Note: Descriptions are shown in the official language in which they were submitted.
This is a divisional application of Application Serial
No. 355,416 filed July ~th 1980 and entitled "Low Residence Tlme
Solid-Gas Separation Device and System"
sAcKGRouND OF INVENTION
Chemical reaction systems utilizing solidsincontactwith a
gaseous or vaporized stream have long been employed. The solids
may participate in the reaction as catalyst, provide heat required
for an endothermic reaction, or both. Alternatively the solids
may provide a heat sink in the case of an exothermic reaction.
Fluidized bed reactors have substantial advantages, most notably
an isothermal temperature profile. However, as residence time
decreases the fluidized bed depth becomes shallower and increasingly
unstable. For this reason tubular reactors employing solid-gas
contact in pneumatic flow have been used and with great success,
particularly in the catalytic cracking of hydrocarbons to produce
gasolines where reaction residence times are between 2 and 5
second 8 .
As residence times become lower, generally below 2
seconds and specifically below 1 second, the ability to separate
the gaseous products from the solids is diminished because there
is insufficient time to do so effectively. This occurs because
the residence time requirements of separation means such as
cyclones begins to represent a disproportionate fraction of the
allowable reactor residence time. The problem is acute in reaction
systems such as thermal cracking of hydrocarbons to produce
olefins and catalytic cracking to produce gasoline using improved
catalysts where the total reactor residence times between 0.2 and
li'7~0
1.0 seconds. In these reaction systems conventional separation
devices may consume more than 35% of the allowable contact time
between the two phases resulting in product degradation, coke
formation, low yields and varying severity.
In non-catalytic, temperature dependent endothermic
reactions, rather than separating the phases, it is possible to
quench the entire product stream after the requisite reaction;
period. However, these solids are usually recycled and are
regenerated by heating to high temperatures. A quench of the
reactor effluent prior to separation would be thermally inefficient.
However, it is economically viable to make a primary separation of
the particulate solids before quench of the gaseous stream. The
residual solids in the quenched stream may then be separated in
a conventional separator inasmuch as solids gas contact is no
longer a concern.
In some reaction systems, specifically catalytic reactions
at low or moderate temperatures, quench of the product gas is
undesireable from a process standpoint. In other cases the quench
is ineffective in terminating the reaction. ThuS, these reaction
systems require immediate separation of the phases to remove
catalyst from the gas phase. Once the catalyst has been removed,
the mechanism for reaction is no.longer present.
The prior art has attempted to separate the phase
rapidly by use of centrifugal force or deflection means.
Nicholson U.S. Patent 2,737,479 combines reaction and
separation steps within a helically wound conduit containing a
plurality of complete turns and having a plurality of gaseous
~ ~'7~
product drawoffs on the inside surface of the conduit to separate
solids from the gas phase by centrifugal force. Solids gravitate
to the outer periphery of the conduit, while gases concentrate at
the inner wall, and are removed at the drawoffs. Although the
Nicholson reactor-separator separates the phases rapidly, it
produces a series of gas product streams each at a different stage
of feed conversion. This occurs because each product stream
removed from the multiple product drawoffs which are spaced along
the conduit is exposed to the reaction conditions for a different
time period in a reaction device which has inherently poor contact
between solids and gases.
Ross et al U.S. Patent 2,878,891 attempted to overcome
this defect by appending to a standard riser reactor a modification
of Nicholson's separator. Ross's separator is comprised of a
curvilinear conduit making a separation through a 180 to 240 turn.
Centrifugal force directs the heavier solids to the outside wall
of the conduit allowing gases that accumulate at the inside wall
to be withdrawn through a single drawoff. ~hile the problem of
product variation is decreased to some extent, other drawbacks of
the Nicholson apparatus are not eliminated.
Both devices effect separation of gas from solids by
changing the direction of the gas 90 at the withdraw point, while
allowing solids to flow linearly to the separator outlet. Because
solids do not undergo a directional change at the point of
separation, substantial quantities of gas flow past the withdraw
point to the solids outlet. For this reason both devices require
a conventional separator at the solids outlet to remove excess gas
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from the solid particles. Unfortunately, product gas removed in
the conventional separator has remained in intimate contact with
the solids, has not been quenched, and is therefore, severely
degraded.
