Master of Science / Department of Chemical Engineering / Larry Erickson / Oxy-fired boilers are receiving increasing focus as a potential response to reduced boiler emissions limits and greenhouse gas legislation. Among the challenges in cleaning boiler gas for sequestration is attaining the necessary purity of the CO[subscript]2. A key component in the oxy-fired cleaning path is high purity SO[subscript]x and NO[subscript]x removal, often through absorption using the lead-chamber or similar process. Aerosol formation has been found to be a source of product contamination in many flue gas absorption processes. A number of authors presented simulation methods to determine the formation of aerosols in gas absorption. But these methods are numerically challenging and not suitable for day-to-day analysis of live processes in the field. The goal of this study is to devise a simple and practical method to predict the potential for and effect of aerosol formation in gas absorption using information from Aspen Plus, a commonly used process simulation tool. The NO[subscript]x absorber in an oxy-fired boiler CO[subscript]2 purification system is used as a basis for this investigation. A comprehensive review of available data suitable for simulating NO[subscript]x absorption in an oxy-fired boiler slipstream is presented. Reaction rates for eight reactions in both liquid and vapor phases are covered. These are entered into an Aspen Plus simulation using a RadFrac block for both rate-based and equilibrium reactions. A detailed description of the simulation format is given. The resulting simulation was compared to a previously published simulation and process data with good agreement. An overall description of the aerosol formation mechanism is presented, along with an estimate of expected aerosol nuclei reaching the NO[subscript]x absorption process. A method to estimate aerosol quantities produced based on inlet gas nuclei concentration and available condensable water vapor is presented. To estimate aerosol composition and emissions, an exit gas slipstream is used to equilibrate with a pure water aerosol using an Aspen Plus Equilibrium Reactor block. Changing the composition of the initial aerosol feed liquid suggests that the location of aerosol formation may influence the final composition and emissions.

Species interactions are recognised as an important evolutionary process, with foundation species in particular being of exceptional importance. Foundation species are those species exhibiting dynamic physical traits, under strong genetic control, that shape the natural processes of habitats and ecosystems. These traits lead to extended consequences for the associated organisms in their community. Therefore, intra-specific variation of a foundation species can have important evolutionary consequences for habitats, communities and entire ecosystems. One such foundation species is aspen (Populus tremula L.), which has important conservation value, particularly for the high diversity of associated species. In Scotland aspen exists in fragmented clonal patches, but has been found to contain a high diversity of associated organisms some of which have a UK Biodiversity Action Plan (BAP). One such group of organisms of high diversity and conservation value in Scotland are the epiphytic cryptogams (i.e. mosses, liverworts, lichens). To date more than 300 species have been recorded on aspen in Scotland, comprising approximately 40% of the epiphyte flora of Europe. The research presented here uses a combination of natural aspen system and two aspen common gardens to test the effects of aspen genetic diversity on physical traits potentially important for epiphyte diversity. The traits investigated were bark texture and bark phenolic chemistry. Bark texture in the wild clones was found vary significantly between clones and under strong genetic control (up to 40%). Bark phenolic chemistry also showed significant genotypic variation, but could not be correlated with patterns of epiphyte species richness and diversity. Nevertheless, epiphytes showed significant patterns related to aspen genotype, particularly along a gradient of bark texture. The results indicate that epiphyte communities are part of the ‘extended phenotype’ of native aspen populations in Scotland are very important for maintaining current levels of epiphyte diversity. A greater diversity and abundance of aspen genotypes in the landscape are essential for increasing epiphyte species richness and diversity, and for ecosystem health as a whole.

The objectives of this study were to assess the effects of prescribed burning on herbaceous and browse forage quality in the aspen forest type for elk and domestic sheep. Plant samples of selected forage species were taken from burned and nonburned plots within three different prescribed burns in southeastern Idaho. These samples were analyzed for in vitro dry matter digestibility, crude protein, calcium and phosphorus. Data were analyzed using the analysis of variance. There was little improvement in forage quality as a result of prescribed burning, with some reduction in quality in 1983 exhibited by pinegrass (Calamagrostis rubescens). Aspen on August 2 , 1982 had improved elk IVDMD and Ca/P ratios, crude protein and phosphorus levels and decreased calcium content on the burned versus the nonburned areas . By August 22, 1982, only crude protein levels were improved. All of the shrubs analyzed for that date had improved crude protein levels on the burned versus the nonburned areas, but only serviceberry had higher phosphorus levels. In 1983, none of the shrubs or forbs had improved forage quality. Pinegrass decreased in IVDMD and c rude protein on the burned areas, possibly due to a more rapid maturation and increased seed production. Other benefits from prescribed burning included a changing species composition from dense shrub matts to more palatable and nutritious forbs that are not found on unburned areas . This reduction in shrubs also led to greater access of animals to available forage. The aspen type was shown to have a nutritious and valuable understory, irrespective of prescribed burning.

This study investigates geographic patterns of genetic variation in aspen spring phenology to understanding how tree population adapts to climatically risk environments. These finding suggest rules to guide seed transfer between regions. I use a classical common garden experiment to reveal genetic differences among populations from western Canada and Minnesota, and present a novel method to seamlessly map the heatsum required for remotely sensed green-up. Both approaches reveal two major geographic patterns: northern and high elevation aspen populations break bud earlier than sources from the boreal plains, and late budbreak is strongly associated with the driest winter and spring environments. This suggests selection pressures for late budbreak due to both frost and drought risks in early spring, and we therefore caution against transfer of seed to drought regions of the boreal plains. Although such transfers have been shown to increase plantation productivity in short-term tests, non-local planting material may be susceptible to exceptional spring droughts. / Forest Biology and Management

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Published also as Thesis (Ph. D.)--University of Illinois, 1929. / Cover title. "Contribution from the Zoological laboratory of the University of Illinois no. 365." Reprinted from Ecology, vol. XI, no. 2, April, 1930. "Literature cited": p. 426-431.