CLEANER TEXTILE PRODUCTION DANCED Project office c/o Pollution Research Group Chemical Engineering University of Natal Durban, 4041 Tel. +27 31 260 3561 Fax. +27 31 260 1118 Email: email@example.com Practical options that have been implemented at textile factories to make them cleaner, reduce effluent and air emissions and improve their processing times www.nu.ac.za/dancedcleanerproduction Project partners: Improved process control Fully integrated dye vessel control in the dyehouse by means of Arel Control system. Ensures proper usage of water, steam, cooling water etc New cleaner technology Replacing old winches that run at Before… liquor ratios up to 30:1 with modern air jet dyeing machines that run at about 5:1, results in savings in water, energy and chemicals. Reductions in water and effluent of up to 80% may be achieved. Now… Improved stenter process control Improving the process controls on older equipment helps realise cost savings, improvements in production and reduction in processing time without having to invest in new equipment. Here, a Mahlo control system optimises the dwell time of the fabric through the stenter by maintaining a steady temperature profile throughout the stenter. Each chamber has an optical pyrometer at the top to measure the temperature of the fabric as it passes through the stenter. Automatic washing of drums Drum washing in the printing section of a dyehouse – fully automated with fresh water additions controlled by a timer and solenoid valve. Savings of up to 20% in water and effluent. New dyeing technology Airstream jet running at liquor ratio of between 1:3 and 1:5 have replaced older dyeing machines at this factory. The following *potential savings are possible by changing from 1:15 machine to 1:5 jet: effluent: 582 000 kl/yr Steam: 15 000 tonnes/yr Salt (60 g/L): 1000 tonnes/yr *producing 5 tonnes/day, 330 days/yr Adjusting pump on Jets The pump on the Jet dyeing machine at this factory has been lowered by about 15cm, thereby lowering the water circulation, and lowering the liquor ratio for the dyeing. Automatic chemical dispensing A small commission dyehouse has installed automatic dispensing of caustic soda lye to the dye machines. Ensures no risks of spills, leakages and injury to operators. No risk of effluent from clean-ups and costs of cleaning spills. Cont… Automatic chemical dispensing Fully automated dispensing of chemicals to dye machines eliminates spills, wastage and injury. Reduces risk to environment. Cost savings associated with clean-up operations for spills and leakages in manual additions. New treatment for boiler feed water A large cotton dyeing and printing factory has installed a chemical-free system for softening feed water to the boiler. The magnetic device removes Ca2+ and Mg2+ ions in a magnetic field. No chemicals are needed. In this case, cost savings of about R31000 per annum have been achieved, together with savings in make- up water for the chemicals. Better removal of print pastes Improving removal of print pastes from the screen reduces the amount of water needed in the cleaning operation. Operators at this factory uses scrapers to remove excess print pastes,this removes as much paste as possible before screen washing. Less water is used in the rinsing, and less effluent is produced. Here, the water addition is also controlled by a timer. Automatic screen washing Fully automated screen washing in the printing section of the dyehouse. Rinse water is controlled by a timer. Savings in water and effluent of about 30% have been realised. Reusing printing wash-water Large amounts of water is used in washing printed blanket fabrics. Here, a sump has been constructed beneath the washing line to collect wash-water that is of an adequate quality to be re- used in washing-off the blanket fabric after printing. The sump has a capacity of about 3 cubic metres Cont… Reusing printing wash-water The wash-water from the sump is pumped through a filter back to the printing line to be re-used in washing off printed blanket material. Savings in water and effluent of 90% achieved (based on original fresh water consumption before reusing wash-water). Pump Filter Cont… Reusing printing wash-water A solenoid valve and timer controls the addition of fresh water to the washing line. In this way, consumption of fresh water is optimised, and the re-use of wash-water is at an optimal level. Modifying Jet clean-out… Previously, Jet machines like this one were flooded with clean water after a clean-out, to rinse the machine before the next dyeing. Here, the Jet is being rinsed with a hose-pipe with a manually activated spray- nozzle. In this way, the rinse uses about 50 litres of water, rather than 3 700, realising a saving of approximately 7.3 kl per cleaning in water and effluent. Annual reductions in fresh water consumption of about 260 kl have been achieved. Cont… Modifying Jet clean-out This is the amount of formic acid saved by reducing the previous double-clean out after each dyeing and nuetralisation, before the next dyeing. Positive impact by reducing volume and COD of effluent. Displacer in dye pad trough Not clearly visible here, is a displacing unit built into the trough, to reduce the dead volume, so that the amount of dye left at the end of the batch is reduced by about 32%. Less water is used, and the time for mixing the dyes and chemicals has also been shortened. Reducing cooling water flow A solenoid valve and timer controlled by a central Arel system controls the flowrate of cooling water through the Then Airjet dyeing machine. Cooling water flow is optimised, resulting in savings in water and