1 1 - 1 1 - f ./

- TEXTILE DYEBATH RECONSTITUTION AND REUSE

J o n Bergenthal Pro j e c t Manage r

Sverdrup & P a r c e l and A s s o c i a t e s , Iric. St. Louis , Missouri 63101

Robert Hendri k s P r o j e c t O f f i c e r

I n d u s t r i a 1 Environmental Research Laboratory U.S. Environmental P r o t e c t i o n Agency

Research T r i a n g l e Pa rk , North Caro l ina 27711

Dr. Wayne Tincher P ro fes so r

Georgia I n s t i t u t e of Technology A t l a n t a , Georgia 30332

John Eapen Corporate Environmental Manager

Bigelow-Sanford, I n c . G r e e n v i l l e , South Caro l ina 29602

Anthony Tawa P r o j e c t Engineer

Sverdrup & P a r c e l and A s s o c i a t e s , Inc . S t . Lou i s , Missouri 63101

INTRODUCTION

Over 100 b i l l i o n g a l l o n s of wastewater a r e d i scha rged a n n u a l l y i n t h e United S t a t e s from t h e f i n i s h i n g of t e x t i l e p roduc t s . I t i s es t i - mated t h a t about 80 p e r c e n t of t e x t i l e f i n i s h i n g m i l l s d i s c h a r g e t h e i r wastewater t o p u b l i c l y owned t r e a t m e n t works (POTW). Most o f t h i s wastewater r e c e i v e s e i t h e r no t r e a t m e n t o r o n l y pr imary t r e a t - ment, such a s s e t t l i n g , s c r e e n i n g , e q u a l i z a t i o n , o r n e u t r a l i z a t i o n , p r i o r t o d i scha rge t o t h e municipal sewers.

The major t e x t i l e f i n i s h i n g o p e r a t i o n s i n c l u d e f i b e r p r e p a r a t i o n -. ( d e s i z i n g , s cour ing , merce r i z ing , b l e a c h i n g ) , f i b e r c o l o r i n g (dyeing, p r i n t i n g ) , and f u n c t i o n a l f i n i s h i n g . Wastewater r e s u l t s p r i m a r i l y from t h e p r e p a r a t i o n and c o l o r i n g o p e r a t i o n s .

Many wastewater r e c y c l e / r e u s e t e c h n o l o g i e s are a v a i l a b l e t o a l low r e u s e of t h e s e wastewaters. Reference 1 p rov ides a d e t a i l e d d e s c r i p - t i o n of such r e c y c l e / r e u s e t echno log ie s . One of t h e s e t e c h n o l o g i e s , dyebath r e c o n s t i t u t i o n and r e u s e , was s e l e c t e d fo-r f u r t h e r i n v e s t i g a - t i o n as it appears t o o f f e r s i g n i f i c a n t env i ronmen ta l , -bene f i t s and s u b s t a n t i a l c o s t s av ings t o t h e i n d u s t r y , and it a l s o has t h e poten- t i a l f o r widespread use w i t h i n t h e i n d u s t r y .

TEXTILE D Y E I N G

The v a s t ma jo r i ty o f t e x t i l e p roduc t s a r e co lo red by dyeing. I n 1980, approximately 7 . 8 b i l l i o n pounds of f i b e r s were dyed. TO accomplish t h i s dyeing, 171 m i l l i o n pounds of d y e s t u f f s and 1 .28 b i l l i o n pounds of a d d i t i v e s ( a u x i l i a r y chemicals) were used. Most

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-_ a u x i l i a r y chemicals do n o t exhaus t du r ing dyeing and a r e thus d i s - charged with t h e dyeing wastewater. D y e s t u f f s , however, g e n e r a l l y

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exhaust t o over 90 p e r c e n t du r ing dyeing. Assuming a 95 p e r c e n t exhaust ion r a t e , about 8 .5 m i l l i o n pounds of d y e s t u f f s a r e d i scha rged annua l ly i n dyeing wastewater.

Dyeing can b e performed us ing e i t h e r cont inuous o r batch p r o c e s s e s . Approximately h a l f of t h e t e x t i l e f i b e r s dyed i n the U.S. a r e b a t c h dyed. C e r t a i n p r o d u c t s , such a s k n i t f a b r i c s , h o s i e r y , and yarn a r e a lmost exclusi .vely dyed us ing b a t c h p r o c e s s e s . Large amounts o f c a r p e t and some woven f a b r i c s a r e a l s o ba t ch dyed. Batch dyeing remains popular due t o i t s f l e x i b i l i t y , s h o r t - r u n c a p a b i l i t y , and e a s e o f c o n t r o l . Batch p r o c e s s e s , however, a r e g e n e r a l l y i n e f f i c i e n t i n t h e i r usage of water and a u x i l i a r y chemicals .

I n a t y p i c a l b a t c h dyeing o p e r a t i o n , from 1 t o 5 g a l l o n s of water a r e used as dye l i q u o r € o r each pound o f f i b e r s dyed. A u x i l i a r y chemicals and dyes are added t o t h i s dye l i q u o r . A u x i l i a r y chemicals can inc lude exhaust a g e n t s , l e v e l i n g a g e n t s , b u f f e r s and pH c o n t r o l chemicals , r e t a r d i n g a g e n t s , w e t t i n g and d i s p e r s i n g a g e n t s , c a r r i e r s , s o f t e n e r s , l u b r i c a n t s , p e n e t r a n t s , among many o t h e r s . The t o t a l amount of a u x i l i a r y chemicals added w i l l v a r y depending on t h e f i b e r and d y e s t u f f t y p e s , b u t w i l l g e n e r a l l y range from a few p e r c e n t of t h e f i b e r weight (2 o r 3 p e r c e n t 0.w.f.) t o a s much a s 50 p e r c e n t where high c o n c e n t r a t i o n s of exhaus t a g e n t s a r e r e q u i r e d . Dyestuff q u a n t i t i e s a r e g e n e r a l l y a few (less t h a n 4 ) p e r c e n t of t h e f i b e r weight. Following t h e a d d i t i o n o f a u x i l i a r y chemicals and dyes, t h e dyebath temperature i s r a i s e d t o t h e d e s i r e d dyeing temperature and h e l d u n t i l dyeing i s complete and a level dyeing i s achieved. The exhausted dyebath, now c o n t a i n i n g o n l y a few p e r c e n t of t h e o r i g i n a l q u a n t i t y of d y e s t u f f b u t s t i l l most o f t h e a u x i l i a r y chemicals , i s dropped, and t h e dyed p roduc t i s r i n s e d w i t h f r e s h wa te r .

