Note: Descriptions are shown in the official language in which they were submitted.
3~L 1
BACKGROUND OF THE INVENTION
The present invention relates to gas-solid separators.
More particularly, the present invention relates to cyclone
separators of improved design and especially to cyclone separators
~useful in separating entrained solid catalyst from hydrocarbon
vapors or flue gases encountered in the catalytic cracking of
~hydrocarbon.
Cyclone separatorsare widely used as dust collectors
or gas-solid separators. For example, cyclones are widely used
'lin both the reactor and regenerator sections of Fluidized
,ICatalytic Cracking Units (FCCU) for the removal of entrained
catalyst particles from hydrocarbon effluent vapors and flue
gases used and/or produced in the cracking process. The con-
Ilstruction and operation of cyclone separators is well known
~jto those skilled in the art. Briefly, a cyclone separator has
¦la cylindrical upper portion, commonly called a barrel, adjoined
to a lower conic section, the lower, smaller diameter end of
lthe conic section forming a solids outlet. Gas enters the
B barrel portion, tangentially, at one or more ~r~nts, and
!!lexits through a centrally disposed gas outlet extending
through the top wall of the barrel. The dust, e.g. catalyst
¦particles, by virtue of their inertia, tend to move toward
¦Ithe outside walls of the separator and eventually leave through
¦lhe solids outlet. Essentially, a cyclone separator is a
111 ettling chamber in which gravitational acceleration is re-
¦placed by centrifugal acceleration. Under common operating
l -onditions, it is not unusual for the centrifugal separating
I
-2-
1.l
~1703~
force or acceleration to be several hundred times gravitational
force. The high forces imparted to the dust or solid particles
results in a highly erosive effect on the internal walls of the
cyclone thereby resulting in rapid wearing.
Cyclone separators of the type under consideration
are commonly used as last stage dust collectors, as for example,
to remove remaining dust and solid particles from gases such
as flue gases prior to atmospheric venting. Because of
increasing concern for the environment, it is necessary that
such cyclone separators, when they are used as last stage
solids removing devices, be as efficient as possible in order
that the gas vented to the atmosphere will be as pollution free
as possible.
The invention provides for a cyclone separator com-
prising an upper barrel portion having an inlet means and a
solids-free-gas outlet means wherein said separator inlet means
having a cross-sectional inlet area (I) sufficient to provide
a gas inlet velocity in the range of 52 feet per second to 80
feet per second, said solids-free-gas outlet means having a
cross-sectional outlet area (O) sufficient to provide a solids-
free-gas outlet velocity in the range of 52 feet per second to
200 feet per second, the ratio of said solids-free-gas cross-
sectional outlet area (O) to said separator cross-sectional in-
let area (I) being in the range of substantially 0/I = 0.4/1 to
1.0/1.0, and the distance (L) between said gas outlet means
and a solids outlet being related to the diameter (D) of the
upper barrel portion of the cyclone separator in an amount such
that L/D = 4.49-1.09 (O/I).
The invention also provides a method for removal of
entrained solids from gases in an upright cyclone separator
~ - 3 -
1~ ~7~)34
comprising an upper cylindrical barrel portion with a diameter
(D) and having an inlet with a cross-sectional area (I), a
solids-free-gas outlet with a cross-sectional area (O), with
the ratio O/I in the range of 0.4/1 to 1/1, and a solids outlet
at a vertical distance (L) below the solids-free-gas outlet
D with the ratio L/0 about 4, said method comprising: injecting
gases with entrained solids in the inlet at a speed in the
range of substantially 52 feet per second to 80 feet per second;
spinning the injected gases with the entrained solids around
and down the cyclone separator to the solids outlet; and
ejecting resultant solids-free-gases through the gas outlet
at a speed in the range of substantially 52 ~eet per second to
200 feet per second.
The present invention relies on the unexpected finding
that by controlling certain geometrical parameters in the
design and construction of cyclone separators, the latter can
be made much more efficient and wearing of the internal surfaces
due to erosion can be greatly reduced. A cyclone separator of
one embodiment of the present invention comprises an upper,
generally cylindrical barrel portion having a top wall, and a
lower, generally conic portion having a solids outlet at the
smaller diameter, lower end thereof. The lower, open end of
the barrel portion and the conic portion, at its larger diameter
end, are adjoined and together define a separation chamber. The
barrel portion is provided with a gas inlet for introducing a
gas stream tangentially into the separation chamber. A gas
outlet tube, which in the preferred case is generally centrally,
vertically disposed, extends through the top wall of the barrel
portion and has a lower end terminating internally of the
separation chamber. A generally cylindrical, solids discharge
~ - 4 -
~7~34
dipleg conduit has an upper end in open communication with the
solids outlet whereby disentrained solids can be removed from
the separator. The usually rectangular, cross-sectional area,
"I", of the gas inlet is sufficient to provide a gas inlet
velocity of about 80 ft/sec or less whereas the cross-sectional
area, "O", of the gas outlet tube is sufficient to provide a
gas outlet velocity of about 178 ft/sec or less. The ratio O/I
is maintained in the range of from about 0.4/1 to about 1/1.
