Note: Descriptions are shown in the official language in which they were submitted.
~0~6~83
BACKGROUND OF THE INVENTION
This invention relates to an improved process for
regenerating fluidizable catalytic cracking catalyst. In
particular, it is related to a method of operating the
regenerator of a fluid catalytic cracking unit (FCCU) having
a single fluidized dense catalyst phase wherein coke-con-
` taminated fluidizable catalytic cracking catalyst is con-
tacted with an oxygen-containing regeneration gas in order
to obtain a regenerated catalyst having a low carbon content
while producing a regenerator effluent flue gas having a
carbon monoxide content substantially lower than obtained -
heretofore.
The fluidized catalytic cracking of hydrocarbons is
well-known in the prior art and may be accomplished using a
variety of continuous cyclic processes which employ fluid-
ized solids techniques. In such fluid catalytic cracking `~
processes hydrocarbons are converted under conditions such
~; that substantial portions of a hydrocarbon feed are trans-
formed into desirable products such as gasoline, liquefied
petroleum gas, alkylation feedstocks and middle distillate
blending stocks with concomitant by-product formation of an
undesirable nature, such as gas and coke. When substantial
amounts of coke deposition occur, reduction in catalyst
. ~
activity and, particularly, catalyst selectivity results
.i ,.,
~1 thereby deterring hydrocarbon conversion, reducing gasoline
,, production and simultaneously increasing the production of
less desired products. To overcome such catalyst deacti-
vation through coke deposition, the catalyst is normally
withdrawn from the reaction zone and passed to a stripping
zone wherein entrained and absorbed hydrocarbons are ini-
.~ i .
'
--1--
; ~
10~6~3
tially displaced from the catalyst by means of stripping
medium such as steam. The steam and hydrocarbonsare re~
moved and the stripped catalyst is passed to a regeneration
zone where it is contacted with an oxygen-containing gas to
effect combustion of at least a portion of the coke and
thereby regenerate the catalystO Thereafter, the regenera-
ted catalyst is reintroduced to the reaction zone and
therein contacted with additional hydrocarbons.
Generally, regeneration processes provide a regenera-
tion zone wherein the coke-contaminated catalyst is con-
tacted with sufficient oxygen-containing regeneration gas at
an elevated temperature to effect com~ustion of the coke
deposits from the catalyst. Most common of the regeneration
processes are those wherein the contacting is effected in a
fluidized dense catalyst phase in a lower portion of the
regeneration zone constituted by passing the oxygen-con-
taining regeneration gas upwardly through the regeneration
zone. The space above the fluidized dense catalyst phase
contains partially spent regeneration gases and catalyst ;
entrained by the upward 10wing regeneration gas. This
. .
portion of the regeneration zone is generally referred to as
the dilute catalyst phase. The catalyst entrained in the
i dilute catalyst phase is recovered by gas solid separation
- cyclones located in the upper portions of the regeneration
zone and is returned to the fluidized dense catalyst phase.
Flue gas comprising carbon monoxide, other by-product gases
obtained from the combustion of the coke deposits, inert
gases such as nitrogen and any unconverted oxygen is re-
covered from the upper portion of the regeneration zone and
a catalyst of reduced carbon content is recovered from a
. ' ~
.' ~, .
:
~0~6483
lower portion of the regeneration zone.
In the regeneration of catalytic cracking catalyst,
particularly high activity molecular sieve type cracking
catalysts, it is desirable to burn a substantial amount of
coke from the catalyst such that the residual caxbon content
of the regenerated catalyst is very low. A carbon-on-
regenerated-catalyst content of about 0.15 weight percent or
less is desirable. Cracking catalysts with such a reduced
carbon content enable higher conversion levels within the
reaction zone of the FCC unit and improved selectivity to
gasoline and other desirable hydrocarbon products.
Most of the prior art processes for regenerating fluid
catalytic cracking catalyst generally involve contacting the
coke-contaminated catalyst in the fluidized dense catalyst
phase at a temperature of from about 1100F. to about 1200F.
for a sufficient period of time to reduce the carbon content ~-
of the catalyst to the desired level. Such processes are
undesirable in that the carbon content of the regenerated
catalyst is generally reduced only to a level of from about
0.3 to about 0.5 weight percent and because a flue gas is
obtained containing large amounts of carbon monoxide which
must be treated prior to discharge into the atmosphere.
It is known that increasing the temperature of the
fluidized dense catalyst phase will reduce the residual
carbon level of the regenerated catalyst. However, pro-
cesses in which the temperature of the fluidized dense
catalyst phase exceeds about 1200F. generally involve
elaborate modifications to counteract the effects of after-
burning in the dilute catalyst phase. By after-burniny is
meant the further oxidation of carbon monoxide -to carbon
.
..'
.. . .. :
~0464~3
dioxide in the dilute catalyst phase. Whenever after-
burning occurs in the dilute catalyst phase, it is generally
accompanied by a substantial increase in the temperature due
to the large quantities of heat liberated. In such circum-
stances the dilute phase temperature may exceed about
1500F. and, in severe cases, may increase to about 1800F.
or higher. Such high temperatures in the dilute catalyst
phase are deleterious to the entrained catalyst present in
the dilute catalyst phase and result in a permanent loss of
catalytic activity, thu~ necessitating an inordinately high
rate of catalyst addition or replacement to-the process in
order to maintain a desired level of catalytic activity in
the hydrocarbon reaction zone. Such high temperatures are "
. -
additionally undesirable because of the damage which may
result to the mechanical components of the regeneration -
zone, particularly to cyclone separators employed to sepa-
rate the entrained catalyst from the flue gas.
It is kno~^m that commonly employed catalytic cracXing
catalysts such as amorphous silica-alumina, silica-alumina
zeolitic molecular sieves, silica-alumina zeolitic molecular
sieves ion-exchanged with divalent metal ions, rare earth
metal ions, etc., and mixtures thereof, are adversely
'I affected by exposure to excessively high temperatures. At
`~ temperatures of approximately 1500~F. and higher, the struc-
ture of such catalytic cracking catalyst undergo physical -
change, usually observeable as a reduction in the surface
area with resulting substantial decrease in catalytic acti-
- vity. Consequently, it is desirable to maintain the tem-
peratures within the regeneration zone at levels below which `
there is any substantial physical damage to the catalyst.
''~ ;.
-4-
. .; .
,' '
~O~ 3
Known methods for regenerating fluid catalytic cracking
catalysts to low carbon contents, while avoid excessively
high dilute catalyst phase temperatures, are generally
unsatisfactory. In some processes a cooling medium which
may comprise steam, liquid water, unregenerated catalyst,
hydrocarbon oil, flue gas, etc., is brought into heat ex-
change contact with the dilute catalyst phase either to
absorb the heat liberated by after-burning which may occur
therein or to prevent the occurrence of after-burning. See,
for example, U.S. Patents 2,382,382; 2,580,827; 2,454,373;
2,454,466; 2,374,660; 2,393,839; and 3,661,799.
