Fluorochemical research supports SA’s beneficiation strategy
Mineral beneficiation has been identified as a national priority to create employment and to drive economic growth in South Africa. In June last year beneficiation became official government policy through the release of a strategy that identified a number of instruments such as policies, legislation and incentives to be put into place to support local beneficiation.
In support of government policy, the SARChI Chair in Fluoromaterials at the University of Pretoria’s Institute of Applied Materials (IAM) has been researching the beneficiation of fluorspar as part of government’s Fluorochemical Expansion Initiative (FEI). Research into this field is sponsored by the initiative.
According to Prof. Philip Crouse who heads the research chair at IAM, South Africa has the world’s second largest fluorspar (CaF©ü) deposits but has exported up to 95% of this high-potential mineral in the past, despite considerable fluorine-related scientific and technological expertise existing locally. To supply the rapidly growing local and export market, the main barriers to market entry, namely the ability to produce hydrogen fluoride and fluorine gas, have long since been crossed by the local nuclear industry and partnerships have been established with several international companies.
Prof. Crouse has been tasked to bring existing technology residing at the South African Nuclear Energy Corporation Limited (Necsa) in the field of PTFE, PVDF, FEP and PFA to the University of Pretoria in order to develop of a fluoro-polymer capability for local industry. South Africa has fluorspar resources to last us for the next 300 years and has the technical know-how and commercial expertise to support full scale beneficiation of this mineral.
Research to support commercialisation
The SARCHI Chair in Fluoromaterials: Science and Process Integration was established in the Department of Chemical Engineering at the University of Pretoria in 2007, and has been functioning under the IAM umbrella since 2010. Over and above the research conducted into fluoro-polymers sponsored by the Fluorochemical Expansion Initiative, this unit also conducts research into: dry fluorination of inorganic materials; modelling of fluorine electrolysis cells; various projects of interest to the Advanced Metals Initiative (AMI) relating to fluoride-based minerals processing; high-temperature processes for the production of high-value products directly from fluorspar. The Chair works in close collaboration with Necsa and its wholly-owned subsidiary Pelchem.
Most of the research conducted by staff and post-graduate students is aimed at developing the South African chemical industry, with a particular focus on conversions, raw material supply, polymer modification and product design for polymer systems and materials.
The Chair’s activities rest on three pillars - the first and largest being the work done on fluoro-polymers. The second pillar comprises fluoride-based mineral processing and the third, industrial based fluoro-chemistry that has a strong nuclear focus.
Exciting developments in dealing with PTFE scrap
One of the Chair’s most recent research highlights has been in the way industry deals with polytetrafluoroethylene (PTFE) scrap. PTFE, often better known by its DuPont trade name Teflon, is most visibly used as a non-stick coating for pans and other cookware. It is non-reactive, has a very low coefficient of friction, has a very high maximum working temperature, and is highly water repellent. This is partly because of the strength of its carbon-fluorine bonds. The material has many industrial applications, and is often used in containers and pipes for reactive and corrosive chemicals. PTFE was discovered in 1938 and the market in this material and related fluoropolymers has been growing by up to 5% per year. PTFE in general is not melt-processible, and products are cut from large blocks. The scrap produced in the process could not be reused up to now. The Fluoromaterials Chair at IAM has very recently developed a process, an extension of work originally done by Necsa-Pelchem, through which PTFE scrap can be processed and reused as fresh resin. This could certainly make a huge difference to the local and international PTFE industry.
In the process, scrap from this highly versatile material is thermally cracked to produce the constituent monomer in sufficient purity to be directly polymerized - without any additional distillation or further purification steps. The virgin resin has been sintered successfully; in other words, it has been heated to form a coherent mass without melting it. While the process still needs much further tweeking, the first results of this technique, developed by post-graduate students of IAM, have proved to be highly exciting.
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