Maximum olefin production using multi-stage catalytic reactions and regeneration.

Abstract

To provide a method and system for improving olefin production and quality from a hydrocarbon feed that includes fully integrated multi-stage catalyst regeneration zones with multiple reaction zones in series and / or parallel.SOLUTION: Independent control is provided to achieve a lowest possible regenerated catalyst temperature by multi-stage regeneration with at least one partial combustion zone and one complete combustion zone, as a result, a highest possible catalyst-to-oil ratio required to maximize an olefin yield is provided through increased contact decomposition in a multi-stage FCC riser.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Patent Application No. 15 / 969,128, entitled "Maximum Olefin Production Utilizing Multi-Stage Catalysis and Regeneration," filed May 2, 2018, which is incorporated herein by reference in its entirety.

[0002] FIELD OF THE INVENTION Embodiments disclosed herein relate to catalytic cracking reactor systems and processes, such as fluid catalytic cracking (FCC) processes. More particularly, embodiments disclosed herein provide an improved fluid catalytic cracking process that utilizes a multi-stage, preferably two-stage, catalyst regeneration process in which catalyst circulation is independently controlled to adjust the catalyst-to-oil (C / O) ratio as desired to crack a hydrocarbon feedstock and maximize olefin production. [Background technology]

[0003] It is common commercial practice to produce gasoline, kerosene, and diesel fuel by cracking heavier petroleum fractions. One of the primary commercial technologies for achieving this conversion is fluid catalytic cracking (FCC). In FCC, feed petroleum fractions, such as vacuum gas oil, heavy atmospheric gas oil, and the like, are contacted with particles of hot, active catalyst at high temperature and low pressure (about 1 to 5 atmospheres absolute) in the absence of added hydrogen. The catalyst should be in sufficient quantity and at sufficient temperature to vaporize the feed and provide the endothermic heat of reaction, raising the feed's cracking temperature to about 900°F to 1100°F. The oil and catalyst flow together (simultaneously) for a time sufficient to carry out the intended conversion. During the conversion of heavy petroleum fractions to lighter fractions, coke adheres to the catalyst particles, thereby deactivating them. These deactivated catalyst particles are separated from the cracked petroleum products, and volatile hydrocarbons are removed before being transported to a separate regenerator. In the regenerator, the coked catalyst is combined with an oxygen-containing gas, e.g., air, which burns the coke off the catalyst and reactivates and heats the catalyst. The heated, reactivated catalyst is then returned to the riser for further mixing with fresh feed oil, thus completing the cycle. Typical FCC processes are described in more detail in U.S. Patent Nos. 4,064,039; 4,344,926; 4,194,965; 3,963,603; 4,428,822; and 3,879,281, which are incorporated herein by reference in their entireties.

[0004] An exemplary prior art fluid catalytic cracking process includes U.S. Pat. No. 4,332,674 to Dean et al., which discloses a unit consisting of a riser reactor, a catalyst stripper, and a multi-stage regenerator. The regenerator is a two-stage regenerator in series, in which spent catalyst particles are passed sequentially through first and second (relatively low-temperature and high-temperature) catalyst regeneration zones. Once the catalyst has completed its circulation through the regenerator as described hereinabove, the fully regenerated catalyst is withdrawn from the second-stage regenerator and charged to the riser reactor at a desired high temperature and in a sufficient amount to result in substantially complete vaporization of the hydrocarbon feed. The vaporized hydrocarbon feed, in contact with the hot fully regenerated catalyst, proceeds upward through the riser reactor, undergoing catalytic cracking. When both the vaporized catalytically cracked hydrocarbon product and the spent catalyst reach the stripper vessel, the spent catalyst is removed from the cracked product and sent to the stripper zone for removal of volatiles, then to the bottom of the regenerator, thereby completing the FCC unit cycle.

[0005] The process of U.S. Pat. No. 4,332,674 provides a CO2-rich combustion gas recovered from a low-temperature first-stage regenerator, and a CO2-rich combustion gas containing excess oxygen is recovered from a high-temperature second-stage regenerator. Both combustion gas streams exit the regenerators in parallel and do not mix in either regenerator. Rejecting the CO2-rich combustion gas from the first-stage regenerator results in low regenerator temperatures in both the first and second-stage regenerators. In particular, the lowest regenerator temperature provides the highest possible catalyst-to-oil ratio required to crack heavier feedstocks. On the other hand, higher regenerator temperatures result in low catalyst circulation and high catalyst deactivation, negatively impacting overall yield.

[0006] U.S. Patent No. 6,503,460 to Miller et al. discloses staged catalytic combustion zones in a single regenerator vessel using baffles. As described in this patent, baffles can be used to achieve a partial combustion zone above the baffle and a complete combustion zone below within the same catalyst bed. However, U.S. Patent No. 6,503,460 does not provide a configuration that can utilize catalyst from two different combustion zones within the regenerator to feed multiple riser reactors and maximize olefins.

