Performace of the University of Toronto infraiszer MK III as a monosizer and multi-cut classifier

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PERFORMANCE OF THE UNIVERSITY OF TORONTO INFRASIZER MK 111

AS A MONOSIZER

AND

MUL TI-CUT CLASSIFIER

December, 1980

by TECHNISC!' LUCHTVAA T- : . h:l • , 2 i .:~1 1981 Kluyverweg 1 - DELFT

A. H.

van

Flotow and

B. Etkin

UTIAS Technical Note No. 227

CN ISSN 0082-5263

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PERFORMANCE OF TEE UNIVERSr,ry OF TORONTO INFRAISZER MI<: III AS A MONOSIZER AND MULTI-CUT CLASSIFIER

by

A. H. von F1otow and B. Etkin

Submitted September, 1980

November ~ 1980

UTIAS Technica1 Note No. 227 eN ISSN 0082-5263

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Acknowledgement

Financial support for the research reported herein was provided from NSERC Operating Grant No. A0339. The experiments were conducted in the UTIAS· laboratory, and the photographs were analyzed on the Faculty image analysis system located in the Department of Metallurgy and Materials Science.

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S~y

This paper'presents results of a series of experiments conducted

to de fine the performance of the Infrasizer MK lIl. For free-flowing

spherical particles in the range ,tested '(50 to 230 ~m), the performance,

both as a multi-cut device and in monosize production, is excellent. The sharpness of cut index is only a few percent higher than the ideal value of 1.00 and monosize fractions can be produced with standard

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Contents Page Acknowledgement ii S~y iii List of Symbols v INTRODUCTION 1

FACTORS AFFECTING TEE PERFORMANCE OF TEE INFRASIZER MK III 1

EXPERIMENTAL RESULTS 2

COMMENrS AND CONCLUSIONS

4

R E F E R E N C E S 5 FIGURES

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Contents Page Acknowledgement i i Summary iii List of Symbols v INTRODUCI'ION 1

FACTORS AFFECTING TEE PERFORMANCE OF ·THE INFRASJZER MK I I I 1

EXPERIMENTAL RESULTS 2

COMMENl'S AND CONCLUSIONS ·4

REFERENCES 5

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c

_c

m cc

n

List of Symbols

contamination of coarse product; m f/m c c contamination of fine product; mfc/mf mean diameter of a sample

cut size

diameter of a particle that hàs probability p of reporting to coarse stream

coarse grade efficiency (probability that a partiele af si ze d reports tQ coarse stream)

mass of feed

part of feed wi th d

<

~O

part of feed with d > d

50

mass of finefraction

part of fine fraction with d < d

50

part of fine fraction with d > d

50

mass of coarse fraction

part of coarse fraction with d < d

50

part of coarse fraction with d

>

d

50

feed rate, particles per sec per unit length of feed slot fine recovery; mff/~f

coarse recovery; m _cc

lIL

J:I'C

air velocity in infrasizing region

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INTRODUCTION

The University of Toronto Infrasizer MK III is an air clas2ifier,

separating a mixture of particles on the basis of settling (terminal) velocity

[1, 2]. The output of the Infrasizermay be collected in an arbitrary number of fractions, each consisting of partieles having terminal velocities within same correspondingly arbitrary range. Ifthe classification desired is into only two portions , 'fine' and 'coarse', the many output strea.Jl).S can be com-bined into two, giving efficient operation as a single-point classifier. Alternatively, monosize produets may be obtained and refined by recycling.

The purpose of this paper is to report the results of a series of experi-ments conducted to quantify the performance. Numerical results defining efficiency both in single-point classification and in monosize production are given. The performance is evaluated by standard methods, to allow cam-parison with other c1assifiers [3].

FACTORS AFFECTING THE PERFORMANCE OF THE INFRASIZER MK III

The performance of the Infrasizer, as of any classifier, is a function of feed material and operating conditions . These factors have been detailed in previous papers

[1, 2J.

Variation either of feed material or of operating conditions may influence performance to yield results ranging from excellent to poor.

Feed material properties that must be considered include - size distribution

- shape and density distribution

- rheologiCal properties (e.g., surface forces) Operating conditions which are important include

- laboratory environment (primarily temperature and humidity)

- feed rate - -air velo city

Obviously these factors are related. Surface forces, which can be modified by humidity, may cause agglomeration, thus increasing the 'apparent

size of the particles • The feed rate permissible .is related to air velocity and particle size

[2J.

