Fluid catalytic cracking process and apparatus

Abstract

Provided herein are apparatuses and methods for converting a hydrocarbon feed to light olefins and other hydrocarbons. The methods and apparatuses include a conventional riser reactor combined with a mixed flow (e.g., including both countercurrent and co-current catalyst flow) fluidized bed reactor that is designed for maximizing light olefin production. Effluent from the riser reactor and the mixed flow reactor are processed in a catalyst disengagement vessel, and catalyst used in each reactor can be regenerated in a common catalyst regeneration vessel. Furthermore, integration of the dual reactor scheme with a catalyst cooler provides flexibility for an oil refinery to switch between operating with a dual reactor flow scheme, a catalyst cooler only flow scheme, or both simultaneously.

Description

TECHNICAL FIELD

[0001] Embodiments herein generally relate to systems and methods for improving the productivity and / or flexibility of hydrocarbon processing using a hybrid catalyst system. Some embodiments disclosed herein relate to a fluid catalytic cracking system that allows for flexibility in the operation of the equipment in which the hydrocarbon feedstock is converted, such as for converting vacuum gas oil and / or heavy oil residue into very high yields of light olefins such as propylene and ethylene, aromatics, and high octane gasoline. BACKGROUND

[0002] In recent years, the production of light olefins through the fluid catalytic cracking (FCC) process has been considered one of the most attractive propositions. In addition, there is an increasing demand for petrochemical product building blocks such as propylene, ethylene, and aromatics (benzene, toluene, xylene, etc.). Furthermore, the integration of a refinery with a petrochemical complex has become a preferred option for both economic and environmental reasons.

[0003] Global trends also show an increase in the demand for middle distillates (diesel) compared to gasoline products. In order to maximize middle distillates from the FCC process, it is necessary to operate the FCC at lower reactor temperatures and different catalyst formulations. The downside of this change is a decrease in light olefin yields due to the FCC unit operating at much lower reactor temperatures. This will also reduce the feedstock for alkylation units.

[0004] Several fluid bed catalytic processes have been developed over the past two decades to adapt to the changing market demands. For example, US 7479218 discloses a fluid catalytic reactor system in which the riser-reactor is divided into two sections of different radii to improve the selectivity for light olefin production. The first section of the riser-reactor with the smaller radius is used to crack heavy feed molecules into naphtha boiling range products. The increased radius section, the second section of the riser-reactor, is used to further crack the naphtha boiling range products into light olefins such as propylene, ethylene, etc. While the concept of the reactor system is fairly simple, the degree of selectivity for light olefins is limited due to the following reasons: (1) the naphtha boiling range feed stream is in contact with partially coked or deactivated catalyst; (2) the temperature in the second section of the reaction section is much lower than the first region due to the endothermic nature of the reactions in both sections; and (3) the lack of high activation energy required for the cracking of light feed molecules compared to heavy hydrocarbons.

[0005] Other patents and publications related to fluid catalytic cracking units can include US6106697, US7128827, and US7323099, US7658837, US2007 / 0205139, WO2010 / 067379, US6869521, US7611622, US5944982, US20060231461, US6149875, and US7381322, among others.

[0006] Various patents also discuss limitations of FCC units, noting that the capacity of an FCC unit can be limited by the regenerator operating at temperatures close to the metallurgical design limit. Hot regenerated catalyst can be cooled in a "catalyst cooler" by generating steam (for example), or by performing an endothermic reaction such as dehydrogenation of an alkane. Various patents discussing catalyst cooler operation can include EP0325437, EP0197486, US4923834, and US4374750, among others. SUMMARY

[0007] It has been discovered that a dual reactor scheme can be used to crack hydrocarbons, including cracking C4, lighter C5 fractions, naphtha fractions, methanol, and the like to produce light olefins, where the dual reactor scheme has no limitations on selectivity and operability, meets thermal balance requirements, and also maintains a low parts count. It has also been discovered that by integrating the dual reactor scheme of the embodiments herein with a catalyst cooler, flexibility in plant operation can be obtained.

[0008] The selected embodiments disclosed herein use a conventional riser reactor in combination with a mixed flow (for example, including both countercurrent and concurrent catalyst flow) fluidized bed reactor designed for maximizing light olefin production. Effluent from the riser and mixed flow reactors are processed in a common catalyst disengaging vessel, and catalyst used in each riser and mixed flow reactor can be regenerated in a common catalyst regeneration vessel. This flow scheme is effective for maintaining high cracking activity, overcomes thermal balance issues, and also improves the yield and selectivity of light olefins from various hydrocarbon streams, and also simplifies product quenching and unit equipment, as will be described in greater detail below. In addition, integration of the dual reactor scheme with a catalyst cooler provides flexibility for a refinery to switch between operating with the dual reactor flow scheme, a catalyst cooler only flow scheme, or both simultaneously.

[0009] In an aspect, the embodiments disclosed herein relate to a system for processing hydrocarbons. The system can include a riser reactor configured to contact a mixture of first particles and second particles with a hydrocarbon feedstock to convert at least a portion of the hydrocarbon feedstock and recover a riser reactor effluent comprising a mixture of hydrocarbons and the first and second particles. The first particles can have a smaller average particle size and / or a lower density than the second particles. Further, the first particles and the second particles can independently be catalytic or non-catalytic particles. The system can also include a reactor configured to contact the mixture comprising the first particles and the second particles with a second hydrocarbon feedstock to convert at least a portion of the second hydrocarbon feedstock. The reactor can be fluidly connected with a overhead product line for recovering from the reactor a reactor effluent comprising the first particles, a first portion of the second particles, and the hydrocarbons; a bottoms product line for recovering from the reactor a second stream comprising a second portion of the second particles. A particle separator can be configured to separate the second particles from the reactor effluent and produce a hydrocarbon effluent comprising the hydrocarbons and the first particles and the second stream comprising the separated second particles. A feed line for returning the separated second particles from the particle separator to the reactor can be provided. A separation system can be configured to receive the hydrocarbon effluent and the riser reactor effluent and perform the following separations: (i) separating the first particles from the hydrocarbons in the hydrocarbon effluent and (ii) separating the mixture of the first and second particles from the mixture of hydrocarbons in the riser reactor effluent, producing (a) a combined hydrocarbon effluent stream and (b) a mixture of the first and second particles. The system can also include a regenerator for regenerating the mixture of the first and second particles recovered in the separation system. Further, the system can include a particle cooler configured to alternately, intermittently, or simultaneously exchange heat between (i) hot regenerated particles comprising the mixture of the first and second particles from the catalyst regenerator and (ii) the second catalyst particles recovered through the bottoms product line. Further, a flow line for recovering the cooled particles from the particle cooler and feeding the cooled particles to the regenerator can be provided.

[0010] In another aspect, embodiments disclosed herein relate to a method for converting hydrocarbons. The method can include feeding a hydrocarbon feedstock and a mixture of first particles and second particles to a riser reactor. The first particles can have a smaller average particle size and / or a lower density than the second particles, and the first and second particles can independently be catalyzed or non-catalyzed particles. The mixture of first and second particles can be contacted with a second hydrocarbon feedstock to crack the hydrocarbon feedstock and form a riser reactor effluent comprising the hydrocarbons and the mixture of first and second particles. The riser reactor effluent can be fed to a separator to separate the first and second particles from the hydrocarbons, thereby recovering a hydrocarbon product from the separator. The separated first and second particles can be fed to a regenerator to regenerate the first and second particles. During a first time period, regenerated first and second particles from the regenerator can be fed to a reactor. A hydrocarbon feedstock can also be fed to the reactor. In the reactor, the hydrocarbon feedstock can be contacted with the regenerated first and second particles, and a top product is recovered from the reactor, the top product comprising a cracked hydrocarbon effluent, at least a portion of the second particles, and the first particles. The second particles can be separated from the top product to provide a first stream comprising the first particles and the cracked hydrocarbon effluent and a second stream comprising the separated second particles. The first stream can be fed to the separator. The separated second particles in the second stream can be returned to the reactor. During a second time period, regenerated first and second particles from the regenerator can be fed to a particle cooler. In the particle cooler, heat exchange can occur between a heat exchange medium and the regenerated first and second particles, and cooled particles are recovered from the particle cooler and fed to the regenerator.

