Characterization of Tar Generated during Updraft Gasification of Woody Biomass in Auto-thermal Packed Bed Reactor

Abstract

This study presents characteristics of tar formed during updraft gasification of biomass by using mass spectrometry and thermogravimetric analysis. Tar content in producer gas is higher at the lower-middle part of the reactor which represents a pyrolytic zone. Tar is composed of C, H, N and O by 70.62%, 10.62%, 0.57% and 18.20%, correspondingly and its HHV is around 35.27 MJkg-1. ToF-MS analysis for ion mass-to-charge ratio (mz-1) indicates high intensities from 280 mz-1 to around 380 mz-1. In comparison with tar taken from the trap, tar samples captured along the bed heights have relatively low peaks at 500 mz-1, 555 mz-1and 615 mz-1. Devolatilization of tar up to 700 K follows a similar trend regardless of presence or absence of oxidizing agent. Tar has about 22.17% fixed carbon content whose combustion and gasification at heating rate of 20 Kmin-1 occurred above 700 K. Average devolatilization for volatile matter in tar during non-isothermal pyrolysis, combustion and gasification was about 2.29%min-1. Average degradation of fixed carbon during non-isothermal combustion and non-isothermal gasification was found to be 3.45%min-1 and 0.54%min-1, respectively. For isothermal combustion and gasification at 1,273 K, degradation of fixed carbon was about 3.73%min-1 and 0.95%min-1, respectively.