Case Study #242
1. Headline: EP3 - Pollution Prevention Assessment for a
Textile Dyeing Facility
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 textile dyeing facility. The
objective of the assessment was to propose a program of
pollution prevention that would: (1) reduce the quantity
of toxics, raw materials, and energy used in the
manufacturing 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.
Facility Background
This facility is an integrated textile mill. Starting with
polyester and rayon viscose fibers, the facility produces
dyed yarn and fabric with an average content of 65 percent
polyester and 35 percent rayon. The facility employs 270
workers who work 296 days per year. In 1993, production
volume was 1,134,059 kg of material dyed, with an
additional 1,227,974 kg of fabric finished but not dyed.
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 Cleaner Production Application:
Manufacturing Process
Textile dyeing at this facility involves a number of steps
that must be carried out in proper sequence and under
optimal conditions. In general, the process involves
filling tanks containing fabrics with water, and
sequentially (1) heating, (2) rinsing, (3) adding dyes,
bleaches, and other chemicals, (4) cooling, and (5)
combing or ironing the fabric. This process involves
numerous changes of water, and several additions of dyes,
bleaches, and other chemicals. All fabric is dyed in jets
with nominal capacities of 50 kg, 150 kg, 350 kg and 750
kg of fabric. Yarn is dyed in a 200 kg cone-dryer.
Existing Pollution Problems
At the time of the assessment, there were a number of
pollution problems at the facility, including excessive:
(1) use of water, (2) use of chemicals, (3) suspended
solid concentrations in wastewater, (4) energy use due to
lack of process standardization, leaking steam traps, and
lack of process standardization, leaking steam traps, and
lack of a peaking generator, and (5) emissions from the
oil-fired boiler.
Pollution Prevention Opportunities
The assessment identified eight pollution prevention
opportunities that could address the problems identified
above, with significant environmental and economic
benefits to the facility. Below are listed the
opportunities for pollution prevention recommended for the
facility, and presents the environmental benefits, savings
and implementation costs for each.
Summary of Recommended Pollution Prevention Opportunities:
--Recycling of dye cooling water--Install piping and
valves - conserve water. Costs of $750 (US) with a
financial benefit of $400 (US) per year and a pay back
period of 20 months.
--Recycling of air conditioning system water--Install
piping and a tank - conserves water and chemicals. Costs
of $6,700 (US) with a financial benefit of $4,900 (US) per
year and a pay back period of 14 months.
--Softener system-- Install a digital hardness monitor -
conserves water and chemicals. Costs of $3500 (US) with a
financial benefit of $1,700 (US) per year and a pay back
period of 24 months.
--Solids in effluent--Install screens in drain lines -
reduces pollutant level in wastewater. Costs of $600
(US).
--Operator work system--Deliver training reduces power and
water consumption
--Steam traps--implement maintenance plan - reduces VOCs.
--Bleaching-- Recycle rinse water - reduces use of water
and chemicals. Costs of $2,200 (US).
--Boilers--Install a digital monitoring system- reduces
emissions. Costs of $1000 (US).
--Power consumption--Install a peak load generator.
The total costs of the opportunities is $14,750 (US) with
estimated financial benefits of $7000 (US).
Of the opportunities identified, three were studied in
enough detail to quantify potential savings. For an
investment of just under $ 11,000 (US), the facility can
reduce its water and salt consumption and save about $
7,000 (US) per year. The average payback period for these
actions is approximately 20 months. Additional savings
from bleach rinse recycling, steam trap repair, and boiler
combustion efficiency changes were not quantified.
Recycling of Cone-dye Cooling Water. Well water with a
hardness of approximately 600 ppm is pumped to a tank with
a capacity of 60 cubic meters. From there, it is sent
through a softener that reduces hardness to 3-5 ppm. This
softened water is used for most factory processes. The
cone-dyeing operation uses soft water for non-contact
cooling water through the jacket of the dye tank. Non-
contact cooling water is also used to cool the dye bath
recirculating pump packing gland. Recycling these two
streams is an opportunity and could be accomplished by
sending the water back to the soft water pool that at the
present time receives the cooling water from the jet
dryers.
Recycling of Air Conditioner System Water. The air
conditioner systems for the spinning and weaving rooms use
soft water evaporation for cooling. The water currently
used is taken from the softeners that serve the dye room.
Fifty percent of this water is lost to evaporation, while
the rest is dumped into the sewer system. This water use
has caused problems in the dye room by causing shortages
of soft water. The plant has purchased, but not installed,
new softeners solely to produce water for the air
conditioner system. When the new softeners are installed,
the non-evaporated air conditioning system water should be
recycled back to the new softener system.
Improving Softener Regeneration and Service. The current
dye room softener system has three softeners, each of
which treat well water. In the wash, regeneration, and
rinse steps, the operators calculate the water hardness
using a colorimetric method. The wash time is excessive
and the point at which the softeners are regenerated is
chosen solely on the basis of time since the last
regeneration, resulting in the loss of soft water. A
digital system should be installed to determine the
rinsing and service hardness end points, allowing
operators to determine the exact end point for the wash
period and the maximal supply capacity of each softener.
Reduce Suspended Solids in Effluent. Five screens should
be installed in dye room drains with the objective of
reducing suspended solids in the effluent. The screens
should be designed and installed to allow easy periodic
cleaning. It is possible that in the near future the plant
will need to install an industrial waste water treatment
system; any decrease in loading now will allow a reduction
in waste water treatment plant initial investment and
running cost.
Improve Worker Training. Operators of the dye machines
have different methods for operating each machine, even
though a procedure sheet is supposedly followed. At each
shift change, the new operator switched to a different
method, e.g., increasing the number of rinsing steps or
changing the timing for the different processes. Because
of this lack of process standardization, there are energy,
water, and chemical losses. Training courses in standard
operating procedures should be conducted.
Develop a Maintenance Plan for Steam Traps. Heat transfer
losses caused by leaking steam traps amounts to about 10-
15 percent of energy costs. Using leaking steam traps not
only wastes energy, but also results in inefficient dye
bath heating and the cost of damage to steam lines,
valves, fittings, and other equipment. A training course
for workers in the operation of ultrasonic equipment
should be established and a preventive plan for
maintenance of steam traps should be developed.
Recycling Bleaching Process Rinse Water. There is an
opportunity to recycle rinse waters from the bleaching
process by installing a 25 cubic meter tank to store the
rinse water of one batch and use it for the one that
follows. Thirty-six tons of product would need to be
bleached to recover the initial $ 2,200 (US) investment.
Improve Boiler Combustion Efficiency Monitoring. The
combustion efficiency of the oil-fired boiler is not
monitored continuously, but measured by an outside
contractor four timer a year. Installation of a digital
monitoring system will allow the efficiency of the
combustion to be determined whenever parameters change,
such as when a new lot of oil is received. This change
will result in reductions in fuel use and particulate
matter emissions. Payback time will depend on the amount
of combustible efficiency improvement.
Utilization of a Peaking Generator. During 1993, the
factory paid a total of $ 105,600 (US) in maximum and peak
demand power charges. Installation of a peaking generator
could yield substantial reductions in net power costs,
although net emissions effects will be negligible. If a
natural gas generator is chosen and bio-gas from the local
landfill is used, there may be a small net positive effect
on emissions. While the size, and therefore cost, of the
needed generator cannot be calculated, other textile
plants have indicated a payback time of approximately 11
months.
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, recycling, process
modification, good housekeeping, new technology, material
substitution, EP3, polyester, rayon, viscose, steam strap,
bleaching, air-conditioning, USAID
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.