CHE Plant Design I Example

7/28/2019 CHE Plant Design I Example

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Example

Benzene, Toluene and Xylenes are important upstream products widely used inpetrochemical industry. They can be produced from naphtha by catalytic reforming reaction. '

Reaction products from reforming reactor are separated and purified to produce high qualitygrade Benzene, Toluene and Xylenes. During production process, contaminated product

stream (product stream with several compounds mixed together) is also produced as a

byproduct. A sample composition of the byproduct stream is shown in Table 1. Thisbyproduct stream can be converted to valuable products by additional processes such as

hydrodealkylation, isomerization and dismutation processes.

. Table 1

Composition of Byproduct Stream

v,tto/o

Benzene 6Toluene 47

Ethylbenzene 11

m-Xylene* 34

o-Xylene Balance

Hydrodealkylation of Toluene, Ethylbenzene and Xylene can be operated with or withoutcatalyst. Operating conditions of the reactor depend on the operating mode selected. Ourresearch laboratory conducted several experiments using special type of catalyst and

concluded that the reactions proceed as follow

CaHs-CHt + Hz - CaHa + CHd, (l)CaCs-CzHs + Hz - CaHa + CzHa (2)

CaHs-(CHz)z + 2Hz - 2CoHa + 2CHt, (3)

2CaHe ' CeHs-CaHs + Hz (4)

Reaction (4) is the only side reaction occured. Each reaction proceeds at different rate andgives different conversion at reactor outlet. Using data available from our experiments it is

estimated that conversion of reactions (2) to (4) are as follow

xz = 1 - 0.381rr

x3 = 0.746 xr

x4 = 0.012 (xr + xz)

Where xt, x2, J[3 and x4 ara conversions of Toluene, Ethylbenzene, Xylenes and Benzene,

respectively. Conversions of reactions (1) to (3) are estimated at the reactor inletconcentration of each reactant but conversion of reaction (4) is estimated at the reactor outletconcentration.



High purity grade product and byproduct are to be produced from_.this process. Hydrogenfeedstream is not a pure hydrogen gas and it contains approximately 5.8 wtTo of methane. Anexcess amount of hydrogen is required at the reactor inlet and at the process inlet.

The company plans to design a catalytic hydrodealkylation process for the production ofBenzene at Toluene conversion (x1) of 0.8. High purity Toluene or mixed Xylene can also

produced as byproducts if desired. Product stream has a capacity of 350,000 tonnes per year

ofBenzene.



0

- Liquid F€ed otreorn is ehown in Frgure I

0

- (ro.o f,ti sheo,rn consrsto of hgdrogevr ond meth&he r s;r nrl/ I

6

covnpositron of \ptodn*- sheam

comoontvrt rrhl'l

hemeY\c

to\wns ^-----.-------- 01

Bh5\btnzent =-- 11

m-Xg\cnt

0 - Xulgns '----.'------ l trtn hburnct')J

Cornp,nerrto in Feed gh^eqfi ([nput structure )

mrnponent rrrPut

ftgdrqevr #* rerc{aYrt

t'\etha,tas # imPut\

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Toluerte reocta,nt

\lbunzerrei- reoffount

'm - Igltne =+ reo,ctanl

0 -Xt5le[€, & re,q,cta,nt

0 tv"uurr emtinuous aso,ooo or"ir

veg lovg rtnrliovr tiYne a r"rr

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CI xor input ,irnraru coinlpt rr\

- Liquid feed s+rea,ln qrlila,iYrs benz€ylertotuev,e, ethrllbgv'zent, wr -(glene r 0 -(ylene.

Beyrxne is our pimarg pruduct a,nd is nol considffed l0 be prewnt in l*X o,moufr.

0the,r cornpoYrcnts ore rcarta/nt



fn'put- o,,l-Ff - oh'Errtlrs

Deriinafion ' Leo,ys btnxvre in liqurd feed olrcont

mmF,n*rt or.nu+ * - ,rn di,m codeBp.

-

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Lquid product -=- Primary prodrd

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m - XXlcvrt :- L\qild rearturnrt ^z-------'\--'- r Necgcte

\

o -xgltnt Liqutd rtar,toflt ^-Recgclt

J+

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I

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rreiqhhun,g *rnpnrnf miorlu rnrui tdtonlr

- $mQ nmot ornnil';n,qni J d od;'ti,rrn:,

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atre"rn A

ct/ B teb/r,

: toq hn/ rJ

(rsuo )

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- rt o4 atafe Proce,S

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Oesiqrr Cohvertioh 'X1 ' 0 '8

[t = o'bq5

ls = o'st?

lq = o'o1s



|1V,1

if

lbluene mqm fulonte

Ce,Hr - CH, * hr )

tzl

+? 1({?}q2

CsHs * gH+

78 1b

utrlz).tb.!+rlq2 q2

818 2,2

Ethgtberrzcvre mo,sa hhryr(

Cul1s- Cthr t H,

-,CsHg + C2Hg

$b27tb0

iS fl A Cttt +s(ttl ,0 Ct1)

lob to[ tOt

11 o'2' B't- - t'l

[glcvreo mo.ss bilo*cg

CrH+' lcho), * zHl

-)CrH, + 2CHn

1oL tt ?\ Z2

1+ bL JL (st) !4,"1 arcer)

10b 10b 101

'b L 1'[ 2u'r 11

btxwwe produoe : r bq,g + E.l t 2L.r " Ao'( +Pg

t 0,1 + l,q : l.t h5

t:L + \l " 1q,2 hu

s.l tpl

(r

c

I

zCgHt

rTr

(to.q '( 0.011) q tm produi $on*tnv x (Jvry0RrolT cx*) )

[tgdroqen re4uirtd :

l,tetharrs prodwe .

E|\a,r,lt pr0duca :

side renctlb"rt

1.qs

- crhr - cst+r tHz

15q 2.

l!! tt*s) t lttslt*,'*,



----

qq,.2.7-

6:$ 7.

7

4

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= Tsnr hg

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Fee,d

it fsed

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= Z.ru tPg

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ligtho[e # 0.1?

-

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-ipheirgl

a50

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267\4 U 2-bboo

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CHE Plant Design I Example

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