Spinning waste streams

The first large scale application of ion exchange to effluent treatment was in the recovery of water, ammonia, and basic copper sulfate from the waste streams encountered in the cuprammonium rayon process. Originally a phenolic type condensation resin was employed, but more recently carboxylic acid acrylic-based exchangers have been introduced. A similar process exists for zinc recovery from the spinning acids of viscose rayon plants, except that in this operation a sulfonic acid resin is employed. 

As manufactured, PET is a relatively weak, amorphous (non-crystalline) polymer which has to be crystallised and orientated by stretching to give it its textile properties. Orientation is carried out during the spinning operation. Equally important nowadays is the use of PET as a replacement for glass in soft drink bottles. Although more expensive than the polyolefins or PVC, it has a distinctive appearance and can be readily separated from a waste stream. Its recovery for recycling will be discussed in Chapter 4. 

To recover hydrogen sulfide from the spent spinning bath acids as completely and at as high a concentration as possible, a vacuum degassing plant was constructed. The concentrated waste-gas stream of ca. 200m /h can be utilized directiy in the sulfuric acid plant (rich gas). 

By careful enclosure of the spinning machines and the apparatus in the acid station and by using novel exhaustion systems, the total waste-air stream of 180 000 m /h (STP) has been reduced to 10 000 m /h (STP). The entire spinning machine waste air can therefore be routed via the waste-gas purification plant (CS2, H2S). Lean gas from the acid station is used as combustion air in the sulfuric acid plant. 

OLR has proved feasible in the fashion context, both in collection of pre- and postconsumer textile waste for use in other products, and in collection of used bottles for recycling into textiles. Garments are suitable as a feedstock for products of lesser value, for example carpet underlay or insulation, with many applications possible. However, the varieties of fibre types and colours mean that the resulting shoddy is in unattractive greys or blacks that are unsuitable for spinning into apparel-quality yam. The wide variety of products that utilise pre-consumer textile waste and even post-consumer textile waste demonstrates that the recycling of textiles works when entering product streams of lesser value. 

The total waste water volume depends mainly on the vacuum generation (steam-jet pumps consume far more water than water seal pumps with closed seal water loops) and on the spinning and conditioning steps. The options for re-use and treatment of the various waste water streams depend on the given composition [46, TWGComments, 2005]. 

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