CYCLONE

CYCLONE SEPARATOR

Abrégé français

L'invention concerne un cyclone (1). Celui-ci comprend un carter vertical (2) ouvert au niveau de son extrémité inférieure (4), pourvu d'un couvercle (5) au niveau de son extrémité supérieure, dans lequel est ménagée une ouverture centrale (6). Il comporte également une conduite d'entrée (10) pour assurer une entrée tangentielle d'un mélange de gaz et de particules de catalysation provenant de la sortie (12) d'un réacteur à colonne montante (15) d'une installation de craquage catalytique à lit fluidisé. Ce cyclone comprend également une conduite de déchargement des particules (16) communicant avec l'extrémité inférieure ouverte (4) du carter vertical (2), et une conduite de sortie des gaz (18) dont une section verticale (20) s'étend à travers l'ouverture centrale (6) ménagée dans le couvercle (5). En outre, ce cyclone (1) comprend un tube à extrémité ouverte (23) placé dans l'ouverture centrale (6) afin de définir une conduite d'entrée de gaz annulaire (25) entre la section verticale (20) et le tube à extrémité ouverte (23) et des moyens (30) assurant un tourbillon, placés dans la conduite d'entrée de gaz annulaire (25).

Abrégé anglais

Cyclone separator (1) comprising a vertical housing (2) open at its lower end
(4) provided with a cover (5) at its upper end having a central opening (6),
an inlet duct (10) for tangential entry of a mixture of gas and catalyst
particles from the outlet (12) of a riser reactor (15) of a fluid-bed
catalytic cracking plant, a particles discharge duct (16) communicating with
the open lower end (4) of the vertical housing (2), and a gas outlet duct (18)
having a vertical section (20) which extends through the central opening (6)
in the cover (5), which cyclone separator (1) further comprises an open-ended
pipe (23) arranged in the central opening (6) so as to define an annular gas
inlet conduit (25) between the vertical section (20) and the open-ended pipe
(23), and swirl imparting means (30) arranged in the annular gas inlet conduit
(25).

Revendications

C L A I M S
1. Cyclone separator comprising a vertical housing open
at its lower end provided with a cover at its upper end
having a central opening, an inlet duct for tangential
entry of a mixture of gas and catalyst particles from the
outlet of a riser reactor of a fluid-bed catalytic
cracking plant, a particles discharge duct communicating
with the open lower end of the vertical housing, and a
gas outlet duct having a vertical section which extends
through the central opening in the cover, which cyclone
separator further comprises an open-ended pipe arranged
in the central opening so as to define an annular gas
inlet conduit between the outer surface of at least part
of the vertical section of the gas outlet duct and the
inner surface of the open-ended pipe, and swirl imparting
means arranged in the annular gas inlet conduit.
2. Cyclone separator according to claim 1, wherein the
ratio of the outer diameter of the vertical section of
the gas outlet duct to the diameter of the central
opening in the cover is in the range of from 0.3 to 0.7.
3. Cyclone separator according to any one of claims 1-2,
wherein the lower end of the gas outlet duct is located
below the lower edge of the inlet duct for tangential
entry of a mixture of gas and catalyst particles.
4. Cyclone separator according to any one of claims 1-3,
wherein the open-ended pipe extends to part of the height
of the inlet duct for tangential entry of a mixture of
gas-and catalyst particles.
5. Cyclone separator according to claim 4, wherein the
distance between the lower end of the open-ended pipe and
the upper edge of the inlet duct for tangential entry of
a mixture of gas and catalyst particles is between 10%
and 60% of the height of said inlet duct.

6. Cyclone separator according to any one of claims 1-5,
wherein the swirl imparting means are either fixed to the
inner surface of the open-ended pipe or to the outer
surface of the vertical section of the gas outlet duct,
but not fixed to both surfaces.
7. Cyclone separator according to any one of claim 1-6,
wherein the swirl imparting means are between 2 and
8 swirl vanes.
8. Process to separate catalyst particles from a gaseous
product leaving a fluid catalyst cracking riser reactor
in a cyclone separator according to any one of
claims 1-7, wherein the cyclone separator is arranged in
the upper part of a reactor vessel and the gaseous
product is fed to the cyclone via the inlet duct for
tangential entry of the gaseous product resulting in that
a gaseous product is removed from the cyclone through the
gas outlet duct and catalyst particles are removed from
the cyclone through the particles discharge duct after
which discharged catalyst particles are collected in the
lower part of the reactor vessel where product adhered to
the particles is stripped off by means of stripping gas
supplied to the lower part of the reactor vessel,
resulting in a gaseous mixture of stripping vapour,
stripped product and catalyst particles passing upwards
towards the dilute phase zone in the upper part of the
reactor vessel, wherein the gaseous mixture is drawn into
the cyclone through the annular gas inlet conduit.

