System and process for controlling residence time in a downer reactor

Abstract

The downer reactor assembly includes an outer separator vessel, at least one downer reactor extending vertically from an upper end to a lower end within the outer separator vessel, and a mushroom-shaped distributor end cap positioned at the lower end of the at least one downer reactor. A process for cracking a hydrocarbon feedstock includes providing a catalyst feed to the at least one downer reactor assembly. The catalyst feed is discharged below the mushroom-shaped distributor cap at the lower end of the at least one downer reactor. The process includes separating hydrocarbon vapors from the catalyst feed under gravity and distributing the upwardly flowing hydrocarbon vapors separated from the catalyst feed through nozzle holes in the mushroom-shaped distributor cap.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the benefit of priority to U.S. Patent Application No. 63 / 374,239, filed Aug. 31, 2022, the entire disclosure of which is incorporated herein by reference.

[0002] (Field of the Invention) The present disclosure relates to a downer reactor, and more particularly to a downer reactor terminated by a vertical primary separator.

Background Art

[0003] Conventional downer reactors terminate with a vertical primary separator that separates most of the catalyst from the vapor. The vapor with entrained catalyst exiting the separator is further separated in a close - coupled cyclone system before entering the main fractionator. The separated catalyst falls into the reactor / stripper through respective dip legs. The vapor residence time in the downer ranges from 0.5 to 1 second. Since the downflow system is a stacked unit, the height of the downer affects the overall height of the system and thus the required capacity and capital expenditure (CAPEX). The downer height - to - diameter ratio is adjusted to minimize the overall height while reducing the scale - up risk regarding the downer diameter and its impact on catalyst - feed contact.

[0004] In conventional double downer systems, light and paraffinic hydrocarbon feedstocks with boiling points below 660°F are processed in a light feed (LF) downer and its respective reactor, while highly decomposable feedstocks with boiling points above 660°F are processed in a heavy feed (HF) downer and its reactor. The objective of processing is typically to maximize the total amount of olefin produced. LF, being paraffinic, requires very demanding operating conditions in terms of longer residence times, higher temperatures, and higher catalyst-to-oil ratios. Catalyst temperature and catalyst-to-oil ratio are set by the regenerator temperature. Vapor residence time depends on the diameter and height of the downer. As mentioned above, typical vapor residence times in downer systems are 0.5–1 second. Increasing residence time beyond 1 second requires either increasing the diameter at a constant downer height or increasing the height at a constant downer diameter. Both options involve trade-offs in capital cost and performance.

[0005] Conventional techniques have been considered satisfactory for their intended purposes. However, there is always a need for improved downer reactors. This disclosure provides a solution to this need. [Overview of the project]

[0006] The downer reactor assembly includes an outer separation vessel, at least one downer reactor extending vertically from the top to the bottom of the outer separation vessel, and a mushroom-shaped distributor end cap positioned at the bottom of the at least one downer reactor.

[0007] One or more embodiments include any of the assemblies described in the preceding paragraph, and at least one Downer reactor may include two Downer reactors.

[0008] One or more embodiments include any assembly from the preceding paragraph, and the mushroom-shaped partition end caps can be positioned at the lower end of each of the two downer reactors.

[0009] One or more embodiments include any assembly from the preceding paragraph, and the mushroom-shaped partition end cap may include a convex surface facing the upper end of at least one downer reactor.

[0010] One or more embodiments include any of the assemblies described in the preceding paragraph, and at least one downer reactor may include an inlet close to the top end.

[0011] One or more embodiments include any of the assemblies described in the preceding paragraph, and the lower end of at least one downer reactor can be configured and adapted to be immersed in the catalyst bed.

[0012] One or more embodiments include any assembly from the preceding paragraph, and the mushroom-shaped distributor end caps can be configured and fitted so as to be immersed in the catalyst bed.

[0013] One or more embodiments include any assembly from the preceding paragraph, the assembly may include a tightly coupled cyclone system above the lower end of at least one downer reactor. One or more embodiments include any assembly from the preceding paragraph, the vapor residence time in at least one downer reactor is in the range of 0.5 to 1 second.

[0014] In another embodiment, a process for decomposing a hydrocarbon feedstock includes providing a catalyst feedstock to at least one downer reactor assembly. The catalyst feedstock is discharged below a mushroom-shaped distributor cap at the lower end of at least one downer reactor. The process includes separating hydrocarbon vapors from the catalyst feedstock under gravity and distributing the upward-flowing hydrocarbon vapors separated from the catalyst feedstock through nozzle holes in the mushroom-shaped distributor cap.

