Browsing by Subject "coal"
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Item Description of Alethopteris from the Williamson #3 Mine, Lucas County, Iowa: anatomical variation, diversity, paleoecology(Texas A&M University, 2004-09-30) Slone, Elizabeth Dunbar JonesFor more than 100 years, Pennsylvanian permineralized peats have been studied for their exceptionally preserved plant remains. Late Atokan-early Desmoinesian coal balls from the Williamson # 3 deposit in south-central Iowa were preserved by the permineralization of soluble carbonate into pores in the peat and plant cells creating carbonate nodules. These nodules, referred to as coal balls, protect the plant remains from the compaction associated with coal allowing for the analysis of anatomically preserved plants from Pennsylvanian. The Williamson #3 deposit is unusual because it is dominated by a diverse assemblage of gymnosperms. Other deposits of similar age in Iowa are dominated by a mixture of cordaitalean gymnosperms, tree-ferns, and medullosan gymnosperms; while, other North American deposits are dominated by lycopsids with tree-ferns and seed-ferns as the subdominant vegetation. Because vegetation types differ with environment, analysis of the Alethopteris pinnules from the Williamson #3 Mine provides insight into the ecology of a peat-producing swamp during the Pennsylvanian, and allows for the comparison of this deposit to others in North America. The focus of this study is the description of a distinct morphotype of Alethopteris from the Williamson #3 Mine. Alethopteris pinnules described from other mines were used to compile a traits list and compare measured and descriptive characteristics. The objective of this study is to gain a better understanding of changes in swamp vegetation during the Pennsylvanian, and the effect of environmental variation on the dominant vegetation in peat swamps.Item Implications of Carbonate Petrology and Geochemistry for the Origin of Coal Balls from the Kalo Formation (Moscovian, Pennsylvanian) of Iowa(2012-10-19) Jones, CourtneyCoal balls are carbonate concretions formed in peat during the Pennsylvanian and early Permian. Microprobe and microscope analysis reveal that polycrystals of high-Mg calcite (HMC), which are also high in Sr, are the earliest calcium carbonate to form in the Williamson No. 3 coal balls from the Kalo formation in Iowa. This HMC has early diagenetic rims of ferroan and non-ferroan low-Mg calcite (LMC) suggesting diagenesis in meteoric water. The combination of HMC followed by LMC suggests the earliest coal ball carbonate formed in a hydrologically dynamic environment, where saltwater influx into the mire was followed by a return to meteoric pore water. Subsequent generations of carbonate are ferroan and non-ferroan LMC and appear to result from diagenesis of the original HMC fabric with LMC rims. HMC polycrystals from coal balls are among the first abiotic HMC to be reported from the mid-Pennsylvanian; coal balls may be a good source of Pennsylvanian HMC. Coal balls that formed in porous peat (i.e. wood and surficial leaf mats) commonly have abundant radiating arrays of HMC polycrystals. Coal balls that formed in matrix-rich, low porosity peats consist primarily of permineralizing anhedral calcite, which is ferroan LMC. The link between the HMC and porous permeable peat is supported by the distribution of HMC and ferroan LMC in plant cells. Wood cells, which have porous walls, are filled with HMC; fiber cells, which have impermeable walls, are filled with ferroan LMC. This study demonstrates a link between pore volume, porosity, plant cell type, and carbonate fabric.Item Investigation Of Synergistic NOx Reduction From Cofiring And Air Staged Combustion Of Coal And Low Ash Dairy Biomass In A 30 Kilowatt Low NOx Furnace(2013-08-01) Lawrence, Benjamin DanielAlternate, cost effective disposal methods must be developed for reducing phosphorous and nitrogen loading from land application of animal waste. Cofiring coal with animal waste, termed dairy biomass (DB), is the proposed thermo-chemical method to address this concern. DB is evaluated as a cofired fuel with Wyoming Powder River Basin (PRB) sub-bituminous coal in a small-scale 29 kW_(t) low NO_(x) burner (LNB) facility. Fuel properties, of PRB and DB revealed the following: a higher heating value of 29590 kJ/kg for dry ash free (DAF) coal and 21450 kJ/kg for DAF DB. A new method called Respiratory Quotient (RQ), defined as ratio of carbon dioxide moles to oxygen moles consumed in combustion, used widely in biology, was recently introduced to engineering literature to rank global warming potential (GWP) of fuels. A higher RQ means higher CO_(2) emission and higher GWP. PRB had an RQ of 0.90 and DB had