distillation column design multicomponent
TRANSCRIPT
-
8/12/2019 Distillation Column Design Multicomponent
1/23
Chapter # 05 Equipment design
5.6 DESIGN OF DISTILLATION COLUMN
In industry it is common practice to separate a liquid mixture by distillating the
components, which have lower boiling points when they are in pure condition
from those having higher boiling points. This process is accomplished by partial
vaporization and subsequent condensation.
5.6.1CHOICE BETWEEN PLATE AND PACKED COLUMN:
Vapour liquid mass transfer operation may be carried either in plate column
or packed column. These two types of operations are quite different. selection
scheme considering these factors fewer than four headings.
i! "actors that depend on the system i.e. scale, foaming, fouling factors,
corrosive systems, heat evolution, pressure drop, liquid holdup.
ii! "actors that depend on the fluid flow moment.
iii! "actors that depends upon the physical characteristics of the column and
its internals i.e. maintenance, weight, side stream, size and cost.
iv! "actors that depend upon mode of operation i.e. batch distillation,
continuous distillation, turndown, intermittent distillation.
The relat!e "ert# $% &late $!er &a'(e) '$l*"+ are a# %$ll$,#:
i! #late column are designed to handle wide range of liquid flow rates
without flooding.
ii! If a system contains solid contents, it will be handled in plate column,
because solid will accumulate in the voids, coating the packing
materials and making it ineffective.
Production of gasoline from naphtha $%&
-
8/12/2019 Distillation Column Design Multicomponent
2/23
Chapter # 05 Equipment design
iii! 'ispersion difficulties are handled in plate column when flow rate of
liquid are low as compared to gases.
iv! "or large column heights, weight of the packed column is more than
plate column.
v! If periodic cleaning is required, man holes will be provided for cleaning.
In packed columns packing must be removed before cleaning.
vi! "or non(foaming systems the plate column is preferred.
vii! 'esign information for plate column are more readily available and
more reliable than that for packed column.
viii! Inter stage cooling can be provide to remove heat of reaction or solutionin plate column.
ix! )hen temperature change is involved, packing may be damaged.
*.&.+ D#tllat$+ C$l*"+ De#-+ Ste
'esignation of design basis
perating conditions
'etermination of equilibrium stages
-ize of the column
'esign of plate
Production of gasoline from naphtha $%
-
8/12/2019 Distillation Column Design Multicomponent
3/23
Chapter # 05 Equipment design
5.6. De#-+at$+ $% De#-+ Ba##:
C$"&$+e+t#Fee) "$l
%ra't$+
T$& "$l %ra't$+B$tt$" "$l
%ra't$+/+ %.0&0 %.10+
2/0 %.%$$+ %.%+%*
2+/& %.%$$% %.%+%%
23/1 %.%$+ %.%+3+
20/$% %.%+0 %.%0*$
2*/$+ %.%+*+ 45 %.%033 %.%%3
2&/$0 %.%01+ /5 %.%%%& %.$%&
2/$& %.$+6% %.+1&
2&/& %.$*60 %.3*3
2&/*((2/3 %.$%+% %.++&
2&/$$((2/3 %.%%3 %.%$&
2*/6((2/3 %.%%00 %.%$%
5.6./ OPE0ATING CONDITIONS:
perating #ressure $*.+ atm
Strea"# Te"&erat*re
"eed $+*
o
2Top -tream 01 o2
7ottom stream +*% o2
8eflux stream 0% o2
5.6./ DETE0MINATION OF EUILIB0IUM STAGES:
Production of gasoline from naphtha $%1
-
8/12/2019 Distillation Column Design Multicomponent
4/23
Chapter # 05 Equipment design
9quilibrium data at operating conditions
'etermination of minimum reflux ratio
'etermination of minimum number of stages
'etermination of ideal stages
E2*l3r*" )ata at $&erat+- '$+)t$+:
C$"&$+e+t# K4ALUES0ELATIE
OLATILIT
/+ ::
2/0 $&.0%% *$.+*%
2+/& *.*%% $.$1123/1 3.+%% $%.%%%
20/$% $.+%% 3.*%
2*/$+ %.*&% $.*%
2&/$0 %.3+% $.%%%
2/$& %.$3% %.0%&
2&/& %.%1% %.+*%
2&/*((2/3 %.$1+ %.*&6
2&/$$((2/3 %.$%+ %.3+%
2*/6((2/3 %.+$1 %.&1%
M+"*" 0e%l*7 0at$:
7y using 2oulburn method,
=nH
dHAB
nL
dL
AB X
X
X
XR
!$;
$min
-
8/12/2019 Distillation Column Design Multicomponent
5/23
Chapter # 05 Equipment design
=$$*.33 o2
4ower pinch Temperature
!;3
$PBp TTTT +=
!01+*%!;3
+;01 +=
= $1+.&& o2
4ight 5ey composition in
rf = ratio of composition of light key to heavy key in the liquid part of feed.
