Note: Descriptions are shown in the official language in which they were submitted.
l 16900g ~ I
. 1 BACKGROUND OF THE INVENTION
The invention is concerned with increasing the portion
I of heavy petroleum crudes which can be utilized as catalytlc -
cracking feedstock to produce premium petroleum products, E
particularly motor gasoline of high octane number. The heavy
ends of many crudes are high in Conradson Carbon and metals which
are undesirable in catalytic cracking feedstocks. The present
invention provides an economically attractive method for
. selectively removing and utilizing these undesirable components
from the residues of atmospheric and vacuum distillations,
commonly called atmospheric and vacuum residua or "resids". The
undesirable CC (for Conradson Carbon) and metal bearing compounds
present in the crude tend to be concentrated in the resids
because most of them are of high boiling point. The invention
provides a méthod for processing whole crudes high in Conradson
Carbon and metals to provide feeds-tock for catalytic cracking.
When catalytic cracking was first introduced to the
petroleum industry in the 1930's, the process constituted a major
advance in its advantages over the previous technique for I~
increasing t~e yield of motor gasoline from petroleum to meet a t
fast-g~owing demand for that premium product. The catalytic ~i
~ ~ process prod es aoundan~ yields oi high octane naptha
. , /
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; 30 . .
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"~ lt~i9009 ~ ~
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1 from petroleum fractions boiling above the gasoline range,
upwards of about 400F. Catalytic cracking has ~een greatly
improved by intensive research and development efforts and plant
capacity has expanded rapidly to a present-day status in which
6 the catalytic cracker is the dominant unit, the "workhorse" of a
petroleum refinery.
As installed capacity of catalytic cracking has
increased, there has been increasing pressure to charge to those
units greater proportions of the crude entering ~he refinery.
Two very effective restraints oppose that pressure, namely
Conradson Carbon and metals content of the feed. As these values
rise, capacity and efficiency of the catalytic cracker are
adversely affected.
The effect of higher Conradson Carbon is to increase
1~ the portion of the charge converted to "coke" deposited on the
catalyst. As coke builds up on the catalyst, the active surface
of the catalyst is masked and rendered inactive for the desired
conversion. It has been conventional to burn off the
inactivating coke with air to "regenerate" the active surfaces,
2D after which the catalyst is returned in cyclic fashion to the
reaction stage for contact with and conversion of additional
charge. The heat generated in the burning regeneration stage is
recovered and used, at least in part, to supply heat of
vaporization of the charge and endothermic heat of the cra-cking
2~ reaction. The regeneration stage operates under a maximum
temperatur llm tation to avold heat damage of the
-2-
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; 9 0 ~ ~3 t`
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1 catalyst. Since the rate of coke burning is a function of
temperature, ~ follows that any re~eneration stage has a
limlt of coke wh~ch can be burned in unit time. As CC of
the charge stock is increased, coke burning capacity becomes
6 a bottleneck which forces reduction in the rate of charg~ng
feed to the unit. This is in addition to the d1sadvantage 1
~hat part o~ the charge has been diverted to an undesirable , t
reaction product.
Metal bearlng ~ractions contain, inter alia, nickel -
10 and vanadium which are potent catalysts ~or production o~ .
cok~ and hydrogen. These metals, when present in the chargs, t
are depos1ted on the catalyst as the molecules in which they
occur are cracked and tend to build up to levels which
become very troublesome. The adverse effects o~ increased
18 coke are as revie~ed above. The lighter ends of the crac~ed
product, butane and lighter~ are processed through fraction-
ation equipment to separate components of value greater than
fuel to furnaces, primarily propane, butane and the oleflns
of like carbon number. Hydrogen, being incondensible in the
20 "gas plant", occupies space as a gas in the compresslon and
fractionating train and can easily overload the system when
excessive ~ounts are produced by high metal content I,
catalyst, causing reduction in charge rate to maintaln the
FCC unit and auxilaries o~erative.
26 These problems have lon~ been recognized in ~he art
and many ex~,edients have been proposed~ Thermal con~ersions
o~ ~esid8 produce lar~si ~uant~ties of solid ~uei (coke) ~nd
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1 the pertinent processes ars characterized as coking, of
which two varieties are presently practiced commercially.
