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
8/18/2019 28937 deinking plant.pdf
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
8/18/2019 28937 deinking plant.pdf
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 .
8/18/2019 28937 deinking plant.pdf
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
. .
8/18/2019 28937 deinking plant.pdf
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.
8/18/2019 28937 deinking plant.pdf
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 .
8/18/2019 28937 deinking plant.pdf
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
8/18/2019 28937 deinking plant.pdf
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 .
8/18/2019 28937 deinking plant.pdf
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
. .
8/18/2019 28937 deinking plant.pdf
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.
8/18/2019 28937 deinking plant.pdf
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) .
8/18/2019 28937 deinking plant.pdf
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
8/18/2019 28937 deinking plant.pdf
13/18
8/18/2019 28937 deinking plant.pdf
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
8/18/2019 28937 deinking plant.pdf
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
8/18/2019 28937 deinking plant.pdf
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
8/18/2019 28937 deinking plant.pdf
17/18
I
8/18/2019 28937 deinking plant.pdf
18/18
1 11
12
Figure
8.
Over V i e w
of
A Semi-Industrial Deinking Plant in Italy