U.S. patent application number 13/444148 was filed with the patent office on 2012-10-18 for integrated hydrotreating hydrodewaxing hydrofinishing process.
This patent application is currently assigned to EXXONMOBIL RESEARCH AND ENGINEERING COMPANY. Invention is credited to Michael Brian Carroll, Eric D. Joseck, David Mentzer.
Application Number | 20120261307 13/444148 |
Document ID | / |
Family ID | 47005620 |
Filed Date | 2012-10-18 |
United States Patent
Application |
20120261307 |
Kind Code |
A1 |
Joseck; Eric D. ; et
al. |
October 18, 2012 |
INTEGRATED HYDROTREATING HYDRODEWAXING HYDROFINISHING PROCESS
Abstract
Provided is a three stage hydroprocessing process for producing
lubricant base stocks with a stripping/separating zone between the
first two hydroprocessing zones and a separating zone following the
third hydroprocessing zone. The stripping/separating zone occurs at
high pressure and temperature with no disengagement between or
following the hydroprocessing zones and without the use of a liquid
pump prior to the second hydroprocessing zone. The process pressure
is greatest at the entrance to the first hydroprocessing zone.
There is also recycle of compressed gaseous effluent from the last
separating zone to the stripping zone, the first hydroprocessing
zone, the second hydroprocessing zone, and/or the third
hydroprocessing zone.
Inventors: |
Joseck; Eric D.; (Burke,
VA) ; Carroll; Michael Brian; (Mantua, NJ) ;
Mentzer; David; (Marshall, VA) |
Assignee: |
EXXONMOBIL RESEARCH AND ENGINEERING
COMPANY
Annandale
NJ
|
Family ID: |
47005620 |
Appl. No.: |
13/444148 |
Filed: |
April 11, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61474897 |
Apr 13, 2011 |
|
|
|
Current U.S.
Class: |
208/58 ; 208/212;
208/89; 208/97 |
Current CPC
Class: |
C10G 65/043 20130101;
C10G 2300/1077 20130101; C10G 2400/10 20130101; C10G 2300/1059
20130101; C10G 65/10 20130101; C10G 2300/4081 20130101; C10G
2300/1022 20130101; C10G 65/12 20130101; C10G 2300/107 20130101;
C10G 2300/4093 20130101; C10G 2300/207 20130101 |
Class at
Publication: |
208/58 ; 208/97;
208/212; 208/89 |
International
Class: |
C10G 65/12 20060101
C10G065/12 |
Claims
1. A continuous process for producing lube base stocks comprising:
a. passing a hydrocarbon feedstock to a first hydroprocessing zone
and hydroprocessing the feedstock under first hydroprocessing
conditions to form a first hydroprocessed product, said first
hydroprocessing zone having a first hydroprocessing catalyst
system, temperature and pressure; b. passing the first
hydroprocessed product to a stripping/separating zone; c.
stripping/separating of the first hydroprocessed product of
dissolved H.sub.2S and NH.sub.3 to form a liquid effluent and a
sour gas, and subsequently scrubbing the sour gas to remove
H.sub.2S and NH.sub.3 to form a first gaseous effluent; d. passing
the liquid effluent from the stripping/separating zone and at least
a portion of the first gaseous effluent to a second hydroprocessing
zone and hydroprocessing the liquid effluent under second
hydroprocessing conditions to form a second hydroprocessed product,
said second hydroprocessing zone having a second hydroprocessing
catalyst system, temperature and pressure; e. passing the second
hydroprocessed product to a third hydroprocessing zone and
hydroprocessing the liquid effluent under third hydroprocessing
conditions to form a third hydroprocessed product, said third
hydroprocessing zone having a third hydroprocessing catalyst
system, temperature and pressure; f. passing the third
hydroprocessed product to a separating zone and separating the
third hydroprocessed product into a second gaseous effluent and
liquid products, including one or more lube base stocks; g.
compressing the second gaseous effluent and recycling at least a
portion of the compressed second gaseous effluent back to one or
more of the first hydroprocessing zone, the stripping/separating
zone, the second hydroprocessing zone, or the third hydroprocessing
zone, wherein the process pressure is highest at the entrance to
the first hydroprocessing zone, and with the proviso that no
liquids pump exists between stripping/separating zone and the
second hydroprocessing zone.
