U.S. patent application number 11/555048 was filed with the patent office on 2008-05-01 for upgrading heavy hydrocarbon oils.
This patent application is currently assigned to Chevron U.S.A. Inc.. Invention is credited to Daniel Chinn, Zunqing He, Lin Li, Lixiong Li.
Application Number | 20080099376 11/555048 |
Document ID | / |
Family ID | 39345443 |
Filed Date | 2008-05-01 |
United States Patent
Application |
20080099376 |
Kind Code |
A1 |
He; Zunqing ; et
al. |
May 1, 2008 |
UPGRADING HEAVY HYDROCARBON OILS
Abstract
A process using supercritical water to upgrade a heavy
hydrocarbon feedstock into an upgraded hydrocarbon product or
syncrude with highly desirable properties (low sulfur content, low
metals content, lower density (higher API), lower viscosity, lower
residuum content, etc.) is disclosed. The process does not require
external supply of hydrogen nor does it use externally supplied
catalysts.
Inventors: |
He; Zunqing; (San Rafael,
CA) ; Chinn; Daniel; (Bay Point, CA) ; Li;
Lixiong; (Panama City, FL) ; Li; Lin; (Albany,
CA) |
Correspondence
Address: |
CHEVRON CORPORATION
P.O. BOX 6006
SAN RAMON
CA
94583-0806
US
|
Assignee: |
Chevron U.S.A. Inc.
|
Family ID: |
39345443 |
Appl. No.: |
11/555048 |
Filed: |
October 31, 2006 |
Current U.S.
Class: |
208/264 ;
208/177 |
Current CPC
Class: |
C10G 31/08 20130101 |
Class at
Publication: |
208/264 ;
208/177 |
International
Class: |
C10G 45/00 20060101
C10G045/00; C10G 31/00 20060101 C10G031/00 |
Claims
1. A process for upgrading hydrocarbons comprising, (a) mixing
hydrocarbons with a fluid comprising water in a mixing zone to form
a mixture; (b) passing the mixture to a reaction zone; (c) reacting
the mixture in the reaction zone under supercritical water
conditions in the absence of externally added hydrogen for a
residence time sufficient to allow upgrading reactions to occur;
(d) withdrawing a single-phase reaction product from the reaction
zone; and (e) separating the reaction product into gas, effluent
water, and upgraded hydrocarbon phases.
2. A process according to claim 1, wherein the hydrocarbons are
heavy hydrocarbons selected from the group consisting of whole
heavy petroleum crude oil, tar sand bitumen, heavy hydrocarbon
fractions obtained from crude petroleum oils, heavy vacuum gas
oils, vacuum residuum, petroleum tar, coal tar and their
mixtures.
3. A process according to claim 1, wherein the fluid comprising
water enters the mixing zone at a temperature greater than the
critical temperature of water.
4. A process according to claim 1, wherein the conditions in the
mixing zone include a temperature higher than the critical
temperature of water and a pressure greater than the critical
pressure of water.
5. A process according to claim 1, wherein the supercritical water
conditions include a temperature from 374.degree. C. to
1000.degree. C. a pressure from 3,205 psia to 10,000 psia an
oil/water volume ratio from 1:0.1 to 1:10 and where the residence
time is from 1 minute to 6 hours.
6. A process according to claim 1, wherein the supercritical water
conditions include a temperature from 374.degree. C. to 600.degree.
C., a pressure from 3,205 psia to 7,200 psia, an oil/water volume
ratio from 1:0.5 to 1:3 and where the residence time is from 8
minutes to 2 hours.
7. A process according to claim 1, wherein the supercritical water
conditions include a temperature from 374.degree. C. to 400.degree.
C., a pressure from 3,205 psia to 4,000 psia, an oil/water volume
ratio from 1:1 to 1:2 and where the residence time is from 20 to 40
minutes.
8. A process according to claim 1 wherein the mixture in the
reaction zone is reacted in the absence of any catalyst or
promoter.
9. A process according to claim 1, wherein the water is drinking
water, treated wastewater, untreated wastewater, river water, lake
water, seawater, produced water or their mixtures.
