Note: Descriptions are shown in the official language in which they were submitted.
z~
This application is a d.ivision oE co-pending
application Serial No. 361,734 filed September 30, 1980.
The present invention relates to improvernents in
Thermal Regenerative Cracking (TRC) apparatus and process, as
described in U.S. Letters Patent Nos. 4,061,562 and 4,097,363
to McKinney et al.
According -to one broad aspect, the presen-t invention
relates to a TRC process wherein the telnperatUre in the
cracking zone is between 1300 and 2500F. and wherein the
hydrocarbon feed or the hydrosulfurization residual oil along
with the entrained inert solids and the diluent gas are passed
through the cracking zone for a residence time of 0.05 to 2
seconds, the improvelnents comprising the process o.r generating
uel oil and removing coke deposits on said solids comprising
the steps of generating a fuel gas from fuel and air;
delivering the fuel gas to a transfer line; mixing the
particulate solids with the fuel gas in the transfer line to
elevate the temperature of the solids; and combusting the fuel
gas in the transfer line to elevate the temperature of the
solids and remove the coke from the solids; and the process for
separating by centrifugal force particulate solids from the
dilute mixed phase stream of gas and solids comprising the
steps of adding the mixed phase stream to a chamber having a
flow path of essentially rectangular cross section from an
inlet of inside diameter Di disposed normal to the flow path,
said flow path having a height H equal to D1 or 4 inches,
whichever is greater, and a width W greater than or equal to
0.75 Di bu~ less than or equal to 1.25 Di, disengaging solids
from gas by centriEugal force within said chamber along a bed
of solids found at a wall opposite to the inlet as the gas
flows through said flow path, the gas changing direction 180,
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and the solids being projected 90 toward a solids outlet,
wi-thdrawing the gaseous portion o:E the inlet stream from a gas
outlet, disposed 180 from the inlet, the gas portion
containing about 20~ residual solids, said gas outlet located
between -the solids outlet and inlet, the gas outlet being at a
distance no grea-ter than ~ Di from the inlet as measured
between respective centerlines, and withdrawing the solids by
gravity through the solids outlet.
According to another broad aspect, the present
invention relates to a TRC apparatus wherein the temperature in
the reaction chamber is between 130a and 2500F and wherein
the hydrocarbon fluid feed or the hydrosulfurization residual
fluid feed oil along with the entrained inert solids and the
diluent gas are passed through the reaction chamber for a
residence time of 0.05 to 2 seconds, the improvements wherein
the apparatus for admixing the inert solids rapidly and
intimately with the fluid feed introduced simultaneously
thereto comprises an upper reservoir containing the particulate
solids; a conduit extending downwardly from the reservoir to
the reaction chamber, said conduit being in open communication
with the reservoir and reaction chamber: and a solids-gas
separator designed to efEect rapid removal of particulate
solids from a dilute mixed phase s-tream o~ solids and gas, said
separator comprising a chamber for disengaging solids from the
incoming mixed phase stream, said chamber having rectilinear or
slightly arcuate longitudinal walls to form a flow path
essentially .rec-tangular in cross section, said chamber also
having a mixed phase inlet, a gas phase outlet, and a solids
phase outlet, with the inlet at one end of the chamber disposed
normal to the flow path, the solids outlet at the other end of
the chamber, said solids outlet suitable for downflow of
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.~
discharged solids by gravity, and the gas outlet therebetween
orien-ted to e.~fect a 180 change in direction o~ the gas.
According to yet another broad aspect, the present
invention relates to a TRC apparatus wherein the temperature in
-the reaction chamber cracking ~one is between 1300 and 2500F
and wherein the hydrocarbon fluid feed or the hydrosul~urized
resiaual oil fluid ~eed along with the entrained inert
par-ticulate solids and the diluent gas are passed through the
cracking zone for a residence time of 0.05 to 2 seconds, the
improvement comprising a solids-gas separator designed to
effect rapid removal of particulate solids from a dilute m:ixed
phase stream of solids and gas, said separator comprising a
chamber for disengaging solids from the incoming mixed phase
stream, said chamber hav.ing rectilinear or slightly arcuate
longitudinal ~alls to form a flow path essentially rectangular
in cross section, said chamber also having a mixed phase inlet,
a gas phase outlet, and a solids phase outlet, with the inle~
at one end of the chamber disposed normal to the flow path, the
solids outlet at the other end of the chamber, said solids
outlet suitable for down~low of discharged solids by gra~ity,
and the gas ou-tlet therebetween oriented to effec-t a 1~0
change in direction of the gas.
According to a still further broad aspect, the present
invention relates to a TRC apparatus wherein the temperature in
the reaction chamber is between 1300 and 2500F and wherein
the hydrocarbon feed or the hydrosulfurized residual oil along
with the en-trained inert particula-te solids and the diluent ~as
are passed through the reaction zone for a residence time of
0.05 to 2 seconds, the improvement comprising a solids-gas
separation system to separate a dilute mixed phase stream of
gas and particula-te solids into an essen-tially solids free gas
-2b-
stream, the separa-tion system comprising a chamber for rapidly
disen~aging about 80% of the par-ticula-te solids from the
incoming dilute mixed phase stream, said chamber having
approximately rectilinear or slightly arcuate longitudinal side
walls to form a flow path of heiyht H and width W approxima-tely
rectangular in cross section, said chamber also having a mixed
p~ase inlet of inside width Di, a gas outlet, and a solids
outlet, said inlet at one end of the chamber disposed normal to
-t~e flow path whose height H is equal to at least Di or 4
inches, whichever i5 greater and whose width W is no less than
0.75 Di but no more than 1~25 Di, said solids outlet at the
opposite end of the chamber and being suitable for downflow oF
discharged solids by gravity, and said gas outlet therebetween
at a distance ~o greater than ~ Di from the inlet as measured
between respective centerlines and oriented -to efEect a 180
change in direction of the gas whereby resultant centrifugal
forces direct the solid particles in the incoming stream toward
a wall o~ the chamber opposite to the inl~t forming thereat and
maintaining an essentially static bed of solids, the surEace of
the bed defining a curvilinear pa-th o~ approximately 90~ for
the outElow of solids to the solids outlet, a secondary
solids--gas separator, said secondary separator removing
essen-tially all o~ the residual solids, a first conduit
connecting the gas outlet from the charnber to the secondary
separator, a vessel for the discharge of solids, a second
conduit connecting said vessel and the chamber, and pressure
balance means to maintain a height of solids in said second
conduit -to provide a positive seal between the chamber and
vessel.
According to at least one further broad aspect, the
present invention relates to a TRC process wherein -the
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temperature in the reac-tion chamber is between 1300 amd 2500F
and wherein the hydroc~rbon fluid feed or the
hydrosulfurization residual oil along with the entrained inert
solids and the diluent gas are passed through the reaction
chamber for a residence time of 0.05 to 2 secondsl the
improvemen-t comprising a rnethod Eor separating by centrifugal
Eorce particulate solids from a dilute mixed phase s-tream oE
gas and solids, the method comprising the steps of adding the
mixed phase stream to a chamber having a flow path of
ess~ntially rectangular cross section from an inlet of inside
diameter Di disposed normal to the flow path, said flow path
having a height H equal to Di or 4 inches, whichever is
greater, and a width W grea-ter than or equal to 0.75 Di but
less than or equal to 1.25 Di, disengaging solids from gas by
centrifugal force within said chamber along a bed of solids
found at a wall opposite to the inlet as the gas flows through
said flow path, the gas changing direction 180, and the solids
being projected 90 toward a solids outlet, withdrawing -the
ga~eOUS portion of the inlet s-tream from a gas outlet, disposed
180 from the inlet, the gas portion containing about 20%
residual solids, said gas outlet located between the solids
outlet and inlet, the gas outlet being at a distance no greater
than 4 Di frorn the inlet as measured between respective
cen-terlines and withdrawing the solids by gravity through the
solids outlet.
The invention will be more fully appreciated by
reference to the accompanying drawings in w~ich:
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Figure 1 is a schematic diagram of a TRC system and
process according to -the prior art.
Figure 2 is a schematic diagram of the fuel gas
generation system and process of the subject inven-tion.
Figure 3 is an alternative embodiment wherein the
fuel gas is burned to fuel gas to provide additional heat for
tl-e particulate solids.
Figure 4 is a cross-sectional elevational view of the
solids feeding device and system as applied to tubular
reactors and for use with gaseous feeds.
Figure S is an enlarged view of the intersection of
the solid and gas phases within the mixing zone of the
reaction chamber.
Figure 6 is a top view of the preferred plate
geometry, said plate serving as the base of the gas
distributlon chamber.
Figure 7 is a graph of -the relationship between bed
density, pressure drop, bed height and aera-tion gas velocity
in a fluidized bed.
Figure 8 is a view through line 8-8 of Figure 5.
Figure 9 is an isometric view of the plug which
extends into the mixing zone to reduce flow area.
Figure 10 is an alternative preferred embodiment of
the control features of the present invention.
Figure 11 is a view along line 11-11 of Figure 10
showing the header and piping arrangements supplying aeration
gas to the clean out and fluidization nozzles.
Figure 12 is an alternate embodiment of the preferred
invention wherein a second feed gas is contemplated.
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1 FIGURE 13 is a view of the apparatus of FIGURE 12
through line 13-13 of FIGURE 12.
3 FIGURE 14 is a schematic diagram of the sequential
4 thermal cracking process and system of the present invention~
S FIGURE 15 is a schematic flow diagram of the
6 separation system of the present invention as ap~ended to a
7 typical tu~ular reactor.
8 FIGURE 16 is a cross sectional elevational view of
g the preferred embodiment of the separator~
FIGURE 17 is a cutaway view throu~h section 1~-17
11 of FIGURE 16.
12 FIGURE 1~ is a cutaway view through section 18-18
13 of FIGURE 16 showing an alternate geometric configuration oE the
14 separator shell.
FIGURE 19 is a sketch of the separation device of
16 the present invention indicating gas and solids phase flow
17 patterns in a separator not having a weir.
18 FIGURE 20 is a sketch of an alternate embodiment
19 of the separation device having a weir and an extended separatlon
chamber.
21 FIGURE 21 is a sketch of an alternate er~odiment of
22 the separation device wherein a stepped solids outlet is employ~d,
23 said outlet having a section collinear with the flow path as well
as a gravity flow section.
FIGU~E 22 is a variation of the embodiment of FIGVRE
26 21 in which the solids outlet of FIGURE 20 is used, but is not
27 stepped.
28 FIGURE 23 is a sketch of a variation of the
29 separation device of FIGURE 8 wherein a venturi restriction is
incorporated in the collinear section of the solids outlet.
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1 FIGURE 24 is a variation of the embodimen~ of
2 FIGURE 23 oriented for use with a riser type reactor~
3 FIGURE 25 is a sectional elevational view of the
4 solids quench boiler using the quench riser;
S FIGURE 26 ls a detailed cross sectional elevational
~ view of the quench exchanger of the system;
7 FIGURE 27 is a cross sectional plan view taken
8 through line 27-27 of FIGURE 26;
9 FIGURE 28 is a detailed drawlng of the reactor
outlet and fluld bed quench riser particle entry area.