Other methods employ multiple catalyst regen~ration
zones to provide sufficient residence time for contacting
the coke~rcontaminated catalyst with an oxygen-containing
regeneration gas to burn the coke deposits therefrom at a
temperature at which after-burning will not occur. See,
for example, U.S. Patents 3,563,911; 2,477,345; 2,788,311;
3,494,858; 2,414,002; and 3,647,714. Still other methods
such as those disclosed in U.S. Patents 2,831,800 and
i~ 20 3,494,858 teach multiple zone regeneration of coke-con-
taminated catalyst, but are silent with respect to control
of dilute phase temperatures. Still another approach em-
ployed involves indirect heat exchange such as steam gene-
.
ration coils employed in the fluidized dense catalyst phase.
All of the above methods are unsatisfactory in that the
processes involved cumbersome additional processing steps
for absorbing h~at liberated due to after-burning in the
: dilute catalyst phase or require expensive facilities for
.
the treatment of the regeneration flue gas stream, because
of the avoidance of after-burning in the regeneration zone
., ~
, .
-5-
~,
' :
and the resultant substantial carbon monoxide content in the
flue gas, generally ranging from about 2 to about 6 volume
percent, or higher.
Summary of the Invention
~ _ . . . ..
Now, according to the present invention, an improved
method for regenerating a coke-contaminat~d cracking cata-
lyst has been discovered wherein a regenerated catalyst
; having a low residual carbon content of about 0.15 weight
percent or less is obtained and wherein the carbon monoxide
content of the flue gas from the regeneration process may be
maintained at about 500 ppm or less, and preferably 10 ppm
or less.
The process of the present invention comprises con-
tinously introducing a cok~-contaminated catalyst from a
fluid catalytic cracking unit into a fluidized dense cata-
lyst phase of a regeneration zone maintained at a tempera-
ture of from about 1250F. to about 1350F., and contacting
the coke-contaminated catalyst therein with an oxygen-
containing regenera~ion gas in an amount in excess of that
: . .
required for burning essentially all of the coke to carbon
dioxide and to provide from about 1 to about 10 mol% oxygen
- in the regeneration flue gas. The coke-contaminated cata-
lyst is maintained within the dense phase fluidized bed for
- a period of at least about 3 minutes, and up to about 10
~ minutes, as required, to provide a regenerated catalyst with
;~ a residual carbon content of about 0.15 weight percent or
less in a single regeneration step. - -
By following the method of the present invention the
amount of carbon monoxide contained in the partially spent
regeneration gases leaving the fluidized dense catalyst
.
--6--
.,,
,:'
. ,. . , . : . , ;
.
phase is maintained at a sufficiently low level such that
the amount of after-burn in the dilute catalyst phase is ;
such that the temperatures obtained therein are maintained
at less than about 1455F., and generally within a range of
about 1375F. to about 1455F. This process affords re-
generated catalysts at lower residual carbon contents than ~;
heretofore known, while maintaining regeneration zone tem-
- peratures at levels below those at which the catalyst suf-
fers any substantial loss of activity, or at which mecha-
10 nical components of the regeneration zone are damaged. `-
Moreover, the instant process has the further advantage of
producing a regenerator flue gas having a carbon monoxide
content of about 500 ppm or less without employing addition-
al flue gas treating facilities. A still further benefit of
the process of this invention resides in the substantially
reduced inventory of catalyst required in the regeneration ~-
zone, as contrasted with regeneration processes known in the
art.
~ Detailed Description of the Invention
; 20 According to the process of this invention, a fluidiz-
able catalytic cracking catalyst which has been partially
deactivated by the deposition of carbonaceous deposits upon
the surface thereof (hereinafter rsferred to as coke-con-
taminated catalyst) in a fluidized catalytic cracking pro-
cess is introduced into a fluidized dense catalyst phase of
a regeneration zone wherein it is contacted with an oxygen-
containing regeneration gas for the purpose of burning the
carbonaceous deposits from the catalyst thereby to xestore
its activity. The regeneration zone generally comprises a
regeneration vessel in which there is a fluidized dense
.
; -7-
': :
; .
~ ' ' ,, . ' ' ' '
,;,
,
S~46~3
catalyst phase in the lower portion thereof and a dilute
catalyst phase in the upper portion thereof. The oxygen-
containing regeneration gas is introduced into the lower
portion of the regeneration zone thereby to maintain the
catalyst in a fluidized dense catalyst state. A flue gas is
recovered from the top of the regeneration zone comprising
carbon monoxide and other by-products of the combustion of
the coke deposits contained on the coke-contaminated cata-
lyst.
The fluidized dense catalyst phase is generally main-
tained at a density of from about 10 to about 60 lb/ft3 and
preferably at a density of from about 20 to about 40 lb/ft3
by the upward flow of the oxygen-containing regeneration
gas, which is introduced at a lower portion in the regene-
ration zone. The catalyst in the lower portion of the
regeneration zone is maintained in a fluidized dense cata-
lyst phase in order to obtain good heat transfer throughout
the bed and to avoid localized hot spots and their conco-
mitant high temperatures, which are known to adversely
affect the catalyst. In order to maintain the catalyst in a -
fluidized state, a superficial vapor velocity of the regenera-
tion gas of from about 0.2 to about 6.0 ft/sec. is general-
ly maintained. The regeneration vessel is generally sized
to provide a superficial vapor velocity within the aforemen-
,.~ . .
tioned range when operating with the desired residence timefor the catalyst in the regeneration æone and with the
required amount of oxygen-containing regeneration gas to
, effect the combustion of the coke from the catalyst in the
,...................................................................... ...
reaction zone. Additionally, it is possible to control the
superficial vapor velocity within the desired range by em-
', ' ~
,
;~
;i -8-
,
~ - -
6~3
ploying an operating pressure within the re~eneration zone
within the range of from about 1 to about 50 psig, and
~ preferably from about 15 to about 45 psig. If, within these
-~ operating parameters, there is nevertheless insufficient
oxygen-containing regeneration gas to provide the desired
superficial vapor velocities, steam or an inert diluent gas
may be combined with the oxygen-containing regeneration gas
to provide the desired superficial vapor velocity.
Surprisingly, it has been found that if the fluidized
dense catalyst phase is maintained at a temperature in the
range of from about 1275F to about 1350F., while con-
tacting the coke-contaminated catalyst with an oxygen-
containing regeneration gas in the desired amounts, there is
obtained a regenerated catalyst with a residual carbon-on-
regenerated-catalyst content of 0.15 weight percent or less,
and a regeneration zone flue gas in which the carbon monox-
ide content is approximately 500 ppm or less, and generally
10 ppm or less. These results are surprisingly, in that it is
known that at regenerator temperatures of from about 1100F.