10. A process for upgrading hydrocarbons comprising: (a) mixing
hydrocarbons with a fluid comprising water in a mixing zone to form
a mixture; (b) passing the mixture to a reaction zone; (c) reacting
the mixture in the reaction zone under supercritical water
conditions in the absence of externally added hydrogen and catalyst
for a residence time sufficient to allow upgrading reactions to
occur; (d) withdrawing a single-phase reaction product from the
reaction zone; and (e) separating the reaction product into gas,
effluent water, and upgraded hydrocarbon phases.
11. A process according to claim 10, wherein the hydrocarbons are
heavy hydrocarbons selected from the group consisting of whole
heavy petroleum crude oil, tar sand bitumen, heavy hydrocarbon
fractions obtained from crude petroleum oils, heavy vacuum gas
oils, vacuum residuum, petroleum tar, coal tar and their
mixtures.
12. A process according to claim 10, wherein the fluid comprising
water enters the mixing zone at a temperature greater than the
critical temperature of water.
13. A process according to claim 10, wherein the conditions in the
mixing zone include a temperature greater than the critical
temperature of water and a pressure greater than the critical
pressure of water.
14. A process according to claim 10, wherein the supercritical
water conditions include a temperature from 374.degree. C. to
1000.degree. C., a pressure from 3,205 psia to 10,000 psia, an
oil/water volume ratio from 1:0.1 to 1:10 and where the residence
time is from 1 minute to 6 hours.
15. A process according to claim 10, wherein the supercritical
water conditions; include a temperature from 374.degree. C. to
600.degree. C., a pressure from 3,205 psia to 7,200 psia, an
oil/water volume ratio from 1:0.5 to 1:3 and where the residence
time is from 8 minutes to 2 hours.
16. A process according to claim 10, wherein the supercritical
water conditions include a temperature from 374.degree. C. to
400.degree. C. a pressure from 3,205 psia to 4,000 psia, an
oil/water volume ratio from 1:1 to 1:2 and where the residence time
is from 20 to 40 minutes.
17. A process according to claim 10, wherein the water is drinking
water, treated wastewater, untreated wastewater, river water, lake
water, seawater, produced water or their mixtures.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to upgrading of heavy
hydrocarbons such as whole heavy oil bitumen, and the like using
supercritical water.
BACKGROUND OF THE INVENTION
[0002] Oil produced from a significant number of oil reserves
around the world is simply too heavy to flow under ambient
conditions. This makes it challenging to bring remote, heavy oil
resources closer to the markets. One typical example is the Hamaca
field in Venezuela. In order to render such heavy oils flowable,
one of the most common methods known in the art is to reduce the
viscosity and density by mixing the heavy oil with a sufficient
diluent. The diluent may be naphtha, or any other stream with a
significantly higher API gravity (i.e., much lower density) than
the heavy oil.
[0003] For a case such as Hamaca, diluted crude oil is sent from
the production wellhead via pipeline to an upgrading facility. Two
key operations occur at the upgrading facility: (1) the diluent
stream is recovered and recycled back to the production wellhead in
a separate pipeline, and (2) the heavy oil is upgraded with
suitable technology known in the art (coking, hydrocracking,
hydrotreating, etc.) to produce higher-value products for market.
Some typical characteristics of these higher-value products
include: lower sulfur content, lower metals content, lower total
acid number (TAN), lower residuum content, higher API gravity, and
lower viscosity. Most of these desirable characteristics are
achieved by reacting the heavy oil with hydrogen gas at, high
temperatures and pressures in the presence of a catalyst. In the
case of Hamaca, the upgraded crude is sent further to the end-users
via tankers.
[0004] These diluent addition/removal processes and
hydrogen-addition or other upgrading processes have a number of
disadvantages:
1. The infrastructure required for the handling, recovery, and
recycle of diluent could be expensive, especially over long
distances. Diluent availability is another potential issue.
2. Hydrogen-addition processes such as hydrotreating or
hydrocracking require significant investments in capital and
infrastructure.
