U.S. patent application number 11/669986 was filed with the patent office on 2007-08-02 for process for desalting crude oil.
This patent application is currently assigned to SYNTROLEUM CORPORATION. Invention is credited to Ramin Abhari, Ziad Ghandour, H. Lynn Tomlinson.
Application Number | 20070175799 11/669986 |
Document ID | / |
Family ID | 38198470 |
Filed Date | 2007-08-02 |
United States Patent
Application |
20070175799 |
Kind Code |
A1 |
Tomlinson; H. Lynn ; et
al. |
August 2, 2007 |
PROCESS FOR DESALTING CRUDE OIL
Abstract
The invention provides a process for desalting crude by
combining water and raw crude oil in a mixer to produce a mixture.
Desalted crude oil and a brine mixture are separated from the
mixture. The water is obtained as a byproduct of a Fischer-Tropsch
plant.
Inventors: |
Tomlinson; H. Lynn; (Tulsa,
OK) ; Ghandour; Ziad; (Los Angeles, CA) ;
Abhari; Ramin; (Bixby, OK) |
Correspondence
Address: |
BAKER & MCKENZIE LLP
Pennzoil Place, South Tower
711 Louisiana, Suite 3400
HOUSTON
TX
77002-2716
US
|
Assignee: |
SYNTROLEUM CORPORATION
Tulsa
OK
|
Family ID: |
38198470 |
Appl. No.: |
11/669986 |
Filed: |
February 1, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60764702 |
Feb 2, 2006 |
|
|
|
Current U.S.
Class: |
208/251R ;
518/726 |
Current CPC
Class: |
C10G 33/00 20130101;
C10G 31/08 20130101; C10G 2/32 20130101 |
Class at
Publication: |
208/251.00R ;
518/726 |
International
Class: |
C10G 45/00 20060101
C10G045/00 |
Claims
1. A process for desalting crude comprising: a) combining water and
raw crude oil in a mixer to produce a mixture; b) separating from
the mixture a desalted crude oil and a brine mixture; wherein the
water is obtained as a byproduct of a Fischer-Tropsch plant.
2. The process of claim 1, further comprising preheating the water
and/or the raw crude oil before combining them.
3. The process of claim 1, further comprising adding a demulsifier
to the mixer.
4. The process of claim 1, wherein the process occurs at an oil
producing site.
5. The process of claim 1, wherein the process occurs at an oil
refining site.
6. The process of claim 4, further comprising re-injecting the
brine mixture into a hydrocarbon formation at the oil producing
site.
7. The process of claim 1, further comprising processing the brine
mixture for reuse.
8. The process of claim 1, further comprising processing the brine
mixture for discharge.
9. The process of claim 1, wherein the process occurs on a movable
platform.
10. A process for desalting crude comprising: a) forming an
emulsion of crude oil and Fischer-Tropsch water; and b) breaking
the emulsion to obtain a desalted crude oil and a brine
mixture.
11. The process of claim 1 wherein the Fischer-Tropsch water
contains less than 1% inorganic salts.
12. The process of claim 1 wherein the Fischer-Tropsch water
contains less than 0.5% inorganic salts.
13. The process of claim 1 wherein the Fischer-Tropsch water
contains less than 0.01% inorganic salts.
14. The process of claim 1 wherein the desalted crude oil contains
less than 40 wppb inorganic salts.
15. The process of claim 1 wherein the desalted crude oil contains
less than 10 wppb inorganic salts.
Description
PRIOR RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application Ser. No. 60/764,702, filed on Feb. 2, 2006, which is
hereby incorporated in it's entirety.
FEDERALLY SPONSORED RESEARCH STATEMENT
[0002] Not applicable.
REFERENCE TO MICROFICHE APPENDIX
[0003] Not applicable.
FIELD OF THE INVENTION
[0004] The invention relates to a desalting process for crude oil.
More specifically, the invention relates to a desalting process for
crude oil that uses water produced from a Fischer-Tropsch
plant.