` In delayed coking, the feed is heated in a furnace and
passed to large drums maintained at 780 to 8400F. During f
the long residence time at this temperature, the charge i~
con~erted to coke and distillate products taken off the top
of the drum for recovery of "coker gasoline", "coker gas '
oil" and gas. The other coking process now in use employs
- a fluidized bed of coke in the form of small granules at
1~ about 900 to 1050F. ~he resid charge undergoes conv~rsio~
on the surface of the coke particles during a residence
time on the order of two minutes, depositing additional
coke on the surfaces o~ particles in the fluidized bed.
Coke particles are trans~erred to a bed fluidized by alr !
1~ to burn some of the coke at temperatures upwards of 1100F.,
thu~ heating the residual coke which is then returned to
- the coking ~essel for conversion of additional charge.
; These cok~ng processes are known to induce extensi~e~
cracking of components which would be valuable for FCC
20 charge, resulting in gasoline ~f lower octane number (frsm i
thermal cracking) than ~ould be obtained by catalytic
cracking of the same components. The gas oils produced are
olefinic, containlng signiflcant amounts of diolefins whlch
are prone ~o degradation to coke in furnace tubes ~nd on
. 2~ cr~cking-catalysts. It is often desirable to treat the gas
oil~q by expensi~e hydrogenation techniques before char,~ing
t;o cataly~~G crac~cir~. Cok~ng does reduce mQtals ~nd
.30. . ,~
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Conradson Carbon but still leaves an inferior gas oil for charge
to catalytic cracking.
Catalytic charge stock may also be prepared from
resids by "deasphalting" in which an asphalt precipitant such as
liquid propane is mixed with the oil. Metals and Conradson
Carbon are drastically reduced but at low yleld of deasphalt oil.
Solvent extractions and various other techniques have
been proposed for preparation of FCC charge stock from resids.
Sorbent extraction, in common with propane deasphalting, func-
tions by selection on chemical type, rejecting from the chargestock the aromatic compounds which can crack to yield high
octane components of cracked naptha. Low temperature, liquid
phase sorption on catalytically inert silica gel is proposed by
Shuman and Brace, OIL ~ND GAS JOURNAL, April 16, 1~53, page 113.
SU~MARY OF THE INVENTION
These problems of the prior art are now overcome in
a process of contacting an emulsion of water in a resid or a
crude oil having an appreciable Conradson Carbon (CC) content
and usually a high metals content with an inert solid of low
surface area at temperatures above the volumetric average boiling
point of the feedstocks for very short residence times of about
five seconds or less, preferably less than two seconds, separat-
ing oil from the solid and quenching the oil below cracking
temperature as rapidly as possible.
According to the present invention, there is provided
a process for upgrading a petroleum charge of a crude oil or a
residual fraction thereof which contains high boiling components
of substantial Conradson Carbon number which comprises emulsify-
ing water in said charge as the internal phase of a water in oil
emulsion, contacting the emulsion of water in said charge in a
confined rising vertical column with a finely divided solid
~ 1~9~
contact material consisting essentially of an inert solid
material having a microactivity for catalytic cracking not
substantially greater than 20 at low severity, including a
temperature of at least about 900F. for a period of time less
than 2 seconds and less than that which induces substantial
thermal cracking of said charge, at the end of said period of
time separating from said inert solid a decarbonized hydrocarbon
fraction of reduced Conradson Carbon number as compared wi-th
said charge and reducing -temperature of said separated fraction
to a level below that at which substantial thermal cracking takes
place to terminate said period of time.
