Conversion of engine fuel range distillates to light olefins in multi-riser fluid catalytic cracking (FCC) unit

Abstract

Methods and systems for fluid catalytic cracking (FCC) hydrocarbon feeds using a multi-riser FCC reactor are described. The conditions in each riser may be tailored for processing different feeds. For example, one riser may be configured to crack heavy hydrocarbons, such as vacuum gas oil (VGO), to produce medium and light products. Other risers may be configured to crack lower and / or medium hydrocarbons to produce light olefins. Embodiments of the disclosed methods and systems can be used to provide a range of products with greater amounts of light olefins.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. non-provisional patent application serial number 17 / 843,586 filed on June 17, 2022, which is incorporated herein by reference. Field of the Invention

[0003] The present application relates to reactor systems used in fluid catalytic cracking (FCC) systems and, more particularly, to methods and systems for selectively shifting the product distribution from an FCC process toward lighter olefin products based on the feedstock using multiple risers, each riser being optimized based on the feedstock.

[0004] introduction

[0005] Fluid catalytic cracking (FCC) is a process commonly used in oil refineries to improve the yield of transportation fuels such as gasoline and distillates. The FCC process uses a reactor called a riser, essentially a pipeline, in which hydrocarbon feeds are contacted with catalyst particles to achieve conversion of the feeds into more valuable products. FCC units convert gasoline or residual oil feeds by "cracking" the hydrocarbons into smaller molecules. The resulting hydrocarbon gas and catalyst mixture all flow in the riser, hence the name fluid catalytic cracking.

[0006] The FCC units used in today's refineries can mainly convert heavy feeds (such as vacuum gasoline, reduced crude oil, atmospheric tower bottom oil, vacuum tower bottom oil, etc.) into transportation fuel products (such as gasoline, diesel, fuel oil and liquefied petroleum gas). The global demand for transportation fuels such as diesel is on a downward trend, while the demand for petrochemicals continues to grow. The reduction in demand for transportation fuels can be attributed to the improvement of motor vehicle fuel efficiency and the use of alternative fuel sources such as hydrogen and chemically stored electricity (batteries and fuel cells). The lower demand for transportation fuels will lead to its oversupply in the market. On the other hand, due to the increase in population and consumer demand, the demand for petrochemical products will continue to grow. Propylene is an important raw material for the production of polypropylene, acrylonitrile, propylene oxide, oxo alcohols and various industrial products. The demand for propylene is increasing in all regions of the world, mainly driven by the demand for polypropylene, which accounts for more than 60% of all propylene demand. The propylene market is expected to grow at an average annual rate of 4% in the next few years.

[0007] In recent years, FCC plays an increasing role in producing propylene as a valuable by-product. Therefore, it is envisioned that FCC will upgrade excess transportation fuels such as naphtha, kerosene, diesel and oxygenates to light olefins such as propylene and ethylene. However, co-processing diesel, kerosene and / or naphtha and vacuum gas oil (VGO) or residual oil in conventional single riser FCC is challenging because the conditions required for cracking the distillate oil with lower boiling points to propylene and ethylene are completely different from the conditions required for VGO and / or residual oil. If diesel and VGO or residual oil are co-processed in a single riser, most of the diesel will be converted into light cycle oil (LCO), which is lower in quality than diesel, and does not produce propylene of considerable amount. Similarly, co-processing kerosene and VGO or residual oil in a single riser tends to mainly produce gasoline and (LCO).

[0008]

[0006] Therefore, there is a need in the art to shift the product range of the FCC process toward greater amounts of light olefins such as propylene and ethylene.