[0011] Other aspects and advantages will be apparent from the following description and the appended claims. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a simplified process flow diagram of a system for cracking hydrocarbons and producing light olefins according to one or more embodiments disclosed herein.

[0013] Figure 2 is a simplified process flow diagram of a system for cracking hydrocarbons and producing light olefins according to one or more embodiments disclosed herein.

[0014] Figures 3-6 is a simplified process flow diagram of a separator for use in a system according to one or more embodiments disclosed herein. DETAILED DESCRIPTION

[0015] As used herein, the terms "catalyst" and "particulate" and similar terms can be used interchangeably. In summary, and as further described below, embodiments herein are based on the separation of mixed particulate materials by size and / or density to achieve advantageous effects in a reactor system. Particles or particulate materials used to promote catalytic or thermal reactions can include, for example, catalysts, absorbents, and / or heat transfer materials that do not have catalytic activity.

[0016] In an aspect, embodiments herein relate to fluid catalytic cracking units and processes for flexibly converting hydrocarbon feedstocks, such as light hydrocarbons (ethane, propane, butane), medium hydrocarbons (e.g., C5-C9 hydrocarbons), and for converting heavy hydrocarbon feeds (such as vacuum gas oil and / or heavy oil resid). The systems and processes herein can produce very high yields of light olefins (such as propylene and ethylene), aromatics, and gasoline or middle distillate with high octane, while minimizing the yield of heavier products. To achieve this goal, the secondary reactor can be a mixed flow reactor (including, in some embodiments, both co-current flow of particles relative to vapor flow and counter-current flow) or a catalyst concentration reactor or a particle concentration reactor (selectively removing smaller or lower density portions of mixed particles / catalyst) that can be integrated with a conventional fluid catalytic cracking reactor, such as a riser reactor.

[0017] Heavy hydrocarbon feeds are catalytically cracked in a riser reactor, which is a gas flow co-current type reactor, into naphtha, middle distillate, and light olefins. To improve the yield and selectivity of light olefins (ethylene and propylene), cracked hydrocarbon products from the riser reactor, such as C4 and naphtha boiling range hydrocarbons (olefins and paraffins), can be processed in a secondary reactor (mixed flow reactor or concentration reactor). Alternatively or additionally, external feed streams, such as C4, naphtha, or other hydrocarbon fractions from other processes such as a steam cracker, a metathesis reactor, or a delayed coking unit, and naphtha boiling range streams, such as straight run naphtha or from delayed coking, visbreaking, or natural gas condensate, as well as other hydrocarbon feedstocks, can be processed in the secondary reactor to produce light olefins such as ethylene and propylene. Integration of the secondary reactor according to embodiments disclosed herein with a conventional FCC riser reactor can overcome the shortcomings of existing processes, can substantially improve the overall conversion and light olefin yield, and / or can improve the ability to process heavier feedstocks.

[0018] The integration of the secondary reactor according to the embodiments disclosed herein with a conventional FCC riser reactor can be facilitated by (a) the use of a common regeneration vessel, (b) the use of two types of catalyst, one selective for cracking heavier hydrocarbons and the other selective for cracking C4 and naphtha boiling range hydrocarbons for light olefin production, and (c) the use of a mixed flow reactor or a concentration reactor whose flow regime will partially separate the two types of catalyst, favoring the contact of C4 or naphtha feed with the catalyst selective for cracking these feeds and producing light olefins.

[0019] To improve the operating window of the secondary reactor and provide greater process flexibility, the secondary reactor can be operated in a flow regime to entrain catalyst selective for cracking heavier hydrocarbons and to entrain a portion of the catalyst selective for cracking C4 and naphtha boiling range hydrocarbons. The cracked hydrocarbon products and entrained catalyst are then fed to a separator to separate the catalyst selective for cracking C4 and naphtha boiling range hydrocarbons from the cracked hydrocarbon products and catalyst selective for cracking heavier hydrocarbons. This solids separation vessel is an external vessel to the reactor and is operated under a flow regime that enhances its separation based on the physical properties of the two types of catalyst, such as particle size and / or density. The separated catalyst selective for cracking C4 and naphtha boiling range hydrocarbons can then be returned to the reactor to continue the reaction and provide an enhanced concentration of catalyst selective for cracking C4 and naphtha boiling range hydrocarbons within the reactor, improving the selectivity of the overall process while also improving the flexibility of the overall process due to the enhanced operating window.

[0020] The availability of feedstocks, the demand for specific products or mixtures of products, and maintenance requirements can require further process flexibility. The system herein additionally provides a particle or catalyst cooler that can be fluidly connected to both the regeneration vessel and the secondary reactor. A flow control system and associated valves can be provided to selectively direct the flow of (a) mixed particles from the regenerator to the particle cooler, (b) mixed particles from the regenerator to the reactor, and / or (c) larger or denser particles from the secondary reactor to the particle cooler. The particle cooler can intermittently or simultaneously exchange heat between (i) hot regenerated particles from the catalyst regenerator and (ii) larger or denser particles recovered from the secondary reactor. The resulting cooled particles or cooled catalyst can then be fed to the regenerator. The cooled particles from the particle cooler can help to cool and control the regeneration temperature occurring in the regenerator, thereby helping to maintain the regenerator at operating temperatures well below the metallurgical design limits.

[0021] As described above, the cracking system can use two types of catalysts, each of which is beneficial for different types of hydrocarbon feed. The first cracking catalyst can be a Y-type zeolite catalyst, an FCC catalyst, or other similar catalysts that can be used to crack heavier hydrocarbon feedstocks. The second cracking catalyst can be a ZSM-5 or ZSM-11 type catalyst or similar catalysts that can be used to crack C4 or naphtha boiling range hydrocarbons and selectively produce light olefins. To facilitate the dual reactor scheme disclosed herein, the first cracking catalyst can have a first average particle size and density, and can be smaller and / or lighter than the particles used for the second cracking catalyst, such that the catalysts can be separated based on density and / or size (e.g., based on the terminal velocity or other characteristics of the catalyst particles).

[0022] In the catalyst regeneration vessel, spent catalyst recovered from both the riser reactor and the secondary reactor is regenerated. After regeneration, a first portion of the mixed catalyst from the regeneration vessel can be fed to the riser reactor (co-current flow reactor). A second portion of the mixed catalyst from the regeneration vessel can be fed to either or both of the secondary reactor or the particle cooler.

[0023] In the co-current flow (riser) reactor, the first hydrocarbon feed can be contacted with the first portion of the regenerated catalyst to crack at least a portion of the hydrocarbons to form lighter hydrocarbons. An effluent including a first cracked hydrocarbon product and a spent mixed catalyst fraction can then be recovered from the co-current flow reactor.

[0024] In use, the secondary reactor can be operated at a fluidization state sufficient to entrain the first cracking catalyst and the second cracking catalyst, while a hydrocarbon product is recovered as an effluent from a top outlet of the secondary reactor. In other embodiments, the secondary reactor is operated at a fluidization state sufficient to entrain the first cracking catalyst and a portion of the second cracking catalyst, while a hydrocarbon product is recovered as an effluent from a top outlet of the secondary reactor. The effluent is then fed to a separator to separate the cracked hydrocarbon product and the first cracking catalyst from the second cracking catalyst. The vapor / first cracking catalyst stream recovered from the separator can then be routed for separation. As described above, the second cracking catalyst recovered from the separator can be recycled back to the secondary reactor to continue the reaction.

[0025] Both the first effluent (cracked hydrocarbons and spent mixed catalyst from the riser reactor) and the second effluent (cracked hydrocarbons and separated first cracking catalyst from the secondary reactor) can be fed to a disengagement vessel to separate the spent mixed catalyst fraction and the first cracking catalyst from the separated first and second cracked hydrocarbon products. The cracked hydrocarbon products (including light olefins, C4 hydrocarbons, naphtha boiling range hydrocarbons, and heavier hydrocarbons) can then be separated to recover the desired products or product fractions.

[0026] In use, the particle cooler can receive hot mixed particles from the regenerator and / or larger or denser particles from the secondary reactor. For example, the particles can be fed through heat exchange tubes, while a heat exchange medium, such as air, water, steam, heat exchange oil, or a hydrocarbon feedstock to be preheated, can pass through and across the heat exchange tubes, exchanging heat with the particles. In some embodiments, the particle cooler can be a screw baffle heat exchanger. Other types of particle coolers or catalyst coolers can also be used. After cooling, the particles can be returned to the regenerator to help maintain the temperature of the contents of the regenerator, as described above.

