FIELD OF THE INVENTION

[1] The invention relates to an improved process for recovery of catalyst in a reactor, including a process for recovery of catalyst in a reactor used in the manufacture of acrylonitrile and methacrylonitrile utilizing an improved cyclone configuration. An ammoxidation reactor and process includes an outer ring of sets of multistage cyclones suspended in the reactor. More specifically, a ratio of square meter of first stage inlet area of a cyclone per square meter of available cross sectional area of the reactor is about 0.03 to about 0.05.

BACKGROUND

Various processes and systems for the manufacture of acrylonitrile and methacrylonitrile are known; see for example, U.S. Patent No. 6,107,509.

Typically, recovery and purification of acrylonitrile/methacrylonitrile produced by the direct reaction of a hydrocarbon selected from the group consisting of propane, propylene or isobutylene, ammonia and oxygen in the presence of a catalyst has been accomplished by transporting the reactor effluent containing acrylonitrile/methacrylonitrile to a first column (quench) where the reactor effluent is cooled with a first aqueous stream, transporting the cooled effluent containing acrylonitrile/methacrylonitrile into a second column (absorber) where the cooled effluent is contacted with a second aqueous stream to absorb the acrylonitrile/methacrylonitrile into the second aqueous stream, transporting the second aqueous stream containing the acrylonitrile/methacrylonitrile from the second column to a first distillation column (recovery column) for separation of the crude acrylonitrile/methacrylonitrile from the second aqueous stream, and transporting the separated crude acrylonitrile/methacrylonitrile to a second distillation column (heads column) to remove at least some impurities from the crude acrylonitrile/ methacrylonitrile, and transporting the partially purified acrylonitrile/methacrylonitrile to a third distillation column (product column) to obtain product acrylonitrile/methacrylonitrile. U.S. Pat. Nos. 4,234,510; 3,885,928; 3,352,764; 3,198,750 and 3,044,966 are illustrative of typical recovery and purification processes for acrylonitrile and methacrylonitrile.

[3] Conventional fluidized bed reactors comprise a plenum attached to a head of the reactor at the center of a top portion of reactor, and cyclones hanging from support rods attached to the reactor head around the plenum. The cyclones are configured to capture catalyst that has traveled up from the fluidized bed in the reactor, and return the captured catalyst back down to the fluidized bed, thereby reducing catalyst from being conveyed to the plenum and out of the top of the reactor with acrylonitrile product.

[4] In a typical acrylonitrile process, propylene, ammonia and oxygen are reacted in the presence of a catalyst in a fluidized bed reactor to produce acrylonitrile.

Acetonitrile and hydrogen cyanide (HCN) are also produced. The produced acrylonitrile, acetonitrile and HCN are typically conveyed out of top portion of the reactor through a plenum. The plenum is typically located at a center of the top portion of the reactor, and is attached to the head of the reactor. To reduce catalyst from being conveyed to the plenum and out of reactor with acrylonitrile, acetonitrile and HCN, cyclones have been used to capture catalyst in an upper portion the reactor, and return the captured catalyst to a lower portion of the reactor. A typical reactor includes an outer ring of cyclones hanging from the reactor ceiling that are positioned around the inside periphery of the reactor. In a typical reactor, each cyclone has a riser pipe that extends vertically up from the cyclone and then angles at an upward angle to the side surface of the outer periphery of the plenum. In a typical reactor, a reactor vapor stream (e.g., a reactor stream comprising acrylonitrile, acetonitrile and HCN) rises up from a fluidized catalyst bed, and enters an inlet of a cyclone near the inside periphery of the reactor. In each cyclone, the reactor stream is directed through the cyclone, and upon exit from the cyclone, enters a corresponding riser pipe, and is directed first vertically and then at an upward angle through the riser pipe, and exits the riser pipe and enters in inlet of the plenum at the side surface of the outer periphery of the plenum. The reactor effluent gas is thus withdrawn from only the outer periphery of the reactor and the reactor gas circulation patterns established accordingly. U.S. Pat. Nos. 7,442,345; 7,323,038; and 5,221,301 describes reactors with cyclones and cyclone operation.

[5] While the manufacture of acrylonitrile/methacrylonitrile has been commercially practiced for years there are still areas in which improvement would have a substantial benefit. One of those areas of improvement would be more efficient reactor operation, particularly when scaling up from conventional feed rates to higher feed rates to the reactor.

