Synthetic Membranes - American Chemical Society

21 Ultrafiltration and Hyperfiltration in the Pulp and Paper Industry for By-Product Recovery and Energy Savings

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 2, 2015 | http://pubs.acs.org Publication Date: May 27, 1981 | doi: 10.1021/bk-1981-0154.ch021

PER H. CLAUSSEN Niro Atomizer, Inc., 9165 Rumsey Road, Columbia, MD 21045

The development work w i t h regard t o a p p l i c a t i o n of DDS-RO(1) membrane filtration systems f o r treatment of e f f l u e n t s from the pulp and paper i n d u s t r y s t a r t e d in Norway in the beginning of 1972. Both l a b and pilot trials were s u c c e s s f u l and a Norwegian patent (2) was granted f o r s e p a r a t i o n of l i g n o s u l f o n a t e from spent sulfite l i q u o r (SSL) by ultrafiltration ( U F ) . In 1974 a major Norwegian manufacturer of lignin products s t a r t e d r e g u l a r p r o d u c t i o n of U F - l i g n o s u l f o n a t e s . The p l a n t has been expanded s e v e r a l times and today the p r o d u c t i o n is some thousand tons per year of product. A c o o p e r a t i o n agreement was made in 1973 between DDS-RO and the F i n n i s h Pulp and Paper Research Institute w i t h the aim t o develop products and processes on the b a s i s o f membrane filtration of e f f l u e n t s from the pulp and paper i n d u s t r y . The coopera t i o n w i t h Dr. Kaj Forss' s e c t i o n a t FPPRI has been very s u c c e s s f u l . For i n s t a n c e , through an extensive development program UF has been found t o be a f e a s i b l e t o o l f o r the p r e p a r a t i o n of lignin f o r the Karatex (3) plywood binder. This adhesive, which is made from ultrafiltered spent sulfite l i q u o r (SSL) o r kraft b l a c k l i q u o r (KBL), can be used f o r partial replacement of the much more expensive petroleum based phenol-formaldehyde r e s i n i n plywood and other wooden boards. The Swedish Company EKA and DDS-RO have worked together on a 2-year l a r g e s c a l e pilot o p e r a t i o n in a Swedish k r a f t mill for c o l o r removal from c a u s t i c e x t r a c t i o n bleach e f f l u e n t by UF (4). The r e s u l t s of the program were s u c c e s s f u l both w i t h regard to c o l o r removal efficiency, reliability and membrane lifetime and the first full s c a l e installation will be made t h i s year in Japan. With the i n c r e a s i n g f u e l p r i c e s , it becomes more and more important t o f i n d energy efficient c o n c e n t r a t i o n methods f o r industrial e f f l u e n t s . H y p e r f i l t r a t i o n (HF).also c a l l e d r e v e r s e osmosis is in s e v e r a l cases the most f a v o r a b l e method. Toten S u l p h i t e Mill in Norway r e a l i z e d t h i s in 1976 when a 0097-6156/81/0154-0361$05.00/0 © 1981 American Chemical Society

In Synthetic Membranes: Volume II; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

362

SYNTHETIC MEMBRANES:

HF

AND

UF

USES

a demand f o r a d d i t i o n a l water removal c a p a c i t y occurred, and they i n s t a l l e d a HF-system. Over the years s u b s t a n t i a l f u e l savings have been made. So f a r t h i s paper has been d e a l i n g w i t h the past. The t a b l e below shows the s i t u a t i o n today w i t h regards to DDS-RO i n s t a l l a t i o n s i n the pulp and paper i n d u s t r y . At the end of 1980 about 30,000 f t . of membrane area of DDS make w i l l be i n o p e r a t i o n i n t h i s i n d u s t r y . By-product c a p a c i t y w i l l be 15,000-20,000 tons per year of product s o l i d s by UF. Water removal c a p a c i t y i s approximately 100,000 g a l l o n s per day.


