GB1568777A

GB1568777A - Air distribution apparatus

Info

Publication number: GB1568777A
Application number: GB48526/77A
Authority: GB
Original assignee: Texaco Development Corp
Current assignee: Texaco Development Corp
Priority date: 1977-02-11
Filing date: 1977-11-22
Publication date: 1980-06-04
Also published as: FI773662A; IT7820171A0; JPS5399077A; IT1174358B; CA1104962A; DE2758327A1; DE2758327C2; ZA777029B

Description

(54) AIR DISTRIBUTION APPARATUS (71) We, TEXACO DEVELOPMENT CORPORATION, a corporation organised and existing under the laws of the State of Delaware, United States of America, of 135 East 42nd Street, New York, New York 10017, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed. to be particularly described in and by the following statement: This invention relates to gas distribution apparatus and in particular apparatus for distnbution of an oxygen containing gas, e.g. air, in the catalyst regenerator of a fluid catalytic cracking unit.

U.S. Patent No. 3,433,733 discloses a method and apparatus for fluid catalytic cracking of a hydrocarbon feed stock in order to produce desired reaction products.

Generally, the process consists of mixing together feed stock and hot catalyst in a riser/reactor prior to entry into a tapered reactor/separator chamber. The catalyst is removed from the reactor/separator chamber in a spent condition and is directed to a regenerator wherein the carbonaceous deposit on the catalyst, referred to as "coke". is burned from the catalyst with air. The regenerated catalyst is then re-used in the process. In U.S. Patent No. 3,433.733, an air distributor is positioned in the lower portion of the regenerator for distributing an air supply into a zone of spent catalyst in the regenerator. The efficiency of the regeneration process is dependent upon a uniform distribution of air through the spent catalyst zone. It has been found desirable to distribute the air outwardly of the air distributor at certain pressure differentials between air pressure in the distributor and air pressure in the regenerator to cause the air to effectively bubble and thus distribute through the zone of spent catalyst. However, it has also been found that the velocity of the air leaving the air ring may be so high at such desired pressure differential levels that the air actually causes some attrition of the catalyst. In order to prevent this attrition, it has been necessary to deliver the air at pressures below the higher pressure differential levels for the most efficient distribution of the air through the spent catalyst zone in the regenerator.

U.S. Patent No. 3.912.460 discloses an air distribution system for evenly distributing air in the spent catalyst zone of a regenerator in a fluid catalytic cracking process. A horizontal distributing ring is positioned in the spent catalyst in the regenerator. The ring comprises two tapered semi-circular tubes which are interconnected at their small ends: a splitter tube joint and the two larger ends of the tapered semi-cylindrical tubes are connected to a pressurized air supply. Air is distributed outwardly into the spent catalyst zone of the regenerator through openings in the semi-cylindrical tubes.

Other patents of interest include U.S.

Patent No. 3,867,103 which discloses the utilization of Venturi-shaped nozzles for use in mixing a hydrocarbon and acid to form an emulsion in a catalytic conversion apparatus. U.S. Patent No. 3.848.811 discloses a particular structure for a nozzle which discharges a liquid such as oil into a fluidized bed of particulate material such as catalyst in a fluid catalytic cracking system. And, U.S. Patent No. 3.632,304 discloses a heater nozzle which directs combustion gas into a reactor for providing a combustion gas stream for treating catalyst. None of these patents disclose structure which is precisely capable of achieving the results of the invention set forth herein.

The invention provides a gas distribution apparatus for delivering an oxygen-carrying gas. e.g. air. to a zone of spent catalyst in a regenerator of a fluid catalytic cracking process which apparatus comprises a header support assembly adapted for mounting in a regenerator of a fluid catalytic cracking process, said header support assembly supporting a hollow header ring having a plurality of openings therein; a gas supply line attached to said header support assembly and gas supply means for supplying gas through said gas supply line to said hollow header ring at a pressure which causes a maximum desired effective pressure differential between said ring and in said regenerator: and a plurality of nozzles mounted in said openings in said header ring. and arranged to receive gas at inlet ends of the nozzles from said header ring and to direct such gas passing in use through the nozzles outwardly into said spent catalyst zone, the nozzles having bores which diverge in a direction from the nozzle inlet ends to the nozzle outlet ends and the bore of each nozzle being flared outwardly from said nozzle inlet end to said nozzle outlet end at an angle not to exceed 15", the length of said flared nozzle bore being sufficient to decrease the velocity of said gas from the nozzle inlet end to its outlet end to a velocity level which will not damage the catalyst.

