Thesis (M.S.)--Ohio University, August, 2009. / Title from PDF t.p. Includes bibliographical references.

We investigate several aspects of the numerical solution of the radiative transfer equation in the context of coal combustion: the parallel efficiency of two commonly used opacity models, the sensitivity of turbulent radiation interaction (TRI) effects to the presence of coal particulate, and an improvement of the order of temporal convergence using the coarse mesh finite difference (CMFD) method. There are four opacity models commonly employed to evaluate the radiative transfer equation in combustion applications; line-by-line (LBL), multigroup, band, and global. Most of these models have been rigorously evaluated for serial computations of a spectrum of problem types [1]. Studies of these models for parallel computations [2] are limited. We assessed the performance of the Spectral-Line- Based weighted sum of gray gasses (SLW) model, a global method related to K-distribution methods [1], and the LBL model. The LBL model directly interpolates opacity information from large data tables. The LBL model outperforms the SLW model in almost all cases, as suggested by Wang et al. [3]. The SLW model, however, shows superior parallel scaling performance and a decreased sensitivity to load imbalancing, suggesting that for some problems, global methods such as the SLW model, could outperform the LBL model. Turbulent radiation interaction (TRI) effects are associated with the differences in the time scales of the fluid dynamic equations and the radiative transfer equations. Solving on the fluid dynamic time step size produces large changes in the radiation field over the time step. We have modifed the statistically homogeneous, non-premixed flame problem of Deshmukh et al. [4] to include coal-type particulate. The addition of low mass loadings of particulate minimally impacts the TRI effects. Observed differences in the TRI effects from variations in the packing fractions and Stokes numbers are difficult to analyze because of the significant effect of variations in problem initialization. The TRI effects are very sensitive to the initialization of the turbulence in the system. The TRI parameters are somewhat sensitive to the treatment of particulate temperature and the particulate optical thickness, and this effect are amplified by increased particulate loading. Monte Carlo radiative heat transfer simulations of time-dependent combustion processes generally involve an explicit evaluation of emission source because of the expense of the transport solver. Recently, Park et al. [5] have applied quasidiffusion with Monte Carlo in high energy density radiative transfer applications. We employ a Crank-Nicholson temporal integration scheme in conjunction with the coarse mesh finite difference (CMFD) method, in an effort to improve the temporal accuracy of the Monte Carlo solver. Our results show that this CMFD-CN method is an improvement over Monte Carlo with CMFD time-differenced via Backward Euler, and Implicit Monte Carlo [6] (IMC). The increase in accuracy involves very little increase in computational cost, and the figure of merit for the CMFD-CN scheme is greater than IMC. / Graduation date: 2012

Nigeria is presently being faced with a growing electricity demand problem following its population growth rate. The total installed capacity is far less than the current demand for electricity supply. As a way of bridging out this supply gap, the federal government is mobilizing all of its potential energy options. Coal is widely used for power generation in many countries. But today, the continued usage of coal for power generation is being challenged by the disturbing global warming phenomenon. This is due to the quantity of uncontrolled carbon dioxide emission from traditional coal-fired power plants. The aim of this dissertation is to critically analyse the future of the Nigerian coal power stations following the need to do carbon dioxide emission control necessary for ensuring a sustainable environment. Achieving this aim entails the appraisal of environmental regulation standards and cost structures of carbon dioxide (C02) emission reduction options for the coal power stations. Controlling carbon dioxide emission from existing coal power stations requires retrofit system that captures and effectively sequestrates the captured CO2. The cost and performance effect of the CO2 retrofit system on the existing power plant can be simulated with standard computer software models. In this study the lECM-cs computer modelling tool for power plants was used in determining the cost and performance impacts of applying an Amine-based C02 capture system to the Oji river power station in Nigeria. With the lECM-cs model, it was established that reducing C02 emission imposes an additional cost on the power plant which increases the unit cost of electricity generated. This additional cost index requires economic justification for its acceptance. This is due to the need to demonstrate its viability judging from the cost of electricity generated from other sources in the Nigerian economy. For the Oji river case, the station is old and requires extensive renovation. This causes a cost escalation over and above the cost associated with the CO2 sequestration system. As such, Oji coal power station does not have an economic future if C02 emission sequestration becomes obligatory. The future of coal power stations in Nigeria can be considered from two scenarios: one where the current national environmental standard is retained and another where it is revised. The revision classifies CO2 as a pollutant which makes its emission reduction imperative for coal power plants. Under the current standard, building modern large capacity pulverized coal-fired power plants with improved steam cycles should be encouraged. But with the review of the national standard, the focus should be on building new large capacity coal power stations with integrated CO2 emission control. This will ensure an environmentally friendly future for coal power stations in Nigeria. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2009.

