Apparatus for mixing in catalytic cracker reactor

Abstract

The present invention provides a catalytic cracking reactor comprising a conduit, configured to allow the passage of a flow of catalyst particles, and an injection zone comprising a ring of feed injectors extending inwardly from the wall of reactor and angled to inject feed into the flow of catalyst particles, characterised in that the reactor also comprises a contacting device protruding into the reactor from the inner wall of said reactor upstream of the injection zone.

Claims

1. A fluid catalytic cracking riser reactor comprising a conduit, configured to allow the passage of a flow of catalyst particles, and an injection zone comprising a ring of feed injectors extending inwardly from the wall of reactor and angled to inject feed into the flow of catalyst particles, characterised in that the reactor also comprises a contacting device protruding into the reactor from the inner wall of said reactor upstream of the injection zone, wherein the contacting device comprises an annular element with an outer diameter equal to that of the inner diameter of the reactor.

2. A fluid catalytic cracking riser reactor according to claim 1, wherein the contacting device comprises a composite of refractory material and a metal structure.

3. A fluid catalytic cracking riser reactor according to claim 1, wherein the distance between the downstream edge of the contacting device and the upstream edge or underside of the feed injectors is not more than 25 inches (63.5 cm).

4. A fluid catalytic cracking riser reactor as claimed in claim 1, wherein the cross-sectional area of the flow of catalyst particles is reduced by at least 10% and not more than 35%, based on the cross-sectional area of the reactor upstream of the contacting device.

5. A fluid catalytic cracking riser reactor as claimed in claim 1, wherein the reactor is a riser reactor configured to allow the upwards passage of a flow of catalyst particles.

6. A method of mixing a fluidised stream of catalyst particles with a hydrocarbon feed, said method comprising the steps of: a) creating a stream of fluidised catalyst particles in a fluid catalytic cracking riser reactor; b) passing said stream of fluidised catalyst particles past a contacting device protruding into the reactor from the inner wall of said reactor, wherein the contacting device comprises an annular element with an outer diameter equal to that of the inner diameter of the reactor; c) subsequently passing the stream of fluidised catalyst particles through an injection zone comprising a ring of feed injectors extending inwardly from the wall of reactor and contacting said stream of fluidised catalyst particles with hydrocarbon feed provided through said feed injectors; d) passing the stream of fluidised catalyst particles contacted with hydrocarbon feed to a downstream section of the reactor to convert the hydrocarbon feed to a converted product in the presence of the catalyst particles.

7. A method as claimed in claim 6, wherein the hydrocarbon stream comprises high boiling hydrocarbons and the converted product comprises lighter hydrocarbons boiling in the heating oil, gasoline or lighter range.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates an example of a prior art injection zone in an FCC riser.

(2) FIGS. 2a and 2b illustrate contacting devices according to the present invention.

(3) FIGS. 3 and 4 illustrate a suitable contacting device.

(4) FIG. 5 illustrates a part of a catalytic cracking riser reactor of the present invention.

SUMMARY OF THE INVENTION

(5) The present invention provides a catalytic cracking reactor comprising a conduit, configured to allow the passage of a flow of catalyst particles, and an injection zone comprising a ring of feed injectors extending inwardly from the wall of reactor and angled to inject feed into the flow of catalyst particles, characterised in that the reactor also comprises a contacting device protruding into the reactor from the inner wall of said reactor upstream of the injection zone.

(6) The present invention also provides a method of mixing a stream of fluidised catalyst particles with a hydrocarbon feed, said method comprising the steps of: a) creating a stream of fluidised catalyst particles in a reactor; b) passing said stream of fluidised catalyst particles past a contacting device protruding into the reactor from the inner wall of said reactor; c) subsequently passing the stream of fluidised catalyst particles through an injection zone comprising a ring of feed injectors extending inwardly from the wall of reactor and contacting said stream of fluidised catalyst particles with hydrocarbon feed provided through said feed injectors; d) passing the stream of fluidised catalyst particles contacted with hydrocarbon feed to a downstream section of the reactor to convert the hydrocarbon feed to a converted product in the presence of the catalyst particles.

