Page 329 - Process Equipment and Plant Design Principles and Practices by Subhabrata Ray Gargi Das

11.7 Design illustration e flash distillation 331

For inlet nozzle (from Eqs. 11.39 and 11.40)
1=2 1=2
(
u max ¼ 122=r mix ¼ 122=ð2:0935Þ ¼ 84:32 m=sec
u min ¼ 0:6 u max ¼ 50:5m=sec
From Eq. (11.41) ID of nozzle d i;nozzle (m) is given by

pd 2 10:558 1
i;nozzle
4 u max ¼ 2:0935 10 3 3600
or

1=2
10:558 4
¼ 0:145 m
d i;nozzle ¼ 3
2:0935 10 3600 p 84:32
00
We choose 6 NB, schedule 40 steel pipe with inner diameter 6.065 ¼ 154 mm and outer diameter
00
6.625 ¼ 168 mm as feed nozzle.
00
Drum internal diameter
From Eqn. 11.37, d min , the minimum diameter (m) of the vessel is given by
1:8095 1
d min u vap:max ¼ m =sec
p 2 3
4 3600 3:595 10 4
or
1=2
1:8095 4

¼ 0:53 m ¼ 530 mm
d min ¼ 4
3600 3:595 10 p 6:346
We choose an additional cushion of w150 mm for diameter and set d ¼ 700 mm ¼ 0.7 m.
Deciding vessel height and checking for h T =d limits (Refer Fig. 11.16)
h v ¼ h 1 þ h 2

Feed nozzle od ¼ 168 mm
h 1 ¼ 900 mm þ od=2 ¼ 900 þ 168=2 ¼ 984 mm

Minimum acceptable h 1 ¼ 1200 mm
Hence, h 1 ¼ 1200 mm
h 2 ¼ 300 mm þ od=2 ¼ 300 þ 168=2 ¼ 384 mm; say 390 mm
Minimum acceptable h 2 is 450 mm. Hence, h 2 ¼ 450 mm
Height of vapour space (excluding vessel head) is h v ¼ h 1 þ h 2 ¼ 1200 þ 450 ¼ 1650 mm.
Residence time of liquid is 3e5 min for vapoureliquid separator.