U.S. patent application number 10/499286 was filed with the patent office on 2006-07-27 for process to regenerate fcc spent catalyst.
Invention is credited to Ye-Mon Chen, Hubertus Wilhelmus Albertus Dries, Rene Samson.
Application Number | 20060165605 10/499286 |
Document ID | / |
Family ID | 19189715 |
Filed Date | 2006-07-27 |
United States Patent
Application |
20060165605 |
Kind Code |
A1 |
Chen; Ye-Mon ; et
al. |
July 27, 2006 |
Process to regenerate fcc spent catalyst
Abstract
A process to supply solid particles to a fluidized bed via a
riser which has a substantially vertical upper part terminating at
an outlet opening in the fluidized bed and wherein the solid
particles are transported towards the fluidized bed in the riser
with a lift gas, which lift gas and solid particles are contacted
at an upstream part of the riser and wherein between the upstream
part and the outlet opening the interior of the riser is provided
with a plurality of axially spaced mixing elements.
Inventors: |
Chen; Ye-Mon; (Sugar Land,
TX) ; Dries; Hubertus Wilhelmus Albertus; (Cm
Amsterdam, NL) ; Samson; Rene; (Amsterdam,
NL) |
Correspondence
Address: |
Charles W Stewart;Shell Oil Company
Intellectual Property
PO Box 2463
Houston
TX
77252-2463
US
|
Family ID: |
19189715 |
Appl. No.: |
10/499286 |
Filed: |
December 19, 2002 |
PCT Filed: |
December 19, 2002 |
PCT NO: |
PCT/EP02/13878 |
371 Date: |
June 18, 2004 |
Current U.S.
Class: |
424/46 ;
128/200.23 |
Current CPC
Class: |
Y02P 20/584 20151101;
C07D 401/12 20130101; Y02P 20/55 20151101; C07D 235/28
20130101 |
Class at
Publication: |
424/046 ;
128/200.23 |
International
Class: |
A61K 9/14 20060101
A61K009/14; A61L 9/04 20060101 A61L009/04; A61M 11/00 20060101
A61M011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2001 |
JP |
2001-401044 |
Claims
1. A process to supply solid particles to a fluidized bed via a
riser which has a substantially vertical upper part terminating at
an outlet opening in said fluidized bed and wherein the solid
particles are transported towards said fluidized bed in the riser
with a lift gas, which lift gas and solid particles are contacted
at an upstream part of the riser and wherein between said upstream
part and the outlet opening the interior of the riser is provided
with a plurality of axially spaced mixing elements.
2. The process of claim 1, wherein the mixing element has the shape
of a segment of arc.
3. The process of claim 2, wherein a first disk surrounds the upper
opening of the riser at the uppermost end of said riser; a second
disk, is spaced upwardly from, and rigidly connected to, said first
disk, thereby forming a substantially open space there-between; a
deflection cone is attached, at its base, to said second disk, said
deflection cone pointing downward and being centred over the outlet
of said conduit, said deflection cone adapted to direct said spent
catalyst and said transfer gas in a substantially uniform, radially
outward direction through said space formed between said first disk
and said second disk, thereby providing a continuous
circumferential discharge of said mixture of solids and lift gas
from the outer circumference of said space formed between said
first disk and said second disk into said fluidised bed in a
substantially uniform radially outward direction.
4. The process of claim 3, wherein the solid particles are FCC
catalyst particles, which are supplied to a fluidized regenerator
bed.
5. The process of claim 4, wherein the lift gas is air.
6. The process of claim 1, wherein a first disk surrounds the upper
opening of the riser at the uppermost end of said riser; a second
disk, is spaced upwardly from, and rigidly connected to, said first
disk, thereby forming a substantially open space there-between, a
deflection cone is attached, at its base, to said second disk, said
deflection cone pointing downward and being centred over the outlet
of said conduit, said deflection cone adapted to direct said spent
catalyst and said transfer gas in a substantially uniform, radially
outward direction through said space formed between said first disk
and said second disk, thereby providing a continuous
circumferential discharge of said mixture of solids and lift gas
from the outer circumference of said space formed between said
first disk and said second disk into said fluidised bed in a
substantially uniform radially outward direction.
7. The process of claim 1, wherein the solid particles are FCC
catalyst particles, which are supplied to a; fluidized regenerator
bed.
8. The process of claim 2, wherein the solid particles are FCC
catalyst particles, which are supplied to a; fluidized regenerator
bed.
Description
[0001] The present invention is related to a Process to supply
solid particles to a fluidized bed via a riser which has a
substantially vertical upper part terminating at an outlet opening
in said fluidized bed and wherein the solid particles are
transported towards said fluidized bed in the riser with a lift
gas, which lift gas and solid particles are contacted at an
upstream part of the riser. The invention is especially directed to
a process for improving distributions of both spent catalyst and
lift gas into a regenerator of a fluid catalytic cracking unit.
