TOPPING UNIT

The Topping unit consists of the following –

▪ Atmospheric distillation unit
▪ Stabilization
▪ Re-distillation

ATMOSPHERIC DISTILLATION UNIT

Atmospheric Distillation Unit is the primary crude oil fractionating unit. This unit was designed for
processing 1.5 million MT of ALC (Arabian Light Crude) and Murban crude oil in 330 days per year of
continuous operation. The aim of the Atmospheric Distillation Unit is to fractionate the crude oil in
order to give the following-
• Gas
• Total Gasoline (TG)
• Kerosene-I (K-I)
• Kerosene-II (K-II)
• Light Gas Oil (LGO)
• Heavy Gas Oil (HGO)
• Residue (RCO)
The total gasoline is supplied to the stabilization column C-1103 in which gasoline de-butanization is
carried out. This de-butanized gasoline is then fractionated into light and heavy gasoline in the Re-
distillation column C-1104.

PROCESS DESCRIPTION
The feed (crude oil) is pumped directly from the crude oil storage tank by the feed pump P-1101 and
after preheating in various heat exchangers it is introduced in furnace F-1101AB. The flow rate of the
feed is controlled by FRCV-1101 & 1102. In the Furnace the feed (crude) is heated to 366 0C and so
it (the feed) is partially vaporized. This partially vaporized feed is then sent to the Atmospheric
Distillation Column C-1101, which is equipped with 33 trays. In this column the crude is fractionated
to give the following products-
• TG
• K-I
• K-II
• LGO
• HGO
• Residue

1
TG is condensed in the aero condenser EM-1123, then in the water cooler E-1110AB. The pressure of
the reflux drum B-1102 is controlled by departure of gas to the flare through PICV-1101. In this reflux
drum, gasoline and water are separated by decantation. Part of the gasoline is taken out by pump
P-1109A/B to be refluxed under temperature control (TRCV-1102) at the top of the column. The other
part is taken out by pump P-1110 A/B and sent as feed for the stabilization column C-1103 under the
level control LCV-1103 of B-1102. Water is evacuated by gravity to the sewer under the level control
LCV-1104.

KEROSENE-I is withdrawn from tray no. 26. It flows by gravity into the stripper column C-1102A
under the level controller of the stripper LC1105. The stripping of Kerosene is done by the
superheated steam. The stripped kerosene-I is taken out by the pump P-1103. After exchanging heat
with the crude in exchanger E-1101, it is cooled in the water cooler E-1111 and then sent to the
storage tank under the flow control FRC-1104.
KEROSENE-II is withdrawn from tray no. 20. It flows by gravity into the stripper column C-1102B
under the level controller of the stripper LC-1106. The stripping of kerosene-II is done by
superheated steam. The stripped product is taken out by pump P-1104 and sent to the exchanger
E1102 in which there is a heat exchange with the crude. It is then cooled in the water cooler E1112
and then sent to the storage tank under the flow control FRC-1105.
PICV-1101B
FG
EM-1123 A-F
T RC- FR FLARE
1102 1104
E-1110 AB
33
B-1102
CW CW LCV-1104

C-1101 26
TG
T O C1103

STEAM
FI-1104 LC-1105
C-1102 P-1109 A/B P-1110 A/B

E-1101
CRUDE 20 K-I
P-1103A E-1111
E-1104
FI-1105 LC-1106 CRUDE CW
CRUDE STEAM
E-1120 E-1105 P-1103B E-1102
E-1112
K-II
P-1104
FI-1106 LC-1107 CRUDE CW
P-1108 12 STEAM
HG (Bottom E-1106
E-1103
of C-1104) 9 LGO
P-1105A E-1113
FI-1107 LC-1108 CW
STEAM CRUDE CRUDE
FEED P-1105B
E-1107
(CRUDE) HGO
FROM OVERFLASH P-1106 E-1114
LI QUID CW
F-1101 FI-1101
CRUDE
FROM
E-1118
F-1101 B-1101 STEAM
Bot tom H ot
F RCV- C irculation
1101 of C -1103
&1102 P-1120A
P-1120B E-1108 E-1115
CRUDE RCO
OIL E-1109
CW
P-1107 A/B CRUDE CRUDE CRUDE

