Note: Descriptions are shown in the official language in which they were submitted.
7~S
~TREATING
TO PRODUCE FU~L PRODUCTS
BACKGROUND OF INVENTION
Field o Invention:
This invention pertains to processing hydrocarbon feed-
stocks containing precipitable impurities which deposit out
during conventional preheating, and pertains particularly to
processing raw shale oil con,taining depositable metallic com-
pounds to produce catalytically hydroprocessed fuels suitable
for jet and diesel engine usage.
Desciption of Prior Art:
It has been observed that when raw shale oil is catalyti-
cally hydrogenated to produce improved lighter oil products,
the preheating ~ ipment passages are usually fouled by fine particulate
deposits from the shale oil at temperatures above about 400F.
Such deposits produce high pressure drop and even plugging of
flow passages and are very troublesome and undesirable. Specific
problems which are encountered during hydrotreating operations
on shale oil feedstock include repeated fouling preheater flow
passages by particulate deposits at temperatures above approxi-
mately 400F, and fouling the fixed-bed catalytic reactor by
very fine particulate deposits having high iron content, caus-
ing excessive pressure drop and inadequate oil conversion.
These deposits are evidently from chemical compounds
which contain principally iron and arsenic compounds which
cannot be readily filtered out of the liquid feedstream at
ambient temperature conditions. Thus, a solution has been
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sought for avoiding or preventing such contaminant problems in
processing raw shale oil, so as to permit continuous catalytic
processing of such oils to produce upgraded fuel products.
Multi-stage catalytic processing of heavy petroleum crude
oils and residuum is known. For example, U.S. 3,705,849 to
Alpert discloses a process for desulfurization of petroleum re-
siduum feedstocks using ebullated catalytic bed hydrogenation
reactors in series to reduce hydrogen consumption and increase
catalyst life. U.S. 3,773,653 to Nongbri and U.S. 3,788,~73
to Wolk disclose similar multi-stage catalytic conversion pro-
cesses for petroleum residuum. Also, U.S. 3,887,455 to Hammer
discloses a process for hydrotreatment of heavy crudes and re-
sidua using ebullated catalytic beds or fixed-bed reactors in
series, using catalyst having smaller pore size in the second
reactor.
U.S. 4,046,670 to Seguchi discloses a process for thermal
cracking heavy petroleum oil in tubular-type heating furnace,
and wherein an inorganic substance containing iron oxide is
added to the feed as an anti-clogging agent. U.S. ~,181,596 to
Jensen discloses treating shale oil retort effluent to lower
pour point and reduce contaminants, such as soluble arsenic
and iron, by cooling the effluent and maintaining the liquid
phase in a critical temperature range of 600-800E' for 1-120
minutes.
Also, U.S. 4,158,622 to Schwarzenbek discloses a two-stage
hydrogenation process for hydrocarbons containing particulate
fines such as shale oil, utilizing an ebullating bed catalytic
reactor from which the vapor portion is passed to a stationary
bed reactor for further hydrotreatment. Despite this prior
activity, a need still exists for processing raw shale oil which
contains precipitatable inorganic materials and compounds so as
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to avoid fouling of equipment passages and catalytic beds and
provide improved operations.
SUMMARY OF INVENTION
This inventi~n provides a method for preheating hydrocar-
bon feedstocks containing precipitable compounds which cause flow
passage fouling problems, and for hydroprocessing such hydrocar-
bon liquids such as raw shale oil to produce upgraded fuels suit-
able for jet and diesel usage. The hydrocarbon feed is heated
indirectly to a mGderate temperature below which any precipita-
tion of inorganic compounds occurs, such as about 400-600F,
and is then passed to an ebullated catalyst first stage bed re-
action step for initial hydroprocessing. The resulting effluent
liquid is phase separated and the vapor portion is passed to one
or more fixed catalytic bed hydrotreating steps usually operated
at more severe conditionsi i.e., at higher temperature and pres-
sure conditions, or lower space velocity, for further processing.
The specific process steps include preheating the feed;
e.g., raw shale oil, to a temperature at least about 350F to
separate sediment and water, but avoiding a temperature at which
precipitation and fouling occurs in the preheater flow passage.
Then, passing the heated feedstream with hydrogen to a first
stage hydrocracking operation using an ebullated catalyst bed
type reactor to provide further feed stream heating via the heat
of hydrogenation and depositing the precipitated solids on the
catalyst.
