Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ 12~7
MULTI-ZONE PROCESS AND REACTOR FO~ CRACKING H~A~Y
HYDROCARBON FEEDS
BACKGROUND OF INVE~TION
.
Thi~ invention pertains to an improved multiple zone
fluidi~ed bed cracking process for ~onversion of heavy
hydrocarbon feeds to produce lighter hydrocarbon liquids and
fuel gas. It pertain~ particularly to such conver~ion pro-
cess and apparatus utilizi~g multiple zo~es of a fluidized
bed of par~iculate carrier mat~rial to facilitate cracking
the feed i~ the upper zone and gasification of tars and coke
deposited on and within the carrier in a lower refractory
lined gasification zone.
Con~iderable work has previously been done for the multi-
stage gasificatiorl of heavy oil feeds in fluidized beds, some
proce~es u~ing a partic~late carrier material for depoQition
of carbon, and ~or the~ multiple-~tage ga~ification of coal.
Some typlcal pertinent patent~ include U. $. Patent 2, 8S1~ 943
to Finneran, and UO S. Paterlt 2, 885, 343 to Woebc~;e di~clos~
th~ u3e of a c:irculating particulate carrier for co3ce laydown
from crude and . re~idual oil f~ed~tock~ . Also, U- S . Patent
2,875,150 to Schuman and U.S. Patent 3,202,603 toKeith disclose a
multiple-bed hydro-gasificatio~l proce~s for residual oils
and tar eeds using a particulate carri~r material for
hydrocracking the heavy oil feed to produce gas and liquid
fraction~. But no di~closure is made regarding important
proc~s3 steps and con~truction fea~ures required or a multi-
zone reactor ve~sel of commercial scal~.
There has thus been an unfulfill~d need for a practical
conversion and gasification proce~ for heavy hydrooarbon
feeds such as residual oi~ to produce distillable liquids a-nd
fuel gas, and which would also effectively gasify tars and
coke evolved from the feed within the same reactor vessel and
produce clean fuel gas and liquid products, and provide a
reactor design suitable for commercial-scale operations.
^ SUMMAR _ F INVE~TI0~
The present invention provides a multi-zone reaction
process and apparatus for cracking and conversion of heavy
hydrocarbon feeds, such as crude oil and residua feedstocks
and mixture~ of such oils with coal, to produce light2r
lower boiling hydrocar~on liquid and gaseous products. The
invention utilizes a multi-zone reactor vessel having an
upper cracking or conversion zone and a lower gasification or
combustion zone, ~eparated by an intermediate stripping zon~
which contains a par~i~ula~e packing ma~erial of sufficent
voidage to permit downward passage o par~iculate carrier
material~ The upper and lower ZOlleS as well as the stripping
zone contain a bed o~ particulate carrier material, which is
continuously circulated through the three zones.
Becaus~ of the high temperatures required in the gasifi
cation and stripping zone6, such as 1400-2000F, these zones
are entirely lined with refractory materials so as to effec-
tively limit temperature of th~ metal walls to safe levels,
and thus avoid undesirable ~loss of ~trength and also prevent
corrosion and erosion of the ba e metals. The reactor design
is adapted to utilize the inh~rent high temperature strength
of thPse refractory material for structural purposes in
unique and advantageous ways. The coarse packing material
used in the intermediate stripping zone is supported by an
annular shaped apertured refractory grid member, whic'n
preferably has an arch-shaped cross section. This grid is in
turn supported at its outer and inner circular edges by
the refractory lining structuresof the annular-shaped lower
gasification chamber or zone.
~ he hot particulate carrier material is recirculated from
the lower gasification or combustion zone upwardly to the
upper cracking or conversion zone through a vertical
transfer conduit. This conduit comprises a tube of
temperature-resiStan~ metal which is refractory-lined to pre-
vent arosion by the upflowiny particle~. The conduit metal
tub~ is supported entirely from the inner refractory lining
or column of the annular-shaped gasification chamber.
