Coal continues to be burned by direct combustion in packed or moving bed in small size domestic furnaces, medium size industrial furnaces, as well as small power stations. Recent stringent restrictions on exhaust emissions call for a better understanding of the process of combustion of coal in beds. The present study is a prelude to developing methods of analysis to obtain this improved understanding. A one-dimensional steady-state computational model for combustion of a bed of solid fuel particles with a counterflowing oxidant gas has been developed. Air, with or without preheating, is supplied at the bottom of the bed. Spherical solid fuel particles (composed of carbon and ash) are supplied at the top of the bed. Upon sufficient heating in their downward descent, the carbon in particles reacts with oxygen of the flowing gas. The governing equations of conservation of mass, energy, and species are integrated numerically to obtain the solid supply rate whose carbon content can be completely consumed by a given gas supply rate. The distributions of solid and gas temperatures, of concentrations of various gas species, of carbon content in solid, and of velocity and density of gas mixture are also calculated along the bed length. The dependence of these distributions on the solid and gas supply rates, the air supply temperature, the size of solid fuel particle, and the initial carbon content in solid is also investigated. The calculated distributions are compared with the available measurements from literature to find reasonable agreement. More gas supply is needed for complete combustion at higher solid supply rate. At a given gas supply rate, more solid fuel particles can be consumed at higher gas supply temperature, for larger particle size, and for lower initial carbon content in solid. The temperature of the bed becomes higher for higher solid supply rate, higher gas supply temperature, larger solid particle diameter, or lower initial carbon content in solid. These reasonable results lead one to encourage extension of the model presented here to more complex problems involving combustion of coals in beds including the effects of drying and pyrolysis. / Graduation date: 1994

Thesis (Ph. D.) -- University of Tennessee, Knoxville, 2006. / Title from title page screen (viewed on Jan. 31, 2007). Thesis advisor: Paul R. Bienkowski. Vita. Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains xii, 161 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 132-137).

Thesis (Ph. D.)--University of Nevada, Reno, 2007. / "December, 2007." Includes bibliographical references. Online version available on the World Wide Web.

Thesis (Ph. D.)--University of Tennessee, Knoxville, 2004. / Title from title page screen (viewed Feb. 16, 2005). Thesis advisor: Wayne T. Davis. Document formatted into pages (xvi, 157 p. : col. ill., col. maps). Vita. Includes bibliographical references (p. 137-141).

Thesis (M.S.)--Youngstown State University, 2008. / Includes bibliographical references (leaves 39-42). Also available via the World Wide Web in PDF format.

Dissertation presented in partial compliance with the requirements for the Masters Degree in Technology: Chemistry, Durban University of Technology, 2009. / This study was mainly a response to a challenge faced by ESKOM in its coal-fired power stations. In spite of using high purity water to drive the turbines, the latter were damaged by ‘pitting’, possibly related to acids generated at high temperatures. In the light of this a relatively simple method for determination of short chain organic acids was identified by comparing the efficacies of several methods. It was found that high performance liquid chromatography (HPLC) method preceded by derivatization (with o-nitrophenyl hydrazine) is suitable for analyzing mixtures of simple acids at ppb levels. Calibration was effected by using methanoic acid (formic acid), ethanoic acid (acetic acid), propanoic acid (propionic acid) and butanoic acid (butyric acid). The HPLC instrument used was from Thermo Separations with P2000 pump, SN 4000 interface and UV1000 with a column heater. A comparative study between the HPLC methods using ion exclusion and partition chromatography was carried out in order to find a suitable method that can be used with aqueous environmental samples. The two essential columns that were used were ion exclusion Phenomenex Rezex OA column and a Nucleodur C8 column. The method of partition chromatography using a C8 column showed the most success using a mobile phase consisted of acidified water using HCl (pH4.5) along with a 60:40 Acetonitrile/Methanol mixture. Both isocratic and gradient programs were utilized. Limits of detection were improved from 800ppb (formic acid), 480ppb (acetic), 350ppb (propionic) and 680ppb (butyric acid) to 25ppb (acetic), 60ppb (propionic) and 90ppb (butyric). Samples used in analysis were collected from the main stream, economiser, condensers, polishing plant and turbines of the Tutuka Power Station in Mpumalanga province and analysed using with final developed method / Eskom Tertiary Support Programme. Durban University of Technology

