Method for starting up an argon separation column of an apparatus for air separation by cryogenic distillation and unit for implementing the method

A method for starting up a column for separating argon by cryogenic distillation, the method comprising the steps of:

• sending an argon-enriched fluid coming directly or indirectly from a double air separation column to an argon separation column, wherein the double air separation column comprises a first column and a second column, which are interconnected thermally;
• measuring a nitrogen content at a top of the argon separation column,
• wherein during start-up of the column:
• a. sending a top gas from the argon separation column to the atmosphere, upon a determination that the nitrogen content at the top of the argon separation column is above a first threshold, and
• b. sending the top gas from the argon separation column to a denitrogenation column for separation therein upon a determination that the nitrogen content at the top of the argon separation column is below a second threshold, which is lower than or equal to the first threshold;
• and withdrawing an argon-rich fluid product from the denitrogenation column.