U.S. patent application number 14/537284 was filed with the patent office on 2015-03-05 for method for multi-staged hydroprocessing using quench.
The applicant listed for this patent is UOP LLC. Invention is credited to Nicholas W. Bridge, Robert L. Bunting, RIchard K. Hoehn, Paul A. Sechrist.
Application Number | 20150060331 14/537284 |
Document ID | / |
Family ID | 52581649 |
Filed Date | 2015-03-05 |
United States Patent
Application |
20150060331 |
Kind Code |
A1 |
Sechrist; Paul A. ; et
al. |
March 5, 2015 |
METHOD FOR MULTI-STAGED HYDROPROCESSING USING QUENCH
Abstract
Methods for processing a hydrocarbonaceous feedstock flows are
provided. In one embodiment, the method includes providing two or
more hydroprocessing stages disposed in sequence, each
hydroprocessing stage having a hydroprocessing reaction zone with a
hydrogen requirement and each stage in fluid communication with the
preceding stage. The hydrocarbonaceous feedstock flow may be
separated into portions of fresh feed for each hydroprocessing
stage, and the first portion of fresh feed to the first
hydroprocessing stage is heated. The heated first portion of fresh
feed may be supplied with hydrogen from the hydrogen source in an
amount satisfying substantially all of the hydrogen requirements of
the hydroprocessing stages to a first hydroprocessing zone. The
unheated second portion of fresh feed is injected counter current
to the process flow as quench at one or more locations in one or
more of the reaction zones.
Inventors: |
Sechrist; Paul A.; (South
Barrington, IL) ; Bunting; Robert L.; (Chicago,
IL) ; Bridge; Nicholas W.; (Lakewood, IL) ;
Hoehn; RIchard K.; (Mount Prospect, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UOP LLC |
Des Plaines |
IL |
US |
|
|
Family ID: |
52581649 |
Appl. No.: |
14/537284 |
Filed: |
November 10, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13441144 |
Apr 6, 2012 |
8900443 |
|
|
14537284 |
|
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|
Current U.S.
Class: |
208/59 ; 208/210;
208/264; 208/89; 208/97 |
Current CPC
Class: |
C10G 65/12 20130101;
C10G 65/10 20130101; C10G 65/02 20130101; C10G 2300/4006 20130101;
C10G 65/04 20130101 |
Class at
Publication: |
208/59 ; 208/89;
208/97; 208/210; 208/264 |
International
Class: |
C10G 65/12 20060101
C10G065/12; C10G 65/10 20060101 C10G065/10; C10G 65/04 20060101
C10G065/04 |
Claims
1. A method of processing a hydrocarbonaceous feedstock comprising:
hydroprocessing a feed in two or more hydroprocessing stages
disposed in sequence and in fluid communication, each
hydroprocessing stage having a hydroprocessing reaction zone with
and each stage disposed to receive a process flow comprising at
least a liquid and to produce a hydroprocessed effluent; and
controlling the temperature of the hydroprocessing stages using
mixed vapor and liquid quench streams wherein a mixed vapor phase
and liquid phase quench stream is injected into each
hydroprocessing reaction zone counter current to the process flow,
wherein the mixed vapor phase and liquid phase quench stream from
the first stage hydroprocessing reaction zone provides a portion of
the process flow to a second stage hydroprocessing reaction zone
and wherein the mixed vapor phase and liquid phase quench streams
comprise at least a portion of the feed.
2. The method of claim 1 wherein the mixed vapor and liquid quench
streams comprises at least a portion of one of the hydroprocessed
effluents.
3. The method of claim 1 wherein the mixed vapor and liquid quench
streams are injected into the reaction zone using spray nozzles
arranged in a pattern so that the spray coverage from a first
nozzle overlaps with the spray coverage of a second nozzle.
4. The method of claim 3 wherein the pattern of spray nozzles
provide uniform spray coverage across the cross sectional area of
the reaction zone.
5. The method of claim 1 wherein at least one reaction zone
comprises multiple catalyst beds and multiple mixed vapor and
liquid quench streams are injected into the reaction zone with at
least one quench stream injected in between each pair of catalyst
beds.
6. The method of claim 1 wherein the hydroprocessing stages are
three-phase reaction zones.
7. The method of claim 1 wherein the injection of the mixed vapor
and liquid quench streams into a reaction zone results in counter
current axial flow of the mixed vapor and liquid quench streams.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation-in-Part of copending
application Ser. No. 13/441,144 filed Apr. 6, 2012, which
application claims priority from Provisional Application No.
61/472,903 filed Apr. 7, 2011, now expired, the contents of which
are hereby incorporated by reference in its entirety.
FIELD
[0002] The field generally relates to hydroprocessing of
hydrocarbon streams and, more particularly, to hydroprocessing
using multiple hydroprocessing stages. A vapor-liquid quench stream
is introduced counter current to the flow to control the
temperature in the reactors.
BACKGROUND OF THE INVENTION
[0003] Petroleum refiners often produce desirable products such as
turbine fuel, diesel fuel, middle distillates, naphtha, and
gasoline, among others, by hydroprocessing a hydrocarbonaceous
feedstock derived from crude oil or heavy fractions thereof.
Hydroprocessing can include, for example, hydrocracking,
hydrotreating, hydrodesulphurization and the like. Feedstocks
subjected to hydroprocessing may include vacuum gas oils, heavy gas
oils, and other hydrocarbon streams recovered from crude oil by
distillation. For example, a typical heavy gas oil comprises a
substantial portion of hydrocarbon components boiling above about
371.degree. C. (700.degree. F.) and usually at least about 50
percent by weight boiling above 371.degree. C. (700.degree. F.),
and a typical vacuum gas oil normally has a boiling point range
between about 315.degree. C. (600.degree. F.) and about 565.degree.
C. (1050.degree. F.).
[0004] Hydroprocessing concerns reacting the feedstock in the
presence of a hydrogen-containing gas with suitable catalyst(s) to
convert constituents of the feedstocks to other forms, to extract
contaminants from feedstock, etc. In many instances,
hydroprocessing is accomplished by contacting the selected
feedstock in a reaction vessel or zone with the suitable catalyst
under conditions of elevated temperature and pressure in the
presence of hydrogen as a separate phase in a substantially
three-phase system (i.e., hydrogen gas, a substantially liquid
hydrocarbon stream, and a solid catalyst). Such hydroprocessing
apparatuses are commonly undertaken in a trickle-bed reactor where
the continuous phase throughout the reactor is gaseous.
[0005] Many reactor systems comprise multiple beds of catalyst and
many employ multiple reactors. Due to the nature of the reactions,
temperature control of the reactors and the catalyst beds is
important.
SUMMARY OF THE INVENTION
[0006] Methods for hydroprocessing a hydrocarbonaceous feedstock
are provided that utilize multiple catalyst beds in the reactors or
staged hydroprocessing reaction zones to sequentially treat the
hydrocarbonaceous feed. One or more quench streams are used to
control the temperature of the catalyst beds and the reactors. The
quench stream may be generated within the process, obtained from a
source, or be a portion of the feed. The quench stream is mixed
phase vapor and liquid.
