U.S. patent application number 11/247250 was filed with the patent office on 2006-04-06 for high frequency energy application to petroleum feed processing.
Invention is credited to Serik M. Burkitbayev.
Application Number | 20060073084 11/247250 |
Document ID | / |
Family ID | 24849305 |
Filed Date | 2006-04-06 |
United States Patent
Application |
20060073084 |
Kind Code |
A1 |
Burkitbayev; Serik M. |
April 6, 2006 |
High frequency energy application to petroleum feed processing
Abstract
The present invention provides a method and apparatus for
maintaining the active life of a catalyst in organic feed
processing by applying a series of electromagnetic radiation pulses
to the catalyst in a reactor. The pulsing of the catalyst
selectively heats and cools the catalyst and can regulate the
relative internal pressure of the catalyst particles to stimulate
the acceleration of oil macromolecules mass-exchange through the
catalyst pores and surface. This allows for the removal of cracked
oil molecules from the particles. The application of
electromagnetic pulses also regulates the activity of the catalyst.
The electromagnetic radiation reduces the formation of coke on the
catalyst and increases the life of the catalyst in the reactor.
Further, the present invention provides a method and apparatus for
removing water and salt from an organic feed. Water and salt is
removed by applying a series of electromagnetic radiation pulses to
the organic feed. A first pulse condenses water contained in the
feed and induces salt to dissolve in the condensed water. A second
pulse vaporizes a portion of the condensed water droplets to bring
the droplets to the surface of the organic feed.
Inventors: |
Burkitbayev; Serik M.;
(Almary, KZ) |
Correspondence
Address: |
MCGUIREWOODS, LLP
1750 TYSONS BLVD
SUITE 1800
MCLEAN
VA
22102
US
|
Family ID: |
24849305 |
Appl. No.: |
11/247250 |
Filed: |
October 12, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10243681 |
Sep 16, 2002 |
6994774 |
|
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11247250 |
Oct 12, 2005 |
|
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09709307 |
Nov 13, 2000 |
6451174 |
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10243681 |
Sep 16, 2002 |
|
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Current U.S.
Class: |
422/186 ;
204/157.15 |
Current CPC
Class: |
Y10S 44/905 20130101;
B01J 8/42 20130101; B01J 8/20 20130101; C10G 2300/703 20130101;
C10G 49/02 20130101; C10G 32/02 20130101; B01J 2219/0892 20130101;
B01J 2208/00707 20130101; B01J 19/128 20130101; B01J 2219/1227
20130101; B01J 19/12 20130101; C10G 15/08 20130101; Y10S 44/904
20130101; B01J 19/126 20130101; B01J 19/0026 20130101; B01J
2219/0854 20130101; B01J 19/121 20130101; B01J 2219/0877
20130101 |
Class at
Publication: |
422/186 ;
204/157.15 |
International
Class: |
C07C 1/00 20060101
C07C001/00; B01J 19/08 20060101 B01J019/08 |
Claims
1. A dewatering device comprising: a container for holding organic
feed; an electromagnetic radiation generator wherein the generator
provides at least two pulses having different frequencies; and a
window transparent to electromagnetic radiation positioned on the
container to allow electromagnetic radiation from the generator to
reach at least a portion of the organic feed.
2. The device of claim 1 wherein the electromagnetic radiation
generator generates radiation selected from the group consisting of
VHF, UHF, microwave, infrared, and laser radiation.
3. The device of claim 1 wherein the frequency of the
electromagnetic radiation produced by said electromagnetic
radiation generator is at least about 0.4 MHz.
4. The device of claim 1 wherein the frequency of the
electromagnetic radiation produced by said electromagnetic
radiation generator ranges from about 0.4 MHz to about 100 HHz.
5. A dewatering apparatus comprising: a pipe for transporting an
organic feed wherein a portion of the pipe is transparent to
electromagnetic radiation; an electromagnetic radiation generator
wherein the generator provides at least two pulses having different
frequencies through the transparent portion of the pipe; and a
drain on the pipe spaced a distance from the transparent portion
form removing water from the organic feed after the organic feed
has been treated with electromagnetic radiation.
6. The device of claim 5 wherein the electromagnetic radiation
generator generates radiation selected from the group consisting of
VHF, UHF, microwave, infrared, and laser radiation.
7. The device of claim 5 wherein the frequency of the
electromagnetic radiation produced by said electromagnetic
radiation generator is at least about 0.4 MHz.
8. The device of claim 5 wherein the frequency of the
electromagnetic radiation produced by said electromagnetic
radiation generator ranges from about 0.4 MHz to about 100 HHz.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a divisional application of co-pending U.S.
application Ser. No. 10/243,681, filed Sep. 16, 2002, which is a
divisional application of U.S. application Ser. No. 09/709,307,
filed Nov. 13, 2000, now U.S. Pat. No. 6,451,174, of which benefit
and priority is claimed hereby under 35 U.S.C. .sctn. 120 and the
disclosure of which are expressly incorporated by reference in
their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates broadly to a method and
apparatus for exposing a processing catalyst to high frequency
energy in the presence of an organic feed such as a hydrocarbon
feed. Further, the invention is directed to pulsing high frequency
energy to remove water and salt from organic feeds such as
petroleum feeds.
BACKGROUND OF THE INVENTION
[0003] In all oil processes using catalysts, deactivation of the
catalyst occurs due to poisoning of catalysts and due to coke
formation on the catalyst. The precipitation of heavy metals, such
as nickel, vanadium, iron, can also result in the deactivation of
the catalyst. The accumulation of coke on the catalyst causes
periodic (in case of cyclic operating plants) or continuous (for
plants with a moving catalyst layer) regeneration of the catalyst.
In some instances the plant must shut down to unload the catalyst
from the reactor for catalyst regeneration. Some systems have a
separate system for catalyst regeneration connected to the reactor.
With traditional methods for regenerating the catalyst there is the
loss of catalytic material, deterioration due to abrasion, and loss
in activity. Microwave energy has been applied to catalytic
hydroprocessing systems. However, these systems typically utilize a
plasma initiator in the reactor resulting in more complicated
hydroprocessing systems.
[0004] There is a need for a process that eleminates the need to
remove the catalyst from the hydroprocessing reactor and extends
the life of the catalyst. Further, there is a need for a less
complicated system that does not require plasma initiators.
[0005] Prior to hydroprocessing organic feeds, the organic feed
that comes from the oil field usually contains water. The oil must
generally be free of water before it can be sold or transported in
pipelines. Often the water is highly dispersed throughout the oil
forming an emulsion. This emulsion is very expensive to separate.
There is a need for cost effective method for removing trace
amounts of water from the organic feed.
SUMMARY OF THE INVENTION
[0006] The present invention includes a method for processing an
organic feed comprising the steps of exposing the organic material
to a catalyst, and applying more than one pulse of electromagnetic
radiation to at least a portion of said catalyst wherein each pulse
of electromagnetic radiation is sufficient to raise the temperature
of the catalyst above the temperature of the organic feed. The time
between each pulse is sufficient to allow the catalyst to cool to a
temperature of at least about the temperature of the organic feed.
Preferably, the pulses are applied while the catalyst is in contact
with the organic feed. The frequency between at least two pulses
may be different. Further, the time between pulses may be
different. Preferably, the electromagnetic radiation has a
frequency of at least about 1 MHz. The electromagnetic radiation
may have a frequency ranging from about 1 MHz to about 100 HHz. The
electromagnetic radiation may be selected from the group consisting
of VHF, UHF, microwave, infrared, and laser radiation. The pulse
may have a duration ranging on the order of about 10.sup.-6 to
about 10.sup.0 seconds. The time between pulses may range on the
order from about 10.sup.-6 to about 10.sup.2 seconds. The steps of
exposing the organic feed to the catalyst and applying more than
one pulse to at least a portion of the catalyst are preferably
effective for processing at least a portion of the organic feed.
The processing may be selected from the group consisting of simple
cracking, hydrocracking, hydrogenation, hydroisomerization,
hydrodesulfiuization, and reforming. The steps of exposing the
organic feed to the catalyst and applying more than one pulse to at
least a portion of the catalyst may be effective for reducing the
formation of coke on the catalyst. Preferably, each pulse is
sufficient to regenerate the activity of the catalyst. The organic
feed may be selected from the group consisting of hydrocarbon
liquids, hydrocarbon vapor, petroleum feed, liquified coal,
dispersed coal, oil, crude oil, fractions of oil, naptha, gasoline,
jet fuel, and combinations thereof.
[0007] The present invention also includes a method for dewatering
an organic feed comprising the steps of applying a pulse of
electromagnetic radiation to the organic feed sufficient to
vaporize at least a portion of a water droplet contained in the
organic feed to form a liquid-vapor water complex wherein the
liquid-vapor water complex rises to the surface of the organic feed
and forms a water complex, and removing the water complex from the
organic feed. More than one pulse of electromagnetic radiation may
be applied to the organic feed. More than one complex may combine
to form a water droplet sufficient to fall to a bottom portion of
the organic feed. In one embodiment, the pulse may be sufficient to
vaporize water in the organic feed. The method may further comprise
a heating pulse of electromagnetic radiation wherein the heating
pulse creates a temperature gradient over the volume of the organic
feed. The electromagnetic radiation may have a frequency of at
least about 0.4 MHz. The electromagnetic radiation may have a
frequency ranging from about 0.4 MHz to about 100 HHz. Preferably,
the electromagnetic radiation may be sufficient to induce salts
contained in the organic feed to concentrate in the liquid-vapor
water complex. The duration of the pulse may range on the order of
about 10.sup.-6 seconds to about 10.sup.1 seconds. The duration of
the pulse may range on the order of about 10.sup.-6 seconds to
about 10.sup.0 seconds. The organic feed may be selected from the
group consisting of hydrocarbon liquids, hydrocarbon vapor,
petroleum feed, liquified coal, dispersed coal, oil, crude oil,
fractions of oil, naptha, gasoline, jet fuel, and combinations
thereof. The water may be removed from the organic feed by
skimming. The electromagnetic radiation may be selected from the
group consisting of VHF, UHF, microwave, infrared, and laser
radiation.