11 FI~URE 29 is a schema~ic diagram of the system of
12 the invention for vaporizing heavy oil.
13
14
16 DESCRIPTION OF THE PREFERRED E~1BODIME~TS
17
18 The improvements of the subject invention are
e~hodied in the environment of a thermal regeneration cracking
reactor ~TRC) which is illustrated in FIGURE 1.
21
2~ , Referring to FIGURE 1, in the prior art TRC process~
~3 and system, thermal cracker feed o.il or residual oil, with or
24 I'without hlended distillate heavy gas, entering throu~h line 10
~25 !`and hydrogen entering through line 12 pass through hydrodesulfurized
26 zone 14. ~ydrosulfurization effluent passes through line 16 an~
27 enters flash chamber 19 from which hydrogen and contamina~ing gases
28 ~including hydrogen sulfi.de and ammonia are removed overhead through
29 ~line 20, while flash liquid is removed through line 22. The flash
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1 : liquid passes through preheater 24, is adrnixed with dilutlon
2 l steam entering tllrough line 26 and then flo~s to the bottom
3 1 of thermal cracking reactor 28 through line 30O
4 1l A stream of hot regenerated solids is charged
l throuyh line 32 and admixed with steam or other fluidizing gas
6 .~ entering through line 34 prior to entering the bottom of riser
7 ,l 28. The oil, steam and hot solids pass in entrained flow up-
B , wardly through riser 28 and are discharged through a curved
9 seg~ent 36 at the ~op of the riser to induce centrifugal separ-
atlon of solids from the effluent stream. A stream containing
11 most of ~he solids passes ~hrough riser discharge segment 38 and
12 can be mixed, if desired, with make-up solids entering through
13 ~ line 40 before or after enlering solids separator-stripper 42.
14 Another stream containing most of the cracked product is dis-
~5 charged axially through conduit 44 and can be cooled by means of
16 a quench stream entering through line 46 in advance of solids
17 separator-stripper ~8.
18 " Stripper steam is charged to solids separators 42
19 `I and 48 through lines 50 and 52, respectively. Product streams
1 are removed from solids separators 42 and 48 through lines 54
21 ~ and 56, respectively, and then combined in line 58 for passage
~2 ' to a secondary quench and product recovery trainj not shown.
23 Coke-laden solids are remo~ed from so~ids separators 42 and ~8
24 through lines 60 and 62, respectively, and cornbined in line 64
for passage to coke burner 66. If required, torch oil can be
26 added to burner 66 through line 68 while stripping steam may be
27 ~~ added through line 70 to strip combustion gases from the heated
2B 1I solids. Air is charged to the burner through line 69. Com~ustlon
29 I gases are removed from the burner through line 72 for passage
I to heat. and energy recovery systems, not shown, while regenerated
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1 ~ hot solids wh.ich are relatively free of coke are removed from
2 the burner tnrough line 32 for recycle to riser ~8. In order
3 to produce a cracked product containing ethylene and molecular
4 hydrogen, petroleum residual oil is passed through the catalytic
I hydrodesulfurized zone in the~resence of hydrogen at a tem-
6 perature between 650F and 900F, with the hydrogen being
7 chemlcally combined with theoil during the hydrocycling step.
8 The hydrosulfurization residual oil passes through the thermal
9 cracking zone together with the entrained inert hot solids
. functioning as the heat source and a diluent gas at a temperature
11 l, between about 1300F and 2500F for a residual time between
12 ~ about 0.05 to ~ seconds to produce the cracked product and
13 ethylene and hydrogen. For the production of ethylene ~y
14 thermally cracking a hydrogen feed at least 90 volume percent
~ of which comprises light gas oil fraction of a crude oil
1~ boiling between 400F and 650F, the hydrocarbon feed, along
17 1 with diluent gas and entrained inert hot gases are passed
18 i through the cracking zone at a temperature between 1300F and
19 ~500F for a residence time of 0.05 to 2 seconds. The weight
I ratio of oil gas to fuel oil is at least 0.3, while the cracking
21 ! severity corresponds to a methane yield of at least 12 weight
22 percent based on said feed oil. Quench cooling of the produc~
immediately upon leaving the cracked zone to a temperature
~4 below 1300F ensures that the ethylene yield is greater than
25 : the methane yield on a weight basis.
26
27
28
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1 (a) Improved Fuel Gas Generation For Solids
2 Heatins.
4 FIGURE 2 illustrates the improved process and system cf
the invention as may be e~bodied in a prior art TRC system, in lieu
6 ,of the coke burner 66 (FIG~ 1). Particulate solids and hyd ~ arbon feed gas
7 ,'enter a tubular reactor 13A throuah ~nes llA and 12A respec~vely. Ihe cracked
8 1 effl~lent from the tubular reactor 13A is separated from the pa~c~ate solids
9 in a separator 14A and quenched in line 15A by quench material
injected from line 17A. The solids separated fxom the effluent
11 are delivered through line 16A to a solids separator. The residual
12 solids are removed from the quenched product gas in a secondary
13 separator 18A and delivered to the solid stripper 22A. The solids-
14 ~Ifree product ~as is taken overhead from the secondary separator
~,18A through line l9A.
16
17
18
19
21
22
23
24
26
27
28
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696-147
1 I The particulate solids in the solid stripper 22A,
2 having delivered heat during the thermal cracking in the tubular
3 I reactor 13A, must be reheated and returned to the tubular reactor
4 1 13A to continue the cracking process.
' The particulate solids prior to being reheated~ are
6 ~stripped of gas in the solid stripper 27A by steam delivered to
7 l the solid stripper 22A through line 23A.
8 After the particulate solids have been stripped of
g gas impurities in the solid s-tripper 22A, the particulates solids
~t '
Y 10 are at a temperature of about 1,450F.
11 ~ The fuel gas generation apparatus of the inven~ior.
12 ~ consists of a combustion vessel 30A, and pre-heat equipment for
13 1 fuel/ air (or 2) and steam which are ~elivered to the combustion
14 , vessel 30A. Pre-heaters 32A, 34A, and 36 are shown in fuel llne
! 38A, air line 40A, and steam line 42A respectively,
i6 , 'l'he system also includes a transfer line 44A intc
17 I which the combusted fuel gas from the combustion vessel 30A ar.d
18 the stripped particulate solids from the solid stripper 22A aLe
19 , mixed to heat and decoke the particulate solids. The transfef
,~ line 44A is sized to afford sufficient residence time for the
21 1 steam emanating from the combustion vessel 30A to decompose by
22 !, the reaction with carbon in the presence of hydrogen and to remove
the net carbon from the solids-gas mixture. In the preferred
24 , embodiment the transfer line 44 will be about 100 feet long~ A
,25 1 line 26A is provided for pneumatic transport gas if necessary~ ;
26 A separator, such as a c~clone separa~or 46~ is
27 I provided to separate the heated decoked particulate solids from
28 ¦I the fuel gas. The particulate solids from the separator 46A are
29 ,~ returned through line 48A to the hot solids hold vessel 27A
',~ and the fuel gas is taken overhead through line 50A.
.,
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1 In the process, fuel, air and steam are delivered
2 through lines 38A, 40A and 42A respectively to the combustion
vessel 30A and combusted therein to a temperature of about
4 2,300F. to produce a fuel gas having a high ratio of CO to CO2
S and at least an equivalent molal ratio of H20 to H2. The H20
6 to H2 ratio of the fuel gas leaving the combustion vessel 30A
7 ; is above the ratio required to decompose steam by reaction witn
8 carbon in the presence of hydrogen and to insure that the net
9 carbon in the fuel gas-particulate solids will mix will be
removed before reaching the separator 46A.
11 ~he fuel gas from combustion vessel 30A at a
12 ; temperature of about 2,300F. is mixed in the tubular vessel 44A
13 l~ with stripped particulate solids having a temperature of about
14 1,450F. The particulate solids and fuel gas rapidly reach an
equilibrium temperature of 1,780F. and continue to pass through
16 the tubular vessel 44A. During the passage through the tubulac
17 vessel 44A the particulate solid-fuel gas mixture provide the
18 ~' heat necessary to react the net coke in the mixture with steam.
19 ll As a result, the particulate solid-fuel gas mixture is cooled
by about 30F. i.e., from 1,780F. to 1,750F.
21 I The particulate solid-fuel gas mixture is separated
22 in the separator 4ÇA and the fuel gas is taken at 1,750~F. through
line 50A. The particulate solids are delivered to the hot soli~s
24 l, hold vessel 27A at 1,750F. and then to the tubular reactor 13A.
,25 In the alternative embodiment of the invention
26 1 illustrated in FIGURE 3, only fuel and air are delivered to the
27 combustor 30 and burned to a temperature of about 2,300F. to
28 ' provide a fuel sas. The fuel gas at 2,300F. and particulate
29 1I solids at about 1,450~. are mixed in the transfer line 44A to
a temperature of about 1,486F. Thereafter air is delivered
I to the transfer line 44A throug~ a line 54A. The fuel gas in
! .
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696-147
1 ~he line 94A is burned to elevate the temperature of the partlcu-
2 ~late solids to about 1,750F. The resultant flue gas is separated
3 Ifrom the hot solids in the separator 46A and discharged through
4 I the line 52A. The hot particulate solids are returned to ~he
! system to provide reaction heat.
6 'I An example of the system and process of FIG~RE 3
7 ~ follows. 7,000 pounds per hour of fuel pre-heated to 600F. in
3 the preheater 32A and 13 MM SCFD of air heated to 1,000F. are
9 ;burned in the combustor 30A to 2,300F. to produce 15.6 M~l SCFD
' of fuel ~as.
11 The 15 MM SCFD of fuel ~as at 2,300F. is mixed in
12 the transfer line 44A with 1 ~ pounds per hour of stripped pdr~iCU-
i3 late solids from the solids stripper 22A. The particulate sollds
4 ;have 1,600 pounds per hour of carbon deposited thereon~ The com-
i5 posite fuel gas-particulate solids gas mixture reaches an
16 equilibrium temperature of 1,480F. at 5 psig in about 5 milll-
17 ,'seconds. Thereafter, 13 ~l SCFD of air is delivered to ~he
18 'transfer line 44A and the 15.6 ~M SCFD of fuel gas is burned
19 !with the air to elevate the solids temperature to 1,750F. and
buxn the 1,600 pounds per hour of carbon from the particulate
21 ,solids.
22 The combusted ~as from the transfer line 44A is
23 separated from the solids in the separator 46A and discharged
24 as flue gas.