[0007] The feed may be divided into portions, and an initial
portion is heated and directed to a first hydroprocessing reaction
zone. A second feed portion may be used as the quench stream. The
quench is introduced counter current to the flow of feed,
reactants, and products. The quench may be introduced at one or
more locations included between reactors and between catalyst beds
within a reactor.
[0008] The feed for the second and subsequent zones comprises the
treated effluent from the preceding reaction zone, which acts as a
diluent and hydrogen source. The feed for the second and subsequent
zones may also comprise a portion of the unheated, untreated feed
supplied for hydroprocessing in the second and perhaps subsequent
reaction zones which act as a quench to control the reaction zone
charge temperature. In one such embodiment, the ratio of the
untreated feed to treated effluent is less than 1, and in other
embodiments, no more than 0.5 and preferably no more than 0.2.
[0009] In another such embodiment, the hydrogen content of the
process flow is sufficient to maintain a substantially three-phase
hydroprocessing zone (hydrogen gas phase, the liquid process flow
and the solid catalyst) in at least the initial reaction zone. As
hydrogen is consumed in each subsequent reaction zone, the hydrogen
content of the process stream continuously decreases, such that one
or more of the subsequent reaction zones may be substantially
liquid-phase reaction zones throughout. However, a portion of
hydrogen in excess of the overall chemical hydrogen consumption is
provided to maintain a vapor phase at the outlet of the last
reaction zone. In each such embodiment, it is unnecessary to
utilize a recycle gas compressor to supply the required hydrogen to
each reaction zone, thus realizing significant capital cost savings
and operational efficiencies of the apparatus.
[0010] In still another embodiment, a multi-stage hydroprocessing
method and apparatus is provided that utilizes sequential
hydroprocessing reaction zones as generally discussed above. In
such embodiments, the temperature of the process flow as it passes
over the catalyst in one or more of the reaction zones increases
due to the exothermal nature of reactions in the zone. The heated
effluent from each such reaction zone may be mixed with the
unheated fresh feed designated for the next downstream
hydroprocessing reaction zone, which is at a lower temperature than
the effluent. Thus, the fresh feed may be used to quench the
temperature of the combined process flow into the subsequent
reaction zones. In this embodiment, accordingly, the temperature of
the fresh feed, distribution of catalyst in each zone, as well as
the distribution of the fresh feed flow to each zone, may be
selected such that the temperature of the combined process flow is
within the range required for the efficient operation of all of the
hydroprocessing reaction zones. The quench is introduced counter
current to the process flow.
[0011] As with the method and apparatus above, hydrogen is added
only at the beginning of the process in an amount effective to
provide sufficient hydrogen for each of the hydroprocessing reactor
zones and an additional quantity of hydrogen to minimally maintain
the reactor effluent in two phases. When this hydrogen is added at
the beginning of the process, the portion of the fresh feed to the
first reaction zone ensures that the reaction zone is a
substantially three-phase reaction zone. The hydrogen in the
process stream is consumed in each reaction zone, and therefore
subsequent reactions zones may be substantially liquid-phase
reaction zones. Such reaction zones are in a substantially liquid
phase throughout. Thus, these embodiments also virtually eliminate
the need for hydrogen recycle gas compressors and the accompanying
cost and other inefficiencies.
[0012] In another embodiment, the ratio of the treated effluent to
the untreated fresh feed for each reaction stage may be significant
and may be different for different reaction stages, for example,
the ratios may be 3 to 1, 5 to 1 or 10 to 1 or greater, depending
on the needs of the particular reaction stage. These ratios can be
obtained as only a portion of the feedstock is introduced at each
reaction stage, and the treated effluent, which acts as a diluent
and hydrogen carrier, is provided from the preceding reaction
stage. Thus, the methods and apparatus herein provide high ratios
of treated effluent to untreated feed without correspondingly high
externally recycled product volumes. Thus, relatively high overall
liquid process flow volumes, or the need for high volume, high
capacity recycle pumps and related apparatuses may be avoided. In
one such embodiment, the hydrogen requirement may be obtained from
an external source, such as a make-up gas compressor. The make-up
hydrogen flow may be supplied directly to the substantially
three-phase hydroprocessing zone and is supplied in an amount
sufficient to satisfy the requirements of the substantially
three-phase reaction zone. The make-up hydrogen flow also provides
excess hydrogen in an amount sufficient to satisfy the requirements
of the subsequent substantially liquid-phase hydroprocessing
zones.
[0013] Accordingly, the methods and apparatus satisfy the hydrogen
requirements of the reaction zones without using a hydrogen recycle
gas compressor. They further reduce or eliminate the need for heat
exchangers, recycled liquid or gas quench streams, or other
temperature control devices between or in the process flow path.
Indeed, the methods and apparatus use the unheated feed as quench
to the second and perhaps each subsequent reaction zone after the
first reaction zone to moderate the temperature of the process
stream through all of the reaction zones. As a result, considerable
cost savings and operational efficiencies may be achieved by
reducing or eliminating the need for heat exchangers in the
reaction zones, and the accompanying maintenance difficulties and
expense.
[0014] Other embodiments encompass further details of the process,
such as preferred feedstocks, catalysts, and operating conditions
to provide but a few examples. Such other embodiments and details
are hereinafter disclosed in the following discussion of various
embodiments of the process.
BRIEF DESCRIPTION OF THE DRAWING
[0015] FIG. 1 is one exemplary flow scheme of a hydroprocessing
method. FIG. 1 shows exemplary locations of the quench system in an
overall hydroprocessing method.
[0016] FIG. 2 is more detailed schematic of one embodiment the
quench header, quench arms, and quench spray devices where the
spray devices are arranged in a rectangular type pattern.
[0017] FIG. 3 is more detailed schematic of one embodiment the
quench header, quench arms, and quench spray devices where the
spray devices are arranged in a linear type pattern.
[0018] FIG. 4 is more detailed schematic of one embodiment the
quench header, quench arms, and quench spray devices where the
spray devices are arranged in a circular type pattern.
[0019] FIG. 5 is more detailed schematic of one embodiment the
quench header, quench arms, and quench spray devices where the
spray devices are arranged in a linear-radial type pattern.
[0020] FIG. 6 is more detailed schematic of the counter current
injection of the quench fluid into the hydroprocessing zone.
DETAILED DESCRIPTION
[0021] The methods described herein are particularly useful for
hydroprocessing a hydrocarbonaceous feedstock containing
hydrocarbons, and typically other organic materials, to produce a
product containing hydrocarbons or other organic materials of lower
average boiling point, lower average molecular weight, as well as
reduced concentrations of contaminants, such as sulfur and nitrogen
and the like. In one embodiment, the present hydroprocessing
methods provide methods and apparatus for the sequential treatment
of a feedstock utilizing multiple reaction zones, which may utilize
a combination of sequential addition of feedstock to the process
flow, a combination of substantially three-phase hydroprocessing
reaction zones and substantially liquid phase reaction zones. The
methods and apparatuses also utilize an initial hydrogen addition
that provides all the hydrogen requirements for each of the
reaction zones without the use of hydrogen sourced from a hydrogen
recycle gas compressor. In other words, the hydrogen is not
recycled within the hydroprocessing unit, but is supplied from
outside the hydroprocessing unit. Consequently, the source of
hydrogen is out of downstream communication with hydroprocessing
reaction stages except perhaps through a make-up gas compressor.
which is sourced from refinery wide hydrogen supply as opposed to a
recycle gas compressor which would be within the hydroprocessing
unit of the refinery. Some hydrogen excess from the hydroprocessing
unit may be routed to the refinery-wide hydrogen supply.