DYEBATH REUSE

The p o s s i b i l i t y exis ts o f r e u s i n g t h e exhausted dyebath f o r subse- quent dyeings, t h u s making use of the a u x i l i a r y chemicals f o r more than one c y c l e o f dyeing. T h i s r e s u l t s i n p roduc t ion c o s t s a v i n g s and a l s o d e c r e a s e s t h e volume o f wastewater and q u a n t i t y of p o l l u t - a n t s d i scha rged . To realize t h i s p o s s i b i l i t y of dyebath r e u s e , a ., method was needed f o r a n a l y z i n g t h e exhausted dyebath t o determine t h e q u a n t i t i e s o f d y e s t u f f s remaining and the reby compute t h e add q u a n t i t i e s f o r t h e n e x t dyeing.

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Much of t h e work i n developing t h e dyebath a n a l y t i c a l techniques and r e c o n s t i t u t i o n methods was performed a t t h e School of Text i le Engi- nee r ing a t t h e Georgia I n s t i t u t e of Technology i n t h e 1970 ' s (Refer- ences 2 , 3 and 4 ) -

The work desc r ibed h e r e i n expands upon t h e work conducted p r e v i o u s l y on dyebath r e c o n s t i t u t i o n and r euse i n t h e fo l lowing ways:

. . \

1 . I t examines t h e a p p l i c a t i o n o f dyebath reuse a t a m i l l t h a t is f a i r l y t y p i c a l of many dyehouses, y e t i s not a "pe r fec t " cand ida te f o r t h i s technology.

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O Dye formulat ions had t o be modified t o use a s m a l l e r number of dyestuiffs b e f o r e r e c o n s t i t u t i o n became t e c h n i c a l l y f e a s i b l e .

O Q u a l i t y c o n t r o l requirements a r e s t r i c t a t t h i s m i l l , t hus pos ing a s t i f f t e s t o f t h e a b i l i t y o f dyebath reuse t o produce accep tab le dyeings .

O Overflow r i n s i n g i s t y p i c a l l y used a t t h i s m i l l , t he reby a f f e c t i n g no t o n l y t h e dyebath ana lys i s / r econ- s t i t u t i o n methods, but a l s o a f f e c t i n g t h e economics of dyeba t h r e u s e .

2 . I t p r e s e n t s t h e f i r s t development of environmental d a t a f o r t h i s wastewater r e c y c l e / r e u s e technology, t hus al lowing t h e environmental b e n e f i t s of dyebath r euse t o be q u a n t i f i e d .

3 . I t updates t h e equipment used i n dyebath a n a l y s i s t o i n - c lude a modern desk-top computer, a commercially a v a i l a b l e i n t e r f a c e f o r t h e spectrophotometer/computer, and so f tware w r i t t e n i n t h e BASIC computer language t o a l low f o r g r e a t e r comprehension and a d a p t a b i l i t y t o a v a r i e t y of desk-top computers. The r equ i r ed equipment and programs a r e de- s c r i b e d i n Reference 5 .

I n a d d i t i o n , t h i s p r o j e c t included t h e development of a d e t a i l e d u s e r ’ s manual t h a t examines t h e t echn iques used i n t h e development and f u l l - s c a l e t e s t i n g of t h e technology a t t h i s m i l l . These t e c h - n iques can be d i r e c t l y a p p l i e d by o t h e r m i l l s wishing t o examine t h e f e a s i b i l i t y of dyebath r euse (Reference 5 ) .

DYEBATH REUSE STUDIES

In o r d e r t o develop in fo rma t ion on t h e f u l l - s c a l e implementation and c o s t o f dyebath r e c o n s t i t u t i o n and r e u s e , a demonstrat ion of t h e technology was performed a t a t e x t i l e m i l l . A c a r p e t m i l l owned and o p e r a t e d by Bigelow-Sanford, I n c . was s e l e c t e d f o r t h e f u l l - s c a l e e v a l u a t i o n . The m i l l performs atmospheric b a t c h dyeing p r i m a r i l y of nylon c a r p e t , d i s c h a r g i n g about 1 m i l l i o n g a l l o n s p e r day of waste- wa te r t o t h e municipal c o l l e c t i o n system. i

Two p o p u l a r , u s i n g dyebath r e c e n t l y been

large-volume c a r p e t s t y l e s were s e l e c t e d f o r dyeing r euse p rocedures . The dye r e c i p e s f o r t h e s e s t y l e s had r e fo rmula t ed t o u t i l i z e a sma l l number of d y e s t u f f s .

Many o i t h e d i f f e r e n t shades now have r e c i p e s con ta in ing va ry ing amounts of t h e same t h r e e d y e s t u f f s . This i s an e s s e n t i a l s t e p i n implementing dyebath r e u s e s i n c e t h e r e s i d u a l dyes i n t h e dyebath from t h e j u s t completed dyeing m u s t be t h e same ones t h a t a r e t o be used i n dyeing t h e n e x t shade.

Dyebath a n a l y s e s were conducted us ing a v i s i b l e - l i g h t spectrophoto- meter and a desk-top computer. Dyestuff absorbance c o e f f i c i e n t s were

f o r each of t h e d y e s t u f f s . These c o e f f i c i e n t s a r e t h e k-values i n t h e Lambert-Beer equa t ion :

f i r s t determined i n t h e l a b o r a t o r y a t v a r i o u s wavelengths of l i g h t ..

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is= kC where A = absorbance of t h e d y e s t u f f , and C = c o n c e n t r a t i o n of t h e d y e s t u f f .

These va lues were then used t o ana lyze exhausted dyebaths t o d e t e r - mine t h e amounts of d y e s t u f f s t h a t remained a t t h e end of a dyeing .