2. The continuous process of claim 1, wherein the hydrocarbon feed
is chosen from atmospheric gas oils, vacuum gas oils, coker gas
oils, hydrocrackates, raffinates, extracts, hydrotreated oils,
atmospheric and vacuum resids, deasphalted oils, dewaxed oils,
slack waxes, petrolatum, Fischer-Tropsch waxes and mixtures
thereof.
3. The continuous process of claim 1, wherein the first
hydroprocessing zone is a hydrocracker or a hydrotreater.
4. The continuous process of claim 1, further including at least
one heat exchanger between the first hydroprocessing zone and the
stripping/separating zone.
5. The continuous process of claim 1, wherein the
stripping/separating zone includes a pressure stripper and a flash
separator.
6. The continuous process of claim 1, wherein the
stripping/separating zone includes a pressure stripper followed by
an amine scrubber followed by a water wash tower.
7. The continuous process of claim 6, wherein the amine scrubber
uses an amine solution to remove hydrogen sulfide from the sour
gas.
8. The continuous process of claim 6, wherein the water wash tower
uses water to remove ammonia from the sour gas.
9. The continuous process of claim 5 or 6, wherein the pressure
stripper uses at least a portion of the compressed second gaseous
effluent for stripping.
10. The continuous process of claim 1, further including at least
one heat exchanger between the stripping/separating zone and the
second hydroprocessing zone.
11. The continuous process of claim 1, wherein the second
hydroprocessing zone is a hydrodewaxer or a hydrocracker.
12. The continuous process of claim 11, wherein the second
hydroprocessing zone uses at least a portion of the compressed
second gaseous effluent.
13. The continuous process of claim 1, wherein the third
hydroprocessing zone is a hydrofinisher or a hydrodewaxer.
14. The continuous process of claim 13, wherein the hydrofinisher
uses at least a portion of the compressed second gaseous
effluent.
15. The continuous process of claim 1, further including at least
one heat exchanger between the second hydroprocessing zone and the
third hydroprocessing zone.
16. The continuous process of claim 1, further including at least
one heat exchanger between the third hydroprocessing zone and the
separating zone.
17. The continuous process of claim 1, wherein the separating zone
includes a flash separator.
18. The continuous process of claim 1, further including purging at
least a portion of the second gaseous effluent from the
process.
19. The continuous process of claim 1, wherein the tube base stock
is chosen from Group I, Group II and Group III.
20. The continuous process of claim 1, wherein the first
hydroprocessing zone catalyst system is chosen from Ni/Mo, Co/Mo,
Ni/W and combinations thereof.
21. The continuous process of claim 1, wherein the second
hydroprocessing zone catalyst system includes a molecular sieve
chosen from ZSM-5, ZSM-22, ZSM-23, ZSM-35, ZSM-48, SAPO-11, SAPO-41
and combinations thereof.
22. The continuous process of claim 1, wherein the third
hydroprocessing zone catalyst system is chosen from Ni/Mo, Ni/W or
Pd and/or Pt, MCM-41, MCM-48, MCM-50 and combinations thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a non-provisional application that claims priority
to U.S. Provisional Patent Application No. 61/474,897 filed on Apr.
13, 2011, herein incorporated by reference in its entirety.
FIELD
[0002] This disclosure relates to an integrated hydrotreating
hydrodewaxing hydrofinishing process. More particularly, the
hydrotreater operates at a higher pressure than the hydrodewaxer
with interstage stripping/separating occurring between the two and
without the use of a pump between the stripper/separator and the
hydrodewaxer.
