JPH10176171A - Process for fluidized catalytic cracking of hydrocarbon by using collector for catalyst separation and stripping - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce the formation of stripping wastes in an FCC (fluidized catalytic cracking) process. SOLUTION: This invention provides an apparatus for cyclone separation, wherein a particulate solid and a gaseous fluid are discharged from a discharge opening 16 to a separation vessel 11. The separated gaseous fluid is led from the separation chamber by bringing at least a part of the catalyst fed into the separation chamber from the external into contact with the recirculation gas entering the chamber through a plurality of limited openings around the bottom of the separation vessel. This apparatus permits the still more effective utilization of the stripping medium utilizable in an FCC process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a process for the fluid catalytic cracking ("FCC") of hydrocarbons using a new apparatus for separating solid catalyst particles from gases and stripping hydrocarbons from the catalyst. It is about.
The invention also relates to separating the catalyst and gaseous substances from the mixture in a cyclone separation vessel of the FCC process.

[0002]

BACKGROUND OF THE INVENTION Cyclone processes for separating solids from gases are well known and commonly used. Of these methods, the hydrocarbon processing industry is particularly well-known for the chemical conversion of gas stream components, or for the catalytic conversion of particles in contact with a gas stream to produce a physical change of particles. It is a hydrogen reactant. In the FCC process, a well-known example is a process in which a gas stream that contacts the finally divided catalyst particles is used to cause contact between the gas and the particles. The FCC process, together with the separation equipment used in the process, is disclosed in US-A-4701307 and US-A-4701307.
-A-479237.

[0003] The most common method for separating particulate solids from a gas stream is cyclonic separation.
Is used. This cyclone separation is well known, with the heavier solid particles moving outwards from the lighter gas, the gas moving upwards, and the solids moving down the gas containing the solid particles in a sinusoidal manner so that they can move down. It works by giving speed. Cyclone separators typically employ a relatively small diameter cyclone having a sinusoidal inlet located outside a cylindrical vessel forming the outer housing of the cyclone.

Cyclones for separating particulate matter from gaseous matter are well known to those skilled in the field of FCC processing. In the operation of the FCC cyclone, the gaseous substance and the catalyst are introduced in a sine direction to form a spiral flow path, which creates a spiral shape, and the centripetal acceleration associated with the outer spiral forms the catalyst particles in the container. And the gaseous material enters the inner vortex and is eventually discharged from the upper outlet.
Heavier catalyst particles accumulate on the sidewalls of the cyclone vessel,
Eventually it falls to the bottom of the cyclone and is circulated through the FCC facility via outlets and dip leg conduits. Cyclone configurations and modifications thereto are basically disclosed in US-A-4670410 and US-A-2535140.

[0005] The FCC process is a representative example of many processes for rapidly separating gaseous fluids and solids as they exit the conduit. In the FCC process, one way to achieve such an initial rapid discharge is to connect the conduit containing the reaction fluid and catalyst directly to a conventional cyclone separator. Although such a method promotes separation, connecting solids and gaseous fluids directly to a cyclone separator has several disadvantages. Since the mixture discharged into the cyclone contains a high percentage of solids, a large cyclone is required for direct discharge. In addition, the delivery of the mixture is accompanied by instability, the cyclone does not work well,
If the process were interrupted, the pressure would pulsate and the vapor separated in the cyclone would pass an unacceptable amount of solids. These problems are commonly experienced in processes such as fluidized catalytic cracking. Thus, there is a need for a less restrictive system for effecting an initial separation between a mixture of solid particles and a substrate fluid.

[0006] US-A-4397738 and US-A-4482451 disclose another configuration of cyclone separation in which a mixture of gas and solid particles is sinusoidally discharged from a central conduit into a containment vessel. This containment vessel has a relatively large diameter and usually first separates the solids from the gas. These types of configurations have the advantage of discharging solids from a central conduit,
It differs from the usual cyclone configuration in that a container having a relatively large diameter is used as a containment container. In such an arrangement, a second and more complete separation of the solids from the gas takes place in a conventional cyclone vessel after the initial stage of the separation.