Furthermore, according to the present invention, there
is provided in a process for preparing premium products from
crude petroleum by fractionally distilling the crude petroleum
to separate gasoline and distillate gas oil from a residual
fraction having a substantial Conradson Carbon number and metals
content and charging the distillate gas oil to catalytic crack-
ing; the improvement which comprises: (a) emulsifying liquid
water in said residual fraction and contacting the resultant
emulsion in a rising confined vertical column with an inert
solid material having a low surface area and a microactivity for
catalytic cracking not substantially greater than 20 at low
severity, including a temperature of at least about 900F., for
a period of time less than that which induces substantial
thermal cracking of said residual fraction, and such that the
quantity of such decarbonized petroleum fraction is less than
said residual fraction by a weight percent no greater than
three times said Conradson Carbon number, (b) at the end of
said period of time separating from said inert solid a decarbon-
ized hydrocarbon fraction of reduced Conradson Carbon number andmetals content as compared with said residual fraction, (c)
-- 6
~ ~g~
reducing temperature of the said separated fraction to a level
below that at which substantial thermal cracking takes place,
(d) adding said decarbonized hydrocarbon to said distillate
gas oil as additional charge to said catalytic cracking, (e)
subjecting said inert solid separated from said decarbonized
hydrocarbon fraction and now containing a combustible deposit
to air at elevated temperature to remove said combustible deposit
by burning and thereby heat the inert solid in a burner, ~f)
separating heated inert solids from hot vapors produced in
step (e), and (g) cycling at least a portion of said separated
hot inert solid from step (e) to step (a), (h) and at least
periodically withdrawing metal loaded inert solid from step (e)
without cycling it to step (a).
The invention is best performed at very low contact
times, say one second or less, down to about 1/2 second if
possible. The necessary short residence time is conveniently
achieved by supply of the solid in a size of about 20 to 150
microns particle diameter mixed with the emulsion of water in
hydrocarbon charge in a riser. The oil is introduced at a
temperature below thermal cracking temperature in admixture with
steam and/or water to reduce partial pressure of volatile
components of the charge. The catalytically inert solid is
supplied to a rising column of charge at a temperature and in an
amount such that the mixture is at a temperature upwards of
900F. to 1050F. and higher, sufficient to vaporize most of the
charge.
At the top of the riser the solid is rapidly separated
from oil vapors and the latter are quenched to temperatures at
which thermal cracking is essentially arrested. During the
course of this ~ery short contact, the heavy components of high
CC value containing the majority of the metal content are laid
- 6a -
down on the solid particles. This deposition may be a coalescingof liquid droplets, adsorpbion, condensation or some combination
of these mechanisms. In any event, there appears to be little
or no conversion of a chemical nature. Particularly, -thermal
cracking is minimal. The quantity removed from the charge under
preferred conditions is very nearly that indicated by CC of the
feedstock charged. Further, the hydrogen content of the deposit
on the solids is believed to be about 6%, below the 7 to 8%
normal in FCC coke.
The solids, now bearing deposits of the Conradson
Carbon and metals components of the hydrocarbon feedstock, are
contacted with a source of oxygen, (air, for example)
- 6b -
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I by any of the techniques suited to regeneration of 7CC catalyst,
preferably under conditions of full CO combustion to less thanl
1000 p.p.m. CO in the flue gas. Combustion of the deposited¦
material from the inert solids generates the heat required in the~
contacting step when the combusted inert solid is recycled to the~
riser for subsequent contact with new charge of hydrocarbonl
feedstock in the contactor. During repeated cycling between the¦
contactor and burner, portions of inert solid are removed from
the system and repiaced with fresh inert solid in order to
maintain a suitable level of metals on the solid while it is in
the contactor.
DESCRIPTION OF THE DRAWING
A system for preparing in situ the inert solid used
~ in a fluidized residual oil treating unit whose purpose is to~
lS remove high boiling components of the crude on the inert solid
wh~reb~ ~n dson Carbon (C ) values and metal ccntent
2~ ~ _7_
.~ ,, . ~1
g
are reduced to levels tolerable in catalytic cracking is
shown in the single figure of the annexed drawing.
DESCRIPTION OF PREFERRED EMBODIMENTS
The decarbonizing, demetallizing step which char-
acterizes the present invention is preferably conducted in
a contactor very similar in construction and operation to
riser reactors employed in modern FCC ~mits. Hydrocarbon
feedstock high in Conradson CarbonJ typically a resid feed,
either a vacuum resid boiling above 900F. or an atmospheric
resid which may contain components boiling as low as 500 F.,
is introduced to the lower end of a vertical conduit.
Whole crude oils high in CC may also be employed in the
process. Steam and/or water in amounts to substantially
decrease hydrocarbon partial pressure is added with the
feedstock. Pressures will be sufficient to overcome pres-
sure drops, say 15 to 50 p.s.i.a. The charge may be pre-
heated in a furnace, not shown, before introduction to the
riser contactor, to any desired degree below thermal crack-
ing temperature, e.g., 200 to 800 F., preferably 300 to
700F. Higher temperatures will induce ~hermal cracking of
the feed with production of low octane naptha.
