Given the increasing threat of climate change, governments, firms and other actors the world over are working to reorganise their activities within a more sustainable framework. In this regard, the removal of Nitric Oxides (NOX) and Sulfur Dioxide (SO2) from flue gases has been one of India’s principle challenges and a serious problem for over two decades. This is the situation in which the work by Professor Snigdha Khuntia, of Ahmedabad University’s School of Engineering and Applied Science, aims to make a difference.
The research project that she is engaged in has received three-years’ worth of funding as part of the early career research grant from the Government of India’s Science and Engineering Research Board. The objective of the project is to develop a more efficient method for the simultaneous removal of NOX and SO2 from flue gases.
Currently, there are certain techniques that have been honed for the removal of these chemicals individually. For instance, what is known as ‘Selective catalytic reduction’ (SCR) is considered one of the most effective methods for the removal of NOx and has been studied extensively. However, the individual treatment strategy poses high investment and operating costs. To overcome these limitations, various new methods have been proposed. One possibility for the the simultaneous removal of SO2 and NOX is the use of a combination of wet flue gas desulfurization (WFGD) and SCR. Other proposals involve methods such as wet scrubbing, adsorption, electron beam irradiation, corona discharge, dielectric barrier discharge, radio frequency discharge, and electrochemical-catalytic cells. Still, except wet scrubbing and the adsorption process, the other methods mentioned above involve high cost of energy. The wet scrubbing process is performed under ambient temperature and it is highly adaptable to various flue gas loads but it results in high volume of liquid wastes and lower efficiency.
To overcome the above limitations, Professor Khuntia’s project is working on improving the efficiency of a method for the simultaneous removal of NOX and SO2 using hydrogen peroxide and converting NOX and SO2 to HNO3 and H2SO4, respectively. In order to increase the removal efficiency of NOX and SO2, Reactive oxygen species (such as •OH radicals) generated from O3 have been found to be useful. Therefore, the project aims to enhance the in-situ generation of •OH radicals by using O3+H2O2, O3+UV or O3+catalyst. These reactions are carried out at low-moderate temperature, and in order to further enhance the generation of •OH radicals and minimize the ozone/H2O2 usage, suitable catalysts are developed. The manganese based catalysts are more suitable for the dissociation of ozone into •OH.
Once fully developed, the project’s results would a make a significant contribution to our capacity for purifying flue gas of environmentally hazardous chemicals, and doing so in a cost-effective and efficient manner. This would constitute a significant step in the current battle against climate change, especially with regard to India’s path towards greater sustainability.