[0015] One or more embodiments include any of the processes of the preceding paragraph, and the mushroom-shaped partition may include a convex surface facing the upper end of at least one downer reactor.

[0016] One or more embodiments include any of the processes of the preceding paragraph, and discharging the catalyst feed at the lower end of at least one downer reactor may include discharging at least a catalytic portion of the catalyst feed into the catalyst bed.

[0017] One or more embodiments include any of the preceding paragraph processes, which may include providing an additional residence time to the upward-flowing vapor after discharge in order to facilitate additional conversion of the unreacted hydrocarbon portion of the catalyst feed discharged from the lower end of at least one downer reactor.

[0018] One or more embodiments include any of the processes described in the preceding paragraph, and the mushroom-shaped distributor end caps can be configured and fitted to be immersed in the catalyst bed.

[0019] One or more embodiments include any of the processes described in the preceding paragraph, the process of discharging upward-flowing vapor into a tightly coupled cyclone system.

[0020] These and other features of the systems and methods of this disclosure will become more readily apparent to those skilled in the art from the following detailed description of preferred embodiments, which will be interpreted in conjunction with the drawings. [Brief explanation of the drawing]

[0021] Preferred embodiments of the Disclosure will be described in detail below, with reference to specific figures, so that those skilled in the art to which this Disclosure perceives how to fabricate and use the devices and methods of this Disclosure without having to perform any unnecessary experiments. [Figure 1] This is a schematic plan view of a reactor and separation vessel having a downer reactor assembly according to an embodiment of the present disclosure, showing a mushroom-shaped distributor end cap. [Figure 2] This is a schematic perspective view of a mushroom-shaped distributor end cap of a downer reactor assembly according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0022] Herein, with reference to the drawings, similar reference numerals in the drawings identify similar structural features or embodiments of the present disclosure. For illustrative and illustrative purposes only, rather than limiting, schematic diagrams of exemplary embodiments of downer reactor assemblies according to the present disclosure are shown in Figure 1, which are generally designated by reference numeral 100. Other embodiments or aspects thereof of downer reactor assemblies according to the present disclosure are shown in Figure 2 and described throughout this specification. The systems and methods described herein can be used to maximize the total amount of olefins produced by increasing the vapor residence time without increasing either the downer diameter or height.

[0023] As shown in Figure 1, the double downer reactor assembly 100 includes at least one reactor 102 having an outer separation vessel 104. The downer reactor assembly 100 includes two downer reactors 106 terminating at reactor 102, for example. Reactor 102 may be a light feed (LF) reactor and / or a heavy feed (HF) reactor. The downer reactor assembly 100 can process light and paraffinic hydrocarbon feedstocks in combination with a catalyst in an LF downer, for example, in the first downer reactor of the two downer reactors 106, while heavier and more decomposable hydrocarbon feedstocks are processed in combination with a catalyst in an HF downer, for example, in the second downer reactor of the two downer reactors 106. In assembly 100, instead of a separator at the bottom of the downer reactor 106, the downer reactor 106 is discharged below the mushroom distributor end cap 108 located within the separation vessel 104, where the catalyst is separated by gravity and the vapor is distributed through the nozzle 112 of the mushroom distributor 108 into the catalyst bed 110 above it. The residence time in a given downer reactor 106 is approximately 1 second. If necessary, additional residence times of several minutes can be achieved in the fluidized bed 110, as described below.

[0024] As shown in FIGS. 1 and 2, the mushroom-shaped distributor end cap 108 is positioned above the lower end 120 of each of the two downer reactors 106. The mushroom-shaped distributor end cap 108 includes a convex surface 116 facing the upper end 118 of the downer reactor 106. Each downer reactor 106 includes an inlet 114 proximate to the upper end 118. The catalyst entering the inlet 114 is schematically indicated by the downward arrow. The lower end 120 of each downer reactor 106 is configured and adapted to be immersed in the catalyst bed 110. The mushroom-shaped distributor end cap 108 is also configured and adapted to be immersed in the catalyst bed 110. The assembly 100 includes a close-coupled cyclone system 124 above the lower end 120 closer to the upper end 118 than the lower end 120 of the downer reactor 106. The vapor residence time in the downer reactor 106 ranges from 0.5 to 1 second. In the fluid catalyst bed 110 below the downer reactor 106, additional residence time is achieved in minutes. If necessary, the height A of the catalyst bed level 122 above the mushroom-shaped distributor is varied to achieve the residence time required for further conversion of the unreacted feed exiting the downer reactor 106. The vapor, together with the stripping vapor, enters the main fractionator after passing through the cyclone system.