[0005] 3. Hydrogen-addition processes also have high operating
costs, since hydrogen production costs are highly sensitive to
natural gas princes. Some remote heavy oil reserves may not even
have access to sufficient quantities of low-cost natural gas to
support a hydrogen plant. These hydrogen-addition processes also
generally require expensive catalysts and resource intensive
catalyst handling techniques, including catalyst regeneration.
4. In some cases, the refineries and/or upgrading facilities that
are located closest to the production site may have neither the
capacity nor the facilities to accept the heavy oil.
[0006] 5. Coking is often used at refineries or upgrading
facilities. Significant amounts of by-product solid coke are
rejected during the coking process, readings to lower liquid
hydrocarbon yield. In addition, the liquid products from a coking
plant often need further hydrotreating. Further, the volume of the
product from the coking process is significantly less than the
volume of the feed crude oil.
[0007] A process according to the present invention overcomes these
disadvantages by using supercritical water to upgrade a heavy
hydrocarbon feedstock into an upgraded hydrocarbon product or
syncrude with highly desirable properties (low sulfur content, low
metals content, lower density (higher API), lower viscosity, lower
residuum content, etc.). The process neither requires external
supply of hydrogen nor must it use catalysts. Further, the process
in the present invention does not produce an appreciable coke
by-product.
[0008] In comparison with the traditional processes for syncrude
production, advantages that may be obtained by the practice of the
present invention include a high liquid hydrocarbon yield; no need
for externally-supplied hydrogen; no need to provide catalyst,
significant increases in API gravity in the upgraded hydrocarbon
product; significant viscosity reduction in the upgraded
hydrocarbon product; and significant reduction in sulfur, metals,
nitrogen, TAN, and MCR (micro-carbon residue) in the upgraded
hydrocarbon product.
[0009] Various methods of treating heavy hydrocarbons using
supercritical water are disclosed in the patent literature.
Examples include U.S. Pat. Nos. 3,948,754, 3,948,755, 3,960,706,
3,983,027, 3,988,238, 3,989,618, 4,005,005, 4,151,068, 4,557,820,
4,559,127, 4,594,141, 4,840,725, 5,611,915, 5,914,031 and 6,887,369
and EP571454.
[0010] U.S. Pat. No. 4,840,725 discloses a process for conversion
of high boiling liquid organic materials to lower boiling materials
using supercritical water in a tubular continuous reactor. The
water and hydrocarbon are separately preheated and mixed in a
high-pressure feed pump just before being fed to the reactor.
[0011] U.S. Pat. No. 6,887,369 discloses a supercritical water
pretreatment process using hydrogen or carbon monoxide preferably
carried out in a deep well reactor to hydrotreat and hydrocrack
carbonaceous material. The deep well reactor is adapted from
underground oil wells, and consists of multiple, concentric tubes.
The deep well reactor described in the patent is operated by
introducing feed streams in the core tubes and returning reactor
effluent in the outer annular section.
SUMMARY OF THE INVENTION
[0012] The present invention relates to a process for upgrading
hydrocarbons comprising mixing hydrocarbons with a fluid comprising
water in a mixing zone to form a mixture; passing the mixture to a
reaction zone; reacting the mixture in the reaction zone under
supercritical water conditions in the absence of externally added
hydrogen for a residence time sufficient to allow upgrading
reactions to occur, withdrawing a single-phase reaction product
from the reaction zone; and separating the reaction product into
gas, effluent water, and upgraded hydrocarbon phases.
BRIEF DESCRIPTION OF THE DRAWING
[0013] FIG. 1 is a process flow diagram of an embodiment of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reactants
[0014] Water and hydrocarbons, preferably heavy hydrocarbons are
the two reactants employed in a process according to the present
invention.
[0015] Any heavy hydrocarbon can be suitably upgraded by a process
according to the present invention. Preferred are heavy
hydrocarbons having an API gravity of less than 20.degree.. Among
the preferred heavy hydrocarbons are heavy crude oil, heavy
hydrocarbons extracted from tar sands, commonly called tar sand
bitumen, such as Athabasca tar sand bitumen obtained from Canada,
heavy petroleum crude oils such as Venezuelan Orinoco heavy oil
belt crudes, Boscan heavy oil heavy hydrocarbon fractions obtained
from crude petroleum oils, particularly heavy vacuum gas oils,
vacuum residuum as well as petroleum tar, tar sands and coal tar.