[0027] Accordingly, the processes disclosed herein integrate a secondary mixed flow or catalyst concentration reactor, an external solids separator, a particle cooler, and a riser reactor with common product separation and regeneration, where catalyst or particles concentrated in the secondary reactor can be used highly selectively to crack C4 and naphtha boiling range hydrocarbons to produce light olefins. Common regeneration provides a heat balance, and common product separation (decoupling vessels, etc.) provides the advantages of simple operation and reduced part count, among others. Further, switching operation to use only the particle cooler, only the secondary reactor, or both simultaneously provides flexibility in process operation.

[0028] Referring now to Figure 1 , a simplified process flow diagram of a system for cracking hydrocarbons and producing light olefins according to embodiments disclosed herein is illustrated. The system includes a dual reactor configuration for maximizing the yield of propylene and ethylene from petroleum residuum feedstocks or other hydrocarbon streams. For example, a first reactor 3 can be a riser reactor for cracking a heavier hydrocarbon feed. A second reactor 32 is a fluidized bed reactor, which can be equipped with baffles or internal members. C4 olefins and / or light naphtha products from the first reactor 3 or similar feed streams from external sources can be processed in the second reactor 32 to increase the yield of light olefins, including propylene and ethylene, as well as aromatics / high octane gasoline.

[0029] The heavy petroleum residue feed is injected through one or more feed injectors 2 located near the bottom of the first reactor 3. The heavy petroleum feed contacts hot regenerated catalyst introduced through the J-bend 1. The catalyst fed to the first reactor 3 is a catalyst mixture including a first catalyst selective for cracking heavier hydrocarbons, such as a Y-type zeolite based catalyst, and a second catalyst selective for cracking C4and naphtha boiling range hydrocarbons to produce light olefins, such as ZSM-5 or ZSM-11, which can also be used in combination with other catalysts. One or both of the particle size and density of the first and second catalysts can be different. The first catalyst, such as a Y-type based zeolite, can have a particle size in the range of 20 to 200 microns and an apparent bulk density in the range of 0.60 to 1.0 g / ml. The second catalyst, such as ZSM-5 or ZSM-11, can have a particle size in the range of 20 to 350 microns and an apparent bulk density in the range of 0.7 to 1.2 g / ml. (Although Figure 1 The operation of the described system is related to catalyst, but non-catalytic particulates can also be used to provide thermal cracking of the feedstock.

[0030] The heat for vaporization of the feed and / or raising the temperature of the feed to the desired reactor temperature, such as in the range of 500°C to about 700°C, and for the heat of endotherm (heat of reaction) can be provided by the hot regenerated catalyst from the regenerator 17. The pressure in the first reactor 3 is typically in the range of about 1 barg to about 5 barg.

[0031] After the major portion of the cracking reaction is complete, the mixture of products, unconverted feed vapors, and spent catalyst flows into a two-stage cyclone system housed in a cyclone enclosure 8. The two-stage cyclone system includes a primary cyclone separator 4 for separating the spent catalyst from the vapors. The spent catalyst is discharged through a primary cyclone dipleg (or leg) 5 into a stripper 9. Fine catalyst particles entrained with separated vapors from the primary cyclone separator 4 and product vapors introduced from the second reactor 32 through outlet line 36a and single-stage cyclone separator 36c are separated in a secondary cyclone separator 6. The collected catalyst mixture is discharged through a dipleg 7 into the stripper 9. Vapors from the secondary cyclone separator 6 are discharged through a secondary cyclone separator outlet 12b that can be connected to a plenum 11 and then sent to a main fractionator / gas plant (not shown) for recovery of products, including the desired olefins. If necessary, the product vapors are further cooled by introducing light cycle oil (LCO) or steam as a quench medium through a distributor line 12a.

[0032] The spent catalyst recovered through the diplegs 5, 7 is subjected to stripping in the stripping column 9 to remove interstitial vapors (hydrocarbon vapors trapped in the pores of the catalyst particles) by countercurrent contact with steam introduced through the steam distributor 10 into the bottom of the stripping column 9. The spent catalyst is then transferred through the spent catalyst standpipe 13a and the first lift line 15 to the regenerator 17. A spent catalyst slide valve 13b located on the spent catalyst standpipe 13a is used to control the flow of catalyst from the stripping column 9 to the regenerator 17. A small portion of combustion air or nitrogen can be introduced through the first distributor 14 to assist in the smooth transfer of the spent catalyst.

[0033] The coked or spent catalyst from the first lift line 15 is discharged through the spent catalyst distributor 16 into the dense regenerator bed 24. Combustion air is introduced by the air distributor 18 located at the bottom of the regenerator bed 24. The coke deposited on the catalyst is then burned off in the regenerator 17 by reaction with the combustion air. For example, the regenerator 17 can be operated at a temperature in the range of about 640 °C to about 750 °C and at a pressure in the range of about 1 barg to about 5 barg. Catalyst fines entrained with the flue gas are collected in the first stage cyclone 19 and the second stage cyclone 21 and discharged through the respective diplegs 20, 22 into the catalyst bed of the regenerator. The flue gas recovered from the outlet of the second stage cyclone 21 is directed through the regenerator plenum 23 to the flue gas line 50 for downstream waste heat recovery and / or energy recovery.

[0034] A first portion of the regenerated catalyst mixture is withdrawn through the regenerated catalyst standpipe 27, which is in flow communication with the J-bend 1. The flow of catalyst from the regenerator 17 to the first reactor 3 can be regulated by the first slide valve 28 located on the regenerated catalyst standpipe 27. The opening of the first slide valve 28 is adjusted to control the flow of catalyst to maintain the desired top temperature in the first reactor 3.

[0035] In addition to the lift steam, a feed stream (such as C4 olefins and naphtha or a similar external stream) is injected into the J-bend 1 as a lift medium through the gas distributor 1a located at the Y-section to enable the smooth transfer of the regenerated catalyst from the J-bend 1 to the first reactor 3. The J-bend 1 can also function as a dense bed reactor for the cracking of the C4 olefins and naphtha stream into light olefins under conditions conducive to such reactions, such as a WHSV of 0.5 to 50 h -1 -1, a temperature of 640 °C to 750 °C, and a residence time of 3 to 10 seconds.

[0036] A second portion of the regenerated catalyst mixture is withdrawn through standpipe 30. A second slide valve 31 can be used to control the flow of catalyst from regenerator 17. After withdrawal, the mixed catalyst can flow through standpipe 30 into second reactor 32, particulate cooler 70, or both, depending on the operation of other valves within the system, such as third slide valve 63 or fourth slide valve 38, described further below.

[0037] Dual reactor mode

[0038] In a first mode of operation with only the second reactor, mixed catalyst can flow from regenerator 17 and be directed to second reactor 32. In this mode, fourth slide valve 38 can be closed, while third slide valve 63 is open. The flow rate of catalyst can be based on a vapor outlet (first flow line 45) temperature set point, for example. C4 olefins and naphtha streams are injected into the bottom section of the catalyst bed by one or more feed distributors 34 (first feed distributor 34a, second feed distributor 34b) in either liquid or vapor phase. Second reactor 32 operates in a mixed flow manner, where a portion of the regenerated catalyst flows downward (from the top to the bottom of the reactor bed), while a portion of the regenerated catalyst mixture and the feed hydrocarbon streams flow upward (from the bottom to the top of the reactor bed).

[0039] Second reactor 32 can be equipped with baffles or structured internals (not shown) that facilitate close contact and mixing of the catalyst and feed molecules. These internals can also help to minimize channeling, bubble growth, and / or coalescence. Second reactor 32 can also be enlarged at different sections along the length to maintain a constant or desired superficial gas velocity within those sections.

[0040] The concentrated particulates accumulated in second reactor 32 can be stripped intermittently or continuously at the very bottom of second reactor 32 to separate entrained hydrocarbon feed / product using steam as the stripping medium introduced through second distributor 35. If desired, spent particulates can be withdrawn from second reactor 32 through second flow line 69.

