Riser reactor system

Abstract

To provide a reactor and process for fluid catalytic cracking (FCC) of a hydrocarbon feed in a riser reactor.SOLUTION: There is provided a process for FCC, comprising: injecting a hydrocarbon feed into an evaporation zone of a riser reactor; injecting a first catalyst into the evaporation zone, wherein the first catalyst is mixed with the hydrocarbon feed to generate a hydrocarbon stream in the evaporation zone, and wherein the temperature of the evaporation zone is less than 625°C; and passing the hydrocarbon stream from the evaporation zone to a cracking zone of the riser reactor to generate a cracked product in the cracking zone.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for fluid catalytic cracking (FCC) of a hydrocarbon feed. More specifically, the present invention relates to an apparatus and method for vaporizing the feed and mixing the feed with catalyst (i.e., hydrocarbons) in a zone designated as such in an FCC riser reactor, and for injecting the feed / catalyst into the FCC riser reactor at multiple injection points in an effort to reduce thermal cracking and dry gas production during feed vaporization and improve feed / catalyst mixing. [Background technology]

[0002] The process of fluid catalytic cracking (FCC) is an important conversion process that is often performed in modern oil refineries. The FCC process is a chemical process that uses catalysts to convert high boiling hydrocarbon fractions derived from crude oil into more valuable FCC end products such as gasoline components (naphtha), fuel oil, and olefin gases (i.e., ethene, propene, butene). A typical FCC unit includes at least one of each including an FCC reactor (i.e., riser reactor), a regenerator, and a separator. The riser reactor and the regenerator are considered the main components of the FCC unit. For example, the majority of the endothermic cracking reactions of the hydrocarbon feed and coke deposits take place in the riser reactor, while the regenerator is utilized to reactivate the catalyst by burning the accumulated coke deposits.

[0003] During FCC operation, the heated catalyst flows from the regenerator and into the bottom section of the riser reactor where it contacts the heated hydrocarbon feed. Upon contact, the catalyst vaporizes and cracks or breaks the long chain molecules of the feed into new shorter molecules, thereby forming a feed-catalyst mixture. The vaporized feed fluidizes the solid catalyst, which causes the feed-catalyst mixture to expand and flow upward in the riser reactor for further cracking, thereby resulting in one or more desired cracking products. Additionally, coke formation begins to deposit on the catalyst during the reaction, gradually deactivating the catalyst.

[0004] The desired cracking products are withdrawn from the top of the riser reactor and flow to the bottom section of the separator, and the deactivated catalyst is withdrawn from the bottom of the riser reactor and flows to the regenerator. The cracking products flowing to the separator, also called the main fractionator, are distilled into more valuable FCC end products. The regenerated, or reactivated, catalyst leaving the regenerator is recycled to the bottom section of the riser reactor, and the cycle is repeated. Often, fresh catalyst can be added along with the regenerated catalyst to optimize the cracking process.

[0005] Although the FCC process has been commercially established for over 75 years, technological advances are continually evolving to meet new challenges and provide overall continuous improvements. For example, market competitors have introduced various processes, technologies, and equipment related to FCC riser reactors, such as redesigning feed injection nozzles in an effort to improve feed and / or catalyst distribution and feed / catalyst mixing, creating multiple catalyst injection points to increase product yields and selectivity of the cracking reaction, and redesigning reaction systems to eliminate or reduce non-selective thermal cracking and dry gas generation. Some of these developments are discussed below.

[0006] U.S. Patent No. 4,795,547 and U.S. Patent No. 5,562,818 disclose the use of micronized Two bottom inlet nozzles with different diverter cone designs at the outlet of the feed pipe carrying the regenerated catalyst are described. The function of these diverter cones is to redirect the axially flowing feed stream to a radially discharging feed at the outlet in an effort to enhance mixing of the regenerated catalyst with the feed.

[0007] U.S. Patent No. 5,565,090 describes a riser reactor with multiple catalyst injection points for obtaining aromatics yields from naphtha feedstock during a catalytic reforming process. Catalyst meets the feedstock at the base of the riser reactor and is injected into the resulting mixture of feedstock, reactants, and catalyst at an intermediate point along the length of the riser. Preferably, 2 to 10 catalyst injection points are provided, including one at the base of the riser and 1 to 9 intermediate points. Approximately 10 to 95% of the catalyst meets the feedstock at the lower end of the riser reactor and approximately 1 to 70% of the catalyst is injected at any single other point along the length of the riser.

[0008] US Patent No. 5,055,177 describes a method and apparatus for separating a catalyst phase from a gas suspension phase as it is discharged from an outlet of a riser conversion zone to rapidly separate the cracking catalyst from the hydrocarbon vapor / catalyst particle suspension in an FCC process. In particular, the hydrocarbon vapor / catalyst particle suspension passes directly from the riser to a series of cyclone separators that separate the catalyst particles from the suspension in an effort to reduce excessive cracking of the hydrocarbon conversion products and to facilitate recovery of the desired products. The cyclone separators connected in series within a single reactor vessel include a riser cyclone separator, a primary cyclone separator, and a secondary cyclone separator. Summary of the Invention [Problem to be solved by the invention]

[0009] Despite various attempts, continued progress remains necessary for enhanced FCC processes, components, and technologies, including improvements related to temperature and velocity profiles across the riser reactor, uniformity during mixing of the feed and catalyst, and performance during catalytic reactions, among other desired improvements.

[0010] It is an object of the present invention to provide an apparatus and method for fluid catalytic cracking (FCC) of a hydrocarbon feed.

[0011] It is an object of the present invention to provide an apparatus and method for containing the feed vaporization and feed / catalyst mixing in a zone designated as such in an FCC riser reactor, and for injecting the feed and catalyst into the FCC riser reactor at multiple injection points in an effort to reduce thermal cracking and dry gas production during feed vaporization and improve feed / catalyst mixing.

[0012] It is an object of the present invention to provide an apparatus and method in which feed vaporization and feed-catalyst mixing are directed to specific zones within an FCC riser reactor.

