Optimised NOx Abatement Strategy Using Ionic Liquids

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GRØN DYST 2014 Technical University of Denmark

Optimised NOx Abatement Strategy Using Ionic Liquids
Author:P.L. Thomassen (Department of Chemistry, Technical University of Denmark, Denmark)
Date: 2014-06-27     Track: Main     Session: 1

NOx formation as a side product of high temperature incineration is inevitable when air is used as oxygen source. The harmful effects of NOx gasses are well documented and include acid rain, ozone layer depletion and severe health effects (induces cell mutation and respiratory diseases among others). Due to these harmful effects, emission limits are decreasing rapidly both on land and at sea. Therefore, it is becoming increasingly important to find a viable solution to the emission concerns. The most widely used method for NOx removal is Selective Catalytic Reduction (SCR). SCR is very efficient but also has limitations especially for mobile units due to an immense size of the installations. Furthermore, SCR uses ammonia to reduce the NOx to N2. Ammonia is a potential pollutant if it is released to the environment. Ammonia is also toxic and very corrosive adding a serious health risk to the use. Previous work carried out by my colleagues and I introduced an alternative method in which the NOx gasses are absorbed and oxidised to nitric acid using ionic liquids (ILs). This way fossil fuel resources used to produce ammonia is saved and a potent pollutant is turned into a valuable product of commercial grade. The end product of the process, nitric acid (HNO3), is one of the most produced chemicals on a global scale, with annual production reaching 60 million tonnes in the U.S. alone. Nitric acid is produced from ammonia, which is oxidised to NO and then oxidised further to HNO3. Therefore, directly oxidising NO in the flue gas would save 2 moles of ammonia for each mole of HNO3 produced, giving a superb overall nitrogen atom efficiency. This project presents a newly invented and patent pending design in which NO is oxidised and absorbed in two separate steps.