Australian Wool Textile Research (continued)

As well as investigating less conventional treatment, e.g. ultra-filtration, CSIRO, Geelong, investigated the utilisation of the wool contaminants themselves to facilitate contaminant removal. The principle underlying this was to cause the concentration of the dissolved salts (sheep-perspiration and other salts) in the liquor to increase to a level at which the solid suspended solids more readily aggregated and therefore were more readily separated by centrifuging. This was achieved in practice[33] by reducing the volume of water in the first section of the scour and by recycling the liquor repeatedly, recovering grease and dirt (as a spadeable sludge) from the liquor by a series of centrifuges. At equilibrium, theoretically, the water taken out with the dirt and grease and that on the clean wool would balance the water continually fed to this stage. In practice, however, in two full-scale industrial plants, it was found that equilibrium could not readily be achieved, and that the recovery of dirt was below the efficiency expected.

Investigating the causes of these anomalies, the Geelong researchers[34] realized that the presence of protein contaminants (from the sheep's skin and/or from remnants of fibre growth) mixed with the grease on the wool was having very significant effects on the scouring mechanism (Fig. 23). This opened up a completely new approach to wool scouring and effluent treatment,[35] the first practical result of which has been the development of a process[36] for improving the recovery of dirt from waste liquors at much lower cost than conventional treatments. The new knowledge also augers well for the development of new scouring systems that will enable scourers to have better control over the quality of their products while processing at higher rates.[37]

23 Micrographs showing stages in the removal of contaminants from greasy wool by solution of detergent. (a) shows initial swelling of contaminants. (band c) show removal of swollen protein contaminant/grease globules complex and (d) shows the clean fibre.

While the scouring of wool has been placed on a more scientific basis over the past four decades, until recently little major development had occurred in the next process, carding. Despite a novel approach[38] by CSIRO that got as far as long-term commercial evaluation, the inventors of the first carding machine -Bourn and Paul (see p.258) -would have easily recognized the basic principles that they are applied. They would, of course, be amazed by the production of the machines and the quality of the product, but this has all been achieved principally by the application of improved engineering techniques through empirical development or by the application of electronics.

Australian Academy of Technological Sciences and Engineering