Master of Engineering (Hons.)
Department of Materials Engineering
Phelan, Dominic, The modelling of matt droplet coalescence in the Vanykov process, Master of Engineering (Hons.) thesis, Department of Materials Engineering, University of Wollongong, 1999. http://ro.uow.edu.au/theses/2505
The Vanyukov Process is a nonferrous bath smelter incorporating side injection of the blast into a slag-matte emulsion. Used primarily for the smelting of copper and nickel sulphide ores, a claimed advantage over other commercial nonferrous smelters is the phenomena of coalescence of matte droplets in the bath. The subsequent increase in the rate of phase separation step is thought to lead to an increase in the overall efficiency of the process. The study of coalescence and breakage of dispersed phases in agitated emulsions has concentrated primarily upon mechanically stirred systems, where dispersed and continuous phases are approximately the same density. Gas agitated systems are less well reported and studies into coalescence in the Vanyukov process are the least published. The technique of cold modelling has been utilised by a range of researchers to address fluid flow issues, particularly in the steel industry. The methods are equally applicable to studies into nonferrous systems, and this was the experimental technique used in this study. A 1/6 scale model using an aqueous/paraffin oil analogue was adopted to represent a tuyere section from a Vanyukov Reactor. Digital cameras and image analysis was used in the study of the relationship between gas flow rates and mean droplet diameters. The effect of tuyere diameter on droplet diameters was also assessed. Analysis of droplet dispersions indicated that the use of digital camera technology was acceptable, however the technical specification of the camera had a significant bearing upon results generated. Of the two cameras utilised, both showed the same trend between gas flow rate and mean droplet diameter. However, the camera with improved feamres of high resolution and S-VHS signal processing, produced clearer images allowing more accurate measurement of droplets. In particular, droplets in the range 50 to l(X)|Lim could be measured, improving the accuracy of the results obtained. The results indicate that a relationship between gas flow rate and droplet size exists. It was observed that a maximum droplet size is obtained with a gas flow rate of 961/min, which equates to 430Nm^/m^/h in a full scale Vanyukov reactor. For flow rates lower than this value, coalescence is less likely to occur, and for flow rates increasing from 96 to 140 1/min, a steadily decreasing mean droplet diameter is observed. No relationship was found between tuyere diameter and mean droplet diameter, over the gas flow rates and diameters studied.