[0002] In a typical Fluid Catalytic Cracking Unit (FCCU) consisting
of a regenerator, a riser reactor and a stripper, finely divided
regenerated catalyst is drawn from the regenerator through the
regenerator standpipe and contacts with a hydrocarbon feedstock in
a lower portion of a reactor riser. Hydrocarbon feedstock and steam
enter the riser through feed nozzles. The mixture of feed, steam
and regenerated catalyst, which has a temperature of from about
200.degree. C. to about 700.degree. C., passes up through the riser
reactor, converting the feed into lighter products while a coke
layer deposits on the surface of the catalyst, temporarily
deactivating the catalyst. The hydrocarbon vapours and catalyst
from the top of the riser are then passed through cyclones to
separate spent catalyst from the hydrocarbon vapour product stream.
The spent catalyst enters the stripper where steam is introduced to
remove hydrocarbon products from the catalyst. The spent catalyst
then passes through a spent catalyst transfer line to enter the
regenerator where, in the presence of air and at a temperature of
from about 620.degree. C. to about 760.degree. C., the coke layer
on the spent catalyst is combusted to restore the catalyst
activity. Regeneration is performed in a fluidized bed. The
regenerated catalyst is then drawn from the regenerator fluidized
bed through the regenerator standpipe and, in repetition of the
previously mentioned cycle, contacts the feedstock in the reactor
riser.
[0003] Catalyst regeneration is a critical step in FCCU operation.
The success of the step depends on the contacting efficiency
between the spent catalyst and oxygen-containing gas in the
regenerator. While the operation of an FCCU with a single catalyst
inlet opening was acceptable for many years, the potential benefit
of improving catalyst distribution in the regenerator has become
apparent more recently. An ideal condition for catalyst
distribution is that the time for distribution and mixing of
catalyst should be less than that for coke combustion. As the
regenerator diameter increases, the radial mixing time of catalyst
becomes longer. At the same time, as the regeneration temperature
increases, the time required for combustion becomes shorter. Hence,
the benefit of improving spent catalyst distribution is more
significant for an FCCU comprising a regenerator vessel of large
diameter or in which regeneration is conducted at higher
temperature.
[0004] Another important aspect of the spent catalyst distribution
is to control afterburn, which is characterized by substantial
temperature increase in the dilute phase of the regenerator above
the fluidized bed. If the lift gas, most commonly air, coming along
with the spent catalyst is not well distributed, gas will form
large bubbles at the discharge of the spent catalyst distributor,
rising quickly through the fluidized bed with little time for
combustion, and releasing oxygen-rich gas into the dilute phase.
This leads to afterburn and poor combustion efficiency of the
transport gas in the fluidized bed.
[0005] EP-A-622116 discloses a device which distributes spent
catalyst and lift gas by means of a central vertical spent catalyst
riser terminated with a junction connecting to multiple, horizontal
conveying conduits and discharging catalyst at the ends of the
horizontal conduits to discrete distribution points.
[0006] Although the above prior art device is directed at
distributing spent catalyst as best as possible within the
regenerator there is room for improvement in this respect.
[0007] It is an objective of the instant invention to improve
solids distribution in a fluidized bed when supplying said solids.
Another objective is to achieve this improvement while making use
of the above and other prior art devices to supply spent catalyst
to the fluidized bed wherein the device comprises a riser with a
substantially vertical upper part.
[0008] This objective is achieved with the following process.
Process to supply solid particles to a fluidized bed via a riser
which has a substantially vertical upper part terminating at an
outlet opening in said fluidized bed and wherein the solid
particles are transported towards said fluidized bed in the riser
with a lift gas, which lift gas and solid particles are contacted
at an upstream part of the riser and wherein between said upstream
part and the outlet opening the interior of the riser is provided
with a plurality of axially spaced mixing elements.
[0009] Applicants have found that when such mixing elements are
present in the riser according to the process of the invention an
improved distribution of solids and lift gas in the fluidized bed
is achieved. Furthermore the improvement can be achieved by making
use of the spent catalyst inlet devices of the prior art. Thus by
simple retrofitting the riser of these prior art devices an
improved distribution can be achieved.
[0010] The mixing elements, which are present on the surface of the
interior of the riser, will result in that the solids and gas will
flow more evenly upwards through the riser. It has been found
surprisingly that this more evenly flow through the whole length of
the riser, which can range from 6 to 30 meters, would have such a
major advantageous impact in the distribution of solids and gas in
the fluidized bed in which gas and solids are dispersed into.