[0041] As described above, spent catalyst from first reactor 3, second reactor 32 is regenerated in common regenerator 17, which can operate in a full combustion mode. Mixed catalyst is received from first reactor 3, and smaller and / or lighter particulates from second reactor 32 are received through outlet line 36a, each stripped in stripper column 9 and fed collectively to regenerator 17 through first riser line 15.

[0042] As described above, the second reactor 32 uses two different catalysts, which can differ in one or both of particle size and density, such as a lighter and smaller Y-zeolite or FCC catalyst and a larger and / or denser ZSM-5 / ZSM-11 shape selective pentasil zeolite. The superficial gas velocity maintained in the second reactor 32 is such that substantially all or a majority of the lighter, smaller catalyst (e.g., Y-zeolite / FCC catalyst) and a portion of the heavier, larger catalyst (e.g., ZSM-5 / ZSM-11) are carried out of the reactor with the cracked hydrocarbons and steam recovered through the first flow line 45. A portion of the larger and / or denser catalyst can remain within the second reactor 32, forming a dense phase bed toward the lower portion of the reactor, as described above.

[0043] Accordingly, the effluent from the second reactor 32 recovered through the first flow line 45 can include a mixture of cracked hydrocarbon products, unreacted hydrocarbon feedstock, steam (stripping medium), and catalyst, including substantially all of the lighter and / or smaller catalyst and a portion of the larger and / or denser catalyst introduced to the reactor. The effluent can then be transported through the first flow line 45 to a solids separator 47. The solids separator 47 can be a separator configured to separate the two types of catalyst based on their physical properties (i.e., particle size and / or density). For example, the solids separator 47 can use the difference in inertial or centrifugal forces to separate the FCC catalyst from the ZSM-5. The solids separator 47 is an external vessel to the second reactor 32 and operates under fluid dynamic properties that enhance separation of the two types of catalyst based on their physical properties.

[0044] After separation in the solids separator 47, the smaller and / or lighter catalyst (Y-zeolite / FCC catalyst) is then transported from the solids separator 47 through an outlet line 36a to a common disengager or cyclone closure vessel 8 equipped with a riser reactor cyclone separator and / or reaction termination system. The larger and / or denser catalyst (ZSM-5 / ZSM-11) can be returned to the second reactor 32 through a return line 49 for continued reaction with the hydrocarbon feed introduced through the feed distributor 34.

[0045] The entrainment of substantially all of the lighter / smaller catalyst and a portion of the larger and / or denser catalyst, the subsequent separation, and the recycle of the larger and / or denser catalyst to the second reactor 32 can allow for a significant build-up of the larger and / or denser catalyst in the second reactor 32. Because this catalyst has a higher selectivity for the cracking of C4and naphtha boiling range hydrocarbons, the build-up of the larger and / or denser catalyst can provide selectivity and yield advantages. In addition, the operation of the reactor in a fluidized flow regime to entrain both types of catalyst can provide for improved operability or flexibility of operation of the reactor, as described above.

[0046] A hydrocarbon feed such as heavy vacuum gas oil or heavy resid feed, light cycle oil (LCO), or steam can be injected into the outlet line 36a as a quench medium by the third distributor 36b. The flow rate of this quench medium can be controlled by setting the temperature of the stream entering the cyclone enclosure 8. All vapors from the second reactor 32, including those fed through the third distributor 36b, are discharged through a single stage cyclone separator 36c to the dilute phase of the cyclone enclosure 8. The use of a hydrocarbon feed as a quench medium is preferred because it serves the dual purpose of cooling the product from the second reactor 32 as well as increasing the yield of middle distillate.

[0047] The first reactor 3, such as a riser reactor, can be operated in a fast fluidized regime (e.g., at a gas superficial velocity in the range of about 3 to about 10 m / s at the bottom section) and in a pneumatic conveying regime at the top section (e.g., at a gas superficial velocity in the range of about 10 to about 20 m / s).

[0048] The WHSV in the second reactor 32 is typically in the range of about 0.5 h -1 to about 50 h -1 ; the residence time of vapors and catalyst can vary from about 2 seconds to about 20 seconds. When different feeds are introduced, it is preferred to inject the C4feed at a height lower than the naphtha feed injection location. However, interchange of the feed injection locations is possible.

[0049] Supplemental catalyst can be introduced, if necessary, through one or more third flow lines 42, fourth flow lines 43. For example, fresh or supplemental FCC or Y-type zeolite catalyst or a mixture of both can be introduced through the third flow line 42 to the regenerator 17, and fresh or supplemental ZSM-5 / ZSM-11 catalyst can be introduced through the fourth flow line 43 to the second reactor 32. For example, the overall system catalyst inventory can be maintained by withdrawing a mixture of catalyst from the regenerator bed 24. The catalyst inventory and build-up of the preferred catalyst within the second reactor 32 can be controlled by controlling the operation of the reactor and the solids separator 47, as described below.

[0050] In some embodiments, the first portion of regenerated catalyst is withdrawn from the regenerator 17 into a regenerated catalyst (RCSP) hopper 26 through a withdrawal line 25 in flow communication with the regenerator 17 and the regenerated catalyst standpipe 27. The catalyst bed in the RCSP hopper 26 floats with the bed level of the regenerator 17. The regenerated catalyst is then transferred from the RCSP hopper 26 to the first reactor 3 through the regenerated catalyst standpipe 27, which is in flow communication with the J-bend 1. The flow of catalyst from the regenerator 17 to the first reactor 3 can be regulated by a first slide valve 28 (RCSP slide valve) located on the regenerated catalyst standpipe 27. A pressure equalization line 29 can also be provided.

[0051] The fifth flow line 60 can also be used to facilitate the transfer of particles from the top of the second reactor 32 to the cyclone enclosure 8, as shown in Figure 1 As described above with respect to Figure 1 The second reactor 32 uses two different catalysts, which can differ in one or both of particle size and density, such as a lighter and / or smaller Y zeolite or FCC catalyst and a larger and / or denser ZSM-5 / ZSM-11 shape selective pentasil zeolite. The superficial gas velocity maintained in the second reactor 32 is such that substantially all of the lighter, smaller catalyst (e.g., Y zeolite / FCC catalyst) and a portion of the larger and / or denser catalyst (e.g., ZSM-5 / ZSM-11) is carried out of the reactor with the cracked hydrocarbons and steam recovered through the first flow line 45.

[0052] Accordingly, the effluent from the second reactor 32 recovered through the first flow line 45 can include a mixture of cracked hydrocarbon products, unreacted hydrocarbon feedstock, steam (stripping medium), and catalyst, including substantially all of the lighter, smaller catalyst and a portion of the larger and / or denser catalyst introduced to the reactor. The effluent can then be conveyed through the first flow line 45 to a solids separator 47. The solids separator 47 can be a separator configured to separate the two types of catalyst based on their physical properties (i.e., particle size and / or density). The solids separator 47 operates under hydrodynamic conditions that enhance the separation of the two types of catalyst based on their physical properties.

[0053] After separation in the solids separator 47, the smaller / lighter catalyst (Y-zeolite / FCC catalyst) is then transported from the solids separator 47 through an outlet line 36a to the common disengager or cyclone closure vessel 8 which houses the riser reactor cyclones and / or reaction termination system. The larger and / or denser catalyst (ZSM-5 / ZSM-11) can be returned to the second reactor 32 for continued reaction with the hydrocarbon feed introduced through the feed distributor 34.

[0054] Continuously or intermittently, a portion of the effluent containing both types of catalyst transported through the first flow line 45 can be diverted to bypass the solids separator 47. The diverted portion of the effluent can be flowed around the solids separator 47 through a fifth flow line 60 which can include a diverter or first flow control valve 62. The effluent can then continue back to the cyclone closure vessel 8 through a sixth flow line 64 to separate the hydrocarbon products from the catalyst. The sixth flow line 64 can combine with the effluent and smaller catalyst recovered from the solids separator 47 through the outlet line 36a and can be introduced upstream or downstream of the third distributor 36b. Alternatively, the diverted effluent in the fifth flow line 60 can be fed directly to the disengager / cyclone closure vessel 8.

[0055] While a first flow control valve 62 is illustrated in Figure 1 While a first flow control valve 62 is illustrated in

[0056] As described above, the use of increased carrier fluid flow and / or the use of a diverter can advantageously provide for the accumulation of catalyst in the second reactor 32 selective for cracking naphtha boiling range hydrocarbons.

