Reduction of NOx adsorbed on char with microwave energy Original Research Article

Microwave energy was used to regenerate the NOx saturated char samples. It was found that the temperature of gas produced from microwave regenerations was close to the room temperature, and CO and CO2 were released approximately 10 seconds after microwave energy was applied. These observations suggest that the sites occupied by NOx may absorb more microwave energy than pure char. Consequently, these adsorption sites heat up rapidly and may turn into hot spots in a very short time. The reduction reactions of adsorbed NOx by carbon takes place at these hot spots. The NOx are adsorbed on char in the forms of NO2 and HNO3 when moisture and oxygen are present in the feed gas. This study shows that the higher percentage of HNO3 in the adsorbed NOx results in higher temperatures of product gas and hence higher reduction efficiency of the adsorbed NOx. Therefore, it is inferred that the sites occupied by HNO3 may absorb more microwave energy than those by NO2. Up to 90% of the adsorbed NOx was reduced in this microwave regeneration process.