Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
The field of catalytic cracking and particularly
fluid catalyst operations have undergone significant
development improvements due primarily to advances in
catalyst technology and product distribution obtained
therefrom. With the advent of high activity catalyst and
particularly crystalline zeolite cracking catalysts, new
areas of operating technology have been encountered
requiring even further refinements in processing tech-
niques to take advantage of the high catalyst activity,
selectivity and operating sensitivity. The present
invention therefore is concerned with a combination
operation comprising hydrocarbon conversion and regener-
ation of the catalyst employed therein. In a particular
aspect the present invention is concerned with the tech-
nique of regenerating a low coke producing crystalline
zeolite hydrocarbon conversion catalyst containing de-
activating deposits of carbonaceous material.
SUMMARY OF THE INVENTION
The present invention relates to the conversion
of hydrocarbon feed materials in the presence of high
activity fluidizable crystalline zeolite containing
catalyst particles and the regeneration of the catalyst
particles to remove deactivating coke deposits by burning.
In a more particular aspect the present invention is
concerned with the method and system for regenerating
fluidizable catalyst particles and particularly a crystal-
line zeolite containing cracking catalyst containing
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carbonaceous dèposits under highly efficient regenerating
conditions promoting the recovery of heat available through
the burning of the carbonaceous deposits of a hydrocarbon
conversion operation. In yet another aspect, the invention
is concerned with a particular relationship of operating
para~eters coupled in a manner promoting a suspended catalyst
phase removal of deactivating deposits of carbonaceous material
from high activity hydrocarbon conversion catalyst particles
and heating thereof to an elevated temperature.
Thus, the invention in its brsadest sense relates to
a process for regenerating a crystalline zeolite hydrocarbon con-
version catalyst which comprises mixing a catalyst containing
crystalline zeolite hydrocarbon conversion catalyst deactivated with
carbonaceous deposits with sufficient hot regenerated catalyst to
provide a mix temperature of at least 1135F. This catalyst mixture
suspended in oxygen containing regeneration gases is then passed
upwardly through a riser discharging into a dense fluid bed
of catalyst particles. Sufficient oxygen containing re-
generating gases are passed into the dense fluid bed of
catalyst to carry the catalyst upwardly through a dispersed
phase of catalyst particles into a catalyst separating and
collecting zone. The temperature of the catalyst mixture
passing through the dense catalyst phase and the dilute
catalyst phase is raised to at least 1350F. and a portion
of this hot regenerated catalyst separated from the dispersed
catalyst phase is recycled directly to the riser mixing
zone.
In order to achieve the desired mix temperature, a
ratio of regenerated catalyst particles to deactivated
30 catalyst particles in the range of 0.5 to 4.0/1 is pre-
ferably used, with a ratio of 0.8 to 4.0/1 being particularly
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preferred.
In one aspect of the hydrocarbon conversion-catalyst
regeneration system of the present invention, a relatively
dense fluid upflowing catalyst mass in open communication
with an upflowing more dispersed phase catalyst regeneration
is employed for effecting a relatively high temperature
regeneration of catalyst particles and combustion of
formed carbon monoxide. Regenerated catalyst is collected
and transferred to an adjacent riser hydrocarbon conversion
operation wherein at a temperature of at least about 900F.
conversion of a hydrocarbon feed such as gas oil and higher
and lower boilding materials is accomplished with the hot
regenerated cracking catalyst. The catalyst employed is
preferably a high activity crystalline zeolite catalyst of
fluidizable particle size which is transferred in suspended
phase condition through one or more riser conversion zones
providing a hydrocarbon residence time in the range of 0.5
to about 10 seconds and more usually less than about 8 seconds.
High temperature riser conversions of 1000F. at 1 to 4
seconds hydrocarbon residence time is desirable for some
operations before separating vaporous
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hydrocarbon materials comprising hydrocarbon conversion
products from suspended catalyst. Cyclonic separation of
catalyst frorn hydrocarbons is particularly desirable for
restricting hydrocarbon residence time. During the
hydrocarbon conversion step, carbonaceous deposits accumu-
late on the catalyst particles and the particles entrain
some hydrocarbon vapors upon removal from the catalyst
separation step. The entrained hydrocarbons are thereafter
removed from the catalyst with stripping gas in a
separate catalyst stripping zone. Hydrocarbon conversion
products separated from the catalyst and stripped materials
are combined and passed to a product fractionation step.
Stripped catalyst containing deactivating amounts of
carbonaceous material hereinafter referred to as coke
is then passed to the catalyst regeneration operation
of the present invention.