Furthermore, the lower end of the refractory-lined eentral
conduit is reduced in diameter and provides the refractory-
coated seating ~urface for a control valve, which controls
the recirculation rate of the particulate carrier solids from
the lower gasification zone or ~hamb~r upward to the cracki~g
or co~verion zone. Al o, the control valve has a plug member
which is refractory-coated to provide erosion protection and
long service life. The recirculation of particulate solids
is facilitated by a transport ga~ which is passed upwardly
through the valve plug a embly to a point above the valve
eat. Also, the valve pluy i5 cooled effectively by the
upflowing gas tream, which is pre~erably steam or a process
gas stream provided at a t~ature not exceedin~ about 750~F.
DESC~IPTION OF DRAWI~GS
Figure 1 is a cross-sectional view of the overall multi-
zone reactor configuration showing internal detaila of the
reactor assembly, including support details for the refrac-
tory lining and grid.
Figure 2 is an isometric view of two typical sectors of
the annular~shaped apertured refractory grid structure.
Figure 3 is a cross-sec~ional view showing configuration
of the solids recirculation control valve assembly and
conduit.
DESCRIPTIO~ OF P~EFERRED EMBODIMENT5
.,
As shown in Figure 1, a feedstxeam of heavy petroleum
crude or residuum oil a~ 10, such as obtained from previous
distillation step~a I i~ pressurized at 12, and preh ated as
required at 13, 3uch as to 250-Ç00F t~mperature. The pr~-
heated stream is introduced through a suitable sparger device
14a into the upper prLmary cracking zone 14 of multi-zone
reactor 16. Zone 14 contains a fluidized bed 15 of a
particulate solid carrier material 17, which is maintained at
a temperatur2 within the range of 900-1400F so that the
heavy hydrocarbon feed material is further heated and ther-
mally cracked therein. Reactor pres~ure is usually main-
tained withi~ t~e range of 200-800 p5ig, although higher
pressures could be used. The bed 15 i5 fluidized by
upflowing reducing g~ses produced in a lower zone. Some coke
produced in ~he cracXing reaction is deposited on and wi~hin
the carrier material 17. The resulting product gas along
with som~ fine par~icles of carrier material are pas3ed
upwardly through a cyclone separator 30 and the gas exits
from the reactor.
The majority of the par~iculate carrier material in zone
14, usually containing 3-25 W % coke deposits and heavy
liquid hydrocarbons, descends through the adjacent inter-
mediate packed stripping zone 18 where some liquids ar2
stripped from the particles by upflowing gases. The
~tripped dry solids then descend to the lower gasification
zone 20 containing fluidized bed 21, which is maintained at a
temperature within the range of 1700-2000F. Here char and
coke deposited on and within the carrier material are
gasified in the presence of an oxygen conta.ining gas and
steam introduced into the bed 21 at nozzLe 22 through
distrihutor 23. 5Ome tars formed in the upper fluidized bed 15
~nd deposited on and within the carrier material 17 may be
ca~ried to the lower bed 21, where the tars are gasified and
removed, from the carrier. Some tars may undergo secondary
cracking to lighter liquid and gaseous hydrocarbons in the
stripping zone 18.
The selection of a 3uitable particulate carrier materi 1
17 wi~h respect to its absorptive characteristic~ a~d pore
distribution i~ ~uch a to collect substantially all tars,
char and coke ~rom cracXed pxoducts evolved in the upper zone
14 and bed 15~ After gasification o~ tar~, char and coke in
the lower fluidized bed 21, the particulate carrier material
17 i recirculated to the upper bed with the aid of a
tran~port gas supplied a~ 24, such as steam or product
recycle gas, an~ pa~s~d through vertical transer conduit
28 and control valve a3sembly 50~
The lower gasification zone 20 is mads annular-shape~ and
is lined with a refractory material provided on its outer
wall 25, in the lower head 16b, and inner wall 26, such as
"Greencast" No. 94 obtainable from A.P. Green Co. The inner
refractory wall 26 is made cylindrical-shaped and is
preferably supported from the refractory material lining
provided in the ~eactor lower head 16b.
Multiple opening~ 27 are provided in the lower end of
inner refractory wall 26 for pas3age of the solid carrier
particles 17 from the gaslfication chamber 20 to the lower
end of transfer conduit 2S. These op~nings 27 are preferably
provided with tubular liners 27a, composed of a hard refrac- -~
tory material which is more resi~tant to abrasion and erosion
by the flowing solid particles 17 than refractory structure
26. Alternatively, multiple passages 27 can be provided in
the solid refractory material in lower head 16~.. In any
event, it i~ e~ential that the inl~t to pas~ages 27 be
located at a point below the distributor 23 for introducing
the oxygen-containing yas into fluidized bed 20, to prevent
any oxygen-containing ga~ being pas~ed into ths vertical
conduit 28~ which i~ preferably ~entrally located in the
reactor.
