U.S. patent application number 13/777508 was filed with the patent office on 2014-08-28 for reconfiguration of recirculation stream in upgrading heavy oil.
This patent application is currently assigned to Chevron U.S.A. Inc.. The applicant listed for this patent is Julie Chabot, Bo Kou, Bruce Edward Reynolds. Invention is credited to Julie Chabot, Bo Kou, Bruce Edward Reynolds.
Application Number | 20140238897 13/777508 |
Document ID | / |
Family ID | 49725360 |
Filed Date | 2014-08-28 |
United States Patent
Application |
20140238897 |
Kind Code |
A1 |
Kou; Bo ; et al. |
August 28, 2014 |
RECONFIGURATION OF RECIRCULATION STREAM IN UPGRADING HEAVY OIL
Abstract
Methods for hydroprocessing heavy oil feedstocks are disclosed.
A heavy oil feedstock, a hydrogen-containing gas, and a slurry
catalyst are passed through a plurality of upflow reactors
operating under hydrocracking conditions to convert at least a
portion of the heavy oil feedstock to lower boiling hydrocarbons,
forming upgraded products. At least a portion of the mixture
comprising the upgraded products, unconverted heavy oil feedstock,
the hydrogen-containing gas, and the slurry catalyst from an upflow
reactor other than the first upflow reactor is sent back to at
least one upstream upflow reactor as a recycled stream.
Inventors: |
Kou; Bo; (Albany, CA)
; Chabot; Julie; (Novato, CA) ; Reynolds; Bruce
Edward; (Martinez, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kou; Bo
Chabot; Julie
Reynolds; Bruce Edward |
Albany
Novato
Martinez |
CA
CA
CA |
US
US
US |
|
|
Assignee: |
Chevron U.S.A. Inc.
San Ramon
CA
|
Family ID: |
49725360 |
Appl. No.: |
13/777508 |
Filed: |
February 26, 2013 |
Current U.S.
Class: |
208/59 |
Current CPC
Class: |
C10G 65/10 20130101;
C10G 2300/10 20130101; C10G 2300/4081 20130101; C10G 2300/107
20130101; C10G 2300/1077 20130101; C10G 47/26 20130101; C10G
2300/1022 20130101; C10G 2300/1033 20130101; C10G 2300/1088
20130101; C10G 2300/1074 20130101 |
Class at
Publication: |
208/59 |
International
Class: |
C10G 65/10 20060101
C10G065/10 |
Claims
1. A process for upgrading a heavy oil feedstock, the process
employing a plurality of upflow reactors configured in series
comprising a first upflow reactor and a last upflow reactor, the
process comprising: combining a heavy oil feedstock, a
hydrogen-containing gas, and a slurry catalyst in the first upflow
reactor under hydrocracking conditions to convert at least a
portion of the heavy oil feedstock to lower boiling hydrocarbons,
forming upgraded products; passing a mixture comprising the
upgraded products, unconverted heavy oil feedstock, the
hydrogen-containing gas, and the slurry catalyst sequentially
through each subsequent upflow reactor, wherein each subsequent
upflow reactor is maintained under hydrocracking conditions with
additional hydrogen-containing gas to convert at least a portion of
the heavy oil feedstock to lower boiling hydrocarbons, forming
additional upgraded products; recycling at least a portion of the
mixture comprising the upgraded products, unconverted heavy oil
feedstock, the hydrogen-containing gas, and the slurry catalyst
from at least one upflow reactor other than the first upflow
reactor mixture back to at least one upstream upflow reactor
forming a recycled stream; and passing a mixture comprising the
upgraded products, unconverted heavy oil feedstock, the
hydrogen-containing gas, and the slurry catalyst from the last
upflow reactor to a separator, whereby the upgraded products are
removed with the hydrogen-containing gas as an overhead stream, and
the slurry catalyst and the unconverted heavy oil feedstock are
removed as a non-volatile stream.
2. The process of claim 1, wherein the process employs at least two
upflow reactors configured in series.
3. The process of claim 1, wherein liquid in the first upflow
reactor is recirculated at a rate of from 3 to 15 times the rate of
the heavy oil feedstock.
