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Journal of Cleaner Production 16 (2008) 152e158www.elsevier.com/locate/jclepro
Note from the field
Process modification in the scouring process of textile industry
Atichart Tanapongpipat, Citapar Khamman, Kejvalee Pruksathorm, Mali Hunsom*
Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Phaya Thai Road, Bangkok 10330, Thailand
Received 27 January 2006; accepted 16 June 2006
Available online 22 August 2006
Abstract
The effects of scouring parameters on the scouring efficiency, including the weight ratio of de-sizing agent and fabric (5e80 g/g fabric),temperature of de-sizing agent tank (60e90 �C) and dipping time (2e8 s), were investigated. The results demonstrated that weight loss of sizingagent was significantly observed only in the de-sizing agent tank particularly in the first de-sizing tank and was found to a small extent in watertank. The optimum condition in the scouring machine was found at a de-sizing agent to fabric ratio of 20 g/g fabric, with a temperature of thefirst de-sizing agent tank of 80 �C, a temperature of the second de-sizing agent tank of 90 �C, and dipping time of fabric of 7 s. According tothese conditions, more than 89% of the sizing agent was eliminated and only 3.52 mg/g fabric of sizing agent remained in the scoured fabricwhich was in an acceptable range for feeding to the down stream process known as dyeing process. Application of our results to actual textileplant has shown that there is a cost reduction due to improved utilization of rinse water, chemicals and energy in the process and consequentdecreases in the generation of wastewater. Furthermore, the production capacity was increased from 30 m/min to 34.4 m/min.� 2006 Elsevier Ltd. All rights reserved.
Keywords: Cleaner production; Scouring process; Nylon; Sizing agent; Textile industry
1. Introduction
The concept of cleaner production (CP) has been practicedfor many years in many countries [1]. Such CP activities in-clude measures such as pollution prevention, source reduction,waste minimization and eco-efficiency. At its heart, theconcept is about the prevention rather than the control of pol-lution [2].
In this work, the concept of CP including the waste min-imization and process modification was carried out in the tex-tile industry because, in our country, the textile was thesecond largest export commodity registering over US$ 5.2billion in 1999 and more than US$ 5.7 billion in 2003.One principal problem that textile industries have been facingis the re-dyeing process. When such process is carried out, itleads to a loss of many resources such as water, energy, de-sizing agent and dyestuff, time, man-hour, etc. Moreover,
* Corresponding author. Tel.: þ66 2 2187523 5; fax: þ66 2 2555831.
E-mail address: [email protected] (M. Hunsom).
0959-6526/$ - see front matter � 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jclepro.2006.06.016
a large amount of dark color wastewater containing dyestuff,salts, high de-sizing agent oxygen demand (COD) derivedfrom additives, total dissolved solid (TDS), total suspendedsolid (TSS) and fluctuating pH is generated leading to theproblem of wastewater management. One factor that can re-duce the efficiency in dyeing process is the contamination ofsizing agent in the fabric at high quantity. Namely, during theyarn preparation, various kinds of sizing agent are added intothe fabric to increase the strength and to reduce the rippingof the yarn during the fabric process. These sizing agentshave to be eliminated from the fabric surface before feedingsuch fabric to the down stream process. The process used toeliminate the sizing agent is known as the scouring processand its efficiency depends upon many parameters such as op-erating condition, type of de-sizing agent, etc. The bioscour-ing process was used to eliminate the sizing agent from wooland cotton [3]. The results indicated that, for cotton, the pec-tinase enzyme showed excellent activity even in organic me-dia, and the effectiveness of scouring was equivalent or betterthan that achieved by the conventional alkaline process or bi-oscouring in the aqueous media. On the other hand, for wool,
153A. Tanapongpipat et al. / Journal of Cleaner Production 16 (2008) 152e158
it was found that felting property and tensile strength of woolfabrics treated by protease in reverse micellar system weresuperior to those in aqueous media. The commercial enzymepectinase from Aspergillus niger (Pontypridd, Wales, UK)was used to scour raw knitted fabric cotton/polyester (50/50), 146 g/m2 [4]. It was found that the bioscouring processwas very sensitive to the surfactant and the pH regulationwhereas temperature seems to be less important. Aly et al.[5] attempted to scour cotton fabrics made of Giza 70 andGiza 75 by using various enzymes including bioprip, cellu-soft L and denilite enzymes. They demonstrated that thescouring was affected by using either bioprip enzyme at60 �C and pH 9 or cellusoft L enzyme at 50 �C and pH 5for 60 min. Ossola and Galante [6] demonstrated that theefficiency of the scouring process of the flax rove in thedecreasing order of effectiveness was pectinase> xylanase¼galactomannanase¼ protease> lipase� laccase. The effectof low temperature plasma treatment on the scouring of nat-ural fabrics was also investigated [7]. The results demonstratedthat low temperature plasma treatment could increase thescouring rate of cotton and wool fabrics. Although the previousresults demonstrated that using various kinds of enzymes seemsto be effective to eliminate sizing agent in the fabric, applica-tion of such may not be practical in actual textile industrydue to their high production cost. Therefore, the processesoptimization and modification are the alternative proceduresto get the better scouring efficiency and environmentallyfriendly as the CP concept. In this work, the effects of variousparameters in the scouring machine were investigated.
