Title of Invention	"FLUID CATALYTIC CRACKING REACTOR"
Abstract	Fluid catalytic cracking reactor comprising an elongated reactor riser and a reactor vessel, wherein the reactor vessel comprises a dense phase fluidized stripping zone and a catalyst outlet at its lower end, a cracked vapour outlet at its upper end and a cyclone separator fluidly connected to the outlet of the reactor riser, which cyclone separator is provided with a dipleg which lower open end terminates below the upper bed level of the dense fluidized stripping zone, the dense phase fluidized stripping zone comprising a horizontal plate positioned below the lower open end of the dipleg, characterized in that the plate is a circular plate having a raised border and the lower open end of the dipleg is restricted and the diameter (d3) of the circular plate inclusive the raised border is between 1.2 and 0.9 times the diameter of the dipleg.

Title of Invention

"FLUID CATALYTIC CRACKING REACTOR"

Abstract

Fluid catalytic cracking reactor comprising an elongated reactor riser and a reactor vessel, wherein the reactor vessel comprises a dense phase fluidized stripping zone and a catalyst outlet at its lower end, a cracked vapour outlet at its upper end and a cyclone separator fluidly connected to the outlet of the reactor riser, which cyclone separator is provided with a dipleg which lower open end terminates below the upper bed level of the dense fluidized stripping zone, the dense phase fluidized stripping zone comprising a horizontal plate positioned below the lower open end of the dipleg, characterized in that the plate is a circular plate having a raised border and the lower open end of the dipleg is restricted and the diameter (d3) of the circular plate inclusive the raised border is between 1.2 and 0.9 times the diameter of the dipleg.

