Bottom Ash Bridging in Pulverized-Coal Boilers: Mechanisms, Diagnosis and Prevention

Ravikant Sankhe, Subodh Raut, Aditya Gavhale

Abstract: Bottom ash bridging is the formation of a self-supporting arch, crust or consolidated clinker mass across the furnace bottom or hopper flow path. The event is rarely caused by a single factor. It normally develops through the interaction of ash chemistry, localized temperature variations in the furnace, combustion atmosphere, deposit residence time, hopper geometry, quenching performance and the extent of ash-removal. High furnace temperature, inadequate cooling, delayed discharge, hopper geometry & conditions, coal-quality variation and air & water leakage as primary contributors. This paper outlines the critical observations into a mechanism-based framework suitable for operating guidance, root-cause analysis, and monitoring. Particular emphasis is placed on the difference between ash softening, sintering, and complete melting; the role of iron, calcium and alkali fluxes; localized reducing conditions; and the fact that agglomeration can begin below the standard initial-deformation temperature measured by ash-fusion test. A robust prevention strategy should combine fuel & ash characterization, furnace heat-flux and combustion control, continuous ash extraction, uniform hopper cooling and water sealing, condition monitoring of grinders, gates, conveyors and hydraulic systems, and disciplined post-event deposit analysis. Plant-specific operating limits must be based on the boiler OEM design, actual coal blend, and historical operating data rather than the generic temperature limits alone.

Keywords: bottom ash, bridging, ash fusion temperature, combustion control, sintering, pulverized-coal boiler

How to Cite?: Ravikant Sankhe, Subodh Raut, Aditya Gavhale, "Bottom Ash Bridging in Pulverized-Coal Boilers: Mechanisms, Diagnosis and Prevention", Volume 15 Issue 9, September 2026, International Journal of Science and Research (IJSR), Pages: 1913-1919, https://www.ijsr.net/getabstract.php?paperid=SR26928172843, DOI: https://dx.doi.org/10.21275/SR26928172843

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