Study on the comprehensive influence of Si-Al-based additives on hydrogen production and K deposition during biomass gasification

Green hydrogen production through gasification is a prospective utilization of biomass. Operational issues (slagging, corrosion and catalyst poisoning) due to inherent alkali metal deposition are main factors affecting gasification. The adoption of Si-Al-based additives as alkali metal inhibitors is a promising approach. In this work, the influence of additive types and placement methods on K deposition and gasification characteristics were studied through a decoupled gasification with online analysis. As a result, separative placement (Sep) method could reduce K deposition without decreasing hydrogen yield compared to mechanical mixture (Mix) method. This advantage is particularly prominent in char gasification. SiO₂ is recommended to be added by the Mix to react with alkali and alkaline earth metal species individually to inhibit K release. This match could reduce peak of K deposition content by 55.80 % with less impact on hydrogen yield. Meanwhile, Al₂O₃ is recommended to be added by the Sep due to its unique comprehensive performance, which could increase hydrogen yield by 4.34 % and reduce peak of K deposition content by 52.72 %. Two recommended addition strategies could be used in different scenarios. This study is expected to guide the design of corrosion-resistant reactors and multifunctional catalysts.