Crude argon column

II) Turbine (12) Rectification column (pressure section) (13), (16), (19) combined condenser-evaporator unit (14) Rectification column (low-pressure section) (15) Crude argon column (17) Pure argon column (18) Reboiler (20) Ar- process pump (21) Internal compression pump (22) Throttle valve. 

The oxygen-enriched Hquid from the sump of the pressure column is also expanded and then, on the one hand, fed as liquid into the low-pressure column (i) and, on the other hand, evaporated in the two combined evaporator-condenser units (16), (19) on top of the crude argon column (15) and the pure argon column (17). This cools the two argon columns head condensers, thereby providing the necessary reflux for these columns. The evaporated oxygen - enriched liquid is fed into the low-pressure column. 

Withdrawal of the argon-rich gaseous feed to the crude argon column. 

The rectification in the crude argon column is almost a pure binary separation between O2 and Ar and can be best visualized and understood in the McCabe-Thiele Diagram, shown in Fig. 2.5. This diagram indicates for each tray the Ar-concentration y of the vapour directed towards the tray and the concentration x... 

Fig. 2.5 McCabe-Thiele diagram for the binary Oj/Ar-mixture of the crude argon column.

The minimal number of theoretical separation stages which is required for the crude argon column to accomplish the O2—Ar separation, is estimated with the Fenske formula. This formula holds for infinite reflux, L/ V 1. This condition is almost fulfilled since typically only 1 part out of 30 parts of ascending vapour is withdrawn as crude argon from the top of the crude argon column, whereas 29 parts of liquid remain as reflux. 

The large volume of the crude argon column requires a long start-up time for the argon production ... 

Example The crude argon column of an air separator, having an argon production of2000 m and a process air input of240 000 m h , has a diameter of about... 

Also due to the low pressure drop of a packed crude argon column, it became possible to recover pure argon only by means of cryogenic distillation. 

Rectification in the Low-pressure, Crude and Pure Argon Column... 

There are two basic types of argon-purification subsystems in industrial use (1) the catalytic-combustion system as shown in Fig. 6.32 and (2) the adsorption system. The first subsystem adds hydrogen to the argon stream removed from the crude argon separation column. This mixture is compressed to 0.5 MPa and the oxygen is removed by combustion or combination with the hydrogen in a catalytic-combustion furnace. This results in an argon... 

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