BACKGROUND
[0003] It has long been recognized that one of the most valuable
products generated through the refining of crude mineral oils is
lubricating oils. It is common practice to recover lubricating oil
basestocks by solvent extracting, with a selective solvent,
undesirable components such as aromatics, sulfur compounds, and
nitrogen compounds from straight vacuum distillates, and then
solvent dewaxing to improve low temperature properties. However,
with the decline in the availability of paraffinic base crudes, and
a corresponding increase in the proportion of naphthenic and
asphaltic base crudes, it is becoming increasingly difficult to
meet the demand for lubricating oil base stocks, or base oils.
Catalytic hydroprocessing has been used to supplement or replace
these conventional solvent-based processes and to enable use of
poorer quality feedstocks and/or produce better quality lube
basestocks.
[0004] One method of classifying lubricating oil basestocks is that
used by the American Petroleum institute (API). API Group I
basestocks are the lowest quality classification. API Group II
basestocks are differentiated from Group I basestocks by having a
saturates content of 90 wt % or greater, a sulfur content of not
more than 0.03 wt %, and a VI greater than 80 but less than 120.
API Group III basestocks are the same as Group II basestocks except
that the VI is at least 120. Solvent processing alone, or in
combination with mild hydrotreating, is commonly used for
production of Group I basestocks. Catalytic hydroprocessing is
generally required for production of Group II and Group III
basestocks from an appropriate feed.
[0005] Techniques for preparing Group II and Group iii basestocks
such as hydrocracking or solvent extraction require severe
operating conditions such as high hydrocracking pressure and
temperature or high extraction temperature and solvent:oil ratio to
reach these higher basestock qualities.
[0006] Unfortunately, hydroprocessing for producing a lube
basestock is hindered due to differing sensitivities for the
catalysts involved in the various stages. This limits the selection
of feeds which are potentially suitable for use in forming Group II
or higher basestocks. The catalysts used for the initial
hydroprocessing of the oil fraction often have a relatively high
tolerance for contaminants such as sulfur or nitrogen. By contrast,
catalysts for catalytic dewaxing usually suffer from a low
tolerance for contaminants. In particular, dewaxing catalysts that
are intended to operate primarily by isomerization, which usually
contain noble metals, are typically quite sensitive to the amount
of sulfur and/or nitrogen present in a feed. If contaminants are
present, the activity and selectivity of these dewaxing catalysts
will be reduced, and the activity and selectivity may not recover
after removal of the contaminants.
[0007] To accommodate the differing tolerances of the catalysts
involved in lube basestock production, the following features are
typically incorporated into the basestock production process.
First, an initial hydroprocessing step (such as distillate
hydrocracking or raffinate hydroconversion) is run under
sufficiently severe conditions to convert most of the organic
sulfur and nitrogen in the feed into H.sub.2S and NH.sub.3. Second,
a separation step is used between the hydroprocessing step and the
dewaxing step which removes substantially all of these gaseous
contaminants prior to the dewaxing step. The separation step
requires extra equipment to be used during the tube production,
which increases the overall cost of the process.
[0008] A common method to remove contaminants such as NH.sub.3 and
H.sub.2S from a hydroprocessing unit effluent is stripping--with a
clean gas stream--to separate the gaseous effluent from the
liquids. The stripping is typically conducted at low temperature
and pressure. The hydrotreating step is frequently followed by a
further hydroprocessing step, such as hydrodewaxing, containing a
catalyst which is sensitive to the presence of sulfur and nitrogen
contaminants. Stripping steps involve considerable investment and
operating costs as stripping usually involves depressurization and
cooling followed by pumping and heating to repressurize and reheat
the feed to the next hydroprocessing step.
[0009] U.S. Pat. No. 6,635,170 discloses a two stage
hydroprocessing process with stripping zones between the
hydroprocessing zones and following the last hydroprocessing zone.
The stripping occurs at high pressure and temperature with no
disengagement (significant lowering of pressure) between or
following the hydroprocessing zones. There is also recycle of high
temperature gaseous effluent from the last stripping zone to the
first stripping zone. The second stage hydroprocessing process
occurs at a higher pressure than the first stage hydroprocessing
process as evidenced by the inclusion of a pump between the first
stripper and the second stage hydroprocessing process. The pump
adds additional capital investment cost and operating costs to the
process.
