Page 330 - Process Equipment and Plant Design Principles and Practices by Subhabrata Ray Gargi Das

332 Chapter 11 Distillation

We consider 4 min (240 s)
9:9434 3 3
m ¼ 0:663 m
3600
r Liquid holdup ¼ 240
This shall correspond to the normal level at the average of high and low level of liquid. We consider
a level span of 300 mm, and further considering 300 mm above the high level, we locate the inlet
nozzle centre line (see Chapter 17 for additional details).
Depth of liquid filled space (excluding vessel bottom dished end) is
0:663
¼ 1:72 m
h L ¼
2
p
4 ð0:7Þ
rh T = d ¼ðh L þ h V Þ=d ¼ð1:72 þ 1:68Þ=0:7 ¼ 4:86 < 5
Hence, a vertical vessel is acceptable.
Vapour and liquid outlet nozzles
Typical nozzle velocities for vapour and liquid services are w15 m=sec and 2e3 m/s, respectively.
For vapour exit nozzle based on 15 m/s vapour velocity,

2 5032:88
p

d V;nozzle 15 ¼
4 3600
d V;nozzle ¼ 0:344 m ¼ 344 mm
00
Closest internal diameter standard nozzle (pipe) is 14 NB, Schedule 40, with inner diameter ¼
13:376 ¼ 340 mm f is used as vapour nozzle.
00
For liquid nozzle based on 2.5 m/s velocity,
8:7485
p 2
d L;nozzle 2:5 ¼
4 3600
1=2
9:9434 4
¼ 0:0375 m ¼ 37:5mm
d L;nozzle ¼
p 2:5 3600
We provide a minimum nozzle size of 2 NB, Schedule 40(d i ¼ 2:067 ¼ 52:5mm f) as liquid
00
00
nozzle.
Vessel support and other nozzles for vent, drain, level measurement, temperature sensing and safety
valve mounting are also to be provided as per guidelines provided in Chapter 17. One may use the
information in Chapter 17 for details on instrumentation and other nozzles.
11.8 Batch distillation
Batch distillation, as the name suggests, is a process where the distillation is carried out on batches of
feed. In its simplest form, there is only one stage of vapoureliquid contacting and that involves a
‘charge still’ that may have heating coils or jacket integral to the vessel. The vessel is charged with a
fixed amount of liquid mixture that is to be separated by boiling and subsequent condensation. In some
cases, there can be an external heater through which the still charge is circulated and the heated charge
flashes on return to the still. The vapour leaving the still goes to a condenser from where the condensed