Page 323 - Process Equipment and Plant Design Principles and Practices by Subhabrata Ray Gargi Das

11.6 Flash distillation 325

Vertical drum
The critical dimensions of a vertical drum are shown in Fig. 11.16.

Vapour outlet

h
1

Feed DØ High
inlet level of
liquid
h 2
Normal level
Low level
h
L

Liquid outlet
FIGURE 11.16
Vertical flash drum with its critical dimensions.

The minimum diameter (d min )in m is
2 1=2
v:
d min ¼ ffiffiffip m v = r u v;max (11.37)
p
d min is normally rounded off to the next higher multiple of 10 mm and incremented in steps of 150 mm,
if required to be revised. All variables in Eqn. 11.37 have to be in consistent units.
Feed inlet nozzle
Some amount of feed vaporises in the feed nozzle and hence the same cannot be sized based only
) density of the vapour
mix
on volumetric flow of entering liquid. Inlet nozzle size is based on average (r
and liquid leaving.
¼ðm L þ m v Þ=ðm L = r þ m v = r Þ; kg=m 3 (11.38)
mix L v
r
Maximum and minimum allowable inlet nozzle velocity are estimated from the following
empirical expressions
p ffiffiffiffiffiffiffiffi
mix ; m=sec (11.39)
u max;nozzle ¼ 122= r
u min;nozzle ¼ 0:6 u max;nozzle ; m=sec (11.40)