DETAILED DESCRIPTION OF THE INVENTION

(7) The present inventors have determined that providing a contacting device in a reactor upstream of the ring of feed injectors, through which the hydrocarbon feed is provided to the reactor, results in improved mixing of the hydrocarbon feed with a fluidised flow of catalyst particles. The invention provides a simple solution to the problem of providing a rapid and uniform dispersal of hydrocarbon feed into a fluidised flow of catalyst particles.

(8) The reactor is suitably a reactor for use in a fluidised catalytic cracking (FCC) process. In such a process, finely divided catalyst particles are provided to the reactor and fluidised by addition of a fluidising medium. The catalyst particles may be fresh catalyst particles or regenerated catalyst particles or a mixture thereof. The fluidising medium may be a diluent material, typically steam or low molecular fluidizing gas, of a hydrocarbon stream. The fluidised catalyst stream flows through the reactor. The reactor may be a downer reactor in which the fluidised catalyst stream flows downwardly through the reactor. Preferably, the reactor is a riser reactor and the fluidised catalyst stream flows upwardly through the riser reactor.

(9) In the present invention, a contacting device is provided in the reactor upstream of a ring of feed injectors. The fluidised catalyst stream, therefore, is brought into contact with said contacting device before passing into an injection zone.

(10) The contacting device comprises an insert that is securely fastened to the wall of the reactor. Typically, the contacting device comprises an annular element with an outer diameter equal to that of the inner diameter of the reactor.

(11) The contacting device may comprise metal, ceramics, ceramets or mixtures thereof. In one embodiment of the invention, the contacting device comprises a composite of refractory material and a metal structure. In this embodiment, the metal structure may be connected to the outer wall of the reactor to ensure that the location of the contact device does not change during operation despite temperature shocks. Further, the metal structure provides reinforcement to the combination of a metal structure and refractory material so that it becomes stronger and less prone to erosion. This is particularly advantageous when the reactor has been provided with an internal refractory lining.

(12) In view of the erosive nature of the reactor mixture the refractory material is suitably selected such that it is highly wear resistant. The material is preferably also tastable to facilitate the shaping of the contact devices. Suitably the refractory material is selected from the group consisting of alumina, silica, calcium oxide, titanium oxide, magnesium oxide, iron oxide and mixtures thereof. Also the refractory may contain phosphorus oxide.

(13) The contacting device may be of any cross-sectional shape that the skilled person deems suitable for a specific use. The skilled person will optimise the advantages, in particular the turbulence effects, whilst minimising any disadvantage, such as pressure drop. In certain embodiments, the contacting device may have the cross-sectional profile of a rectangle. In other embodiments non-rectangular cross-sections may be desirable. For examples, a tapered shape angled out from the reactor's inner wall may be suitable. Suitable devices are described in U.S. Pat. No. 9,283,532, WO2017/003991 and WO2008017660.

(14) When the contacting device is in the shape of an annulus, the whole annulus may be assembled in one piece. However, it is advantageous to assemble such an annulus in more than one module. This is not only easier to assemble, but it also provides the possibility of local repair. In this embodiment, the number of modules suitably ranges from 4 to 25.

(15) A particular advantage of the present invention is that contacting devices constructed in this manner may be retro-fitted to reactors, allowing improvement of existing reactors without the need for major reconstruction. The contacting device is positioned upstream of the ring of feed injectors. Typically, the contacting device will be place immediately upstream of the ring of feed injectors. Preferably the distance between the downstream edge of the contacting device and the upstream edge of the feed injectors is not more than 25 inches (63.5 cm). The distance between the downstream edge of the contacting device and the upstream edge or underside of the feed injectors will depend on the geometry of the reactor and whether the reactor is swaged or not and can be altered depending on both the geometry and flow conditions within the reactor.

(16) The position of the contacting device upstream of the ring of feed injectors diverts the flow of catalyst particles to match more closely the dispersion of the hydrocarbon feed from the feed injectors. The contacting device will reduce the passageway in the reactor. Preferably, the passageway is reduced by not more than 35 percent, based on the passageway of the reactor upstream of the contacting device. Suitably, the reduction of the passageway is at least 10 percent, based on the passageway of the reactor upstream of the contacting device.

(17) The position of the contacting device upstream of the ring of feed injectors provides the added advantage of protecting the feed injectors themselves from erosion and damage caused by the flow of catalyst particles.

