Biomass Co-firing Effect on Coal Feeder and Draught Plant for 50 MW Class CFB Boiler Type CFPP

Abstract

For Indonesia's renewable energy mix target in the electricity generation sector, biomass co-firing in existing Coal Fired Power Plant (CFPP) is one of the applicable methods in the context of Indonesia's electricity generation industry. Among the various applicable power plant, Circulating Fluidized Bed (CFB) boiler-type CFPP is one of the power plant types applicable for co-firing. As various CFB manufacturers claim, CFB boilers can consume substantial biomass fraction, up to 30% of the original fuel mass flow rate. However, biomass co-firing will increase the load factor of the boiler equipment, such as coal feeders and combustion air supply draft fans. This paper shows that up to 30% of biomass co-firing can increase coal feeder working-level until 100.68% with typical coal and 108.76% with design coal. Primary Air (PA) and Secondary Air (SA) fan load also increased to 100.86% compared to typical coal and 100.99% compared to design coal. As for Induced Draft (ID) fan loading can reach up to 101.10% with typical coal and 102.25% with design coal. Also, 30% biomass co-firing results in higher auxiliary power consumption. Draft fan power consumption increases by 31.43 kW with typical coal and 43.29 kW with design coal. This study recommends that power plant engineers conduct such analysis to compare the baseline power profile and equipment capacity to the off-design basis of high fraction biomass co-firing. The purpose of the analysis is to identify the various limiting factors that may arise from high fraction co-firing, such as limitation of draft fan capacity and/or reduction of efficiency that arise due to the increase in auxiliary power consumption.