Study on the mechanism of iron-rich coal gasification slag on NO conversion in high temperature flue gas of cement kiln

Abstract

As a kind of air pollutant, nitrogen oxide cause serious human, environmental and ozon layer issues. Non-ammonia catalytic materials have a more simple and environments-friendly reaction process without secondary pollution, and therein are considered as an ideal catalyst for the reduction of NO in the flue gas of cement kilns. In this paper, the denitrification performance of coal gasification slag was investigated systematically at different temperatures and oxygen concentrations in cement kiln flue gas. The transformation mechanism of NO was studied by analyzing the changes of surface element valence state, the adsorption and desorption of NO and the formation of intermediate during the reaction process. The results show that the conversion rate of NO in flue gas can reach 83.49 % when the temperature is 1000 °C and the oxygen concentration is 1 %. The charged ionic groups are generated by the isomorphous substitution of Fe3+ in coal gasification slag, and play an important role in the decomposition of NO as active components. It can increase the number of surface oxygen vacancies, and accelerate the fracture of NO bonds into active components; Meanwhile, Fe3+ could coordinate with O− and NO− (generated by NO fracture) to form Fe3+-O− and Fe3+–NO−, which can be decomposed into Fe2+, N2 and O2 at high temperature.