4. The process of claim 1, wherein liquid in the first upflow
reactor is recirculated at a rate of from 3 to 10 times the rate of
the heavy oil feedstock.
5. The process of claim 1, wherein the recycled stream from an
upflow reactor other than the first upflow reactor is recirculated
at a rate of from 3 to 15 the rate of the heavy oil feedstock.
6. The process of claim 1, wherein the recycled stream from an
upflow reactor other than the first upflow reactor is recirculated
at a rate of from 3 to 10 the rate of the heavy oil feedstock.
7. The process of claim 1, wherein the recycled stream comprises
from 0.3 to 30 wt. % of slurry catalyst.
8. The process of claim 1, wherein the heavy oil feedstock is
selected from the group consisting of atmospheric residuum, vacuum
residuum, tar from a solvent deasphalting unit, atmospheric gas
oils, vacuum gas oils, deasphalted oils, olefins, oils derived from
tar sands or bitumen, oils derived from coal, heavy crude oils,
synthetic oils from Fischer-Tropsch processes, and oils derived
from recycled wastes and polymers.
9. The process of claim 1, wherein the slurry catalyst comprises
catalyst particles having an average particle of from 1 to 20
microns.
10. The process of claim 1, wherein the hydrocracking conditions
include a temperature of from 392.degree. F. to 842.degree. F.
(200.degree. C. to 450.degree. C.), a reactor pressure of from 1450
to 3626 psig (10 to 25 MPa), a liquid hourly space velocity of from
0.05 to 10 h.sup.-1, and a hydrogen treat gas rate of from 300 to
10,000 SCF/bbl (53.4 to 1781 m.sup.3/m.sup.3).
Description
TECHNICAL FIELD
[0001] This disclosure relates to methods for upgrading heavy oil
feeds with a slurry catalyst composition.
BACKGROUND
[0002] The petroleum industry is increasingly turning to heavy oil
feeds such as heavy crudes, resids, coals, tar sands, etc., as
sources for refining feedstocks for the manufacture of useful
fuels. These feedstocks are characterized by high concentrations of
asphaltenes rich residues and low API gravities, with some being as
low as less than 0.degree. API.
[0003] Heavy oil feedstock typically contains high concentrations
of heavy metals. Some of the heavy metals, such as nickel and
vanadium, tend to react quickly, leading to deposition or trapping
of vanadium-rich solids in processing equipment such as reactors.
The solid deposition reduces available volume for reaction, which
can significantly reduce the availability of a heavy oil feedstock
processing system for the manufacture of commercial products.
[0004] High shear rate and high catalyst content in a liquid
recirculation reactor, e.g., an upflow reactor such as ebullating
bed or slurry reactor, can reduce vanadium trapping during heavy
oil upgrading. Unfortunately, control over these variables has been
very limited to date. In ebullating bed reactors, which are
typically equipped with either one internal or one external
recirculation pump, liquid recirculation from the pump can provide
the required shear and upflow. However, the shear rate must be high
enough to fluidize or expand the catalyst bed, but not too high to
carry over the catalyst into downstream reactor(s) and/or
separator(s). In heavy oil feedstock upgrading processes that
utilize slurry reactors, such an upper limit in recirculation rate
is eliminated since the slurry catalyst flows with the liquid
phase. However, the maximum recirculation rate in conventional
slurry reactors is still determined by the capacity of the
recirculation pump, since there is only a single pump used to
provide recirculation in each reactor.
[0005] In slurry reactors, the catalyst content in the front
reactor can be increased by catalyst recycle. Conventionally,
catalyst is directly recycled from the hot separator, but the
amount of recycle catalyst is limited by the catalyst concentration
in the hot separator, the slurry recycle rate and the overall heat
balance. Other recycle modes can be used, such as recycle after
stripper bottoms product concentration, vacuum distillation or
catalyst de-oiling, but these modes require larger downstream
process units to prepare such recycle streams.
[0006] There is still a need for improved methods to upgrade/treat
process heavy oil feeds, particularly improved methods for better
raw material utilization with less solid deposition.
