Pressurized Pyrolysis Behaviors Of Biomass And Coal And Gasification Reactivities Of Derived Chars

Pyrolysis is an important technology to convert biomass and coal into high-value products. This research focused on pressurized pyrolysis behaviors of biomass and coal and gasification reactivities of derived chars. The main research contents are included as follows.To investigate the effects of pressure (0.1-5.0 MPa) on the pyrolytic behaviors, the pyrolysis of rice husk was conducted in a fixed-bed reactor with a sweeping nitrogen gas at the constant linear velocity of gas flow or the constant volume flow rate. Results showed that the pressurized pyrolysis was favorable for the preferential deoxygenation of bio-oil as a result of the intensified dehydration and decarboxylation. It leaded to significant increase in high heating value (HHV) of bio-oil. The bio-oil from pressurized pyrolysis embraced more acetic acid, phenols and guaiacols.The pressurized co-pyrolysis of biomass and coal was carried out in the same reactor as described above, in which rice husk (RH), Yuxi (YX) coal and Dawanggou (DWG) coal were used as raw materials. Increasing pressure also accelerated deoxgeneration of tar derived from the co-pyrolysis, with the enhanced yields of BTX (beneze, toluene and xylene) and PCX (phenol, cresol and xylenol). The HHVs of tars from the co-pyrolysis were higher than those from the pyrolysis of RH. For the blends of RH and DWG coal, some synergistic effect appeared with respect to the char and tar yields, but this effect was insignificant for the water and gas yields.Non-isothermal steam gasification of chars were conducted to determine their gasification reactivity. The active sites and XRD patterns of chars were also analyzed. Results demonstrated that the gasification reactivates increased in order of RH char> YX char> DWG char. The reactivities of the co-pyrolysis chars were lower than the calculated values, which enabled the gasification to occur more largely at higher temperature. As a consequence, the yields of CO2 and H2 were lower than the calculated values, whereas the yields of CO became higher.