Hydrocyclones for Size Classification in Continuous Crystallizers

Chapter 10

Hydrocyclones for Size Classification in Continuous Crystallizers 1

2

1

Johan Jager , Sjoerd de Wolf , Herman J. M. Kramer , and Esso J. de Jong 1

1

2

Downloaded by UNIV LAVAL on July 12, 2016 | http://pubs.acs.org Publication Date: September 21, 1990 | doi: 10.1021/bk-1990-0438.ch010

Laboratory for Process Equipment and Laboratory for Measurement and Control, Delft University of Technology, Mekelweg 2, Delft, Netherlands

The experimental results reported in this paper demonstrate the ability of a flat-bottom hydrocyclone to separate the coarse fraction of ammonium sulfate crystals from a slurry which contains crystals of a wide size range. It appears that the grade efficiency curve, which predicts the probability of a particle reporting to the underflow of the cyclone as a function of size, can be adjusted by a change in the underflow diameter of the hydrocyclone. These two observations lead to the suggestion to use hydrocyclone separation to reduce the c r y s t a l size distribution which is produced in crystallisers, whilst using a variable underflow diameter as an additional input for process control. The number o f i n p u t s w h i c h a r e a v a i l a b l e f o r c o n t r o l l i n g c r y s t a l l i s a t i o n p r o c e s s e s i s l i m i t e d . Possible inputs for a continuous evaporative c r y s t a l l i s a t i o n p r o c e s s a r e , c r y s t a l l i s e r temperature, r e s i d e n c e time and rate of evaporation. These inputs affect the c r y s t a l s i z e d i s t r i b u t i o n (CSD) through o v e r a l l changes i n the n u c l e a t i o n r a t e , the number of new c r y s t a l s per u n i t time, and the growth r a t e , the increase i n l i n e a r s i z e per u n i t t i m e , and t h e r e f o r e do n o t d i s c r i m i n a t e d i r e c t l y with r e s p e c t to s i z e . Moreover, i t has been observed t h a t , f o r a 970 l i t r e continuous c r y s t a l l i s e r , the e f f e c t o f the residence time and the production rate i s l i m i t e d . Size c l a s s i f i c a t i o n , on the other hand, does a l l o w d i r e c t manipulation of the CSD. ( 1 ) Fines removal, the s e l e c t i v e removal of small c r y s t a l s from a w e l l - m i x e d c r y s t a l l i s e r , i s g e n e r a l l y used to remove excessive f i n e s , thus increasing the average s i z e . An i n c r e a s e i n the f i n e s r e m o v a l r a t e immediately reduces the number o f s m a l l c r y s t a l s contained i n the reactor. (2) Product c l a s s i f i c a t i o n , the s e l e c t i v e removal of the large c r y s t a l s as the product, i s generally used to reduce the c o e f f i c i e n t of v a r i a t i o n (CV) of the c r y s t a l s produced. O097-6156/90/0438-O130$06.00/0 © 1990 American Chemical Society

Myerson and Toyokura; Crystallization as a Separations Process ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

10.

Hydrocyclonesfor Size Classification

JAGER ETAL.

m nu CV = / C - 2 " 1

where

t

1

3

1

0

0

131

%

h

m. = j

moment of the c r y s t a l s i z e d i s t r i b u t i o n

Usually, this (L50m) (1).