SUMMARY
[0007] In one aspect of the invention, there is provided a process
for upgrading a heavy oil feedstock, the process employing a
plurality of upflow reactors configured in series comprising a
first upflow reactor and a last upflow reactor, the process
comprising:
[0008] combining a heavy oil feedstock, a hydrogen-containing gas,
and a slurry catalyst in the first upflow reactor under
hydrocracking conditions to convert at least a portion of the heavy
oil feedstock to lower boiling hydrocarbons, forming upgraded
products;
[0009] passing a mixture comprising the upgraded products,
unconverted heavy oil feedstock, the hydrogen-containing gas, and
the slurry catalyst sequentially through each subsequent upflow
reactor, wherein each subsequent upflow reactor is maintained under
hydrocracking conditions with additional hydrogen-containing gas to
convert at least a portion of the heavy oil feedstock to lower
boiling hydrocarbons, forming additional upgraded products;
[0010] recycling at least a portion of the mixture comprising the
upgraded products, unconverted heavy oil feedstock, the
hydrogen-containing gas, and the slurry catalyst from at least one
upflow reactor other than the first upflow reactor mixture back to
at least one upstream upflow reactor as a recycled stream; and
[0011] passing a mixture comprising the upgraded products,
unconverted heavy oil feedstock, the hydrogen-containing gas, and
the slurry catalyst from the last upflow reactor to a separator,
whereby the upgraded products are removed with the
hydrogen-containing gas as an overhead stream, and the slurry
catalyst and the unconverted heavy oil feedstock are removed as a
non-volatile stream.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a flow diagram that schematically illustrates an
embodiment of a heavy oil upgrade process with three upflow
reactors configured in series.
DETAILED DESCRIPTION
[0013] The following terms will be used throughout the
specification and will have the following meanings unless otherwise
indicated.
[0014] "Heavy oil" feed or feedstock refers to heavy and
ultra-heavy crudes, including but not limited to resids, coals,
bitumen, shale oils, tar sands, etc. Heavy oil feedstock can be
liquid, semi-solid, and/or solid. Examples of heavy oil feedstock
that can be upgraded as described herein include, but are not
limited to, Canada tar sands, vacuum resid from Brazilian Santos
and Campos basins, Egyptian Gulf of Suez, Chad, Venezuelan Zulia,
Malaysia, and Indonesia Sumatra. Other examples of heavy oil
feedstock include bottom of the barrel and residuum left over from
refinery processes, including "bottom of the barrel" and "residuum"
(or "resid")--atmospheric tower bottoms, which have a boiling point
of at least 343.degree. C. (650.degree. F.), or vacuum tower
bottoms, which have a boiling point of at least 524.degree. C.
(975.degree. F.), or "resid pitch" and "vacuum residue"--which have
a boiling point of 524.degree. C. (975.degree. F.) or greater.
[0015] Properties of heavy oil feedstock can include, but are not
limited to: a TAN of at least 0.1 (e.g., at least 0.3, or at least
1); a viscosity of at least 10 mm.sup.2/s; and an API gravity of at
most 20 (e.g., at most 10, or less than 5). A gram of heavy oil
feedstock typically contains at least 0.0001 g of Ni/V/Fe; at least
0.005 g of heteroatoms; at least 0.01 g of residue; at least 0.04 g
of C.sub.5 asphaltenes; at least 0.002 g of Micro Carbon Reside
(MCR) per g of crude; at least 0.00001 g of alkali metal salts of
one or more organic acids; and at least 0.005 g of sulfur. In one
embodiment, the heavy oil feedstock has a sulfur content of at
least 5 wt. % and an API gravity of from -5 to +5.
[0016] In one embodiment, the heavy oil feedstock comprises
Athabasca bitumen (Canada) having at least 50% by volume vacuum
resid. In another embodiment, the heavy oil feedstock is a Boscan
(Venezuela) feed with at least 64% by volume vacuum residue. In one
embodiment, the heavy oil feedstock contains at least 100 ppm V
(per gram of heavy oil feedstock). In another embodiment, the V
level ranges between 500 and 1000 ppm. In a third embodiment, the
heavy oil feedstock contains at least 2000 ppm V.
