Energy efficient intensification of leaching by ultrasound controlled cavitation
| Reference number | |
| Coordinator | Luleå tekniska universitet - Institutionen för samhällsbyggnad och naturresurser |
| Funding from Vinnova | SEK 500 000 |
| Project duration | August 2017 - April 2018 |
| Status | Completed |
| Venture | The strategic innovation programme for Swedish mining and metal producing industry - SIP Swedish Mining Innovation |
Purpose and goal
The project is a further development of an ultrasound controlled cavitation reactor for minerals and by-products that are known to be very difficult to leach (Scheelite). The purpose was to evaluate the effects of longer exposure time, as well as higher temperature, static pressure and cavitation intensity through optimization. Scaling is done by extending the tube structure and adapting to a higher static pressure. The cavitation intensity is also increased by a modification of the nozzle for flow initiation of cavitation bubbles. Two industrial partners are linked to the project.
Expected results and effects
The cavitation intensity is controlled by ultrasound, temperature and flow initiation of cavitation bubbles. Excitation signals and process parameters are optimized in relation to materials and the leaching reagent. The method can increase the yield two times compared to reference. The process is highly temperature dependent. For higher cavitation intensity, the reactor is modified for a static pressure 8 times atmospheric. Overheating can be handled through better materials and new geometries for better cooling effect. The next step is a pilot scale implementation.
Planned approach and implementation
The effect of ultrasound controlled cavitation in a leaching process is evaluated with a concentrate of Scheelite (CaWO4) in a basic leaching reagent (NaOH, 30 mol). 8 tests are performed with a modified reactor, excited at 22 kHz and 39 kHz at 60°C and 77°C. The cavitation intensity was also varied with hydrodynamic cavitation via a newly developed nozzle. The reactor was modified to cope with overpressure as well as long exposure time (which changed Piezo material). Long-term exposure and higher process temperature were of particular interest. The samples were analyzed by ICP-OES.