Corncob is one of the most abundant agro-industrial wastes globally. It represents a bioenergy feedstock of 1500–5500 million tons per year. The shape and size of the corncob are suitable for gasification without pretreatment (size reduction, densification, or drying) in a downdraft gasifier. However, its volatile content (about 80% DAF) can generate high tar content, representing a challenge to adopt this technology. In the present work, an evaluation of the effect of air-steam mixture and calcium carbonate CaCO3 as a promoter of both reforming and gasification reaction was carried out using corn cob without grains as raw material in a 40 kW gasifier. An analysis of variance of four experimental treatments was used to determine the main statistical and interactive effects on the syngas composition, hydrogen yield (yH2), syngas lower heating value (LHVgas), and cold gas efficiency (CGE). Results reveal the highest gasification performance achieved hydrogen production yields of 310 Nml/g, an LHVgas value of 4.8 MJ/Nm3, and cold gas efficiency of 59.18% with steam and CaCO3. Statistical analysis indicated that CaCO3 and steam influence H2 production by increasing 15.8% and 10.8%, respectively, with a CaCO3/biomass ratio of 1% (w/w) and a Steam/biomass ratio of 11% (w/w). Main statistical effects were found for CGE increase of 5% with the addition of steam, 10% with CaCO3, and synergy of 10% using CaCO3 and steam simultaneously.
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