[0017] The terms "treatment," "treated," "upgrade," "upgrading,"
and "upgraded," when used in conjunction with a heavy oil
feedstock, describes a heavy oil feedstock that is being or has
been subjected to hydroprocessing, or a resulting material or crude
product, having a reduction in the molecular weight of the heavy
oil feedstock, a reduction in the boiling point range of the heavy
oil feedstock, a reduction in the concentration of asphaltenes, a
reduction in the concentration of hydrocarbon free radicals, and/or
a reduction in the quantity of impurities, such as sulfur,
nitrogen, oxygen, halides, and metals.
[0018] The upgrade or treatment of heavy oil feeds can generally be
referred herein as "hydroprocessing." Hydroprocessing is meant as
any process that is carried out in the presence of hydrogen,
including, but not limited to, hydroconversion, hydrocracking,
hydrogenation, hydrotreating, hydrodesulfurization,
hydrodenitrogenation, hydrodemetallization, hydrodearomatization,
hydroisomerization, hydrodewaxing and hydrocracking including
selective hydrocracking. The products of hydroprocessing can show
improved viscosities, viscosity indices, saturates content, low
temperature properties, volatilities and depolarization, etc.
[0019] Heavy oil upgrading is utilized to convert heavy oil or
bitumens into commercially valuable lighter products, e.g., lower
boiling hydrocarbons including liquefied petroleum gas (LPG),
gasoline, jet, diesel, vacuum gas oil (VGO), and fuel oils.
[0020] "Hydrogen" refers to hydrogen, and/or a compound or
compounds that when in the presence of a heavy oil feed and a
catalyst react to provide hydrogen.
[0021] "Slurry catalyst" (or sometimes referred to as "slurry" or
"dispersed catalyst") refers to a liquid medium, e.g., oil, water,
or mixtures thereof, in which catalyst and/or catalyst precursor
particles (aggregates, particulates or crystallites) are dispersed
within. The term slurry catalyst refers to a fresh catalyst, or a
catalyst that has been used in heavy oil upgrading and with
diminished activity (not a fresh catalyst). A slurry catalyst can
be a supported or an unsupported catalyst.
[0022] "Fresh catalyst" refers to a catalyst or a catalyst
precursor that has not been used in a reactor in a hydroprocessing
operation. The term fresh catalyst herein also includes
"re-generated," "rehabilitated" or "recovered" catalysts, e.g.,
catalyst that has been used in at least a reactor in a
hydroprocessing operation ("used catalyst") but its catalytic
activity has been restored or at least increased to a level well
above the used catalytic activity level. The term "fresh catalyst"
can be used interchangeably with "fresh slurry catalyst."
[0023] "Catalyst precursor" refers to a compound containing one or
more catalytically active metals, from which compound a catalyst is
eventually formed. It should be noted that a catalyst precursor can
be catalytically active as a hydroprocessing catalyst. "Catalyst
precursor" can be referred to herein as "catalyst" when used in the
context of a catalyst feed.
[0024] In one embodiment, the slurry catalyst feed stream contains
a fresh catalyst in a medium (diluent). In another embodiment, the
slurry catalyst feed contains a well-dispersed catalyst precursor
composition capable of forming an active catalyst in situ within
the feed heaters and/or the contacting zone. The catalyst particles
can be introduced into the medium (diluent) as powder in one
embodiment, a precursor in another embodiment, or after a
pre-treatment step in a third embodiment. In one embodiment, the
medium (or diluent) is a hydrocarbon oil diluent. In another
embodiment, the liquid medium is the heavy oil feedstock itself. In
yet another embodiment, the liquid medium is a hydrocarbon oil
other than the heavy oil feedstock, e.g., a VGO medium or
diluent.
