MANUFACTURE OF TEXTILES # 11

Background:

Hilados y Tejidos Garib S.A. (Hitega) in Chile is an integrated textile mill producing dyed yarn and fabric with an average content of 65 per cent polyester and 35 per cent rayon. It employs 270 people, and in 1993, produced 1 134 059 kg of dyed material, and an additional 1 227 974 kg of fabric that was finished but not dyed. The textile dyeing process used at the Hitega textile mill involves numerous changes of water, and several additions of dyes, bleaches and other chemicals.

As part of the Environmental Pollution Prevention Project (EP3) sponsored by the US Agency for International Development, a cleaner production assessment was carried out at the facility by an expert in textile dyeing and a pollution prevention specialist.

The assessment identified eight opportunities, which would reduce:

Cleaner Production Principle:

Recovery, reuse and recycle; Process modification

Cleaner Production Application:

The various CP options identified are as follows:

Recycling of cone-dye cooling water: During the cone-dyeing operation, the dye bath is cooled by passing soft water through the jacket of the dye tank. The main source of  process water is well water which is softened to a hardness of 3-5 ppm, and is then used for most of the processes. Non-contact cooling water is also used to cool the dye bath recirculating pump packing gland. Recycling these two streams of water can be accomplished by sending this non contact cooling water back to the soft water pool, which receives the cooling water from facility jet dryers.

Recycling water from the air conditioner system: The air conditioner system used in the spinning and weaving rooms also uses soft water evaporation for cooling. The water is currently taken from the softeners serving the dye room, but 50 per cent of this is lost through evaporation, and the rest is dumped into the sewer system. This has caused water shortages in the dye room. New softeners are being installed to produce water solely for the air conditioner system, which will recycle the non-evaporation water back to the new system.

Improving softener regeneration and service: During the washing, regeneration and rinsing processes in the dye room, the wash time is currently excessive, and the point at which softeners are regenerated is chosen on the basis of time since the last regeneration. This results in a loss of soft water. A digital system would enable the rinsing and service hardness end points to be determined, allowing operators to judge more accurately the exact end point for the wash period and the maximal supply capacity of each softener. Rinse waters can also be recycled from the bleaching process, by installing a tank to store the water from one batch and using it for the one that follows.

Maintenance plan for steam traps: Heat transfer losses caused by leaking steam traps currently amount to around 1-10 per cent of energy costs. Leaking steam traps not only waste energy, but also result in inefficient dye bath heating, and damage to steam lines, valves, fittings, and other equipment. Workers should be trained in the operation of steam trap testing equipment, and a preventive plan for the maintenance of steam traps should de developed. Installation of a digital monitoring system allowed the combustion efficiency of the oil-fired boiler to be monitored whenever parameters change such as when a new lot of oil is received. This change resulted in reductions in fuel use and emissions of particulate matter.

Reducing suspended solids in effluent: Screens installed in the dye room drains reduce suspended solids in effluent. If the plant needs to install an industrial waste water treatment system in the future, any decrease in current loading will allow a reduction in the initial investment and running costs of such treatment plant.

Environmental and Economic Benefits:

The implementation of these suggestions will result in water, energy and chemical conservation, reduced emissions and solids in effluent. Three of the opportunities were studied in detail to quantify savings, as shown below:

Constraints:

None reported.

Contacts:

Mr. Carlos Kanterovitz

Hilados y Tejidos Garib S.A, Rodrigo de Araya No.951

Macul Santiago, Chile

Tel: +56 2 238 4007; Fax: +56 2 238 5091

 

Maurice Knight

Core Program Manager for Chile, EP3

RCG/Hagler Bailly, Inc, 1525 Wilson Bd, Suite 750

Arlington, Va 2209-2406, USA

Tel: +1 703 351 8166; Fax: +1 703 351 6166

Review Status:

This case study was originally published in the UNEP IE document "Cleaner Production Worldwide", Volume II. In the process of preparing the document the case study underwent a technical review. Subsequently a second technical review was carried out in September 1998 by Dr. Prasad Modak, Environmental Management Centre, Mumbai, India.