Systems and processes for temperature control in fluid catalytic cracking

Abstract

A fluid catalytic cracking ("FCC") system includes a catalyst regenerator configured and adapted to regenerate a spent catalyst feed to produce a regenerated catalyst. The system includes a reactor downstream from an outlet of the catalyst regenerator to receive the regenerated catalyst from the catalyst regenerator. The system includes a spent catalyst riser between an outlet of the reactor and an inlet of the regenerator. The spent catalyst riser includes a torch oil injection nozzle configured and adapted to provide heat to the catalyst regenerator. A process for controlling catalyst temperature in an FCC system includes regenerating the spent catalyst feed in the catalyst regenerator to produce a regenerated catalyst feed, drawing at least a portion of the regenerated catalyst feed to the reactor, receiving the spent catalyst from the reactor in the spent catalyst riser, and heating the spent catalyst in the spent catalyst riser using the torch oil injection nozzle. In an embodiment, the reactor is a downer.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of priority to U.S. Patent Application No. 63 / 374,242, filed September 1, 2022, the entire disclosure of which is incorporated herein by reference.

[0002] FIELD OF THE INVENTION The present disclosure relates to fluid catalytic cracking systems and processes, and more particularly to downer fluid catalytic cracking systems and processes. [Background technology]

[0003] The fluidized catalytic cracking ("FCC") process is widely used to convert hydrocarbon feedstreams, such as vacuum gas oils and other relatively heavy oils, into lighter, more valuable hydrocarbon products. The basic components of a downer FCC system include at least one reactor, a spent catalyst riser, and a catalyst regenerator. In some cases, a catalyst cooler is installed on the catalyst regenerator to control the regenerator temperature within reasonable limits when processing heavy feedstocks.

[0004] Torch oil is used to preheat the regenerator and catalyst during FCC startup. This is the usual method for starting up an FCC unit. After loading the catalyst, the regenerator is preheated by a direct-fired air preheater. Flue gas from the air preheater passes through the fluidized catalyst bed in the regenerator at temperatures up to 1100-1200°F. After the catalyst bed reaches approximately 700-800°F, supplemental fuel, typically in the form of feed or light cycle oil (LCO), is injected directly into the hot catalyst. This temperature causes the supplemental fuel to self-combust. The supplemental fuel is commonly referred to as torch oil. The heat released from the torch oil combustion further heats the catalyst bed to approximately 1300°F before the catalyst circulation begins. Torch oil can generally be burned continuously in the regenerator to provide the necessary additional heat when the hydrocarbon feed does not produce enough coke in the riser to meet the heat load required for cracking the feed.

[0005] Several patents describe the use of torch oil in regenerators. In U.S. Pat. No. 3,909,392, localized combustion of torch oil leads to high catalyst particle temperatures, sintering the catalyst, and loss of active sites on the catalyst, resulting in significant catalyst deactivation. The loss of catalytic activity necessitates an increase in catalyst make-up rate, thus increasing operating costs. In WO 2016 / 200565, torch oil injection is staged in this high-efficiency regenerator, but the net effect is less severe than the drawbacks mentioned above. In WO 01 / 74972, the flow regime in the spent catalyst lift line is not ideal for fuel combustion due to limited backmixing, which creates the possibility of catalyst deactivation even when torch oil injection is staged to limit heat release per injection location. In WO 01 / 7497, the effects of direct torch oil injection in the regenerator include refractory damage, uneven catalyst flow, and the potential for slug flow due to excessive torch oil injection.

[0006] Prior art techniques have been considered satisfactory for their intended purposes. However, there is a continuing need for improved catalyst heating. The present disclosure provides a solution to this need. Summary of the Invention

[0007] The fluid catalytic cracking ("FCC") system includes a catalyst regenerator configured and adapted to regenerate a spent catalyst feed to produce regenerated catalyst. The system includes a reactor downstream from an outlet of the catalyst regenerator to receive the regenerated catalyst from the catalyst regenerator. The system includes a spent catalyst riser between the outlet of the reactor and the inlet of the regenerator. The spent catalyst riser includes a torch oil injection nozzle configured and adapted to provide heat to the catalyst regenerator.

[0008] One or more embodiments include the system of any preceding paragraph, wherein the spent catalyst riser can include a mixing zone downstream from the outlet of the reactor and upstream from the inlet of the catalyst regenerator.