[0057] One reactor + catalyst cooler mode

[0058] In a second mode of operation, one reactor plus catalyst cooler, the mixed catalyst from the regenerator 17 can be directed to the particle cooler 70. In this mode, the fourth slide valve 38 can be open while the third slide valve 63 is closed. The flow rate of catalyst into the particle cooler 70 through the standpipe 30 can be based on one or more of the temperature of the regenerator 17 or the outlet temperature of a heat exchange medium 72 which is in direct or indirect heat exchange with the catalyst flowing through the particle cooler 70, among other possible control variables.

[0059] In some embodiments, the particle cooler 70 is a screw baffle heat exchanger in which the catalyst particles traverse the tube side of the heat exchanger while the heat exchange medium 72 traverses the shell side of the heat exchanger. The catalyst particles can then be recovered through standpipe 37. The catalyst can then be transferred through standpipe 37, fourth slide valve 38, and second lift line 40 to regenerator 17. Blower air can be used as the carrier gas 39 to transfer the catalyst to regenerator 17. As noted above, use of a particle cooler 70 can be beneficial to maintain the temperature of the regenerator, as well as to provide heat for one or more processes or utility streams in the plant.

[0060] Dual reactor + particle cooler mode

[0061] In a third mode of operation, two reactors plus particle cooler, mixed catalyst from regenerator 17 can flow to both second reactor 32 and particle cooler 70. In this mode, both fourth slide valve 38 and third slide valve 63 can be open, and a portion of the mixed catalyst from standpipe 30 can be directed to second reactor 32, while the remaining portion can be directed to particle cooler 70. The operation of the particle cooler and second reactor are the same as described above for the first two modes, in which both hydrocarbon conversion (through second reactor 32) and cooling of the regenerator contents (through particle cooler 70) are provided.

[0062] During this mode, for example, based on a set point of the temperature of heat exchange medium 72, fourth slide valve 38 is controlled to allow a portion of the mixed catalyst from regenerator 17 to enter particle cooler 70. For example, second slide valve 31, which is typically controlled by the vapor outlet temperature (first flow line 45), will allow a large amount of mixed catalyst to flow from regenerator 17 to both second reactor 32 and particle cooler 70. Based on the control scheme, the rate of this catalyst flow is typically greater than the rate of catalyst flow to particle cooler 70. After filling particle cooler 70, additional mixed catalyst will flow to second reactor 32. Additional lift steam at the transfer line below second reactor 32 can be used to facilitate the transfer of mixed catalyst flow to second reactor 32.

[0063] Referring now to Figure 2 , a simplified process flow diagram of a system for cracking hydrocarbons and producing light olefins according to embodiments disclosed herein is illustrated, in which like numbers represent like parts. Similar to the process scheme shown in Figure 1 , as described above, Figure 2 , the system shown includes two reactors and a particle cooler, and two types of particles, such as lighter and / or smaller Y-type or FCC catalyst and larger and / or denser ZSM-5 or ZSM-11 catalyst, are introduced into second reactor 32, particle cooler 70, or both.

[0064] In this embodiment, the second slide valve 31 is a three-way valve that can be used to direct catalyst to the second reactor 32 for a dual reactor mode of operation, or to the particle cooler 70 for a one reactor plus particle cooler mode. Although illustrated as a three-way valve, two separate standpipes 30 can also be used to provide catalyst flow to each of the second reactor 32 and the particle cooler 70, respectively.

[0065] As mentioned above, spent particles at the bottom of the second reactor 32 can be withdrawn through a second flow line 69. As shown, the particle cooler 70 can also be used to recover heat from the concentrated spent particles in the second reactor 32, and / or to facilitate the transport of larger or denser particles from the second reactor 32 to the regenerator 17 for regeneration and continued use in the conversion of hydrocarbons. Figure 2

[0066] The concentrated particles accumulated in the second reactor 32 can be stripped at the very bottom of the second reactor 32 to separate entrained hydrocarbon feed / product using steam as a stripping medium introduced through a second distributor 35. A second flow control valve 74 can be provided to withdraw particles from the bottom of the second reactor 32 intermittently or continuously. The spent catalyst recovered at the bottom of the second reactor 32 can then be transferred to the regenerator 17 via the particle cooler 70, standpipe 37, and second lift line 40 through a spent catalyst distributor 41. Combustion air or nitrogen can be introduced through the first distributor 14 to enable smooth transfer of catalyst to the regenerator 17. A fourth slide valve 38 can be used to control the flow of catalyst from the second reactor 32 to the regenerator 17. The spent catalyst from both the first reactor 3, the second reactor 32 is then regenerated in a common regenerator 17, which can be operated in a full combustion mode.

[0067] In operation, the catalyst bed in the second reactor 32 is expected to operate in a turbulent bed, a bubbling bed, or a fast fluidization regime. As shown, a light naphtha feed, such as the light naphtha product from the primary reactor or first reactor 3, can be fed into the second reactor 32 through a first feed distributor 34a and converted to light olefins in the presence of the mixed catalysts. The lift gas in the second reactor 32 along with the product gas lifts the solids, including both catalysts, through a first flow line 45 to a solids separator 47 and then back to the regenerator 17. Due to the difference in size and / or density of the two catalyst particles, most of the ZSM-5 or ZSM-11 catalyst particles will be separated from the Y-type or FCC catalyst in the solids separator 47 and transferred back to the second reactor 32 through a backflow line 49. Most of the Y-type or FCC catalyst particles will be transferred back to the cyclone enclosure 8 for gas-solids separation.

[0068] ​The steam fed through the second distributor 35 can be used as a lift gas along with the hydrocarbon feed fed through the first feed distributor 34a, second feed distributor 34b. The catalyst can fill the second reactor 32 and in some embodiments no catalyst bed is observed. The lift gas in the second reactor 32 along with the product gas lifts the solids (including both catalysts) through the first flow line 45 to the solids separator 47. Due to the difference in size and / or density of the two catalyst particles, most of the ZSM-5 or ZSM-11 catalyst particles will be separated from the Y-type or FCC catalyst in the solids separator 47 and transferred back to the second reactor 32 through the return line 49. Most of the Y-type or FCC catalyst particles will be transferred back to the cyclone enclosure 8 for gas-solids separation.

[0069] As described above, the system according to the embodiments herein can include a solids separator 47 configured to separate the two types of catalysts based on their physical properties such as particle size and / or density. The solids separator 47 can be a cyclone separator, a screen separator, a mechanical sifter, a gravity chamber, a centrifugal separator, a baffle chamber, a louver separator, an in-line or pneumatic classifier, or other types of separators that can be used to effectively separate particles based on size and / or hydrodynamic properties.

[0070] Examples of separators or classifiers that can be used in the embodiments herein are shown in Figures 3-6 . In some embodiments, the solids separator 47 can be a U-shaped inertial separator, as shown in Figure 3 , for separating two solid particles or catalysts having different particle sizes and / or particle densities. The separator can be built in the form of a U-shape, having an inlet 700 at the top, a gas outlet 84 at the other end of the U-shape, and a main solids outlet 80 at the base of the U-shaped separator.

[0071] A mixture of solid particles or catalysts having different sizes 720 is introduced with a carrier gas stream through the inlet 700, and an inertial separation force is applied to the solids by no more than one turn to separate the solid particles of different sizes. The larger and / or denser solid particles 78 preferentially enter the downcomer or dipleg connected to the base of the U-shape in section 73 / 76, while the lighter or smaller solid particles preferentially are carried with the gas stream to the outlet 82, where a mixture of small particles and gas can be recovered. The main solids outlet 80 at the base of the U-shaped separator (the inlet to the downcomer or dipleg that flows the larger and / or denser catalyst particles back to the second reactor 32) should be large enough to accommodate the normal solids / catalyst flow.

[0072] By controlling the gas flow rates into the down-leg and out of the main gas stream outlet, the overall separation efficiency and selectivity of the U-shaped inertial separator to separate larger and / or denser particles from smaller and / or less dense particles can be manipulated. This extends to a fully sealed dipleg where the only gas flow out of the dipleg is that which is entrained by the presence of the solids / catalyst stream. As the U-shaped inertial separator provides the ability to manipulate the separation efficiency, as described above, the medium sized particles that can accumulate in the system can be periodically or continuously entrained with the hydrocarbon product recovered from the solids separator 47 for separation in the cyclone enclosed vessel 8 and regeneration in the regenerator bed 24.

