3. The production of large amounts of heavy naphtha is
inevitable in refineries across Pakistan, amongst other
components which are also of immense importance p-
xylene holds extraordinary importance for Pakistan in
virtue of its value in both foreign and domestic markets.
P-xylene forms major raw material for the production of
terephthalic acid (TPA) which further converts into
polyethylene terephthalate (PET).
4. Toluene Methylation Process
PAREX Process
Isomerization of meta-xylene
0
10
20
30
40
50
60
70
Initial Investment/ $ Million
Initial Investment/ $ Million
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
Yield of Para-xylene
Yield of Para-xylene
8. Material
Carbon
steel
L:B:H Ratio 1:2:2
Height (H) 50 ft
Air pre heat (F) 400
Furnace length (ft) 25 ft
No. of tubes 32
Tubes skin
temperature (F)
1000
Flux (Btu/hr.ft2) 11500
Furnace Duty
(MMBtu/hr)
17.67
Stream tag 3
Description Octafiner Charge
Temperature 135 oF
Pressure 217 psig
9. M P
M O
2M TOL + TMB
ERGUN EQUATION:
CHEMICAL REACTION:
Meta Xylene Conversion = 29.19 %
Para Xylene Selectivity = 65%
Ortho Xylene Selectivity = 33.4%
% COKE = e-αt
REACTION TIME = 5.513 sec
10. Material Carbon
steel
Type Of Column Packed
Diameter Of Bed
(ft)
7
Diameter Of
Particle (in)
0.25
Porosity (φ) 0.45
Bulk Density Of
Catalyst (lb/ft3)
25.82
Designed Height
Of Packing (ft)
13.6
Catalyst Precoked
ZSM-5
Stream tag 3 4
Description
Reactor feed
from furnace
Reactor
Effluent
Temperature 135 oF 952 oF
Pressure 217 psig 173 psig
12. Material Carbon
steel
L/D 3.3
Length of Vessel
(ft)
15.19
Diameter of Vessel
(ft)
4.59
Volumetric Flow
rate (ft3/s)
42.89
Terminal Velocity
(ft/s)
2
Maximum Allowable
Velocity (ft/s)
2.58
Height of Liquid
Holdup Section (ft)
5
Retention Time
(min)
2
Stream tag 4 5 6
Description Reactor
Effluent
Light Aromatic
column feed
Fuel
gas
Temperature 95 oF 95 oF 95
oF
Pressure 160 psig 14 psig 140
psig
13. Heat Duty (MMBtu/hr) 3.8
No. Of Tubes 408
Length Of Tube(ft) 16
Outer Diameter of Tube
(in)
0.75
Pitch (in) 1
Tube Passes 8
Pressure Drop In Tubes
(psi)
2.26
Heat Transfer Area
(ft2)
1250
Internal Diameter of
Shell (in)
27
Baffle Spacing (in) 5.4
Pressure Drop in Shell
(psi)
1.34
Stream tag 5 7
Description Light Aromatic
column feed
Column
Bottoms
Temperature 95 oF 322 oF
Pressure 14 psig 14 psig
14. Mass Flow Rate
(lb/hr)
46895
Differential
Pressure (psi)
280
Horsepower (KW) 13.116
Horsepower (HP) 17.65
Efficiency 54.8
Brake Horsepower
(HP)
32.2
Stream tag 1
Description Octafiner charge
Temperature oF 60
Pressure psig 0
15.
16. Guide Words Parameters Causes Consequences Actions
Less
Less Flash
drum pressure
- Lower feed
temperatur
e
Higher liquid
level.
Install pressure
and
temperature
controller prior
to the drum.
- Leakage in
the Flash
drum
Vapor lost and
not recovered
at the top.
Install pressure
indicator on the
drum or replace
vessel.
Less level of
liquid in the
flash drum
- Blockage
in the inlet
stream
No separation
occurs.
Low level
alarm.
High
High Flash
drum pressure
- Blockage
in the
vapor
stream
Risk of drum
explosion.
Install pressure
alarm.
High liquid
level in the
flash drum
- Blockage
in the
liquid
stream
Less liquid
leaving the
flash drum.
Install high
level indicators
and high level
alarm should
be installed.
- Liquid
stream too
cold
Less vapor
fraction,
chances non-
condensable
will enter the
column that
follows.
- Install
temperatur
e
controller
on the feed
stream.
17. Guide
Words
Parameter Causes Consequences Actions
Less Pressure
- Leakage in the
column
- Vapor lost and
not recovered at
the top.
Install pressure
indicator on the
column or replace
vessel.
Level
- Blockage in the
inlet stream
- No separation
occurs.
Low level alarm.
Flow
- Pipe partially
blocked
- Pipe leakage
- Level decrease in
distillation
column
- Off specification
product
- Back flow of
material
Install check valve
Temperature
- Furnace Failure
- Low power
supply
- Low energy
steam
- Reaction favor to
reactant
formation
Install monitoring
system and
temperature
sensor
Supply enough
energy
High Level
- Output pipe
blockage
- Overpressure of
reflux drum
- Condensed
liquid flow back
in liquid
Install high level
alarm
Scheduling
inspection
Temperature
- Furnace
Malfunction
- Temperature
control failure
- Difficult to
remove excess
heat
- Steam become
superheated
Install temperature
sensor
Regular system
checking
Flow
- High pressure
from source
- Flooding in
Distillation
Install bypass line
with a manual
21. Mass Flow rate
Process Stream
18000 lb/hour
Mass Flow rate
Ethylene
Refrigerant
15000 lb/hour
Inlet
Temperature of
Ethylene
-71 F
Outlet
temperature of
Ethylene
-18 F
Inlet
temperature of
Process Stream
-11 F
Outlet
Temperature of
Process Stream
-45 F
Mass Flow rate
Process Stream
10375 lb/hour
Mass Flow rate
Propane
Refrigerant
9000 lb/hour
Inlet temperature
of Propane
-1 F
Outlet
Temperature of
Propane
59 F
Inlet temperature
of Process
Stream
64 F
Outlet
Temperature of
Process Stream
25 F
2nd Stage Crystallizer1st Stage Crystallizer
24. Purchased Cost of Equipments (PCE) $1394897.8
Physical Plant Cost (PPC) $3040976
Fixed Capital Investment (FCI) $4575263
Working Capital Investment (WCI) $823547
Variable Costs $21766416
Utilities Costs $55023
Fixed Costs $2276826
Annual Production Cost $33660539
Profit Per Year $184828
Payback
period
13.59 years
25. Discounted Purchased Cost of
Equipments (DPCE)
$209234
Discounted Physical Plant Cost
(DPPC)
$456129
Discounted Fixed Capital Investment
(DFCI)
$686286
Discounted Working Capital
Investment (DWCI)
$123531
Discounted Variable Costs $21766416
Discounted Utilities Costs $55023
Discounted Fixed Costs $2276826
Discounted Annual Production Cost $33660539
Discounted Profit Per Year $184828
Payback
period
2.04 Years
