Professor Mitchell's primary area of research is concerned with characterizing the physical and chemical processes that occur during the combustion and gasification of pulverized coal and biomass. Coals of interest range in rank from lignite to bituminous and biomass materials include yard waste, field and seed crop residues, lumber mill waste, fruit and nut crop residues, and municipal solid waste. Experimental and modeling studies are concerned with char reactivity to oxygen, carbon dioxide and steam, carbon deactivation during conversion, and char particle surface area evolution and mode of conversion during mass loss.
Mitchell’s most recent research has been focused on topics that will enable the development of coal and biomass conversion technologies that facilitate CO2 capture. Recent studies have involved characterizing coal and biomass conversion rates in supercritical water environments, acquiring the understanding needed to develop chemical looping combustion technology for applications to coals and biomass materials, and developing fuel cells that use coal or biomass as the fuel source. Studies concerned with characterizing coal/biomass blends during combustion and gasification processes are also underway.