A novel optimization formulation of Fluid Catalytic Cracking unit

CATEGORY: FCCU - FLUID CATALYTIC CRACKING UNIT
Industrial Engineering and Systems Management (IESM), International Conference on Proceedings of 2013, 28-30 Oct. 2013, Page(s): 1 - 5 Conference Location : Agdal, Rabat, Morocco
A novel optimization formulation of Fluid Catalytic Cracking unit
Saleh, Khaled
Abstract
Masdar Institute of Science and Technology, Abu Dhabi, United Arab Emirates
Ibrahim, Hebatallah ; Jayyousi, Majd ; Diabat, Ali
Increasing gasoline and propylene production from Fluid Catalytic Cracking Units (FCCUs) is an area of great concern. A major challenge is determining how to balance the design and operation of FCCU between maximum gasoline and propylene production.
Researchers from UAE propose a novel Mixed Integer Nonlinear programing problem (MINLP) formulation that minimizes the total cost of gasoline and propylene production by obtaining optimal operating settings that generate optimal yields of both products as per their respective economic value. They present case study is to verify the formulation effectiveness. The problem is solved using Matlab genetic algorithm toolbox.
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Use of Computational Modeling for FCC Reactor Cyclone Erosion Reduction at the Marathon Petroleum Catlettsburg Refinery

CATEGORY: FCCU – FLUID CATALYTIC CRACKING UNIT
The 14th International Conference on Fluidization – From Fundamentals to Products, January 1, 2013
Use of Computational Modeling for FCC Reactor Cyclone Erosion Reduction at the Marathon Petroleum Catlettsburg Refinery
Peter Blaser, CPFD Software LLC, USA
Scott Thibault, CPFD Software LLC, USA
Jeffrey Sexton, Marathon Petroleum Company LP, USA
Abstract
Modifications to the Fluid Catalytic Cracking (FCC) reactor internals at Marathon Petroleum Company’s (MPC’s) Catlettsburg Refining facility were planned to mitigate severe erosion in the reactor cyclones. A computational model, specific for gas-particle flows, was created to calculate erosion patterns in the reactor cyclones. The erosion characteristics of candidate redesigns were compared and contrasted with the validated model of the existing unit.
Computational Model
The CPFD®, or Computational Particle Fluid Dynamics, method was used to simulate the gas-particle flow inside the upper portion of the reactor. The CPFD method solves the transient fluid and particle mass, momentum and energy equations in three dimensions. The fluid is described by the Navier-Stokes equation with strong coupling with the discrete particles. The particle momentum has been adapted from the Multi-Phase, Particle-In-Cell (MP-PIC) numerical approach which is a Lagrangian description of particle motion coupled with the continuum fluid. The CPFD method is utilized by the commerciallyavailable Barracuda Virtual Reactor™ software package, which has been validated for a wide range of fluid-particle flow problems including refractory erosion studies. Barracuda VR™ was used for this erosion study.
Free Full Text Source: http://dc.engconfintl.org/cgi/viewcontent.cgi?article=1044&context=fluidization_xiv

A Typical Radiotracer Test Design: Application To A Fluid Catalytic Cracking Unit

CATEGORY: FCCU – FLUID CATALYTIC CRACKING UNIT
e-Περιοδικό Επιζηήμης & Τεχνολογίας
e-Journal of Science & Technology (e-JST)
A Typical Radiotracer Test Design: Application To A Fluid Catalytic Cracking Unit
H. A. Affum 1, P.S. Adu 1, C.P.K. Dagadu 1, A. Coleman 1, M.A. Addo 1
afmyn79@yahoo.com
1 National Nuclear Research Institute, Ghana Atomic Energy Commission, P. O. Box LG 80, Legon-Accra, Ghana
Abstract
The concept of residence time distribution (RTD) is an important tool for performance assessment of industrial units and reactors. This paper discusses the residence time distribution concept, how to obtain the residence time distribution curve of a process reactor using radioactive tracers (radiotracers) and its importance in process performance assessment. Focussing on the fluid catalytic cracking unit (FCCU) of a petroleum refinery, radiotracer tests to determine catalyst and vapour traffic velocities and slip through the riser and its implications for efficient cracking, and the flow distribution through the riser and regenerator are discussed.
Introduction
The residence time distribution (RTD) of a chemical reactor is a probability distribution function that describes the amount of time a fluid element could spend inside the reactor (Fogler, 2005). Chemical engineers use the RTD to characterize the mixing and flow within reactors and to compare the behaviour of real reactors to their ideal models. This is useful, not only for troubleshooting existing reactors, but in estimating the yield of a given reaction and designing future reactors. The RTD can be determined through numerical methods and experimental means. In the experimental determination of the RTD, tracers which are chemical substances with measurable properties like absorbance, fluorescence, pH and salt conductivity are employed (Wittrup, 2007, IAEA, 1990). However, the applications of radiotracers are methods of choice for obtaining the distribution in industrial process vessels (Dagadu et al, 2012, Lelinski et al. 2002). The Radiotracer RTD method has been extensively used in industry to optimize processes, solve problems, improve product quality, save energy and reduce pollution (Mumuni et al., 2011; Pant et al., 2009, 2001; Pant &Yelgoankar, 2002; Yelgoankar et al., 2009). Though the RTD technology is applicable across a broad industrial spectrum, the petroleum and petrochemical industries, mineral processing and wastewater treatment sectors are identified as the most appropriate target beneficiaries (IAEA, 2008). This paper discusses the RTD concept, how to obtain the residence time distribution curve of a process unit and its importance in process performance assessment. Focussing on the FCCU of a petroleum refinery, radiotracer tests to determine catalyst and vapour traffic velocities and slip through the riser, flow distribution through the reactor and the regenerator are discussed.
Free Full Text Source: http://e-jst.teiath.gr/issue_30/Affum_30.pdf