[0007] In addition to separating the solid catalyst from the hydrocarbon gas, to operate the FCC process more efficiently, the hydrocarbon is stripped from the solid catalyst as it passes from the reactor to the regenerator. There is a need. Stripping is typically performed using steam to displace the material adsorbed on the surface of the solid catalytic material and inside the pores. In order to recover the maximum amount of product while minimizing the combustion of hydrocarbons that could cause the temperature of the regeneration zone to rise excessively in the regenerator, hydrocarbons should be removed from the catalyst surface as much as possible. It is important to strip much.

[0008] US-A-4689206 discharges a mixture of catalyst and gas sinusoidally into a separation vessel while simultaneously feeding gas from a lower stripping zone into a series of baffles to remove carbonization from the catalyst in the separation vessel. A separation and stripping unit for an FCC process to remove hydrogen is disclosed. Although the device shown in this patent is capable of stripping hydrocarbon gas to some extent from the catalyst in the separation vessel, this device uses all of the gases available for stripping hydrocarbons in the separation vessel. It does not ensure that the stripping gas entering the separation vessel is efficiently utilized by dispersing it well within the catalyst phase.

While it is advantageous to strip and recover as much hydrocarbons as possible from FCC catalysts, refiners are pressing for the need to minimize the amount of conventional stripping media used to cause stripping. Have been. This need arises from the difficulties in disposing of acidic steam resulting from contacting the catalyst with steam in a conventional stripping operation. Thus, while more efficient hydrocarbon stripping from FCC catalysts is required for more efficient process operation, the amount of preferred stripping media is limited.

[0010]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and the stripping efficiency of cyclone separation, which can discharge particles mainly into the separation chamber, is to reduce all available stripping gas in the separation vessel. At the same time
Operating the reaction vessel in such a way that the gas is passed in such a way as to increase the effectiveness of the stripping in the separation chamber has been found to be surprisingly improved and surrounds the separation chamber. The gaseous fluid in the reaction vessel is held in the reaction vessel at a pressure higher than the pressure in the separation chamber. By increasing the pressure, a gas flow is created from inside the reaction vessel surrounding the separation chamber into the separation vessel. The effectiveness of the stripping is increased by directing a portion of this gas through some flow constraints to the interior of the catalyst bed within the separation chamber located above the bottom of the separation chamber. This flow constraint ensures that the gas entering the separation chamber is uniformly distributed so that it can be effectively used as a stripping medium.

[0011]

Accordingly, in one embodiment, the present invention is a process for fluid catalytic cracking of a hydrocarbon feed. In this process, a hydrocarbon feedstock and solid catalyst particles are fed into a riser addition zone, which comprises a conduit that creates a mixture of solid particles and a gaseous fluid. The mixture is fed through a conduit into a separation vessel, which occupies the central part of the separation vessel, while the separation vessel is located inside the reactor.
The conduit discharges the mixture sinusoidally through the discharge opening. The catalyst particles enter a first catalyst bed located at the bottom of the separation vessel and come into contact with a first stripping gas of the first bed. Catalyst particles from the first bed enter a second bed located in a separation vessel below the first catalyst bed. The catalyst particles are contacted with a second stripping gas, which is the first stripping gas.
To supply a portion of the stripping gas. Catalyst particles from the second bed enter the stripping zone and come into contact with a third stripping gas in the stripping zone. A third stripping gas enters the second catalyst bed and provides at least a portion of the second stripping gas. A purge medium enters the top of the reaction vessel, and at least a portion of the purge gas passes through a plurality of restriction openings disposed around the outer periphery of the separation vessel at the bottom of the catalyst bed to form a first purge gas. Supply a portion of the stripping gas. Stripped catalyst particles are recovered from the first stripping zone. A gaseous fluid containing the first stripping gas and catalyst particles collected from the top of the separation vessel is withdrawn from the separation vessel to an outlet.

