Page 291 - Process Equipment and Plant Design Principles and Practices by Subhabrata Ray Gargi Das

11.4 Fractionator 293

Hat
Vapour
Chimney

Draw off
Chimney
tray pan
Vapour

Column Side draw
shell
nozzle
Internal reflux
to lower tray

FIGURE 11.7
Schematic diagram of a chimney tray in a column.

Tower and tower internals
The vapoureliquid contacting inside the distillation column is effected either in the trays or in the
packed sections. These are detailed in Chapter 14.

11.4.1 Process design of fractionating tower e equilibrium stage approach
Process design with equilibrium stage approach is traditional and is carried out in two phases:

• Estimation of the number of theoretical stages of contact required for the desired extent of
separation.
• Calculating the actual number of contacting stages (trays/plates) or the actual packing depth
required in case of packed columns for realising the estimated number of theoretical stages of
contact. This is accounted for by considering an efficiency of contacting to approach equilibrium.
The next step is sizing of tower height and diameter.
Typical output of process design contains the details mentioned in Table 11.2.