Process For Catalytic Cracking Associated With An Amine Treatment Unit With Improved CO2 Balance (IFP Energies Nouvelles)

CATEGORY: FCCU – FLUID CATALYTIC CRACKING UNIT
PATENT
Process For Catalytic Cracking Associated With An Amine Treatment Unit With Improved CO₂ Balance (IFP Energies Nouvelles)
Inventors:
Digne, Romina (Lyon, FR)
Feugnet, Frederic (Lyon, FR)
Do, Mai Phuong (Courbevoie, FR)
Application Number:
13/719302
Publication Date:
06/20/2013
Assignee:
IFP Energies Nouvelles (Rueil-Malmaison Cedex, FR)
Document Type and Number:
United States Patent Application 20130152791
Abstract:
The present invention describes a process for catalytic cracking associated with a unit for amine treatment of regeneration fumes from the catalytic cracking unit, which process uses at least one counter-pressure turbine to operate the cracked gas compressor and/or the regenerative air blower which can be used to improve the CO2 balance by delivering a CO2 credit.
FIELD OF THE INVENTION
The present invention relates to the field of the capture of carbon dioxide (CO2) emitted by fumes originating from regeneration in catalytic cracking units (abbreviated to FCC).
The capture of CO2 is an essential aspect in the battle against the greenhouse effect, since CO2 is one of the principal culprits. In order to limit the phenomenon of climate warming, the carbon dioxide is extracted from combustion fumes with a view to being sequestrated in an underground reservoir. Most carbon dioxide waste comes from industrial activity, i.e. on average 60% globally, of which 40% comes from fumes from power stations for the production of electricity.
In refineries, the fluid catalytic cracking (FCC) unit may be considered as one of the highest CO2 emitters with almost 20% of emissions from it alone; the other sources are in the various reheating or distillation furnaces. When reducing CO2 emissions from a refinery, then, it is clear that FCC constitutes a prime target.
The present invention proposes a solution that calls upon known capture technology, termed amine capture, but develops a utilities balance which is greatly in surplus in terms of HP steam (high pressure) and LP steam (low pressure) from the integrated FCC/amine capture unit process by means of a judicious choice of the drives for the two compressors of the process and of intense energy recovery. Thus, an integrated FCC/amine capture unit process is obtained with very low or even negative CO2 emissions. This is then known as a process with a CO2 credit.
EXAMINATION OF THE PRIOR ART
The prior art describes an integrated FCC/amine treatment unit process in which all or a portion of the regeneration fumes are sent to the amine treatment unit. The catalytic cracking unit is equipped with an external exchanger using a portion of the catalyst removed from the regeneration zone as the hot fluid and the heat required for the amine treatment unit is integrally provided by the steam generated by said external exchanger. In the prior art, the quantity of steam generated in the process is insufficient to treat all of the FCC fumes.
Thus, patent FR 2 939 693 describes an integrated process for the capture of CO2 emitted by at least a portion of the fumes exiting from the regeneration zone of a catalytic cracking unit (denoted FCC), using a unit for the amine treatment (denoted AMN) of said fumes, in which the catalytic cracking unit is equipped with an external exchanger using a portion of the catalyst removed from the regeneration zone as the hot fluid, the heat necessary to regenerate the amine in the amine treatment unit being integrally provided by the catalytic cracking unit by using the steam generated by said external exchanger.
In the context of the present invention, this external exchanger will be denoted (CCE).
Free Full Text Source: http://www.freepatentsonline.com/y2013/0152791.html

Process For Maximum Distillate Production From Fluid Catalytic Cracking Units (FCCU) (Stone & Webster Process Technology, Inc.)

