Research On Gasification Characteristics Of Biochar From Corn Stalk With Steam And Oxygen Atmosphere

The concept of“lucid waters and lush mountains”is at the center of China’s eco-civilization conservation,and green development is closely linked to the country’s future and people’s well-being.To ensure the sustainability of the ecological environment and energy use,establishing a energy system based on“carbon neutral”should be a top priority in eco-civilization conservation.Biomass is the only clean,renewable energy source with zero CO₂emissions that can be stored and transported.Gasification technology is the optimal choice to convert carbon-neutral biomass resources into high-grade gases.The gasification of biochar is the rate-limiting step in biomass gasification,and gasification technology is greatly restrained by the reaction rate.Through a gasification experiment with corn stalk biochar as raw material,this project identifies the effect of gasification conditions on stalk biochar’s gasification reactivity,explores the relationship between stalk biochar’s structural characteristics and its gasification properties,and clarifies the occurrence mechanism and directivity of synergy in H₂O-O₂co-gasification.Orthogonal tests were first conducted with gasification temperature,steam concentration and oxygen concentration as single factor conditions.In a single atmosphere of steam or oxygen as well as in a mix atmosphere,gasification experiments were then performed on corn stalk biochar.According to the results,in the H₂O-O₂mixing gasification,there was a positive synergy between oxygen gasification and steam gasification reaction.At oxygen concentrations greater than 1%,the efficiency of carbon conversion was higher than that of steam or oxygen gasification alone.The promotion of steam gasification by oxygen was based on higher steam concentrations.The activation energy of 51%H₂O+1%O₂mixing gasification was obviously below that of H₂O gasification at different carbon conversions.Through measurements by nitrogen adsorption,infrared spectrum and Raman spectrum,the physicochemical structures of corn stalk biochar before and after the addition of oxygen to the steam were characterized.Based on the evolution of corn stalk biochar’s gasification reaction conditions and physicochemical structure,the occurrence mechanism and directivity of synergy in co-gasification were studied.In terms of physical structure,the gasified biochar had a relatively complete and similar pore structure with roughly the same pore size distribution,mostly micropores and mesopores.The addition of oxygen strengthened the pore structure and increased the pore volume,specific surface area and adsorption,which microscopically verified the promotion of steam gasification by oxygen at higher steam concentrations.Rising temperatures encouraged the opening and expanding of pores by H₂O and O₂,thus increasing the proportion of mesopores.Besides,there was a linear rise in the adsorption,pore volume and specific surface area of biochar,which provided a favorable environment for gasification reaction.Oxygen showed a more significant positive synergy with steam gasification.In terms of chemical structure,the gasification reaction led to the breakage of oxygen-containing functional groups and the polycondensation of the aromatic rings in corn stalk biochar,with greater biochar aromaticity after gasification.The absorption intensity of aromatic C-H increased with the gasification of oxygen,and the absorption intensity of aromatic nucleus C-O structure increased with the gasification of steam.In the H₂O-O₂mixing gasification,oxygen caused more functional groups to break as the steam concentration increased.The aromatic rings in biochar had greater condensation,and the number of C-O structures increased,occurring more significant positive synergy.At different temperatures,H₂O-O₂co-gasification resulted in more C-O and C=O structures on the aromatic rings than H₂O gasification,demonstrating positive synergy at different temperatures.The synergy of H₂O-O₂was more significant at lower temperatures.The research findings are expected to provide a reference for the gasification application of corn stalk biochar,implying their practical engineering significance.