Software was developed f o r t h e desk-top computer t o allow it t o per - form a l l t h e c a l c u l a t i o n s needed t o determine how much dye and a u x i l i a r y chemicals remained i n a used dyebath , and how much had t o be added t o perform t h e nex t dye ing . I n t h i s way, t h e a c t u a l pro- cedures needed t o reuse a dyebath could be c a r r i e d o u t i n on ly a few minutes by dyehouse personnel .

A d e t a i l e d and ve ry a c c u r a t e a n a l y s i s of t h e a u x i l i a r y chemical q u a n t i t i e s remaining i n t h e dyebath i s n o t needed nor would i t be e a s y t o o b t a i n . I n s t e a d , t h e computer c a l c u l a t e d amounts of a u x i l i a r , y chemicals r equ i r ed t o be added t o r e c o n s t i t u t e t h e dyebath by us ing a s imple mass ba lance equa t ion , based on t h e volume of dyebath reused, t h e volume o f coo l ing water added, and assumptions a s t o t h e degree of exhaus t ion of a u x i l i a r y chemicals . C e r t a i n a u x i l i a r y chemicals w i l l completely exhaus t o r evapora t e dur ing dye ing , and t h e pe rcen t makeup w i l l t hus be 100 p e r c e n t . Examples a r e defoamers, v o l a t i l e chemica ls , and f i n i s h e s t h a t adsorb on to the t e x t i l e f i b e r s .

Bench-Scale Tests

The a c t u a l dyebath r euse s t u d y c o n s i s t e d of 26 series of dyeings. Each series c o n s i s t e d of from 5 t o 10 dyeings us ing t h e same dyebath.

The f i r s t 15 series were bench-scale dyeings. These bench-scale dye ings provided o p p o r t u n i t i e s t o become f a m i l i a r w i th dyebath reuse concepts and procedures , t o t es t t h e shade-matching c a p a b i l i t y of dyebath reuse, and t o r e s o l v e any problems t h a t a r o s e , whi le s t i l l on a smal l s c a l e . S i x shades from each o f t h e two c a r p e t s t y l e s were s e l e c t e d f o r dyeing. For each of t h e s e shades , t h e dyebath was reused u n t i l a series o f f i v e dye ings was completed. This accounted f o r t h e f i r s t 12 series. The f i n a l t h r e e bench-scale series each s t a r t e d wi th a l i g h t shade and g r a d u a l l y progressed t o dyeing da rke r shades a s t h e dyebath was reused . The dyed c a r p e t samples from t h e s e bench-sca le dyeings were ana lyzed wi th a DianoIHardy I1 spec t rophoto- meter t o e v a l u a t e t h e a b i l i t y of dyebath r euse t o produce accep tab le shade matches.

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Table 1 p r e s e n t s c o l o r d i f f e r e n c e d a t a f o r each o f t h e r e c o n s t i t u t e d bench-sca le dye ings . The f i r s t dyeing of each shade was c a l l e d t h e s t a n d a r d , s i n c e i t was dyed conven t iona l ly i n a f r e s h b a t h . These c o l o r d i f f e r e n c e s g ive a q u a n t i t a t i v e measure of t h e un i fo rmi ty of t h e c a r p e t sample dyed i n r e c o n s t i t u t e d b a t h s . I t should be noted t h a t , i n c o n t r a s t t o f u l l - s c a l e dye ings , no dye adds were at tempted du r ing bench- o r p i l o t - s c a l e t r a i l s . I n f u l l - s c a l e dye ing , s i g n i f i - c a n t c o l o r d i f f e r e n c e s a r e c o r r e c t e d by adding more dye t o t h e dye- b a t h and con t inu ing t h e dyeing u n t i l t h e shade becomes accep tab le .

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A review of Table 1 shows t h a t 87-percent of t h e r e c o n s t i t u t e d dye- i ngs had c o l o r d i f f e r e n c e s from t h e s t anda rd of less than 3 S t a r l a b u n i t s (approximate ly 6 MacAdam u n i t s ) . These r e l a t i v e l y sma l l c o l o r d i f f e r e n c e s would normally be co r rec t ed i n product ion dyeing by making a dye add. These bench-scale dyeings t h e r e f o r e showed t h a t good shade matching w i t h dyebath r e c o n s t i t u t i o n and reuse was poss- i b l e a t t h i s m i l l .

P i l o t - S c a l e Tests

Fol lowing t h e success of t h e bench-scale dye ings , e i g h t a d d i t i o n a l dyebath r euse s e r i e s were conducted us ing a p i l o t - s c a l e beck. The p i l o t - s c a l e beck and dyeing procedures more c l o s e l y resemble f u l l - s c a l e dyeing a s compared t o bench-scale dyeings. Thus, t h e p i l o t - s c a l e dye ing would provide a n oppor tun i ty t o t es t dyebath reuse under c o n d i t i o n s t h a t approximate f u l l - s c a l e dye ing , and r e so lve any prob- lems t h a t might a r i s e . Both s i n g l e shade and mult i -shade series were dyed f o r each c a r p e t s t y l e .

Because t h e r e u s e of h o t dyebaths could p o s s i b l y cause un leve l dye- i n g s , t h i s a s p e c t was s t u d i e d p r i o r t o beginning r e c o n s t i t u t i o n dyeings i n t h e p i l o t - s c a l e beck. Seve ra l c a r p e t p i e c e s were dyed

dyeing tempera ture ( t empera tu re a t which dye i s added) on r e s u l t a n t c a r p e t q u a l i t y . I n i t i a l t empera tures of 120°, 140°, 160°, and 180°F were t e s t e d . V i sua l i n s p e c t i o n showed no apparent d e t e r i o r a t i o n i n q u a l i t y a t i n i t i a l dye ing tempera tures a s h igh a s 180°F f o r S t y l e 1. Problems i n l e v e l n e s s were noted a t 180°F f o r S t y l e 2 b u t , a t 140°F and lower, no d i f f i c u l t i e s were encountered. I t was thus dec ided t o coo l r ecyc led dyebaths t o 140°F o r lower b e f o r e reuse t o avoid level- n e s s problems.

