Chemical Engineering April 2012 - 22

Off-gas
Stripper
Newsfront
Hydrocracker
product
cost is so much lower that it is much
more cost-effective.
Meanwhile, Molycorp., Inc. (Greenwood
Village, Colo.; www.molycorp.
com) is ramping up production dramatically
at its rare earths mine and
process plant in Mountain Pass, Calif.
The expansion will increase production
from about 3,500 metric tons (m.t.) this
year to 19,050 m.t./yr of ten rare earth
materials (total U.S. consumption of
rare earths is 15,000-18,000 m.t./yr).
In another catalyst development,
an FCC catalyst system designed in a
collaboration between Grace Davison
and Rive Technology, Inc. (Monmouth
Junction, N.J.; www.rivetechnology.
com) has reduced undesirable bottoms
production by 7% in a full-scale test at
Country Mark's 27,000-bbl/d refinery
in Mount Vernon, Ind. The improved
conversion rate amounts to a profit
improvement of $0.72/bbl, says Larry
Dight, Rive's senior vice president for
research and development.
The catalyst system integrates
Rive's " molecular highway " zeolite
technology (Figure 1) with Grace Davison's
knowhow in zeolite manufacturing
and catalyst formulation. The
" highways " consist of a tunable percentage
of interconnected mesopores
of about 40 Å dia. These mesopores
allow the cracking of large molecules
that are too large to enter the standard
micropores of <10 Å that make
up the bulk of the zeolite. They also
permit the passage of large product
molecules of gasoline or light cycle oil
that might otherwise be trapped and
overcracked in the micropores.
Dight says the partners have now
developed a more robust and less expensive
manufacturing process and
have produced a " substantial quantity "
of the catalyst in preparation for
a second test in a different refinery
this fall, prior to commercialization.
The catalyst will likely cost more than
a standard catalyst, he says, but this
will be more than offset by the increased
performance.
Hydrocracking
An undesirable side reaction of hydrocracking,
used to obtain middle distillate
fuels from heavy vacuum-gas
oils, is the production of heavy polynuclear
aromatics (HPNAs), which
Steam
Diesel
Kerosene
HPNA
trim
UCO = Unconverted oil
HUCO = Heavier unconverted oil
Recycle oil
UCO
Steam
HUCO bleed
0.5-1%
of feed
FIGURE 2. The HPNA Trim process reduces the ultimate UCO bleed by as much as 80%
build up in the unconverted recycle oil
stream and can deactivate the catalyst
and foul cold heat-exchanger surfaces.
Normally, the buildup is controlled by
purging 2-5 vol.% of the unconverted
oil (UCO) stream, says Mike Hunter, a
principal engineer with Haldor Topsoe,
Inc. (Orange, Calif.; www.topsoe.com).
The company has developed a method
that reduces the ultimate UCO bleed
by as much as 80%.
The process, called HPNA Trim (Figure
2), takes a normal bleed stream,
but feeds it to the top of a small,
packed stripper column (see diagram).
Steam is injected into the bottom of
the column and strips out the lighter
portion of the UCO, which is returned
to the bottom of the hydrocracker's
main fractionation tower. The heavier
portion of the UCO stream, containing
the HPNAs, is recovered from the
bottom of the stripper column. Hunter
says the process is being offered commercially,
with an estimated payback
time of four to seven months.
Two hydrocracking processes that
had for long been considered uneconomical
prior to today's high oil prices
are now being commercialized. One is
the Veba Combi Cracker (VCC) process,
offered by KBR (Houston; www.kbr.
com) in collaboration with BP (London;
www.bp.com), and the other is a slurry
hydrocracking process from UOP LLC
(Des Plaines, Ill.; www.uop.com).
VCC had been more or less in waiting
for nearly 60 years - it was used
in Germany to produce liquid fuel from
coal during the Second World War, then
to upgrade heavy oil residue (resid) in
the 1950s. BP acquired the technology
in 2001 and has since improved it.
Now, KBR has contracts for three
22 CHEMICAL ENGINEERING WWW.CHE.COM APRIL 2012
plants, one to be built for TAIF Group
(Kazan, Russia) and two plants for
Yangchang Petroleum Group (Beijing,
China). The Russian plant is scheduled
to go onstream in 2015 and will
convert 50,000 bbl/d of vacuum residue
into naphtha and diesel fuel. The
Chinese plants, each of about 10,000
bbl/d, are set for startup in 2013 and
2014. One will produce diesel fuel from
coal tar (from a coking plant), and the
other will make diesel fuel from a mixture
of refinery vacuum resid and pulverized
coal.
VCC has two stages. First, feed is
slurried with a proprietary additive
in a slurry phase reactor at 200 bar
and more than 400°C, then it is hydrotreated.
The second stage employs
a combination of standard nickel-molybdenum
and zeolite catalysts in a
fixed bed. John Derbyshire, president
of KBR Technology, says the process
achieves better than 95% conversion
of heavy oil, and the naphtha and diesel
products require no further downstream
processing.
UOP's process, called Uniflex, will
be commercialized by National Refinery
Ltd. (Karachi, Pakistan). When
the facility goes onstream in 2016 it
will produce 40,000 bbl/d of diesel fuel
and 4,500 bbl/d of lube base oils.
Uniflex is an upgraded version of
technology acquired years ago from
Natural Resources Canada (Canmet;
Ottawa). Heavy oil or vacuum resid is
slurried with fine particles of a base
metal catalyst and fed into the bottom
of an upflow reactor. Hydrogen reacts
with the feed at 1,800-2,000 psig and
800-880°F, converting about 90% of
the oil to distillate and naphtha. n
Gerald Parkinson
and jet fuel
Naphtha
Fractionator
http://www.molycorp http://www.rivetechnology http://www.topsoe.com http://www.kbr http://www.bp.com http://www.uop.com http://WWW.CHE.COM
Chemical Engineering April 2012

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