With China leading the world in magnesium production (about 80% of total volume), relying on the Pidgeon method, the process of producing the metal results in the generation of the air pollutant PM 2.5 (fine particulate matter) and the release of significant amounts of carbon dioxide into the atmosphere. (The Pidgeon method is a thermal reduction process in which the material temperature is raised, in this case by burning coal.
The technique heats dolomite ore--a raw material for magnesium--and silicon iron to high temperatures, then cooling the evaporated magnesium to obtain the metal.)
Now, Japanese researchers have devised a green magnesium smelting method employing microwaves that uses 70% less energy than conventional methods.
The research group, led by Professor Yuji Wada and Adjunct Professor Satoshi Fujii of the Tokyo Institute of Technology, School of Materials and Chemical Technology, published their findings in the journal Scientific Reports.
Dolomite ore (MgO, CaO), a raw material for magnesium metal, does not readily absorb microwave energy and does not generate heat. When electrically conductive ferrosilicon (FeSi) used as a reducing agent was mixed with the raw dolomite material and made into an antenna structure, it more easily absorbed the microwave energy and reduced in temperature. Internal heating and contact point heating, which are microwave characteristics, were observed, and the average reaction temperature for this smelting was lowered from the conventional 1,200-1,400°C to 1,000°C.
Professor Wada’s team’s methodology involved a small-scale experimental reactor in which 1g of magnesium metal was smelted successfully. To estimate the energy accurately, a demonstration furnace about 5x larger than the experimental furnace was produced and experiments were conducted, resulting in the successful smelting of about seven grams of magnesium metal, at an energy reduction level of about 68.6 percent less compared with the conventional method.
Future developments point to the application of this research to the smelting of other metal materials as an energy conservation method to reduce global carbon dioxide pollution.
Copyright notice: Reproduction of material without written permission is strictly prohibited.