Full Text	The invention is related to a fluid catalytic cracking (FCC) reactor comprising an elongated reactor riser and a reactor vessel. The reactor vessel comprises a dense phase fluidized stripping zone and a catalyst outlet at its lower end and at its upper end a cracked vapour outlet and a cyclone separator fluidly connected to the outlet of the reactor riser. The cyclone separator is provided with a dipleg which lower open end terminates below the upper bed level of the dense phase fluidized stripping zone. An apparatus as described above is disclosed in IN 162282. According to this publication the dipleg of the so-called close-bottomed cyclone separators are submerged in the catalyst bed to provide a seal, preventing cracked vapour to flow through the dipleg. A problem often encountered is that pressure surges occur in the reactor riser due to for example equipment malfunctions, sudden vaporisation of water present in the hydrocarbon feedstock and/or various unit pressure upsets. In the event of a pressure surge the pressure imposed on the system by the catalyst bed around the submerged end of the dipleg as described in IN 162282 will not be sufficient to prevent cracked vapour from flowing through the dipleg. This phenomenon is also referred to as "carry under"of the gasses flowing through the cyclone. This is disadvantageous because the cracked vapour contains relatively higher amounts of coke precursors than for example the hydrocarbons which are normally entrained by the catalyst which is discharged through the dipleg. These coke precursors give rise to an undesirable coke formation in the open volume above the dense fluidized bed of the stripping zone. This coke formation can result in that an FCC reactor needs to be shut down before the end of a process run. Removal of the coke is furthermore very laborious and time consuming. The above problem is overcome by positioning a horizontal plate just below the lower open end of the dipleg. The plate ensures that in the event of a pressure surge no drastic increase in downflow of cracked vapour occurs via the dipleg. It is believed that this is achieved due to the back-pressure resulting from the catalyst being pressed, by the pressure surge, through the restricted opening between the plate and the catalyst discharge opening of the dipleg. Typically the plate has a diameter of more than 1.5 times the dipleg diameter. Examples of such prior art devices are illustrated in US-A-2958653 and US-A-5139748. A disadvantage of the reactor vessel according to the prior art is that the plates occupy a large horizontal space in the reactor vessel. This results in that the vessel needs to have a larger diameter or that less diplegs and thus less cyclones can be used in one reactor vessel. Such geometrical limitations are for example encountered when more than one primary cyclone dipleg and more than one secondary cyclone dipleg are submerged in the dense phase fluidized stripping bed. The present invention aims to provide an apparatus for performing an FCC process which apparatus minimises the risk that cracked vapours flow through the dipleg of the closed-bottomed cyclones in case of pressure surges. Another object of the invention is to provide a compact design for the lower open end of the cyclone dipleg. The above aims are achieved with the following fluid catalytic cracking reactor. Fluid catalytic cracking reactor comprising an elongated reactor riser and a reactor vessel, wherein the reactor vessel comprises a dense phase fluidized stripping zone and a catalyst outlet at its lower end, a cracked vapour outlet at its upper end and a cyclone separator fluidly connected to the outlet of the reactor riser, which cyclone separator is provided with a dipleg which lower open end terminates below the upper bed level of the dense phase fluidized stripping zone, the dense phase fluidized stripping zone further comprising a horizontal plate positioned below the lower open end of the dipleg, wherein the plate is a plate having a raised border and the lower open end of the dipleg is restricted. It has been found that when the reactor according to the invention is used the area of the plate can be much smaller than when using a flat plate and a non-restricted open ended dipleg. Tests have shown that this embodiment comprising the modified plate and dipleg opening will under normal conditions achieve the same objectives with regard to limiting gas carry under as the non-modified plate and dipleg of the prior art. The modified plate and dipleg furthermore avoid excessive gas carry under when the dense fluidized bed level of the stripping zone is temporally lower or when a pressure surge from the reactor riser takes place. This modified design also prevents the upflow of stripping and stripped gas out of the bed into the dipleg. Further preferred embodiments will become apparent from the description below. The invention can find application in new FCC reactors or by modification of existing FCC reactors. Existing FCC reactors which may be modified to a reactor according the present invention will suitably comprise a reactor vessel comprising cyclone separation means fluidly connected to the downstream end of a reactor riser and a stripping zone at its lower end. Examples of such FCC reactors are illustrated in Figures 1-16, 1-17, 1-19, 1-21 and 1-22 as published in "Fluid Catalytic Cracking Technology and Operation" by Joseph W. Wilson, PennWell Publishing Company, Tulsa Oklahoma (US), 1997, pages 31-39. The illustrated reactors describe both embodiments wherein the upper end of the reactor riser is placed within the reactor vessel or placed outside the reactor vessel. For the present invention the location of the upper end of the reactor riser is not essential. The cyclone separator which is provided with the plate at its lower dipleg end is a so-called rough cut cyclone or primary cyclone, in which the first separation is performed between catalyst and cracked vapour. Suitable 1 to 4 primary cyclones are fluidly connected to one reactor riser. The reactor vessel may be provided with further separation stages, for example secondary cyclones, to further separate catalyst fines from the cracked vapour. One primary cyclone may be fluidly connected to suitably 1 to 4 secondary cyclones. The design of the primary cyclone can vary, provided it is fluidly connected to a dipleg extending downwards. The cyclone may for example be a horizontal cyclone as described in EP-A-332277 or a conventional vertical cyclone. The dipleg itself has a relatively large cross-sectional area to accommodate the large quantities of catalyst which usually flow through such diplegs. The lower end is submerged in the dense fluidized bed of catalyst of the stripping zone. The height of the catalyst bed above the outlet opening of the dipleg should be sufficient to avoid, under normal operation, any gas carry under. This height can be easily determined by one skilled in the art. The flow of catalyst in such a primary cyclone according to the present invention is suitably between 100 and 500 kg/m2.s as measured at the cross-sectional area of the dipleg just above the restriction. We Claim : 1. Fluid catalytic cracking reactor comprising an elongated reactor riser (1) and a reactor vessel (14), wherein the reactor vessel (14) comprises a dense phase fluidized stripping zone (20) and a catalyst outlet (22) at its lower end, a cracked vapour outlet (17) at its upper end and a cyclone separator (3) fluidly connected to the outlet (2) of the reactor riser (1), which cyclone separator (3) is provided with a dipleg (24) which lower open end terminates below the upper bed level (23) of the dense phase fluidized stripping zone (20), the dense phase fluidized stripping zone (20) comprising a horizontal plate (25) positioned below the lower open end (28) of the dipleg (24), characterized in that the plate (25) is a circular plate having a raised border (26) and the lower open end (28) of the dipleg is restricted (27) and the diameter (d3) of the circular plate (25) inclusive the raised border (26) is between 1.2 and 0.9 times the diameter of the dipleg. 2. The fluid catalytic cracking reactor as claimed in claim 1, wherein the diameter (d3) of the circular plate is the same as the diameter of the dipleg (24). 3. The fluid catalytic cracking reactor as claimed in any of the claims 1-2, wherein the distance (d2) between the base of the plate (25) and the open lower end of the dipleg (24) is between 0.2 and 0.8 times the diameter of the dipleg (24). 4. The fluid catalytic cracking reactor as claimed in any of the claims 1-3, wherein the raised border (rim, 26) extends between 20 and 40% of the distance d2 above the base of the plate (25), wherein the distance d2 is the distance between the base of the plate and the open lower end of the dipleg (24). 5. The fluid catalytic cracking reactor as claimed in any of the claims 1-4, wherein the openings are present in the raised border (26), near to the bottom of the plate, in order to make the plate self- draining. 6. The fluid catalytic cracking reactor as claimed in any of the claims 1-5, wherein the plate (25) is coated with an erosion resistant material. 7. Use of the fluid catalytic cracking reactor as claimed in claims 1-6 in a fluid catalytic cracking process.