[0008] Still further, the present invention includes a method for
removing salt from an organic feed comprising the steps of applying
a first pulse of electromagnetic radiation to the organic feed
sufficient to heat water contained in the organic feed to increase
the solubility of salt in the water and applying a second pulse
sufficient to vaporize a portion of the water containing the salt
to form a liquid-vapor complex and to bring the complex containing
the salt to the surface of the organic feed to form a liquid
complex, and removing the liquid complex from the hydrocarbon
liquid. The electromagnetic radiation may have a frequency of at
least about 0.4 MHz. Preferably, the electromagnetic radiation may
have a frequency ranging from about 0.4 MHz to about 100 HHz. The
duration of the first pulse may range on the order of about
10.sup.-6 seconds to about 10.sup.1 seconds. The duration of the
second pulse may range on the order of about 10.sup.-6 seconds to
about 10.sup.0 seconds. The organic feed may be selected from the
group consisting of hydrocarbon liquids, hydrocarbon vapor,
petroleum feed, liquified coal, dispersed coal, oil, crude oil,
fractions of oil, naptha, gasoline, jet fuel, and combinations
thereof. The water may be removed from the organic feed by
skimming. The electromagnetic radiation may be selected from the
group consisting of VHF, UHF, microwave, infrared, and laser
radiation.
[0009] The present invention includes a reactor comprising a column
having a channel therethrough and side walls that will reflect
electromagnetic radiation. Also included is an electromagnetic
radiation generator wherein the generator provides at least two
pulses having different frequencies, and a window positioned on a
side wall wherein the window is transparent to electromagnetic
radiation and allows radiation from the generator to reach the
channel. The electromagnetic radiation generator is positioned such
that each pulse of electromagnetic radiation is introduced in the
reactor at an angle and reflected over the length of the channel.
The electromagnetic radiation generator may generate radiation
selected from the group consisting of VHF, UHF, microwave,
infrared, and laser radiation. The frequency of the electromagnetic
radiation is preferably at least about 1 MHz. The frequency of the
electromagnetic radiation may ranges from about 1 MHz to about 100
HHz. In a preferred embodiment, the walls of the reactor are
stainless steel. The window may be ceramic.
[0010] Still further, the present invention includes a reactor
comprising a column having a channel therethrough and side walls.
The reactor includes a plurality of electromagnetic radiation
generator spaced a distance apart from one another along the length
of the column wherein each generator provides pulses of
electromagnetic radiation. Also provided is a window for each
generator positioned on the side wall wherein each window is
transparent to electromagnetic radiation and allows radiation from
the generator to reach the channel. The electromagnetic radiation
generator may generate radiation selected from the group consisting
of VHF, UHF, microwave, infrared, and laser radiation. The
frequency of the electromagnetic radiation is preferably at least
about 1 MHz. The frequency of the electromagnetic radiation may
range from about 1 MHz to about 100 HHz. The walls of the reactor
may be stainless steel. The window may be ceramic. Each generator
may pulse electromagnetic radiation at a different frequencies.
Each generator may generates at least two pulses of electromagnetic
radiation having different frequencies.
[0011] Further, the present invention includes a reactor comprising
a column having a channel therethrough and side walls. A plurality
of electromagnetic radiation generators are spaced a distance apart
from one another along the length of the column wherein each
generator provides a band of radiation across a cross-section of
the column along a portion of the length of the column. A window
for each generator is positioned on the side wall wherein each
window is transparent to electromagnetic radiation and allows
radiation from the generator to reach the channel. The
electromagnetic radiation generator may generate radiation selected
from the group consisting of VHF, UHF, microwave, infrared, and
laser radiation. The frequency of the electromagnetic radiation is
preferably at least about 1 MHz. The frequency of the
electromagnetic radiation may range from about 1 MHz to about 100
HHz. The walls of the reactor may be stainless steel. The window
may be ceramic. Each generator may generate electromagnetic
radiation at a different frequency. Each generator may generate
bands of radiation that spans different lengths of the column.
[0012] The present invention also includes a dewatering device
comprising a container for holding organic feed, an electromagnetic
radiation generator wherein the generator provides at least two
pulses having different frequencies, and a window transparent to
electromagnetic radiation positioned on the container to allow
electromagnetic radiation from the generator to reach at least a
portion of the organic feed. The electromagnetic radiation
generator may generate radiation selected from the group consisting
of VHF, UHF, microwave, infrared, and laser radiation. The
frequency of the electromagnetic radiation is preferably at least
about 0.4 MHz. The frequency of the electromagnetic radiation may
range from about 0.4 MHz to about 100 HHz.
[0013] The present invention includes a dewatering apparatus
comprising a pipe for transporting an organic feed wherein a
portion of the pipe is transparent to electromagnetic radiation.
Also included is an electromagnetic radiation generator wherein the
generator provides at least two pulses having different frequencies
through the transparent portion of the pipe. The apparatus include
a drain on the pipe spaced a distance from the transparent portion
form removing water from the organic feed after the organic feed
has been treated with electromagnetic radiation. The
electromagnetic radiation generator may generate radiation selected
from the group consisting of VHF, UHF, microwave, infrared, and
laser radiation. The frequency of the electromagnetic radiation is
preferably at least about 0.4 MHz. The frequency of the
electromagnetic radiation may range from about 0.4 MHz to about 100
HHz.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a plot showing the required temperature for
conversion for a catalyst as a function of time.
[0015] FIG. 2 is a diagram showing the mass exchange in the
classical system.
[0016] FIG. 3 is a diagram illustrating a scheme of mass exchange
in the present invention.
[0017] FIG. 4 is a diagram illustrating the internal temperature
and pressure of the catalyst particles under electromagnetic pulse
heating.
[0018] FIG. 5 is a diagram illustrating a scheme for the depression
of coke precipitation.
[0019] FIG. 6 is a diagram illustrating an embodiment of a reactor
in accordance with the present invention.
[0020] FIG. 7 is a diagram illustrating another embodiment of a
reactor in accordance with the present invention.
[0021] FIG. 8 is a diagram illustrating another embodiment of a
reactor in accordance with the present invention.
[0022] FIG. 9 is a diagram illustrating a model for the dewatering
and desalination process.
[0023] FIG. 10 is diagram illustrating a droplet concentration
mechanism under nonhomogeneous irradiation.
[0024] FIG. 11 is a diagram of a dewatering device in accordance
with one embodiment of the present invention.
[0025] FIG. 12 is a diagram of a dewatering apparatus in accordance
with one embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODHVIENTS
[0026] All oil processes that use catalysts are complicated by
catalyst deactivation. The deactivation is typically due to
poisoning the catalyst with sulfur and due to coke precipitation on
the catalyst. Further, the precipitation of heavy metals such as
nickel, vanadium, and iron results in catalyst deactivation. The
accumulation of coke catalyst requires regeneration of the
catalyst. In cyclic operating plants, the catalyst must be
periodically regenerated and in plants with a moving catalyst
layer, the catalyst must be continuously regenerated. Some
procedures require the plant to shut down so the catalyst may be
unloaded from the reactor followed by catalyst regeneration. Some
systems have a cyclic system where the catalyst is transferred from
the reactor to a regeneration column followed by the transfer of
the catalyst to the reactor without shutting down the system. The
regeneration column operates at high temperatures and requires
additional power and cost to operate. When the catalyst is
subjected to a regeneration process some of the catalyst material
is lost, the catalyst particles experience deterioration due to
abrasion, and the activity of the catalyst decreases. As a general
rule, it is not possible to completely restore the catalyst
activity during regeneration.
[0027] The time scale for the hydrocracking reaction is on the
order of microseconds. The life-time of individual catalyst
particles in the reactor column is on the order of a second. In
some technologies, the life of the catalyst is extended due to
millisecond time scale contact with the organic feed.
[0028] There is a need for a system and process that avoids coking
of the catalyst and eliminates the need for catalyst regeneration
systems or columns. Further, there is a need for a system and
process that does not interrupt the catalytic process by
withdrawing the catalyst from a reactor. Additionally there is a
need for taking advantage of the microsecond time scale of reaction
for hydrocracking by selectively activating the catalyst in the
reactor to maximize the increase of the activity of the catalyst in
the reactor.
[0029] The above problems are solved by applying a high frequency
field ("HF-field") to organic feeds in processing systems. As used
herein, "organic feed" includes but is not limited to hydrocarbon
liquids, hydrocarbon vapor, petroleum feed, liquified coal,
dispersed coal, oil, crude oil, fractions of oil, naptha, gasoline,
jet fuel, and combinations thereof. The raw material of the organic
feed and the associated petroleum products are known to be good
dielectrics. Catalysts activated for work in a reactor are also
good dielectrics. However, coke and metal precipitation on the
surface of the catalyst particles ("precipitation-deactivatoos")
are conductors. When an electromagnetic field is applied to the
catalyst in the organic feed, the heating of the
precipitation-deactivators occur while the organic feed remains at
the initial temperature. The result is that the rate of coke
formation remains constant due to invariant rates of hydration and
thermal cracking in oil crude. However, the rate of coke
sublimation sharply increases due to the interaction of coke with
hydrogen. This process causes the elimination or considerable
reduction of coke amounts on the surface of the catalyst. The
present invention can be used to suppress the coking of a catalyst
during hydroprocessing and reforming.
[0030] Deactivation of the catalyst occurs when carbon material
precipitates on the surface and in pores of the catalyst. The term
"coke" as used herein, is given its ordinary meaning known to those
skilled in the art and generally refers to the deposit of carbon on
the surface of the catalyst that results in deactivation of the
catalyst. The coke deposit may contain hydrogen as well as
nitrogen. The C:N ratio may approach to 2, and the properties
depend on the type of catalyst, the material being processed, and
the conditions of the catalytic process.
[0031] Typically, catalysts are used in the hydroprocessing,
reforming and cracking of oil. All of these processes are performed
in the presence of a reducing gas such as hydrogen.
[0032] Hydroprocessing in the oil refining industry is the
processing of oil in the presence of the catalyst and hydrogen
under certain conditions. Hydroprocessing includes, but is not
limited to, processes know as hydrocracking, hydroclearing,
hydrogenation, hydroisomerization, hydrodesulfurization, and
hydrodenitration. Hydrocracking is a process in which the molecular
mass of the raw material is reduced. Typically the molecular mass
of the material is reduced by at least 50% during hydrocracking.
Hydroclearing is a process where the molecular mass of a small part
(less than 10%) of the raw material is reduced. Virtually the
molecular mass of the raw material has not changed substantially.
Hydrodesulfurization is a process that removes sulfur from the raw
material and hydrodenitration is a process that removes nitrogen
from the raw material.