2

2

Main Features of the Systems. The 450 f t . h o r i z o n t a l mounted module UF 35-42 and the 300 f t . v e r t i c a l module HF 40-28 are the key components of the described systems, shown i n f i g u r e 2 and 3. Both the UF and the HF systems are m u l t i s t a g e continuous p l a n t s according to the concept on f i g u r e 4. Process c o n t r o l concept i s simple but e f f i c i e n t and r e l i a b l e , w i t h thermostatic c o n t r o l of supply of steam or c o o l i n g water to the heat exchangers and f l o w / s o l i d s c o n c e n t r a t i o n c o n t r o l e i t h e r on b a s i s of i n - l i n e refractometer at the end of the system or r a t i o c o n t r o l between feed and concentrate flow. F i g u r e 5 i s showing a t y p i c a l U F - i n s t a l l a t i o n i n the pulp and paper i n d u s t r y at Iggesund K r a f t M i l l i n Sweden. Figure 6 i s showing the H F - i n s t a l l a t i o n at Toten S u l p h i t e m i l l i n Norway. Membranes of v a r i o u s polymer m a t e r i a l s are used i n the UF systems a l l o w i n g o p e r a t i n g temperatures up to 190°F and pH from 0 to 14, which i s f a v o r a b l e when o p e r a t i n g on p u l p i n g e f f l u e n t s that e i t h e r are i n the upper or the lower end of the pH-range and w i t h temperatures c l o s e to the l i m i t s f o r the system. The systems a l s o a l l o w c l e a n i n g w i t h strong a l k a l i n e or a c i d chemicals, a l s o oxydants as H 2 O 2 and NaOCl which i n some cases i s necessary to keep the membranes s u f f i c i e n t l y clean i n the long run. For HF c e l l u l o s e acetate membranes are used s e t t i n g l i m i t s f o r temperature, 85°F, as w e l l as f o r pH, 2.5 to 8.0. S t i l l with those l i m i t a t i o n s i t i s p o s s i b l e to keep the systems at an accept ably high performance l e v e l f o r extensive periods of time, when o p e r a t i n g on spent s u l p h i t e l i q u o r . A proper p r e f i l t r a t i o n of the l i q u i d s i s r e q u i r e d and i s mainly done i n a s e l f - c l e a n i n g r o t a r y drum f i l t e r w i t h a 25micron web. 2

A p p l i c a t i o n s , Experience. U l t r a f i l t r a t i o n of SSL. This processing has been going on on a r e g u l a r commercial b a s i s s i n c e 1974 f o r manufacture of l i g n o s u l f o n a t e products w i t h a l i g n o s u l f o n a t e content i n the 90%+ range ( 5 ) . Not only the l i g n o s u l f o n a t e content of the product i s of importance, o f t e n a l s o the molecular


21.

CLAUSSEN

UF and HF in the Pulp and Paper Industry


Yr. I n s t a l l e d 1974-1979 1976 1978 1978

Country Norway Norway N.America Canada

Product Lignosulfonates NH4-SSL Lignosulfonates Ca-SSL

Under C o n s t r u c t i o n 1980 UF 1980 UF 1980 UF

Finland Finland Japan

Kraft liquor Lignosulfonates Kraft bleach effluent

Larger P i l o t 1978 1980 1980

Sweden Italy Argentina

Kraft bleach e f f l u e n t Ca-SSL NSSC waste l i q u o r

Figure 1.

Figure 2.

System UF HF UF HF

Plants UF HF HF

DDS-Ro installations in the pulp and paper industry

2

The 450-ft horizontally mounted UF module UF 35-42


363


364

SYNTHETIC

MEMBRANES:

HF

AND U F

2

Figure 3. The 300-ft vertical HF module HF 40-28


USES


CLAUSSEN


Figure 4. Continuous membrane filtration system

Figure 5. Typical UF installation at Iggesund Kraft Mill in Sweden


365


366

SYNTHETIC

MEMBRANES:

HF

AND

UF

USES

weight d i s t r i b u t i o n of the l i g n o s u l f o n a t e , F i g u r e 7, i s showing the molecular weight d i s t r i b u t i o n of the l i g n o s u l f o n a t e i n SSL and i n the two f r a c t i o n s from UF, the concentrate and the f i l t r a t e ( 6 ) . The l i g n o s u l f o n a t e s from UF are mainly used as dispersants. I t took a few years before the modules, the membranes, pretreatment and membrane c l e a n i n g procedures were s u f f i c i e n t l y developed, but today the UF systems operate as s t e a d i l y and r e l i a b l e as other u n i t o p e r a t i o n s i n t h i s i n d u s t r y . The process concept i s simple and energy e f f i c i e n t , the pumps are the only moving p a r t s . No chemicals r e q u i r e d f o r the o p e r a t i o n except f o r minor q u a n t i t i e s of harmless c l e a n i n g agents. Membrane c l e a n i n g frequency i s mainly once every one or two days. L i f e t i m e expectancy, based on l a t e s t experience i s one year