Full Text

The invention is related to a fluid catalytic cracking (FCC) reactor comprising an elongated reactor riser and a reactor vessel. The reactor vessel comprises a dense phase fluidized stripping zone and a catalyst outlet at its lower end and at its upper end a cracked vapour outlet and a cyclone separator fluidly connected to the outlet of the reactor riser. The cyclone separator is provided with a dipleg which lower open end terminates below the upper bed level of the dense phase fluidized stripping zone.
An apparatus as described above is disclosed in IN 162282. According to this publication the dipleg of the so-called close-bottomed cyclone separators are submerged in the catalyst bed to provide a seal, preventing cracked vapour to flow through the dipleg.
A problem often encountered is that pressure surges occur in the reactor riser due to for example equipment malfunctions, sudden vaporisation of water present in the hydrocarbon feedstock and/or various unit pressure upsets. In the event of a pressure surge the pressure imposed on the system by the catalyst bed around the submerged end of the dipleg as described in IN 162282 will not be sufficient to prevent cracked vapour from flowing through the dipleg. This phenomenon is also referred to as "carry under"of the gasses flowing through the cyclone. This is disadvantageous because the cracked vapour contains relatively higher amounts of coke precursors than for example the hydrocarbons which are normally entrained by the catalyst which is discharged through the dipleg. These coke precursors give rise to an undesirable coke formation in the open volume above the

dense fluidized bed of the stripping zone. This coke formation can result in that an FCC reactor needs to be shut down before the end of a process run. Removal of the coke is furthermore very laborious and time consuming.
The above problem is overcome by positioning a horizontal plate just below the lower open end of the dipleg. The plate ensures that in the event of a pressure surge no drastic increase in downflow of cracked vapour occurs via the dipleg. It is believed that this is achieved due to the back-pressure resulting from the catalyst being pressed, by the pressure surge, through the restricted opening between the plate and the catalyst discharge opening of the dipleg. Typically the plate has a diameter of more than 1.5 times the dipleg diameter. Examples of such prior art devices are illustrated in US-A-2958653 and US-A-5139748.
A disadvantage of the reactor vessel according to the prior art is that the plates occupy a large horizontal space in the reactor vessel. This results in that the vessel needs to have a larger diameter or that less diplegs and thus less cyclones can be used in one reactor vessel. Such geometrical limitations are for example encountered when more than one primary cyclone dipleg and more than one secondary cyclone dipleg are submerged in the dense phase fluidized stripping bed.
The present invention aims to provide an apparatus for performing an FCC process which apparatus minimises the risk that cracked vapours flow through the dipleg of the closed-bottomed cyclones in case of pressure surges. Another object of the invention is to provide a compact design for the lower open end of the cyclone dipleg.
The above aims are achieved with the following fluid catalytic cracking reactor. Fluid catalytic cracking reactor comprising an elongated reactor riser and a reactor vessel, wherein the reactor vessel comprises a