Other examples of heavy hydrocarbon feedstocks which can be used
are oil shale, shale oil, and asphaltenes.
Water
[0016] Any source of water may be used in the fluid comprising
water in practicing the present invention. Sources of water include
but are not limited to drinking water, treated or untreated
wastewater, river water, lake water, seawater produced water or the
like.
Mixing
[0017] In accordance with the invention, the heavy hydrocarbon feed
and the fluid comprising water are contacted in a mixing zone prior
to entering the reaction zones. In accordance with the invention,
mixing may be accomplished in many ways and is preferably
accomplished by a technique that does not employ mechanical moving
parts. Such means of mixing may include, but are not limited to,
use of static mixers, spray nozzles, sonic or ultrasonic
agitation.
[0018] The oil and water should be heated and mixed so that the
combined stream will reach supercritical water conditions in the
reaction zone. Various heating sequences may be employed to
accomplish this result. For example, oil and water streams may be
heated separately at different temperatures so that supercritical
water mixes with and heats the remaining oil so that the entire
stream will reach supercritical conditions in the reaction zone.
Other methods of mixing and heating sequences may be used as will
be recognized by those skilled in the art.
Reaction Conditions
[0019] After the reactants have been mixed, they are passed into a
reaction zone in which they are allowed to react under temperature
and pressure conditions of supercritical water, i.e. supercritical
water conditions, in the absence of externally added hydrogen, for
a residence time sufficient to allow upgrading reactions to occur.
The reaction is preferably allowed to occur in the absence of
externally added catalysts or promoters, although the use of such
catalysts and promoters is permissible in accordance with the
present invention.
[0020] "Hydrogen" as used herein in the phrase, "in the absence of
externally added hydrogen" means hydrogen gas. This phrase is not
intended to exclude all sources of hydrogen that are available as
reactants. Other molecules such as saturated hydrocarbons may act
as a hydrogen source during the reaction by donating hydrogen to
other unsaturated hydrocarbons. In addition, H.sub.2 may be formed
in-situ during the reaction through steam reforming of hydrocarbons
and water-gas-shift reaction.
[0021] The reaction zone preferably comprises a reactor, which is
equipped with a means for collecting the reaction products
(syncrude, water, and gases), and a bottom section where any metals
or solids (the "dreg stream") may accumulate.
[0022] Supercritical water conditions include a temperature from
374.degree. C. (the critical temperature of water) to 1000.degree.
C., preferably from 374.degree. C. to 600.degree. C. and most
preferably from the 374.degree. C. to 400.degree. C., a pressure
from 3,205 (the critical pressure of water) to 10,000 psia,
preferably from 3,205 psia to 7,200 psia and most preferably from
3,205 to 4,000 psia, an oil/water volume ratio from 1:0.1 to 1:10,
preferably from 1:0.5 to 1:3 and most preferably about 1:1 to
1:2.
[0023] The reactants are allowed to react under these conditions
for a sufficient time to allow upgrading reactions to occur.
Preferably, the residence time will be selected to allow the
upgrading reactions to occur selectively and to the fullest extent
without having undesirable side reactions of coking or residue
formation. Reactor residence times may be from 1 minute to 6 hours,
preferably from 8 minutes to 2 hours and most preferably from 20 to
40 minutes.
Reaction Product Separation
[0024] After the reaction has progressed sufficiently, a single
phase reaction product is withdrawn from the reaction zone, cooled,
and separated into gas, effluent water, and upgraded hydrocarbon
phases. This separation is preferably done by cooling the stream
and using one or more two-phase separators, three-phase separators,
or other gas-oil-water separation device known in the art. However,
any method of separation can be used in accordance with the
invention.
