Studies in reaction engineering of nitrogen oxides abatement: I. Ammonia/flyash interactions and their impact on flue gas treatment technologies. II. Gas/solid catalytic monolith reactor design

Federal regulations currently do not require--directly or indirectly--flue gas treatment (FGT) for stationary source nitrogen oxides emission reduction. FGT implementation is encouraged, however, and eventually may be required to bring certain airsheds into compliance with the National Ambient Air Quality Standard for ozone. Selective catalytic reduction (SCR) is a flue gas treatment technology showing promise for widespread implementation.; SCR reactors are typically straight-channel honeycomb or parallel plate monoliths. An alternative design is to replace the uniform catalyst coating with strips of catalyst oriented perpendicular to the flow. To evaluate the performance of this reactor, a series solution in terms of confluent hypergeometric functions was derived for the concentration profile above a strip of arbitrary catalytic activity. A series of short strips can be used to reduce the catalyst loading required to obtain a desired conversion.; Another alternative reactor design is obtained by replacing the catalyst-coated straight walls with wavy walls. The perturbation analysis of Chow and Soda (1972) for laminar flow in periodically constricted tubes was generalized to permit the efficient computation of higher-order solutions to the stream function. The series diverges for the range of independent variables of interest in SCR reactor design. An algebraic approximation to the friction factor for a sinusoidal periodically constricted tube is presented; it is valid for a limited range of the independent variables.; Ammonia adsorption and reaction on flyash was measured to assess potential interactions in flue gas treatment unit operations such as SCR reactors and electrostatic precipitators (ESP). Adsorption isotherms and isobars are presented for flyash collected from an ESP hopper. Multilayer ammonia adsorption was observed below 120{dollar}spcirc{dollar}C and is mediated by physisorbed water and/or condensed water on the flyash. Adsorption decreases with increasing temperature up to about 350{dollar}spcirc{dollar}C. In this regime, the activation energy for adsorption is small; flyash is covered with acidic sites which readily adsorb ammonia. The nature, number and strength of the sites changes with temperature. Ammonia adsorption exhibits a minimum at about 350{dollar}spcirc{dollar}C; adsorption at higher temperatures is activated. Pseudo-first-order behavior was observed for ammonia reaction with oxygen on flyash above 400{dollar}spcirc{dollar}C.; Based on the experimental results obtained in this study, ammonia/flyash interactions are not expected to interfere with SCR for current or (proposed) future operating conditions. When adding ammonia as an electrostatic precipitator conditioning agent, the observed adsorption onto flyash will be very sensitive to operating conditions. This could influence the performance of the flue gas conditioning system. Finally, the saturation capacity for ammonia adsorption onto flyash exceeds the maximum threshold established for flyash reuse as a cement additive. (Abstract shortened by UMI.)...