The air ~elocity must be matched to particle size and density to permit efficientuse of the cellection zone.

The present experiments were performed with a feed .material consisting of solid glass beads of uniform density in the size range 50 to 230 microns. Although the beads were predominantly spherical, some irregular glass frag-ments, ellipsoids and fused beads contaminated the feed. These non-spherical particles were not counted in the statistical analysis. Agglomeration did not occur to a significant degree.

Theexperiments were performed at room temperature and humidity; these factors were not monitored. Several feed rates were used, both above and

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below the onset of signif.icant particle interaction [2J. The Infrasizer air velocity was chosen to use the available 'collection zone optimally.

I

EXPERIMENTAL RESULTS

Part A - Performance as a Multi-Cut Classifier

A perfect single-point elassifier would be one in which all particles smaller than a certain size go to the fine stream while all particles larger than that si ze go to the 'coàrse stream. Similarly, a peTfect multi-cut classifier would direct each particle ,unambiguously to ane of several output streams. Real classifiers of course perform imperfectly. Some mate-rial will

al. ways be found in the 'wrong output stream. This imperfection can be quanti ta-tively described in a variety of ways. Some 'measuresthat have become standard for single-point classifiers are (see Fig. 1):

, Recovery

Thefine recovery is the ratio Rf = mff/IDff. The coarse recovery has an equivalent def.inition, Rc = mcc/IDfc' A perfect classifier would have fine and coarse recoveries of unity.

Contamination

The'fine contamination is the mass fraction of the fine stream corre-sponding to particles larger than the cut size, i.e., Cl' =mfc/mf. Coarse contamination has a similar definition, Cc = mcf/rnc. A perfect classifier has contaminations of zero.

Sharpness of Cut

The 'probability that a particle from the feed goes to the coarse stream (the coarse _{grade efficiency Gc (3J) is a function of partiele size. The} ideal form of Gc(d) is a step-function. In reality, it increases gradually from very small values ,for very small particles towards uni ty for thelargest particles, indicating the presence of somemisplaced particles. With this form of Gc, the cut size requires further, definition, and the recovery and contamination values are no longer ideal. The cut size is normally defined to be the equiprobable 'size d50 - the size of partieles that have a 50%

chance of reporting to either 'stream. Tbe deviation from ideal classification is characterized by the sharpness index ~ the ratio of the size of the particles wi th a 75% chance of reporting to the coarse stream to the size of the partieles 'With a 25% chance of reporting to the c'oar&,e stream. This is denoted 75cf>25

=

d_75/d2

5'

A sharpness index of unity would indicate ideal classification, and a value of three 'is considered poor 13J. Alternatively, the sizes corresponding

to probabilities other than 75 and,25 percent have been used (e.g., 90 and 10, and 84 and 50).

Experimental Procedure

Two samples of similar composition, each weighing 200 gIn, were classified. T,he feed rates were chosen to yield values of .062 (Run A) and .66 (Run B) for

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the nondimensional parameter nd2/Vx (conservatively based on d

=

50 microns) .

. Thus one sample was classified with particle concentrations' low enough to produce negligible ·particle interaction, the other with severe particle interactions [2].

Theparticles were collected in special bounce~inhibitingtraysdistri buted on the tunnel floor as shown in Fig. 2. The content of each tray was weighed and sampled. Microphotographs of the samples were taken, and measure-ments of 100 particles yielded values for themean, the standard devi.ation

and a histogram of diame ter distributions for each tray. These data were processed to yield the ·curve·s of Figs. 3 to 7.

The average diameter is seen to vary smoothly with downstream distance (Fig. 3), the shape of the curve reflecting approximately the law for settling velocity at low Reynolds number, i.e., Vt '" d2 , whence d '" (X/H)-1/2 .. The

standard deviations (Figs. 4', 5) are seen to exhibit substantial scatter, in part fr om sampling error and in part fram measurement error. The latter was determined to be about 1% of d. The precision is best in the 'range x .= H te 4H, and for low feed rate, when

aid '"

4%. Figure 5 presents . the

standard deviation normaJ.ized wi th respect to its theeretically achievable limit which is set by finite tray width [2]. This is seen to be a very sensitive 'indicator of performance, showing appreciable degradation at the higher -feed rate.