SUMMARY

[6] Accordingly, an aspect of the disclosure is to provide a safe, effective and cost effective method and apparatus that overcomes or reduces the disadvantages of conventional processes.

[7] An ammoxidation reactor includes an outer ring of sets of multistage cyclones suspended in the reactor. Each multistage set of cyclones includes a first stage cyclone having a first stage inlet configured to receive a reactor stream flowing up from a fluidized catalyst bed in the reactor and separate at least a portion of catalyst from the reactor stream. A ratio of cumulative square meter of first stage inlet area per square meter of available cross sectional area of the reactor is about 0.03 to about 0.05.

[8] An ammoxidation process includes reacting a hydrocarbon stream in a fluidized catalyst bed in a reactor to produce a reactor stream. The process further includes separating catalyst from the reactor stream in an outer ring of sets of multistage cyclones, each multistage set of cyclones including a first stage cyclone having a first stage inlet configured to receive a reactor stream flowing up from a fluidized catalyst bed in the reactor and separate at least a portion of catalyst from the reactor stream. A ratio of cyclone inlet velocity in meters/second to a reactor effluent velocity in meters/second is 15 or greater. For the purposes of this application (i) reactor effluent velocity will be based on volumetric effl ent flow rate at the exit nozzle of the reactor and the available reactor cross-sectional area ("CSA") and (ii) the available reactor cross-sectional area is the cross-sectional area excluding cooling coils and dip legs area, and for the purposes of this application may optionally be approximated to be about 90% of open CSA.

[9] An ammoxidation reactor includes a reactor internal diameter of about 9 m to about 1 lm, a reactor internal diameter to reactor cylindrical height (tangent to tangent) ratio of about 0.45 to about 0.6 and a height of a first stage cyclone about 2% to about 10% of a height of the reactor (tangent to tangent).

[10] An ammoxidation process includes reacting a hydrocarbon stream in a fluidized catalyst bed in a reactor to produce a reactor stream. The reactor internal diameter is between about 9 m and 1 lm, the ratio of reactor internal diameter to reactor cylindrical height (tangent to tangent) is about 0.45 to about 0.6 and a height of a first stage cyclone is about 2% to about 10% of a height of the reactor (tangent to tangent).

[11] An ammoxidation process includes reacting a hydrocarbon stream in a fluidized catalyst bed in a reactor to produce a reactor stream. The process includes separating catalyst from the reactor stream in an outer ring of sets of multistage cyclones, each multistage set of cyclones. The multistage set of cyclones includes a first stage cyclone having a first stage inlet configured to receive a reactor stream flowing up from a fluidized catalyst bed in the reactor and separate at least a portion of catalyst from the reactor stream. In this aspect, about 300 to about 900 m/sec ² centrifugal force is provided in the first stage cyclone.

[12] The above and other aspects, features and advantages of the present disclosure will be apparent from the following detailed description of the illustrated embodiments thereof which are to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[13] A more complete understanding of the exemplary embodiments of the present invention and the advantages thereof may be acquired by referring to the following description in consideration of the accompanying drawings in which like reference numbers indicate like features and wherein:

[14] FIG. 1 is a diagram of an embodiment in accordance with aspects of the

disclosure.

[15] FIG. 2 is a diagram of the embodiment shown in FIG. 1 taken along line 2— 2. [16] FIG. 3 illustrates a single cyclone.

DETAILED DESCRIPTION

[17] The following includes description in connection with acrylonitrile production.

The following description, however, may be applied to other applications that involve fluidized bed reactors. For example, the following description may be applied to fluidized bed reactors that include multiple cyclones, wherein the cyclones are configured to capture catalyst that has traveled up from the fluidized bed in the reactor, and return the captured catalyst back down to the fluidized bed, thereby reducing catalyst from being conveyed to the plenum and out of the top of the reactor with acrylonitrile product. In one aspect, catalyst is configured to facilitate the reaction of a hydrocarbon, ammonia, and oxygen in the reactor to produce the reactor stream, wherein the reactor stream includes acrylonitrile.