[0025] Heavy Oil Feedstock
[0026] In one embodiment, the heavy oil feedstock suitable for use
in hydroconversion processes disclosed herein is selected from the
group consisting of atmospheric residuum, vacuum residuum, tar from
a solvent deasphalting unit, atmospheric gas oils, vacuum gas oils,
deasphalted oils, olefins, oils derived from tar sands or bitumen,
oils derived from coal, heavy crude oils, synthetic oils from
Fischer-Tropsch processes, and oils derived from recycled wastes
and polymers. In the reactor, at least a portion of the heavy oil
feedstock (higher boiling point hydrocarbons) is converted to lower
boiling hydrocarbons, forming an upgraded product.
[0027] Slurry Catalyst
[0028] The slurry catalyst is useful for, but not limited to,
upgrading processes such as thermal hydrocracking, hydrotreating,
hydrodesulfurization, hydrodenitrification, and
hydrodemetallization. The catalyst can be used as the sole catalyst
in the slurry hydroprocessing systems and in combination with other
catalysts in other types of hydroprocessing systems such as
processes employing fixed bed catalysts or ebullated bed catalysts.
Some slurry catalysts suitable for use in the various embodiments
of this invention are known in the art. See, e.g., U.S. Pat. Nos.
7,396,799 and 7,410,928.
[0029] In one embodiment, the slurry catalyst composition is
prepared by a series of steps, involving mixing a Group VIB metal
oxide, such as molybdenum, and aqueous ammonia to form an aqueous
mixture, and sulfiding the mixture to form a slurry catalyst. The
slurry catalyst is then promoted with a Group VIII metal. In one
embodiment, the slurry catalyst is then mixed with a hydrocarbon
oil and combined with hydrogen gas to produce an active slurry
catalyst. In one embodiment, the slurry catalyst is kept mixed in
storage until combined with feed in a hydroconversion process.
[0030] In one embodiment, the slurry catalyst comprises catalyst
particles (or particulates) having an average particle size of at
least 1 micron in a hydrocarbon oil diluent. In another embodiment,
the slurry catalyst comprises catalyst particles having an average
particle size of from 1 to 20 microns (e.g., from 2 to 10 microns).
In one embodiment, the slurry catalyst comprises a catalyst having
an average particle size ranging from colloidal (nanometer size) to
1 to 2 microns. In another embodiment, the slurry catalyst
comprises a catalyst having extremely small particles that are
molecular/colloidal in size (i.e., less than 100 nm, less than 10
nm, less than 5 nm, or less than 1 nm), which can aggregate into
particles having an average size of from 1 to 10 microns in one
embodiment, and from 1 to 20 microns in another embodiment, and
less than 10 microns in yet a third embodiment.
[0031] In one embodiment, a sufficient amount of slurry catalyst is
fed to the reactor for each reactor to have a slurry (solid)
catalyst concentration of at least 500 wppm to 3 wt. % (catalyst
metal to heavy oil ratio). Catalyst metal refers to the active
metal in the catalyst, e.g., for a NiMo sulfide slurry catalyst in
which Ni is used as a promoter, the catalyst metal herein refers to
the Mo concentration. In embodiments, the amount of catalyst feed
in the reactor is from 500 to 7500 wppm of the catalyst metal in
heavy oil feed (e.g., from 750 to 5000 wppm catalyst metal).
[0032] Heavy Oil Upgrade System
[0033] In one embodiment for the upgrade of heavy oil feedstock, a
plurality of upgrading reactors connected in series is employed,
with the reactors being the same or different in configuration.
Examples of reactors that can be used include stacked bed reactors,
fixed bed reactors, ebullating bed reactors, continuously stirred
tank reactors, fluidized bed reactors, spray reactors,
liquid/liquid contactors, slurry reactors, liquid recirculation
reactors, and combinations thereof. In one embodiment, the reactor
is an upflow reactor.
[0034] In embodiments, the process employs at least two upgrading
reactors connected in series (e.g., at least three upgrading
reactors connected in series, or at least four upgrading reactors
connected in series).
[0035] In the reactor, heavy hydrocarbon oil feedstock is admixed
with a slurry feed comprising a catalyst and a hydrogen-containing
gas at elevated pressure and temperature and hydroprocessed
(preferably hydrocracked) for the removal of heteroatom
contaminants, such as sulfur and nitrogen.