[0011] The mixing elements can be any extension of the interior of
the riser wall towards the riser interior resulting in a smaller
cross sectional opening than the opening at a point where no mixing
element is present. Such a smaller opening will create turbulence
and a higher local gas velocity resulting in local radial mixing of
the gas-solids mixture flowing in the riser. The axial spacing of
the mixing elements is not critical, usually it should be larger
than the diameter of the riser. Examples of such devices are
venturi shaped rings fixed on the interior of the riser. If a
refractory is present in the riser it is preferred to use specially
shaped refractory building blocks as mixing element. An example of
such a mixing element is disclosed in U.S. Pat. No. 3,353,925 and
U.S. Pat. No. 5,851,380 for a FCC reactor riser.
[0012] Preferably the mixing element has the shape of a segment of
arc as described in WO-A-9814533. These mixing elements are
preferred over the elements disclosed in U.S. Pat. No. 3,353,925
and U.S. Pat. No. 5,851,380 because the pressure drop over the
length of the riser provided with such elements is lower. The
mixing elements have the shape of a segment of arc and a
rectangular cross-section. The horizontal penetration depth of the
flat mixing element towards the center of the riser is equal to the
rise of the segment of arc.
[0013] Suitably one to at most four arc shaped mixing elements can
be positioned at a specific elevation in the riser. The arc shaped
mixing elements can be arranged directly above another in the
riser. However, suitably the arc shaped mixing element(s) is (are)
arranged staggered with respect to the arc shaped mixing element(s)
positioned just above or below said elements. For example if two
opposite arc shaped mixing elements are used per elevation the
adjacent mixing elements are suitably arranged perpendicular to
each other. The angle need not be 90.degree., it can be any acute
angle.
[0014] In addition, the flat mixing element(s) can further include
a lip pointing inwards.
[0015] The central planes of the flat mixing elements 10 are
arranged perpendicular to the central longitudinal axis of the
riser. In an alternative embodiment the mixing elements can be
arranged tilted downwards with respect to the central longitudinal
axis of the riser 1. For example the angle between a central plane
and the central longitudinal axis is between 5.degree. and
20.degree..
[0016] In the riser a dilute phase fluidized bed will be present.
Preferably the more dilute phase fluidized bed has a catalyst or
solids density of below 500 kg/m.sup.3 and more preferably between
20 and 400 kg/m.sup.3. The superficial gas velocity in the more
dilute phase fluidized bed is preferably between 1.5 and 20
m/s.
[0017] At the upper end of the riser means to distribute the solids
and the lift gas in the dense fluidized bed are suitably present.
Such means may for example be a device as described in the above
referred to EP-A-622116 or similar devices comprising outwardly
conveying conduits to distribute the solids. A device found
especially suitable is described in WO-A-242394 and is incorporated
herein by reference. Such device comprises of:
[0018] a first disk surrounding the upper opening of the vertical
riser at the uppermost end of said riser;
[0019] a second disk, spaced upwardly from, and rigidly connected
to, said first disk, thereby forming a substantially open space
therebetween;
[0020] a deflection cone attached, at its base, to said second
disk, said deflection cone pointing downward and being centred over
the outlet of said conduit, said deflection cone adapted to direct
said spent catalyst and said transfer gas in a substantially
uniform, radially outward direction through said space formed
between said first disk and said second disk, thereby providing a
continuous circumferential discharge of said mixture of solids and
lift gas from the outer circumference of said space formed between
said first disk and said second disk into said fluidised bed in a
substantially uniform radially outward direction.
[0021] The lift gas may be any gaseous medium and the choice will
depend on the process in which the invention is applied. When spent
catalyst solids are supplied to a FCCU regenerator the lift gas may
be for example steam or nitrogen. Preferably an oxygen containing
gas, suitably air or oxygen-enriched air is used.
[0022] When the process according to the present invention is used
in a FCCU the solids will be catalyst suitably be conventional FCC
catalyst as for example described in "Fluid catalytic cracking:
Science and Technology", Ed. Magee J. S., Mitchell M. M. Jr., 1993,
Elsevier Science Publishers B. V., pages 1-6. Additives, for
example ZSM-5 or Zeolite Beta containing additives, to enhance
propene selectivity may also be present.
[0023] The invention shall be further illustrated by means of FIG.
1.
[0024] FIG. 1 shows the lower end of a FCCU regenerator vessel (1)
comprising of a fluidized bed (2) of catalyst particles, an upper
fluidized bed level (3), means to add fluidizing gas (4), a
catalyst discharge conduit (5) for discharge of regenerated
catalyst particles and means to supply spent catalyst via a riser
(6) having a substantially vertical upper part. Riser (6) is
provided at its upper end with means (7) to evenly discharge
catalyst and lift gas in the fluidized bed (2). These means are
thus located below upper bed level (3). The riser is provided with
axially spaced mixing elements (8). At the lower end of said riser
(6) spent catalyst, as discharged from a FCC stripper (not shown)
via (9), and lift gas as provided at inlet point (10) is mixed.
* * * * *