Mercury Control for Coal-fired Power Plants

Abstract

Mercury is a toxic, persistent pollutant that accumulates in the food chain, especially in fish, and causes major environmental health concerns. There are many sources of natural and anthropogenic emissions, but combustion of coal is known to be the major anthropogenic source of mercury (Hg) emissions in the U.S. and worldwide. To address this, the U. S. Environmental Protection Agency (EPA) has recently promulgated the Clean Air Mercury Rule (CAMR) to reduce Hg emissions from coal-fired utility boilers. This rule makes the United States the first country in the world to regulate mercury emissions from such plants. However, atmospheric mercury is a global problem and mercury emissions from U.S. coal-fired boilers represent only a small fraction of the total worldwide emissions. Mercury emissions from Asia — especially from countries with rapidly growing economies, such as China and India — account for almost 60% of worldwide anthropogenic mercury emissions. Mercury can be controlled as a co-benefit of existing NO x , SO x , and PM control technologies and via sorbent injection technology. The level of control is strongly affected by the type of mercury emitted (elemental, ionic, or particulate-bound), coal type, chlorine levels, and type of air pollution controls used. With knowledge of the impact of each of these, mercury can be controlled, and improved methods to achieve further control can be developed.