JONSSON and W I N G

i s i s o f l e s s i nient and f r a c t i o

The u l t r a f i l t r a t i o n process has been employed on a labora tory sca le t o remove s o l i d s from d i l u t e paper m c h i n e w h i t e water (ref.4). A membrane o f suspended s o l i d s of over 99 % was achieved.

The treatment of paper m i l l w h i t e water by membrane f i l t r a t i o n was i n v e s t i - p ted , both on labora tory - and p i l o t - p l a n t scales, i n a c o l l e c t i v e p r o j e c t o r r i e d o u t by t h e Swedish Foundat ion f o r Membrane Technology (ref.5). The

tudied on a labora tory scale. I n a second stage, the i n v e s t i g a t i o n was extended

Reverse osmosis gave a very c l e a n permeate i n the labora tory tes ts . B u t a

neral f i n d i n g o f the l a b o r a t o r y t r i a l s was t h a t tube modules are the o n l y ones

f t ab le for membrane f i l t r a t i o n of paper m i l l wh i te water. And, a t t h e time,

'uctioii

u l t r a f i l t r a t i o n

i e r i n d u s t r y d u r i

. r i a l a p p l i c a t i o n s

i s presented. ResearC'

the Swedish Foundatio

i

l a t i o n i n the pu lp an Packaging Inc, USA

the c losed w h i t e wat

PERMEATE PAPER MACHINE

WHITE WATER

800 L / U I N 7000 L/U IN

10s:

coo: BOO.

XA:

AL:

2 . 5 G / L 2070 HWL 935 U W L 249 U G / L 2 . 3 WG/L

V CONCENTRATE

200 L / U I N

TDS: 2 . 0 G/L COD: 1120 HG/L 800: 835 NG/L Nh: 229 U W L AL: 0 . 7 WG/L

TOS: 4 . 7 G / L COO: 4200 U W L BOD: 1590 H W L NA: 260 UG/L AL: 7 .7 nG/L

z

' ' 9 2 U l t r a f i l t r a t i o n o f paper machine irrhjte water. The riiimbranes used were

*'rdtdre 50°C and the f l o w v e l o c i t y 4.4 m/s.

, b u t changes i n the tem.

I from Paterson Candy I n t ( P C I ) . The opera t ing pressure was 8 bar, the tem-

186 JUNSSON and WIX-tERSTFDT

The treatment of bleach ef f luent w i t h reverse osmosis has been shown t o 1(.,4

a permeate stream of high puri ty ( re f .8) . Membrane re jec t ions of b o t h i norgaqfc

and organic components were above 90 % f o r t o t a l so l ids concentrat ions in the

range 5-30 g / l .

inves t iga ted ( r e f . 9 ) . I n t h i s case RO was used t o remove 90 % of the water frca

a stream continain: 5 g/1 to ta l sol ids . The concentrate was then fur ther c:;c-

cent ra ted by f reeze concentration t o about 200 g/l .

Continuous multi-stage u l t r a f i l t r a t i o n has, however, been demonstrated t 3 be a t echnica l ly and economically feasible colour removal process f o r k r a f t ca:,st ic

e x t r a c t ion ef f 1 uent .

A combination of reverse osmosis and f reeze concentration has a l s o heen

The drawback with these processes, i s t h a t they a re q u i t e expensive.

A long-term f i e l d demonstration of u l t r a f i l t r a t i o n f o r colour rermval hi l i

becn conducted a t Champion InternatiGfial Mill Canton, North Carol ina, ( r e f . i $ j s

The reported r e s u l t s ( r e f s . 11-12] are encouraging, b u t no commercial i n -

s t a l l a t i o n has followed as of today, as a r e s u l t of t h i s work. Pos i t ive rescitt, from u l t r a f i l t r a t i o n of the f i r s t caus t ic extract ion washer on the s o f % w m d .&P#

l i n e a t a French mill have a l so been reported ( re f .13) .