[0036] In one embodiment, the upflow reactor includes a reactor
outlet, a reactor inlet, a recirculation pump for generating a
liquid recirculation flow rate, and at least one internal mixing
device. The recirculation pump can be disposed within the upflow
reactor itself or outside the upflow reactor.
[0037] The hydroprocessing (or hydrocracking) can be practiced in
either countercurrent flow mode, where the feedstream flows
countercurrent to the flow of hydrogen-containing treat gas, or
co-current flow mode.
[0038] Process conditions in each upflow reactor include a
temperature of from 392.degree. F. to 842.degree. F. (200.degree.
C. to 450.degree. C.), a reactor pressure of from 1450 to 3626 psig
(10 to 25 MPa), a liquid hourly space velocity of from 0.05 to 10
h.sup.-1, and a hydrogen treat gas rate of from 300 to 10,000
SCF/bbl (53.4 to 1781 m.sup.3/m.sup.3).
[0039] In the reactors under hydrocracking conditions, at least a
portion of the heavy oil feedstock is converted to lower boiling
hydrocarbons, forming upgraded products. The mixture of the
upgraded products, the unconverted heavy oil feedstock, the slurry
catalyst, the hydrogen-containing gas is sent to the next reactor
in series, which is also maintained under hydrocracking conditions.
In the next reactor with additional hydrogen-containing gas feed
and optionally with additional heavy oil feedstock, at least a
portion of the heavy oil feedstock is converted to lower boiling
hydrocarbons, forming additional upgraded products.
[0040] In the traditional configuration, the internal or external
recirculation pump at each reactor delivers the slurry back to the
same reactor. The slurry is only recirculated internally within the
same reactor by the pump. In an embodiment of this invention, the
recirculation pumps at downstream reactors (i.e., not the front-end
or first reactor) send slurry to their upstream reactors. The
slurry should have the same composition as the reactor that it
originates from. The recirculation rate of the recycled stream from
at least one downstream reactor is at least 3 times the rate of the
incoming heavy oil feed stream (e.g., at least 5 times the rate of
the incoming heavy oil feed stream). In embodiments, the
recirculation rate of the recycled stream from at least one
downstream reactor ranges from 3 to 15 times the rate of the
incoming heavy oil feed stream (e.g., from 3 to 10 times the rate
of the incoming heavy oil feed stream, from 3 to 8 times the rate
of the incoming heavy oil feed stream, from 5 to 10 times the rate
of the incoming heavy oil feed stream, or from 5 to 8 times the
rate of the incoming heavy oil feed stream). In embodiments, it is
believed that with higher recirculation rates provided by the
recycle stream, heavy metals are passed through the system more
quickly leading to less trapping or deposition on the processing
equipment.
[0041] In embodiments, the recycle stream is pumped to the first
upflow reactor at a sufficient rate to provide a liquid superficial
velocity in the first upflow reactor of greater than 6 cm/s (e.g.,
from 8 to 20 cm/s, from 10 to 20 cm/s, from 10 to 18 cm/s, from 12
to 20 cm/s, or from 12 to 18 cm/s).
[0042] In embodiments, it is believed that with additional recycled
catalyst provided by the recycled stream, more catalytic surface
area (via the catalyst slurry in the recycled stream) is available
to spread the heavy metal deposition, there is less trapping or
deposition on the processing equipment. The additional catalyst
surface area provided by the recycled stream minimizes overloading
the catalyst surface with heavy metal deposits, leading to reduced
deposition on the processing equipment (walls, internal, etc.).
[0043] In embodiments, the recycled stream contains from 0.3 to 30
wt. % of slurry catalyst (e.g., from 0.5 to 20 wt. % of slurry
catalyst, or from 1 to 15 wt. % of slurry catalyst).
[0044] In addition to the benefits of the higher recirculation rate
(i.e., shear rate) and higher catalyst content which facilitate
vanadium removal, the process disclosed herein has other positive
operational benefits. Quench streams are typically added before
reactors in conventional heavy oil upgrading processes to remove
heat generated during hydrocracking Since the inter-reactor flow is
much higher in the process disclosed herein over conventional
processes, the "hot" effluent from a reactor can be absorbed by the
"cold" recycled feed thereby eliminating the need for conventional
quench streams. Moreover, the less need for quench can also mean
the less need for preheating a feed stream, since the large recycle
stream provides the heat needed to reach a target temperature.