[0009] One or more embodiments include the system of any preceding paragraph, wherein the torch oil injection nozzle can be positioned to inject torch oil into the mixing region.

[0010] One or more embodiments include the system of any preceding paragraph, wherein the spent catalyst riser can include an air injector downstream from the torch oil injection nozzle.

[0011] One or more embodiments include the system of any preceding paragraph, wherein the spent catalyst riser can include an air injector upstream from the torch oil injection nozzle.

[0012] One or more embodiments include the system of any preceding paragraph, wherein the spent catalyst riser can include at least one air injector upstream from the torch oil injection nozzle and at least one air injector downstream from the torch oil injection nozzle.

[0013] According to another embodiment, a process for controlling catalyst temperature in an FCC system includes regenerating a spent catalyst feed in a catalyst regenerator to produce a regenerated catalyst feed, drawing at least a portion of the regenerated catalyst feed to a reactor, receiving spent catalyst from the reactor in a spent catalyst riser, and heating the spent catalyst in the spent catalyst riser using a torch oil injection nozzle.

[0014] One or more embodiments include the process of any preceding paragraph, wherein the reactor is downstream from an outlet of the catalyst regenerator and is capable of receiving regenerated catalyst from the catalyst regenerator.

[0015] One or more embodiments include the process of any preceding paragraph, wherein the spent catalyst riser can be positioned between the outlet of the reactor and the inlet of the catalyst regenerator.

[0016] One or more embodiments include the process of any preceding paragraph, wherein the spent catalyst riser can include a mixing zone downstream from the outlet of the reactor and upstream from the inlet of the catalyst regenerator.

[0017] One or more embodiments include the process of any preceding paragraph, wherein heating the spent catalyst can include injecting torch oil into the mixing region with a torch oil injection nozzle.

[0018] One or more embodiments include the process of any preceding paragraph, wherein the process can include injecting air downstream from the torch oil injection nozzle with an air injector.

[0019] One or more embodiments include the process of any preceding paragraph, wherein the process can include injecting air upstream from the torch oil injection nozzle with an air injector.

[0020] One or more embodiments include the process of any preceding paragraph, wherein the process can include injecting air upstream from the torch oil injection nozzle with a first air injector and injecting air downstream from the torch oil injection nozzle with at least one second air injector.

[0021] These and other features of the systems and methods of the present disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings. [Brief explanation of the drawings]

[0022] Preferred embodiments of the present disclosure are described in detail herein below with reference to specific figures so that those skilled in the art to which the present disclosure pertains will readily understand how to make and use the devices and methods of the present disclosure without undue experimentation. [Figure 1] FIG. 1 is a schematic plan view of an FCC system with catalyst heating constructed in accordance with an embodiment of the present disclosure, showing a torch oil injection nozzle in a spent catalyst riser configured and adapted to provide heat to a catalyst regenerator. [Figure 2] FIG. 2 is an enlarged schematic plan view of the FCC system of FIG. 1 showing the torch oil injection nozzle in the spent catalyst riser. DETAILED DESCRIPTION OF THE INVENTION

[0023] Reference is now made to the drawings, in which like reference numerals identify like structural features or aspects of the present disclosure. For purposes of explanation and illustration, and not limitation, a schematic diagram of an exemplary embodiment of a fluid catalytic cracking ("FCC") system is shown in FIG. 1, designated generally by reference numeral 100. Another embodiment of an FCC system according to the present disclosure, or aspects thereof, as illustrated, is provided in FIG. 2. The systems and methods described herein avoid direct injection of torch oil into the regenerator, thereby avoiding certain problems associated with conventional localized combustion of torch oil within the regenerator, such as high catalyst particle temperatures accompanied by severe catalyst deactivation due to catalyst sintering and loss of active sites on the catalyst.

[0024] As shown in FIG. 1 , an FCC system 100 includes a catalyst regenerator 102 configured and adapted to regenerate a spent catalyst feed to produce a regenerated catalyst. The system 100 includes a light feed (LF) reactor 104a and a heavy feed (HF) reactor 104b, respectively, downstream from respective outlets 108a and 108b of the catalyst regenerator 102, from which the regenerated catalyst is received. The system 100 includes a spent catalyst riser 106 between respective outlets 110a and 110b of the reactors 104a and 104b and an inlet 112 of the regenerator 102. The spent catalyst riser 106 includes a mixing zone 118 downstream from the outlets 110a and 110b of the reactors 104a and 104b and upstream from the inlet 112 of the catalyst regenerator 102. The spent catalyst from the LF reactor 104a and the spent catalyst from the HF reactor 104b are mixed together in a mixing zone 118 at the bottom of the spent catalyst lift riser 106. The mixed catalyst from is transported using air to the regenerator 102 where coke deposited on the catalyst is burned off.