Another drawback of these devices i5 the limitation on
scale-up to commercial size. As conduit diameter increases the
path traveled by the mixed phase stream increases proportionately
so that large diameter units have separator residence times approach-
ing those of conventional cyclones. Increasing velocity can reduce
residence time, but as velocities exceed 60 to 75 ft./sec. erosion
by particles impinging along the entire length of the curvilinear
path becomes progressively worse. Reduction of the flow path
length by decreasing the radius of curvature of the conduit also
reduces residence time, but increases the angle of impact of
solids against the wall thereby accelerating erosion.
Pappas U.S. Patent 3,074,878 devised a low residence time
separator using deflection means wherein the solid gas stream flow-
ing in a tubular conduit impinges upon a deflector plate causing the
solids, which have greater inertia, to be projected away from a
laterally disposed gas withdrawal conduit located beneath said
deflector plate. Again, solids do not change direction while the
gas phase changes direction relative to the inlet stream by only
90 resulting in inherently high entrainment of solids in the
effluent gas. While baffles placed across the withdrawal conduit
reduce entrainment, these baffles as well as the deflector plate
are subject to very rapid erosion in severe operating conditions of
high temperature and high velocity. Thus, many of the benefits of
1.~718~0
separators of the prior art are illusory because of limitations in
their efficiency, operable range, and scale-up potential.
It is an object of the separator of this invention to
obtain a primary separation of particulate solids from a mixed
phase gas-solid stream.
According to one broad aspect, the present invention
relates to a solids-gas separator for effecting rapid reliable
removal of particulate solids from a dilute mixed phase stream of
solids and gas, said separator comprising an elongated chamber for
disengaging solids from the incoming mixed phase stream, said
elongated chamber including first and second opposed ends, and an
elongated peripheral shell having opposed top and bottom portions,
said chamber further comprising: a mixed phase inlet extending
through the top portion of the peripheral shell of said chamber
adjacent said first end of said chamber and perpendicular to the
longitudinal axis thereof, said mixed phase inlet being of generally
circular cross section with an inside diameter of Di; a solids
phase outlet extending through the bottom portion of the peripheral
shell of said chamber adjacent the second end of said chamber, said
solids phase outlet being generally perpendicular to the longitudinal
axis of said chamber and generally parallel to said mixed phase
inlet, said solids phase outlet being aligned for down flow of
discharged solids by gravity; a gas outlet extending through the top
portion of the peripheral shell of said chamber and parallel to
said mixed phase inlet said gas outlet being disposed intermediate
said mixed phase inlet.and said solids outlet, and at a distance from
said mixed phase inlet which is no greater than 4.0 Di as measured
between their respective center lines; and a flow path extending
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18~0
generally parallel to the longitudinal axis of said chamber between
the first and second ends th reof, said flow path being in
communication with said mixed phase inlet, said solids outlet and
said gas outlet, said flow path being essentially rectangular in
cross section and having a height equal to at least Di or 4 inches,
whichever is greater, and a width between 0.75 Di and 1.25 Di,
said flow path including a static bed accummulation area adjacent
the bottom portion of said peripheral shell and extending from said
first end of said chamber to said solids outlet such that when said
mixed phase stream is directed through said mixed phase inlet the
gas included therein will undergo a 180 change in direction to be
removed from said chamber through said gas outlet and such that
the solids in said mixed phase stream will form a generally
arcuate static bed in said static bed accummulation area of said
chamber, whereby the solids in said mixed phase stream will impinge
upon said static bed as said solids are directed towards said solids
phase outlet thereby minimizing erosion of said chamber by said
solids .
According to another broad aspect, the present invention
relates to a solids-gas separation system to separate a dilute
mixed phase stream of gas and particulate solids into an essentially
solids free gas stream, the separation system comprising: a
chamber for rapidly disengaging about 80% of the particulate solids
from the incoming dilute mixed p.hase stream, said chamber having
approximately rectilinear or slightly arcuate longitudinal side walls
to form a flow path of height H and width W approximately rectangular
in cross section, said chamber also having a mixed phase inlet of
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~ '7:l.8~0
inside width Di, a gas outlet, and a solids outlet, said inlet
being at one end of the chamber disposed normal to the flow path
whose height H is equal to at least Di or 4 inches, whichever is
greater, and whose width W is no less than 0.75 Di but no more than
1.25 Di, said solids outlet being at the opposite end of the chamber
and being aligned for downflow of discharged solids by gravity, said
solids outlet including a first section which is collinear with the
flow path and a second section normal to said first section and
aligned for downflow of solids by gravity, said first section
further being stepped away from a wall of the chamber opposite the
mixed phase inlet, and said gas outlet being disposed intermediate
said mixed phase inlet and said solids outlet at a distance no
greater than 4 Di from the inlet as measured between respective
centerlines and oriented to effect a 180 change in direction of
the gas whereby resultant centrifugal forces direct the solid
particles in the incoming stream toward said wall of the chamber
opposite to the inlet forming thereat and maintaining an essentially
static bed of solids, the surface of the bed defining a curvilinear
path extending through a generally circular arc of approximately
90 for the outflow of solids to the solids outlet, a secondary
solids-gas separator in communication with said gas outlet, said
secondary separator removing essentially all of the residual solids,
a vessel in communication with said solids outlet and said secondary
separator, said vessel receiving the discharg~ of solids from said
chamber and said secondary separator, and pressure balance means
to maintain a height of solids in said vessel to provide a positive
seal between the chamber and the vessel.