[0045] In one embodiment, it is not necessary to recycle catalysts
from the hot separator, vacuum distillation, or de-oiling unit, as
in conventional heavy oil upgrading processes, eliminating the
required high-temperature recycle pumps and other related
equipment. In the process disclosed herein, catalyst recycling is
realized by the existing recirculation pump for each reactor.
[0046] In embodiments where the process disclosed herein employs at
least two upgrading reactors connected in series, the last reactor
is limited to recirculation from a single pump. Recirculation in
any upstream reactor can come from two or more pumps. Therefore,
loss of any single pump may not lead to a total loss of
recirculation.
[0047] In embodiments, a separation unit can be located between two
upflow reactors, a prior upflow reactor and a subsequent upflow
reactor. At least a portion of the mixture containing the upgraded
products, unconverted heavy oil feedstock, slurry catalyst and
hydrogen-containing gas is sent to the separator, e.g., an
interstage flash separator (ISF), whereby upgraded products are
removed with the hydrogen-containing gas as an overhead stream and
the unconverted heavy oil feedstock and the slurry catalyst are
removed as a non-volatile stream. In one embodiment, the process
disclosed herein employs at least three upflow reactors and at
least two separation units wherein at least one of the separation
units zones is an ISF located in between two upflow reactors, a
prior upflow reactor and a subsequent upflow reactor.
[0048] Following the last reactor in any number of upflow reactors,
a mixture containing the upgraded products, unconverted heavy oil
feedstock, the hydrogen-containing gas, and the slurry catalyst is
passed to a separator, whereby the upgraded products are removed
with the hydrogen-containing stream as an overhead stream, and the
slurry catalyst and the unconverted heavy oil feedstock are removed
as a non-volatile stream.
[0049] FIG. 1 is a schematic of an embodiment of a heavy oil
upgrade process with three upflow reactors configured in series,
e.g., reactors 10, 20, and 30. Fresh feed 1 comprising a heavy oil
feedstock, hydrogen-containing gas and slurry catalyst enters the
bottom of reactor 10. Effluent stream 11 comprising upgraded
materials along with hydrogen-containing gas, slurry catalyst, and
unconverted heavy oil exits the top of reactor 10 and is sent to
the bottom of the next reactor 20 in series. A recycle stream 22
containing upgraded materials along with hydrogen-containing gas,
slurry catalyst, unconverted heavy oil, is recycled back to the
bottom of reactor 10. Additional feedstream(s) containing
hydrogen-containing gas, optional VGO feed, optional (additional)
heavy oil feed, and optional catalyst feed can be combined with
effluent stream 11 for further upgrade in reactor 20.
[0050] Effluent stream 21 comprising upgraded materials along with
hydrogen-containing gas, slurry catalyst, and unconverted heavy oil
exits the top of reactor 20 and is sent to the bottom of the next
reactor 30 in series. A recycle stream 32 containing upgraded
materials along with hydrogen-containing gas, slurry catalyst,
unconverted heavy oil, is recycled back to the bottom of at least
one of reactors 10 and 20. Additional feedstream(s) containing
hydrogen-containing gas, optional VGO feed, optional (additional)
heavy oil feed, and optional catalyst feed can be combined with
effluent stream 21 for further upgrade in reactor 30.
[0051] Effluent stream 31 comprising upgraded materials along with
hydrogen-containing gas, slurry catalyst, and unconverted heavy oil
exits the top of reactor 30 and is sent to a separator (not shown),
e.g., a high pressure separator, wherein products and gases are
separated from the non-volatile fraction, e.g., slurry catalyst and
unconverted heavy oil.
EXAMPLES
[0052] The following illustrative examples are intended to be
non-limiting.
