Morphological and chemical differences within superheater deposits from different locations of a black liquor recovery boiler

Roland Balint; Markus Engblom; Jonne Niemi; Daniel Lindberg; Timo Saarinen; Jaakko Rautala; Mikko Hupa; Leena Hupa

doi:10.1016/j.energy.2022.126576

Morphological and chemical differences within superheater deposits from different locations of a black liquor recovery boiler

Roland Balint^*
, Markus Engblom
, Jonne Niemi
, Daniel Lindberg
, Timo Saarinen
, Jaakko Rautala
, Mikko Hupa
, Leena Hupa

^*Corresponding author for this work

Laboratory of Molecular Science and Engineering

Research output: Contribution to journal › Article › Scientific › peer-review

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Abstract

The effects of two deposit ageing mechanisms were identified by analysing superheater ash deposits from a kraft recovery boiler. Local differences in deposit morphology and chemical composition were identified under the electron microscope. Temperature-gradient-induced diffusion of alkali chloride vapours toward the steel was evident. Two deposit types were identified, based on local chemical compositions: “Type 1” deposits had an innermost porous layer of fine, sintered fume particles enriched in K and Cl, that deposited after homogeneous condensation in the gas phase. “Type 2” deposits formed via sulfation of initially deposited fume particles rich in K and Cl. Thus the innermost layer was enriched in K and S, while concurrently depleted in Cl. Differences in the local first melting temperature (T0) within the innermost regions of the two deposit types were identified. T0 reached a minimum within the innermost region of Type 1 deposits, implying an increased risk for melt formation and corrosion. Whereas for Type 2 deposits, T0 was increased closest to the steel, reducing the risk for melt formation and superheater corrosion. The presented results provide a better understanding of intra-depositional changes taking place after initial deposition, helping assess risks of deposit-related operational problems in the boiler.

Original language	English
Article number	126576
Journal	Energy
Volume	267
DOIs	https://doi.org/10.1016/j.energy.2022.126576
Publication status	Published - 15 Mar 2023
MoE publication type	A1 Journal article-refereed

Funding

The financing through a research grant awarded by the Fortum Foundation [Application number 20190123] is highly acknowledged. This work has been partly carried out within the Åbo Akademi CLUE2 Research Consortium (2017–2022). Support from ANDRITZ Oy, Valmet Technologies Oy, UPM-Kymmene Oyj, Metsä Fibre Oy, and International Paper Inc. is gratefully acknowledged. Additional support from the Academy of Finland projects “Understanding the dynamics of intradeposit chemistry and morphology for control of corrosion in high temperature processes“ [Decision number 310266] and “New insights on the effects of temperature gradients on high temperature corrosion” [Decision number 338322] is highly appreciated. We want to thank Linus Silvander for carrying out SEM/EDX analyses. The financing through a research grant awarded by the Fortum Foundation [Application number 20190123 ] is highly acknowledged. This work has been partly carried out within the Åbo Akademi CLUE 2 Research Consortium (2017–2022). Support from ANDRITZ Oy, Valmet Technologies Oy, UPM-Kymmene Oyj, Metsä Fibre Oy, and International Paper Inc. is gratefully acknowledged. Additional support from the Academy of Finland projects “Understanding the dynamics of intradeposit chemistry and morphology for control of corrosion in high temperature processes“ [Decision number 310266] and “New insights on the effects of temperature gradients on high temperature corrosion” [Decision number 338322] is highly appreciated. We want to thank Linus Silvander for carrying out SEM/EDX analyses.

Keywords

Superheater deposits
Temperature gradient
Ageing mechanism
Local melting behaviour

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10.1016/j.energy.2022.126576

Morphological and chemical differences within superheater deposits from different locations of a black liquor recovery boilerFinal published version, 14.7 MBLicence: CC BY