An advantage of a gas according to the invention is that it can deliver with maximum uniform gas distribution an oxygencarrying gas such as air into a zone of spent catalyst in a regenerator of a fluid catalytic cracking process. Another advantage is that gas can be delivered into the spent catalyst zone of a fluid catalytic cracking process regenerator at a non-damaging velocity.

A further advantage is that a pluralitv of gas distribution nozzles can be provided in a gas distribution header located in a regenerator of a fluid catalytic cracking process for delivering an oxygen-containing gas at pressure differential levels between the header and the regenerator that optimizes gas distribution and at the same time controls the nozzle exit velocity to minimize attrition of the catalyst from air flow.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a side view in section of a regenerator of a fluid catalytic cracking process having the air distribution system of this invention positioned therein; Figure d is a sectional view of the air distribution system header ring which mounts the air distribution nozzles of the preferred embodiment of this invention; and Figure 3 is a sectional view taken along line 3--3 of Figure 7 illustrating the structural detail of the air distribution system nozzles.

Referring to the drawing, the letter R generally designates a regenerator used in a fluid catalytic cracking process such as disclosed in U.S. Patent No. 3.433,733. The regenerator R includes a new and improved air distribution apparatus, generally designated by the letter A, adapted for mounting in the lower portion of the regenerator R. In a fluid catalytic cracking process such as disclosed in U.S. Patent No. 3.433,733. the lower portion 10 of the regenerator R illustrated in Figure 1 actually receives spent catalyst from a reactor. The spent catalyst is in particulate form. the size of the particles being sufficiently small that the catalyst may be fluidized in air. The air distribution system A is designed to provide the necessary oxygen to combust with coke on the spent catalyst to combust and burn the coke off the catalyst in order to rejuvenate the catalyst. The rejuvenated catalyst is then re-used in the fluid catalytic cracking process. The spent catalyst is collected in a zone or bed 11 in the lower portion 10 of the regenerator R. The purpose of the air distribution system A is to distribute bubbled air through the spent catalyst zone or bed 11 so that the coke covering the spent catalvst is combusted with the air and burned off the catalyst.

In the preferred embodiment of this invention. the air distribution system A includes a blower 12 which provides air under pressure to regenerator opening 14 through air supply line 15. A central housing 16 is mounted over the opening 14 in the regenerator R.

The housing 16 includes a first housing section 16a and a second housing section 16b. The housing section 16a is basically a hollow. cvlindrical structure which is mounted over the regenerator opening 14 by any suitable means such as welding. The housing section 16a includes a dome-shaped top section 17 having opening 17a therein.

The second housing section 16b is welded or otherwise mounted over the first housing section opening 17a. The second housing section 16b is also a hollow and generally cvlindrical section. The housing section 16b is enclosed at the top thereof.

The hollow housing sections 16a and 16b cooperate to form a plenum chamber 18 which receives air through the air supply line 15. The first housing section 16a has a circumferential row of openings 19 positioned in substantially horizontal alingment.

Each of the openings 19 has mounted therein a nozzle N of the preferred embodiment of this invention as illustrated in detail in Figure 3. The second housing section 16b also has a row of circumferentially spaced openings 20 therein which receive nozzles N of this invention.

Three radial support arms 31, 22 and 23 are welded in three openings 24 in the first housing section 16a. Each of the radial support arms 21-23 are hollow pipe members having an approximate L-shape as viewed in Figure The three radial supports arms 21-23 cooperate with the first and second housing sections 16a and 16b to provide a header support assembly for supporting a hollow.

header ring 25.

The header ring 25 includes three openings 26 which align with and receive the radial support arms 21-23, which are attached to the header ring 25 by welding or other suitable means. The header ring 25 further includes two rows 30 and 31 of nozzles N which are mounted in two rows of header ring openings 30a and 31a, respectively. In addition, several drain nozzles D, which are of the same configuration as the nozzles N to be described herein, are positioned in header ring openings 33 which are located at the very bottom of the header ring 25 and are circumferentially spaced about the ring. The number of drain nozzles D is substantially fewer than the number of nozzles N in rows 30 and 31 in the header ring 25.

Complete distribution of air through the air distribution system A into the spent catalyst zone 11 in regenerator R is critical to efficient rejuvenation of the catalyst. The nozzles N of the preferred embodiment of this invention are designed to deliver air to the spent catalyst zone 11 in the regenerator R at a safe velocity level in order to provide for maximum dispersion of the air through the spent catalyst zone 11.