[0053] A heavy oil upgrading process according to FIG. 1 (3 upflow
reactors in series wherein both the second and the third reactor
recirculation pumps discharge to the inlet of the first reactor and
the third reactor recirculation pumps discharge to the inlet of the
second reactor) was simulated and compared to a conventional heavy
oil upgrading process as described in U.S. Pat. No. 7,390,398 (3
upflow reactors is series wherein only one pump is available for
each reactor).
Example 1
[0054] The maximum liquid superficial velocity in each reactor of
the process as described in U.S. Pat. No. 7,390,398 was about 6
cm/s. In the process according to FIG. 1, the liquid superficial
velocity can reach 18 cm/s in the first reactor and 12 cm/s in the
second reactor, thus providing much higher shear rate to facilitate
vanadium removal.
Example 2
[0055] With <3000 ppm of Mo from fresh catalyst and once-through
operation, the first reactor of the process as described in U.S.
Pat. No. 7,390,398 contains <4000 ppm Mo or <2 wt. % solids.
In the process according to FIG. 1, all three reactors have
essentially the same catalyst contents. At about 93% vacuum resid
conversion, the first reactor can reach about 2.4 wt. % Mo or 12
wt. % solids, which is about six times that of the conventional
design, while the second reactor will see the same benefit wherein
the catalyst content is boosted about 3 to 4 times that of the
conventional design.
Example 3
[0056] In the conventional process, the inter-reactor stream is
cooled down by about 150.degree. F. to compensate for the highly
exothermic consumption of about 700 SCF/bbl hydrogen. Assuming 8
times recirculation rate per fresh feed at each pump, there is only
9.degree. F. temperature increase between the first and second
reactor in the configuration according to FIG. 1. The temperature
rise from the second and third reactors will be about 17.degree. F.
Such a temperature profile is well within the current operating
envelope and no quench is needed unless the reactors need to be
operated more isothermally.
Example 4
[0057] In the conventional process such as described in U.S. Pat.
No. 7,390,398, fresh feed needs to be heated to about 700.degree.
F. In the process disclosed herein, the feed needs to be heated at
500.degree. F. to 600.degree. F. Moreover, much less temperature
increase along reactor height is observed. With recirculation pump
within the same reactor, a large temperature increase is observed
along reactor height. In the process according to FIG. 1, the
temperature increase was reduced by 2/3 and 1/2 in the first and
second reactors, respectively.
Example 5
[0058] In the conventional process, there can be up to a 20.degree.
F. to 30.degree. F. temperature increase in the reactor when
recirculation is provided by a single pump. In the process
according to FIG. 1, it is expected to that only about a 7.degree.
F. to 10.degree. F. temperature increase and only about a
10.degree. F. to 15.degree. F. will be observed in the first and
second reactors, respectively.
[0059] For the purposes of this specification and appended claims,
unless otherwise indicated, all numbers expressing quantities,
percentages or proportions, and other numerical values used in the
specification and claims, are to be understood as being modified in
all instances by the term "about." Accordingly, unless indicated to
the contrary, the numerical parameters set forth in the following
specification and attached claims are approximations that can vary
depending upon the desired properties sought to be obtained. It is
noted that, as used in this specification and the appended claims,
the singular forms "a," "an," and "the," include plural references
unless expressly and unequivocally limited to one referent. As used
herein, the term "include" and its grammatical variants are
intended to be non-limiting, such that recitation of items in a
list is not to the exclusion of other like items that can be
substituted or added to the listed items. As used herein, the term
"comprising" means including elements or steps that are identified
following that term, but any such elements or steps are not
exhaustive, and an embodiment can include other elements or
steps.
[0060] Unless otherwise specified, the recitation of a genus of
elements, materials or other components, from which an individual
component or mixture of components can be selected, is intended to
include all possible sub-generic combinations of the listed
components and mixtures thereof.
[0061] The patentable scope is defined by the claims, and can
include other examples that occur to those skilled in the art. Such
other examples are intended to be within the scope of the claims if
they have structural elements that do not differ from the literal
language of the claims, or if they include equivalent structural
elements with insubstantial differences from the literal languages
of the claims. To an extent not inconsistent herewith, all
citations referred to herein are hereby incorporated by
reference.
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