26
27
28
29
%9
(b) Improved Solids Feeding Device and System~
Again referring to Figure 4 in lieu of the system of
the prior art (See Figure 1) wherein the stream of solids plus
Eluidizing gas contact the flash liquid-dilution steam mixture
entering reactor 28~ structurally the apparatus 32B of the
subject invention comprises a solids reservoir vessel 33B and
a housing 34B for the internal elements described belowO The
housin~ 34B is conically shaped in the embodiment of Figure 4
and serves as a transition spool piece between the reservoir
33B and the reactor 32B to which it is flangeably connected
via flanges 35B~ 36B, 37B and 38Bo The particular geometry of
the housing is functional rather than critica].~ The housing
is itself comprised of an outer metallic shell 39B~ preferably
of steel ? and an inner core 40B of a castable ceramic
material. It is convenient that the material of the core 40B
forms the base 41B of the reservoir 33B~ /
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Set into and supported by the inner core 40B is a
2 I gas distribution chamber 42B, said chamber being supplied with
3 gaseous feed from a header 43B. While the chamber 42B may be
4 ' of unitary construction, it is preferred that the base separating
the chamber 42B from reaction zone 44B be a removable plate 45B.
6 One or more conduits 46B extend downwardly from the reservoir
7 33B to the reaction zone 44B, passing through the hase 41B,
8 and the chamber 42B. The conduits 46B are in open communication
9 with both the reservoir 33B and the reaction zone 44B providing
thereby a path for the flow of solids from the reservoir 33B ~D
11 ' the reaction zone 44B. The conduits 46B are supported by the
12 material of the core 40B, and terminate coplanarly with a pla~e
13 45B, which has apertures 47B to receive the conduits 46B. The
14 region immediately below the plate 45B is hereinafter referred
to as a mixing zone 5~ which is also part of the reaction zone
16 44.
17 As shown in FIGURE 5, an enlarged partial view of ~he
18 intersection of the conduit 46~ and the plate 45B, the apertures
19 47B are larger than the outside dimension of conduits 46B, for~ning
,therebetween annular orifices 48B for the passage of gaseous ~eed
~1 from the chamber 42B. Edges 49B of the apertures 47B are pre--
22 ferably convergently beveled, as are the edges 50B, at the tip
of the conduit wall 51B. In this way the gaseous stream from
the charnber 4~B is angularly injected into the mixing zone53B
1l and intercepts thesolids phase flowing from conduits 46B. A
26 Iprojectlon of the gas flow would form a cone shown by dotted lines
27 1l 52B the vertex of which is beneath the flow path of the solids.
28 IBy introducing the gas phase angularly, the two phases are mixed
29 I rapidly and uniformly, and form a homogeneous reaction phase.
The ~.~ixing of a solid phase with a gaseous phase is a function of
1~
.,
,,
2~3
the shear surface between the solids and gas phases, and the
flow area. A ratio of shear surface to flow area ~S/A) of
infinity defines perfect mixing; poorest mixing occurs when the
solids are introduced at the wall of the reaction zone. In the
system of the present invention, the gas stream is introduced
annularly to the solids which ensures high shear surface. By
also adding the gas phase transversely through an annular feed
means, as in the preferred embodiment, penetration of the
phases is obtained and even faster mixing results. By using a
plurality of annular gas feed points and a plurality of solid
feed conduits, even greater mixing is more rapidly promoted,
since the surface to area ratio for a constant solids flow area
is increased. Mixing is also a known function o~ the L/D of
the mixing zone. A plug creates an effectively reduced
diameter D in a constant L, thus increasing mixing.
The Plug 54B, which extends downwardly from plate 45B,
as shown in Figures 4 and 5, reduces the flow area, and forms
discrete mixing zones 53B. The combination of annular gas
addition around each solids feed point and a confined discrete
mixing zone greatly enhances the conditions for mixing. Using
this preferred embodiment, the time required to obtain an
essentially homogeneous reaction phase in the reaction zone 44B
is quite low. Thus, this preferred method of gas and solids
addition can be used in reaction systems having a residence
time below 1 second, and even below 100 milliseconds. In such
reactions the mixing step must be performed in a fraction of
the total rssidence time, generally under 20% thereofO If this
criteria is not achieved, localized and uncontrolled reaction
occurs which deleteriously affects the product yield and
distribution. This is caused by the maldistribution of solids
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696-147
1 I normal to the flow through the reaction zone 44B thereby creating
2 temperature and or concentration gradients therein.
3 The flow area is further reduced b~ placing the
4 1 apertures 47s as close to the walls of the mixing zone 53B as
;i possible. FIGURE 6 shows the top view of plate 45B having in
6 complete circular aper~ures 47B symmetrically spaced along the
7 circumference, The plug 54B, shown by the dotted lines and
8 in FIGURE g, is below the plate, and establishes the discrete
9 ; mixing zones 53B described above. In this embodiment~ the
apertures 47B are completed by the side walls 55B of gas
11 distribution chamber 42B as shown in FI~URE 5. In order to
12 prevent movement of conduits 46B by vibration and to retain t~e
13 uniform width of the annular orifices 48B, spacers 56B, are
14 1 used as shown in FIGURE ~. However, the conduits 46B are pr
marily supported within the housing 3~B by the material of the
16 core 40B as stated above.
17 Referring to FIGURE 9, the plug 54B serves to
13 reduce the flow area and define discrete mixing zones 53B~
i9 ~he plug 54B may also be convergently -tapered so that there
is a gradual increase in the flow area of the mixing zone 53s
21 until the mixing zone merges with remainder of the reaction
22 1 zone 44B. Alternatively, a plurality of plugs 54B can be use~
23 Ij to obtain a mixing zone 53B of the desired geometric con-
24 figuration~
25 I Referring again to FIG~RE 4, the housing 34B may
~6 preferably contain a neck portion 57B with corresponding lining
27 1 58B of the castable ceramic material and a flange 37B to cooperate
28 with a flange 38B on the reaction chamber 31B to mount the neck
29 ~I portion 57B~ This neck portion 57B defines mixing zone 53B,
'
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;! -15-
696-147
and allows complete removal of the housing 34B without dis-
2 i assembly of the reactor 313 or the solids reservoir 33B~ Thus,
3 1 installation, removal and maintenance can be accomplished
4 ' easily. Ceramic linings 60B and 62B on the reservoir 33B
S ~ and the reactor walls 613 respectively are provided to prevent
6 erosion.
7 , The solids in reservoir 33B are not fluidized
8 ; except solids 63B in the vicinity of conduits 46B. Aeration
9 gas to locally fluidize the solids 63B is supplied by nozzles
64B syrnrnetrically placed around the conduits 46B. Gas to
11 I nozzles 64Bis supplied by a header 65B, Preferably, the header
12 65Bis set within the castable material of the core 40B, but
13 this is depend~nt on whether there is sufficient space in the
14 housing 34B~ A large mesh screen 66B is placed over the inlets
~ of ~he conduit 64B to prevent debris and large particles from
16 entering the reaction zone 4~B or blocking the passage of the
17 particulate solids through the conduits 46B.
18 By locally fluidizing the solids 63B, the solids
19 ~63B assume the characteristics of a fluid, and will flow thrGugh
j the cond~lits 96B. The conduits 46B have a fixed cross sectional
21 1l area, and serve as orifices having a specific response to a
22 ,change in orifice pressure drop. Generally, the flow of
23 ; fluidized solids through an orifice is a function of the pressilre
24 drop through the orifice. That orifice pressure dropl in turn,
'isa function of bed height, bed density~ and system pressure~
26 , However, in the process and apparatus of this
27 , invention the bul)c of the solids in reservoir 33B are not
28 I fluidized. Thus, static pressure changes caused by varia~ions
29 in ~ed height are only 510wly communicated to the inlet of the
coriduit 46B. Also the bed density remains approximately cons-tant
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,1
ntil the polnt of incipient fluldization is reached, that is,
2 point "a" of FIGURE 7. In the present invention, however, it
3 l is essential that the amount of aeration gas be below that
4 , amount. Any aeration gas flow above that at point "a" on
S 1 ~IGUR~ 7 will effectively provide a fluidized bed and thereby
6 lose the benefits of this invention. By adjustment of the
7 aeration gas flow rate, the pressure drop acroCs the non-
8 ; fluidized bed can be varied. Accordingly, the pressure drop
9 ; across the orifice is re~ulated and the flow of solids thereby
~ regulated as shown in FIGURE 7. As gas flow rates below
11 incipient flui~ization, significant pressure increases
12 above the orifice can be obtained without fluidizing the bul~ of
13 the solids. Any effect which the bed height and the bed denslty
1~ variations have on mass flow are dampened considerably by the
presence of the non-fluidized reservoir solids and are essentidlly
16 eliminated as a signiricant factor. Further the control provided
17 by this invention affords rapid response to changes in solids
18 mass flow regardless of the cause.
~ " ,
19 Together with the rapid mixing features descr-bed
above, the present invention offers an integrated system for
21 , feedin~ particulate solids to a reactor or vessel, especially
~2 to a TRC tubular reactor wherein very low reaction residence
23 ~ times are encountered.
24 ' FIGURES loandll depict an alternate preferred embodi
I ment of the control features o~ the present invention. In this
26 embodiment the reservoir 33B extends downwardly into the core
material ~OB to form a secondary or control reservoir 71B~ The
~8 ~I screen 66B is positioned over the entire control reservoir 71B.
~9 ' The aeration nozzles 64B project down~Jardly to fluidize ~ssentially
~i these solids 63B beneath the scree~ 66~o The bot~om 41B of the
l!
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696-1~7 ,
1 ; reservoir 33B is again preferably formed of the same material
2 i as the core 40B.
3 A plurality of clean out nozzles 72B are preferably
4 , provided to allow for an intermittent aeration gas discharge
which removes debris and large particles that may have accumulated
6 on the screen 66B. Porous stone filters 73B prevent solids from
7 entering the nozzles 72B. Headers 65B and 74B provide the gas
8 supply to nozzles 64B and 7 2B respectively.
9 . The conduits 46B communicate with the reservoir 71B
' through leading section 4 6'B, The leading sections 461B are
11 formed in a block 75B made of castable erosion resistent ceramic
12 material such as Carborundum Alfrax 201. The block 75Bis
13 ~ removable, and can be replaced if eroded~ The entrance 75B to
14 each section 46'B can be sloped to allow solids to enter more
, easily. In addition to being erosion resistent, the block
i6 75B provides greater longevity because erosion may occur without
17 . loss of the preset response function. Thus, even if the conduit
18 leading sections 46'B erode as depicted by dotted lines ~7B~
19 the remaining leading section 46'Bwill still provide a known
' orifice size and pressure drop response. The conduits 46B
21 l, are completed as before using erosion resistent metal tubes
22 !~51B, said tubes being set into core material 40B and affixed
~3 l~ to the block 75B.
24 I FIG~RE llis a plan view of FIGURE ~o along section
1 9-9 showing an arrangement for the no2zles 64B and 72B, and the
26 I heade~s 65B and 74B. Gas is supplied to the headers 65B and 74B.
~; through feed lines 79B and 80B respectively, which extend out~
~8 ~ beyond the shell 34B. It is not necessary ~hat the headers be
29 set into the material of the core 40B, although this is a
convenience from the fabxication standpoint. Uniform flow
!
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.,
I
1 j distribution to each of the nozzles is ensured by the hydraullcs
2 of the nozzles themselves, and does not require other devices
3 such as an orifice or venturi. The gas supplied to feed lines
4 1 79B and 80B is regulated via valve means not shown.