[0033] Various hydroprocessing technologies include preprocessing
an organic feed to eliminate sulfur, nitrogen and metals that can
contaminate reforming catalysts. Also important is the elimination
of sulfur from kerosene, jet, diesel and furnace fuel. Other
hydroprocessing systems include hydrogenation of olefinic and
aromatic molecules. Further, hydroprocessing technologies may
improve the quality of lubricating oil such as the color, color
stability, storing stability at the expense of the resinification
reducing, and reducing the acidity. The preprocessing of
catalytically cracked gas-oil crude in a boiling layer can increase
the output of liquid products, thereby reducing catalyst
consumption. Hydroprocessing can reduce corrosion by reducing the
sulfur content in the organic feed. Preprocessing may reduce
nitrogen, metals and aromatic substances contained in the raw
material. Hydroprocessing systems are also important in reducing
the sulfur content in stillage residuals of atmospheric and vacuum
distillation systems to improve the fuel and prepare products for
further processing and improving their conversion.
[0034] Catalytic reforming is a method of oil processing, in which
naphtha (C.sub.5, 28-200.degree. C.) is passed through a series of
catalytic reactors being under high temperature and moderate
pressure (7-10 atm.) to increase the content of aromatic
hydrocarbons or to increase the octane number in gasoline. As a
general rule, the parent naphtha is subjected to a preliminary
hydroprocessing step to eliminate impurities that inhibit the
reaction or contaminate the reforming catalyst. Naphtha can be
obtained directly from crude oil or by the fractionation of other
oil processing products such as through coking. Fundamental
reactions of reforming are dehydrogenation, naphthene
isomerization, dehydrocyclization, isomerization of paraffins and
hydrocracking.
[0035] Reforming plants generally produce motor fuels, such as
gasoline, and aromatic compounds. During the reforming process,
hydrogen is generated which can be used in other hydroprocessing
steps.
[0036] Catalytic cracking is the thermocatalytic processing of the
oil to reduce the molecular mass of the oil. The process is
typically carried out at 470-530.degree. C. and 70-370 kPa with a
silica-alumina supported catalyst. The duration of raw
vapor-catalyst contact about 2.5-5 s. Cracking is applied to
gas-oils from straight-run distillations, vacuum gas-oils,
fractions of products generated during the hydrocracking, coking,
and deasphalting. The most preferable raw material is that one
having high content of naphthenic and paraffin hydrocarbons.
Fundamental reactions of catalytic cracking are the cleaving of a
carbon-carbon bond, isomerization, dealkylation,
dehydrocyclization, polymerization, and condensation. The catalysts
are typically sensitive to metal contamination. To prevent the
catalyst from being contaminated the raw material can undergo
hydroclearing to remove amounts of metals such as V, Ni, Cu, Fe, Na
prior to catalytic cracking the material.
[0037] At temperature of 1000.degree. C. the formation coke, C,
goes according to the reactions:
2H.sub.2O+C=>CO.sub.2+2H.sub.2-18.0 kcal (1)
2H.sub.2O+C=>CO.sub.2+2H.sub.2+18.2 kcal (2)
[0038] During hydroprocessing and reforming, the last reaction is
typical. The free energy change is calculated by formula .DELTA.
.times. .times. F = RT .function. ( ln .function. ( p CH 4 p H 2 2
) - ln .times. .times. K p ) ( 2 ' ) ##EQU1##
[0039] where K.sub.p is the reaction equilibrium constant. The
evolving of free carbon corresponds to the inequality
.DELTA.F>0.
[0040] The reaction (2) describes interaction of methane and
hydrogen. The thermal dissociation of hydrocarbon corresponds to
the reaction C n .times. H m = nC + m 2 .times. H 2 ( 3 )
##EQU2##
[0041] The reaction (3) is an inconvertible one, since the
elementary structures such as methane, propane, and butane are
formed during the synthesis of hydrocarbons from carbon and
hydrogen. Therefore, the reaction (3) should be considered together
with (1) and (2). For hydroprocessing, equations (2) and (3) must
be considered together.
[0042] In case of liquid fuel, the hydrocarbon part is usually
described according to formula C.sub.nH.sub.1.5n, i.e. m=1.5n (see
formula (3)). Assuming that methane only is generated, the balance
between the parent and final products in (3) and (2) respectively
is C n .times. H m m 4 .times. CH 4 + C .function. ( n - m 4 )
##EQU3##
[0043] Taking m into account, n - m 4 = 0.625 .times. n > 0.
##EQU4## The complicated catalytic dissociation of hydrocarbon is
inevitably accompanied by evolution of free carbon in the form of
coke. In a reducing atmosphere of hydrogen the equation becomes the
following: C n .times. H m + p .times. H 2 n .times. CH 4 + 1 2
.times. ( 2 .times. p + m - 4 .times. n ) .times. H 2 ( 4 )
##EQU5##
[0044] A necessary condition for the reduction in coke formation
appears to be: 2p+m-4n>0 (5)
[0045] This will vary depending on the type of hydroprocessing
reactions.
[0046] The condition of type (5) is a necessary one, but not a
sufficient one. The sublimation of carbon is provided by chemical
reactions of types (1) and (2). It is necessary for these reactions
to go at a comparatively high rate. Letting the rate constant of
the reaction (3) be equal to K.sub.n results in n moles of free
carbon being obtained from one mole of complicated hydrocarbon. The
conversion rate for one mole of carbon (according to the reaction
(2) is equal to NsK.sub.1 (K.sub.p P.sub.CH-P.sup.2.sub.H) Where
K.sub.1 is the kinetic coefficient. If we omit methane
contribution, coking does not occur, if the following inequality is
fulfilled: nK n .ltoreq. K 1 .times. K P .times. NSp H 2 2 , o
.times. r .times. .times. p H 2 .gtoreq. nK n K 1 .times. K P
.times. NS ( 6 ) ##EQU6##
[0047] where N, S is the granules' concentration and the surface
area of a granule covered by coke, respectively. If the hydrogen
pressure in a system is less than a critical value p C = nK n K 1
.times. K p .times. NS ##EQU7## then the accumulation of coke on
the catalyst takes place. If p.sub.H<p.sub.C, coke is not only
unaccumulated, but soot is also generated before the carbon turns
into gaseous hydrocarbons.
[0048] The values of the constants K.sub.n and K.sub.1K.sub.p and
their dependence on temperature are known. K.sub.p follows the
following equation: 1 .times. .times. g .times. K p = 1 .times.
.times. g .function. ( p CH 4 p H 2 2 ) = 4732 T - 5 .times. ,
.times. 737 ( 7 ) ##EQU8##
[0049] K.sub.p is measured in atm.sup.-1. Values for K.sub.p
corresponding to the temperature range of 350-1500.degree. C. are
shown in Table I. TABLE-US-00001 TABLE I Values of equilibrium
constants for the reaction (2) Temp., .degree. C. K.sub.p,
atrm.sup.-1 350 43.441 400 13.198 450 4.749 500 1.944 550 0.8863
600 0.4425 650 0.2383 700 0.1371 750 6.47*10.sup.-2 800
5.328*10.sup.-2 850 3.555*10.sup.-2 900 2.463*10.sup.-2 950
1.763*10.sup.-2 1000 1.304*10.sup.-2 1050 9.870*10.sup.-2 1100
7.677*10.sup.-3 1150 6.086*10.sup.-3 1200 4.922*10.sup.-3 1250
4.053*10.sup.-3 1300 3.393*10.sup.-3 1350 2.880.10.sup.-3 1400
2.478*10.sup.-3 1450 2.158*10.sup.-3 1500 1.903*10.sup.-3
[0050] As shown above, more complicated gaseous hydrocarbons such
as saturated hydrocarbons, ethane, propane, and butane can be
generated concurrently with methane according to reaction (3).
Non-saturated hydrocarbons can also be generated, although these
processes are suppressible in a hydrogen atmosphere during
hydroprocessing. Unfortunately, the equilibrium constants for these
complicated hydrocarbons are unknown. However, it is likely that
the evolution of these complicated hydrocarbons is limited because
of the necessity to include a much greater number of carbon atoms
and hydrogen molecules in the elementary processes. The formation
of similar hydrocarbons can affect the sublimation of carbon at the
expense of methane generation, owing to a concentration reduction
on one hand, and possible free carbon generation due to the
dissociation of the complicated hydrocarbons on the other hand. The
water vapor and hydrogen equilibration of the conversion reactions
for some higher hydrocarbon are known values to those skilled in
the art. The registration of the coke, generation reactions and its
sublimation is arduous enough and requires special consideration.
However, it's necessary to keep in mind, that according to
experimental data, methane only is produced, and there are no
higher hydrocarbons among the reaction products at a temperature
higher than 600.degree. C. Seemingly, the kinetic coefficient
K.sub.1 poorly depends on temperature.
[0051] The interaction of methane homologs and saturated
hydrocarbons with water vapor and hydrogen can be described using
the following basic reactions: [0052] A1) conversion of ethane:
C.sub.2H.sub.6+2H.sub.2O=2CO+5H.sub.2-83.0 kcal, [0053] A2)
conversion of propane: C.sub.3H.sub.8+3H.sub.2O=3CO+7H.sub.2-119.0
kcal, [0054] A3) conversion of ethylene:
C.sub.2H.sub.4+2H.sub.2O=2CO+4H.sub.2-54.1 kcal, [0055] A4)
conversion of propylene: C.sub.3H.sub.6+2H.sub.2O=2CO+6H.sub.2-97.0
kcal, [0056] A5) hydrogenation of ethane:
C.sub.2H.sub.6+H.sub.2=CH.sub.4+15.6 kcal, [0057] A6) hydrogenation
of propane: C.sub.3H.sub.8+2H.sub.2=3CH.sub.4+28.9 kcal.
[0058] Table II shows values of the equilibrium constants for these
reactions where K A 1 = p CO 2 + p H 2 5 p C 2 .times. H 6 .times.
p H 2 .times. O 2 , K A 2 = p CO 3 + p H 2 7 p C 3 .times. H 8
.times. p H 2 .times. O 3 , K A 3 = p CO 2 + p H 2 4 p C 2 .times.
H 4 .times. p H 2 .times. O 2 , K A 4 = p CO 3 + p H 2 6 p C 3
.times. H 6 .times. p H 2 .times. O 3 , K A 5 = p CH 4 2 p C 2
.times. H 6 .times. p H 2 , K A 6 = p CH 4 3 p C 3 .times. H 8
.times. p H 2 2 . ##EQU9## TABLE-US-00002 TABLE II Equilibration
constants for reactions of methane homologs and unsaturated
hydrocarbons conversion by water vapor and hydrogen Temp Reactions
.degree. C. A1 A2 A3 A4 A5 A6 327 .sup. 3.805*10.sup.-7 5.686*
10.sup.-8 0.1065 5.592*10.sup.-4 1.50*10.sup.6 .sup. 4.62*10.sup.11
427 .sup. 1.467*10.sup.-2 0.2015 69.759 49.678 2.03*10.sup.5 .sup.