[0013] It is an object of the present invention to provide an apparatus and method in which feed vaporization and mixing with catalyst are directed to specific zones within an FCC riser reactor and catalyst is injected at multiple injection points along the length of the FCC riser.

[0014] Other advantages and features of the embodiments of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description, while indicating preferred embodiments of the invention, is given by way of example only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. [Brief description of the drawings]

[0015] Certain exemplary embodiments are described with reference to the following detailed description and drawings.

[0016] [Figure 1] 1 is a schematic diagram of an FCC unit including a riser reactor system with multi-stage catalyst injection according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram of the riser reactor system with multi-stage catalyst injection shown in FIG. 1 in accordance with an embodiment of the present invention. [Diagram 3] FIG. 3 is a schematic diagram of an injection device of the second stage of the riser reactor system with multi-stage catalyst injection shown in FIG. 2 according to a first embodiment of the present invention. [Figure 4] FIG. 3 is a schematic diagram of an injection device of the second stage of the riser reactor system with multi-stage catalyst injection shown in FIG. 2 according to a second embodiment of the present invention. [Diagram 5] 3 is a graphical comparison of the temperature profile of a conventional riser reactor as compared to the temperature profile of a riser reactor system with multi-stage catalyst injection shown in FIG. 2 in accordance with an embodiment of the present invention. [Figure 6] 3 is a graphical comparison of the radial distribution profile of axial velocity of a conventional riser reactor compared to the radial distribution profile of axial velocity of a riser reactor system with multi-stage catalyst injection shown in FIG. 2 according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Most of the endothermic cracking reactions during the FCC process take place in the FCC riser reactor, which may consist of one or more reaction zones. In a conventional FCC riser reactor, both the vaporization of the feed and the cracking reaction may occur in the same reaction zone of the reactor, usually at elevated temperatures, e.g., at least 630°C. In other typical FCC riser reactors, several riser reactors may be used in series, each containing at least one reaction zone operating within an elevated temperature range to continuously vaporize and crack the feed.

[0018] In order to produce maximum yields of desired end products, a substantial majority, preferably all, of the vaporized feed must be vaporized and homogeneously mixed with the catalyst before cracking of the vaporized feed is initiated. Otherwise, incomplete vaporization of the feed may lead to the formation of undesirable by-products, such as coke, due to oil-oil contact. As previously discussed with respect to conventional riser reactors, elevated temperatures may also promote premature thermal cracking of the vaporized feed. Undesirable thermal cracking may lead to the generation of unnecessary dry gases, with a corresponding impact on the production yield of more valuable products, such as light olefins.

[0019] In thermal cracking processes, elevated temperatures and pressures are used to crack the feed without the use of a catalyst. Conversely, in FCC processes, the vaporized feed is cracked upon contact with a hot catalyst at lower temperatures and pressures when compared to thermal cracking conditions. Whether or not a catalyst is used to initiate the cracking reaction, elevated reaction temperatures in the riser reactor, such as above about 630° C., favor premature thermal cracking of the feed. In this regard, increasing the temperature across the riser reactor decreases the yield of high-value products while increasing low-value products such as heavy fuels and light gases (e.g., methane and ethane).

[0020] It has now been advantageously found that the described problems, caused inter alia by thermal cracking, dry gas generation and lack of uniform feed / catalyst mixing, can be overcome by the present invention, which relates to a riser reactor of the present invention for use in an FCC process and to an FCC process for catalytically cracking a hydrocarbon feed in the riser reactor of the present invention. The riser reactor of this embodiment comprises an evaporation zone and a cracking zone. The riser reactor includes separate, unique zones containing a feed / catalyst mixing zone, a feed vaporization zone, and a feed / catalyst mixing zone. A substantially majority, and preferably essentially all, of the feed vaporization is confined to the vaporization zone of the present riser reactor embodiments, and the temperature in the vaporization zone is less than 625° C., preferably less than 550° C., and more preferably less than 525° C. Since minimal cracking occurs in the vaporization zone, a substantially majority of the vaporized feed is cracked in the cracking zone of the present riser reactor embodiments.

[0021] Surprisingly, it has been found that the riser reactor of the present invention with an evaporation zone configured for vaporization of the feed and for containing the feed / catalyst mixture reduces thermal cracking from occurring before catalytic cracking of the feed begins because the temperature of the evaporation zone is less than 625° C., preferably less than 550° C., and more preferably less than 525° C. Along with the reduction in thermal cracking, other advantages provided by embodiments of the present invention include reduced production of dry gas (e.g., methane, ethane) and increased FCC unit capacity since various FCC equipment such as wet gas compressors are not overloaded with excess dry gas, thereby providing higher product yields.

[0022] In a typical FCC unit, the majority of the catalyst is injected into the bottom section of the riser reactor, resulting in a catalyst concentration that is higher than the feed concentration in that particular section. However, when catalyst injection occurs on one side of the riser reactor, the local catalyst concentration will be higher along that side than the cross-sectional average catalyst concentration of the riser reactor. When this occurs, it can lead to non-uniformity of catalyst distribution in the riser reactor. However, the present embodiment includes at least two catalyst injection points along the length of the riser reactor, including at least one catalyst injection point in the evaporation zone and at least one catalyst injection point in the cracking zone, resulting in a more evenly distributed catalyst concentration. In this regard, the majority of the catalyst concentration that would have been injected into the bottom section during conventional operation is now injected into both the evaporation zone (i.e., first stage catalyst injection) and the cracking zone (i.e., second stage catalyst injection). Thus, in the present embodiment, a lower, or diluted, catalyst concentration is now present in the evaporation zone, located in the bottom section of the riser reactor. Beneficial advantages of multiple catalyst injection points include more thorough and uniform feed / catalyst mixing along the entire length of the riser reactor. It is noted that in other embodiments of the invention, additional stages of catalyst injection (e.g., a third and / or fourth stage catalyst injection) may be implemented.