I__--

--_ I-

1733 L I N I N

coo 2200 PPH

-

t (EKA) p u t a la rge p i l o t plar: t a l membrane area was 168 if& 3

ocessed. T h i s ULTRASEP plar l t w15

n J a p a n was p u t i n t o oper i t fon . In January 1981 an U l t r a f i l t r a t i o n plant aas i n s t a l l e d a t the Si i i yo Kffki

Mill , Jtpz!! f e r the concentration of the E-stage eff luei l t fia

1 t r a f i 1 tra t i on pl arr brane a t w of the I; he reduction of COC:

o t a l s o l i n s i s lobe

w o t h e r Japdnfse irii 111 cnt of E-st:ge e t f i c e r r

fit w i t h N i L t o tubular r1t i s t rea ted by UF. 11 t r a t e i s taken bjck i v

heat value of tire cc ne replacement CGst. TI nes was changed a f t e r d t o be two years d u e

-_-_I__ f e f f luent aff - f i rs t f u 1 1 - sca 1 e menib)

i n t o operation i n Ap, n t of an e f f luent h i 9 u l p h i t e mil l . The t o )

factured by P C I , i s e

i w a k r i n i

the k r a f t p u l p production l ines (ref.14-16). The annual capaci ty of th is i:.",p sl

110 000 tons of hleaLhed pulp. The ULTRASEP i n s t a l l a t i o n replaces the C l l 1 f

method of t r e a t i n g bleach ef f luents , using lime prec ip i ta t ion . Polyc.u1Pq02r;Q membranes a r e used and the to ta l membrane area i s 672 m2. The UF plant f.;

tored and cont ro l led by a micro computer from the control panel o f the bft 'KA

plant . Cleaning, i s done once a day, and is control led by the micro cOWUt*r* Fig. 4 gives the operation figures. I n the plant 104 m3/h of bleach e f f i

i s t r e a t e d , giving 13 m /h concentrate which i s returned t o the recowrY $Ysc The permeate may par t ly be used as wash l iquor i n the brown washer but w d l

discharged. Durfng the f i r s t year of operation the reduction of COO in t h e meate stream was reported t o be 82 %, the colour reduction 94 %, and the re t i o n of suspended s o l i d s 100 %. The f i r s t s e t of membranes had a l f f 2 t f r r r

The operat ing cost of the UF p lan t amount t o approximately 2 * % -

3

lars per ton of pulp produced (ref.14).

About 240 000 tons of bleached su lphi te pulp a re produced annitally a t t k c

Domsjo mil l . Previously the wood was s tored i n the form of chips i n chip r * l e a ,

before i t was fur ther processed. During t h i s s torage process, t h e wood m s t . t r 4 a

and the pi tch content decreased. B u t the long s torage time in the chip p l l e : 5

now replaced by mechanical treatment of the pulp in a so-ca l led FROTAPULPih. Through the introduction of the frotapulper the s torage time i n the C ~ I C t i l p

has been reduced, and a t the same time, the s t rength o f the pulp pr0durc.l hie,

increased. The amount o f pitch introduced in to the system has however 1 n c . c t t . p . :

as a r e s u l t of the new process, and the progressive closirlg of the water s j i t f n l

a t the mill has lead t o problems of build-up of unwanted substances, suck as pitch and resins .

I n order t o reduce the pitch level i t has been found t o be necessary to h l c t f

off some of the pitch-rich water. For environmental reasons, t h i s water n,s: :e pur i f ied before i t is released. The i n s t a l l a t i o n o f the u l t r a f i l t r a t i o n i l d n t at the Domsjo m i l l , as shown in Fig.5 has lead t o an 80-85 % reduction in t h e ~ { t c *

l e v e l , as well as a reduction o f 70 % in C O D . During u l t r a f i l t r a t i o n the u f t z h

content increases from 0.5 t o 10 %. The permeate i s rec i rcu la ted througll t4e

bleach plant . The concentrate i s fu ther t rea ted t o obta in 80 % concentratton dnd

i s t h e n taken t o the recovery boi le r .

