The separation of oil in water dispersions is an important process, with research
principally concentrating upon polymeric and ceramic filters where the filtration
mechanism is predominantly by capture within the depth of the filter. This work
utilises novel metal filters which possess a non-tortuous pore channel and so filter by
a sieving mechanism. An evaluation of a variety of types of metal surface filters was
conducted with a large proportion of the research focusing upon a filter possessing
circular pores which open into a conical shape. Rejection of challenging emulsified
oil droplets was solely by exclusion due to size at this pore.
Enhancement of emulsion filtration was combined with the surface filters using a
selection of rod and helical inserts within a tubular filter to modify the flow
conditions; in the case of helical inserts to produce a centrifugal velocity upon the less
dense oil droplets away from the filter surface. Further filtration enhancement was
produced by air backflushing to alleviate fouling of the filter surface and electrolytic
generation of bubbles to capture oil drops on bubbles. The latter method increased the
overall feed size and should have increased the centrifugal separation by lowering
particle or aggregate density.
Research is also reported into the mechanism of rejection of emulsified oil droplets
using filters with circular pores. The mechanism has been evaluated and shown to
depend on the capillary pressure of deformable oil drops impinging upon the pore. A
mathematical model is described, which predicts the deformation of drops using the
physical properties of contact angle and interfacial tension combined with the
properties of pore size, shape and droplet size.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.