[0007] Other prior art FCC processes use a single catalyst regeneration zone and two series reaction zones, such as a riser cracking reaction zone followed by a bed cracking reaction zone. Fully regenerated catalyst from the single-stage regenerator enters the lower part of the riser reactor and cracks the feed oil to produce, for example, gasoline-rich products. These products leave the top of the riser reactor and enter a catalyst bed reaction zone supported by a reactor cone and a lower stripper section. As the products from the riser reactor exit the top of the riser reactor, they undergo further cracking in the bed cracking reaction zone, resulting in further breakdown of the gasoline-rich products into lighter olefins. This process produces more than 40% LPG, of which approximately 20% is propylene. This process requires a high catalyst-to-oil ratio, for example, up to 12, high-severity operation, i.e., reactor outlet temperatures in the range of 1025°F to 1150°F, and high steam consumption to reduce the partial pressure of the hydrocarbon feed. U.S. Pat. No. 4,980,053 discloses a similar process.

[0008] However, the technology disclosed in U.S. Pat. No. 4,980,053, for example, is limited to processing light feedstocks such as vacuum gas oil. Light feedstocks have low coke yields, resulting in reasonable regenerator temperatures between 1250°F and 1350°F when the coke is burned in a single-stage, full-combustion mode regenerator. Furthermore, this process requires high catalyst circulation rates at the desired reaction temperatures to maximize olefin yields, which may not be achievable due to the lack of independent control over catalyst circulation through the system. Catalyst circulation is tied to regenerator temperature, which is further tied to coke production in the riser and coke combustion in the regenerator. Heavier feedstocks, such as residual oils, increase coke yields, resulting in high regenerator temperatures when the coke is burned in a single-stage regenerator. High regenerator temperatures limit catalyst circulation, affecting product yields and resulting in catalyst deactivation.

[0009] U.S. Patent No. 8,491,781 to Gauthier et al. discloses a process using fully regenerated catalyst from the same regenerator unit fed into two separate riser reactors operating in parallel. The two riser reactors consist of a primary riser reactor for cracking a heavy hydrocarbon cut, usually residual oil, and another additional secondary or supplemental riser reactor is used to crack one or more light feeds consisting of light gasoline (C5-150°C) to maximize propylene yield. The secondary riser reactor operates at a higher severity than the primary riser reactor for catalytic cracking of gasoline to propylene. The feed to the secondary riser reactor is generally gasoline or C produced by cracking a heavy feed by FCC. 4+ It contains a significant amount of long chain olefins, generally 5 carbon atoms or greater, obtained from an olefin oligomerization unit or any other process that produces long chain olefins.

[0010] However, in the process of U.S. Pat. No. 8,491,781, both riser reactors are fed with catalyst streams from the same regeneration zone, i.e., fully regenerated catalyst. Catalyst circulation is set based on the outlet temperatures of the individual riser reactors and a common regenerator temperature. If additional circulation is required only in the secondary riser reactor at a constant riser outlet temperature, the circulation cannot be increased without affecting the main riser reactor, since the common regenerator supplies catalyst to both risers. The only way to increase catalyst circulation to the secondary riser reactor is by increasing the riser severity, i.e., operating at a higher outlet temperature, which results in higher dry gas production. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] U.S. Patent No. 4,064,039 [Patent Document 2] U.S. Patent No. 4,344,926 [Patent Document 3] U.S. Patent No. 4,194,965 [Patent Document 4] U.S. Patent No. 3,963,603 [Patent Document 5] U.S. Patent No. 4,428,822 [Patent Document 6] U.S. Patent No. 3,879,281 [Patent Document 7] U.S. Patent No. 4,332,674 [Patent Document 8] U.S. Patent No. 6,503,460 [Patent Document 9] U.S. Patent No. 4,980,053 [Patent Document 10] U.S. Patent No. 8,491,781 Summary of the Invention [Problem to be solved by the invention]

[0012] In view of the above, therefore, it is an object of the present invention to provide an integrated system that connects a multi-stage catalyst regeneration system with a multi-stage reaction system to enhance catalytic cracking of gas oil or residual oil or mixtures to maximize olefins. More specifically, it is an object of the present invention to provide flexibility to such processes to produce more olefins, specifically propylene. The disclosed process utilizes two stages of the catalyst regeneration process to independently control and regulate catalyst circulation. At least one regeneration stage provides partial combustion and one stage provides complete combustion, thereby controlling the minimum regenerator temperature in both partial and complete combustion regenerations through the rejection of CO2-rich combustion gases from the partial combustion regeneration process.

