Establishing a process to reduce, recycle and reuse the waste electrolyte from fluorine generation

[摘要] Waste electrolyte from fluorine cells is a major waste problem for the fluorinechemical industry. Processes have to be developed to reduce, recycle andre-use the spent electrolyte that has up to now been stockpiled. Thisdissertation is a compilation of the research work that has been done to derivea process to treat waste electrolyte for re-use.Different conversion processes were investigated to develop a WasteManagement plan for the fluorine generating facility in respect of theelectrolyte.Gravity settling, centrifuging, filtration, the addition of KF.HF to the to theelectrolyte to decrease the HF concentration in the electrolyte andconsequently decrease the solubility of Fe, Cu and Ni and addition of NaOH tothe 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 theelectrolyte is timeously. The implementation of sedimentation as an industrialseparation process to purify waste electrolyte of excess metal impurities istherefore impractical. The results indicated that sparging molten electrolytewith N2 gas to remove HF (thus precipitating soluble Fe, Cu and Ni, andremoving moisture to reduce corrosion of metal components), followed bysediment centrifuging, appears to be a practical basis for an industrial wasteelectrolyte 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 forthe need to direct companies in South Africa to address environmentalconcerns with high priority. In South Africa there is very little awareness of theconcept of Clean Technology. Not only must the level of contamination bereduced before waste is released into the environment, but natural resourceslike 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 thedegradation of the environment. The assessment carried out by the ETRGshowed that the chemical industries are classed among the top 5 generatorsof 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 arenot a matter of choice any more. Each new facility that is developed shouldmeet the challenge of generating as little waste as possible.Unfortunately, many old industries and facilities did not focus on increasingefficiency and minimising waste. These old facilities experience a challengenow to develop technology to make them part of this Cleaner Production andTechnology era.Cleaner Production implies generating less effluent or waste and recyclingwaste to be used as raw material in the same or another facility. CleanerProduction also concentrates on the increase of efficiency but this is oftenlimited by the chemical properties of substances. This research was based onthe ideas for implementation of Cleaner Production in the fluorine generationfacility at Necsa.Waste reduction almost always implies investment in equipment anddevelopment of new technologies. However there is ample evidence to showthat the cost of rehabilitation of contaminated environment is exceedingly highin comparison with the precautionary steps taken to prevent contamination.Waste/Effluent Management have become new buzz words in the industrialenvironment.

[发布机构] University of the Witwatersrand