+. UF i s made on both fermented and unfermented SSL. On a Pekilo-fermented l i q u o r Kaj Forss et a l (6) found a 50% h i g h e r production c a p a c i t y f o r a UF system of a given s i z e and a given product composition compared w i t h UF of the unfermented l i q u o r . The d i a f i l t r a t i o n water requirement was 55% l e s s f o r the fermented l i q u o r . Further d e t a i l s from the above mentioned o p e r a t i o n s cannot be d i s c l o s e d as the i n v o l v e d companies, due to the competitive s i t u a t i o n , p r e f e r to give out as l i t t l e i n f o r m a t i o n as p o s s i b l e . UF of K r a f t Black L i q u o r . L i g n i n from k r a f t b l a c k l i q u o r has f o r years been used to a l i m i t e d extent as extender f o r b i n d e r s i n v a r i o u s board products. With the r a p i d l y i n c r e a s i n g p r i c e s and the o u t l o o k of i n s u f f i c i e n t s u p p l i e s of PF r e s i n i n the f u t u r e , there i s a growing i n t e r e s t f o r l i g n i n f o r such a p p l i c a t i o n s . An extensive development program i n F i n l a n d , conducted by Dr. Kaj F o r s s , has shown that UF i s a simple, e f f i c i e n t and i n e x pensive method f o r t a i l o r i n g a l i g n i n product f o r t h i s purpose. By s e l e c t i o n of the proper membrane and p r o c e s s i n g parameters, i t i s p o s s i b l e i n a simple way to get a product w i t h the content- of l i g n i n and molecular weight d i s t r i b u t i o n r e q u i r e d f o r an a c t i v e binder i n g r e d i e n t which combines c h e m i c a l l y w i t h PF r e s i n f o r plywood. So f a r , a 40% replacement of PF r e s i n has been made without change i n the p r o p e r t i e s of the plywood. S u c c e s s f u l u l t r a f i l t r a t i o n / d i a f i l t r a t i o n has been made on 15% TDS l i q u o r from pulp washers, as w e l l as 30% TDS l i q u o r from t a l l o i l soap skimming. I t appears from Figure 8, that f o r a l i g n i n product w i t h a l i g n i n content i n the 80-90% range, based on product s o l i d s , the p r o d u c t i o n c a p a c i t y of a system of a given s i z e i s almost the same i n the two cases, but the 30% l i q u o r r e q u i r e s more water to get to the same l i g n i n content.


CLAUSSEN


21.


367

Figure 6. HF installation at Toten Sulfite Mill in Norway

Figure 7.

Molecular-weight distribution of lignin in SSL and UF concentrate and filtrate


368

SYNTHETIC

MEMBRANES:

