Abstract
Biomass char is accepted as an environmentally friendly energy resource, and is promising for NO removal in industrial furnaces. NO reduction with biomass char (rice husk) was investigated in a fixed-bed quartz reactor. The influence of CO concentration, reaction temperature, initial NO concentration, and char loading on the NO reduction were evaluated. The results showed that the overall NO reduction reaction was dominated by the direct reaction of NO with char without CO. Increasing CO concentration resulted in an enhanced catalytic reaction between NO and CO over the char surface and a decreased carbon consumption of char. With decreasing temperature, the influence of CO concentration on NO reduction was strengthened. Over the test temperature range, char provided a surface to catalyze the NO–CO reaction at excess CO/NO ratio. Increasing the initial NO concentration led to an increasingly significant influence on NO reduction with the enhanced CO/NO ratio. With increased char loading, the enhancement of NO reduction became unobservable for excess CO/NO ratio. Reaction orders of NO and activation energy for NO reduction by char were 0.71 and 60.21 kJ·mol−1, respectively, against 0.82 and 34.60 kJ·mol−1, respectively, for NO reduction by CO, catalyzed by char.
Highlights
Nitrogen oxides (NOx), one of the major air pollutants, contribute to the formation of photochemical smog and the depletion of ozone [1,2,3]
The enhancement of NO reduction became unobservable for excess CO/NO ratio
Ammonia is classified as a major air pollutant
Summary
Nitrogen oxides (NOx), one of the major air pollutants, contribute to the formation of photochemical smog and the depletion of ozone [1,2,3]. The heterogeneous NO reduction of char can be influenced by many factors, such as CO concentration, temperature, and initial NO concentration These parameters have a strong effect on the carbon-consuming reduction and catalytic reduction mechanisms and on determining which mechanism dominates. Fewer studies systematically report the influence of these reaction parameters on heterogeneous NO reduction using biomass char with and without CO, which can vary in a wide concentration range. Rice husk biomass char—a byproduct in the pyrolysis of rice husk, which is the most common agricultural waste in China [35]—is used for investigation, considering that it is cost-effective and available [36] Both experimental and kinetics studies of NO reduction with rice husk char were conducted, in the absence and presence of CO. Through this paper, a reference that is expected to promote the industrial application of NO reduction using biomass char can be provided
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