also results

i n a s m a l l e r mass based average s i z e

m

4

L50m = — m


3

As a r e s u l t of the s e l e c t i v e removal o f the l a r g e s t c r y s t a l s , the s p e c i f i c surface area tends to increase, which imposes a decrease i n the c r y s t a l growth r a t e and e v e n t u a l l y causes a decrease i n the average c r y s t a l s i z e . Therefore a product c l a s s i f i c a t i o n step should preferably be combined with fines removal. C o n v e n t i o n a l l y , an annular s e t t l i n g zone separated by a b a f f l e from the well-mixed region o f the c r y s t a l l i s e r i s used f o r f i n e s r e m o v a l (2) . A l a r g e s e t t l i n g a r e a i s u s u a l l y needed f o r the combination o f a low cut s i z e and a l a r g e f i n e s r e m o v a l r a t e , whereas a minimum h e i g h t i s required to minimise the influence of t u r b u l e n c e i n the mixed r e g i o n o f the c r y s t a l l i s e r (3.) • T h e s e r e q u i r e m e n t s i n c r e a s e the c r y s t a l l i s e r volume s i g n i f i c a n t l y . Furthermore the separation c h a r a c t e r i s t i c s cannot e a s i l y be changed a f t e r the plant construction. P r o d u c t c l a s s i f i c a t i o n i s g e n e r a l l y r e a l i s e d by p r o d u c t discharge through an e l u t r i a t i o n l e g which also serves as a washing s t e p to remove contaminated mother l i q u o r . The stable operation of such an e l u t r i a t i o n l e g i s d i f f i c u l t and the s e p a r a t i o n e f f i c i e n c y i s unsatisfactory. Previous results (1) show that values of both the average s i z e and the c o e f f i c i e n t of v a r i a t i o n i n the product stream delivered from the e l u t r i a t i o n l e g d i f f e r e d only s l i g h t l y from those i n the c i r c u l a t i o n mains i n a f o r c e d c i r c u l a t i o n p i l o t p l a n t c r y s t a l l i s e r , as i l l u s t r a t e d i n Table 1. There i s a c l e a r need for other s i z e c l a s s i f i e r s which combine a h i g h s e p a r a t i o n e f f i c i e n c y w i t h f l e x i b i l i t y and compactness. Hydrocyclones have a small volume, are simple i n o p e r a t i o n and are s t a n d a r d s i z e c l a s s i f i c a t i o n equipment, f o r example i n c l o s e d c i r c u i t grinding a p p l i c a t i o n s . The recent development o f the f l a t bottom hydrocyclone, which permits c l a s s i f i c a t i o n i n the coarse s i z e r a n g e , c r e a t e s an a d d i t i o n a l m o t i v e t o s t u d y t h e u s e o f h y d r o c y c l o n e s f o r C r y s t a l S i z e D i s t r i b u t i o n (CSD) c o n t r o l . Furthermore, t h r o t t l i n g o f a f l a t botom h y d r o c y c l o n e d o e s n o t n e c e s s a r i l y provoke blockage but allows continuous control of i t s cut s i z e when a c o n t r o l l e d t h r o t t l i n g v a l v e i s u s e d . There i s a c l e a r incentive for i t s use i n t h i s a p p l i c a t i o n since i t may provide an a d d i t i o n a l process input. This paper presents the grade-efficiency curves of a 75 nmi f l a t bottom cyclone (RWB 1613) p r o v i d e d by the Amberger K a o l i n Werke (AKW). I t i s tested for the ammonium sulfate-water system f o r both f i n e s removal and p r o d u c t c l a s s i f i c a t i o n . I t s r e s u l t s w i l l be compared w i t h the r e s u l t s for fines removal obtained when using an


CRYSTALLIZATION AS A SEPARATIONS PROCESS

132

Table 1: Classification results by Grootscholten L50m product pm.

RUN


80.4.1 80.4.2 80.9.1 80.9.2 80.17.1 80.17.2 80.18.1 80.19.1 80.19.2 80.20.1 80.20.2 80.21.1 80.21.2 80.21.3

380 431

367 397 415 435

CV product %

22 21

24

420 405

23 23 28 26 24

410

30

435 380

31 22

400

24

395 350

23 25

L50m mains pm.

CV mains

370

24 34 26

412 350

388 400 405 395 382 365 415 362 365 385

340

%

24 26 32 35 29 35

30 29 30 27 27

SOURCE: Data arefromref. 1. annular zone cyclone feed investigated active inputs

s e p a r a t o r . I n a d d i t i o n , the e f f e c t o f v a r y i n g the flow as w e l l as the apex diameter o f the cyclone are i n o r d e r t o p r e d i c t whether o r not these c o u l d be i n CSD-control.

