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1.0 INTRODUCTION TO PRODUCTION OF ETHYL BENZENE
1.5 PROCESS SELECTION
In order to produce ethyl benzene as a desired product, there are a few process available which are
by unique process of toluene, super fractionation of mixed aromatic hydrocarbon and alkylation of
benzene with ethylene.The most suitable process for production ethyl benzene is alkylation of
benzene with ethylene. This process produce high purity of ethyl benzene as a main product
compared to other manufacturing process. Less of pure ethylene and benzene has been used in this
process. This process also has low operating condition and the cost of production is lower than
other process.
1.6 REACTION SCHEME THERMODYNAMIC
thyl benzene is produced by alkylation of benzene with ethylene, illustrated by the
following chemical reaction!
C"H"C#H$C"H%C#H%benzene
ethylene ethylbenzene
&enzene alkylation process, for the production of ethyl benzene, consists of three basic steps. The
alkylation reaction takes place at high pressure and low temperature. Typically, ethylene!benzene
molar ratios between '.(% and '.# are used. The reactor inlet temperature is controlled by recycling
a small portion of the reactor effluent. In transalkylation step, in which poly ethyl benzene at
presence of benzene are converted to ethyl benzene on a reverse alkylation process. Transalkylation
takes place in a separate reactor. Then in separation step, in which unreacted benzene, poly ethyl
benzenes and other components enter benzene recovery column and separated from each other. The
bottom for the benzene recovery column is sent to a product column, where ethyl benzene of )
**.*+ purity is taken overhead. or this reason # distillation columns has been used. The final
product is obtained in liquid phase.
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2.1 CHEMICAL DESIGN FOR DISTILLATION COLUMN
2.2 INTRODUCTION
igure (! -istillation column T/'(
-istillation column is use to produce high purity of liquid product at operating condition. 0ince
this criteria is crucial, therefore a suitable distillation column need to be chosen wisely since it
will effects the purity and amount of production. The purpose of T/'( is to separate the
ethylbenzene others chemical in stream (1. 2s a result , ethyl benzene discharged from the top of
T/'# as a liquid together with other light component. The bottom outlet of T/'# contains no
benzene.
STREAM 17
FLOWRATE : 13,321.5 kg/hr
COMPONENT :
Benzene ,
Eh!"#enzen$
T%&"ene
STREAM 1'
FLOWRATE : 2(,3(5.)kg/hr
COMPONENT : Benzene,Eh!"#enzene,
1,(*+ Eh!"#enzene
STREAM 1-
FLOWRATE : 11 2(.5kg/hr
COMPONENT :Benzene,
Eh!"#enzene,
1,(*+ Eh!"#enzene
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3ame 4nit eed Top &ottom
50("6 50(76 50(16
8apor fraction ' ' '
Temperature 9 7/." 1(.$ ($%.$
:ressure k:a ((' ('% (#'
;olar flow kmol
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=here
xi ? concentration of component i in liquid
phase yi ? concentration of component i in
vapor phase @i ? equilibrium constant of
component i
The saturated component solved by using the 2ntoinneAs equation as follows !
=here :sat ? saturated pressure in mmBg
T ? Temperature in 9
2, &, 9 ?2ntoineAs coefficient
9omponent 2 & 9
&enzene 7.'"$/7 (#*".*/ ##*.*("
thylbenzene ".*%7(* ($#$.#%% #(/.#(
(,$ diethylbenzene ".**1# (%11./( #'(.*7
Table #.# ! 2ntoineAs coefficient
or bubble point calculation at feed stream which is stream ("irst use Tb ? 7/."
o9 5 /$"."@6
:ressure ? ((' k:a ? 1#%.( mmBg
or bubble point calculation at bottom stream which is stream (1
irst use Tb ? ($%.$o9
:ressure ? (#' k:a ? *''.( mmBg
Component Xi, f %sat & mm'() *i *iXi,f&enzene 0.6244 618.$1 0.#49 0.468
0.33#3 98.02 0.12 0.04
(.$ 0.0381 1#.1$ 0.02 0.000#62
Total 1.0 0.$08
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or dewpoint
calculation at top stream which is stream (7
irst use Tb? 1(.$
o9
:ressure ? ('% k:a ? 717.% mmBg
#./ ! C4LI&DI4; 9>30T23T
The equilibrium constant can be calculated as follows !