[18] In an aspect, the apparatus includes an outer ring of sets of cyclones, preferably multistage cyclones. The cyclones of the outer ring hang from head of the reactor and are positioned around an inside periphery of the reactor. Each multistage set of cyclones including a first stage cyclone having a first stage inlet configured to receive a reactor stream flowing up from a fluidized catalyst bed in the reactor and separate at least a portion of catalyst from the reactor stream. In this aspect, a ratio of square meter of first stage inlet area per square meter of available cross sectional area of the reactor is about 0.03 to about 0.05, in another aspect, about 0.035 to about 0.045, and in another aspect, about 0.0375 to about 0.0425. In another aspect, a ratio of square meter of first stage inlet area per square meter of available cross sectional area of the reactor per cubic meter of catalyst bed volume is about 0.00006 to about 0.0002, in another aspect, about 0.0001 to about 0.00018, and in another aspect, about 0.00013 to about 0.00016. In another aspect, a ratio of square meter of first stage inlet area per square meter of available cross sectional area of the reactor per metric ton of catalyst of about 0.00015 to about 0.00035, in another aspect, about 0.0002 to about 0.0003, and in another aspect, about 0.00022 to about 0.0028.

[19] The available cross sectional area (CSA) of the reactor is determined as follows:

Available CSA = (total CSA)(%CSA with internals)

Total CSA = (reactor radius)\

% CSA with internals = ((open area) - (coil area + dipleg area)) / (open area)

[20] The catalyst bed volume is determined as follows:

Catalyst bed volume = ((reactor radius)V)(bed height)

Bed height = ((catalyst inventory *1000)/fluidized density) / (ji/4)(reactor diameter) ² (0.93)

[21] Multistage cyclones include different configurations. For example, they could be multiple cyclones in series, such as two, three or four stage cyclones in series. Another configuration of a three stage cyclone could equally include a single first stage cyclone and two parallel second stage cyclones downstream of the single first stage cyclone. The object of the cyclone design is to capture as much of the catalyst as possible from the reactor effluent gas as possible whilst minimizing the pressure drop in so doing and minimizing the risk of blockage of the cyclones. Having multiple cyclones enables the pressure drop, and the associated cut size of catalyst caught, by each cyclone to be optimized. Where a multistage cyclone consists of three stages in series, each set of cyclones of the outer ring set includes first, middle, and last cyclones in series, wherein typically the first cyclone is the nearest cyclone of the set to the outer periphery of the reactor, the middle cyclone is between the first and last cyclones, and the last cyclone of the set is the nearest cyclone to the plenum. The last cyclone of each set of multistage cyclones of the outer ring is positioned around an inside periphery of a plenum, and has a riser pipe that extends vertically up from the third cyclone and then angles at an upward angle to a side surface of the outer periphery of the plenum. This configuration results firstly in the reactor effluent gas being withdrawn from the outer periphery of the reactor and secondly in the coarsest catalyst recovered being returned to the outer periphery of the reactor and the finest catalyst recovered being returned closer to the center of the reactor.

[22] In one aspect, the present apparatus and processes achieve a more uniform

collection of catalyst across the reactor cross sectional area from the effluent gas and/or a more uniform return of catalyst across the cross sectional area of the reactor to the fluidised bed. This can be achieved by ensuring a more uniform distribution of cyclone inlet nozzles across the reactor cross-sectional area and also a more uniform distribution of catalyst return dip legs across the reactor cross-sectional area. Where multi-stage cyclones are employed it is also possible to configure the cyclones sets such that the particle size of catalyst returned to the fluidized bed is more uniformly distributed across the reactor cross sectional area.

[23] In one aspect, it has been discovered a ring of single-stage or single cyclones of a reactor may be prone to plugging within the cyclones and insufficient separation of catalyst from reactor stream flowing from the fluidized catalyst bed. This plugging and insufficient separation may lead to undesirable catalyst loss and processing problems downstream of the reactor due to catalyst entrained in the reactor stream exiting the reactor. It has been further discovered that a ring of two-stage or two cyclones in series may be prone to plugging within the cyclones and insufficient separation of catalyst from reactor stream flowing from the fluidized catalyst bed than three stage or three cyclones in series. This plugging and insufficient separation may lead to undesirable catalyst loss and processing problems downstream of the reactor due to catalyst entrained in the reactor stream exiting the reactor.