__.---

f l C C O V E R Y DOIl E R

E V A P O R A T I O N

S C R E E N I N G

Concentrdtion of _ s p ~ z e s o l i d s content of 5 n mil l s . The mayimum

___-_-__

25 %. This i s due ic US only provide a l i i a l s have shown t h a t

a f lux of a b o u t 40 111 6.8 kWh/m3 permeate N

ermeate h a d a s o l i d s c o n t r a s t t o modern r~ s u l p h i t e mil ls i s c((

v i a bl e conc e n t ra t i 0 n

ns are overloaded. TI) 1976 DDS i n s t a l l e d ( (

l a t i o n was fol loded I n Quebec, Cdnada. I I 1a t ioqs. Both cil

S RO modules with a riles with a to ta l 31

t c d from 6 t o 12 %

CONCENTRAlE 1 % )

&ONSUMP T I O N

_..- -..

Concentration 011

nts from De Danskrr

der sulphi te mil ls i s considerably lower. I n these m i l l s reverse osmosis may

stems are overloaded. Two such cases a re Toten and Reed Mil 1 s ( r e f s . 19-22). 11 viable concentration a l te rna t ive in ciijes i&isrc^ exist!ng evapnration

Ctnttated from 6 to 12 % t o t a l so l ids and a t the Reed p lan t from 12 t o 18 %.

&clluloseacetat membranes are used i n both p lan ts . Membrane l i fe t imes of more ;Pia9 a year a re obtained, despite the f a c t t h a t the pH i s on the low s ide of the

.%NSSON and WIMMERSTEDT 189

J %ncentration of spent sulphi te l iquor T ~ Q so l ids content of spent sulphi te l iquor ( S S C ) i s t y p i c a l l y 15-16 I in

n mills. The maximum concentration t h a t can be obtained by reverse osmosis -25 %. This i s due t o the increasing osmotic pressure of t h e solut ion. RO

thus only provide a limited supplement t o evaporation f o r these l iquors . Trials have shown t h a t SSL can be concentrated from 11 t o 22 % t o t a l s o l i d s a a f lux o f about 40 l/m2h. ( ref . 18). The energy consumption was aproxima- 1~ 6.8 kWh/m3 permeate which i s much lower than f o r m l t i - s t a g e evaporation.

permeate had a s o l i d s content of 0.01 % and a COO content of 1100 nig/l. In cont ras t t o modern mil ls the solids content before evaporation i n many

KceDtdble pH range. The membrane cleaning frequency b t h systems.

is 2-6 times a week f o r

1 OTEN R E E D

INSTALLATION YEAR MEMBRANE AREA Id1 CUNF ICURA T I ON PROWCT pn ros FEED I % ) TUS CONCENTRATE I X ) POYER CCNSUUPTION I Kh4i/t? PERHEATE)

1976 332

4 STAGE NH4-SSL 2-2 .5 6-10 12 7 . 5

1978 4413 4 STAGE CA-SSL 3-3.5 10- 12 18 8 . 8

e Domsja H i 1 1 , SWr y I n t . (PC!), hd5

' '9. 6. Concentration of spent sulphi te l iquor . Feautures of the reverse osmo- Plants from De Danske Sukkerfabrikker (DDS) a t Toten and Reed Mills ( re f .21) .

l e v e l i n p o l l u t i o n c h a r a c t e r i s t i c s (BOD, COD, co lou r and so l i ds ) was obtained.

However, a ser ious decrease i n f l u x r a t e due t o f o u l i n g was experienced. F o n l i n p was thought t o be caused by c o l l o i d a l o rgan ics i n the feed.

The concentrat ion o f spent l i q u o r from chemical thermomechanical pulp (CTM?)

by reverse osmosis i s c u r r e n t l y being s tud ied i n a c o l l e c t i v e p r o j e c t by the

Swedish Foundation f o r Membrane Technology. The p r o j e c t i s being c a r r i e d out f n

co-operation w i t h the Swedish Fo res t Products Research Laboratory (STFI ) . 4 t

STFI t h e p o s s i b i l i t y o f t r e a t i n g the RO concent ra te together w i t h black l i q u u r i n a k r a f t black l i q u o r recovery system i s being inves t iga ted .

