28937 deinking plant.pdf

8/18/2019 28937 deinking plant.pdf

1/18

DEVELOPMENT

O F

A

TOTAL

CLOSED

WATER

SYSTEM

FOR

A

D E I N K I N G PLANT

Milos Krof ta ,

P.E . ,

Ph.D., President

Krof t a Engin eering Corp orat io n, Lenox, MA 01240

U S A

Lawrence

K.

Wang,

P.E.,

Ph.D., Manager

LenOX

I n s t i t u t e

f o r Research Inc . , Lenox, MA

0 1 2 4 0 USA

ABSTRACT

Waste paper i s recyc led as pu lp f o r rep roduc t ion o f pape rs

o r b oa rd s . The p u l p c o n t a i n i n g sec on d ary f i b e r s n ee ds t o

be p u r i f i e d i n a d e in ki ng p l a n t .

A

t o t a l c l o s e d w ate r

system has now been developed f o r water rec lam atio n i n

de ink ing p l an t s . The pu lp wi th ink s i s f i r s t p rocessed

w it h a foaming u n i t (Foamer) and th en a washing un i t (Stock

Washer). The was te wat er i s c l a r i f i e d by a d i s s ol v e d a i r

f l o t a t i o n c l a r i f i e r ( S u p ra c el l ) f o r wa ter r ec lam ati on . A

f r a c t i o n a t o r ( S p r a y F i l t e r ) i s a d d i t i o n a l l y u se d f o r

recovery of

long

f i b e r s f rom washing water . The s ludg e

i s

thi cke ned on a th ic ke ne r (Twin Wi rep res s) . The newly

deve loped wa te r rec lama t ion and de ink ing sys tem i n I t a l y i s

h i g h l y e f f i c i e n t a nd c o s t - e f f e c t i v e . For aca dem ic a nd

e n g i n e e r i n g c o n t r i b u t i o n s sp e c i a l e m p h a s i s

i s

p l ac e d on t h e

d e s ig n of i n d i v i d u a l t r e a tm e n t u n i t s and t h e e n t i r e


2/18

The next group of pre se nt wastepaper de in king

1s

c o n s i d e r a b l y

smaller

and used f o r th e produc t ion of t i s s u e

papers . The gen era l t r en d toward a lways hig he r and high er

b r i g h t n e s s a nd s o f t n e s s of t i s s u e p ap er p l a c e s c o n s i d e r a b l e

demand f o r

a

continuous improvement of

t h e

de ink ing

technology

.

With c ons i de ra b l e d i s t a nc e fo l l ows t h e de i nk i ng of p r i n t e d

books with

a

ve ry h i gh ba s i c va l ue of t h e o r i g i na l pa pe r

f i b e r bu t wi t h a l s o ve ry h i gh demand on c l e a n l i n e s s and

b r i g h t n e s s .

For decades two p r i n c ip a l d e inki ng systems have been

competing:

( a )

Foam f l o t a t i o n de i nk i ng , e x t r a c t i ng i nk by

foam. M ineral f i l l e r and pa per f i n e s

a r e

mainly recovered

t h e r e f o r e t h e y i e l d

i s

h i g h b u t t h e p h y s i c a l s t r e n g t h of

t h e d e i n k e d s t o c k

i s

poo r; and (b ) Washing dein ki ng where

i nk , m in era l f i l l e r and f i b e r f i n e s

a r e

washed out

a t

high

d i l u t i o n a n d a papermaking f i b e r of good q u a l i t y

is

o b t a i n e d w i t h s a c r i f i c e of lo we r y i e l d .

Both abov e sy s te m s a r e p r e f e r e n t i a l f o r c e r t a i n w a st ep a pe r

gr ade s and f i n a l uses of de inked s to ck wi thout much

f l e x i b i l i t y t o a d j u s t t o d i f f e r e n t wastepaper g ra de s o r

d i f f e r e n t f i n a l usage.