The feed diluted by steam rises in the contactor
1 at high velocity such as 40 feet per second. Hot inert
solid in finely divided form is introduced to the feed from
a standpipe 2 in a quantity and at a temperature to provide
a mixture at a temperature in excess of 900F. to volatilize
all components of the feed except the very heavy compo~mds
of high CC and high metal content.
- 8 -
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4 1 The solid contacting a~ent is essentially inert in
the sense that it induces minimal cracking of heavy hydro-
carbons by khe standar~ microactivity test conducted by
measurement of amount o~ ~as oi~ converted to gas, gæsoline
5and coke by contact with the solid in a fixed
~ ~ bed. Charge in that test is o.8 ~rams of mid-Continent
gas oil of 27 ~PI contacted ~r~th 4 grams of catalyst during
48 second oil delivery time at 910~. This results in a
~ catalyst to oil ratio of 5 at weight hourly space velocity
1o(~rHsv) of 15. By that test, the solid here émployed exhibits
a microactivity less than 20, preferably about 10. A
: preferred solid is microspheres of calc.ined kaolin clay.
Other solids include low surface area ~orms of sllica gel
and bauxite.
15 Durin~ initial start-up of the decarbonizing contactor,
an available charge of low surface area inert solid is used.
..
. ~ Surface area is below 100 m /g (BET using nitrogen absorption~,
preferabl~J below about 50 m /g, and most preferably below
about 25 m /g. For ex~nple, microspheres of calcined clay
,
20 may be employed. These micr~ospheres may be obtained from a
co~nercial source and used for start-up of the contactor/burner
system of the invention or they-can be produced by spray drying
an aqueous suspenslon o~ h~Jdrated clay, preferably fine
particle size kaolin clay, to produce microspheres and then
? 2~ calcinin~ the microspheres at temperatures in the range o~
about l600DF~ to 2100F. Reference is ~ade to U.S. 3,647,718
to Haden et al. for details of preparation of suitable
microspheres from-hydrated kaolin rlay, noting that ~n the
~, . .
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,
1169009
patent s~ch microspheres are used as a reactant with caustic to
form high surface zeolite in situ, whereas in the present
invention the microspheres are used in low surface area form and
they do not undergo zeolite crystallization which would
0 undesirably increase surface area and contribute unwanted
catalytic activity. Typically the calcined clay microspheres
have a surface area below about 15 m.2/g. and analyze about 51%
to 53% (wt.) SiO2, 41 to 45% A1203, and from O to 1% H20,
the balance being minor amounts of indigenous impurities, notably
iron, titanium and alkaline earth metals. Generally iron content
(expressed as Fe203) is about 1/2% by weight and titanium
(expressed as TiO2 is approximately 2%).
Other solids of low catalytic activity may be
employed. Examples are: rutile, low surface area forms of
~1~ alumina, magnesium oxide, sillimanite, andalusite, pumice,
mullite, calcined coleminite, feldspar, fluorspar, bauxite,
barytes~ chromite, zircon, magnesite, nepheline, syenitet
olivine, wollastonite, manyanese ore, ilmenite, pyrophyllite,
talc (calcined fosterite), calcined dolomitel calcined lime, low
surface area silica (e.g., quartz), perlite, slate, anhydrite,
and iron oxide ore. In general, solids of low cost are
recommended since it will usually be necessary to discard a
sizeable por~ion of the contact agent in the system from time to
time and replace it with fresh agent to maintain a suitable level
2~ of metals. Since the solid is preferably of low porosity,
resulting in deposition primarily on external surfaces, the
invention contemplates abrading the particles as in a column of
air at veloFity to permit refluxing of
':'~0
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.
solids for removal of external meta] deposits with optional
recycle of portions of metal-depleted abraded particles in
the system. Typically inert fluidizable particles used for
start-up have a diameter in the range of 20 to 150 microns.