Table 1 : Ki value for stream 16
Component Xi, t %sat & mm'() *i *iXi,t&enzene 0.9943 #91.4 1.00$ 0.9993
0.00$4 132.68 0.1# 0.00918
(.$ 0 24.#2 0.03 0
Total 1.0 1.00
Component Xi, b %sat & mm'() *i +i, b&enzene 0.00168 4062.$8 0.00$ 0.0000084
thylbenzen 0.8964 96#.3# 1.0#$ 0.96363
(.$ diethylbenzene 0.1024 266.3# 0.30 0.030#2
Total 1.0 1.00
Component Xi, b %sat & mm'() *i +i, b&enzene 0.00168 4062.$8 0.00$ 0.0000084
thylbenzen 0.8964 96#.3# 1.0#$ 0.96363
(.$ diethylbenzene 0.1024 266.3# 0.30 0.030#2
Total 1.0 1.00
9omponent Ei, t Fi, t @i, t&enzene 0.9943 0.9993 (.''%
thylbenzene 0.00$4 0.00918 (.7
(.$ diethylbenzene 0 0 '
Total (.' (.'
9omponent Ei, f Fi, f @i&enzene 0.6244 0.468 '.7$%
thylbenzene 0.33#3 0.04 '.((*
(.$ diethylbenzene 0.0381 0.000#62 '.'#
Total (.'
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Table 2 : Ki value for stream 17
Table 3 : Ki value for stream 18
#.$
DL2TI8 8>L2T2LITI0
Delative volatility,G is the volatility separation factor in vaporliquid system. In other
words, it is the volatility of one component divided by the volatility of the other. The
greater the value of G, the easier will be the desired separation. The relative volatility can
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be calculated between any two components in a mixture. &ased on @ values the relative
volatility can be expressed as belows
which is subscript L@ for light key and B@ is for heavy key.
The component separated are called light key, which more volatile . The component more
volatile than light key are called light key components and will be present in the bottom
in small amount. The component less volatile than the heavy key are called heavy
component and will be present in the distillate in small amount.5Heankoplis,#'($6. Light
component is the component of feed mixture which is desired to be kept out of the bottom
product while heavy key component is a component of feed mixture which is desired to
be kept out of the top product. Thus, the selection of key component is as below!
Light key ? &enzene
Beavy key ? thylbenzene
9omponent @ i, f G f
&enzene '.7$% ".#"
thylbenzene '.((* (
(,$ -iethylbenzene '.'# '.("1
T#"e ( : 0 "&e %r re4 1'
9omponent @ i, t G t
&enzene (.''% '.%*
thylbenzene (.7 (
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(,$ -iethylbenzene ' '
T#"e 5 : 0 "&e %r re4 17
9omponent @ i, b G b
&enzene '.''% '.''%
thylbenzene (.'7% (
(,$ -iethylbenzene './ '.#1
T#"e ' : 0 "&e %r re4 1-
The following approximation may be used to calculate the average relative volatility !
=here is Gf ? relative volatility of light key to heavy key at feed of column
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Gt ? relative volatility of light key to heavy key at top of column
Gb ? relative volatility of light key to heavy key at bottom of column
9omponent GL@,B@ Gavg
eed Top &ottom
&enzene 5 L@ 6 ".#" '.%* '.''% '.$$7
thylbenzene5B@6 ( ( ( (
(,$ -iethylbenzene '.("1 '.#1 '.##$
Table #.(#, G average value for all stream
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#.% DL4E D2TI>
The minimum reflux ratio can be estimated by using the method of approximation
evolved by 9olburn 5(*$(6 and the exact procedure of 4nderwood 5(*$16. The equation
can be express as belows
Gi ? relative volatility of component i with respect to some reference
Dm ? minimum reflux rati
Ei,d ? concentration of component i in the tops at minimum reflux
is the root of the following equation
xi,f ? concentration of component i in the feed
q ? depends on the condition of the feed
The value of q is given by
Bv,feed ? Latent heat of the feed
9p,feed ? 0pecific heat of the feed
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T 7/." 9
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Tbubble 7/." 9
0pecific heat (//.% J
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ix i ,f
i
&y using Hoal 0eek operation in ;icrosoft >ffice xcel the satisfactory value of is
(.'7**/7
9omponent Ei, f G i G iEi ixi , f
i
&enzene
'."#$$
".#" /.*( '.7%
thylbenzene
'.//7/
( './/7/ $.#(*"
(,$ -iethylbenzene'.'/1(
'.("1 '.''" '.''7
Total (.''
Table ! , data for calculation at feed stream
The value of is then substitute into the equation as below
ixi ,d
i=Rm+1
9omponent Ei, d G i G iEi ix i ,d
i
&enzene
'.**$/
'.%* '.%* (.#'$
thylbenzene
'.''%$
( '.''%$ '.'"1
(,$ -iethylbenzene
'
' ' '
Total (.''