To evaluate the performance as a single-cut device, the 24 output streams were mathematically combined into two streams, one including all trays up- I stream of the division (the coarse stream), the otherincluding all trays downstream of the division (bhe 'fine stream). Tnis was done for eleven

different locations of the dividing line to yield the curves of Figs.

8

to 12. Figures 8 and 9 are representative of many others and illustrate how the

various performance parameters were obtained. Figure 8 is for a cut af ter tray No. 9, and shows the computer generated values of Gc(x) from which 75~5 was obtained. Figure

9

shows the feed, coarse and fine distributionsfor this

cut, together with the recovery and contamination values. The departure of the ·dotted line from the 'solid line on Fig. 9 represents the~tent of

non-.ideal behaviour. It may be seen that at both feed rates used, the .Infrasizer performs exceptionally well as a single-point classifier. The Sharpness of Cut index is typically between 1.0 and 1.2; the fine and coar'se recoveries lie between 95 and 100 percent; and the fine and coarse contaminationsare less

than 5 percent. The coarse recovery and contaminations deteriorate for the higher feed rate, suggesting the entrainment of fine particles in the wakes

of coarse particles.

Part B - Performance in Monbsize Production

, A feature -of the Infrasizer MK 111 is . the ease with which a variety of monosized samples -canbe produced fram a single feed stream (Figs.

3, 4).

Both the mean size and the diameter range (above a certain minimum) of the

'monosize samples are controllable. In addi tion, several different samples may be produced during a singler.un. The size range of each sample is con-trolled by the width of the collection tray. In this study the collection region was subdivided in such a way' that the 'size range of e-ach output sample was approximately proportional to i ts mean si ze •

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, In order to study the repeatability of particle ·trajectories and the

value'of multi-stage ~eration, several products of a run identical to run A

in 'operating conditions, but differ:i:ng slightly in feed composi tion were

_ s.aved and processed fUrther. Eac,h sample was passed through the -Infrasizer

several times and its mean and standard deviation determined afeer each pass.

Theseresults are summarized in Figs. 13 and ,14. As·expected, the mean size

of, all·' samples remained within a few microns ' from run to run, ,and the standard

deviation decreased. The 'small variations in mean size (both',increases arId

'decreases, Fig,. 13) are probably a consequence 'of the 'sampling error - each

s~1e consisted of between 60 and i.OO partieles •

Another expected result is the steady increase inyield (Fig. 14).

, This would be 'caused by 'the 'i terati ve loss of particles that in an ideal

IIifrasizer would ,land outside 'or near ,the edge of the collection tray. The

·losses indicated in Fig. 14 would be made up both of particles that do not

belong in the collection tray but 'erroneously arrived there on the previous

passes, ahd of particlesthat belong in the collection tray but erroneously

arrive ,in a neighbouring one. The 're sult of these losses of unwanted and

borderline 'particles should be 'a narrowing ofthe' range of particle 'size in

the 'output stream f'rom one iteration t.o the nex-t. This 'is .reflected by the

'values of 'standard deviation given in Fig. 13.

COMMENTS AND CONCLUSIONS

The Infrasizer MK III has been shown to be a classifier of cansiderable merit for free-flowing particles with equivalent aerodynamic diameters in

the range 50 to 230 Jlm. As a multi-..cut 'device, the sharpness of cut values

of 75~25 ~ 1.1 speak for themselves. In monosize produotion, samples with

standard deviations of ~

5%

of mean diameter are obtainable with a single

pass.

No certain statements can De made 'about the performance for particles

outside -the size range tested. However, experience wi th the app ar a tus

suggests that quite oomparable performance can be obtained wi th much larger

particles, up to say 3 mm, provided that the collection means is designed .

to trap the particles and prevent them from bouncing into the wrong tray. It is intrinsic to this classifier, as to others, that particles will only

follow the correct trajectories if they do not stick together ·to form clumps.

