D. Tech. Mechanical Engineering. / Investigates and/or rank the performance of locally available materials (i.e. limestone, dolomite, or calcrete) as sorbents in the capture of SO2 emissions from coal-fired power plants. Two experimental procedures were adopted in this work: the pH-stat method was used to simulate conditions encountered in wet flue gas desulphurisation (WFGD); and the fixed-bed reactor was used to simulate conditions encountered in the dry in-duct flue gas desulphurisation (DFGD) process. It is important to note that most studies of using calcium-based materials as sorbents for SO2 removal have been carried out in overseas countries. These studies were carried out using materials and research conditions prevailing in the particular countries. Furthermore, all South African coal-fired power stations burn low grade coal allowing the high grade coal to be exported. As a result, coal-fired power stations in South Africa emit higher emissions than the overseas power stations which are operated on high grade coals. Thus the results achieved internationally may not be directly translated to the South African conditions.

Energy mix modellers often use a constant emissions factor model, which more or less implies a constant heat rate, when trying to show the emissions reduction benefits of integrating renewable power generation system on the grid. This approach does not consider the fact that there is a deterioration in the heat rate with load for the Coal Fired Power Plants that need to accommodate the additional renewable supply. If varying heat rate were to be included in a study, it is often limited to plant specific cases. This PhD presents a novel Variable Turbine Cycle Heat Rate (V-TCHR) model for predicting the part load Turbine cycle heat rate (TCHR) response of various Coal Fired Power Plant (CFPP) architectures, without detail knowledge of the entire steam cycle parameters. A total of 192 process models of representative CFPP architectures were developed using a Virtual Plant software. The models had different combinations of the degree of reheat; the throttle temperature; throttle pressure; and condenser cooling technology. The part load response of all the models were simulated using the software.

No description available.

Thesis (MDF)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Coal export mines in the Mpumalanga Highveld region of South Africa generate growing volumes of discard coal estimated to be in excess of a billion tonnes. It presents a significant pollution hazard. Discard coal has a usable carbon content that can be used in the generation of power through the application of fluidized bed combustion technology. The objective of this study was to evaluate its potential as an economically viable fuel source for generation of electricity at the Witbank coalfields. This study was motivated by advances in fluidized combustion technology and significant changes in the South African electricity market in recent years. A holistic approach was adopted considering regulatory policy, market, technical, environmental and economic factors in the use of discard coal as an alternative fuel source. The policy and regulatory environment was assessed from the perspective of the private sector as project developer and the most likely source of funding, given government’s funding constraints. An evaluation of the future pricing structure of electricity, energy resource mix, demand growth, future development of the coal market, production of discard coal and the cost of coal was conducted. Levelised cost of electricity methodology was used to conduct the economic feasibility for comparison with the cost of Eskom’s pulverised coal technology for its new power stations. The study found that generating electricity from discard coal presents a significant commercial opportunity as its levelised cost of electricity was found to be lower than Eskom’s levelised cost of electricity for its new power stations. Plant sizes of 125 MW to 1 000 MW were considered. For plant capacities of about 500 MW and larger, the cost of electricity was found to be competitive with the current average electricity price taking into account the cost of transmission/distribution and interest charges. This is on condition that the electricity is sold to Eskom or wheeled through Eskom’s grid and sold to third parties. Otherwise, plant capacity will be limited to the maximum demand from large local users, which is expected to be considerably less than 500 MW. Currently there is no regulatory certainty on wheeling mechanisms and charges and it is an area where major policy development is required. The development of a project could be hampered by policy uncertainty and because of Eskom’s monopoly position as single buyer. The favourable results and findings of the economic evaluation conducted during this study warrant further detailed feasibility studies.