The recycle hydrogen stream and/or a heavy recycle oil
fraction, such as about 650F+ are heated sufficiently to make
up the additional heating to achieve a reaction temperature of
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over about 750F in the ebullated catalyst bed unit. Useful
reaction conditions are 800-860F temperature, 1800-3000 psig
hydrogen partial pressure, and space velocity of 0.7-3 Vf/hr/Vr.
Following an initial catalytic hydrogenation step in an
ebullated bed reacto~, it has been ~mexpectedly found that by
further processing heavy feedstocks such as shale oil in a down-
flow fixed bed catalytic hydrotreater operated at extreme con-
ditions of temperature and pressure, remarkably high quality
products can be produced even in the presence of high partial
pressure of H2S and NH3. The extreme condikions employed are
temperatures in excess of 780F and hydrogen partial pressures
in excess of 1800 psig. This temperature produces some further
hydrotreating which allows the liquid products of this operation,
boiling below 510F, to meet military specification for JP-4 jet and
diesel fuels. This hydrotreating step also facilitates denitro-
genation of the product.
Operations conducted on processed raw shale oil having a
nitrogen content of about 1.27 W ~ and a sulfur content of 0.75
W ~ have produced fuel oil products having a nitrogen content of
less than 4 ppm and a sulfur content less than 0.01 W % to meet
JP-4 fuel specifications.
DESCRIPTION OF THE DRAI~ING
Figure 1 is a schematic flowsheet of a two-stage catalytic
reaction process using indirect heating of a hydrocarbon feed-
stream upstream of an ebullated catalyst bed hydrogenation step,
followed by further catalytic hydrotreating in a fixed bed re-
actor.
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DESCRIPTION OF PREFERRED Er~BO~IMENTS
As shown in Figure 1, raw shale oil feedstock at 10 is
heated in heater 12 to a temperature below which contained inor-
ganic compounds precipitate, such as 350-400F and not above
about 600~F, using a convenient source of heat such as low Btu
gas. Sediment and water are removed at 13. The preheated oil 14
is introduced with hydrogen 15 into an ebullated bed catalytic re-
actor unit 16. The reactor has provision for fresh catalyst
addition either with the feed at 14a or by addition into the re-
actor vessel at 17 and withdrawal of used catalyst at 18 as shown.
Reaction conditions are usually 825-860F temperature, 2000-2600
psig hydrogen partial pressure, and liquid hourly space velocity
within the range of 0.7-1.5 Vf/hr~Vr. The reactor contains ebul-
lated bed 16a of particulate catalyst. Suitable catalyst is com-
mercially available cobalt-molybdenum or nickel-molybdenum on
alumina support and having a narrow particle si~e within the broad
range of 0.003 to 0.060 inch. Catalyst and solids are withdrawn
either from the reactor at connection 18 or with non-vaporized
product from the hot separator 20. Reactor effluent stream 19 is
passed to hot separator 20, from which vapor stream 21 is passed
to hydrotreater 30. Hot separator liquid at 22 is flashed in
two stages 24 and 26 at successively lower pressure, and the re-
sulting combined vapors 23 are passed to vapor product line 27.
The residual liquid 28 from the last flash step 26 is partially
recycled to the reactor for further cracking, and the remainder
2a burned as fuel or discarded.
The resulting hydrocarbon-containing stream at 27 is intro-
duced directly to downflow fixed-bed catalytic hydrotreater 30
with hydrogen at substantially the same high temperature and
pressure conditions existing from reactor 16. In the hydrotrea-
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ter 30, which is preferably operated at extreme hydrotreatingconditions of 800~825F temperature range, 1800-2500 psig hy-
drogen partial pressure, and space velocity of 0.8-1.5 Vf/hr/
Vr, the vapor product is further cracked and virt~lly completely de-
sulfurized and denitrogenated.
Suitable catalyst is nickel-molybdenum or alumina support
and having particle size of 0.060-0.125 inch. The reaction tem-
perature will increase through the c:atalyst bed due to the exo-
thermic reaction. Hydrotreater 30 may be comprised of two or
more catalyst beds in series, with the temperature rise in the
beds being controlled by injecting cool hydrogen gas between the
beds such as at 30a.
