An Experimental Observation of the Thermal Effects and NO Emissions during Dissociation and Oxidation of Ammonia in the Presence of a Bundle of Thermocouples in a Vertical Flow Reactor

Abstract

Ammonia ( NH 3 ) dissociation and oxidation in a cylindrical quartz reactor has been experimentally studied for various inlet NH 3 concentrations (5%, 10%, and 15%) and reactor temperatures between 700 K and 1000 K. The thermal effects during both NH 3 dissociation (endothermic) and oxidation (exothermic) were observed using a bundle of thermocouples positioned along the central axis of the quartz reactor, while the corresponding NH 3 conversions and nitrogen oxides emissions were determined by analysing the gas composition of the reactor exit stream. A stronger endothermic effect, as indicated by a greater temperature drop during NH 3 dissociation, was observed as the NH 3 feed concentration and reactor temperature increased. During NH 3 oxidation, a predominantly greater exothermic effect with increasing NH 3 feed concentration and reactor temperature was also evident ; however, it was apparent that NH 3 dissociation occurred near the reactor inlet, preceding the downstream NH 3 and H 2 oxidation. For both NH 3 dissociation and oxidation, NH 3 conversion increased with increasing temperature and decreasing initial NH 3 concentration. Significant levels of NO X emissions were observed during NH 3 oxidation, which increased with increasing temperature. From the experimental results, it is speculated that the stainless-steel in the thermocouple bundle may have catalysed NH 3 dissociation and thus changed the reaction chemistry during NH 3 oxidation.