Clean coal technologies

Clean coal technology is a collection of technologies being developed to mitigate the environmental impact of coal energy generation. When coal is used as a fuel source, the gaseous emissions generated by the thermal decomposition of the coal include sulphur dioxide (SO₂), nitrogen oxides (NO_x), carbon dioxide (CO₂), mercury, and other chemical byproducts that vary depending on the type of the coal being used. These emissions have been established to have a negative impact on the environment and human health, contributing to acid rain, lung cancer and cardiovascular disease. As a result, clean coal technologies are being developed to remove or reduce pollutant emissions to the atmosphere. Some of the techniques that would be used to accomplish this include chemically washing minerals and impurities from the coal, gasification (see also IGCC), improved technology for treating flue gases to remove pollutants to increasingly stringent levels and at higher efficiency, carbon capture and storage technologies to capture the carbon dioxide from the flue gas and dewatering lower rank coals (brown coals) to improve the calorific value, and thus the efficiency of the conversion into electricity.

Clean coal technology usually addresses atmospheric problems resulting from burning coal. Historically, the primary focus was on SO₂ and NO_x, the most important gases in causation of acid rain, and particulates which cause visible air pollution and deleterious effects on human health. Concerns exist regarding the economic viability of these technologies and the timeframe of delivery, potentially high hidden economic costs in terms of social and environmental damage, and the costs and viability of disposing of removed carbon and other toxic matter.

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