BACKGROUND OF THE INVENTION
[0005] Crude oil entering a petroleum refinery contains a number of
impurities harmful to the efficient operation of the refinery and
detrimental to the quality of the final petroleum products. Some
impurities include, but are not limited to, salts of magnesium,
sodium and calcium, potassium, nickel, vanadium, copper, iron and
zinc, and are unstable at elevated temperatures. If allowed to
remain in the crude oil, the salts contribute to corrosion in the
main fractionator unit and other regions of the refinery system
where temperatures are elevated, as well as any area where water
condenses. These impurities also contribute to heat exchanger
fouling, furnace coking, catalyst poisoning and end product
degradation.
[0006] Crude oil desalting removes most of the impurities and is a
common emulsion breaking method where the emulsion is first
intentionally formed. Water is added in an amount of approximately
between 5% and 10% by volume of crude. The added water is
intimately mixed with the crude oil to contact the impurities
therein, thereby transferring these impurities into the water phase
of the emulsion. The emulsion is usually resolved with the
assistance of emulsion breaking chemicals, which are
characteristically surfactants. Alternatively, the emulsion may be
resolved by application of an electrical field to polarize the
water droplets. Once the emulsion is broken, the water and
petroleum media form distinct phases. The water phase is separated
from the petroleum phase and subsequently removed from the
desalter. The petroleum phase is directed further downstream for
processing through the refinery operation.
[0007] As oil refineries move to heavier crudes having higher
inorganic salt content, the performance of the desalter is becoming
increasingly important. Therefore, a clean water supply, free from
metals and salts, which will improve the performance of the
desalter is needed.
SUMMARY OF THE INVENTION
[0008] Large amounts of water, with very low inorganic content, are
produced at a Fischer-Tropsch plant. The water normally has to be
processed for discharge into the environment or transported offsite
for disposal. Using the Fischer-Tropsch byproduct water in a
desalting process unit would utilize existing crude desalting
infrastructure facilities and utilities, lessen the environmental
impact of the processing units and provide "cleaner" water to the
desalter process thereby increasing desalter importance.
[0009] Embodiments of the invention provide a process to desalt
crude oil utilizing the water byproduct from a Fischer-Tropsch
plant. Embodiments of the invention provide a process for desalting
crude by combining water and raw crude oil in a mixer to produce a
mixture. Desalted crude oil and a brine mixture are separated from
the mixture.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a flow diagram of an embodiment of an inventive
crude desalting method.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0011] Unless otherwise specified, all quantities, percentages and
ratios herein are by weight.
[0012] The term "desalted crude oil" means a crude oil which
following desalting treatment has less than 70% of the salt content
present in the crude oil prior to desalting, or may be less than
75%, less than 80%, less than 90%, less than 95%, and most
preferably 99.75% of the salt content present in the crude oil
prior to desalting.
[0013] The term "brine" means an aqueous stream containing
inorganic salts.
[0014] The term "FT water" means an aqueous stream which is
produced by a Fischer-Tropsch plant.
[0015] Referring to FIG. 1, a desalting unit 10 is described. Crude
oil 12 and water 14 are fed into a static mixer 16. An emulsion 18
is formed and fed to a settling tank 20. Products from the settling
tank 20 include a desalted crude oil 22 and a brine mixture 24. The
conditions of the static mixer are around 250.degree. F.
(121.1.degree. C.) and pressures high enough to prevent
vaporization of either water or hydrocarbons. These conditions will
vary depending on the make-up of the crude oil 12 and water 14.
[0016] The water 14 fed to the static mixer 16 is from a
Fischer-Tropsch (FT) plant, "FT water". FT plants produce about as
much FT water as hydrocarbon product. Because the FT water
originates from a process in which the feedstock is a natural gas,
the FT water is virtually free of minerals and/or salts.