, * x . '-f us ing conven t iona l procedures t o determine t h e e f f e c t of i n i t i a l

The f i r s t p i l o t - s c a l e dyebath reuse experiments used l i v e steam f o r h e a t i n g , b u t it was noted t h a t t h i s caused t h e dyebath pH t o d r i f t s i g n i f i c a n t l y from i t s i n i t i a l va lue , r e s u l t i n g i n poor d y e s t u f f exhaus t ion . Use o f steam c o i l s f o r h e a t i n g e l imina ted t h i s problem, b u t r e s u l t e d i n i n s u f f i c i e n t mixing of t h e dyebath and r e s u l t a n t s i d e - t o - s i d e shade v a r i a t i o n s . A s a r e s u l t , f o r a l l subsequent p i l o t - s c a l e dye ings , l i ve steam was used, and pH was c l o s e l y moni- t o r e d and main ta ined . -.

Color d i f f e r e n c e d a t a were obta ined f o r t h e p i l o t - s c a l e dye ings as desc r ibed p r e v i o u s l y . The r e s u l t s a r e shown i n Table 2. I n g e n e r a l , c o l o r d i f f e r e n c e s from s t anda rd f o r a l l S t y l e 1 dyeings were s l i g h t l y g r e a t e r t h a n f o r S t y l e 2. Also, f o r b o t h s t y l e s , c o l o r d i f f e r e n c e s were s l i g h t l y g r e a t e r f o r c a r p e t s dyed i n r e c o n s t i t u t e d b a t h s t h a n f o r t h o s e dyed i n f r e s h b a t h s . Neve r the l e s s , a l l b u t one of t h e r e c o n s t i t u t e d dye ings had a c o l o r d i f f e r e n c e from s t anda rd of less t h a n 5 S t a r l a b u n i t s .

S ide - to - s ide c o l o r d i f f e r e n c e measurements were a l s o t aken , and s i m i l a r t r e n d s were observed. S l i g h t l y b e t t e r r e s u l t s were seen f o r

t h a n f o r S t y l e 1 dyeings . Nearly t h r e e - f o u r t h s of a l l t h e recon- s t i t u t e d dye ings had s i d e - t o - s i d e v a r i a t i o n s of less than 2 S t a r l a b u n i t s -

f r e s h b a t h s than f o r r e c o n s t i t u t e d b a t h s , and f o r S t y l e 2 dye ings 9

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Mult ishade dye series were conducted s o t h a t t h e shades dyed gener- a l l y progressed from l i g h t t o da rk , a l though some dark-to-medium sequences were inc luded . The r e s u l t i n g c o l o r d i f f e r e n c e s were a c c e p t a b l e . L ight - to-dark sequences a r e recommended f o r dyebath reuse, wherever p o s s i b l e . D r a s t i c changes from a dark t o l i g h t shade should be avoided.

The f i r s t and l a s t dyeings i n s e r i e s 1 7 and 22 were t e s t e d f o r c o l o r f a s t n e s s by s t anda rd t e s t methods inc lud ing 60-hour xenon, wet and d r y c rock ing , b l e e d , and shampoo t e s t s . Nei ther c a r p e t s t y l e was a f f e c t e d i n i t s f a s t n e s s p r o p e r t i e s a f t e r f i v e dyeings i n t h e same dye l i q u o r .

I n summary, t h e r e s u l t s of t h e p i l o t - s c a l e dyeings aga in showed t h a t a c c e p t a b l e p roduc t q u a l i t y was a t t a i n a b l e wi th dyebath r e c o n s t i t u t i o n and r euse . A s a r e s u l t , p r e p a r a t i o n s f o r f u l l - s c a l e dyebath recon- s t i t u t i o n and r euse t r i a l s were s t a r t e d .

Full- 'Scale Demonstrat ion

A week-long p l a n t demonst ra t ion of dyebath reuse was conducted a t Bigelow's Summerville, Georgia , m i l l . The p r i n c i p a l o b j e c t i v e of f u l l - s c a l e r e c o n s t i t u t i o n t r i a l s a t t h e m i l l was t o demonstrate t h i s reuse method's t e c h n i c a l f e a s i b i l i t y . The m i l l demonst ra t ion would a l low any problems t h a t might develop a t f u l l - s c a l e t o be i d e n t i f i e d and r e so lved .

Another impor tan t o b j e c t i v e of t h i s e f f o r t was t o c o l l e c t wa te r , chemical , and energy sav ings d a t a a s s o c i a t e d wi th dyebath r e c o n s t i t u - t i o n . Environmental d a t a on o l l u t a n t reduct ions due t o dyebath

a n o p p o r t u n i t y t o o b t a i n t h e s e d a t a . r e c o n s t i t u t i o n were n o t a v a i l a b 19 e e lsewhere , and so t h e s e t r i a l s were

The f i r s t problem t o be confronted i n a t t empt ing t o perform f u l l - s c a l e r e c o n s t i t u t i o n dye ings a t t h e m i l l was t o determine t h e l o g i s - t i c s o f dyebath r euse . Three g e n e r a l approaches were cons idered:

1. r e c o n s t i t u t e dyebath i n - s i t u fo l lowing ho t -pu l l and sepa r - a t e r i n s i n g of dyed c a r p e t ; -i

2. t r a n s f e r exhaus ted dyebath t o a ho ld ing t ank , r i n s e and p u l l c a r p e t i n normal f a sh ion , and r e t u r n dyebath t o beck f o r n e x t dye ing; and

3 . t r a n s f e r exhaus ted dyebath t o an empty, ad jacen t dyebeck f o r r euse .

For t h e purposes o f a 1-week demonst ra t ion , t h e t h i r d approach was t h e s i m p l e s t and most economical a l t e r n a t i v e . I n a permanent i n - s t a l l a t i o n , t h e f i r s t o r second approach would normally be used.

Three a d j a c e n t becks w i t h c a p a c i t i e s of approximately 7,000 gal lons,z each were s e l e c t e d f o r t h e s e t r i a l s . There were s e v e r a l impor tan t c o n s i d e r a t i o n s i n deve loping a system t o t r a n s f e r t h e exhaus ted dyebaths from one beck t o a n o t h e r :

o t h e t empera tu re o f t h e dyebath t o be t r a n s f e r r e d might be a s h igh a s 140'F;

845

- o t h e dyebath t r a n s f e r .-had t o be accomplished r e l a t i v e l y

qu ick ly ; and

o t h e volume of dyebath t r a n s f e r r e d had t o be known

To s a t i s f y t h e s e c o n d i t i o n s , a temporary pump and p ip ing arrangement was set up f o r t h e demonstrat ion a s shown i n F igu re 1.