--7--
i`"~.
~ 1'71BQ()
DESCRIPTION OF FIGURES
FIGURE 1 is a schematic flow diagram of the separation
system of the present invention as appended to a typical tubular
reactor.
FIGURE 2 is a cross sectional elevational view of the
preferred embodiment of the separator.
FIGURE 3 is a cutaway view through section 3-3 of
FIGURE 2.
FIGURE 4 is a cutaway view through section 3-3 of
FIGURE 2 showing an alternative geometic configuration of the
separator shell.
FIGURE S is a sketch of the separation device of the
present invention indicating gas and solids phase flow patterns
in a .separator not having a weir.
FIGURE 6 is a sketch of an alternate embodiment of the
separation device having a weir and an extended separation chamber.
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a"~ ~.
.
~i'7~0
FIGURE 7 iS a s]cetch oE an alternate embodiment of the
separation device wherein a stepped solids outlet is employed,
said outlet having a section collinear with the flow path as well
as a gravity flow section.
FIGURE 8 is a variation of the embodiment of FIGURE 7
in which the solids outlet of FIGURE 7 is used, but is not stepped.
FIGURE 9 is a sketch of a variation of the separation
device of FIGURE 7 wherein a venturi restriction is incorporated
in the collinear section of the solids outlet.
FIGURE 10 is a variation of the embodiment of FIGURE 9
oriented for use with a riser type reactor.
DESCRIPTION OF INVENTION
FIGURE 1 is a schematic flow diagram showing the
installation of the separator system of the present invention in a
typical tubular reactor system handling dilute phase solid-gas
mixtures. Solids and gas enter tubular reactor 13 through lines ll
and 12 respectively. The reactor effluent flows directly to
separator 14 where a separation into a gas phase and a solids phase
stream is effected. The gas phase is removed via line 15, while
the solid phase is sent to stripping vessel 22 via line 16. Depend-
ing upon the nature of the process and the degree of separation, an
inline quench of the gas leaving the separator via line 15 may be
made by injecting quench material from line 17. Usually, the
product gas contains residual solids and is sent to a secondary
separator 18, preferably a conventional cyclone. ~uench material
should be introduced in line 15 in a way that precludes back flow
of quench material to the separator. The residual solids are
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removed from separator 18 via line 21, while essentially solids
free product gas is removed overhead through line 19. Solids from
lines 16 and 21 are stripped of gas impurities in fluidized bed
stripping vessel 22 using steam or other inert fluidizing gas
admitted via line 23. Vapors are removed from the stripping vessel
through line 24 and, if economical or if need be, sent to down-
stream purification units. Stripped solids removed from the vessel
22 through line 25 are sent to regeneration vessel 27 using
pneumatic transport gas from line 26. Off gases are removed from
the regenerator through line 28. After regeneration the solids are
then recycled to reactor 13 via line 11.
The separator 14 should disengage solids rapidly from the
reactor effluent in order to prevent product degradation and ensure
optimal yield and selectivity of the desired products. Further, the
separator 14 operates in a manner that eliminates or at least
significantly reduces the amount of gas entering the stripping vessel
22 inasmuch as this portion of the gas product would be severely
degraded by remaining in intimate contact with the solid phase. This
is accomplished with a positive seal which has been provided between
the separator 14 and the stripping vessel 22. Finally, the separator
14 operates so that erosion is minimized despite high temperature
and high velocity conditions that are inherent in many of these
processes. The separator system of the present invention is designed
to meet each one of these criteria as is described below.