2. Experimental
The effects of various parameters including effect of de-siz-ing agent and water, weight ratio of de-sizing agent and fabricin the range of 5e80 g/g fabric, temperature of de-sizing agenttanks (60e90 �C), and dipping time (2e8 s) on the scouringefficiency were first determined in the laboratory scale by us-ing the equipment emulated from the conventional scouringequipment of textile industry. Fig. 1 displays the conventionalconfiguration of the scouring equipments employed in the tex-tile industry. It generally consisted of two de-sizing agenttanks and three water tanks. The first tank, containing water,was used to wet and clean some impurities such as dust
from the fabric surface. The second and third tanks, containingchemical agent, were used to eliminate the sizing agent fromthe fabric structure. The weight ratio of de-sizing agent andfabric is maintained constant at 40 g/g fabric. The operatingtemperatures of both de-sizing agent tanks were maintainedapproximately at 80 �C and 90 �C, respectively. The last twotanks were the rinsing water tanks, which were utilized towash the de-sizing agents on the fabric surface. The tempera-tures of both tanks were controlled at around 80 �C and 60 �C.The de-sizing agent used in the process was the liquid mixtureof NaOH, detergent, and chelating agent. The investigated fab-ric was nylon with initial sizing agent content of 33.02 mg/gnylon. In each experiment, the amount of aqueous solutionin each tank was fixed at 1.8 l. The efficiency of the scouringprocess was determined by using the weight loss of sizingagent per unit weight of fabric. High loss of sizing agent refersto the high efficiency of the scouring process.
3. Results and discussion
3.1. Effect of de-sizing agent and water on thescouring efficiency
The experiments in laboratory scale were preliminarily per-formed to determine the effect of de-sizing agent and water onthe scouring efficiency by using the dipping time of 8 s, tem-perature of all tanks of 80 �C, and weight ratio of de-sizingagent and fabric of 40 g/g fabric. The results as exhibited inFig. 2(a) showed that the significant weight loss of sizingagent of approximately 18.49 mg/g fabric was obviously ob-served in a de-sizing agent tank whereas only 0.5e2.3 mg/gfabric of sizing agent was lost in water tanks. To confirmthe effect of de-sizing agent on the weight loss of sizing agent,similar experiment was carried out by changing the sequenceof de-sizing agent and water tanks. The results plotted inFig. 2(b) demonstrated that when the fabric was submergedin water from tank 1 to tank 3, only 0.5e1.2 mg/g fabricwas lost in the process. When the fabric was consequently sub-merged in the de-sizing agent tank, approximately 16.72 mg/gfabric was lost from the fabric. These results confirm that onlyde-sizing agent has strong influence on the weight loss ofsizing agent whereas the water has not. From such results, itdemonstrates that only one rinsing water tank was adequate
Tank # 3De-sizing
agent
Tank # 1Water
Tank # 4Water
Tank # 5Water
Tank # 2De-sizing
agent
Fig. 1. Scheme of conventional scouring process.
154 A. Tanapongpipat et al. / Journal of Cleaner Production 16 (2008) 152e158
0.51 1.19 0.88
16.72
0.02 0.050
5
10
15
20
25
Wate
r tan
k # 1
Wate
r tan
k # 2
Wate
r tan
k # 3
De-sizi
ng ag
ent ta
nk
Wate
r tan
k # 4
Wate
r tan
k # 5
Wei
gh lo
ss o
f si
zing
age
nt (
mg/
g fa
bric
)
(b)
2.29
0.50 0.51 0.47
18.49
0
5
10
15
20
25
De-sizi
ng ag
ent t
ank
Wate
r tan
k # 1
Wate
r tan
k # 2
Wate
r tan
k # 3
Wate
r tan
k # 4
Wei
ght l
oss
(mg/
g fa
bric
)
(a)
Fig. 2. Weight loss of sizing agent in de-sizing agent and water tanks.
in the process because it has no influence on the elimination ofthe sizing agent in the fabric as the chemical did. Many watertanks lead to high amount of water consumption and highquantity of wastewater generation.
