Oxygen-Carrier-Aided Combustion in a Bench-Scale Fluidized Bed

Abstract

In a circulating fluidized bed (CFB) boiler, one of the basic functions of the bed materials is to transport heat between different parts of the boiler to decrease heat gradients and, thereby, smoothen the operation. A novel concept, oxygen-carrier-aided combustion (OCAC), replaces some or all of the bed materials with an oxygen carrier, which is a metal oxide that, through chemical redox reaction, not only transports heat but also transports oxygen between oxygen-lean and oxygen-rich areas of the boiler. The oxygen carrier also acts as internal oxygen storage, which increases the total amount of available oxygen in the boiler. The concept of OCAC was demonstrated by Thunman et al. at Chalmers University of Technology, where the bed material (sand) in a 12 MW boiler was replaced with iron titanium mineral (ilmenite). In this work, a small fluidized bed reactor is used to mimic the condition in OCAC with regard to fuel conversion as well as NO formation and to test other oxygen carrier materials. Four oxyg...