Characteristics of nitrogen oxide emissions from combustion synthesis of a CuO oxygen carrier

Abstract

Chemical looping combustion is a technology used for CO2 capture. Here, the characteristics of nitrogen oxide emissions from the combustion synthesis of CuO oxygen carriers were investigated by a thermogravimetric analyzer, Fourier-transform infrared spectroscopy, mass spectrometry, and thermodynamic and kinetic calculations. In addition, the NO and NO2 emissions were tested by an ultraviolet flue gas analyzer. The effects of gas flow rate, combustion atmosphere, heating rate, and the amount of urea complexant on nitrogen oxide emissions, and the feasibility of NOx reduction by NH3 during combustion were discussed. The chemical phases, element distributions, phase structure of precursors, and the valence states of Cu in the solid products were analyzed. The results showed that the combustion synthesis of CuO produced heat and erupted gas-phase products. NOx and N2O species were mainly generated from nitrogen in the precursors. The urea complexant also greatly contributed to NOx emissions, and the NOx emissions from urea-based precursors reached 5500 mg/m3, which was almost ten times higher than that of the urea-free precursors. An air atmosphere favored NO, NO2, and N2O generation. An even and complete combustion produced less nitrogen oxide emissions. The grinding of precursors into particles reduced NOx emissions by 3–89%.