1.04*10.sup.10 527 43.281 11.775*10.sup.4 9.437*10.sup.3
2.757*10.sup.5 4.47*10.sup.4 5.90*10.sup.8 627 2.268*10.sup.4
1.331*10.sup.8 4.528*10.sup.5 2.394*10.sup.8 1.33*10.sup.4
5.98*10.sup.7 727 3.505*10.sup.6 1.716*10.sup.11 11.018*10.sup.7
5.530*10.sup.10 4.97*10.sup.3 9.15*10.sup.6 827 2.184*10.sup.8
6.084*10.sup.13 1.308*10.sup.8 4.780*10.sup.12 2.22*10.sup.3
1.97*10.sup.6 927 6.902*10.sup.9 8.175*10.sup.15 1.109*10.sup.9
1.988*10.sup.14 -- --
[0059] When the water vapor is doubled, methane homologs and
olefins are almost completely converted at 400-500.degree. C.
[0060] To complete the picture, the reactions of methane conversion
include the following reactions: [0061] A7)
CH.sub.4+H.sub.2O=CO+3H.sub.2-49.3 kcal, [0062] A8)
CH.sub.4+CO.sub.2=2CO+2H.sub.2-59.3 kcal, [0063] A9)
CH.sub.4+0.5O.sub.2=CO+2H.sub.2+8.5 kcal, [0064] A10)
CH.sub.4+H.sub.2O T CO+3H.sub.2+9.8 kcal.
[0065] Table III contains the values of the equilibrium constants
for methane reactions: K A 7 = p CO + p H 2 4 p CH 4 .times. p H 2
.times. O , K A 8 = p CO 2 + p H 2 2 p CH 4 .times. p CO 2 , K A 9
= p CO + p H 2 2 p CH 4 .times. p O 2 0.5 , K A 3 = p CO 2 + p H 2
p CO .times. p H 2 .times. O , ##EQU10## TABLE-US-00003 TABLE III
Values of constants for reactions of methane conversion Reactions
Temp., .degree. C. A7 A8 A9 A10 327 5.058*10.sup.-7 1.868*10.sup.-8
2.169*10.sup.12 27.08 427 2.687*10.sup.-4 2.978*10.sup.-5
1.028*10.sup.12 9.017 527 3.120*10.sup.-2 7.722*10.sup.-3
6.060*10.sup.11 4.038 627 1.306 0.5929 4.108*10.sup.11 2.204 727
20.33 19.32 3.056*10.sup.11 1.374 827 3.133*10.sup.2 3.316*10.sup.2
2.392*10.sup.11 0.9444 927 2.473*10.sup.3 3.548*10.sup.3
1.957*10.sup.11 0.6966 1027 1.428*10.sup.4 2.626*10.sup.4
1.652*10.sup.11 0.5435 1127 6.402*10.sup.4 1.452*10.sup.5
1.425*10.sup.11 0.4406
[0066] The structure of converted gas is determined by a position
of the equilibrium of independent reactions (A7) and (A10). The
reaction (A8) is a derivative, and the reaction (A9) can be
omitted, since in the temperature range of 327-1127.degree. C., the
K.sub.A9 equilibrium constant is so great that the concentration of
nonreacting oxygen is practically equal to zero in the equilibrium
gas mixture. Added oxygen will react with hydrogen, generating
water vapor.
[0067] The values of the equilibrium constants for complicated
hydrocarbons (A1)-(A6) are much higher than for the reactions of
methane conversion with water vapor (A7)-(A10). According to
experimental data, at temperatures higher than 600.degree. C., only
methane is present in the products of the reaction, and higher
hydrocarbons are absent.
[0068] There is definite clarity concerning K.sub.p, but the
situation with K.sub.n is slightly indefinite. First, though the
reaction of catalytic dissociation is written by the simple formula
(3), this is a general formula and there is a range of intermediate
products, which also react, and there is a series of pathways
resulting in the final product. While K.sub.p is understood and
depends on the parent raw structure, it can only roughly be reduced
to the dependence on n.
[0069] Turning now to the mechanism of coke generation. Coke
generation is the most frequent reason for deactivation of
catalysts in hydroprocessing, reforming and cracking. To keep the
necessary conversion rate while minimizing coke precipitation, it
is necessary to increase the operation temperature of a process.
Currently, increasing the temperature becomes difficult because of
the power deficiency of the furnace and limited heat resistance of
the furnace materials. As a result, large product losses are
realized during hydrocracking. In cyclic plants they have to
terminate the cycle in order not to reduce the product output.
[0070] Therefore evaluation of the rate of coke generation is
necessary for designing a conventional reactor for the appropriate
process. The rate of coke generation increases as the temperature
in the reactor increases, the hydrogen partial pressure decreases,
the conversion grade increases (for example, sulfur extraction at
desulfarization), the boiling-point of the raw product increases,
and as the content of cracked products in raw material increases.
By the end of the cycle, the coke percentage in the catalyst can
vary from 3-4% for light straight-run naphtha and up to 25% and
more for residual oils. The selectivity of the catalytic process
(e.g., reforming or cracking) can change with the growth of coke
precipitation. Frequently it is economically justified to terminate
the process before reaching the thermal limit of a plant. The
catalyst must be regenerated to recover the activity of the
catalyst by removing the accumulated coke precipitation from the
surface of the catalyst.
[0071] Coke generation can begin under the same conditions with or
without the presence of a catalyst, but under certain conditions
the catalyst can accelerate the generation and precipitation of
coke. The generation of coke particles on a catalyst in a
gas-synthesis atmosphere (mixture of .about.50% H.sub.2, .about.40%
CO and CO.sub.2, .about.10% CH.sub.4) has been previously studied.
The presence of metals from the iron group in the catalyst causes
increased coke generation. The presence of strong alkalis such as
K.sub.2O, increase the rate of coke generation. If the catalyst
contains compounds such as SiO.sub.2 and Al.sub.2O.sub.3, which are
able to react with alkali, the basicity of the catalyst decreases
significantly while the rate of free carbon generation remains
low.
[0072] Catalysts for oil processing typically use aluminum oxide or
alumina in .eta.- or .gamma.-form as a support. Further some
catalysts utilize zeolites. The iron and sodium oxide contents are
limited to: Fe (0.03-0.05 mass %), and Na.sub.2O (0.03-0.09 mass
%). The catalyst granules serve as a vehicle for the carbon
particles, which growth occurs at the expense of carbon
precipitation and fastening. The catalyst itself does not influence
the rate of free carbon generation.
[0073] Catalysts for hydroprocessing are typically mixtures of
transition metals dispersed over the surface of support. Both
molybdenum and tungsten are typically used to provide high activity
of the catalyst. Cobalt and nickel do not possess significant
activity, but act as a promoter by increasing the activity of the
molybdenum or tungsten catalysts. Tungsten catalysts are usually
promoted with nickel, and molybdenum catalysts are typically
promoted with nickel or cobalt.
[0074] Table IV itemizes some chemical components and physical
properties of the four typical catalysts of hydroprocessing. These
include (1) a cobalt-molybdenum low density catalyst having
particles of 3.2 mm diameter, (2) a nickel-molybdenum high density
catalyst having particles of 1.6 mm diameter, (3) a
cobalt-nickel-molybdenum catalyst having particles 1.3 mm long and
of the same diameter, and (4) a cobalt-molybdenum catalyst having
particles of 1.0 mm diameter, which contains silicon oxide and is
intended for reactors with boiling or extended layer of the
catalyst. TABLE-US-00004 TABLE IV Properties of typical
hydroprocessing catalysts Components (mass % of dry substance) 1 2
3 4 Chemical composition and properties MoO.sub.3 15.0 18.5 16.2
13.5 CoO 3.2 -- 2.5 3.2 NiO -- 3.3 2.5 -- SiO.sub.2 -- -- 4.0
Physical properties Specific surface (m.sup.2/g) 310 180 230 330
Pores volume (cm.sup.3/g) 0.80 .53 0.52 0.60 Particles diameter
(mm) 3.2 1.6 1.3 1.0 Average length (mm) 5.8 4.6 4.1 3.3 Fill
weight (g/cm.sup.3) 0.58 0.83 0.74 0.70 Average crushing strength
per unit 1.91 1.41 1.50 1.00 of layer length (kg/mm)
[0075] The structure of catalysts listed in Table III is typically
supplemented up to 100% with aluminum oxide and with small
additives of SO.sub.4 (0.3-2 mass %), Na.sub.2O (0.03-0.09 mass %)
and Fe (0.03-0.05 mass %).
[0076] Fresh and ready hydroprocessing catalysts typically contain
metals such as, Co, Ni, and Mo in oxide form. Within the reactor,
these metals are transferred into the sulfide form to provide the
required activity and selectivity of the catalyst.
[0077] At the present time, reforming catalysts typically contain
an aluminum oxide support coated by precious metals. Aluminum oxide
may be either the n or x crystalline form.
[0078] The .eta.-form contains more acid centers than the x-form,
and serves as a support for most of the monometallic platinum
catalysts. It has more developed initial surface. During catalysis
and regeneration, the surface area of the support is reduced. The
diminution of the surface area limits the service life of the
catalyst to only a few cycles.
[0079] The .gamma.-oxide has less acidity than the .eta.-form, but
is more thermostable and keeps the initial surface area during the
exploitation and regeneration better than the .eta.-oxide. The
reforming catalysts based on .gamma.-oxide can undergo several
hundreds of regeneration cycles before replacement is necessary due
to surface area reduction. The lower acidity of the catalyst being
placed on .gamma.-oxide is compensated by adding an appropriate
amount of halogen to the catalyst.
[0080] Reforming catalysts typically have a specific surface area
of 175-300 m.sup.2/g and a total pore volume (measured with water
filling) of 0.45-0.65 cm.sup.3/g. The catalyst particles typically
have the form of cylinders or balls with a diameter of 1.6-2.1 mm.
The crushing strength of these catalysts is around 1.3-3.2 kg/mm
and the density is ranges from about 0.51-0.78 g/cm.sup.3.
