textile industry

INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

CASE STUDY # 237

1. Headline: Pollution Prevention Assessment for a Textile

Dyeing Facility Serving Fabric Manufacturers

2. Background:

What is EP3?

The United States Agency for International Development

(USAID) is sponsoring the Environmental Pollution

Prevention Project (EP3) to establish sustainable programs

in developing countries, transfer urban and industrial

pollution prevention expertise and information, and

support efforts to improve environmental quality. These

objectives are achieved through technical assistance to

industry and urban institutions, development and delivery

of training and outreach programs, and operation of an

information clearinghouse.

EP3's Assessment Process

EP3 pollution prevention diagnostic assessments consist of

three phases: pre-assessment, assessment, and post-

assessment. During pre-assessment, EP3 in-country

representatives determine a facility's suitability for a

pollution prevention assessment, sign memoranda of

agreement with each facility selected, and collect

preliminary data. During assessment, a team comprised of

US and in-country experts in both pollution prevention and

the facility's industrial processes gathers more detailed

information on the sources of pollution, reducing this

pollution. Finally, the team prepares a report for the

facility's management detailing its findings and

recommendations (including cost savings, implementation

costs, and payback times). During post-assessment, the EP3

in-country representative works with the facility to

implement the actions recommended in the report.

Summary

This assessment evaluated a dye house serving a variety of

fabric manufacturers. The objective of the assessment was

to identify actions that would: (1) reduce the quantity of

toxics, raw materials, and energy used in the dying

process, thereby reducing pollution and worker exposure,

(2) demonstrate the environmental and economic value of

pollution prevention methods to the dyeing industry, and

(3) improve operating efficiency and product quality.

The assessment was performed by an EP3 team comprised of

an expert in textile dyeing and a pollution prevention

specialist.

Overall, the assessment identified 37 pollution prevention

opportunities --classified as first, second, and third

priority opportunities-- that could reduce energy use at

this facility and avoid the release of over 14 metric tons

of air emissions each year, in addition to unquantified

reductions in the release of global warming gases and

heavy metals. Water use could be reduced by 125,000 cubic

meters per year, and chemical releases to surface waters

could also be reduced. Finally, it may be possible to

avoid the disposal of 330 cubic meters of solid waste per

year.

Facility Background

This facility is a dye house serving fabric manufacturers.

The facility operates two eight-hour shifts, six days per

week, employing seventy shift workers and twenty technical

and administrative employees. In 1992, the facility

processed 350,000 kg of cotton and 360,000 kg of wool

fabric.

3. Cleaner Production Principle: The assessment identified

various cleaner production applications including: process

modification, good housekeeping, new technology,

recycling, and material substitution.

4. Description of the Cleaner Production Application

Manufacturing Process

In general, cotton dyeing involves two procedures,

desizing and bleaching, and dyeing. Each procedure

involves a number of steps that must be carried out in

proper sequence and under optimal conditions. Wool dyeing

also involves several procedures: (1) washing, (2) podding

(heating thin wool fabrics in boiling water to improve

appearance and brightness) and (3) dyeing. White fabric is

desized and bleached in becks, with nominal capacities of

500 liters, 1,000 liters, and 1,500 liters of water.

Fabrics to be dyed are desized and then dyed in jets.

Existing Pollution Problems

At the time of the assessment, there were a number of

pollution problems at the facility, including (1)

excessive loss of water, chemicals, and heart energy from

the becks, (2) excessive use of water in the rinsing

process due to residual solution left at bottom of the

beck, (3) excessive suspended solids, primarily lint

washed off fabric, (4) leakage of detergent-laden water

from the wool washing machines, (5) excessive pH of

effluent from the decarbonizing acid bath, (6) excessively

hot effluent, (7) excessive oil and grease and sulfate

concentrations in effluent, (8) leakage from steam coils,

(9) hydrogen sulfide generation at the wool laundry sump,

(10) disposal of dry, cotton combings and shavings, and

sodium sulfate bags (materials that could be recycled),

(11) excessive air emissions of particulates, and (12)

lint and sulfuric acid mist in the wool laundry room.

This facility uses about twice as much water as the

average commission batch dyer its size; thus, many of the

recommendations focus on reducing water consumption and

the energy required to heat it for various dyeing

processes.

Pollution Prevention Opportunities

The assessment identified almost 40 pollution prevention

opportunities that could address the problems identified,

with significant environmental and economic benefits to

the facility. The assessment team prioritized these

opportunities based on pollution prevented and

implementation cost. Below is a list of the high priority

opportunities recommended for the facility and presents

the environmental benefits, savings and implementation

costs, and estimated payback period for each (a complete

list of recommendations is available from the EP3

Clearinghouse). Many of the recommendations can be

implemented with no capital investment. Further, many can

be implemented almost immediately, and most are not

dependent upon other projects for their initiation.

Summary of Recommended Pollution Prevention Opportunities

--Steam traps--

1. Repair leaking traps-reduces air

emissions and fuels costs. The cost is

estimated at $700 (US) to replace the traps.

The financial benefit is $47,000 (US) per year

with a payback period of 1 week.

2. Improve knowledge of steam trap

selection-reduces energy use and avoids purchase

and repair of traps. No cost to implement.

3. Purchase and use steam leak detector-

reduces fuel consumption. Costs are $1100 (US)

for the instrument.

--Steam system--Evaluate steam system components and

layout and add at least two stream traps-reduces energy

and prolongs the life of components and reduces bath and

boiler water contamination. Costs are estimated at $12

(US) for insulation and $500 (US) for traps.

