Investigation of fluidized bed agglomerate growth process using simulations and SEM-EDX characterization of laboratory-generated agglomerates

Abstract

This study elucidates the sequential progression of agglomerate growth in fluidized beds through an investigation of physics and chemistry of particle-particle interaction. In fluidized bed gasification and combustion systems, agglomeration occurs by sticking of ash particles that are wetted by slag-liquid. Penn State has developed an agglomeration modeling methodology that considers non-uniform temperature, gaseous atmosphere and heterogeneity in ash chemical composition to predict slag-liquid formation and agglomerate growth rate. Simulations performed on three high rank coals with a consideration of these heterogeneous conditions, along with a microscopic (SEM) particle-level analysis of agglomerates facilitated an understanding of steps involved in their formation.The results of this study indicated that agglomerate growth in fluidized bed systems is initiated at the particle-level by low-melting components rich in iron- and calcium-based minerals. Agglomeration can begin at lower temperatures than the fluidized bed operating temperatures of 850 °C and the severity of agglomerate growth issues can be identified based on the slag-liquid level in the system. Understanding the stages involved in the process of agglomerate growth discussed in this paper can help develop early detection methods and mitigation strategies.