Assessment of Atmospheric Dispersion of Fly Ash within the Vicinity of Van Eck Coal-Fired Power Station, Windhoek, Namibia

Abstract

Increase in population led to the growth of industrialisation which has stimulated the development of alternatives to produce electricity, including the use of coal. Coal-fired power plants produce an abundant amount of electricity, addressing the ever-increasing electricity demand. Power plants produce fly ash as a result of coal combustion for electric power generation. The Van Eck Power Station is the oldest and only coal-fired plant in Namibia that is located at the outskirts of Windhoek. The power plant produces electricity from the combustion of coal. Its refurbishment began in 2013, to improve its efficiency and allow for longer operational period. Van Eck’s rehabilitation included coal feeders which reduce emissions and new grates for boiler units which reduce ash emissions to ensure that the plant is a cleaner coal-fired power plant.

Fly ash is produced when coal is pulverised and blown with air into the boiler's combustion chamber where it directly burns and generates heat. Trace elements in coal deposits would not only contaminate the air, soil and underground water but also have an impact on human health. The thesis was aimed at assessing the possible pollutant elements found in fly ash and soil in areas surrounding the Van Eck Power Station. The thesis was also aimed at modelling the distribution and dispersion of those elements at a particular distance in areas around the Van Eck power plant using the Gaussian Plume Model. Soil samples were obtained from sites within the vicinity of Van Eck Power Station, and XRF Analysis was used to determine the concentration of elements in the soil. To obtain samples of fly ash, fall out buckets filled with distilled water were mounted on poles away from the main source of pollution. The deionised water was analysed using the Inductively Coupled Plasma (ICP-OES) Analysis method for the detection of elements. Gravimetric analysis was also applied to measure the weight of dust, which in the report is expressed as fly ash.

The study revealed more concentration of sulphur oxides specifically as sulphites and sulphates, as well as Zinc, while the rest of the elements of interest were detected significantly in low amount. Others were below the level of detection in both the fly ash and soil sampling. Also, soil sampled near the power plant was detected with a high amount of SOx and Zinc. Fly ash collected showed that areas near the power plant contain more pollutants than areas further from the power plant. Ash captured through the dust-fallout bucket method within the jurisdiction of the power plant was above the South African dust monitoring criteria. The model illustrated that elements during the day were more absorbed than reflected during the night.

Based on the research analysis, it was found that the power plant does not produce an abundant amount of pollution due to off-peak operations. However, comprehensive results

may be obtained if this type of research is repeated on a different, specified timeframe. The station may require control efficiency compliance measures for noxious gases and particulate matter (PM) concentrations. These results will be important in the formulation of emission limits, air quality guidelines and control of emission of pollutants. Air quality modelling is essential in baseline reports of projects.