~IGURES 12 and 13 show the pextinent parts of an
6 al~ernate embodiment of the invention wherein a second gas dis-
7 tribution assembly for feed gas is contemplated. As in the other
8 embodiments, a gas distribution chamber 42B terminating in annular
orifice 48B surrounds each solids delivery conduit 46B. Howe~er,
; rather than a common ~IJall between the chamber 47B and the cor,duit
46B, a second annulus 83B is formed between the chamber 42B
12 ; and the conduit 46B. ~7alls 81~ and 51B define the chambers
13 83B. Feed is introduced through both the annular opening 48B
14 in the chamber 42B and the annular opening 84B in the annulus
83B at an angle to the flow of solids from the conduits 46i3.
16 The angular entry of the feed gas to the mixing zone 53Bis
17 provided by beveled walls 49B and 85B, which define the openirgs
18 il 48B and beveled walls 50B and 89B which define the openings
19 'I84B. Gas is introduced to the annulus 83B through the header
~l86B~ the header being set into the core 40Bi~ convenient.
21 ,, FIGURE i2 is a plan view of the apparatus of FIG~lRE
22 1 13 through section 11-11 showing the conduit openings and the
~3 annular feed openings 48B and 84B. Gas i5 supplied through feed
2~ lines 87Band88Bto the headers 43B and 86B and ultimately
, to the mixing zones through the annular openings. Uniform flow
26 from the chambers 42B and 83B is ensured by the annular orifices
27 j, 48B and 84B. Therefore, it is not essential that flow dis-
28 1l~ tribution means such as venturis or orifices be included in
29 !~ the header 43B. The plug 54B is shaped symmetrically to
define discrete mixing zones 53B.
,, --1 9--
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696-1471,
.1 .
; Mixing efficiency is also dependent upon the velocities
2 of the gas and solid phases. The solids flow throu~h the conduits
3 I`46B in dense phase flow at mass velocities from preferably 200
4 to 500 pounds/sq. ft.~sec) although mass velocities between 50 and
l'1000 pounds/sq. ft./sec./ may be used depending on the character-
6 istics of the solids used. The flow pattern of the solids in the
7 absence of gas is a slowly diverging cone. With the introduction
8 of the gas phase through the annular orifices 48B at velocities
9 , between 30 and 800 ft./sec., the solids develop a hyperbolic flow
pattern which has a high degree of shear surface. Preferably, the
11 ,gas velocity through the orifices 48B is between 125 and 250 fto/
12 secO Higher velocities are not preferred because erosion is
13 accelerated; lower velocities are not preferred because the hyper-
14 ;bolic shear surface is less developed.
~ The initial superficial velocity of the two phases in
16 the mixing zone 53B is preferably about 20 to 80 ft./sec.,
17 'although this velocity changes rapidly in many reaction sys~ems~
18 'such as thermal cracking, as the gaseous reaction products are
19 formed. The actual average velocity through the mixing ~one 53B
l and the reaction zone ~4B is a process consideration, the velocity
21 j being a function of the allowed residence time therethroughO
22 ! By em~loying the solid feed device and method of tne
23 present inventions, the mixing length to diameter ratio necessary
24 Ito intimately mix the two phases is greatly reduced~ This ratio
is used as an informal criteria ~hich defines good mixing. Gen-
26 lerally, an L/D(lenyth/dia.~ ratio of from 10 to 40 is required~
27 IUsing the device disclosed herein, this ratio fs less than 5, wi~h
28 Iratios less than 1.0 being possible~ Well designed mixing devices
29 jlOf the present invention may even achieve essentially complete
Imixing at L/D ratios less than 0.5.
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~_1 7
1 (c) Improved Sequential Thermal Cracking
2 Process.
urning now to the sequential cracking process 2C
of the subjeet inven.ion, as illustrated in YIGURE 1~, in lieu of
reactor 28 (see FIGUR~ 1) of the prior art, the system of the
, invention includes a solids heater 4C, a primary reactor 6C, a
8 1'
secondary reaetor 8C and downstream equipment. ~he downstream
9 1.
e~ui,oment is c~mprised essentially of an indireet heat exchanger lCC,a
1 1 \
13
14
16
17
1~ \
19
21
22
23
24
26
2`7
28
~9
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696-1~7
, .
l I fractionation tower 12C, and a recycle line 14C from ~he
2 fractionation tower 12C to the entry of the primary reactor
3 6C.
4 I The system also includes a first hydrocarbon feed
' line 16C, a second hydrocarbon feed-quench line 18C~ a transfer
line 20C and an air delivery line 22C.
7 The first hydrocarbon feed stream is introduced
8 into the primary reactor 6C and contacted with heated solids
9 from the solids heater 4C. The first or primary reactor 6C
in which the first feed is cracked is at high severity conditions~
ll The hydrocarbon feed, from line 16C~ may be any hydrocarbon gas
12 or hydrocarbon liquid in the vaporized state which has been used
i3 heretofore as a feed to the conventional thermal cracking process.
l~ Thus~ the feed introduced into the primary reactor 6C may be
lS ~ selected from the group consisting of low molecular weight hydro-
16 carbon gases such as ethane, propane, and butane, light hydro-
17 carbon liquids such as pentane, hexane, heptane and octane, low
la boiling point gas oils such as naphtha having a boiling range
l9 between 350 to 650F, high boiling point gas oils having a
I boiling range between 650 to 950F and compatible combinations
21 of same. These constituents may be introduced as fresh feed
22 or as recycle streams through the line 14C from downstream
23 , puri~ication facilities e.g., fractionation to~er 12C. DilutiGri
steam may also be delivered with the hydrocarbon through lines
l 16C an~ 14C. The use of dilution steam reduces the partial
26 l' pressure, improves cracking selectivity and also lessens the
27 ~' tendency of high boiling aromatic components to form coke.
28 i The preferred primary feedstock for the high
29 severity reaction is a light hydrocarbon material selected from
I the group consisting of low molecular weiqh~, hydrocarbon gases~
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696-147 l, ~ ~ ~ w ~ ~ ~
1 light hydrocarbon liquids, light gas oils ~oiling between 350
2 and 650F, and combinations of same. These feedstocks offer the ,
3 ~ greatest increase improvement in selectivity at high severity
4 and short residence times.
The hydrocarbon feed to the first reaction zone is
6 ; preferably pre-heated to a temperature of between 600 to 1200F
7 before introduction thereto. The inlet pressure in the line 16C
8 is 10 to 100 psig. The feed should be a gas or gasified liquid
9 The feed increases rapidly in tem2erature reaching thermal equi-
librium with the solids in about 5 milliseconds. As mixing of
11 the hydrocarbon with the heated solid occurs, the final tem-
12 perature in the primary reactor reaches about 1600 to 2000F. At
13 these temperatures a high severity thermal cracking reaction takes
lq place. Tlle residence time maintained within the primary reactor
is about 50 milliseconds, preferably between 20 and 150 milli-
16 seconds, to ensure a high conversion at high selectivity. Typl-
~7 cally, the ~SF (Kinetic Severity Function) is about 3~5 (97%
18 conversion of n-pentane). Reaction products of this reaction ~-lre
19 olefins, primarily ethylene with lesser amounts of propylene and
butadiene, hydrogen, methane~ C4 hydrocarbons, distillates suc~
21 as gasoline and gas oilsl heavy fuel oils, coke and an acid gas.
22 ; Other products may be present in lesser quentities. Feed con-
23 ! version in this first reaction zone is about between 95 to 100~ by
24 weight of feed, and the yield of ethylene for liquid feedstocks
is about 25 to 45~ by weight of the feed, with selectivities o~
26 about 2.5 to 4 pounds of ethylene per pound of methane.
27 A second feed is introduced through the line 18C
28 ~ and combines with the cracked ~as from the primary reactor 6C
29 between the primary reactor 6C and the secondary reactor 8C~ The
' combined stream comprising the second unreacted feed, and the
i
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6 9 ~ -1 a 7
1 first reacted feed passes ~hrough the secondary reactor 8C under
2 , low severity reaction conditions. The second feed introduced
3 l! through the line 18C is preferably virgin feed stock but may
4 11 also be comprised of the hydrocarbons previously mentioned~
including recycle streams containing low molecular weight
6 ; hydrocarbon gases, light hydrocarbon liquids, low boiling
7 point, light compatible gas oils, high boiling point gas oilst
8 and combinations of same.
9 i Supplemental dilution steam may be added with the
~ secondary hydrocarbon stream entering through s-tream 18C. ~owever,
11 ; in most instances the amount of steam initially delivered to the
12 primary reactor 16C will be sufficient to achieve the requisite
13 , partial pressure reduction in the reactors 6C and 8C. It should
14 be understood that the recycle stream 14C is illustrative, and not
specific to a particular recycle constituent.
16 The hydrocarbon feed delivered through the line 18C
17 ' is preferably virgin gas oil 400-650F. The second feed is pr-~
18 !, heated to between 600 to 1200F. and upon entry into the seco!dary
lg I reactor 8C quenches the reaction products from the primary re-
actor to below 1500F~ It has been found that in general 100
21 pounds of hydrocarbon delivered through the line 18C will quench
22 l~ 60 pounds of effluent from the primary reactor 6C. At this ter"-~
23 l, perature level, the cracking reactions of the first feed are
2~ ~l essentially terminated. However, coincident with the ~uenching
~l of the effluent from the prlmary reactor, the secondary feed
26 ~I entering through line 18C is thermally cracked at this tempera~ure
27 ! (1500 to 1200F) and pressures of 10 to 100 psig at low severity
28 by providing a residence time in the secondary reactor between
29 1 150 and 2000 milliseconds, preferably between 250 to 500 milll-
seconds. Typically, the KSF cracking severity in the secondary
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69fi-147
I;
. .
1 I reactor is about O.S at 300 to 400 milliseconds.
2 I The inlet pressure of the second feed in line 18C is
3 between 10 and 100 psig, as is the pressure of the first feed.
4 Reaction products from the low severity reaction zone comprise
, ethylene with lesser amounts of propylene and butadiene, hydro-
6 gen, methane, C4 hydrocarbons, petroleum distillates and gas
7 oils, heavy fuel oils, coke and an acid gas. Minor amounts of
8 other products may also be produced. ~eed conversion in this
9 second reaction zone is about 30 to 80% by weight of feed,
~ and the yield of ethylene is about 8 to 2G% by weight of feed,
11 ! with selectivities of 2.5 to 4.0 pounds of ethylene per pound
12 of methane
13 Although the products from the high severity reac~ion
14 are combined with the second feed, and pass through the second
~ reaction zone, the low severity conditions in the second reaction
zone are insufficient to appreciably alter the product dis-
17 I tribution of the primary products from the high severity react~on
18 ` ~one. Some chemical changes will occur, however these reaction
~ '
19 products are substantially stabilized by the direct quench
provided by the second feed.