A t t h e end of a dyeing, t h e exhausted dyebath was pumped t o an a d j a - c e n t beck a l r e a d y loaded wi th c a r p e t f o r t h e nex t dyeing. The dyed c a r p e t i n t h e f i r s t beck was then r in sed and pu l l ed i n t h e normal f a s h i o n . Meanwhile, a sample o f t h e exhausted dyebath was ana lyzed , and t h e computer q u i c k l y p r i n t e d o u t t h e amounts of dyes and chemi- c a l s t o add f o r t h e nex t dyeing.

The c a r p e t s t y l e s and shades used i n t h e s e f u l l - s c a l e t r i a l s were selected a t t h e beginning of t h e 1-week demonst ra t ion from scheduled p roduc t ion f o r t h a t p e r i o d . With t h e excep t ion of t h e p rocedura l changes necessa ry t o p h y s i c a l l y perform dyebath r e c o n s t i t u t i o n , a l l p r i o r and subsequent dyehouse a c t i v i t i e s r e l a t i v e t o t h e s e dyeings were unchanged. They were t r e a t e d a s p roduc t ion runs by a l l m i l l p e r sonne l and, acco rd ing ly , d i d n o t receive any more o r any less a t t e n t i o n dur ing t h e i n s p e c t i o n p rocess than conven t iona l ly dyed p roduc t ion . The success o f t h e s e dyeings was t o depend upon whether t h e v a r i o u s post-dyeing i n s p e c t i o n s r e s u l t e d i n t h e i r be ing shipped a s f i r s t q u a l i t y p roduc t ion wi thout t h e need f o r redyes . No quan t i - t a t i v e shade matching measurements were made. Based on these c r i t e r i a , a l l dyeings were s u c c e s s f u l . Table 3 summarizes t h e f u l l - scale dyebath r e s u l t s . The dyeing problems t h a t occur red i n series 24 were a t t r i b u t e d t o a ya rn l o t change r a t h e r t h a n any problems caused by dyebath r euse .

< Y = f

One o f t h e i n c e n t i v e s f o r dyebath r euse i s t h e sav ings i n water , energy , and a u x i l i a r y chemical us'age. T h e i r use was c l o s e l y moni- t o r e d du r ing t h e r e c o n s t i t u i o n ser ies . Table 4 summarizes t h e s a v i n g s t h a t occur red due t o dyebath r euse . Water and chemical s av ings range , f o r t h e most p a r t , from 25 t o 50 p e r c e n t of normal usage . Dyestuff s av ings were minimal, and a r e n o t l i s t e d on t h e t a b l e . Defoamer usage was t h e same i n r euse dyeings a s i n con-

i n a dye c y c l e . v e n t i o n a l dyeings; i . e . , a l l defoamer was assumed t o have evaporated ' i

These f u l l - s c a l e exper iments showed t h a t t h e e a s e of o b t a i n i n g s a t i s - f a c t o r y dye ings w i t h r e c o n s t i t u t e d b a t h s was comparable i f n o t super- i o r t o t h a t of conven t iona l dye ing procedures . The numbers o f bo th adds and redyes were w i t h i n t h e m i l l ' s t y p i c a l f requency f o r t h e s e s t y l e s . The s t r i c t q u a l i t y c o n t r o l s t a n d a r d s of t h i s m i l l were no t a n impediment t o dyebath r euse .

The major problem encountered wi th f u l l - s c a l e dyebath r e c o n s t i t u t i o n was t h a t of pH c o n t r o l . S e v e r a l pH adjus tments of r e c o n s t i t u t e d dyebaths by monosodium phosphate (MSP) o r Tr i sodium phosphate (TSP) a d d i t i o n were r equ i r ed e a r l y i n t h e dye series, e s p e c i a l l y wi th .2

S t y l e 1 c a r p e t . However, a s expe r i ence was gained wi th t h e behavior o f t h e s e pH c o n t r o l agen t s and /o r t h e r ecyc led dyebath became more b u f f e r e d , no ad jus tments were requ i r ed a f t e r a d d i t i o n of normal makeup a u x i l i a r y chemical q u a n t i t i e s . Improved b a t h c o n t r o l may even

846

be r e a l i z e d through r econs t i t . 5 t ion . This i s because t h e e f f e c t s of pH and c h l o r i n e v a r i a t i o n s i n incoming source water a r e l e s sened , r e s u l t i n g in more uniform dyebaths .

, - J

I n s p i t e of t h e success of t h e s e dye ings , t h e r e a r e some a s p e c t s of t h e r e c o n s t i t u t i o n procedure used here t h a t can be e v a l u a t e d more f u l l y . Maximizing t h e reuse of dyes and chemicals by minimizing t h e amount of coo l ing , and thus d i l u t i n g , water should be f u r t h e r i n - v e s t i g a t e d . S ince t h i s w i l l a l s o a f f e c t t h e tempera ture of t h e recyc led dyebath , t h e e f f e c t s on product q u a l i t y must b e c l o s e l y watched. These a s p e c t s were n o t f u l l y eva lua ted because t h e reuse procedures used i n t h e s e t r i a l s were developed t o emulate a s c l o s e l y a s p o s s i b l e t h e m i l l ' s convent iona l dyeing procedures . This approach was adopted t o minimize t h e number of v a r i a b l e s between conven t iona l dye ings and r e c o n s t i t u t e d dyeings. However, t h e s e mod i f i ca t ions should be explored by t h e m i l l i f dyebath r e c o n s t i t u t i o n and reuse i s implemented f u l l - s c a l e .

ENVIRONMENTAL BENEFITS

Wastewater samples were c o l l e c t e d both dur ing t h e p i l o t - s c a l e and f u l l - s c a l e dye ings . The r e s u l t s of t h e f u l l - s c a l e d a t a a r e p re sen ted below t o c h a r a c t e r i z e t h e p o t e n t i a l environmental b e n e f i t s of dyebath r euse .