Accordingly, the hydrogen source is out of downstream communication
with the hydroprocessing reaction zones but optionally through a
make-up gas compressor. As used herein, the term "communication"
means that material flow is operatively permitted between
enumerated components. The term "downstream communication" means
that at least a portion of material flowing to the component in
downstream communication may operatively flow from the component
with which it communicates. The term "upstream communication" means
that at least a portion of the material flowing from the component
in upstream communication may operatively flow to the component
with which it communicates.
[0022] The methods and apparatus provide for a simplified approach
to providing the hydrogen requirements of the reaction zones
utilizing, in one embodiment, hydrogen addition before the first
reaction zone that is sufficient to supply hydrogen for each of the
subsequent reaction zones plus an additional quantity of hydrogen
to minimally maintain the reactor effluent in two-phases. The
methods and apparatus do not require the use of high volume
externally recycled liquid streams and the pumps and apparatuses
necessary to provide such recycle streams. In yet other
embodiments, the methods and apparatus provide for the control of
the temperature of the process flow into and through each reaction
zone using the sequentially added fresh feedstock flow.
[0023] In other embodiments, the use of both substantially
three-phase and substantially liquid-phase reaction zones provides
the flexibility to subject the process flow to different
hydroprocessing reactions, such as hydrotreatment and
hydrocracking, as well as the order of such hydroprocessing
reactions in the process sequence. Thus, the methods and
apparatuses provide significant flexibility in the processing of
the feedstock.
[0024] The hydrocarbonaceous feedstocks that may be processed using
the methods and apparatuses comprise mineral oils and synthetic
oils (e.g., shale oil, tar sand products, etc.) and fractions
thereof that may be subjected to hydroprocessing and hydrocracking
Illustrative hydrocarbon feedstocks include those containing
components boiling above about 150.degree. C. (300.degree. F.),
such as atmospheric gas oils, vacuum gas oils, deasphalted, vacuum,
and atmospheric residua, hydrotreated or mildly hydrocracked
residual oils, coker distillates, straight run distillates,
solvent-deasphalted oils, pyrolysis-derived oils, high boiling
synthetic oils, cycle oils, and catalytic cracker distillates, and
Fischer-Tropsch derived liquids. One preferred feedstock is a gas
oil or other hydrocarbon fraction having at least about 50 wt-%,
and preferably at least about 75 wt-%, of its components boiling at
a temperature above about 371.degree. C. (700.degree. F.). For
example, another preferred feedstock contains hydrocarbon
components which boil above about 288.degree. C. (550.degree. F.)
with at least about 25 percent by volume of the components boiling
between about 315.degree. C. (600.degree. F.) and about 565.degree.
C. (1050.degree. F.). Other suitable feedstocks may have a greater
or lesser proportion of components boiling in such range.
[0025] The substantially liquid hydrocarbonaceous feedstock is
subjected to the sequential, staged treatment in two or more
hydroprocessing reaction zones. In one embodiment, the feedstock is
separated to provide feed streams for each reaction zone. The feed
rate for each such fresh feed stream is selected based on the
composition of the hydrocarbonaceous feedstock, the desired
hydroprocessing treatment, and the requirements for each reaction
zone. The feed rates for each such fresh feed stream may be the
same or they may vary from reaction zone to reaction zone,
depending on the needs of the process and apparatus.
[0026] Each of the hydroprocessing reaction zones has a hydrogen
requirement, and these hydrogen requirements will differ depending
on the type of hydroprocessing carried out in the zone. For
example, substantially three-phase reactors typically utilize a
substantially continuous gaseous phase. The three-phase environment
will provide a more kinetically favorable environment for
conversion of the hydrocarbonaceous oil and, therefore, may have
greater hydrogen requirement. In other embodiments, a
hydroprocessing zone may be a substantially liquid-phase zone, with
a substantially liquid phase throughout. The substantially
liquid-phase hydroprocessing zones generally contain a relatively
limited hydrogen flow. In other substantially three-phase reaction
zones, the gaseous phase may not be continuous, and in other
substantially liquid-phase reaction zones the substantially liquid
phase may not be continuous.
[0027] In some embodiments, the fresh feeds stock does not contain
recycled product from the hydroprocessing zones. In other
embodiments, a recycle stream may be incorporated in to the fresh
feedstock prior to hydroprocessing the feedstock to provide
additional volume to the process zone to provide added
hydrogen-carrying capacity to the product stream. In such
embodiments, any recycled product typically is introduced into the
feedstock before the above mentioned hydrogen stream is mixed with
the feedstock, and no further recycled product is incorporated into
the process flow. Typically, such recycled product is stripped of a
vaporous phase of hydrogen, hydrogen sulfide, nitrogen or nitrogen
containing compositions, and any other vapor phase materials. In
another embodiment, this recycle stream also is supplied and mixed
with the above mentioned hydrogen stream before it is introduced to
the feedstock.
[0028] In one embodiment, the fresh feed to the first reaction zone
is provided and mixed with a hydrogen flow from a make-up gas
compressor or other similar hydrogen sources. The hydrogen flow is
mixed into the fresh feed for the first reaction zone and is
provided at a rate at least sufficient to satisfy of the hydrogen
requirements of the first and subsequent reaction zones. In some
instances, the amount of added hydrogen will include an amount in
excess of the predicted hydrogen requirements of the apparatus as
reserve in event the hydrogen consumption exceeds the expected
amount at a particular stage or in the apparatus as a whole.
[0029] In other embodiments, hydrogen is added to the fresh feed
stream to provide sufficient hydrogen for the gas phase in the
substantially three-phase reaction zones as well as to provide, and
in some embodiment, to exceed the saturation point of the liquid
process flows so that in any subsequent substantially liquid phase
reaction zones there is a small vapor phase throughout the
substantially liquid phase. Thus, there is, in some embodiments,
sufficient additional hydrogen in the small vapor phase to provide
additional hydrogen to the liquid phase of the substantially liquid
phase reaction zones mentioned below to provide additional
dissolved hydrogen in the substantially liquid-phase as the
reactions consume hydrogen so that a substantially constant
reaction rate throughout the reactor can be achieved. For example,
the amount of added hydrogen may be about 10 to 20 wt-% greater
than the expected collective hydrogen requirements of each
hydroprocessing stage. In one such embodiment, the amount of
hydrogen is sufficient to supply the three-phase zones and also
range from about 120 to about 150 percent of saturation of the
substantially liquid phase zones. In yet other embodiments, it is
expected that the amount of hydrogen may be up to about 500 percent
of saturation to about 1000 percent of the saturated liquid phase
zones. The hydrogen is carried in the effluent from each reaction
zone in either a dissolved form, a gaseous phase, or both a gaseous
phase and in solution in the liquid effluent streams. In this
embodiment, no other hydrogen is added to the apparatus. In other
embodiments, supplemental hydrogen may be added to or between
reaction zones. It will be appreciated, however, that the amount of
hydrogen added to the first reaction zone can vary depending on the
feed composition, operating conditions, desired output, and other
factors. In other embodiments, alternative substantially
three-phase reaction zones known to those skilled in the art may be
used. The fresh feed to the first reaction zone is subjected to the
hydroprocessing treatment provided by that reaction zone. In one
such embodiment, the hydroprocessing zone is a substantially
three-phase, trickle bed reaction zone with a solid phase catalyst
bed, a substantially liquid phase hydrocarbonaceous feed and a
substantially continuous gaseous phase extending substantially the
length of the catalyst bed.