cooling-water treatment chemicals. Recovering heat from exhaust air Heat exchangers consisting of bundles of glass tubes recover heat from the hot stenter exhaust. This is used to heat- up the incoming cool air. In this way, the energy consumption is reduced and less CO2, SO2 and NOx released to atmosphere. In this case, about 40 degrees of heat is recovered, resulting in a reduction in thermal fuel of about 40%. Heat exchange Dyebath effluent has a high heat content, that may be recovered to heat up boiler feed water or process water used for hot rinses. Generally every 1 degree recovered saves 1% of boiler fuel. In this case, dyebath effluent is used to heat the incoming water to about 60 degrees celsius. This has reduced boiler fuel consumption by 20%, CO2 emissions by 543 tonnes/year and SO2 emissions by 2.50 tonnes/year Solid waste management Sorting and collecting fabric wastes at source in the factory makes solid waste management easier. In this case, the fabric waste is collected and stored on-site. The fabric waste is then sold to a waste handler. Cont… Solid waste management Plastic, cloth, cardboard, fluff, cone and drum wastes have been segregated in the factory and assembled at this point. This ensures that all sources of wastes are accounted for, and that the solid wastes are handled in the proper manner. The wastes are collected and recycled by an independent waste contractor Solid Waste Management: before Textile factories produce large amounts of solid wastes: Yarn and fabric waste Plastic wastes Cardboard wastes Metal Glass Packaging These wastes are often dumped at municipal dumping grounds or landfill sites through waste contractors. Cont… Solid Waste Management: before… A large portion of the solid wastes from textile factories is made up of cardboard packaging, plastic wrappers and tapes. These are simply dumped at municipal sites. Local people then sift through these wastes to collect any material they might find useful. Cont… Solid Waste Management: before… The solid wastes dumped at municipal sites is then “scavenged” for any useful material. Here, the fabric wastes are being sorted and collected by locals. This is dangerous and poses severe health and safety risks to these people. Cont… Solid Waste Management: after… The factory has now separated all solid wastes at source, through a collection system in each department of the factory. These are then collected and used by a recycling company. This has reduced the solid waste burden of this factory by a significant amount Cont… Solid Waste Management: after At this factory all fabric and yarn wastes are separated at source, weighed and stored in a central holding area. Recyclers then purchase this material for a variety of end uses. Chemical Leak and Spill Handling Proper management of chemical leaks and spills demonstrates environmental responsibility. A system for cleaning up leaks and spills also saves the company money that would have been spent on costly clean- ups and fines. The health and safety of factory workers are also improved. Chemical Drum Reuse Chemical drums are often sent for disposal together with the general solid wastes. In this factory, all the used drums are collected and stored at a central point. The chemical suppliers then collect the drums for re- conditioning and reuse for some other purpose. Chemical Leak and Spill Handling Signage is important for workers handling dangerous bulk chemicals. At this factory, the correct work instructions for the chemical handling, and off-loading process has been written near the bulk tank to prevent accidents to workers, spills and dangerous incidents. Caustic recovery from mercerising At this factory, caustic effluent from the mercerizing range is pumped through a series of evaporators to concentrate the effluent. This concentrate is then reused in the mercerizing range. About 11 tonnes/day of caustic is recovered, realising significant cost savings (about R14000/day) and reduction in effluent pollution load. Reusing cooling water At this large fully integrated mill, dyeing and printing cotton, cooling water is recycled to this tank from where it is pumped out to the various process cooling water users. Savings in fresh water of 50m3/day, treatment chemicals and effluent has been realised. Heat exchange The pictures here show how hot dyebath effluent is used to heat incoming process water to about 70 DegC in a baffled heat exchanger. On a daily basis this represents a saving of about 12000 kWh of energy. For an HFO fired boiler, this represents a cost saving of about R1200/day, and reductions in emissions of about 14 kg SO2 per day, and 3044 kg CO2 per day. Heat recovery from mercerizing effluent The pictures here show a pipe heat exchanger with a bundle of tubes that is used to heat process water, through recovering heat from the mercerizing effluent. About 20 DegC is recovered, representing a saving of about 20% in boiler fuel. About 3510 kWh/day is saved, reducing HFO consumption by about 297 litres/day. This represents a cost saving of about R356/day, and reduction in SO2 emissions of 4 kg/day, and CO2 emissions of 890 kg/day. Condensate recovery and reuse A marked piping system has been constructed around this Combi steamer, where recovered condensate is reused as hot process water in the dye works. Roughly 250 kl/day, is recovered. Savings in water and effluent of about 500 kl/day has been realised. Waste segregation at source At a large factory that processes woven cotton, cone and fabric wastes are separated at source, and assembled at a central point outside the production area the factory. On a monthly basis about 