U.S. patent application number 14/302950 was filed with the patent office on 2015-12-17 for ionic liquid treatment of vacuum slop cut to increase hydrocracking feed.
The applicant listed for this patent is UOP LLC. Invention is credited to Soumendra M. Banerjee, Deepak Bisht, Vasant P. Thakkar.
Application Number | 20150361351 14/302950 |
Document ID | / |
Family ID | 54835630 |
Filed Date | 2015-12-17 |
United States Patent
Application |
20150361351 |
Kind Code |
A1 |
Banerjee; Soumendra M. ; et
al. |
December 17, 2015 |
IONIC LIQUID TREATMENT OF VACUUM SLOP CUT TO INCREASE HYDROCRACKING
FEED
Abstract
A process and apparatus for increasing vacuum gas oil recovery
from a vacuum column are described. The process includes separating
a residue crude oil stream from a crude oil separation column in a
vacuum column into at least one vacuum gas oil fraction, and a
contaminant-rich slop fraction containing at least one contaminant;
contacting the contaminant-rich slop fraction with a lean ionic
liquid in a contaminant removal zone to produce a mixture
comprising a contaminant-lean slop fraction and a rich ionic liquid
comprising at least a portion of the at least one contaminant; and
separating the mixture to produce a treated slop effluent
comprising the contaminant-lean slop fraction and a rich ionic
liquid effluent comprising the rich ionic liquid.
Inventors: |
Banerjee; Soumendra M.; (New
Delhi, IN) ; Thakkar; Vasant P.; (Elk Grove Village,
IL) ; Bisht; Deepak; (Gurgaon, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UOP LLC |
Des Plaines |
IL |
US |
|
|
Family ID: |
54835630 |
Appl. No.: |
14/302950 |
Filed: |
June 12, 2014 |
Current U.S.
Class: |
208/57 ; 208/236;
208/254R; 208/61; 422/187 |
Current CPC
Class: |
C10G 21/20 20130101;
C10G 21/24 20130101; C10G 55/06 20130101; C10G 7/06 20130101; C10G
67/0418 20130101; C10G 67/0445 20130101; C10G 21/28 20130101 |
International
Class: |
C10G 21/27 20060101
C10G021/27; C10G 67/04 20060101 C10G067/04 |
Claims
1. A process for increasing vacuum gas oil recovery from a vacuum
column comprising: separating a residue crude oil stream from a
crude oil separation column in a vacuum column into at least one
vacuum gas oil fraction, and a contaminant-rich slop fraction
containing at least one contaminant; contacting the
contaminant-rich slop fraction with a lean ionic liquid in a
contaminant removal zone to produce a mixture comprising a
contaminant-lean slop fraction and a rich ionic liquid comprising
at least a portion of the at least one contaminant; and separating
the mixture to produce a treated slop effluent comprising the
contaminant-lean slop fraction and a rich ionic liquid effluent
comprising the rich ionic liquid.
2. The process of claim 1 further comprising introducing the
treated slop effluent into a secondary conversion zone comprising
at least one of a hydrocracking or a hydrotreating zone and a fluid
catalytic cracking zone.
3. The process of claim 2 further comprising: combining the treated
slop effluent with the at least one vacuum gas oil fraction to form
a combined fraction before introducing the treated slop effluent
into the secondary conversion zone.
4. The process of claim 1 further comprising regenerating the rich
ionic liquid effluent to remove at least a portion of the at least
one contaminant from the rich ionic liquid effluent forming a
regenerated ionic liquid and an extract stream containing at least
the portion of the at least one contaminant.
5. The process of claim 4 further comprising separating the
regenerated ionic liquid from the extract stream.
6. The process of claim 5 further comprising recycling the
regenerated ionic liquid to the treatment zone.
7. The process of claim 5 wherein separating the residue crude oil
stream from the crude oil separation column in the vacuum column
into the at least one vacuum gas oil fraction, and the
contaminant-rich slop fraction comprises separating the residue
crude oil stream from the crude oil separation column in the vacuum
column into the at least one vacuum gas oil fraction, the
contaminant-rich slop fraction, and a vacuum residue fraction; and
further comprising combining the extract stream with the vacuum
residue fraction.
8. The process of claim 7 further comprising introducing the
combined extract stream and vacuum residue fraction to a delayed
coker zone.
9. The process of claim 1 wherein the contaminant-rich slop
fraction comprises between about 5 wt % to about 30 wt % of a total
of the at least one vacuum gas oil fractions.
10. The process of claim 1 wherein the at least one vacuum gas oil
fraction comprises a light vacuum gas oil fraction and a heavy
vacuum gas oil fraction.
11. The process of claim 1 wherein the contaminant-rich slop
fraction has a boiling point in a range of about 490.degree. C. to
about 565.degree. C.
12. The process of claim 1 wherein the ionic liquid comprises an
organic cation and an anion, and wherein the organic cation is
selected from the group consisting of: ##STR00002## where
R.sup.1-R.sup.21 are independently selected from C.sub.1-C.sub.20
hydrocarbons, C.sub.1-C.sub.20 hydrocarbon derivatives, halogens,
and H.
13. The process of claim 1, wherein the ionic liquid comprises an
organic cation and an anion, and wherein the anion comprises at
least one of a carboxylate, an acetate, a tosylate, a cyanate, a
halide, a sulfate, a hydrogen sulfate, a sulfonate, a sulfonyl
imide, a phosphate, a borate, a carbonate, or a heterocyclic
anion.