CATEGORY: FCCU – FLUID CATALYTIC CRACKING UNIT
PATENT
Process For Maximum Distillate Production From Fluid Catalytic Cracking Units (FCCU) (Stone & Webster Process Technology, Inc.)
Pub. No.:
WO/2013/074775
International Application No.:
PCT/US2012/065257
Publication Date:
23.05.2013
Applicants:
Stone & Webster Process Technology, Inc. [US/US]; 1430 Enclave Parkway Houston, Texas 77077 (US)
Inventors:
GBORDZOE, Eusebius; (US).
BORIES, Marc; (FR).
LETZSCH, Warren Stewart; (US).
LEROY, Patrick; (FR).
SANTNER, Chris; (US).
ROSS, Joseph, L., Jr.; (US)
Abstract
The present invention provides an improved fluidized catalytic cracking process coupled with a two stage regeneration process in which the activity of the circulating catalyst is independently controlled for cracking hydrocarbon feedstocks or the vapors at low severity to produce maximum light cycle oil/distillate in one riser whilst cracking recycle streams comprising heavy cycle oil (HCO), light cracked naphtha (LCN) etc. in a second riser operating at high severity to produce LPG.
I. FIELD OF THE INVENTION
[0001] The present invention relates to a reactor for increasing or maximizing middle distillate production from hydrocarbon feedstocks. More specifically, the present invention is directed to a unique process and reactor system that increases or maximizes middle distillate, e.g. light cycle oil, production from hydrocarbon feedstocks.
II. BACKGROUND OF THE RELATED ART
[0002] It is common commercial practice to produce gasoline, heating oil and diesel fuel by cracking heavier petroleum fractions. One of the major commercial techniques for accomplishing this conversion is fluid catalytic cracking (FCC). In FCC, a feed petroleum fraction such as vacuum gas oil, heavy atmospheric gas oil, etc., is contacted with particles of hot, active catalyst at high temperatures and low pressures of about 1 to 5 atmospheres absolute in the absence of added hydrogen. The catalyst should be in sufficient quantity and at a sufficient temperature to vaporize the oil feed, raise the oil feed to a cracking temperature of about 900 to 1100 °F and supply the endothermic heat of reaction. The oil and catalyst flow together (concurrently) for a time sufficient to carry out the intended conversion.
During the conversion of the heavy petroleum fraction to lighter fractions, coke is laid down on the catalyst particles thereby deactivating them. These deactivated catalyst particles are separated from the cracked petroleum product, stripped of volatile hydrocarbons and transported to a separate regenerator. In the regenerator the coked catalyst is combined with an oxygen containing gas, e.g., air, whereby coke is burned off the catalyst and the catalyst is both reactivated and heated. The heated, reactivated catalyst is then returned into admixture with further heavy oil feed, thus completing the cycle. Typical FCC processes are described
in greater detail in U.S. Pat. Nos: 4,064,039; 4,344,926; 4, 194,965; 3,963,603; 4,428,822; and 3,879,281, incorporated herein by reference in their entirety.
[0003] A particularly successful approach, which significantly diminishes the problems associated with severe operating conditions including high temperatures, is described, for example, in U.S. Pat. Nos. 4,664,778; 4,601,814, 4,336, 160; 4,332,674 and 4,331,533. In such processes, a combination of high temperature fluidized catalytic cracking-regeneration operation is provided for the simultaneous conversion of both of the high and low boiling components contained in gas oils and residual oils with high selectivity to gasoline and lighter components, and with low coke production. These high temperature conversion processes have been made possible in part due to the use of two-stage catalyst regeneration processes. In the first stage of such regeneration processes, catalyst particles, which have hydrocarbonaceous materials such as coke deposited on them, are regenerated under conditions of oxygen concentration and temperature selected to particularly burn hydrogen associated with hydrocarbonaceous material. These conditions result in a residual level of carbon left on the catalyst and the production of a carbon monoxide (CO)-rich flue gas. This relatively mild first regeneration serves to limit local catalyst hot spots in the presence of steam formed during hydrogen combustion so that the formed steam will not substantially reduce the catalyst activity. A partially regenerated catalyst substantially free of hydrogen in the remaining coke and comprising residual carbon is thus recovered from the first regenerator stage and passed to a second stage higher temperature regenerator where the remaining carbon is substantially completely burned to CO2 at an elevated temperature up to 1500 °F. This second stage regeneration is conducted under conditions and in the presence of sufficient oxygen to burn substantially all residual carbon deposits and to produce CO2 -rich fluid gas.
[0004] The regenerated catalyst is withdrawn from the second stage and charged to the riser reactor at a desired elevated temperature and in an amount sufficient to result in substantially complete vaporization of the hydrocarbon feed. The catalyst particles are typically at a temperature above 1300 °F and often above 1400 °F, such that at the selected catalyst feed rate and hydrocarbon feed rate the vaporizable components of the hydrocarbon feed are substantially completely vaporized rapidly in the riser reactor whereby subsequent catalytic cracking of the feed is accomplished.
[0005] A schematic of an FCC unit employing this technology is shown in Fig. 1.