[0073] In some embodiments, a gas distributor 75 or additional steam / inert gas can be provided near the top of the main solids outlet 80, such as near the top of the standpipe inlet. The additional lift gas provided within the separator can further promote the separation of larger and / or denser solid particles from less dense and / or smaller solid particles as the additional gas can preferentially lift the lighter solid particles to the gas outlet 84, resulting in better solids fractionation.

[0074] The cross-sectional area of the U-shaped separator at the inlet 700, outlet 82, and throughout the U-shaped separator, including segments 73, 76, can be adjusted to manipulate the superficial gas velocity within the device to control the separation efficiency and selectivity. In some embodiments, the position of one or more separator walls can be adjustable, or movable baffles can be provided within one or more segments of the separator, which can be used to control the separation efficiency and selectivity. In some embodiments, the system can include a particle size analyzer downstream of the outlet 82, enabling the flow configuration through the U-shaped separator to be adjusted in real-time to achieve the desired separation.

[0075] The use of U-shaped inertial separators connected in series or a combination of U-shaped inertial separators and cyclone separators can provide flexibility to allow both the target overall separation efficiency and the target selectivity of larger and / or denser particles over smaller and / or less dense particles to be achieved simultaneously.

[0076] The second reactor 32 can also be equipped with baffles or structured internals, such as the modular grid described in U.S. Patent 7,179,427. Other types of internals that improve contact efficiency and product selectivity / yield can also be used. The internals can enhance the distribution of catalyst throughout the reactor and improve the contact of the feed vapor with the catalyst, thereby increasing the average reaction rate, enhancing the overall activity of the catalyst, and optimizing the operating conditions to increase the production of light olefins.

[0077] The embodiments disclosed herein use a Y-type zeolite or a conventional FCC catalyst to maximize conversion of heavy hydrocarbon feed. The Y-type zeolite or FCC catalyst has a smaller and / or lighter particle size than ZSM-5 or similar catalysts used to enhance light olefin production in a countercurrent flow reactor. ZSM-5 or similar catalysts have a larger particle size and / or are denser than Y-type zeolite or FCC catalysts used to enhance separation of catalyst types in each of the mixed flow reactor and the solids separator. The superficial gas velocity of the vapor in the second reactor is maintained such that the Y-type zeolite or FCC catalyst and a portion of the ZSM-5 or ZSM-11 catalyst are allowed to be entrained out of the mixed flow reactor, and the solids separator can utilize the difference in single particle terminal velocity or the difference between minimum fluidization / minimum bubbling velocities to separate the ZSM-5 / ZSM-11 and return it to the mixed flow reactor. This concept allows for elimination of a two-stage FCC system, resulting in a simplified and efficient process. The catalysts used in this method can be a combination of Y-type zeolite / FCC catalyst and ZSM-5 or other similar catalysts such as those mentioned in US 5043522 and US 5846402.

[0078] The entrainment of both catalysts from the mixed flow reactor, subsequent separation, and the circulation and accumulation of the ZSM-5 / ZSM-11 catalyst in the mixed flow reactor eliminates any potential limitations on the superficial gas velocity in the secondary reactor. As a result, the use of a solids separation vessel provides process flexibility in the secondary reactor, allowing the secondary reactor to be operated in a boiling bed, turbulent bed, or fast fluidization regime, rather than limiting the operation to only a boiling bed regime. The solids separation vessel can be a cyclone separator or other vessel in which solids and gas are introduced at a common inlet and particles are separated based on size and / or density through degasification, inertia, and centrifugal force, with the majority of the smaller FCC-type particles being entrained with the vapor outlet and the larger and / or denser ZSM-5 or ZSM-11 -type particles being returned to the second reactor 32 through a dense phase standpipe or dipleg.

[0079] In addition to the U-shaped particle separator described in U.S. Patent No. 10, 1 1 1, 1 1 1, Figure 3 In addition to the U-shaped particle separator described in U.S. Patent No. 10, 1 1 1, 1 1 1, Figures 4-6 Various additional particle separation devices for use in the embodiments herein are also illustrated. Reference is made to U.S. Patent No. 10, 1 1 1, 1 1 1, Figure 4A baffle chamber separator 900 for separating catalyst or other particles based on size and / or density can include an inlet 910, such as a horizontal pipe. The vapor and particles contained in the horizontal pipe then enter a chamber 912 before being deflected by a baffle 914. The chamber 912 is connected to a first vertical outlet 916 and a first horizontal outlet 918. The baffle 914 can be located in the middle of the chamber 912, near the inlet 910, or near the first horizontal outlet 918 of the chamber. The baffle can be angled or movable such that the baffle can be used to deflect more or less catalyst particles and can be configured for a particular mixture of particles.

[0080] The methods herein can utilize the baffle chamber separator 900 to separate larger and / or denser particles from smaller and / or less dense particles contained in a carrier gas, such as a hydrocarbon reaction effluent. The baffle chamber separator 900 can be configured to separate at least a portion of a second particle type from the carrier gas and a first particle type, recover the second particle type through the first vertical outlet 916 and recover a mixture including the carrier gas and the first particle type through the first horizontal outlet 918. The separator can further include a distributor (not shown) disposed within or near the first vertical outlet for introducing a fluidization gas to facilitate additional separation of the first particle type from the second particle type.

[0081] Reference is now made to Figure 5 FIG. 1 illustrates a louver separator used in accordance with embodiments herein. Similar to the other separators illustrated and described, the louver separator 1000 can be used to separate catalyst or other particles based on size and / or density. The louver separator 1000 can include a vertical inlet 1010 connected to a chamber 1012, where one or more vertical sides of the chamber are equipped with narrow slot outlets 1016, which can be described as louvers. The number of louvers can vary depending on the application, such as the desired mixture of particles to be separated, and the angle of the louvers can be adjusted in order to control the amount of vapor passing through and exiting the louver outlets. The chamber 1012 is also connected to a first vertical outlet 1014 at the bottom of the chamber.

[0082] The methods herein can utilize the louver separator 1000 to separate larger and / or denser particles from smaller and / or less dense particles contained in a carrier gas, such as a hydrocarbon reaction effluent. The louver separator 1000 can be configured to separate at least a portion of a second particle type from the carrier gas and a first particle type, recover the second particle type through the first vertical outlet 1014 and recover the carrier gas and the first particle type through the narrow slot outlets 1016. The separator can further include a distributor (not shown) disposed within or near the first vertical outlet for introducing a fluidization gas to facilitate additional separation of the first particle type from the second particle type.

[0083] Reference is now made to Figure 6FIG. 11 illustrates an inertial separator 1100 used in accordance with embodiments herein. Similar to other separators illustrated and described, the inertial separator 1100 can be used to separate catalyst or other particles based on size and / or density. The separator can include an inlet 1110 located at the top of a chamber 1112 and extending into the chamber 1112. In some embodiments, the height or placement of the inlet 1110 within the chamber 1112 can be adjustable. The separator can also include one or more side outlets 1114, 1116, such as one to eight side outlets, and a vertical outlet 1118. The separator can also include a distributor (not shown) disposed within or near the vertical outlet 1118 for introducing a fluidization gas.

[0084] A mixture 1172 of solid particles or catalysts of different sizes is introduced through the inlet 1110 with a stream of carrier gas. Based on the pressure differential, the gas in the mixture 1172 preferentially directs to the side outlets 1114, 1116, and by causing the particles and carrier gas to spin from the extended inlet 1110 within the chamber 1112 to the side outlets 1114, 1116, an inertial separation force is exerted on the solids, which separates the different sized / density particles. Larger and / or heavier solid particles 1174 preferentially enter a standpipe or dipleg (not shown) connected to the base of the separator in the section downward, while lighter or smaller solid particles 1176 are preferentially carried with the gas stream to the side outlets 1114, 1116, where a mixture of small particles and gas can be recovered.

[0085] In each of the separators described herein, by controlling the gas flow rate into the downward standpipe / separation chamber and out of the main gas stream outlet, the overall separation efficiency of the separator and the selectivity of separating heavier and / or larger particles from lighter or smaller particles can be manipulated. This extends to a fully sealed dipleg, where the only gas flow out of the dipleg is that which is entrained by the presence of the solid / catalyst stream.