Fig. 3.1 : ATMOSPHERIC DISTILLATION

2
Part of the heat of the atmospheric column is recovered below the withdrawal tray of kerosene-II by
circulating reflux. The circulating reflux is withdrawn from tray no. 17, taken out by pump P-1108,
partially sent to the E-1105 where it exchanges heat with the crude and partially sent to re-boiler
E-1120 of the re-distillation column C-1104. The outlet temperature of the reboiler is controlled by the
circulating reflux flow rate directed to this one, which is controlled by TRCV-1104 located at the outlet
of E-1105. The whole circulating reflux then exchanges heat with the crude in E-1104 and is re-
introduced in the column on tray 21 after flow rate control of FRCV-1108. The temperature of the
circulating reflux is controlled by TICV-1101 acting on the bypass of E-1104.

LIGHT GAS OIL is withdrawn from tray no. 12. It flows by gravity into the stripper column C-1102C
under the level controller LC1107 of the stripper. The stripping of the light gas oil is done by
superheated steam. The light gas oil is taken out by the pump P-1105 and is sent to the exchangers
E-1106 & E-1103, where it exchanges heat with the crude. It is then cooled in the water cooler E1113
and is sent to the storage tank after controlling the flow by FRC-1106.

HEAVY GAS OIL is withdrawn from tray no. 9. It flows by gravity to the stripper column C-1102D
under the level controller LC-1108 of the stripper. The stripping of the heavy gas oil is done by
superheated steam. The heavy gas oil is taken out by the pump P-1106 and is sent to the exchanger
E-1107, where it exchanges heat with the crude. It is then cooled in the water cooler E1114 and is
sent to the storage tank after controlling the flow by FRC-1107.

THE ATMOSPHERIC RESIDUE is stripped by the superheated steam in the bottom of the atmospheric
column. The stripped residue is taken out by the pump P-1107 and partially sent to E-1109 A/B,
where it exchanges heat with the crude, partially to the reboiler E-1118 of the stabilization column
C1103. The outlet temperature of the reboiler is controlled by the flow rate of the residue directed to
this one, which is controlled by TRCV 1103 located at the outlet of E-1109B.
Then the residue exchanges heat with the crude in E-1108 and is cooled in the water cooler E-1115.
The Atmospheric residue flow rate is controlled by the bottom level controller of C-1101 (LIC-1102).
FRC-1103 indicates the flow rate of residue to storage.

3
STABILIZATION SECTION

OBJECTIVES 1103 is controlled by LC-1110, which acts on

the LPG flow to Merox-III. The stabilized
Objective of this unit is to separate the light gasoline is taken out from the bottom of the
components (Propane & Butane) of the Total column C-1103 and is introduced into the re-
Gasoline of C-1101 and thus stabilize the distillation column C1104 under level controller
Gasoline. So the name of this unit is LC 1109, after exchanging heat with the feed
debutanizer or stabilizer. in E-1116. The re-boiling of the column is done
by the reboiler E-1118 , which is heated by
PROCESS DESCRIPTION part of the atmospheric residue. The outlet
temperature of the reboiler is controlled by
The gasoline of the atmospheric distillation TRCV-1103 acting on the flow rate of
unit is pumped by P-1110 and is pre-heated by atmospheric residue going through E-1118.
stabilized naphtha in heat exchanger
E-1116 A/B. After preheating, the gasoline is FG

PICV-1102A PICV-1102B
introduced in the stabilization column C-1103, 70-72 0C
9.2-9.4 BAR.G
9.0 BAR.G
E-1117
25
FI-1108
which is equipped with 25 trays. The inlet 24
23
22
21 B-1103
temperature of the gasoline feed to the
CW LC-1110
20
19
40-42 0C