The unit consists of one riser reactor, a packed stripper and a multi-stage regenerator. The shown regenerator is a two-stage regenerator where the spent catalyst particles are passed, successively, to first and second (relatively lower and higher temperature) catalyst regeneration zones. Once the catalyst completes its cycle through the regenerator as described herein above, the fully regenerated catalyst is withdrawn from the second stage regenerator and charged to the riser reactor at a desired elevated temperature and in an amount sufficient to result in substantially complete vaporization of the hydrocarbon feed. The vaporized hydrocarbon feed upon contact with hot fully regenerated catalyst undergoes a catalytic cracking, while proceeding upward in the riser reactor. Once both vaporized catalytically cracked hydrocarbon products and the spent catalyst reach the stripper vessel, the spent catalyst is removed from the cracked products, directed to a stripper zone for removal of volatiles and then directed to the bottom section of the regenerator, thereby completing the FCC unit cycle.
[0006] As will be appreciated by those skilled in the art, while gasoline is usually the most valuable product of the FCC unit, other products can seasonally increase in value to the point where it is advantageous to increase their yields. For example, in winter the value of light cycle oil (LCO), when used as a blending component in heating oil, can be greater than that of gasoline. As will be appreciated by those skilled in the art, the above-described FCC processes have the potential capability for increasing selected product yields, for example, gasoline or light cycle oils (LCO)/distillate, from a given hydrocarbon feedstock. As an FCC unit operation is shifted from a gasoline producing mode, for example, into a maximum distillate producing mode or operation, the LCO yield and cetane quality thereof improves and, thus, can be used more favorably for blending to form, for example, a diesel fuel product. In another embodiment, such processes also have the potential capability of producing large yields of olefins, especially propylene and butylenes, for use as valuable alkylation gasoline charge stock, or in the manufacture of petrochemicals. Under such circumstances, it is therefore often desirable to operate the FCC processes in such a manner so as to increase or maximize the production of a given product or products depending on the demand.
[0007] One approach of increasing LCO yield is to reduce the FCC unit cracking severity so that conversion declines. At the lower conversion, yields of heavy products (light cycle oil, heavy cycle oil, and clarified oil) will increase while yields of light products (gasoline, LPG, and gas) and coke will decrease. The cracking severity can be reduced in several ways such as reducing catalyst activity, lowering riser reactor temperature, gas residence time, reducing the catalyst/oil ratio by increasing feed preheat temperature. In particular, it is known that LCO distillate yields can be increased by restricting riser outlet cracking temperature to within the range of about 870 °F to about 970 °F, and more particularly with the range of about 900 °F to about 950 °F. Alternatively, it is also known that the conversion can be controlled in FCC processes by the amount of hot regenerated catalyst cycled through the riser reactor in a given amount of time, e.g. catalyst-to-oil ratio.
Thus, LCO/distillate and other fuel products production is maximized as conversion of the hydrocarbon feedstock to gaseous product yield including C3/C4 olefins and lower boiling range material is decreased.
[0008] However, decreasing the catalyst-to-oil ratio or restricting the riser cracking outlet temperature in order to maximize LCO/distillate production is accompanied by several disadvantages. First, a lower catalyst-to-oil ratio decreases the rate of catalytic activity. Moreover, as the riser outlet temperature is decreased, the temperature in the riser feed zone or mixed zone also decreases, which might impair the feed vaporization, especially in the case of heavy feed processing. It is well known by those skilled in the art that Mixed Temperature Control (MTC) technology will help vaporize the feed by artificially increasing the riser mixed zone temperature in the feed zone without necessarily increasing the riser outlet temperature.
[0009] In another approach, a catalyst may be substituted that would allow the refiner to maintain the cracking severity as high as possible while maximizing LCO yield. Catalysts which contain an active matrix provide more cracking sites for the large hydrocarbon molecules typically found in heavy cycle oil and clarified oil. This greater matrix cracking activity, which is usually associated with high alumina content and a high surface area, allows such catalysts to upgrade bottoms to light cycle oil. While the catalytic route to maximizing LCO yield may be attractive, to change a catalyst in a commercial FCC unit can take several weeks or months to complete and makes this approach unpractical when LCO demand changes suddenly.
[0010] In yet another approach, the FCC unit feed may be fractionated to remove light ends in the LCO boiling range before subjecting the feed to the cracking process. The feed fractionation method of increasing light cycle oil, however, is prohibitively expensive if existing equipment cannot be used.
[0011] In view of the above, it is therefore an object of the present invention to provide a high temperature fluidized catalytic cracking-regeneration process wherein the production of a desired product or products from catalytic cracking of gas oils or residual oils or mixtures thereof and the like is maximized. More particularly, it is an object of this invention to provide such processes with flexibility to produce more distillates through manipulation of catalyst activity by using partially regenerated catalyst, cat-oil ratios, lower riser outlet temperature and the use of riser MTC to enhance feed vaporization.
[0012] It is a further object of the present invention to provide such processes as described above wherein the catalytic cracking process is carried out successively in separate riser reactors each independently operating under selected conditions.
[0013] Additional objects of the present invention will become apparent from the following summary and detailed discussion of preferred embodiments of this invention.
SUMMARY OF THE INVENTION