~1 The virgin gas oils normally contain aromatic
22 molecules with paraffinic hydrocarbon side chains. For some
23 gas oils the nurnber of carbon atoms associated with such
24 ~ paraffinic side chains will be a large fraction of the total
number of carbon atoms in the molecule, or the gas oil will
~6 have a low "aromaticity".
27 ; In the secondary reactor~ these molecules will
2~ I undergo dealkylation - splitting of the paraffin molecules/
29 ll leaving a reactive residual methyl aromatic, which will tend
to react to form high boilers. The paraffins in the boiling
.1,
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696-1~7
1 l~ range 400 to 6S0F are separated from the higher boiling
2 ; aromatics in column 1? and constitute tlle preferred recycle
3 ~ to the primary reactor.
4 , Other recycle feed stocks can include propylene,
butadiene, butenes and the C5 - 400F pyrolysis gasoline.
6 ~ The total effluent leaves the secondary reactor
7 and is passed through the indirect quench means 10C to generate
8 ~ steam for use within and outside the system. The effluent is
9 then sent to downstream separation facilities 12C via line 24C~
10 i The purification facilities 12C employ conventional
11 separation methods used currently in thermal cracking processes~
12 FIGURE 2 illustrates schematically the products obtained. Hydro-
13 gen and methane are taken overhead throush the line 36C. C4 and
14 lighter olefins, C5 - 400F and 400-650F fractions are removed
from the fractionator 12C through lines 26C, 28C and 30C re-
16 spectively. Other light paraffinic gases of ethane and propane
17 are recycled through the line 14C to the high severity primary
18 reactorO The product taken through line 28C consists of liquid
~ '
l9 ' hydrocarbons boiling between C5 and 400F, and is preferably
exported although such material may be recycled to the primary
21 ~ reac~or 6C if desired. The light gas oil boilinq between 400
22 to 650F is the preferred recycle feed, but may be removed through
23 l line 30C. The heavy gas oil which boils between 650-950F is
2q exported through stream 32C, while excess residuim, boiling
~ above 950F is removed from the battery limits via stream 34C
~6 The heavy gas oil and residuim may also be used as fuel within
27 the system.
2~ ~ In the preferred embodiment of the process, the
29 I second feed would be one which is not recommended for high
~ severity operation~ Such a feed would be a gas oil boiling
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696-147 1 ~
. . .
1
~ above 400F whlch COTItalns a slgniflcant amount of high molecular
,~ weiyht aromatic components. Generally, these components have
3 ; paraffinic side chains which will form olefins under proper
conditions. However, even at moderate severity, the dealkylated
aromatic rings will polymerize to form coke deposits. By pro-
6 cessing the aromatic gas oil feed at low severity, it is possib1e
7 to dealkylate the rings, but also to prevent subsequent poly~
8 merization and coke Eormation. As a consequence of the low
9 severity, however, the yield of olefins is low, even though
selectivity as previously defined is high. Hence, low severity
11 reaction effluents often have significant amounts of light
12 paraffinic gases and paraffinic gas oils. These light gases
13 ~ and paraffinic gas oils are recycled preferably to the high
14 I severity section, such compounds being the preferred feeds
i5 ll thereto. The aromatic components of the effluent are removed
1~ I from the purification facilities 12C as part of the heavy gas
17 ! oil product, and either recycled for use as fuel within the
18 system, or exported for further purification or storage.
19 An illustration of the benefits of the process of
the invention is set forth below wherein feed cracked and the
21 I resultant product obtained under conventional high severity
22 cracking and quenching conditions is compared with the same feed
23 sequentially cracked in accordance with this invention.
24
-
25 , \
26
27
28 ,
29
i
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696-147
1 (d) Improved Residerlce Time Solid~Gas Separation
2 Device and System.
- Referring to FIGURE 15 in the subject invention, in lieu
separation zone or curved segment region 36 and the quench area
6 44 of the prior art TRC system (see FIGUR~ 1), solids and gas enter
7 the tubular reactor 13D through lines llD and 12D respectively.
8 The reactor effluent flows directly to separator 14D where a
9 separation into a gas phase and a solids phase stream is effected.
The gas phase is removed via line 15D, while the solid phase is
11 sent to the s-tripping vessel 22D via line 16D. Depending upon
12 the nature of the process and the degree of separation, an in line
13 quench of the gas leaving the separator via line 15D may be made
14 by injecting quench material from line 17D. Usually, the product
sas contains residual solids and is sent to a secondary separator
16 ~18D, preferably a conventional cyclone. Quench material should
17 be introduced in line 15D in a way that precludes back flow of
18 quench material to the separator. The residual solids are removed
from separator 18D via line 21D, while essentially solids
free product gas is removed overhead through line l9D. Solids
from lines 16D and 21D are stripped of gas impurities in
22 fluidized bed stripping vessel 22D using steam or other inert
23 fluidizing gas a~nitted via line 23D. Vapors are removed from
24 the stripping vessel through line 24D and, if economical or if
26 need be, sent to down-stream purification units~ Stripped solids
27 ~ _
28
29
-
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696-147
1 ll removed from the vessel 22D through line 25D are sent to re-
2 ,I generation vessel 27D using pneumatic kransport gas from line
3 , 26D. Off gases are removed from the regenera-tor through line 28D.
4 1 After regeneration the solids are then recycled to reactor 13D
, via line llD.
6 , The separator 14D should disenga~e solids rapidly
7 ;~ from the reactor effluent in order to prevent product degradation
8 i and ensure optimal yield and selectivity of the desired products.
9 l Further, the separator 14D operates in a manner that eliminates
j or at least significantly reduces the amount of gas entering the
11 stripping vessel 22D inasmuch as this portion of the gas product
12 would be severely degraded by remaining in intimate contact with
13 the solid phase. This is accomplished with a positive seal which
14 has been provided between the separator 14D and the stripping
' vessel 22D. Finally, the separator 14D operates so that
16 erosion is minimized despite high temperature and high velocity
17 , conditions that are inherent in many of these processes~ The
18 separator system of the present invention is designed to meet
19 each one of these criteria as is descri~ed below.
FIGUR~16 is a cross sectional elevational view
21 1I showing the preferred embodiment of solids-gas separation devlce
2 ~ j 14D of the present lnvention. The separator 14D is provided
23 with a separator shell 37D and is com?rised of a solids-gas
~4 , disengaging chamber 31D having an inlet 32D for the mixed phas2
~ stream, a gas phase outlet 3i3D, and a solids phase outlet 34D.
26 The inlet 32D and the solids outlet 34D are preferably locate~
27 ' at opposite ends of the chamber 31D. While the gas outlet 33~
28 , lies at a point therebetween. Clean-out and maintenance manways
29 35D and 36D may be provided at either end of the chamber 31D.
; The separator shell 37D and manways 35D and 36D preferably are
29-
,j
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6~6-la7
, ~ :
1 l lined w~ eroslon resi~tent linings 3~D, 39D and 41D re-
2 spectively which may be required if solids at hi~h velocities
3 j are encountered. Typical commercially available materials
4 for exosion resistent llning include Carborundum Precast
Carbofrax D, Carborundum Precast Alfrax 201 or their equivalent
6 h thermal insulation lining 4OD may be placed between shell 37D
7 ~ and lining 38D and between the manways and their respective
8 1 erosion resistent linings when the separator is to be used
9 in high temperature service. Thus, process te~peratures above
0 1500F. (870C.) are not inconsistent with the utilization of
11 this device.
12 FIGURE 17shows a cutaway view of the separator
13 along section ~4. For greater strength and ease of construction
14 the separator 14D shell is preferably fabricated from cylindrical
sections such as pipe SOD, although other materials may, of
16 ~ course, be used. It is essential that longitudinal side walls
17 51D and 52D should be rectilinear, or slightly arcuate as in-
18 , dicated by the dotted lines 51D and 52D. Thus, flow path 31D
19 through the separator is essentially rectangular in cross
~ section having a height H and width W as shown in FIGURE 17.
21 The embodiment shown in FIGURE 17 defines the geometry of the
22 flow path by adjustment of the lining width for walls 51D and
23 j 52D. Alternatively, baffles, inserts, weirs or other means
24 ~I may be used. In like fashion the configuration of walls 53D
~5 `~ and 54D transverse to the flow path may be similarly shaped,
26 although this is not essential. FIG~RE 18is a cutaway view
along Section 4-4 of FIGURE16 wherein the separation shell 37~
28 1 is fabricated from a rectangular conduit. Because the shell 37D
29 has rectilinear walls 51D and 52D it is not necessary to adjust
the width of the flow path with a thickness of lining. Linings
' -30-
`~_
-
38D and 40D could be added for erosion and thermal resistence
respectively.
Again referring to Figure 16 inlet 32D and outlets
33D are disposed normal to flow path 31D (shown in Figure 17)
so that the incoming mixed phase stream from inlet 32D is
re~uired to undergo a 90 change in direction upon entering
the chamber. As a further requirement, however, the gas phase
outlet 33D is also oriented so that the gas phase upon leaving
the separator has completed a 180 change in direction.
Centrifugal force propels the solid particles to the
wall 54D opposite inlet 32D of the chamber 31D, while the gas
portion, having less momentum, flows through the vapor space
of the chamber 31D. Initially, solids impinge on the wall
54D, but subseguently accumulate to form a static bed of
solids 42D, which ultimately form in a surface configuration
having a curvilinear arc 43D of approximately 90. Solids
impinging upon the bed are moved along the curvilinear arc 43D
to the solids outlet 34D which is preferably oriented for
downflow of solids by gravity. The exact shape of -the arc 43D
is determined by the geometry of the particular separator and
the inlet stream parameters such as velocity, mass flowrate,
bulk density, and particle si~e. Because the force imparted
to the incoming solids is directed against the static bed 42D
rather than the separator 14D itself, erosion is minimal.
Separator efficiency, defined as -the removal of solids from
the gas phase leaving through outlet 33D, is, therefore, not
affected adversely by high inlet velocities up to 150
ft./sec., and the separator 14D is operable over a wide range
of dilute phase densities, preferably between 0.1 and 10.0
lbs./ft3. The separator 14D of the present invention achieves
efficiencies of about ~0%, although the preferred embodiment,
discussed below, can obtain over 90~ removal of solidsO
., ~
-31-
It has been found that separator efficiency is
dependent upon separator geometry inasmuch as the flow path
must be essentially rectangular and the relationship between
height H, and the sharpness of the U-bend in the gas flows.
Referring to ~igures 16 and 17 we have found that for
a given height H of chamber 31D, efEiciency increases as the
180 U-bend between inlet 32D and outle-t 33D becomes
progressively sharper; that is, as outlet 33D is brought
progressively closer to inlet 32D. Thus, for a given H the
efficiency of the separator increases as the Elow path and,
hence, residence time decreases. Assuming an inside chamber
di of inlet 32D, the preferred distance CL between the
centerlines of inlet 32D and outlet 33D is less than 4.0 di~
while the most preferred distance between said centerlines is
between 1. 5 and 2. ~ di. Below 1. 5Di better separation is
obtained but difficulty in fabrication makes this embodiment
less attractive in most instances. Should this latter
embodiment be desired, the separator 14D would probably
require a unitary casting design because inlet 32D and outlet
20 33D would be too close to one another to allow welded
fabrication.