[24] In another aspect, it has been discovered that a ring of sets of multi-stage, or two or more, preferably three-stage or three cyclones in series positioned around an inside periphery of a reactor may be less prone to plugging within the cyclones than single-stage or two-stage cyclones. In one aspect, it has been discovered that a ring of sets of multi-stage, or two or more, preferably three-stage or three cyclones in series may provide more separation of catalyst from a reactor stream flowing from the fluidized catalyst bed than single-stage cyclones. In this aspect, the reactor includes about 0.35 to about 0.65 cyclones per meter of reactor cross- sectional area, in another aspect, about 0.40 to about 0.65, in another aspect, about 0.45 to about 0.65, in another aspect, about 0.45 to about 0.60, and in another aspect, about 0.50 to about 0.55 cyclones per meter of reactor cross-sectional area.

[25] In another aspect, higher pressure drops through cyclone systems are obtained by using sets of multi-stage cyclones in series rather than using sets of three cyclones in parallel. The higher pressure drops may provide more efficient separating of catalyst from a reactor stream. Equally however, the use of multi-stage cyclones can lead to optimization of pressure drop and separation in each stage.

[26] FIG. 1 is side view of apparatus 100 in accordance with aspects of the disclosure.

Referring to FIG. 1, apparatus 100 includes reactor 10. Reactor 10 may include an inlet 12 configured to receive a feed 14. Feed 14 may include ammonia and/or a hydrocarbon selected from the group consisting of propane, propylene and isobutylene, and combinations thereof. Reactor 10 may include an inlet 16 configured to receive air. Oxygen in the air reacts with the hydrocarbon and ammonia in reactor 10 in the presence of a catalyst (not shown in FIG. 1). Air may be compressed by an air compressor (not shown in FIG. 1) and fed to reactor 10 through inlet 16. Acrylonitrile is produced in reactor 10 from the reaction of the hydrocarbon, ammonia, and oxygen in the presence of a catalyst in reactor 10. In accordance with the disclosure, reactor 10 includes plenum 18, an outer ring 20 of sets 22 of multistage cyclones 24, and an inner ring 26 of sets 28 of multistage cyclones 30.

[27] Multistage cyclones 24 of outer ring 20 hang from head 32 of reactor 10 and are positioned around inside periphery 34 of reactor 10. As shown in FIG. 1, multistage cyclones 24 of outer ring 20 may hang from outer ring supports 25 that are attached to head 32. Each set 22 of multistage cyclones 24 of outer ring 20 includes first cyclone 36, optionally a middle cyclone 38, and last cyclone 40 in series, wherein first cyclone 36 is the nearest cyclone of the set to outside periphery 34 of reactor 10, middle cyclone 38 is between the first cyclone 36 and last cyclone 40, and last cyclone 40 of the set is the nearest cyclone to plenum 18. Last cyclone 40 of each set 22 of multistage cyclones 24 of outer ring 20 is positioned around an outside periphery 42 of plenum 18, and has a riser pipe 44 that extends vertically up from last cyclone 40 and then angles at an upward angle to a side surface 46 of outer periphery 42 of plenum 18. Riser pipe 44 includes a first section 48 that extends vertically up from the last cyclone 40. Riser pipe 44 has a second section 50 that angles upwardly to side surface 46 of plenum 18. Plenum 18 includes inlets 47 that are configured to receive reactor effluent 4 from riser pipe 44 corresponding to each last cyclone 40 of outer ring 20. Reactor effluent 4 may comprise acrylonitrile produced in reactor 10.

In an aspect, multistage cyclones 30 of inner ring 26 hang from bottom surface 51 of plenum 18. As shown in FIG. 1, multistage cyclones 30 of inner ring 26 may hang from inner ring supports 31 that are attached to bottom surface 51 of plenum 18. By positioning inner ring 26 of sets 28 of multistage cyclones 30 from the bottom surface 50 plenum 18, more cyclones may be used than in a typical reactor. In an aspect, each set 28 of multistage cyclones 30 of inner ring 26 includes first a cyclone, optionally middle cyclone, and last cyclone 56 in series, wherein a first cyclone is the nearest cyclone of inner ring 26 of set 28 to inside periphery 34 of reactor 10, middle cyclone is between first cyclone and last cyclone 56, and last cyclone 56 of set 28 is the nearest cyclone to plenum 18. Last cyclone 56 of each set 28 of multistage cyclones 30 of inner ring 26 is positioned directly under plenum 18, and has a riser pipe 58 that extends vertically up from last cyclone 56 to inlet 60 of bottom surface 50 of plenum 18. As shown in FIG. 1, riser pipe 58 may be the same as or comprise inner ring support 31. Inlets 60 are configured to receive reactor effluent 4 from riser pipe 58 corresponding to each last cyclone 56 of inner ring 26. As previously noted, reactor effluent 4 may comprise acrylonitrile produced in reactor 10. Reactor effluent stream 4 comprising acrylonitrile produced in reactor 10 may be conveyed for further processing, e.g., to a quench vessel (not shown in FIG. 1).

