FLASH DRUM DESIGN
Transcript of FLASH DRUM DESIGN
FLASH DRUM DESIGN
ChE 4253 - Design IChE 4253 - Design I
Vertical vessel Horizontal Vessel
FLASH DRUM DESIGN
ChE 4253 - Design IChE 4253 - Design I
Installed Units
FLASH DRUM DESIGN
ChE 4253 - Design IChE 4253 - Design I
Deflectors, and Diffusers
FLASH DRUM DESIGN
ChE 4253 - Design IChE 4253 - Design I
Demisters
FLASH DRUM DESIGN
ChE 4253 - Design IChE 4253 - Design I
Control Schemes
FLASH DRUM DESIGN
ChE 4253 - Design IChE 4253 - Design I
Dimensions to decide
DhVhLhf
FLASH DRUM DESIGN
ChE 4253 - Design IChE 4253 - Design I
Calculations to make
Ratchford Rice Equation (look for it!!)
F L V= +
i i iFz Lx Vy= +
i i iy K x=
1ii
x =∑1i
iy =∑
1 ( 1)
1 ( 1)
ii
i
i ii
i
zxV KF
K zyV KF
⎧ =⎪ ⎡ ⎤+ −⎪ ⎣ ⎦⇒ ⇒⎨⎪ =⎪ ⎡ ⎤+ −⎣ ⎦⎩
FLASH DRUM DESIGN
ChE 4253 - Design IChE 4253 - Design I
Dimensions to decide
D related to vapor velocity. hV related to vapor velocity. hL related to level control hf related to flooding
FLASH DRUM DESIGN
ChE 4253 - Design IChE 4253 - Design I
D related to vapor velocity.
Permitted velocity
Where do these come from ?
( )L Vperm
V
v K ρ ρρ−
=
2 3 4ln (ln ) (ln ) (ln )lv lv lv lvA B F C F d F E FK e + + + +=
1.8774780.8145800.1870740.0145230.001015
ABCDE
= −= −= −= −= −
L Llv
V V
WFW
ρρ
=
FLASH DRUM DESIGN
ChE 4253 - Design IChE 4253 - Design I
D related to vapor velocity.
Stokes
drag
gravity-Buoyancy
( )L Vperm
V
v K ρ ρρ−
⇒ =
6vis d dF R vπμ=
34( )3g L V dF g Rρ ρ π= −
( )2 2 31 4( )2 3drag vis drag g D D V d L V dF F F F C R v g Rπ ρ ρ ρ π+ ≈ = ⇒ = −
visF dragF
gF
212drag D V dF C A vρ=
83
d
D
gRKC
=drag visF F>>
FLASH DRUM DESIGN
ChE 4253 - Design IChE 4253 - Design I
Dimensional analysis for drag: Force is dependent on velocity, cross sectional area, density and viscosity.
Two nondimensional numbers:
Therefore
Thus is a function of the particle Reynolds number.
/Re dv A πμ
= 212
dragD
V d
FC
Avρ=
(Re, ) 0b Df C =2
(Re)12
DD c
V d
FC fAvρ
= =
DC8
3 (Re)c
dgRKf
=
( , , , , ) 0a drag d Vf F v A ρ μ =
FLASH DRUM DESIGN
ChE 4253 - Design IChE 4253 - Design I
But, what should be used? The criteria is that 5% of the liquid
is entrained.
Thus
; were obtained
fitting experimental data.
Therefore
Demisters should take care of 4% (or less) of the 5%.
L Llv
V V
WFW
ρρ
=
4 4D
perm V
VD Avπ π ρ
= =
2 3 4ln (ln ) (ln ) (ln )lv lv lv lvA B F C F d F E FK e + + + +=
dR
FLASH DRUM DESIGN
ChE 4253 - Design IChE 4253 - Design I
Who came up with this rule and why?
What is so magic about 3 ft? (Room for demister?)
Again, why 2ft? (Residence Time, Failure Analysis,Other Control issues?)
or ~2 minutes residence time.
Finally: Nozzle size
136"2Vh diameter of feedline= +
112"2fh diameter of feedline= +
V f LL h h h= + +
2
4
poolL
Vh
Dπ=
FLASH DRUM DESIGN
ChE 4253 - Design IChE 4253 - Design I
Final considerations
IF 3 increase Vpool (Why???)
IF 5 Use horizontal drum (Why???)
Different design protocol: Why?
LD<
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