Theory P r i n c i p l e Of O p e r a t i o n . F i g u r e 1 demonstrates schematically the working p r i n c i p l e s o f a h y d r o c y c l o n e . T h e f e e d f l o w i s f e d t a n g e n t i a l l y to the upper part o f the hydrocyclone where i t forms a primary vortex along the inside o f the wall and l e a v e s through the underflow. Since the underflow i s t h r o t t l e d , only part o f the stream i s discharged as underflow, carrying the coarse s o l i d s o r even a l l of the s o l i d s w i t h i t . Most o f the l i q u i d from which the coaser s o l i d s have been removed by the c e n t r i f u g a l a c t i o n o f the primary v o r t e x , l e a v e s through the o v e r f l o w forming an upward s p i n n i n g secondary vortex. In t h i s secondary vortex a separation a g a i n takes p l a c e and the e j e c t e d f i n e p a r t i c l e s move r a d i a l l y , r e - j o i n the primary vortex, and are mainly discharged through the underflow. The s e p a r a t i n g c h a r a c t e r i s t i c s a r e i n f l u e n c e d by both the c y c l o n e geometry and the operating conditions. T h r o t t l i n g the underflow o r i n c r e a s i n g the o v e r f l o w diameter usually r e s u l t s i n a coarser cut s i z e f o r a given cyclone whereas increasing the f e e d flow tends t o decrease the cut s i z e with a corresponding increase i n the pressure drop. A number o f t h e o r i e s have been developed t o d e s c r i b e and p r e d i c t t h i s b e h a v i o u r , b u t e x p e r i m e n t a l t e s t s a r e necessary to determine the operating c h a r a c t e r i s t i c s f o r a s p e c i f i c a p p l i c a t i o n . The p r e s e n t a t i o n o f such experimental data i s the purpose o f t h i s paper. For background information the reader i s referred t o reviews g i v e n i n (4) (5J (6) and i n t h r e e conference proceedings (J_) (8)

(2).



JAGER ETAL.


Underflow Figure 1: The working p r i n c i p l e s of a f l a t bottom hydrocyclone.


133



134

C i r c u l a t i n g Bed C l a s s i f i e r . A f l a t bottom hydrocyclone or c i r c u l a t i n g bed c l a s s i f i e r (CBC) i s chosen f o r t h i s a p p l i c a t i o n because o f i t s reported c a p a b i l i t y to separate at a coarse cut s i z e and i t s improved c o n t r o l a b i l i t y (10). The f l a t bottom (10) reduces t h e v e l o c i t y o f the v o r t e x by w a l l f r i c t i o n . In a d d i t i o n , the i n c r e a s e d s o l i d s c o n c e n t r a t i o n near to the b o t t o m o f the h y d r o c y c l o n e (11) causes an i n c r e a s e i n the e f f e c t i v e v i s c o s i t y . These effects create convection near to the cyclone bottom which i s downwards a t t h e w a l l and upwards i n t h e c e n t r e and which f a c i l i t a t e s the discharge of s o l i d s and prevents blockage when the c y c l o n e i s choked. The s o l i d s concentrate i n the c i r c u l a t i n g flow, thus forming a c i r c u l a t i n g f l u i d i s e d bed. By v a r y i n g the h e i g h t o f t h i s bed a change i n the cut s i z e , by a factor as large as 6, can be achieved for a given cyclone length (10). According to i t s i n v e n t o r (10) t h i s f l u i d bed acts as a r o t a t i n g f l u i d bed i n which the coarse material i s concentrated at the w a l l whereas o t h e r i n v e s t i g a t o r s (12) modify t h i s o p i n i o n by i n c l u d i n g the enhanced s o l i d s mixing effects which adversely e f f e c t the separation e f f i c i e n c y . D e f i n i t i o n s . The p e r f o r m a n c e o f a h y d r o c y c l o n e i s g e n e r a l l y characterised by means of a grade e f f i c i e n c y or Tromp-curve which i s the f r a c t i o n a l mass r e c o v e r y expressed as a function of p a r t i c l e size. Thus, s o l i d s recovery i s defined as: A

s o l i d s underflow s o l i d s feedflow

,

M l

The T r o m p - c u r v e f o r the removal o f coarse p a r t i c l e s w i t h underflow i s defined by: 9