Flow control of the particulate carrier material 1
flowing into transfer conduit 28 at it5 bottom end is pro-
vided by control valve assembly 50O The carrier material is
~u~pended and lLfted to 1~pp~r bed 15 by the transport gas
supplied at connection 24. The upp~r end of ~o~duit 28 ter-
minates within fluidized b~d 15- Some of the carrier
material may be carried by 'che eiEfluenl: gas from zone 14 to
3,~ an internal cyclon~ separator system 30, which serv~s to trap
the ma jority of par~iculate carrier material a~d re~urn it to
cracking zone 14. Makeup carrier material may be added to
*Trademark 6
the reactor as needed, usually through a pressure-lock hopper
system 31. Spent carrier material may be similarly withdra~n
at conduit 32.
The intermediate stripping zone 18 contains a coarse
solid packing material 19 having size a-t least about 10 times
greater than the particula~e carrier material and provides
qufficient voidage to permit downward passage of the
particulate solids. Packing material 19 may comprise ceramic
Raschig rings, saddles, or similar materials and shapes,
This packing 19 is supported by an annular-shaped apertured
grid structure 34. To limit pressure drop across the inter-
mediate stripping section 18, and to facilitate the downward
flow o~ particulate solids 17 therethrough, the packing
material 19 can have a relatively coarse size, such as
0.5~2.0 inch effective diameter. The apertures 34a provided
in grid 34 for gas and so~ids flow are sized to prevent any
downflow o packing 19 and can likewise be made relatively
large and have various shape~ such as circular, square,
elongated and uch, as is generally shown in Figure 2.
Depending on the feedsto~k used, i.e., heavy oil or oil-
coal ~lurry, gas and liquid products, along with the minor
amount of small particle size unconverted coke and a larger
portion of smaLl particle size ash, leave the reactor as
stream 37 and pass to an external cyclone solids separation
system 38. This separation step remove~ any remaining coke
and ash particles from the product gas stream a~ a dispo~aL
tr~am 39. The resulting cyclone effluent stream 40 is then
otherwise
usually quenched at 41, such as by an oil streamJ or~cooled
to reduce it~ temperature and limit or prevent further unde-
sired reactions. The cooled gas and liquid~ are then
separated using conventional fractionation means at 44 to
il
~4~
provide a product gas stream 45, light liquid stream 46, and
heavier liquid fraction 47. If desired, a por~ion 4~ o~ th~
heavy fraction can be recycled to the cracking zone 14 for
further reaction.
With further reference to annular-shaped apertured grid
34 which supports the coarse packing 19 in stripping section
18, it is made of a strong refractory material suitable for
withstanding extended temperature~ of about 2000F, such as
"Cerox 600" obtainable from C-E ~efractories, Inc. The grid
1` has an arch-shaped cross-section so as to remain tight and in
compres~ion to prevent any loss of packing 19 from above,
even if a crack should develop in the grid. The grid is
composed of multiple sectors 35, two of which are typically
shown i~ Figure 2. Th use of such radial sectors permits
the grid to be installed through a manway opening, such as
manway 33 located at the top of the reactor. These sectors
35 rest on outer and inner circular shoulder surfac~ 25a and
26a respectively in the refractory lining 25 and wall 26. The
sectors 35 are held in place mainly by the weight o the
.~ coarse p~cXing 19 located immediately above, and for which
they provide support. The apertuxes 34a are ~ized to pr~vent
the packing material 19 from passing therethrough, and can be
made any shape such as circular, square, or elongated. If
de ired, the upper surface of grid sectors 35 can be made
dLmpled ~o ~s to prevent pieces of packing material 19 from
obstructing the grid openings 34a.