[0025] Because the majority of the hydrocarbon feed to the systems shown in FIGS. 1 and 2 is light crude oil, the total amount of coke produced from the cracking reactions in the LF reactor 104a and the HF reactor 104b is insufficient to maintain the desired regenerator temperature necessary to burn off the coke from the catalyst and provide the heat required for the cracking process. To overcome the heat balance deficiency, a large amount of torch oil is required. Injecting the required amount of torch oil into the regenerator 102 would lead to drawbacks, such as high catalyst particle temperatures with severe catalyst deactivation due to catalyst sintering and loss of active sites on the catalyst, increased operating costs due to loss of catalyst activity, and catalyst attrition and refractory damage, among others. Instead, the embodiment of FIGS. 1 and 2 includes a mixing zone 118 designed to adequately mix the two spent catalyst streams and simultaneously provide adequate turbulence for torch oil injection. The spent catalyst riser 106 includes a torch oil injection nozzle 114 configured and adapted to provide heat to the catalyst regenerator 102 through the mixing zone 118. This configuration reduces catalyst deactivation. A torch oil injection nozzle 114 injects supplemental fuel, such as torch oil, into the spent catalyst riser 106 to provide heat to maintain the regeneration temperature. Torch oil droplets from the torch oil nozzle 114 contact the hot catalyst particles, deposit on them, and vaporize or, in some cases, decompose. Because only about 40% of the total combustion air is supplied through the spent catalyst riser 106, the generated steam burns under substoichiometric conditions. The steam and combustion gases act to lift the catalyst into the regenerator 102, where they are uniformly distributed within the catalyst bed of the regenerator 102. Turbulent mixing energy is achieved by a balance between the diameter D1 of the mixing zone 118 relative to the diameter D2 of the lift line 117 and the lift gas velocity. Air lift gas is provided in stages by air injectors 115a and 115b. The air injection distributor is provided as a first injector 115 a at the bottom of the mixing region 118 , with the remainder injected at air injector nozzles 115 b located at the top of the mixing region 118 just above the torch oil injection nozzles 114 .Although the first injector 115a is shown schematically as a cross section of a ring-type distributor, one skilled in the art will readily understand that the first injector 115a can consist of a single nozzle or multiple nozzles and can be a ring-type distributor or a showerhead-type distributor.

[0026] 1 and 2, the torch oil injection nozzle 114 is positioned to inject torch oil into the mixing zone 118. The spent catalyst riser 106 includes air injectors 115a and 115b upstream and downstream from the torch oil injection nozzle 114. The spent catalyst riser 106 includes at least one air injector 115a upstream from the torch oil injection nozzle 114 and one air injector 115b downstream from the torch oil injection nozzle 114. Heating at the torch oil injection nozzle 114 before reaching the regenerator 102 allows the catalyst from both the LF reactor 104a and the HF reactor 104b to be uniformly coated with oil or coke before entering the regenerator 102. Any vapors formed from oil cracking or flashing on the catalyst surface aid in catalyst transport into the regenerator 102. Air injectors 115a and 115b inject torch oil to create a highly turbulent zone within spent catalyst riser 106. This turbulent zone provides better mixing and heat transfer characteristics than a typical bubbling bed.

[0027] Additionally, by avoiding direct injection of torch oil into the regenerator 102, localized combustion of the torch oil can also be avoided. Localized combustion of torch oil in certain conventional applications can result in high catalyst particle temperatures, accompanied by severe catalyst deactivation due to catalyst sintering and loss of active sites on the catalyst. Loss of catalyst activity requires an increased catalyst make-up rate, thus increasing operating costs. Direct injection of torch oil into the regenerator 102 can also cause catalyst attrition and refractory damage. The system 100 is more efficient than injecting torch oil into the stripper of an FCC unit, high-severity FCCU, or similar. This option deposits coke / hydrocarbons evenly on the catalyst as it travels through the stripper, although approximately 40% of the torch oil is converted to coke. The remainder evaporates or cracks into vapor products, which, together with the cracked vapors, enter the main fractionator. This "efficiency" loss in transferring all the torch oil to the catalyst results in a higher flow rate of torch oil to satisfy the heat balance.

