Gasification reactivity and synergistic effect of conventional and microwave pyrolysis derived algae chars in CO2 atmosphere. Issue 3 (June 2019) - Parvez, Ashak Mahmud
Abstract: This research focuses on the isothermal and non-isothermal CO2 gasification of an algal (Chlorella) char prepared via two different thermal processing systems, i.e . conventional and microwave-assisted pyrolysis. It was found that chars prepared via microwave irradiation showed higher CO2 gasification reactivity than that of chars prepared via the conventional method. Meanwhile, the activation energy of microwave char was found to be 127.89 kJ/mol, which was 46.3 kJ/mol lower than that of conventional char, indicating improved reactivity of microwave char. The systematic characterisation of both conventional and microwave chars shows that the higher reactivity of microwave char could be attributed to its large BET surface area, low crystalline index and high active sites. In addition, it was found that microwave heating contributed to high reactivity of chars through generating large amount of primary char, the formation of hot spot and high specific surface area and pore volume. Results of co-gasification under isothermal conditions revealed the existence of greater synergistic effects between coal char and microwave algae char than those of coal char and conventional algae char. Furthermore, based on the relative Rs (average gasification rate), a novel index proposed to quantify the interactions in co-gasification process, Australian coal char/microwave assisted char blend experienced 10% higher interactions compared to Australian coal char/conventional assisted char blend. Graphical abstract: Highlights: Microwave algae char was more reactive compared to conventional algae char. The activation energy of microwave char has been calculated as 127.89 kJ/mol, which was 46.3 kJ/mol lower than that of conventional char. Significant interactions were noticed in Australian coal char/microwave algae char blend. Relative Rs was used as a quantitative index to characterize the interactions in co-gasification process. Primary char, hot spot formation and high specific surface area were contributed to improved reactivity in microwave algae char.