The reverse osmosis t r i a l s were performed w i t h tube membranes, ZF99, f r o m

PCI. The r e j e c t i o n o f d isso lved s o l i d s by these t h i n - f i l m composite membranes

was high. The q u a l i t y o f the permeate was such t h a t it cou ld be reused as fresh

water. i t was noted t h a t the f l u x was s t rong ly i n f l uenced by the feed tempera-

ture; the f l u x increase was 2 l/m2h per degree Ce lc ius (see Fig. 8). The revei'sc

osmosis experiments demonstrated t h a t a spent l i q u o r w i t h a t o t a l dry solids 2 content o f 1 % can be concentrated t o 5 % w i t h an average f l u x o f 45 l/m h , a t

an w e r a t i n g temperature of 60°C. This p r o j e c t i s t o be continued and the

d e t a i l s o f the work are s t i l l unpublished.

major p a r t o f t he s o l i d s i n spent s u l p h i t e l i q u o r i s l ignosulphonate. The con- pos i t i on var ies w i th the type o f wood pulped and d iges t i ng process, !xi: !:

general SSL contains approximately 60 X l i g n i n , 30 % reducing sugars arid 10 f:

inorganic mater ia ls. Using u l t r a f i l t r a t i o n i t i s poss ib le t o separate the W- i n t o p u r i f i e d f r a c t i o n s o f , i n p a r t i c u l a r sugars and l ignosulphonate ( r e f s . 28-32).

The p u r i f i e d sugars are o f commercial value f o r fermentat ion purposes.

Aerobic fermentat ion processes produce p r o t e i n f o r use as animal feed, and ale@-

hol i s produced by anaerobic fermentat ion. The enr iched l ignosulphonate fr-actiiEl

i s conmercial ly used i n many app l i ca t i ons , such as i n d u s t r i a l detergents, dispersants, p rec ip i t a tes , b inders and'adhesives.

purity o f approximately 80 %. I n combinat ion wi th d i a f i l t r a t i o n a COnCentfatC '' 25 % t o t d l s o l i d s con ta in ing 95 X l i gnosu lphonate i s produced (ref~.19,3!-~ ' ) '

With simple u l t r a f i l t r a t i o n , it i s on ly poss ib le t o ob ta in a lignosulPh~ssir

mechanical pu lp ing proces

a n t produci qg p u r i f iedl

ty is 2 500 tons o f hi44

mbrane area i s 336 m2. A t Borregaard Indus t r -

c t i o n of v a n i l l i n . Sin(<

ed t o produce a cleaneit

I t r a t i o n reiiioves the I C reduce the capaci ty off

onal advaqtage o f reduc:

9 U l t r a f i l t r a t i o n off

Y. The t o t a l solids 11 Paterson Candy In t . ,

process, about

o r i g i n a l raw wood ma en t pu lp ing l i quo r .

the k r a f t (su l phatc )

g process, the l i g n i l l

ock for chemical pro^^

b lack l i q u o r (KBL) s((

Eplaced by another heaR ? the ex t ra processing ii

Ple, i n adhesives.

r i . n $. 3 Z l t r a f i i t r a t i o n o f spent su lphi te l iquor a t Borregaard Indus t r ies ,

b w a y . The t o t a l s o l i d s level i s increased from 8-10 % t o 22 %. The UF p l a n t , ff-%n Paterson Candy I n t . , has a t o t a l membrane area of 1 116 3. The operat ing i'essure i s 10 bar and t h e power consumption 380 kW (ref .37) .

' .2 V l E a f i l t r a t i o n o f k r a f t black l iquor in the k r a f t ( su lpha te) process, which today i s the dominating chemical

:*Jl?ing process, the l ign in occurs as a lka l i l ign in , which can be u t i l i z e d as t~ .,tack f o r chemical processes. however, in removing a lka l i l ign in frore the

t r d f t black l i q u o r (YBL) some o f the heat value i s l o s t (about 35 X ) , a n d has t o replaced by another heat source. The cost o f the product thus has t o pay for

the extra processing and the loss o f eneryy. Alkali lignin can be used, for ' ' I ' D J ~ , in adhesives.