[0081] Various metals are used with reforming catalysts. Platinum
is often used. Some reforming catalysts include rhenium to form a
platinum-rhenium catalysts. Rhenium increases the stability of the
catalyst when coke is generated, allowing the physical conditions
of the process to be raised, while preserving the duration of the
cycle to be the same as the monometallic platinum catalyst.
Typically, platinum catalysts will contain other metals such as,
tin, germanium, and lead. The loading of metals on the support are
typically less than 1% by mass of the reforming catalyst.
[0082] Commercially available catalysts usually contain precious
metals either in oxide, or in reduced and sulfurized form. If the
catalyst is in the oxide form, the catalyst has to be reduced and
sulfurized before being exposed to the organic feed. To use the
catalyst, about 0.06% by mass of the catalyst is injected into each
reactor after the reduction. For these purposes they usually use
H.sub.2S.
[0083] At present time amorphous and crystalline aluminosilicates
are used as the cracking catalysts, and the most, widely adopted
ones are the very crystalline aluminosilicates known generally as
zeolites. Industrial applications include both X and Y type
zeolites having the structure represented by the formula:
Na.sub.pAl.sub.pSi.sub.192-pO.sub.384gH.sub.2O
[0084] where p varies from 96 to 74 for X and from 74 to 48 for Y,
and g ranges from 270 down to 250 as the aluminum content
decreases. The industrial catalysts range from about 10 to about
20% by mass zeolite. The zeolite has an abrasion resistant
aluminosilicate matrix that makes up the main mass of the catalyst.
The matrix has a developed pore system, which provides the access
to active zeolite centers residing inside the particles. Relative
to cracked raw material the matrix is almost completely inert. The
activity of industrial zeolite catalysts is conditioned solely by
the presence of zeolite. The industrial catalysts are usually
subjected to ionic interchange with ionic mixtures, rare-earth
metals, ammonium, and magnesium ions or with mixtures of the
latter.
[0085] In case of the fresh catalyst, the specific surface area of
zeolites range from about 550-650 m.sup.2/g, whereas the same
parameter for the matrix depends on type of the catalyst and varies
from 40 to 350 m.sup.2/g. Usually matrices with low specific
surface areas are used, since such catalysts have reduced
selectivity of coke generation and they are stable against the
metal contamination. Industrial catalysts with a specific surface
area of about 100-400 m.sup.2/g typically have a total pore volume
of 0.20-0.50 cm.sup.3/g and an average pore diameter of about
5.0-5.0.times.10-.sup.9 m.
[0086] The comparison of temperatures for the beginning of coke
generation under the same conditions with and without the catalyst
show that the beginning of coke generation corresponds to the
beginning of thermal cracking.
[0087] The breaking of the C--C-linkage followed by the formation
of two large short-lived radicals is the primary reaction during
cracking. Alkene molecules and relatively steady radicals such as
H, CH.sub.3, C.sub.2H.sub.5, are generated at the break on the
weakest linkages. Interacting with a hydrocarbon molecule, the
radicals will convert into H.sub.2, CH.sub.4, and C.sub.2H.sub.6,
respectively, with the generation of a new radical which continues
the chain reaction. Reactions of dehydrogenation, isomerization,
polymerization and condensation of intermediate and parent
substances occur simultaneously with cracking. As a result of the
two last processes, there is so-called cracking residue that are
fractions that typically have a boiling point higher than
350.degree. C. and oil coke is generated. Cracking can only occur
in presence of heat and the catalyst. Thermal cracking begins at
about 300-350.degree. C. From 370-425.degree. C., the rate of
cracking doubles as the temperature is increased by 12.degree. C.
From 450-600.degree. C. the rate of cracking doubles as the
temperature is increased by 14-17.degree. C. An increase in
duration of the process favors coke generation and
accumulation.
[0088] Thermal cracking causes the formation of hydrocarbon
radicals. Due to convection-diffusion interchange, the radicals
reach the exterior surface of the catalyst particles. Because the
radicals are short-lived, most radicals are only able to reach the
exterior surface of the particle and not get into the pores of the
particle. The initial soot particles can form on the surface of the
particle. As discussed below, soot may form on any alkali center
that may be present on the surface of the catalyst. Similar
particles effectively seize radicals, and, in particular, those
having a carbon atom at the extremity. The break-off of an adsorbed
radical causes the growth of carbon on the catalyst. The growth of
carbon on catalyst granule surfaces limits access to interior
active centers, and eventually blocks these centers resulting in
deactivation of the catalyst. Otherwise, when soot formation takes
place directly on the catalyst's active surface (for example, in
case of iron catalysts in Fisher-Tropche process) the carbon
particles are generated inside the catalyst particles causing their
enlargement and destruction.
[0089] It is necessary to discuss the extent of coke and metal
precipitation in various technological processes. This value,
naturally, depends on the type of raw material being processed
since deactivation of the catalyst also decreases the selectivity
of the process. As was mentioned above, during hydroprocessing, the
coke content on the catalyst can vary from 3-4% by mass for the
light straight-run oil- and to over 25% by mass for residual oils.
Further crude oils typically contain nickel and vanadium. The raw
material having high content of these metals should be subjected to
hydrodesulfurization or preliminarily upclassed before further
stages. The amount of nickel and vanadium precipitated onto wasted
hydroprocessing catalyst varies within a wide range and depends on
the content of these metals in the raw material and the type of the
catalyst and quality requirements for the product. Usually these
metals account from about 10 to about 30% by mass of the wasted
catalyst. Metals precipitate on the exterior surface of the
catalyst, and the metal accumulation accelerates coke generation.
Typical iron content ranges from about 0.1-1.0% by mass.
[0090] During catalytic reforming, the working cycle duration
varies within a wide range depending on the rate of coke
precipitation, which affects the product quality and is determined
by parameters of the process and properties of raw material. The
coke content on a bimetallic catalyst working in half-regenerative
plant ranges from about 20-25% by mass. Coke precipitation during
cracking reaches about 10-20% of the catalyst's mass.
[0091] Usually the regeneration of the catalyst is implemented when
coke precipitation gets to about 1-2%. In this situation, the
particle surfaces are not completely covered with coke and the
catalyst retains its activity. Cracking as well as hydroprocessing
of heavy raw material containing heavy metals such as Ni, V, and
Fe, results in fast precipitation on the exterior surface of the
catalyst. These ratios intensify the formation of coke and light
gases. The regeneration of the exterior particle's surface passes
at the expense of abrasion in the moving catalyst. Thus, the metal
precipitation is removed, but it results in large losses and rises
in the price of the catalyst. The metal content on the catalyst can
reach 25% by mass.
[0092] The model for coke generation correlates with the observed
kinetics of coke accumulation. FIG. 1 shows a typical curve for
hydroprocessing catalyst deactivation. The plot can be divided into
an initial stabilization region (1) where the reaction temperature
increases by 5-10.degree. C. during first days the catalyst, a
constant rate of deactivation region (2), and an accelerated
deactivation section (3) where the rate of deactivation rapidly
increases due to an avalanche coking effect and temperature
growth.
[0093] In the initial stabilization region (1), radicals of
hydrocarbon neutralize the alkaline centers initially available on
the catalyst's surface. During the constant rate of deactivation,
the centers become growth centers for soot particles, and linearly
gain mass. During the region of accelerated deactivation, growth of
centers results in increase of radical seizure causing nonlinear
catalyst deactivation.
[0094] The coke generation mechanisms were discussed with reference
to catalytic cracking. A possible classification method for these
mechanisms is as follows:
[0095] 1) Coke being obtained by the dehydrogenation of residual
nonvolatile fractions or thermal cracking of the organic feed;
[0096] 2) Coke being obtained by the noncatalytic method, but due
to metals preliminary precipitating out of the organic feed onto
the catalyst surface;
[0097] 3) Coke remaining in the catalyst's pores; and
[0098] 4) Coke being generated directly during catalytic
cracking.
[0099] The last mechanism is considered to be the most preferable
for catalytic cracking. The development of the coke generation
concept discussed above is applicable to hydroprocessing and
reforming.
[0100] The mathematical model for coke generation will now be
discussed. Let n.sub.0 be the concentration of raw molecules and
n.sub.p be the concentration of radicals. If temperature of thermal
cracking activation is T.sub.a, then the following amount of
radicals are generated per unit time: n 0 .times. B .times. .times.
exp .function. ( - T a T ) ##EQU11##
[0101] where B is constant depending on the amount of carbon atoms
n in a raw molecule. T.sub.a is an average value.
[0102] For the same volume, the following number of radicals perish
per unit time can be represented as n.sub.pn.sub.0C, where C is the
constant depending on n.
[0103] At equilibrium, we have following concentration of radicals:
n p = A 1 .times. exp .function. ( - T a T ) ##EQU12##
[0104] where A.sub.1=B/C and depends on n. It is important that
n.sub.p does not depend on concentration of raw molecules, while
the inequality n.sub.p<<n.sub.0 exists.
[0105] Let there be N particles of the catalyst in unit of volume
where S is the exterior surface of a particle. A number of alkaline
centers that interact with radicals are designated as f(c), where c
is the alkaline elements concentration in the catalyst. If the
elements are uniformly distributed over the volume of the catalyst
particles and they are not surface-active, then
f(c).about.c.sup.2/3. Putting in the mass transfer constant L,
which depends on n, we can write the formula for the rate of soot
accumulation on a single particle ( d m d t ) ##EQU13## and in the
volume unit of the catalyst ( d M d t ) .times. : ##EQU14## d m d t
= aSf .function. ( c ) .times. n p = ASf .function. ( c ) .times.
exp .function. ( - T a T ) , d M d t = N .times. d m d t ( 8 )
##EQU15##
[0106] where A=.alpha.A.sub.1 and depends on n.
[0107] The most interesting point is temperature dependency. Soot
accumulation has an exponential character. If we use data on
thermal cracking, T.sub.a.about.25300 K (by the formula
Ta=(.DELTA.T).sup.-1 T.sup.2 ln 2). The value of T.sub.a depends on
type of the raw material. However, the value of T.sub.a discussed
above will be used for evaluations below.
[0108] Besides thermal cracking, a certain contribution to soot
generation can be given by hydrocracking, which is catalyzed by
acid centers of the catalyst. It is a very slow reaction and its
contribution can also be calculated.