[0009] Overview

[0010] Disclosed herein is a method for cracking hydrocarbons using a multi-riser fluid catalytic cracking (FCC) reactor, the method comprising: cracking a heavy hydrocarbon feed in a first riser using a first FCC condition to form a first effluent enriched in medium and / or light hydrocarbons, and cracking one or more light and / or medium hydrocarbon feeds in one or more risers different from the first riser under FCC conditions different from the first FCC conditions to form one or more effluents enriched in light olefins. According to some embodiments, the heavy feed comprises one or more hydrocarbons having an average carbon number of 18 or more. According to some embodiments, the heavy feed comprises one or more components selected from vacuum gas oil (VGO), reduced crude oil, atmospheric bottoms, vacuum bottoms, residual oil, and deasphalted oil (DAO). According to some embodiments, the first effluent is enriched in hydrocarbons having a carbon number of 3 to 18. According to some embodiments, one or more light and / or medium hydrocarbon feeds comprise distillates. According to some embodiments, one or more light and / or medium hydrocarbon feeds comprise one or more hydrocarbons having an average carbon number of 1 to 18. According to some embodiments, one or more light and / or medium hydrocarbon feeds include one or more components selected from jet fuel, diesel, naphtha, kerosene, C4 and oxygenates. According to some embodiments, the first FCC condition includes maintaining the outlet temperature of the first riser at 510°C to 575°C. According to some embodiments, the first FCC condition includes mixing steam and heavy hydrocarbon feeds at a concentration of 1% by weight to 6% by weight in the first riser. According to some embodiments, FCC conditions different from the first FCC condition include maintaining the outlet temperature of one or more risers different from the first riser at 550°C to 675°C. According to some embodiments, FCC conditions different from the first FCC condition include mixing steam with one or more light and / or medium hydrocarbon feeds at a concentration of 5% by weight to 20% by weight. According to some embodiments, the method also includes providing at least a portion of the first effluent to one or more risers different from the first riser. According to some embodiments, providing at least a portion of the first effluent to one or more risers different from the first riser comprises: fractionating the first effluent using a fractionation system to produce a fractionated stream enriched in one or more components of the first effluent, and recycling the fractionated stream from the fractionation system to one or more risers different from the first riser. According to some embodiments, the fractionated stream is enriched in one or more naphthas and C4. According to some embodiments, cracking one or more light and / or medium hydrocarbon feeds in one or more risers different from the first riser comprises: cracking the medium feed in the second riser under second FCC conditions, and cracking the light feed in the third riser under third FCC conditions different from the second FCC conditions. According to some embodiments, the medium feed comprises one or more of gasoline, kerosene, jet fuel, and diesel fuel.According to some embodiments, the second FCC condition comprises maintaining the outlet temperature of the first riser at 550°C to 675°C. According to some embodiments, the light feed comprises one or more of naphtha, C4 and oxygenates. According to some embodiments, the FCC reaction in each of the risers comprises cracking using a catalyst mixture comprising Y zeolite and a shape selective zeolite. According to some embodiments, the shape selective zeolite is ZSM-5.