Description

CA 02263691 1999-02-17
WO ~ 0 PCTrEP97/04881
CYCLONE SEPARATOR
The present invention relates to a cyclone separator
which is applied as a separation stage in a reactor
vessel of a reactor riser containing fluid-bed catalytic
cracking plant.
A fluid-bed catalytic cracking plant includes a
reactor vessel, a vertical reactor riser having an upper
outlet which is in fluid communication with a separator
system arranged in the reactor vessel, and a regenerator
vessel. During normal operation, regenerated catalyst
particles and hydrocarbonaceous feed are supplied to the
inlet end of the reactor riser in which catalytic
cracking of the feed takes place to form a mixture of
gaseous product and catalyst particles. The mixture
leaves the reactor riser at a high temperature of
between 500 and 540 C or higher. The mixture of gaseous
product and catalyst particles ls passed into the
separator system where gaseous product is separated from
catalyst particles. The gaseous product is removed from
the upper end of the reactor vessel, and the catalyst
particles are discharged to the lower part of the
reactor vessel where they are stripped. Stripped
catalyst particles are passed to the regenerator vessel
where coke deposited on the particles during cracking is
burnt-off at a high temperature to obtain combustion
products and regenerated catalyst. The combustion
products are removed from the upper end of the
regenerator vessel and regenerated catalyst is re-used.
Such a fluid-bed catalytic cracking plant is
described in European patent application publication
No. 488 549. The known separator system comprises a
cyclone separator and an auxiliary cyclone separator to

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provide a two-stage separation. The cyclone separator
comprises a vertical housing open at its lower end
provided with a cover at its upper end having a central
opening, an inlet duct for tangential entry of a mixture
of gas and catalyst particles from the outlet of the
riser reactor, a particles outlet duct communicating
with the open lower end of the vertical housing, and a
gas outlet duct having a vertical section which extends
through the central opening in the cover and which has
an outer diameter which is smaller than the diameter of
the central opening. The central opening and the outer
surface of the gas outlet duct define an annular inlet
port.
The cyclone separator is arranged in the upper part
of the reactor vessel, so that during normal operation
stripping gas present in the reactor vessel can be drawn
into the cyclone separator through the annular inlet
port by the difference in pressure between the interior
of the reactor vessel and the interior of the cyclone
separator.
It is an object of the present invention to improve
the efficiency of the known cyclone separator in
particular at the level in the cyclone separator where
the separation efficiency is low.
To this end the cyclone separator according to the
present invention comprises a vertical housing open at
its lower end provided with a cover at its upper end
having a central opening, an inlet duct for tangential
entry of a mixture of gas and catalyst particles from
the outlet of a riser reactor of a fluid-bed catalytic
cracking plant, a particles discharge duct communicating
with the open lower end of the vertical housing, and a
gas outlet duct having a vertical section which extends
through the central opening in the cover, which cyclone
separator further comprises an open-ended pipe arranged

CA 02263691 1999-02-17
7 ~ '
3 ~ r,
in the central opening so as to define an annular gas
inlet conduit between the outer surface of at least part
of the vertical section of the gas outlet duct and the
inner surface of the open-ended pipe, and swirl imparting
means arranged in the annular gas inlet conduit.
US-A-5362379 discloses a cyclone separator comprising
a vertical housing provided with an inlet duct for
tangential entry of a mixture of gas and solids particles
from the outlet of a riser reactor of a fluid-bed :~
catalytic cracking plant. The cyclone separator comprises
an open-ended pipe arranged in the central opening of the
cover so as to define an annular gas inlet conduit
between the outer surface of at least part of the
vertical section of a gas outlet duct and the inner
surface of the open-ended pipe. According to this
publication the stripping gas is directed away from the
solids-rich gas region within the separator. As a result,
the solids present in the stripping gas will not be
effectively separated from the gaseous stream in the
cyclone as in the cyclone separator according to the
invention.
DE-A-4136935 discloses a cyclone separator comprising
a vertical housing provided with an inlet duct for
tangential entry of a mixture of gas and solids
particles. The cyclone is further provided with means to
alter the pressure and flow patterns in the vicinity of
the opening of the gas outlet tube when the cyclone is in
operation. These means are for example a downward
directed gas flow in an annular space around the vertical
gas outlet tube. This annular space may be provided with
swirl imparting means.
The invention will now be described by way of example
~ in more detail with reference to the accompanying drawing
showing schematically a partial longitudinal section of
the cyclone separator of the present invention.
AMENDED SHEE~