[0013] Additional objects of the present invention will become apparent from the following summary and detailed discussion of preferred embodiments of the invention. [Means for solving the problem]

[0014] According to one embodiment, an improved method for increasing olefin production from a hydrocarbon feed utilizing multi-stage catalyst regeneration is disclosed, the method comprising the steps of: a) delivering partially regenerated catalyst from a multi-stage catalyst regenerator through at least one catalyst partial regeneration zone to a secondary riser reactor and fully regenerated catalyst from at least one catalyst full regeneration zone to a primary riser reactor; b) cracking the hydrocarbon feed in a first reaction zone of the primary riser reactor to produce a first cracked product comprising olefins and spent catalyst, and delivering the first cracked product and spent catalyst to a bed cracking reaction zone in a reactor vessel. c) separating the first and second cracked products from the spent catalyst in the reactor vessel; d) recovering the first and second cracked products comprising olefins and separating the uncracked bottoms and partial cracked products from the cracked products; e) cracking the recycle feed comprising at least one of the uncracked bottoms, partial cracked, and cracked products of step (d) in the secondary riser reactor to produce a third cracked product and additional spent catalyst; f) separating and recovering the third cracked product comprising olefins from the additional spent catalyst and delivering the additional spent catalyst to the reactor vessel; and g) passing the spent catalyst from the reactor vessel to a multi-stage catalyst regenerator comprising a partial catalyst regeneration zone and a full catalyst regeneration zone, wherein the spent catalyst is partially regenerated to provide a partially regenerated catalyst, and a portion of the partially regenerated catalyst is delivered to the full catalyst regeneration zone to provide a fully regenerated catalyst.

[0015] According to another embodiment, a method for increasing olefin production from a hydrocarbon feed in a two-stage reactor utilizing multi-stage catalyst regeneration is disclosed. The method includes the steps of: a) delivering fully regenerated catalyst from a multi-stage catalyst regenerator to a primary riser reactor through at least one catalyst full regeneration zone; b) cracking a hydrocarbon feed in the primary riser reactor to produce a first cracked product and spent catalyst; c) further cracking the first cracked product in a bed cracking reaction zone at the top of the primary riser reactor to produce a second cracked product comprising olefins; d) separating the first cracked product and the second cracked product comprising olefins from the spent catalyst in a reactor vessel comprising a bed cracking reaction zone; e) recovering the first cracked product and the second cracked product comprising olefins; and f) passing the spent catalyst from the reactor vessel to a multi-stage catalyst regenerator comprising at least one catalyst full regeneration zone and at least one catalyst partial regeneration zone, wherein the spent catalyst is partially regenerated in the catalyst partial regeneration zone to provide a partially regenerated catalyst, and transferring the partially regenerated catalyst to the catalyst full regeneration zone to provide a fully regenerated catalyst.

[0016] A method for catalyst regeneration using partial combustion in the first stage in series, i.e., two or more stages, provides the lowest regenerated catalyst temperature through the rejection of carbon monoxide (CO)-rich combustion gas from the first stage regenerator, resulting in the highest possible catalyst-to-oil ratio required to maximize olefins. This method provides catalyst flow from the first to the second or consecutive zones in series, with the air inlet and combustion gas outlet preferably paralleled to maximize CO production in the partial combustion zone and minimize regenerated catalyst temperature. However, the air inlet and combustion gas outlet can be in series if desired for added flexibility. Partial combustion first stage regeneration operates in an oxygen-deficient environment, requiring less air. In addition, less air is required in the second regeneration zone because less coke is transferred from the first regeneration zone to the second regeneration zone, thus reducing the overall amount of air required to burn coke from the catalyst.

[0017] This method accommodates heavier feedstocks with high coke yields that can be easily handled with a two-stage regeneration process that utilizes a partial burn combustion mode in the first regeneration zone followed by a full burn combustion mode in the second regeneration zone. The degree of coke combustion in each regeneration zone can be controlled independently, which can be used to further control the regenerator temperature and adjust catalyst circulation as desired. This embodiment provides the flexibility to process all types of feedstocks, ranging from light to heavy feedstocks.

[0018] The embodiments disclosed herein provide a reduced size second stage regenerator and its internals, thus further reducing equipment costs. By feeding a combination of fully regenerated and partially regenerated catalyst to the secondary riser, secondary riser operation is fully optimized. [Brief explanation of the drawings]

