Effect of additives on the reduction of nitrogen oxides using cyanuric acid

Abstract

The addition of cyanuric acid to hot exhaust flows has been shown in the past to selectively remove much of the nitric oxide (NO) emitted from combustion sources. Known as the RapreNOx process, this approach to pollution control does not require a heterogeneous catalyst, yet is capable under appropriate conditions of reducing over 90% of the NO. The primary product of the NO reduction mechanism is not molecular nitrogen, but rather nitrous oxide (N20). This thesis presents an experimental investigation of the use of additives with cyanuric acid. Each of the following eight compounds were tested individually in an effort to determine whether they were capable of improving the NOX reduction performance achieved with cyanuric acid alone: methane, ethylene, propane, methanol, ethanol, ethylene glycol, hydrogen, and hydrogen peroxide. It was desired to find an additive or additives which would do one or more of the following: (1) lower the temperature at which reduction is initiated; (2) broaden the temperature band within which reduction is achieved; (3) increase the maximum amount of reduction. It was found that, with the exception of methanol and hydrogen peroxide, these additives had the tendency to shift the reduction "window" toward slightly lower temperatures. For those additives tested at more than one concentration, the higher concentration typically produced a more pronounced shift, with an accompanying broadening of the reduction window. Methanol proved to be largely ineffective as an additive due to its strong tendency to convert NO to N02. Hydrogen peroxide displayed a trend not seen in any other additive, namely a shift of the window to slightly higher temperatures.