It has been found desirable to have a sufficiently high pressure differential between the pressure of the air in the header ring 25 and the pressure of air exiting the nozzles N (which is the same as air pressure in the bed 11) to cause the air to uniformly disperse for high area contact with the spent catalyst particles. However, it has been found that air in prior art systems such as disclosed in U.S. Patent No. 3,912,460 which exits a header ring at such sufficiently high pressure differential levels has a velocity that is so high that it may actually cause some attrition of the catalyst. The nozzles N of the preferred embodiment of this invention are designed to deliver air to the spent catalyst zone 11 at a velocity below a potentially damaging level.

Referring in particular to Figures 2 and 3, each of the nozzles N is formed of a frusto-conical, cylindrical section 40 having a bore 41 therethrough. Each nozzle N diverges or flares in the bore 41 from nozzle inlet or entrance 42 to nozzle exit 43. Each nozzle N is an integral unit formed of cast Stellite or other suitable material. "Stellite" is a registered Trade Mark.

Mount means generally designated by the number 44 is provided for mounting each of the nozzles N in openings such as 32a in the header ring 25. The mount means 44 includes a mounting ring 46. When cast Stellite is utilized, the frustro-conical section 40 is formed by casting. However, cast Stellite is not capable of direct attachment to the header ring 25 through welding. In order to render the frustro-conical section 40 attachable to the header ring 25 by welding. the mounting ring 46 is attached to the frustro-conical section 40 during casting.

The mounting ring 46 may then be welded to the header ring 25. If another suitable nozzle material is utilized which can be welded to the header ring 25, it is contemplated to form the mounting ring as an integral portion with the frustro-conical section for direct welding connection to the header ring 25. Nozzle entrance 42 is formed by an inside nozzle rim 47 which is positioned flush with interior wall 25a of the header ring 25.

The nozzle N may be defined as having a cross-sectional interior. circular area Ai at nozzle entrance 42 and a cross-sectional interior. circular area Ae at nozzle exit 43.

The cross-sectional area Aj. and thus the interior diameter at the nozzle entrance 42, is less than the cross-sectional area A,. and thus the interior diameter at the nozzle exit 43. such that the bore 41 tapers inwardly or diverges form the nozzle entrance 42 toward the nozzle exit 43. The angle of such taper may be defined at 48 as being up to 15 . but preferably 7". The length 1 of the nozzle, as well as the angle 48 of taper, will vary according to application.

The air distribution system A provides air to the header ring 25 in a pressure range to provide a sufficiently high pressure differential between the pressure in ring 25 (which is approximately the same at entrance pressure Pj) and the pressure in bed 11 (which is the same at nozzle exit pressure Pe) to provide for maximum uniform distribution of air into the bed 11. At such pressure levels, the tapered interior bore 41 of the nozzle section 40 acts to reduce the entrance velocity Vj of air to a lesser exit velocity V0 which will not cause significant damage to the catalyst. Thus utilizing the nozzles N of this invention. the air distribution system A can deliver air to the spent catalyst zone 11 at maximum pressure differential levels to cause maximum uniform dispersion of the air into the spent catalyst zone 11 but at a safe. reduced velocity level which will not cause substantial attrition of the spent catalyst.

Erample In a fluid catalytic cracking unit such as described in U.S. Patent No. 3,433,733, the nozzle N of this invention has a length 1' exterior to the header 25 of three inches.

The area A1 at the nozzle entrance 42 is defined by a diameter of 1.55 inches (3.875 cm.) and the area A0 at the exit is defined by a diameter of 1.65 inches (4.19 cm. ). The air pressure in the ring 25 is at 40.0 psi (2.80 kg./sq. cm.) and the pressure drop from the ring 25 to the bed 11 is 1.5 (105.95 gr./sq.

cm.) to 2.5 psi (175.76 gr./sq. cm.). The divergence of the bore 41 causes a reduction in velocity from an entrance velocity Vj of 219 feet per second (66.75 m./sec.) to safe exit velocity V0 of 175 feet per second (53.34 m./sec.).

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size. shape and materials as well as in the details of the illustrated construction may be made without departing from the spirit of the invention.

