Emulsion treatment centres

In many industrialised countries oily wastes are collected and treated in commercial or public emulsion treatment centres. The supply of oil emulsions varies very considerably in type of oils, concentration, contamination with other materials, etc. Following coarse pre-filtration and decantation, oil/water emulsions can be treated very successfully with ceramic membranes. The concentrate is returned to the decanter, and microfiltered again after removal of the free oil, until all oil is removed. The extracted water can be fed into a biological treatment plant, or discharged directly, depending on the composition of the original emulsion and/or local regulations. 

Effective methods of continuous treatment are also available. Addition of a chemical product to the furnish always involves a considerable dilution (as the volume of water used in the industry is vast), but treatment directly onto a surface by spray apphcation can be much more concentrated. For this reason it is often more cost-effective if the problem of deposition is defined to a limited part of the papermaking process. The most common method comprises continuous spraying of a water-soluble cationic polymer onto the surface treated. This cationic polymer will then react with anionic water-soluble macromolecules in the furnish (anionic trash) to form a coating. This coating, which is very thin and flexible, is sacrificial, and anything that deposits on this sacrificial coating will be removed from the surface as the deposit is redissolved. Often the polymer is formulated with other materials (like surfactants) to enhance the performance. For centre press rolls spraying a release wax emulsion seems to be the most successful application. 

There are two issues here — first. Technological how to lower the water content in the froth-treatment product, and second, scientific what makes the water emulsion so stable. In this paper, I will focus on the latter and describe the results of collaborative studies performed by a group of researchers from the NSERC Research Chair in Oil Sands headed by Dr Jacob Masliyah from the Department of Chemical and Materials Engineering, University of Alberta in Edmonton, CANMET Western Research Centre (Canadian Government research laboratory), and Syncrude s Edmonton Research Centre. 

Although most emulsions and foams are not thermodynamically stable, in practise they can be quite stable and may resist explicit demulsification, antifoaming and defoaming treatments. Figure 3 shows a magnetic resonance imaging (MRI) slice taken through the centre of an emulsion sample which one of the authors (LLS) had collected from an... 

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