The regeneration technique and system of the
present invention is unique in many respects for accomplish-
ing the efficient removal of carbonaceous material or coke
deposits on the catalyst particles. The recovery of heat
available through such a coke rernoval operation is
particularly desirable. The regeneration technique of
this invention relies upon forming an initial mix of
deactivated catalyst with hot regenerated catalyst to
provide a predetermined mix temperature which is discharged
into the lower portion of an upflowing dense fluid mass
of catalyst of decreasing density of suspended catalyst
particles. A relatively high temperature profile is
maintained in the catalyst regeneration combination
of this invention in which the density of catalyst particle
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in regeneration gas varies considerably and is generally in
the ran(~e of about 2 to 40 lbs/cu. ft. but it may be as low
as about 1.5 lbs/cu. ft. The regeneration gas velocity
in the upflowing mass of catalyst is preferably at least
3 ft./sec. to obtain the desired upward catalyst flow in
a restricted regeneration zone of smaller diameter in the
upper portion than in the lower portion thereof and tapered
therebetween. In some respects the regeneration zone
resembles a bud vase in cross section to which the catalyst
mix is introduced by riser means.
The high temperature profile of the regeneration
operation is initially promoted by the mixing of hot
regenerated catalyst with stripped deactivated catalyst
in the lower portion of an initial riser mixing zone to
provide an initial catalyst mix temperature of at leaat
1175F. and preferably about 1200F. so that upon contact
with oxygen containing regeneration gas such as air com-
bustion of carbonaceous deposits is rapidly promoted.
Thus, in the system of the present invention a required
amount of hot regenerated catalyst mixed with coke
deactivated catalyst in the riser is conveyed with oxygen
containing gas into the lower portion of an upflowing
relatively dense fluid mass of catalyst undergoing
regeneration. Additional regeneration gas at an elevated
temperature is passed into the bottom or lower portion
of the dense catalyst mass portion of the regeneration
operation. In the dense fluid mass section of catalyst
regeneration, additional secondary regeneration oxygen
containing gas or air is added to the catalyst thereby
causing it to move upwardly through the regeneration
zone. Provision is also made for adding supplemental
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oxyge~n containing regeneration gas to one or more upper
portions of the riser regeneration zone to promote the
conversion of CO to CO2. In this arrangement, it has
been found that to high a particle density in the upflowing
dispersed catalyst phase may operate to quench the conversion
of CO to CO2 desired to be accomplished before discharge
from the riser regenerator into the enlarged catalyst
settling zone. Elowever, maintaining a particle density
in the suspended catalyst phase below about ~ lbs/cu. ft.
and more usually about 5 lbs/cu. ft. permits burning
of CO in an upper portion of the riser regeneration section
as well as in the enlarged settling section under even
lower catalyst particle density conditions.
The riser regeneration zone or regeneration vessel
may take on substantially any shape, cylindrical, tapered
or shaped as shown in the drawing or a combination thereof
which will provide the restricted operating parameters
of the invention as herein defined.
The regenerating technique and system of this
invention relies upon forming an initial high mix temp-
erature with regenerated and coke deactivated catalyst
to initiate coke burning temperature conditions. A dense
and dispersed catalyst phase regeneration system promoting
the conversion of formed CO to CO2 is particularly promoted
and the recovery of heat thus generated is absorbed by
catalyst particles dispersed therein. In this combination
the combustion gas-catalyst particle suspension discharged
from the upper end
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of the riser regeneration zone will normally reach a tem-
perature of at least about 1350F., preferably 1350 - 1400F.,
e.g. 1380F. In such a system the first oxygen containing
regeneration gas stream is introduced with the catalyst
mix to the bottom or lower portion of a relatively large mass
of catalyst in the lower portion of the re~eneration zone and
secondary regeneration gas is introduced to a lower portion
of the cross sectional area of the large mass of catalyst
in regeneration section as required. One or more downstream
regeneration gas inlets are also provided to promote a more
complete conversion of coke deposits and CO to CO2. Preheating
of the primary regenerated gas stream is desirable and more
usually practiced with low coke producing crystalline zeo-
lite catalyst conversion systems so that an initial catalyst
mix temperature of at least 1175F. in the dense fluid bed
of catalyst will be more easily attained.
In the arrangement of the present invention it is
contemplated supplementing residual carbonaceous material
such as coke transferred to the regeneration system by the
introduction of torch oil. In a particular aspect it is
contemplated adding torch oil to the spent catalyst passed
to the riser mixing zone or the torch oil may be added with
the air passed to the riser mixing zone. It also is con-
templated adding the-torch oil to an air line burner exit
to aid with vaporization of the torch oil. On the other hand,
a second torch oil vaporizer may be separately employed for
injecting torch oil at spaced apart intervals across a lower
portion of the dense fluid bed of catalyst to be regenerated.
It is preferred in the combination operation of this invention
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to inject the torch oil to the riser mixing zone along with
regeneration air as more specifically shown in the drawing.