[0025] The composition of gaseous product obtained by treatment of
the heavy hydrocarbons in accordance with the process of the
present invention will depend on feed properties and typically
comprises light hydrocarbons, water vapor, acid gas (CO.sub.2 and
H.sub.2S), methane and hydrogen. The effluent water may be used,
reused or discarded. It may be recycled to e.g. the feed water
tank, the feed water treatment system or to the reaction zone.
[0026] The upgraded hydrocarbon product, which is sometimes
referred to as "syncrude" herein may be upgraded further or
processed into other hydrocarbon products using methods that are
known in the hydrocarbon processing art.
[0027] The process of the present invention may be carried out as a
continuous or semi-continuous process or a batch process. In the
continuous process the entire system operates with a feed stream of
oil and a separate feed stream of supercritical water and reaches a
steady state; whereby all the flow rates, temperatures, pressures,
and composition of the inlet, outlet, and recycle streams do not
vary appreciably with time.
[0028] While not being bound to any theory of operation, it is
believed that a number of upgrading reactions are occurring
simultaneously at the supercritical reaction conditions used in the
present process.
[0029] In a preferred embodiment of the invention the major
chemical/upgrading reactions are believed to be:
Thermal Cracking: C.sub.xH.sub.y.fwdarw.lighter hydrocarbons
Steam Reforming:
C.sub.xH.sub.y+2xH.sub.2O=xCO.sub.2+(2x+y/2)H.sub.2
Water-Gas-Shift: CO+H.sub.2O.dbd.CO.sub.2+H.sub.2
Demetalization:
C.sub.xH.sub.yNi.sub.w+H.sub.2O/H.sub.2.fwdarw.NiO/Ni(OH).sub.2+lighter
hydrocarbons
Desulfurization:
C.sub.xH.sub.yS.sub.z+H.sub.2O/H.sub.2.dbd.H.sub.2S+lighter
hydrocarbons
[0030] The exact pathway may depend on the reactor operating
conditions (temperature, pressure, O/W volume ratio), reactor
design (mode of contact/mixing, sequence of heating), and the
hydrocarbon feedstock.
[0031] The following Examples are illustrative of the present
inventions but are not intended to limit the invention in any way
beyond what is contained in the claims which follow.
EXAMPLE 1
Showing Typical Laboratory Process
[0032] FIG. 1 shows a process flow diagram for a laboratory unit
for practicing some embodiments of the invention. Oil and
supercritical water are contacted in a mixer prior to entering the
reactor. The reactor is equipped with an inner tube for collecting
the products (syncrude, unreacted water, and gases), and a bottom
section where any metals or solids comprising a "dreg stream" of
indeterminate properties or composition may accumulate. The
shell-side of the reactor is kept isothermal during the reaction
with a clamshell furnace and temperature controller. Preferred
reactor residence times are 20-40 minutes, with preferred oil/water
volume ratios on the order of 1:3. Preferred temperatures are
around 374.degree.-400.degree. C., with the pressure; at
3,200-4,000 psig. The reactor product stream leaves as a single
phase, and is cooled, and separated into gas, syncrude and effluent
water. The effluent water is recycled back to the reactor. Sulfur
from the original feedstock accumulates in the dreg stream for the
most part, with lesser amounts primarily in the form of H.sub.2S
found in the gas phase and water phase.
[0033] As the next examples will show, very little gas is produced
in most cases. With suitable choice of operating conditions, it is
also possible to reduce or nearly eliminate the "dreg stream."
Elimination of the dreg stream means that a greater degree of
hydrocarbon is recovered as syncrude, but it also means that metals
and sulfur will accumulate elsewhere, such as in the water and gas
streams.