~0 to about 1200F. and higher, an a~terburn of the carbon
monoxide contained the regeneration gases leaving the top of
the fluidized dense catalyst phase is initiated and high
temperatures of 1500F. and higher result in the dilute
catalyst phase. It is known that temperatures above about
1500F. are detrimental to the catalyst. The essence of the
instant invention resides in maintaining the fluidized dense
catalyst phase at a temperature such that the after-burn of
carbon monoxide to carbon dioxide is initiated in the
fluidized dense catalyst phase and is completed in the di-
lute catalyst phase with only a moderate increase in tem-
~',
.~
: _g_
,..
- . ... .
~464~3
perature, such that the temperature in the dilute phase of
the regeneration zone does not exceed about 1455F. This
controlled afterburn is accomplished by controlling the
amount of carbon monoxide in the regeneration gases leaving
the fluidized dense catalyst phase, such that the tempera- :
ture in the dilute catalyst phase is in the range of from
about 1375F. to about 1455F. and preferably from about
1400F. to about 1455F.
In view of the environmental considerations, it is im~
10 portant that the concentration of carbon monoxide, which is -known to be a severe air pollutant, be maintained at as low
a level as possible in the regeneration flue gas. In the
;process of this invention carbon monoxide concentrations in
the regeneration flue gas may be maintained at 500 ppm or
less, and generally at 10 ppm or less, without additional
treatment of the regeneration flue gas.
The amount of oxygen-containing regeneration gas
necessary in the practice of the process of this invention
will depend upon the amount of coke-contamination on the
catalyst being introduced into the regeneration zone.
Generally, oxygen in provided in an amount sufficient to
effect the complet~ combustion of coke from the catalys~ and
to provide an oxygen concentration in the flue gas from the
regeneration zone of from about 1 to about 10 mol% and
preferably from about 3 to about 10 mol%. The oxygen-con- -
taining regeneration gas is generally introduced into the
lower portion of the regeneration zone, however, if desired,
a portion of the oxygen-containing regeneration gas may be
introduced into the dilute catalyst phase. It is by supply-
ing this excess oxygen that it is possible to reduce the
...
.,
, ' --10--
_ .. . . . . .
.' `~ , ' ' ,
~L~)464~3
.;
carbon monoxide content of the regeneration flue gas to the
., ~
low levels hereinbefore mentioned.
In one embodiment of the method of the present inven-
tion still higher oxygen-containing regeneration gas rates
are employed in order to provide temperature moderation in
the fluidized dense catalyt phase and/or in the dilute
catalyst phase of the regeneration zone.
The oxygen-containing regeneration gas which may be
employed in practicing the process of this invention in-
- 10 cludes gases which contain molecular oxygen in admixture
with other inert gases. Air is a particularly suitable
regeneration gas. Additional gases which may be employed
include oxygen in combination with carbon dioxide and/or
other inert gases. Additionally, if desirable, steam may be
added as a part of the regeneration gas mixture.
In practicing the method of the present invention to
obtain a regenerated catalyst having a carbon-on-regenera-
ted-catalyst content of about 0.15 weight percent or less,
it is necessary to maintain the coke-contaminated catalyst ~;
in the fluidized dense catalyst phase at the aforementioned
conditions for a period of from about 3 to about 10 minutes.
.: .
~ of course, longer residence times may be employed, although
Q~, generally there is no advantage in so doing. It is an
:
advantage of the process of the present invention that
catalyst residence times in the regeneration zone may be
substantially decreased over residence times employed in
. .
other prior art processes. Thus, it is possible to operate
~, the process of this invention at a substantially reduced
, catalyst inventory within the fluidized catalytic cracking
unit. The residence time of the catalyst within the flu-
: .
--1 1--
~0~6483
idized dense catalyst phase is maintained at the desired
level by adjustment of the depth of the fluidized dense
catalyst phase within the regeneration zone. ;
In general, the amount of coke contained on the coke-
contaminated catalyst obtained from conventional fluid
catalytic cracking operations will be in the range of from
about 0.8 to about 1.0 pounds of coke per pound of catalyst.
This amount of coke, if burned to produce a regenerated
catalyst with a carbon content of about 0.15 weight percent
10 or less, will provide sufficient heat in the regeneration -~
zone to maintain the fluidized dense catalyst phase at the
desired temperature. However, if the coke content of the
contaminated catalyst is too low to maintain the desired
~ . .
temperature in the fluidized dense catalyst phase of the ;~
regeneration zone, torch oil may be introduced into the
fluidized dense catalyst phase to supply the necessary heat
energy.
This invention will now be further illustrated in the -
following examples which are not to be considered as a
limitation on the scope of the invention.
EXAMPLE I
A continuous fluidized catalytic cracking process was
operated in a pilot unit wherein hydrocarbon charge and
fresh regenerated catalyst were combined in the lower por-
, tion of a riser and wherein catalyst and hydrocarbon vapor
- discharged from the top of said riser into a reaction ves-
sel. In said reaction vessel, hydrocarbon vapor disenga~ed
' the used cracking catalyst and the cracking catalyst was
maintained as a fluidized bed with the reaction vessel below
the riser outlet by the action of primary stripping steam.
. ;' .
-12-
.: ' : ~, .......................... ,, . .,, ,, . :
. ... : . . . . .
~ 46~83
From the reaction vessel used catalyst was continuously
withdrawn into a stripping section wherein strippable hy-
drocarbon vapors were removed from the catalyst by the
stripping action of steam. From the stripping section, used
catalyst was continuously transferred into a reg~neration
vessel. The regeneration vessel comprised an upright cylin-
drical vessel having means for introducing used catalyst
continuously thereto, means for withdrawing regenerated
catalyst, a sparger near the bottom of the introduction of
oxygen-containing regeneration gas, e.g., air, a cyclone
separator near the top of said vessel for the separation of
- catalyst from the flue gas resulting from the regeneration
of the catalyst, and a vent pipe for removing flue gas from
; the regeneration vessel. The regeneration vessel was equip-'"
ped with valves, piping, thermocouples, pressure gauges,
sample taps and flow measuring devices necessary to obtain
the data shown in this example. In this example, used
catalyst at a temperature of about 950F. was continuously
added to the regeneration vessel through a catalyst entry
nozzle. In the regeneration vessel, the catalyst was main-
` tained in a dense fluidized bed employing air. The catalyst
regeneration was operated at increasing dense phase tempera-
tures. Orsat analysis of the flue gas and residual carbon
analysis of regenerated catalyst were made at different
operating conditions. The operating conditions and test
, results are shown in Table 1 below.
`, :':"
''Y ' ,;'' '
; ,:
;' .
.' :
~ -13-: ,' .
