Experimental and Kinetic Study at High Temperatures of the NO Reduction over Eucalyptus Char Produced at Different Heating Rates

摘要

The NO reduction process over eucalyptus char has been studied in a laboratory-scale quartz reactor. Experiments were performed with char obtained from the pyrolysis of eucalyptus at a low heating rate (LHR) and high heating rate (HHR) and a final temperature of 900 °C. The LHR char sample was prepared in a fixed-bed reactor using a pyrolysis heating rate of 10 °C min 1, while a fluidized-bed reactor was employed to obtain chars at a HHR. The parameters considered in the study of the char/NO interaction comprise the inlet NO concentration, temperature, and pyrolysis heating rate. The inlet NO concentration was varied, ranging from 300 to 1100 ppm at a temperature of 900 °C. To analyze the temperature influence, char/NO interaction tests were also performed in the 750-900 °C temperature range for a given NO concentration of 900 ppm. It has been found that the NO reduction ability is significant for the eucalyptus chars considered, showing that temperature has a marked effect on the NO reduction process. Results have also revealed that HHR char is more active toward NO reduction compared to LHR char. The differences in NO reactivity between LHR and HHR chars are further discussed in terms of the chemical and physical char properties. Kinetic parameters of the NO reduction process over eucalyptus char have also been determined from the experimental data using an intrinsic rate equation denned as a function of the available active site concentration, which fitted properly the random pore model.