14. A process for increasing the vacuum gas oil recovery from a
vacuum column comprising: separating a residue crude oil stream
from a crude oil separation column in a vacuum column into at least
one vacuum gas oil fraction, a contaminant-rich slop fraction
containing at least one contaminant, and a vacuum residue fraction;
contacting the contaminant-rich slop fraction with a lean ionic
liquid in a contaminant removal zone to produce a mixture
comprising a contaminant-lean slop fraction and a rich ionic liquid
comprising at least a portion of the at least one contaminant;
separating the mixture to produce a treated slop effluent
comprising the contaminant-lean slop fraction and a rich ionic
liquid effluent comprising the rich ionic liquid; introducing the
treated slop effluent into a secondary conversion zone comprising
at least one of a hydrocracking zone, a fluid catalytic cracking
zone, and a VGO hydrotreating zone; and regenerating the rich ionic
liquid effluent to remove at least a portion of the at least one
contaminant from the rich ionic liquid effluent forming a
regenerated ionic liquid and an extract stream containing at least
the portion of the at least one contaminant.
15. The process of claim 14 further comprising: combining the
treated slop effluent with the at least one vacuum gas oil fraction
to form a combined fraction before introducing the treated slop
effluent into the secondary conversion zone.
16. The process of claim 14 further comprising separating the
regenerated ionic liquid from the extract stream.
17. The process of claim 14 further comprising recycling the
regenerated ionic liquid to the treatment zone.
18. The process of claim 14 wherein the contaminant-rich slop
fraction comprises between about 5 wt % to about 30 wt % of a total
of the at least one vacuum gas oil fractions.
19. The process of claim 14 wherein the contaminant-rich slop
fraction has a boiling point in a range of about 490.degree. C. to
about 565.degree. C.
20. An apparatus for increasing vacuum gas oil recovery comprising:
a crude oil separation column having an inlet and at least a bottom
outlet; a vacuum column having an inlet and at least an upper and a
lower outlet, the inlet of the vacuum column being in fluid
communication with the bottom outlet of the crude oil separation
column; a contaminant removal zone having an inlet and an outlet,
the inlet of the contaminant removal zone being in fluid
communication with the lower outlet of the vacuum column; a
secondary conversion zone having an inlet and an outlet, the inlet
of the secondary conversion zone being in fluid communication with
the upper outlet of the vacuum column and the outlet of the
contaminant removal zone.
Description
BACKGROUND OF THE INVENTION
[0001] Vacuum towers are important units in a refinery because they
produce the feed for the secondary conversion units, such as
hydrocracking and hydrotreating units, and fluid catalytic cracking
(FCC) units. The operation and yields of from the vacuum towers
affect the operation of the downstream conversion units. Improved
vacuum tower operation is critical to meet the demands of the
increasingly heavier world crude slate.
[0002] Vacuum gas oil (VGO) is a hydrocarbon fraction that may be
converted into higher value hydrocarbon fractions such as diesel
fuel, jet fuel, naphtha, gasoline, and other lower boiling
fractions in the downstream conversion units. However, VGO feed
streams have higher amounts of nitrogen and are more difficult to
convert. For example, the degree of conversion, product yields,
catalyst deactivation, and/or ability to meet product quality
specifications may be adversely affected by the nitrogen content of
the feed stream. It is known to reduce the nitrogen content of the
VGO stream by catalytic hydrogenation reactions such as in a
hydrotreating process unit. It is also known to remove nitrogen
from the VGO stream using ionic liquids.
[0003] Increasing the VGO recovery in the vacuum tower would not
only provide a large economic incentive per barrel of crude, but
also reduce the need for capital expenditures. Reduced vacuum
residue production resulting from deep cut tower operation helps to
mitigate the effects of heavier crude slates, reducing the need for
additional delayed coking capacity.
[0004] However, increasing the VGO yield while processing heavier
crudes requires revamping existing columns for deep cut operations.
Typical vacuum distillation units have a VGO endpoint in the range
of 560.degree. C. Deep cut vacuum operations recover more VGO by
increasing the endpoint to as high as 600.degree. C. However, the
challenge is to design the column internals to minimize the amount
of contaminants that come out with the VGO. The downstream
hydroprocessing units are very sensitive to the contaminants in the
feed VGO stream. Furthermore, there are significant equipment and
utility costs associated with this type of change. For example, the
feed furnace, vacuum tower, heat exchangers, and vacuum jet
equipment all play important roles in the ultimate capacity, low
pressure capability, and revamp cost of each specific unit. All of
these factors, as well as others, must be evaluated in order to
reach any conclusions concerning possible changes to the
refinery.
[0005] Therefore, there is a need for improving the VGO yields
without the need to change the operation of the vacuum tower
significantly.
SUMMARY OF THE INVENTION
[0006] One aspect of the invention is a process for increasing
vacuum gas oil recovery from a vacuum column. In one embodiment,
the process includes separating a residue crude oil stream from a
crude oil separation column in a vacuum column into at least one
vacuum gas oil fraction, and a contaminant-rich slop fraction
containing at least one contaminant; contacting the
contaminant-rich slop fraction with a lean ionic liquid in a
contaminant removal zone to produce a mixture comprising a
contaminant-lean slop fraction and a rich ionic liquid comprising
at least a portion of the at least one contaminant; and separating
the mixture to produce a treated slop effluent comprising the
contaminant-lean slop fraction and a rich ionic liquid effluent
comprising the rich ionic liquid.
