Atmospheric Emissions from Thermal (Coal-Fired) Power Plants and Associated Environmental Impacts

Abstract

Power plants, which are major point source of air pollutants, contribute significantly to the overall ambient air particulate matter (PM) loading. Due to low grade of coal utilized in the power plants, emitted gases and PM affect the environment as well as public health. Gaseous as well as particulate emissions from power plants depend on types of coal and combustion conditions. Coal is subjected to various processes from arrival up to the combustion in a power plant. Particle size distribution and composition of PM emitted by coal combustion sources vary according to various formation and transformation processes to which they are subjected during their lifetime such as grade of coal, pulverization, and storage and combustion conditions including type of boiler, etc. Gaseous emissions in large amount from stack of power plants include gases such as sulfur dioxide, carbon monoxide, oxides of nitrogen, carbon dioxide, and volatile organic compounds. Respirable particulate matter is also emitted at a large scale in the form of fly ash, bottom ash, and flue gas. Toxicity associated with suspended PM can deteriorate human health by penetrating and affecting human respiratory system. Apart from this, these emissions can alter the atmospheric radiation balance by inducing climate forcing, and provide excess condensation nuclei for fog and cloud formation, thereby significantly altering the regional level weather conditions and patterns. Advanced techniques to track the precursors of PM such as stable isotope analysis and metal identification along with various modeling methods can be used quite effectively for understanding the sources and health hazards related to power plants. These mechanisms can be understood by making use of a tracer (such as stable isotope ratios, for example, δ13C or elemental ratios), which can track down the PM formation processes either in the stack exiting flue gases or further downstream from the source. Emissions from coal-fired power plants also contain certain toxic trace metals, which can severely affect the health of general public.