The surface area of the inert solid particles is usually
within the range of 10 to 15 m /g. It is noted that the
surface areas of commercial fluid zeolite catalysts is con-
siderably higher, generally exceeding values of 100 m /g.
as measured by the B.E.T. method.
Length of the riser contactor 1 is such as to pro-
vide a very short time of contact between the feed and the
contacting agent, less than 2 seconds, preferably 0.5 sec-
onds or less. The contact time should be long enough to
provide good uniformity of contact between feed and contact-
ing agent, say at least 0.1 second.
At the top of the riser, e.g., 15 to 20 feet above
the point of introduction of contacting agent from standpipe
2 at a feed velocity of 40 feet per second, vaporized hydro-
carbons are separated as rapidly as possible from particulate
solids bearing the high CC deposits and metals. This may be
accomplished by discharge from the riser into a large dis-
engaging zone defined by vessel 3. However, it is preferred
that the riser vapors discharge directly into cyclone
separators 4 from which vapors are transferred to vapor line
5 while entrained solids drop into the disengaging zone by
diplegs 6 to stripper 7 where steam admitted by line 8
evaporates traces of volatile hydrocarbons from the solids.
,, '~ !
1169009 r
1 The mixture of steam and hydrocarbons, together with entrained
solids, enters cyclone 9 by mouth 10 to disengage the suspended
solids for return to stripper 7 by dipleg 11. As well known ~.
in the fluld cracking art, there may be a plurality of cyclones
4 and cyclones 9 and the cyclones may be multistage, with gas
phase from a first stage cyclone discharging to a second s-tage
cyclone. r
In one embodiment, the cyclones 4 may be of the stripper
cyclone type described in U.S. Patent 4,043,899. In such case
the stripping steam admitted to the cyclone may be at a low
. ~ temperature, say 400 to 500F., and serve to perform part or
all of the quenching function presently to be described.
The vaporized hydrocarbons from cyclones 4 and 10
passing by way of line 5 are then mixed with cold hydrocarbon
lS ~ liquid introduced by iine 12 to quench thermal cracking. The
quenched product is cooled in condenser 13 and passed to
accumulator 14 from which gases are removed for fuel and water
; is taken from sump 15, preferably for recycle to the contactor c
for seneration of steam to be used as an aid in vaporizing
charge at the bottom o~ the riser and/or removing heat from
the burner. Condenser 13 is advantageously set up as a heat
exchanger to preheat charge to the-contactor or preheat
charge to the FCC unit hereinafter described and the like. ~ L
In one embodiment, the quenching is advantageously
conducted in a column equipped with vapor-liquid contact
~ ¦ zones such disc and do~lghn~lt. tr~ys nd v~ lve trsys. I
30 ~ 1,
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-12- I
I
Bottoms from such column quencher could go directly to catalytic
cracking with overhead passing to condenser 13 and accumulator
14.
The liquid hydrocarbon phase from accumulator 14 is
a decarbonized and demetallized resid fraction which is now
satisfactory charge for catalytic cracking. This product of
contact in riser 1 may be used in part as the quench liquid at
line 12. The balance is preferably transferred directly to a
catalytic cracker by line 16.
Returning now to stripper 7, the inert solid particle
bearing a deposit of high CC and metallic compounds passes by
a standpipe 17 to the inlet of burner 18. Standpipe 17 dis-
charges to a riser inlet 19 of burner 18 where it meets a ris-
ing column of air introduced by line l9 and is mixed with hot
inert particles from burner recycle 20 whereby the mixture is
rapidly raised to a temperature for combustion of the deposits
from treating resid, 1,150 to 1,500 F. The mixture enters an
enlarged zone 21 to form a small fluidized bed for thorough
mixing and initial burning of deposits. The flowing stream of
air carries the burning mass through a restricted riser Z2 to
discharge at 23 into an enlarged disengaging zone. The hot,
burned particles, now largely free of combustible deposit, fall
to the bottom of the disengaging zone from which a part enters
recycle 20 and another part enters the standpipe 2 for supply
to contactor 1 after steam stripping. By reason of the very
high temperatures attainable in this type of burner and in the
presence of a stoichiometric excess of oxygen, C0 will burn
:: ~
to provide a flue gas containing very little of that gas.
In other types of burners, the combustion products may
contain substantial amounts of CO which can be burned for
its heating value in CO boilers of the type commonly used
in FCC ~mits.