M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology, 2016 / Natural organic matter if not removed from water used for electricity generation has dire consequences that affect the long term plant health. The main problem is that organic matter at higher temperature and pressure disintegrate into smaller organic acids and carbon dioxide. This causes the cycle water and steam to be acidic and this can result in corrosion of the plant. The raw water from the Komati (Arnot power station) and Usutu (Kriel power station) scheme were analysed to determine the organic profile and seasonal variation. There was a noticeable variation in the quality of the water with an increase in DOC during rainy season. The water was found to be containing hydrophobic as well as hydrophilic molecules that could be quantified with a liquid chromatography organic detector (LC-OCD). Current water treatment processes employed at the two stations, Arnot and Kriel, has demonstrated the capability of removing organics to just over 50 percent at the pre-treatment section. The water treatment plant includes demineralisation plant that was able to produce water that met Eskom’s target specifications of less than 250 ppb DOC values. Qualitative and quantitative analysis of the steam-condensate water was done by use of an ion chromatography method. The determined organic anions were found to be acetates, formats and lactates.

M.Ing. (Engineering Management) / South African power demand has been increasing over the past years due to increase in energy consumption from industrial, commercial and residential sectors. In order to meet the growing power demand Eskom Holdings Limited SOC (Eskom) has implemented a number of initiatives such as the energy efficiency programme, power generating capacity increase and refurbishment of the operational coal fired power stations. Energy efficiency initiatives have been designed to encourage residential, commercial and industrial customers to use energy efficient technologies which consume less energy compare to conventional technologies. Power generating capacity increase programme includes construction of new base and peaking generating power plants (such as Medupi, Kusile and Ingula) and return to service of the old generating plants (such as Camden, Komati and Grootvlei). The refurbishment programme or coal refurbishment involves upgrading of operational coal fired power stations with the objective of extending their life expectancy, improve performance and to ensure compliance to latest safety standards...

M.Sc. / This report details the identification of potential sites suitable for both renewable and non-renewable electricity generating technologies in South Africa. Eskom through its Integrated Electricity Planning Process (IEP) determines future-planning scenarios based on demand and supply side options, while considering expected growth in demand for electricity. Site suitability can have a significant influence on the viability of options selected through IEP ...

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering, 2016 / Global climate change is among the major challenges the world is facing today, and can be attributed to enhanced concentrations of Greenhouse Gases (GHG), such as carbon dioxide (CO2), in the atmosphere. Therefore, there is an urgent need to mitigate CO2 emissions, and carbon capture and storage (CCS) is amongst the possible options to reduce CO2 emissions. Against this background, this work investigated the synthesis and performance evaluation of Polyaspartamide (PAA) adsorbent for CO2 capture. In particular, the effect of the presence of water-soluble amines in the amine-grafted poly-succinimide (PSI) (referred to as Polyaspartamide (PAA) adsorbent), was investigated. Methyl Amine (MA) and Mono-Ethanol Amine (MEA) were employed as water-soluble amines and the effect of changes in their concentration on CO2 adsorption capacity was investigated as well. Water-soluble amines were incorporated to allow water solubility of the adsorbent paving the way for freeze-drying to improve the geometric structure (surface area, pore volume and pore size) of the adsorbent. Initially, the PSI was loaded with Ethylenediamine (EDA), forming PSI-EDA. The water-soluble amines were grafted to PSI-EDA, with the EDA added to improve the chemical surface of the adsorbent for CO2 capture. NMR and FTIR analyses were performed and confirmed the presence of MA and MEA amine groups in the PAA, thereby indicating the presence of the grafted amines on the backbone polymer. BET analysis was performed and reported the pore volume, pore size and surface area of the freeze-dried material. It was observed that the physical properties did not change significantly after the freeze-drying compared to literature where freeze-drying was not employed. An increase in adsorption capacity with an increase in MA and MEA concentrations in MA-PAA and MEA-PAA samples was observed. At low amine concentrations (20% amine and 80% EDA grafted), MEA-PAA was observed to exhibit higher adsorption capacity compared to the MA-PAA samples. At high amine (100% amine grafted) concentrations, MA-PAA samples displayed higher adsorption capacity. Three runs were performed on each sample and the results obtained were reproducible. The best adsorption capacity obtained was 44.5 g CO2/kg Ads. Further work was then performed to understand the effects of operating variables on CO2 adsorption as well as the interactive effect using the Response Surface Methodology approach. The experiments were done by use of CO2 adsorption equipment attached to an ABB gas analyzer. A central composite design of experiment method with a total of 20 experiments was employed to investigate three factors, namely, temperature, pressure and gas flow rate. Six regression models were drawn up and mean error values computed by use of Matlab, followed by response surfaces as well as contours, showing the influence of the operating variables on the adsorption capacity as well as interaction of the factors were then drawn up. The results obtained displayed that each of the factors investigated, temperature, pressure and gas flowrate had an incremental effect on the adsorption capacity of PAA, that is, as each factor was increased, the adsorption capacity increased up to a point where no more increase occurred. Adsorption was seen to increase for both an increase in gas flowrate and adsorption pressure to a maximum, thereafter it starts to decrease. A similar trend was observed for the interaction between temperature and pressure. However, the interaction between gas flowrate and temperature was such that, initially as the temperature and the gas flowrate increase, the adsorption capacity increases to a maximum, thereafter, the temperature seizes to have an effect on the adsorption capacity with a combined effect of decreasing temperature and increasing gas flowrate resulting in a further increase in adsorption capacity. It was confirmed that the operating variables as well as the flow regime have an effect on the CO2 adsorption capacity of the novel material. The highest adsorption capacity was obtained in the pressure range 0.5 bar to 1.7 bar coinciding with the temperature range of 10 oC to 45 oC. The interaction of gas flowrate and adsorption pressure was such that the highest adsorption capacity is in the range 0.8 bar to 1.5 bar which coincides with the gas flowrate range from 35 ml / min to 60 ml / min. In conclusion, the best adsorption capacity of 44.5 g / kg via the TGA and 70.4 g / kg via the CO2 adsorption equipment was obtained from 100 % MA grafted PSI. / GR2016