[0012]

DETAILED DESCRIPTION OF THE INVENTION In another embodiment, the present invention is an apparatus for separating solid particles from a stream composed of a mixture of a gaseous fluid and solid particles. The apparatus comprises a reaction vessel, a separation vessel disposed within the reaction vessel, and a mixture conduit extending into the separation vessel and forming an outlet provided therein. The outlet directs the stream sinusoidally into the vessel and imparts a sinusoidal velocity to the stream. The particle outlet formed by the separation container discharges particles from the lower part of the container. The stripping vessel is located below the separation vessel. The gas recovery conduit defines an outlet for extracting gaseous fluid from within the separation vessel, and the cyclone separator is in communication with the gas recovery conduit. A plurality of nozzles are provided above the bottom of the separation vessel and extend around the separation vessel to allow the separation vessel to communicate with the reaction vessel.

By maintaining the catalyst bed in the separation vessel and blowing the stripping fluid from the reaction vessel into the concentration bed of the separation vessel located above the bottom of the separation vessel, all available gas in the reaction vessel is Are used as stripping media. These gases include a purge gas that enters the top of the reaction vessel and displaces the hydrocarbons that collect at the top of the vessel, while at the same time
Replaces the cracked hydrocarbon gas from the cyclone dip leg. The decomposed gas in the cyclone dip leg is decomposed to a point where it is essentially inert because of its long stay in the cyclone dip leg, so it is particularly useful as a stripping gas. It is valid. By using all the gas already present in the reaction vessel as the stripping medium passing through the separation vessel, the overall required amount of stripping steam required to achieve the desired degree of stripping Can be reduced. Reducing the steam requirement is particularly advantageous for refiners who are facing the increased processing costs associated with the treatment of the acidic water generated thereby.

[0014] In addition, the method and apparatus of the present invention can further reduce the amount of steam by utilizing stripping gas in a more efficient manner as compared to the prior art. In the prior art, until stripping of the catalyst in the separation vessel, the stripping gas is passed through the usually large bottom opening of the separation vessel. This gas usually does not enter these openings uniformly and tends to preferentially flow to either side. The stripping gas is pumped from the reaction vessel through a plurality of nozzles into the enrichment bed of the separation vessel so that the stripping gas flows evenly along the entire circumference of the vessel. By circulating in this way, the gas is effectively used as a stripping gas.

The apparatus according to the invention comprises a mixture conduit containing a mixture of solid particles carried by the gaseous fluid therein, a separation vessel for discharging the particles and the gaseous fluid mixture. This separation vessel is preferably a cylindrical vessel. The cylindrical container facilitates the swirling of the gaseous fluid and solids as they are discharged in a sinusoidal manner into the separation vessel from the discharge opening of the mixture conduit. The separation vessel preferably has one opening at the lower inside of the discharge opening and works well in the presence of certain obstructions, such as conduits or other equipment through which the opening passes. I do.

The discharge opening and the portion of the conduit upstream of the discharge opening are configured to impart a sinusoidal velocity to the discharged mixture of gaseous fluid and solid. The discharge opening may be formed using vanes or baffles that impart the required sinusoidal velocity to the discharged gaseous fluid and solids. Preferably, the discharge outlet is configured with a conduit or arm extending outward from the central mixture conduit. By using a curved arm section upstream of this discharge conduit, the momentum required by the gaseous fluids and solids as they exit the discharge opening to continue sinusoidal movement through the separation vessel is reduced. Granted. The separation vessel is configured to draw catalyst particles from the bottom of the vessel so that the heavier solid particles sink below the lighter gaseous fluid and separate. A bed of solid particles is located at the bottom of the separation vessel and extends inside the separation vessel. The separated gas from the separation vessel contains more catalyst therein, which are usually separated inside a cyclone separation unit. Preferred separation devices are of the type having an inlet directly connected to the outlet of the separation vessel. Further details of such types of separation arrangements are given in US-A-4482451.

A fundamental feature of the present invention is the location of a plurality of restriction openings arranged along the outer circumference of the separation vessel. These outlets are located above the bottom outlet of the separation vessel and slightly below the top of the concentrated catalyst phase held inside the separation vessel. For better flow, the restrictor openings create a pressure drop of at least 1.7 kPa (0.25 psi). This restriction opening is preferably in the form of a nozzle forming an orifice which directs the gas stream into the concentrated catalyst phase of the separation vessel. The nozzle preferably has an orifice opening diameter of 25.4 mm (1 inch or less) and a gap along the outer circumference of the separation vessel of 305 mm (12 inches) or less, more preferably 152 mm (6 inches) or less. To obtain a uniform pressure drop, all of the restriction openings are preferably arranged at the same height on the walls of the separation vessel.

