Disposal And Hydrogen Generation Of Biogas Slurry Produced From Biomass Anaerobic Digestion Via Catalytic Reforming

Biogas slurry is the high organic content wastewater produced from biomass anaerobic digestion.As anaerobic digestion is gradually being popularized and applied worldwide,the treatment and utilization problem of biogas slurry is drawing growing attention.According to the characteristics of biogas slurry,this work proposed a pioneering method which uses catalytic reforming technology to treat the organic content in biogas slurry and produce hydrogen from it.A series of experimental and theoretical studies were conducted to provide a fundamental knowledge about biogas slurry catalytic reforming.(1)Catalytic reforming experiments were conducted on acetic acid and phenol.Acetic acid was chosen as the model compound of carboxylic acids with high content in biogas slurry,and phenol was chosen as the model compound of phenols with serious harmfulness in biogas slurry.The results indicate that Al₂O₃ with different crystalline phases could affect the reduction towards Ni⁰ and eventually affects the catalytic performance of Ni/x-Al₂O₃ catalyst towards acetic acid reforming.Different silicon to aluminum ratio could influence the acidity,hydrophobicity as well as Ni⁰ formation of the Ni/ZSM-5 catalyst,which eventually affect its catalytic performance towards phenol reforming.(2)Catalytic reforming experiments of cattle manure–,fish intestine–and wheat straw–digested biogas slurries were conducted.The results indicate that Ni/?-Al₂O₃catalyst is capable to catalyze biogas slurry steam reforming reaction.Optimal hydrogen yield of 13.85 L_hydrogen/L_{biogas slurry} and hydrogen content in gaseous product of 80 vol%could be obtained from cattle manure–digested biogas slurry in 750?.(3)Biogas slurry samples before and after catalytic reforming were collected.The mass flow scheme and energy flow scheme of biogas slurry catalytic reforming were established and discussed.The results indicate that biogas slurry catalytic reforming could remove more than 90%of polluting contents in biogas slurry,and its fuel production capability is in an equivalent level with the upstream biogas production process.Meanwhile,when the heat recovery efficiency reached 93.11%,the whole process would be net in energy consumption.(4)A new method for assessing the environmental impacts of biomass energy conversion processes was proposed.Various feedstocks and technologies were evaluated via this method.The results indicate that,biogas slurry catalytic reforming could enhance the carbon conversion and carbon footprint reduction of anaerobic digestion by 31.2%and 50.0%.The environmental risk quantified by the method proposed in this study as also reduced by 24.1%.