C-1103 18
17
column is controlled by the by-pass of 16
15
14
FIC-1102

stabilized gasoline around E-1116 A/B. 130-133 0C

13
TRCV-1105
DRAIN

12 P-1111 A/B
11
10
09 LPG TO
The overhead vapor product of the column C- 08
07
FIK-101 MEROX-III
FR-1101
06

1103 is condensed in the water cooler E-1117 05

04
03
02
and is introduced directly into B-1103. The 01
LC-1109

178-182 0C
pressure of the balloon B-1103 is controlled by 9.8-9.9 bar.g

PICV-1102B, releasing vapor to the fuel gas

E-1116A

system. The liquid of B1103 is taken out by the

TRCV-1127

E-1118
TOPPING RESIDUE
pump P-1111 A/B, one portion is re-introduced NAPTHA
E-1116B TO C-1104
in the column C-1103 above tray 25 as reflux TG
FROM
after controlling the temperature by TRCV- C-1101
Fig. 3.2 : STABILIZATION SECTION

1105 and another portion is withdrawn and

sent to Merox-III as LPG. The liquid level of B-

4
RE-DISTILLATION SECTION

OBJECTIVES

The objective of the re-distillation unit is to

fractionate the stabilized gasoline of C-1103 The re-boiling of the column C-1104 is done by
and produce light gasoline (LG) and heavy E-1120 which is heated by a part of the
gasoline (HG). circulating reflux of C-1101. The outlet
temperature of the reboiler is controlled by
PROCESS DESCRIPTION TRCV-1104 acting on the circulating reflux flow
through E-1120.
The stabilized gasoline of C-1103 is introduced
into the re-distillation column C-1104, which is 82-85 0C
EM-1124 A/B FLARE

0.3-0.6 bar.g PICV-1103A

equipped with 20 trays.

PICV-1103B
0.6 bar.g
20 FG
19
18
17
C-1104 B-1104
The overhead vapor product of the column C- 16
15
LC-1112

14
13
1104 is condensed by aero condenser EM-1124 85-88 0C 12
11
10 FICV-1103
09
and then sent to the accumulator B-1104. The 08
07
DRAIN
06
05
pressure of the B-1104 is controlled by 04
03
P-1113 A/B

02 E-1122 FR-1102
LCV-1109 LG TO
departure of the gas to the flare system
01
85-88 C 0 STORAGE
CW

through PICV-1103A. The liquid level of B- FI-1109

LC-1111

130-132 0C
1104, known as light gasoline, is pumped out 0.7 bar.g
INTERMEDIATE
REFLUX
by P-1113. One portion of this liquid is used as
FR-1103
E-1121
HG TO
column head reflux and the other portion is STORAGE
P-1112 A/B CW

sent to the storage or merox unit for

sweetening through water cooler E-1122. The
STABILIZED
level of B-1104 is controlled by LC-1112, which NAPTHA FROM Fig. 3.3 : RE-DISTILLATION SECTION
C-1103
acts on the light gasoline flow.

The heavy gasoline is pumped out by P-1112

from the bottom of the column C-1104. After
cooling in the water cooler E-1121, it is sent to
the storage under level controller LC-1111 of
C-1104.

