On-line analysis on fast pyrolysis of lignocellulosic biomass: Thermal behavior and kinetic analysis of hemicellulose

Thermal conversion of lignocellulosic biomass can provide various products for the energy demand of low carbon city. Pyrolysis is the initial step of other thermochemical method, which is also a potential technology for biomass conversion. Previous research mainly focuses on the thermal behavior of the whole component in lignocellulosic biomass during pyrolysis. The organic component has a significant influence on the products distribution and kinetic characteristic. Thus, in this research hemicellulose (HCE) was selected as one of the typical organic components in biomass. Products distribution and characteristic of gas were explored by a tube furnace and an on-line mass spectrometer from 650 ^o C to 850 ^o C. Iso-conversional method was applied to obtain the kinetic parameters of gaseous products (H2、CO、CH4 and CO2) from HCE. The results indicated that gas and tar were the main products from fast pyrolysis of HCE. The yield of gas increased from 26.65 wt.% to 44.63 wt.% as the increase of temperature. CO and CO2 were the main content of gaseous, which accounted about 80 % the gas. The volume of H2 increased from 5.28 vol.% to 15.82 vol.% when temperature increased from 650 ^o C to 850 ^o C. The high heating value of the gaseous products was between 10.95 and 12.52 MJ·Nm ^-3 . Releasing properties of the main volatile products from HCE were also obtained, and the intensity of gaseous was similar with the yield changing. The activation energy for CO2, CO, CH4, and H2 were 22.35 kJ·mol ^-1 , 36.13 kJ·mol- ¹ , 26.65 kJ·mol ^-1 , 21.66 kJ·mol ^-1 . The pre-exponential of H2, CO, CH4 and CO2 was 0.3436 s ^-1 , 1.5898 s ^-1 , 1.0298 s ^-1 , 0.4937 s ^-1 , respectively.