[0011] Also disclosed herein is a fluid catalytic cracking (FCC) reactor comprising: a first riser configured to crack a heavy hydrocarbon feed using a first FCC condition to form a first effluent enriched in medium and / or light hydrocarbons, and one or more additional risers, the one or more additional risers being configured to crack one or more light and / or medium hydrocarbon feeds under FCC conditions different from the first FCC conditions to form one or more effluents enriched in light olefins. According to some embodiments, the heavy feed comprises one or more hydrocarbons having an average carbon number of 18 or more. According to some embodiments, the heavy feed comprises one or more components selected from vacuum gas oil (VGO), reduced crude oil, atmospheric bottoms, vacuum bottoms, residual oil, and deasphalted oil (DAO). According to some embodiments, the first effluent is enriched in hydrocarbons having a carbon number of 3 to 18. According to some embodiments, one or more light and / or medium hydrocarbon feeds comprise distillates. According to some embodiments, one or more light and / or medium hydrocarbon feeds comprise one or more hydrocarbons having an average carbon number of 1 to 18. According to some embodiments, one or more light and / or medium hydrocarbon feeds include one or more components selected from jet fuel, diesel, naphtha, kerosene, C4 and oxygenates. According to some embodiments, the first FCC condition includes maintaining the outlet temperature of the first riser at 510°C to 575°C. According to some embodiments, the first FCC condition includes mixing steam and heavy hydrocarbon feeds at a concentration of 1% by weight to 6% by weight in the first riser. According to some embodiments, FCC conditions different from the first FCC condition include maintaining the outlet temperature of one or more risers different from the first riser at 550°C to 675°C. According to some embodiments, FCC conditions different from the first FCC condition include mixing steam with one or more light and / or medium hydrocarbon feeds at a concentration of 5% by weight to 20% by weight. According to some embodiments, the reactor is configured to provide at least a portion of the first effluent to one or more risers different from the first riser. According to some embodiments, providing at least a portion of the first effluent to one or more risers different from the first riser comprises: fractionating the first effluent using a fractionation system to produce a fractionated stream enriched in one or more components of the first effluent, and recycling the fractionated stream from the fractionation system to one or more risers different from the first riser. According to some embodiments, the fractionated stream is enriched in one or more of naphtha and C4. According to some embodiments, cracking one or more light and / or medium hydrocarbon feeds in one or more risers different from the first riser comprises: cracking the medium feed in the second riser under second FCC conditions, and cracking the light feed in the third riser under third FCC conditions different from the second FCC conditions. According to some embodiments, the medium feed comprises one or more of gasoline, kerosene, jet fuel, and diesel fuel.According to some embodiments, the second FCC condition comprises maintaining the outlet temperature of the first riser at 550°C to 675°C. According to some embodiments, the light feed comprises one or more of naphtha, C4 and oxygenates. According to some embodiments, the FCC reaction in each of the risers comprises cracking using a catalyst mixture comprising Y zeolite and a shape selective zeolite. According to some embodiments, the shape selective zeolite is ZSM-5. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A multi-riser FCC reactor is shown.

[0014] Figure 2 A process using a multi-riser FCC reactor is shown.

[0015] Details

[0016] Figure 1An embodiment of a multi-riser FCC reactor 100 as disclosed herein is illustrated. The general function of an FCC reactor is known in the art and is only briefly discussed here. The reactor 100 has three risers—102, 104, and 106. However, other embodiments may have more or fewer risers, such as two, four, five risers, etc. As described in more detail below, each of the risers may be configured for a different feedstock. The feedstock is provided to the first riser 102 at a first feed nozzle 114. According to some embodiments, any riser may include more than one nozzle. The catalyst is provided to the first riser at a first valve 116. Valve 116 may be, for example, a slide valve. The feedstock is provided to the second riser 104 at a second feed nozzle 118, and the catalyst is provided through a second valve 120. The feedstock is provided to the third riser 106 at a third feed nozzle 122, and the catalyst is provided through a third valve 124. Each of the first, second and third risers is docked with a dedicated cyclone separator 126, 128 and 130, respectively, which separates most of the catalyst from each hydrocarbon riser effluent. The reactor includes a booster system 132 and one or more upper riser cyclone separators 134. Although the illustrated embodiment has a common upper cyclone separator, other embodiments may have a dedicated first-stage and second-stage cyclone separator system for each riser. The booster system 132 and one or more upper riser cyclone separators 134 are configured to remove the remaining catalyst from the hydrocarbon product before the product leaves the reactor as a reactor effluent. According to some embodiments, there may be a separate pipeline instead of a single reactor effluent pipeline as shown. The reactor includes a separator section 108, a stripper section 110 and a regenerator section 112. As is known in the art, spent catalyst separated using cyclones (e.g., 126, 128, 130, and 134) is provided to the stripper section 110, where hydrocarbons are stripped from the catalyst, for example, using steam. The stripped catalyst is then provided to the regenerator section 112, where the catalyst is heated to burn off the coke. Hydrocarbons recovered from the catalyst during the stripping process and hydrocarbons separated by the cyclones leave the reactor through exhaust port 132, while coke deposited on the catalyst is burned off in the regenerator section 112, and flue gases generated by the combustion of the coke escape through exhaust port 136. The regenerated catalyst can be recycled to the riser.

