Kinetics investigation on the reduction of NO using straw char based on physicochemical characterization

Abstract

NO reduction using straw–char has been investigated in a fixed bed, and the effects of char-preparation temperature, reduction temperature, char concentration C char and NO concentration C NO were considered. Straw char was prepared at three temperatures, 873, 1073 and 1273 K. The characterization was conducted by employing SEM–EDS, XRD, BET and TGA. Results show that the char prepared at 1073 K holds the most developed pore structure and surface area, the best combustion activity, and the highest NO reduction rate. The reduction rate of NO linearly increases with increasing char concentration, but decreases with increasing NO concentration following a power-function relation. A transition temperature region from dynamic-control to diffusion-control is found to be around 1173 K. In the dynamic-control region, the apparent activation energy E of char–NO reaction is in the range of 89.78–95.41 kJ mol −1, affected inconspicuously by the char-preparation temperature. The reaction rate between NO and straw–char is given by r NO = k 0 · exp - 11 , 069 T · C NO 0.89 · C char .