Study On The Characteristics Of Hydrogen-rich Gas Produced From Biomass Pyrolysis With Calcium-based Catalyst Enhanced By Magnetic Field

Biomass resources are rich in China and have broad prospects for utilization.Biomass are treated by thermochemical conversion technologies that not only solve the waste problem of biomass resources,but also produce the hydrogen-rich gas.The traditional thermochemical conversion technologies have the problems of high pyrolysis temperature,high contents of CO₂ and tar in pyrolysis gas,and low energy conversion efficiency.In this paper,the characteristics of hydrogen-rich gas produced from biomass pyrolysis with calcium-based catalyst enhanced by magnetic field were studied.In this study,thermogravimetric experiments of biomass with calcium-based catalyst were performed using thermogravimetric analyzer,and the kinetic analysis was carried out.The experiments of biomass catalytic pyrolysis with calcium-based catalyst were carried out using TG-FTIR and PY.The thermodynamic simulation of the pyrolysis process was explored using the Fact Sage software.The experiments of biomass pyrolysis with calcium-based catalyst for the preparation of hydrogen-rich gas were performed using pyrolysis device with external magnetic field,and the effects of biomass catalytic pyrolysis enhanced by magnetic field were investigated.The optimized operating conditions of biomass pyrolysis enhanced by magnetic field for preparing hydrogen-rich gas were obtained.The results showed that:The results of thermogravimetric experiment showed that the biomass pyrolysis process could be divided into four stages: drying,pre-pyrolysis,rapid pyrolysis,and carbonation.With the increasing of heating rate,the maximum weight loss rate increased,and the total weight loss reduced.The kinetic analysis indicated that the apparent activation energy of biomass pyrolysis was reduced by the Ca O catalyst and10wt%Ni/Ca O catalyst.The apparent activation energy of sawdust was 52.65 k J·mol-1with the Ca O catalyst,and it was 51.35 k J·mol-1 with the 10wt%Ni/Ca O catalyst.It was indicated that the catalytic effect of 10wt%Ni/Ca O catalyst was better than Ca O catalyst.The results of thermogravimetry-infrared experiment and thermodynamic simulation indicated that the optimized temperature of biomass pyrolysis to prepare hydrogen-rich gas was 650?.The thermodynamic simulation results showed that the calcium-based catalysts could break the limit of thermodynamic equilibrium,which resulted in the H2 content in the pyrolysis gas of sawdust reaching 77.32% at 650?,and the H₂ content in the pyrolysis gas of herb residues reaching 77.35 %.The rapid pyrolysis experiments showed that the relative content of aromatichydrocarbon in pyrolysis oil could increase at high temperature.The decarboxylation reaction and phenolic hydroxyl reaction of the pyrolysis process were promoted by calcium-based catalyst,which led to the deoxygenation of oxygen-containing macromolecules in the pyrolysis oil and the secondary pyrolysis of the tar,and changed the distribution of pyrolysis gas components.The magnetic field could strengthen the biomass pyrolysis with calcium-based catalyst,which increased the H2 content and decreased the CO₂ content in the pyrolysis gas.With the increasing of the pyrolysis temperature,the effect of the magnetic field weakened,and the H2 content increased firstly and then decreased,the CO₂ content remained almost constant in the beginning and then increased.Considering the above results,10wt%Ni/Ca O catalyst and 650? were determined to be the optimal operating parameters for preparing hydrogen-rich gas of biomass pyrolysis enhanced by magnetic field.