This scholarships is offered through the Applied Centre for Structural & Synchrotron Studies (ACeSSS) and the Mawson Institute
Alumina refineries encounter serious fouling problems due to sodium aluminosilicate scale precipitation caused by the processing of reactive silica-containing caustic aluminate liquors. The Bayer process is used by the alumina industry for the large scale production of alumina from bauxite ore. The formation, deposition and growth of scale on the surfaces of Bayer plant heat transfer equipment (eg evaporators, boilers, tubular heat exchangers etc.) can have a significant negative impact on process efficiency. Formation of very hard titanate scale, in addition to sodium aluminosilicate scale, particularly in high temperature heat exchangers is also an issue encountered when titanium, mostly in the forms of anatase and rutile, is present in the bauxite. Despite extensive research to understand and characterise the underlying scaling mechanisms the development of scale mitigation strategies has only been partially successful.
Cytec has developed the MAX HT polymeric family of scale inhibitors which are injected into the liquor feed either at the spent liquor (post-gibbsite, Al(OH)3, precipitation) evaporators or heat exchanges. It has been found that these additives are highly effective for the low solids environment of 'double stream' plants where the liquor is heated prior to bauxite ore addition. However, the current family of products are not effective on 'single stream' Bayer plants where the liquor and slurry are mixed prior to liquor heating and digestion.
We aim to improve understanding of the mechanisms and kinetics of sodium aluminosilicate and titanate scale/particle growth; to understand the adsorption processes undergone by selected polymeric scale inhibitors onto solid surfaces under simulated single stream processing conditions pertinent to digester heat exchangers; and to aid in the development of a strategy by which to slow the unwanted growth of these scale phases within Bayer liquors.
The PhD project, as a part of the project 'Scale Growth and Inhibition in a Single Stream Bayer Plant' supported by the Cytec Pty, will focus on autoclave leaching of bauxite and corresponding precipitation of scale to study the kinetics of the scale formation and growth, as well as the kinetics of the adsorption and mechanism of action of scale inhibitors. Synchrotron small angle X-ray scattering will be specifically used to study homogeneous nucleation of aluminosilicate phases in the presence and absence of scale inhibitors and the reaction mechanisms, in addition to conventional techniques of ToF-SIMS, UV-Vis, infra-red microscopy, SEM and XRD to be used in the study.
Payment information
Tax-free $26,669 p.a. Allowances are also available for relocation and thesis preparation. There will be opportunities to attend national and international conferences relevant to the research.
Eligibility
Applicants should have an Honours degree or Bachelors degree with relevant experience in physics, chemistry, physical chemistry, chemical engineering, materials science or a related field. Application eligibility is not constricted to Australian residents.
How to apply and closing date
For application information please contact Dr Jun Li (Ph 61-8-83025032, email Jun.li@unisa.edu.au) and Professor Andrea Gerson (email Andrea.Gerson@unisa.edu.au).
The application deadline is the 30 April 2010.