109~6~33
TABLE 1
Run No. 1 2 3 4 5 6 7 8
Ai~ to re-
generator,
SCF/H 606 605 615 657 690 738 791 899
Dense Phase
Temperature,
F. 1245 1243 1252 1280 13301391 1491 1411
Flue Gas
10 Analysis(Orsat)
- CO2,mol.% 11.8 12.0 12.0 13.0 14.816.4 12.0 12.0
O ,mol.% 0.6 0.4 0.2 0.2 0.8 1.4 5.4 6.2
C~,mol.% 7.8 7.6 6.4 5.6 1.8 0.0 0.6 0.0
Carbon on
regenerated
Catalyst, wt.%0.32 0.43 0.3 0.2 0.12 0.12 0.12 0.11
Coke Yield
(% of fresh feed) - 7.53 7.26 7.70 7.16 7.37 6.19 6.68
As can be seen from the data tabulated in Table 1
above, as the dense phase catalyst bed temperature increased,
the amount of carbon monoxide present in the flue gas de-
creased. At about 1391F. (Run 6) the carbon monoxide
content of the flue gas tested 0% by the Orsat analysis
method. Substantially all the carbon monoxide from the
combustion of coke was converted into carbon dioxide within
the dense phase bed. Consequently, very little or no "after- ;
burning" occurred in the dilute phase. The results shown in
column 6 of this experiment, wherein carbon monoxide in the
~ flue gas is substantially eliminated, wherein residual
i, 30 carbon upon the regenerated catalyst is reduced to about
0.12 weight percent, and wherein after~burning of carbon
monoxide in the dilute phase is not excessive, demonstrate
,~ the advantage of the present invention over regeneration
processes known to the prior art.
EXAMPLE II
The process as described in Example I was operated to
demonstrate the necessity for obtaining a sufficient tem-
.. . .
-14-
:
, .
., : ,. : :
.
,:
. . .
~ o~ s3
perature in the dense phase regenerator bed for substanti-
ally reducing the Co content in the flue gas and reducing
the residual carbon-on-regenerated-catalyst. The second run
was operated at a constant regenerator temperature of about
1130F. The air rate was increased to provide substantial
excess oxygen in the flue gas. However, as can be seen from
the data shown in Table 2 below, the CO content of the flue
gas was not substantially reduced and the residual carbon-
on-regenerated-catalyst was not reduced.
TABLE 2
Run No. 1 2 3 4 5 6 7 8
Air to
Regenerator
SCF/H 449 449 487 522 557 593 638 638
Dense Phase
Temperature
F. 1122 1106 1114 1036 1130 1116 1129 1132
Flue Gas
Analysis (Orsat)
20 C02,mol.% 11.8 11.0 11.4 11.0 8.8 8.0 8.6 9.8 -
O ,mol.% 0.6 0.8 0.9 1.0 3.2 3.0 4.4 5.0
' C~,mol.% 4.6 6.2 5.2 6.0 6.0 5.0 6.0 5.0
Carbon on
Regenerated
Catalyst, wt.%0.16 0.12 0.45 0.45 0.13 0.20 0.23 0.17
Coke Yield
(% of fresh
feed) 4.84 5.07 5.29 5.79 5.44 5.47 6.05 5.99
The results of this experiment demonstrate that the
30 temperature of the regenerator dense phase catalyst bed must
be increased above normally accepted fluid catal~st regenera-
tion temperatures to promote substantially complete con-
version of Co to CO2. Further, excess air at relatively low
regeneration temperatures is not sufficient to convert
substantially all the CO to CO2 within the regeneration
. :
zone.
; ~.
-15-
464~33
EXAMPLE III
The fluidized catalytic cracking unit (FCCU) of Example
I was operated to determine the feasibility of operating the
FCCU regenerator with excess oxygen and dense phase catalyst
bed temperatures sufficiently high to reduce the flue gas CO
concentration to about 10 ppm or less and reduce carbon-on-
regenerated-catalyst tCORC) to a low value, preferably about -
0.12 weight percent or less. Cracking runs on the FCCU were
made on a once through gas-oil charge basis at constant
charge rate. Reactor operating conditions (riser ou-tlet
temperature, catalyst bed level, and regenerator air rates)
were adjusted to obtain a range of regenerator temperatures
and flue gas excess oxygen concentrations. Conclusions from
- this example include: carbon monoxide concentrations in the
flue gas of about 10 ppm or less were obtained without
excessive after-burning of CO to CO2, when operating at
, ,.
'~ regenerator bed temperature of about 1375F. and higher and
with abou-t 1-5 mol.% excess oxygen in the flue gas; carbon-
. on-regenerated-catalyst was decreased to less than 0.1
` 20 ~ weight percent by operating at regenerator bed temperatures
of about 1375F. and higher and with about 1-5 mol.% excess
oxygen in the flue gas; coke yield was substantially reduced
`t` at constant conversion by increasing regenerator tempera-
.~ tures from the 1100-1250F. range to about 1375F. and
- higher; and cracked naphtha octane values increased about 2
RON (clear) at constant conversion by increasing the regen-
erator temperatures from the 1100-1250F. range to about
1375F. and higher.
~- Charge stock employed in this experiment was a refinery
virgin gas oil FCCU charge. Properties of this charge stock
~"
.'
~ 16 -
:~ ,
'
. . , , ., . . , , . , .: ' '
6~3
are shown in Table 3 following.
TABLE 3
CHARGE STOCK EVALUATION
Description FCCU ~AS-OIL FEED
"
Gravity, API 29.5
Aniline Point, F. 180.5
Sulfur, X-Ray wt.% 0.41
ASTM Distillation, F.
IBP/5
lO/20 540/5~4 ~`
30/40 611/638
658
60/70
80/90
95/EP
Bromine Number
Conradson Carbon Residue, wt.% 0.19
Aromatics, wt.% 40.2
Refr~ctive Index at 25C 1.486
20 Basic Nitrogen, wppm 199
Total Nitrogen, wppm 32
Viscosity, ~entistokes at 100F +80
W Absorbance at 285 ~. 4.41 `~
Pentane Insolubles, wt.% 0.07 -
The two initial FCCU runs (2616A and 2616B) were made - :.
to determine the approximate minimum regenerator tempera~
- tures required to initiate burning of CO in the regenerator :
.
dense phase bed as excess oxygen was added. For run 2616A
the reactor bed level and riser outlet temperature were ad-
. ,:
justed to give a regenerator bed temperature of about
1120F. The regenerator air rates then were adjusted to
obtain less than 1 vol.% 2 in the flue gas and were main~
- tained at this level for the first two hours of the run.
During these first two hours, carbon-on-regenerated-catalyst
(CORC) was found to be in the range of 0.3-0.5 weight
percent and flue gas CO2 to CO ratio ranged from 1.8/1 to
~;
:, ' .: '
' -17- ~.:
`:
.: . .
.. . , . ~ . .~ . . .. . . . .
Lo~ 33
2.6/1. Thereafter, the regenerator air rate was increased
: every two hours in increments of about 30-40 SCFH in an
; attempt to burn CO to C02 in the regenerator bed. Pertinent
operating data and yields from run 2616A are shown in Tables
4A and 4B, following.
,~
,., ~
:
.:
,
. , .
.,
:
. ~ .
.
, . . .
..
