Carbon Footprint for Mercury Capture from Coal-Fired Boiler Flue Gas

Abstract

Power production from coal combustion is one of two major anthropogenic sources of mercury emission to the atmosphere. The aim of this study is the analysis of the carbon footprint of mercury removal technologies through sorbents injection related to the removal of 1 kg of mercury from flue gases. Two sorbents, i.e., powdered activated carbon and the coke dust, were analysed. The assessment included both direct and indirect emissions related to various energy and material needs life cycle including coal mining and transport, sorbents production, transport of sorbents to the power plants, and injection into flue gases. The results show that at the average mercury concentration in processed flue gasses accounting to 28.0 µg Hg/Nm3, removal of 1 kg of mercury from flue gases required 14.925 Mg of powdered activated carbon and 33.594 Mg of coke dust, respectively. However, the whole life cycle carbon footprint for powdered activated carbon amounted to 89.548 Mg CO2-e·kg−1 Hg, whereas for coke dust this value was around three times lower and amounted to 24.452 Mg CO2-e·kg−1 Hg. Considering the relatively low price of coke dust and its lower impact on GHG emissions, it can be found as a promising alternative to commercial powdered activated carbon.