Cryogenic air rectification system, control unit, air separation unit and method of cryogenically separating air

A control unit configured to control an air rectification system, the air rectification system comprising a high a pressure column, a low pressure column and an argon removal unit coupled to a condenser evaporator, wherein

• the system is configured to pass gas from a position above an oxygen section of the low pressure column as an argon removal feed gas to a lower region of the argon removal unit,
• the system is configured to condense gas from an upper region of the argon removal unit in the condenser evaporator to form a condensate,
• the system is configured to pass further gas from the upper region of the argon removal unit out of the system,
• the system is configured to pass at least a part of the condensate as a reflux to the upper region of the argon removal unit,
• the control unit is configured to control an oxygen content of the argon removal feed gas as a controlled variable using a flow of the further gas from the upper region of the argon removal unit being passed out of the system as a manipulated variable on the basis of a oxygen content determined in the argon removal feed gas using a feedback control structure
• the condenser evaporator is configured to at least partly evaporate a coolant forming an evaporated gas, and
• the system is configured to pass the evaporated gas, or a part thereof, uncontrolledly into the low pressure column.

A method for cryogenically separating feed air using an air rectification system comprising high a pressure column, a low pressure column and an argon removal unit coupled to a condenser evaporator, wherein

• gas from a position above an oxygen section of the low pressure column is passed to a lower region of the argon removal unit as an argon removal feed gas,
• gas from an upper region of the argon removal unit is condensed in the condenser evaporator to form a condensate,
• further gas from the upper region of the argon removal unit is passed out of the system,
• at least a part of the condensate is passed as a reflux to the upper region of the argon removal unit,
• a control unit controlling an oxygen content of the argon removal feed gas as a controlled variable using a flow of the further gas from the upper region of the argon removal unit being passed out of the system as a manipulated variable on the basis of a oxygen content determined in the argon removal feed gas using a feedback control structure is used
• a coolant is at least partly evaporated in the condenser evaporator, forming an evaporated gas, and
• the evaporated gas, or a part thereof, is passed uncontrolledly into the low pressure column.