(144a) Lawrence K. Cecil Award Lecture: Environmental Aspects in the Utilization of Fossil Fuels

Authors: 
Lighty, J. S., Boise State University
A major theme of my research has been investigating pollutant formation during the combustion of fossil fuels, namely solid fuels and liquids. This lecture will look at research and the resulting implications in environmental regulations, spanning from the early 1990's to today. A focus will be on more recent work dealing with global warming, namely carbon capture via chemical looping combustion and black carbon, or soot, formation and oxidation from engines.

Carbon dioxide is a major contributor to climate forcing with fossil energy combustion for being a component of these emissions. Carbon capture and storage is a potential method to the reduction of carbon dioxide to the environment. Oxy-fuel combustion, where a solid fuel is burned with oxygen diluted with recycled flue gas, is an effective method of carbon capture as the resulting flue gas is mainly carbon dioxide and water. This is in contrast to combustion in air, where the flue gas contains nitrogen as well. Chemical looping combustion has the potential to be a more energy effective method of oxygen generation as compared to air separation, which is energy intensive. Specifically, our group at the University of Utah has been studying chemical looping with oxygen uncoupling, where a copper oxide oxygen carrier is used in a fuel reactor (reducing copper oxide on an inert) and then “looped” to an air reactor (oxidizing the copper oxide). In the fuel reactor, the reduction of the cupric oxide to cuprous oxide results in oxygen release which is used to burn the solid fuel, in this case coal. The talk will focus on the role of chemical engineering fundamentals, i.e. mass and energy balances, mass transfer, and kinetics, in designing effective systems for solid fuel, in this case coal, combustion. Results from lab scale tests, ASPEN modeling, and computational fluid dynamics modeling (CFD) utilizing a commercial code, Barraucda-VR®, will be discussed.

Studies have suggested that the contribution of black carbon, or soot, to global warming could be secondary to that of carbon dioxide. In addition, the emission of black carbon or soot has important implications for ambient fine particulate concentrations, and hence, adverse health effects. An immediate remedy is to simply reduce the amount of soot emitted to the atmosphere. For industrialized countries, a major source of soot is from diesel engines. While reducing the formation of soot from engines is certainly an important aspect, our research has focused on the oxidation kinetics of soot. Results have suggested that soot nanostructure, which is a function of fuel type, is an important parameter in changes in the rates of soot oxidation. The development of effective soot oxidation rate equations for a particular fuel is critical in the ability to predict emissions from engines.

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