D E S I G N O F I N D I V I D U A L D E I N K I N G A N D

WATER

RECLAMATION


3/18

F re fe re n t ia l l y and t h e subsequent wash ing can

be

made i n

As

shown

i n

F i g u r e

I,

the Foamer

i s

composed of a sha ll ow

tank 111 with

a

f e e d w e l l [ 2 1 where t he was te paper s lu r r y

en te r s w i th app ro xima te ly

4

bone dry co nsi st en cy . The

p a p e r s l u r r y

i s

d i l u t e d a t t h e e n t ra n c e w it h r ec yc le d

c l a r i f i e d w at er t o a pp ro xi ma te ly

0.8%

consis tency and some

foaming chemica ls a r e added a t t h e

same

spo t .

A

r e c y c l e

pump E31 f e e d s an e j e c t o r

[ 4 1

t h a t d i s ch a rg e s t a n g e n t i a l l y

i n t o t h e t ank

[ 1 1

cr ea t i ng a c i r c u l a r movement of s to ck i n

t h e tank . With a blower [51

a i r i s

added i n t o t h e e j e c t o r

a t low p re ss ur e. T hi s a i r i s d i sp e rs e d i n t h e e j e c t o r and

e n t e r s i n t o t h e t a nk , p ro du ci ng

a

l a r g e amount of foam t h a t

t r a v e l s

on t h e to p of t he c i r c u l a t i n g s tock . The foam

i s

co n t in u o u sly c o l l e c t ed by t h e foam co l l e c t o r [ 6 1 and

ex t r ac te d i n t o th e foam suc t io n tank 171, where a suc t io n

blower holds a l i g h t vacuum. The foam co l l ap se s i n t h e

foam su c ti on tank and

i s

ex t rac ted con t inuous ly by

a

water

lo ck an d d i s ch ar g ed i n t o th e s lu d ge co l l ec t i o n t ank . The

c lean ed s to ck

i s

d i sc h ar g ed i n t h e c e n t e r of t h e t a nk

[ 1 1

a t t h e bot tom open ing and over flows t h e te le sc op ic

a d j u s t a b l e

weir

[ 8 1 . From there i t i s pumped t o t h e

ewer s t a g e s o r c an r e s u l t i n a b r i g h t e r p ulp .


4/18

The e f f l u e n t from t h e t h r e e t h i c k e n i n g p h as e s

i s

s e p a r a t e l y

c o l l e c t e d a nd d i s ch a r ge d i n t o t h e K r o ft a S pray

F i l t e r

f o r

f u r t h e r f i b e r r ec ov e ry . The e f f l u e n t from t h e S pr ay F i l t e r

i s

f i n a l l y d i sc h ar g ed i n t o K r of ta Supracel l f o r

water

t r ea tment and rec lamat ion .

K r o f t a Suprac e l l

A D

i s s o l v e d

A i r

F1o t a t i on C l a r i f i

e y

P ro gr es si ve ly f o r l a r g e i n s t a l l a t i o n s

a

s e p a r a t e S u p r a c e l l

c l a r i f i e r

i s

i n s t a l l e d o n t h e a l k a l i n e p u l p e r - e x t r a c t o r

l o o p for recov ery of chem icals and he at .

F i g u r e 3 shows t h e Sup race l l des ign . The i n l e t 18 and 1 1 1 ,

o u t l e t

[ 2 1 ,

and s l u d g e removal mechanisms [61

a re

conta ined

i n t h e c e n t r a l r o t a t i n g s e c t i o n . T hi s s e c t i o n and t h e

s p i r a l s co op [61 r o t a t e arou nd t h e ta n k a t

a

speed

synchronized wi th the f low.

Waste water,

f i r s t p as si n g

t h r o u g h t h e

a i r

d i s s o l v i n g t u b e , is r e l e a se d t h rough a

r o t a r y j o i n t [51 i n t h e c en t e r of t he t a nk . I t t h e n p a s s e s

i n t o t h e d i s t r i b u t i o n duc t [ 1 1 1 t h a t moves fo rwa rd wi t h t h e

same v e l o c i t y as t h e incoming wa te r th us c r ea t i ng "Zero

V e l o ci t y" . The f l o t a t i o n p r o c e s s e s t a k e p la ce i n t h i s

q u i e s c e n t

s t a t e .

