A Scale-Up Project for Operating a 115 MWth Biomass-Fired CFB boiler with Oxygen Carriers as Bed Material

Paper in proceedings, 2018

Oxygen Carrier Aided Combustion (OCAC) is a concept that uses an oxygen-active bed material to increase the overall efficiency in fluidized bed (FB) combustors. The introduction of oxygen carriers (OCs) in existing FB plants is an attractive opportunity to investigate OCs under industrially-relevant conditions at a low economic risk. In this way, important experience and knowledge of the physiochemical properties of OCs can be gained during long-term operation, which in turn can be used for the scale-up of oxygen-looping techniques, e.g. chemical-looping combustion. The overall aim of this experimental study was to investigate, develop and collect data to increase the knowledge of how OCs can be deployed in commercial FB boilers, while at the same time granting the plant operator benefits from an increased revenue. This paper summarizes the first results from an experimental campaign performed during three weeks of OCAC operation in a 115 MWth commercial CFB boiler, which is fired with a mix of recycled waste-wood and wood chips. During the campaign, the silica-sand bed material was gradually replaced by the mineral ilmenite. It was shown that ilmenite operation, in comparison to operation with silica-sand, facilitated a reduction in the air surplus by as much as 30 %, while increasing the boiler load from 115 MWth to 123 MWth. During ilmenite operation no problems related to the external or internal bed-material logistics nor in the overall boiler operation. However, during ilmenite operation slightly higher emissions of NOx and consumption of ammonia were detected in comparison to operation with silica-sand.