Reducing Pressure Loss in Circulating Fluidized Bed Boiler: A Comparative Study of Innovative and Conventional Bell-Type Air-Caps

Abstract

The research is motivated by the need to improve the efficiency of the fluidization process in Circulating Fluidized Bed (CFB) boiler, particularly through optimizing the design of the air cap as the primary air distributor. Fluidization is essential in CFB boiler for enhancing mixing, heat transfer, and combustion efficiency. This study aims to examine the influence of air cap geometry on the fluidization regime, focusing on achieving stable and uniform fluidization. The research involved preparing bed materials, specifically silica sand and coal, and conducting fluidization tests using bell-type air cap. The results showed that innovative bell-type air cap significantly enhance fluidization efficiency, reducing pressure loss by up to 29% compared to conventional designs. This reduction in pressure loss indicates a more energy-efficient process, as less power is needed for fluidization. At higher fluid velocities (220 cm/s), the pressure loss reduction remains notable, though it slightly decreases from 13% to 17%. Additionally, the study highlights differences in fluidization behaviour between the materials: silica sand, classified as Geldart group B, fluidizes easily, while low-rank coal, in Geldart group D, exhibits cohesive properties and a tendency to form agglomerates, complicating fluidization.