[0010] It would be desirable to have an in integrated
hydroprocessing hydrodewaxing hydrofinishing process with an
improved interstage stripping/separating process between the
hydroprocessor and the hydrodewaxer in order to minimize the
capital investment and operating costs.
SUMMARY
[0011] The present disclosure relates to a continuous process for
producing lube base stocks including: [0012] a. passing a
hydrocarbon feedstock to a first hydroprocessing zone and
hydroprocessing the feedstock under first hydroprocessing
conditions to form a first hydroprocessed product, said first
hydroprocessing zone having a first hydroprocessing catalyst
system, temperature and pressure; [0013] b. passing the first
hydroprocessed product to a stripping/separating zone; [0014] c.
stripping/separating of the first hydroprocessed product of
dissolved H.sub.2S and NH.sub.3 to form a liquid effluent and a
sour gas, and subsequently scrubbing the sour gas to remove
H.sub.2S and NH.sub.3 to form a first gaseous effluent; [0015] d.
passing the liquid effluent from the stripping/separating zone and
at least a portion of the first gaseous effluent to a second
hydroprocessing zone and hydroprocessing the liquid effluent under
second hydroprocessing conditions to form a second hydroprocessed
product, said second hydroprocessing zone having a second
hydroprocessing catalyst system, temperature and pressure; [0016]
e. passing the second hydroprocessed product to a third
hydroprocessing zone and hydroprocessing the liquid effluent under
third hydroprocessing conditions to form a third hydroprocessed
product, said third hydroprocessing zone having a third
hydroprocessing catalyst system, temperature and pressure; [0017]
f. passing the third hydroprocessed product to a separating zone
and separating the third hydroprocessed product into a second
gaseous effluent and liquid products, including one or more tube
base stocks; [0018] g. compressing the second gaseous effluent and
recycling at least a portion of the compressed second gaseous
effluent back to one or more of the first hydroprocessing zone, the
stripping/separating zone, the second hydroprocessing zone, or the
third hydroprocessing zone, [0019] wherein the process pressure is
greatest at the entrance to the first hydroprocessing zone, and
with the proviso that no liquids pump exists between
stripping/separating zone and the second hydroprocessing zone.
[0020] The present disclosure describes an improved method for
removing nitrogen- and sulfur-containing contaminants from
multi-zone hydroprocessing schemes without the need for
disengagement, i.e., low-pressure stripping which involves
depressurization, stripping and re-pressurization, and the
attendant costs for such an operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a schematic illustrating one exemplary embodiment
of the integrated hydrotreating hydrodewaxing hydrofinishing
process disclosed herein.
DETAILED DESCRIPTION
[0022] All numerical values within the detailed description and the
claims herein are modified by "about" or "approximately" the
indicated value, and take into account experimental error and
variations that would be expected by a person having ordinary skill
in the art.
[0023] Hydrocarbon feeds for the integrated hydrotreating
hydrodewaxing hydrofinishing process disclosed herein include whole
and reduced crudes and fractions thereof. Non-limiting examples
include distillates such as atmospheric and vacuum gas oils, and
coker gas oils, hydrocrackates, raffinates, extracts, hydrotreated
oils, atmospheric and vacuum resids, deasphalted oils, dewaxed
oils, slack waxes, petrolatum, Fischer-Tropsch waxes and mixtures
thereof.
[0024] Hydroprocessing is used herein to denote various processes
involving treatment of a feed in the presence of hydrogen and
include processes which involve at least one of boiling range
reduction, removal of contaminants, viscosity reduction, viscosity
index (VI) increase, pour point reduction and aromatics saturation.