an RQ of 0.92. For comparison purposes, methane has an RQ of 0.50. For unknown fuel composition, gas analyses can be adapted to estimate RQ values. The LNB was modified and cofiring experiments were performed at various equivalence ratios (phi) with pure coal and blends of PRB-DB. Standard emissions from solid fuel combustion were measured; then NO_(x) on a heat basis (g/GJ), fuel burnt fraction, and fuel nitrogen conversion percentage were estimated. The gas analyses yielded burnt fraction ranging from 89% to 100% and confirmed an RQ of 0.90 to 0.94, which is almost the same as the RQ based on fuel composition. At the 0.90 equivalence ratio, unstaged pure coal produced 653 ppm (377 g/GJ) of NOx. At the same equivalence ratio, a 90-10 PRB:LADB blended fuel produced 687 ppm (397 g/GJ) of NO_(x). By staging 20% of the total combustion air as tertiary air (which raised the equivalence ratio of the main burner to 1.12), NO_(x) was reduced to 545 ppm (304 g/GJ) for the 90-10 blended fuel. Analysis of variance showed that variances were statistically significant because of real differences between the independent variables (equivalence ratio, percent LADB in the fuel, and staging intensity).Item Mercury emission control for coal fired power plants using coal and biomass(2009-05-15) Arcot Vijayasarathy, UdayasarathyMercury is a leading concern among the air toxic metals addressed in the 1990 Clean Air Act Amendments (CAAA) because of its volatility, persistence, and bioaccumulation as methylmercury in the environment and its neurological health impacts. The Environmental Protection Agency (EPA) reports for 2001 shows that total mercury emissions from all sources in USA is about 145 tons per annum, of which coal fired power plants contribute around 33% of it, about 48 tons per annum. Unlike other trace metals that are emitted in particulate form, mercury is released in vapor phase in elemental (Hg0) or oxidized (Hg2+, mainly HgCl2) form. To date, there is no post combustion treatment which can effectively capture elemental mercury vapor, but the oxidized form of mercury can be captured in traditional emission control devices such as wet flue gas defulrization (WFGD) units, since oxidized mercury (HgCl2) is soluble in water. The chlorine concentration present during coal combustion plays a major role in mercury oxidation, which is evident from the fact that plants burning coal having high chlorine content have less elemental mercury emissions. A novel method of co-firing blends of low chlorine content coal with high chlorine content cattle manure/biomass was used in order to study its effect on mercury oxidation. For Texas Lignite and Wyoming coal the concentrations of chlorine are 139 ppm and 309 ppm on dry ash free basis, while for Low Ash Partially Composted Dairy Biomass it is 2,691 ppm. Co-firing experiments were performed in a 100,000 BTU/hr (29.3 kWt) Boiler Burner facility located in the Coal and Biomass Energy laboratory (CBEL); coal and biomass blends in proportions of 80:20, 90:10, 95:5 and 100:0 were investigated as fuels. The percentage reduction of Hg with 95:5, 90:10 and 80:20 blends were measured to be 28- 50%, 42-62% and 71-75% respectively. Though cattle biomass serves as an additive to coal, to increase the chlorine concentration, it leads to higher ash loading. Low Ash and High Ash Partially Composted Dairy Biomass have 164% and 962% more ash than Wyoming coal respectively. As the fraction of cattle biomass in blend increases in proportion, ash loading problems increase simultaneously. An optimum blend ratio is arrived and suggested as 90:10 blend with good reduction in mercury emissions without any compromise on ash loading.Item Modeling of the reburn process with the use of feedlot biomass as a reburn fuel(2009-05-15) Colmegna, GiacomoCoal fired power plants will face many challenges in the near future as new regulations, such as the Clear Sky Act, are being implemented. These regulations impose much stricter limits on NOx emissions and plan to impose limits on mercury emissions from coal fired boilers. At this time no technologies are currently being implemented for control of Hg and this explains the strong interest in this area by the Department of Energy (DOE). Reburn technology is a very promising technology to reduce NOx emissions. Previous experimental research at TAMU reported that Feedlot Biomass (FB) can be a very effective reburn fuel, for reduction of NOx up to 90%-95%; however, little work has been done to model such a process with Feedlot Biomass as reburn fuel. The present work addresses the development of a reburn model to predict NOx and Hg emissions. The model accounts for finite rate of heating of solid fuel particles, mixing with NOx laden hot