[0014] In accordance with the present invention, an improved fluidized catalytic cracking-regeneration process is provided wherein the desired product, such as middle distillate, is increased or maximized by selectively restricting the respective riser catalytic cracking activity to optimal or more preferable ranges by controlling the input of catalyst with desired micro- activity defined by the micro activity test (MAT) according to ASTM D-3907 and temperature from the multi-stage regenerator to achieve a desired rate of conversion of the feedstock. To this end, the desired selective catalytic cracking reactions can be accomplished by separately adjusting cracking conditions in separately maintained riser
reactors, wherein the catalyst within each riser reactor is provided by a shared multi-stage regenerator.
[0015] Accordingly, the present invention provides a method for maximizing middle distillate production and quality from a hydrocarbon feed, said method comprises:
a) delivering a partially-regenerated catalyst to a first riser reactor and a fully- regenerated catalyst to a second riser reactor and optionally to said first reactor;
b) cracking the first feed chosen between a hydrocarbon feed and a recycle feed comprising at least uncracked bottoms in the first riser reactor to produce a first cracked product and spent catalyst;
c) separating said first cracked product including a middle distillate from said spent catalyst in a single reactor vessel;
d) recovering said first cracked product including said middle distillate and separating uncracked bottoms from said first cracked product;
e) cracking the second feed chosen between the recycle feed or the hydrocarbon feed, but different from the first feed, in the second riser reactor to produce a second cracked product;
f) separating the second cracked product including a middle distillate from spent catalyst in said single reactor vessel; and
g) passing the spent catalyst from the first and second riser reactors to a multistage catalyst regenerator unit,
wherein said multi-stage catalyst regeneration unit provides said partially-regenerated catalyst and said fully-regenerated catalyst having different MAT activity for use in said first and/or said second riser reactors.
[0016] The multi-stage catalyst regenerator unit of the method comprises a single two-stage catalyst regenerator unit and the spent catalyst is partially regenerated in a first regeneration stage of said two-stage catalyst regenerator, a first portion of said partially-regenerated catalyst is delivered to the first riser reactor; a second portion of said partially-regenerated catalyst is delivered to a second regeneration stage of said two-stage catalyst regenerator, to produce fully regenerated catalyst, and said fully-regenerated catalyst is delivered to said second riser reactor and, optionally, to said first riser reactor.
[0017] Further, the present invention is directed to a hydrocarbon cracking system for maximizing middle distillate production and quality from a hydrocarbon feed comprising, a multistage-stage catalyst regeneration unit that provides partially-regenerated catalyst and/or fully-regenerated catalyst, respectively, to a first riser reactor and a second riser reactor, each receiving a different feed chosen between hydrocarbon feed and recycle feed, and a single reactor vessel to send coked catalyst to said regeneration unit, wherein the catalyst of said system has a different MAT activity in said partially-regenerated catalyst and said fully regenerated catalyst.
[0018] The system's multi-stage catalyst regenerator unit comprises a single two-stage catalyst regeneration unit having a first regeneration stage and a second regeneration stage and wherein the catalyst is a partially-regenerated catalyst at the exit of the first regeneration stage and a fully-regenerated catalyst at the exit of the second regeneration stage.
[0019] One advantage of the present invention is that it is possible to operate the
FCCU with the same catalyst with different catalyst MAT activities that is, partially regenerated catalyst in the feed to a first riser reactor (Rl) and fully regenerated catalyst is feed to a second riser reactor (R2), wherein the second riser reactor can be considered a recycle riser. As a result, the bottom products obtained from riser reactor (Rl) at the low MAT activity, will be easy to crack in the riser reactor (R2) using a higher MAT catalyst and at higher severity, i.e., operating conditions such as higher riser outlet temperature.
[0020] This FCCU configuration takes advantage of the flexibility offered by any multi-stage regenerator configuration, e.g., two-stage regenerator, where the carbon on regenerated catalyst (CRC) from the first regenerator (RG l) in partial burn conditions can be manipulated by adjusting the operating conditions, such as, combustion air flowrate. For a given catalyst type characterized by unit cell size, Figure 4 shows how the MAT activity will change for each 0.1 wt% change in the CRC. Another method for controlling the CRC and the temperature of the catalyst in the first regenerator (RGNl) is to recycle hot fully regenerated catalyst from the second regenerator (RGN2) to RGNl in order to add, at the desired proportion, hot regenerated catalyst to decrease the average CRC on the catalyst and increase RGNl temperature. Further in this regard, a catalyst cooler can be installed in the recycle line from RGN2 to RGNl to provide operational flexibility for decoupling the control of the average CRC and the average temperature of the catalyst in RGNl. Another option is to install the catalyst cooler either on RGNl or RGN2 vessel.
[0021] An object of the present invention is to operate the FCCU in a conversion region that maximizes LCO production and cetane index while minimizing slurry yield.
[0022] The process of the present invention will be better understood by reference to the following detailed discussion of preferred embodiments and the attached FIGURES which illustrate and exemplify such embodiments. It is to be understood, however, that such illustrated embodiments are not intended to restrict the present invention since many more modifications may be made within the scope of the claims without departing from the spirit thereof.
Free Full Text Source: http://patentscope.wipo.int/search/en/WO2013074775

