Experimental Investigation of Combustion Characteristics during Oxygen Carrier Aided Combustion of Solid Recovered Fuel and Coal in a 1 MWth Circulating Fluidized Bed Reactor

This presentation investigates results on oxygen carrier aided combustion (OCAC) of solid recovered fuel (SRF) and hard coal in a circulating fluidized bed (CFB) boiler, using ilmenite as bed material. In the OCAC process, the oxygen carrier (OC) is used as a bed material with the ability to incorporate and release oxygen, resulting in a decrease of local excesses or demands of oxygen. This effect has been proven to buffer combustion, which results in lower CO concentrations in the flue gas while at the same time allowing an increase in boiler load. During the test campaign described in this paper, a reduction of CO concentration of more than 70% has been measured. The NO concentration in the flue gas has shown varying results in different experiments. While there was a reduction in one case, increased NO values were found elsewhere, which are in line with the slight increase of up to 7 % during this test campaign. The pilot plant used to conduct the experiments has an inner diameter of 0.59 m, a height of 8.6 m, a thermal load of 1 MWth and a high operational flexibility. The combustion tests were performed using 100% SRF and a mixture of SRF and coal in the ratio of nearly 80/20 by heating value to investigate the combustion characteristics. It was found that even though an increase in SRF share shifts the combustion towards higher reactor region and lowers the pressure inside the reactor, stable operation can be maintained. The combustion conditions inside the reactor were investigated using two in-bed gas measurements, where the components O2, CO and CO2 are measured as horizontal profiles through the entire reactor width of 590 mm.