The gas flow to the reaction vessel, which enters the restriction opening of the separation vessel as stripping medium, comes from various sources. The main source is the purge media entering the reaction vessel. Without purging, the interior of the reaction vessel surrounding the separation chamber and the directly connected cyclone arrangement is relatively inactive during reactor operation. The purge medium performs the necessary function of sweeping the relatively inert interior to remove hydrocarbons and prevent coke formation inside the vessel. Since this purge medium is usually steam, it readily provides a source of stripping gas. Another stripping medium is obtained from the catalyst outlet of the cyclone. The recovered catalyst leaving the cyclone drags more gas,
This gas enters the reaction vessel. These gases are relatively inertized by prolonged stays in the cyclone dip leg, which breaks down heavy components.

In order to make effective use of the stripping gas stream from the reaction vessel in the process of the present invention, a special pressure balance between the separation vessel, the surrounding reaction environment and the restriction opening is used. The pressure balance of the present invention maintains the pressure in the reaction vessel at a higher level than the pressure in the separation vessel.
Maintaining the required pressure balance requires a structure in which the concentrated catalyst phase extends upward above the bottom of the reactor and enters the separator. In light of the purposes of the present invention, concentrated catalyst phase is defined as a catalyst density of at least ^{320kg / m 3 (20lb / ft} 3). The concentrated catalyst phase extends into the separation vessel inside the lower part to a position above the restriction opening. The height of the concentrated catalyst phase above the restriction opening is limited by the maximum pressure difference through the cyclone from the cyclone inlet to the dip leg outlet. The maximum pressure difference through this cyclone can be increased by increasing the length of the cyclone dip leg.

The restricted opening or nozzle is located above the bottom of the separation vessel to maintain the head of the enrichment catalyst between the restriction opening and the bottom of the separation vessel. Since the pressure inside the reaction vessel is always higher than the pressure at the restriction opening in the separation vessel in the present invention, at least a part of the gas from the reactor is transferred to the bottom opening of the separation vessel. Instead of flowing through the restriction opening. Preferably, placing all of the gas from the reactor into the restriction opening will keep the head of the catalyst below the restriction opening inside the separation vessel, maintaining a greater pressure drop than through the restriction opening. The catalyst is recirculated prior to stripping the catalyst in the separation vessel.

The accompanying drawings schematically show the separation configuration of the reaction vessel 10. The central conduit in the form of a reaction riser extends upward from the lower portion of the reaction vessel 10 in a typical FCC configuration. This central conduit or riser is preferably arranged vertically inside the reaction vessel 10 and extends upward from the bottom of the reaction vessel or downward from the top of the reaction vessel. The riser 12 terminates in a curved conduit in the form of an arm 14 in the upper part of the separation vessel 11. The arm 14 discharges a mixture of a gaseous fluid and a solid constituting the catalyst.

By discharging the gas and the catalyst in a restricted direction from the discharge opening 16, the gas and the catalyst are discharged along the inner periphery of the separation vessel.
A spiral pattern below the discharge opening 16 is created. The catalyst particles that are heavier than the centrifugal acceleration associated with this helical motion are moved to the outer portion of the separation vessel. The catalyst from the discharge opening 16 collects at the bottom of the separation vessel 11 to form a concentrated catalyst bed 17.

The gas, which is less dense than the solid, changes direction more easily and begins upward spiraling with the gas,
Eventually, it moves into a gas recovery conduit having an inlet 20 functioning as a gas outlet to the separation vessel 11. In a preferred form of the invention (not shown), the inlet 20 is located below the outlet opening 16. The gas entering the gas recovery conduit 18 through the inlet 20 typically contains a light additional amount of catalyst particles. Inlet 20 collects gas from the discharge conduit and stripping gas as described below. The addition of catalyst particles to the gas entering conduit 18 is typically 16 kg / m ³ (1 lb / f
t ³ ) or less, typically 1.6 kg / m ³ (0.1 lb / ft ³ ) or less.

