Ind. Eng. Chem. Res. 1994,33, 2412-2420
2412
Experimental Evaluation and Modeling of Agglomerating Fine Powder Fluidized Beds N. K. Yadav and B. D. Kulkarni National Chemical Laboratory, Pune 41 1 008, India
L. K. Doraiswamy' Department of Chemical Engineering, Iowa State University, Ames, Iowa 50011
The effects of fines on the behavior of a fluidized-bed reactor have been investigated using a commercial catalyst for propylene ammoxidation. Experimental studies show that the catalyst powder agglomerates and that there exists a critical level of fines in the bed (around 30%) for which the fluid-bed behavior in terms of bed expansion, aeratability, and cluster size is optimum. The results also suggest that the dense phase should indeed be treated as two distinct phases: cluster and emulsion. A general mathematical model to account for these two phases is proposed. 1. Introduction
Considerable research has been devoted to the study of fluidization of aeratable and cohesive powders (Geldart, 1973; Rietema, 1967, 1984; Musters and Rietema, 1977; Donsi et al., 1975; D'Amore et al., 1979; Abrahamsen and Geldart, 1980a-c; Geldart et al., 1984;Yang, 1984;Geldart and Wong, 1984, 1985; Molerus, 1982; Dry et al., 1983; Rowe, 1978, 1980a,b, 1983, 1986; Wang et al., 1985; Van Swaaij, 1978; Kono et al., 1986a,b; Kono, 1989; Foscola and Gibilaro, 1984;Chauki et al., 1985;Hartley et al., 1985). The basic objective has been to characterize the hydrodynamic features of such powders and to ascertain the role of fines in determining fluidization behavior. The general conclusion is that the commonly employed twophase theory of Toomy and Johnstone (1952) for determining gas distribution in fluid beds is inadequate when applied to fine powder systems. Fluid-bed experiments with commercial catalysts containing fines (including our own) indicate that the powder agglomerates while it is being fluidized. The size of the agglomerates varies with the extent of fines (d, < 44 pm) in the bed. The bed collapse experiments indicate the existence of a dense phase comprising a cluster phase (looselybound particles) and an emulsion phase (more loosely bound or free moving particles). The higher permeability or voidage of the emulsion phase as compared with that of the cluster phase allows it to settle down fast while the cluster phase settles slowly. Fluidized-bed modeling requires a knowledge of the division of the gas between the various phases. As the dense phase permeability changes with gas throughput and with the level of fines in the bed, a model which takes into account the variation of dense phase voidage with variation in fines and gas throughput becomes necessary. The study presented here attempts to formulate such a model. 2. Experimental Results
The details of the two-dimensional fluid-bed system used are shown schematically in Figure 1. Measurements of expanded bed heights and the corresponding pressure drops at different fluidizing gas (nitrogen) flow rates were made in a 0.01 m X 0.3 m X 1.0 m rectangular section of a Perspex column. The distributor was made of a brass
* Author to whom correspondence should be addressed.
plate with 120 equispaced holes of 1 mm diameter and supported on a fine wire mesh (200 mesh size). The grid pressure drop was approximately 10% of the bed pressure drop. A scale attached to the column enabled the measurement of bed heights at various flow rates of nitrogen. The fluidizing gas was at the ambient temperature, and superficial gas velocities of up to 7.5 cm/s were used. The catalyst used in these studies was the industrial catalyst for the ammoxidation of propylene which we designate as AC (see Table 1 part a). (This catalyst is proprietary to Sohio, and hence further details cannot be given.) It was