It has been found that the height of flow path ~1
should be at least equal to the value of Di or 4 inches in
height, whichever is greater. Practice teaches that if ~ is
less than Di or 4 inches the incoming stream is apt to disturb
the bed solids 42D, thereby re-entraining solids ln the gas
product leaving through outlet 33D. Preferably H is on the
order of twice Di to obtain even greater separation
efficiency. While no-t otherwise limi-ted, it is apparent that
30 too large an H eventually merely increases residence time
wi-thout substantive increases in efficienc~. The width W of
the flow path is
- 32 -
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696-147
1 preferably between 0.75 and 1.25 times Di, most preferably between
2 I 0.9 and 1.10Di.
3 Outlet 33D may be of any inside diameter. However~
4 , velocities greater than 75 ft./sec. can cause erosion because
', of residual solids entrained in the gas. The inside diameter
6 ~ o outlet 34D should be sized so that a pressure differential
7 1 between the stripping vessel 22D shown in EIGURE1s and the
8 , separator 14D exist such that a static height of solids is
g I formed in solids outlet line 16D. The static height of solids
in line 16D forms a positive seal which prevents gases from
11 l entering the stripping vessel 22D~ The magnitude of the
12 pressure differential between the stripping vessel 22D and the
13 separator 14D is determined by the force required to move the
14 ;' solids in bulk flow to the solids outlet 34D as well as the
1 ehight of solids in line 16D. As the differential increases
16 , the net flow of sas to the stripping vessel 22D decreases.
17 Solids, having ~ravitational momentum, overcome the differential,
18 while gas preferentially leaves through the gas outlet 33D.
19 sy reaulating the pressure in the stripping vessel
' 22D it is possible to control the amount of ~as going to the
21 stripper. The pressure regulating means may include a check
22 or "flapper" valve 29D at the outlet of line 16D, or a pressure
23 l control 29D device on vessel 22Do Alternatively, as suggested
24 j~ above, the pressure may be re~ulated by selecting the size of
! the outlet 34D and conduit 16D to obtain hydraulic forces
26 ~I acting on the system that set the flow of gas to the stripper
27 1 32D. ~hile su~h gas is degraded, we have found tha-t an increase
28 ' in separation efficiency occurs with a bleed of ~as to the
29 ' stripper of less than 10~, preferably between 2 and 7~. Economic
~ and process considerations would dictate whether this mode of
-33-
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696-1~7 ~
,1 .
1 1 operation should be used. It is also possible to design the
2 system to obtain a net backflow of gas from the stripping
3 ~I vessel. This ~as flow should be less than 10~ of the total
4 ~ feed gas rate.
sy establishing a minimal flow path, consistent
6 ~ with the above recor~nendations, residences times as low as
7 0.1 seconds or less may be obtained, even in separators
8 ,I having inlets over 3 feet in diameter. Scale-up to 6 feet
9 l' in diameter is possible in rnany systems where residence times
' approaching 0.5 seconds are allowable.
11 In the preferred embodiment of FIGURE 16, a weir 44D
12 ' is placed across th~ flow path at a point at or just beyond the
13 i gas outlet to establish a positive height of solids prior to
14 li solids outlet 34D. By installing a weir (or an equivalent
I restriction) at this point a more stable bed is established
16 thereby reducing turbulence and erosion~ Moreover, the weir
17 , 44D establishes a bed which has a crescent shaped curvilinear
18 arc 43D of slightly more than 90~0 An arc of this shape
19 diverts gas towards the gas outlet and creates the U-shaped
I gas glow pattern illustrated diagrammatically by line 45D in
21 FIGURE 16. Without the weir 44D an arc sor,lewhat less than or
22 equal to 90 would be formed, and which would extend asymptoti-
23 cally toward outlet 34D as shown by dotted line 60D in the
24 'i schematic diagram of the separator of FIGURE 19. While neither
efficiency nor gas loss (to the stripping vessel) is affected
26 ! adversely, the flow pattern of line 61D increase~ residence timet
27 ~ and more importantly, creates greater poten~ial for erosion at
28 l areas 62D, 63D and 64D.
29 The separator of FIGURE 20 is a schematic diagram of
! another embodiment of the separator 14D, said separator 14D
-3~-
!
696-1~7 ~9~2~
1 1 having an extended separation chamber in the lon(Jitudinal
2 1; dimension. Here, the horizontal distance L between the gas
3 outlet 34D and the weir 44D is extended to establish a solids
4 ! bed of greater leng-th. L is preferably less than or equal
I to 5 Di. Although the gas flow pattern 61D does not develope
6 I the preferred V-shape, a crescent, shaped arc is obtained
7 which limits erosion potential to area 64D. Embodiments
8 11 shown by FIGURES 19 and 20are useful when the solids loadinq
9 j of the incoming stream is low. The e~bodiment of FIGURE 19
also has the minimum pressure loss and may be used when the
11 velocity of the incoming stream is low.
12 As shown in FI5UR~21 it is equally possible to use a
13 , stepped solids outlet 65D having a section 66D collinear with
14 the flow path as well as a gravity flow section 67D. Wall 68D
-5 replaces weir 44D, and arc 43D and flow pattern 45 are similar
16 ; to the preferred embodiment of FIGURE 16. Because solids accumu-
17 i late in the restricted collinear section 66D, pressure losses
18 are ~reater. This embodiment, then, is not preferred where the
19 incoming stream is at low velocity and cannot supply sufficien-t
force to expel the solids through outlet 65D. However~ because
21 of the restricted solids flow path, better deaeration is obtained
22 l and gas losses are minimal.
23 j FIGURE 22 illustrates another embodiment of the
24 ~ separator 14D of FIGURE 21wherein the solids outlet is steppeG.
l` Althoush a weir is not used, the outlet restricts solids flow
,26 which helps from the bed 42D. As in FIGURE 20, an extended L
27 distance between the gas outlet and solids outlet may be used~
28 The separator of FIGURE21 or22 may be used in
29 I conjunction with a venturi, an orifice~ or an equivalent flow
restriction device as shown in FIGURE 28. The venturi 69D having
I -35-
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696-147 !,
1 ~, dimensions Dv (diameter at venturi inlet), Dv~ (diameter of
2 I venturi tl-roat), and ~ (angle of cone formed by projec~ion
3 , of convergent venturi walls) is placed in the collinear section
4 66D of the outlet 65D to greatly improve deaeration of solids.
The embodiment of FIGURE 24 is a variation of the separator
6 shown inFIGURE 23. Here, inlet 32 and outlet 33D are oriented
7 for use in a riser type reactor. Solids are propelled to the
8 wall 71D and the bed thus formed is kept in place by the force
g of the incoming stream. As before the gas portion of the feed
, follows th~ U-shaped 2attern of line 95D. However, an asymptotic
11 bed will be formed unless there is a restriction in the solids
12 outlet. A weir would be ineffective in establishing bed height~
13 and would deflect solids into the gas outlet. For ~his reason
14 ' the solids outlet of FIG~RE 23 is preferred. ~Sost preferably,
; the venturi 69D is placed in collinear section 66D as shown in
16 ; FIGURE24 to improve the deaeration of the solids. Of course,
17 each of these alternate embodiment may have one or more of ~he
1~ optional design features of the basic separator discussed in
19 relation to FIGURES 1~ 17 and 18.
The separator of the present invention is rnore
21 clearly illustrated and explained by the examples which follow.
22 In these examples, which are basedon data obtained during
23 experimental testiny of the separator design, the separator
24 has critical dimensions specified in Table I. These dimensions
(in inches except as noted) are indicated in the various drawlng
26 figures and listed in the Nomenclature below.
Distance between inlet and gas outlet centerlines
28 ' Di Insi~e diameter of inlet
29 ~ Dog Inside diameter of gas outlet
30 , Dos Inside diameter of solids outlet
Dv Diameter of venturi inlet
Dvt Diameter of venturi t~roat
-36-
;
~ ~ ~ ~4
H Height of flow p~th
Hw Height of weir or step
L Length from gas outlet to weir or step as
indicated in Figure 6
W Width of flow path
Angle of cone formed by projection of
convergent venturi walls, degrees
Table 1
Dimensions of Separators in Examples 1 to 10, i.nches*
Example
Dimension 1 2 3 4 5 6 7 8 9 10
CL 3.875 3.875 3.875 3.875 3.8753.87511 11 3.5 3.5
Di 2 2 2 2 2 2 6 6 2 2
Dog1.751.75 1.75 1.75 1.75 1.75 4 4
Dos 2 2 2 2 2 2 6 6 2 2
Dv ~ ~ _ 2
Dvt ~ - ~ ~ ~ ~ ~ 1
H 4 4 4 4 4 4 12 12 7.5 6
Hw 0~750.75 0.75 0.75 0.75 0.75 2.252.25 0 4
20 L 0 2 2 0 0 0 10 0
W 2 2 2 2 2 ~ 6 6 2 2
0,degrees - - - - - - - - - 28
* Except as noted
Example 1
In this example a separator of the preferred embodiment
of Figure 16 was tested on a feed mixture of air and silica
alumina. The dimensions of the apparatus are specified in Table
I. Note that the distance L from the gas outlet to the weir was
zero.
-37-
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696-147
1 ll The inlet stream was comprised of BS ft, 3/min.
2 1l of air and 52 lbs./min. of silica alumina having a hulk densit~
3 ~, of 70 lbs./ft3 and àn average particle size of 100 microns.
4 ~ The stream density was 0.612 lbs./ft.3 and the operation was
;, performed at ambient te~perature and atmospheric pressure.
6 I The velocity of the incoming stream through the 2 inch inlet
7 ~ was 65.5 ft./sec., while the outlet gas velocity was 85.6 ft./sec.
8 l' through a 1.75 inch diameter outlet. A positive seal of solids
9 ' in the solids outlet prevented gas from being entrained in the
solids leaving the separator. Bed solids were stabilized by
11 placing a 0.75 inch weir across the flow path.
12 I The observed separation efficiency was 89.1%,
13 and was accomplished in a yas phase residence tirne of approximately
1~ 1 0.008 seconds. Efficiency is defined as the percent removal of
I solids from the inlet stream.
16 Example 2
17 ' The gas-solids mixture of Example 1 was processed
18 in a separator having a configuration illustrated by FIGURE 20.
19 I In the example the L dimension is 2 inches; all other dimensions
are the same as Example 1. By extendin~ the separation chamber
21 along its longitudinal dimension, the flow pattern of the gas
22 ' began to deviate from the U-shaped discussed above. As a result
23 , residence time was longer and turbulence was increased. Separa,tion
24 ,l efficiency for this example was 70.8~.
1l Example 3
26 1 The separator of Example 2 was tested with an inlet
27 ~ stream comprised of 85 ft.3/min. of air and 102 lbsi/min. of
28 I silica alumina which gave a stream density of 1.18 lbs./ft.3
29 1 or approximately twice that of Example 2. Separation efficiency
l improved to 83.8%.
il
-3~-
;
2g~
Example 4
The preferred separa-~or of Example 1 was tested at the
inlet flow rate of Example 3. Efficiency increased slightly to
91.3%.