,'~` '
; I :
,.~''
. -18-
.:
. '' 5 z ~ ~ co co 10464B3
o ~
_. -:
C) ~ o~o Ln CO o ~ ..
o U~
C ~3~0 ~ o
.
' I ~ ooo, I
. ~
. .. _.... . _ . '~"
$V ~o ~ ~ .~ ' , , .
. ~ ~ . :
~,, ; ~' O ,~"
I Lq lo~
~ Dl
~' I
;' l ~ ~ ~ '
_ _ ~o
b ' ' o
,` '~ ~ ~ I . ~ ~ I
.; ~ ~1 r~
~3 v~ ,~ ~n n ~
N N t:~ N B
N ~ ~D CO O
~ .
. _ . ~ '
. ,1~ ~ .~ , .
.1 - ,'
19-
.'~ .
- ~0~6~83
~ 8 ,~.o=~ :
.. ~ o __
~ ,3 __
~ ~ ~ 1
.~ . `~1 C~ ~ ~
~,~ ~ o . :'
~ ~ ~ . . ~ ~
¦H ~ 3 ~ o "~ ~
U~ d co ~~ ~D ': '.
. ~ u~InLn
_ o~ 3
~ ;1 ~ r~ 1~ ~
~: ,,
~: ' ~ ~
. _ .
,, , "_ ~ ~ ,
.
--2 0--
.. . ,
- . -: .
`; ~L04~83
As can be seen in Table 4, carbon monoxide
concentration in the flue gas was not reduced to low values
- acceptable for pollution control during this run with low
- regenerator bed temperatures, even though up -to 6.4 mol
percent excess oxygen was present in the flue gas. The CO2
to CO rakio at the end of this run was lower than at the
start of the run and no significant increase in regenerator
bed temperatures was experienced as would be expected if
additional CO had been burned to CO2 within the regenerator ~^~
bed. However, the CORC was improved to about 0.2 weight
percenk as a result of a higher oxygen content within the
regenerator bed. From this run, it is seen that the 1120F.
. . .
regenerator bed temperature at the start of the run was too
low for obtaining a CO burn within the regenerator bed.
The second run, 2516B, using the same procedure as
for run 2616A, except reactor conditions (reactor bed level
and riser outlet temperature) were adjusted to give a
regenerator bed temperature of 1245F. at -the start of the
run with less than 1.0 mol percent oxygen in the flue gas.
Thereafter, the air rate was increased in the increments of
40-50 SCFH to provide additional oxygen in the regenerator.
Operating conditions and yields for run 2615B are summarized
in Table 5, following.
., ' .,
.
.:,., ',
.
.. : .
,~ ~ , . . ..
. - .,- . .
-21-
....
.
.. , . . ~ . . .
: . . . : , , .: . , .
~046483
_ ~c
~ ~ z r~
,~ C) O O O') H N ~)
Ql O ~ ~ I I co I I o~ ~ ~ '~
~ _ _ .
o\ ~ ~ ~ ~' O (D `~ CO I :
. ~1 t-- ~ ~D (D ~ ~ ~-- ~ ~ I ' '~
~ a) I .................... I
. rl ¦ O r-i ~I H r-l O O N O
~ ~_ Lt~ LO 15~ Ll~ Il') Ll') If)
rl9 ..
.` (I) ~ t` CO ~ N ~D ID 15~ r`
~ ~ ~i' O ci) a) c~
~ D ~ t-- .,
Q) o\
X ' l
, O ~ l .,
c) 3 i .
_~D O U~D O ~ O '-- ' :
.~ O (D ~ cn (D ~0 0 0
O o\ . ~
~ O ~ co
C~ C~ I
. ___ .._
o ,
~ O ¦ N N N ID ~.D H 1S~ ~ Lt) : .
rd4 ~
~) ~; l
~ ..~"., ., _ :
H X a)
~ .~.
~ h ~1 4 o oo N N N N N N O
~ Z 4 ~ O I 1- r- (D tD co o~ c~ c~ ~ . .
O 1~ O I ~ ~ 1
; H ~ ~ ~ l -. .
~, H __
O 4 ~ 1 ~ ~1 ~I N Lr~
, E~ ' rl -.
~:1U c~ a) C) . . . . . . . . .
~:1 c~ C) O ~ u> u~ o
' ¢ ~: ~ ~ F~ V~ ~ .
. . I ~ t` ~ ~ Lr) ~ ~
1~ !:~; ~4 I ~ D
O E~ O I a~ ~
- ~ C~ ~ _ .~__, . ,
~ ~ C 1~ ' =t ~ (D
'' F4 1}~; ~ I o~
E~ _ _
4 b~ I co co a) co CD a) co a~ ~D
:i c) ~ ~1) I t` t-- t-- t-- t-- r- r~ L-- cn
4 I .........
) P~ ¦ N N N N N N N N N
, ' . .__.. ~ ., ,. . .
1~ l
.~ O $
O N ~ ~D CO O N =I' tD
;1, . ~ r-l 1~l r-l r-l
rl
:~ . ` E-
:' , _
-! m
~D
-22-
... . . , , :
: .
046~33
: _ _ ,
'~ ,, ~ . , , ~ . . . . . , 1,
~ ~D ~r ~ a) o r~ t~l t~ ~r
~ ~ 8~ o o o o j: ~
. ~ o o o , o t~, ~ ~ ~ . .
_ ~ ,~ ~,
~ ~ ~ t~l t"l tD ~ O U') ~ ~
~LI O ~ O O O O ~ ) 0~ ~ O ,' ,
~ B r O C' ~ ~ 10` 0 ~ ~0 ~ ~S ~ ~S ~:
{~ o' o oi o O O O o I g
~' , ' . , . ~ ~ ~ V
3 ~ o Ln- ~ o~ t~ r
~ t~o t~ t~ t;o a~ ~ t~ ~ O
~1 8~ o o o o o ~ ~ S
H~ ~ ~ ~ o . . ~
U~ ~ ~~ t~ ~
~ 8~ ~ B
~ : ~ ~ 8
, - !~ ~ ~ ~ o~ t~ o
_ fi
.~ ~ : ~ ~ 8
;'' ' . ~ ~ n O ~o O ~ $
., . ~u ~
., . , . . _ ~
,~. - .' ~ ~o~o~ooOoo~
.'~ -. ~ ~ ~ o ", . :.
.~, ~ O~ ~
~ Ç~ . ~
L~
. '
. . . -23- . `
. .
; ` , . .
' -
~09~83
From Table 5, it is seen that as the air rate was
increased there was a corresponding increase in the re-
generator bed temperature, a decrease in the CO content of
the flue gas, and a reduction in the level of carbon-on-
regenerated-catalyst. The data indicate that at 1.4 mol
percent oxygen in the flue gas and 1391F. regenerator bed
temperature, substantially all CO was being consumed in the
regenerator. Incremental increases in the regenerator air
rate were continued until about 5 to 6 mol percent oxygen in
the flue gas was obtained. As air rate increased the
regenerator bed temperature to about 1410-1420F. where it
lined out with very little CO in the flue gas. At this
lined out condition, there was little or no after-burning, ~`
(i.e., burning of CO to CO2 in the dilute phase above the
catalyst dense phase bed), indicating that essentially all
CO was burned to CO2 in the regenerator dense phase catalyst
bed.