[29] FIG. 2 is a diagram of the embodiment shown in FIG. 1 taken along line 2— 2.

As shown in FIG. 2, outer ring 20 may comprise twelve (12) sets 22 of multistage cyclones 24. When each of the twelve (12) sets 22 comprise first, middle, and last cyclones, a reactor in accordance with the disclosure includes thirty-six (36) cyclones of outer ring 20. As shown in FIG. 2, inner ring 26 may comprise two (2) sets 28 of multistage cyclones 30. When each of the two (2) sets 28 includes first, middle, and last cyclones, a reactor in accordance with the disclosure includes six (6) cyclones of inner ring 26. In an aspect, reactor 10 may include forty-two (42) cyclones - thirty-six (36) cyclones of outer ring 20, and six (6) cyclones of inner ring 26. Cyclones of each set 22 of multistage cyclones 24 are further shown in FIG. 2 as cyclones 1A-3A, 1B-3B, 1C-3C, 1D-3C, 1E-3E, 1F- 3F, 1G-3G, 1H-3H, 11-31, 1J-3J, 1K-3K, 1L-3L, and 1M-3M. Cyclones of each set 28 of multistage cyclones 30 are further shown in FIG. 2 as cyclones 1N-3N and 1P-3P.

[30] Each cyclone may be configured to use centrifugal force to separate catalyst from a reactor stream made in the fluidized catalyst bed in the reactor. The first cyclone in each set 22 of outer ring 20 may comprise an inlet 82. Inlet 82 may be configured to receive reactor stream made in the fluidized catalyst bed in the reactor. The following description is provided with respect to the set 22 of outer ring 20 identified as cyclones 1A, 2 A, and 3 A, but may equally apply to the other sets 22 of outer ring 20. Catalyst may be separated from reactor stream in cyclone 1A, and the reactor stream may then be conveyed from cyclone 1A to cyclone 2A, wherein further catalyst may be separated from the reactor stream. The reactor stream may then be conveyed from cyclone 2A to cyclone 3A, wherein further catalyst may be separated from the reactor stream. The reactor stream may then be conveyed from cyclone 3 A to plenum 18 via riser pipe 44. In this aspect, the centrifugal force will be about 300 to about 900 kg m sec ² /kg of particles, in another aspect about 400 to about 800 kg m sec ² /kg of particles, and in another aspect, about 500 to about 700 kg m/sec ² /kg of particles. Centrifugal force may be determined using standard formulas using the cyclone inlet velocity.

[31] The following description is provided with respect to the set 28 of inner ring 26 identified as cyclones IN, 2N, and 3N, but may equally apply to the other sets 28 of inner ring 26. Catalyst may be separated from reactor stream in cyclone IN, and the reactor stream may then be conveyed from cyclone IN to cyclone 2N, wherein further catalyst may be separated from the reactor stream. The reactor stream may then be conveyed from cyclone 2N to cyclone 3N, wherein further catalyst may be separated from the reactor stream. The reactor stream may then be conveyed from cyclone 3N to plenum 18 via riser pipe 58 (see Fig. 1).

[32] In an aspect, acrylonitrile produced in reactor 10 may exit last cyclone 40 of each set 22 of outer ring 20 or exit last cyclone 56 of each set 28 of inner ring 26, and enter plenum 18. Effluent stream 4 comprising acrylonitrile may exit the plenum and out of a top portion 62 of reactor 10 through outlet 64. In an aspect, each cyclone 24 of outer ring 20, and each cyclone 30 of inner ring 26 may be configured to separate catalyst that may be entrained in the stream comprising acrylonitrile that enters each cyclone, and return the separated catalyst back to the catalyst bed in reactor 10 through a corresponding catalyst return dip leg 66. Catalyst return dip legs 66 may be supported by catalyst dip leg support beams 68 (see Fig. 1).