[0023] In addition to reduced thermal cracking / drying gas production and more uniform feed / catalyst mixing, the synergistic behavior exhibited by the combination of lower vaporization zone temperature and multi-catalyst injection also includes ideal plug flow conditions and more uniform radial gas / solid velocity profiles throughout the riser reactor. In this regard, the beneficial effects of the riser reactor of the present invention promote increased catalyst selectivity / activity during the cracking reaction and increased product yields.

[0024] Furthermore, the synergistic effects displayed by the riser reactor of the present invention provide several other benefits and advantages. Due to the lower temperature of the evaporation zone compared to a typical FCC riser reactor, the riser reactor of the present invention exhibits an overall lower and more uniform temperature profile over the entire length of the reactor, thereby avoiding the higher temperature profile of the riser reactor (e.g., at least 700°C). The overall lower temperature of the riser reactor embodiment advantageously provides more flexibility with respect to the type of materials utilized within the FCC unit, including the use of materials that are sensitive to higher temperatures. Furthermore, with separate evaporation and cracking zones, the present invention provides the unexpected advantage of avoiding increased equipment costs and operational complexity when additional equipment, such as, for example, several riser reactors in series, is implemented.

[0025] Modern FCC units are capable of processing a wide variety of feedstocks and catalysts, The present invention may be configured to adjust operating conditions to maximize the production of valuable FCC end products, such as gasoline, middle distillates, or light olefins, to meet the market demands of the market. The feeds described for this embodiment may include a variety of feedstocks known to those skilled in the art, such as heavy gas oil (HGO), vacuum gas oil (VGO), residual feedstocks that may be otherwise blended into residual fuel oil, atmospheric gas oil (AGO), crude oil fractions, process intermediates, and product recycles. However, for purposes of this embodiment, the type of feed and the method of injection of the feed are subject to conventional standards and techniques and are not discussed herein.

[0026] The catalysts used and recycled for catalytic cracking within the scope of the present embodiment may be any suitable catalyst known in the art to have cracking activity under suitable catalytic cracking conditions. For example, preferred cracking catalysts for use in the present embodiment may include conventional regenerated and / or new cracking catalysts composed of cracking active molecular sieves dispersed in a porous inorganic refractory oxide matrix or binder, as well as shape-selective cracking additives such as ZSM-5 and other cracking-enhancing additives designed to selectively crack feed constituents of a particular boiling range. Nevertheless, for the purposes of the present embodiment, the type of catalyst and catalytic cracking conditions used in the present invention are subject to conventional standards and techniques and are not discussed herein.

[0027] FIG. 1 is a schematic diagram of an FCC unit 100 including a riser reactor system with multi-stage catalyst injection according to an embodiment of the present invention. As shown in FIG. 1, a hydrocarbon feed (referred to herein as "feed") via line 102 is introduced into the bottom section of a riser reactor 104. The riser reactor 104 may be a reaction vessel suitable for catalytic cracking reactions as known in the art and may be configured as an internal riser reactor or an external riser reactor. A hot regenerated catalyst (referred to herein as "catalyst") via line 106 flows from a regenerator 108 and into the bottom of the riser reactor 104 to mix and react with the feed to form a feed-catalyst mixture. Specifically, the feed vaporizes upon contact with the hot catalyst in the bottom of the riser reactor 104. As the feed vapor flows upward along the height of the riser reactor 104, the catalyst is fluidized and transported by the vapor, resulting in the formation of a feed-catalyst mixture. Optionally, but preferably, a lift gas via line 110 can be introduced into the bottom of the riser reactor 104 to further fluidize the catalyst and promote proper feed-catalyst mixing.

[0028] The feed and catalyst mixture is subjected to elevated temperatures while passing upwardly through the riser reactor 104. Such elevated temperatures are sufficient to break or crack the long chain molecules of the feed vapor into new shorter molecules to produce one or more cracking products while simultaneously depositing coke on the catalyst, i.e., the spent catalyst. The cracking products and spent catalyst mixture exits the top section of the riser reactor 104 and flows to a reactor vessel 112 that includes at least one separator 114. The separator 114 may be any conventional system that defines a separation zone or a stripping zone, or both, and provides a means for separating the cracking products from the spent catalyst.

[0029] The separated cracked products pass from separator 114 via line 116 to a main fractionator system 118, which may include any system known to those skilled in the art for recovering and separating the cracked products into various end products. The end products exiting main fractionator system 118 may include, for example, olefins (e.g., C2-C4 olefins), gasoline, and middle distillates, which are passed from system 118 via lines 120, 122, and 124, respectively, for continued use.

[0030] The separated spent catalyst is passed from separator 114 and through line 126 to regenerator 1. The regenerator 108 defines a regeneration zone and provides a means for contacting the spent catalyst with an oxygen-containing gas, such as air, under carbon combustion conditions to remove coke deposits. The oxygen-containing gas is introduced into the regenerator 108 via line 128 and ignition gas passes from the regenerator 108 via line 130. The regenerated catalyst flows from the regenerator 108 via line 106 and to the riser reactor 104 to repeat the cycle of operation.

[0031] Figure 2 is a schematic diagram of a riser reactor system with multi-stage catalyst injection as shown in Figure 1, in accordance with an embodiment of the present invention. Like numbers are used with respect to Figure 1. As shown in Figure 2, the riser reactor 204 may be of any type, including, for example, an internal or external riser reactor and / or a riser reactor that includes a lift pot 232 located at the lower end of the riser reactor 204.