±

;

the

AV(i)

e f f i c i e n c y for i n t e r v a l i •

(2) 0

AV(i)

u +

(1-0)

AV(i)

Q

where AV(i)

Q

= volume f r a c t i o n i n the i

u

* volume f r a c t i o n i n the i

t

h

i n t e r v a l reporting to the

overflow AV(i)

f c

^ i n t e r v a l reporting to the

underflow The e f f i c i e n c y for the removal of fines with the overflow i s defined by: (1-0) AV(i) e f f i c i e n c y at i n t e r v a l i =

(3) 0

AV(i) + (1-0) u

AV(i)

Q

From these grade e f f i c i e n c y curves the nominal cut s i z e , that i s the s i z e w i t h an e f f i c i e n c y of 30%, and the c l a s s i f i e r imperfection can be determined. The imperfection i s defined by:


10.


JAGER ETAL.

Imperfection =

135

!?. 2

(4) d

50

A small imperfection corresponds to a sharp s e p a r a t i o n . W i t h i n the f i e l d o f c r y s t a l l i s a t i o n the s o - c a l l e d c l a s s i f i c a t i o n function i s used to define s o l i d s c l a s s i f i c a t i o n i n terms o f number p o p u l a t i o n densities. n = number o f c r y s t a l s per u n i t s i z e per u n i t volume).


A(i) =

P

r

o

d

u

c

crystalliser

t

(5)

or (AV(i) M s l ) / ( p k c

A (l) =

(4V(±) M s l ) / ( p k c

or

3

L (i)

v

3

L (i)

v

AL(i)) AL(i))

p r Q d u c t

f e e d

(AV(i) Msl) . A(i) = — — Product t

(AV(i)

Msl)

f e e d

where Nsl L(i) AL(i) k P v

c

= = = = =

kilogrammes s o l i d s per cubic meter s l u r r y average s i z e i n i n t e r v a l i i n t e r v a l width volume of c r y s t a l / L c r y s t a l density 3

The shape of t h i s c l a s s i f i c a t i o n function i s i d e n t i c a l to the shape of the grade e f f i c i e n c y curve f o r product c l a s s i f i c a t i o n but the ordinate values are changed. Experimental The experiments were c a r r i e d out i n a 75 mm f l a t bottom cyclone provided by the Amberger Kaolin Werke (RWB 1613). Apexes and v o r t e x f i n d e r s o f s e v e r a l diameters were a v a i l a b l e . The cyclone length could be chosen as 0.25 m, 0.45 m or 0.65 m (Figure 2 ) . The c y c l o n e was fed from a t h e r m o s t a t i c a l l y c o n t r o l l e d s t o r a g e tank using a v a r i a b l e speed mohno pump. The feed flow was measured by a magnetic f l o w m e t e r , whereas the underflow and overflow were measured manually. Samples from the f e e d , under- and o v e r - f l o w were taken m a n u a l l y , f i l t e r e d , dried and subsequently sieved using a set of 20 Veco micro-precision s i e v e s . The e x p e r i m e n t a l s e t - u p i s shown i n Figure 3» P r i o r to a set of experiments, the storage tank was f i l l e d with the product from a 20 l i t r e continuous c r y s t a l l i s e r i n order to ensure s i m i l a r i t y between the separation experiments and the actual working c o n d i t i o n s o f the c y c l o n e . The b a t c h was reproduced f o r every s e t o f experiments because i n the course of time, the fines were p r e f e r e n t i a l l y dissolved. The average s o l i d s c o n c e n t r a t i o n was o f the o r d e r o f 1 - 10 % (m / m ) . Sampling was only started after about 20 minutes o f o p e r a t i o n i n o r d e r to ensure s t e a d y - s t a t e conditions o f the cyclone. 3

3


136


Vortex finder 0160


Vortex finder

X=20mm X=25mm X=30mm

Apex stopper

Apex stopper

10mm 12mm 14mm 16mm

F i g u r e 2: The dimensions hydrocyclone.