20 tonnes of fabric waste is recycled. The solid wastes is sold to recyclers. Reusing effluent for screen washing A large dyeing and printing company segregates effluent at source. The relatively low strength effluent is then pumped to a storage tank, from where the water is reused in washing print screens. Significant savings in water of 10 m3/day and effluent has been achieved. Sorting and recycling solid wastes This factory separates and collects cone, drum and tube waste at source, and assembles them at a central point. The waste is then recycled to the suppliers. On a monthly basis, 153 drums are recycled. Recycling general wastes Plastic, cardboard and packaging waste has been separated at source within this factory. The waste is then assembled at a central collection point, and sold to recycling companies. Plastic: 3.026 tonnes/month Cardboard cores: 18.11 tonnes/month Packaging: 11.7 tonnes/month Recycling fabric wastes Yarn wastes and fabric off- cuts have been sorted and collected at source at this factory. The wastes are then assembled at a central collection point, where it is weighed and sold to recycling companies. Yarn waste: 25 tonnes/month Fabric waste: 20 tonnes/month Reducing wastes from carpet weaving A large carpet manufacturer has separated wastes from the weaving process at source, and assembled the wastes at a central point for recycling. The Spool setting and Spool gripping in the weaving process produces the most amount of solid wastes in this factory. Waste collection for recycling Waste collection from Spool weaving Waste collection from spool setting Recycling solid wastes General waste, oil waste and metal wastes are collected at source at a large carpet manufacturer. These wastes are then assembled at a central collection point for recycling Separation at source Recycling oil wastes Recycling metal wastes CP audit course… An audit course for training auditors in waste minimisation was successfully completed at the University of Natal, Durban. The course was attended by people from industry, consultants, research institutes and textile education organisations. The course is being presented by Susan Barclay, Pollution Research Group – University of Natal from June to November 2000 CP audit course… The course consisted of 8 modules, each having theoretical and practical component. Course participants completed each module at the University, and then completed the practical auditing at a factory in Durban. They then provided regular progress reports at each training session. Each participant will be awarded with a University accredited certificate on successful completion of a the final report CP audit course The overwhelming success of this training has prompted the course organizers to give a second identical course in Cape Town. The details are as follows: Contact: SUSAN BARCLAY Pollution Research Group Tel. 031-2603375 E-mail: firstname.lastname@example.org Course diary Module 1: 6 and 7 November 2001 Module 2: 27 and 28 November 2001 The course participants, Durban Module 3: 4 and 5 February 2002 Module 4: 25 and 26 February 2001 Module 5: 20 March 2002 Chemical Score system An important outcome of the study tour was the specific request from Chemical Score Chart local industry for assistance in implementing a chemical score system for our industry. The Exposure Score, A.B.C 60 Bad scores 50 score system is a management 40 system for ranking chemicals 30 20 according to their use, 10 biodegradability, Good scores bioaccumulation and toxicity. A 0 0 1 2 3 4 pilot project is currently being run Toxicity Score, D for Durban factories by a visiting Danish expert and students. This A: amount used project is due to be completed by B: biodegradability December 2001, and would have C: bioaccumulation resulted in compiling the Score D: toxicity reports for 10 local factories. The The exposure score is calculated by A*B*C, project also aims to promote then compared with D on an XY system of coordinates to provide an overall score. interaction between chemical suppliers, factories and local regulatory bodies. Score system in practice 64 56 The score report on Exposure (AxBxC) 48 Exposure and Toxicity 40 32 effects of each 24 chemical used in the 16 production process. 8 0 0 1 2 3 4 D1 Score (Fauna) A large carpet manufacturer The chemicals has now incorporated the with the worst Score system for scores have been separated and environmental ranking of marked for more chemicals into their overall detailed investigations, and chemical management possible programme. replacement. Study tours to Denmark A study tour to Denmark has increased awareness in CP in the SA textile pipeline, promoted interchange of information on specific practices related to CP in cotton exhaust reactive dyeing, and helped overcome management barriers to implementing CP in local dyehouses. In November 2000, top management representatives from the local Study tour group: 14 to 25 November 2000 industry and government departments undertook a study tour of factories, government departments and educational institutions in Denmark. Study tours to Denmark Key players from the SA textile manufacturing industry observed CP practices in Danish dyehouses, learned about the Danish experience in implementing their CP programme and visited regulatory councils and municipal treatment works. This has helped to overcome barriers to implementing CP in SA factories. All the factories represented in this tour have now implemented CP options related to reducing water and effluent in the dyeing and washing-off of cotton products.
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