[0032] A first catalyst flow through distributor inlet 206 is introduced into lift pot 232, where lift gas through line 210 is also injected into lift pot 232. A sufficient amount of lift gas is provided to circulate and lift catalyst particles in an upward direction, so that the particles flow to the vaporization zone 234 of riser reactor 204. Examples of lift gas include steam, light hydrocarbon gas, vaporized petroleum and / or petroleum fractions, and / or any mixture thereof. From a practical standpoint, steam is most preferred as the lift gas. Light hydrocarbon gases may include, for example, hydrogen, methane, ethane, ethylene, and / or mixtures thereof. However, the use of vaporized oil and / or oil fractions (preferably vaporized liquefied petroleum gas, gasoline, diesel, kerosene, or naphtha) as the lift gas may be advantageous and may simultaneously act as a hydrogen donor to prevent or reduce coke formation. In a preferred embodiment, both steam and vaporized oil and / or oil fractions, light hydrocarbon gas, and / or mixtures thereof can be used as lift gas. The lift gas can be introduced as a single stream or as multiple streams, each stream may be from the same source or from different sources. For example, one stream may be steam and another stream may be vaporized oil and / or oil fractions, light hydrocarbon gas, and / or mixtures thereof.

[0033] While the hot catalyst particles pass upward into the evaporation zone 234, the first feed via distributor inlet 202 is also introduced into zone 234 where heat from the catalyst particles vaporizes the feed. In a typical process, the first feed is preheated before being injected into the evaporation zone 234, and a lift gas may also be used to assist in vaporizing the feed. Additionally, various techniques known in the art may be implemented during injection of the feed to enhance feed atomization and feed / catalyst contact and mixing.

[0034] As the vaporized feed and catalyst particles mix, a first feed / catalyst mixture (hereafter referred to as "hydrocarbon") 236 is formed in the vaporization zone 234. In this embodiment, the vaporization zone 234 extends substantially across the entire diameter (depicted by dotted line 238) of the riser reactor 204. Thus, the vaporization of the feed and the mixing of the feed / catalyst occurs substantially, and most preferably completely, within the vaporization zone 234 and across the diameter 238 of the riser reactor 204. The extension of the vaporization zone 234 across substantially the entire diameter 238 of the riser reactor 204 maintains a uniform temperature profile in the zone 234 and across the riser reactor 204. This uniformly maintained temperature profile avoids over-cracking valuable products into less valuable products in the rise-reactor 204 and minimizes thermal cracking that may produce undesirable by-products, such as dry gas and coke.

[0035] As previously mentioned, the catalyst temperature is determined by the vaporization rate of the feed and the time required for vaporization in the vaporization zone 234. The temperature of the first catalyst in the evaporation zone 234 affects both the likelihood of cracking of the feed that is not a primary feed. Advantageously, the temperature of the first catalyst in the evaporation zone 234 is sufficient to completely vaporize the first feed, but to substantially prevent thermal cracking of the hydrocarbons 236 that exit the evaporation zone 234 and enter the cracking zone 240 of the riser reactor 204. In particular, according to the present invention, catalytic and thermal cracking of the hydrocarbons 236 exiting the evaporation zone 234 is reduced to a substantially minimum level, and more preferably essentially no thermal cracking, in the evaporation zone 234, because the temperature of the zone is maintained below 625°C, preferably below 550°C, and most preferably below 525°C.

[0036] According to various embodiments, operating variables can be monitored in an effort to affect the temperature of the evaporation zone 234 to thereby ensure complete vaporization and minimal thermal cracking of the first feed within the zone 234. Examples of monitored operating variables include temperature, feed flow rate, and catalyst circulation rate, among others. Based on readings of such variables, the amount of first catalyst flow injected into the evaporation zone 234 via the distributor inlet 206 can be adjusted to provide enough heat to completely vaporize the first catalyst, but not overheat the first feed, thereby reducing and / or eliminating thermal cracking of the feed in the evaporation zone 234. In embodiments, the temperature range of the evaporation zone 234 is maintained below 625°C, preferably below 550°C, and most preferably below 525°C. The amount of the first catalyst stream injected into the vaporization zone 234 via the distributor inlet 206 ranges from about 10% to 90%, more preferably about 30% to 60%, and most preferably 45% to 55% of the total catalyst injection, while the ratio of the total catalyst stream to the feed is preferably in the range of 1:1 to 30:1, more preferably 3:1 to 15:1, and most preferably 5:1 to 10:1. By injecting an amount of catalyst sufficient to only vaporize the first mixture and maintain a substantially non-cracking temperature range, the temperature of the vaporization zone 234 of the present riser reactor 204 is lower than the temperatures used to vaporize the feed in conventional FCC riser reactors.

[0037] Although not the subject of this embodiment, each of the monitored operating variables may be computer controlled by process control systems commonly used in the art. For example, the variables may be monitored remotely, whereby automatic adjustments are made based on the output of the variables, thereby reducing the need for manual changes and adjustments. It should be noted that variables other than those mentioned above that are related to regulating the temperature of the evaporation zone 234 may be monitored.

[0038] The increased rate of flow due to the production of vaporized feed acts as a means to carry the hydrocarbons 236 further up into the riser reactor 204 as they pass from the vaporization zone 234 and into the cracking zone 240. The cracking zone 240 is located above the vaporization zone 234 and extends across substantially the entire diameter 238 of the riser reactor 204. The sizes, including length and diameter, of the vaporization zone 234, cracking zone 240, and riser reactor 204 of the embodiments may vary depending on the operating parameters and the level of hydrocarbon feed conversion and production capacity desired, among other variables.

[0039] Because the temperature of the hydrocarbons 236 leaving the evaporation zone 234 to flow to the cracking zone 240 is below the thermal cracking temperature, minimal catalyst deactivation due to reaction coke deposition occurs in zone 234. Thus, a substantially majority of the catalyst in the hydrocarbons 236 flowing to the cracking zone 240 is available to catalyze the cracking reaction. Furthermore, because cracking of the hydrocarbons 236 feed is reduced to a substantially minimum level in the evaporation zone 234, the hydrocarbons 236 may be considered to be partially cracked as they flow to the cracking zone 240.