dense phase fluidized stripping zone and a catalyst outlet at its lower end, a cracked vapour outlet at its upper end and a cyclone separator fluidly connected to the outlet of the reactor riser, which cyclone separator is provided with a dipleg which lower open end terminates below the upper bed level of the dense phase fluidized stripping zone, the dense phase fluidized stripping zone further comprising a horizontal plate positioned below the lower open end of the dipleg, wherein the plate is a plate having a raised border and the lower open end of the dipleg is restricted.
It has been found that when the reactor according to the invention is used the area of the plate can be much smaller than when using a flat plate and a non-restricted open ended dipleg. Tests have shown that this embodiment comprising the modified plate and dipleg opening will under normal conditions achieve the same objectives with regard to limiting gas carry under as the non-modified plate and dipleg of the prior art. The modified plate and dipleg furthermore avoid excessive gas carry under when the dense fluidized bed level of the stripping zone is temporally lower or when a pressure surge from the reactor riser takes place. This modified design also prevents the upflow of stripping and stripped gas out of the bed into the dipleg. Further preferred embodiments will become apparent from the description below.
The invention can find application in new FCC reactors or by modification of existing FCC reactors. Existing FCC reactors which may be modified to a reactor according the present invention will suitably comprise a reactor vessel comprising cyclone separation means fluidly connected to the downstream end of a reactor riser and a stripping zone at its lower end. Examples of such FCC reactors are illustrated in Figures 1-16, 1-17, 1-19, 1-21 and 1-22 as published in "Fluid Catalytic

Cracking Technology and Operation" by Joseph W. Wilson, PennWell Publishing Company, Tulsa Oklahoma (US), 1997, pages 31-39. The illustrated reactors describe both embodiments wherein the upper end of the reactor riser is placed within the reactor vessel or placed outside the reactor vessel. For the present invention the location of the upper end of the reactor riser is not essential.
The cyclone separator which is provided with the plate at its lower dipleg end is a so-called rough cut cyclone or primary cyclone, in which the first separation is performed between catalyst and cracked vapour. Suitable 1 to 4 primary cyclones are fluidly connected to one reactor riser. The reactor vessel may be provided with further separation stages, for example secondary cyclones, to further separate catalyst fines from the cracked vapour. One primary cyclone may be fluidly connected to suitably 1 to 4 secondary cyclones. The design of the primary cyclone can vary, provided it is fluidly connected to a dipleg extending downwards. The cyclone may for example be a horizontal cyclone as described in EP-A-332277 or a conventional vertical cyclone. The dipleg itself has a relatively large cross-sectional area to accommodate the large quantities of catalyst which usually flow through such diplegs. The lower end is submerged in the dense fluidized bed of catalyst of the stripping zone. The height of the catalyst bed above the outlet opening of the dipleg should be sufficient to avoid, under normal operation, any gas carry under. This height can be easily determined by one skilled in the art.
The flow of catalyst in such a primary cyclone according to the present invention is suitably between 100 and 500 kg/m2.s as measured at the cross-sectional area of the dipleg just above the restriction.

