Method for regulating a device for separating air by cryogenic distillation
AssigneeL'Air Liquide, Societe Anonyme pour l'Etude et l’Exploitation des Procedes Georges Claude
InventorsJohn PACHON MORALES, Jean-Francois RAUCH, Jean-Pierre TRANIER
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Abstract
In a method for regulating a device for separating air by cryogenic distillation, during the change from a low-flow mode to a high-flow mode, two flow rates of reflux sent to the low-pressure column of a double column are increased more rapidly than the flow rate of gaseous air sent to the medium-pressure column of the double column in order to ensure the stability of the oxygen content in the argon bulge of the low-pressure column during the mode change.
Claims13
A method for regulating a device for separating air by cryogenic distillation in a device comprising a first column operating at a first pressure and a second column operating at a second pressure lower than the first pressure, the bottom of the second column being heated by a gas from the first column, and a third column, wherein
- sending cooled, purified gaseous air to the first column;
- sending a first, oxygen-enriched, liquid from the bottom of the first column to the second column;
- sending a second liquid that is liquefied air or that is withdrawn from an intermediate level of the first column to the second column;
- sending a third nitrogen-enriched liquid and optionally a fourth nitrogen-enriched liquid from an upper part of the first column to the second column;
- withdrawing an oxygen-enriched fluid from the second column;
- sending an argon-enriched gas from the second column to the third column for separation therein;
- withdrawing a fluid enriched in argon compared to the argon-enriched gas that feeds the third column at the top of the third column;
- and
- operating the device in two modes including a first mode in which the gaseous air sent to the first column has a first flow rate and a second mode in which the gaseous air sent to the first column has a second flow rate that is greater than the first flow rate,
- wherein:
- i) upon a condition in which the flow rate of gaseous air sent to the first column increases by at least n % per minute when changing from the first mode to the second mode, the flow rate of the first liquid arriving in the second column is increased by at least % per minute, where x is non-zero, and the flow rate of the second liquid arriving in the second column is increased by at least % per minute, where x′ is non-zero, during at least part of a period during which the increase in the flow rate of air is at least n % per minute, and/or
- ii) upon a condition in which the flow rate of gaseous air sent to the first column reduces by at least n % per minute when changing from the second mode to the first mode, the flow rate of the first liquid arriving in the second column is reduced by at least % per minute, where y is non-zero, and the flow rate of the second liquid arriving in the second column is reduced by at least % per minute, where y′ is non-zero, during at least part of a period during which the reduction in the flow rate of air is at least n % per minute,
- wherein n is equal to or greater than 1.
Dependencies are inferred from the claim text.