Use of heavy fraction of bio-oil as fuel for hydrogen production in iron-based chemical looping process

• DOI: 10.1016/j.ijhydene.2014.08.122
• Publication Date: 2014-10-26T12:15:55Z
• Authors: Rui Xiao; Shuai Zhang; Shaohua Peng; Dekui Shen; Kunlei Liu
• Keywords: Ilmenite; Chemical-Looping Combustion; Thermogravimetric analysis; Carbon fibers

Abstract Chemical looping hydrogen (CLH) process with renewable energy sources as fuel shows the potential of producing pure hydrogen with inherent capture of CO 2 in a low-cost and sustainable way. The heavy fraction (HF) of bio-oil, derived from the fast pyrolysis of biomass and characterized as an energy carrier with difficulty in upgrading itself to bio-fuel or chemicals, was used in this study to generate H 2 . Four low-cost iron-based oxygen carriers including an ilmenite and three iron ores were initially evaluated with respect to their reducibility and the ability to minimize carbon or iron carbide (Fe 3 C) formation in a thermogravimetric analyzer (TGA). The reactivity and cyclic performance of the selected best candidate was then assessed in a laboratory scale fixed-bed reactor with HF bio-oil as fuel. The screening test in TGA showed that ilmenite was superior over the three iron ores in terms of promoting CO conversion and minimizing carbon or Fe 3 C formation. Ilmenite could maintain its increasing reducibility with the increase of surrounding CO concentration, in contrast with the iron ores that were deactivated seriously by the formed carbon or Fe 3 C. Subsequent CLH test with ilmenite and HF bio-oil showed that the reducibility and H 2 production capacity of ilmenite were strongly dependent on the operating temperature. The steam oxidation step at 950 °C yielded H 2 concentration and hydrogen yield exceeding all of those observed at the other investigated temperatures because of the deepest reduction degree of ilmenite at 950 °C. The decrease in the reducibility and H 2 production capacity of ilmenite in the cyclic test could be ascribed to the poorer physical structure of ilmenite with cycles.