We Claim :
1. Fluid catalytic cracking reactor comprising an elongated reactor riser (1) and a reactor vessel (14), wherein the reactor vessel (14) comprises a dense phase fluidized stripping zone (20) and a catalyst outlet (22) at its lower end, a cracked vapour outlet (17) at its upper end and a cyclone separator (3) fluidly connected to the outlet (2) of the reactor riser (1), which cyclone separator (3) is provided with a dipleg (24) which lower open end terminates below the upper bed level (23) of the dense phase fluidized stripping zone (20), the dense phase fluidized stripping zone (20) comprising a horizontal plate (25) positioned below the lower open end (28) of the dipleg (24), characterized in that the plate (25) is a circular plate having a raised border (26) and the lower open end (28) of the dipleg is restricted (27) and the diameter (d3) of the circular plate (25) inclusive the raised border (26) is between 1.2 and 0.9 times the diameter of the dipleg.
2. The fluid catalytic cracking reactor as claimed in claim 1, wherein
the diameter (d3) of the circular plate is the same as the diameter
of the dipleg (24).
3. The fluid catalytic cracking reactor as claimed in any of the claims
1-2, wherein the distance (d2) between the base of the plate (25)
and the open lower end of the dipleg (24) is between 0.2 and 0.8
times the diameter of the dipleg (24).
4. The fluid catalytic cracking reactor as claimed in any of the claims
1-3, wherein the raised border (rim, 26) extends between 20 and
40% of the distance d2 above the base of the plate (25), wherein

the distance d2 is the distance between the base of the plate and the open lower end of the dipleg (24).
5. The fluid catalytic cracking reactor as claimed in any of the claims
1-4, wherein the openings are present in the raised border (26),
near to the bottom of the plate, in order to make the plate self-
draining.
6. The fluid catalytic cracking reactor as claimed in any of the claims
1-5, wherein the plate (25) is coated with an erosion resistant
material.
7. Use of the fluid catalytic cracking reactor as claimed in claims 1-6
in a fluid catalytic cracking process.

Documents:

1052-DELNP-2003-Abstract-(25-09-2008).pdf

1052-delnp-2003-abstract.pdf

1052-delnp-2003-assignments.pdf

1052-DELNP-2003-Claims-(20-11-2008).pdf

1052-DELNP-2003-Claims-(25-09-2008).pdf

1052-delnp-2003-claims.pdf

1052-DELNP-2003-Correspondence-Others-(20-11-2008).pdf

1052-DELNP-2003-Correspondence-Others-(25-09-2008).pdf

1052-delnp-2003-correspondence-others.pdf

1052-DELNP-2003-Description (Complete)-(25-09-2008).pdf

1052-delnp-2003-description (complete).pdf

1052-DELNP-2003-Drawings-(25-09-2008).pdf

1052-delnp-2003-drawings.pdf

1052-DELNP-2003-Form-1-(20-11-2008).pdf

1052-DELNP-2003-Form-1-(25-09-2008).pdf

1052-delnp-2003-form-1.pdf

1052-delnp-2003-form-18.pdf

1052-DELNP-2003-Form-2-(20-11-2008).pdf

1052-DELNP-2003-Form-2-(25-09-2008).pdf

1052-delnp-2003-form-2.pdf

1052-delnp-2003-form-3.pdf

1052-delnp-2003-form-5.pdf

1052-DELNP-2003-GPA-(20-11-2008).pdf

1052-delnp-2003-gpa.pdf

1052-delnp-2003-pct-101.pdf

1052-delnp-2003-pct-210.pdf

1052-delnp-2003-pct-409.pdf

1052-delnp-2003-pct-416.pdf

1052-DELNP-2003-Petition-137-(20-11-2008).pdf

1052-delnp-2003-pettion-138.pdf

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Patent Number

225805

Indian Patent Application Number

1052/DELNP/2003

PG Journal Number

01/2009

Publication Date

02-Jan-2009

Grant Date

02-Dec-2008

Date of Filing

07-Jul-2003

Name of Patentee

SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.

Applicant Address

CAREL VAN BYLANDTLAAN 3O NL-2596 HR THE HAGUE, THE NETHERLANDS.

Inventors:

#	Inventor's Name	Inventor's Address
1	DRIES HUBERTUS WILHELNUS	BADHUISWEG 3, NL,-1031, CM AMSTERDAM, NETHERLAND

PCT International Classification Number

C10G 11/18

PCT International Application Number

PCT/EP2002/01871

PCT International Filing date

2002-02-21

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	01200663.1	2001-02-22	EUROPEAN UNION