FIGURE 2 is a cross sectional elevational view showing the
preferred embodiment of solids-gas separation device 14 of the
present invention. The separator 14 is provided witn a separator
'' i ; ' ~ ' : .,
~71~3~0
shell 37 and is comprised of a solids-gas disengaging chamber 31
having an inlet 32 for the mixed phase stream, a gas phase outlet
33, and a solids phase outlet 34. The inlet 32 and the solids
outlet 34 are preferably located at opposite ends of the chamber 31,
while the gas outlet 33 lies at a point therebetween. Clean-out
and maintenance manways 35 and 36 may be provided at either end of
the chamber 31. The separator shell 37 and manways 35 and 36 ;
preferably are lined with erosion resistent linings 38, 39 and 41
respectively which may be required if solids at high velocities are
encountered. Typical commercially available materials for erosion
resistent lining include Carborundum Precast Carbofrax* D,
Carborundum Precast Alfrax* 201 or their equivalent. A thermal
insulation lining 40 may be placed between shell 37 and lining 38
and between the manways and their respective erosion resistent
linings when the separator is to be used in high temperature service.
Thus, process temperatures above 1500F. (870C.) are not inconsist-
ent with the utilization of this device.
FIGURE 3 shows a cutaway view of the separator along
section 3-3. For greater strength and ease of construction the
separator 14 shell is preferably fabricated from cylindrical
sections such as pipe 50, although otner materials may, of course,
be used. It is essential that longitudinal side walls 51 and 52
should be rectilinear, or slightly arcuate as indicated by the
dotted lines 51a and 52a. Thus, flow path 31A throuyh the separator
is essentially rectangular in cross section having a height H and
width W as shown in FIG~R~ 3. The embodiment shown in FIGURE 3 de-
fines the geometry of the flow path by adjustment of the lining width
--10--
*Trademarks
'
1 8~0
for walls 51 and 52. Alternatively, baffles, inserts, weirs or
other means may be used. In like fashion the configuration of
walls 53 and 54 transverse to the flow path may be similarly shaped,
although this is not essential. FIGURE 4 is a cutaway view along
Section 3-3 of FIGURE 2 wherein tne separation sbell 37 is fabricat-
ed from a rectangular conduit. Because the shell 37 has rectilinear
walls 51 and 52 it is not necessary to adjust the width of the flow
path with a thickness of lining. Linings 38 and 40 could be added
for erosion and thermal resistence respectively.
Again referring to FIGURE 2, inlet 32 and outlets 33 and
34 are disposed normal to flow path 31A (shown in FIGURE 3) so that
the incoming mixed phase stream from inlet 32 is required to under-
go a 90 change in direction upon entering the chamber. As a
further requirement, however, the gas phase outlet 33 is also
oriented so that the gas phase upon leaving the separator has
aompleted a 180 change in direction.
Centrigugal force propels the solid particles to the wall
54 opposite inlet 32 of the chamber 31, while the gas portion, having
less momentum, flows through the vapor space of the chamber 31.
Initially, solids impinge on the wall 54, but subsequently accumulate
to form a static bed of solids 42 which ultimately form in a surface
configuration having a curvilinear arc 43. Solids impinging upon
the bed are moved along the curvilinear arc 43 to the solids outlet
34, which is preferably oriented for downflow of solids by gravity.
The exact shape o~ the arc 43 is detcrmined by thc geomctry of the
particular separator and the inlet stream parameters such as
velocity, mass flowrate, bulk density, and particle size. Because
--11--
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~ ~'7~ ~ V
the force imparted to the incoming solids is directed against the
static bed 42 rather than the separator 14 itself, erosion is
minimal. Separator efficiency, defined as the removal of solids
from the gas phase leaving through outlet 33, is, therefore, not
affected adversely by hign inlet velocities, up to 150 ft./sec.,
and the separator 14 is operable over a wide range of dilute phase
densities, preferably between 0.1 and 10.0 lbs./ft3. The separ;ator
14 of the present invention achieves efficiencies of about 80~,
although the preferred embodiment, discussed below, can obtain over
90% removal of solids.
It has been found that separator efficiency is
dependent upon separator geometry, and more particularly, the flow
path must be essentially rectangular, and there is an optimum
relationship between the height H and the sharpness of the U-bend
in the gas flow.