WHAT WE CLAIM IS: 1. A gas distribution apparatus for delivering an oxygen-carrying gas. e.g. air. to a zone of spent catalyst in a regenerator of a fluid catalytic cracking process which apparatus comprises a header support assembly adapted for mounting in a regenerator of a fluid catalytic cracking process. said header support assembly supporting a hollow header ring having a plurality of openings therein: a gas supply line attached to said header support assembly and gas supply means for supplying gas through said gas supply line to said hollow header ring at a pressure which causes a maximum desired effective pressure differential between said ring and in said regenerator; and a plurality of nozzles mounted in said openings in said header ring. and arranged to receive gas at inlet ends of the nozzles from said header ring and to direct such gas passing in use through the nozzles outwardly into said spent catalyst zone. the nozzles having bores which diverge in a direction from the nozzle inlet ends to the nozzle outlet ends and the bore of each nozzle being flared outwardly from said nozzle inlet end to said nozzle outlet end at an angle not to exceed 15". the length of said flared nozzle bore being sufficient to decrease the velocity of said gas form the nozzle inlet end to its outlet end to a velocity level which will not damage the catalyst.

2. Apparatus as claimed in claim 1.

wherein the bore of each nozzle is flared outwardly from the nozzle inlet end to the nozzle outlet end at an angle of approximatelv 7".

3. Apparatus as claims in claim 1 or claim 2. wherein each nozzle inlet terminates in an annular rim which is substantiallv flush with the interior wall of said hollow header ring.

4. Apparatus as claimed in any preceding claim, wherein said header support assembly includes a substantially enclosed hollow cylindrical housing forming plenum chamber mounted over said supply line for receiving gas from said gas supply line; and radial pipe members mounted on said housing and extending radially outwardly thereform, said header ring being mounted on said radial pipe members.

5. Apparatus as claimed in claim 4.

wherein said substantially enclosed housing section includes a plurality of openings circumferentially spaced thereabout; and a plurality of nozzles, each having a bore which diverges from an inlet end to an outlet end thereof. and said nozzles being mounted in said housing at their inlet ends.

6. Apparatus as claimed in claim 4 or claim 5. wherein said substantially enclosed hollow cylindrical housing includes a first cylindrical, hollow housing section having said radial pipe members mounted thereon and extending outwardly to support said header ring; a second cylindrical. hollow housing section position on said first housing section. said first and second housing sections having openings therein; and a plurality of nozzles mounted in said openings in said first and second housing sections. each nozzle having a bore which diverges from an inlet end te an outlet end thereof and said nozzles being mounted in said housing at their inlet ends.

7. A gas distribution apparatus for delivering an oxygen-containing gas to a zone of spent catalyst in a regenerator of a fluid catalytic cracking process. substantially as hereinbefore described with reference to and as illustrated in. the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. nozzle N of this invention has a length 1' exterior to the header 25 of three inches. The area A1 at the nozzle entrance 42 is defined by a diameter of 1.55 inches (3.875 cm.) and the area A0 at the exit is defined by a diameter of 1.65 inches (4.19 cm. ). The air pressure in the ring 25 is at 40.0 psi (2.80 kg./sq. cm.) and the pressure drop from the ring 25 to the bed 11 is 1.5 (105.95 gr./sq. cm.) to 2.5 psi (175.76 gr./sq. cm.). The divergence of the bore 41 causes a reduction in velocity from an entrance velocity Vj of 219 feet per second (66.75 m./sec.) to safe exit velocity V0 of 175 feet per second (53.34 m./sec.). The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size. shape and materials as well as in the details of the illustrated construction may be made without departing from the spirit of the invention. WHAT WE CLAIM IS:

1. A gas distribution apparatus for delivering an oxygen-carrying gas. e.g. air. to a zone of spent catalyst in a regenerator of a fluid catalytic cracking process which apparatus comprises a header support assembly adapted for mounting in a regenerator of a fluid catalytic cracking process. said header support assembly supporting a hollow header ring having a plurality of openings therein: a gas supply line attached to said header support assembly and gas supply means for supplying gas through said gas supply line to said hollow header ring at a pressure which causes a maximum desired effective pressure differential between said ring and in said regenerator; and a plurality of nozzles mounted in said openings in said header ring. and arranged to receive gas at inlet ends of the nozzles from said header ring and to direct such gas passing in use through the nozzles outwardly into said spent catalyst zone. the nozzles having bores which diverge in a direction from the nozzle inlet ends to the nozzle outlet ends and the bore of each nozzle being flared outwardly from said nozzle inlet end to said nozzle outlet end at an angle not to exceed 15". the length of said flared nozzle bore being sufficient to decrease the velocity of said gas form the nozzle inlet end to its outlet end to a velocity level which will not damage the catalyst.

2. Apparatus as claimed in claim 1.

5. Apparatus as claimed in claim 4.