[0030] The fresh feed may be separated into portions for respective
reaction zones. Only the first portion for the first reaction zone
is heated to a predetermined temperature before entering the first
reaction zone. The first portion of feed may be heated by a heat
exchanger or by a fired heater or both. Additionally or
alternatively, the hydrogen stream mixed with the first portion may
also be heated to bring the first portion of feed to the
appropriate temperature. A second portion of feed is not heated, so
it bypasses the heaters which may include heat exchangers and fired
heaters. The temperature of the first portion of feed is typically
is selected to optimize the hydroprocessing reactions in the first
reaction zone, in terms of a minimum temperature to provide
efficient hydroprocessing reactions over the catalyst bed. The
hydroprocessing reactions typically are exothermal and heat the
process flow as it proceeds through each reaction zone. Thus, the
inlet or entrance temperature to the first reaction zone also may
be selected to ensure that the process flow and catalyst bed
temperatures do not exceed the maximum temperatures that permit the
efficient operation of the catalyst bed and the hydroprocessing
reactions. The heat absorbed by the process flow, and the hydrogen
that was not consumed in the first reaction zone are carried out of
the first reaction zone as the effluent from the reaction zone,
with a first reaction zone outlet temperature and outlet hydrogen
content.
[0031] The reactions are typically highly exothermic reactions
during which large amounts of heat may be generated. The generated
heat can substantially increase the temperature of the reaction
mixture and the catalyst. The temperature of the first catalyst bed
can be controlled by the temperature of the feedstock. However, the
temperature in each succeeding bed, if uncontrolled, will be higher
than the temperature in the preceding bed due to the heat generated
by the exothermic reactions occurring in and the heat absorbed by
the fluid streams. In order for the reactions in each bed to be
conducted under proper intended conditions and to preserve the
catalyst within each bed, the temperature of each succeeding bed is
controlled by injecting a quench medium at or near the exit of the
preceding bed. Quench gas is most often the cooling medium of
choice, often the quench gas is hydrogen both because it is readily
available and it serves to replenish hydrogen needed for the
reaction.
[0032] However, in the process herein, a readily available material
which can be used as the quench fluid is a portion of the feed or a
portion of the first stage reaction zone product stream, or a
portion of a recycle stream such as line 46 of FIG. 1. The quench
stream herein is introduced counter current to the process flow.
The quench stream may be injected in association with a quench zone
containing standard quench equipment such as the quench delivery
system, the spillway, the liquid fraction collection tray, the
mixing chamber with outlet weir, perforated pre-distributor tray,
and bubble cap, modified bubble cap or riser chimney tray.
[0033] As indicated earlier, the quench material introduced into
the reactor via lines 16, 18, and 20 consists of either feed via
stream 12 or recycled product via line 46. These streams are both
relatively cool and therefore exist in the liquid phase before
entering the reactor. After entering the reactor beds 28, 32, and
36, the quench material will begin to heat via conduction as the
material flows through the quench distributor, shown as 200 in FIG.
6. It may be possible that the temperature rise will be sufficient
to vaporize at least a portion of the quench material before
reaching the quench nozzles 200. The amount of vapor generated will
be dependent on the properties of the feed 12 or recycle liquid 46,
the operating pressure of the reactor, and operating temperature of
the reactor 28, 32, 36. It is expected that the remainder of the
quench material will vaporize upon contact with the material 602
flowing to the quench zone from the reactor bed immediately above
the quench zone. The vapor generated will consist of hydrocarbons
in the feed or recycle liquid having the lowest boiling point
[0034] Unlike applications employing a vapor quench, using a mixed
phase vapor and liquid quench herein requires greater efforts to
achieve proper mixing between the quench and the reactants and
products in reaction zone and to achieve uniform distribution of
the quench across the reactor cross section. Without increased
mixing and uniform distribution efforts, portions of the reactants
and products of the reaction zone can bypass the quench decreasing
the effectiveness of the quench. For example, the temperature of
the bed may not be uniformly controlled and hot spots may develop
where fluid is able to bypass the quench medium.
[0035] To increase the mixing of the mixed phase vapor-liquid
quench and the reaction mixture, the vapor-liquid quench is
injected counter current to the flow of the reaction mixture. Spray
nozzles as opposed to jets are a suitable device for providing an
area containing spray droplets. The positioning of multiple spray
nozzles is designed to provide uniform coverage of sprayed
vapor-liquid quench over the cross sectional area of the reactor
bed. Surprisingly, injecting the vapor-liquid quench in a counter
current mode enhances the mixing of the vapor-liquid quench and the
reaction mixture, and thereby increases the effectiveness of the
quench cooling. The injection may be directed to result in counter
current axial flow of the vapor-liquid phase quench. The
temperature of the quench stream would be determined in conjunction
with other process conditions such as the minimum temperature for
cold flow properties. It is often desirable to provide the
vapor-liquid quench at the coolest possible temperature. The amount
of quench stream needed is determined by analyzing the amount of
material to be cooled, the temperature of the material to be
cooled, and the temperature of the quench stream.
[0036] The effluent from the first or subsequent hydroprocessing
reaction zone then may be quenched with a second, unheated portion
of fresh feedstock as described above to cool the reaction zone
effluent, which provides diluent and hydrogen for a second
hydroprocessing reaction zone. The quench stream may be introduced
between two or more catalysts beds within a single hydroprocessing
zone in addition to or instead of being introduced between the
hydroprocessing reaction zones. Again, the quench stream(s) would
be introduced counter current to the process flow. The second
portion of fresh feed, in one embodiment, does not include added
hydrogen and is at a lower temperature than the first portion of
fresh feedstock. Accordingly, the temperature of the second portion
of fresh feed, when mixed with the heated effluent from the first
reaction zone, will provide a combined effluent and process flow
into the second hydroprocessing reaction zone with a temperature
reduced from the temperature of the effluent at the outlet of the
first or preceding hydroprocessing zone. Thus, one consideration in
selecting the amount and flow rate of this second portion of fresh
feed is the desired hydrogen content and temperature of the process
flow into the second or subsequent hydroprocessing reaction
zone.