We have not found this to be a serious problem for particles generally larger

than about 50 Jlm. However, for smaller ones, agglomeration may be a serious

impediment to accurate classification. If the feeding means is such as to

produce 'effective'dispersion of the particles, then the Infrasizer MK III

can,beexpected to perfarm well down to ab out 10 Jlm. Our current research

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1. Raimondo, S. Haasz, A. A. Etkin, B. 2. Etkin, B. Haasz, A. A. 3 . Allen" T. REFERENCES

"TheDevelopment of a Horizontal Elutriator: The Infrasizer MK III", Universi ty of Toronto, Institute for Aerospace Studies, Report No. 235, March'1979. "Performance Characte:dstics of the University of Toronto Infrasizer MK III", Proceedings of Conference on Fine Particles Processing, Vol. 1, pp. 209-231, Published by AIME, New York, 1980.

Particle Size Measurement, 2nd Ed., Chapman

&

Hall, L ond on , 1975.

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(EACH POINT REPRESENTS ONE TRAY).

(17)

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(18)

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(19)

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(20)

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(21)

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FIG. 9 E~LE OF CUMULATIVE DISTRIBUTIONS; FEED, FINE AND COARSE.

(22)

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(23)

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(24)

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(25)

(26)

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(27)

UTIAS Technical Note No. 227

Institute for Aerospace Studi es, Uni vers ity of Toronto (UTlAS)

4925 Dufferin Street, Downsview, Ontario, Canada, I~3H 5T6

PERFORWINCE OF THE UNIVERSlTY OF TORONTO INFRASIZER MK III AS A MONOSIZER

ANO KIL Tl-CUT CLASS 1 Fl ER

von Flotcw, A. H., Etkin, B.

I. Air classifiers 2. Powder technology 3. Particle separation

I. von Flotow, A. H., Etkin, B. 11. UTIAS Techni ca I Ilote No. 227

~

This paper presents results of a series of experiments conducted to define the performance

of the Infrasizer MK lIl. For free-flowing spherical partieles in the range tested (50 to

230 ",m), the performance, .both 'as a multi-cut device and in monosize production, is excellent.

The sharpness of cut index is only a few percent higher than the ideal value of 1.00 and

monosize fractions can be produced with standard deviation about 4% of the average diameter.

UTiAS Technical Note No. 227

Institute for Aerospace Studies, University of Toronto (UTlAS)

4925 Dufferin Street, Downsview, Ontario, Canada, M3H 5T6

ANO JoIJL Tl-CUT CLASS 1 FI ER

von Flotow, A. H., Etkin, B.

1. Air classifiers 2. Powder technology 3. Particle separation

I. von Flotow, A. H .. Etk1n, B. Il. UTlAS Technical Note Ilo. 227

~

Thi spaper presents resul ts of a ser i es of experiments conducted to defi ne the performance of the Infrasizer MK ll1. For free-flowing spherical partieles in the range tested (50 to

230 !!m), the performance, .both 'as a multi-cut device and in monosize production, is excellent.

monosize fractions can be produced with standard deviation about 4% of the average diameter.

Available copies of th is report are limited. Return this card to UTIAS, if you require a copy. Available copies of this report are limited. Return th is card to UTIAS, if you require a copy.

Institute for Aerospace Studies, University of Toronto (UTIAS) 4925 Dufferin Street, Oownsvi ew, Ontari 0, Canada, M3H 5T6

PERFORWINCE OF THE UNIVERSlTY OF TORONTO INFRASIZER MK III AS A MONOSlZER

ANO KlLTI-CUT CLASSIFIER von Flotow, A. H., Etkin, B.

1. Air classifiers 2. Powder technology 3. Particle separation

1. von Flotow, A. H., Etkin, B. Il. UTIAS Technical Note No. 227

~

Th1 spaper presents resul ts of a seri es of experiments conducted to defi ne the performance of the Infrasizer MK lIl. For free-flow1ng spherical particles in the range tested (50 to 230 !!m), the performance, .both 'as a multi-cut device and in monosize production, is excellent.

monosfze fractions can be produced with standard deviation about 4% of the average diameter.

Institute for Aerospace Studies, University of Toronto (UTIAS) 4925 Dufferin Street, Downsview, Ontario, Canada, M3H 5T6

AND KIL Tl-CUT CLASS 1 FI ER

von Flotow, A. H .. Etkin, B.

1. Air classifiers 2. Powder technology 3. Partiele separation

1. von Flotow, A. H .. Etkin, B. 1I. UTIAS Technical Note No. 227

~

This paper presents results of a series of experiments conducted to define the performance of the Infrasizer MK lIl. For free-flowing spherical particles in the range tested (50 to 230 !!m), the performance, .both 'as a multi -cut device and in monosi ze production , is excell ent.

