Ts-4 Process Modification in the Scouring Process of Textile Industry

8/9/2019 Ts-4 Process Modification in the Scouring Process of Textile Industry

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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

Abstract

The effects of scouring parameters on the scouring efficiency, including the weight ratio of de-sizing agent and fabric (5e

80 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 sizing

agent 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 water

tank. 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 the

first 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 to

these conditions, more than 89% of the sizing agent was eliminated and only 3.52 mg/g fabric of sizing agent remained in the scoured fabric

which was in an acceptable range for feeding to the down stream process known as dyeing process. Application of our results to actual textile

plant has shown that there is a cost reduction due to improved utilization of rinse water, chemicals and energy in the process and consequent

decreases in the generation of wastewater. Furthermore, the production capacity was increased from 30 m/min to 34.4 m/min.

Keywords: Cleaner production; Scouring process; Nylon; Sizing agent; Textile industry

1. Introduction

The concept of cleaner production (CP) has been practiced

for 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, the

concept 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$ 5.2

billion in 1999 and more than US$ 5.7 billion in 2003.

One principal problem that textile industries have been facing

is the re-dyeing process. When such process is carried out, it

leads to a loss of many resources such as water, energy, de-

sizing agent and dyestuff, time, man-hour, etc. Moreover,

a large amount of dark color wastewater containing dyestuff,

salts, high de-sizing agent oxygen demand (COD) derived

from additives, total dissolved solid (TDS), total suspended

solid (TSS) and fluctuating pH is generated leading to the

problem of wastewater management. One factor that can re-

duce the efficiency in dyeing process is the contamination of

sizing agent in the fabric at high quantity. Namely, during the

yarn preparation, various kinds of sizing agent are added into

the fabric to increase the strength and to reduce the ripping

of the yarn during the fabric process. These sizing agents

have to be eliminated from the fabric surface before feedingsuch fabric to the down stream process. The process used to

eliminate the sizing agent is known as the scouring process

and 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 wool

and 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 better

than that achieved by the conventional alkaline process or bi-

oscouring in the aqueous media. On the other hand, for wool,* Corresponding author. Tel.: 66 2 2187523 5; fax: 66 2 2555831.

E-mail address: [email protected] (M. Hunsom).
mailto:[email protected]://www.elsevier.com/locate/jclepromailto:[email protected]


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it was found that felting property and tensile strength of wool

fabrics treated by protease in reverse micellar system were

superior to those in aqueous media. The commercial enzyme

pectinase 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 process

was 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 and

Giza 75 by using various enzymes including bioprip, cellu-

soft L and denilite enzymes. They demonstrated that the

scouring was affected by using either bioprip enzyme at

60 C and pH 9 or cellusoft L enzyme at 50 C and pH 5

for 60 min. Ossola and Galante [6] demonstrated that the

efficiency of the scouring process of the flax rove in the

decreasing order of effectiveness was pectinase > xylanase

galactomannanase protease> lipase laccase. The effect

of low temperature plasma treatment on the scouring of nat-

ural fabrics was also investigated [7]. The results demonstrated

that low temperature plasma treatment could increase thescouring rate of cotton and wool fabrics. Although the previous

results demonstrated that using various kinds of enzymes seems

to be effective to eliminate sizing agent in the fabric, applica-

tion of such may not be practical in actual textile industry

due to their high production cost. Therefore, the processes

optimization and modification are the alternative procedures

to get the better scouring efficiency and environmentally

friendly as the CP concept. In this work, the effects of various

parameters 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 fabric

in the range of 5e80 g/g fabric, temperature of de-sizing agent

tanks (60e90 C), and dipping time (2e8 s) on the scouring

efficiency were first determined in the laboratory scale by us-

ing the equipment emulated from the conventional scouring

equipment of textile industry. Fig. 1 displays the conventional

configuration of the scouring equipments employed in the tex-

tile industry. It generally consisted of two de-sizing agent

tanks 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, containing

chemical agent, were used to eliminate the sizing agent from

the fabric structure. The weight ratio of de-sizing agent and

fabric is maintained constant at 40 g/g fabric. The operating

temperatures of both de-sizing agent tanks were maintained

approximately at 80 C and 90 C, respectively. The last two

tanks 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 mixture

of NaOH, detergent, and chelating agent. The investigated fab-

ric was nylon with initial sizing agent content of 33.02 mg/g

nylon. In each experiment, the amount of aqueous solution

in each tank was fixed at 1.8 l. The efficiency of the scouring

process was determined by using the weight loss of sizing

agent per unit weight of fabric. High loss of sizing agent refers

to the high efficiency of the scouring process.