[0086] In some embodiments, a gas distributor or additional steam / inert gas can be disposed near the top of the heavy / dense particle outlet section, such as near the top of the standpipe inlet. The additional lift gas provided within the separator can further promote the separation of heavier and / or larger solid particles from lighter or smaller solid particles, as the additional gas can preferentially lift the lighter solid particles to the gas outlet, resulting in better solid fractionation.

[0087] The particle separators described herein can be disposed externally or internally to a vessel. Further, in some embodiments, for example, the large / dense particle outlet of the particle separator can be fluidly connected to an external vessel, providing selective cycling or feeding of the separated particles to a desired reactor to maintain a desired catalyst balance.

[0088] The various modes of operation described above can allow an operator to vary system operation to provide a desired product mixture, taking into account the availability of feedstocks, the demand for particular products or product mixtures, and maintenance requirements. The flexibility of this process can allow an operator to operate the second reactor during a first time period, and operate the particle cooler during a second time period. Additionally, or alternatively, the operator can choose to operate the system with both the second reactor 32 and the particle cooler 70 running during a third time period. Thus, the embodiments herein provide the device operator with the flexibility needed to effectively operate the device, increase the production of olefins and light hydrocarbons as needed, and adjust the operation based on product demand.

[0089] The embodiments disclosed herein, by the above-described method, significantly increase the concentration of the desired catalyst in the secondary reactor (second reactor 32), thereby increasing the light olefin yield. Furthermore, the process also serves as a method to separate the extraction and addition of ZSM-5 and ZSM5-11 from the extraction and addition of the FCC catalyst. In summary, the FCC process proposed in the present disclosure creates a desired environment in the second reactor 32 that is rich in ZSM-5 or ZSM-11 catalyst additives, which can preferentially convert light naphtha products, such as those derived from the primary reactor, to improve light olefin yield, while maximizing middle distillate yield by imposing optimal operating conditions in the primary reactor or riser.

[0090] Another benefit of the embodiments disclosed herein is that the integrated dual reactor scheme overcomes the heat balance limitations in a standalone C4 / naphtha catalytic cracking process. Due to the integration with the catalyst regenerator, the secondary (mixed flow) reactor acts as a heat sink, minimizing the need for a catalyst cooler when processing a resid feedstock.

[0091] The product vapors from the secondary reactor are delivered to the first stage reactor / disengagement vessel or reaction termination device, where they are mixed with the product from the first stage and / or an external quench medium (such as LCO or steam) and quenched to minimize unwanted thermal cracking reactions. Alternatively, the product outlet line of the secondary reactor / solids separator can also be used to introduce additional amounts of heavy feed or to change the routing of part of the feed from the first stage reactor (riser reactor). This serves two purposes: (1) the catalyst in the solids separator vapor outlet line is predominantly Y-type zeolite / conventional FCC catalyst, which preferentially cracks these heavy feed molecules to middle distillate, and (2) this cracking reaction is endothermic, thus helping to reduce the temperature of the effluent product vapors and also reducing their residence time.

[0092] In some embodiments disclosed herein, an existing FCC unit can be retrofitted with a secondary reactor as described above. For example, a reactor of appropriate size can be fluidly connected to an existing catalyst regeneration vessel to provide catalyst feed and return from the mixed flow vessel, and fluidly connected to an existing disengagement vessel to separate the hydrocarbon product and catalyst. In other embodiments, a mixed flow reactor can be added to a base FCC unit intended to operate in gasoline mode, light olefin mode, or diesel mode.

[0093] The reactor systems described above with respect to Figure 1 and Figure 2 The reactor systems described above primarily involve the production of light olefins, and advantageous concentration of catalysts in a mixed catalyst system to improve the reactivity and selectivity of the system. Such reactor systems can also be used in other mixed catalyst systems where concentration of one of the catalysts can be advantageous.

[0094] Embodiments herein can utilize various types of catalysts or particles to perform the desired reactions, where a common regenerator can be used to regenerate the catalyst mixture, and the separators are advantageously positioned to enrich one or more reactors using specific catalysts contained in the catalyst mixture. Embodiments herein can be used to improve unit operations and increase the selectivity and flexibility of the reaction system, such as for applications involving light olefin production, gasoline desulfurization, and heavy oil processing.

[0095] As described above, light olefin production can include various light, intermediate, and heavy hydrocarbon feeds to the riser. The feed to the second reactor 32 can include naphtha (such as straight run naphtha or recycled catalytic naphtha), as well as other feeds. The catalyst mixture for light olefin production can include smaller and / or less dense catalysts, such as FCC catalysts (e.g., zeolite Y), and heavier / denser catalysts (such as ZSM-5 or ZSM-11), as well as other combinations. Other cracking catalysts can also be used. Various catalysts for cracking hydrocarbons are disclosed in U.S. Patent Nos. 7,375,257, 7,314,963, 7,268,265, 7,087,155, 6,358,486, 6,930,219, 6,809,055, 5,972,205, 5,702,589, 5,637,207, 5,534,135, and 5,314,610, among others.

[0096] As noted above, embodiments involving gasoline desulfurization can include various light, intermediate, heavy hydrocarbon feeds to the riser. The feed to the second reactor 32 can also include naphtha (such as straight run naphtha or recycled catalytic naphtha), as well as other feeds. The catalyst mixture for light olefin production can include smaller and / or less dense catalysts, such as FCC catalysts (e.g., zeolite Y), as well as larger and / or more dense catalysts with desulfurization functionality (such as MgO / AI2O3 with various metal promoters). Other desulfurization catalysts as disclosed in U.S. Patents Nos. 5,482,617, 6,482,315, 6,852,214, 7,347,929, and the like can also be used. In some embodiments, the catalyst mixture can include a cracking catalyst composition with desulfurization activity, such as those catalyst compositions disclosed in US5376608 and the like.

[0097] As noted above, embodiments involving heavy oil processing can include various light, intermediate, heavy hydrocarbon feeds to the riser. The feed to the second reactor 32 can include hydrocarbons or hydrocarbon mixtures with a boiling point or boiling range above about 340°C. Hydrocarbon feedstocks that can be used in the processes disclosed herein can include various refinery and other hydrocarbon streams, such as petroleum atmospheric or vacuum resid, deasphalted oil, deasphalter pitch, hydrocracked atmospheric column or vacuum column bottoms, straight run vacuum gas oil, hydrocracked vacuum gas oil, fluid catalytic cracking (FCC) slurry oil, vacuum gas oil from ebullated bed hydrocracking processes, shale-derived oil, coal-derived oil, tar sand bitumen, tall oil, biologically-derived crude oil, black oil, and other similar hydrocarbon streams, or combinations of these streams, each of which can be a straight run, process-derived, hydrocracked, partially desulfurized, and / or partially demetallized stream. In some embodiments, the resid hydrocarbon fraction can include hydrocarbons with a standard boiling point of at least 480°C, at least 524°C, or at least 565°C. The catalyst mixture for heavy hydrocarbon processing can include smaller and / or less dense catalysts, such as FCC catalysts (e.g., zeolite Y), as well as larger and / or more dense catalysts (such as active matrix catalysts, metal trapping catalysts), coarse / dense Ecat (equilibrium catalyst), matrix or binder type catalysts (such as kaolin or sand), or high matrix / zeolite FCC catalysts. Other cracking catalysts can also be used, such as one or more of those disclosed in, for example, US5160601, US5071806, US5001097, US4624773, US4536281, US4431749, US6656347, US6916757, US6943132, and US7591939, and the like.

[0098] The systems herein can also be used for the pretreatment of heavy crude oils or virgin crude oils, such as those recovered from tar sands or bitumen. For example, the second reactor 32, such as the reactor in Figure 1 or Figure 2 The second reactor 32, such as the reactor in

[0099] The embodiments herein describe the separation of the catalyst mixture from the separator and the effective preferential concentration of the catalyst within the mixture in the reactor. As shown in the figures, the catalyst concentrated in the reactor is shown to be returned from the separator near the top of the reactor or vessel. The embodiments herein also contemplate returning the catalyst from the separator to the middle or lower portion of the reactor, and the location of return of the catalyst can depend on the hydrocarbon feed being processed, the type of catalyst in the mixture, and the desired catalyst gradient within the reactor vessel. The embodiments herein also contemplate returning the catalyst to multiple locations within the reactor. While providing the ability to increase the concentration of a particular catalyst or particle within the mixture in a given reactor, the embodiments herein can also be used with a catalyst system; the particle separator and systems described herein can increase the catalyst / oil ratio, thereby extending the catalytic contact time.