The patented Spiral Scoop [61

t a k e s

up

t h e f l o a t e d s lu d g e , p ou ri ng

it

i n t o t h e s t a t i o n a r y c e nt er

s e c t i o n w h e r e it i s d i sc ha rge d by g r a v i t y fo r d i sposa l .

C l a r i f i e d w a t e r

i s

removed by e x t r a c t i o n p ip e s [91 which

a r e a t t a c h e d t o t h e moving c e n t e r s e c t i o n . The c l a r i f i e d

. .


5/18

sludg e thi cke nin g, and dewatering.

I n o p e r a t i o n , t h e sl u d ge

i s

fed by pump from the sludg

t an k t o t h e v e r t i c a l f l o c c u l a t i o n c ompartment on t o p of t h

pr es s and composed of ad ju s t ab le undula ted p l a t es

F l o c c u l a t in g c h em ic al s a r e f e d i n a lo ng w i t h t h e s lu dg e.

Th e f l o c c u l a t e d s l u d g e l e a v e s t h e f l o c c u l a t i n g c o m p a r t m e n

a t

th e bo ttom and en t e r s t h e ve r t i c a l mix ing compartmen

where m u l t i p l e h o r i z o n t a l p l a t e s g e n t l y a g i t a t e t h e s lu dg e

The wire coming ou t of t h e mixing departm ent i s i n c l i n e

upwards and t h e f i r s t dewa ter ing t a ke s p lace . Then t h

wire with t h e s ludg e t u r n s downward i n t o t h e wedgeshape

compartment composed of two

wires

which squeeze th

sludge between them.

The two

wires

w it h th e slud ge sandwiched between them, ru

wrapped f o r h a l f t u rn a ro un d t h e l a rg e p e r f o ra t e d dru

which i s l o c a t e d a t t h e lower s i d e of t h e p r e s s .

Afte

l e av in g t h e drum, th e doub le

wires

move up around sever

r o l l e r s f o r f u r t h e r d ew at er in g. The r o l l e r s h av

p ro g re s s i v e l y sm a l l e r d i a me t er f o r b e t t e r d ew at er in g.


6/18

Fol lowing such semi- indus t r ia l t e s t s i t can be determine

( a ) The o b ta in ed q u a l i t y of t h e de in ked s to ck ( b r ig h tn e s

c l e a n l i n e s s , m ine ra l f i l l e r s and f i n e s c o n t en t )

(b)

Yie

and f i b e r and f i l l e r l o s s under d i f f e re n t p rocedures ;

(

Consumption of ch em ic al s, power, w ate r and h e a t ; (

S p e c i f i c ca pa ci ty of equipment (pumping t i m e , chemica

a c t i n g t i m e , foaming product ion , c l ea n i ng requirement

s to ck wash in g p a ram e te r s, r e cy c led w ater c l a r i f i c a t i o

requirements , e tc . )

;

( e ) Ov er al l economic as pe ct o f t

d e in k in g ; ( f ) S p e c i f i c d e s ig n of t h e d e in k in g p l an t and th

in d i v i du a l mach ines capac i ty .

The sem i- i ndu s t r ia l de inking p l an t can be use f u l ly opera t

a l s o by chemical companies manufacturing s pe c i a l chemica

f o r d ei nk in g a p p l i c a t i o n i n or de r t o e v a l u a t e t h

performance of t h e new chem ical s.

Su f f ic ie n t amounts of de inked s to ck can be p roduced

order t o make paper sh ee ts on smal l paper machines and

e l ab or a t e th e combina tion of th e s to ck wi t h o th er ra

mater ia l s

.

The de in ki ng p l a n t was des ig ne d wi th a maximum

v e r s a t i l i t y , a ll ow in g d i f f e r e n t c om bi na ti on s of t

de ink ing p rocess .


7/18

;t

is

. f o r t h e se pa ra t i on of coa r se imp ur i t i e s . Su

i m p u r i t i e s sh o u l d b e e x t r a c t e d a h e a d

of

def i b e r i n g a c t i

or

easier

e l i m i n a t i o n .