An adhesive (Karatex) from high m l e c u l a r weight l ignin h a s been develop($ ).

the Finnish Pulp and Paper Research I n s t i t u t e ( ref .33,38) . The l ignin i s separated from k r a f t black l iquor by u l t r a f l l t r a t i o n . The fractionatiop, c c :cI

KBL i s car r ied o u t by u l t r a f i l t r a t i o n and d i a f i l t r a t i o n in a s imi la r wa f ract ionat ion of SSL ( re f .39) . A material balance f o r the process i s 9:

Fig. 10. Ultrafiltration-diafiltration on 15 % TUS ( t o t a l dry s o l i d s ) 1 1 q L c r

from pulp washers gives a product with 90 % puri ty in a l k a l i l ign in . Tt , t y i e i d

of t o t a l s o l i d s i s about 25 % and the y i e i d o f l i g n i n about 55 %. Thc ---.--.- ' PL e - .,%

RECOVERY S Y S T E: !.I

from the process, containing 75 % o f the t o t a l s o l i d s and 45 % of the a l k d l ! l ign in , i s returned t o the recovery system for evaporation and combustlo-.

_I."...__

t K R A F T BLACK LlOUOR

200 L/i4lN

Fig. 10 Material balance f o r the u l t r a f i l t r a t i o n o f k r a f t black l f r l u f i r i r c z +

The Karatex-process i s patented, and the patent r igh ts are held by 3 Ft Company, Metsal i i ton Teol l isuus OY ( r e f . 40). A commercial-size plant h3S

ins ta l led i n Finland, a n d i s a 4-module ( 1 6 8 in2) continuous p l a n t w i t h *31

.K. B a n s a l , A I C h E Syii . Eriksson, Meiiibrane 6 (19811, ( i n Swedistt , Sandstram, Treatinerr SVL-85 Report No 18 ( 1 . Sivik and M. Jacob:: SVL-85 Report No 24 / / .J. Simpson and G . R . .J. Wiley, L.E. Dambn roc. (1978) 63-70. .A. Fremont and M . H . .A. Fremont, D.C. Tatt f f l u e n t s by U l t r a f i l tt

A . Fremont and D.J. t r a f i l t r a t i o n , E P A I?? Muratore, M. Pichom

.H. Haagensen, Case S5 nske Sukkerfabrikker

.TRASEP, Sanyo Kokusnj tlallstrijm e t a]. , MI

ternal report by t h e Mizuhara, Y. E l u w t n i

per Plant Wasfe M a t e PFpper and J . ringll . Claussen, 4 t h Int:

agner, I . Chcpn. E . . Clausscn, i861-CB! C 1 au s sen, i4c;nbra n !dflcy, G.A. Duhpyv

u t ian Control Fedeb Kjellberg and P . Cr t r a t i o n , SSVL-pro j m Eviksson, P i l o t P l a

11, RPyor t L I J T K ~ I H / ( r!! E ( . Erikcson, r a i l p i 111 r'ence, Boston (1983)

Eriksson, A I C h E SymII J. Zawielski. S.0. Pi1

SCHtfGERL, A . MOHRMANN, WJ ITUT FUR TECHNISCHE CHE:

00 H a n n o v e r

h e s e p a r a t i o n o f t h e COIT h i n g s o l u t i o n s were car2 e u s i n g d i f f e r e n t Carrie

t h e s e p a r a t i o n of t h e r o c o a l e s c e n c e , t h e y wen

ong t h e s e p a r a t i o r . t ech1 and more i m p o r t a n c e i n

se lect ive w i t h i n p a r t . 1 c o n c e n t r a t i o n s , sol

p o s s i b l e t o overcomff t e c h n i q u e , w!inre a ::

RINCIPLES OF THE L I Q U E

s a q u e o u s o u t e r p h a s e ii i s s e p a r a t e d by a l iqu

t and a n e x t r a c t a n t fro) i n w h i c h a n e n r i c h m e n t m e t a l - e x t r a c t a n t compl

a q u e o u s p h a s e and t h e mi 6 t h e mernbrane and decom