3. Results and discussion

3.1. Effect of de-sizing agent and water on the

scouring efficiency

The experiments in laboratory scale were preliminarily per-

formed to determine the effect of de-sizing agent and water on

the scouring efficiency by using the dipping time of 8 s, tem-

perature of all tanks of 80 C, and weight ratio of de-sizing

agent and fabric of 40 g/g fabric. The results as exhibited in

Fig. 2(a) showed that the significant weight loss of sizing

agent of approximately 18.49 mg/g fabric was obviously ob-

served in a de-sizing agent tank whereas only 0.5e

2.3 mg/gfabric of sizing agent was lost in water tanks. To confirm

the effect of de-sizing agent on the weight loss of sizing agent,

similar experiment was carried out by changing the sequence

of de-sizing agent and water tanks. The results plotted in

Fig. 2(b) demonstrated that when the fabric was submerged

in water from tank 1 to tank 3, only 0.5e1.2 mg/g fabric

was lost in the process. When the fabric was consequently sub-

merged in the de-sizing agent tank, approximately 16.72 mg/g

fabric was lost from the fabric. These results confirm that only

de-sizing agent has strong influence on the weight loss of

sizing agent whereas the water has not. From such results, it

demonstrates that only one rinsing water tank was adequate

Tank # 3

De-sizing

agent

Tank # 1

Water

Tank # 4

Water

Tank # 5

Water

Tank # 2

De-sizing

agent

Fig. 1. Scheme of conventional scouring process.


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in the process because it has no influence on the elimination of

the sizing agent in the fabric as the chemical did. Many water

tanks lead to high amount of water consumption and high

quantity of wastewater generation.

The significance of both de-sizing agent tanks on the

weight loss of sizing agent was further investigated at a tem-

perature of 80 C, dipping time of 8 s and weight ratio of

de-sizing agent and fabric of 20 g/g fabric. The results as dis-

played in Fig. 3 indicated that the weight loss of sizing agent

was more significantly observed in the first de-sizing agent

tank than that in the second de-sizing agent tank, namely,greater than 18 mg/g fabric of sizing agent was eliminated

in the first tank whereas approximately 0.91 mg/g fabric

was dislodged in the second de-sizing agent tank. These re-

sults can be confirmed by the data collected from scouring

process in the actual textile plant as shown in Fig. 4, which

demonstrates the relationship between the weight loss of de-

sizing agent as a function of parameters of the aqueous

solution (temperature, pH, TSS, TDS and alkalinity) in both

the chemical tanks. It can be seen that the parameters in the

first chemical tank was more fluctuant than that of the second

chemical tank. This fluctuation was due to the contamination

of the sizing agent in the aqueous solution. So, this behavior

can confirm the previous results (Fig. 3) in that the more siz-

ing agent can be removed in the first de-sizing agent tank than

in the second tank. Although, the relationship between theweight loss of sizing agent and temperature (Fig. 4(a)) and

pH (Fig. 4 (b)) of the first de-sizing agent tank was not cer-

tainly observed, the TSS, TDS, M-alkalinity and P-alkalinity

showed the relationship with the weight loss of sizing agent.