[0017] An FT plant for converting hydrocarbon gases to liquid or
solid hydrocarbon products includes a synthesis gas unit, which
includes a synthesis gas reactor in the form of, for example, an
autothermal reforming reactor (ATR) containing a reforming
catalyst, such as a nickel-containing catalyst. A stream of light
hydrocarbons to be converted, which may include natural gas, is
introduced into the reactor along with oxygen (O.sub.2). The oxygen
may be provided from compressed air or other compressed
oxygen-containing gas, such as oxygen enriched air, or may be a
pure oxygen stream. The light hydrocarbon stream may also arise
from gasified coal. The ATR reaction may be adiabatic, with no heat
being added or removed from the reactor other than from the feeds
and the heat of reaction. The reaction is carried out under
sub-stoichiometric conditions whereby the oxygen/steam/gas mixture
is converted to syngas. Examples of Fischer-Tropsch systems are
described in U.S. Pat. Nos. 4,973,453; 5,733,941; 5,861,441;
6,130,259, 6,169,120 and 6,172,124, the disclosures of which are
herein incorporated by reference.
[0018] Techniques for producing a synthesis gas, or syngas, which
is used as the starting material of a Fischer-Tropsch reaction are
well known in the art and include oxidation, reforming and
autothermal reforming. The Fischer-Tropsch reaction for converting
syngas, which is composed primarily of carbon monoxide (CO) and
hydrogen gas (H.sub.2) may be characterized by the following
general reaction: 2nH.sub.2+nCO.fwdarw.(--CH.sub.2--)n+nH.sub.2O
(1)
[0019] Non-reactive components, such as nitrogen, may also be
included or mixed with the syngas. This may occur in those
instances where air or some other non-pure oxygen source is used
during the syngas formation.
[0020] The syngas is delivered to a synthesis unit, which includes
a Fischer-Tropsch reactor (FTR) containing a Fischer-Tropsch
catalyst. Numerous Fischer-Tropsch catalysts may be used in
carrying out the reaction. These include cobalt, iron, ruthenium as
well as other Group VIIIB transition metals or combinations of such
metals, to prepare both saturated and unsaturated hydrocarbons. For
purposes of this invention, a non-iron catalyst may be used. The
F-T catalyst may include a support, such as a metal-oxide support,
including silica, alumina, silica-alumina or titanium oxides. For
the purposes of this reaction, a Co catalyst on transition alumina
with a surface area of approximately 100-200 m.sup.2/g is used in
the form of spheres of 50-150 .mu.m in diameter. The Co
concentration on the support may also be 15-30%. Certain catalyst
promoters and stabilizers may be used. The stabilizers include
Group IIA or Group IIIB metals, while the promoters may include
elements from Group VIII or Group VIIB. The Fischer-Tropsch
catalyst and reaction conditions may be selected to be optimal for
desired reaction products, such as for hydrocarbons of certain
chain lengths or number of carbon atoms. Any of the following
reactor configurations may be employed for Fischer-Tropsch
synthesis: fixed bed, slurry reactor, ebullating bed, fluidizing
bed, or continuously stirred tank reactor (CSTR). For the purposes
of this reaction, a slurry bed reactor is used. The FTR may be
operated at a pressure of 100 to 550 psia (689 to 3792 kPa) and a
temperature of 350.degree. F. to 500.degree. F. (176.6 to
260.degree. C.). The reactor gas hourly space velocity ("GHSV") may
be from 1000 to 8000 hr-1. Syngas useful in producing a
Fischer-Tropsch product useful in the invention may contain gaseous
hydrocarbons, hydrogen, carbon monoxide and nitrogen with
H.sub.2/CO ratios from about 1.8 to about 2.4. The products derived
from the Fischer-Tropsch reaction may range from methane (CH.sub.4)
to high molecular weight paraffinic waxes containing more than 100
carbon atoms and water.
[0021] In an embodiment of the invention, the FT plant and the
desalting process are located at an oil-producing field. Such field
may be located on shore, near shore or off shore. The associated
gas from the oil-producing field is converted to hydrocarbons in
the FT plant and the byproduct water from the FT plant, FT water,
is sent to the desalting unit 10. The associated gas typically
contains 92 mol % methane, 3 mol % ethane, 2 mol % propane, 0.5 mol
% butanes, and 2.5 mol % C.sub.5-C.sub.8 paraffins but may vary
depending on the oil-producing field. The desalted crude oil 22 can
be sent for further processing in the field or sent to a refinery.
