Columns, air separation

Since helium and neon have boiling points considerably below that of nitrogen, these gases will collect on the nitrogen side of the condenser-reboiler associated with the double-column air separation system. Recovery of these gases is accomplished by periodic venting of a small portion of the gas from the dome of the condenser and transfer to a small condenser-rectifier refrigerated with... 

The block of inter-linked columns offers robust simulation of a combination of complex distillation columns, as heat-integrated columns, air separation system, absorber/stripper devices, extractive distillation with solvent recycle, fractionator/quench tower, etc. Because sequential solution of inter-linked columns could arise convergence problems, a more robust solution is obtained by the simultaneous solution of the assembly of modelling equations of different columns. 

Fig. 3.1 Diagram of a two-column air separator with noble gas production. (1) Rectification column (pressure section) (2) Rectification column (low-pressure section) (3,5, 7) Combined condenser-evaporator unit ...

After a double-column air-separation system has been in continuous operation over long periods of time, the effectiveness of the heat transfer in the condenser-reboiler is observed to decrease. This is attributed to the gradual accumulation of neon and helium in the nitrogen, which lowers the partial pressure of the nitrogen so that it will not condense at the condenser design temperature. This problem can be solved by periodically venting some of the accumulated gas from the dome of the condenser either to the atmosphere or to a neon-separation system. 

Fig. 6.33. Neon-recovery subsystem. Crude neon and helium are recovered from the dome of the lower-column condenser in a double-column air separation system.

The bottom product from the lower column of a double-column air separation unit consists of 40% nitrogen, 59% oxygen, and 1% argon on a molar basis. Determine the saturated temperature of liquid when the pressure in the column is 0.405 MPa. What is the composition of the vapor that is in equilibrium with this saturated reboiler liquid ... 

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