The regenerating technique of the present invention
relies upon a particular relationship of operating parameters
which will accomplish the removal of carbonaceous deposits
down to at least .OS weight percent and preferably as low
as about .03 weight percent or lower in combination with
limiting the amount of carbon monoxide in the combustion
flue gases not to exceed about 0.15 mole percent. Thus
it is essential to the processing concepts of this invention
to rapidly initiate burning of deposited carbonaceous
material at an elevated temperature of at least about
1175 F. with an amount of oxygen containing regenerating
gas such as air providing a catalyst temperature rise
of at least about 100 degrees and preferably sufficient
to heat the catalyst particles carried through the
regeneration system to an elevated temperature of at least
1300F. Furthermore, to reap the advantage of the heat
generated in the system, the regeneration gas flow rate
is selected to provide a density of catalyst particles in
the enlarged bottom portion of the regeneration zone within
the range of 10 to 40 lbs/cu. ft. and in the upper more
dispersed catalyst phase section thereof adjacent the
discharge therefrom at a density of catalyst particles
as low as about 2 lbs/cu. ft. and preferably not above
about 8 lbs/cu. ft.
It will be recognized from the above discussion
that a relatively delicate balance in operating parameters
is maintained to obtain a desired coke burning and removal
thereof without producing undesired oxygen and carbon
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monoxide concentrations in the combustion flue gases and
these operating restrictions are dictated in substantial
measure by the ratio of hot regenerated catalyst that can
be mixed with spent catalyst obtained from hydrocarbon
conversion. For example, it has been observed that low
initial catalyst mix ratios of regenerated catalyst to spent
catalyst are accompanied by high concentrations of carbon
monoxide and oxygen being emitted from the regenerator
riser to the outlet cyclones. However, as the carbon
on spent catalyst is increased by a change in feed reaction
conditions etc. or by the addition of torch oil, for
example, in the regeneration system, the mix ratio of
regenerated catalyst to spent catalyst must be adjusted
as required to provide the desired temperature profile
in the regenerator.
BRIEF DESCRIPTION OF THE DRAr~ING
.
The figure presents diagrammatically in elevation
one arrangement of apparatus for accomplishing the catalytic
conversion of hydrocarbons and the regeneration of catalyst
particles in an upflowing catalyst regeneration zone
wherein an upflowing relatively dense fluid mass of
catalyst is transformed into a more dispersed catalyst
phase regeneration operation before separation of flue
gases of restricted CO content from regenerated catalyst
particles is accomplished.
DISCUSSION OF SPECIFIC EMBODIMENT
Referring now to the drawing, a hydrocarbon
feed such as a gas oil boiling range feed is introduced
by conduit 2 to the bottom of a riser conversion zone 4.
Hot regenerated catalyst in conduit 6 provided with flow
control valve 8 enters the bottom portion of riser 4 for
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admixture with the oil feed to form a catalyst-oil
suspension at an elevated conversion temperature of at
least about 850F. and more usually at least 1000F.
Additional gasiform reactant material comprising C5 and
lighter hydrocarbons, related alcohols and ethers may
also be introduced with the gas oil feed. The suspension
formed is passed upwardly through the riser conversion
zone under hydrocarbon conversion conditions promoting
the cracking of the gas oil feed to lower and higher
boiling products including carbonaceous material deposited
on the catalyst. The products include gasoline, fuel
oils and normally gaseous hydrocarbon products. The
hydrocarbon feed with suspended catalyst particles may
be maintained in the riser conversion zone for a
hydrocarbon residence time within the range of 1 to 10
seconds. However, a hydrocarbon residence time within
the range of 0.5 to 4 seconds may be employed with
particular advantage when using hydrocarbon conversion
temperatures up to about 1100F. Spaced apart hydrocarbon
feed inlets 2' and 2" are provided in riser 4. The
suspension is discharged from the upper end of the
riser conversion zone into two or more cyclonic separating
means 14 and 14' as shown. Stripping gas and stripped
hydrocarbons pass through cyclonic separating means
16. Of course cyclone separators 14 and 16 may each be a
plurality of cyclonic separation means suitably connected
to accomplish the results desired. Gasiform hydrocarbon
material and stripping gas obtained as provided below is
withdrawn by conduits 18 and 20 communicating with plenum
chamber 22 and withdrawal conduit 24. Conduit 24 communicates
with product separation equipment not shown. Catalyst
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particles separated by the velocity reduction above discussed
and by cyclonic means are collected as a bed of catalyst
26 which moves downwardly through a stripping vessel and
countercurrent to rising stripping gas such as steam
introduced by conduit 28. The stripping gas maintains
the bed of catalyst 26 in a fluid condition and removes
entrained hydrocarbon vapors and other strippable material
flom the catalyst as the catalyst moves downwardly through
the stripping zone. Stripped catalyst is withdrawn by
standpipe 30 provided with flow control valve 32 and is
passed to the bottom portion of a riser mixing-catalyst
regeneration zone 34 shown. Riser 34 discharges into the
lower portion of a dense fluid bed or mass of catalyst to
be regenerated as herein provided. Regenerated catalyst
obtained as hereinafter defined, withdrawn by standpipe
36 and provided with flow control valve 38 communicates
with the lower portion of riser 34 and provides the hot
regenerated catalyst at a temperature of at least 1300 F.
for mixing with the spent catalyst at a lower temperature
in the range of about 850F. up to about 1000F.
