Study On The Effects Of Metals In Biochar On Gas-solid Simultaneous Catalytic Conversion Of Biomass

Based on the gas-solid simultaneous gasification process of biochar and pyrolytic vapor in the integrated processes of biomass for hydrogen production, the effects of metals (K, Ca, Mg, Fe, Zn, and A1) in biochar on the catalytic gasification and reforming processes of biochar were investigated in this paper.The catalytic reforming of model pyrolytic vapor (MPV) over biochar in the fixed bed was investigated. The carbon conversion and potential hydrogen yield of biomass pyrolytic vapor were increased respectively from 68.46% to 86.88% and 42.16% to 82.76% in the presence of biochar. The catalytic reforming activities of different metals were found with the following sequence:K>Ca>Mg>Fe>Zn>Al. Meanwhile, the alkali and alkaline earth metals (AAEM) like K, Ca, and Mg were found to play the dominating roles in the conversion of MPV. The carbon conversion and potential hydrogen yield of pyrolytic vapor were increased by increasing temperature and ratio of steam to pyrolytic vapor.The effects of metals on biochar catalytic gasification were investigated. The catalytic activities of metals on biochar catalytic gasification were in the sequence:K>Ca>Mg>Zn >Fe>Al. AAEM (K, Ca and Mg) and Fe can promote water-gas shift reaction, while A1 had an inhibition effect on water-gas shift reaction. The increasing of temperature and steam were beneficial for biochar catalytic gasification. When carbon conversion was more than 90% (Steam=20 g/h and T=900℃), biochar and demineralized biochar needed 40 min and 115min respectively.The effects of metals on simultaneous catalytic conversion of biochar and biomass pyrolytic vapor (bio-oil) were investigated. The potential hydrogen yield was increased from 45.70 to 82.19 mmol/g bio-oil with the presence of metals in the biochar. And the tar yield was decreased from 24.88 to 13.84 mg/g bio-oil. The catalytic conversion of biochar and bio-oil were followed by the sequence K>Ca>Mg>Fe>Zn>Al. Meanwhile, the potential hydrogen and tar yields were 143.50 mmol/g bio-oil and 4.96 mg/g bio-oil when adding the metal of K. The performance of AAEM was comparable with Ni in catalytic reforming bio-oil. Al had an inhibition on the catalytic activity of biochar so that the soot yield was increased. Naphthalene was the primary tar in reaction temperature of 900℃, and had a strong thermal stability. Fe was deactivated by coking and sintering easily.