[0017] As described above, the conditions of each of the risers can be adjusted based on the feedstock being reacted in the riser. Controllable conditions in each riser include temperature, residence time of the feedstock in the riser, partial pressure of the feedstock, and the ratio of catalyst to feedstock. The partial pressure of the feedstock is controlled by controlling the amount of steam injected into the riser. Typically, lighter reactants require more steam for cracking than heavier components, and paraffin feeds require more steam than olefin feeds.

[0018] It is important to control the temperature in each riser because the cracking reaction is endothermic, which means that heat must be provided to the reactor process to heat the feedstock and maintain the reaction temperature. The required temperature depends on the specific feedstock, and generally lighter molecules require higher temperatures than heavier molecules to maintain the reaction. The heat used to maintain the reaction in the riser is provided by the heat generated during catalyst regeneration. During the conversion process of heavy feeds, coke is formed. The coke is deposited on the catalyst and eventually burned with an oxygen source such as air in the regenerator section 112. The combustion of coke is an exothermic process that can provide the heat required for the cracking reaction. The combustion heat generated by the regeneration increases the temperature of the catalyst, and the hot catalyst is recycled to contact the feed in the riser, thereby maintaining the overall heat balance in the system. The amount of catalyst provided to the riser can be adjusted, for example, by a control valve (e.g., Figure 1 Valves 116, 120 and 124 in the riser) regulate the amount of catalyst provided to the riser and control the heat provided to the riser. In balanced operation, no external heat source or fuel is required to supplement the heat from the combustion of coke. If a sufficient amount of heavy material is processed to form a sufficient amount of coke to provide the heat required for heat balance in all risers, a balanced operation can be obtained. Oxygenated compounds are generally exothermic, so even if the coke production is small, the heat can be balanced by properly selecting the feed. If additional heat is needed to maintain thermal balance, a coke forming agent can be added to the feed to increase the amount of coke formed, which is then burned. Alternatively, fuel can be added to the regeneration process. U.S. Patent No. 8,383,052 describes how to maintain thermal balance in an FCC reactor, and its entire contents are incorporated herein.

[0019] Figure 2 An embodiment of a process 200 is illustrated that includes a multi-riser FCC reactor 202. The multi-riser FCC reactor 202 may be a three-riser reactor, such as reactor 100 ( Figure 1 ), or may have more or fewer risers. Figure 2Some examples of possible feed streams for reactor 202 are illustrated. Note that the illustrated feeds are for example only and are not exhaustive. Reactor 202 will typically have at least one riser (referred to herein as a "heavy riser") configured for heavy feeds such as vacuum gas oil (VGO), reduced crude oil, atmospheric bottoms, vacuum bottoms, residual oil, and / or deasphalted oil (DAO). Typically, "heavy feed" as used herein refers to a feed material having an average carbon number greater than 18. According to some embodiments, the heavy riser may be configured to crack the heavy feed into a stream of enriched fuel products (such as gasoline, diesel, fuel oil, liquefied petroleum gas, etc.) and / or naphtha.

[0020] Reactor 202 may also be configured with one or more risers configured to crack medium and / or light feeds into a stream enriched in light olefins such as ethylene and / or propylene. Typically, "medium feed" refers to a feed material having an average carbon number of about 8 to 18, while "light feed" refers to a feed material having an average carbon number of about 1 to 8. Examples of these medium and / or light feeds include paraffins, cycloparaffins, monoolefins, diolefins, cycloolefins, naphthenics, and aromatics, as well as hydrocarbon oxygenates. Further representative examples include light paraffin naphtha; heavy paraffin naphtha; light olefin naphtha; heavy olefin naphtha; mixed paraffin C4; mixed olefin C4 (such as raffinate); mixed paraffin C5; mixed olefin C5 (such as raffinate); mixed paraffin and cycloparaffin C6; non-aromatic fractions from an aromatic extraction unit; products containing oxygenates from a Fischer-Tropsch unit; or the like; or any combination thereof. Hydrocarbon oxygenates may include alcohols having a carbon number ranging from 1 to 4, ethers having a carbon number ranging from 2 to 8, and the like. Examples include methanol, ethanol, dimethyl ether, methyl tert-butyl ether (MTBE), ethyl tert-butyl ether, tert-amyl methyl ether (TAME), tert-amyl ethyl ether, and the like.

