1

SETTING MATERIAL BAUNCES POR TEmILE WET PROCESSING

S- A . Tarabadkar,

Bombay Textile

S, Varadaraj'an and R. P . Kamble

Research Association, Bombay

INTRODUCTION

The textile industry uses large quantity of water for different

purposes. Much of this water is discharged with appreciable

quantities of organic and inorganic chemicals (dyes, pH control

agenta, lubricants, surfactants, auxiliaries), which require

extensive treatment of the waste water a8 it contributes to the

pollution problem associated with textile processing. Although

the establishment of direct effluent discharge standards for

industrial wastes has a major effect on the treatment and

discharge of textile waste water, the capital investment and

operating expenses associated with these standards require a

critical examination of all the available options for pollution

reduction and waste water treatment.

In the past, the problem of pollution resulting from textile

processing has generally been eased by construction of waste

treatment facilities. As requirements became more stringent, the

waste treatment plant was expanded or additional treatment

processes were added

however, has consumed

and has .increased the

to meet the standards. This approach,

large sums of non-income producing capital

operating costs of many textile plants. In

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short, it has now become neceeeary to examine alternate methods of

textile wet processes for waste reduction and pollution control.

The introduction of the recent 'Environmental Audit' will

therefore be much helpful and enable the processor to take a

comprehensive look at the process to facilitate the understanding

of material flows and focus his attention on areas where waste

reduction is po~sible.

This paper discueses certain aspects of Betting up material

balance which is one of the key steps in the 'Environmental

Audit', for textile wet processes.

SEM'ING OF HATERIAL BALANCE

Material balance is one of the important steps in the

Environmental Audit designed to gain a better understanding of the

inputs and outputs, especially waste of any process/operation. It

may be defined as a precise account of the input8 and outputs of

an operation. The material balance enablee the proceseor to

identify major sources of waete, aseess the deviation# from the

norms in terms of waste production, identify areas of unexplained

l O s € ~ 3 0 and to pinpoint operations which contribute to flows that

exceed discharge regulations.

The principal steps involved in setting up material balance are :

0 Appraisal of process inputs :

- Determination of inputs

- Recording of waste usage

- Measurement of current levels of waste reuse/cycle

I1 . 2

0 Appraisal of proceess output8 :

- Quantificatiion of products/by-products

- Accounting for waste water

- Accounting for gaseous emission

. I .

?

Raw 1

Material

.

> Power OR >

Water/Air -3 PFtocESS

UNIT OPERATION

b -

- Accounting for off-site wastes

Product

including Wastee for

b By-pmduc ts

Recovery

From the above information of process inputs and outputs, a

preliminary material balance may be derived and subsequently

evaluated and refined for arriving at accurate material

balance. A schematic diagram illustrating the various steps

involved in setting up material balance is given below.

PIG. 1 : Typical Components of a Material Balance

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A material balance may be prepared proceermiae e.g., desizing,

Bcouring, bleaching, dyeing and finishing, etc. at a scale

appropriate for the level of details required in the study.

The enqrgy input to a unit operation should be considered while

setting up material balance. However, energy u ~ e deserves a full

audit in its own right. For waste auditing purposes, it would

auffice to note the energy sources and whether waete reduction

could reduce energy costs. If energy usage is a particularly

prominent factor, separate energy audit should be undertaken.

O n e of the important steps for calculating material balance is

selection of appropriate tie compounds. For example, raw

materials such as water, cauatic soda, etc., may be taken for.

textile wet processing operations.

typical case studies exemplifying the steps involved in

setting material balance are gjven in the following.

CASE sTUDIES <

Study Study No.:

Material Balance in S i z i n g Section

A survey was carried out by BTRA in the eioing section of a mill

manufacturing grey fabric, to establieh a material balcnnce with

respect to the starch consumed in the sizing section.

The details of the survey are as follows :

Name of the Machine - West Point Sizing Machine 1.4

Sizing Recipes

A. Terry Catton Size ( 16 to 17% Liizse)

1. Fabrilose

2. Mutton Tallow

3. French Chalk

4. G U

5. CMC

6. Sapcotex

7. PVA

44

1.75

2.0

2.0

2.0

0.5

4.0

B. Cotton Siae (13 to 14%)

............................................................. Sr.No. Name of the Ingredient Quantity (kg)

1. Maize Starch 34

2. Fabr i lose 10

3. Mutton Tallow 2.5

4. Plasto Siae 5.0

1.5

June 5674

July 6807

32848

39827

August 77 16 43923

Table - 2 : For Terry Cotton

Apr i 1 2232 12156

May

June

July

August

September

1886

1421

1199

1932

2122

9934

6811

6256

'9404

10610

The following data wae used for working out the values of

starch conaumption on fabric and rstasch wastage, details of

which are given in the tabular form.