[0037] In one embodiment, the ratio of the first reaction zone
effluent and the second portion of fresh feed is about 3 to 1 or 5
to 1 or greater, i.e., the effluent flow to the fresh feed flow. In
other embodiments, the ratio of effluent to fresh feed may be
increased or decreased depending on the specific feed, effluent
hydrogen content and temperature, and the nature and requirements
of the second and subsequent reaction zones. These ratios can be
obtained without substantially increasing the overall process flow
through the apparatus because only a portion of the feedstock is
introduced at each reaction stage, and the treated effluent, which
acts as a diluent and hydrogen carrier, is provided from the
preceding reaction stage. Thus, the methods and apparatus herein
provide high ratios of treated effluent to untreated feed without
correspondingly high overall external recycle and overall product
flow volumes from reactor circuit separators, fractionation columns
or the like. Thus, high volume, high capacity recycle pumps and
related apparatuses typically used to supply high volume recycle
flows are not necessary.
[0038] In at least one embodiment, the hydrogen content of the
process flow to the second reaction zone, comprising a first
effluent and the second portion of fresh feed, is sufficient to
supply the entire hydrogen requirement of a second hydroprocessing
reaction zone, which in some embodiments is also a substantially
three-phase reaction zone without a recycle gas compressor.
[0039] The effluent from the second reaction zone typically will
have an increased temperature due to the exothermal hydroprocessing
over the catalyst beds in the second reaction zone. The hydrogen
content in the second reaction zone effluent is reduced by the
hydrogen consumed in the second reaction zone and exits the zone at
a temperature reflecting absorption by the process flow of
additional heat from the hydroprocessing reactions. In several
embodiments, the process flow into the second hydroprocessing
reaction zone contains sufficient unreacted hydrogen to operate as
a substantially three-phase, trickle bed reaction process. The
hydrogen in the process flow typically is sufficient to maintain
the required continuous gaseous phase, while providing sufficient
hydrogen for hydroprocessing process of that reaction zone.
[0040] In an embodiment, the heated effluent from the second
hydroprocessing zone may be then mixed with a third unheated
portion of fresh feed to quench the effluent and to provide the
process flow to a third hydroprocessing reaction zone. As with the
second portion of fresh feed, the amount and rate of addition will
depend on the temperature and hydrogen content of the second
effluent. As with the previous stage, the ratio of treated effluent
from the second stage to third portion of fresh feed is about 3 to
1 or 5 to 1 or greater. The amount and flow rate of the third
portion of fresh feed will provide a process feed to the third
reaction zone with sufficient hydrogen for further hydroprocessing,
at temperatures within the range desired for the process. In such
embodiments, the temperature of the process flow will increase as
the flow is reacted over the catalyst bed. Thus, as with the second
reaction zone, it often is desirable to quench the second effluent
to reduce the temperature of the feed into the subsequent reaction
zone sufficiently to ensure that the process flow and catalyst bed
temperatures do not exceed the maximum temperatures permitting the
efficient operation of the catalyst bed(s).
[0041] Given the hydrogen consumption of the previous two reaction
zones, if the hydrogen content of the process flow in the third
reaction zone falls below about the minimum required for
substantially three-phase reaction zones, then it may be desirable
to use a substantially liquid-phase reaction apparatus for the,
e.g., third and subsequent hydroprocessing reaction zones. In one
such reaction apparatus, a substantially liquid phase of the
process flow extends continuously over the hydroprocessing catalyst
bed. Such substantially liquid-phase reaction zones do not require
as much hydrogen as the substantially three-phase reaction zones,
as the hydrogen is dissolved or suspended in the substantially
liquid phase. As with the previous stages, the process flow is
passed over the catalyst beds, and the amount of hydrogen consumed
and temperature increase of the process flow will depend on the
process flow inlet temperature, catalyst and type of
hydroprocessing reaction.
[0042] In embodiments with further hydroprocessing stages,
essentially the same steps are repeated as long as there is
sufficient hydrogen in the process flow for additional
hydroprocessing treatments after further additions of the fresh
feed. In one embodiment of the method the catalyst systems may be
distributed among the reaction zones to provide an increasing
catalyst volume and a correspondingly decreasing LHSVRC (liquid
volume per hour of reactor charge per volume of catalyst in the
reaction zone) with each additional hydroprocessing reaction zone.
Such catalyst volume increases may assist in maintaining a desired
treatment efficiency as the process flow progresses through the
reaction stages tending toward substantially liquid-phase reaction
zones, or as the concentration of catalyst activity inhibitors
increase in the process flow. The overall temperature of the
process flow may increase with each hydroprocessing step to
compensate for the increased concentration of inhibitors that may
accumulate in the process flow.
[0043] The effluent from the last reaction zone is typically sent
to a separation zone for removal of excess hydrogen, contaminants,
and vapor phase products. In one embodiment, the final effluent is
sent to a hot separator where the unreacted hydrogen is removed
from the process flow, as are hydrogen sulfide, ammonia and other
contaminants. In other embodiments, the hot separator also extracts
vaporous or low boiling point hydrocarbons, which are then routed
to fractionators or to other processes.
[0044] In one embodiment, the separation zone preferably is a high
pressure flash vessel, where any vapor formed in the
hydroprocessing zones can be separated from a substantially liquid
phase. By one approach, the high pressure flash vessel operates at
a temperature from about 232.degree. C. (450.degree. F.) to about
468.degree. C. (875.degree. F.), a pressure from about 3.5 MPa (500
psig) to about 16.5 MPa (2400 psig) to separate such streams. This
separation zone is configured to separate any vaporous materials
(such as gaseous hydrogen, hydrogen sulfide, ammonia, and/or C1 to
C4 gaseous hydrocarbons and the like), which can then be directed
to a recovery apparatus. In general, any dissolved hydrogen in the
separated substantially liquid stream remains dissolved therein at
the pressures and temperatures of the separation zone.
[0045] As mentioned above, the substantially three-phase
hydroprocessing zone used in the methods and apparatus may have a
hydrogen requirement that effectively maintains the substantially
three-phase hydroprocessing zone with a substantially continuous
gas-phase throughout the reaction zone. For example, in some
three-phase hydroprocessing zones, the hydrogen requirements may be
from about 600 to about 7500 SCF/B or from about 100 to about 200
Nm.sup.3/m.sup.3 (about 600 to about 1200 SCF/B). The substantially
three-phase hydroprocessing zone, for example, may be a
hydrotreating zone, a hydrocracking zone, or another conversion
zone that provides an effluent that contains excess hydrogen due to
the operation of the substantially three-phase zone.
[0046] In one form, one or more substantially three-phase reaction
zones may be, for example, hydrotreating reaction zones operated as
a trickle bed reactor without a recycle gas stream or a recycle gas
compressor to supply the hydrogen requirement for this reaction
zone. In this form, the hydrotreating reactor reduces the
concentration of sulfur and nitrogen in the fresh hydrocarbonaceous
feed in the presence of suitable catalyst(s) that are primarily
active for the removal of heteroatoms, such as sulfur and nitrogen,
from the hydrocarbon process flow.
[0047] In one such embodiment, suitable hydrotreating catalysts are
conventional hydrotreating catalysts and include those which are
comprised of at least one Group VIII metal, preferably iron, cobalt
and nickel, more preferably cobalt and/or nickel and at least one
Group VI metal, preferably molybdenum and tungsten, on a high
surface area support material, preferably alumina. Other suitable
hydrotreating catalysts include zeolitic catalysts, as well as
noble metal catalysts where the noble metal is selected from
palladium and platinum. In another embodiment, more than one type
of hydrotreating catalyst may be used in the same reaction vessel.