From Table 5 it is seen that as the regenerator bed
temperature increased from 1245F. to 1410F. during run
2616B, carbon-on-regenerated-catalyst (CORC) decreased from
about 0.43 weight perceNt to about 0.04 weight percent; CO
content of the flue gas decreased substantially from about 7
mol percent to about 0.2 mol percent; and debutanized
naphtha octane increased from about 90 Research Octane
(clear) to about 93.7 Research Octance (clear). Further,
from Table 5 it is seen that gas-oil conversion did not
change significantly during the course of run 2616B, despite
a significant decrease in catalyst to oil ratio.
As the regenerator temperature increased from 1245F.
to 1410F. in the course of run 2616B, it was necessary to
;
-24-
,:
. . :
~0~1~4~3
reduce catalyst circulation into the riser reaction zone in
order to maintain a cons-tant riser outlet temperature.
Hydrocarbon charge rate was content, consequently the
catalyst to oil weight ratio was reduced. In normal, low
temperature regeneration, operation of fluid catalytic
cracking processes, lower catalyst to oil ratios are ex-
pected to result in lower fresh feed conversion values,
other conditions being maintaine~ constant. Evidently,
during run 2616B reduction of fresh ~eed conversion due to
10 lowering catalyst to oil ratios was offset by increased ;;
conversion due to increased effective catalyst activity as
carbon-on-regenerated-catalyst decreased from 0.43 to 0.04
weight percent.
Run 2616B was successful in demonstrating that high
temperature regeneration of fluid catalytic cracking cata-
lyst could be accomplished at temperatures in the range of
about 1245-1420F., with excess oxygen present in the re-
generator wherein substantially all the CO was burned to CO2
in the regenerator dense phase bed and wherein no severe
after-burning occurred in the regenerator dilute phase or in
the flue gas line. However, CO content of the flue gas was
indicated, by results of ORSAT analysis, to be in the 0-0.4
mol percent range. The range, 0-0.4 mol percent, of Yalues
obtained for CO concentration in the flue gas was considered
to be too large, considering stability of operations during
run 2616B. Consequently, a program of testing the accuracy
of ORSAT analysis of low CO concentrations in flue gas was
undertaken. As a result o~ this testing, it was found that
ORSAT analysis of flue gas for CO concentrations in the 0-
0.4 mol percent range were highly inaccurate as compared to
'
.
-25-
1~46a,L83
'
gas chromatographic techniques and results from MSA Model
47133 CO detector. Results from -the gas chromotograph and
MSA detector supported each othe~r and indicated that CO
concentration in the flue gas was less than 10 ppm under
conditions wherein the regenerator dense phase bed tempera-
ture was in the range o 1380-1430F., and wherein 1.0 mol
; percent or more excess oxygen was present in the flue gas.
Conclusions, which may be drawn from the results
obtained in run 2616B, and reported in Table 5, include that
10 for an FCCU regenerator operating at about 1250F. with a
normal air supply (i.e., sufficient air to provide about
1/1 CO~/CO ratio in the flue gas), substantially all CO can
be burned to CO2 within the regenerator dense phase catalyst
bed with very little or no afterburn of C0 in the regenera-
tor dilute phase by increasing air flow to the regenerator
dense phase catalyst bed sufficiently to maintain at least
about 1.0 mol percent oxygen, and preferably about 3.5 mol
~:~ percent oxygen, in the flue gas. Addi-tion of such excess
oxygen to a regenerator dense phase catalyst bed operating
s 20 at a temperature of at least about 1250F. initiates a CO
burn within the regenerator dense phase bed. Initiation of
this CO burn causes the dense phase bed temperature to
increase to a temperature in the range of about 1380-1420F.
whereupon essentially all the CO is burned to CO2 within the
`~ regeneration dense phase catalyst bed and very little or no
, afterburn of CO to CO2 occurs in the regenerator dilute
phase. This result is unexpected for normal regenerator
temperatures below about 1250F., an increase in air supply
- to the regenerator results in initiation of a CO afterburn
',
,
-26-
"',;
,`~, ' '
:
~Oq~64~33
in the regenerator dilute phase.
As is well-known to those familiar with FCCU's, an
afterburn is combustion of CO to C02 in the regenerator
. ~
dilute phase, or in the flue gas line, above the dense phase
catalyst bed. If not controlled, an afterburn can result in
excessively high flue gas temperatures which can damage
cyclones and other regenerator internal parts. An after-
burn is normally controlled by, among other methods, mini-
mizing air supply to the regenerator so that little or no
excess oxygen is present in the dilute phase as combustion
gases leave the dense phase catalyst bed.
; EXAMPLE IV
.4 ' '
.. . .
Upon completion of the fluidized catalytic cracking
runs of Example III, demonstrating that essentially all CO
could be burned to Co2 in a regenerator dense phase catalyst
bed at temperatures (1380-1430F.) compatible with molecular
sieves cracking catalysts in the presence of excess oxygen,
without initiation of severe afterburn in the regenerator
-, dilute phase which might cause damage to the regenerator
.,~ .
20 structural members or to the catalyst, additional fluid `
catalytic cracking runs were undertaken to demonstrate the
advantage of such high temperature, low flue gas CO con-
centration regeneration operations over more conventional,
lower temperatures regeneration operations. In this ex-
ample, four high temperatures regeneration test runs were
made on the fluidized catalytic cracking unit of Example I
at successively higher fresh feed rates and successively
lower FCCU regenerator catalyst inventories down to the
minimum regenerator catalyst inventory attainable. For com-
- 30 parison, two runs were made at more conventional FCCU low
... .
~ .
-27- ;
" .
' - . ' ' ' ~ ' ; ' ' ' ~ ,' .,
, . ' ; . .
.. : .. ~
104~4~33
temperature test runs and comparison runs demonstrate that
for the high temperature, low flue gas CO concentration
runs, reduction of regenerator datalyst inventories to about
4.6 lbs. catalyst per bbl. daily fresh feed capacity could
be obtained without effecting the level of CO emissions (10
ppm in flue gas) or the low level of carbon-on-regenerated-
catalyst (0.12 wt.%). Also, the high temperature, low flue
gas CO regeneration operations result in higher debutanized
naphtha yields with higher clear octane values, and lower
10 coke yields compared to more conventional regeneration
operations at the same conversion and operating conditions.
Fresh charge stock used in this example was a FCCU gas
oil feed obtained from a petroleum refinery. Test results
on this fresh feed are shown in Table 6, following. Recycle
feed comprised heavy cycle gas oil recovered from -the FCCU
cracked products. In all runs of this example, fresh feed
and recycle were charged to a single riser of the FCCU.