Examples of typical hydroprocessing schemes include hydrotreating,
hydrocracking, hydrofinishing (a.k.a, hydrofining), hydrodewaxing,
hydroisomerization, and raffinate hydroconversion. Such
hydroprocessing schemes are well known in the art and are described
in standard reference works such as "Petroleum Refining" by James
H. Gary and Glenn E. Handwerk, Third Edition, Marcel Dekker, New
York.
[0025] Hydrocracking involves at least some conversion of the
boiling range of the feed to lower boiling products. Hydrocracking
catalysts are generally more acidic than hydrotreating catalysts
and include Group VIA and Group VIII metals on supports such as
alumina, especially fluorided alumina, silica-alumina and zeolites.
Examples include Group VIA and Group VIII metal, e.g., Ni/Mo on
silica-alumina, Group VIA and Group VIII metal on zeolite, e.g.,
Ni/Mo on zeolites such as X or Y, Pd on zeolite and Ni/W on
zeolite. Hydrocracking conditions include temperatures of
260-480.degree. C., pressures of 800-3000 psig, LHSV of 0.1-10
h.sup.-1 and treat gas rates of 1000-10000 scf/bbl.
[0026] Hydrotreating is typically used to reduce the sulfur,
nitrogen, and aromatic content of a feed, and is not primarily
concerned with boiling point conversion of the feed. Catalysts
usually contain at least one of Group VIA and Group VIII metal on a
less acidic support such as alumina or silica. Examples include
Ni/Mo, Co/Mo and Ni/W catalysts. Hydrotreating conditions typically
include temperatures of 315-425.degree. C., pressures of 300-3000
psig, Liquid Hourly Space Velocities (LHSV) of 0.2-10 h.sup.-1 and
hydrogen treat rates of 500-10000 scf/bbl.
[0027] Hydrodewaxing is used for the removal of straight-chain,
paraffinic molecules from feeds. Hydrodewaxing can be accomplished
by selective hydrocracking or by hydroisomerizing these
straight-chain molecules. Hydrodewaxing catalysts are suitably
molecular sieves such as crystalline aluminosilicates (zeolites) or
silico-aluminophosphates (SAPOs), preferably 10-ring sieves such as
ZSM-5, ZSM-22, ZSM-23, ZSM-35, ZSM-48, SAPO-11, SAPO-41 and the
like. These catalysts may also carry a metal hydrogenation
component, preferably Group VIII metals, especially Group VIII
noble metals. Hydrodewaxing conditions include temperatures of
275-425.degree. C., pressures of 300-3000 psig, LHSV of 0.1-5.0
h.sup.-1 and treat gas rates of from 500-5000 scf/bbl.
[0028] Hydrofinishing is usually concerned with product quality
issues such as daylight stability, color, haze, heteroatom removal,
aromatics and olefin saturation and the like. Catalysts can be
those used in hydrotreating including, e.g., Ni/Mo, Ni/W or Pd
and/or Pt on a support such as alumina. Group VIII and/or Group VI
metals supported on a bound support from the M41S family, such as
bound MCM-41 are particularly advantageous. The M41S family of
catalysts are mesoporous materials having high silica contents
whose preparation is further described in J. Amer. Chem. Soc.,
1992, 114, 10834. Examples include MCM-41, MCM-48 and MCM-50.
Hydrofinishing conditions include temperatures of 200-350.degree.
C., pressures of 200-3000 psig, LHSV of 0.1-5 h.sup.-1 and treat
gas rates of 100-5000 scf/bbl.
[0029] Hydroprocessing involves at least one reactor having an
inlet temperature and pressure and an outlet temperature and
pressure, and commonly occurs in multiple zones (or stages)
involving sequences such as hydrotreating/hydrocracking,
hydrotreating/hydrodewaxing, hydrotreating/hydroisomerization,
hydrocracking/hydrodewaxing, hydrocracking/hydrofinishing,
hydrodewaxing/hydrofinishing,
hydrotreating/hydrodewaxing/hydrofinishing and the like. Typical
hydroprocessing configurations include hydrotreating followed by
hydrocracking, hydrotreating or hydrocracking followed by
hydrofinishing or hydrodewaxing, hydrotreating followed by
hydrodewaxing followed by hydrofinishing, and 2-stage hydrocracking
or hydrotreating in which at least two reactors are sequentially
staged. One particularly advantageous 3-stage combination of
hydroprocessing configurations includes hydrotreating followed by
hydrodewaxing followed by hydrofinishing. This particular
configuration is particularly advantageous for producing lube base
stocks.
