Discovery and development of the thermal DeNOx process

Abstract

The discovery and development of the Thermal DeNO, process are described. One important aspect of that development was the continuation of the basic research in order to develop the computer model of the NO reduction chemistry. This model proved useful in optimizing the application of the Thermal DeNO, process to boilers and furnaces, in understanding other potential applications, e.g., gas turbines, automobiles, fluid bed combustors, and low-Btu gas, and in understanding problems in the chemistry such as the self-inhibition effect and the lack of an effect from addition of sulfur oxides.

The role of NNH in NO formation and control

“…[109]. In line with a number of other experimental studies [108,110,111], the data of Duo et al document that the presence of combustibles shifts the window for the process to lower temperatures by replenishing the radical pool. In addition to the shift in onset temperature, increasing amounts of combustibles also cause a narrowing of the process window.…”

“…The early experiments of Lyon and coworkers [106][107][108] indicated that NO 2 was not formed in the Thermal DeNO x process, pointing to a small rate constant for NNH + O 2 [1]. The detection of considerable amounts of NO 2 at higher oxygen concentrations [105] prompted Miller and Glarborg [21,22] Since O 2 is present in much larger quantities than NO in the process, the introduction of the NNH + O 2 reaction allowed the NNH lifetime to be shortened.…”

ULTRA LOW NOx INTEGRATED SYSTEM FOR NOx EMISSION CONTROL FROM COAL-FIRED BOILERS

“…The detailed mechanism consists of approximately 66 species and 440 elementary steps and contains both reburn and NO/NH 3 chemistry. The adequacy of the mechanism was confirmed (in a limited sense) by comparison of the SENKIN calculations with the experimental He/O 2 /NO/NH 3 plug-flow data of Lyon and Hardy (Lyon andHardy 1986, Jesse et al, 1993) as shown in Figure 5.5-1. The gaseous composition of a post-flame, fuel-rich zone with a stoichiometry of 0.7 was approximated by computing the corresponding adiabatic, equilibrium compositions of mixtures of coal (medium volatile bituminous) and air.…”

Gas Turbine Combustion and Ammonia Removal Technology of Gasified Fuels

“…Other studies on the high temperature gas phase reaction of NH 3 include: Lyon [73,74], and Lyon et al [75], on selective non-catalytic reduction of NOx from the combustion exhaust gas; results by Muzio et al [76], on the effects of urea and other amines on NOx reduction in exhaust gas, where under fuel rich conditions, selective reduction is achieved only at temperatures above 1373 K [77,78]; Chen et al [79], on the effects of various selective reducing agents on NOx reduction in staged-air added coal-fired combustors; Kasaoka et al [80], on NH 3 decomposition characteristics in fluidized-bed combustion of coal or mud; and Zhao et al [81], on the effects of small amounts of CO and H 2 on NH 3 reduction in pulverized coal combustion. However, these studies dealt with NH 3 decomposition characteristics in an atmosphere of low CO and H 2 concentration, and high oxygen conditions; they made several efforts to reduce NO to N 2 with NH 3 in the exhaust, or to decompose NH 3 to N 2 in fluidized-bed combustion.…”

“…In each CO concentration system, NO shows the same decomposition tendencies as NH 3 , up to the temperature that minimizes the remaining NO concentration in the mixed gas. The influence of added H 2 in low concentration on the reaction temperature is well known in the case of a non-catalytic reduction of NO from exhaust gas [75]. That is, the optimum reaction temperature window for the NO reduction decreases as the concentration of low level H 2 added to the system rises.…”