The the

P o l l u t a n t

Flow ( g a l . / l b ) BOD COD TSS TDS Phenol ics Tota l -P

Pe rcen t Reduction i n Discharge S e r i e s #25 S e r i e s #26

2 4 13 32 47 25

0 28

34 33 33 0

43 0

44

c o n c e n t r a t i o n s o f v a r i o u s p o l l u t a n t s i n t h e dyebath i n c r e a s e d a s dyebath was r eused . Th i s i s suspec ted t o be due t o t h e bu i ldup

of y a r n f i n i s h e s t h a t a r e removed from t h e c a r p e t d u r i n g dyeing. D e s p i t e t h e s e h i g h e r c o n c e n t r a t i o n s , t h e n e t e f f e c t of dyebath r euse - i

is t o reduce t h e mass of p o l l u t a n t s a c t u a l l y d i scha rged , a s compared t o conven t iona l dye ing . Th i s n e t r educ t ion i s due t o t h e s m a l l e r amounts o f a u x i l i a r y dye ing chemicals needed t o perform reuse dye- i n g s . The l a c k o f suspended s o l i d s r educ t ion i n t e s t series #26 i s a n e x c e p t i o n t o t h i s o b s e r v a t i o n and cannot be expla ined .

The l a r g e r r e d u c t i o n s i n wastewater volume and p o l l u t a n t d i s c h a r g e i n S e r i e s 2 6 , a s compared t o S e r i e s 2 5 , were due t o a t t empt s t o reduce t h e volume o f over f low c o o l i n g water used i n t h e dye c y c l e . Less c o o l i n g water r e s u l t s i n less d i l u t i o n of t h e dyebath. Consequent ly , s m a l l e r amounts o f a u x i l i a r y chemicals a r e needed t o r e c o n s t i t u t e t h e dyebath f o r r e u s e . T h i s r e s u l t s i n both water u se /d i scha rge reduc- t i o n s and p o l l u t a n t d i s c h a r g e r educ t ions . F u r t h e r o p t i m i z a t i o n iq2 t h i s a r e a w i l l r e s u l t i n even g r e a t e r environmental b e n e f i t s .

COSTS

The c a p i t a l c o s t of permanent ly i n s t a l l i n g dyebath reuse a t two of t h e m i l l ' s dyebecks i s about $80,000. This i nc ludes a pump; a 6,000

a47

g a l l o n dyebath s t o r a g e tank; a s socsa t ed p i p i n g , v a l v e s , and c o n t r o l s ; and t h e dyebath a n a l y s i s equipment and computer. This two-beck system is i l l u s t r a t e d i n F igure 2 .

Yearly o p e r a t i n g c o s t s a r e e s t ima ted t o be $5 ,000 . Yearly s a v i n g s , a s shown i n Table 5 , a r e $60,000 f o r two becks. This r e s u l t s i n a payback pe r iod of about 1 .5 y e a r s . The p rospec t s f o r reducing t h e payback pe r iod even f u r t h e r a r e good. Many a r e a s e x i s t f o r opt imiz- ing t h e dyebath reuse p r o c e s s , thereby i n c r e a s i n g t h e chemical and energy sav ings .

OUTLOOK FOR USE I N INDUSTRY

As noted above, ba t ch dyeing accounts f o r h a l f of t h e t o t a l amount of t e x t i l e dyeing. Due t o t h e h ighe r water and chemical usage of b a t c h dyeing, w e l l over h a l f of t h e wastewater volume and p o l l u t a n t l oad ing from dyeing r e s u l t s from ba tch dyeing o p e r a t i o n s .

I n c e r t a i n i n d u s t r y s e c t o r s , dyeing i s performed almost e x c l u s i v e l y by ba tch o p e r a t i o n s , and thus t h e m i l l s i n t h e s e s e c t o r s can be regarded a s p o t e n t i a l u s e r s of dyebath reuse technology. These s e c t o r s i nc lude k n i t f a b r i c f i n i s h i n g , h o s i e r y f i n i s h i n g , and y a r n f i n i s h i n g . A l a r g e amount of c a r p e t dyeing i s s t i l l performed i n ba t ch o p e r a t i o n s , a l though t h e r e is a t r e n d toward product ion of more cont inuous dyed/pr in ted c a r p e t . Most l a r g e woven f a b r i c f i n i s h i n g m i l l s employ cont inuous dye ing , though some s m a l l e r m i l l s s t i l l have s i g n i f i c a n t ba t ch dyeing o p e r a t i o n s . O v e r a l l , a l a r g e number of m i l l s can p o t e n t i a l l y adopt t h i s r e c y c l e technology.

Dyebath r euse has been t e s t e d o r demonstrated wi th a wide v a r i e t y of p roduc t s and t e x t i l e f i b e r s . Examples inc lude nylon h o s i e r y and c a r p e t ; p o l y e s t e r f a b r i c , c a r p e t , and ya rn ; a c r y l i c yarn ; and c o t t o n f a b r i c . Dyestuff c l a s s e s t h a t have been t e s t e d o r demonstrated inc lude a c i d , b a s i c , d i r e c t , d i s p e r s e , and r e a c t i v e .

A t many m i l l s , n o t all produc t ion w i l l be amenable t o dyeing by dyebath r euse . However, even t h e convers ion of a few machines t o t h i s r e c y c l e technology w i l l have s u b s t a n t i a l c o s t and environmental b e n e f i t s . A m i l l t h a t i s i d e a l l y s u i t e d t o employ dyebath r euse technology w i l l g e n e r a l l y on ly d e d i c a t e h a l f of i t s dye machines t o r euse dyeing. Th i s i s t o ensu re t h a t f l e x i b i l i t y i n product ion i s main ta ined .