- 17% Pick-up for Terry Cotton Size

- 14% Pick-up for Cotton Size

- 10% Wastage of Starch due to Dusting

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Table- 3 : For Terry Cotton (17% Size)

April 2232 12156 1633 223 376

May 1886 9934 1334 189 363

June 1421 6811 915 142 364

July 1199 6256 840 ” 120 239

August 1932 9404 1263 193 476

September 2122 10610 1423 212 487

Apr i 1 34884 6079 3980 ‘ 808 1491

MErY 28670 4832 327 1 483 1078

June I 32848 5674 3748 567 1359

*July 39827 8807 4544 68 1 1582

August 43923 7716 5012 772 1932

September 29279 5434 334 1 543 1550

--------------------____________c_______--------------------------

Average 34905 6090 3983 608 1499 ..................................................................

Thus based on the figures worked out, the material balance for

starch consumed works out as follows :

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Conenamtion 7889 kg

V I + on Fabric __

5219 kg

Transport & Drainage Weighment 1420 kg 463 kg (18%) (6%)

7651 of the total starch consumption can be attributed to : the

starch of

dust. The remaining 24% of the starch, i.e., 1883 kg wae wasted

in the following operations :

consumed on the fabric and the starch lost in the f o r m

0 During Transportation

0

0 Drainage of Size

During Weighing and Preparation of Size

The size wastage can be avoided to a considerable extent by

implementing the following measure8 :

0 The hand washing8 after the weighing of sizing ingredients

should be done over empty size mixing tanka. .

o The size supply line valves mu& be checked regularly to stop

any size leakages.

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Size should not be wasted alongwith the ateam condensate

during the recycling of size. It should be separately

collected in a bucket.

~

Better housekeeping measures must be implemented in storing

the size ingredient%,

Size overflow from the sow-box should be avoided. This ia

generally due to injection of excess ateam. It can be L

avoided by installing a dial type thermometer in every sow-

box.

Effect of Starch Wastage on Treatment Costs

The starch wastage of 1420 kg will exert on additional BOD load of

677 kg (477 g/kg of starch) which will ultimately add to the

treatment cost.

Case Study No.2

Haterial &lance in’ Mercerizil.ltg Section

The bleeached cotton fabric (4OS x 408 : 92 x 80) w a s mercerized

in a chain mercerizer. The details of the machine and proceas

were as follows :,

Average Machine Speed (m/min) : 60

No. of Impregnators : 2

Volume of Impregnators (1) : 1587 and i6ao No. of Pits under the Stenter : 5

Volume of Each Pit (1) : 2380

No. of Washing Tanks : 4

Volume of Each Tank (1) : 2083

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Process Description

The bleached cotton fabric was padded with a solution of 300 g/l

caustic eoda and was passed through the stenter. The treated

fa was waahed in coun%ercurrent warrhing tanks for a period of

8 hr. During this period, 6000 kg of bleached fabric wars

mercerized. The caustic soda consumed wae 1980 kg for 6000 kg of

bleached fabric. The caustic soda content on the fabric after

~

impregnation was 33% and at the delivery end of the machine, it

was found to be 0.5%. Thus, cauetic soda

carried away by the fabric was ---------- i . e . 30 kg. 6000 x 0 .5

100

The caustic soda accumulated in the pitls and washers after the

successive washing operation was worked out a8 follows :

1. A t the iFsnd af &he Trial

(g/l) x (Volume in 1) = - 45

- 40

- 35

30

20

- -

10

6

4

2

- - c

-

X

X

X

X

X

X

X

X

X

2380

2380

2380

2380

2380

2083

2083

2083

2083

Total

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(Weight in kJg)

107.1

96.2

83.3

71.4

47.6

20.83

12.5 .