[0030] The above hydroprocessing schemes typically involve a
disengagement step between hydroprocessing steps, which involves
depressurization to remove contaminants, and product and/or
intermediates separation. The individual hydroprocessing zones may
use a single reactor or may use multiple reactors. A common
practice in the art is to disengage with a significant lowering of
the pressure, i.e., depressurize between hydroprocessing steps.
That is, disengagement refers to a substantial lowering of the
pressure between subsequent downstream and upstream hydroprocessing
steps. More specifically, there is at least a 100 psi, or at least
a 200 psi, or at least a 400 psi decrease in pressure between the
outlet pressure of one hydroprocessing step and the inlet pressure
of a subsequent downstream hydroprocessing step. No disengagement
refers to no significant lowering of the pressure between
subsequent downstream and upstream hydroprocessing steps, that is
less than a 100 psi pressure decrease between hydroprocessing
steps. The reason for such disengagement is to strip the effluent
from the first hydroprocessing step (or zone), such as a
hydrotreater, before passing the effluent to a second
hydroprocessing step, such as a hydrodewaxer. An interstage
stripping zone is employed to remove gaseous contaminants created
in the first hydroprocessing step such as H.sub.2S and NH.sub.3 and
may also be used to strip light (low boiling) products from the
effluent. Such gaseous contaminants may adversely impact the
performance of catalysts in the second hydroprocessing step or
zone, such as a hydrodewaxer. However, before passing the stripped
effluent to the second hydroprocessing step, it is usually
necessary to repressurize and reheat the effluent. A pump is
typically used to repressurize the liquid effluent from the
stripping zone.
[0031] The present process involves a first separation zone
following the first hydroprocessing zone, a second hydroprocessing
zone and a second separation zone. Unlike the common practice in
the art, in the present disclosure, the first and second separation
zones are conducted at nearly the same pressure of the preceding
hydroprocessing zone. That is, there is little to no pressure drop
(less than 100 psi) between subsequent hydroprocessing zones. There
is no disengagement, i.e., depressurization between first and
second hydroprocessing zones or following the third hydroprocessing
zone and the second separation zone. That is, there is less than a
100 psi decrease in pressure between the first and second
hydroprocessing zones or following the third hydroprocessing zone
and the second separation zone in the present disclosure. Further,
gases stripped from the second separation zone may be recycled to
the first separation zone or recycled to the first hydroprocessing
zone or recycled to the second or third hydroprocessing zones. The
different hydroprocessing zones are typically operated at different
temperatures. Thus it is preferred to include at least one heat
exchanger (or heater) between hydroprocessing zones or between
hydroprocessing zones and separation zones.
[0032] High pressure separators are known in the art. They may
include flash drums, pressure strippers which include pressure
separators for separating liquids and gases at high temperatures or
combinations thereof. These units are designed to operate at high
temperatures such as the temperature of the preceding
hydroprocessing zone. High pressure strippers generally operate in
countercurrent mode with regard to the stripping gas.
[0033] In one non-limiting exemplary embodiment, the first
hydroprocessing zone results in the generation of contaminants
which might reduce the efficiency of a subsequent hydroprocessing
zone or stage. Examples of such sequences include hydrotreating
followed by hydrodewaxing, hydrotreating followed by hydrocracking,
hydrocracking followed by hydrodewaxing, hydrotreating followed by
hydrofinishing, and raffinate hydroconversion followed by
hydrodewaxing. Typical contaminants generated in the first
hydroprocessing zone include water, ammonia and hydrogen
sulfide.