-

tock Ches t i s provided with slow running

v e r t i c

a g i t a t o r . Req ui re d s t o r a g e of t h e s t o c k

i s

approximate

one hour. I f r equ i red , ad d i t i on a l steam hea t ing can

p ro vi de d i n t h e c h e s ts .

Def lake r I51

Deflaker i s u se d a f t e r t h e s t o c k c h e s t s o r betw een t h e tw

s t o ck c h es t s i n or de r t o f i n e l y s e p a r a te a l l f i b e r bundles

fleadbox

I71

The headbox o ve r t h e Foamer i s used f o r m e te r in g t h e s t o

t o t h e c on ti nu ou s o p e r a t i o n of t h e s u c c e s s i v e p l a n

C l a r i f i e d w a t e r

i s

r ec yc l ed t o d i l u t e t h e s to ck t o

c o n s i s t e n c y r e q u ir e d f o r f u r t h e r p ro c es s i n g. T

consis t ency can be se t between

0.8 1.8%.

Addi t ion


8/18

c l e a n .

Because of t h e l a r g e su r f ac e and low volume t h e r e t e n t i o

t i m e i n t h e Foamer i s low (5-10 minutes).

Cvclon [91

The cyclon i s f o r Foam e x tr a c t i o n and co l la ps i ng , an

d i s c h a r g es c o l l a p s e d foam d i r e c t l y i n t o t h e s l u d g

compartment

[ 151 .

Vibra t ina Screen [l l

T h e v i b r a t i n g s c r e e n i s used t o a d d i t i o n a l l y s c r e en t h

foamed s toc k and e l im ina te coar se r im pur i t i e s

A l t e rn a t el y t h e v i b r a t i n g s c r e e n ca n a l s o

be

used ahead o

t h e Foamer, sc re en in g s t oc k be fo re foaming. The

r e j ec t

a r e f e d i n t o t h e s lu dg e ta nk .

Tr ic lean and Elu r i c o n e [ l l L

They

a re

s u p p l i e d by B i r d Company and

used

f o r a d d i t i o n a

el im in at io n of l i g h t and heavy contaminants . Th

c l ea n l in e s s of t h e d eink ed s to c k

i s as

impor tan t as t h

br ig h t ne ss and removal of th e ink and th e re f o re t h e KrOf

Deinking Plant

i s

prov ided wi th

a l l

p r e s e n t l y a v a i l a b l

s to ck c l ean in g d ev ice s .


9/18

K r o _ f f a a v F i l t e r

1 1 3 1

K r o f t a S p r a y F i l t e r

i s

a f r a c t i o n a t o r t o re co ve r l o n g e

f i b e r s from t h e S tock Washer e f f l ue n t . s uc h e f f l u e n t i

sprayed through a f i n e mesh s cr ee n (100-200 micron)

Longe r f i be r s a r e recovered and added t o t h e de inked s tock

A t l a r g e r i n s t a l l a t i o n s t h e f i b e r recov ery i s o

co ns id er ab le economical importance.

The Sto ck Washer doe s no t form a mat and t h e r e f o r e washe

o u t t h e c o l l o d i a l in k p a r t i c l e s and m in er al

f i l l e r

an

f i n e s , f a r b e t t e r t h a n any drum t h i c k e n e r or d i s c f i l t e

t h a t a lw ay s fo rm s a mat a nd r e t a i n s c o l l o i d a l i nk i n t h

st oc k. However a t t h e same

time

some longer f i b e r s e scap

and s uch f i b e r s a r e re c ove re d w it h t he K r o ft a Spra y F i l t e

t h a t i s a ra th er ine xpe nsiv e machine.

K r o f t a

SuDrace l l

C l a r i f i er [14L

T h e K r o f t a S u p r a c e l l C l a r i f i e r i s i l l u s t r a t e d i n Figure 3

The Suprace l l i s widely used i n many of th e l a r g e s

de inking p l a n t s ove r t he world and

i s

a n e s s e n t i a l p a r t

o

su ch d ei nk in g i n s t a l l a t i o n s . With t h e S u p r a c e l l a l l S to c

. .