Namely, high values of TSS, TDS, M-alkalinity and P-alkalinity

led to high weight loss of sizing agent such as sample num-

bers 2, 19, and 20. Likewise low values of them conducted

small weight loss of sizing agent such as sample 18. This

tendency, however, was not clear for all samples because it

relates 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 actual

ratio of de-sizing agent to fabric used in the textile industry

was about 40 g/g fabric. In this part, the author attempted to

reduce the de-sizing agent cost in the actual process by reduc-

ing the de-sizing agent to fabric ratio. The experiment was

conducted 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 plotted

in Fig. 5 demonstrated that weight loss of sizing agent was

0.511.19 0.88

16.72

0.02 0.050

5

10

15

20

25

Wate

rtank

#1

Wate

rtank

#2

Wate

rtank

#3

De-sizin

gagent

tank

Wate

rtank

#4

Wate

rtank

#5

Weighlossofsizing

agent(mg/gfabric)(b)

2.29

0.50 0.51 0.47

18.49

0

5

10

15

20

25

De-sizin

gagent

tank

Wate

rtank

#1

Wate

rtank

#2

Wate

rtank

#3

Wate

rtank

#4

Weightloss(mg/gfabric)

(a)

Fig. 2. Weight loss of sizing agent in de-sizing agent and water tanks.

18.49

0.91

0

5

10

15

20

25

Tank

#1

Tank

#2

Weightlossofsizingagent

(mg/gfabric)

Fig. 3. Weight loss of sizing agent in both de-sizing agent tanks.


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observed when the ratio of de-sizing agent and fabric increased

from 5 to 14 g/g fabric, namely, it slightly increased from

16.7 mg/g fabric to 18.2 mg/g fabric or approximately 7e

9%. However, the significant increase in the weight loss of

sizing agent was then found when increasing the de-sizing

agent to fabric ratio from 14 to 20 g/g fabric. It increased

from 18.2 mg/g fabric to 24.3 mg/g fabric or approximately

to 33.5%. Further increasing ratio of de-sizing agent to fabric

to 80 g/g fabric cannot promote the increase of weight loss of

sizing agent in fabric. According to this study, it can be said

0

20

40

60

80

100

120

140

0 5 10 15 20 25 30

Sample number

Temperature

(C)

0

10

20

30

40

50

60

70

80

Weight

loss(mg/gfabric)

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


(b)

0

50

100

150

200

250

300

350

0 5 10 15 20 25 30

Sample number

TSS(mg/gfabric)

0

10

20

30

40

50

60

70

80


(c)

0

5,000

10,000

15,000

20,000

0 5 10 15 20 25 30

Sample number

TDS(mg/gfabric)

0

10

20

30

40

50

60

70

80


(d)

0

2

4

6

8

0 5 10 15 20 25 30

Sample number

P-alkalinity(mg/l)

0

10

20

30

40

50

60

70

80


0

2

4

6

8

0 5 10 15 20 25 30

Sample number

M-alkalinity(mg/l)

0

10

20

30

40

50

60

70

80


(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.


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that the optimum de-sizing agent to fabric ratio was found ata ratio of 20 g/g fabric which is approximately 50% less than

that 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 the

actual process consisting of three water tanks and two de-

sizing agent tanks. The first water tank was used for wetting

and cleaning the fabric from impurity such as dust. The next

two tanks were de-sizing agent tanks containing de-sizing

agent with weight ratio of 20 g/g fabric and the last two tanks

containing 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 agent

tanks was varied in the range of 60e90 C. Fig. 6(a) demon-

strates the effect of temperature in the first chemical tank in

the range of 60e90 C by using constant temperature of the

second 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 approximately

24.4 mg/g fabric at 80 C and afterwards it was rather

constant. On the other hand, the effect of temperature in the

second de-sizing agent tank was also studied in the range of

60e80 C by using the fixed temperature of the first chemical

tank. The results demonstrated in Fig. 6(b) referred that the

weight loss of sizing agent was constant in the range of

operating temperatures of 60e80 C, but it would increase

to approximately 29.5 mg/g fabric at 90 C. From this inves-

tigation, it can be said that optimum temperatures in the first

and 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 the

rapid velocity of fabric fed into the scouring machine.

16.7

18.0 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)

Weightloss(mgsizingagent/gfabric)

Fig. 5. Weight loss of sizing agent as a function of de-sizing agent to fabric ratio.

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 (C)

Weightloss(mgsizingagent/g

fabric)

(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 (C)

Weightloss(mgsizingagent/g

fabric)

(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.