[33] Catalyst return dip legs 66 may be configured to return separated catalyst through catalyst return outlets 70 to the bed of the reactor at section 72 of reactor 10. Section 72 of reactor 10 may include cooling coils 74. Cooling coils 74 may be configured to convey a heat transfer material 76, e.g., water/steam, through coils 74 and cool the bed in reactor 10. Heat transfer material 76 may enter coils 74 through inlets 78, and then exit coils 74 through outlets 80. The bed in reactor 10 may be a fluidized catalyst bed.

[34] The fluidized bed reactor is at the heart of an acrylonitrile plant. Failure to

correctly design a new reactor could at a minimum significantly affect the efficiency, reliability or production capacity of an entire acrylonitrile plant and in the extreme lead to an extended shut-down of production whilst reactor modifications or change-out could be implemented. The operation of a fluidized bed is highly sensitive to the specific operating conditions selected and the industry is highly cautious in changing operating conditions and/or the design of the reactor or its internals. As the fluidized bed dimensions change (eg. reactor diameter, internals, bed height, ratio of bed pressure drop to grid pressure drop) and catalyst characteristics change (particle size, particle size distribution, fines content, attrition characteristics), so too can the critical circulation patterns in the fluidized bed.

One of the most sensitive parameters which could affect fluidization performance is the scale-up of the reactor diameter. It is also one of the parameters that leads to most scale-up caution since there are limited mitigation options available, absent reactor change-out, to correct a scale-up of diameter that has gone too far. Through significant experimentation and optimization, it has now been found that, when using a catalyst with an average particle diameter between about 10 and 100 μ, with a particle size distribution where about 0 to 30 weight percent is greater than about 90 μ, and about 30 to 50 weight percent is less than 45 μ, a reactor internal diameter of greater than about 9 m up to about 11 m can be combined with suitable operating conditions and reactor internals to achieve acceptable fluidization conditions for the production of acrylonitrile and methacrylonitrile. It has furthermore been found that at these larger diameters it is also possible to operate a relatively high bed height to bed diameter ratios, thus maximizing the catalyst inventory whilst minimizing the increase in the diameter. It has also been determined that so long as the catalyst is within the above range of particle characteristics and preferably has an attrition loss of between about 1 and 4%, the fluidization velocity (based on effluent volumetric flow and reactor cross-sectional area ("CSA") excluding cooling coils and dip legs area) can be operated at up to 1.0 m/s, preferably between 0.55 and 0.85, for reactors having a 9 to 11 m internal diameter. Attrition loss may be determined using known methods, such as for example, Hartge et al., The 13 ^th International Conference on Fluidization - New Paradigm in Fluidization Engineering, Art. 33 (2010), methods based on ASTM D4058 and ASTM D5757, and U.S. Patent No.

8,455,388 which are all incorporated herein in their entirety by reference. In a related aspect, total catalyst loss from the reactor may be about 0.35 to about 0.45 kg/metric ton of acrylonitrile produced.

[36] Even at up to the indicated velocities it has been found possible to operate with acceptable catalyst loses while operating the reactor with a top pressure of about 0.50 to about 0.58 kg/cm ² and/or cyclones with a pressure drop of 15 kPa or less, and a fines disengagement height above the top of the fluidized bed of about 5.5 to about 7.5 m. Thus when utilizing a reactor internal diameter of about 9 to about 11 m, using a catalyst with an average particle diameter between about 10 and 100 μ, with a particle size distribution where about 0 to about 30 weight percent is greater than about 90 μ, and about 30 to about 50 weight percent is less than 45 μ, a ratio of reactor diameter to a reactor cylindrical height (tangent to tangent) of about 0.45 to about 0.6 has been found to be effective when operating with a fluidization velocity (based on effluent volumetric flow and reactor cross- sectional area excluding cooling coils and dip leg area) between about 0.4 m and 1.05 m/s preferably between about 0.55 and 0.85 m/s. This therefore leads to potential for increased production capacity per unit reactor volume (tangent to tangent) of between 0.005 and 0.015 metric tons per hour per cubic meter of reactor volume, in another aspect, about 0.0075 to about 0.0125, and in another aspect, about 0.009 to about 0.01 metric tons per hour per cubic meter of reactor volume.