At such time that the metals level of the inert
solid becomes excessive and spent inert solid must be with-
drawn to maintain metals at an acceptable level and/or in
response to the need for additional inert solid because of
increased Conradson Carbon in incoming-feedstock, addi-
tional inert must be added to the system. This is accom-
plished by spray drying a slurry of precursor of low sur-
face area inert particles into the upper (dilute) phase of
the burner by selection of the proper spray nozzle to ob-
tain beads of the particle size desired which is typically
predominantly in the size range of 20 to 150 microns. A
slurry or suspension, preferably one based on an aqueous
vehicle, is sprayed near the top of the burner into an
atomizer spinning at high speed. This distributes the
slurry into fine droplets throughout the upper interior
~ portion of the burner. The droplets contact an upflowing
:~ '
current of hot gases produced by the combustion of carbon-
aceous deposit on inert solid in the bottom of the burner.
` The mist dries in the form of fine beads.
To facilitate in situ spray drying, it may be
advantageous to disperse the feed slurry by incorporating
~; a suitable dispersing agent into the slurry before it is
sprayed. In the case of aqueous slurries of clay a polyanionic
salt dispersant such as sodium silicate or a sodium condensed
- 14 -
~ . . ~ .
9~9
phosphate salt (e.g., tetrasodium pyrophosphate) is recom-
mended. By employing a dispersant (deflocculating agent),
the slurry may be produced at high solids levels and harder
fluidizable particles are usually obtained when the higher
solids content slurries are sprayed into the burner. When
a deflocculating agent is employed with the preferred kaolin
clay, slurries containing about 55 to 60% solids may be
prepared. These high solids slurries are preferred to the
40 to 50O slurries which do not contain a deflocculating
agent. Several procedures can be followed in mixing the in-
gredients to form the slurry. One procedure, by way of ex-
ample, is to add water to a finely divided solid precursor
and then incorporate the deflocculating agent. The compo-
nents can be mechanically worked together or individually to
produce slurries of viscosity characteristics conducive to
appropriate operation of the spray nozzles.
Referring now to the annexed drawing, feed slurry
containing precursor of inert solid is transferred to tank
29 and kept mixed by pump 30 discharging through restriction
orifice 31 to tank 29 through a jet nozzle (not shown) to
induce mixing of the contents of the tank. When additional
inert solid is needed for operation of the contactor, slurry
from tank 29 is discharged through Flow Recorder Controller
(FRC) 40 located in line 32 and pumped through spray nozzle 33
into the dilute phase 24 of burner 18. In normal operation,
flow of slurry from tank 29 through nozzle 33 into burner 1~
will be continuous as soon as the system has been started up
and combustion of deposited carbonaceous material in burner
~ ~ t.
9 0 ~
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~ 18 has been initiated. In those operations in which additional t
: inert solid is generated in situ on an intermittent basis and
line 32 is not in operation, line 32 will be continuously purged ;
with steam through line 42. Steam is restrained from flowing
into pump 30 discharge by check valves 41 so that all the steam s
injected into line 32 flows through FRC~40 to spray nozzle 33 ~
and into the dilute phase 24 of burner 18. s:
The rate of slurry pumped into burner 18 through the
above described system is controlled to form new microspheres so
1~ that the total metals level on the circulating microspheres
inventory is maintained below the level at which the metals
produce undesirable reactions with the hydrocarbon feed in s~
. contactor 1. Normally this will be from 0.5 to 5 weight ~ metals
: ~ but preferably around 2 weight ~ on the circulating inventory.
As the level or quantity of microspheres increases
in the unit because of the addition of new spray dried material
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being injected as described abo-ve, equilibrium microspheres can
be withdrawn through either line 38 or line 39 into the equilib-
rium inert storage hopper 35. Withdrawal of microspheres is ac-
complished by using steam ejector 37 to lower the pressure on
storage hopper 35 and opening up either line 38 or line 39. The
pressure differential between the operating pressure of the burn-
er 18 and the vacuum of the storage hopper 35 provides the driv-
ing force for flow of microspheres from burner 18 to storage
hopper 35. Gases entrained with the microspheres are removed
through ejector 37 and the degassed microspheres settle to the
bottom of storage hopper 35. Fresh microsphere storage hopper
34 is provided for adding microspheres manufactured off site.