seived, and particles smaller than 44 pm were considered as fines and the remaining fraction as coarse. Synthetic mixtures containing 0, 10, 20, 30, 40 and 50% fines by weight were prepared. The analysis is shown in Table 1 part b. The two-dimensional bed was loaded with 1.5 kg of catalyst powder. The fluidizing gas flow was gradually increased until all the grid holes started functioning. The bed height measurements were taken when flow was stabilized under both increasing and decreasing flow conditions. The data are presented in Figure 2. An important point to note is that particle agglomeration can also occur due to generation of static electricity as a result of the vigorous movement of solids, especially when the container is a polymeric material such as Perspex as in the present case. We have taken care to ground the electrostatic charge generated due to friction with reactor walls. The agglomeration of powder material was also confirmed with a suitably grounded circular glass column of a 7.5 cm diameter fluid bed using the same powder material. The commercial reactor for acrilonitrile using the same catalyst is also electrically grounded to avoid fire and explosion hazards due to high static voltage. It may therefore be safely assumed that agglomeration of catalyst reported in this work is not a feature of the particular apparatus used. 2.1. Main Fluidization Properties of the Powders Used. Bed expansion and collapse experiments were conducted for catalyst powders AC-1 and AC-2, and the results are presented in Figure 3. Catalyst AC-1 is catalyst AC with 30% fines, and AC-2 is catalyst AC with a higher fines content. The variation of bed voidage with U/U,f in the range 1-40 for catalyst AC-1 shows an exponential increase in the voidage, especially in the range 1C U /U d C 15. The bed voidage for ( U fUrn,)> 20 approaches a fully fluidized-
0SSS-5SS5/94/2633-2412~0~.50/0 @ 1994 American Chemical Society
Ind. Eng. Chem. Res., Vol. 33, No. 10, 1994 2413
4
200 MESH SCREEN
4- 1mm
L
@
@
5mm S m Tube C o n m t i m
1
- +- GAS CYLINDER
2- ORIFICE METER
3- ROTAMETER 4 -MANOMETER 5 - TWO-WAY VALE 6-FLUID
BED
7 - PRESSURE TAPPING CONNECTIONS B- DISTRIBUTOR PLATE 9
- CYCLONE
FLOW
GASI INLET
I
I
I
Figure 1. Schematic diagram of a two-dimensional fluid bed.
Table 1
a. Particle Size Analysis of Catalyst AC 0 28-
particlesizecut,pm 105-90 90-75 75-63 63-45 45-37 C37 wt fraction, X 0.09 0.06 0.32 0.23 0.07 0.23 0.21
b. Particle Size Distributionsof Catalyst AC with Different Proportions of Fines wt fraction,X,at % fines 0 10 20 30 40 50 size cut, pm 105-90 0.128 0.115 0.103 0.09 0.077 0.064 90-75 0.086 0.077 0.068 0.06 0.051 0.042 75-63 0.457 0.411 0.365 0.32 0.274 0.228 63-45 0.328 0.285 0.262 0.23 0.197 0.164 0.0 45-37 0.023 0.046 0.07 0.093 0.116 0.0 c37 0.076 0.153 0.23 0.306 0.383 1.217 1.231 1.23 1.3 1.3 1.3 PP 1.18 1.215 1.219 1.227 1.233 1.243 PBT 1.1 1.15 1.15 1.15 1.15 1.15 Pb 69 64 60 55 50 46 d,, w
bed voidage of 0.25 and 0.28 for catalysts AC-1 and AC-2, respectively. The experiments indicate that the catalyst bed tends to defluidize and channel near U l U d = 1 due to the cohesive forces prevailing in the bed. The instability in fluidized-bed behavior increases with increase in fines, as observed with catalyst AC-2. This is indicated by a considerable scatter of data points near Ud. An important factor in characterizing fluid-bed behavior is the bed voidage exponent of Richardson and Zaki (1954). This was found for both catalysts AC-1 and AC-2 by preparing logarithmic plots of bed voidage ( E ) versus gas
-
0.14
CATALYST-AC(Rcfer Toblt 0 % FINES
,
-_ 0 07-
20 o/'
30%
I
,
F NES FINES
-X-X-40%
_ _-
FINES
50
O/o
FINES
2414
Ind. Eng. Chem. Res., Vol. 33, No. 10, 1994 10
0.3O
I
I
,
I
I
,
r
I
30
20 I
,
I
I
I
I
!