[0034] The process is further described with reference to a
representative process shown in FIG. 1. Fresh hydrocarbon feed
through line 1 and compressed hydrogen-rich recycle gas through
line 2 are combined through line 3 to the first hydroprocessing
zone 30 which is advantageously a hydrotreater or hydrocracker
operating under minimum conversion to meet both the cleanliness
(hydrodesulfurization/hydrodenitrogenation) requirements of the
hydrodewaxing step 33 and the viscosity index targets of the lube
products portion of stream 13 under hydroprocessing conditions to
produce a hydrotreated/hydrocracked product, hydrogen sulfide,
ammonia, and light hydrocarbon gases.
[0035] The products from the hydrotreater/hydrocracker are passed
through line 4 to heat exchanger 40 through line 5 to a first
separation zone 31 which is a stripper/separator comprising a
single or multiple separation stages. In one form, the
stripper/separator 31 may be a flash separator including a high
pressure separator drum followed by a pressure stripper, in another
advantageous form, the stripper/separator 31 may be a pressure
stripper followed by an amine scrubber followed by a water wash
tower. In this form, liquid product comprising
hydrotreated/hydrocracked product 5 is stripped with hydrogen-rich
recycle gas represented by line 19. Hydrogen, light hydrocarbons,
hydrogen sulfide, and ammonia are separated from the hydrotreated
or hydrocracked liquid product through line 21, pass through heat
exchanger 41, through line 22, and then to a separator 32 to
separate out any condensed liquids 23. The overhead gas 24 goes
through gas processing steps (36 and 37) to produce a clean
hydrogen-rich treat gas 26 for further utilization in the
hydrodewaxing step 33 and/or hydrofinishing step 34. In particular,
an amine scrubber 36 uses a countercurrent flow of amine solution
50 to remove hydrogen sulfide through line 51. In addition, a water
wash tower 37 uses a countercurrent flow of water 52 to remove
ammonia through line 53. The preceding gas processing steps result
in a clean hydrogen-rich treat gas stream 26 that may be used in
the hydrodewaxer 33 and/or hydrofinisher 34.
[0036] The stripped hydrotreated or hydrocracked liquid effluent
stream 6 passes through a heat exchanger 42, through line 7, is
then mixed with clean hydrogen-rich treat gas 26, and then flows
through line 8 to the hydrodewaxing step 33. Unlike prior art
process configurations, a liquid pump is not required to pressurize
the stripped hydrotreated/hydrocracked liquid effluent stream 6
after the stripper/separator 31 and prior to the hydrodewaxer 33
because of the higher pressure at the exit 6 of the
stripper/separator 31 compared to the entrance 8 of the
hydrodewaxer 33. There is also no disengagement or significant
lowering of the pressure (no depressurization) between any of the
hydroprocessing zones (30, 33, 34), or disengagement between the
stripper/separator 31 and the hydrodewaxer 33. For purposes of
pressure balance, the first hydroprocessing zone 30 is operated at
a higher pressure than the second hydroprocessing zone 33. In
addition, the second hydroprocessing zone 33 is operated at a
higher pressure than the third hydroprocessing zone 34.
[0037] The stripped hydrotreated or hydrocracked liquid effluent
stream 6 that enters the hydrodewaxer zone 33 thus contains almost
no hydrogen sulfide or ammonia. This may be advantageous if the
catalyst used in hydrodewaxing zone 33 is sensitive to these
contaminants. The equilibrium is shifted in favor of desorption of
any remaining hydrogen sulfide and ammonia in the liquid product
from the first hydroprocessing zone 30. Not only is greater
catalyst protection afforded for the second hydroprocessing zone
33, but higher reaction rates may also occur. By not depressurizing
between or after hydroprocessing zones, a considerable expense
savings occurs as the need for depressurizing and repressurizing
gaseous streams is also avoided. Moreover, a considerable capital
investment cost and related operating costs are avoided by the
elimination of a liquid pump between the stripper/separator 31 and
the hydrodewaxer 33 for the liquid effluent 6 from the
stripper/separator.