The gas recovery conduit 18 pumps the separated gas into a cyclone 22, which further removes particulate matter from the gas in the gas recovery conduit. Cyclone
The 22 operates in the usual way as a normal directly connected cyclone, with gas entering in a sinusoidal fashion, creating a vortex inside the cyclone and creating the well-known inner and outer vortex that separates the catalyst from the gas. . The product stream having a relatively low content of catalyst particles exits the reaction vessel through outlet 24.

The catalyst recovered by cyclone 22 exits the bottom of the cyclone through dip leg conduit 23 and passes through the lower portion of reaction vessel 10 where it collects and the catalyst passes through separation bottom 11 through open bottom 19. Leaving to form a concentrated catalyst bed 28, which has a top surface 28 'in the outer part of the separation vessel 11, while at the same time
28 "inside the separation vessel 11. The catalyst from the catalyst bed 28 travels down through the stripping vessel 30. The stripping fluid, usually steam, is a distributor.
It enters into the lower part of the stripping vessel 30 through 31. Countercurrent contact between the catalyst and the stripping fluid through a series of stripping baffles 32 removes the catalyst from the product gas as it continues its downward movement through the stripping vessel. The gas may be fluidized by a distributor 29 at the top of the catalyst bed 28 or an additional stripping medium may be used.

The stripped catalyst from stripping vessel 30 travels through conduit 15 to a catalyst regenerator 34, which regenerates the catalyst by contact with a gas containing oxygen. The high temperature contact between the oxygen-containing gas and the catalyst oxidizes coke deposits from the surface of the catalyst. After regeneration, the catalyst particles enter the bottom of the reactor riser conduit 12 via conduit 33, where the fluidized gas from conduit 35 moves the catalyst particles gasdynamically through the riser. The mixture of the catalyst and the carrier gas continues its upward movement inside the riser, the nozzle 36 feeds the raw material into the catalyst, the contact with which vaporizes the raw material and the discharge opening 16 as described above. Increase the amount of gas exiting through.

[0027] Inside the outer cyclone 22 and separation vessel 11, referred to as outer in the volume 38 is maintained at a positive pressure P ₂ with respect to the pressure P ₃ and the separation container inside the pressure P ₁ inside the cyclone, whereby the nozzle 37 To increase the amount of purge media that enters the top of the vessel through. The purge medium typically contains steam and is used to maintain a low level of hydrocarbon partial pressure in the outer interior volume to prevent coking problems as described above.

The present invention increases the number of constrained openings in the shape of the nozzle 40 so that all of the purge media entering the nozzle 37 is stripped or pre-stripped in the upper portion 41 of the enriched catalyst bed 17. Used effectively. The minimum positive pressure P ₂ is equal to the pressure at the reactor outlet 16, P _RX, and the pressure drop is associated with an additional pressure drop through the head of the catalyst above nozzle 40 and through nozzle 40. As long as the extent that the pressure drop of the nozzle 40 can be ignored, the minimum positive pressure is equal to P _1. The height of the enriched catalyst bed 41, indicated by X in the figure, is a fundamental requirement for operation according to the invention. This is because it provides a place to fully utilize the stripping media available for most of the initial stripping as the catalyst enters the separation vessel. Height X typically extends at least 30 cm (1 ft) above. As previously mentioned, the height X is limited by the available length of the dip leg 23. As the height X increases, the height of the catalyst head also increases, which increases the value of the pressure P ₁ and the minimum pressure of P ₂ . Since pressure P ₃ is equal to the value obtained by subtracting the cyclone pressure drop from the pressure P _RX, the pressure of the upper portion of the cyclone is kept constant for P _RX. Thus, the increasing pressure at dip leg 23 raises the level of concentrated catalyst inside dip leg 23. As a result, the height X is the concentrated catalyst level 42 and the body part of the cyclone
You have to keep it below the level that would enter 43. Therefore, in a preferred embodiment of the present invention, the pressure P ₁
Is adjusted based on the catalyst level in the separation vessel 11.

