen gas and low-pressure liquefied air obtained by reducing the pressure of the aforementioned medium-pressure liquefied air, thereby liquefying the medium-pressure nitrogen gas to produce medium-pressure liquefied nitrogen and vaporizing the low-pressure liquefied air to produce low-pressure air. An oxygen tower that distills a portion of the high-pressure liquefied air generated in the first rectification column, or a portion of the medium-pressure liquefied air generated in the second separation step, to separate it into waste air and liquefied oxygen, An oxygen evaporator that vaporizes the liquid oxygen in the oxygen tower to generate rising gas, A product nitrogen discharge line that discharges a portion of the aforementioned high-pressure nitrogen gas as a product, A product liquid nitrogen discharge line that discharges either or both of the aforementioned high-pressure liquid nitrogen and / or the aforementioned medium-pressure liquid nitrogen as product liquid nitrogen, A product oxygen outlet line that outputs the oxygen gas or a portion of the liquid oxygen as a product, A valve is provided in a line for introducing a portion of the high-pressure liquefied air or a portion of the medium-pressure liquefied air into the oxygen tower. A valve is provided in the line that introduces a fluid to the oxygen evaporator for heat exchange with the liquefied oxygen in the oxygen tower, A nitrogen production apparatus characterized by comprising the following features.

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