[37] It is desirable to ensure that reactor efficiency (including in terms of reagent conversion and catalyst losses) is optimized whilst increasing the specific capacity of the reactor. The design of the cyclone is critical to the operating pressure of the reactor, the catalyst losses (including caused by attrition) and the required height of the reactor (tangent to tangent). It has been found that the above satisfactory reactor operating window can be achieved with ratio of first stage cyclone inlet velocities to reactor effluent velocities of about 20 to about 30 and/or ratio of a height of a first stage cyclone is about 4% to about 7% of a reactor height (tangent to tangent). As shown in Fig. 3, the cyclone height is determined from a distance from a top 101 of the cyclone to a distal section 107 of the cyclone.

[38] In an aspect, reactor 10 may be configured to have a greater throughput capacity for a predetermined catalyst than a conventional reactor having the same predetermined catalyst and predetermined reactor height. In an aspect, a method is provided for increasing reactor throughput capacity for a predetermined catalyst and predetermined reactor height. The method includes increasing reactor diameter while maintaining a predetermined top pressure. The method may comprise maintaining a predetermined reactor design velocity.

[39] In an aspect, a process includes operating or reacting in a reactor a hydrocarbon, wherein the reactor has a predetermined reactor internal diameter of more than about 40% to about 60% a cylindrical height of the reactor (tangent to tangent), and in another aspect, about 45% to about 55%. This is in contrast to a conventional process that includes operating a reactor having a reactor diameter that is about 40% of the reactor height.

[40] In an aspect, the process includes operating or reacting in a reactor a hydrocarbon, wherein the reactor has a fluidized bed height that is about 40% to about 60% of the reactor cylindrical height (tangent to tangent), in another aspect, about 42% to about 50%, in another aspect, about 45% to about 55%, and in another aspect, about 44% to about 47%. This is in contrast to a conventional process that includes operating a reactor having a fluidized bed height that is about 25% of the reactor height (tangent to tangent) and thus, a greater disengagement height.

[41] In an aspect, the process includes operating or reacting in a reactor a hydrocarbon, wherein the reactor has a fluidized bed height that is about 70% to about 110% of the reactor diameter, in another aspect, about 70% to about 100%, in another aspect, about 75% to about 90%, in another aspect, about 80% to about 90%, in another aspect, about 85% to about 95%, and in another aspect, about 85% to about 90%. This is in contrast to a conventional process that includes operating a reactor having a fluidized bed height that is about 65% of the reactor diameter. [42] In an aspect, the process includes operating or reacting in a reactor a hydrocarbon, wherein the reactor has a top pressure in the range of about 0.50 to about 0.65 kg/cm ² , in another aspect, about 0.52 to about 0.58 kg/cm ² , in another aspect, about 0.54 to about 0.6 kg/cm ² , and in another aspect, about 0.5 to about 0.55 kg/cm ² . A reactor top pressure in this range provides the benefit of improved catalyst performance over a reactor top pressure that is higher than this range. In an aspect, the method includes operating the reactor in the range of about 0.54 to about 0.56 kg/cm ² .

[43] In an aspect, the process includes operating or reacting in a reactor a hydrocarbon, wherein the effluent volumetric flow has a velocity of about 0.5 to about 1.05 m/sec (based on effluent volumetric flow and reactor cross-sectional area ("CSA") excluding cooling coils and dip legs area, i.e., -90% of open CSA). It has been found that it is possible to design and operate the reactor system using this velocity whilst also achieving good fiuidization/catalyst performance and reasonable catalyst entrainment/catalyst losses from cyclones, such that velocities may be maintained in about this range to the extent possible as reactor capacity is increased. In an embodiment, the reactor may be operated with a velocity of up to about 0.75 m/sec to about 0.95 m/sec (based on 90% CSA and effluent gas), and maintain a top pressure of about 0.50 to about 0.65 kg/cm ² , and in another aspect, about 0.52 to about 0.58 kg/cm ² . In one aspect, a ratio of cyclone inlet velocity in meters/second to a reactor effluent velocity in meters/second is about 15 or greater, in another aspect, about 20 or greater, in another aspect, about 15 to about 30, in another aspect, about 20 to about 30, in another aspect, about 22 to about 25, in another aspect, about 23 to about 26, and in another aspect, about 27 to about 29.

