Simultaneous NO/CO2 removal by Cu-modified biochar/CaO in carbonation step of calcium looping process

A novel method to realize the simultaneous NO/CO2 removal by Cu-modified biochar and CaO in the carbonation stage of calcium looping was proposed. Cu-modified biochar was added in the carbonation stage as a NO reductant, meanwhile CaO was added as a CO2 sorbent. The simultaneous NO/CO2 removal performance of Cumodified coconut shell char/CaO in the carbonation stage of calcium looping was investigated in a bubbling fluidized bed reactor. CO is generated by the oxidation of the coconut shell char in the presence of O-2 in the carbonation. Cu-modified biochar and the generated CO efficiently reduce NO. Cu in Cu-modified biochar shows a strong catalysis on NO reduction by both char and CO. Besides, Cu enhances the conversion of CO to CO2, which is absorbed by CaO. CaO also catalyzes NO removal by CO, but the catalytic effect gradually becomes weak as the carbonation proceeds. When Cu content in Cu-modified coconut shell char is 0.77%, mass ratio of Cu-modified biochar to CaO is 1:16 and O-2 concentration is 3%, NO removal and CO2 capture efficiencies of Cumodified biochar/CaO in the carbonator are 94% and 80% at 650 degrees C, respectively. To reach the same NO removal efficiency of 94% in the carbonator, the required addition amount of Cu-modified biochar is only approximately 20% of untreated biochar.