( i n mm) o f a RWB 1613

flat


bottom



JAGER ETAL.

Figure 3* The experimental set-up.



138

The r e s u l t s which r e p r e s e n t the use o f an a n n u l a r zone were obtained using a 970 l i t r e continuous evaporative c r y s t a l l i s e r . This c r y s t a l l i s e r was equipped w i t h a f i n e s d i s s o l u t i o n and a r e c y c l e s y s t e m , which a l l o w s the f i n e s d i s s o l u t i o n r a t e to be changed without changing the cut s i z e , by varying the recycle rate (13).


Results A t y p i c a l grade e f f i c i e n c y curve for the product c l a s s i f i c a t i o n step i s g i v e n i n F i g u r e 4. A value of nearly 100 percent i s attained at large s i z e s , whereas normally a value e q u a l to o r l a r g e r than the s o - c a l l e d dead f l u x i s a t t a i n e d at small s i z e s . This i s caused by the d i l u t e d d i s c h a r g e o f the coarse f r a c t i o n . I t r e p r e s e n t s the minimum amount of r e s i d u a l fines i n the product after one separation stage. In f i n e s r e m o v a l , both the cut s i z e and the grade e f f i c i e n c y are d i f f i c u l t to assess because o f the l i m i t e d a c c u r a c y o f the s i e v e a n a l y s i s t e c h n i q u e and the p r o b l e m s i n v o l v e d i n the determination of the s o l i d s concentration i n the overflow. For a .65 m c y c l o n e , w h i l s t u s i n g a 20 mm v o r t e x f i n d e r d i a m e t e r , an apex diameter of 16 mm and a feed flow o f 1.6 1/s, s o l i d s r e c o v e r y i s over 99 %' This recovery corresponds to a cut s i z e between 50 - 100 pm. T y p i c a l d i s t r i b u t i o n s of s i z e by weight, f o r the feed flow as w e l l as the overflow are shown i n Figure 5. Results are summarised i n Table 2.

Table 2; Experimental r e s u l t s and conditions Fines removal

flow [1/s] 1.6

feed c6nc. L50m [um] [*] 6.6

347

CV [X]

flow [1/s]

36

0.4

underflow cone. L50m [*] [um]

28

351

CV

[*] 35

Product c l a s s i f i c a t i o n

flow [1/s]

0.7 0.7 1.4 1.4 2.0 2.0

feed cone. L50m [um] [*]

2.2 3-8 2.4 3.4 2.7 3.0

454 485 361

373 364 371

CV

flow [1/s]

[*] 46 47 47 48 47 46

underflow cone. L50m [um] [%]

0.10

15

0.23 0.15

11 24 21

0.10 0.16

29 31

0.07

apex CV

[*]

468 496 446

43 46 38

425

41

438 424

39 39

10 16 10 16 10 16

In the 970 l i t r e p i l o t p l a n t c r y s t a l l i s e r , w h i l s t using an annular zone, fines are removed at an approximate s i z e o f 50 pm at a c o n c e n t r a t i o n o f 0.03 % (m /m ) at a flowrate of 1.7 1/s. Again, 3

3



10.

JAGER ETAL.


T 800

600

1

139

r 1000

1200

—— Crystal size |m) x K H Figure 4: A t y p i c a l grade e f f i c i e n c y curve for the product c l a s s i f i c a t i o n step.

14000 HE

o Fines + Feed

12000

^ 100008000

400

600

800

1000

1200

1400

— ^ C r y s t a l size [m] x10*

6

Figure 5: T y p i c a l s i z e d i s t r i b u t i o n s by volume, for the feed flow and the o v e r f l o w , i f the h y d r o c y c l o n e i s o p e r a t e d f o r f i n e s removal. The o r d i n a t e v a l u e i s d e f i n e d by volume p e r c e n t a g e divided by i n t e r v a l width.