Burning of fossil fuels by coal-fired power plants (CFPPs) is one of the largest sources of environmental mercury in the United States and there have been conflicting reports of local impacts due to CFPPs in the US. Illinois has 23 coal-fired electrical generating plants that may be contributing to elevated environmental mercury concentrations that have contributed to mercury advisories for 13 bodies of water located throughout the state. The objective of the current study is to determine if there is a pattern of total mercury concentrations in sediment and tadpoles collected from ponds located upwind and downwind of 4 coal-fired electrical generating plants in Illinois. Baldwin, Joppa, Newton, and Southern Illinois Power Cooperative (SIPC) coal-fired power plants were chosen for study. Three sediment samples were collected from ponds located 3-5, 8-10, and 13-15 km downwind and from ponds located 3-5 km upwind of each power plant and analyzed for total mercury concentration. Temperature of overlying water (C), pH, oxidation-reduction potential (mV), and texture were determined for each sediment sample. Bullfrog (Lithobates catesbeiana) or Green frog (Lithobates clamitans) tadpoles were collected opportunistically from 29 of the 44 ponds chosen for study. Each tadpole was identified to species and Gosner stage, and then weighed and measured for total length prior to total mercury analysis. For Baldwin, Joppa, and SIPC power plants, no significant pattern of total mercury could be determined from either sediment or tadpole data. For Newton power plant, total mercury concentrations were significantly greater 3-5 km downwind for sediment, and 8-15 km downwind for tadpoles compared to concentrations at upwind locations. Sediment total mercury concentrations were not significantly correlated with any of the characteristic variables (e.g. pH). Tadpole total mercury was significantly negatively correlated with length and weight, but not significantly correlated with any of the sediment variables. Sediment and tadpole concentrations were not significantly correlated.

M.Ing. / Eskom's power stations receive their main supply of coal from mines next to the power stations. The coal supply contracts only specify maximum allowable variations of some coal quality parameters. The quality of the supplied coal can, however, vary greatly within a few hours. The boilers in the power plant are optimized for a certain quality of coal, while the supplied coal is burnt as it is received from the mine. The variations in the coal quality can, therefore, have a negative impact on both the life expectancy and maintenance costs of the power plant as well as the controllability of the boiler. The effects of short term variations in the coal qualities can be reduced by segregating the supplied coal into separate stockpiles according to coal quality parameters such as ash content and volatile matter, and then blending different portions from these stockpiles to a preferred coal quality before the coal goes to the boilers. A self organising feature map neural network was proposed in this research, to determine how to separate the supply coal, according to measured coal quality data. Furthermore, linear programming was proposed to determine the proportions to be taken from each stockpile in order to achieve a more consistent blended coal again. The segregating and blending systems are described in this thesis; and they were tested by means of a simulation based on measured coal quality data from a power station. It was shown that it is possible to successfully segregate coal from a single supply and then blend the different stockpiles to render coal with less short term variations in its quality parameters. The blending process uses stockpile size as its main driver to optimize the selection of the proportions, such that the most coal is taken from the largest stockpile, while the resultant coal quality remains within the specified constraints.

M.Tech. (Mechanical Engineering) / Eskom fossil fuel power stations operate under various conditions and the ageing fleet of fossil fuel power stations are under strain due to the rising demand in electricity. The quest for cheaper electricity in growing businesses and bringing foreign investment into South Africa is significant for economic growth. Therefore, minimizing operation costs and improving availability, reliability and thermal heat rate are key objectives for the operation of the business. Thermal heat rate calculation is a method used to assess the performance of fossil fuel power stations. It provides an indication of the thermal performance which reflects the condition and operation of the plant. This dissertation refers to the tools used to measure the condenser performance and to identify the reason for unhealthy condenser performance and an increase in thermal heat rate. Problem: Poor condenser performance causes significant losses in generation and thermal heat rate in fossil fuel plants. Loss in generation and thermal heat rate is caused by condenser backpressure. This has an adverse effect on turbine thermal heat rate and henceturbine efficiency. The performance of the condenser affects the turbine performance to a large extent. Decreased condenser performance will increase the turbine thermal heat rate, i.e. kJ/kWh, because of the increased steam consumption per kWh of energy generated and therefore lowering the overall turbine efficiency. This will result in poor thermal heat rate efficiency resulting in an increased coal burn rate, i.e. kg/kWh, and an increased fuel bill and carbon foot print for the fossil fuel power station. The aim of this dissertation is to determine the effects of condenser performance on thermal heat rate and to provide the engineering and operating personnel with a guide for monitoring condenser back pressure in order to improve turbine thermal heat rate and turbine efficiency. Method and Procedure: Chapter 4 describes the method and procedure used for the pre and post outage evaluation to cost-effectively determine the current condition of the condenser and to quantify the increase in thermal heat rate due to condenser degradation. The pre and post outage evaluation offered an opportunity to evaluate and quantify the effectiveness of the maintenance program and the value of the capital layout undertaken during the scheduled Unit outage. Findings: Chapter 5 discusses the findings of the pre and post outage data analysis of the condenser using the EtaPRO system as the tool. Re-tubing 50% of the condenser inner loop tubes and cleaning the other 50% of the outer loop tubes demonstrated a decrease in condenser backpressure and therefore an improvement in thermal heat rate. This will also result in an improvement in turbine cycle efficiency and reduce coal cost.