MSc dissertation -
Faculty of Engineering and the Built Environment / Waste electrolyte from fluorine cells is a major waste problem for the fluorine
chemical industry. Processes have to be developed to reduce, recycle and
re-use the spent electrolyte that has up to now been stockpiled. This
dissertation is a compilation of the research work that has been done to derive
a process to treat waste electrolyte for re-use.
Different conversion processes were investigated to develop a Waste
Management plan for the fluorine generating facility in respect of the
electrolyte.
Gravity settling, centrifuging, filtration, the addition of KF.HF to the to the
electrolyte to decrease the HF concentration in the electrolyte and
consequently decrease the solubility of Fe, Cu and Ni and addition of NaOH to
the electrolyte to convert soluble Fe to the insoluble triple salt were tested.
Gravity settling and centrifuging were shown to produce the best solution.
However, significant sedimentation of the insoluble metal impurities in the
electrolyte is timeously. The implementation of sedimentation as an industrial
separation process to purify waste electrolyte of excess metal impurities is
therefore impractical. The results indicated that sparging molten electrolyte
with N2 gas to remove HF (thus precipitating soluble Fe, Cu and Ni, and
removing moisture to reduce corrosion of metal components), followed by
sediment centrifuging, appears to be a practical basis for an industrial waste
electrolyte treatment process.
During an assessment carried out by the Economics Trends Research Group
(ETRG) (3) at the University of Cape Town a strong argument was made for
the need to direct companies in South Africa to address environmental
concerns with high priority. In South Africa there is very little awareness of the
concept of Clean Technology. Not only must the level of contamination be
reduced before waste is released into the environment, but natural resources
like water must be conserved, and energy consumption must be reduced.
Public concern over degradation of the environment can no longer be ignored.
Globally, the chemical industries are considered to be the main culprits in the
degradation of the environment. The assessment carried out by the ETRG
showed that the chemical industries are classed among the top 5 generators
of toxic and hazardous waste in every country. The metallurgical sector
(mining) is in most cases classed as the top waste generator.
Development and implementation of technologies that are more efficient are
not a matter of choice any more. Each new facility that is developed should
meet the challenge of generating as little waste as possible.
Unfortunately, many old industries and facilities did not focus on increasing
efficiency and minimising waste. These old facilities experience a challenge
now to develop technology to make them part of this Cleaner Production and
Technology era.
Cleaner Production implies generating less effluent or waste and recycling
waste to be used as raw material in the same or another facility. Cleaner
Production also concentrates on the increase of efficiency but this is often
limited by the chemical properties of substances. This research was based on
the ideas for implementation of Cleaner Production in the fluorine generation
facility at Necsa.
Waste reduction almost always implies investment in equipment and
development of new technologies. However there is ample evidence to show
that the cost of rehabilitation of contaminated environment is exceedingly high
in comparison with the precautionary steps taken to prevent contamination.
Waste/Effluent Management have become new buzz words in the industrial
environment.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/1840 |
| Date | 17 November 2006 |
| Creators | Fourie, Elna |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 7428554 bytes, application/pdf, application/pdf |
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