The effects of NOx and SO2 emissions
One of the most significant sources of pollutants is power generation. It contributes approximately 70% of SO2 emissions, 20% of NOx emissions and 40% mercury emissions into the environment which impair human health. Emissions from transport vehicles also contribute to pollution that is why different options are used to address vehicular emissions. Pollutants can remain in the air for days or even years and prevailing winds can transport them across borders and national boundaries. Once mercury reaches lakes, rivers and oceans, it results into predatory fish and fish eating birds and mammals accumulating mercury concentrations that are millions of times higher than what is usually found in air and water. Pollutants also fall from the air in wet form or dry form and impacts on public health, degradation of visibility and the acidification of bodies of water. Additionally, pollutants harm coastal ecosystems and accelerate the degradation of buildings, structures and statues worldwide.
How does Selective Catalyst Reduction work?
Selective Catalyst Reduction works by injecting ammonia vapor into a flue gas stream to reduce the NOx emissions by over 80% to 90%. SCR technology is designed to permit NOx reductions reactions to take place in an oxidizing atmosphere. It is called selective because it reduces the amount of nitrogen oxide emissions through the injection of ammonia as a reluctant within the catalyst system. Ammonia which is the reducing agent reacts with nitrogen oxide to convert pollutants to nitrogen, water and small amounts of carbon dioxide. These elements are common in the air that humans and living animals breathe. The source of the reluctant is usually automotive-grade urea or more commonly known as Diesel Exhaust Fluid that will rapidly hydrolyze to produce the oxidizing ammonia in the exhaust stream.
The efficiency of Selective Catalyst Reduction has been commercially implemented in Japan since 1980 and in Germany since 1986 on power stations that burn low-sulfur coal or in some cases medium-sulfur coal. At present, there are 15 GWe of coal-fired SCR capacity in Japan. Germany has 30 GWe that brings the worldwide total to about 53 GWe. During the 1990’s full-scale SCR systems begun to be installed in US coal-fired power plants using high sulfur coals. This followed the implementation of stringent regulations to limit nitrogen emissions in all states. SCR technology is also considered as more cost effective for large industrial boilers and process heaters operating at high at moderate capacity. SCR is also the most widely used technology for large gas turbines.