8.33

2. A t the Beginning of Trial

r Input

CaU8t iC soda 134 kg (6-72X) 1980 kg (loo%) F

AccupRlLATION

( d l ) x (Volume in 1) = 38 X 2380 - -

Cawtic Content on the Fabric A f t e r bheri- cation 90 kg ( 1 - 5 X )

8

30

22

16

12

Caustic

10

- Unaccounted

6

4

2

X

X

X

X

X

X

X

X

2380

2380

2380

2380

2083

2083

2083

2083

Total

(Weight in kg)

90.4

71.4

52.4

38.1

28.6

16.7

10.4

6.2

2.1

316 -------

Cautstic Soda Accumulation = 450 - 316 = 134 kg.

Haterial Balance

The dilute caustic soda eolution collected in the collection tanks

was 36,600 1 of 45 g/1 strength. Thus, the amount of caustic soda

collected by way of recovery waa ---------- = 1848 kp 36625 x 45

1000

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Thus, based on the details available the material balance for

caustic soda works out as follow8 :

SCOUR WASHER , .

Fabric

bese Study No.3

Further

Haterial Balance in Scouring Razuge

J

*swiw P r o c e s s Detafls

T r e a t m e n t

Production Rate (m/min) : 70

Flow Rat8 (1) : 200-220

Percentage Moisture on Fabric : 80% pick-up

Water on Fabric (l/kg) : 15

Material (100% Cotton) : 100

Quantity (m/kg) : 5

r

Process water balance and chemical balance which are worked out

are given below; these are on the basis of 1000 kg of production.

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Chemical Balance

Chemical Input Output % BOD Output (kg) BOD (kg)

NaOH 4 6 46 0 0

Detergent 1.3 1.3 50 0.65

Trisodium Phorphate

1.5 1.5 0 0

Chelate 0 . 4 0 . 4 50 0.2

Triethanol Amine ’ 0.7 0.7 50 0.4

Cotton Wax 30 30 50 15.0

Analytical Checks

BDD (ker) : 16.4

Total SS (kg) : 5

Total Dissolved Solids (kg) : 49.9

PH

Oil and Grease (kg)

: 12.5

: 30

Case Study No.4

Detection of Kerosene Vapour in a Curing Machine

At, t h e request from the mill, trial wap conducted to determine the

kerosene vapour content in a curing machine. This trial is a

classic example of meaerurement of kerosene vapour content in the

exhaust air in the absence of a direct ‘Read on’ type instrument

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by establishing a material balance as an indirect method. The

kerosene vapours were eatimated by measuring the difference in the

weight of fabric before and after the curing operations and

estimating the weight of the air exhaueted. These two separately

eatimated values were combined and the percentage of kerosene

vapour in the exhaust air was calculated.

The details of the trial are as follows :

1. Details of Exhaust Air Flow

1.1 Maust duct No-1

Fan Installed (HP) : 5

Duct Size (in. x in.) : 20 x 16

Average Air Velocity (m/min) : 296

Average A i r Flow (m /min)

(Exhaust air flow was meaaursd with the help of 'Velometer')

Dampers Open ( % ) : 50

: 62 3

1.2 hkhauat duct No.2

Fan Installed (HP) : 2

Duct Size (in. x in.) : 8.5 x 8.5

Average Air Velocity (m/min) : 212

Average Air Flow (m /min) : 10 3

3 1.3 Total Air Flow : 1.1 + 1.2 = 62 + 10 = 72 m /min

2. Details of Estimation of Kerosene on Fabric

Machine Type 'Ham' Curing Machine

Width of Fabric (cm) : 89

Quality Number : 4218/90

Quantity ( m h g ) : 9

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Consumption of Print Paste : About 0 kg/1000 m

Speed of Curing Machine : 26 MPN

Temperatugs of Curing : 148 Machine ( C)

h e 1 1 Time (min) : 4.4

Printing Coverage ( % ) : 80

Fabric Running (ends) : 2

Estimation of kerosene was carried out on two sets of fabric.

Set I

Before Curing 106.5 0.958263 111.14

set I1

Before Curing 109 I 5 1.0072 108.72

After .I_ determining the difference in weight of the fabric

before and after curing, the data was used in calculating the

composition of exhaust to find out the per cent volume of

kerosene in exhkust .

~.