The significance of both de-sizing agent tanks on theweight loss of sizing agent was further investigated at a tem-perature of 80 �C, dipping time of 8 s and weight ratio ofde-sizing agent and fabric of 20 g/g fabric. The results as dis-played in Fig. 3 indicated that the weight loss of sizing agentwas more significantly observed in the first de-sizing agenttank than that in the second de-sizing agent tank, namely,greater than 18 mg/g fabric of sizing agent was eliminatedin the first tank whereas approximately 0.91 mg/g fabricwas dislodged in the second de-sizing agent tank. These re-sults can be confirmed by the data collected from scouring
18.49
0.91
0
5
10
15
20
25
Tank # 1
Tank # 2
Wei
ght l
oss
of s
izin
g ag
ent (
mg/
g fa
bric
)
Fig. 3. Weight loss of sizing agent in both de-sizing agent tanks.
process in the actual textile plant as shown in Fig. 4, whichdemonstrates the relationship between the weight loss of de-sizing agent as a function of parameters of the aqueoussolution (temperature, pH, TSS, TDS and alkalinity) in boththe chemical tanks. It can be seen that the parameters in thefirst chemical tank was more fluctuant than that of the secondchemical tank. This fluctuation was due to the contaminationof the sizing agent in the aqueous solution. So, this behaviorcan confirm the previous results (Fig. 3) in that the more siz-ing agent can be removed in the first de-sizing agent tank thanin the second tank. Although, the relationship between theweight loss of sizing agent and temperature (Fig. 4(a)) andpH (Fig. 4 (b)) of the first de-sizing agent tank was not cer-tainly observed, the TSS, TDS, M-alkalinity and P-alkalinityshowed the relationship with the weight loss of sizing agent.Namely, high values of TSS, TDS, M-alkalinity and P-alkalinityled to high weight loss of sizing agent such as sample num-bers 2, 19, and 20. Likewise low values of them conductedsmall weight loss of sizing agent such as sample 18. Thistendency, however, was not clear for all samples because itrelates to various parameters in scouring process such as con-centration of de-sizing agent at interval, operating tempera-ture, etc.
3.2. Effect of weight ratio of de-sizing agent and fabric
According to the above results, the de-sizing agent has sig-nificant effect on the efficiency of scouring process. The actualratio of de-sizing agent to fabric used in the textile industrywas about 40 g/g fabric. In this part, the author attempted toreduce the de-sizing agent cost in the actual process by reduc-ing the de-sizing agent to fabric ratio. The experiment wasconducted in a laboratory scale with the weight ratio of de-sizing agent and fabric in the range of 5e80 g/g fabric at a tem-perature of 80 �C and a dipping time of 8 s. The results plottedin Fig. 5 demonstrated that weight loss of sizing agent was
155A. Tanapongpipat et al. / Journal of Cleaner Production 16 (2008) 152e158
0
20
40
60
80
100
120
140
0 5 10 15 20 25 30
Sample number
Tem
pera
ture
(°C
)
0
10
20
30
40
50
60
70
80
Weight loss (m
g/g fabric)
Tank 1
Tank 2
Weight loss
Tank 1
Tank 2
Weight loss
Tank 1
Tank 2
Weight loss
Tank 1
Tank 2
Weight loss
Tank 1
Tank 2
Weight loss
Tank 1
Tank 2
Weight loss
(a)
0
2
4
6
8
10
12
14
16
18
20
0 5 10 15 20 25 30
Sample number
pH
0
10
20
30
40
50
60
70
80
Weight loss (m
g/g fabric)
(b)
0
50
100
150
200
250
300
350
0 5 10 15 20 25 30
Sample number
TSS
(m
g/g
fabr
ic)
0
10
20
30
40
50
60
70
80
Weight loss (m
g/g fabric)
(c)
0
5,000
10,000
15,000
20,000
0 5 10 15 20 25 30
Sample number
TD
S (
mg/
g fa
bric
)
0
10
20
30
40
50
60
70
80
Weight loss (m
g/g fabric)
(d)
0
2
4
6
8
0 5 10 15 20 25 30
Sample number
P-al
kalin
ity (
mg/
l)
0
10
20
30
40
50
60
70
80
Weight loss (m
g/g fabric)
0
2
4
6
8
0 5 10 15 20 25 30
Sample number
M-a
lkal
init
y (m
g/l)
0
10
20
30
40
50
60
70
80
Weight loss (m
g/g fabric)
(e) (f)
Fig. 4. Physical properties of aqueous solution in the chemical tanks of the scouring process of textile industry and weight loss of sizing agent.
