Fuel NOx pollution production during the combustion of a low caloric value fuel gas

Abstract

The objective of this investigation is to identify and qualify physical mechanisms and parameters that affect the combustion of low caloric value fuel gases (LCVG) and the formation of NO, pollutants produced from fuel bound nitrogen. Average physical properties of a low caloric value gas were determined from the products of several industrial coal gasifiers. A computer model was developed, utilizing the PHOENICS computational fluid dynamics software, to model the combustion of LCVG. The model incorporates a three-dimensional physical design and is based on an actual industrial combustor. The combustor model utilizes a multi-staged design. Two initial air/fuel ratios are simulated, with three variations each on downstream inlet air. The production of NOx is modeled by the kinetic and turbulent mixed destruction of ammonia (NH3). The destruction of NH3 is described using equations developed in prior experiments. The influences of the method of distribution of the inlet flow on the temperature profiles, pressure profiles, and the velocity vector plots, are analyzed to determine the effects on the destruction of NH3 (production of NO,) for six different inlet flow distributions. The temperature, destruction of NH3 (production of NOx), pressure, and velocity vector equations are all coupled. The six different inlet flow distributions demonstrate the importance of the initial air/fuel ratio and the mass flow rates of the downstream inlet air. Equal staging of downstream air causes the most effective combustion. Higher temperatures in the primary combustion zone reduce the destruction of NH3 (production of NOx).