[0007] Another aspect of the invention involves an apparatus for
increasing vacuum gas oil recovery. In one embodiment the apparatus
includes a crude oil separation column having an inlet and at least
a bottom outlet; a vacuum column having an inlet and having at
least an upper and a lower outlet, the inlet of the vacuum column
being in fluid communication with the bottom outlet of the crude
oil separation column; a contaminant removal zone having an inlet
and an outlet, the inlet of the contaminant removal zone being in
fluid communication with the lower outlet of the vacuum column; a
secondary conversion zone having an inlet and an outlet, the inlet
of the secondary conversion zone being in fluid communication with
the upper outlet of the vacuum column and the outlet of the
contaminant removal zone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is an illustration of one embodiment of the
invention.
[0009] FIGS. 2A and 2B are a simplified flow scheme showing
different embodiments of the contaminant removal zone.
DETAILED DESCRIPTION OF THE INVENTION
[0010] The present invention provides a method for increasing the
VGO yields without the need to alter the existing vacuum tower
significantly. In general, the invention involves removing
contaminants from the slop fraction from a vacuum tower using an
ionic liquid.
[0011] A slop fraction is withdrawn from the vacuum tower below the
heavy vacuum gas oil (HVGO) draw. Much of the contamination will be
in the slop fraction, rather than in the light VGO (LVGO) and HVGO
fractions. The slop fraction is treated with an ionic liquid to
remove the contaminants. The treated slop fraction can then be
combined with the LVGO and HVGO fractions. Thus, the process
increases the feed to the downstream processing unit without having
much of an impact on the vacuum column. In addition, the vacuum
residue stream is reduced due to the use of the treated slop
cut.
[0012] The ionic liquid can be regenerated using known regeneration
methods and recycled to the contaminant removal zone.
[0013] An extract stream rich in contaminants from the regeneration
zone can be combined with the vacuum residue stream from the vacuum
tower, and the combined stream can be sent to a delayed coker unit
for further processing.
[0014] FIG. 1 illustrates one embodiment of the process. A crude
oil stream 105 is introduced into a crude distillation zone 110
where it is separated into two or more fractions. For example, as
illustrated, the crude oil stream 105 is separated into fraction
115 which contains light naphtha, liquefied petroleum gas (LPG),
and offgas, which is C.sub.2- hydrocarbons, heavy naphtha fraction
120, kerosene fraction 125, diesel fraction 130, heavy gas oil
(HGO) fraction 135, and residue crude oil fraction 140.
[0015] The residue crude oil fraction 140 is sent to vacuum tower
145 where it is separated into two or more streams. The residue
crude oil fraction can vary from 325.degree. C.+ to 370.degree. C.+
material depending on the unit configurations and limitations. For
example, the residue crude fraction 140 can be separated into
vacuum diesel fraction 150, LVGO fraction 155, HVGO fraction 160,
slop fraction 165, and vacuum residue fraction 170.
[0016] In general, the LVGO fraction 155 comprises petroleum
hydrocarbon components boiling in the range of from about
340.degree. C. to 430.degree. C., and the HVGO fraction 160 boils
from about 430.degree. C. to 550.degree. C., or 430.degree. C. to
520.degree. C. The endpoint between the LVGO and the HVGO can vary
from 410.degree. C. to 450.degree. C. depending on the
characteristics of the crude and the mode of operation. The slop
fraction 165 comprises components boiling in the range of about
520.degree. C. to about 570.degree. C. The TBP T5 point for the
slop fraction is about 490.degree. C. about to 530.degree. C., and
the TBP T95 point is about 550.degree. C. to about 600.degree. C.
For deep cut distillation, the slop fraction can range from
520.degree. C. to 600.degree. C. There can be an overlap between
the HVGO fraction and the slop fraction. The vacuum residue
fraction 170 boils in the range of 550.degree. C. to 600.degree.
C.
[0017] As a result of the withdrawal of the slop fraction, there is
no need to pull additional VGO up the flash zone. The end point of
the VGO can be kept low, and a majority of the contaminants, such
as sulfur, nitrogen, metals, and Conradson Carbon Residue (CCR)
will concentrate in the slop fraction. Normally, the sulfur,
nitrogen, metals, and CCR content would increase with the endpoint
of the VGO; thus, limiting the endpoint would improve the control
of the VGO quality.
[0018] The flow of the slop fraction 165 is in the range of about 5
wt % to about 30 wt % of the total VGO stream, but the majority of
the contaminants are concentrated in the slop fraction 165.
[0019] The slop fraction 165 is then contacted with ionic liquid in
contaminant removal zone 175 to remove the contaminants. The term
"contaminant" means one or more species found in the slop fraction
165 that is detrimental to further processing. Contaminants
include, but are not limited to, nitrogen, sulfur, metals (e.g.,
nickel, iron, and vanadium), heavy polynuclear aromatic (HPNA)
hydrocarbons, and Conradson carbon residue or carbon residue.
Generally, the slop fraction 165 may contain from about 100 ppm-wt
to about 30,000 ppm-wt nitrogen; from about 1000 ppm-wt to about
50,000 ppm-wt sulfur; and from about 100 ppb-wt to about 2000
ppm-wt of metals. In an embodiment, the nitrogen content of the
slop fraction 165 ranges from about 200 ppm-wt to about 5000
ppm-wt. In another embodiment, the sulfur content of the slop
fraction 165 ranges from about 1000 ppm-wt to about 30,000
ppm-wt.