CONCLUSIONS

This p r o j e c t demonstrated t h e t e c h n i c a l f e a s i b i l i t y of ba t ch dyebath r e c o n s t i t u t i o n and reuse a t a c a r p e t m i l l . I t demonstrated how s e v e r a l t e c h n i c a l problems common t o a wide v a r i e t y of m i l l s were overcome. These problems inc luded s e l e c t i n g product s t y l e s and shades t h a t can be inco rpora t ed i n a dyebath r euse scheme; reformu- l a t i n g dye r e c i p e s t o use a s i n g l e group of d y e s t u f f s t o dye many shades ; demonst ra t ing t h a t dyebath reuse can be accomplished on a p o r t i o n of product ion w i t h i n t h e normal product ion schedule ; produc- i n g h igh -qua l i ty product w i t h r ecyc led dyebaths; and adap t ing t h e dyebath r euse procedures t o conform t o t h e mil l ' s s t anda rd dyeing procedures , i nc lud ing such c o n s i d e r a t i o n s a s i n i t i a l dyebath tempera- t u r e and t h e use of overf low coo l ing .

i

* t

848

Environmental b e n e f i t s a r e s i g n i f i c a n t , even when dyebath r euse i s p r a c t i c e d i n a non-optimal f a sx ion . P o l l u t a n t and water use reduc- t i o n s of 25 t o 50 p e r c e n t were observed. Environmental b e n e f i t s a r e maximized when d i l u t i o n of t he dyebath through steam condensa t ion and overflow coo l ing i s kep t t o a minimum.

Dyebath reuse i s economical ly a t t r a c t i v e , even when p r a c t i c e d i n a non-optimal f a sh ion . A payback pe r iod of 1 .5 y e a r s was determined f o r t h i s m i l l . Again, economic b e n e f i t s a r e maximized when d i l u t i o n of t he dyebath i s minimized.

Based on these results and e s t i m a t e s , t h i s m i l l is making p l a n s t o a c q u i r e , i n s t a l l , and modify necessary equipment i n t h e nea r f u t u r e t o enable r e c o n s t i t u t i o n t o be implemented a t c e r t a i n becks .

Because of t h e l a r g e amount of ba t ch dyeing performed i n t h e

ba th reuse , t h i s wastewater r e c y c l e l r e u s e technology can be expected t o grow i n use. S p e c i f i c a r e a s f o r u s e i nc lude k n i t f a b r i c d y e r s , c a r p e t dye r s , and ya rn dye r s . Larger ho i se ry m i l l s may a l s o f i n d dyebath reuse advantageous.

. i n d u s t r y , and t h e low c a p i t a l c o s t and a t t r a c t i v e economics of dye-

6 ' - 6 *- 4 REFERENCES

1. Bergentha l , J o n F. Wastewater Recycle and Reuse P o t e n t i a l f o r I n d i r e c t Discharge T e x t i l e F i n i s h i n g Mills, Volume 1, Report EPA-600/2-84-070a, NTIS No. PB84-174150, March 1984.

2. Cook, F. L . , e t a l . In -P lan t Demonstration o f Dyebath Reuse Applied t o Hos iery Dyeing, DOE Con t rac t EY-76-S-05-5099, A p r i l 1979.

3 . Tincher , Wayne C . , F. L . Cook, and L . A. Barch. "Reusing Dye- ba ths i n Jet Dyeing," T e x t i l e Chemist and C o l o r i s t , Vol. 13, No. 12 (December 1 9 8 l ) , pp. 266-269.

4. T inche r , Wayne C . , e t a l . In -P lan t Demonstration of Energy Opt imiza t ion i n Beck Dyeing of Carpe t , F i n a l Report DOE/CS/ 40081-T1, 1980. ._

5. Bergentha l , Jon F. and A . J . Tawa. I n v e s t i g a t i o n of Dyebath R e c o n s t i t u t i o n and Reuse, Volume 2 - Opera t ions Manual, Report EPA-600/2-84-100b, NTIS No. PB84-206473, May 1984.

849

S e r i e s

- TABLE 1

BENCH-SCALE SHAD) MATCHING RESULTS

Average C o l o r D i f f e r e n c e s ( S t a r l a b U n i t s ) Bath Bath Bath Ba t t i Bath Bath

Number Shade {fl If 2 // 3 #4 #5 #6

1

2

3

3 A 4

5

6

7

8

9

105 S t d 0 .78

106 S t d 0 .63

103 S td 5.86

103 S t d 2.29

104 S t d 1.81

102 S td 0 .86

10 1 S t d 1.10

205 S t d 0.87

206 S t d 1 .21

204 S t d 0 .58

2 .16

0 .41

3.11

3 .13

5 .11

1 .32

2.08

1 .73

1.35

0.52

1.55

0.89

3.42

3.74

1.98

2.37

1 .28

1.01

1.42

0.92 -- -- -- S t d 0.91 -- 10 202

10A 202 -- -- 1.15 1.30 0.99

11 203 S t d 0.09 12 20 1 Std 2.05 2.46 3.06 2.63

13 Mul t i 0.42 1.17 5.65 2.89 4.47 3 .86

14 Mul t i 0.95 1.06 1.98 2.37 N / A

-- 0.67 0.34 1.58 --

--

-- -- 15 Mul t i 1.05 2.60 1.75 2.10 1.77

N/A - Data not a v a i l a b l e

..

850

TABLE 2 PILOT-SCALE SHADE MATCHING AND LEVELNESS RESULTS

Shade Matching

Series Number 17 18 19 20 21 22 23 03

ul F

Levelness

Carpet S t y l e

1 1 1 2 2 2 2

S e r i e s Carpet Number S t y l e 17 1 18 1 19 1 20 2 2 1 2 22 2 23 2

Shade 103 101 Mult i 201 203 206 Mult i

Color D i f f e rence From Standard ( S t a r l a b U n i t s ) Bath Bath Bath Bath Bath Bath Bath Bath Bath

# 9 # 1 82 83 84 85 11 6 # 7 # 8 3.08 4.11 4.64 4.28 3.41 -- -- -- 1.10 2.43 3.97 1.34 1.52 -- -- -- -- 1.50 1.78 1.54 1.22 1.11 5.53 4.00 3 .56 3.85 0.83 1.17 0.93 N/A 2.69 N/A -- -- -- 0.45 0.68 0.69 N/A 1.50 -- -- -- -- 1.90 1.83 1.74 2.62 2.40 -- -- -- -- 1.66 1.04 3.78 3.80 1.66 1 .21 2.75 2.50 3.10

