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The process that is used to lessen NOx emissions and control air pollution is called Selective Catalytic Reduction. The harmful emissions are converted into nitrogen and water. This process involves catalytic reactions of either ammonia steam or air injected into exhaust pipes holding the NOx gases. The gases then mix thoroughly reducing the NOx once they pass through the catalytic bed. The catalyst main function is to promote the reduction of the NOx and this does not affect it. In general, the by-product produced when urea acts as a reducing agent is referred to as Carbon Dioxide. This technology reduces the emissions of NOx by 70 to 95 %.

Power plants usually discharge huge volumes of the NOx gases as the power that is used is acquired from ignition of fuels. With this technique, these emissions have been reduced considerably. The process is made up of the reactor chamber, the catalyst bed, which holds the catalyst modules as well as an Ammonia injection grid system.

During the process, an ammonia steam or even air is injected into the exhaust pipes, which contain the NOx gases. The ammonia passes through the catalytic bed helping in the reduction of nitrogen oxides as well as non-malignant nitrogen gas. The technique uses different agents including aqueous ammonia, urea and anhydrous ammonia. Apart from urea, the other agents are known to have certain disadvantages.

One major disadvantage of this technique is the ammonia slip, which is the release of unused ammonia. This takes place maintenance of the necessary temperatures is not carried out or when excess ammonia is injected into the system. Another setback is the emission of ammonium bisulphate and ammonium sulfate. These are as a result of the combination of the excess ammonia with sulfates that are found in the air. The sulfates are linked to respiratory inflammations and coughs.

It has been proven that the correct use of these catalysts can be accredited for successfully removing 90% or more levels of these toxic gases. Various coal fired boilers in Virginia, which possess these catalyst systems, are capable of reducing the discharges by 60% to 65 %. On the other hand those fired by gas have managed to reduce more that 90%.

How the SCR systems started The systems originated in the US and were used by Engelhard Corporation from 1957. By this time, the system had not been scientifically tested. The system was further developed in Japan and the US in the 60’s with research mainly focusing on the use of reducing agents that were not only more durable but also more pocket friendly.

Various ceramic materials can be used to produce the catalysts. They include, Titanium Oxide. These catalytic components are basically oxides that are obtained from the base metals zeolites and precious metals. Base metal catalysts are the cheapest but least durable.

Best content writer in association with Cormetech Inc., the leading producer of titania-based ceramic honeycomb catalyst for NOx emissions control and NOx reduction used in Selective Catalytic Reduction (SCR) systems for air pollution control.