In such embodiment, the Group VIII metal is typically present in an
amount ranging from about 2 to about 20 wt-%, preferably from about
4 to about 12 wt-%. The Group VI metal will typically be present in
an amount ranging from about 1 to about 25 wt-%, preferably from
about 2 to about 25 wt-%.
[0048] In another embodiment, one or more substantially three-phase
reaction zones are, for example, hydrocracking reaction zones, such
as a mild hydrocracking zone, which is also operated as a trickle
bed reactor and without a recycle gas stream or a recycle gas
compressor to supply the hydrogen requirements for the
substantially three-phase reaction zone. Depending on the desired
output, the hydrocracking zone may contain one or more beds of the
same or different catalyst. In one embodiment, for example, when
the preferred products are middle distillates, the preferred
hydrocracking catalysts utilize amorphous bases or low-level
zeolite bases combined with one or more Group VIII or Group VIB
metal hydrogenating components. In another embodiment, when the
preferred products are in the gasoline boiling range, the
hydrocracking zone contains a catalyst which comprises, in general,
any crystalline zeolite cracking base upon which is deposited a
minor proportion of a Group VIII metal hydrogenating component.
Additional hydrogenating components may be selected from Group VIB
for incorporation with the zeolite base.
[0049] The zeolite cracking bases are sometimes referred to in the
art as molecular sieves and are usually composed of silica, alumina
and one or more exchangeable cations such as sodium, magnesium,
calcium, rare earth metals, etc. They are further characterized by
crystal pores of relatively uniform diameter between about 4 and
about 14 Angstroms (10.sup.-10 meters). It is preferred to employ
zeolites having a relatively high silica/alumina mole ratio between
about 3 and about 12. Suitable zeolites found in nature include,
for example, mordenite, stilbite, heulandite, ferrierite,
dachiardite, chabazite, erionite and faujasite. Suitable synthetic
zeolites include, for example, the B, X, Y and L crystal types,
e.g., synthetic faujasite and mordenite. The preferred zeolites are
those having crystal pore diameters between about 8-12 Angstroms
(10.sup.-10 meters), wherein the silica/alumina mole ratio is about
4 to 6. One example of a zeolite falling in the preferred group is
synthetic Y molecular sieve.
[0050] The natural occurring zeolites are normally found in a
sodium form, an alkaline earth metal form, or mixed forms. The
synthetic zeolites are nearly always prepared first in the sodium
form. In any case, for use as a cracking base it is preferred that
most or all of the original zeolitic monovalent metals be
ion-exchanged with a polyvalent metal and/or with an ammonium salt
followed by heating to decompose the ammonium ions associated with
the zeolite, leaving in their place hydrogen ions and/or exchange
sites which have actually been decationized by further removal of
water. Hydrogen or "decationized" Y zeolites of this nature are
more particularly described in U.S. Pat. No. 3,130,006 B1.
[0051] Mixed polyvalent metal-hydrogen zeolites may be prepared by
ion-exchanging first with an ammonium salt, then partially back
exchanging with a polyvalent metal salt and then calcining In some
cases, as in the case of synthetic mordenite, the hydrogen forms
can be prepared by direct acid treatment of the alkali metal
zeolites. In one embodiment, the preferred cracking bases are those
which are at least about 10 percent, and preferably at least about
20 percent, metal-cation-deficient, based on the initial
ion-exchange capacity. In another embodiment, a desirable and
stable class of zeolites is one wherein at least about 20 percent
of the ion exchange capacity is satisfied by hydrogen ions.
[0052] The active metals employed in the preferred hydrocracking
catalysts of the present invention as hydrogenation components are
those of Group VIII, i.e., iron, cobalt, nickel, ruthenium,
rhodium, palladium, osmium, iridium and platinum. In addition to
these metals, other promoters may also be employed in conjunction
therewith, including the metals of Group VIB, e.g., molybdenum and
tungsten. The amount of hydrogenating metal in the catalyst can
vary within wide ranges. Broadly speaking, any amount between about
0.05 percent and about 30 percent by weight may be used. In the
case of the noble metals, it is normally preferred to use about
0.05 to about 2 wt-%.
[0053] The method for incorporating the hydrogenating metal is to
contact the zeolite base material with an aqueous solution of a
suitable compound of the desired metal wherein the metal is present
in a cationic form. Following addition of the selected
hydrogenating metal or metals, the resulting catalyst powder is
then filtered, dried, pelleted with added lubricants, binders or
the like if desired, and calcined in air at temperatures of, e.g.,
about 371.degree. C. to about 648.degree. C. (about 700.degree. F.
to about 1200.degree. F.) in order to activate the catalyst and
decompose ammonium ions. Alternatively, the zeolite component may
first be pelleted, followed by the addition of the hydrogenating
component and activation by calcining
[0054] The foregoing catalysts may be employed in undiluted form,
or the powdered zeolite catalyst may be mixed and copelleted with
other relatively less active catalysts, diluents or binders such as
alumina, silica gel, silica-alumina cogels, activated clays and the
like in proportions ranging between about 5 and about 90 wt-%.
These diluents may be employed as such or they may contain a minor
proportion of an added hydrogenating metal such as a Group VIB
and/or Group VIII metal. Additional metal promoted hydrocracking
catalysts may also be utilized in the process of the present
invention which comprises, for example, aluminophosphate molecular
sieves, crystalline chromosilicates and other crystalline
silicates. Crystalline chromosilicates are more fully described in
U.S. Pat. No. 4,363,718 B1 (Klotz).
[0055] By one approach, the hydrocracking conditions may include a
temperature from about 232.degree. C. (450.degree. F.) to about
468.degree. C. (875.degree. F.), a pressure from about 3.5 MPa (500
psig) to about 16.5 MPa (2400 psig) and a liquid hourly space
velocity (LHSV) from about 0.1 to about 30 hr.sup.-1. In some
embodiments, the hydrocracking reaction provides conversion of the
hydrocarbons in the process stream to lower boiling products, which
may be the conversion of at least about 5 vol-% of the process
flow. In other embodiments, the per pass conversion in the
hydrocracking zone may be in the range from about 15 percent to
about 70 percent and, preferably, the per-pass conversion is in the
range from about 20 percent to about 60 percent. In such
embodiments, the processes herein are suitable for the production
of naphtha, diesel or any other desired lower boiling
hydrocarbons.
[0056] In one embodiment, the substantially liquid-phase reaction
zones used in the methods and apparatuses may be, for example,
substantially liquid-phase hydrotreating zones operated under
hydrotreating conditions to produce an effluent including hydrogen
sulfide and ammonia. In this embodiment, the substantially
liquid-phase hydrotreating reaction conditions for the
hydroprocessing zone may include a temperature from about
204.degree. C. (400.degree. F.) to about 482.degree. C.
(900.degree. F.), a pressure from about 3.5 MPa (500 psig) to about
16.5 MPa (2400 psig), a liquid hourly space velocity of the fresh
hydrocarbonaceous feedstock from about 0.1 hr.sup.-1 to about 10
hr.sup.-1 with a hydrotreating catalyst or a combination of
hydrotreating catalysts. Other conditions may also be used
depending on the specific feeds, catalysts, and composition of the
effluent stream desired.