[0100] As described in the above embodiments, the second reactor is integrated with an FCC riser reactor and separation system. The reactor is in flow communication with other vessels, allowing for selective catalytic processing and integrated hydrocarbon product quenching, separation, and catalyst regeneration. This integrated reactor system provides one or more of the above-mentioned advantages and features of the embodiments of the methods disclosed herein, which can provide an improved or optimal process for the catalytic cracking of hydrocarbons to produce light olefins.

[0101] The embodiments herein can use two types of catalyst particles, such as Y-zeolite / FCC catalysts with smaller particle size and / or lower density and ZSM-5 particles that are larger and / or denser than the former. A separator with selective circulation can be used to preferentially separate the Y-zeolite from the ZSM-5 catalyst. Using this catalyst system allows for entrainment of the lighter and smaller particles, thereby retaining the ZSM-5 type particles in an additional new reactor bed. The reactants undergo selective catalytic cracking in the presence of the ZSM-5 type catalyst, which preferably maximizes the yield of light olefins from the C4 and naphtha feed streams. The separator is a device that is able to facilitate the separation of the two types of catalysts due to their difference in particle size and / or density. An example of a separator with selective circulation can be a cyclone separator, a screen separator, a mechanical sifter, a gravity chamber, a centrifugal separator, an in-line or pneumatic classifier, or other types of separators that can be used to efficiently separate particles based on size and / or hydrodynamic performance. The separator is connected to the top of the second reactor, which is in flow communication with the second reactor as well as the regenerator and the first reactor / stripping column.

[0102] The reactor can be provided with baffle or modular grid internal internals. This provides intimate contact of the catalyst with the hydrocarbon feed molecules, helps in bubble break-up and avoids bubble growth due to coalescence of catalyst or feed, channeling or bypassing.

[0103] Typically, fresh catalyst make-up for maintaining catalyst activity is introduced into the regenerator bed using plant air. Instead, it is proposed to use steam or nitrogen as the transport medium to inject the desired high concentration catalyst / additive directly into the second reactor bed. This helps in gradual build-up of concentration and favorable selectivity.

[0104] The reactor configuration described herein provides sufficient flexibility and operating window to adjust operating conditions such as weight hourly space velocity (WHSV), catalyst and hydrocarbon vapor residence time, reaction temperature, catalyst / oil ratio, etc. For example, in some embodiments, the second reactor top / bed temperature is controlled by adjusting the catalyst flow from the regenerator, which indirectly controls the catalyst / oil ratio. Whereas the reactor bed position can be controlled by manipulating the spent catalyst flow from the reactor to the regenerator, which controls the WHSV and catalyst residence time.

[0105] While the present disclosure includes a limited number of embodiments, those skilled in the art having benefit of the present disclosure will appreciate that other embodiments can be devised without departing from the scope of the present disclosure. Accordingly, the scope thereof should only be limited by the appended claims.

Claims

1. A system for processing hydrocarbons, comprising: a riser reactor configured to contact a mixture of first particles and second particles with a hydrocarbon feedstock to convert at least a portion of the hydrocarbon feedstock and recover a riser reactor effluent comprising mixed hydrocarbons and the mixture of first and second particles, wherein the first particles have a smaller average particle size and / or a lower density than the second particles, and wherein the first and second particles can independently be catalytic or non-catalytic particles; a reactor configured to contact a mixture comprising the first particles and the second particles with a second hydrocarbon feedstock to convert at least a portion of the second hydrocarbon feedstock, wherein the reactor is fluidly connected to: an overhead product line for recovering from the reactor a reactor effluent comprising the first particles, a first portion of the second particles, and hydrocarbons; a bottoms product line for recovering from the reactor a second stream comprising a second portion of the second particles; a particle separator configured to separate the second particles from the reactor effluent and produce a hydrocarbon effluent comprising the hydrocarbons and the first particles and a second stream comprising the separated second particles; a feed line for returning the separated second particles from the particle separator to the reactor; a separation system configured to receive the hydrocarbon effluent and the riser reactor effluent and to separate (i) the first particles from the hydrocarbons in the hydrocarbon effluent and (ii) the mixture of first and second particles from the mixed hydrocarbons in the riser reactor effluent, producing (a) a combined hydrocarbon effluent stream and (b) a mixture of first and second particles; a regenerator for regenerating the mixture of first and second particles recovered in the separation system; a particle cooler configured to alternately, intermittently, or simultaneously exchange heat between (i) hot regenerated particles comprising a mixture of first and second particles from the regenerator and (ii) second particles recovered through the bottoms product line with a heat exchange medium; a flow line for recovering cooled particles from the particle cooler and feeding the cooled particles to the regenerator.

2. The system of claim 1, further comprising: a stripping column intermediate the separation system and the regenerator for stripping additional hydrocarbons from the separated particles and feeding the stripped particles to the regenerator.

3. The system of claim 1, further comprising: a second separation system for separating the combined hydrocarbon effluent stream recovered from the separation system into two or more hydrocarbon fractions comprising a naphtha fraction; and a feed line for feeding the naphtha fraction to the reactor as the hydrocarbon feedstock.

4. The system of claim 1, further comprising: a first feed line for feeding fresh second particles to the reactor; a second feed line for feeding fresh first particles to the regenerator.

5. The system of claim 1, further comprising a flow control system and associated valves configured to selectively direct flows of: (a) first particles and second particles from the regenerator to the particle cooler, (b) first particles and second particles from the regenerator to the reactor, and / or (c) second particles from the reactor to the particle cooler.

6. A method for converting hydrocarbons, comprising: feeding a hydrocarbon feedstock and a mixture of first particles and second particles to a riser reactor, wherein the first particles have a smaller average particle size and / or a lower density than the second particles, and wherein the first particles and second particles can independently be catalyzed or non-catalyzed particles; contacting the mixture of first particles and second particles with the hydrocarbon feedstock to crack the hydrocarbon feedstock and form a riser reactor effluent comprising a mixture of hydrocarbons and first particles and second particles; feeding the riser reactor effluent to a separation system to separate the first particles and second particles from the hydrocarbons; recovering a hydrocarbon product from the separation system; feeding the separated first particles and second particles to a regenerator; regenerating the first particles and second particles in the regenerator; during a first time period: feeding the regenerated first particles and second particles from the regenerator to a reactor; feeding a second hydrocarbon feedstock to the reactor and contacting the second hydrocarbon feedstock with the regenerated first particles and second particles; recovering an overhead product from the reactor, the overhead product comprising a converted hydrocarbon effluent, at least a portion of the second particles, and the first particles; separating the second particles from the overhead product to provide a first stream comprising the first particles and the converted hydrocarbon effluent and a second stream comprising separated second particles; feeding the first stream to the separation system; and returning the separated second particles in the second stream to the reactor; and during a second time period: feeding the regenerated first particles and second particles from the regenerator to a particle cooler; exchanging heat in the particle cooler between a heat exchange medium and the regenerated first particles and second particles; recovering cooled particles from the particle cooler and feeding the cooled particles to the regenerator, and during a third time period: feeding second particles from the reactor to the particle cooler; and recovering second particles from the particle cooler; feeding the recovered second particles to the regenerator.

7. The method of claim 6, further comprising recovering a bottoms product comprising second particles from the reactor.

8. The method of claim 7, further comprising stripping additional hydrocarbons from the second particles in the reactor and feeding the stripped particles to the regenerator.

9. The method of claim 6, further comprising: feeding fresh second particles to the reactor; feeding fresh first particles to the regenerator.

10. The method of claim 6, further comprising, during a fourth time period: feeding regenerated first particles and second particles from the regenerator to both the reactor and the particle cooler, and simultaneously: operating the reactor as in the first time period; and operating the particle cooler as in the second time period.

10. The method of claim 6, further comprising, during a fourth time period: feeding regenerated first particles and second particles from the regenerator to both the reactor and the particle cooler, and simultaneously: operating the reactor as in the first time period; and operating the particle cooler as in the second time period.

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