INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

CASE STUDY # 180

1. Headline: Efficient Recovery and Reuse of Caustic Soda

from Mercerizing Washwaters

2. Background: See below.

3. Cleaner Production Principle: Good housekeeping, internal

recycling

4. Description of Cleaner Production Application: This

technology involved the efficient recovery and reuse of

caustic soda from mercerizing wastewater.

Case Study Summary

Process and Waste Information: A plant floor study

examined mercerizing machines and a caustic soda recovery

plant in a textile mill. It was observed that only 75% of

the caustic soda from washwaters was collected, compared

to the normal 85%. Also, the caustic soda recovery plant

only recovered 81% of the soda, as opposed to the normal

90%.

The probable causes of the low collection and recovery

rates were inefficient washing in the mercerized material,

poor squeeze and high quantities of caustic left on the

fabric, overflowing/leakage of dilute caustic soda

solutions from the washing tank, and seepage from the

underground storage tanks. The probable causes of poor

recovery were the improper filtration of caustic soda

solution prior to recovery, poor heat transfer coefficient

in the recovery plant due to scaling of the metallic tubes

of the heat exchanger, lower vacuum obtained by the

barometric condenser, and the inefficient removal of

non-condensate gases from the evaporation body. Necessary

corrective steps were taken yielding significant cost

savings.

State of Development: System was fully implemented.

Balances and Substitutions:

Quantity Quantity

Material Category Before After

Waste Generation: Information not provided.

Feedstock Use: 1,190 kg/day 775 kg/day

Water Use: Information not provided.

Energy Use: Information not provided.

5. Economics

Investment Costs: Information not provided.

Operational and Maintenance Costs:

Before After

Particulars Study (kg) Study (kg)

Mercerizing production/

day of fabric 10,000 10,000

Caustic soda input/day 3,500 3,500

Collection from washwaters 2,630 2,975

Reuse of dilute solutions

in bleaching 310 475

Caustic soda recoverable 2,320 2,500

Recovery of caustic soda 2,000 2,225

Total caustic soda consumed

in mercerizing (Total input less

recovery/reuse) 1,190 775

Saving of caustic soda/day = 415 kg

Savings per day = 2,282.50 rupees

Savings per year = 684,750 rupees

6. Advantages: Savings in caustic produced monetary benefits

of 684,750 rupees per year and improved the quality of the

fabric.

7. Constraints: No information provided.

8. Contacts and Citation

Type of Source Material: Conference proceedings

Citation: "Seminar on avenues for Cost Reduction in

Chemical Processing of Textiles", held on February 26,

1985 by Bombay Textile Research Association, Bombay 400

086, BTRA No.06.3.1 Bombay Textile Research Association

(BTRA) Member Mill, Bombay, India

9. Keywords: India, textile, mercerizing, good housekeeping,

recycling, caustic soda, ISIC 2299.

10. Reviewer's Comments: This case study was originally

compiled by the UNEP Working Group of Textiles. It

underwent a UNEP IE funded technical review in 1994 for

quality and completeness. It was edited for the ICPIC

diskette in July of 1995.

( Docno UNEP 11: DOCUMENT NOT AVAILABLE 11-06)