140


the e f f i c i e n c y cannot be assessed a c c u r a t e l y . F i g u r e 6 shows the t y p i c a l d i s t r i b u t i o n s o f s i z e by weight for the fines removed as well as the product flow of the c r y s t a l l i s e r . The separation i s much sharper than when using the hydrocyclone. However, the differences between an experiment whereby 1.4 1/s of the t o t a l fines flow of 1.7 1/s i s dissolved and an experiment at the same residence time of 1.25 brs without f i n e s d i s s o l u t i o n , are n e g l i g i b l e . T h i s i s p r o b a b l y due to the s m a l l c u t s i z e which i s attained with the present configuration. Increasing the cut s i z e by using an i n s e r t i n the annular zone, may be one method of increasing the e f f e c t of fines removal. In p r o d u c t c l a s s i f i c a t i o n , a 0.25 m cyclone was used. The cut s i z e i s considerably increased to a maximum cut s i z e o f about 400 ym. Figure 7 shows the e f f i c i e n c y curves determined at a flowrate of 0.7 1/s, 1.4 1/s and 2.1 1/s using an apex diameter of 10 mm. These r e s u l t s i n d i c a t e t h a t , at flowrates which are s u f f i c i e n t l y high to transport the p a r t i c l e s i n the o v e r f l o w , the grade e f f i c i e n c y i s r e l a t i v e l y i n s e n s i t i v e for changes i n the flowrate. Figure 8 shows the e f f i c i e n c y curves determined at a flowrate of 1.4 1/s u s i n g the apex diameters o f 10 mm and 16 mm respectively, which i l l u s t r a t e s the v a r i a t i o n which can be obtained by varying the apex-diameter. A moving average f i l t e r , with a window of three points, was applied to reduce the measurement n o i s e i n the s m a l l e r s i z e range i n both F i g u r e s 7 and 8. F i g u r e 9 shows the weight d i s t r i b u t i o n s f o r the feedflow, the underflow and the overflow, at an apex diameter o f 10 mm and a flowrate of 1.4 1/s. At these conditions the difference i n s i z e between the feed flow and the underflow i s most pronounced at a value of 100 pm. The other conditions are l i s t e d i n Table 2. The e f f e c t o f t h r o t t l i n g , i s s i g n i f i c a n t , as i n d i c a t e d i n Figure 8, which indeed suggests that an additional process-input can be created. A s h i f t of the grade e f f i c i e n c y curve o f about p l u s o r minus 50 pm i s found. Discussion F i n e s r e m o v a l . The a n n u l a r zone enables a sharp separation to be made because of the low s o l i d s concentration which p r e v a i l s i n the upper p a r t o f t h i s zone. F u r t h e r m o r e , i t i s a simple separation technique and, as such, i s very successful. As a r e s u l t o f the low cut s i z e , i t s e f f e c t on t h e a v e r a g e s i z e p r o d u c e d i n t h e c r y s t a l l i s e r i s n e g l i g i b l e . At a h i g h e r s o l i d s c o n c e n t r a t i o n a reasonable separation i s also attained using the hydrocyclone. The disadvantage of the annular zone i s i t s large volume, which is .6 m i n t h i s a p p l i c a t i o n as opposed to 0.003 m f o r the hydrocyclone. I f , s i z e c l a s s i f i c a t i o n i s to be a p p l i e d i n a b a t c h c r y s t a l l i s a t i o n operation (14) t h i s might be a serious disadvantage. Furthermore, a hydrocyclone i s more e a s i l y exchanged i f a change i n cut s i z e i s required. 3

3

Product c l a s s i f i c a t i o n . In product c l a s s i f i c a t i o n promising r e s u l t s have b e e n o b t a i n e d . The d i f f e r e n t i a t i o n between underflow and feedflow i s c o n s i d e r a b l e , e s p e c i a l l y i f the performance o f an e l u t r i a t i o n l e g i s considered. Furthermore, an a d d i t i o n a l degree of


10. JAGER ETAL.


141

14000-


E

Figure 6. Typical size distributions by volume for the finesflowand the product flow obtainedfroma 970-L pilot plant crystallizer operated withfinesremoval. The ordinate value is defined by volume percentage divided by interval width.

