Metal-Modified Active Coke for Simultaneous Removal of SO2 and NOx from Sintering Flue Gas

A series of active coke (AC)-based adsorbents modified by different metal combinations (Na/Ba/Cu, Na&Cu/Na&Ba, and Na&Ba&La/Na&Ba&Ce), supporting different contents of metal and calcined at different temperatures, was investigated for simultaneous removal of SO2 and NOx. The activity test results showed that supporting 8% NaCO3, 7% Ba­(NO3)2 & 8% NaCO3, and 10% Ce­(NO3)2 & 7% Ba­(NO3)2 & 8% NaCO3 on the AC was best in unitary, bibasic, and ternary metal modifications, respectively. Supporting 10% Ce­(NO3)2 & 7% Ba­(NO3)2 & 8% NaCO3 was the best of all. The Fourier transform infrared spectroscopy result showed that the sodium modification made some unsaturated groups and metal chelate complexes form on the AC, so that the removal performance improved. Barium added to 8% Na–AC augmented the amount of unsaturated groups to improve the performance further. The addition of cerium to 7% Ba–8% Na–AC made more unsaturated groups and metal chelate complexes form, thus raising the performance again. The Brunauer–Emmett–Teller (BET) result showed that the unmodified (AC) and modified (10% Ce–7% Ba–8% Na–AC) ACs were predominantly microporous materials, and the pore size distribution and pore width of the modified AC was more extensive and multiple, which were beneficial for the removal of SO2 and NOx. Moreover, the removal performance improved significantly as the calcination temperature increased from 200 to 600 °C, whereas it slumped as the calcination temperature increased from 600 to 800 °C. It was explained by the results of X-ray diffraction and BET that CeO2, which was one of the active ingredients on the AC, increased with the increase of the calcination temperature and the higher the sample calcined at a temperature, the worse the pore structure of the carrier.