Unraveling the role of alkali metal in the biochar for enhancing the chemical looping ammonia generation efficiency

Abstract

Chemical looping ammonia generation (CLAG), efficiently converting C-based material, N2 and H2O into NH3 and CO, is considered to be one of the promising NH3 production technologies. Using biochar as the C-based material is supposed to further improve the “green” level of NH3 but there is rare report about that. This paper was desired to fill this gap. Peanut shell biochar, lotus shell biochar and corncob biochar were used to study the chemical looping ammonia generation performances of the N-support. It was found that metals contained in the biochar significantly affected the nitridation process; alkali metals were simulative while alkaline-earth metals were inhibitory, which indicated that the corncob biochar exhibit the best nitriding properties. In addition, K, with the best positive effect for nitridation, was found to be with negligible negative effect for ammoniation. Furthermore, the carbon conversion efficiency and NH3 production could be still improved by 8.46 % and 9.23 % if the corncob biochar was modified with 2 wt% K (simulating 120 cycles of nitridation/ammoniation reaction). The obtained results indicated that the biochar is a promising carbon source for CLAG.