[0021] Distillate is an example of a medium / light feed that can be cracked in the riser of reactor 202 to produce light olefins. As used herein, the term distillate may refer to one or more of naphtha, diesel, kerosene and jet fuel. Distillate may be a light distillate or a medium distillate, as those terms used in the art. According to some embodiments, reactor 202 may have a separate riser for different medium / light components. For example, a reactor may have a riser for diesel range materials, another riser for jet fuel and another riser for naphtha. According to some embodiments, a feed with a boiling point or very similar characteristics may be provided to a common riser. Ideally, the reaction conditions in each riser may be optimized to convert its specific feedstock into light olefins. In addition, reactor 202 may include a riser configured to process feeds from different methods in a refinery. For example, an embodiment of reactor 202 may have a riser configured to receive distillates from a crude oil distillation column, and those distillates may include straight run naphtha and / or straight run diesel as components. The reactor may also have another riser that may receive naphtha from other processes, such as naphtha from a coker and / or from a visbreaker.

[0022] like Figure 1 As illustrated, the hydrocarbon products from each riser generally exit the reactor as a single, combined reactor effluent. Thus, the reactor effluent includes effluents from each riser, including a stream (streams) enriched in fuel / naphtha products from the heavy riser and a stream enriched in lighter products (e.g., light olefins) obtained from one or more light / medium feed risers. Alternatively, each riser may have a dedicated effluent line. Again referring to Figure 2, the reactor effluent can be provided to the fractionation system 204. The fractionation system will not be described in detail here, because fractionation is generally well-known in the art, and the specific configuration will depend on the specific circumstances. Typically, the fractionation system may include one or more distillation towers, which are configured to separate the reactor effluent into its components to produce a series of products, as illustrated in the figure. The embodiment of method 200 is configured to transfer the product range to a heavier amount of light olefins such as ethylene and / or propylene. According to some embodiments, one or more streams from the fractionation system 204 can be recycled back to the FCC reactor 202. For example, a stream enriched in naphtha and / or C4+ material can be recycled to one of the risers of the reactor 202 as a feed. Thus, some embodiments of process 200 may include cracking a heavy stream in a heavy riser to produce a first effluent stream enriched in lighter components such as fuel products, C4 and / or naphtha, providing the first effluent stream to a fractionation system and fractionating the first effluent stream to produce one or more second streams, and recycling the one or more second streams back to one or more light / medium risers of the FCC reactor where they are further cracked to produce light olefins.

[0023] Conventional FCC processes configured to make gasoline, etc. generally use Y-zeolite catalysts, which are configured to crack larger (C9+) molecules. Other examples of catalysts that can be used for fluid catalytic cracking include USY, REY, RE-USY, faujasite, and other synthetic and naturally occurring zeolites and mixtures thereof. Embodiments of the disclosed double riser methods described herein can use this catalyst in combination with a catalyst that is better configured to crack light feeds to produce light olefins. Examples of light feed catalysts include shape selective zeolites, which are configured to crack molecules in the range of naphtha. Examples of catalysts suitable for cracking light feeds include ZSM-5 and similar catalysts. Other catalysts include ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, and ZSM-48. The ratio of Y zeolite catalyst and shape selective zeolite is optimized based on the raw materials and product targets involved.

[0024] As an example of how a multi-riser FCC reactor can be used to provide light olefins, consider reactor 100 ( Figure 1). It is assumed that riser 102 is a heavy riser (i.e., a riser configured for cracking heavy feeds). The conditions in riser 102 can be optimized to crack heavy feeds to produce an effluent enriched in medium range products such as naphtha or fuel products. It is assumed that riser 104 is configured to crack medium range feeds and riser 106 is configured to crack light feeds, each producing an effluent enriched in light olefins. In this embodiment, it is assumed that the heavy feed is VGO, the medium feed is straight run diesel, and the light feed is a light naphtha cycle. Table 1 below lists example ranges of temperature, residence time, partial pressure control (i.e., steam amount), and catalyst / oil ratio for each riser. As explained herein, each riser can be individually customized according to its specific feed. Note that the lightest component, light naphtha (riser 106), has the highest temperature and the highest amount of steam; the medium weight feed diesel (riser 104) has medium temperature and medium steam; and the heaviest feed VGO (riser 102) has the lowest temperature and the least steam.

