Experimental study on hydrogen from tar in fluidized bed catalyzed with calcium-based catalyst

• The catalytic reforming of actual tar instead of tar model compounds at high and low temperature are studied. • Continuous addition of tar was made in the fluidized bed for the experiment. • The effects of dolomite, limestone, and their mixtures as bed materials for H 2 -rich syngas production were compared. • The optimal blending ratio of dolomite and limestone at different temperatures has been determined. Tar in syngas constitutes the major constraint on scaling biomass gasification technologies. Catalytic reforming is regarded as an effective method for removing tar. In this study, the catalytic effects of dolomite and limestone on hydrogen production via tar steam reforming were investigated by using a fluidized bed reactor. The study analyzed how temperature and the limestone-to-dolomite ratio influence syngas composition. The results showed that both catalysts exhibited significant catalytic activity in tar steam reforming. Elevated temperatures intensified the tar decomposition. Meanwhile, the water–gas shift reaction was weakened, due to the decrease in the CO 2 adsorption capacity of CaO. Therefore, although the H 2 yield increased, the H 2 proportion decreased. Within the experimental temperature range, the maximum H 2 yields by using dolomite and limestone as catalysts were 1.29 L/g (at 900 °C) and 1.17 L/g (at 950 °C), respectively. Below 660 °C, the H 2 yield using limestone as the bed material is higher than that using dolomite, but at higher temperatures the opposite is true. The higher CaO fraction in limestone enhances CO 2 adsorption and hydrogen generation at low temperatures. However, at elevated temperatures, the sintering and agglomeration of CaO diminish CO 2 capture efficiency. The MgO component in dolomite provides structural scaffolding to mitigate particle coalescence. Moreover, the maximum values of H 2 concentration or yield across all temperatures were exclusively attained within limestone-dolomite hybrid catalyst systems. However, the optimal H 2 concentration and maximum H 2 yield occurred under different temperature and mixing ratio conditions. Therefore, catalyst formulation should be tailored to specific process requirements.