As the slurry is pumped through spray nozzle 33 into
the dilute phase 24 of burner 18, there is countercurrent flow
of slurry and hot flue gases which are employed to dry the
microspheres.
:
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;
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1 In other types of burners, the combustion products may contain t
substantial amounts of CO which can be burned for its heating
value in CO boilers of the type commonly used in FCC units. t
In the type of burner shown, the gaseous products
5 of combustion at 1200~F., containing carbon dioxide, some
residual oxygen, nitrogen, oxides of sulfur and perhaps a
trace of CO are the flue gas used to provide the heat
necessary in the spray drying of the slurry.
In a typical residual unit using 1 pound of inert
per barrel of fresh feed and producing 7 weight % coke, and ~;
. burning all the CO to CO2 with a burner dischaxge 23 outl'et
of 1400F., the continuous injection of a 60% solids aqueous
slurry of hydrated kaolin clay will reduce the temperature
of t~e gases entering cyclones 25, S to 10F. !
1 15 ~ At these temperatures, free mosture is removed from
the slurry and water of hydration twater of crystallization~
~is also removed from the raw clay ingredient. Typically the
majority of particles produced have a diameter in the range T
of 20 to 150 microns and are calcined at 1200F. to 1400~F.
by adding the spray dried particles to the ~urner as described
above thereby converting the clay into the material known as
"metakaolin".
Other solids of low catalytic activity, low surface i~
area (below about 100 m2/g, preferably below about 50 m2/g) .
and most preferably below about 25 m2/g, and of liké particle
; . size may be generated in situ as described above. The -
preferred precursor is hydrated clay, most preferably hydrated
; Xaolin clay. Exemplar~ of other precursors which are
I '~
.' ,'
.~ a-
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convertible to low surface area beads by spray drying into
hot combustion gases are coleminate, magnesite, fosterite,
dolomite and lime. Precursors which have low surface area
before spraying into hot gases include rutile, selected
forms of alumina, magnesia, sillimanite and other materials
listed above for use in start-up. Generally the particles
of the precursors are finer than 325 mesh when formed into
slurries for spraying into the burner. In general, solids
of low cost are recomlnended since as mentioned it may be
desirable to discard a sizeable portion of the contact agent
in the system from time to time and replace it with fresh
agent to maintain a suitable level of metals.
Flue gas from outlet 23 and water vapor produced
during drying of the slurry injected through spray nozzle
33 exit burner 18 through cyclones 25 (one of a plurality
of such devices) to disengage entrained solids for discharge
by dipleg 26. The clarified gases pass to plenum 2i from
which flue gas is removed by outlet 28.
Although the system just described bears superfi-
cial resemblance to an FCC unit, its operation is very differ-
ent from FCC. Most importantly, the riser contactor 1 is op-
~ erated to remove from the charge an amount not greatly in
; excess of the Conradson Carbon Number of the feed. This con-
trasts with normal FCC "conversion" of 50 to 70%, measured
as the percentage of FCC product not boiling within the
range of the charge. Percent removed by the present process
is preferably on the order of 10 to 20% on charge and consti-
tuted by gas, and deposit on the solid contacting agent.
Rarely will the amount removed from boiling
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range of the charge exceed a value, by weight, more than
three to five times the Conradson Carbon value of the charge.
This result is achieved by a very low severity of cracking
due to inert character of the solid and the very short
residence time at cracking temperature. As is well known,
cracking severity is a function of time and temperature.
Increased temperature may be compensated by reduced residence
time and vice versa.
The new process affords a control aspect not avail-
able to FCC units in the supply of steam to the riser con-
tactor. When processing stocks of high CC, the burner tem-
perature will tend to rise because of increased supply of
fuel to the burner. This may be compensated by increased
quantity, decreased temperature or increasing the steam sup-
plied to reduce partial pressure of hydrocarbons in the riser
contactor or recycling water from the overhead receiver to be
vaporized in the riser to produce steam.