[0020] The ionic liquid can remove one or more of the contaminants
in the slop fraction 165. The slop fraction 165 will usually
comprise a plurality of nitrogen compounds of different types in
various amounts. Thus, at least a portion of at least one type of
nitrogen compound may be removed from the slop fraction 165. The
same or different amounts of each type of nitrogen compound can be
removed, and some types of nitrogen compounds may not be removed.
In an embodiment, the nitrogen content of the slop fraction 165 is
reduced by at least about 3 wt % with respect to the feed, or at
least about 5 wt %, or at least about 10 wt %, or at least about 15
wt %, at least about 20 wt %, or at least about 30 wt %, or at
least about 40 wt %. The maximum removal is typically about 85 wt
%.
[0021] The slop fraction 165 will typically also comprise a
plurality of sulfur compounds of different types in various
amounts. Thus, at least a portion of at least one type of sulfur
compound may be removed from the slop fraction 165. The same or
different amounts of each type of sulfur compound may be removed,
and some types of sulfur compounds may not be removed. In an
embodiment, the sulfur content of the slop fraction 165 is reduced
by at least about 1 wt % with respect to the feed, or at least
about 2 wt %, or at least 3 wt %, or at least 5 wt %, or at least
10 wt %. The maximum removal is typically about 65 wt %.
[0022] The slop fraction 165 will usually contain various metals,
including, but not limited to, nickel, iron, and vanadium. In an
embodiment, the metal content of the slop fraction 165 can be
reduced by at least about 10% with respect to the feed on an
elemental basis, or at least about 20 wt %, or at least about 25 wt
%, or at least about 30 wt %, or at least about 40 wt %, or at
least about 50%. The maximum removal is typically about 82 wt % for
vanadium, and about 86 wt % for nickel. The metal removed may be
part of a hydrocarbon molecule or complexed with a hydrocarbon
molecule.
[0023] The nitrogen content may be determined using ASTM method
D4629-02, Trace Nitrogen in Liquid Petroleum Hydrocarbons by
Syringe/Inlet Oxidative Combustion and Chemiluminescence Detection.
The sulfur content may be determined using ASTM method D5453-00,
Ultraviolet Fluorescence. The metals content may be determined by
UOP389-09, Trace Metals in Oils by Wet Ashing and ICP-OES. The
Conradson carbon residue may be determined by ASTM D4530. Unless
otherwise noted, the analytical methods used herein such as ASTM
D5453-00 and UOP389-09 are available from ASTM International, 100
Barr Harbor Drive, West Conshohocken, Pa., USA.
[0024] Processes according to the invention remove contaminants
from the slop fraction 165. That is, the process removes at least
one contaminant. It is understood that the slop fraction 165 will
usually comprise a plurality of contaminants of different types in
various amounts. Thus, the process removes at least a portion of at
least one type of contaminant. The process may remove the same or
different amounts of each type of contaminant, and some types of
contaminants may not be removed.
[0025] One or more ionic liquids can be used in the process.
[0026] The ionic liquid comprises an organic cation and an anion.
Suitable organic cations include, but are not limited to:
##STR00001##
[0027] where R.sup.1-R.sup.21 are independently selected from
C.sub.1-C.sub.20 hydrocarbons, C.sub.1-C.sub.20 hydrocarbon
derivatives, halogens, and H. Suitable hydrocarbons and hydrocarbon
derivatives include saturated and unsaturated hydrocarbons, halogen
substituted and partially substituted hydrocarbons and mixtures
thereof. C.sub.1-C.sub.8 hydrocarbons are particularly
suitable.
[0028] The anion can be derived from halides, sulfates, bisulfates,
nitrates, sulfonates, fluoroalkanesulfonates, and combinations
thereof. The anion is typically derived from metal and nonmetal
halides, such as metal and nonmetal chlorides, bromides, iodides,
fluorides, or combinations thereof. Combinations of halides
include, but are not limited to, mixtures of two or more metal or
nonmetal halides (e.g., AlCl.sub.4.sup.- and BF.sub.4.sup.-), and
mixtures of two or more halides with a single metal or nonmetal
(e.g., AlCl.sub.3Br.sup.-). In some embodiments, the metal is
aluminum, with the mole fraction of aluminum ranging from
0<Al<0.25 in the anion. Suitable anions include, but are not
limited to, AlCl.sub.4.sup.-, Al.sub.2Cl.sub.7.sup.-,
Al.sub.3Cl.sub.10.sup.-, AlCl.sub.3Br.sup.-,
Al.sub.2Cl.sub.6Br.sup.-, Al.sub.3Cl.sub.9Br.sup.-,
AlBr.sub.4.sup.-, Al.sub.2Br.sub.7.sup.-, Al.sub.3Br.sub.10.sup.-,
GaCl.sub.4.sup.-, Ga.sub.2Cl.sub.7.sup.-, Ga.sub.3Cl.sub.10.sup.-,
GaCl.sub.3Br.sup.-, Ga.sub.2Cl.sub.6Br.sup.-,
Ga.sub.3Cl.sub.9Br.sup.-, CuCl.sub.2.sup.-, Cu.sub.2Cl.sub.3.sup.-,
Cu.sub.3Cl.sub.4.sup.-, ZnCl.sub.3.sup.-, FeCl.sub.3.sup.-,
FeCl.sub.4.sup.-, Fe.sub.3Cl.sub.7.sup.-, PF.sub.6.sup.-, and
BF.sub.4.sup.-.