10/18

(NTIS-PB82-154196)

Wang,

L. K . ,

" Inves t iga t ion and Des ign . of

A

D e n i t r i f i c a t i o n F i l t e r " , C i v i l E ng ine er i ng f Ort

, Vole 3, p. 347-362,

1984. (NTIS-PB82-199803)

Krofta

M.

and

L.

K. Wang, "Design of Di ss o lv ed A i r

F l o t a t i o n S ystems f o r I n d u s t r i a l P re t re a tm e n t and

Municipal Wastewater Treatment--Design and Energy

Considerat ions", American

m

Enaineers . Na t i o n a l Conference, Houston, Texas, March

27-31, 1983 3 0 pages. (NTIS-PB83-232868)

Krof ta ,

M.

and

L. K.

Wang, "Design of Diss o lv ed

A i r

F l o t a t i o n Systems f o r I n d u s t r i a l P re t re a tm e n t a nd

Municipal

Wastewater

Treatment--Case Hi st or y of

P r a c t i c a l A p p l i cations

,

American

I n s t i t u t e o f

C h c0 o e

ce,

Houston,

Texas, March 27-31, 1983

,

25 pages.

Krof ta ,

M . , L. K .

Wang,

B. C.

Wu and

C. C. J.

Bien,

"Recent

Advances i n Ti tan ium Dioxide Recovery, F i l l e r

Re ten t ion and Whi te

Water

Treatment",

U.S. Dept.

of

Commerce, Nat iona l Techni cal Info rma tion Se rv ic e,

(

NTIS-PB8 3

-

23 2 85

0

3 .

4.

5.

6.


11/18

13.

Dalpke, H. L., " Sp ec ia l D i f f i c u l t i e s wi th E n t i

Closed

Water

C i r c u i t s " ,

D a s

Pap

iec,

( June ) :

1 4 . S t r e e k i n , L E., "Water Reuse i n a Paper Reproces

P l a n t

,

EPA-600/2-76-232, (Oct ober 19 76 ) .

15 . Spr inge r , A. M . , "The R el a t io n be tween Pr ocess W

Q u a l i t y C h a r a c t e r i s t i c s and I t s Reuse P o t e n t i a l

Combination Board

M i l l s ,

W

B u l l

e t i n ,

N o .

2

(September 1975).

16. Ladmiral ,

D.,

" La So c i e t e D e s Usines Royeres Suppr

S a P o l l u t i o n A Uzerche", H'Eau

e

t L ' Environm

( J u n e ) : pp. 8-12, (1975).

17 .

GUSS

D.

B.,

"Closed

Water

Sys tems i n

M i l l s

U

Secondary Fiber

,

s e c o n d a r v F i b e r s

C

onf

erenc

e, Nov. 1977.

236-240, (1975) .


12/18

a

N

F i g u r e 1

K r o f t a F o a m e r - - D i s p e r s e d A i r

F l o t a t i o n

D e i n k i n q

C e l l


13/18


14/18

W

UJ

a

1

ROTAT ING CENTER SECTION

2 CLA RIFIED WATER OUTLET

3 SETTLED SLUDGE SUMP A D lAMETERofSUPRACELL

4

SETTLED SLUDGE OUTLET

B

DEPTHofSUPRACELLTANK

5

ROTARY CONTACT C DEPTH of SUPRACELLTANKw i thB OTTOMSUPPORT

6 SPIRAL SCOOP D MINI MUM OVERA LL HElGHTof SUPRACELL

7 FLOATED SLUDGE OUTLET

8

UNCLARlFlED WATER INLET

9

CLA RIFIED WATER EXTRACT ION PIPES

1

GEAR MOTOR

11

DISTRIBUTION DUCT

Figure 3.

Krof ta Suprace l l - -Dissolved Air F l o t a t io n C l a r i f i e r


15/18

W

W

m

F i g u r e

4.

S p ra y F i l t e r F i g u re

5.

Twin

Wirepress


16/18

C Y C L O N

3

m

I

I

i

i

L. .

H O M O G E N I Z A T O R S C R E E N ;

T

R I C

1E

A N S

f


17/18

I


18/18

1 11

12

Figure

8.

Over V i e w

of

A Semi-Industrial Deinking Plant in Italy

28937 deinking plant.pdf

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