Investigation into the Mechanism of Soot Formation from Biomass Combustion
EMSL Project ID
38792
Abstract
Biomass combustion is currently a significant energy source in developing countries and is likely to become more significant to developed countries due to the search for alternatives to fossil fuel combustion to both increase energy security and to reduce carbon emissions [1]. However, replacing fossil fuels with the combustion of biomass fuels can have significant effects on the atmosphere and hence on climate. It is incumbent on us to build solid fundamental knowledge base that will make it possible to anticipate and limit the negative impact that this change may bring [2-4]. Recent reports suggest that carbonaceous particles produced by the combustion of biomass have a different composition from those produced by fossil fuel combustion; in particular a greater variety of PAHs (polyaromatic hydrocarbons) and their oxygenated compounds are found [5]. Consequently, their atmospheric life cycle and impacts would be expected to be quite different from hydrocarbon fuel soot. Many methods of analyzing soot require sample collection followed by bulk analysis but this does not allow any investigation into the composition of and variation between individual particles and it is subject to sampling artefacts [6]. On-line single particle mass spectrometry offers the possibility to size and chemically analyze individual particles without the need to collect samples. Previous online research has been carried out at the University of Leeds, UK, into soot formation from biomass combustion using ATOFMS (Aerosol Time-of-Flight Mass Spectrometer) and has involved the combustion of eugenol, one of the intermediate species produced by combustion of wood - and n-decane, a conventional hydrocarbon, for comparison [7]. These experiments highlighted the key role of lignin (one of the main components of wood, eugenol is one of its pyrolysis products) in particle formation and the key role of oxygenated compounds. However, because the ATOFMS cannot detect small particles (d<100 nm), and the vast majority of soot particles are often smaller than 150 nm, it had to be run in the free running mode, in which spectra are rarely produced when random coincidences occur. In this mode very few mass spectra are produced and the particle sizes are not measured. It is for that reason that we propose to conduct these experiments using SPLAT II, the only single particle mass spectrometer that can detect and size particles as small as 50 nm. SPLAT II will make it possible to measure the size, composition, density, and fractal dimension of soot particles produces during the combustion of biomass fuels. This new set of experiments will yield a detailed dataset that will help us understand the differences in the mechanism of soot formation and the properties of particles formed in biomass combustion vs. hydrocarbon combustion. Allowing these particles to age under atmospherically realistic conditions will provide knowledge about the differences between the atmospheric life-cycle of biomass and hydrocarbon soot. It is the extremely high sensitivity of SPLAT II to small particles and the ability to provide multidimensional particle characterization that makes these types of experiments possible.
Project Details
Project type
Exploratory Research
Start Date
2010-01-27
End Date
2011-01-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Characterisation of Soot Produced on Combustion of Biomass and Fossil Fuel Proxy Compounds . , Pacific Northwest National Laboratory, Richland, WA. [Unpublished]