[0029] Consistent with common terms of art, the ionic liquid
introduced to the contaminant removal step may be referred to as a
"lean ionic liquid" generally meaning a hydrocarbon-immiscible
ionic liquid that is not saturated with one or more extracted
contaminants. Lean ionic liquid may include one or both of fresh
and regenerated ionic liquid and is suitable for accepting or
extracting contaminants from the hydrocarbon feed. Likewise, the
ionic liquid effluent may be referred to as "rich ionic liquid",
which generally means a hydrocarbon-immiscible ionic liquid
effluent produced by a contaminant removal step or process or
otherwise including a greater amount of extracted contaminants than
the amount of extracted contaminants included in the lean ionic
liquid. A rich ionic liquid may require regeneration or dilution,
e.g. with fresh ionic liquid, before recycling to the same or
another contaminant removal step of the process.
[0030] In an embodiment, the contaminant removal comprises a
contacting step and a separating step. In the contacting step, the
slop fraction 165 comprising a contaminant and a
hydrocarbon-immiscible ionic liquid are contacted or mixed. The
contacting may facilitate transfer or extraction of the one or more
contaminants from the slop fraction 165 to the ionic liquid.
Although an ionic liquid that is partially soluble in the
hydrocarbon may facilitate transfer of the contaminant from the
hydrocarbon to the ionic liquid, partial solubility is not
required. Insoluble hydrocarbon/ionic liquid mixtures may have
sufficient interfacial surface area between the hydrocarbon and
ionic liquid to be useful. In the separation step, the mixture of
hydrocarbon and ionic liquid settles or forms two phases, a
hydrocarbon phase and an ionic liquid phase, which are separated to
produce a hydrocarbon-immiscible ionic liquid effluent and a
hydrocarbon effluent.
[0031] The decontamination process may be conducted in various
equipment which is well known in the art and is suitable for batch
or continuous operation. For example, in a small scale form of the
invention, hydrocarbon and a hydrocarbon-immiscible ionic liquid
may be mixed in a beaker, flask, or other vessel, e.g., by
stirring, shaking, use of a mixer, or a magnetic stirrer. The
mixing or agitation is stopped and the mixture forms a hydrocarbon
phase and an ionic liquid phase which can be separated, for
example, by decanting, centrifugation, or use of a pipette to
produce a hydrocarbon effluent having a lower contaminant content
relative to the incoming hydrocarbon. The process also produces a
hydrocarbon-immiscible ionic liquid effluent comprising the one or
more contaminants.
[0032] The contacting and separating steps may be repeated, for
example, when the contaminant content of the hydrocarbon effluent
is to be reduced further to obtain a desired contaminant level in
the ultimate hydrocarbon product stream from the process. Each set,
group, or pair of contacting and separating steps may be referred
to as a contaminant removal step. Thus, the invention encompasses
single and multiple contaminant removal steps. A contaminant
removal zone may be used to perform a contaminant removal step. As
used herein, the term "zone" can refer to one or more equipment
items and/or one or more sub-zones. Equipment items may include,
for example, one or more vessels, heaters, separators, exchangers,
conduits, pumps, compressors, and controllers. Additionally, an
equipment item can further include one or more zones or sub-zones.
The contaminant removal process or step may be conducted in a
similar manner and with similar equipment as is used to conduct
other liquid-liquid wash and extraction operations. Suitable
equipment includes, for example, columns with: trays, packing,
rotating discs or plates, and static mixers. Pulse columns and
mixing/settling tanks may also be used.
[0033] The slop fraction 165 is contacted with the lean ionic
liquid 180 in the contaminant removal zone 175. The contaminants
are transferred from the slop fraction 165 to the lean ionic liquid
180. The treated slop effluent 185 has considerably less
contaminants than the untreated slop fraction 165.
[0034] The lean ionic liquid stream 180 may be comprised of fresh
ionic liquid stream and/or one or more ionic liquid streams which
are recycled in the process as described below.
[0035] The contact step can take place at a temperature in the
range of about 20.degree. C. to the decomposition temperature of
the ionic liquid, or about 20.degree. C. to about 120.degree. C.,
or about 20.degree. C. to about 80.degree. C.
[0036] The contacting time is sufficient to obtain good contact
between the ionic liquid and the hydrocarbon feed. The contacting
time is typically in the range of about 1 min to about 1 hr, or
about 5 min to about 30 min.
[0037] An optional washing step (not shown) may be used, for
example, to recover ionic liquid that is entrained or otherwise
remains in the treated slop effluent 185 by using water to wash or
extract the ionic liquid from the hydrocarbon effluent. In this
embodiment, a portion or all of treated slop effluent 185 (as feed)
and a water stream (as solvent) are introduced to a washing zone.
The treated slop effluent 185 and water streams are mixed and
separated to produce a washed treated slop effluent 185 and a spent
water stream, which comprises the ionic liquid. The washing step
may be conducted in a similar manner and with similar equipment as
used to conduct other liquid-liquid wash and extraction operations
as discussed above. Various hydrocarbon washing step equipment and
conditions such as temperature, pressure, times, and solvent to
feed ratio may be the same as or different from the contaminant
removal zone equipment and conditions. In general, the hydrocarbon
washing step conditions will fall within the same ranges as given
below for the contaminant removal step conditions.
