Temperature gradient induced changes within superheater ash deposits high in chlorine

Roland Balint, Markus Engblom, Jonne Niemi, Daniel Silva da Costa, Daniel Lindberg, Patrik Yrjas, Leena Hupa and Mikko Hupa

Energy, 2021, vol. 226, issue C

Abstract: Cross-sections of kraft recovery boiler superheater deposits were analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The observed deposit morphology can be explained by temperature gradient induced time-dependent processes such as diffusional transport of alkali chloride vapours, temperature gradient zone melting, formation of melt enriched in Cl and K, and movement of this enriched melt towards the steel. These processes have recently been identified on a laboratory scale under well-controlled conditions, and are now for the first time identified to take place also in actual boiler superheater deposits. The identified processes alter the local deposit composition and melting behaviour close to the steel. The local first melting temperature (T0) close to the steel is lower by 30 °C compared to that of the deposit bulk T0. The observations made in this work give new insight into the melting and ageing behaviour of superheater deposits, relevant for superheater corrosion.

Keywords: Superheater deposit; Temperature gradient; Ageing mechanism; Melt enrichment (search for similar items in EconPapers)
Date: 2021
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Citations: View citations in EconPapers (6)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:226:y:2021:i:c:s0360544221006885

DOI: 10.1016/j.energy.2021.120439

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