[0057] The hydrogen requirements for the substantially liquid-phase
hydrotreating zone are substantially satisfied by the remaining
hydrogen dissolved in the process flow directed to the
hydrotreating zone after the preceding hydroprocessing stages, in
the presence of suitable catalyst(s) that are primarily active for
the removal of heteroatoms, such as sulfur and nitrogen, from the
hydrocarbon feedstock. In another embodiment, the hydrogen
requirements for the substantially liquid-phase hydrotreating zone
are substantially satisfied by the remaining hydrogen dissolved in
the process flow plus an additional quantity of hydrogen, remaining
in the gas phase, which minimally maintains the hydroprocessing
zone effluent in two-phases to a subsequent hydroprocessing zone.
In one such embodiment, suitable hydrotreating catalysts for use in
the present invention are conventional hydrotreating catalysts
mentioned above. In another embodiment, the process is operated in
the presence of excess hydrogen.
[0058] They, for example, include those which are comprised of at
least one Group VIII metal, preferably iron, cobalt and nickel,
more preferably cobalt and/or nickel and at least one Group VI
metal, preferably molybdenum and tungsten, on a high surface area
support material, preferably alumina. Other suitable hydrotreating
catalysts include zeolitic catalysts, as well as noble metal
catalysts where the noble metal is selected from palladium and
platinum. In another embodiment, more than one type of
hydrotreating catalyst may be used in the same reaction vessel. In
such embodiment, the Group VIII metal is typically present in an
amount ranging from about 2 to about 20 wt-%, preferably from about
4 to about 12 wt-%. The Group VI metal will typically be present in
an amount ranging from about 1 to about 25 wt-%, preferably from
about 2 to about 25 wt-%.
[0059] In another embodiment, the substantially liquid-phase
reaction zones may be, for example, hydrocracking zones. The
operation and catalysts used in such substantially liquid phase
hydrocracking zones are similar to those discussed above with
respect to the substantially three-phase, trickle bed reaction
zones.
DETAILED DESCRIPTION OF THE DRAWINGS
[0060] Turning to FIG. 1, an exemplary hydroprocessing method that
eliminates the use of a recycle gas compressor and gains the
efficiencies of a multi-stage method and apparatus is described in
more detail. It will be appreciated by one skilled in the art that
various features of the above described process, such as pumps,
instrumentation, heat-exchange and recovery units, condensers,
compressors, flash drums, feed tanks, and other ancillary or
miscellaneous process equipment that are traditionally used in
commercial embodiments of hydrocarbon conversion processes have not
been described or illustrated. It will be understood that such
accompanying equipment may be utilized in commercial embodiments of
the flow schemes as described herein. Such ancillary or
miscellaneous process equipment can be obtained and designed by one
skilled in the art without undue experimentation.
[0061] With reference to the FIG. 1, an integrated hydroprocessing
unit 10 is illustrated where a hydrocarbonaceous feedstock, such as
a vacuum gas oil or a heavy gas oil, is introduced into the process
via a fresh hydrocarbonaceous feed line 12 and is separated into a
first portion of fresh feed in a first hydrocarbonaceous portion
line 14, a second portion of fresh feed in a second
hydrocarbonaceous portion line 16, a third portion of fresh feed in
a third hydrocarbonaceous portion line 18 and fourth portion of
fresh feed in a fourth hydrocarbonaceous portion line 20. Lines 14,
16, 18 and 20 are all in downstream communication with the fresh
hydrocarbonaceous feed line 12. The hydrocarbonaceous feedstock is
provided at a first temperature which may be at a temperature well
below reactor temperature such as a first temperature between about
200.degree. and about 300.degree. F. (90.degree. and 150.degree.
C.) because the feedstock is not subjected to substantial heating
and preferably not subjected to any heating.
[0062] A hydrogen-rich gaseous stream is provided via a hydrogen
source such as line 22 via a make-up gas compressor 25. In an
embodiment, hydrogen in line 22 is only provided via a make-up gas
compressor 25. Line 22 is in downstream communication with the
make-up gas compressor 25. The hydrogen source 22 may be in
downstream communication with a general refinery hydrogen supply.
The hydrogen-rich gaseous stream from line 22 is admixed with the
first portion of fresh feed in the first hydrocarbonaceous portion
line 14 which is in downstream communication with the hydrogen line
22 to provide an admixture of the first portion of
hydrocarbonaceous feedstock and hydrogen in line 15. The first
portion of fresh feed is heated to the appropriate reaction
temperature with a heater. The heater 17 may be one or more fired
heaters and/or heat exchangers represented by fired heater 17. For
example, the admixture of hydrogen and the first portion in line 15
may be heated in a fired heater 17 and/or a heat exchanger.
Alternatively or additionally, the heater 17 may be located to heat
the first portion of fresh feed upstream of line 15 in line 14.
Alternatively or additionally, the hydrogen in line 22 may be
heated by a heat exchanger 23 or other means and mixed with the
first portion of fresh feed to thereby heat the first portion in
line 15. Any combination of these arrangements may be appropriate
to heat the first portion of fresh feed to a second temperature
that is greater than the first temperature. Portions of fresh feed
in lines 16, 18 and 20 bypass the heater 17 used to heat the first
portion of fresh feed to keep the other portion of feed relatively
cool.
[0063] The heated, combined stream in line 19 is introduced into
the first, Stage I, hydroprocessing reaction zone comprising the
hydroprocessing reactor 24. The first, Stage I, hydroprocessing
reaction zone is in downstream communication with the first
hydrocarbonaceous portion in lines 14, 15 and 19, the hydrogen line
22 and the heater 17 and/or 23. The hydroprocessing reactor 24 may
be a single catalyst bed or may be a single vessel with one or more
catalyst beds. As mentioned above, in one embodiment this is a
substantially three-phase, trickle bed hydroprocessing reactor,
with the hydrogen requirement for the substantially three-phase
reactor supplied from the combined stream of hydrogen from line 22
and fresh feed 14.
[0064] A first effluent stream is removed via a first
hydroprocessed effluent line 26 from the Stage I hydroprocessing
reactor 24. The first hydroprocessed effluent line 26 is in
downstream communication with the second hydrocarbonaceous portion
line 16. The first effluent stream upon entering a second, Stage
II, hydroprocessing reaction zone comprising second hydroprocessing
reactor 28, is injected counter currently with the unheated, second
portion of fresh feed in second hydrocarbonaceous portion line 16
to quench the first effluent stream by absorbing some of the heat
generated in the exothermic hydroprocessing reaction. As discussed
above, the amount and rate of injection of the second portion of
fresh feed will depend on the specific composition of the
hydrocarbonaceous feed, the composition and hydrogen concentration
and temperature of the first effluent. Hydroprocessing reactor 28
may be a single catalyst bed or may be a single vessel with one or
more catalyst beds. In one embodiment, Stage II hydroprocessing
reaction zone also is a substantially three-phase trickle bed
reactor, with sufficient hydrogen in the combined first effluent
and second portion of fresh feed 16 to satisfy the hydrogen
requirements of the second substantially three-phase reactor
28.
