Abstract

The present study reviews the sampling environments and chemical transformations of nitrogen oxides that may occur within probes and sample lines while sampling combustion products. Experimental data are presented for NOx transformations in silica and 316 stainless steel tubing when sampling simulated combustion products in the presence of oxygen, carbon monoxide, and hydrogen. A temperature range of 25° to 400°C is explored. In the absence of CO and H2, 316 stainless steel is observed to promote the reduction of nitrogen dioxide to nitric oxide at temperatures in excess of 300°C, and silica is found to be passive to chemical transformation. In the presence of CO, reduction of N02 to NO is observed in 316 stainless steel at temperatures in excess of 100°C, and reduction of NO2 to NO in silica is observed at 400°C. In the presence of H2, NO2 is reduced to NO in 316 stainless steel at 200°C and NOx is removed at temperatures exceeding 200°C. In silica, the presence of H2 promotes the reduction of NO2 to NO at 300°C and the removal of NOx above 300°C. © 1977 Air & Waste Management Association.