[0040] In addition to the flow of the first catalyst via the distributor inlet 206, the riser reactor 204 of FIG. 2 further comprises a second stage injection device 242, which will be further discussed with respect to FIG. 3 and FIG. 4. The second stage injection device 242 of this embodiment is configured to supply a flow of the second catalyst via the distributor inlet 244 and a flow of the second feed via the distributor inlet 246 to the cracking zone 240. In a preferred embodiment, the ratio of the first catalyst to the second catalyst in the riser reactor 204 may range from about 1:9 to about 9:1 to minimize thermal cracking of the hydrocarbons 236 in the evaporation zone 234 and maximize cracking of the hydrocarbons 236 when subjected to cracking temperatures in the cracking zone 240.

[0041] The second feed flows to device 242 to mix with the second catalyst and thus form a second feed / catalyst mixture (not shown). Preferably, as will be further discussed, the second feed / catalyst mixture is injected into a wall region (not shown) of the riser reactor 204 and flows further to the cracking zone 240. Upon entering zone 240, the second feed / catalyst mixture contacts and mixes with rising hydrocarbons 236 exiting the vaporization zone 234 to enter the cracking zone 240. The elevated temperature of the second feed / catalyst mixture causes further cracking of the hydrocarbons 236, resulting in the production of final cracked products 248 exiting the top section of the riser reactor 204. As will be further discussed, the injection of the second catalyst in this embodiment provides several benefits, including minimizing catalyst backmixing in the wall region, promoting improved uniformity in feed / catalyst mixing, and improving the radial velocity distribution of cracking products in the riser reactor 204.

[0042] Figure 3 is a schematic diagram of a second stage injection device of the riser reactor system with multi-stage catalyst injection shown in Figure 2 according to a first embodiment of the present invention. Like numbers are used with respect to Figures 1 and 2.

[0043] The second stage injection device 342 provides for injecting a second catalyst flow via a distributor inlet 344 and a second feed flow via a distributor inlet 346 into the cracking zone 340 of the riser reactor. The device 342 includes an inner wall 350, an outer wall 352, and a base 354. In accordance with the present invention, the outer wall 352 extends vertically above the inner wall 350 and includes a distributor inlet 344 for receiving the second catalyst flow.

[0044] 3, a half of a longitudinal cross-section within an interior region 356 of the cracking zone 340 is shown, with a central vertical axis 358 of the riser reactor geometry represented by a dotted line. The top section of the interior wall 350 includes an inclined upward slope 360 ​​oriented away from the central vertical axis 358, thereby forming an opening 362 located between the exterior wall 352 and the slope 360 ​​and configured to be fluidly connected to the interior region 356. The inclined upward slope 360 ​​can prevent the ingress of fluid backflow, for example, preventing the hydrocarbons 336 flowing upward along the central vertical axis 358 from flowing into the wall region 364 and / or the second device 342.

[0045] The base 354 of the device 342 includes at least one base opening (not shown) for receiving the second feed stream. The second feed stream flows into a lower section 366 of the device 342 and, upon contact, is vaporized by the hot second catalyst stream. The contact and mixing of the second feed stream and the second catalyst stream forms a second feed / catalyst mixture, hereinafter referred to as a "fluidized ring mixture 368," in a cavity 370 of the device 342. The catalyst particles in the fluidized ring mixture 368 are fluidized by the vaporized feed, such that the mixture 368 flows through an opening 370 of the device 342. It passes through mouth 362 and rises upwardly to be injected into wall region 364. In a preferred embodiment, base 354 may further be used to receive a lift gas in an effort to maintain fluidization of fluid ring mixture 368. In other embodiments, base 354 may include a separate base opening for accommodating a second feed stream and lift gas.

[0046] When moving upward along the central vertical axis 358, the flow of the hydrocarbons 336 can be described as a core-ring pattern, where a concentration of densely aggregated catalyst particles (i.e., dense catalyst layer 372) flows downward in the wall region 364, while a concentration of less densely aggregated catalyst particles (i.e., central catalyst 374) continues to flow upward along the central vertical axis 358. The formation of dense catalyst layer 372 in the wall region 364 often leads to uneven catalyst particle distribution and uneven feed / catalyst mixing throughout the cracking zone 340, as well as uneven gas / solid velocity distribution profiles. Additionally, the dense catalyst layer 372 flowing downward along the wall region 364, or the periphery of the cracking zone 340, can increase the likelihood of backmixing of solid catalyst particles. In the present invention, backmixing is undesirable because it results in the recycling of catalyst that has already passed through a portion of the cracking zone 340 by flowing downward through the dense catalyst bed 372 with non-recirculated catalyst particles flowing upward through the fluidized ring mixture 368. Backmixing often leads to suboptimal feed / catalyst contact, resulting in undesirable cracking reactions, thereby reducing the yield of valuable products.

[0047] However, in this embodiment, the upward flow of fluidized ring mixture 368 into wall region 364 acts to deflect the downward flow of dense catalyst particles 372. Thus, by forcing dense catalyst particles 372 back into interior region 356, improved feed / catalyst contact and improved catalyst distribution is achieved with minimal or no backmixing. Note that in an embodiment, wall region 364 may be understood to include an area within cracking zone 340 where upwardly flowing fluidized ring mixture 368 deflects downwardly flowing dense catalyst layer 372.

[0048] With such improvements, the present embodiment advantageously promotes desirable plug flow conditions, thereby reducing undesirable cracking reactions, as minimized catalyst backmixing occurs, thereby increasing the yield of desired products. Moreover, ideal plug flow conditions reduce the occurrence of secondary and incomplete catalytic reactions, which in turn increases the yield of desired products. Moreover, due to the desirable plug flow conditions, the velocity flow rate through the riser reactor of the present invention is assumed to be more constant and uniform, as compared to the typical velocity profile in a conventional riser reactor. Thus, the present riser reactor embodiment also provides an improved overall radial gas and solids velocity profile, as measured along the length of the riser reactor.

[0049] Figure 4 is a schematic diagram of a second stage injection device of the riser reactor system with multi-stage catalyst injection shown in Figure 2 according to a second embodiment of the present invention. Like numbers are used with respect to Figures 1-3.