[44] As the fluidization velocity is increased so too does the potential for attrition of the catalyst increase. Increased velocity also results in a greater fines

disengagement height above the fluidized bed. The resultant increase in fines can therefore also increase the solids loading on the cyclones. [45] In an aspect, it has been found that by operating a reactor or reacting in a reactor a hydrocarbon, wherein the reactor has a predetermined reactor diameter having a length that is in the range of about 45% to about 60% a length of the reactor height, a length of fluidized bed height that is about 80% to about 95% the length of the reactor diameter, a pressure in the range of about 0.5 to about 0.6 kg/cm ² , and a reactor velocity (based on 90% CSA and effluent gas) of about 0.6 to about 0.65 m/sec, the process may produce up to about 100% or more acrylonitrile product than a method wherein reactor is operated wherein the reactor diameter is about 40% of the reactor height, the fluidized bed height is about 25% of the reactor height, and the fluidized bed height is about 65% of the reactor diameter.

[46] In an aspect, where the reactor diameter is at least 8 m internal diameter and uses the optimized combination of features above, the apparatus and method provides a reactor capacity that is about 12.5 metric tons/hr or 100 ktpa per reactor based on 8000 operating hours per year. Where the reactor diameter is 10.5 m the single reactor capacity can be between 15 and 20 metric tons/hr.

[47] In an aspect, the method and apparatus of the present disclosure provides a more uniform collection of catalyst fines than in conventional methods and apparatuses. In an aspect, by having an outer ring of cyclones hanging from the top of the reactor, and an inner ring of cyclones hanging from the plenum that is centered at the top portion of the reactor, a uniform array of multiple cross-sectional cyclone inlets in different locations is provided, including cyclone inlets of the inner ring of cyclones that are closer to the center of the reactor than cyclone inlets of the outer ring of cyclones.

[48] In an aspect, by returning catalyst fines from the cyclones of the inner ring

straight down to the fluidized bed at locations closer to the center of the reactor, a more uniform fluidized catalyst bed is obtained. The more uniform the fluidized catalyst bed, the more uniform and efficient the operation of the reactor.

Determination of Fluidized Bed Height for Purposes of this Application

[49] The reactor needs to be equipped with at least 3 nozzles for measuring fluidized bed differential pressures as listed below: 1) The 1st of these nozzles is located near the bottom of the fluidized bed (above the air distributor). In this aspect, the nozzles may be about 0.1 to about 0.7 meters above the air distributor, and in another aspect, about 0.2 to about 0.4 meters.

2) The 2nd nozzle is typically located about 2 meters above the 1st nozzle (still within the fluidized bed). The exact distance must be known for the calculations.

3) The 3rd nozzle is located at the top of the reactor (above the fluidized bed).

[50] By measuring the pressure difference between the 1st and 2nd nozzles and also measuring the pressure difference between the 1st and 3rd nozzles, the bed height may be calculated as follows:

Bed Height = (distance between the 1st and 2nd nozzles) x (1st - 3rd differential pressure) / (1st - 2nd differential pressure)

[51] Note that the fluidized bed density is assumed to be approximately constant in the above formula.

[52] The units for the two pressure measurements need to be the same for each but can be any typical unit of pressure (for example lbs/in ² , inches of water column, or millimeters of water column).

[53] The units for the distance between the taps can be any typical unit of distance (for example feet or meters). The bed height will be in the same units chosen.

[54] Differential pressures are preferably measured with two differential pressure transmitters - one for the 1st - 2nd nozzle differential pressure measurement and one for the 1st - 3rd nozzle differential pressure measurement. The nozzles are typically purged with flowing air to keep them clear. In this aspect, air velocity for nozzle purge is about 2 to about 8 m/sec.

[55] While in the foregoing specification this disclosure has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the disclosure is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the disclosure. It should be understood that the features of the disclosure are susceptible to modification, alteration, changes or substitution without departing from the spirit and scope of the disclosure or from the scope of the claims. For example, the dimensions, number, size and shape of the various components may be altered to fit specific applications. Accordingly, the specific embodiments illustrated and described herein are for illustrative purposes only.