Environmentally Friendly Techniques
- De-NOx at room temperature by photochemical reaction using wavelength of 172 nm.
Background ＆ Objectives
NOx emission from marine diesel engines on vessels will be regulated by the International Marine Organization (IMO) near future, which has promised an 80% reduction of NOx emissions. Unfortunately, conventional deNOx systems, SCR or SNCR, cannot directly use, because temperature of flue gas is 180 degC, which is outside the reaction temperature of conventional deNOx systems. And also, effective catalysts cannot use, because the flue gas is containing most amount of sulfur dioxide which damaged catalysis.
A significant body of research has been devoted to investigating NOx removal using photochemical reactions under 172 nm irradiation at atmospheric pressure and room temperature. The advantage of using photochemical reactions under 172 nm irradiation for promoting effective reactions in NOx removal is its energy selectivity; that is, most of the photon energy from an excimer lamp is used to produce ammonia radicals such as NH and NH2.These NHi radicals react with the NOx via an elementary chemical reaction, wherein NOx is eventually converted to N2 and NH4NO3.
An approximate 80% NO removal was attained at room temperature with an NH3/NO ratio = 1.5 and 8.3% O2. The effects of gas flow rates (NO/NH3/O2/N2 gas mixture), oxygen concentrations, and NH3/NO ratios on NOx removal were investigated. The objective of the present study is to elucidate photochemical reaction mechanisms of deNOx.
Novel deNOx device for ships. |
A photochemical reactor |
An excimer lamp generated 172 nm VUV. |
DeNOx characteristics at room temperature |