Hydrocarbon Processing - December 2020 - 41

Special Focus

Plant Design, Engineering and Construction
H. LAI, COOEC Canada Co. Ltd., Calgary, Canada; and
Q. WU, China National Offshore Oil Corp., Beijing, China

Debottleneck H2 production for gasifier
PSA-based plant
The Canadian oil sands reserves in
the area surrounding Fort McMurray, Alberta in Canada contain in excess of 165
Bbbl of recoverable bitumen. Of these
resources, more than 80% are located below the earth's surface and are recovered
using an in-situ technique, such as steamassisted gravity drainage (SAGD).1,2
One oil sands plant with a design
capacity of 72,000 bpd of bitumen is in
southern Fort McMurray, Alberta. The
plant commenced operation in 2008. As
shown in FIG. 1, this plant utilizes SAGD
for in-situ production of bitumen, as well
as full onsite upgrading of bitumen to
premium synthetic crude oil (PSC).
Unlike coker-based upgraders where
asphaltene residue is converted to petroleum coke and hydrogen (H2 ) is produced
through reforming of natural gas, the primary upgrading for this plant is accomplished using solvent deasphalting (SDA)
and thermal cracking to convert the raw
bitumen into a bottomless, sour synthetic
crude and a stream of liquid asphaltenes.
The sour crude is fed to a hydrocracker for
the second upgrading to sweet synthetic
crude, while the asphaltene is gasified to
produce H2 for the hydrocracker and fuel
for power and steam generation.
The upgrader consists of six main
process units: a diluent recovery unit
(DRU), a vacuum distillation unit
(VDU), an SDA unit, a thermal cracking unit (TCU), an asphaltene gasification unit (AGU) and a hydrocracking
unit (HCU). Diluted bitumen (dilbit)
from the SAGD plant is treated and distilled in a DRU to desalt the bitumen
feed, recover diluent and produce light
gasoil. Atmospheric residue (AR) and
thermally cracked AR are routed to the
VDU, where the vacuum gasoil (VGO)
is lifted out of the feed and vacuum resi-

due (VR) is fed to SDA to separate asphaltene from deasphalted oil (DAO)
using supercritical extraction with normal pentane. DAO is thermally cracked
and then distillated into AGO and AR
while asphaltenes are partially oxidized
in four gasifiers to form a synthetic gas
rich in H2 and carbon monoxide (CO).
After being treated to remove H2S, the
raw syngas is purified in a pressure swing
adsorption (PSA) unit to produce highpurity H2. Collected AGO and VGO
with H2 are hydrocracked in the HCU
into the final PSC product.
The operating company planned to
restart the downstream upgrader facility after it was idled in 2016 while the
upstream SAGD central processing facility (CPF) is in operation. To determine

the optimum solutions for the upgrader
restart, the upgrader restart project was
developed to examine restart configuration scenarios and analyze the costs/
benefits of the debottlenecking options.
Historical operating performance has
shown that the existing PSA H2 purification system is incapable of supplying
H2 at the designed production rates. As
a key debottlenecking retrofit, this study
will focus on evaluating and screening
debottlenecking options for the existing
H2 production system.
Operation challenges in H2 production. The H2 production system,

as shown in FIG. 2, utilizes asphaltene
gasifiers to produce the raw syngas, followed by the acid gas removal and PSA

SAGD CPF

Upgrader
Diluent

SAGD
reservoir

Emulsion
HP steam

CPF
FWKO +
treater
Steam
generator

Thermal
cracking unit

Dibit

Diluent
recovery
unit

Vacuum
distillate
unit

Solvent
deasphalting
unit

Sulfur
recovery
unit

Asphaltene

VGO
AGO

H2
Hydrocracker
unit

Syngas

Sulfur

DAO

Asphaltene
gasiﬁcation
unit

Air
separation
unit

Premium
synthetic crude

FIG. 1. Block flow diagram of integrated upgrader with SAGD central processing facility.

S92-cogeneration

Asphaltene

S90-tail gas

Sweet
syngas

Raw syngas
T

S89-H2

T
T

Asphaltene
gasiﬁcation

Acid gas
removal

T100

S88-PSA

PSA

FIG. 2. Existing H2 production sketch.
Hydrocarbon Processing | DECEMBER 2020

Hydrocarbon Processing - December 2020

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