In the enlarged settling section comprising
the upper enlarged portion of the regenerator vessel
about the upper end of riser 34 a dense fluid bed of
catalyst comprising the collected hot freshly regenerated
catalyst particles are maintained in a dense fluid bed
condition by a hot fluidizing gas such as hot CO2 rich
product gas added by conduits 39 and 41. In the bottom
enlarged bulb portion of the catalyst regenerator, a
relatively large dense fluid bed or mass of catalyst
p~ cles is formed providing a mixture temperature of
at least 1175F. and a density of catalyst particles
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within the range of 10 to 40 lb/cu. ft. A first regeneration
gas inlet stream 44 is provided in the bottom portion of
riser 34 to which the catalyst streams are initially fed.
Heating of the regeneration gas or air stream introduced
by conduits 40, 42 and 44 is preferred. Thus with a spent
catalyst temperature of about 960 F. and containing 0.9
wt. ~ carbon thereon, it is desirable to preheat the
regeneration gas to about 325F. and use a 1 to 1 ratio
of spent catalyst to recycle regenerated catalyst at a
temperature of about 1350F. In the dense fluid bed of
catalyst, the temperature of the bed is caused to be elevated
by the burning of carbonaceous material with introduced
oxygen containing regeneration gas. Furthermore, combustion
of carbonaceous material is rapidly initiated by the hot
catalyst mix so that catalyst particles carried into
the dense bed of catalyst by oxygen containing combustion
gases and overhead therefrom will complete the removal
of carbonaceous deposits, transform carbon monoxide to
carbon dioxide and produce a less dense catalyst-combustion
gas suspension temperature of at least 1350F. and preferably
at least about 1375F. As mentioned above, the density of
particles in the upwardly flowing suspension is decreased
in the direction of flow to at least 8 lbs/cu. ft. and
preferably it is reduced to 3-5 lbs/cu. ft. before discharge
from the riser regenerator into an enlarged catalyst
separation zone. In any event the suspended catalyst
phase passing into cyclonic separating means in the
enlarged settling zone will be less than 3 lbs/cu. ft.
The catalyst regeneration-combustion gas
suspension is discharged from the upper end of riser
regenerator 46 through a plurality of outwardly extending
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arms provided with downwardly facing openings. Additional
oxygen containing gas such as air may be added to the
upflowing suspension in riser 46 by one or more spaced inlets
represented by conduit 48. The catalyst-combustion gas
suspension passed upwardly through the restricted cross-
sectional regeneration zone or riser 46 discharges against
the upper closed end 50 which deflects the suspension
outwardly through a plurality of elongated peripheral
slots or suitable arms with openings that open generally
downwardly into an enlarged settling zone 52. Discharging
the suspension into the enlarged zone 52 lowers the
velocity of the suspension thereby causing the catalyst
particles to settle out and separate from flue gases.
In settling zone 52 a major portion of the catalyst
particles separates from the combustion flue gases by a
reduction in gas velocity before the flue gases pass through
a plurality of cyclone separators represented by separators
54 and 56. Combustion flue gases comprising carbon
dioxide rich gases are removed from separators 54 and 56
by conduits 58 and 60, plenum chamber 62 and withdrawal
conduit 64.
Catalyst particles separated at an elevated
regeneration temperature as above identified are collected
as an annular dense fluid bed of catalyst 66 about an upper
portion of regenerator riser 46 at an elevated temperature
up to about 1400F. from which regenerated catalyst is
withdrawn by standpipes 6 and 36 as herein discussed.
The catalyst regeneration method and system of
the present invention is unique over that of the known
prior art by at least the riser mixing of hot freshly
regenerated catalyst with coke contaminated catalyst
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separated from the conversion zone in an amount sufficient
to provide an elevated mix temperature of at least 1175F.
This high temperature mix of catalyst is sufficient for
promoting the combustion of carbonaceous deposits in the
presence of added oxygen containing regeneration gas such
as air in an initial riser contact zone and the conversion
of formed carbon monoxide to carbon dioxide is particularly
promoted on a once through basis in an upflowing suspended
catalyst atmosphere thereabove varying in particle density
from about 40 lb/cu. ft. down to about 3 lbs/cu. ft. and
less.
Having thus generally described the invention
and discussed specific embodiments in support thereof,
it is to be understood that no undue restrictions are
to be imposed by reason thereof.
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