I = relative volatility of components with respect to heavy key.
?fhi = composition of heavier than heavy key components in the feed stream.
Now;
"or components heavier than heavy key
C$"&$+e+t# M$l. Fra't$+#
8%+
2/$& %.$+6 %.0%& %.%*+
2&/& %.$*6 %.+*% %.%0%
2&/*((2/3 %.$%+ %.*&6 %.%*1
2&/$$((2/3 %.%% %.3+% %.%%+
2*/6((2/3 %.%%0 %.&1% %.%%3
?fn = %.$**
Production of gasoline from naphtha $$%
-
8/12/2019 Distillation Column Design Multicomponent
6/23
Chapter # 05 Equipment design
fH
fL
fX
Xr =
%01+.%
%+*+.%=fr = %.*+
!$!;$; fnf
f
nLXr
rX
++=
!$**.%$!;*+.$;
*+.%
++= =%.+6&
f
nLnH
r
XX =
*+.%
+6&.%= = %.*&6
@ow using this equation,
=nH
dHAB
nL
dL
AB X
X
X
XR
!$;
$min
=*&6.%
%%%&.%*.$
+6&.%
%033.%
!$*.$;
$
=$.60
ptimum 8eflux 8atio ranges from ;$.$ A $.*!B8 min.
I choose the optimum reflux ratio, by plotting the graph bCw total annual cost and
reflux ratio. ;Diven in appendix!
reflux ratio taken is 9.9
M+"*" N*"3er $% Sta-e#:
7y using "enskeEs 9quation>
Production of gasoline from naphtha $$$
-
8/12/2019 Distillation Column Design Multicomponent
7/23
Chapter # 05 Equipment design
LK
bLK
HK
dHK
LK
m
X
X
X
X
ln
ln
=
*.$ln
%%3.%
$%&.%
%%%&.%
%033.%ln
= bd
=$0 plates with reboiler
N*"3er $% I)eal Sta-e#:
-
8/12/2019 Distillation Column Design Multicomponent
8/23
Chapter # 05 Equipment design
a = 8elative volatility of light key
Ha = %.$$+ m @sC m+
-o,
!*.$B$$+.%log;*.3+*$=
E
= &1.%+ J
ctual number of stages ;@ actual!
@ actual= @ ideal C 9o
= +3C%.&1
= 30 ;excluding partial condenser!
"eed location
7y, using kirkbridge 9quation>
=
+
log+%&.%logdHK
bLK
fLK
fHK
B
!
"
"
"
"
!
B
=
+
%%%&.%
%%3.%
%+*.%
%01.%
+$$.$&6
+$.$36log+%&.%log
B
!
$3.+=B
!
B! $3.+=
B!t#ta$ +=
( ) B$$3.+30 +=
=B $$
-o feed is entering at $$th plate from bottom.
