At present, the oxygen carriers (OCs) can be roughly derived from three paths of artificially synthesized, natural ores, and solid wastes with metal oxides. During the Fenton oxidation stage of waste water and deep dewatering process of sludge, a great amount of Fe-containing catalysts and sludge conditioners will be used, resulting in a relatively high content of Fe₂O₃ in the incineration ash, and which can be been considered a promising candidate of cost-effective OCs for biomass chemical looping gasification (BCLG). In this study, the preparation conditions of iron-rich sludge ash, such as the calcination temperature and acid washing, were tested for the effects on the direct biomass chemical looping gasification (DBCLG) characteristics. The OCs of iron-rich sludge ash were calcined at 750, 800, 850, 900, and 950 ℃, and the DBCLG testing results showed that the best reaction performance would be obtained at 800 ℃ from the perspective of syngas quality and gasification performance. Furthermore, the iron-rich sludge ash was first washed by the dilute nitric acid solution, and then calcined at 800 ℃. The obtained OCs were tested in the DBCLG experiments for different blending ratios, temperatures, and cyclic runs. It was found that the reaction performances of acid-washed sludge ash were clearly improved, and the gasification indices had an obvious increase. And the cyclic testing results indicated that the reaction performances of acid-washed sludge ash were relatively stable, and which was suitable as the oxygen carrier in the biomass chemical looping gasification.
 

Biomass chemical looping gasification, Cost-effective oxygen carrier, Iron-rich sludge ash, Preparation optimization, Gasification performances