HF

AND

UF

USES


The f i r s t i n d u s t r i a l s c a l e i n s t a l l a t i o n w i l l come on stream towards the end of t h i s year i n F i n l a n d . H y p e r f i l t r a t i o n - P r e c o n c e n t r a t i o n of SSL. P r e c o n c e n t r a t i o n of SSL has been going on s i n c e 1976 a t Toten S u l p h i t e M i l l i n Norway and s i n c e 1978 at Reed's L i g n o s o l P l a n t i n Quebec, Canada. This method of c o n c e n t r a t i n g weak l i q u o r s i n combination w i t h evaporation i s becoming more and more a t t r a c t i v e w i t h the rapid increasing fuel prices. F i g u r e 9 showing energy requirement f o r v a r i o u s evaporator systems compared w i t h h y p e r f i l t r a t i o n , i n d i c a t e s c l e a r l y the advantage of water removal by h y p e r f i l t r a t i o n . F i g u r e 10 i s showing the energy savings that can be achieved by combining HF w i t h an e x i s t i n g evaporator system f o r SSL at a given s i t u a t i o n . By i n t e g r a t i o n of HF, energy input can be reduced by about 50% which should more than pay f o r the HF i n s t a l l a t i o n ; and, at the same time, r e l i e v e the steam b o i l e r or make more steam f o r other operations a v a i l a b l e . For incremental increases i n water removal c a p a c i t y , HF i s , i n most cases, the f a v o r a b l e o p e r a t i o n , due to the energy e f f i c i e n c y and the p o s s i b i l i t y of adding modules stepwise according to the i n c r e a s i n g demand f o r c a p a c i t y . T h i s f a c t has been taken advantage of at Toten and Reed. F i g u r e 11 i s showing some of the e s s e n t i a l f e a t u r e s from those two HF p l a n t s . Both p l a n t s a r e using CA-membranes and d e s p i t e that pH i s on the lower s i d e of the acceptable pH-range, at Toten o c c a s i o n n a l l y below pH2 on average, membrane l i f e t i m e of one year + i s experienced. There have been some f o u l i n g problems i n the systems caused by p i t c h - c o n t a i n i n g small f i b e r s and calcium s u l f i t e . Improved pretreatment and membrane c l e a n i n g procedures are the keys to the b e t t e r performance of the systems. Power consumption f o r the systems i s i n the range 3.5-4.5 Kwh per 1,000 l b s . of water removal. Membrane c l e a n i n g frequency has been 2-6 times a week f o r the two systems. Composition of f i l t r a t e i s not much d i f f e r e n t from that of an evaporator condensate. The U l t r a s e p Color Removal Process f o r C a u s t i c E x t r a c t i o n Bleach E f f l u e n t . An extensive l a r g e s c a l e p i l o t p l a n t program was c a r r i e d out by the Swedish company, EKA, at Iggesund K r a f t M i l l i n Sweden, using a f o u r - s t a g e , continuous DDS-RO u l t r a f i l t r a t i o n system f o r t h i s a p p l i c a t i o n . The system has been i n continuous o p e r a t i o n f o r about two years, s e p a r a t i n g 10% of the t o t a l c a u s t i c e x t r a c t i o n e f f l u e n t , approximately 100 GPM, i n two f r a c t i o n s , 4 GPM of concentrate c o n t a i n i n g 90% of the c o l o r and 96 GPM c o n t a i n i n g 10% of the color.


CLAUSSEN

Q3 ^ ttb§ o < ^ tt(L I o < J

CC CO


C

0

A

N

D

0

U

C

N

T

R

E

S

T

0

F

NA.-LIGNIN IN PRODUCT, PRODUCT CAPACITY DIAFILTRATION WATER REQUIREMENT DURING THE SEPARATION. E

0

-.rr

£ \ i £ o w


N

F

T

M

E

.W •

INITIAL TDS 15%

40

%

369

50

PRECIPITABLE

LIGNIN

60

70

OF PR00UCT

80

SOLIDS

Figure 8. UF of KBL. Content of NA-lignin in product, product capacity, and diafiltration water requirement during the course of the separation.

E n e r g y - E f f i c i e n t C o n c e n t r a t i o n by HF (RO) Common energy

requirements

System

f o r e v a p o r a t o r s and HY

B t u p e r 1,000 l b s , o f water removal

1 e f f e c t w i t h vapor r e c o m p r e s s i o n 6 stage m u l t i p l e e f f e c t evaporator 5 stage m u l t i p l e e f f e c t evaporator 4 stage m u l t i p l e e f f e c t evaporator 3 stage m u l t i p l e e f f e c t evaporator Hyperfiltration

Figure 9.

systems:

50,000 215,000 270,000 345,000 430,000 15,000

Energy efficient concentration by HF (RO)


370

SYNTHETIC

MEMBRANES:

HF AND U F

USES

4 STAGE ME EVAPORATION A COMPARED WITH COMBINATION OF 4 STAGE ME EVAPORATION AND HYPERFILTRATION B ENERGY 56


A.

SSL 200,000 10% TDS

MILL.

BTU/HR

4 STAGE EVAPORATOR ME

LbS/HR.

CONCENTRATE 36,400 L B S / H R 5 5 % TDS

^EVAPORATION 163,600

LbS/HR

ENERGY

ENERGY I

B.

SSL ?00.000 LBS/HR. >0% T D S

I MILL

HYPER FILTRATION

BTU/HR

110,000 L B S / H R 18 2 % TDS

*

3 6 , 4 0 0 L B S / HR. 5 5 % TDS

EVAPORATION

FILTRATE 90.000

^CONCENTRATE

4 STAGE EVAPORATOR ME

73.600

L B S . / HR

LBS/HR

Figure 10. Energy requirement for water removal. Four-stage ME evaporation, A, compared with a combination of the four-stage ME evaporation and HF, B.