Example 5
The separator of Figure 16 was tested at the conditions
of Example 1. Although the separation dirnensions are specified
in Table I note that the distance CL between inlet and gas
outlet centerlines was 5.875 inches, or about three times the
diameter of the inlet. This dimension is outside the most
preferred range for CL which is between 1.50 and 2.50 Di.
Residence time increased to 0.01 seconds, while efficiency was
73.0%.
Example 6
Same conditions apply as for Example 5 except that the
solids loading was increased to 102 lbs./min. to give a strea~m
density of 1.18 lbs./ft.3. As observed previously in Examples 3
and 4, the separator efficiency increased with higher solids
loading -to 90.6%.
Example 7
The preferred separator configuration of Figure 16 was
tested in this Example. However, in this example the apparatus
was increased in size over the previous examples by a factor of
nine based on flow area. A 6 inch inlet and 4 inch outlet were
used to process 472 ft.3/min. of air and 661 lbs./min of silica
alumina at 180F. and 12 psig. The respective velocities were
40 and 90 ft./sec. The solids had a bulk density of 70 lbs./ft3
and the stream density was 1.37 lbs./f-t.3 Distance CL between
inlet and gas outlet centerlines was 11 inches, or 1~83 times
the inlet diameter; distance L was zero. The bed was
-39-
~&w ,
69~-147
1 stabllized by a 2.25 inch weir, and gas loss was prevented
2 by a positive seal of solids. However, the solids were
3 ; collected in a closed vessel, and the pressure differential
4 I was such that a positive flow of displaced gas from ~he
j collection vessel to the separator was observed. This volume
6 ; was approximately 9.4 ft.3/min. Observed separator efficiency
7 was 90.0~, and the gas phase residence time approximately
8 0.02 seconds.
9 Example 8
10 , The separator used in Example 7 was tested with
11 an ldentical feed of gas and solids. However, the solids
12 collection vessel was vented to the atmosphere and the pressure
13 differential adjusted such that 9% of the feed gas, or 42.5 fto /
14 , min. exited through the solids outlet at a velocity of 3.6
, ft./sec. Separator efficiency increased with this positive
16 bleed through the solids outlet to 98.1%.
17 Example 9
18 The separator of FIG~RE 22was tested in a unit
19 I having a 2 inch inlet and a 1 inch gas outlet. The solids out-
let was 2 inches in diameter and was located 10 inches away
21 from tne ~as outlet (dlmension L)o A weir was not used. The
22 feed was comprised of 85 ft.3/min. of air and 105 lbs./min. of
spent fluid catalytic cracker catalyst having a bulk density
24 of 45 lbs./ft.3 and an average particle si~e of 50 microns. This
~ave a stream density of 1.20 lbs./ft.3 Gas inlet velocity was
. 26 65 ft./sec. while the gas outlet velocity was 262 ft./sec. As
~7 in Example 7 there was a positive counter-current flow of
28 ' displaced gas from the collection vessel to the separator.
29 I Th1s flow was approximately 1.7 fto3/ min. at a velocity of
1.3 ft./sec. Operation was at ambient temperature and atmos~
31 pherlc pressure. Separator efficiency was 95.0~.
-40-
,
696-147 l
. I ,
1 ,,Example 10
;!
2 'The separator of ~IGURE23 was tested on a feed
3 comprised of 85 ft.3/ min. of air and 78 lbs./minO of spent
4 il Fluid Catalytic Cracking catalyst. The inlet was 2 inches in
, diameter which resulted in a velocity of 65 ft./sec., the gas
6 , outlet was 1 inch in diameter which resulted in an o~tlet
7 I velocity of 262 ft ./sec. This separator had a stepped
8 solids outlet with a venturl in the collinear section of the
9 outlet. The venturi mouth was 2 inches in diameter, whlle
10the throat was 1 inch. A cone of 281.1~ was formed by pro-
11 jection of the convergent walls of the venturi. An observed
12 efriciency of 92.6~ was measured, and the solids leaving the
i3 ~ separator were completely deaerated except for interstitial gas
14 remaining in the solidsl voids.
8 ~ \
1 9 , \
20 ;
21
22
~3 , \
24
26
27 ' \
28
29 ' \
30 ,,
-41-
-,;~
~11
96-147
1 (e) ImDroved Solids Quench Boiler and
2 Process.
As see~n in FIGURE 25,in lieu of quench zone 44, 46 ~see
6 E'IGURE 1) of the prior art, the composi~e solids quench boiler 2E
7 ~ of the subject invention is comprises essentially of a quench ex~
8 changer 4E, a fluid bed-quench riser 6E, a cyclone seoarator 8E
9 with a solids return line lOE to the fluid bed-riser 6E and a line
1~ 36E for the delivery of gas to the fluid bed-quench riser.
11 The quench exchanger 4E as best seen in FIGURES 26 an~ ~7
~2 ls formed with a plurality o~ concentrically arranged tubes ex-
13 tending parallel to the longitudinal axis of the quench exchanger
14 4E. The outer circle of tubes 16E form the outside wall of the
16
17
18
19
21
22
23
~4
26
27
28
29
\
-~2-
-
5&~1
6n6-147
1 quench exchanger 4E. The tubes 16E are joined together, pre
2 ~ ferably by welding, and form a pressure-tight mem~rane wall which
3 is in effect, the outer wall of the quench exchanger 4E. The
4 inner circles of tubes 18E and 20E are spaced apart and allo~
for the passage of effluent gas and particulate solids there-
6 around. The arrays of tubes 16E, 18E and 20E are manifolded
7 to an inlet torus 24E to which boiler feed water is delivered
8 and an upper discharge torus 22E from which high pressure steam
9 is discharged for system service. The quench exchanger 4Eis
provided with an inlet hood 26E and an outlet hood 28E, to
11 insure a pressure tight vessel. The quench exchanger inlet hood
12 26E extends from the quench riser 6E to the lower torus 24E.
13 The quench exchanger outlet hood 28E extends from the upper
14 ; torus 22E and is connected to the downstream piping equipment
lS by piping such as an elbow 30E which is arranged to deliver tr.e
1~ cooled effluent and particulate solids to the cyclone separator
17 ~ 8E.
18 The fluid bed quench riser 6Eis essentially a sealed
19 vessel attached in sealed relationship to the quench exchanger
4E.The fluid bed-quench riser 6Eis arranged to receive the
21 reactor outlet tube 36E which is preferably centrally disposec~ at
22 the bottom of the fluid quench riser 6E. A slightly enlarged
23 , centrally disposed tube 38E is aligned with the reactor outlet.
24 ;36E and extends from the fluid bed-quench riser 6E into the
quench exchanger 4E. In the quench exchanger 4E~ the centrally
`26 disposed fluid bed-quench riser tube 38E terminates in a conical
27 opening 4UE. The conical opening 40E is provided to facilitate
28 nonturbulent transition from the quench riser tube 38E to the
29 enlarged opening of the quench exchanger 4E. It has been round
that the angle of the cone ~, best seen in FIGURE26, should
31 be not greater --han 10 degrees.
-43-
~r-
S&W~ 3~2~
696-147
1 ¦ The fluid bed 42E contained in the fluid bed quench
2 riser 4E is maintained at a level well above the bottom of the
3 quench riser tube 38E. A bleed line 50E is provided to bleed
4 , solids from the bed 42E~ Although virtually any particulate
~ solids ean be used to provide the quench bed 42E, it has been
6 `, found in practice that the same solids used in the reactor are
7 ' preferably used in the fluidized bed 42E. Illustrations of
8 , the suitable particulate solids are FCC alumina solids.
9 , As best seen in FIG~RE 28,the opening 48E thxough
~ which the fluidized particles from the bed 42E are drawn into
11 ' the quench riser tube 38E is defined by the interior of a coné
12 ' 44E at the lower end of the quench riser tube 38E and a refractory
13 ' cone 46E located on the outer surface of the reactor outlet
14 ' tube 36E. In practice, it has been found that the refractory
~ cone 46E can be formed of any refractory rnaterial. The opening
16 ' 48, defined by the conical end 44E of the quench riser tube 38E
17 and the refractory cone 46E, is preferably 3-4 square feet for
18 a unit of 50 ;~IBTU/HR capacity. The opening is sized to insure
19 I penetration of the cracked gas solid mass velocity of 100 to
' 800 pounds per second per square foot is required. The amoun~
21 l, of solids from bed 42E delivered to the tube 38E is a functior,
22 l' Of the velocity of the gas and solids entering the tube 38E
23 j from the reactor outlet 36E and the size of the opening 48E~
24 In practice, it has been found that the Thermal
ll Regenerative Cracking (TRC) reactor effluent will contain
' 26 ~' approximately 2 pounds of solids per pound of gas at a tem-
~7 1l perature of about 1,400F to 1,600F.
28 , The process of the solids quench boiler 2E of
29 FIGURES 25-2~ is illustrated by the following example. Fffluent
I from a TRC outlet 36E at about 1,500F is delivered to the quenc~
~ -~4-
~i
S&W
6~6-1~7 ~
1 I riser tube 3~E at a velocity of approximately 40 to 100 feet
2 l, per second. The ratio of particula~e solids to cracked effluent
3 j entering or leaving the tube 36E is approximately two pounds o
4 ', solid per pound of gas at a temperature of about 1,500F. At
, 70 to 100 feet per second the particulate solids entrained into
6 , the effluen~ stream by the eductor effect is between twenty five
7 and fifty pounds solid per pound of gas. In 5 milliseconds the
8 ' addition of the particulate solids from the bed 42E which is
9 at a temperature of 1,000F reduces the temperature of the
~ composite effluent and solids to 1,030F. The gas-solids mixture
11 is passed from the quench riser tube 38E tO the quench exchanger
12 4E wherein the temperature-is reduced from 1,030F to 1,000F
13 by indirect heat exchange with the boiler feed water in ~he tubes
14 ; 16E, l~E, and 20E. With 120,000 pounds of effluent per hour~
15 ' 50 MMBTUs per hour of steam at 1,500 PSIG and 600F will be
16 generated for system service. The pressure drop of the gas
17 , solid mixture passing through quench exchanger 4E is 1.5 PSI. The
18 l, cooled gas-solids mixture is delivered through line 30E to the
19 I cyclone separator 8E wherein the bulk of the solids is removed
frbm the quenched-cracked gas and returned through line lOE
21 I to the quench riser 6E~
22
23 l' ~ v
24 ~ \
'26 l \
~7 1, ~
28 '~ ~ \
29
30 l, \
.
, -45-
s~w
696-147
1 (f) Improved Preheat Vaporization System.
3 Again referring to FI~29,in lieu of preheat zone 24 (FI~ 1)
4 of ~e system 2F of the subject invention is e~bodied in a TRC system and is
co~prised of essentially a liquid feed heater 4F, a mixer 8F for flashing
6 steam and the heated feedstock, a separator lOF to separate
7 the flashed gas and liquid, a vapor feed superheater 12F, and
8 a second mi~er 14F for flashing. The system also prefer~ntially
includes a knockout drum 16F for the preheated vapor.
