Hydrogen Production from Chemical Looping Steam Reforming of Biomass Waste Cooking Oil

Abstract

For highly efficient transformation and utilization of waste cooking oil, a new method for hydrogen production by indirect and auto-thermal chemical looping steam reforming (CLSR) of waste cooking oil (WCO) was developed in this work. In conventional and direct CLSR using WCO at a temperature of 650 °C, gas production, hydrogen selectivity, and fuel conversion were low due to the insufficient amount of reducing Ni and heating. Thus, the reactor temperature was increased to 750 °C to pyrolyze enough reducing gas to reduce OCs. Although 84% WCO conversion and 88% hydrogen selectivity were obtained, the OCs deactivated at the last 15 minutes due to the high-temperature sintering of the reduced Ni particles. On this basis, a new type of indirect CLSR with high-temperature steam-assisted pyrolysis of WCO in a two-stages fixed-bed reactor with high stability was developed, which fitted WCO feeding and avoided OCs sintering. The experimental results show that about 90% WCO conversion and about 89% hydrogen selectivity were obtained in indirect CLSR, and the highest hydrogen yield and selectivity were obtained under the conditions of upper pyrolysis temperature of 800 ℃ with a lower CLSR temperature of 600 ℃ and S/C=4.12. In addition, the effect of in-situ CO 2 capture on indirect CLSR achieves the feasibility of hydrogen production and minus carbon emissions. The multiple cycles experiments of indirect CLSR obtained about 90% hydrogen selectivity and fuel conversion, close to 0 CH 4 selectivity, and 24%~26% steam conversion.

Keywords: Oxygen carriers (OCs), chemical looping steam reforming (CLSR), biomass, waste cooking oil (WCO), hydrogen production.