(320b) Influence of Biomass On Fine-Particle and Mercury Emissions in Oxy-Coal Combustion

Oxy-coal combustion elicits continued study as a means for obtaining high-concentration carbon-dioxide (CO₂) flue gas that can be readily purified and sequestered. As with most other modalities for addressing the role of CO₂ in global climate change, oxy-coal combustion must contend with the prospect of wide deployment and site-specific access to and preferences for fuels. Biomass co-combustion with coal is one such preference that has the added benefit of net CO₂ reduction and has been widely studied and implemented for existing, conventional coal combustion modalities, in spite of the many technical challenges presented by the introduction of biomass. While the impact of oxy-coal combustion on other emissions such as fine particles and mercury has been examined (Suriyawong et al., 2006), operational demands may result in biomass co-firing in oxy-coal combustion environments.

Therefore, we will compare the effect of sawdust (biomass) on fine particle formation and mercury emissions in oxy-coal combustion to its effect in conventional coal-air combustion for a laboratory-scale self-sustaining combustor. These results will also be compared with those obtained from earlier controlled studies of oxy-coal combustion in drop-tube and self-sustaining combustion environments. It is expected that different temperature-time profiles would result in different vaporization rates, particularly for sawdust, for oxy-coal combustion compared with coal-air combustion. And, increased formation of alkali salts due to the addition of biomass to oxy-coal combustion may increase the potential for mercury oxidation. Practical implications for fine-particle and mercury capture will be suggested.

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Suriyawong, A., Gamble M., Lee M.H., Axelbaum R. and Biswas P., ?Submicrometer particle formation and mercury speciation under O₂ - CO₂ Coal Combustion?, Energy and Fuels, 20 (6), 2357-2363, 2006.