Syngas production and trace element emissions from microwave-assisted chemical looping gasification of heavy metal hyperaccumulators

Abstract

Phytoremediation is one of the most encouraging options for the elimination of heavy metals from contaminated soil. However, the treatment and exploitation of hazardous harvested hyperaccumulator biomass is a challenge recently. In this investigation, we propose a novel microwave-assisted chemical looping gasification (MACLG) process for the disposal of hyperaccumulator biomass, and syngas fuel production and trace element emissions from MACLG over hematite is evaluated. Experimental results show that the addition of hematite as oxygen carrier (OC) favors the production of H2 and CO. The elevated operation temperature induces a decay in CO2 yield and an increase in H2, CO and CH4 yields. Meanwhile, a higher temperature causes an increased heavy metal percentage in syngas. On the other hand, the augmentation of steam flow and hematite content stimulates an uptrend for CO2 and H2 production and downtrend for CO generation. The percentage of each trace element in char after MACLG reduces with increasing steam flow, and its change in syngas presents the opposite trend. In addition, the proportions of trace elements in spent hematite and syngas tend to increase with an augmented hematite content whereas their portions in char reduce gradually. Moreover, our results suggest that activated carbon is capable of effective adsorption removal of heavy metals in syngas.