.,
.; ~
.. . .
. ,
. .
, '
.',
, .
-28-
.
. TABLE 6
- FRESH CHARGE TEST RESULTS
: DESCRIPTION FCCU ~AS-OIL FEED
Gravity, API 27.9
ASTM Distillation, F(Vol.)
IBP/5 315/524
10/20 553/592
30/40 623/655
685
60/70 713/737
751
:
Pour Point, F. ~65
Refractive Index at 25C 1.4874
...
Sulfur, wt.% 0.49
Total Nitrogen, wppm 354 ;;-
Basic Nitrogen, wppm 142
' Aniline Point, F. 181.5 ;-
Bromine Number 3
- Watson Aromatics, wt.% 42.6
W Absorbance at 285 m. 4.44
Conradson Carbon Residue, wt.~ 0.14
Catalyst employed in the runs of this example was an
ion-exchanged silica-alumina zeolitic molecular sieve cata- `~
lyst as manufactured by Davison Chemical Co. under the ;~
tradename "CBZ-l". Equilibrium catalyst obtained from a
commercial FCCU was employed at start-up of the FCCU, and
fresh catalyst was added on a regular basis to maintain
equilibrium activity.
Detailed data on operating conditions and product
yields from the four high temperature, low CO regeneration
test runs of this example and the two conventional regenera-
. tion test runs are shown in Table 7, following.
; .
,;
. . ~.
,,.
.. j , :
-29-
,,,
, . . .
,
~.. `,' . ' ., ~ . ,
.~ ~ ~ , . , .' . ' !
~v'~
~ ~ OO~ l
~ ~ ~ )
z--- - ~
. ~ d~ CO ~ ~n o
m ~ ,, r~ Ln O 1~ 1~ 0
~ ~ O ~ o o a~ ~D ~
Ln Ln ~ Ln Ln Ln
. _ . _
., . a) ~ ~1 ~ O ~ ~ O
t~ Ln Ln ~n Ln ~ Ln
,
'~; ~ o 1~
3 r~ g o~ D
. r~ co Ln ~n ci~ er
~ l~ i ~ . ~ .
H _ _ _
-l Z ~ ~ ~ Ln ~ ~ L.'l
~_) ~ L,; ~ L,~ i
~ ~:1 ~ ~
~ .~ ~ -- --. . '~
~ ~ ~ ~ o ~ m ~ ~ ~
i~ _ ~! ,~ ¦ ~r ~- Ln ~ Ln Ln .
~ ~ 1~ _ , _ .
t ~ t) . ~ o ~ ~
~5 ~: ~4 ~1 Ln ~r ~ m ~ o
~ æ O ~ ~
', . ~ ~ ~n c~ ~ r. cn .
' . ~ ~i r~ . `:
., __ _ . . , ' ~:
~ ~ . .
.~ . ~ ~ ~ 1` 1` ~ a~ o o .
~ S ;~ ~r ,i ~ :n ~ Lri
~1 . . ~ . .'
!) ~ r~
i Ln o~ n ~ t~
. &~ ~ ~ .
r ~
l ~ ~ O
--30--
,
:.
~ ~ o ~ ~ ~ ~
~ . . . ~ ~ .
c~ O ~ ) 3 o o o o o o ~L0469L~33
_ _ .
,` .~ .~ ~ ~ a) o co . ....
' ~ ~ ~ ~D o ~. ~ O O . , '
.; . ' U~ o o o o o o
~ ~ `. cooo~ .
~ ,0 . ~ u~ ~r ~ ~ o _I
h ~ IJ h ~ ~ --I ~ ~ o . .
~ ~ ~'0 r~ i 0 ~i
, - ~ ~ ' ' " .
., ~ ~1 ~ O'~ ~ O
~ ~ ~'0 ~ D U), .~
_ _ _ , , _ _ . ___--
U~ O ~o ~ ~ ~o I I
.' ~1, _ ~I V__
~ 4 L~ Ir) ~ ~ .
- ~ ~ 8 ~ o ~ ~
_ ~ l~ O ~ ~ O ' ' `' ,.
U~ ~ c? O ~i ~ ~1 ~D CO ~)
~ ~ ~ ~) ~ . ~
~t ~ a~ o ~o o ~ ~7 ~
. O ~ ~ Ul ' , ',
_ _ _ (~
~ ~i 4-1
Z H ~ ~ 1~ . O ~
1, ~q ~ ~3 10 10 10 10
. . ~
. ~ ~! , _ ~ ~ - , .. -
, ~ ~ : ~4 . ~' `.`:"'. '
,, E-l ~ t~ r~ r h~
:: ~ _ o .~ a~ co cr~ r` t~ I-- C~
~r: ~ a) r~l ~ ~ ~ '~1 ~ ~; _ . ...
~ ~ ~ ~::
.' ' ~ , 1~ .. ~ '~ `',''".:
î~ a) F ~ . . .
'.`` ~ ~ o ~ ~ ~ ,~ .' ,'~'
P~ ~r N ~7 N N ~D
~. ~ ~ . ~ ~ ~ ,~
_ ~ C) ' ,,'
;,i: . ' -IJ ~ 1
~ ~ Ui
(d C: Q ~i ~o ~r ~r ~1 a~ ~1 ~ ;
,.~ U 1-1 ~1 ~ ~ tl~
.~ __ . _ .~
'~! S~ 0~ ~ N ~ O
.~ .,-~ ni U o r- u~ In Ir') O
~, ~ u~ n ~ U~ O
_ .,1 ,~
~1 ~Z; N ~ P ~U ~
~ ~ O O' ~ ..
. j ~ ~ D ~ U~ ^ '
,, ~ ~ ~`3 ~, ~, ~_~.: ~
~il , . ~,
! -31-
;!
.. ., . .. . .,. . . .. . . ~ . . . ... . . .
`` ~
~0~6~83
The high temperature, low CO regeneration study com-
prised four high temperature regeneration runs made at
successively higher fresh feed rates and successively lower
regenerator catalyst inventories, down to the minimum allow-
able inventory (24.8 pounds). The 24.8 pounds regenerator
catalyst inventory for runs 2623B and 2624A is significantly
below the 100 lb. inventory used for comparison runs 2609C
and 2609F. From Table 7 it can be seen that regenerator bed
temperature of about 1420-1445F. was maintained for the low
10 CO regeneration test runs and, as in the previous examples
of high temperature regeneration, both CO concentration in
the flue gas and carbon--on-regenerated-catalyst were at very
low levels. As a result of increasing the fresh feed rate
(and consequently the cataIyst circulation rate~ and re-
ducing the regenerator catalyst inventory, the catalyst
residence time in the regenerator was decreased from about `
9.8 minutes for run 2622H at the start of the study to 4.7
minutes for run 2624A and 2633B. At the same time, the
specific coke burning rate (e.g., the weight of coke burned
20 per hour per weight of catalyst in the regenerator) in-
creased from 0.068 to 0.149. Thus, lowering the regenerator
residence time from g.8 to 4.7 minutes and increasing speci-
fic coke burning rate from 0.068 to 0.149 lb/hr/lb. had not `
discernable detrimental effect on either carbon-on-regenera-
ted-catalyst (CORC) or CO emissions in the regenerator flue
s gas, thereby demonstrating utility of the process of the
present invention over a wide range of FCCU regenerator
operating conclitions. No afterburn of CO to CO2 was ex-
perienced in the regenerator dilute phase under high tem-
30 perature regeneration conditions, indicating essentially
... .