- 0.35
40 t
,
I
I
I
(Makeup Cntolyrt )
- 0.30
- 0.25 w
- 0.20 m w
-0.15
ox
0.1
o 20
15
10
U / Umf
Figure 3. Bed voidage variation with U/& ratio for catalysts AC-1 and AC-2. 1.5 rAC-2
0 5
1
'
1
1
'
1
The ratio of tapped bed density PBT to the aerated fluidbed density PBA has been plotted as a function of ( U / U d for catalysts AC-1 and AC-2 in Figure 4. The value lies between 1.3 and 1.4 for U/Umf= 20. Geldart et al. (1984) reported that powders with (PBT/PBA) greater than 1.4 exhibit distinctly cohesive behavior and should be considered as group C powders. A fine powder with a ratio less than 1.25, on the other hand, belongs to group A, while one in the range 1.25-1.4 may exhibit some properties of both. Hence it may be proper to classify these powders as Geldart AC type. When the gas supply to the fluidized bed is suddenly cut off, the bed collapses slowly at a rate U,comparable to the superficial velocity of gas in the dense phase of the bubbling bed (0.1-0.6 cm/s). The bed height measurements were recorded with a high-speed movie camera NAC16HD at 500 frames/s, and the analysis of data was carried out using a NAC projector. The rate of bed collapse dH/ dt, when calculated for catalysts AC-1 and AC-2 (average d, = 50-80 pm, p, = 1.3 g/mL), was about 0.18 cm/s. This rate corresponds to the dense phase gas escape velocity U,. Abrahamsen (1980) also reports values of the bed collapse rate in the range 0.14-0.29 cm/s for similar powders (d, = 40-70 pm and p, = 1.8-3.9 g/mL). 2.2. Experimental Evaluation of the Effect of Fines on Fluid-BedBehavior. (a)Effect on Bed Expansion. The bed expansion plots for catalyst AC-1 with fines contents of 0-50% presented in Figure 2 show that the bed voidage increases and then levels off with increasing superficial gas velocities. The velocity beyond which this occurs is a function of the fines content. This indicates
~
"
'
'
~
~
~
'
~
~
~
that a higher gas flow rate is required to attain maximum bed voidage as the fines level increases in the bed. This may be due to the cohesive forces causing agglomeration of particles, which require higher gas flow rates to fluidize. Unlike the Geldart group A powder, which shows a reduction in bed voidage just above Umb, the catalyst with fines showed no such reduction in bed voidage. It is clear from Figure 2 that with an increase in fines at a certain operating gas flow rate, the bed voidage passes through a maximum. When the voidage maximum for different flow rates is plotted as a function of percentage of fines (Figure 5), it is found that this maxima curve itself shows a maximum at 30-40% fines when compared at the same gas flow rates. (b) Effect on Aeratability. The aeratability measurements of the operating fluid bed provide a good means of characterizing the powder into Geldart groups. The method adopted here is slightly different in the sense that it uses fluidized-bed density as aerated bed density instead of aerated bed density measured in a cup. The ratio of tapped bed density PBT to aerated fluid density OBA for catalyst AC with different fines increases with superficial gas velocity and finally approaches a constant value. These aeratability ratios for the experimental condition U = 5 cm/s are compared at different levels of fines in Figure 6. The aeratability of a fluid bed passes through a maximum for the 30% fines level, beyond which it decreases with further increases in fines. This indicates that a catalyst with 30% fines, normal in an industrial reactor using this catalyst, seems to represent an optimal value, at which the bed expansion and aeratability of the fluid bed are
~
'
Ind. Eng. Chem. Res., Vol. 33, No. 10, 1994 2415
1.0
CATALYST-IC ,".I.,
.*51.
3b 1
t
L
020,
20
% FINES
30
40
L 50
Figure 5. Variation of maximum bed voidage with fines in the bed.
maximum. The aeratability ratio varies between 1.25 and 1.40 which represents a narrow band of values for which the powder exhibits characteristic features of both Geldart group A and group C. (c) Effect on Particle Agglomeration. The concept of particle agglomeration is not new. Several workers in the past have observed agglomeration of fluidized powders during the course of fluidization. Fine particles agglomerate due to several types of forces prevailing in the bed (Chauki et al., 1985; Hartley et al., 1985). However, no effort has been made to study the effect of fines on agglomeration. The bed expansion data for catalyst AC (0-50% fines) as presented in Figure 2 were subjected to regression analysis to determine the slope (n)and intercept (Ui) of the relationship UJUi = en
(1)
where U is the operating superficial gas velocity, e is the fluid-bed voidage, and Ui is the terminal velocity of a single particle. By knowing Vi, the diameter of the particle which would have given this Ui may be calculated from the Lychenko number (Ly).Then, fromLy one can get the Archimedese number (Ar)using the correlation of Pavolov et al. (1979) and hence the size of the particle. The definitions of the two numbers are
I t was observed for catalyst AC that with an increase in the proportion of fines, the size of a particle or a cluster of particles showed a dependence on fines. The cluster size decreased with an increase in fines and reached a minimum of 120 pm for 30% fines. Further increases in fines caused an increase in the cluster size exponentially as indicated in Figure 7. The catalyst with no fines would have a particulate arrangement, where additional fines could go in and occupy the interparticle space without further increase in the value up to a critical fines level. The reduction in the diameter of the cluster indicates that the short range forces due to the presence of fines increase with fines and make the particle shrink under the influence of operating forces. This would happen as long as there is space between
1
30
20
40
50
% FINES
Figure 6. Variation of aeratability ratio p ~ ~ l of p fluidized e ~ bed catalyst AC with fines.