Production of gasoline from naphtha $$3
-
8/12/2019 Distillation Column Design Multicomponent
9/23
Chapter # 05 Equipment design
5.6.5 T0A DESIGN
M$lar Fl$, 0ate $% Strea"#:
"eed, " 3%1.01 kg molChr
Top #roduct, ' $&6.+$ kg molChr
7ottom product, ) $36.+ kg molChr
8eflux, 4n 060.$% kg molChr
a&$*r Fl$, 0ate:
in rectifying section, Vn &&3.3% kg molChr
in stripping section, Vm *$3.$$ kg molChr
L2*) Fl$, 0ate#:
in rectifying section, 4n 060.$% kg molChr
in stripping section, 4m &*+.31 kg molChr
4mC) 0.&1
Ph;#'al C$+)t$+#:Top Bottom
Vapour 'ensity, kgCm3 1.1 30.3&
Production of gasoline from naphtha $$0
-
8/12/2019 Distillation Column Design Multicomponent
10/23
Chapter # 05 Equipment design
4iquid density, kgCm3 *%0.& 6&.3
Vapour flow rate, m3Csec %.601& %.$1*
4iquid flow rate, m3Csec %.%$++ %.%$%+
Vapour G 4iquid velocities can be found by using following formulae respt.
Vapour flow rate =3&%%
%
$'ta(g%m
4iquid flow rate =3&%%
%
$'ta(gLm
Da"eter $% C$l*"+:
( ) ( ) +C$
+ %0.%+.%$$.%
+=
%
%Ltt( $$u
)here>
-
8/12/2019 Distillation Column Design Multicomponent
11/23
Chapter # 05 Equipment design
Vapour velocity, mCs %.30 %.+$3
@ow,
'iameter of column can be calculated as,
%%
)C
u
%!
0=
)here>
'% is the maximum vapour rate, kgCsec
7y putting values we get as,
2olumn 'iameter, 'c $.%* m
)e based our design on bottom diameter.
-o, I take diameter = 3.* ft
$.%& m
Tra; De#-+:
Tower application or service #roduct finishing
Tower inside 'iameter $.%& m
Tray type 2ross flow
Tray spacing %.*%1 m
@o. of down comers C tray $
Ca Data:
Production of gasoline from naphtha $$&
-
8/12/2019 Distillation Column Design Multicomponent
12/23
Chapter # 05 Equipment design
0 in standard cap size is selected for 3.* ft column, so that
all data about cap becomes fixed.
2ap ' = 0 in =%.$%$& m
2ap I' =%.%610 m
#itch &%%K;triangular!
-pacing %.%3$* m
@o. of rowsCtray 1
Inside /eight above tray %.$%%% m
@o. of slotsCcap, @s ;selected from table! *$
/eight of slot, /s, %.%31$ m
)idth of slot, ws %.%%3$* m
skirt /eight, s %.%%&3* m
-hroud ring height, hsr %.%%&3* m
8iser '. %.%&61* m
I'. %.%&&& m
8iser height above tray floor %.%1+**m
D$,+ Fl$, Area> A)%?
It ranges from $% A +% J of tower area.
Thus for $*J of tower area %.$30 m+
L2*) D#tr3*t$+ Area> Ala?
It ranges 1 A +% J of tower area.
Production of gasoline from naphtha $$
-
8/12/2019 Distillation Column Design Multicomponent
13/23
Chapter # 05 Equipment design
nd for $& J of tower area %.$03 m+
E+) Wa#ta-e> Ae,?
It ranges from A ++ J of tower area
nd for $* J of tower area %.$30m+
N$. $% 'a @tra;?
*
e'$adfC
C
a
AAAA
++=
( )
%%1$.%
$30.%$03.%$30.%160.% ++=C
= &% caps
reasL
rea =0
+!
Total cap area =
0
+!C
2ap inside cross(sectional area, ac %.%%&%& m+
Total cap inside cross(sectional areaCtray, c %.0*& m+
8iser inside cross(sectional areaCcap, ar %.%%306 m+
Total riser inside cross(sectional areaCtray, r, %.+%6 m+
8iser outside cross(sectional areaCcap, aro, %.%%313+ m+
Total riser outside cross(sectional areaCtray, ro,%.++6 m+
nnular area per cap. ( )++
0r#*ia
dda =
%.%%33 m+
Production of gasoline from naphtha $$1
-
8/12/2019 Distillation Column Design Multicomponent
14/23
Chapter # 05 Equipment design
Total annular areaCtray, a %.++& m+
8eversal area C cap,arE, %.%%366 m+
Total reversal areaCtray %.+360 m+
-lot areaC cap,as, ;@sB/sB)s! %.%%&$ m+
Total slot area C tray , s, %.3 m+
Tra; Detal#:
4ength of outlet weir Iw,
-
8/12/2019 Distillation Column Design Multicomponent
15/23
Chapter # 05 Equipment design
Per%$r"a+'e $% Tra;:
Top Bottom
0e#)e+'e t"e + )$,+'$"er?