The sharpness of cut i ndex is only a few percent hi gher than the ideal val ue of 1.00 and monosize fractions can be produced with standard deviation about 4% of the average diameter.

(28)

UTIAS Technica1 Note No. 227

Institute for Aerospace Stud; es, U·ni versi ty of Toronto (UTIAS)

PERFORMANCE OF THE UNIVERSITY OF TORONTO IrlFRASIZER MK 111 AS A MONOSIZER

AND ttJLTl-CUT CLASSIFIER

v!ln Flot!lw, A. H .. Etkin, B.

1. Air chssifiers 2. Powder techno1ogy 3. Partic1e separation

I. von F1otow, A. H., Etkin, B. 11. UTIAS Technica1 flote No. 227

~

This paper presents results of a series of experiments conducted to define the performance

of the Infrasizer MK 111. For free-flowing spherical particles in the range tested (50 to

230 Ilm), the performance, .both·as a multi-cut device and in monas1ze production, 1s excellent.

The sharpness of cut index is on1y a few percent higher than the 1deal va1ue of 1.00 and

monosi ze fracti ons can be produced with standard devi ation about 4% of the average di ameter.

Insti tu te for Aerospace Studi es, Uni vers i ty of Toronto (UTIAS) 4925 Dufferin Street, Downsvi ew, Ontari 0, Canada, M3H 5T6

•

PERFORMANCE OF THE UNIVERSlTY OF TORONTO INFRASIZER MK 111 AS A MONOSIZER

AND MUL TI-CUT CLASSIFIER von Flatow, A. H., Etkin, B.

1. Air c1assifiers 2. Powder techno10gy 3. Partic1e separation

I. van F10tow, A. H., Etkin, B. 11. UTIAS Technica1 Note tlo. 227

~

This paper presents results of a series of experiments conducted to define the performance of the Infrasizer MK 111. For free-f1owing spherica1 particles in the range tested (50 ta

230 !lID), the performance, .bath 'as a multi -cut device and in monosi ze production , is excell ent.

The sharpness of cut index is on1y a few percent higher than the idea1 va1ue of 1.00 and monosize fractions can be produced with standard deviation about 4% of the average diameter.

Available copies of this report are limited. Return this card to UTIAS, if you require a copy. Available copies of this report are limited. Return this card to UTIAS, if you require a copy.

Institute for Aerospace Studies, University of Toranto (UTIAS)

PERFORMANCE OF THE UNIVERSITY OF TORONTO IflFRASIZER MK 111 AS A MONOSIZER

ANO MULTI-CUT CLASSlFlER

von F1otow, A. H., Etkin, B.

1. Air c1assifiers 2. Powder techno1ogy 3. Partic1e separation

I. von F1otow, A. H., Etkin, B. 11. UTlAS Technica1 Nate tla. 227

This paper presents results of a series of experiments canducted to define the performance

of the Infrasizer MK lIl. For free-f1owing spherica1 partieles in the range tested (50 ta

~

230 !lID), the performance, .bath 'as a mu1ti-cut device and in monosize production, is excellent. The sharpness of cut index is on1y a few percent higher than the idea1 va1ue of 1.00 and monosize fractions can be produced with standard deviation about 4% of the average diameter.

Jnstitute far Aerospace Studies, University of Toranto (UTIAS) 4925 Dufferin Street, Oownsview, Ontario, Canada, H3H 5T6

PERFORMANCE OF THE UNIVERSITY OF TORONTO INFRASIZER MK III AS A MONOSIZER

AND MULTI-CUT CLASSIFIER

von F1otow, A. H., Etkin, B.

1. Air c1assifiers 2. Powder techno1ogy 3. Partiele separation

I. van F1otow, A. H .. Etkin, B. 11. UTIAS Technica1 /lote No. 227

~

This paper presents resu1ts of a series of experiments conducted to define the performance of the Infrasizer MK 111. For free-f1awing spherica1 particles in the range tested (50 to

2301lm). the performance, .bath 'as a multi-cut device and in monosize production, is excellent.

The sharpness of cut index is on1y a few percent higher than the idea1 va1ue of 1.00 and monosize fractions can be produced with stand~rd deviation about 4% of the average diameter.