are of good quality and require much less downstream treatment. The naphtha
produced is (as in the case of distillate hydrocracking) high in naphthene
content ideal for gasoline production or as feed to an aromatic production process.
The middle distillates also are of high quality with the kerosene fraction
having very low smoke point and the gas oil fraction having a good cetane
number. In the process illustration given in Fig. 15, the light distillate liquid
from the cold flash drum and the associated vapor are routed to a distillate
hydrocracker recovery side for further processing and fractionation. These recovery units consist of a main fractionation tower and a light-ends unit which
includes an absorber column.
Appendix Sizing a Thermal Cracker Heater/Reactor
In this example, it is required to define a thermal cracker in terms of coil volume and
temperature profile in processing an atmospheric residue from Sassan crude. The
25,500 BPSD of the +600
F residue is preheated to 500
F by heat exchange with
the cracker’s products and reflux stream before entering the convection side of the
cracker’s heater/reactor. It is required to produce a conversion (based on gas through
naphtha of 260
F cut point) of 9 wt%, and the heater will be fitted with 4
00 schedule
80 tubes throughout. It will be designed to have three sections which are:
• The convection section with a heat flux of 12,000 Btu/h sq.ft.
• The radiant heater section with a heat flux of 15,000 Btu/h sq.ft.
• The soaker section with a heat flux of 10,000 Btu/h sq.ft.
The heater section and the soaker section are divided by a fire wall. A predicted
temperature profile is given in Fig. 17.
The salient temperature and pressure conditions are as follows:
Convection inlet ¼ 500
F at 330 psig pressure
Heater inlet ¼ 700
F at 320 psig
Soaker inlet ¼ 820
F at 290 psig
Soaker outlet ¼ 920
F at 250 psig
A 600 psig steam is introduced into the heater inlet coil. This will be at 10 wt% of
the residue feed. Details of the residue feed are as follows (a TBP curve of the feed
is given in Fig. 18):
Feed gravity ¼ 18
API 7:88 lbs=gal
ð
Þ :
Feed rate ¼ 25, 500 BPSD ¼ 351, 645 lb=h:
Volume of waxy distillate in the feed to 1, 022
F cut point ¼ 68 vol:%
¼ 17, 340 BPSD
Upgrading the Bottom of the Barrel
557
produced is (as in the case of distillate hydrocracking) high in naphthene
content ideal for gasoline production or as feed to an aromatic production process.
The middle distillates also are of high quality with the kerosene fraction
having very low smoke point and the gas oil fraction having a good cetane
number. In the process illustration given in Fig. 15, the light distillate liquid
from the cold flash drum and the associated vapor are routed to a distillate
hydrocracker recovery side for further processing and fractionation. These recovery units consist of a main fractionation tower and a light-ends unit which
includes an absorber column.
Appendix Sizing a Thermal Cracker Heater/Reactor
In this example, it is required to define a thermal cracker in terms of coil volume and
temperature profile in processing an atmospheric residue from Sassan crude. The
25,500 BPSD of the +600
F residue is preheated to 500
F by heat exchange with
the cracker’s products and reflux stream before entering the convection side of the
cracker’s heater/reactor. It is required to produce a conversion (based on gas through
naphtha of 260
F cut point) of 9 wt%, and the heater will be fitted with 4
00 schedule
80 tubes throughout. It will be designed to have three sections which are:
• The convection section with a heat flux of 12,000 Btu/h sq.ft.
• The radiant heater section with a heat flux of 15,000 Btu/h sq.ft.
• The soaker section with a heat flux of 10,000 Btu/h sq.ft.
The heater section and the soaker section are divided by a fire wall. A predicted
temperature profile is given in Fig. 17.
The salient temperature and pressure conditions are as follows:
Convection inlet ¼ 500
F at 330 psig pressure
Heater inlet ¼ 700
F at 320 psig
Soaker inlet ¼ 820
F at 290 psig
Soaker outlet ¼ 920
F at 250 psig
A 600 psig steam is introduced into the heater inlet coil. This will be at 10 wt% of
the residue feed. Details of the residue feed are as follows (a TBP curve of the feed
is given in Fig. 18):
Feed gravity ¼ 18
API 7:88 lbs=gal
ð
Þ :
Feed rate ¼ 25, 500 BPSD ¼ 351, 645 lb=h:
Volume of waxy distillate in the feed to 1, 022
F cut point ¼ 68 vol:%
¼ 17, 340 BPSD
Upgrading the Bottom of the Barrel
557