[0038] An optional ionic liquid regeneration step may be used, for
example, to regenerate the ionic liquid by removing the contaminant
from the ionic liquid, i.e. reducing the contaminant content of the
rich ionic liquid. In an embodiment, a portion or all of rich ionic
liquid stream 190 (as feed) comprising the contaminant and a
regeneration solvent stream 195 are introduced to ionic liquid
regeneration zone 200. The rich ionic liquid stream 190 and
regeneration solvent stream 195 are mixed and separated to produce
an extract stream 205 comprising the contaminant, and a regenerated
ionic liquid stream 210. The ionic liquid regeneration step may be
conducted in a similar manner and with similar equipment as used to
conduct other liquid-liquid wash and extraction operations as
discussed below. Various ionic liquid regeneration step conditions
such as temperature, pressure, times, and solvent to feed may be
the same as or different from the contaminant removal conditions.
In general, the ionic liquid regeneration step conditions will fall
within the same ranges as given below for the contaminant removal
step conditions.
[0039] In an embodiment, the regeneration solvent stream 195
comprises a hydrocarbon fraction lighter than the slop fraction 165
and which is immiscible with the ionic liquid. The lighter
hydrocarbon fraction may consist of a single hydrocarbon compound
or may comprise a mixture of hydrocarbons. In an embodiment, the
lighter hydrocarbon fraction may comprise at least one of a
naphtha, gasoline, diesel, light cycle oil (LCO), and light coker
gas oil (LCGO) hydrocarbon fraction. The lighter hydrocarbon
fraction may comprise straight run fractions and/or products from
conversion processes such as hydrocracking, hydrotreating, fluid
catalytic cracking (FCC), reforming, coking, and visbreaking. In
this embodiment, extract stream 205 comprises the lighter
hydrocarbon regeneration solvent and the contaminant. In another
embodiment, the regeneration solvent stream 195 comprises water,
and the ionic liquid regeneration step produces an extract stream
205 comprising the contaminant and the regenerated ionic liquid 210
comprising water and the ionic liquid. In an embodiment wherein
regeneration solvent stream 195 comprises water, a portion or all
of spent water stream from the water washing step may provide a
portion or all of regeneration solvent stream 195. Regardless of
whether regeneration solvent stream 195 comprises a lighter
hydrocarbon fraction or water, a portion or all of regenerated
ionic liquid stream 210 may be recycled to the contaminant removal
step. For example, a constraint on the water content of the lean
ionic liquid stream 180 or the ionic liquid/hydrocarbon mixture in
contaminant removal zone 175 may be met by controlling the
proportion and water content of fresh and recycled ionic liquid
streams.
[0040] The extract stream 205 containing the contaminants removed
from the rich ionic liquid stream 190 can be combined with the
vacuum residue fraction 170 from the vacuum tower 145 and sent for
further processing or kept separate from the vacuum residue
fraction.
[0041] The treated slop effluent 185 can be combined with the LVGO
fraction 155, the HVGO fraction 160, or a combined LVGO/HVGO stream
155/160 and sent to the downstream processing unit 208, such as the
hydrocracking unit or an FCC unit.
[0042] The process can include an optional ionic liquid drying step
(not shown). The ionic liquid drying step may be employed to reduce
the water content of one or more of the streams comprising ionic
liquid to control the water content of the contaminant removal step
as described above. A portion or all of regenerated ionic liquid
stream 210 can be introduced to a drying zone. Other streams
comprising ionic liquid may also be dried in the drying zone. To
dry the ionic liquid stream or streams, water may be removed by one
or more various well known methods including distillation, flash
distillation, and using a dry inert gas to strip water. Generally,
the drying temperature may range from about 100.degree. C. to less
than the decomposition temperature of the ionic liquid, usually
less than about 300.degree. C. The pressure may range from about 35
kPa(g) to about 250 kPa(g). The drying step produces a dried ionic
liquid stream and a drying zone water effluent stream. Although not
illustrated, a portion or all of the dried ionic liquid stream may
be recycled or passed to provide all or a portion of the ionic
liquid introduced to the contaminant removal zone 175. A portion or
all of drying zone water effluent stream may be recycled or passed
to provide all or a portion of the water introduced into the
optional washing zone and/or ionic liquid regeneration zone
200.
[0043] FIG. 2A illustrates an embodiment the contaminant removal
zone 175. It comprises a multi-stage, counter-current extraction
column 210 in which the slop fraction 165 and the lean ionic liquid
180 are contacted and separated. The slop fraction 165 enters
extraction column 210 through feed inlet 215 and lean ionic liquid
stream 180 enters extraction column 210 through ionic liquid inlet
220. In the FIGURES, reference numerals of the streams and the
lines or conduits in which they flow are the same. The slop
fraction inlet 215 is located below ionic liquid inlet 220. The
treated slop effluent 185 passes through outlet 225 in an upper
portion of extraction column 210. The rich ionic liquid 190
including the contaminants removed from the hydrocarbon feed passes
through ionic liquid outlet 230 in a lower portion of extraction
column 210.