[0050] A half of a longitudinal cross section through an interior region 456 of the cracking zone 440 is shown in FIG. 4, with the central vertical axis 458 of the riser reactor geometry represented by a dotted line. The second stage injection device 442 is located within the cracking zone 440 and provides a second stage injection of a second catalyst flow via a distributor inlet 444 and a second feed flow via a distributor line 446. The second stage injection device 442 includes an inner wall 450, an outer wall, and a base 454. According to this embodiment, the top section of the inner wall 450 includes an inclined upward slope 460 oriented in a direction toward the interior region 456. As shown in FIG. 4, the outer wall includes a first vertical section 452, a second vertical section 453, and a first vertical section 454. The first vertical section 452 of the outer wall includes a sloped ramp 455 connecting a top end of section 452 to a bottom end of a second vertical section 453. With this configuration, the second vertical section 453 of the outer wall extends vertically just above the inner wall 450 to form an opening 462 that is fluidly connected to the interior region 456. The first vertical section 452 of the outer wall includes a distributor inlet 444 for injecting a second catalyst stream into the device 442.

[0051] The base 454 of the device 442 includes at least one base opening (not shown) for receiving the second feed stream. The second feed stream flows into the lower section 466 of the device 442 and vaporizes upon contact with the second catalyst stream. The mixing of the second feed stream and the second catalyst stream forms a second feed / catalyst mixture, hereinafter referred to as "fluidized ring mixture 468," in the cavity 470 of the device 442. The catalyst particles are fluidized by the vaporized feed, such that the fluidized ring mixture 468 rises upward to flow through the openings 462 and into the wall region 464.

[0052] As it travels upward along the central vertical axis 458, the flow of hydrocarbons 436 can be described as including a core-ring pattern, where a concentration of densely aggregated catalyst particles (i.e., dense catalyst layer 472) flows downward in the wall region 464, while a concentration of less densely aggregated catalyst particles (i.e., central catalyst 474) continues to flow upward along the central vertical axis 458. The formation of dense catalyst layer 472 in the wall region 464 often leads to uneven catalyst particle distribution and uneven feed / catalyst mixing throughout the cracking zone 440, as well as uneven gas / solid velocity distribution profiles. Additionally, dense catalyst layer 472 flowing downward along the wall region 464, or the periphery of the cracking zone 440, can increase the likelihood of backmixing of solid catalyst particles. Backmixing often results in incomplete cracking, thereby reducing product yields.

[0053] However, in this embodiment, the upward flow of the fluidized ring mixture 468 into the wall region 464 acts to deflect the downward flow of the dense catalyst layer 472. Thus, by forcing the dense catalyst layer 472 back into the interior region 456, improved feed / catalyst contact and improved catalyst distribution is achieved with minimal or no backmixing. With such improvements, the present embodiment advantageously promotes desirable plug flow conditions, thereby reducing undesirable cracking reactions, so as to increase the yield of the desired product, since minimized catalyst backmixing occurs. Furthermore, ideal plug flow conditions reduce the occurrence of secondary and incomplete catalytic reactions, which in turn increases the yield of the desired product. Furthermore, because of the desirable plug flow conditions, the velocity flow rate through the present riser reactor is assumed to be more constant and uniform, as compared to the typical velocity profile in a conventional riser reactor. Thus, the present riser reactor embodiment also provides an improved overall radial gas and solids velocity profile, as measured along the length of the riser reactor.

[0054] FIG. 5 is a graphical comparison of the temperature profile of a conventional riser reactor as compared to the temperature profile of the riser reactor system with multi-stage catalyst injection shown in FIG. 2 according to an embodiment of the present invention. As shown in FIG. 5, the temperature in the riser reactor, measured in any desired units known in the art, is plotted against the height of the riser reactor, measured in any desired units known in the art. The temperature profiles of both the conventional riser reactor 502 (depicted in dashed lines) and the temperature profile of the riser reactor system with multi-stage catalyst injection 504 of the present invention (depicted in solid lines) both decline as the height of the riser reactor increases due to the nature of the endothermic cracking reaction. Thus, the temperature profiles described herein relate to the temperature in the riser reactor along a substantially majority of the length of the riser reactor.

[0055] As discussed with respect to FIG. 2 and illustrated by FIG. 5, the hydrocarbon stream in the evaporation zone of the present riser reactor is subjected to a temperature at least 50° C. lower than the temperature in the bottom section of a conventional riser reactor. The evaporation zone in this embodiment is located from just below the first feed injection location of the riser reactor to about 5 meters (m) above the first feed injection location. The advantage of using the present riser reactor system with multi-stage catalyst injection is that it leads to at least a 15% reduction, preferably a 20% reduction, and more preferably a 25% reduction in the overall temperature profile when compared to a conventional riser reactor. In this regard, the hydrocarbon stream in the evaporation zone of the present riser reactor maintains a lower temperature when compared to the feed / catalyst mixture in a conventional riser reactor until it enters the cracking zone. In particular, after injecting the second feed / catalyst mixture into the cracking zone, the first feed / catalyst mixture is subjected to an elevated temperature as the cracking reaction begins, forming a temperature spike 503 as illustrated by the temperature profile of the riser reactor system with multi-stage catalyst injection 504.

[0056] Based on the findings depicted in FIG. 5, it has been surprisingly found that the riser reactor of the present invention promotes an improved temperature profile along the entire length of the reactor since typical elevated temperatures (e.g., 630° C. or higher) are avoided, especially in the evaporation zone. According to this embodiment, the temperature of the evaporation zone is at a lower operating severity temperature, i.e., below 625° C., preferably below 550° C. (as shown in FIG. 5), and most preferably below 525° C., so as to advantageously reduce thermal and catalytic cracking in the evaporation zone. Since thermal cracking in the evaporation zone is reduced, other beneficial effects such as reduced dry gas production and increased FCC unit capacity may be exhibited, which may lead to improved product distribution, i.e., desirable end products. It is noted that the size of the riser reactor of the present invention, including the length and diameter of the riser reactor, may vary depending on the operating parameters and the desired level of hydrocarbon feed conversion and production capacity, among other variables.