EXAMPLE 2
Properties of Product Syncrude
[0034] A Hamaca crude oil was diluted with a diluent hydrocarbon at
a ratio of 5:1 (20 vol % of diluent). The diluted Hamaca crude oil
properties were measured before reacting it with the supercritical
water process as referred to in Example 1. The properties of the
crude were as follows: 12.8 API gravity at 60/60; 1329 CST
viscosity@40.degree. C.; 7.66 wt % C/H ratio; 13.04 wt % MCRT; 3.54
wt % sulfur; 0.56 wt % nitrogen; 3.05 mg KOH/gm acid number; 1.41
wt % water; 371 ppm Vanadium; and 86 ppm Nickel. The diluted Hamaca
crude oil after the super critical water treatment was converted
into a syncrude with the following properties, 24.1 API, gravity at
60/60; 5.75 CST viscosity@40.degree. C.; 7.40 wt % C/H ratio; 2.25
wt % MCRT; 2.83 wt % sulfur; 0.28 wt % nitrogen; 1.54 mg KOH/gm
acid number; 0.96 wt % water; 24 ppm Vanadium; and 3 ppm Nickel.
Substantial reductions in metals and residues were observed, with
simultaneous increase in the API gravity and a significant decrease
in the viscosity of the original crude oil feedstock. There were
modest reductions in the Total Acid number, sulfur concentration,
and nitrogen concentration which could be improved with further
optimization of the reaction conditions.
[0035] Apart from the occasional, small accumulation of a dreg
stream, there is very little coking or solid byproducts formed in
the supercritical water reaction. The material balance was
performed for two separate experimental runs.
[0036] In the experimental run with no dreg stream formed, the
starting feedstock of diluted Hamaca crude at 60 grams produced a
syncrude product of 59.25 grams which corresponds to a high overall
recovery of 99 percent. It was thought that due to the absence of a
dreg stream, the experimental mass balance was impacted in the
determination of the sulfur and metals. The gas phase did not
contain metals species and had little sulfur compounds. It was
hypothesized that a portion of the metal and sulfur may have
accumulated on the walls of the reactor or downstream plumbing.
[0037] In the experimental run with a dreg stream formed, the
starting feedstock of diluted Hamaca crude at 30 grams produced a
syncrude product of 22.73 grams. The dreg stream that was formed
accounted for 5.5 grams. The overall recovery with the dreg stream
was 96.7 percent. In the dreg stream, sulfur accounted for 31% of
the total sulfur with the remaining sulfur in the oil product,
water phase, and gas phase. The metals content of the dreg stream
accounted for 82% of the total metals with the remaining metals in
the oil product. For commercial operations, it lay be preferable to
minimize the formation of a dreg stream, since it represents a 18%
reduction in syncrude product, and generates a lower value product
stream that impacts the process in terms of economics and disposal
concerns.
[0038] Undiluted Boscan crude oil properties were measured before
reacting it with the super critical water process as referred to in
Example 1. The properties of the crude were as follows: 9 API
gravity at 60/60; 1,140 CST viscosity@40.degree. C.; 8.0 wt % C/H
ratio; 16 wt % MCRT; 5.8 wt % Sulfur; and 1,280 ppm Vanadium. The
undiluted Boscan crude oil after the supercritical water treatment
was converted into a syncrude with the following properties: 22 API
gravity at 60/60; 9 CST viscosity@40.degree. C.; 7.6 wt % C/H
ratio; 2.5 wt % MCRT; 4.6% sulfur; and 130 ppm Vanadium.
[0039] A simulated distillation analysis of the original crude oil
vs. the syncrude products from different experimental runs shows
that the syncrude prepared in accordance with the present invention
clearly has superior properties than the original crude.
Specifically, the syncrudes contain a higher fraction of
lower-boiling fractions. 51% of the diluted Hamaca crude boils
across a range of temperatures of less than 1000.degree. F., while
employing a process according to the present invention using
supercritical water depending on process configurations, between 79
to 94% of the syncrude boils across a range of temperatures of less
than 1000.degree. F. 40%, of the undiluted Boscan crude boils
across a range of temperatures of less than 1000.degree. F., while
employing a process according to the present invention using
supercritical water, 93% of the syncrude boils across a range of
temperatures of less than 1000.degree. F.
[0040] There are numerous variations on the present invention which
are possible in light of the teachings and supporting examples
described herein. It is therefore understood that within the scope
of the following claims, the invention may be practiced otherwise
than as specifically described or exemplified herein:
* * * * *