particles available. Fines beyond the critical limit cannot find such space within the voids but, due to agglomerating forces, would add to the cluster resulting in an overall increase in size. 3. Cluster Model of the Fluidized Bed
The cluster model relies on the fact that the particles in a fine powder fluid bed agglomerate under the influence of particle-particle forces prevailing in the bed. The vigorous motion of gas and solids continuously shreds these agglomerates and generates relatively fine and less agglomerated particles. The dynamic equilibrium from such a process would lead to a heterogeneous dense phase consisting of agglomerated particles (clusters) and less agglomerated or free particles as an emulsion. A general model which can be applied to a wide class of particles ranging from Geldart group B to fines of group AC is clearly needed. Geldart group B powder behavior is an asymptotic condition when the cluster phase is absent. The group AJAC boundary is another asymptote when the total bed acta more or less like a cluster and the emulsion phase approaches zero. A general model which takes into account the bubble and associated cloud-wake phases as well as the dense phase consisting of a cluster phase and an emulsion phase is presented below. The development follows along the lines of Rowe et al.'s model (1978) and hence only the additional assumptions and final results are given. 3.1. Theory. Gas flow can be divided into four phases: gas flowing interstitially in the dense phase which consisb of clusters and emulsions, through the wake phase, and through the bubble phase. The particles in the wake move with the bubble and are returned to the fluid bed through the freeboard in the form of clusters and emulsions. As a result, there is a circulation of solids in the bed in the form of cluster and emulsion phases. Gas flowing through the dense phase is divided into cluster phase and emulsion phase portions in amounts depending upon their relative volume fractions and voidages. The cluster model is shown schematically in Figure 8. I t is assumed that the loss of fines through cyclones is negligible. The total gas distributed between the phases can be expressed as where Qc + Qe = Q, i.e., the dense phase gas is expressed as two phases. In the case of group B powders, where the cluster phase is absent, eq 4a reduces to
2416 Ind. Eng. Chem. Res., Vol. 33, No. 10, 1994
Q = Qe + Qw + Qb
(4b) CATALYST-AC
or
Q = 8, + 8, + Qb
(4c)
The flows through the individual phases can be written as Qe
= UgeAfeee
Qc
=
8, &b
Q/A = (8,+ Qc
ugPfccc
(6)
= UgaPfwcw
(7)
= UbAfbcb
(8)
+ Qw + Qb)/A ugefete
(5)
+
=
Ugcfctc
u= + ugwfw%
+ U d b t b (9)
Let us assume that the solids moving with the wake are returned to the bed either in the form of cluster or emulsion phase solids. Equating the upward solids flow in the bubble wake to the average downward flow in the dense phase gives V8JW(l- t,) = -U,,(l - fe - f, - f b ) ( l - tc) = -UBe(l - f c - fw - f b ) ( l - t e )
= fd3
t"
i I 1
(10)
The following additional assumptions are now introduced: 1. The fractional volume of the cloud-wake phase is one-third of the fractional volume of the bubble. fw
Figure 7. Variation of effective cluster diameter with fines in the bed.
'IJBBLE
WAKE/ CLOUD
CLUSTER
EMULSIOF
fw
fC
fe
ABSOLUTE V E L O C I T I E S
FRACTIONAL VOLUME
fb
(11)
I I
P H A S E VOIDAGE
This is an average value arrived at from a large number of measurements. 2. Solids and gas in the wake move at the bubble velocity, and there is no net relative motion.
us,= urn=ub
(12)
3. The dense phase comprises the cluster and emulsion phases with voidages e, and te, respectively. There is no direct evidence of this assumption. However, Kono's studies (1989) provide clear photographic evidence of agglomerates formed in the dense phase, and hence different bulk densities for the agglomerated and unagglomerated phases should be acceptable as an ideal limit. (Actually, there would be variation in densities.) The cluster phase voidage tCis assumed to be equal to the bed voidage at Umf. Ec
= Emf
The dense phase voidage of the bed mean of t, and t e a ti
= (e,
(13) ti
is the arithmetic
+ te)/2
VOLUMETRIC
Ec=
FLOW
D E N S E P H A S E VELOCITIES
Qb
I
Qw
Emf
Ee
QC
Qe
USC
Use
Figure 8. Schematic representation of the cluster model.