The resulting product 31 is cooled at 32 and phase sepa-
rated at 34. The resulting liquid portion is pressure-reduced
at 35 and fractionated at 36 into fuel gas 37, naphtha at 37a,
jet fuel at 38, and diesel fuel products at 38a. Any naphtha
produced is suitable for catalytic reforming to produce gaso-
line. From fractionator 36, the heavier liquid fraction, such
as 650F+, at 39 is heated to above 800F at heater 51 and re-
cycled to the reactor unit 16 for futher processing.
The effluent vapor stream 33 from phase separator 34 is
separated at 40 to remove contaminants such as Cl to C3 gases,
H2S, and NH3 at 42. Hydrogen at 41 is compressed at 44, heated
at 45 to 850-1000F, and recycled directly to the reactor 16.
The Cl and C3 gases at 43 from separation step 40, along wi-th
some natural gas make up at 49, are reformed at 50 to make
additional hydrogen stream 46 as needed in the process.
It is pointed out that the important features of this
process for upgrading hydrocarbon feedstock such as shale oil
are (a) limiting the preheating of the feedstock and supplying
the additional heat by heating the hydrogen and clean recycled
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heavy liquid fraction, and thus avoiding the precipitation of
deposits in the feed preheater Elow passages, (b) precipita-
tion of inorganic compounds on the catalyst in the ebullated
bed reactor, and (c) on-line catalytic hydrotreating step
operated at extreme conditions to pxoduce finished liquid fuel
products. The clean recycled heavy product fraction and hydro-
gen are separately heated using fired heaters to provide the
necessary heat to the ebullated bed catalytic reaction. These
process steps as well as other Eeatures of the process are app-
licable to coal, heavy oil and tar sand bitumen processing, as
well as to preferably processing raw shale oil to produce re-
fined fuel oils products.
This invention is further illustrated by reference to the
following examples, which should not be construed as limiting
the scope of the invention.
FXAMPLE 1
Upgrading operations were conducted with raw shale oil
containing 1.6 W % nitrogen, 20 ppm arsenic, 60 ppm iron and
about 0.06 W % ash impurities. The oil was preheated in a tubu-
lar exchanger to about 700F, and passed with hydrogen to a
downflow-type catalytic reactor containing a fixed bed of com-
mercially available nickel catalyst particles for hydrotreat-
ment. Pressure drop across the preheater tube increased from
about 10 psi to 200 psi over 12 days, so that operations had
to be discontinuecl and the heater coil replaced. Analysis of
the material deposited in the coil and also in the top of the
reactor bed indicated it was about 38 W % oil and 62 W % ash,
containing 2 W % carbon, 45 W % iron and 6.3 W ~ arsenic.
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EXAMPLE 2
Further upgrading operations are conducted using the same
raw shale oil feedstock as in Example 1. However, the oil is
preheated in a tubular heat exchanger to only about 450F, and
then passed into the bottom of an upflow-type reactor containiny
as ebullated bed of commercially available cobolt molybdenum
catalyst extrudate particles. Recycle hydrogen gas is heated
to 925-950F and heavy 650F+ recycle oil is heated to 800-825F
and also introduced into the bottom of the reactor. The reaction
zone conditions are maintained within the range of 825-850F
temperature, 2000-2600 psig partial pressure of hydrogen, and
space veloclty of about 1.2 Vf/hr/Vr. An effluent stream is re-
moved from the upper end of the reactor and passed to further
processing steps to recover product oil. The iron and arsenic
impurities are substantially deposited on the catalyst particles
in the reactor and are removed with the used catalyst, thus a-
voiding difficulties with precipitation of such contaminants
from the shale oil feed causing increased pressure drop and opera-
ting problems in the process, and permitting continuous exten-
ded operations.
EXAMPLE 3
The preheated effluent stream from the ebullated bed catalyst
reactor of Example 1, containing nitrogen content of about 0.9 W
% is passed on to a second stage fixed-bed catalytic reactor for
further processing. The oil is hydrotreated at inlet conditions
of 800-825F temperature and 1800-2000 psig partial pressuxe of
hydrogen by passing over a suitable hydrotreating catalyst, usual-
ly nickel-molybdenum on alumina support at space velocity o~
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about 1.0 Vf/hr/Vr. The resulting hydrotreated oil product has
increased API gravity, a nitrogen content of less than about
4 ppm and sulfur content less than about 0.01 W ~, -thus making
it suitable as high quality fuel for jet and diesel engine use.
Although we have disclosed certain preferred embodiments
of our invention, it is recognized that modifications may be
made theretowithin the spirit and scope of the disclosure and
as defined solely ~y the following claims.
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