Clean syngas and hydrogen co-production by gasification and chemical looping hydrogen process using MgO-Doped Fe2O3 as redox material

Gasification converts biomass into syngas; however, severe cleaning processes are necessary due to the presence of tars, particulates and contaminants. The aim of this work is to propose a cleaning method system based on tar physical adsorption coupled with the production of pure H-2 via a chemical looping process. Three fixed-bed reactors with a double-layer bed (NiO/Al2O3 and Fe-based particles) working in three different steps were used. First, NiO/Al2O3 is used to adsorb tar from syngas (300 degrees C); then, the adsorbed tar undergoes partial oxidization by NiO/Al2O3 to produce CO and H-2 used for iron oxide reduction. In the third step, the reduced iron is oxidized with steam to produce pure H-2 and to restore iron oxides. A double-layer fixed-bed reactor was fed alternatively by guaiacol and as tar model compounds, air and water were used. High-thermal-stability particles 60 wt% Fe2O3/40 wt% MgO synthetized by the coprecipitation method were used as Fe-based particles in six cycle tests. The adsorption efficiency of the NiO/Al2O3 bed is 98% and the gas phase formed is able to partially reduce iron, favoring the reduction kinetics. The efficiency of the process related to the H-2 production after the first cycle is 35% and the amount of CO is less than 10 ppm.