--Dyeing becks--Modify rinsing procedures and becks -

reduces water costs. Implementation cost is $400 (US) for

16 valves flow restrictors and siphon piping. Financial

benefit is $45,000 (US) per year with a resultant payback

period of 1 week.

--Dye baths--Replace sodium sulphate with sodium chloride

reduces sulfate emissions below effluent standards and

reduces chemical costs. there are no costs to implement

and the financial benefit is estimated at $7500 (US) per

year.

--Wool laundries--repair leaks reduces water and energy

use. Fifty dollars (US) for screens and valves with a

financial benefit of $3700 (US) per year and a payback

period of less than 1 week.

--Zonco washer--repair leaks and maintains drain valves

reduces water and energy use. No cost to implement and a

financial benefit of $2,200 (US) per year.

--Sulfur acid decarbonizing--filter acid continuously

reduces release of sulfuric acid to sewer system. Cost

estimates of $700 (US) for in-tank filter, financial

benefit of $300 (US) per year and a pay back period of 2.5

years.

--Floor drains--Install and maintain screens to prevent

lint from entering drains - reduces suspended solids

sedimentable solids and sulfide in effluent. Costs are

$10 (US) for the screens.

--Beck number 10--Relocate steam coil to prevent

boil over - reduces loss of chemicals and energy to

drains. No costs and immediate pay back.

--All becks--repair and maintain steam coils -

reduces fuel consumption and prevents contamination

of dye baths and boiler water. No costs and

immediate pay back.

--Boiler--purchase and install combustion

controls - reduces emissions and fuel use.

Unquantified cost and immediate pay back.

--Jet dryers--Monitor dye bath temperature to

detect out of control condition- avoids chemical loss

to sewer and reduces energy use- Implementation cost

$25 (US) for thermometers.

--Dyeing process--Use datacolor instrument to control

process -- reduces chemical use. No costs and immediate

payback.

--EMOS water supply-- Test plant water

distribution system for leaks - reduces water use. No

cost to implement and immediate pay back.

--Green dryer

1. rebalance internal air flow-

- reduces emissions of H2SO4 mist and

energy use. No costs and immediate pay

back.

2. Install exhaust fan after

rebalancing dryer avoids worker exposure to

sulfuric mist and future medical costs.

Costs estimated at $700 (US).

--Sewer effluent--Determine nitrogen and

hydrocarbon concentrations assures compliance with

effluent standards and helps set reduction

priorities. Cost estimates $200 (US) for testing.

Total costs are estimated at $4,500 (US) and financial

benefits of $105,700 per year.

Of the 19 high priority opportunities recommended, the

savings possible from implementing six have been

quantified. These six recommendations will reduce

operating costs by almost $ 106,000 (US) per year for an

initial investment of $ 1,900 (US). The payback period for

these changes is one week. Another $ 2,600 (US) in

investments is required to implement other changes whose

savings potential cannot be quantified without further

research.

Effect on the Environment

Implementation of the recommended actions will produce

positive environmental impacts in three areas: reduced air

emissions, lower water and chemical use, and reduced

generation of solid waste.

Air Emissions. Many of the proposed changes will reduce

steam consumption and lower fuel use, thereby reducing air

emissions. Repairing all traps should reduce fuel

consumption by 36 percent, or 454 metric tons of number 6

residual oil per year. The expected reductions in air

emissions from this change total over 14 metric tons per

year. In addition, this change will result in reduced

carbon dioxide and heavy metal emissions.

Water and Chemical Use. When all rinsing changes have been

implemented, the facility should consume half the water it

currently does. The yearly reduction in water use will be

about 125,000 cubic meters. Chemical use will decline due

to a number of changes. Sulfate in the effluent will be

reduced by more than 70,000 kg/year by changing to sodium

chloride and filtering the decarbonizing acid bath.

Releases to the sewer of other chemicals such as dye, dye

stabilizers, de-foamers, detergents, sodium hydrosulfite,

bleach, optical brighteners, acetic acid, equalizers, and

boiler treatment chemicals will be reduced as a result of

the recommended changes. Among the changes that will

affect chemical releases are: (1) better process controls,

(2) screening drains and cleaning sumps regularly to

prevent sulfide generation, (3) preventing beck boil-over,

(4) repairing coil steam leaks that contaminate boiler

feed water and process baths, (5) using a lower-foaming

jet-dye detergent, (6) calibrating and shimming becks, (7)

repairing and modifying backs and wool laundries, and (8)

determining sizing formula. Until these changes are made,

it is not possible to calculate the degree to which

releases will be reduced.

Solid Waste. Solid waste discarded by the facility

consists mainly of sulfate chemical bags and shavings and

combings from fabric finishing. Assuming that the eight

sulfate bags generated per day fill one large (0.1 cubic

meter) garbage bag and the combings fill ten bags per day,

the yearly un-compressed volume of these solid wastes is

330 cubic meters. If both wastes are recycled, this volume

of waste can be reused at least once before being

discarded.

5. Economics: See above.

6. Advantages: See above

7. Constraints: See above.

8. Contacts:

EP3 Clearinghouse (UNITED STATES)

TEL: 1 (703) 351-4004

FAX: 1 (703) 351 6166

Internet: apenderg@habaco.com

9. Keywords: textile, dyeing, process modification, good

housekeeping, new technology, material substitution, EP3,

cotton, wool, beck, rinse, water saving, sulfate, drying,

USAID, sulfur

10. Reviewer's comments: This case study was carried out in a

developing country in which EP3 has an established

programme. It was submitted to UNEP IE and edited for the

ICPIC diskette in August 1995. It has not undergone a

formal technical review.