Project Fact Sheet 
GAS FLUXING OF ALUMINUM 

Primary and secondary aluminum producers and foundries remove impurities from 
aluminum by bubbling chlorine through the molten metal as a reactive fluxing gas. 
An example of the application chlorine fluxing is the removal of magnesium from 
close to 64 billion recycled aluminum cans (2 billion pounds of aluminum) annually 
to match the high purity that is representative of aluminum produced from 
electrolytic cells. Primary aluminum producers also use gas fluxing to remove 
trace alkali metals from the electrolyte in the electrolytic cells. 
One significant problem with this process is that chlorine bubbling is poorly 
controlled. Excess chlorine is used to ensure impurities are reduced to 
acceptable levels, which results in both the loss of aluminum (AlCl ) and the 
emission of oxide fumes and toxic gases. Optimizing fluxing gas bubble size, 
frequency and residence time would substantially reduce chlorine usage, increase 
productivity and thermal efficiency of aluminum purification process, and reduce 
toxic gas emissions. 
It is also important to improve the understanding of how gas throughput may be 
increased without splashing and spraying of molten metal as the bubbles burst at 
surface. Studying the fluxing gas bubble characteristics in molten aluminum at 
1,000 oK requires special techniques and equipment. A laboratory-scale 
capacitance probe, previously developed for measuring bubble size, frequency, 
and velocity in liquid aluminum, will be used to study bubble dispersion of 
industrial-scale gas fluxing units. The industrial data will be used to advance 
existing mathematical models for fluxing. Laboratory investigations of bubble 
bursting will be conducted to optimize fluxing unit performance and to contribute 
to development future units. 

3 
Schematic of capacitance probe used to study bubble dispersion. 
OFFICE OF INDUSTRIAL TECHNOLOGIES 
ENERGY EFFICIENCY AND RENEWABLE ENERGY • U.S. DEPARTMENT OF ENERGY

	

 
Goals: The objective of this research is to optimize the gas fluxing of liquid 
aluminum, which will result in an increase in the throughput of commercial fluxing 
units, more efficient use of the chlorine used for fluxing, conservation of energy, 
and minimization of emissions of chlorine/chlorides. 

• Extend the mathematical model for laboratory gas fluxing to one style of 
Year One 
• Use a previously developed laboratory scale capacitance probe to map bubble 
dispersion in an industrial-scale fluxing unit under a variety of industrial 
conditions. 
commercial fluxing unit. 
• Initiate laboratory-scale work on fluxing efficiency impact of spraying and 
splashing of liquid metal by the injected gas. 
Year Two 
• Extend bubble measurements to other commercial fluxing units operated under 
as many process conditions as possible. 
• Use bubble measurement results to modify a mathematical model, and test 
the model against plant data. 
• Complete laboratory work on spraying and splashing, and initiate investigation 
of these phenomena at the commercial scale. 
Year Three 
• Conduct commercial-scale investigation of splashing and spraying from 
bursting bubbles. 
• Predict the optimum design and operating conditions for the existing and new 
fluxing units by using the mathematical model. 

The results of this research will be available in the open literature, which will 
facilitate commercialization of this approach. The University of California's Office 
of Technology Transfer will handle patenting and licensing opportunities that arise 
from this research.