[0025]

[0026] Although specific embodiments of the present invention have been shown and described, it will be appreciated that the above discussion is not intended to limit the present invention to these embodiments. It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention. Therefore, the present invention is intended to encompass alternatives, modifications and equivalents that may fall within the spirit and scope of the present invention as defined by the claims.

Claims

1. A method for cracking hydrocarbons using a multi-riser fluid catalytic cracking (FCC) reactor, the method comprising: cracking a heavy hydrocarbon feed in a first riser using first FCC conditions to form a first effluent enriched in heavy and / or light hydrocarbons, and One or more light and / or medium hydrocarbon feeds are cracked in one or more risers other than the first riser under FCC conditions different from the first FCC conditions to form one or more light olefin-enriched effluents.

2. The method of claim 1, wherein: The heavy feed comprises one or more hydrocarbons having an average carbon number of 18 or more.

3. The method of claim 1, wherein: The heavy feed comprises one or more components selected from the group consisting of vacuum gas oil (VGO), reduced crude oil, atmospheric bottoms, vacuum bottoms, residual oil, and deasphalted oil (DAO).

4. The method of claim 1, wherein: The first effluent is enriched in hydrocarbons having carbon numbers of 3 to 18.

5. The method of claim 1, wherein: The one or more light and / or medium hydrocarbon feedstocks comprise distillates.

6. The method of claim 1, wherein: The one or more light and / or medium hydrocarbon feedstocks comprise one or more hydrocarbons having an average carbon number of 1 to 18.

7. The method of claim 1, wherein: The one or more light and / or medium hydrocarbon feedstocks comprise one or more components selected from the group consisting of jet fuel, diesel, naphtha, kerosene, C4 and oxygenates.

8. The method of claim 1, wherein: The first FCC conditions include maintaining the outlet temperature of the first riser at 510°C to 575°C.

9. The method of claim 1, wherein: The first FCC conditions include mixing steam and a heavy hydrocarbon feed in a first riser at a concentration of 1 wt % to 6 wt %.

10. The method of claim 1, wherein: The FCC conditions different from the first FCC conditions include maintaining an outlet temperature of one or more risers different from the first riser at 550°C to 675°C.

11. The method of claim 1, wherein: The FCC conditions different from the first FCC conditions include mixing steam with the one or more light and / or medium hydrocarbon feeds at a concentration of 5 wt % to 20 wt %.

12. The method of claim 1, further comprising providing at least a portion of the first effluent to one or more risers other than the first riser.

13. The method of claim 12, wherein: Providing at least a portion of the first effluent to one or more risers other than the first riser comprises: fractionating the first effluent using a fractionation system to produce a fractionated stream enriched in one or more components of the first effluent, and The fractionated stream is recycled from the fractionation system to one or more risers other than the first riser.

14. The method of claim 13, wherein: The fractionated stream is enriched in one or more of naphtha and C4.

15. The method of claim 1, wherein: Cracking one or more light and / or medium hydrocarbon feeds in one or more risers different from the first riser comprises: cracking a medium feed in a second riser at second FCC conditions, and The light feed is cracked in the third riser at third FCC conditions different from the second FCC conditions.

16. The method of claim 15, wherein: The medium feedstock comprises one or more of gasoline, kerosene, jet fuel and diesel fuel.

17. The method of claim 15, wherein: The second FCC conditions include maintaining the outlet temperature of the first riser at 550°C to 675°C.

18. The method of claim 15, wherein: The light feed comprises one or more of naphtha, C4 and oxygenates.

19. The method of claim 1, wherein: The FCC reaction in each of the risers comprises cracking using a catalyst mixture comprising Y zeolite and a shape selective zeolite.

20. The method of claim 19, wherein: The shape selective zeolite is ZSM-5.

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