[0109] The balance between carbon precipitation and its chemical
sublimation determines the rate of accumulation. To describe the
rate, the expression for the rate of accumulation (2) and the
formula (8) should be combined. If methane's influence is
considered, the following equations results: d m d t = - K 1
.times. NS .function. ( K p .times. p H 2 2 - p CH 4 ) + NSAf
.function. ( c ) .times. exp .function. ( - T a T ) ( 9 )
##EQU16##
[0110] If the concentration of methane is small, the equation
reduces to: d m d t = - K 1 .times. NSK p .times. p H 2 2 + NSAf
.function. ( c ) .times. exp .function. ( - T a T ) ( 9 ' )
##EQU17##
[0111] At equilibrium, we have d m d t = 0. ##EQU18## The following
paragraph, with the help of this condition, will determine the
equilibrium pressure of hydrogen P.sub.q with no increase of coke
precipitation. If we use this notation, we can recreate the formula
(9') for coke precipitation on the catalyst: d m d t = - NSK 1
.times. K p .function. ( p H 2 2 - p CH 4 2 ) ( 9 '' )
##EQU19##
[0112] The inequality (6) defining conditions for nonexistence of
coke generation was obtained above. For K.sub.p, there is the
expression (7). The coke generation velocity constant K coincides
with the right part of the expression (8) for dM/dt. The condition
(6) granting (7)-(9) can be written as: P H 2 .gtoreq. p C = n K 1
.times. K p .times. Af .function. ( c ) .times. exp .function. ( -
T a 2 .times. T ) ( 10 ) ##EQU20##
[0113] Taking into account that K.sub.p depends on T, we can
explicitly extract the expression for p.sub.c: p c = C .times.
.times. exp .function. ( - T a - T p 2 .times. T ) , ( 11 )
##EQU21##
[0114] where T.sub.p=4732 K (see (7)). Since T.sub.a-T.sub.p>0,
the pressure p.sub.c is an increasing function of T. It means if at
some temperature the condition (10) is met and coke is not evolved,
the condition (10) is broken as the temperature rises and the
system pressure remains the same and coke evolving begins.
[0115] This picture is correct if the temperatures of the catalyst
particles and the raw materials are identical. In this case it is
necessary to analyze the situation, when the temperature
heterogeneity arises in the reactor, and namely, when the
temperature of the catalyst particles exceeds the temperature of
the raw being processed. Let T.sub.1 be the temperature of the raw
material in the reactor, and T.sub.2 is the temperature of the
catalyst particles. Then the condition (6) can be represented as
(analog to (9)-(10)): p H 2 .gtoreq. p C = C .times. .times. exp
.function. ( - T a 2 .times. T 1 + T p 2 .times. ( T 1 + .DELTA.
.times. .times. T ) ( 12 ) ##EQU22##
[0116] where T.sub.2=T.sub.1+.DELTA.T. It is obvious the value of
p.sub.c is the decreasing function of the catalyst overheating
(.DELTA.T). In the range of 300-350.degree. C., if
.DELTA.T.about.70.degree. C., the value of p.sub.c is reduced by
half. The rate of chemical sublimation increases 4 times (see 9').
Qualitatively the situation with coke generation looks as if
hydrogen pressure in a system is increased by 2 fold.
[0117] The value of hydrogen pressure increases for suppressing the
coke generation and depends on many parameters such as process
temperature, pressure, and raw material structure. A 2 fold
increase of hydrogen pressure is usually more than enough to
suppress coke generation.
[0118] It is appropriate to study the formula (9'') closer.
Recreating formula (9'') provides: d m d t = - [ NSK 1 .times. K p
.function. ( p H 2 + p C ) ] .times. ( p H 2 - p C ) ##EQU23##
[0119] If the difference (p.sub.H2-p.sub.C) changes its sign, and
taking into account the expression: p H 2 - p C .function. ( T 1 +
.DELTA. .times. .times. T ) p H 2 - p C .function. ( T 1 ) = K ,
##EQU24##
[0120] the rate of hydrosublimation at the temperature of
(T.sub.1+T) will be K times greater than its rate of precipitation
at temperature T.sub.1. This expression is important when choosing
the processing time for removing coke from the catalyst. In this
case, the period when the catalyst is processed in the field is K
times less than the working time for coke accumulation.
[0121] With the above concepts developed, the effect of exposing a
coked catalyst to a high-frequency electromagnetic field will be
discussed. Coke is a good conductor right up to frequencies of
.about.10.sup.14 s.sup.-1 and its resistivity amounts to
p=0.83.times.10.sup.-3 .OMEGA.cm at a temperature of 500.degree.
C., and 1 .rho. .times. .differential. .rho. .differential. T
.about. 0.9 .times. 10 - 4 .times. grad - 1 ##EQU25##
[0122] For oil coke the value of p can increase 2-3 times depending
on the generation conditions.
[0123] Catalysts do not contain metals in the pure state. The
metals are typically found in sulfide or oxide forms. The catalyst
support is also a dielectric.
[0124] When the catalyst is working, the accumulation of other
conducting components such as metals like Ni, V, and Fe occurs on
the surfaces of catalyst particles. The metals exist in heavy oil
fractions as metalloorganic compounds, which dissociate during
hydroprocessing or cracking, and the metals precipitate onto the
catalyst surface. The metal accumulation causes the acceleration of
coke generation.
[0125] When the catalyst is working during hydroprocessing or
cracking, a conducting material precipitates on the surface and in
the pores of the catalyst particle. Assuming a such a catalyst
particle is exposed to a high-frequency electromagnetic field, the
absorption rate in the conducting surface layer of catalyst
particle can be determined. For simplification, the particles are
assumed to be spherical with a radius R and have a thickness h of
the conducting layer. The depth of the field penetration into the
layer is defined by the formula .delta. = c 2 .times.
.pi..sigma..omega. ( 13 ) ##EQU26##
[0126] where .sigma.=p.sup.-1 is the coke material conductivity,
.omega.=2.pi.v, and c is the speed of light.
[0127] In further evaluations, frequencies in the MHz-range, beyond
the radio transmission frequencies, will be used: .nu..sub.1=1.76
MHz, .nu..sub.2=7.04 MHz and .nu..sub.3=28.16 MHz,
.sigma..sub.1=1.2 mm, .sigma..sub.2=0.6 mm and .sigma..sub.3=0.3 mm
respectively. As a general rule, the thickness of surface
precipitation does not exceed 30% of the catalyst's mass, i.e. the
surface layer's thickness does not exceed 0.1R. Taking into account
the sizes of the catalyst particles, the precipitation thickness
equates to the value of more than 0.1 mm. Thus, the penetration
depth is much greater than the thickness of the coke covering.
Therefore, the field relaxation in the surface layer may be omitted
in order to explain the field structure within a catalyst particle.
However, when defining the radiation absorption for a particle,
this relaxation is fundamental, as they are unambiguously dealt
with each other. It is also necessary to consider that the
wavelength is much greater than the size of the particle. Hence, to
describe the absorption of the electromagnetic field, it is
possible to use Raleigh's theory on absorption of electromagnetic
waves by small particles.
[0128] The absorption section for a spherical particle with radius
of R is .sigma. a = 9 .times. .omega. .times. .times. V .times.
.times. '' c .times. ( 1 2 + .omega. 2 .times. R 2 90 .times. c 2 )
( 14 ) ##EQU27##
[0129] where V is a volume of absorptive area (i.e. the volume of
coke relative to one granule), .epsilon.'' is the imaginary part of
the dielectric permeability s of the conducting covering. For
conductors in the low frequency range, which are low in comparison
with plasma frequency, the following approximation is made: = i
.times. 4 .times. .pi..delta. .omega. = i .times. .times. '' ( 15 )
##EQU28##
[0130] where i is the imaginary unit. Taking coke conductivity and
granules sizes of R=1 mm, the second bracketed term on the right of
the formula (14) considerably exceeds the first one. Let's put in
.phi., the relative coke layer thickness on the surface of the
catalyst particle relative to the radius of the particle. The
formula for the absorption section can be rewritten as .sigma. a =
3 .times. .omega. 3 .times. VR 2 .times. '' 10 .times. c 3 .times.
.phi. ( 16 ) ##EQU29##
[0131] For the two frequencies mentioned above,
.sigma..sub.a1=0.9.times.10.sup.-6.phi. (cm.sup.2),
.sigma..sub.a2=1.5.times.10.sup.-5.phi. (cm.sup.2),
.sigma..sub.a3=0.6.times.10.sup.-4.phi. (cm.sup.2)
[0132] The heat-evolving power for a particle is defined by the
formula W=.sigma..sub.aI, (17)
[0133] where I is the intensity of electromagnetic radiation: I = Q
e S , ##EQU30##
[0134] where Q.sub.e is the emitter power, and S is the area of the
radiation flow section.
[0135] For estimations, the following values are used:
Q.sub.e.apprxeq.250 KWt, S=10.sup.2 cm.sup.2, and
I=2.5.times.10.sup.3 Wt/sm.sup.2. For the frequencies mentioned
above we have: W.sub.1=2.5.times.10.sup.-3 Wt;
W.sub.2=0.4.times.10.sup.-1 Wt and W.sub.3=0.15 Wt.
[0136] To define the probable temperature growth on the surface of
the catalyst particle the following formula may be used: .DELTA.
.times. .times. T = W 4 .times. .times. .pi. .times. .times. R
.times. .times. .ae butted. , ( 18 ) ##EQU31##
[0137] where .ae butted. is the heat conductivity for the
environment of the particle. The characteristic fixing time for the
temperature field is evaluated by the formula .tau. .apprxeq. R 2
.chi. , ( 19 ) ##EQU32##
[0138] where .chi. is the temperature conductivity of the external
environment relative to the granule and is represented by the
formula: .chi. = .ae butted. c .times. .times. .rho. ,
##EQU33##
[0139] where .rho. is the density and c is specific heat at the
constant pressure for the mentioned medium. Since the pressure
differs for different technologies, it is important to note that x
does not strongly depend on pressure and is inversely proportional
to the pressure.
[0140] For estimations, the following values are used: .ae
butted..apprxeq.2.8 10.sup.-4 W/(cm grad) and, .chi..apprxeq.0.02
cm.sup.2/c at the pressure of 10 atm, methane. For granules with
radius of 1 mm, the characteristic time or the thermal relaxation
.tau..apprxeq.0.5 s.
[0141] Using the values of the heat-evolving power for the
frequencies mentioned above, .DELTA.T.sub.1=7.degree. .phi.,
.DELTA.T.sub.2=110.degree. .phi., and .DELTA.T.sub.3=1750.degree.