Rowe's model considers assumptions 1and 2 along with assumption 4. In the development of the cluster model, the dense phase is assumed to be a heterogeneous phase consisting of clusters and the emulsion, and their individual properties are taken into account. As aresult, assumption 4 is slightly different in the sense that the emulsion phase voidage is not the same as the dense phase voidage as used in Rowe's model. The assumption of the average dense phase voidage being the average of the cluster phase and emulsion phase voidages is an approximation. The total material balance gives
or
The above equation is based on the derivation of emulsion phase voidage from average bed voidage. 4. The cloudwake phase is as permeable as the emulsion. te = t,
(15)
Rearranging the above equation and solving for the absolute rise velocity of gas through the cluster phase gives
Ind. Eng. Chem. Res., Vol. 33, No. 10, 1994 2417
At Umf,fb = fw = fe = 0. It is assumed that the total bed is a single cluster of voidage ec = emf, which breaks into smaller fragments of voidage ec at U > U d . Thus
referC AT&lc T A L YI SbTI- A t
i d%pF 3 cmls (when the bed is fully fluidized) the value of fe becomes independent of gas velocity. (b) Bubble and Wake Fractions. The fractional bubble volume fb shows an increasing trend (from 0 to 0.15) initially with an increase in the superficial gas velocity; it is, however, less sensitive to variation in the level of fines for U > 4 cmls indicated by the resulta. Almost the same value cfb = 0.14) has been reported by Rowe et al. (1978) for a similar type of powder. One of the assumptions of the model is that the fractional volume of the cloud and the wake is one-third the fractional volume of the bubble phase. This makes the fractional cloud and wake phase fw dependent on fb. Variations of
.
2418 Ind. Eng. Chem. Res., Vol. 33, No. 10, 1994 Table 2. Values of Absolute Rise Velocity from Published Bed Collapse Data.
CATALYST-IC % F I N E S IRtter Table I b I l d p < 4 4 f i m ) 0-0
.-lo I
cE
0-330 0-330 0-330 0-320N FRF-5 FRF-5 FRF-5
- 20
-
I 30 b 40 0-50
6;
I3
NO
-20 0
2
4
6
8
I
10
U,cm/s
Figure 10. Variation of absolute gas velocity through the cluster phase with superficial gas velocity.
with U calculated from the model equations show a very slowlyincreasingtrend, but f w is practically insensitive to the concentration of fines. With an increase in U the gas in excess of the minimum fluidization velocity forms the bubbles. This happens in the case of coarse powders where the two-phase theory is valid. In the case of fine powders the excess gas over the minimum fluidization velocity geta distributed between the bubble and dense phases, depending upon the variations in the permeability of the dense phase. This exercises a control over bubble size and, therefore, on the fraction of wake carried up with the bubble. (c) Absolute Velocities of Gas throughCluster and Emulsion. The absolute rise velocity of gas through the cluster phase U,, is shown in Figure 10 as a function of superficial gas velocity and percent fines in the bed. The variations in U,, are in the range 0.7-0.9 cm/s. The bed collapse data of Geldart et al. (1984) were subjected to analysis in light of the cluster model. The absolute gas velocity escaping through the dense phase in a collapsing bed was assumed to be the cluster phase gas velocity. An assumption of the cluster model is that the bed a t U < Umf is all cluster phase with the bed voidage equal to emf. The calculated U,,values for the data of different particle systems are shown in Table 2. The data of Geldart et al. (1984) for the powder FRF-5 (d, = 70 pm) show values very close to those predicted from the cluster model. (d) Flow of Gas through Phases. The fractional flow of gas through the cluster phase Q,/Q is plotted in Figure 11 as a function of total gas throughput to the fluid bed operated at different levels of