Catalyst stripper improves FCC unit performance

CATEGORY: FCCU – FLUID CATALYTIC CRACKING UNIT
PTQ - Petroleum Technology Quarterly, Q3 2012
Catalyst stripper improves FCC unit performance
Stripper internals with improved mass transfer characteristics improve the performance of an FCC unit
Rama Rao Marri and Dalip Soni
Lummus Technology, a CB&I Company
FCC unit performance is dictated by a delicate coke and heat balance1,2 because the reactor produces the necessary amount of coke to satisfy the unit heat balance. The heat produced by the combustion of coke in the regenerator supplies the required heat (via circulating catalyst) for the endothermic riser-reactor.
The coke is classified into four types: contaminant coke, catalytic coke, additive coke and catalyst-to-oil coke. Generally, catalytic, contaminant and additive coke production are functions of feed quality, catalyst type and reactor operating temperature. However, catalyst-to-oil coke is a result of the hydrocarbons entrained within the spent catalyst as it enters the regenerator.
This coke includes hydrocarbons absorbed on the catalyst surface and within the catalyst pores. It is very important to strip off these hydrocarbons (coke precursors) by employing an efficient stripper. Removal of these hydrocarbons from the catalyst before it enters the regenerator can significantly improve over-all performance and hence profitability of the FCC unit.
This article discusses the design and implementation of Lummus Technology’s patented ModGrid stripper and the improvements achieved in commercial FCC units.
Free Full Text Source: http://www.cbi-nv.com/images/uploads/technical_articles/Catalyst_Stripper_improves_FCC_unit_performance_-_PTQ_3Q12.pdf

Effect of feedstock properties on the performance of ZSM-5 additive in catalytic cracking reaction

CATEGORY: FCCU – FLUID CATALYTIC CRACKING UNIT
PetroVietnam Journal Vol. 10 (2012) pp. 59-64
Effect of feedstock properties on the performance of ZSM-5 additive in catalytic cracking reaction
Dang Thanh Tung, Ngo Thuy Phuong, Tran Van Tri, Nguyen Sura
Nguyen Huu Trung, Dao Thi Thanh Xuan, Nguyen Hoai Thu,
Vietnam Petroleum Institute
Abstract
In this study, authors present recent laboratory experimental results regarding the application of ZSM-5 additive in catalytic cracking reactions.  Results show that the nature of feedstock significantly influences the performance of ZSM-5. For paraffinic feedstock, ZSM-5 additive not only increases propylene yield and gasoline octane but also improves the bottom cracking ability of Fluid Catalytic Cracking (FCC) catalysts.
The conversion of paraffinic feedstock could increase up to 10wt% while that of aromatic feedstock remains almost unchanged upon the addition of ZSM-5 additive to the FCC catalyst. Mixing 5wt% of ZSM-5 additive with the FCC catalyst also results in increased propylene yields of 13wt% and 8wt% for paraffinic and aromatic feedstock, respectively.  These results can serve as guidance for refineries to flexibly control product yields by adjusting the processed feedstock or the amount of ZSM-5 additive used in the FCC unit.
Free Full Text Source: http://www.vpi.pvn.vn/upload/file/TapChiDauKhi/DTTung-so%2010.pdf

Reduced elevation catalyst return line for a fluid catalytic cracking unit

CATEGORY: FCCU - FLUID CATALYTIC CRACKING UNIT
PATENT
Reduced elevation catalyst return line for a fluid catalytic cracking unit
Patent number: 8202412
Issue date: Jun 19, 2012
Application number: 11/879,259
Inventors: Brian A. Cunningham, Christopher G. Smalley, Rathna P. Davuluri, Dana W. Nouri
Original Assignee: ExxonMobil Research and Engineering Company
The present invention is an improved regenerated catalyst bend assembly for a fluid catalytic cracking unit. In a preferred embodiment, the reduced elevation (“RE-bend” or “REL-bend”) regenerated catalyst return line assembly of the present invention has an outlet elevation that is lower than the inlet elevation of the RE-bend or REL-bend regenerated catalyst return line assembly, and a process for utilizing the assembly in a fluid catalytic cracking unit. The present invention is especially useful in the modification of existing fluid catalytic cracking units to lower the elevation of the outlet of the regenerated catalyst return line assembly, thereby providing needed space to increase the fluid catalytic cracking reactor riser length.
FIELD OF THE INVENTION
 
This invention relates to the fluid catalytic cracking of a hydrocarbon feed. In particular, this invention relates to an improved design for a catalyst return line for returning regenerated catalyst from the regenerator of a fluid catalytic cracking unit to the riser of a fluid catalytic cracking unit and a process for using the catalyst return line in a fluid catalytic cracking unit.
 