gases, size distribution, finite gas phase and heterogeneous chemistry, and oxidation and reduction reactions for NOx and Hg. To reduce the computational effort all the reactions, except those involved in mercury oxidation, are modeled using global reactions. Once the model was validated by comparison with experimental findings, extensive parametric studies were performed to evaluate the parameters controlling NOx reduction. From DOE research programs some experimental data regarding the capture of mercury from power plant is available, but currently no experimental data are available for Hg emission with reburn process. This model has shown a very large mercury reduction using biomass as a reburn fuel. The model recommends the following correlations for optimum reduction of NOx: Equivalence Ratio should be above 1.05; mixing time should be below 100ms (especially for biomass); pure air can be used as the carrier gas; the thermal power fraction of the reburner should be between 15% and 25%; residence time should be at least 0.5s and the Surface Mean Diameter (SMD) of the size distribution should be as small as possible, at least below 100 ?m.Item Non-Reacting Flow Characteristics and Emissions Reduction on Blends of Coal and Dairy Biomass in 30 kW_(t) Low NO_(x) Down-Fired Furnace(2014-08-07) Tiyawongsakul, TiyawutRecently, coal-fired power plants have considered either to retire themselves or to use natural gas as the main energy source instead of coal due to more stringent air pollution regulations for nitrogen oxides (NO_(x)), mercury (Hg) and more recently the required CO_(2) reduction of 30% by 2030. Clean coal technology must be continuously developed in order to prevent people from losing their jobs and to decrease the negative impacts of firing coal on environment. The present research focuses on NO_(x) emissions which arise mainly due to oxidation of fuel-bound nitrogen using low NO_(x) burner (LNB) when fired with Wyoming Powder River Basin coal (PRB) and blends of coal and dairy biomass (DB). The DB was selected as co-fired fuel for possible elimination of DB from dairy feedlots which result in land, air and water pollution if not properly disposed of. LNB adopts staged air introduction in order to limit the availability of oxygen when nitrogen from fuel is released. To achieve the objective, the mixing patterns between fuel particle and air were predicted using non-reacting flow (NRF) simulation inside the cylindrical combustion chamber. The effects of varying burner parameters, fuel particle sizes, main burner equivalence ratios (ER_(mb)) and overall equivalence ratios (ER_(oa)) on mixing characteristics were investigated. Then, the LNB components were modified based on the results from NRF simulation. The modified main burner is a partially premixed swirl burner (fuel mixes with the primary air inside the fuel/primary air nozzle, and the secondary air is swirled by the straight-vane swirler) whose swirl angle and secondary air swirl number are 59? and 1.42 respectively. The circular over-fire air (OFA) nozzles are located 484 mm below the main burner exit, and the OFA is injected into the combustion chamber in the radial direction. The fuels used in the research were: 1) pure PRB and 2) the fuel blend of PRB and DB with the PRB-to-DB ratio of 90 to 10 on mass basis (90-10 PRB-DB blend). Fuel characteristics were first obtained, and empirical chemical formulae were deduced. The CO_(2), O_(2) and NO were measured as a function of ER_(oa) and ER_(mb) (ER_(mb) based on air flow without inclusion of OFA). The gas analyses were used to obtain the burnt fraction, respiratory quotient (RQ, = CO_(2) moles produced/O_(2) moles consumed) and equivalence ratio which is then checked against measured values. Uncertainty analyses were also performed. The optimum conditions for minimum NO_(x) emission that pass the EPA limit (210 g/GJ) were obtained as follows. With ER_(oa) = 0.95, firing pure PRB produced NO_(x) 220 g/GJ without OFA, and 179 g/GJ with OFA (ER_(mb) = 1.10) which is about 18.6 % reduction. Under same conditions, the co-firing of 90-10 PRB-DB blend decreased NO_(x) by 3.6% without OFA, and 22.2% with OFA (ER_(mb) = 1.10) compared to firing pure PRB at ER_(oa) = 0.95 without OFA. Furthermore, co-firing 90-10 PRB-DB blend with OFA at ER_(mb) = 1.10 and ER_(oa) = 0.95 (excess air 5.26%) emitted NO_(x) approximately 171 g/GJ whilst firing pure PRB without OFA at ER_(oa) = 0.85 (excess air 17.65%) emitted NO_(x) approximately 330 g/GJ which is 48% reduction and less than 210 g/GJ (the current EPA limit). This reduction could benefit 500-MWt power plants approximately $113,500 per year in case the efficiency of power plants is 35% and NO_(x) are traded at $15.89 per short ton.