[0044] FIG. 2B illustrates another embodiment of contaminant
removal zone 175 that comprises a contacting zone 235 and a
separation zone 240. In this embodiment, lean ionic liquid stream
180 and slop fraction 165 are introduced into the contacting zone
235 and mixed by introducing slop fraction 165 into the flowing
lean ionic liquid stream 180 and passing the combined streams
through static in-line mixer 245. Static in-line mixers are well
known in the art and may include a conduit with fixed internals
such as baffles, fins, and channels that mix the fluid as it flows
through the conduit. In other embodiments, not illustrated, lean
ionic liquid stream 180 may be introduced into slop fraction 165,
or the lean ionic liquid stream 180 and slop fraction 165 may be
combined such as through a "Y" conduit. In another embodiment, lean
ionic liquid stream 180 and slop fraction 165 are separately
introduced into the static in-line mixer 245. In other embodiments,
the streams may be mixed by any method well known in the art,
including stirred tank and blending operations. The mixture
comprising hydrocarbon and ionic liquid is transferred to
separation zone 240 via transfer conduit 250. Separation zone 240
comprises separation vessel 225 wherein the two phases are allowed
to separate into a rich ionic liquid phase and a hydrocarbon phase.
The rich ionic liquid stream 190 is withdrawn from a lower portion
of separation vessel 225 and the treated slop effluent 185 is
withdrawn from an upper portion of separation vessel 225.
Separation vessel 225 may comprise a boot, not illustrated, from
which rich ionic liquid is withdrawn.
[0045] Separation vessel 225 may contain a solid media 260 and/or
other coalescing devices which facilitate the phase separation. In
other embodiments, the separation zone 240 may comprise multiple
vessels which may be arranged in series, parallel, or a combination
thereof. The separation vessels may be of any shape and
configuration to facilitate the separation, collection, and removal
of the two phases. In a further embodiment, contaminant removal
zone 175 may include a single vessel wherein lean ionic liquid
stream 180 and slop fraction 165 are mixed, then remain in the
vessel to settle into the hydrocarbon and rich ionic liquid
phases.
[0046] In an embodiment, the process comprises at least two
contaminant removal steps. For example, the hydrocarbon effluent
from one contaminant removal step may be passed directly as the
hydrocarbon feed to a second contaminant removal step. In another
embodiment, the hydrocarbon effluent from one contaminant removal
step may be treated or processed before being introduced as the
hydrocarbon feed to the second contaminant removal step. There is
no requirement that each contaminant removal zone comprises the
same type of equipment. Different equipment and conditions may be
used in different contaminant removal zones.
[0047] The contaminant removal step may be conducted under
contaminant removal conditions including temperatures and pressures
sufficient to keep the hydrocarbon-immiscible ionic liquid and
hydrocarbon feeds and effluents as liquids. For example, the
contaminant removal step temperature may range between about
10.degree. C. and less than the decomposition temperature of the
ionic liquid, and the pressure may range between about atmospheric
pressure and about 700 kPa(g). When the hydrocarbon-immiscible
ionic liquid comprises more than one ionic liquid component, the
decomposition temperature of the ionic liquid is the lowest
temperature at which any of the ionic liquid components decompose.
The contaminant removal step may be conducted at a uniform
temperature and pressure or the contacting and separating steps of
the contaminant removal step may be operated at different
temperatures and/or pressures. In an embodiment, the contacting
step is conducted at a first temperature, and the separating step
is conducted at a temperature at least 5.degree. C. lower than the
first temperature. In a non limiting example, the first temperature
is about 80.degree. C. Such temperature differences may facilitate
separation of the hydrocarbon and ionic liquid phases.
[0048] The above and other contaminant removal step conditions such
as the contacting or mixing time, the separation or settling time,
and the ratio of hydrocarbon feed to hydrocarbon-immiscible ionic
liquid (lean ionic liquid) may vary greatly based, for example, on
the specific ionic liquid or liquids employed, the nature of the
hydrocarbon feed (straight run or previously processed), the
contaminant content of the hydrocarbon feed, the degree of
contaminant removal required, the number of contaminant removal
steps employed, and the specific equipment used. In general, it is
expected that contacting time may range from less than one minute
to about two hours; settling time may range from about one minute
to about eight hours. The weight ratio of hydrocarbon feed to lean
ionic liquid introduced to the contaminant removal step may range
from about 1:10,000 to about 10,000:1, or about 1:1,000 to about
1,000:1, or about 1:100 to about 100:1, or about 1:20 to about
20:1, or about 1:10 to about 10:1. In an embodiment, the weight of
hydrocarbon feed is greater than the weight of ionic liquid
introduced to the contaminant removal step.
[0049] In an embodiment, a single contaminant removal step reduces
the contaminant content of the hydrocarbon by more than about 10 wt
%, or more than about 20 wt %, or more than about 30 wt %, or more
than about 40 wt %, or more than about 50 wt %, or more than about
60 wt %, or more than about 70 wt %, or more than about 75 wt %, or
more than about 80 wt %, or more than about 85 wt %, or more than
about 90 wt %. As discussed herein, the invention encompasses
multiple contaminant removal steps to provide the desired amount of
contaminant removal.
[0050] The degree of phase separation between the hydrocarbon and
ionic liquid phases is another factor to consider as it affects
recovery of the ionic liquid and hydrocarbon. The degree of
contaminant removed and the recovery of the hydrocarbon and ionic
liquid may be affected differently by the nature of the hydrocarbon
feed, the variations in the specific ionic liquid or liquids, the
equipment, and the contaminant removal conditions such as those
discussed above.
[0051] The amount of water present in the
hydrocarbon/hydrocarbon-immiscible ionic liquid mixture during the
contaminant removal step may also affect the amount of contaminant
removed and/or the degree of phase separation, i.e., recovery of
the hydrocarbon and ionic liquid. In an embodiment, the
hydrocarbon/hydrocarbon-immiscible ionic liquid mixture has a water
content of less than about 10% relative to the weight of the ionic
liquid, or less than about 5% relative to the weight of the ionic
liquid, or less than about 2% relative to the weight of the ionic
liquid. In a further embodiment, the
hydrocarbon/hydrocarbon-immiscible ionic liquid mixture is water
free, i.e., the mixture does not contain water.
