Ammonia production from nitrogen-rich biomass gasification: Nitrogen transformation from model amino acids

Abstract

Ammonia (NH3) is currently being explored as a sustainable energy carrier. Ammonia production from nitrogen-rich biomass gasification provides a sustainable, distributed, and flexible process to efficient storage and conversion of renewable energy. Nitrogen is primarily in the form of proteins (amino acids) in biomass. Three amino acids, glutamic acid (Glu), glycine (Gly), and phenylalanine (Phe), with distinct structures, were screened as N-containing model compounds to assess the effects of operating conditions on nitrogen chemistry. Results indicate that chemical structure has asignificantimpact on thermal decomposition properties and N-conversion selectivity of amino acids. Gly possesses the highest NH3-N yield (∼56.4%), because the simple amino structure easily detaches as NH3. Nevertheless, Phe, as the representative of aromatic amino acids, has the lowest NH3/HCN ratio. Additionally, it is interesting to find some phenomena in common for the aromatic amino acids and aliphatic amino acids. The introduction of steam is proven to enhance the hydrogenation of char-N, the thermal cracking of tar-N, and the hydrolysis of HCN into NH3, thus promoting the NH3 selectivity. The NH3-N yield increases initially and then suppresses at 700–900 °C, which is impacted by the extent of NH3 decomposition reaction. High steam content can contribute to the enhanced availability of H radicals, consequently resulting in significant release of NH3.