.phi., (20)
[0142] the values of .phi. can be to found using data for extreme
coke and metals precipitation. The change of coke content from 3%
by mass to 25% by mass corresponds to the interval from 0.01 to 0.1
for .phi.. The data generalization through the value of .DELTA.T
according to the formulae (20) is shown in Table V. TABLE-US-00005
TABLE V Temperature growth for catalyst particle surface. Coke v
.sub.1 = v .sub.2 = v .sub.3 = precipitation .phi. 1.76 MHz 7.04
MHz 28.16 MHz 3% 10.sup.-2 0.07.degree. C. 1.1.degree. C.
17.5.degree. C. 25% 10.sup.-1 0.7.degree. C. 11.degree. C.
17.5.degree. C.
[0143] The data analysis shows, that at the rate of electromagnetic
field flow being equal to 250 kWt the technological application can
get the frequency .nu..sub.3=28.16 MHz. The lower frequency
.nu..sub.2 can only be used in case of the field amplification.
[0144] According to formulas (15)-(18), the temperature of the
surface of a catalyst particle increases with frequency as
.omega..sup.2. Therefore, not only .nu..sub.3 frequency, but also
higher frequencies can be used.
[0145] It is important to evaluate the depth of the field
penetration into the catalyst matrix. Considering only the
absorption in the surface layer of the particle, it is possible to
use formula (16) for the absorption section. The depth of
penetration into the matrix is given by the formula 1 p = 1 n g
.times. .delta. a , ##EQU34## where n.sub.g is the concentration or
the catalyst particles. For simplification, n.sub.g=(2R).sup.-3 in
case of dense particle arrangement. Selecting the maximum value for
.sigma..sub.a (.sigma..sub.a max=0.6.times.10.sup.-5 cm.sup.2) and
R=10.sup.-1 cm, l.sub.p min=1.3.times.10.sup.3 cm=13 m is
obtained.
[0146] Thus, any catalytic conversion plant possessing the
reasonable sizes is transparent for HF-field. Certainly, here only
absorption on coke is taken into account. The metal precipitation
may slightly change the numerical evaluations, but the qualitative
conclusions will remain.
[0147] As was indicated above, the processing in the field period
for the catalyst is defined by expression: K = p H 2 - p c
.function. ( T 1 - .DELTA. .times. .times. T ) p H 2 - p c .times.
T 1 ##EQU35##
[0148] If the coke accumulation time is equal to t.sub.H, then the
period of processing is t.sub.H K. For finding K, it is necessary
to have the explicit function of pressure P.sub.c(T), which is
measured experimentally.
[0149] Table V shows that at the low level of coke precipitation, 3
mass %, the heating of the particle surface is not a sufficient
measure for the erosion of coke precipitation. If more intensive
coke clearing is required for the particles, higher frequency
fields other than those produced in Table N may be used.
[0150] The present invention observes the possible selective
acceleration of the erosion of coke precipitation on catalyst
particles using an electromagnetic field in the MHz-HHz range. This
process can be realized in frequency of 28.16 MHz and higher. The
above principles may be applied to hydroprocessing and reforming to
gain the conditions of coke non-accumulation or accelerated
hydrosublimation of coke precipitating on catalyst particle
surfaces.
[0151] The present invention provides increased control over coke
precipitation on the catalyst particles by the use of
electromagnetic fields.
[0152] As discussed above, catalyst systems for processing an
organic feed generally consist of a reactor vessel or column in
which the catalyst is introduced with the organic feed. The organic
feed is processed in the reactor by exposing the feed to the
catalyst at high temperatures. Typically the organic feeds are
introduced through the catalyst stream in route to the reactor.
Much of the cracking of the organic feed occurs in a dispersed
catalyst phase in the transfer line to the reactor. Typically a
sufficient part of the organic feed is not vaporized and the
unvaporized portion quickly cokes the catalyst choking its active
area. Once the active area of the catalyst is covered with coke,
the catalyst loses its activity and must be regenerated.
[0153] The inactive catalyst is transferred to the reactor vessel
to a regeneration vessel in which the catalyst is heated at very
high temperatures to remove coke formation on the surface of the
catalyst. The regenerated catalyst is then sent to the reactor and
the increased temperature of the catalyst results from the
regeneration process is used to catalyze the cracking or
hydroprocessing reaction in the reactor.
[0154] After the injection of hot catalyst into the reactor the
temperature of the catalyst is going to decrease in a few
milliseconds and the relative internal pressure of the catalyst
particles in the reactor is going to become negative. The heat or
thermal energy in the catalyst will be transferred to the organic
feed and vaporize part of the organic feed. The vaporized organic
feed will migrate in the catalyst pores due to the pressure
gradient that is created. Once in contact with the catalyst, the
catalytic reaction such as cracking will take place. As a result of
its endothermic character, the temperature of the particle
decreases even more and the organic feed molecules are maintained
in the catalyst particle, effective blocking the pores of the
catalyst. Further, the decreased temperature of the catalyst
particle reduces their catalytic activity and provokes the
formation of coke on the surface and the pore volume of the
particle.
[0155] FIG. 2 illustrates the mass exchange in the classical
system. FIG. 2 shows a catalyst particle 10 in a reactor 12,
exposed to an organic feed 14. The activity of the fresh catalyst
decreases during the process. Effectively, the drop in activity
takes place in a very short period of time at the beginning the
contact with the organic feed. This period is sufficiently less
than the particles lifetime in the reactor. Since the catalyst
particle loses activity in the initial stages of being exposed to
the organic feed in the reactor, after the relatively long period
of time the particle remains in the reactor, the particle remains
passive and gets covered by coke. The coke covered particle must be
removed to the regeneration column to remove the coke
formation.
[0156] There is a need for a system that reduces coke participation
on the catalyst without withdrawing the catalyst from the reactor
for regeneration. The present invention broadly relates to applying
a high frequency-field to processing organic feeds. More
particularly, the present invention is related to selectively
applying pulses of a high frequency field to catalyst particles
such that the catalyst particles maintain their activity while in
the reactor and while they are in contact with the organic
feed.
[0157] As discussed above, organic feeds such as oil and petroleum
products are known to be good dielectrics. Further, activated
catalysts used in processing reactions are also good dielectrics.
However, coke and metals that have precipitated on the surface of
catalysts are conductors. An electromagnetic field is applied to
the catalyst the heating of coke and metals precipitated on the
catalyst occurs while the oil or organic feed remains at the
initial temperature. The rate of coke formation remains constant
due to invariant rates of hydration and thermal cracking in crude
oil, however, the rate of coke supplemation sharply increases due
to its interaction with hydrogen. This causes the elimination or
considerable reduction of coke formation on the catalyst.
[0158] The present invention can be used for the suppression of
coke formation during various processing reactions and reforming of
organic feeds.
[0159] The process in accordance with the present invention allows
for the reduction and energy and time costs due to the regeneration
of a deactivated catalyst and conventional systems.
[0160] With reference now to FIGS. 3-5, these figures show a
catalyst particle 20 exposed to an organic feed 22 in a reactor 24,
under the influence of electromagnetic radiation. Upon injection of
a hot catalyst into the reactor with an organic feed, the
temperature of the catalyst goes down within a few milliseconds and
the relative internal pressure of the catalyst particles become
negative. During this time, heat or thermal energy is transferred
from the catalyst particles to the organic feed. At this point,
parts of the oil are vaporized and due to the pressure gradient the
organic feed molecules are able to get into the pores of the
catalyst particle. Upon contact with catalyst particle, the
processing reaction such as cracking takes place. These catalytic
reactions are generally endothermic and as a result, the
temperature of the particle decreases until the hydrocarbon
molecules are deposited on the catalyst particle. The relatively
negative particle temperature decreases the catalytic activity of
catalyst particles itself and provokes the formation of coke 28 on
the surface and in the pore volume of the catalyst particle 20
resulting in deactivation of the catalyst particle.
[0161] At this point, as illustrated in FIGS. 4 and 5, a selective
pulse 30 of electromagnetic radiation selectively heats the
catalyst particle 20 to a temperature that is higher than the
surrounding organic feed 22. The pulse of electromagnetic radiation
is preferrably sufficient to raise the temperature of the catalyst
above the temperature of the organic feed. Preferably, the pulse is
sufficient to vaporize a portion of the organic feed surrounding
the catalyst particle. The duration of the pulse may vary depending
on the organic feed, the catalyst, and the frequency of the pulse.
In a preferred embodiment the pulse of electromagnetic radiation is
at least about 1 MHz. Still further, the pulse of electromagnetic
radiation may range from about 1 MHz to about 100 HHz and is
applied for a time on the order of about 10.sup.-6 seconds to about
10.sup.0 seconds. The time between pulses may vary depending on the
organic feed, the catalyst, and the characteristics of the pulse.
In a preferred embodiment the time between pulses is long enough to
allow the catalyst particle to cool to a temperature that is about
the same temperature or lower of the organic feed. In a preferred
embodiment, the time between pulses ranges on the order of about
10.sup.-6 seconds to about 10.sup.2 seconds.
[0162] The source of the electromagnetic pulse may be very high
frequency (VHF), ultra high frequency (UHF), microwave, infrared,
or laser radiation.
[0163] The hot catalyst particles effectively generate a high
relative internal pressure and forces the coke and hydrocarbon feed
precipitation on the surface of the particle off of the surface and
out of the pore volume.
[0164] As shown in FIG. 5, at the end of the electromagnetic pulse
30, the hot particle 20 begins to cool and comes in contact with
vaporized organic feed molecules. The relative pressure of the
catalyst particle becomes negative and a new fresh portion of feed
puts the catalyst particles under pressure gradient. Upon contact
with the hot catalyst particle, a catalytic reaction takes place.
The catalyst particle eventually cools to a temperature such that
the catalytic reaction does not occur and coke begins to form on
the catalyst particle. At this point, another pulse of
electromagnetic radiation is applied to the catalyst particles to
heat the particles to a temperature and internal pressure above the
temperature and pressure of the organic feed and thus the process
of heating the catalyst to remove the cracked organic feed and to
remove coke and other deposits from the catalyst is repeated.
[0165] Turning now to FIG. 6, there is shown a reactor 60 in
accordance with one embodiment of the present invention. The
reactor has a column 62 with side walls 64. A window 66 that is
transparent to electromagnetic radiation is located on the wall 64
of the reactor 60. An electromagnetic radiation generator 68 is
positioned such that electromagnetic radiation passes from the
generator 68 through the window 66 and into the column 62.