[0065] A second effluent stream is removed via a second
hydroprocessed effluent line 30 from the Stage II hydroprocessing
reactor 28. The second hydroprocessed effluent line 30 is in
downstream communication with the third hydrocarbonaceous portion
line 18. The second effluent stream upon being introduced into to a
third, Stage III, hydroprocessing reaction zone comprising third
hydroprocessing reactor 32, is injected, counter currently, with
the unheated, third portion of fresh feed in the third
hydrocarbonaceous portion line 18 to quench the second effluent
stream by absorbing some of the heat generated in the exothermic
hydroprocessing reaction. As with the preceding stage, the amount
and rate of injection of the third portion of fresh feed will
depend on the specific composition of the hydrocarbonaceous feed,
the composition and the hydrogen concentration and temperature of
the second effluent. Hydroprocessing reactor 32 may be a single
catalyst bed or may be a single vessel with one or more catalyst
beds.
[0066] Depending on the hydrogen content of the second effluent
stream, as well as the desired reaction conditions, in one
embodiment the Stage III hydroprocessing reaction zone may be a
substantially three-phase trickle bed reactor, with sufficient
hydrogen in the combined second effluent and third portion of fresh
feed 18 to satisfy the hydrogen requirements of a third
substantially three-phase reactor. In many processes, the hydrogen
content of the second effluent is insufficient to satisfy the
hydrogen requirements of a substantially three-phase reactor, and
thus the third, Stage III reactor 32 is a substantially
liquid-phase reactor as mentioned above.
[0067] A third effluent stream is removed via a third
hydroprocessed effluent line 34 from the Stage III hydroprocessing
reactor 32. The third hydroprocessed effluent line 34 is in
downstream communication with the fourth hydrocarbonaceous portion
line 20. The third effluent stream in the third hydroprocessed
effluent line 34 upon being introduced into to a fourth, Stage IV,
hydroprocessing reaction zone, comprising a fourth hydroprocessing
reactor 36, is injected, counter-currently, with the unheated,
fourth portion of fresh feed 20 to quench the third effluent stream
by absorbing some of the heat generated in the exothermic
hydroprocessing reaction. As with the preceding stage, the amount
and rate of addition of the fourth portion of fresh feed will
depend on the specific composition of the hydrocarbonaceous feed,
the composition and the hydrogen concentration and temperature of
the third effluent. Hydroprocessing reactor 36 may be a single
catalyst bed or may be a single vessel with one or more catalyst
beds. In one embodiment, the Stage IV hydroprocessing reaction zone
also is a substantially liquid-phase reactor zone, with sufficient
hydrogen in the third effluent and fourth portion of fresh feed 20
to satisfy the hydrogen requirements of the fourth, substantially
liquid-phase reactor zone 36. In another embodiment, the Stage IV
hydroprocessing reaction zone also is a substantially liquid-phase
bed reactor, with sufficient hydrogen in the third effluent and
fourth portion of fresh feed 20 to satisfy the chemical hydrogen
requirements of the fourth, substantially liquid-phase reactor 36
and an additional quantity of hydrogen as to minimally maintain the
Stage IV effluent in two phases.
[0068] A final effluent stream is removed from the Stage IV
hydroprocessing reactor 36 via line 38 and is transported via line
38 into a separation zone 40. A vaporous stream is removed from the
separation zone 40 via line 42 and is further separated into a
hydrogen rich stream, contaminants, such as hydrogen sulfide and
ammonia, and low boiling point hydrocarbons. The hydrogen rich
stream may be sent to a general refinery hydrogen supply, but is
not recycled back to the hydroprocessing stages I-IV unless
optionally recycled through a make-up gas compressor 25.
Consequently, the hydrogen line 22 is out of downstream
communication with said hydroprocessing stages I-IV but optionally
through a make-up gas compressor 25. Moreover, the hydroprocessing
stages I-IV are out of downstream communication with a recycle gas
compressor. The remaining liquid phase is removed from the
separation zone via line 44 and is directed to further processing
or to a fractionation zone for further separation into its
constituents.
[0069] An alternative embodiment is shown by dotted line in FIG. 1.
The remaining liquid phase is removed from the separation zone via
44 and, optionally, a portion of the liquid phase is externally
recycled in line 46, such that the external recycle is added as a
diluent as desired to one or more or all of the streams of fresh
feed 14, 16, 18 and 20. In another embodiment, the external recycle
is added as a diluent entirely to the first portion of fresh feed
14. The remaining liquid phase from the separation zone 40 is
directed by line 48 to further processing treatments and/or to a
fraction zone for further separation into its constituents.
[0070] The injection of the quench fluid in lines 16, 18 and 20 is
countercurrent to the flow of reactants and products through the
reactors. FIG. 2 shows one embodiment of the quench liquid
distribution system. A series of spray nozzles 202 are arranged at
each quench elevation in the reactor. Low pressure spray nozzles
202 will be oriented so that they point countercurrent to the
process flow allowing the maximum amount of contact time and mixing
with the process fluid. As much as possible, the spray nozzles will
be spaced so that there is slight overlap between the coverage of
the spray between spray nozzles. Stream 16, 18, or 20 (stream 16 is
shown in FIG. 2-FIG. 5) delivers quench fluid to quench header 200
which is held in place within the reactor by quench header pipe
supports 204. Quench header is in fluid communication with quench
arms 206 which are equipped with multiple quench spray devices such
as spray nozzles 202. The pattern of the quench arms and the spray
nozzles are selected so that the quench fluid is injected evenly
and uniformly over the cross sectional area of reactor 4. The
rectangular pattern shown in FIG. 2 is merely exemplary, other
patterns and spray nozzle locations may be used. For example, one
linear type pattern is shown in FIG. 3; a circular type pattern
having concentric circles is shown in FIG. 4; and a linear-radial
type of pattern is shown in FIG. 5. Other patterns may have square
or other arrangements of the spray nozzles, while still having a
light overlap of the spray regions.
[0071] The hydroprocessing reactors may be a single catalyst bed or
may be a single vessel with one or more catalyst beds. When
multiple catalyst beds are employed, the quench injection may be
located between catalyst beds. The quench injections may be located
between the reactors, at the entry or exit of the reactors, between
different catalyst beds, or any combination of locations.
[0072] FIG. 6 provides a view of the quench injections, such as the
quench injection from line 16 of FIG. 1 into second hydroprocessing
reactor 28 of FIG. 1. Turning to FIG. 6, the injection of the
quench fluid in line 16 is countercurrent to the flow of reactants
and products through second hydroprocessing reactor 28. The quench
fluid 604 is injected via quench header 200 and series of spray
nozzles 202. Spray nozzles 202 are oriented so that they point
countercurrent at least in the axial direction to the process flow
602 allowing the maximum amount of contact time and mixing with the
process fluid.
[0073] The figures and are intended to illustrate exemplary flows
scheme and conditions of the methods and apparatus described
herein, and other flow schemes, methods and apparatuses are also
possible, are not intended as limits to the methods and apparatus.
It will be further understood that various changes in the details,
materials, and arrangements of conditions, compositions, parts and
components which have been herein described and illustrated in
order to explain the nature of the process may be made by those
skilled in the art within the principle and scope of the methods
and apparatus as expressed in the appended claims.
* * * * *