5
 OPERATING PARAMETERS OF THE TOPPING UNIT

ATMOSPHERIC DISTILLATION SECTION PRESSURES

Top of the column C-1103 = 9.2-9.4 BAR.G
TEMPERATURES Bottom of the column C-1103 = 9.8-9.9 BAR.G
Feed to Column C-1101 = 366 C 0
Reflux Balloon B-1103 = 9.0 BAR.G
Top of the column C-1101 = 127-134 0C
Bottom of the column C-1101 = 360-362 0C REDISTILLATION SECTION
Internal Reflux to C-1101 = 135-140 0C
Reflux to C-1101 = 40-42 0C TEMPERATURES
Stack bottom of the furnace F-1101= Feed to column C-1104= 85-88 0C
Maximum. 510 0C Top of the column C-1104= 82-85 0C
Bottom of the column C-1104= 130-132 0C
K-I draw temperature = 180-182 0C LG to storage = 45-50 0C
K-II draw temperature = 200-208 0C HG to storage = 40-48 0C
LGO draw temperature = 312-320 0C
HGO draw temperature = 348-352 0C PRESSURES
Top of the column C-1104= 0.3 BAR.G
PRESSURES Bottom of the column C-1104= 0.7 BAR.G
Top of the column C-1101 = 2.0-2.5 BAR.G Reflux Balloon B-1104= 0.3- 0.7 BAR.G
Bottom of the column C-1101 =2.2-2.7 BAR.G
Reflux drum B-1102 = 0.60-0.95 BAR.G
Flash Drum B-1101 =3.0-3.6 BAR.G
Process steam pressure (PC-1601) = 4.2-4.6
BAR.G

STABILIZATION SECTION

TEMPERATURES
Feed to the column C-1103 = 130-133 0C
Top of the column C-1103 = 70-72 0C
Bottom of the column C-1103 =178-182 0C
Reflux to the column C-1103 = 40-42 0C

6
LIST OF EQUIPMENTS USED IN THE TOPPING UNIT

COLUMNS
C-1101 = Atmospheric Distillation Column (Main Distillation column)
C-1102 = Stripping Column
C-1103 = Stabilization Column
C-1104 = Re-distillation Column

BALLONS
B-1001 = FG Storage
B-1101 = Flash Drum
B-1102 = Reflux Drum for C-1101
B-1103 = Reflux Drum for C-1103
B-1104 = Reflux Drum for C-1104

PUMPS
P-1101 A/B = Feed (Crude) pump to take feed from crude storage tank.
P-1102 = Feed pump to take feed from Flash Drum B-1101.
P-1103 A/B = Kerosene-I Pump.
P-1104 = Kerosene-II Pump.
P-1105 A/B = LGO Pump.
P-1106 = HGO Pump.
P-1107 = Topping Residue Pump.
P-1108 = Internal Reflux Pump of C-1101.
P-1109 A/B = Reflux Pump of C-1101.
P-1110 A/B = TG Pump to C-1103
P-1111 A/B = LPG Pump to Merox-III.
P-1112 A/B = HG Pump to storage.
P-1113 A/B = LG Pump to storage.
P-1120 A/B = Hot reflux Pump of C-1101.

7
HEAT EXCHANGERS

E-1101 = Crude exchanges heat with Kerosene-I.

E-1102 = Crude exchanges heat with Kerosene-II.
E-1103 & E-1106 = Crude exchanges heat with LGO.
E-1104 & E-1105 = Crude exchanges heat with Internal reflux of C-1101.
E-1107 = Crude exchanges heat with HGO.
E-1108, E-1109 A&B = Crude exchanges heat with Topping Residue.
E-1110 A/B = Water cooler that cools overhead gas of C-1101.
E-1111= Water cooler that cools Kerosene-I product.
E-1112 = Water cooler that cools Kerosene-II products.
E-1113 = Water cooler that cools LGO product.
E-1114= Water cooler that cools HGO product.
E-1115 = Water cooler that cools Topping residue.
E-1116 A/B = Pre-heater of TG to C-1103 by Bottom Stabilized naphtha of C-1103.
E-1117 = Water cooler that cools overhead gas product of C-1103.
E-1118 = Bottom Re-boiler of C-1103 that is heated up by Topping Residue.
E-1120 = Bottom Re-boiler of C-1104 that is heated up by Internal Reflux of C-1101.
E-1121 = Water cooler that cools HG product.
E-1122 = Water cooler that cools LG product.

EM-1123 A-F = Aero condenser that condense overhead gas product of C-1101.
EM-1124 A-B = Aero condenser that condense overhead gas product of C-1104.