down comer area, d;
-
8/12/2019 Distillation Column Design Multicomponent
16/23
Chapter # 05 Equipment design
Pre##*re Dr$&:
Caps:Top Bottom
0#er Pre##*re Dr$&> hr?
( )
%6.+
+
$
$$$.%
=
r
%
L
rr
A
%dh
)here>
dr = dia of riser +.&+* in +.&+* inN4 = density of liquid 3$.03 lbC ft
3 06.& lbC ft3
Nv = density of vapour %.*0 lbC ft3 +.$0 lbC ft3
V = volumetric flow rate 33.* ft3Csec &.&++ ft3Csec
r = total riser area +.+* ft+ +.+* ft+
7y solving equation,
hr = #ressure drop ;in inof liquid! %.%6 in %.%*1 in
0e!er#al a+) A++*l*# Pre##*re Dr$&> hra?
( )
$.$
+
$++&1.%
= r%
*"
r
L
ra A
%
aa
a
h
)here>
ar = inside riser area = in+ *.0$ *.0$
ax = 8eversal area = in+ &.$1* &.$1*
Production of gasoline from naphtha $+$
-
8/12/2019 Distillation Column Design Multicomponent
17/23
Chapter # 05 Equipment design
ac = inside area of cap = in+ $$.6 $$.6
7y solving equation,
hra = #ressure drop ;in Oin/of liquid! %.%1& %.%&+
0e'ta+-*lar Sl$t Dr; &re##*re Dr$&>P
sh ?
( )
3.$
+
$P $&3.%
=
+
%C
L
+
A
%dh
)hereL
dc = diameter of cap = in 3.10 3.10
s = total area of slot = ft+ 3.613 3.613
7y solving equation,
hsQ = #ressure drop ;in Oin/of liquid! %.%3&1 %.%+&
T$tal )r; &re##*re )r$&?
PP
+rarC hhhh ++= ;Inches of liquid! %.$6$1 %.$0&
Wet 'a& &re##*re )r$&, ;inof liquid! =
+
$
a
+
L
%
+ a
a
A
%
)here>
as = area of slot Ccap = in 6.*& 6.*&
aa = annular areaC cap = in *.1* *.1*
+
$
a
+
L
%
+ a
a
A
%
%.3& %.3$
"rom graph ;fig 1($$* 4udwig, vol. +, p $&!
The values of 2wareR.
2w %.$1 %.$0
Production of gasoline from naphtha $++
-
8/12/2019 Distillation Column Design Multicomponent
18/23
Chapter # 05 Equipment design
hc= hcQC2w $.%&* $.%0+
hcmax= hrMhraM;/sMs! $.6$* $.1
Since hcis less than hc,max., cap is O.K. and not blowing under the shroud
ring.
He-ht $% L2*) $!er Wer; Top Bottom
"irst calculate,
4gC ;lw!+.* $.3+ $0.01
nd
lwC' %.* %.*
)here>
4g = flow rate of liquid in gallonsCmin
lw =length of weir = ft
-
8/12/2019 Distillation Column Design Multicomponent
19/23
Chapter # 05 Equipment design
U+'$rre'te) @+$. $% 0$,#(inches !.!" !.!"
V%;Nv!$C+ $.0%$ $.%%&&
"rom graph 2v;fig 1($$3 4udwig, vol.+!$.%& %.6
)here>
S = liquid gradient in inches of liquid
Vo = -uperficial velocity based on column area ;ftCsec!
