Pyrolysis conditions and ozone oxidation effects on ammonia adsorption in biomass generated chars

摘要

Ammonia adsorbents were generated via pyrolysis of biomass (peanut hulls and palm oil shells) over a range of temperatures and compared to a commercially available activated carbon (AC) and solid biomass residuals (wood and poultry litter fly ash). Dynamic ammonia adsorption studies (i.e., breakthrough curves) were performed using these adsorbents at 23 ℃ from 6 to 17 ppmv NH3. Of the biomass chars, palm oil char generated at 500 ℃ had the highest NH3 adsorption capacity (0.70 mg/g, 6 ppmv, 10% relative humidity (RH)), was similar to the AC, and contrasted to the other adsorbents (including the AC), the NH3 adsorption capacity significantly increased if the relative humidity was increased (4 mg/g, 7 ppmv, 73% RH). Room temperature ozone treatment of the chars and activated carbon significantly increased the NH3 adsorption capacity (10% RH); resultant adsorption capacity, q (mg/g) increased by ～2,6, and 10 times for palm oil char, peanut hull char (pyrolysis only), and activated carbon, respectively. However, water vapor (73% RH at 23 ℃) significantly reduced NH3 adsorption capacity in the steam and ozone treated biomass, yet had no effect on the palm shell char generated at 500 ℃. These results indicate the feasibility of using a low temperature (and thus low energy input) pyrolysis and activation process for the generation of NH_3 adsorbents from biomass residuals.