[0019] Various embodiments of the overall invention are illustrated by way of example in the accompanying figures. [Figure 1] 1 is a schematic diagram of a fluid catalytic cracking unit including a series two-stage catalyst regeneration integrated with a riser reactor to provide a first stage reaction zone in the riser and a second stage bed cracking reaction zone. [Figure 2] 1 is a schematic diagram of a fluid catalytic cracking unit including dual riser technology, i.e., a two-stage catalyst regeneration in series integrated with primary and secondary riser reactors, where the primary riser reactor provides the first-stage reaction zone and the second-stage bed cracking reaction zone in the riser, and partially regenerated catalyst is added to the secondary riser reactor. [Figure 3] 1 is a schematic diagram of a fluid catalytic cracking unit including dual riser technology, i.e., a two-stage catalyst regeneration in series integrated with primary and secondary riser reactors, where the primary riser reactor provides the first-stage reaction zone and the second-stage bed cracking reaction zone, and fully regenerated and partially regenerated catalyst are added to the secondary riser reactor. [Figure 4] 1 is a schematic diagram of a fluid catalytic cracking unit with two-stage catalyst regeneration having a single regenerator vessel containing two catalyst regeneration zones, the unit including dual riser technology, i.e., primary and secondary riser reactors, where the primary riser reactor provides a first-stage reaction zone and a second-stage bed cracking reaction zone, and the secondary riser is in fluid communication with the bed cracking reaction zone of the primary riser reactor. [Figure 5] 1 is a schematic diagram of a fluid catalytic cracking unit with two-stage catalyst regeneration having a single regenerator vessel containing two catalyst regeneration zones, the unit including dual riser technology, i.e., primary and secondary riser reactors, where the primary riser reactor provides the first stage reaction zone and the second stage bed cracking reaction zone. [Figure 6A] FIG. 1 is a graphical representation of the effect of regenerator temperature on cat / oil ratio and propylene yield for a feed having an API of 24.9 and a CCR of 2.4. [Figure 6B] FIG. 1 is a graphical representation of the effect of regenerator temperature on cat / oil ratio and propylene yield for a feed having an API of 27.5 and a CCR of 0.05. [Figure 6C]FIG. 1 is a graphical representation of the effect of regenerator temperature on cat / oil ratio and propylene yield for a feed having an API of 21.3 and a CCR of 0.2. DETAILED DESCRIPTION OF THE INVENTION

[0020] The disclosed multi-stage catalyst regeneration process enables simultaneous selective processing of high-boiling and low-boiling components contained in gas oils and residual oils. In the first stage of the disclosed regeneration process, catalyst particles loaded with hydrocarbonaceous material, such as coke, are regenerated under conditions of oxygen concentration and temperature ranging from 1150°F to 1300°F selected to specifically combust the hydrogen associated with the hydrocarbonaceous material. These conditions result in residual levels of carbon remaining on the catalyst and the production of carbon monoxide (CO)-rich combustion gases. This relatively gentle regeneration helps limit localized catalyst hot spots in the presence of steam formed during hydrogen combustion, so that the steam formed does not substantially reduce catalyst activity. Thus, a partially regenerated catalyst containing residual carbon, with the remaining coke substantially free of hydrogen, is recovered from this catalyst regeneration stage and passed to a second-stage, high-temperature regenerator where the remaining carbon is substantially completely combusted to CO at elevated temperatures up to 1400°F. This second stage regeneration is carried out under conditions and in the presence of sufficient oxygen to combust substantially all residual carbon deposits and produce CO2-rich combustion gases.

[0021] The regenerated catalyst is withdrawn from the second stage and charged to the riser reactor in a quantity sufficient to result in substantially complete vaporization of the hydrocarbon feed. Because the catalyst particles are typically at a temperature in the range of about 1300°F to about 1400°F, the hot catalyst is rapidly vaporized upon contact with the hydrocarbon feed, followed by subsequent catalytic cracking of the feed.

[0022] According to the embodiment of FIG. 1, a method for cracking a hydrocarbon feed, such as a residue or heavy feedstock, is provided that utilizes a multi-stage catalyst regenerator (200), e.g., two regenerator vessels in series, for two-stage catalyst regeneration. The method operates a first-stage regenerator (8) in a partial burn-off combustion mode to provide a partial catalyst regeneration zone (4), followed by a second-stage regenerator (9) in a full catalyst regeneration zone (5) for a full burn-off combustion mode. The first and second regenerators (8, 9) shown in FIG. 1 are integrated in series. However, the regenerators can be utilized in a parallel configuration, which is not shown in FIG. 1. The partial burn-off regeneration in the first-stage regenerator (8) operates in an oxygen-starved environment, burning off a portion of the coke on the catalyst, typically 50% to 80%, and all entrained hydrocarbons from the stripper, at low regenerator temperatures in the range of 1150°F to 1300°F, which minimizes hydrothermal deactivation of the catalyst. The carbon on regenerated catalyst (CRC) for the partial combustion zone catalyst is typically about 0.3-0.9 wt%. The partially regenerated catalyst from the catalyst partial regeneration zone (4) of the first stage regenerator (8) is then transferred to the catalyst full regeneration zone (5) in the second stage regenerator (9), typically through an internal lift line riser between the two regenerators (8, 9) or through an external transfer line, as shown in FIG. 1. The catalyst is nearly fully regenerated in a full combustion mode with excess oxygen in the second stage regenerator (9), which operates at about 1300°F to about 1400°F. The carbon on regenerated catalyst (CRC) for the full combustion zone catalyst is typically about 0.01-0.1 wt%. The two-stage reaction zone includes a primary or first riser reactor (1) that receives the fully regenerated catalyst (6) from a pipe or conduit in fluid communication with a collection well (3). The primary riser reactor (1) provides a first-stage reaction zone and a second-stage reaction zone. The second-stage reaction zone includes a bed decomposition reaction zone (2) at the top of the riser reactor (1) in the reactor vessel (100). The reactor vessel (100) can be, for example, a single reactor vessel, as shown in FIG. 1, in which the first-stage reaction zone of the primary riser reactor (1) is in fluid communication with the bed decomposition reaction zone (2) within the reactor vessel (100). The bed decomposition reaction zone (2) utilizes a bed temperature of about 840°F to about 1100°F.