The ratio of the distance, "L", between the solids-free-gas out-
let at the lower end of the gas outlet tube and the solidsoutlet at the upper end of the dipleg conduit, to the internal
diameter,
D - 4a -
~ ~ 7 O 3 4
~"D", of the barrel portion of the separator is such as to
~satisfy the equation:
j L/D = -1.09 (O/I) + 4.49.
IlMost preferably, the cyclone is designed such that the ratio
I!L/D is about 4Ø
In a preferred embodiment, the cyclone is provided
¦with a dust bowl which provides communication between the upper
¦¦end of the dipleg conduit and the solids outlet formed in the
¦llower conic portion of the separator. It has been found that
'lla cyclone separator, designed in accordance with the above
! parameters, functions most effectively in removing solids,
e.g. catalyst particulates from gas streams such as hydrocarbons
or flue gases, particularly those used in FCCU.
.15 BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is an elevational view showing, schematically,
a typical arrangement of a regenerator used in a FCCU and in-
corporating the cyclone separators of the present invention.
Fig. 2 is a partial, elevational view, similar to
Fig. 1, but showing in greater detail the unique construction
¦of the cyclone separators of the present invention.
¦ Fig. 3 is a view, partially reduced in size, taken
long the lines 3-3 of Fig. 2.
¦ DESCRIPTION OF THE PREFERRED E~BODIMENTS
While the invention will be described with particular
-eference to the use of the cyclone separators of the present
vention in removing entrained catalyst particle~ from combustion
_5_
~ ~7~34
gases leaving a regenerator used in a FCCU, it is to be
understood that the cyclones disclosed and claimed herein find
utility in any system wherein a cyclone separator can be used
to separate entrained solids from gaseous streams.
The use of a cyclone separator as a means of removing
solids from entrained gases in a regeneration scheme is shown
in United States Patent 3,394,076. The regenerator system shown
in Figure 1 is substantially the same as that shown in the cited
patent. Referring then to Figure 1, the regenerator~ shown gen-
erally as 10, is provided with an inlet conduit 12 through which
is fed spent catalyst from a suitable FCCU reactor (not shown).
A dense phase bed 14 having an upper level 16 is maintained in
regenerator 10. An oxygen containing gas, for example, air, is
- introduced into regenerator 10 through a suitable air ring 18.
Coke or other carbonaceous material coated on the catalyst par-
ticles in regenerator 10 is burned away by the oxygen in the
regeneration gases.
Regenerated catalyst is withdrawn from regenerator
10 through draw-off standpipe 20 and returned for further usage
in the reactor section of the FCCU. Combustion gases leaving
the dense phase bed at level 16 and entrained catalyst particles
pass into the disengaging space 22 in the upper portion of the
regenerator 10. The gases pass through a first stage cyclone
separator 24 via inlet 26. Solids disengaged in separator 24
are returned to bed 14 in regenerator 10 via dipleg 28. The
gases leave cyclone separator 24 via transfer line 30 and enter
second or last stage separator 32. Solids disengaged in separator
32 are returned to the catalyst bed via dipleg 34 while the sub-
stantially solid-free gas passes from separator 32 via gas
¦discharge conduit 35 into plenum 36 located in the upper portion
¦of regenerator lO. The gases in plenum 36 are vented or
otherwise removed from regenerator lO via line 38.
I Turning now to Fig. 2, there is shown, in detail,
~the system depicted schematically in Fig. l. First and second
stage cyclone separators 24 and 32, respectively, are disposed
in regenerator lO by means of suita~le bracing and supports
(not shown). First stage cyclone separator 24 has an upper
l cylindrical barrel portion 40 having a top wall 52, the lower
1 end of barrel portion 40 being open. Adjoined to the lower,
open end of barrel portion 40 is the upper open, greater diameter
end of lower conic portion 42. Barrel portion 40 and conic
portion 42 cooperatively define an internal separation chamber.
Adjoined to the lower end of conic portion 42 is a dust bowl,
shown generally as 25, dust bowl 25 comprising an upper cy-
lindrical barrel section 46 and a lower conic section 48.
Conic section 48 terminates at its lower end, in an outlet
which is connected to the upper end of dipleg 28. A gas inlet
26, which is generally rectangular in cross-sectional shape,
provides a means for introducing a gas stream tangentially into
the barrel portion 40 of cyclone 24. A gas outlet tube 50
extends through the top wall 52 of cyclone 24.
Gas outlet tube 50 communicates with gas transfer
conduit 30 which in turn is in open communication with a
rectangular gas inlet 54 in second stage separator 32. Second
stage separator 32 has an upper cylindrical barrel portion 56
with a top wall 72 and an open, lower end, and a lower conic
portion 58 with an upper, open end. The lower end of barrel
7(~34
;
:' .
portion 56 and the upper end of conic portion 58 are adjoined
and together define a separation chamber 6 a . Conic section
58, at its lower end, defines a circular solids outlet 62 which
lis in open communication with dust bowl 33. Dust bowl 33,
¦¦like dust bowl 25, is comprised basically of an upper cylindri-
¦cal barrel section 64 and a lower conic section 66, the junction
of barrel section 64 and conic section 66 lying in a plane which
passes substantially through the apex, shown as 68, of the
projection (shown in phantom lines) of the conic portion 58
¦ of separator 32. The lower conic section 66 of dust bowl 33
is in open communication with the upper end 70 of cylindrical
dipleg 34.