[0028] A process for controlling catalyst temperature in an FCC system, e.g., system 100, includes regenerating a spent catalyst feed in a catalyst regenerator, e.g., catalyst regenerator 102, to produce a regenerated catalyst feed. The process includes withdrawing at least a portion of the regenerated catalyst feed to at least one reactor, e.g., reactors 104a and 104b. The process includes receiving spent catalyst from the reactor in a spent catalyst riser, e.g., spent catalyst riser 106. The process includes heating the spent catalyst in the spent catalyst riser with a torch oil injection nozzle, e.g., torch oil injection nozzle 114. The process includes injecting air upstream from the torch oil injection nozzle using a first air injector, e.g., air injector 115a, and injecting air downstream from the torch oil injection nozzle using a second air injector, e.g., air injector 115b. The spent catalyst riser is positioned between the reactor outlet, e.g., outlets 110a and / or 110b, and the catalyst regenerator inlet, e.g., inlet 112. Heating the spent catalyst includes injecting torch oil into the mixing zone using a torch oil injection nozzle. In some embodiments, hot spots in the regenerator 102 can be minimized by continuous injection of such large amounts of torch oil.

[0029] The methods and systems of the present disclosure, as described above and shown in the drawings, provide an FCC system designed to provide heat to the catalyst before it reaches the catalyst regenerator with superior properties, including reduced catalyst deactivation. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily understand that changes and / or modifications can be made therein without departing from the scope of the subject disclosure.

Claims

1. 1. A fluid catalytic cracking ("FCC") system comprising: a catalyst regenerator configured and adapted to regenerate the spent catalyst feed to produce a regenerated catalyst; a reactor downstream from the outlet of the catalyst regenerator for receiving regenerated catalyst from the catalyst regenerator; a spent catalyst riser between the reactor outlet and the regenerator inlet, the spent catalyst riser including a torch oil injection nozzle configured and adapted to provide heat to the catalyst regenerator.

2. 10. The system of claim 1, wherein the spent catalyst riser includes a mixing zone downstream from the outlet of the reactor and upstream from the inlet of the catalyst regenerator.

3. The system of claim 1 , wherein the torch oil injection nozzle is positioned to inject torch oil into the mixing region.

4. The system of claim 1 , wherein the spent catalyst riser includes an air injector downstream from the torch oil injection nozzle.

5. The system of claim 1 , wherein the spent catalyst riser includes an air injector upstream from the torch oil injection nozzle.

6. The system of claim 1 , wherein the spent catalyst riser includes at least one air injector upstream from the torch oil injection nozzle and at least one air injector downstream from the torch oil injection nozzle.

7. 1. A process for controlling catalyst temperature in a fluid catalytic cracking ("FCC") system, comprising: regenerating the spent catalyst feed in a catalyst regenerator to produce a regenerated catalyst feed; withdrawing at least a portion of the regenerated catalyst feed to a reactor; receiving spent catalyst from the reactor in a spent catalyst riser; heating the spent catalyst in the spent catalyst riser with a torch oil injection nozzle.

8. 8. The process of claim 7, wherein the reactor is downstream from the outlet of the catalyst regenerator for receiving regenerated catalyst from the catalyst regenerator.

9. 8. The process of claim 7, wherein the spent catalyst riser is positioned between the reactor outlet and the catalyst regenerator inlet.

10. 8. The process of claim 7, wherein the spent catalyst riser comprises a mixing zone downstream from the outlet of the reactor and upstream from the inlet of the catalyst regenerator.

11. 8. The process of claim 7, wherein heating the spent catalyst comprises injecting torch oil into the mixing zone with the torch oil injection nozzle.

12. 8. The process of claim 7, further comprising injecting air downstream from the torch oil injection nozzle with an air injector.

13. 8. The process of claim 7, further comprising injecting air upstream from the torch oil injection nozzle with an air injector.

14. 8. The process of claim 7, further comprising injecting air upstream from the torch oil injection nozzle with a first air injector and injecting air downstream from the torch oil injection nozzle with at least one second air injector.

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