- - - - - - - - - --

Bath Shade //1 103 1.00 --

101 1.58 Mul t i 0.64 201 0.80 203 0.53 206 1.55 Mult i 0.86

Side- to-Side Color D i f f e rence ( S t a r l a b U n i t s ) Bath Bath Bath Bath Bath Bath Bath

#5 # 6 // 7 # 8 - - - - - - - -- -- 82 # 3 #4 4.69 6.69 5.02 0 .62 -- N/A 7.66 2.34 N/A -- -- --

0.94 0.70 N/A 1.01 N/A -- -- 0.68 0.90 N/A 0.48 -- -- -- 1.60 0.87 0.79 0.99 -- -- -- 0.90 1 .81 1.88 1.76 1.72 1.49 4.08

1.59 2.98 1.83 1.70 0 .73 1.50 1.07

-- -- 0.76 2.00

N/A - Data n o t a v a i l a b l e .

TABLE 3 FULL-SCALE DYEING DYEBATH SUMMARY

Add Summary +

S e r i e s Dyebath Shade Number Add Add Add Number Number Shade D e s c r i p t i o n of Adds 1 2 3 -I_ ___ - - - -

24 24 24

25 25 25 25

03 25 N 25 Ln

26 26 26 26 26 26 26 26 26 26

1 2 3

1 2 3 4 5 6

1 2 3 4 5 6 7 8 9

10

111 111 101

101 112 112 103 113 113

21 1 211 212 212 213 214 215 215 216 217

L t . Yellow L t . Yellow L t . Brown

L t . Brown L t . Golden Br. L t . Golden B r . Med. Gray Med. Plum Med. Plum

P a l e Yellow P a l e Yellow Smoke Smoke Buff Beige Bronze Bronze Tan Royal Blue

0 4 3

1 1 1 2 2 0

3 2 1 1 1 2 0 1 0 0

Cool ing Summary Cool ing I n i t i a l

C.W. End Dyebath Ga l lons Temp O F Temp O F Remarks

2 , 700 2 ,700 - -

2 , 700 4,500 4,500 4,500 4,500 --

5,400 3,600 4,500 2,700 2 , 250 3,600 1,800 1,800 1 ,800 - -

148 146 --

138 136 120 138 124 -- 130 120 133 137 134 142 140 138 144 - -

68 95

105 105 100 105

6% 105 92

102 105 104 e 105 93

103 116

t

$ ; I d e n t i f i e s a d d i t i o n o f dyes (D) a n d / o r l e v e l e r ( L ) , and i f add c a r r i e d o u t a t b o i l ( B )

TABLE 3 (cont inued)

Remarks

a - A f o u r t h add c b n s i s t i n g of a d d i t i o n of l e v e l e r and dyeing a t t h e b o i l was a l s o performed. b - The two c a r p e t s removed from t h i s dyebath a f t e r t h e f o u r t h add subsequent ly needed t o be redyed.

c - A yarn l o t change was subsequent ly determined a s t h e cause of d i f f i c u l t i e s i n t h i s dyeing. d - Dyebath dropped a f t e r f i r s t add and one of two r o l l s removed; due t o u n l e v e l dye ing , remaining r o l l

r equ i r ed two more adds u n t i l accep tab le . Reuse S e r i e s Number 24 was t e rmina ted . See Remark " c " . e - Dyeing a c c i d e n t l y performed a t b o i l ; adds performed a t 18O0F.

These were t h e only redyes r equ i r ed o u t of 32 r e c o n s t i t u t e d dyeings (16 dyeba ths ) .

a3 cn w

i

TABLE 4 WATER, ENERGY, ANI3 CHEMICAL SAVINGS

Water Energy Chemical Savings Savings Sa i n s M.S.P. T . S . P . Seques t e ran t 'Leveler

Dyeing ( g a l . ) (10 BTU) ( l b ) (It) ( I b ) ( g a l - ) 8 8

25- 1 2,400 25-2 5,000 25-3 5,200 25-4 4,000 25-5 3,600

5 300 25-6 -L__

T o t a l s f o r S e r i e s 25 25,500

26- 1 26-2 26-3 26-4 26-5 26-6 26-7 26-8 26-9 26-10

T o t a l s f o r Series 26

, i . *- f L '

100 4,700 4,700 7,000 7,650 6,300 6,500 6 ,500 8 ,100 7,900

59,450

0 .0 0 1 .33 -11 1.83 9 1 .83 4 1.58 -1

9 1.83 I_ -

8 . 4 0 10

0 .0 0 1 .78 -1 1.15 6 1.63 0 1 . 7 8 3 1 .73 3 1 .78 2 1 .20 2 1 .68 4

4 2.30 -

15.03 23

0 19 14 14 14 14 -

75

0 11 12 13 11 11 12 14 14 15 -

113

0 5.5 5 5 5 5 ___

25.5

0 5 5.5 5 6 6 5 6 6 .5 6 . 5

51 - 5

0 3 , 0 1 . t j 1 . !j

-0.S 1 . 5 __

7.0

0 2 .5 2 1 2 2 1 0 3 2 --

15.5

854

- TABLE 5

FULL-SCALE DYEBATH REUSE COST SAVINGS

S e r i e s 26 (Carpet S t y l e 2 : 10 dye ings)

Cost I tem Savings from Dyeing Percent Savings

Quan t i ty D o l l a r s v s . Normal Dyeing

Dyes - Orange 0.044 l b $0.10 Red 0.015 l b 0 .10 Blue 0.014 l b 0 .10

Chemicals - MSP 23 l b 12.80 TSP 113 l b 36.70 Seques t e r a n t 5 1 . 5 l b 21.60 Leveler 15.5 g a l . 114.70 Defoamer 0 g a l . 0.00

Water/Sewer 59,500 g a l . 47.00

Energy (Steam) 19,500 l b 53.30

1

35

36

Not e s t ima ted

T o t a l $286.40

Average p e r c y c l e sav ings = $28.60 (based on 10 c y c l e s )

Yearly Savings = $25/cyc le x 1,200 dyeings/beck/year x 2 becks = $60,00O/year

855

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