Preferably, the electromagnetic generator can deliver different
pulses of radiation having different frequencies, represented by
the reference numerals 70 and 72. Preferably, the walls of the
column reflect electromagnetic radiation and the generator 68 is
positioned to provide pulses of radiation 70 and 72 at an angle in
the reactor. The pulses of radiation 70 and 72 will be reflected
off the internal walls of the column. In this way the pulses of
radiation will travel along the length of the column.
[0166] The column may take on a variety of shapes and
configurations. The column may be cylindrical. The source of
electromagnetic radiation may be from VHF, UHF, microwave, infrared
or laser radiation. The window 66 must allow a portion of the
radiation to enter the column. Preferably, the window is made of a
ceramic material. The material used for the window 66 depends on
the source of electromagnetic radiation. These materials are well
know to those skilled in the art. The column should reflect at
least a portion of the entering electromagnetic radiation.
Preferably, the column is made of stainless steel.
[0167] With reference now to FIG. 7, a reactor 80 in accordance
with another embodiment of the present invention is illustrated.
The reactor 80 has a column 82 with side walls 84. A plurality of
electromagnetic radiation generators 86 are positioned along the
length of the column 82. For each generator 86, there is a window
88 that is transparent to electromagnetic radiation. Preferably
each generator 86 delivers at least two pulses of different
frequencies, 90 and 92, respectively, to the column 82. The
generators should be spaced a distance apart along the length of
the column to allow for catalyst regeneration. This configuration
allows for control of the catalyst temperature as the catalyst
travels along the length of the reactor. Each generator 86 may
deliver a pulse having the same frequency as the other generators
or the frequencies may be different.
[0168] Turning now to FIG. 8, another embodiment of the present
invention is illustrated. The reactor 100 is similar to that shown
in FIG. 7. The reactor 100 has a column 102 with side walls 104. A
plurality of electromagnetic radiation generators 106 are
positioned along the length of the column 102. For each generator
106, there is a window 108 that is transparent to electromagnetic
radiation. Preferably each generator 106 delivers electromagnetic
radiation through the window 108 to the column 102. Each generator
provides constant radiation band to the column. The bands of
radiation, represented by 110, 112, and 114, will cover a portion
of the length of the column 102. The bands of radiation and the
lengths of the column that are covered may vary. As the catalyst
particles pass through the column, the particles pass through the
band of radiation. In this way the particles are effectively
pulsed. The time between bands allows the particles to cool before
passing through a second band of radiation. This configuration
allows for control of the catalyst temperature as the catalyst
travels along the length of the reactor. Each generator 106 may
deliver a deliver radiation having the same frequency as the other
generators or the frequencies may be different. The generators
should be spaced a distance apart along the length of the column to
allow for catalyst regeneration. Further the size of the bands may
vary from one generator to the other.
[0169] With reference to FIGS. 6-8, the column may take on a
variety of shapes and configurations. The column may be
cylindrical. The source of electromagnetic radiation may be from
VHF, UHF, microwave, infrared or laser radiation. The windows must
allow a portion of the radiation to enter the column. Preferably,
the window is made of a ceramic material. The material used for the
window depends on the source of electromagnetic radiation. These
materials are well known to those skilled in the art. Preferably,
the column is made of stainless steel.
[0170] Several pulses of electromagnetic radiation may be applied
to the catalyst particles. Depending on how long the catalyst
particles are in the reactor, several pulses of electromagnetic
radiation may be applied. This effectively extends the active life
of the catalyst in the reactor. Whereas previously, the catalysts
were only active in the initial moments upon introduction to the
reactor. Electromagnetic pulses may be applied to maintain the
activity of the catalyst in the reactor.
[0171] The present invention is able to maintain the activity of
the catalyst particles in the reactor. Further the present
invention is able to increase the mass-exchange through the
catalyst particles and switch the catalytic activity on and off
when necessary, and reduce the formation of coke on the catalyst.
As a result, severe and expensive conditions for regeneration of
the catalyst is not necessary.
[0172] With reference now to FIG. 9 and FIG. 10, the next aspects
of the present invention directed to dewatering and desalination of
an organic feed are illustrated. An additional problem with organic
feed processing is the presence of water and salts in the feed. The
principles of using an electromagnetic pulse to reduce coke
formation on a catalyst particle may be applied to the dewatering
and desalination of an organic feed.
[0173] The present invention applies a pulse of electromagnetic
radiation to an organic feed to encourage water that is dispersed
throughout the feed to form larger water droplets. Turning to FIG.
9(a) there is illustrated an organic feed 50 in a holding device
52. Water 54 and salt 56 are also contained in the organic feed.
Electromagnetic radiation 58 is applied to the organic feed. Since
water is not transparent to the pulse of electromagnetic radiation,
the water will absorb the energy. As a result, the temperature of
the water increases, increasing the mobility of the water in the
oil allowing the water to form larger droplets of water. FIG. 10
illustrates the mechanism for concentrating water droplets by
applying electromagnetic radiation 58 to the petroleum feed 50.
[0174] Often the organic feed will contain salts that must be
removed from the feed. The salts are typically soluble in water.
Typical salts include chlorides and sulfates such as calcium
chloride, magnesium chloride, sodium chloride, ferric chloride and
sodium sulfate. Concentrations ranges acceptable for pipelines
range from about 0.1-2% for water and about 8-10 grains per barrel
for salts.
[0175] The solubility of salts is directly related to temperature.
As the temperature increases, the solubility of the salt will
increase. FIG. 9(b), illustrates several possibilities with respect
to water 54 and salt 56 contained in an organic feed 50. In the
classical situation where no electromagnetic radiation is applied,
water and salts are contained in the organic feed. As the
electromagnetic radiation is applied to the feed, the water begins
heat and form droplets. The temperature of the water droplets
increase and salt is drawn into the water droplets as represented
in the classical column of FIG. 9(b). The water droplet with the
salt now absorbs electromagnetic radiation more intensely resulting
in growth and increase in temperature of the droplet allowing for
more salt to become dissolved in the droplet as illustrated in the
salt pump column of FIG. 9(b). In this way, salt is effectively
pumped from the organic feed to the water droplets.
[0176] In one embodiment, a pulse of electromagnetic radiation may
be applied to heat the water contained in the organic feed. The
pulse of electromagnetic radiation may range from about 0.4 MHz to
about 100 HHz. The duration of the pulse may vary depending on the
organic feed and the frequency of the radiation. In one embodiment
the duration of the pulse may range on the order of about 10.sup.-6
seconds to about 10.sup.1 seconds.
[0177] Removal of the water and salt may be accomplished by
applying a second, vaporizing pulse. This second pulse is designed
to selectively vaporize a portion of the droplet without destroying
the shell of the droplet as illustrated in the air lift column of
FIG. 9(b). The second pulse is applied to form a liquid-vapor water
complex. The complex will rise to the surface of the organic feed.
The complex containing water and salt will rise to the surface
where they may be removed by skimming the surface of the feed or by
adding surfactants followed by skimming of the feed. Alternatively,
the complex will contact other complexes and produce a larger water
droplet. The larger droplet may grow large enough to fall to the
bottom of the organic feed.
[0178] The second, vaporizing pulse must be sufficient to vaporize
a portion of the droplet without destroying the shell of the
droplet as illustrated at the bottom of the dewatering column of
FIG. 9(b). The parameters of the second pulse may vary depending on
the organic feed and the frequency of the radiation used. In a
preferred embodiment, the radiation may range from about 0.4 MHz to
about 100 HHz. The duration of the second pulse may vary depending
on the organic feed, the frequency of the radiation for the first
and second pulses, and the duration of the first pulse. In one
embodiment the duration of the second pulse may range on the order
of about 10.sup.-6 seconds to about 10.sup.0 seconds.
[0179] In another embodiment, the radiation may be sufficient to
destroy the shell of the water droplets and vaporize water
contained in the organic feed. This is illustrated in the
dewatering column of FIG. 9(b).
[0180] With reference now to FIG. 11 there is shown one embodiment
of a dewatering device 120 in accordance with the present
invention. The device 120 has a container 122 suitable for holding
an organic feed. The container may include, but is not limited to,
a barrel, an oil tank, plastic holding container or any suitable
container for holding an organic feed. The container 120 either has
a window 122 that is transparent to the electromagnetic radiation
or an opening 124, such that at least a portion of the organic feed
is exposed to the electromagnetic radiation. One or more
electromagnetic generators 126 are placed about the container 120
and positioned such that the electromagnetic radiation passes
either through the window 122 or the opening 124. A drain 128 may
be located near the bottom of the container 120 for draining
condensed water.
[0181] With reference now to FIG. 12, there is illustrated
dewatering apparatus 130 in accordance with one embodiment of the
present invention. The apparatus 130 has a pipe 132 for
transporting an organic feed. A window 134 is located on a portion
of the pipe 130. An electromagnetic generator 136 is position such
that electromagnetic radiation passes through the window 134 into
the pipe 130, thus exposing at least a portion of the organic feed
to the radiation. The pipe 130 may contain a drain 138 after the
generator 136 for draining condensed water from the organic feed.
Further the pipe may contain a vent 140 after the generator 136 for
venting water that has been vaporized. Still further, holding
device 142 may be placed after the generator for collecting the
organic feed. The holding device 142 may have a holding device
drain 144 near the bottom of the holding device for draining
condensed water.
[0182] With reference to FIGS. 11 and 12, the source of
electromagnetic radiation may be from VHF, UHF, microwave, infrared
or laser radiation. The windows must allow a portion of the
radiation to enter the column. Preferably, the window is made of a
ceramic material. The material used for the window depends on the
source of electromagnetic radiation. These materials are well known
to those skilled in the art.
[0183] It will be readily understood by those persons skilled in
the art that the present invention is susceptible to broad utility
and application. Many embodiments and adaptations of the present
invention other than those herein described, as well as many
variations, modifications and equivalent arrangement, will be
apparent from or reasonably suggested by the present invention and
the foregoing description without departing from the substance or
scope of the present invention.
[0184] Accordingly, while the present invention has been described
in detail in relation to its preferred embodiment, it is to be
understood that this disclosure is only illustrative and exemplary
of the present invention and is made merely for purposes of
providing a full and enabling disclosure of the invention. The
foregoing disclosure is not intended to be construed to limit the
present invention or otherwise exclude any other embodiments,
adaptations, variations, modifications or equivalent arrangements,
the present invention being limited only by the claims and the
equivalents thereof.
* * * * *