Table ! data for calculation Dm at stream (*
Dm ( ? (.#7#
Dm ? '.#7#
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D ? (.%Dm
?(.%5'.#7#6
?'.$'1
#." ;I3I;4; 23- TB>DTI92L 34;&D > 0T2H0
;inimum stages
,a
2LF LD LW
2(6.26)(0.56)(0.005)
2.83
XLK
XHK
XHK
XLKblog
Nm=
0.9943
0.0054
0.8964
0.00168blog
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/m 11.#6 sta(es
!eoetial sta(es
R
R+1=
0.408
0.408+1=0.29
Rmin
Rmin+1=
0.272
0.272+1=0.213
Nm
N =0.49
11.76
N =0.49
N=24 theoretical stages(23 trays+1reboiler)
LOCATION OF FEED TRAY
logNe
Ns=0.206log [(!D )(
xf , HK
xf , LK)(Xb, LK
Xd , HK)2
]
=here EL@,- ? mol fraction of light key in distillate
EB@,- ? mol fraction of heavy key in distillate
EB@,& ? mol fraction of heavy key in bottom
EL@,& ? mol fraction of light key in bottom
Ga ? average relative volatility of light key
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logNr
Ns=0.206log[( 101.1170.2 )(
0.6244
0.3373 )( 0.8964
0.00168 )2
]
N r
Ns=0.47
3r 3s?# $
'.$73s 3s? #$
3s? ("./#
This mean feed tray is (" trays from top
#.1 9>L4;3 I9I39F
The prediction of overall column efficiency can be obtained from the correlation given
by >A9onnell below!
=here
Ma ? the molar average liquid viscosity, m3s
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Where 89SA,
89SB %nn n he "&6 e"%! e&%n
Te4;er&re 6e< ;%n =%;> -1.(
Te4;er&re ##"e ;%n =#%%4> 1(5.(
Aerge e4;er&re 113.( C/3-'.( ?
Component 5 5 B XF 7ean isosit"
&m/sm2)
isosit"
&m/sm2)
Benzene 328.49 182.48 0.6244 0.22 0.13#
t!"lben 410.$8 219.6# 0.33#3 0.1$ 0.0$1
1,4 - - 0.0381 3.6 0.13#
Thus the average a can be calculated as below
a ='.(/7 '.'%( '.(/7
? './#%
>verall efficiency is
' ?%( /#.% log5'./#%x /.$"#6
? $*./$ +
2.) N@MBER OF ACT@AL STAES
#! &ng e % %er"" r! een!,
E% =n&4#er % 6e" r! / n&4#er % &" r!
N&4#er % &" r! 23 / .()33 =('.'2 (' r!
-30ITF 23- DL2TI8 ;>L2D ;200
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Component feed Distillate bottom 7ola ei(!t
&(mol)
" ,liq# id
&:(m3)
Benzene 0.6244 0.9943 0.0016
8
#8.11 8#6
t!"lben 0.33#3 0.00$4 0.8964 106.1# 866
1,4 0.0381 0 0.1024 134.22 862
Relative Molar Mass, RMM
RMM = ( Component mole fraction x Molecular weight)
RMM at feed =(0.6!!x"#.$$) % (0.&&"&x$06.$") % (0.0$&!.) =#'.0
g*mol
RMM at +istillate(op -roduct)
=(0.!& x"#.$$) % (0.00'! x$06.$6') % (0 x$&!.$#$) ="#.& g*mol
RMM at ottom -roduct
=(0.00$6# x"#.$$) % (0.0#6! x$06.$") % (0.$0! x$&!.) =&.& g*mol
+ensit/ top
i1uid densit/, 2 = (0.!&x#"6) % (0.00'!x#66) % (0x#6)
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= #"!.06 g*m&
3apor densit/, 23 = ("#.& g*mol * .! m&*mol)("& 4 * &'!.! 4)
($.0' 5ar * $5ar)
= .# g*m&
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.$$ C7M8 +9:M;;R
he important factor that affects the column diameter is vapor flowrate.
he vapor velocit/ should 5e 5elow than which would cause excessive
li1uid entrainment or high pressure drop. o estimate the maximum
allowa5le superficial vapor velocit/, we use owenstein ($6$) e1uation
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or diameter column a5ove than $ m, plate spacing of 0.& to 0.6 m will
normall/ 5e used, and 0.! m ($' in.) can 5e taen as an initial estimate.
(Coulson > Richardon, 00&) 9n this design, taing plate spacing as 0.& m,
the allowa5le superficial vapor velocit/, calculated is=.3> D =.3 2> D =('*1>=.5> 1(.'25
4
1'.) 4 =n"&6ng 1G e! %r>
.$ C7M8 B;9B
?ithout considering the sirt or an/ support, the column height can 5e
calculated using the e1uation 5elow