The liquid feed heater 4F is provided for heating the
hydrocarbon feedstock such as desulfurized Kuwait ~GO to
13 initially elevate the temperature of the feedstock.
The initial mixer 8F is used in the system 2F to
14
initially flash superheated steam from a steam line 6F and the
heated feedstock delivered from the llquid feed heater 4F by
16 a line 18F.
17 The system separator lOF is to separate the liquid and
18 '
vapor produced by flashing in the mixer 8F. Separated gas is
19
21
22
23
~'1 \ .,
26
27
28
29
-46-
-
636-147 1~ 29
1 discharged through a line 22F from the separator overhead and
2 the remaining liquid is discharged through a line 26F.
3 l, A vapor feed superheater 12F heats the gaseous overhead
4 'from the line 22F to a high temperature and discharges the
~;heated vapor through a line 24F.
6 'I The second mixer 14F is provided to flash the vaporized ;
7 `gaseous discharge from the vapor feed superheater 12F and the
8 , liquid bottoms from the separator lOF, thereby vaporizing the
9 composite steam and feed initially delivered to the system 2F.
~ knockout drum 16F is employed to remove any liquid
11 from the flashed vapor discharged from the second mixer 14F
12 ; through the line 28F. The liquid-free vapor is delivered to a
13 reactor through the line 30F.
14 , In the subject process, the heavy oil liquid hydro-
,carbon feedstock is first heated in the liquid feed heater 4F
16 to a tem~erature of about 440 to 700F. The heated heavy
17 , oil hydrocarbon feedstock is then delivered through the line
18 ~18F to the mixer 8F. Superheated steam from the line 6F if
19 mixed with the heated heavy oil hydrocarbon feedstock in the
,Imixer 8F and the steam-heavy oil mixture is flashed to about
21 ~,700 to 800F. For lighter feedstock the flashing temperature
22 will be about 500 to 600F., and for heavier feedstock the
~3 flashing temperature will be about 700 to 900F.
24 ,I The flashed mixture of the steam and hydrocarbon is
` sent to the system separator lOF wherein the vapor or gas is
26 taken overhead through the line 22F and the liquid is
27 discharged through the line 26F. Both the overhead vapor and
28 ' liquid bottoms are in the temperature range of about 700 to
29 ~800F. The temperature level and percent of hydrocarbon
' vaporized are determined within the limits of equipment fouling
~ 47-
s~w
696-147
1 `criteria. The vapor stream in the line 22F is comprised of
2 essentially all of the steam delivered to the system 2F and
3 a large portion of the heavy oil hydrocarbon feedstock.
4 Between 30% and 70% of the heavy oil hydrocarbon feedstock
supplied to the system will be contained in the overhead
6 leaving the separator 10F through the line 22F.
7 The steam-hydrocarbon vapor in the line 22F is delivered
8 to the system vapor feed superheater 12F wherein it is heated to
9 about 1,030F. The heated vapor is taken from the vapor feed
superheater 12F throush the line 24F and sent to the second mixer
11 14F. Liquid bottoms from the separator 10F is also delivered
12 to the second mixer 14F and the vapor-liquid mix is flashed in
13 the mixer 14F to a temperature of about 1,000F.
14 The flashed vapor is then sent downstream through the
' line 28F to the knockout drum 16F for removal or any liquid
16 from the vapor. Finally, the vaporized hydrocarbon feed is
17 ~ sent through the line 30F to a reactor.
18 An illustration of the system preheat process is
19 seen in the following example.
A Nigerian Heavy Gas Oil is preheated and vaporized in
21 ~e system 2F prior to delivery to a reactor. The Nigerian Heavy
22 j Gas Oil has the following composition and properties:
~3 l
~4 Flemental Analysis, Wt.% ProPerties
Carbon 86.69 Flash Point, F. 230.0
Hydrogen 12.69 Viscosity, SUS 210 F 44.2
'26 Sulfur .10 Pour Point, F ~90.0
Nitrogen .047 Carbon Residue, Ramsbottom .09
27 Nickel .10 Aniline Point, C 87.0
~ Vanadium .10
28
29
S&W
696-147
l Distillation
2 I Vol. $
3 1 IsP
10669 ~ 2
4 30755 ~ 6
50820 ~ 4
70874 ~ 4
9094~6
6 ~P1~005~8
8 3 ~ 108 pounds per hour of the Nigerian Heavy Gas Oil is
9 heated to 750F~ in the liquid feed heater 4F and delivered at a
pressure of 150 psia to the mixer 8F. 622 pounds per hour of
ll superheated steam at l,100F. is simultaneously delivered to t~e
12 mixer 8F~ The pressure in the mixer is 50 psia.
13 The superheated steam and Heavy Gas Oil are flashed in
14 , the mixer 8F to a temperature of 760F~ wherein 60 of the Heavy
Gas Oil is vapori7ed.
16 The vapor and liquid from the mixer 8F are separated
17 in the separator lOF ~ 622 pounds per hour of steam and 1, 864 ~ 8
18 pounds per hour of hydrocarbon are taken in line 22F~ as overhead
l9 ; vapor. 1~243~2 pounds per hour of hydrocarbon are discharged
through the line 26F as liquid and sent to the mixer 14~
21 The mixture of 622 pounds per hour of steam and
22 1~864~8 pour-ds per hour of hydrocarbon are superheated in the
23 ,vapor superheater 12F to 1~139QF~ and delivered through line
24 24F to the mixer 14Fo The mixer 14F is maintained at 4S psia.
~5 The 1~243~2 pounds per hour of liquid at 760F~ and
26 the vaporous mixture of 622 pounds per hour of steam and
27 1~864~8 pound per hour of h~drocarbon are flashed in the mixer
28 14F to 990F.
29 The vaporization of the hydrocarbon is effected with a
,Isteam to hydrocarbon ratio of 0.2. The heat necessary to vaporize
_~9_
8~29
S&W
696-147
,, .
1 the hydrocarbon and generate the necessary steam is 2.924 MM
2 ,BTU/hr.
3 ~I The same 3,108 pounds per hour of Nigerian Heavy Gas
4 Oil feedstock vaporiæed by a conventional flashing operation
'Irequires steam in a 1~1 ratio to maintain a steam temperature
6 of 1,434F. The composite heat to vaporize the hydrocarbon and
7 l generate the necessary steam is 6.541 MM BTU/hr. In order to
8 reduce the input energy in the conventional process to the same
9 level as the present invention, a steam temperature of 3,208F~
is requiredt which temperature is effectively beyond design
11 ;llimitations.
12
13 !1 SU~ARY
14 With reference to the new and improved separation
, (see FIGURES 15-24), it is noted that short residence time
16 favors selectivity in C2H4 production. This means that the
17 reaction must be quenched rapidly. When solids are used, they
18 must be separated from the gas rapidly or quenched with the gas.
19 I~If the gases and solids are not separated rapidly (but
separated) as in a cyclone, and then quenched, product
21 degradation will occur. IE the total mix is quenched, to avold
22 rapid separationr a high thermal inefficiency will result since
23 lall the heat of the solids will be rejected to some lower
24 llevel heat recovery. Thus, a rapid high efficiency separator,
,according to the subject invention, is optimal for a TRC process~
26 Similarly, in connection with the subject solids
27 feed device (see FIGURES 4-13~, it is noted that in order to
28 feed ~olids to an ethylene reactor, the flow must be controlled
29 jto within +2 percent or cracking severity oscillations will be
I greater than that presently experienced in coil cracking. The
1, -50-
S&~ 2~
696-147
1 subject feed devlce (local fluidization) minimizes bed height
2 as a variable and dampens the effect of over bed pressure fluct-
3 uations, both of which con-tribute to flow fluctuations. It is
a thus uniquely suited to short residence time reactions. Further,
for short residence time reactions, the rapid and intimate
6 mixing are critical in obtaining good selectivity (minimize
7 mixing time as a percentage of total reactlng ti~e). Both of
8 the features permit the TRC to move to shorter residence times
9 which increase selectlvity. Conventional fluid bed feeding
devices are adequate for longer ti~e and lower temperature
11 reactions (FCC) especi211y catalytic ones where minimal reaction
12 occurs if the solids are not contacting the gas (poor mixing).
13 In connection with the solids quench boiler
14 (see FIGURES 25-28), in the current TRC concept, a 90 percent
separation occurs in the primary separator. This is followed
16 by an oil quench to 1300, and a cyclone to remove the remainder
17 of the solids. The mix is then quenched again with liquid to
18 600F. Thus, all the available heat from the reaction outlet
19 temperature to 600F is rejected to a circulating oil stream.
Steam is generated from the oil at 600 psig, 500F. This
21 scheme is used to avoid exchanger fouling when cracking heavy
22 feeds at low steam dilutions and high severities in the TRC~
23 ~owever, instead of an oil quench, a circulating solids stream
2~ could be used to quench the effluent. As in the reaction itself,
the co~e would be deposited preferentially on the solids thus
26, avoiding fouling. These solids can be held at 800F or above,
27 thus permitting the generation of high pressure ~team (1500 psig~)
28 which increased the overall thermal efficiency of the process.
~9 The oil loop can not operate at these temperatures due to
instabilities (too many light fractions are boiled off, yieldin~3
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696-1~7
1 an oil that is too viscous). The use OL solids can be done for
2 both TRC or a coil, but it is especially suited to a T~C since
3 it already uses solids. ~uring quenchin~, the coke accumulates
4 on the solid. ~t must be burned off. In a coil application,
it would have to be burned off in a separate vessel while in a
6 T~C it could use the regenerator that already exists.
7 ~A7ith reference to the preheat vaporization system of
8 the s-~ject invention ~see ~IGURE 29), it is noted that
9 the TRC has maxirum economic advantA~es when cracking heavy
feedstocks (650F+ boiling ~oint) at low steam dilutions.
11 Selectivity is favored by rapid and intimate mi~ing. ~apid
12 and intirr~ate mixinq is best accomplished with a vapor feed
13 rather than a li~uid feed.
1~ Finally, with reference to the sequential crackin~
system of the invention (see FIGURE 14), it is clear that
16 sequential cracking represents an alternative way of utilizing
17 the heat available in the quench (as opposed to the solids
18 quench boiler) in addi-tion to any yield advantages. It can
a be applied to both T~C and a coil. Its synergism with TRC
is that it permits the use of lon~er solids/gas separation times
21 if the second feed is added prior to any separation. The high
22 amount of heat available in the solids permits the use of lowe~
23 temperatures compared to the coil case.
2~ ~hile there has been described what is considered to be
preferred embodiments of the invention, variations and ~odif-
26 ications therein will occur to those skilled in the art once
2; they become acquainted with the basi_ concepts of the inventior
2~ Therefore, it is intended that the appended claims shall be
'9 construed to include not only the disclosed embodiments but all
such variations and modifications that fall within the true
31 soirit and scope of the invention.
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