[0023] According to the embodiment of Figure 1, the lowest possible temperature of fully regenerated catalyst is provided through the exclusion of carbon monoxide (CO)-rich combustion gas ports (7) from the catalyst partial regeneration zone (4) in the first-stage regenerator (8). This ensures the highest possible catalyst circulation from the regenerator for a given riser outlet temperature, maintaining the same riser cracking heat requirement, thereby increasing the catalyst-to-oil ratio, which further increases catalytic cracking and maximizes olefin yield. This method further increases propylene and LPG yields from existing, known deep catalytic cracking (DCC) technology, essentially providing riser-plus-bed cracking. The increased catalyst circulation leads to increased conversion, propylene yield, and naphtha-to-LPG conversion due to increased catalytic reaction.

[0024] The claimed process is capable of processing various types of feedstocks ranging from light to heavy feedstocks, including recycle streams, whereas conventional DCC technology is limited to processing only light feedstocks.

[0025] 2 provides an embodiment utilizing two-stage regeneration in a multi-stage catalyst regenerator (200), e.g., two regenerator vessels in series integrated with series and parallel riser reactors and multiple reaction zones, where fully regenerated catalyst (6) from a full catalyst regeneration zone (5) in the second stage regenerator (9) is fed into a primary riser reactor (1) containing two reaction zones in series. In this embodiment, partially regenerated catalyst (11) from a partial catalyst regeneration zone (4) in the first stage regenerator (8) is fed into a second or secondary riser reactor (10). The catalyst feed to the two risers operating in parallel is from two separate catalyst regenerators (8, 9), allowing independent control of catalyst circulation to the primary and secondary riser reactors (1, 10). The primary riser reactor (1) provides a first-stage reaction zone and a second-stage reaction zone, including a bed cracking reaction zone (2) at the top of the riser reactor (1), in a single reactor vessel (100). The reactor vessel (100) can be, for example, a single reactor vessel, as shown in FIG. 2, in which the first-stage reaction zone of the primary riser reactor (1) is in fluid communication with a bed cracking reaction zone (2) within the reactor vessel (100). The bed cracking reaction zone (2) utilizes a bed temperature of about 840°F to about 1100°F. According to the embodiment shown in FIG. 2, the primary riser reactor (1) preferably processes heavier feedstocks. Partially regenerated catalyst (11) from the catalyst partial regeneration zone (4) in the first-stage regenerator (8) is fed into a secondary riser reactor (10), which preferably processes lighter feedstocks and / or recycle streams, such as uncracked bottoms and partial cracked product streams. The partial cracking product stream includes products that have the potential to be further reacted or cracked, such as, for example, propylene from gasoline.

[0026] The feed streams to the primary and secondary risers (1, 10) can be switched if necessary to add further flexibility to achieve multiple product specifications. Depending on the feedstock, the catalyst flows to the primary and secondary riser reactors (1, 10) can be reversed, i.e., partially regenerated catalyst to the primary riser reactor (1) and fully regenerated catalyst to the secondary riser reactor (10). In this embodiment, the product vapor from the reaction zone of the primary riser reactor (1) undergoes further reactions in a second reaction zone, including, for example, a bed cracking reaction zone (2) at the top of the riser reactor (1) in a single reactor vessel (100), to convert naphtha vapor from the reaction zone of the primary riser reactor (1) to propylene-enriched LPG.

[0027] The vapor residence time in the first riser reactor (1) is typically about 1 to 5 seconds, more preferably about 2 seconds. The catalyst bed level in the bed cracking reaction zone (2) is maintained to receive a vapor weight hourly space velocity of about 1 to 10 hr to achieve conversion of the naphtha-rich riser vapors to a propylene-rich product stream.

[0028] The claimed process utilizes a primary riser reactor (1) to provide a first and second stage reaction zone, including a bed cracking reaction zone (2), at the top of the riser reactor (1), requires reactor pressures ranging from about 10 psig to 20 psig, preferably 12.5 psig to 15 psig, and utilizes riser steam at about 20-30 wt.% of the feed. In contrast, conventional fluid catalytic cracking units typically operate at reactor pressures of about 25 psig to 40 psig and utilize riser steam at about 7-8 wt.% of the feed.

