Simultaneous reduce NO/CO2/CO emissions by modified peanut shell biochars in Ca-L/CARBONOx process

Abstract

A composite of biochar (BC) derived from peanut shells—with high ash contents—blended with CaO was used in the Ca-L/CARBONOx process. BC was subjected to acid pickling (BC-A), direct nitrogen doping (BC-N), and acid pickling with nitrogen doping (BC-A-N). The efficacy of modified biochar for simultaneous reduce NO/CO2/CO emissions was investigated in this study. The results show that simultaneous NO/CO2 removal was realized in the Ca-L/CARBONOx process using peanut-shell-biochar/CaO. However, higher CO emission was also generated during the process, which increased significantly as the temperature, biochar addition, and oxygen concentration increased. CO2 produced by the oxidation of biochar accelerates CaO consumption and decreases its catalytic effect on NO reduction. The simultaneous NO/CO2 removal ratio declined with the cycle number due to CaO sintering. Acid pickling and nitrogen-doping of biochar significantly decreased the CO and CO2 emissions, whereas sintering of CaO at higher cycle numbers had little effect on NO reduction by BC-A-N.