-32- ~
~cii464B3
complete conversion of CO to CO2 within the regenerator
dense phase bed.
Comparison of the product yield data obtained from the
- four high temperature regeneration runs of this example
(runs 2622H; 2623A; 2623B and 2624A) with yield data from
the conventional regeneration runs (2609C and 2609F) demon-
strate further advantage of the process of the present
invention. Coke yields for the high temperature regenera-
tion runs are about 0.8 to 0.9 wt.% below coke yields for
10 conventional regeneration at the same conversion and opera- ;
ting conditions, which amounts to 14-15% reduction in coke
yield. Total debutanized naphtha yield and octane are
significantly higher for the high temperature low flue gas
CO content regeneration method of the present invention, ;
compared to the conventional regeneration results. -~
EXAMPLE V
In this example three regeneration test runs were made
on the fluidized catalytic cracking unit of Example I. The
runs were made at fluidized dense catalyst phase tempera-
tures of from about 1250F. to about 1375F. The purpose ofthese runs was to demonstrate that at intermediate fluidized
dense catalyst phase temperatures in the regeneration zone
within the range indicated, a regenerated catalyst could be
obtained with a carbon-on-regenerated-catalyst (CORC) con-
tent of about 0.15 wt.% or less and that the afterburn of
`1 carbon monoxide in the dilute catalyst phase could be con-
trolled such that the temperature in the dilute catalyst
phase did not exceed about 1450F.
; The charge stock used in these runs was the same FCCU
, 30 gas-oil feed employed in Example III, the properties of
... . .
.,
,
~33~
'
... . . . : .
. f .' . ~ , . '' ~ ' .
~0~83
which are shown in Table 3. Detailed data on operating
conditions and product yields from the test runs of this
: example are shown in Table 8, following.
., :.
." ,:
.' ' ~
"' '''
~ ` :
:' .
, ',
.,, 1", '.
,~,; .
~ . :
',"f . .:
f '
!~ :
,,,~, ,.
''
~)46fl~83
~ ,~o _, ~ o j ,
., .. ~ ~ _ . , ,'.
,~, ~ '~ g ~ . .
~
,,, ~ ~ .
~, - ',
t ~ p C~
~ 1~ ¢
~ . ~
, ~ ~@ 1~1
~1 ~ ~ ~ a~
.,, . ~ :
.,, . _~ ~ ~ ~ ~ , .
, , ~ ~ .'., ~ ~ ~ G~
K O ~ ~1 N ~ ~`1
,~,', :'
.' . ~ V ~ I
.,~ . ' ~ ,I ,_1 ~ . ".
~ i ~ ~ ~ I
.'~ '.
;". . , ' ' ' ' . ' . , ' ':, . . .'` ', ', ' . ~ .
,: : ' . :, , . ,, ' .,
-- ~046483
..
.,.,. .I _ ~
. ~ ~. a
* 000 .
`........................... . , 8 _~ ~ ~
~-,'. . ~ 1''1 0 0 ,W,
.,, ~ 5~ ~ o o o ~ o ~
.-.................. . ~ o _ ~
.-- _ 8 ~_~
.- ~ ~ .,
O
. . ... _ ,. , ~ ~ ' '~
.~'3. ~ J
- Y ~ ~ ~ U
. ~ u~ .
~¦ ~ ~ 1~ ~
~1
I ~
:~
..
~i ~ . -
'
~ ~ ~ ~ o ~
. ~ . _. __ ' ~ O ~ O
'' . . ~ U~ ~) ~ ~ ~ri O
. ~ i i i ,~ ~ ~0 ' :'~.: ' ,
., . . . ~ $ . ~: ~J ~ * .,
. ~ . ~ _ _T.__ ~ .
- 3 6- ,:
: , l
~ I
:1046~33
As can be seen in Table 8 operation of the regene-
ration process with a fluidized dense catalyst ph~se
tempexature in the range of from approximately 1304F. to
about 1355F. results in a "controlled afterburn" of carbon
monoxide in the dilute catalyst phase wherein temperatures
in the dilute catalyst phase range from about 1417F to about
1455F. In these runs the regeneration air rate was main-
tained at a level such that the oxygen content of the flue
~ gas was in the range of from about 3.95 to about 5.5 mol%.
^- 10 In all runs a regenerated catalyst with a carbon-on-regene-
rated catalyst (CORC) content of approximately 0.15 weight
- percent or less was obtained.
The data from run 2609F (presented in Table 7) il-
lustrates that considerable after-burning will occur if
excess oxygen is present in the regeneration flue gas. In
that run, the fluidized dense catalyst phase was maintained
at a temperature of 1261F. and the afterburn was approxi-
mately 113F with approximately 3 mol% oxygen in the
` regeneration flue gas. Nevertheless, the carbon monoxide
content of the flue gas in that run was high (0.95 mol%),
; ':
:'
..
. , ~ .
!.'
`; .
." .
,
, I
;~ .
,
~ -37-
;` :
, . . ... . . .
.
~ 0~6~3
indicating that a still higher air rate is reguired to burn
substantially all of the carbon monoxide. Additionally, it
may be noted that in runs 2616B (presented in Table 5) the
data indicate that at a fluidized dense catalyst phase
temperature of approximately 1275F. there is some after-
burning as indicated by the slight drop in carbon monoxide
content of the flue gas. Moreover, the data there presented
show that at a fluidized dense catalyst phase temperature of
~ approximately 1315F. there is a considerable afterburn as
- 10 evidenced by the still lower carbon monoxide content of the
flue gas. However, in both these runs the oxygen content of
the flue gas was low (less than 1 mol%) resulting in in-
complete conversion of the carbon monoxide.
The afterburn obtained in the three runs, presented in
Table 8~ ranged from approximately 11F. to 151F. and
were obtained with excess oxygen present in the regeneration
flue gas in an amount of from 3.95 to 5.53 mol%. A com- `~
parison of Run 2616H with Run 2616G2 ~roughly eguivalent
fluidized dense catalyst phase temperatures) illustrates the
.. ~.
20 effect of higher excPss oxygen rates on the reduction of ;~
carbon monoxide in the flue gas.
From the foregoing disclosure and examples, many modi-
fications and variations will appear obvious to those
skilled in the art. All such variations and modifications
~` are to be included in the present invention, and no limi-
tations are intended except those included within the -`~
~; appended claims.
.
-38-
.;. . . . . . .