[0029] According to one embodiment, the catalyst partial regeneration zone (4) operates at a lower temperature than the catalyst full regeneration zone (5). Thus, the cooler catalyst from the catalyst partial regeneration zone (4) to the second riser reactor (10) provides a higher catalyst-to-oil ratio for a given reactor outlet temperature (ROT). Furthermore, the degree of partial regeneration of the catalyst in the catalyst partial regeneration zone (4) can be independently controlled, which can be used to further control the temperature of the catalyst partial regeneration zone (4) and increase or decrease the catalyst circulation to the second riser reactor (10).

[0030] The second riser reactor (10) utilizes an FCC catalyst to provide heat for the reaction. Suitable catalysts for use in the secondary riser reactor include, for example, ZSM-5, which converts naphtha to propylene. The use of ZSM-5 as a fluid catalytic cracking additive has been found to result in little delta coke loading and little regeneration required. It is more efficient to operate the secondary riser reactor on partially regenerated catalyst from the first stage regenerator.

[0031] The presently claimed method and apparatus optimizes separate catalyst feeds to parallel riser reactors from two catalyst regenerators with independent control of catalyst circulation to the riser reactors. Additionally, the process of the present invention reduces the load on the lift line, i.e., the transfer line connecting the first stage regenerator (8) to the second stage regenerator (9). In this manner, a portion of the partially regenerated catalyst (11) from the catalyst partial regeneration zone (4) in the first stage regenerator (8) is fed into the second riser reactor (10), and the remainder of the partially regenerated catalyst in the catalyst partial regeneration zone (4) in the first stage regenerator (8) is transferred to the catalyst full regeneration zone (5) in the second stage regenerator (9) for full catalyst combustion and regeneration.

[0032] According to another embodiment, as shown in FIG. 3, fully regenerated catalyst (6) from the catalyst full regeneration zone (5) in the second stage regenerator (9) is fed into the primary riser reactor (1) via a recovery well (3). The primary riser reactor (1) contains a two-stage reaction zone, including the primary riser reactor (1) providing a first-stage reaction zone and a second-stage bed cracking reaction zone (2) at the top of the riser reactor (1) in a single reactor vessel (100). According to this embodiment, the primary riser processes a heavier feedstock, and the partially regenerated catalyst (11) from the catalyst partial regeneration zone (4) in the first stage regenerator (8) and the fully regenerated catalyst (6a) are fed into the secondary, i.e., second, riser reactor (10). The secondary riser reactor (10) preferably processes lighter feedstocks and / or recycle streams. Depending on the feedstock, the catalyst flows to the primary and secondary risers can be reversed, i.e., partially and fully regenerated catalyst to the primary riser and fully regenerated catalyst to the secondary riser. The embodiment of Figure 3 provides fully regenerated catalyst (6) to the first riser reactor (1) and fully and partially regenerated catalyst (6a and 11) to the second riser reactor (10). Adding a portion of the fully and partially regenerated catalyst (6a and 11) to the second riser reactor (10) provides flexibility to vary the delta coke on the catalyst, i.e., the difference between the coke on the spent catalyst (at the stripper outlet) and the coke on the regenerated catalyst, expressed as a weight percent of the catalyst, required to optimize the heat balance and cracking potential for operation of the second riser reactor (10).

[0033] It should be noted in Figures 2 and 3 that the vapors from the secondary riser (10) can undergo further reaction in a second stage bed decomposition reaction zone (2) above the first stage reaction (not shown, see e.g., Figure 4), or can terminate above the bed decomposition reaction zone (2) as shown.

[0034] In prior art FCC two-stage regeneration processes, all catalyst from the first stage regeneration is transferred to the second stage regeneration. In the disclosed method, less coke is transferred from the first stage regenerator (8) to the second stage regenerator (9), thereby requiring less air in the second stage regenerator (9) and reducing the overall air required to burn the coke. The method of the present invention reduces the size and internals of the second stage regenerator (9), reducing equipment costs. By combining the fully regenerated and partially regenerated catalyst streams (6a and 11) to the second riser reactor (10), the operation of the second riser reactor (10) is fully optimized.

[0035] In Figures 4 and 5, the multi-stage catalyst regenerator is incorporated into a single regenerator vessel (200a), and the catalyst feed to the first or primary riser reactor (1) and the second or secondary riser reactor (10) comes from a catalyst partial regeneration zone and a catalyst full regeneration zone located within the single regenerator vessel (200a). Using internals / packing (12), such as structured packing as shown in Figures 4 and 5, a catalyst partial regeneration zone (4a) above the packing (12) and a catalyst full regeneration zone (5a) below the packing (12) can be achieved. In the single regenerator vessel (200a), the packing (12) separates the catalyst bed into an upper catalyst partial regeneration zone or partially regenerated catalyst zone (4a) and a lower catalyst full regeneration zone or fully regenerated catalyst zone (5a), reducing backmixing to achieve an O2-rich environment in the lower fully regenerated catalyst zone (5a) section and an O2-poor environment in the upper partially regenerated catalyst zone (4a). Due to the cooler flow of spent catalyst added to the upper zone and the partial combustion, i.e., incomplete CO combustion, the upper zone temperature will be lower. Injecting cold air or oxygen or a mixture of air and oxygen above the packing (12) reduces the effect of hot combustion gases coming from the lower section. The low-temperature partially regenerated catalyst in the upper catalyst partial regeneration zone (4a) provides high catalyst circulation to the second riser (10). In this way, the catalyst partial regeneration zone (4a), operating in partial combustion mode, is always at a lower temperature than the catalyst full regeneration zone (5a). Supplying partially regenerated catalyst (11) to the second riser reactor (10) provides higher catalyst circulation, which is required to crack lighter feedstocks and maximize propylene and LPG yields. If desired, the single regenerator vessel (200a) can be modified to provide a catalyst full regeneration zone or fully regenerated catalyst zone (5a) above the packing and place the catalyst partial regeneration zone (4a) below the packing.