Nigeria is presently being faced with a growing electricity demand problem following its population growth rate. The total installed capacity is far less than the current demand for electricity supply. As a way of bridging out this supply gap, the federal government is mobilizing all of its potential energy options. Coal is widely used for power generation in many countries. But today, the continued usage of coal for power generation is being challenged by the disturbing global warming phenomenon. This is due to the quantity of uncontrolled carbon dioxide emission from traditional coal-fired power plants. The aim of this dissertation is to critically analyse the future of the Nigerian coal power stations following the need to do carbon dioxide emission control necessary for ensuring a sustainable environment. Achieving this aim entails the appraisal of environmental regulation standards and cost structures of carbon dioxide (C02) emission reduction options for the coal power stations. Controlling carbon dioxide emission from existing coal power stations requires retrofit system that captures and effectively sequestrates the captured CO2. The cost and performance effect of the CO2 retrofit system on the existing power plant can be simulated with standard computer software models. In this study the lECM-cs computer modelling tool for power plants was used in determining the cost and performance impacts of applying an Amine-based C02 capture system to the Oji river power station in Nigeria. With the lECM-cs model, it was established that reducing C02 emission imposes an additional cost on the power plant which increases the unit cost of electricity generated. This additional cost index requires economic justification for its acceptance. This is due to the need to demonstrate its viability judging from the cost of electricity generated from other sources in the Nigerian economy. For the Oji river case, the station is old and requires extensive renovation. This causes a cost escalation over and above the cost associated with the CO2 sequestration system. As such, Oji coal power station does not have an economic future if C02 emission sequestration becomes obligatory. The future of coal power stations in Nigeria can be considered from two scenarios: one where the current national environmental standard is retained and another where it is revised. The revision classifies CO2 as a pollutant which makes its emission reduction imperative for coal power plants. Under the current standard, building modern large capacity pulverized coal-fired power plants with improved steam cycles should be encouraged. But with the review of the national standard, the focus should be on building new large capacity coal power stations with integrated CO2 emission control. This will ensure an environmentally friendly future for coal power stations in Nigeria. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2009.

PhD (Environmental Management) / Mining and mining-related activities remain the world’s most intensive, primary industrial activity undertaken with severe environmental impact. Coal mining falls within these primary undertakings, while coal burning for energy use further adds to environmental degradation. Coal burning is by far the least expensive and thus the most affordable means of energy supply to the South Africa low-income communities. It is likely that this status quo will continue indefinitely. The use of coal as an energy source in South African communities has been inherited with its resultant environmental (physical), social and economic implications. The physical implications are the actual hazards associated with coal during and after mining activities. “Physical hazards” include processes generating coal dust, coal ash and gaseous emissions, and hazards that manifest themselves from the existence of coal mining at a particular site, such as spontaneous combustion, surface instability and acid mine-water drainage. “Social hazards” are mostly the social and economic effects that are related to health. Social hazards associated with coal mining, coal processing and coal usage include dilution of cultural values, ethics, norms and the growth of informal sectors, for example, settlements and trade. Some of these hazards are immediate, while others are long-term and cumulative. Emphasis was placed on the cumulative effects of mining activities and the need to address issues relating to communities that live close to mining operations. This process of addressing community concerns is known as “creating a sustainable mining community”. South Africa hosted the 2002 World Summit on Sustainable Development and is a signatory of the working plan of action known as the Johannesburg Plan of Implementation. Therefore, one would expect to see that mining communities in South Africa are acting on and benefiting from this plan of action. The aim of this research is to assess the effectiveness of the 2002 World Summit on Sustainable Development and the Johannesburg Plan of Implementation in promoting sustainable mining and sustainable communities through changes in practices, perceptions and community participation in decision making. The research, undertaken during February to June 2007, examines the role of stakeholders and local authorities in basic environmental decisions. Environmental decisions examined were the provision of education and information to the community, uplifting community welfare through corporate social investment and corporate social responsibility. The surrounding communities of eMalahleni (formerly Witbank) in the Mpumalanga (Highveld) coal-mining region – were identified as a suitable area for this case study. Social research tools, comprising multiple-choice and open-ended questions administered to 6 790 respondents (3 930 learners and 2 860 general adult population), 650 voluntary comments, six individual interviews, and a 20 member focus group discussion, were used. Photographic images and personal observation provided meaning to results by presenting the quantitative and qualitative data visually. A blended methodological approach was used to analyse the data using descriptive statistics and a t-test for variance. Tables, bar graphs and pie charts were the various representative techniques deployed during the analysis. Data were analysed comparing statistical input and responses of the learners and the general population. Results presented show that the studied community is aware of some hazards associated with coal from the mining process to indoor combustion. The community studied is aware of the need for pro-active measures to protect their community. Members of the community are not aware of company decisions affecting the community with regard to coal hazards. They are also unaware of the existence and application of environmental legislation. Awareness was not linked to education or information obtained from a reliable source, such as a mining company or a local authority. It was based on personal experience, longevity of dwelling in the community and observation of the health conditions of relatives and friends. Some voluntary comments from the respondents and photographic images are included to support the community’s outlook. The research concluded that there are more unidentified hazards in the community than were covered in the structured questionnaires. The responses received to the questionnaires exposed the mining industry as being dismissive when it came to applying the law. This evasive behaviour emanates from the laxity of the enforcement departments and responsible authorities. More needs to be done to attain the requirements of the Johannesburg Plan of Implementation as agreed upon at the 2002 World Summit on Sustainable Development.