Emission characteristics of char NO during combustion of a single coal-char particle.

The emission characteristics of char NO at combustion temperatures of 1073 to 1173K were experimentally investigated in a differential packed-bed reactor to eliminate the gas-phase reduction of the NO produced. In this study, Taiheiyo (non-caking bituminous) and Taisei (anthracite) coal-chars, and activated sludge-char for comparison, were employed. The ratio of fixed carbon to volatile matter of the original coals was between 0.1 and 4.2. The chars were preliminarily prepared at a devolatilization temperature about 100K higher than the combustion temperatures so that the effect of volatile matter on NO formation could be minimized.The following results were obtained within the range of experimental conditions employed.1) The fractional conversion of char N into NO (ηNO) during the combustion depended on the coal rank ; ηNO of Taisei chars was about 0.8, that of Taiheiyo chars was in the range of 0.3 to 0.6, and that of activated sludge-char was about 0.1. The ηNO gradually decreased with increasing particle diameter.2) The ηNO obtained at a constant burning condition was found to increase with the initial mass ratio of char C to char N.