Referring to FIGURES 2 and 3 we have found that for a
given height H of chamber 31, efficiency increases as the 180
U-bend between inlet 32 and outlet 33 becomes progressively sharper;
that is, as outlet 33 is brought progressively closer to inlet 32.
Thus, for a given H the efficiency of the separator increases as the
flow path and, hence, residence time decreases. Assuming an inside
diameter Di of inlet 32, the preferred distance CL between the
centerlines of inlet 32 and outlet 33 is not greater than 4.0 Di,
while the most preferred distance between said centerlines isbetween
1.5 and 2.5 Di. Below 1.5 Di better separation is obtained but
difficulty in fabrication makes this embodiment less attractive in
most instances. Should this latter embodiment be desired, the
, . . .
- ~'71~
separator 14 would probably require a unitary casting design
because inlet 32 and outlet 33 would be too close to one another
to allow welded fabrication.
It has been found that the height of flow path H should
be at least equal to the value of D or 4 inches in height, whic7never
is greater. Practice teaches that if H is less than Di or 4 inches
the incoming stream is apt to disturb the bed solids 42 thereby re-
entraining solids in the gas product leaving through outlet 33.
Preferably H is on the order of twice Di to obtain even greater
separation efficiency. While not otherwise limited, it is apparent
that too large an H eventually merely increases residence time
without substantive increases in efficiency. The width W of the
flow path is preferably between 0.75 and 1.25 times Di, most
preferably between 0.9 and 1.10 Di.
Outlet 33 may be of any inside diameter. However,
velocities greater than 75 ft./sec. can cause erosion because of
residual solids entrained in the gas. The inside diameter of outlet
34 should be sized so that a pressure differential between the
stripping vessel 22 shown in FIGURE 1 and the separator 14 exist
such that a static heiyht of solids is formed in solids outlet line
16. The static height of solids in line 16 forms a positive seal
which prevents gases from entering the stripping vessel 22. The
magnitude of the pressure differential '~etween the stripping vessel
22 and the separator 14 is determined by the force required to move
the solids in bul~ flow to the solids outlet 34 as well as the
height of solids in line 16. As the differential increases the net
flow of gas to the stripping vessel 22 decreases. Solids, having
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, t'718~0
gravitational momentum, overcome the differential, while gas
preferentially leaves through the gas outlet 33.
By regulating the pressure in the stripping vessel
22 it is possible to control the amount of gas going to the stripper.
The pressure regulating means may include a checi~ or "flapper"
valve 29 at the outlet of line 16, or a pressure control valve 29a
in vapor line 24. The pressure may be regulated by selecting the
size of the outlet 34 and conduit 16 to obtain hydraulic forces
acting on the system that set the flow of gas to the stripper 22.
While such gas is degraded, we have found that an increase in
separation efficiency occurs with a bleed of gas to the stripper
of less than 10%, preferably between 2 and 7~. Economic and
process considerations would dictate whether this mode of operation
should be used. It is also possible to design the system to obtain
a net backflow of gas from the stripping vessel. This gas flow
should be less than 10~ of the total feed gas rate.
By establishing a minimal flow path, consistent with the
above recommendations, residence times as low as 0.1 seconds or less
may be obtained, even in separators having inlets over 3 feet in
diameter. Scale-up to 6 feet in diameter is possible in many systems
where residence times approaching 0.5 seconds are allowable.
In the preferred embodiment of FIGURE 2 a weir 44 is
placed across the flow path at a point at or just beyond the gas
outlet to establish a positive height of solids prior to solids
outlet 34. By installing a weir (or an equivalent restriction) at
this point a more stable bed is established thereby reducing
turbulence and erosion. Moreover, the weir 44 establishes a bed
-14-
00
which has a crescent shaped curvilinear arc 43 of slightly more
than 90. More particularly, radii extending from opposed ends
of the curvilinear arc 43 would be angularly separate~ from one
another by slightly more than 90. An arc of this shape diverts
gas towards the gas outlet and creates the U-shaped gas flow
pattern illustrated diagramatically by line 45 in FIGURE 2. With-
out the weir 44 an arc somewhat less than or equal to 90 would.
be formed, and which would extend asymptotically toward outlet 34
as shown by dotted line 60 in the schematic diagram of the separator
of FIGURE 5. While neither efficiency nor gas loss (to the strip-
ping vessel) is affected adversely, the flow pattern of line 61
increases residence time, and more importantly, creates greater
potential for erosion at areas 62, 63 and 64.