Gas outlet tube 35 extends through the top wall 72
of cylindrical barrel portion 56, gas outlet tube 35 having
a lower end 74 terminating in separation chamber 60. Gas out-
let tube 35 has an upper open end 76 in communication with the
interior of plenum 36. Plenum 36 is defined by a portion of the
upper interior wall of regenerator 10, a cylindrical wall 78
ffixed to the upper, inner wall of regenerator 10, and a domed
shaped bottom wall 80, affixed at its periphery to the lower
end of cylindrical wall 78.
In operation, gas from disengaging space 22 enters
rectangular gas inlet 26 of separator 24 and is introduced
tangentially into the barrel portion 40. Solid particles,
because of their inertia, move toward the walls of separator
¦ 24 and generally spiral downwardly toward dust bowl 25, being
¦ultimately discharged through dipleg 28 into the dense phase
: ¦in regenerator 10. The gas, at least partially free of solids,
passes upwardly through the central gas outlet tube 50 into
transfer conduit 30. The gas then enters second stage cyclone
jl 32 via rectangular inlet 54, the gas being introduced tan-
l gentially into the part of separation chamber 60 defined by
the barrel portion 56 of separator 32~ Solids once again move
to the walls of the separator 32, spiral downwardly into dust
¦bowl 33, and return to regenerator 10 via dipleg 34. The
substantially solid-free gas passes upwardly through the lower
lend 74 of gas outlet tub 35 and is discharged through the upper
iend 76 into plenum 36.
¦ It has been unexpectedly found that, particularly
~in the case of the last stage cyclone separator 32, or if more
than two stages are used, the last several stages, if certain
parameters, with regard to the geometry of the cyclone separator
are adhered to, enhanced efficiency and reduced wearing due to
erosion result. Thus, for example, it is necessary that the
gas inlet, as for example, inlet 54, have a cross-sectional
area, "I", which is sufficient to provide a gas inlet velocity
of about 80 ft/sec or less~ and preferably a gas inlet velocity
¦of from about 52 to about 80ft/sec. Additionally, it is nec-
essary that the gas outlet tube 35 have a cross-sectional area,
"O", sufficient to provide a gas outlet velocity of about 178
ft/sec or less. It is also necessary, to achieve optimum
efficiency and maximum reduction in wear due to erosion! that
~ertain relationships between the cross-sectional areas "I" and
'O" be maintained. Thus it has been found that the ratio O/I
should be in the range of from about 0.4/1 to about 1/1, and ¦
?referably from about 0.6/1 to about 0.45/1. Lastly, it is
_9_
34
necessary for the cyclone separator of the present invention
be designed such that the ratio of the distance, shown as L,
between the solids-free-gas outlet at the lower end of outlet
tube 35 and the solids outlet at the upper end of dipleg conduit
34 to the internal diameter, shown as D, of the barrel portion
56 of cyclone separator 32 be such as to satisfy the equation:
L/D = -1.09 (O/I) + 4.49.
Most preferably, for minimizing erosion of the cyclone internals
by impinging catalyst, the ratio L/D is about 4Ø Cyclone
separators designed in accordance with the above critical para-
meters exhibit maximum efficiency and minimum wear due to
erosion.
In addition to the above parameters, it has also been
found desirable that the diameter of the upper end of the dipleg
conduit, i.e. conduit 34, be from about 0.05 D to about 0.2 D.
Additionally, and as pointed out above, in cases where a dust
bowl such as 33 is employed it is desirable that the apex of
the projection of the lower conic portion of the cyclone
separator lie in a plane passing substantially through the
junction of the barrel section and the conic section of the dust
bowl. It is also possible that the diameter of the dust bowl
and the diameter of the dipleg conduit be substantially the same.
It is further desirable that there be a solids entrance
means 62 to a dust bowl 33 in said cyclone separator having a
diameter D62 relative to the diameter (D) of the upper barrel
portion D60 in the range of substantially 0.2D to 0.8D.
As used herein, the term "diameter(s)" refers to the
internal diameter(s). It will be understood that, generally
speaking, the cyclone separator of the present invention will be
disposed in a generally vertical position. However, it is within
the scope of the invention for the cyclone separators
-- 10 --
34L
of the present invention to be disposed off-vertical.
The invention may be embodied in other specific
forms without departing from the spirir or essential
,characteristics thereof. The present embodiments are
S therefore to be considered in all respects as illustrative
and not restrictive, the scope of the invention being in-
. dicated by the appended claims rather than by the foregoing
description, and all changes which would come within the
meaning and range of the equivalence of the claims are
~therefore intended to be embraced therein.