[0052] Unless otherwise stated, the exact connection point of
various inlet and effluent streams within the zones is not
essential to the invention. For example, it is well known in the
art that a stream to a distillation zone may be sent directly to
the column, or the stream may first be sent to other equipment
within the zone such as heat exchangers, to adjust temperature,
and/or pumps to adjust the pressure. Likewise, streams entering and
leaving contaminant removal, washing, and regeneration zones may
pass through ancillary equipment such as heat exchanges within the
zones. Streams, including recycle streams, introduced to washing or
extraction zones may be introduced individually or combined prior
to or within such zones.
[0053] The invention encompasses a variety of flow scheme
embodiments including optional destinations of streams, splitting
streams to send the same composition, i.e. aliquot portions, to
more than one destination, and recycling various streams within the
process. Examples include: various streams comprising ionic liquid
and water may be dried and/or passed to other zones to provide all
or a portion of the water and/or ionic liquid required by the
destination zone. The various process steps may be operated
continuously and/or intermittently as needed for a given embodiment
e.g. based on the quantities and properties of the streams to be
processed in such steps. As discussed above the invention
encompasses multiple contaminant removal steps, which may be
performed in parallel, sequentially, or a combination thereof.
Multiple contaminant removal steps may be performed within the same
contaminant removal zone and/or multiple contaminant removal zones
may be employed with or without intervening washing, regeneration
and/or drying zones.
[0054] By the term "about," we mean within 10% of the value, or
within 5%, or within 1%.
EXAMPLES
[0055] The examples are presented to further illustrate some
aspects and benefits of the invention and are not to be considered
as limiting the scope of the invention.
[0056] A simulation was run for Arab Heavy crude being processed
though a crude and vacuum distillation unit as illustrated in FIG.
1 with conventional product being drawn from it. The simulation
showed that by choosing the slop fraction and VGO endpoint
appropriately, the contaminants in the VGO fraction can be limited
to acceptable levels. The slop fraction, which has more
contaminants, can be treated with the ionic liquid. The treated
slop fraction can then be blended with the VGO stream to maximize
the throughput to the hydroprocessing and/or FCC unit, thus
maximizing the desired products.
[0057] Table 1 gives the true boiling point (TBP) and some
properties for Arab Heavy crude.
TABLE-US-00001 TABLE 1 TBPCRV C IBP -8.65741 5% 42.40527 10%
96.69801 30% 228.18 50% 362.0511 70% 504.1968 90% 695.1002 100%
854.1088 spgr 0.874 S wpct 2.715 N wppm 1407 Ni wppm 1234 Va wppm
3970 CCR wppm 68624
[0058] The initial boiling point for VGO is 315.degree. C. (TBP),
and the final boiling point for VGO is 520.degree. C. (TBP). The
initial boiling point for the slop fraction is 388.degree. C. (true
boiling point (TBP)), and the final boiling point for the slop
fraction is 570.degree. C. (TBP). This data is for one set of
operating conditions. The final boiling points can be changed based
on how the refiner wants to charge the downstream unit, e.g., the
hydrocracking unit.
Example 1
[0059] Tetrabutyl phosphonium methansulfonate, which is mainly
selective for removal of metals and nitrogen, was used for this
simulation. Table 2 shows the results for this simulation.
TABLE-US-00002 TABLE 2 Removal (%) across Treated Blend ionic Slops
(ex (VGO + liquid Ionic liq Treated VGO SLOPS treatment treatment)
Slops) Flow lb/hr 140370 6614 6614 146984 S wpct 2.94 3.504 5.2
3.322 2.957 N wppm 581.4 1024 71.4 292.864 568.416 Ni wppm 0.59
24.09 86 3.373 0.715 Va wppm 1.83 76.2 68.4 24.079 2.831
Example 2
[0060] In this example, a mixture of tetrabutyl phosphonium
methansulfonate, trihexyl(tetradecyl)phosphonium chloride, and
1-butyl-3-methylimidazolium trifluoromethansulfonate was used for
the simulation. Table 3 shows the results of this simulation.
TABLE-US-00003 TABLE 3 Removal (%) across Treated Blend ionic Slops
(ex (VGO + liquid Ionic liq Treated VGO SLOPS treatment treatment)
Slops) Flow lb/hr 140370 6614 6614 146984 S wpct 2.94 3.504 64.5
1.244 2.864 N wppm 581.4 1024 84.7 156.672 562.288 Ni wppm 0.59
24.09 86 3.373 0.715 Va wppm 1.83 76.2 68.4 24.079 2.831
[0061] While at least one exemplary embodiment has been presented
in the foregoing detailed description of the invention, it should
be appreciated that a vast number of variations exist. It should
also be appreciated that the exemplary embodiment or exemplary
embodiments are only examples, and are not intended to limit the
scope, applicability, or configuration of the invention in any way.
Rather, the foregoing detailed description will provide those
skilled in the art with a convenient road map for implementing an
exemplary embodiment of the invention. It being understood that
various changes may be made in the function and arrangement of
elements described in an exemplary embodiment without departing
from the scope of the invention as set forth in the appended
claims.
* * * * *