The separator of FIGURE 6 is a schematic diagram of
another embodiment of the separator 14, said separator 14 having an
extended separation chamber in the longitudinal dimension. Here,
the horizontal distance L between the gas outlet 33 and the weir
44 is extended to establish a solids bed of greater length L is
preferably less than or equal to 5 Di. Although the gas flow
pattern 61 does not develop the preferred U-shape, a crescent shaped
arc is obtained which limits erosion potential to area 64. Embodi-
ments shown by FIGURES 5 and 6 are useful when the solids loading
of the incoming stream is low. The emoodiment of FIGURE 5 also nas
the minimum pressure loss and may be used when the velocity of the
incoming stream is low.
As shown in FIGURE 7 it is equally possible to use a
stepped solids outlet 65 having a section 66 collinear with the
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t~O
flow path as well as a gravity flow section 67. Wall 68 replaces
weir 44, and arc 43 and flow pattern 45 are similar to the preferred
embodiment of FIGURE 2. Because solids accumulate in the restricted
collinear section 66, pressure losses are greater. This embodiment,
then, is not preferred where the incoming stream is at low velocity
and cannot supply sufficient force to expel the solids through
outlet 65. However, because of the restricted solids flow path,
better deaeration is obtained and gas losses are minimal.
FIGURE 8 illustrates another embodiment of the separator
14 of FIGURE 7 wherein the solids outlet is not stepped. Although
a weir is not used, the outlet restricts solids flow which helps
form the bed 42. As in FIGURE 6, an extended L distance between
the gas outlet and solids outlet may be used.
The separator of Figure 7 or 8 may be used in conjunction
with a venturi, an orifice plate, or an equivalent flow restriction
device as shown in FIGURE 9. The venturi 69 having dimensions DV
(diameter at venturi inlet), DVt (diameter of venturi throat),
and e (angle of cone formed by projection of convergent verturi
walls) is placed in the collinear section 66 of the outlet 65 to
greatly improved deaeration of solids. The embodiment of FIGURE 10
is a variation of the separator shown in FIGURE 9. Here, inlet 32
and outlet 33 are oriented for use in a riser type reactor. Solids
are propelled to the wall 71 and the bed thus formed is kept in
place by the force of the incoming stream. ~s before the gas
portion of the feed follows the ~-shaped pattern of line 45.
However, an asymptotic bed will be formed unless there is a restric-
tion in the solids outlet. A weir would be ineffective in establish-
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7~E~q~O
ing bed height, an~ would deflect solids into the gas outlet. For
this reason the solids outlet of Figure 9 is preferred. Most
preferably, the venturi 69 is placed in collinear section 66 as
shown in FIGURE 10 to improve the deaeration of the solids. Of
course, each of these alternate embodiments may have one or more
of the optional design features of the basic separator discussed
in relation to FIGURES 2, 3 and 4.
The separator of the present invention is more clearly
illustrated and explained by the examples which follow. In these
examples, which are based on data obtained during experimental
testing of the separator design, the separator has critical
dimensions specified in Table I. These dimensions (in inches
except as noted) are indicated in the various drawing figures and
listed in the Nomenclature below:
CL Distance between inlet and gas outlet centerlines
Di Inside diameter of inlet
Dog Inside diameter of gas outlet
Do6 Inside diameter of solids outlet
Dv Diameter of venturi inlet
Dvt Diameter of venturi throat
H Height of flow path
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
e Angle of cone formed by projection of convergent
venturi walls, degrees
. ~
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Table I
Dimensions of Separators in Examples l to 10 inches*
Example
Dimension 1 2 3 4 5 6 7 8 9 10
3.875 3.875 3.875 3.875- 5.875 5.875 - 11 3.5 3.5
Di 2 . 2 2 2 2 2 6 6 2 2
Dog 1.75 1.751.75 1.75 1.75 1.75 4 4 1 1
D L ~ 2 2 2 2 ~ 6 6 2 ~ ~
H 4 4 4 4 4 4 12 12 7.5 6.75
Hw 0 75 0.75 0.75 0.75 0.75 0.75 2.25 2.25 0 4.75
L 0 2 2 0 0 0 0 0 10 0
W 2 2 2 2 2 2 6 6 2 2
e, degress _ _ _ _ _ _ _ _ _ 2~.1
* except as noted
Example 1
In this example a separator of the preferred embodiment
of FIGURE 2 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 tne weir was zero.