After processing at the oil field, the brine mixture 24 can be
re-injected into the oil-producing field. If the crude is desalted
at the oil field, the desalted crude can bypass the existing
desalter at the refinery, which will provide capacity increase
opportunities for desalter-limited refineries.
[0022] In an alternate embodiment, the FT plant is located at an
oil refinery. The desalter in a refinery is typically located
upstream of the atmospheric fractionator (sometimes called a "crude
unit"). The pressures and temperatures in the crude unit are
between 10-50 psig (68.9-344 kPa) and 200-750.degree. F.
(93.3-398.8.degree. C.). The FT plant and refinery can be
integrated to utilize existing refinery and utilities
infrastructure. The brine mixture 24 can be processed in existing
refinery facilities. This integration provides an opportunity to
expand the refinery crude desalting capacity independent of the
water demineralization facilities.
[0023] In a preferred embodiment, the static mixer 16 and the
settling tank 20 are parts of the desalting unit 10. In alternate
embodiments, the desalting unit 10 is any common desalting unit
that uses water.
[0024] In an alternate embodiment, the crude oil 12 and FT water 14
are preheated before entering the static mixer 16. In another
embodiment, a demulsifying surfactant is added to the settling tank
20. The slight acidity of the FT water 14 (pH typically between
3-5), coming from dissolved acid byproducts of FT synthesis, is
expected to help with demulsification. As such, the demulsifying
surfactants may not be needed or required at significantly smaller
concentrations.
[0025] In yet other embodiments of the invention, other equipment
for producing an oil/water emulsion may be used in lieu of static
mixer 16. Such other types of equipment include, for example,
pressure-reducing valves, continuous-flow stirred tanks with
side-entering or top-entering propeller mixers, in-line turbine
agitators, or jet mixers. Any alternative mixing method and/or
apparatus may be used so as to achieve the formation of the
emulsion. Since desalting is a mass-transfer limited process, the
higher the water-oil contact area, the better the performance. This
means that the emulsion droplets need to be small enough to provide
a high surface area for migration of salts from oil to water, but
not so small that residence times required for coalescence in the
settler become too long.
[0026] In other embodiments of the invention, other techniques
and/or equipment for separating emulsions may be used in lieu of a
surfactant and/or settling tank 20. For example, electrostatic
precipitators, dehydrators, or cyclonic separators could
alternatively be used to break the emulsion. Any method and/or
process sufficient to achieve separation of the emulsion into an
aqueous phase and an oil phase, wherein the oil phase contains no
free water may be used.
[0027] In various embodiments of this invention, the desalting
process may be located at a refinery, at a well site, or on a
movable platform, such as a barge or ship.
[0028] Other sources of water for the desalting of crude can be
found in a FT plant. In a preferred case, the FT plant is part of a
Natural Gas-to-Liquids plant where the reformer also produces a
water product ("ATR water"). The ATR water is also low in total
dissolved solids (TDS) and will provide desalting capacity.
Exemplary compositions of the FT water stream and the ATR water
stream are in Table 1, but embodiments of the invention should not
be limited by these. TABLE-US-00001 TABLE 1 Chemical analysis of
water from FT Reactor and Autothermal Reformer FT ATR water water
Relative production ratio 1 0.08 pH 4.2 7.89 Conductivity (mS)
180.5 9133 TDS (mg/L) 50.5 25 TSS, total suspended solids 0.0 3.0
(mg/L)
[0029] Also, in the hydroprocessing of FT synthesis products, the
conversion of alcohols and, to a lesser extent, carboxylic acids,
ketones and aldehydes, produce water. This "process water" is also
very low in solids and, as such, will provide desalting
capacity.
[0030] While the invention has been described with respect to a
limited number of embodiments, the specific features of one
embodiment should not be attributed to other embodiments of the
invention. No single embodiment is representative of all aspects of
the inventions. Moreover, variations and modifications therefrom
exist. For example, other desalting process units can be used in
place of the static mixer and settling tank. Additionally, heat
exchangers and preheaters may be designed for maximum heat
efficiency. The appended claims intend to cover all such variations
and modifications as falling within the scope of the invention.
* * * * *