[0057] FIG. 6 is a graphical comparison of the radial distribution profile of axial velocity of a conventional riser reactor as compared to the radial distribution profile of axial velocity of a riser reactor system with multi-stage catalyst injection shown in FIG. 2 according to an embodiment of the present invention. As depicted in FIG. 6, the velocity is plotted versus the length of the riser reactor. Specifically, the gas velocity as measured in any desired units known in the art ("U g " ) and solid velocity (" U s ") is plotted versus the riser reactor center area ("r=0") versus the riser reactor wall area ("r=R") as measured in any desired units known in the art. Solids ("s") relate to catalyst particle constituents and gases ("g") relate to vaporized feed or product constituents, both constituents being components that form the hydrocarbon / catalyst mixture flowing within the riser reactor.

[0058] As previously described with respect to Figures 3 and 4, the riser reactor of the present invention includes a second stage injection device for injecting a second catalyst stream and a second feed stream into the cracking zone. The second catalyst and the second feed mix together to form a second catalyst / feed mixture, which acts to further crack the partially cracked hydrocarbon stream flowing from the vaporization zone to the cracking zone. As illustrated by the gas and solid velocity profiles depicted in Figure 6, the further benefits of implementing a second stage injection device in the riser reactor of the present invention are readily apparent when compared to a conventional riser reactor that does not incorporate second stage injection. As shown in Figure 6, the solid velocity of the catalyst particles in the conventional riser reactor is depicted by the dashed line 602, and the solid velocity of the riser reactor of the present invention is depicted by the solid line 604. The solid velocity of the riser reactor of the present invention 604 is more uniform than the solid velocity of the conventional riser reactor 602. In particular, the solids velocity (r=R) of the riser reactor 604 of the present invention in the wall region X is , showing that catalyst backmixing in the wall region is significantly reduced.

[0059] Similarly, the gas velocity of the vaporized feed in the conventional riser reactor is depicted by dashed line 606, and the gas velocity of the vaporized feed in the inventive riser reactor is depicted by solid line 608. The gas velocity in the inventive riser reactor 608 is more uniform than that in the conventional riser reactor 606. As depicted in FIG. 6, the gas stream in the inventive riser reactor 608 continues to maintain a significant velocity even as the gas stream in the conventional riser reactor 606 approaches the wall region. This means that the flow (of both catalyst and gas) in the inventive riser reactor is more "plug flow", resulting in higher conversion (i.e., higher yield) as well as a more desirable product distribution.

[0060] The objectives of the present invention included minimizing the generation of dry gas during thermal cracking of the hydrocarbon feed and vaporization of the feed, and improving the feed / catalyst mixing and overall temperature and gas / solid velocity profile during the FCC process. The riser reactor of the present invention and the method of catalytically cracking a hydrocarbon feed using the riser reactor of the present invention achieve the objectives of the present invention. As described in the previous embodiment, the riser reactor of the present invention includes at least one vaporization zone, and vaporization of the feed and mixing of the feed with the catalyst are contained in the at least one vaporization zone before passing to the at least one cracking zone for further cracking. The riser reactor of the present invention limits the temperature of the vaporization zone to less than 625°C, preferably less than 550°C, more preferably less than 525°C, thereby suppressing the thermal cracking reaction in the vaporization zone. Thus, a substantially majority, more preferably essentially all, of the cracking of the vaporized feed occurs in the cracking zone rather than the vaporization zone of the present riser reactor embodiment. Another advantage provided by the embodiments of the present invention, due to the reduction in thermal cracking during feed vaporization and feed / catalyst mixing, included an overall lower (and more uniform) temperature profile as opposed to that of a conventional riser reactor. As a result, another surprising benefit provided by the present embodiments due to the lower temperature profile includes reduced dry gas production / coke deposits and increased FCC unit capacity for higher yields of desired products.

[0061] Furthermore, the enhancements provided by the riser reactor of the present invention are augmented by multi-stage catalyst injection. After a first stage of catalyst injection into the vaporization zone, the technique of this embodiment may include a second stage of catalyst injection into the cracking zone. By evenly distributing the catalyst concentration along the entire length, not just within the vaporization zone, the riser reactor of this embodiment provides more complete and uniform feed / catalyst mixing along the entire length of the riser reactor.

[0062] In addition to improved catalyst distribution, the vaporized feed distribution is also improved as the solid catalyst particles flowing through the wall region are pushed back towards the central region of the riser reactor. In this regard, the present embodiment provides a more uniform and thus improved radial solid velocity profile along the entire length of the riser reactor of the present invention. The synergistic behavior provided by the improved gas and solid velocity profiles of the present embodiment promotes reduced backmixing, improved solid / gas mixing, and ideal plug flow conditions, which in turn enhances the catalytic reaction to provide higher yields of desired products.