(18) The feed injectors may comprise any suitable feed injection nozzles. In typical FCC practice, the feed exits the nozzles as a spray in a fan pattern. The nozzles are usually angled to tip the fan pattern in a downstream direction. The angle of the nozzles will typically be in a range of from of at least 20 and less than 70 with respect to a transverse plane passing through the nozzles, liquid entering the injectors.

(19) Within the injection zone, the fluidised catalyst particles are contacted with the hydrocarbon feed provided through the feed injectors. The present invention allows excellent rapid dispersal of the feed throughout the catalyst particles.

(20) The stream of fluidised catalyst particles contacted with the hydrocarbon feed are then passed downstream of the injection zone and the hydrocarbon feed is converted to a converted product in the presence of the catalyst particles. This may occur as part of the flow through the reactor or, in some embodiments, may occur at least in part within a catalyst bed disposed within a downstream section of the reactor.

DETAILED DESCRIPTION OF THE DRAWINGS

(21) The invention will now be further described with reference to the exemplary, non-limiting drawings.

(22) FIG. 1 illustrates the problem to be overcome by the present invention. FIG. 1 shows a cross section of a riser reactor at the injection zone. A number of feed injectors (1) protrude from the inner wall of the riser reactor (2). The combined spray pattern (3) in a typical reactor set up is shown. This leads to a quiescent zone (4) in which the stream of fluidised catalyst particles passing up through the injection zone contacts a reduced level of feed.

(23) FIGS. 2a and 2b illustrate the invention. A contacting device (5) is provided upstream of the injection zone. In FIG. 2a, the area of passageway for the fluidised catalyst particles is reduced by the contacting device by 23% based on the passageway of the riser reactor upstream of the contacting device. In FIG. 2b, the area of passageway for the fluidised catalyst particles is reduced by the contacting device by 31% based on the passageway of the riser reactor upstream of the contacting device. In both Figures, it can clearly be seen that the area of quiescent zone (4) is considerably reduced when compared with FIG. 1.

(24) FIG. 3 illustrates a contacting device (5), comprising a section (5a) constructed of refractory material connected via metal structures (5b) through the inner wall (6) of a riser reactor to the outer metal wall (7) of said reactor.

(25) A different cross-sectional view of the same contacting device is shown in FIG. 4.

(26) FIG. 5 illustrates a view within the reactor illustrating the contacting device (5) protruding into the reactor upstream of the feed injectors (1). The flow of the stream of fluidised catalyst particles (8) passes the contacting device upstream of the injection zone. Within the injection zone, the feed injectors (1) provide a hydrocarbon feed and said hydrocarbon ked is contacted with said fluidised catalyst particles.

EXAMPLES

(27) The following non-limiting examples are provided as further description of the present invention.

(28) The invention was tested using a computational fluid dynamics (CFD) simulation. The modelling was configured to represent a standard riser reactor configuration and process conditions. The same basic riser reactor and process conditions were used for each scenario, except for the modifications described for each scenario. Four different scenarios were modelled. In scenario 1 (base case; comparative) an unmodified riser reactor was simulated. In scenario 2, a contacting device was added upstream of the feed injectors. Scenario 3 (comparative) involved a reduction in the diameter of the riser reactor upstream of the feed nozzles. Scenario four adapted scenario 3 with the addition of a contacting device upstream of the feed nozzles. The results of the simulations are shown in Table 1.

(29) TABLE-US-00001 TABLE 1 wt % of feedstock wt % of unvaporized vaporized within 0.2 feedstock remaining 0.2 seconds of injection seconds after injection by feed nozzles by feed nozzles Scenario 1 93.0 7.0% Scenario 2 95.1% 4.9% Scenario 3 94.7% 5.3% Scenario 4 96.2% 3.8%

(30) Adding a contacting device upstream of the feed nozzles in scenario 2 was clearly shown in these simulations to increase feedstock vaporization by over 2 wt % through better contacting of the injected oil with the hot flowing catalyst when compared with scenario 1. Some, but not all, of this improvement can be achieved (scenario 3) by replacing the lower section of the riser with one with a lower diameter. However, the addition of a contacting device (e.g. scenario 2) does not require a replacement of the lower section of the riser and can be retro-fitted to an existing reactor.

(31) Even further benefit was demonstrated by the combination of a smaller lower riser and a contacting device (scenario 4).