[0036] Figures 4 and 5 present two different embodiments as examples of how vapors from the secondary riser (10) can end up in or above the bed decomposition reaction zone (2). In Figure 5, the product vapors from the secondary riser reactor (10) do not undergo further reaction in the second-stage bed decomposition reaction zone (2) above the first-stage reaction zone.

[0037] According to the embodiment shown in Figure 4, fully regenerated catalyst (6) from the lower catalyst full regeneration zone (5a) section of the single regenerator vessel (200a) below the packing / internals (12) is fed into the primary riser reactor (1) for processing of medium to heavier feeds. Partially regenerated catalyst (11) from the upper catalyst partial regeneration zone (4a) in the top section of the single regenerator vessel (200a) above the packing / internals (12) is fed into the secondary riser reactor (10) for processing of lighter feeds and / or recycle streams.

[0038] According to the embodiment presented in Figure 4, the catalyst flow from a single regenerator vessel (200a) utilizing separate regeneration zones within the single regenerator vessel (200a) is fed to parallel riser reactors, i.e., a first or primary riser reactor (1) and a second or secondary riser reactor (10). Depending on the feedstock, the catalyst flow to the riser reactors (1) and (10) can be reversed, e.g., partially regenerated catalyst (11) to the primary riser reactor (1) and fully regenerated catalyst (6) to the secondary riser reactor (10). According to this embodiment, product vapor from the primary riser reactor (1) undergoes further reactions in a second-stage bed cracking reaction zone (2) in the single reactor vessel (100) above the first-stage reaction zone of the riser reactor (1), and the product from the secondary riser (10) is terminated in the bed cracking reaction zone (2) to maximize olefin yield.

[0039] Similar to the embodiment of FIG. 3, the use of a single regeneration vessel (200a) as presented in FIGS. 4 and 5 can be adapted to feed partially and fully regenerated catalyst to the secondary riser (10) and fully regenerated catalyst to the primary riser reactor (1), as well as to feed fully and partially regenerated catalyst to the primary riser reactor (1) and fully regenerated catalyst to the secondary riser (10).

[0040] The embodiments of Figures 4 and 5 are useful for processing light to heavier, preferably intermediate, feedstocks to further maximize olefins and reduce regenerator air utilization, reducing size and cost.

[0041] Figures 6A, 6B, and 6C graphically illustrate three examples of the presently claimed process based on three different feedstocks ranging from light to heavy. As discussed, the disclosed process provides flexibility to control regenerated catalyst temperature and achieve the lowest possible overall temperature, resulting in the highest possible catalyst-to-oil ratio required to maximize olefins, specifically propylene, compared to the prior art. These examples demonstrate the effect of reducing the overall regenerator temperature on overall catalyst circulation, i.e., catalyst-to-oil ratio and propylene yield. The graphs in Figures 6A-6C demonstrate that catalyst circulation and propylene yield increase as the overall temperature decreases relative to when existing FCC technology operates, compared to the present process.

[0042] The above description and examples are merely illustrative of the present invention and should not be construed as limiting the scope of the invention. Various modifications will become apparent to those skilled in the art in view of the foregoing disclosure. It is intended that all such modifications that fall within the scope and spirit of the appended claims be embraced thereby.

Claims

1. 1. A method for increasing olefin production from a hydrocarbon feed, comprising: a) delivering partially regenerated catalyst from a multi-stage catalyst regenerator through at least one catalyst partial regeneration zone to a secondary riser reactor and fully regenerated catalyst from at least one catalyst full regeneration zone to a primary riser reactor; b) cracking the hydrocarbon feed in a first reaction zone of the primary riser reactor to produce a first cracked product comprising olefins and spent catalyst, and passing the first cracked product and spent catalyst to a bed cracking reaction zone in a reactor vessel to produce a second cracked product; c) separating the first and second cracked products from the spent catalyst in the reactor vessel; and d) recovering the first and second cracked products comprising olefins and recovering an uncracked bottoms and partial cracked product from the first and second cracked products. e) cracking the recycle feed comprising at least one of the uncracked bottoms, partially cracked, and cracked products of step (d) in the secondary riser reactor to produce a third cracked product and additional spent catalyst; f) separating and recovering the third cracked product comprising olefins from the additional spent catalyst and delivering the additional spent catalyst to the reactor vessel; g) passing the spent catalyst from the reactor vessel to the multi-stage catalyst regenerator comprising the catalyst partial regeneration zone in a first regenerator vessel and the catalyst full regeneration zone in a second regenerator vessel, wherein the spent catalyst is partially regenerated to provide the partially regenerated catalyst and a portion of the partially regenerated catalyst is delivered to the catalyst full regeneration zone to provide the fully regenerated catalyst; The method, wherein the first regenerator vessel and the second regenerator vessel in the multi-stage catalyst regenerator operate in series with one another for catalyst flow.