[0025] The process for decomposing the hydrocarbon feedstock includes providing a catalyst feedstock to a downer reactor assembly, e.g., downer reactor assembly 100, as schematically indicated by the arrow pointing to the inlet 114 of downer reactor 106. This catalyst feedstock is combined with the hydrocarbon feedstock (LF or HF) to decompose the hydrocarbon feedstock (which may be in the form of hydrocarbon vapor). The process includes discharging the catalyst feedstock at the lower end of the downer reactor, e.g., the lower end 120, below a mushroom-shaped distributor cap, e.g., a mushroom-shaped distributor cap 108. At the lower end 120, it is intended that at least a portion of the hydrocarbon feedstock (e.g., in the form of hydrocarbon vapor) is also discharged. The process includes separating the catalyst feedstock from the hydrocarbon feedstock under gravity and distributing the upward-flowing vapor (e.g., hydrocarbon vapor) separated from the catalyst feedstock through a nozzle opening in the mushroom-shaped distributor cap, e.g., nozzle opening 112. Discharging the catalyst feed at the lower end of the downer reactor includes discharging the catalyst feed into a catalyst bed, e.g., catalyst bed 110. The process includes providing an additional residence time to the upward-flowing vapor (e.g., hydrocarbon vapor) after discharge to facilitate additional conversion of the unreacted hydrocarbon portion of the catalyst feed discharged from the lower end of at least one downer reactor. The mushroom-shaped distributor end cap is configured and adapted to be immersed in the catalyst bed. In some embodiments, the process includes discharging the upward-flowing vapor into a two-stage cyclone system, e.g., a tightly coupled cyclone system 124.

[0026] Embodiments of the present disclosure provide an increased feed conversion rate in the downer treatment of light hydrocarbon feedstock. The reactor system 100 incorporates dense bed cracking with the ability to control dense bed gas residence time and hydrocarbon partial pressure. Embodiments of the present disclosure provide a downer reactor with improved selectivity for propylene without increasing CAPEX and operational expense (OPEX). Embodiments of the present disclosure provide an increased catalyst utilization rate that offsets partial catalyst bypass in the downer.

[0027] The methods and systems of the present disclosure provide a system and method for a downer reactor assembly having excellent properties including increased controllability and improved selectivity to propylene without increasing CAPEX and OPEX costs, as described above and shown in the drawings. The systems and methods of the present invention can be applied to HS-FCC technology or the like. The apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, but those skilled in the art will readily understand that changes and / or modifications can be made without departing from the scope of the subject disclosure.

Claims

1. Downer reactor assembly, an outer separation container; The outer separation container comprises at least one downer reactor extending vertically from the upper end to the lower end, The at least one downer reactor includes a mushroom-shaped distributor end cap positioned above the lower end of the downer reactor, The aforementioned mushroom-shaped distributor end cap is configured to be immersed in the catalyst bed during use. A downer reactor assembly wherein the mushroom-shaped distributor end cap is equipped with a nozzle, the nozzle being configured to distribute upward-flowing hydrocarbon vapor, separated from the catalyst feed discharged from the lower end of the at least one downer reactor, through the nozzle into the catalyst bed located above the mushroom-shaped distributor end cap.

2. The assembly according to claim 1, wherein the at least one downer reactor comprises two downer reactors, and the mushroom-shaped distributor end cap is positioned above the lower end of each of the two downer reactors.

3. The assembly according to claim 1, wherein the mushroom-shaped distributor end cap includes a convex surface facing the upper end of the at least one downer reactor.

4. The assembly according to claim 1, wherein the at least one downer reactor includes an inlet adjacent to the upper end.

5. The assembly according to claim 1, wherein the lower end of at least one downer reactor is configured to be immersed in a catalyst bed.

6. The assembly according to claim 1, further comprising a tightly coupled cyclone system positioned above the lower end of the at least one downer reactor.

7. The assembly according to claim 1, wherein the vapor residence time in at least one downer reactor is in the range of 0.5 to 1 second.

8. A process for breaking down hydrocarbon supply materials, To provide a catalyst feed to at least one downer reactor assembly, At least one downer reactor bottom is used to discharge the catalyst feed below a mushroom-shaped distributor end cap immersed in the catalyst bed, Separating hydrocarbon vapor from the catalyst feed under gravity, A process comprising distributing upward-flowing hydrocarbon vapor separated from the catalyst feed into the catalyst bed located above the mushroom-shaped distributor end cap, through a nozzle provided on the mushroom-shaped distributor end cap.

9. The process according to claim 8, wherein the mushroom-shaped distributor end cap includes a convex surface facing the upper end of at least one downer reactor.

10. The process according to claim 8, further comprising discharging the upward-flowing steam into a two-stage cyclone system.

Images