CA 02263691 1999-02-17
- 3a
The cyclone separator 1 of the present invention
comprises a vertical housing 2 whlch has a discharge
opening 3 at its lower end 4 and which is provided with a
cover 5 at its upper end 6. The cover 5 has a central
opening 8.
The cyclone separator 1 further comprises an inlet
duct 10 extending between the upper outlet opening 12 of
a riser reactor 15 and the inlet opening 14 of the
cyclone separator 1 for tangential entry of a mixture of :~
gas and catalyst particles into the cyclone separator 1.
It also comprises a particles discharge duct 16
communicating with the discharge opening 3 in lower end 4
of the vertical housing 2, and a gas outlet duct 18.
The gas outlet duct 18 has a vertical straight
section 20 which extends through the central opening 8-in
the cover 5.
The cyclone separator further comprises an open-ended
pipe 23 fixed in the central opening 8, wherein an
annular gas inlet conduit 25 is defined between the outer
surface of the lower part of the vertical section 20 of
the gas outlet duct 18 and the inner surface of the open-
ended pipe 23. In the annular gas
MVM15/TS8530PCT
AMENDED SHEEl'

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-- 4
inle~ condult 25 swirl imparting means in the form of
swirl vanes 30 are arranged.
The cyclone separator 1 of the present invention is
arranged in the upper part 23 of a reactor vessel. Since
such a reactor vessel is welL known, it will not be
discussed in detail and only its roof 35 is shown. As a
fluid-bed catalytic cracking plant is well known, other
parts of such a plant are not shown.
During normal operation a mixture of gaseous product
and catalyst particles leaves the reactor riser 15
through opening 12. The mixture is drawn into the inlet
duct 10 which opens into the housing 2 so that the
mixture enters tangentially into the upper end 6 of the
housing 2 of the cyclone separator 1. As a result there
is a swirling mixture within the housing 2, and gaseous
product is removed from the housing 2 through gas outlet
duct 18. Catalyst particles fall to the lower end 4 of
the housing 2, and they are discharged via the particles
discharge duct 16. The discharged catalyst particles are
collected in the lower part (not shown) of the reactor
vessel where product adhered to the particles is
stripped off by means of stripping gas supplied to the
lower part of the reactor vessel. As a result a gaseous
mixture of stripping vapour and stripped product passes
upwards towards the dilute phase zone in the upper part
of the reactor vessel under the roof 35.
This gaseous mixture also contains small amounts of
entrained catalyst particles, and these catalyst
particles have to be removed from the gaseous mixture.
To this end gaseous mixture is drawn into the upper end
6 of housing 2 through the annular gas inlet conduit 25.
The swirl imparting means in the form of swirl vanes 30
will impart a swirling motion on the gaseous mixture,
and in this way initial separation of entrained catalyst
~ ....

CA 02263691 1999-02-17
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particles is effected, which separatlon continues as the
mixture descends in housing 2.
Suitably the swirl imparting means 30 are so
arranged that the direction of rotation which they
impart is the same as the diEection of rotation of the
mixture of gaseous product and catalyst particles from
the reactor riser 15, so that the latter swirl is
amplified which further improves the overall efficiency
of the cyclone separator 1.
The ratio of the outer diameter of the vertical
section 20 to the diameter of the central opening 8 is
suitably in the range of from 0.3 to 0.7.
The lower end 37 of the gas outlet duct 18 is
located below the lower edge 39 of the inlet opening 14.
However, the open-ended conduit 23 does not extend that
far into the cyclone separator 1; it only extends to
part of the height of the inlet opening 14. The distance
between the lower end 40 of the open-ended conduit 23
and the upper edge 41 of the inlet opening 14 is between
10% and 60% of the height of the inlet opening 14. This
is done to maximize the effect which the rotation
imparted by the swirl imparting means 30 has on the
fluid leaving opening 14.
To accommodate differences in thermal expansion
between the housing 2 and the gas outlet duct 18, the
swirl imparting means 30 are either fixed to the inner
surface of the open-ended pipe 23 or to the outer
surface of the vertical section 20 of the gas outlet
duct 18, but not fixed to both surfaces.
The number of swirl vanes 30 is suitably between 2
and 8, very suitably between 3 and 6.
The gas outlet duct 18 can be connected directly to
a plenum chamber (not shown) which is provided with a
gas outlet (not shown) extending through the roof 35, in
which case the separator system includes one separation

CA 02263691 1999-02-17
W 098/'~37~0 PCT~EP97/04881
stag~ only. In an alternative embodiment the gas outlet
duct 18 can be connected to an auxiliary cyclone
separator (not shown), of which the gas outlet which
opens into the plenum chamber, in which case the
separator system includes two separation stages.
The upper end of the reactor riser 15 can be
arranged in the reactor vessel (as shown in the Figure),
or it can be located outside the reactor vessel, so that
the inlet duct has to extend through the side wall of
the reactor vessel.

Dessin représentatif