BACKGROUND OF THE INVENTION
 
Conversion of high molecular Weight petroleum feeds to more valuable products by catalytic processes such as fluidized catalytic cracking is important to petroleum processes. In the fluidized catalytic cracking process, higher molecular Weight feeds are contacted With fluidized catalyst particles in the riser reactor of the fluidized catalytic cracking unit. The contacting betWeen feed and catalyst is controlled according to the type of product desired. In catalytic cracking of the feed, reactor conditions such as temperature and contact time are controlled to maximize the products desired and minimize the formation of less desirable products such as light gases and coke.
 
Miscellaneous fluidized catalytic cracking reactor riser and reactor vessel designs have been utilized in the past. HoWever, With the advance of zeolitic cracking catalysts With greatly improved cracking activity, most modern fluidized catalytic cracking reactors utilize a short-contact time cracking configuration in Which the amount of time that the catalyst and the fluidized catalytic cracker feedstream are in contact is limited in order to minimize the amount of excessive cracking Which results in the increased production of less valued products such as light hydrocarbon gases as Well as increased coking deposition on the cracking catalysts. Most short-contact time fluidized catalytic cracking configurations utilize a reactor riser cracking configuration Wherein the catalyst is contacted With the fluidized catalytic cracker feedstock in a reactor riser, and the catalyst and the hydrocarbon reaction products are separated shortly after the catalyst and hydrocarbon mixture leaves the reactor riser and enters the fluidized catalytic cracking reactor. Although there are many different fluidized catalytic cracking reactor designs in use, most use mechanical cyclones internal to the reactor to separate the catalyst from the hydrocarbon reactor products as quickly and efliciently as possible. This rapid separation process has the benefits of both minimizing post-riser reactions betWeen the catalyst and the hydrocarbons as Well as providing a physical means for separating the products to be sent for further processing from the spent catalyst Which is sent to a regenerator stage prior to reintroducing as regenerated catalyst back into the reaction process.
 
These significant improvements in catalyst technology have led to most conventional fluidized catalytic cracking reactors being designed for short contact time processes. That is, it is desired that cracking reactions be significantly limited to the reaction in the reactor riser folloWed by a very fast separation of hydrocarbons from the catalysts in order to prevent unWanted reactions or “over cracking” of the hydrocarbon feedstocks and/ or reaction products. Therefore, most modern fluidized catalytic cracking units incorporate a quick hydrocarbon/catalyst separation mechanism after the hydrocarbon/catalyst stream leaves the reactor riser. Mechanical

cyclones, as discussed above, are generally the most common method utilized for making the bulk of the catalyst/oil separation in the fluidized catalytic cracking processes.
 
HoWever, even With these improved catalysts, in some instances it may desirable to design a fluidized catalytic cracking reactor riser With an increased overall length or extend the length of an existing reactor riser. Especially in the case of an existing reactor fluidized catalytic cracking unit, it may be beneficial extend the length of an existing reactor riser to either 1) increase the amount of reaction time in the reactor riser, and/ or 2) increase the velocity in the reactor riser While still maintaining a similar overall riser reaction time. Other reasons for desiring to extend the reactor riser may be to incorporate larger feed zones into the reactor riser featuring improved injection and contact zone designs, or adding additional hardWare or auxiliary equipment associated With the lift gas injection or the feed zone.
 
HoWever, especially in the case of an existing reactor riser, it may be diflicult to extend the length of an existing reactor riser due to the existing return bend assembly configurations. Typically, these existing catalyst return line assembly configurations are either a “U-bend” configuration or a “J-bend” configuration. A U-bend is typically a 180° inclusive angle bend of constant radius connecting the regenerated catalyst return line With the reactor riser. Since the bend is essentially 180° in curvature With a constant bend radius, the top of each end of the U-bend in substantially at the same elevation in a fluidized catalytic cracking unit. In contrast, the elevation of the outlet of the J-bend assembly is higher than the inlet of the J-bend assembly by using a combination of tWo bends of differing inclusive bend radii separated by a section of straight pipe connecting the tWo bends.
 
U-bend and J-bend fluidized catalytic cracking unit catalyst return line configurations are illustrated in U.S. Pat. Nos. 3,923,642 to Luckenbach et al.; 5,171,423 to Kruse; 5,175, 943 to Eastham et al.; 5,552,119 to Holmes; 5,554,341 to Wells et al.; 5,846,403 to SWan et al.; and 6,610,255 to Cao et al. These U-bend and J-bend fluidized catalytic cracking unit catalyst return line configurations have been used extensively for many years in the industry.
 
In some existing fluidized catalytic cracking units, it may be easier to increase the length of the reactor riser if the regenerated catalyst return line assembly is of the J-bend configuration rather than the U-bend configuration, since it may be easier to increase the length of the reactor riser by changing the bend angles and straight line offset length or angle. HoWever, increasing the acuteness of the bend angles in the J-bend assembly to increase the reactor riser length can impart an increase pressure drop in the return bend/reactor riser circuit thereby resulting in detrimental effects on the fluidized catalytic cracking system capacity and performance.
 
