Microwave Augmented Reduction Using Hydrogen Enriched Methane

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The extractive metallurgy industry generates over five percent of the total greenhouse gas emissions. As a result of the increasing concern for climate change, this industry is moving towards more sustainable operating practices with regards to energy efficiency and environmental stewardship. Microwave processing is a relatively new technique, which is being studied for application in mineral processing and metallurgical extraction. In the last decade, it has been shown that microwave heating has a number of potential advantages for heating materials of interest in pyrometallurgical processes, in particular metal oxides. It can provide volumetric, rapid and selective heating and also the electrical energy source can be relatively clean. Additionally in comparison to fossil fuels, the amounts of off--gases, carbon dioxide and dust can be reduced. Thus, it would be advantageous to develop a reduction process which can utilize these potential heating characteristics for improved energy efficiency. In the short term, the combination of renewable energy resources with a microwave augmented existing energy source and a more environmentally friendly reductant may be part of a transitional solution. The utilization of natural gas (95% methane) as a reducing agent, which has less of an environmental impact and can also be potentially very reactive, would be advantageous. Renewable energy sources can be utilized to produce the microwaves and to manufacture hydrogen to add to methane.  One approach to deal with these environmental issues is to investigate alternative energy sources and reducing agents in order to improve the energy efficiency and to reduce the carbon footprint. In this regard, it is proposed to continue research on the utilization of microwaves for metal extraction and focus on the utilization of methane as a reducing agent for metal oxides. This will involve a three-pronged methodology using the following methane-based reducing agents: (1) essentially pure methane or natural gas, (2) hydrogen-enriched methane or natural gas (HENG) and (3) reactive carbon/adsorbed carbon produced from the decomposition of methane. Microwave heating alone is relatively inefficient due to the energy losses during the conversion of electricity to microwaves in the magnetron. It is proposed to combine microwaves with a conventional heating source, in a microwave augmented heating process with an overall improved efficiency. Also, microwaves may catalyze the decomposition of methane. Thus, the overall objective of this research is to combine the relatively new microwave heating technology together with the somewhat underutilized potential of methane as a reducing agent and in particular produce carbon in a very reactive form. This arrangement could lead to improved energy efficiencies, significantly reduced greenhouse gas emissions and reduced impact of pyrometallurgical processes on the environment. This would of benefit to both the industry and society.