Features I n s t a l l a t i o n year S i z e s q . f t . membrane a r e a Configuration Product % TDS f e e d % TDS c o n c e n t r a t e Maximum feed r a t e GPM Max f i l t r a t i o n r a t e GPM Avg. f i l t r a t i o n r a t e a t max. f e e d Nominal power consumption approx. Kw. Nominal power concumption Kwh p e r 1000 l b s . f i l t r a t e No.of membrane r e p l a c e m e n t s

Toten

Reed

1976 4215 4 stage cont. N H 4 - S S L pH 2-2.5 6-10 12 88 44

1978 4817 4 stage cont. Ca-SSL pH 3-3.5 10 - 12 18 132 44

15

13

75

90

3.4 3

4.0 1

Figure 11. Features of the HF plants at Totel and Reed as of August 15, 1980



21.

CLAUSSEN

UF and

HF

in the Pulp and

Paper Industry

371

PRE-BLEACHED PULP

6000 TT? Effluent 40 tons Total Solids Total Chloride 7 tons 70 tons Color Pt 12 tons COD 4 tons BOD 3

Concentrate 250 m Solids 18 tons Chloride 1 ton Color Pt 63 tons COD 8 tons BOD 2 tons 3

5750 m 22 tons (12 tons org.) (10 tons NaCl) 6 tons Chloride 7 tons Color Pt 4 tons COD 2 tons BOO

Permeate Solids

Figure 12.

Ultrasep system for color removal. Materials balance for 600 tons of kraft pulp.


SYNTHETIC MEMBRANES: HF AND


372

dustry.

fully,

UF USES

F i g u r e 12 i s showing the d i s t r i b u t i o n of other e s s e n t i a l substance; f o r i n s t a n c e , BOD, COD, c h l o r i d e and TDS i n the two fractions. The o p e r a t i o n ran smoothly w i t h few major problems. Membrane c l e a n i n g frequency was, on average, once every three weeks. D i f f e r e n t membranes were used; the l a s t set was i n continuous o p e r a t i o n f o r more than 8,000 hours without s i g n i f i c a n t change i n performance. This process i s found to be competitive to e x i s t i n g c o l o r removal processes, both w i t h regard to economy and c o l o r removal efficiency. To which degree i t i s going to be u t i l i z e d i s depending on what k i n d of r e g u l a t i o n s there w i l l be w i t h regard to emmissions from b l e a c h p l a n t s . However, the f i r s t i n d u s t r i a l i n s t a l l a t i o n of i t s k i n d w i l l be made t h i s year i n Japan. ABSTRACT. Membrane filtration has been in o p e r a t i o n f o r more than five years on a commercial s c a l e in the pulp and paper inContinuous, m u l t i - s t a g e p l a t e and frame based systems are being used f o r purification, and molecular distribution c o n t r o l of l i g n o s u l f o n a t e from spent sulfite l i q u o r and preconc e n t r a t i o n of weak spent sulfite l i q u o r before evaporation. Larger s c a l e , long term pilot operations w i t h the s i m i l a r systems f o r s e p a r a t i o n of lignin from k r a f t b l a c k l i q u o r and c o l o r removal from bleach p l a n t e f f l u e n t s are going on successa d v i s i n g new and comprehensive a p p l i c a t i o n s f o r membrane filtration process in this i n d u s t r y . The aspect of saving fossile energy is a common f e a t u r e of most such operations as hyperfiltration i s typical low energy c o n c e n t r a t i o n method and the lignin products in many cases r e p l a c e petroleum based chemicals. Literature Cited 1.

2. 3.

4. 5. 6.

DDS Modules, U.S. Patent 3,872,015, GB patent 1,390,671, Italy patent 978,747, S w i t z e r l a n d patent 542,639, New Zealand patent 169,679. L. Janzen, P.H. Claussen, Norway patent 127,545, Swiss patent 560,289, P o r t u g a l , France, Brazil, Italy patents. K. F o r s s , A. Fuhrman, Karatex adhesive, F i n l a n d patent 167,647, U.S. patent 4,105,606. Patents GDR, A u s t r i a , GB, Hungary, e t c . J . Manson, EKA AB Sweden. Proceedings from I n t e r n a t i o n a l Pulp Bleaching Conference i n Toronto, June, 1979. P.H. Claussen, Pulp and Paper Canada, March, 1978. K. F o r s s , R. Kokkonen, H. Sirelius, P.E. Sagfors, Pulp and Paper Canada, December, 1979.

RECEIVED December 17,

1980.


Synthetic Membranes - American Chemical Society

Recommend Documents