Retrofitting a U-bend regenerated catalyst return line configuration to increase the reactor riser length can be even more problematic. In order to increase the reactor riser length Without extending the regenerator standpipe, the bend radius of the U-bend assembly must be decreased. Decreasing the radius of the U-bend assembly results in tWo problems. First, the decreased radius U-bend noW has an overall shorter span and thus the tWo ends of the U-bend cannot align With both the regenerator standpipe and the reactor riser. Secondly, even if either the regenerator standpipe or the reactor riser can be relocated to fit up With the shorter radius U-bend, the pres sure drop in the neW shorter radius U-bend Will typically be greater than the original longer radius U-bend.

Additionally, especially in the case of modifying existing FCC units, desired changes in the length of reactor risers may result in interferences With existing equipment and transfer lines.
 
Therefore, there exists a need in the industry for a regenerated catalyst bend assembly With differing configuration characteristics that can improve the ease of installation especially When retrofitting existing units. It is even more desired that this neW regenerated catalyst bend assembly alloW reactor risers of increased length to be installed Without increasing the overall pres sure drop across the overall catalyst return line bend/reactor riser as compared With a bend assembly of the prior art.
 
SUMMARY OF THE INVENTION
A preferred embodiment of the present invention is an improved regenerated catalyst bend assembly for a fluid catalytic cracking unit. In a preferred embodiment, the reduced elevation (“RE-bend” or “REL-bend”) regenerated catalyst return line assembly of the present invention has an outlet elevation that is loWer than the inlet elevation of the RE-bend or REL-bend regenerated catalyst return line assembly. Another preferred embodiment of the present invention is a process for catalytically cracking a hydrocarbon feedstream utilizing the regenerated catalyst bend assembly of the present invention. The present invention is especially useful in the modification of existing fluid catalytic cracking units to loWer the elevation of the outlet of the regenerated catalyst return line assembly, thereby providing needed space to increase the fluid catalytic cracking reactor riser length.
 
One preferred embodiment of the present invention is a regenerated catalyst conduit for fluidly connecting a regenerator standpipe to a reactor riser of a fluid catalytic cracking unit, comprising:
 
a) a first bend With a bend radius, R1, and an inlet end and an outlet end; and
 
b) a second bend With a bend radius, R2, and an inlet end and an outlet end;
 
Wherein the inlet end of the first bend is physically connected to the outlet end of the regenerator standpipe, the outlet end of the first bend is physically connected to the inlet end of the second bend, the outlet end of the second bend is physically connected to the inlet end of the reactor riser, and R1 is not equal to R2.
 
In another preferred embodiment of the regenerated catalyst conduit of the present invention, the outlet end of second bend is at a loWer elevation than the inlet end of the first bend. In a more preferred embodiment, the first bend radius, R1, is greater than the second bend radius, R2. In an even more preferred embodiment, the internal angle of the first bend, 011, is greater than the internal angle of the second bend, 012.
Free Full Text Source: http://www.google.com/patents/US8202412?dq=cracking+refinery

Modelling and Optimization of Fluid Catalytic Cracking Unit (FCCU) Using Hysys

CATEGORY: FCCU – FLUID CATALYTIC CRACKING UNIT
International Journal of Emerging trends in Engineering and Development, Issue 2, Vol.3 (April-2012)
Modelling and Optimization of Fluid Catalytic Cracking Unit (FCCU) Using Hysys
Olabode Yusuf Raji*, Usman Aliyu El-Nafaty, Mohammed Jibril, Baba Yahya Danjuma
bode2000eh@gmail.com
elnafaty@yahoo.com
jibrilmuhammad@yahoo.com
ydbdanjuma@yahoo.com
Chemical Engineering Programme, Abubakar Tafawa Balewa University, Bauchi, P. M. B. 0248, Bauchi-Nigeria
ABSTRACT
The aim of this study is to obtain a computer based model that can simulate and optimize the performance of an existing industrial fluid catalytic cracking (FCC) unit in steady state. The objective of this unit is to convert residues into high added value products (Fuel gas and Gasoline).
The cracking reactions in the riser reactor occur in a transported bed with the fluid (nC25) and the solids catalyst (Magnesiev-370) in regenerator flow under operating conditions. One of the main advantages of this model is that it uses HYSYS software that is robust, flexible and versatile. This model is particularly suitable for control studies that facilitate good performance of FCC. To simulate the FCC, the model was based on these products: gas oil, flue gas, gasoline (C5+) and bottom oil and thus has been developed based on operational data of FCC. The simulation studies were performed to optimize the unit by manipulating various process variables such as the molar flow rate of recycle bottom oil and reflux ratio, which were subject to constraint Reid Vapor Pressure (RVP) of gasoline. The objective function was to maximize net profit of the desired products. The net profit calculation was done successfully upon applying the Sequential Quadratic Programming (SQP) method to optimize the process, the results show tremendous improvement from N21.521Trillion to N25.214 Trillion, about 17.16% increase and reflux ratio showed an inverse proportionality with respect to net profit while both desired products showed good performance outputs.
Free Full Text Source: http://rspublication.com/ijeted/ijeted%20april%2012/1.pdf