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3. "pos i t ion of Exhaust

3.1 #bight of Kerosene Evaporated :

For 1st rset (end) : difference in.weight x speed x width of f ab r i c

: 6.06 x 26 x 0.89 = 140.2 s h i n

For 2nd set (end) : 3-38 x 26 x 0.89 = 78.2 g/min

3.2 Total Weight of Kerosene : 140.2 + 78.2 = 218.4 Evaporated (g/min)

i .e. 0.2184 kg/min

3.3 Specif ic Volume of : 0.098 3 Vapour (m /kg)

3 . 4 Total Volume of Kerosene : 0.021

Vagour (m3/min

3.5 Total A i r Flow (m3/min) : 72

0.021 3.8 Composition of t h e - ----- x 100 = 0.03%

Exhauat (Volume 72 Percentage of Kerosene)

"hue based on t h e t r i a l conducted, the percentage of volume

was found t o be 0.03% of the exhaust.

Cam Study No.5

Water Con"ption &lance

In a Compoaite mill, it w a s found through surveys conducted; t h a t

of t he t o t a l w a t e r consumed, the e f f luen t generated was around 75-

80%. About 15-16% accounted for evaporative loasee and the rest

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waa unaccounted. These un'accounted I *,

loseee were due to leakages in

pipee, trouqhs, improper fixture@, negligence in water U B W ~ S

pattern of the water consumed and 'the effluent

enerated is shown below.

Evaporative LOSEWS (15-16X)

'I' Input

Water Consumed %a1 Effluent (100%)

A survey wae carried out in one of the mille to establish the

water conmmption balance by measuring the effluent discharged.

The main purpose of carrying out the survey was to work out a

proper balance between the actual water consumption and the

effluent generated and also the various loasee.

Data obtained from .the mill showed that the total water

conaumptiop was around 1120 m3/day. The industrial effluent

discharged wae 762 m3/day (68%). The domestic and sanitary

effluent discharged amounted to 67 m /day (6%) considering (15%)

168 m3/day as evaporative losses, the unaccounted loases,

estimated were 11%.

3

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InduetrialgECffluent

Dopllestic & sanitary ~

Effluent 67 m /day (6%)

762 BI /day (68%) ~

On detailed examination for the unaccounted losses it was revealed

that the -in contributing factors were negligent use o f water in

the mills, leakage8 in the pipes, leakages in waeh tanks, improper

fistureer, etc.

A general pattern of the water conewnption in a composite mill is

given below. Teble-1.5 givee an idea of the water consumption for

varioue, procseees. The mills can compare their results with this

Table to find out whether the water consumed for variouer processes

carried out ia within limite.

Dyeing 15 - 20 Printing 10 - 15 Boilers 0 - 12 Humidification 0 - 12

UTILITY OF MATERIAL BALANCE

These material balance studiea will give definite insight to the

wet processor regarding the process being followed in the mills

and will enable him to reduce the volume and toxicity of the

digcharges and also to think in terms of recycling and reusing ~~

useful constituents, such as water and colorant.

It is possible for a wet processor to reduce the waste volume in

order to get greater treatment efficiency on a "per kg of product"

basis, through these studies.

The following points may be considered for waste volume reduction.

0 Improved waaher designs. I

o

0 "Tailored rinses" - to fit particular shade, style or

Overflow v/er recirculating rinaes in package dyeing.

severity of treatment.

0 More careful control and testing to ensure that "over

rinsing" of fabric does not take place.

o Closed steam heating coils in dye becke, etc., rather than

open steam, to allow return of condensate.

o

0

U s e of counterflow principle on continuousj ranges.

Vacuum extract on package dye machines.

0 Inplant reuse of lightly contaminated rinse waters f o r other

"more concentrated" chemical processes.

Liquor ratio consideration in batch processes. 0

o Elimination of reworks by more careful control of processes

and greater automation.

0 Automatic cut-off on water losses.

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Similarly, it is also possible to reduce the waste strength by

identifying the compounds which contribute to the pollution load

and replacing them with less polluting compounds and also reducing

the amount of unnecessary chemicals.

For example, chemicals such as sodium chloride, sodium sulphate,

sodium hydrosulphite, etc., are commonly used cheap Chemical6 in

t h e dyehouse. Since they are cheap, it is not unusual to see them

overused. These chemicals cannot be removed by biological methods

and management should therefore insist on minimum uee of these

chemicals;. Furthermore, sodium hydrosulghite has bean found to

contain residual zinc catalyet, a heavy toxic metal banned in

effluent discharges.

Many solvents contain phenols and many lubricating oils and

greaees contain substantial amount of zinc and lithium. H e m e it

is not advisable to pour these chemicals down the plant drain

after use.

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