fines. The fractional gas flow through the cluster phase decreases with an increase in gas throughput. For a bed operating close to Umf conditions much of the gas flowsthrough the cluster phase. Any increase in velocityresults in a reduction of the cluster phase, and new phases such as bubbles and emulsions come into existence. The flow therefore gets distributed among the various phases. The increase in the emulsion phase gas flow is shown by a maximum in Figure 1 2 for various levels of fines in the bed. (Values of the flow fraction greater than 1observed in Figures 12-14 are due to disparities in bed height measured during the increasing and decreasing flow rate modes of operation.) The decrease in (Q,/Q) beyond the maximum indicates that the gas now finds additional passage through the bubbles which start forming in the bed. A plot showing the total dense phase gas flow fraction (Qce/Q)as a function of Q and percent fines is shown in Figure 13. The rising part of the curve indicates the region of bed expansion where the permeability of the bed increases without visible bubble formation; the decreasing part indicates that with an increase in gas throughput more bubbles are formed and fw
Ar Arcton-12 9G4 Air 9G4 Air 9G4 Air B-20 B-20 B-20 N2 Ar Arcton-12 F0.3 Air Fe/7 Air F2/5 Air FSG Air Ballotini-S Ballotini-S Ballotini-S Ballotini-S Ballotini-S Alumina R(P) A R(P) R(P) R(P) M M M R(P)
28 28 28 30 70 70 70 70 70 70 55 55 55 26 26 26 26 26 26 79 68 77 125 71 60 43 53 60
0.526 0.28 0.27 0.325 0.54 0.53 0.43 0.37 0.28 0.575 0.25 0.25 0.25 0.19 0.165 0.165 0.19 0.185 0.35 0.23 0.34 0.234 0.31 0.25 0.16 0.15 0.25 0.25
0.39 0.345 0.33 0.57 0.93 0.89 0.88 0.92 0.81 1.26 0.483 0.476 0.47 0.255 0.22 0.205 0.25 0.255 0.50 0.23 0.325 0.22 0.45 0.64 0.39 0.23 0.38 0.41
0.526 0.469 0.453 0.555 1.013 1.003 0.866 0.708 0.531 1.097 0.544 0.548 0.549 0.440 0.386 0.387 0.450 0.445 0.839 0.448 0.779 0.554 0.709 0.584 0.363 0.355 0.572 0.569
3.668 3.668 3.668 3.423 2.397 2.397 2.397 2.397 2.397 2.397 4.095 4.095 4.095 5.637 5.637 5.637 5.637 5.637 5.637 14.179 16.250 12.668 5.113 2.043 2.832 3.473 3.114 2.676
65 29 47 58 38 41 41 41 56
0.190 0.29 0.14 0.21 0.14 0.22 0.24 0.19 0.16
0.38 0.50 0.29 0.29 0.32 0.55 0.47 0.42 0.35
0.439 0.448 0.301 0.458 0.277 0.403 0.440 0.348 0.342
3.485 3.541 4.985 3.700 5.800 3.271 3.271 3.271 3.904
*
a Geldart et al. (1984, 1980). U,, bed collapse rate, cm/s. u d , dense phase gas velocity, cm/s. U,,,cluster phase gas velocity, cm/ s. e N&, cohesion number for the system = c/pddpg.
CATALYST-AC IRtOr Table I b
~
FINES
‘dT-4:””’ .-IO x I
- 20 - 30
b-40
0-50
0 , LTRSIrnin
Figure 11. Variation of fractional gas flow through the cluster phase with total gas flow rate.
hence flow through the dense phase decreases. The dense phase gas flow is higher for 20 % and 30 % fines as compared to other fines concentrations, perhaps due to the higher permeability of the cluster and emulsion phases. The fraction of gas flow through the bubbles (Qb/Q) is plotted as a function of the total gas throughput Q and percent fines in Figure 14. This plot indicates that the gas flow through the bubble phase is the lowest for 30% fines in the bed. For this condition a relatively high fraction of gas passes through the dense phase. It is interesting to note that other bed properties such as cluster size, bed voidage, and aeratability are also
Ind. Eng. Chem. Res., Vol. 33, No. 10, 1994 2419 Table 3. Quick and Slow Bed Collapse Velocities (Corresponding, Respectively, to Interstitial Velocities through the Emulsion and Cluster Phases)
1.5 CATbLYST-4C
%FINES
.
I w e r Table l b I i d p < 4 4 f i r n )
1.0
0-0 10
I1
-
x-20 30
A
A-40 0
- 50
I
reference Geldart and Wong (1984)
Kono et al. (1986)
Kono et al. (1986) Q,LTRS/min
Figure 12. Variation of fractional gas flow through the emulsion phase with total gas flow rate. CATALYST-AC % F I N E S I R d u T3lc tbI idp
