TREATMENT OF WASTE OIL-IN-WATER EMULSIONS FROM A COPPER METALWORKING INDUSTRY BY VACUUM EVAPORATION: EFFECT OF OPERATING CONDITIONS
Sustainable process-product development & green chemistry
Sustainable & Clean Technologies - Ia: Extraction & Remediation (T1-4a)
Keywords: o/w emulsions, vacuum evaporation, metalworking, coagulant salt, pH
Oil-in-water emulsions are common to many industries for lubrication and refrigeration purposes. These fluids lose their functional properties with use generating waste oily emulsions that must be treated before disposal, to remove the free, soluble and emulsified oil by techniques such as sedimentation, centrifugation, ultrafiltration or evaporation. Three different waste oil-in-water emulsions were treated by vacuum evaporation and results are reported in this work.
The emulsions were provided by a local copper manufacturing company and were generated in different parts of the process: i. a synthetic emulsion used for cooling in the melting process, ii. a semi-synthetic emulsion used for lubrication and cooling in the smoothing process, and iii. a semi-synthetic emulsion used in the wire drawing process.
Experiments were carried out to study the performance of vacuum evaporation on emulsion treatment. Operating parameters, such as evaporation pressure and heating temperature, on emulsion treatment were studied. The use of a pre-treatment step by destabilization-enhanced centrifugation, with the addition of coagulants or a flocculant, and its influence on the emulsion vacuum evaporation was also studied.
It may be concluded, as a general trend, that at high heating temperatures, the evaporation rate is faster but the quality of the condensate effluent (measured in terms of COD, conductivity, turbidity and DBO5) decreases. The influence of the operating pressure on the quality of condensate effluents was not so obvious. However, an increase in the evaporation rate was observed when the operating pressure was increased. Furthermore, COD reductions higher than 95 % were achieved.
The addition of coagulant salts to the waste emulsions lowers their pH’s, and leads to a decrease of the quality of the condensate effluents, while the evaporation rate is hardly affected. An increase in the quality of the condensate effluents was achieved when the emulsion pH was adjusted by adding NaOH.
Finally, the laboratory experimental results were used in order to improve the operation of a plant evaporator, of 60 L/h capacity, and the optimum operating conditions were selected.
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Presented Wednesday 19, 11:36 to 11:54, in session Sustainable & Clean Technologies - Ia:Extraction-Remediation (T1-4a).