[0063] While the technology of the present invention is susceptible to various modifications and alternative forms, the illustrative examples set forth above are presented by way of example only. It is to be understood that the technology is not intended to be limited to the specific examples disclosed herein. Indeed, the present embodiments are intended to be illustrative and not restrictive of the scope of the technology. This includes all alternatives, modifications, and equivalents within the scope of this patent. This specification includes the disclosure of the following inventions. [Item 1] A process for fluid catalytic cracking (FCC) of a hydrocarbon feed in a riser reactor, comprising: injecting the hydrocarbon feed into a vaporization zone of the riser reactor; injecting a first catalyst into the evaporation zone, wherein the first catalyst is mixed with the hydrocarbon feed to generate a hydrocarbon stream in the evaporation zone, the temperature of the evaporation zone being less than 625°C; passing said hydrocarbon stream from said vaporization zone into a cracking zone of said riser reactor to generate cracked products in said cracking zone. 2. The process of claim 1, further comprising adjusting the amount of a first catalyst injected into the evaporation zone to minimize cracking of the hydrocarbon stream in the evaporation zone. 3. The process of claim 1, wherein vaporization of the hydrocarbon feed and mixing of the hydrocarbon feed with the first catalyst occurs across the diameter of the riser reactor and within the vaporization zone. 4. The process of claim 1, further comprising injecting a second catalyst into a wall region located in the cracking zone to further crack the hydrocarbon stream, wherein the injection of the second catalyst minimizes catalyst backmixing in the wall region and changes the radial velocity distribution of the cracked products in the cracking zone. 5. The process of claim 4, wherein the ratio of the first catalyst to the second catalyst injected into the riser reactor is adjusted to minimize cracking of the hydrocarbon stream in the vaporization zone and maximize cracking of the hydrocarbon stream in the cracking zone. [Item 6] A riser reactor for fluid catalytic cracking (FCC) of a hydrocarbon feed, comprising: an evaporation zone comprising a first catalyst distributor receiving a first catalyst and a feed distributor receiving the hydrocarbon feed, the first catalyst being mixed with the hydrocarbon feed to generate a mixture of hydrocarbon streams in the evaporation zone, the temperature of the evaporation zone being less than 625°C; a cracking zone receiving said mixture of hydrocarbon streams, said cracking zone cracking said hydrocarbon streams to produce cracking products in said cracking zone; a separation zone receiving the cracked product from the cracking zone, wherein spent catalyst is separated and removed from the cracked product in the separation zone. 7. The invention of claim 1 or 6, wherein the hydrocarbon stream passing from the evaporation zone and into the cracking zone is partially cracked. [Item 8] The riser reactor described in Item 6, wherein the cracking zone is provided with a second catalyst distributor located in a wall region of the cracking zone for receiving a second catalyst, and minimal catalyst backmixing occurs in the wall region of the riser reactor and changes in the radial velocity distribution of the cracked product occur in the cracking zone. 9. The riser reactor of claim 6, wherein minimal cracking of the hydrocarbon stream occurs in the vaporization zone and maximum cracking of the hydrocarbon stream occurs in the cracking zone. [Item 10] The invention according to Item 5 or 6, wherein a ratio of the first catalyst to the second catalyst in the riser reactor is about 1:9 to 9:1. [Item 11] The invention according to item 4 or 10, wherein the ratio of total catalyst to hydrocarbon feed in the riser reactor is about 1:1 to 30:1. Item 12. The riser reactor of item 6, wherein the evaporation zone extends across the entire diameter of the riser reactor.

Claims

1. 1. A process for fluid catalytic cracking (FCC) of a hydrocarbon feed in a riser reactor, comprising: injecting a first hydrocarbon feed into a vaporization zone located at the bottom of the riser reactor; injecting a first catalyst into the evaporation zone; mixing the first catalyst with the first hydrocarbon feed to generate a hydrocarbon stream in the evaporation zone; vaporizing a hydrocarbon stream in an evaporation zone, the temperature of said evaporation zone being less than 625°C; passing the hydrocarbon stream from the vaporization zone to a cracking zone located above the vaporization zone of the riser reactor to generate cracked products in the cracking zone; and injecting a second hydrocarbon feed and a second catalyst into an injection device to form a mixture of the second hydrocarbon feed and the second catalyst that is injected as an upward flow into a wall region located in said cracking zone.

2. 10. The process of claim 1 further comprising adjusting the amount of first catalyst injected into the evaporation zone to be in the range of 10% to 90% of the total catalyst injection.

3. 2. The process of claim 1, wherein vaporizing the hydrocarbon stream and mixing the first hydrocarbon feed with the first catalyst occurs across a diameter of the riser reactor and within the vaporization zone.

4. 10. The process of claim 1 further comprising injecting additional catalyst into the riser reactor.

5. 10. The process of claim 1, further comprising injecting a lift gas into the lower end of the riser reactor, the lift gas being selected from steam, vaporized petroleum, vaporized petroleum fractions, light hydrocarbon gases, or mixtures thereof.

6. 1. A riser reactor for fluid catalytic cracking (FCC) of a hydrocarbon feed, comprising: a vaporization zone located at the bottom of the riser reactor, the vaporization zone including a first catalyst distributor receiving a first catalyst and a feed distributor receiving a first hydrocarbon feed; a cracking zone located above the evaporation zone, the cracking zone including a second stage injection device in a wall region thereof for supplying a second catalyst stream and a second hydrocarbon feed stream to a wall region of the cracking zone.

7. 10. The process of claim 1, wherein the riser reactor is operated under ideal plug flow conditions.

8. the second stage injection device includes an inner wall, an outer wall, and a base; the outer wall extends vertically above the inner wall and includes an inlet for receiving a second catalyst flow; a top of the inner wall includes an inclined upward slope oriented in a direction away from a central vertical axis of the riser reactor, forming an opening located between the outer wall and the upward slope and configured to be fluidly connected to the riser reactor; The riser reactor of claim 6 , wherein the base includes at least one opening for receiving the second hydrocarbon feed stream.

9. the second stage injection device includes an inner wall, an outer wall, and a base; a top of the inner wall includes an inclined upward slope oriented in a direction toward an interior region of the riser reactor; the outer wall includes a first vertical section, a second vertical section, and an inclined slope connecting a top end of the first vertical section to a bottom end of the second vertical section; a second vertical section extending vertically above the inner wall to form an opening fluidly connected to the riser reactor; the first vertical section includes an inlet for injecting a second catalyst stream into the second stage injection device; The riser reactor of claim 6 , wherein the base includes at least one base opening for receiving the second hydrocarbon feed stream.

10. 10. The process of claim 1, wherein the ratio of total catalyst to first hydrocarbon feed in the riser reactor is from about 1:1 to 30:

1.

11. 7. The riser reactor of claim 6, wherein the evaporation zone extends across the entire diameter of the riser reactor.

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