The maximum value of the pressure P ₂ is also limited relative to pressure P ₁ by the distance that extends downward from the nozzle 40 of the lower portion 44 of the floor 17. When the pressure P ₂ exceeds an amount equal to the catalyst head in the upper than the height Y of the pressure P _1, flows into the inside through the opening 19 the gas from the outside within the volume 38 to flow the lower bottom of the separation device . Thus, height Y acts as a constraint on the pressure drop across nozzle 40 and does not exceed the pressure created by the head of height Y catalyst. Thus, there is no limit on the amount of purge media that enters the process through the nozzle 37, no matter how much stripping or purge gas flows into the regeneration vessel, they flow through the bottom opening 19 into the separation vessel. The height Y provides a minimum distance corresponding to the desired pressure drop across the nozzle 40, in order to supplement as much of the stripping medium as possible to effect recirculation and stripping within the separation vessel 11, Eliminate gas flow to bottom opening 19. When the pressure drop across the nozzle 40 is reduced to a point that blocks gas flow from the outer volume 38 through the bottom opening 19, the top 28 of the floor 28 is at the floor level 28 '.
And between the height of the nozzle 40. In addition, as the flow of purge gas decreases, the top level of bed 28 approaches nozzle 40. Preferably, the height Y of the catalyst is maintained at a level such that all gaseous substances in the outer internal volume 38 pass through the nozzle 40 and do not cause gas flow to the separation vessel 11 through the opening 19. Is done. In most configurations, the distance Y is set to be at least equal to 30 cm (1 ft). Thus, in a preferred configuration, all of the stripping gas from bed 28 flows into bed portion 44 and
All stripping gas from 44 has an outer volume 38
Together with the gas from the bed as a stripping medium.

[0030]

In the FCC process of the present invention, the formation of waste can be suppressed by stripping the catalyst particles by performing the hydrocarbon stripping extremely effectively.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a separation vessel 11 and an FCC reaction vessel 10 used in the method of the present invention.

[Explanation of symbols]

 10 Reaction vessel 11 Separator 12 Conduit 15 Conduit 16 Outlet opening 17 First catalyst bed 20 Outlet 28 Second catalyst bed 30 Stripping zone

Claims (1)

[Claims] 1. An FCC process for fluidized bed catalytic cracking of a hydrocarbon feed comprising the following steps: (A) feeding hydrocarbon feedstock and solid catalyst particles into a riser conversion zone comprising a conduit (12) for producing a mixture of solid particles and a gaseous fluid; (b) the catalyst particles and gaseous fluid Wherein the conduit (12) occupies a central portion of the separation vessel (11), and the separation vessel (11) is a reaction vessel.
(10) through the conduit (12) arranged in the separation vessel (1).
(C) discharging the mixture from the conduit through the discharge opening (16) into the separation vessel (11) in a sinusoidal manner; (d) lowering the catalyst particles in the lower part of the separation vessel (11). Into the first catalyst bed (17), which is located at
Contacting the catalyst particles with a first stripping gas within 7), (e) removing the catalyst particles from the first bed (17) to the lower side of the first catalyst bed (17). Feeding the catalyst particles to a second bed (28) located in the reaction vessel, contacting the catalyst particles with a second stripping gas, the first stripping gas;
The second stripping device to supply a portion of the gas.
Sending gas into the first catalyst bed (17); (f) stripping the catalyst particles from the second bed (28).
Into the stripping zone (3).
0) contact a third stripping gas in the second
The third stripping gas to provide at least a portion of the second stripping gas to the second catalyst bed (2).
(G) feeding the purge medium (via nozzle 37) to the upper portion of the reaction vessel (10);
(H) providing a portion of the first stripping gas to the purge medium through a plurality of restriction openings formed at the bottom of the first catalyst bed (17) and on the outer periphery of the separation vessel. Sending a portion; (i) recovering catalyst particles separated (via conduit 15) from the stripping zone (30); and (j) removing the first particle from the top of the separation vessel (11). Remove gaseous fluid containing stripping gas and catalyst (2
0) and removing the gaseous fluid from the separation vessel for recovery