The inlet stream was comprised of 85 ft.3/min. of air and
52 lbs./min. of silica alumina having a bulk density of 70 lbs./ft.3
and an average particle size of 100 microns. The stream density was
0.612 lbs./ft.3 and the operation was performed at ambient temper-
ature and atmospheric pressure. The velocity of the incoming stream
through the 2 inch inlet was 65.5 ft./sec., while the outlet gas
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velocity was 85.6 ft./sec. through a 1.75 lnch diameter
outlet. A positive seal of solids in the solids outlet
prevented gas from being entrained in the solids leaving
the separator. Bed solids were stabilized by placing a 0.75 inch
weir across the flow path.
The observed separation efficiency was 89.1%, and was
accomplished in a gas phase residence time of approximately O.Q08
seconds. Efficiency is defined as the percent removal of solids
from the inlet stream.
Example 2
The gas-solids mixture of Example 1 was processed in a
separator having a configuration illustrated by FIGURE 6. In the
example the L dimension is 2 inches; all other dimensions are the
same as Example 1. By extending the separation chamber along its
longitudinal dimension, the flow pattern of the gas began to
deviate from the U-shaped discussed above. As a result residence
time was lon~er and turbulence was increased. Separation efficiency
~or this example was 70.8~.
Example 3
The separator of Example 2 was tested with an inlet
stream comprised of 85 ft.3/min. of air and 102 lbs./min. of silica
alumina which gave a stream density of 1.18 lbs./ft.3, or approxi-
mately twice that of Example 2. Separation efficiency improved to
83.8%.
Example 4
The preferred separator of Example lwas tested at the
inlet flow rate of Example 3. Efficiency increased slightly to
--19--
'"'''' ' .
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~.~7~8~
91.3~
Example 5
The separator of FIGURE 2 was tested at the conditions
of Example 1. Although the separation dimensions 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 Dl. 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 stream
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 configurtion of FIGURE 2 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./ft.3 and the
stream density was 1.37 lbs./ft.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 stabilized by a 2.25
inch weir, and gas loss was prevented by a positive seal of solids.
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. ~ .
'718~0
However, the solids were collected in a closed vessel, and the
pressure differential was such that a positive flow of displaced
gas from the collection vessel to the separator was observed. This
volume was approximately 9.4 ft.3/min. Observed separator
efficiency was 90.0%, and the gas phase residence time approximately
0.02 seconds.
Example 8
The separator used in Example 7 was tested with an
identical feed of gas and solids. However, the solids collection
vessel was vented to the atmosphere and the pressure differential
adjusted such that 9~ of the feed gas, or 42.5 ft.3/min., exited
through the solids outlet at a velocity of 3.6 ft./sec. Separator
efficiency increased with this positive bleed through the solids
outlet to 98.1%.
Example 9
The separator of FIGURE ~ was tested in a unit having a
2 inch inlet and a 1 inch gas outlet. The solids outlet was 2
inches in diameter and was located 10 inches away from the gas
outlet (dimension L). A weir was not used. The feed was comprised
of ~S ft.3/min. of air and 105 lbs./min. of spent fluid catalytic
cracker catalyst having a bulk density of 45 lbs./ft.3 and an
average particle size of 50 microns. This gave a stream density of
1.20 lbs./ft.3 Gas inlet velocity was 65 ft./sec., while the gas
outlet velocity was 262 ft./sec. As in Example 7 there was a
positive counter-current flow of displaced gas from the collection
vessel to the separator. Thi5 flow was approximately 1.7 ft.3/min.
at a velocity of 1.3 ft./sec. Operation was at ambient temperature
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:
., ' .
O
and atmospheric pressure. Separator efficiency was 95.0%.
Example lO
The separator of FIGURE 9 was tested on a feed comprised
of 85 ft.3/min. of air and 78 lbs./min. of spent Fluid Catalytic
Cracking catalyst. The inlet was 2 inches in diameter which
resulted in a velocity of 65 ft./sec., the gas outlet was l inch
in diameter which resulted in an outlet velocity of 262 ft./sec,.
This separator had a stepped solids outlet with a venturi in the
collinear section of the outlet. The venturi mouth was 2 inches
in diameter, while the throat was 1 inch. A cone of 28.1 was
formed by projection of the convergent walls of the venturi. An
observed efficiency of 92.6~ was measured, and the solids leaving
the separator were completely deaerated except for interstitial
gas remaining in the solids' voids.
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