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Similarly, it indicates the large production capacity per unit

time. Fig. 7 shows the weight loss of sizing agent on fabric

as 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 the

first de-sizing agent tank of 80 C and temperature of the

second de-sizing agent tank of 90 C. The results indicated

that when the dipping time increased from 2 s to 7 s, the

weight loss of sizing agent increased slightly from 24.35

mg/g fabric to approximately 29.07 mg/g fabric and then

became 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 around

34.4 m/min. At this condition, greater than 89% of sizing

agent was eliminated from the fabric surface and the amount

of the sizing agent remaining in the fabric was lower than

3.52 mg/g fabric which is acceptable to feed into the down

stream process.

Table 1 exhibits the comparison of operating conditions

and properties of the scoured fabric between laboratory

and the actual textile processes. It showed that the ratio of

de-sizing agent to fabric used in this work was lower than

that of the actual process of approximately 50%. The dip-

ping time which was corresponding to the velocity of fabric

in the scouring machine was faster than that in actual pro-

cess of around 15%. It means that the production capacity

can 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 remaining

sizing agent in fabric was approximately 3.52 mg/g fabric

which is lower than that obtained by using the actual textile

plant.

The operation costs used in the new optimum condition

including the costs of rinsing water, chemicals, wastewater

management and energy were also calculated and compared

with that used in the conventional process as demonstrated

in Table 1. It can be seen that the application of the new

optimum condition leads to the decrease of operation cost of

approximately 50%.

4. Conclusion

The concept of CP concerned with waste minimization and

process modification was performed in the scouring process of

textile industry. The results indicated that only the de-sizingagent had significant effect on weight loss of sizing agent

whereas water did not. Therefore, one rinsing water tank

was enough to clean the de-sizing agent from the fabric.

This decreased the quantity of wastewater discharged from

the process by approximately 20%. For the chemical tanks,

the first de-sizing agent tank in the scouring machine had

more influence on the weight loss of sizing agent than that

of the second de-sizing agent tank. Namely, the weight losses

of sizing agent were approximately 24 mg/g fabric and

0.91 mg/g fabric for the first and the second de-sizing agent

tanks, respectively. The optimum condition in the scouring

process was found at the de-sizing agent to fabric ratio of

20 g/g fabric, temperature in the first and second de-sizing

agent tanks of 80 C and 90 C, respectively, and the dipping

time of 7 s. Application of our results reduces the amount of

chemicals, rinse water and energy used in the process. In ad-

dition, the production capacity was increased from 30 m/min

to 34.4 m/min. The barrier that may be faced when this im-

provement is carried out is the variation of the amount of

the sizing agent in the fabric surface in the actual textile plant.

When this situation occurs, the producers have to use the ratio

of the de-sizing agent to fabric greater than 20 g/g fabric or

with safety factor of approximately 20e50%. This will lead

to a decrease in savings from the new process. The other bar-

rier is that this condition can only be used with nylon.

24.35

25.85

27.44

29.5029.07

0

5

10

15

20

25

30

35

2 4 6 7 8

Dipping time (s)

Weighlossofsizingagen

t(mg/gfabric)

Fig. 7. Weight loss of sizing agent as a function of dipping time.

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-sizingagent 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 USD 35.8 Baht.b Fabric with 1.524 m width.


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Acknowledgement

The authors would like to thank the Thailand Research

Fund under the IRPUS projects for the financial support of

our project and the Cleaner Technology Consortium at Chula-

longkorn University.

References

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[2] International institute for sustainable development. Available from:

; 2005.

[3] Sawada K, Ueda M. Enzyme process of textiles in reserve micellar solu-

tion. J Biotechnol 2001;9:263e9.

[4] Calafell M, GarrigaP.Effectof some processparameters in theenzymaticscour-

ingof cottonusingan acidpectinase.EnzymeMicrobTechnol2004;34:326e31.

[5] Aly AS, Moustafa AB, Hebeish A. Bio-technological treatment of cellu-

losic textiles. J Clean Prod 2004;12:697e705.

[6] Ossola M, Galante YM. Scouring of flax rove with the aid of enzymes.

Enzyme Microb Technol 2004;34:177e86.

[7] Sun D, Stylios GK. Effect of low temperature plasma treatment on

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Ts-4 Process Modification in the Scouring Process of Textile Industry