Figure 7. Three grade efficiency curves for the product classification step at the flow rates indicated, while using an apex diameter of 10 mm.


142



1.0

Figure 8. Two grade efficiency curves for product classification at the apex diameters shown at aflowrate of 1.4 Us.

3500

Figure 9. The volume distributions at aflowrate of 1.4 L/s and an apex diameter of 10 mm. The ordinate value is defined by volume percentage divided by interval width.


10.

JAGER ETAL.


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freedom i s i n t r o d u c e d by a c o n t r o l l a b l e apex d i a m e t e r , w h i c h possibly enables a better control of c r y s t a l l i s e r s to be achieved. Product degradation, after 25 average r e s i d e n c e times i n the combined system o f c y c l o n e , pump and storage tank i s n e g l i g i b l e . However, a disadvantage of the hydrocyclone can be that i t produces a l a r g e amount o f s m a l l n u c l e i by a t t r i t i o n . In the p r e s e n t investigations these fines dissolve p r e f e r e n t i a l l y i n the s t o r a g e t a n k and c a n , t h e r e f o r e , not be d e t e c t e d . Under c r y s t a l l i s i n g conditions the e f f e c t of these fines might be very disadvantageous.


Acknowledgments The outhors wish to thank the Netherlands Technology Foundation (STW), AKZO, DOW, DSN, DUPONT de NEMOURS, RHONE POULENC, SUIKER UNIE and UNIELEVER f o r t h e i r f i n a n c i a l support o f the UNIAK-research programme. The support o f P r o f . D r . H . Trawinsky i n s e l e c t i n g and supplying the AKW hydrocyclone, and the support o f h i s s t i m u l a t i n g d i s c u s s i o n s i s g r a t e f u l l y acknowledged. I r . M. Wouters contributed to t h i s paper during h i s f i n a l year study as an M S c - s t u d e n t , w h i l e J . Koch and J . Weergang from the Hogeschool Utrecht c a r r i e d out a large number of the experiments reported.

Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

Grootscholten, P.A.M.; Jancic S.J., In Industrial Crystallizaton 84, Eds. Jancic S . J . ; DeJong E.J, Elsevier, Amsterdam, 1984; pp 203 - 210. DeLeer, B.G.M., Ph.D. Thesis, Delft University of Technology, Delft, 1981. Grootscholten, P . A . M . , Ph.D. Thesis, Delft University of Technology, Delft, 1982. Rietema, K.; Verver C.G. (Eds.), Cyclones In Industry, Elsevier, Amsterdam, 1961. Bradley, D, The Hydrocyclone, Pergamon, Oxford, 1965. Svarovsky, L . , Hydrocyclones, Technomic, London, 1985. Proc. International Conference on hydrocyclones, Cambridge, 1980. Proc. 2nd International Conference on hydrocyclones, Bath, 1984. Proc. 3rd International Conference on hydrocyclones, Oxford, 1987. Trawinsky, H.F., Filtration & Separation, Jan/Feb 1985. VanDuijn, G.; Rietema, K., Chem. Eng. Science, 1983, 38, pp 1651 - 1673. VanDuijn, G . , Ph.D. Thesis, Delft University of Technology, Delft, 1982. Jager, J.; DeWolf, S.; Kramer, H.J.M.; DeJong, E.J., AIChE Annual Meeting, San Francisco, 1989. Zipp, G.L.; Randolph, A.D., Ind. Eng. Chem. Res., 1989, 28, pp 1446 - 1448.

RECEIVED May 12, 1990


Hydrocyclones for Size Classification in Continuous Crystallizers

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