The water so added) whether fresh or recycled in
the system, is advantageously emulsified in the charge or in
a portion of the charge which is then mixed with the main
body of the charge before introduction to the system. When
liquid water as the internal phase of a water and oil emul-
sion is rapidly heated to temperatures far above the boiling
point of water, the water vaporizes with explosive violence
to atomize the oil surrounding the emulsified water globules
and thus promote dispersion and vaporization of the oil
charge.
Vaporization can be further promoted by recycle of
hydrocarbons lighter than the heavy end of the charge, say
a fraction boiling above 100 F. and below about 1,050F.
- 20 -
.
which may be derived from fractionation of the decarbonized
product, by fractionation of FCC reactor effluent or other
suitable source.
Means are known for introduction of the charge to
FCC reactors in a manner to promote prompt and intimate
contact of charge with fluidizable solids at the bottom of
a riser. The purposes of this invention are well served by
these devices. A particularly attractive device of this
type is the multiple nozzle injector described in ~nited
States Patent No. 4,149,964, granted April 17, 1979.
The riser contact with inert solid thus provides
a novel sorption technique for removing the polynuclear aro-
matic compounds of resids (high CC and metals~ while these
are carried in a stream of low hydrocarbon partial pressure
by reason of steam supplied to the riser.
The decarbonized, demetallized resid is good qual-
ity hydrotreating, hydrocracking or FCC charge stock and may
be transferred to the feed line of an FCC reactor (not shown)
operated in the conventional manner. Hot regenerated cata-
lyst is transferred from an FCC regenerator (not shown) by
a standpipe for addition to the reactor charge. Spent cata-
lyst from the FCC reactor passes by a standpipe to a conven-
tional FCC while cracked products leave reactor by transfer
line to fractionation ~not shown) for recovery of gasoline
and other conversion products.
EXAMPLES
The effect of contacting in the manner described
above has been demonstrated in laboratory scale equipment.
- 21 -
.,
The apparatus employed is a circulating fluidized bed pilot
plant which simulates behavior of commercial FCC riser
reactors. The reactor is equipped to provide a stream of
nitrogen through the riser and for addition of catalyst and
charge. The riser is lagged and heated to maintain isothermal
conditions. The nitrogen flow serves the same function as
the steam described above for reduction in partial pressure
of hydrocarbons. In the rlms described below residual stocks
and the microspheres set forth above were contacted under the
conditions recited. Inspection data on the charge stock are
given in Table I.
TABLE I
DESCRIPTION OF CHARGE STOCKS
Example 1 _ 2
Gravity, API 27.9 23
Ramsbottom Carbon, % 0.35 2.5
Metals, p.p.m.
Ni 1 10
Cu
V 1 20
Distilla*ion, F.
I~P 438 420
10% 554 478
30% 659 711
50% 750 829
70% 847 979
76% - 1,046
9 0% 99 1
94% 1,050
~6~
Feedstock 1 is a typical mid-continent FCCU feed
where Feedstock #2 is a blend of ~1 and Cenex atmospheric
bottoms. This Cenex feed is processed commercially in a
vacuum unit where 55 vol.% is yielded as FCC feed and the
other 45 vol.% as asphalt. In order to produce a pitch
material, the asphalt can be processed in a propane de-
asphalter where 50 vol.% of the asphalt is yielded as
pitch and the other 50 vol.% burned as fuel oil in the
refinery.
Conditions of contact and resultant products
are shown in Table II.
~',
~ 1~90~
TABLE II
CONTACT CONDITIONS AND PRODUCTS
Example 1 2
Rise contactor temp., F. 915 935
Contact time, seconds0.66 0.97
Contact solid temp., F.1,203 1,185
Oil partial pressure, p.s.i.a.2.83 4.62
Oil prehea' temp., F.641 659
Solids/oil, wt. 12.5 12.2
Mol ratio, N2/oil 3.7 2.2
Products, wt.%
Gas 7.9 7.6
Liquid 90.4 85.5
Deposit on solid 1.7 6.9
Liquid Product
Metals, p.p.m.
Ni - 1.5
Cu - 1.0
;~ V - 1.0
Ramsbottom Carbon - 0.6
Distillation, F.
IBP 170 173
10% 466 475
- 30% 597 610
50% 684 704
70% 775 803
90% 894 967
93% _ 1,033
EP 1,028
;
::
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