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)