[0038] The hydrodewaxed product 9 is cooled in heat exchanger 43
and flows through line 10 to the hydrofinishing step 34. The
hydrofinished product 11 is heated/cooled in heat exchanger 44 and
flows through line 12 to the second separation step 35 for
separation into liquid product 13 and a hydrogen-rich gas 14. The
liquid is further separated into one or more tube base stocks and
lighter products. The tube base stock products may be an API Group
I, Group II or Group III lube base stock as described above, and
more advantageously a Group II or Group III tube base stock. The
separation step 35 may include a flash separator for separating the
liquid product from the hydrogen-rich gas 14. All or a portion of
the hydrogen-rich gas 14 from the separation step can be recycled
through a recycle gas compressor 60 followed by flow through line
20 to the hydrotreating step 30, stripping/separating section 31,
hydrodewaxing section 33, hydrofinishing section 34. The high
pressure hydrogen-rich gas 20 from recycle gas compressor 60 may be
sent to one or more of the 3-zones of the integrated process
described above and such high pressure hydrogen-rich gas 20 is at a
high pressure than any other point in the process. Distributing to
the integrated process the high pressure hydrogen-rich gas 20
facilitates ease of distribution to anywhere in the process as
required.
[0039] A hydrogen-rich makeup gas stream 17 and purge gas stream 15
serve to maintain hydrogen partial pressure in the system. The
hydrogen-rich makeup gas stream 17 may be at a lower pressure than
the overall system pressure, and correspondingly it is input into
the suction side of the recycle compressor 60. The pressure in the
process disclosed herein is greatest at the hydroprocessing zone 30
and then decreases through the subsequent hydroprocessing zones
(hydrodewaxing step 33 and hydrofinishing step 34). A liquids pump
(not shown) may be used to pressurize the fresh feed line 1 prior
to entering the hydrotreater 30, and hence the highest pressure
though the process depicted in FIG. 1 is at the point entering 3
the first hydroprocessing step 30. Each hydroprocessing reactor 30,
33, and 34 may include one or more quench zones within multiple
beds. These quench zones may be liquid and/or gas quenched. The
fresh liquid hydrocarbon feed 1 or a fraction of the liquid product
13 may be used for the liquid quench medium. Hydrogen gas (recycled
20 or make-up 17) may be used for the gas quench medium. The
relative amounts of flow of gaseous product through the process may
be controlled by valves (not shown).
[0040] The integrated hydroprocessing hydrodewaxing hydrofinishing
process with an interstage stripping/separating process without a
pump between the hydroprocessor and the hydrodewaxer results in one
or more of the following advantages from the elimination of a
liquid pump between the first and second hydroprocessing zones and
by operating without the need for disengagement (significant
lowering of the process pressure) between process steps: decreased
process capital investment cost, decreased need for fresh hydrogen
gas, and decreased process operating costs.
[0041] All patents and patent applications, test procedures such as
ASTM methods, UL methods, and the like), and other documents cited
herein are fully incorporated by reference to the extent such
disclosure is not inconsistent with this disclosure and for all
jurisdictions in which such incorporation is permitted.
[0042] When numerical lower limits and numerical upper limits are
listed herein, ranges from any lower limit to any upper limit are
contemplated. While the illustrative embodiments of the disclosure
have been described with particularity, it will be understood that
various other modifications will be apparent to and can be readily
made by those skilled in the art without departing from the spirit
and scope of the disclosure. Accordingly, it is not intended that
the scope of the claims appended hereto be limited to the examples
and descriptions set forth herein but rather that the claims be
construed as encompassing all the features of patentable novelty
which reside in the present disclosure, including all features
which would be treated as equivalents thereof by those skilled in
the art to which the disclosure pertains. The disclosure has been
described above with reference to numerous embodiments and specific
examples. Many variations will suggest themselves to those skilled
in this art in light of the above detailed description. All such
obvious variations are within the full intended scope of the
appended claims.
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