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science June 2015 / Lephalale is the home of Matimba, one of Eskom’s coal-fired power stations. Matimba is the biggest power station with a dry cooling system in the world. There are other industries (including coal mines) currently in operation in close proximity to the station. This industrial area is expected to grow as more industrial activities are planned for the following years. These activities will aggravate the levels of air pollution and possibly result in it being a “hot spot” for air pollution. The impact of air quality on health is covered by the National Ambient Air Quality Standards (NAAQS), but the impact of air quality on the terrestrial and aquatic ecosystem is not known. Therefore, this study focuses on the deposition of nitrogen oxides (NOx) (as nitrogen dioxide (NO2)) and sulphur dioxide (SO2) within Lephalale in the Waterberg-Bojanala Priority Area. Additionally, inter-annual variability of NOx and SO2 ambient concentrations and back trajectories of air masses were analysed. The study obtained ambient air quality data and meteorological data from Eskom for the period 2008–2012, while additional meteorological data were obtained from the Agricultural Research Council (ARC) and the South African Weather Service (SAWS). An inferential model was used to estimate the dry deposition flux of SO2 and NOx (as NO2), and the Hybrid Single Particle Langrangian Integrated Trajectory (Hysplit) Model was used to cluster back trajectories of air masses. The results of the seasonal dry deposition velocities of SO2 (0.17 to 0.23 cm/s) and NOx (0.10 to 0.15 cm/s) (as NO2) were higher in summer and lower in winter. They were also within the magnitude of the deposition velocities found in previous studies in the Highveld. The high deposition velocities in summer were attributed to photosynthetically active vegetation, turbulence and solar radiation. However, seasonal dry deposition fluxes of SO2 and NOx were higher in winter across the years. The higher flux values in winter were attributed to higher ambient concentrations of the trace gases. Additionally, the annual dry deposition flux of SO2 ranged between 0.43 and 0.67 kg S ha-1 yr-1, while NOx (as NO2) ranged between 0.84 and 1.05 kg N ha-1 yr-1 over the period studied. The annual deposition flux values found in the current study are lower than those found in previous studies in the Highveld. This difference could be because of the lower ambient concentrations of SO2 and NOx observed in this study. There is an inter-annual variability of the ambient concentrations of SO2 and NOx during the period 2008–2012. However, the difference is not large or statistically significant. The dominant direction of the back trajectories of air masses is east and southeast across all seasons for the entire period of 2008–2012. This lack of seasonal pattern in back trajectories and source regions cannot explain the seasonal changes in ambient concentrations (SO2 and NOx). Hence, climatic factors (e.g. change in weather) or seasonal changes in combustion source intensity must be responsible.

No description available.