3.01+ %.&11
2v = correction factor for uncorrected liquid gradient
@o. of rows = 1
C$rre'te) @9 +'he# $% l2*) =.119 =.==5
T$tal Pre##*re Dr$&@Tra; :; in inches of liquid!
ht
-
8/12/2019 Distillation Column Design Multicomponent
20/23
Chapter # 05 Equipment design
3.%% +.1*
8ange for pressure drop is +( 0 in of water Ctray
-o pressure drop is with in the range
#ressure drop for trays ;in in,of water!
"or +3 plate above, and $$ plate below &6.$&$ 3$.3*
;mm of /g! 19.99 5.59
D$,+'$"er Pre##*re Dr$&:
'own comer friction loss plus underflow loss, hdu
+
006*&.%
=d
g
duA
Lh %.%366 in %.%+06 in
in mm of /g %.%0** %.%0&*+
)here>
d = down comer area in ft+
L2*) he-ht + )$,+ '$"er:
/d= hw M how M hd M htM S %.+% m %.$6* m
/d U -t which is in range.
Free He-ht + D$,+'$"er:
" = -tM hw( /d %.316 m %.0% m
Production of gasoline from naphtha $+*
-
8/12/2019 Distillation Column Design Multicomponent
21/23
Chapter # 05 Equipment design
Thr$, $!er ,er:
tw= %.1 howB "W$C+ $%1.6 mm 66.6 mm
D;+a"' Sl$t Seal:
hds= hssM how M SC+ 1*.&6 mm 6.+& mm
L2*) E+tra+"e+t:
( )d*f
AA
e(#$f$#'rat%
+= $.*$ mCsec %.+66 mCsec
)hereL
Vf = -uperficial velocity based on active area mCsec
2alculateL
+
$
*.$%3.+
+%L
%2
t
%+
3.*+ +.%0
"rom graph, ;fig 1($$& 4udwig, vol. +, p $&6!
)e C ;how M hss MhsX ! %.* %.%+*
nd
Wein Kg/min m2 0.024 0.002!
Production of gasoline from naphtha $+&
-
8/12/2019 Distillation Column Design Multicomponent
22/23
Chapter # 05 Equipment design
9ntrainment in 5gCmin ;)eB;cA +d!!%.36 %.$*
9ntrainment ratio %.%%1 %.%%3%&
The value of entrainment is low, so spacing is quite good.
He-ht $% C$l*"+:
/eight of column ; +% inches tray spacing!
/c= ;@ actualA $! -t M /
= ;30 A $! %.*%1 M $.6$1
= $1.* m
SPECIFICATION SHEET OF DISTILLATION
COLUMN D49=
I)e+t%'at$+:
Item 'istillation column
Item @o. T($%+
@o. required $
Tray type 7ubble cap tray
F*+'t$+: -eparation of 4ight /.2 from /eavy /.2
O&erat$+: 2ontinuousProduction of gasoline from naphtha $+
-
8/12/2019 Distillation Column Design Multicomponent
23/23
Chapter # 05 Equipment design
Materal ha+)le)
"eed Top 7ottom
Yuantity 3%1..01 5gmolChr $&6.+$$ kgmolChr $36.+ 5gmolChr
2ompositions
4ight key
/eavy key
+.*+ J
0.1+ J
0.3 J
%.%& J
%.3% J
$%.& J
Temperature $+* o2 01o2 +*% o2
De#-+ Data
#ressure = $*.+ atm 8eflux ratio = +.6+L$
@o.of trays = 30 2ap size = %.$%$&m
'iameter of column= $.%& m @o. of 2apsCtray = &%
-hell thickness = $$.11mm )eir length = %.1%%+* m
2orrosion allowance=+.%mm )eir height =&.+ mm
Tray spacing = %.*%1 m 'own comer area =%.$30 m+
/eight of column = $1.* m verall efficiency = &1J
Top 7ottom
#ressure dropCtray = 3.%% +.1* in. of water
9ntrainment ratio = %.%%1 %.%%3%&
Production of gasoline from naphtha $+1