observed when the ratio of de-sizing agent and fabric increasedfrom 5 to 14 g/g fabric, namely, it slightly increased from16.7 mg/g fabric to 18.2 mg/g fabric or approximately 7e9%. However, the significant increase in the weight loss ofsizing agent was then found when increasing the de-sizing
agent to fabric ratio from 14 to 20 g/g fabric. It increasedfrom 18.2 mg/g fabric to 24.3 mg/g fabric or approximatelyto 33.5%. Further increasing ratio of de-sizing agent to fabricto 80 g/g fabric cannot promote the increase of weight loss ofsizing agent in fabric. According to this study, it can be said
156 A. Tanapongpipat et al. / Journal of Cleaner Production 16 (2008) 152e158
16.718.0 18.2
22.3
24.3 24.4 24.2 24.0
0
5
10
15
20
25
30
5 10 14 17 20 40 60 80
Chemical : Fabric (g/g fabric)
Wei
ght l
oss
(mg
sizi
ng a
gent
/g f
abri
c)
Fig. 5. Weight loss of sizing agent as a function of de-sizing agent to fabric ratio.
that the optimum de-sizing agent to fabric ratio was found ata ratio of 20 g/g fabric which is approximately 50% less thanthat used in actual textile process.
3.3. Effect of temperature in de-sizing agent tanks
In this part, the experimental set up was imitated from theactual process consisting of three water tanks and two de-sizing agent tanks. The first water tank was used for wettingand cleaning the fabric from impurity such as dust. The nexttwo tanks were de-sizing agent tanks containing de-sizingagent with weight ratio of 20 g/g fabric and the last two tankscontaining water was used to eliminate the de-sizing agent onfabric surface. The temperature in all water tanks was con-trolled at 80 �C and the temperature of both de-sizing agenttanks was varied in the range of 60e90 �C. Fig. 6(a) demon-strates the effect of temperature in the first chemical tank inthe range of 60e90 �C by using constant temperature of thesecond chemical tank (80 �C). It showed that the weight
loss of sizing agent obtained from this condition increasedslightly from 18.5 mg/g fabric at 60 �C to approximately24.4 mg/g fabric at 80 �C and afterwards it was ratherconstant. On the other hand, the effect of temperature in thesecond de-sizing agent tank was also studied in the range of60e80 �C by using the fixed temperature of the first chemicaltank. The results demonstrated in Fig. 6(b) referred that theweight loss of sizing agent was constant in the range ofoperating temperatures of 60e80 �C, but it would increaseto approximately 29.5 mg/g fabric at 90 �C. From this inves-tigation, it can be said that optimum temperatures in the firstand second de-sizing agent tanks were 80 �C and 90 �C,respectively.
3.4. Effect of dipping time
The dipping time indicates the time that the fabric is sub-merged in the solution. The shorter dipping time means therapid velocity of fabric fed into the scouring machine.
18.5
21.3
25.124.4
0
5
10
15
20
25
30
35
60 70 80 90
Temperature in the 1st chemical tank (ºC)
Wei
ght l
oss
(mg
sizi
ng a
gent
/g f
abri
c)
(a)
23.9 24.0 24.6
29.5
0
5
10
15
20
25
30
35
60 70 80 90
Temperature in the 2nd chemical tank (ºC)
Wei
ght l
oss
(mg
sizi
ng a
gent
/g f
abri
c)
(b)
Fig. 6. Weight loss of sizing agent as a function of temperature at (a) constant temperature of the second chemical tank of 80 �C and (b) constant temperature of the
first chemical tank of 80 �C.