2. 10. The process of claim 1, wherein the third decomposition product undergoes further reaction in a bed decomposition reaction zone.

3. 10. The process of claim 1, wherein a portion of the fully regenerated catalyst is fed to a secondary riser reactor.

4. 10. The method of claim 1, wherein the portion of the partially regenerated catalyst delivered to the catalyst full regeneration zone has a delivery temperature that is lower than the temperature of the fully regenerated catalyst exiting the catalyst full regeneration zone.

5. 10. The method of claim 1, wherein the temperature of the partially regenerated catalyst delivered to the full catalyst regeneration zone ranges from about 1150°F to about 1300°F.

6. 10. The method of claim 1, wherein the temperature of the fully regenerated catalyst exiting the fully regenerated catalyst zone ranges from about 1250°F to about 1500°F.

7. 2. The process of claim 1, wherein the hydrocarbon feed is selected from the group consisting of vacuum gas oil, heavy atmospheric gas oil, atmospheric resid, vacuum resid, coker gas oils, visbreaker gas oils, deasphalted oils, hydrocracker bottoms, vegetable oils, and heavy conversion products produced from biomass, and any combination or hydrotreated counterpart thereof.

8. The cracked products of the first and second riser reactors are ２ and lighter, C ３ -C ６ Light olefins and paraffins, C ６ -C ８ Light FCC gasoline, light cracked naphtha (LCN), benzene and C ８ -C ９ Intermediate FCC gasoline containing hydrocarbons, C ９ -C １１ Heavy FCC gasoline containing hydrocarbons, and C ５ 10. The method of claim 1, further comprising one or more gaseous product streams comprising materials boiling in the range of from the boiling point of 1000 to about 430°F, middle distillates boiling in the range of from about 330°F to about 630°F, and other gasoline boiling range products including uncracked bottoms boiling in the range of from about 650°F to about 900°F.

9. The recycled feed is C ４ 10. The process of claim 1, wherein the product comprises at least one product from the group consisting of light FCC gasoline (LCN), light cycle oil (LCO), heavy cycle oil product (HCO), and slurry oil.

10. 10. The method of claim 1, wherein the recycle feed stream comprises hydrocarbons from other refineries and petrochemical units.

11. 10. The method of claim 1, wherein the recycle feed stream is cocaine cannabsa.

12. The method of claim 1, wherein the first riser reactor operates at an outlet temperature of from 840°F to about 1100°F.

13. The method of claim 1, wherein the secondary riser reactor operates at an outlet temperature of from 950°F to about 1200°F.

14. 10. The process of claim 1, wherein the catalyst to oil (C / O) ratio of the primary riser reactor is less than the catalyst to oil ratio of the secondary riser reactor.

15. 10. The process of claim 1, wherein the catalyst-to-oil (C / O) ratio of the primary riser reactor is about 0.2 wt / wt to about 1 wt / wt less than the catalyst-to-oil ratio of the secondary riser reactor.

16. 10. The method of claim 1, wherein the spent catalyst is stripped before the catalyst is regenerated.

17. 10. The method of claim 1, wherein the cracked products from the secondary riser reactor are quenched.

18. 10. The method of claim 1, wherein the multi-stage catalyst regenerator comprises two separate regenerator vessels stacked together in series or arranged side by side.

19. 20. The method of claim 18, wherein the combustion gas outlets from the first regenerator vessel and the second regenerator vessel are in series or parallel.

20. 10. The process of claim 1, wherein the bed decomposition reaction zone is at the top of the primary riser reactor.

21. 10. The method of claim 1, wherein the multi-stage catalyst regenerator comprises internals and / or packing.

22. 2. The method of claim 1, wherein a multi-stage catalyst regenerator and reactor vessel are in a hydrocarbon cracking system for maximizing olefin production, the multi-stage catalyst regenerator provides partially regenerated catalyst and / or fully regenerated catalyst to a first riser reactor having two reaction zones in series and a second riser reactor, respectively, each riser reactor receiving a different feed selected between a hydrocarbon feed and a recycle feed, and the reactor vessel includes one of the reaction zones of the first riser reactor and a region for receiving and sending a coked catalyst to the multi-stage catalyst regenerator.

Images