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title = "Morphological and chemical differences within superheater deposits from different locations of a black liquor recovery boiler",

abstract = "The effects of two deposit ageing mechanisms were identified by analysing superheater ash deposits from a kraft recovery boiler. Local differences in deposit morphology and chemical composition were identified under the electron microscope. Temperature-gradient-induced diffusion of alkali chloride vapours toward the steel was evident. Two deposit types were identified, based on local chemical compositions: {\textquotedblleft}Type 1{\textquotedblright} deposits had an innermost porous layer of fine, sintered fume particles enriched in K and Cl, that deposited after homogeneous condensation in the gas phase. {\textquotedblleft}Type 2{\textquotedblright} deposits formed via sulfation of initially deposited fume particles rich in K and Cl. Thus the innermost layer was enriched in K and S, while concurrently depleted in Cl. Differences in the local first melting temperature (T0) within the innermost regions of the two deposit types were identified. T0 reached a minimum within the innermost region of Type 1 deposits, implying an increased risk for melt formation and corrosion. Whereas for Type 2 deposits, T0 was increased closest to the steel, reducing the risk for melt formation and superheater corrosion. The presented results provide a better understanding of intra-depositional changes taking place after initial deposition, helping assess risks of deposit-related operational problems in the boiler.",

keywords = "Superheater deposits, Temperature gradient, Ageing mechanism, Local melting behaviour",

author = "Roland Balint and Markus Engblom and Jonne Niemi and Daniel Lindberg and Timo Saarinen and Jaakko Rautala and Mikko Hupa and Leena Hupa",

year = "2023",

month = mar,

day = "15",

doi = "10.1016/j.energy.2022.126576",

language = "English",

volume = "267",

journal = "Energy",

issn = "0360-5442",

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T1 - Morphological and chemical differences within superheater deposits from different locations of a black liquor recovery boiler

AU - Balint, Roland

AU - Engblom, Markus

AU - Niemi, Jonne

AU - Lindberg, Daniel

AU - Saarinen, Timo

AU - Rautala, Jaakko

AU - Hupa, Mikko

AU - Hupa, Leena

PY - 2023/3/15

Y1 - 2023/3/15

N2 - The effects of two deposit ageing mechanisms were identified by analysing superheater ash deposits from a kraft recovery boiler. Local differences in deposit morphology and chemical composition were identified under the electron microscope. Temperature-gradient-induced diffusion of alkali chloride vapours toward the steel was evident. Two deposit types were identified, based on local chemical compositions: “Type 1” deposits had an innermost porous layer of fine, sintered fume particles enriched in K and Cl, that deposited after homogeneous condensation in the gas phase. “Type 2” deposits formed via sulfation of initially deposited fume particles rich in K and Cl. Thus the innermost layer was enriched in K and S, while concurrently depleted in Cl. Differences in the local first melting temperature (T0) within the innermost regions of the two deposit types were identified. T0 reached a minimum within the innermost region of Type 1 deposits, implying an increased risk for melt formation and corrosion. Whereas for Type 2 deposits, T0 was increased closest to the steel, reducing the risk for melt formation and superheater corrosion. The presented results provide a better understanding of intra-depositional changes taking place after initial deposition, helping assess risks of deposit-related operational problems in the boiler.

AB - The effects of two deposit ageing mechanisms were identified by analysing superheater ash deposits from a kraft recovery boiler. Local differences in deposit morphology and chemical composition were identified under the electron microscope. Temperature-gradient-induced diffusion of alkali chloride vapours toward the steel was evident. Two deposit types were identified, based on local chemical compositions: “Type 1” deposits had an innermost porous layer of fine, sintered fume particles enriched in K and Cl, that deposited after homogeneous condensation in the gas phase. “Type 2” deposits formed via sulfation of initially deposited fume particles rich in K and Cl. Thus the innermost layer was enriched in K and S, while concurrently depleted in Cl. Differences in the local first melting temperature (T0) within the innermost regions of the two deposit types were identified. T0 reached a minimum within the innermost region of Type 1 deposits, implying an increased risk for melt formation and corrosion. Whereas for Type 2 deposits, T0 was increased closest to the steel, reducing the risk for melt formation and superheater corrosion. The presented results provide a better understanding of intra-depositional changes taking place after initial deposition, helping assess risks of deposit-related operational problems in the boiler.

KW - Superheater deposits

KW - Temperature gradient

KW - Ageing mechanism

KW - Local melting behaviour

U2 - 10.1016/j.energy.2022.126576

DO - 10.1016/j.energy.2022.126576

M3 - Article

SN - 0360-5442

VL - 267

JO - Energy

JF - Energy

M1 - 126576

ER -

Morphological and chemical differences within superheater deposits from different locations of a black liquor recovery boiler

Abstract

Funding

Keywords

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