157A. Tanapongpipat et al. / Journal of Cleaner Production 16 (2008) 152e158
Similarly, it indicates the large production capacity per unittime. Fig. 7 shows the weight loss of sizing agent on fabricas a function of dipping time in the range of 2e8 s at de-siz-ing agent to fabric ratio of 20 g/g fabric, temperature of thefirst de-sizing agent tank of 80 �C and temperature of thesecond de-sizing agent tank of 90 �C. The results indicatedthat when the dipping time increased from 2 s to 7 s, theweight loss of sizing agent increased slightly from 24.35mg/g fabric to approximately 29.07 mg/g fabric and thenbecame quite constant. Therefore, it can be said that the op-timum dipping time was around 7 s, which was correspond-ing to the velocity of fabric in scouring machine of around34.4 m/min. At this condition, greater than 89% of sizingagent was eliminated from the fabric surface and the amountof the sizing agent remaining in the fabric was lower than3.52 mg/g fabric which is acceptable to feed into the downstream process.
Table 1 exhibits the comparison of operating conditionsand properties of the scoured fabric between laboratoryand the actual textile processes. It showed that the ratio ofde-sizing agent to fabric used in this work was lower thanthat of the actual process of approximately 50%. The dip-ping time which was corresponding to the velocity of fabricin the scouring machine was faster than that in actual pro-cess of around 15%. It means that the production capacitycan be increased by operating the system at our find out con-dition. By employing this condition, more than 89% of siz-ing agent was eliminated from the fabric and the remainingsizing agent in fabric was approximately 3.52 mg/g fabricwhich is lower than that obtained by using the actual textileplant.
The operation costs used in the new optimum conditionincluding the costs of rinsing water, chemicals, wastewatermanagement and energy were also calculated and comparedwith that used in the conventional process as demonstratedin Table 1. It can be seen that the application of the new
24.3525.85
27.4429.5029.07
0
5
10
15
20
25
30
35
2 4 6 7 8
Dipping time (s)
Wei
gh lo
ss o
f si
zing
age
nt (
mg/
g fa
bric
)
Fig. 7. Weight loss of sizing agent as a function of dipping time.
optimum condition leads to the decrease of operation cost ofapproximately 50%.
4. Conclusion
The concept of CP concerned with waste minimization andprocess modification was performed in the scouring process oftextile industry. The results indicated that only the de-sizingagent had significant effect on weight loss of sizing agentwhereas water did not. Therefore, one rinsing water tankwas enough to clean the de-sizing agent from the fabric.This decreased the quantity of wastewater discharged fromthe process by approximately 20%. For the chemical tanks,the first de-sizing agent tank in the scouring machine hadmore influence on the weight loss of sizing agent than thatof the second de-sizing agent tank. Namely, the weight lossesof sizing agent were approximately 24 mg/g fabric and0.91 mg/g fabric for the first and the second de-sizing agenttanks, respectively. The optimum condition in the scouringprocess was found at the de-sizing agent to fabric ratio of20 g/g fabric, temperature in the first and second de-sizingagent tanks of 80 �C and 90 �C, respectively, and the dippingtime of 7 s. Application of our results reduces the amount ofchemicals, rinse water and energy used in the process. In ad-dition, the production capacity was increased from 30 m/minto 34.4 m/min. The barrier that may be faced when this im-provement is carried out is the variation of the amount ofthe sizing agent in the fabric surface in the actual textile plant.When this situation occurs, the producers have to use the ratioof the de-sizing agent to fabric greater than 20 g/g fabric orwith safety factor of approximately 20e50%. This will leadto a decrease in savings from the new process. The other bar-rier is that this condition can only be used with nylon.
Table 1
Comparison of conditions and characteristics of scoured fabric between this
work and actual textile plant
Characteristics and conditions This work Actual textile
plant
Weight ratio of de-sizing agent
and fabric (g/g fabric)
20 40
Temperature of the first de-sizing
agent tank (�C)
80 80
Temperature of the second de-sizing
agent tank (�C)
90 90
Dipping time (s) 7 (34.4 m/min) 8 (30.0 m/min)
Weigh loss of sizing agent
(mg/g fabric)
29.50 24.92e26.73
Residual sizing agent in scoured
fabric (mg/g fabric)
3.52 6.29e8.10
Operation cost
Chemical reagent (USDa/m2 fabricb) 0.361 0.722
Water (USD/m2 fabric) 0.116 0.232
Wastewater management
(USD/m2 fabric)
0.071 0.141
Energy cost (USD/m2 fabric) 0.004 0.007
a 1 USD¼ 35.8 Baht.b Fabric with 1.524 m width.
158 A. Tanapongpipat et al. / Journal of Cleaner Production 16 (2008) 152e158
Acknowledgement
The authors would like to thank the Thailand ResearchFund under the IRPUS projects for the financial support ofour project and the Cleaner Technology Consortium at Chula-longkorn University.
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