Following combu~tion in lower ga3ification zone 20 of the
coXe deposited on the particulate carrier material 17, the
hot decoked carrier solids are passed radially inwardly
-:- throu~h openings 27 and control valve 50, and are thereby
transferred from gasifica~ion zone 20 t~rough updraf~ conduit
*Trademark 8
r~ ' .,
28 by use of the transport gas supplied at 24. This conduit
28 is preferably centrally located in reactor 16, and
comprises a pressure-tight. heat-resistant metal tube 29
which h~s re~ractory lining 29a, which prevents metal erosion
by the upflowing particulate carrier solids 17. A suitable
refractory lining material is RESCO CAST No. AA-22, produced
by RE5C0 ~roducts, Inc., which is placed within tube 29.
Updraft conduit assembly 28 i~ rigidly attached to and
supported from the upper end of inner refractory lining or
column 26, and is preferably attached to the refractory
column 26 at point 28a, such as by bolts 28b which ar~ cast
into refractory wall 26.
Figure 3 shows a cross-sectional view of control valve
assembly 50, comprising refractory-coated v~lve seat 51 and
cooled valve plug 54 ~hich controls recycle of the hot decoked
particulate solids 17 from the lower combustion zone 20 to
the upper cracking zone 14. The central conduit 28 is
reduced in diameter at its lower end 28b sufficient to pro-
vide the valve sea~ member 51. If desired, seat element 51
can be made removable from condui~ end 28b, such as by bolted
1ange joint S2, for purpose of repair or replacement as
needed.
Valve plug assembly 54 comprises metal tube 55 which has
an enlargement portion 56 located intermediate the tube ends,
and serves as the valve plug tructure mating with seat
memb~r 51. Th2 upper por~ion of tube 55 and enlargement 56
are coated with re~ractory material 57. The enlaryement 56
contains horizontal plate element S8, and also contains
multiple openings 58a in plate 58 and openings 55a in tube
~,~ 55, which serve to divert the upward flow of transport gas
through the openings to effectively cool the metal portions
~4~
of the plug assembly 54. Also, the tube 55 and its re~rac-
tory coating 57 extend above seating surface 51 by
distance at least equal o the inner diameter of seat 51,
and preferably by 1.5-10 times that diameter. Refrac~ory
material 59 is also provided around tube 55 below enlarge-
ment 56 to prevent tube erosion by the solids 17 flowing
radially inwaxdly. The gas flowing upward through tube ;5
and its extension 55b facili~ates recirculation of the hot
carrier solids 17 upwardly through valve seat 51 and conduit
28.
The transport gas used for suspending and transferring
the hot particulate solids 17 upwardly through conduit 28 is
introduced at opening 24 and passes upwardly through tube 55
at a velocity of a~ least about 6 ft/sec. and preferably at
10-40 ft/sec. This gas flow also serves to cool the valve
plug 54. Thi5 transport and cooling gas is preferably a
process gas 3tream, such a~ steam or recycled product fuel
gas having initial temperature not exceeding about 750F.
Packing gland 60 is provided around tube 5S to prevent
transport gas bypacsing the tube and also to prsvent par-
ticulate carrier solids 17 from entering gas flow passageway
G2 around tube 55. The packing gland 60 is covered by
refractory plate 64 for erosion protection~ The val~e plug
assembly 54 i moved axially as needed using a suitahle
actuator device (not ~hown) to control the upward flow of
particulate solids 17, by actuator rod ~6, which i~ connected
to tube 55 by radial bracket 67 and i5 pressure sealed by
lo~er packing gland 68. The entire valve plug assembly
54 is removable from the lower e~d of central conduit ~8 and
valve ~eat 51 by disconnecting bolted flange 70 and removing
the assembly downwardly for inspection or repair.
During start~up of the multi-zone reactor 16 from cold or
near ambie~t conditions, the central conduit 28 is heated and
expands in a downward direction. Plug assembly ~4 i3
likewise withdrawn by the actuator devic~ (not shown) to
prevent any excessive compressive force being developed bet-
ween the valve plug 54 and seat surface 51. The transport
gas supplied at 24 flows upwardly through tube 55 to facili-
tate the recirculation of particulate carrier solids 17 from
the lower gasification zone 20 to the upper cracking zone 14.
Although we have disclosed certain preferred embodiments
of our invention, it is recognized that modifications can be
made thereto and that some features can be employed without
others, all within the spirit and scope of the invention
which is defined solely by the following claims.
. .
