Cold-end corrosion in biomass combustion - role of calcium chloride in the deposit

Alessandro Ruozzi; Emil Vainio; Hanna Kinnunen; Leena Hupa

doi:10.1016/j.fuel.2023.128344

Cold-end corrosion in biomass combustion - role of calcium chloride in the deposit

Alessandro Ruozzi, Emil Vainio, Hanna Kinnunen, Leena Hupa

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

6 Citations (Scopus)

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Abstract

Using sustainable fuels in power production may lead to an increased risk of corrosion of various boiler parts. In biomass and waste combustion, hygroscopic and deliquescent deposits can cause corrosion of, e.g., preheaters and flue gas cleaning equipment. In the colder part of the boiler, calcium chloride (CaCl2) may form when utilizing fuels containing chlorine. Calcium chloride is a deliquescent salt which can absorb moisture from the flue gas leading to the dissolution of the salt itself. When calcium chloride deliquesces, it forms a corrosive electrolyte that can cause severe corrosion. In this work, full-scale corrosion probe measurements in a biomass boiler and laboratory experiments were carried out to study whether calcium compounds and especially CaCl2
might cause corrosion at different temperatures and humidity conditions. The impact of CaCl2 on the corrosion of carbon and stainless steel was studied in more details at various temperatures (80, 100 and 120 ◦C) and flue gas
moisture levels (15–25 vol% H2O) in a laboratory furnace. Different exposure times were used (24, 72 and 168h), and the effect of mixtures of CaCl2 and calcium carbonate (CaCO3) was also studied. The corrosion rate was
gravimetrically measured, and the sample cross-sections were analysed with SEM-EDX to verify the impact of different elements on the corrosion. Full-scale measurements showed chlorine-induced low-temperature corrosion. The main species in the deposit were calcium and chlorine, and corrosion was observed at conditions at which CaCl2 deliquesces. The laboratory work showed that although the deposit contains mainly calcium carbonate, which is not deliquescent, the highest corrosion rate (>1 mm/year) was found with 5 wt% CaCl2 in the salt deposit mixture. The tests showed that the corrosion rate is linear with time, and severe corrosion of carbon steel occurs when CaCl2 deliquesces. Stainless steel did not show any measurable corrosion at the conditions tested.

Original language	English
Article number	128344
Number of pages	11
Journal	Fuel
Volume	349
DOIs	https://doi.org/10.1016/j.fuel.2023.128344
Publication status	Published - 1 Oct 2023
MoE publication type	A1 Journal article-refereed

Funding

Funding from the Graduate School at Åbo Akademi is gratefully acknowledged. Support by the Academy of Finland (Properties and behaviour of deliquescent salts and deposits in biomass and waste thermal conversion - Towards improved efficiency and reliability, Decision No. 333917) is also gratefully acknowledged. In addition, the support from the CLUE 2 -project partners Andritz Oy, Valmet Technologies Oy, UPM-Kymmene Oyj, Metsä Fibre Oy, and International Paper Inc., are gratefully acknowledged. We want to thank Linus Silvander for carrying out the SEM/EDX analyses and Jaana Paananen for her help in the laboratory. Funding from the Graduate School at Åbo Akademi is gratefully acknowledged. Support by the Academy of Finland (Properties and behaviour of deliquescent salts and deposits in biomass and waste thermal conversion - Towards improved efficiency and reliability, Decision No. 333917) is also gratefully acknowledged. In addition, the support from the CLUE2-project partners Andritz Oy, Valmet Technologies Oy, UPM-Kymmene Oyj, Metsä Fibre Oy, and International Paper Inc. are gratefully acknowledged. We want to thank Linus Silvander for carrying out the SEM/EDX analyses and Jaana Paananen for her help in the laboratory.

Keywords

CaCl2
Cold-end corrosion
Hygroscopic deposits
Biomass combustion
Deliquescent salts

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10.1016/j.fuel.2023.128344Licence: CC BY

1-s2.0-S0016236123009572-mainFinal published version, 8.17 MBLicence: CC BY

https://urn.fi/URN:NBN:fi-fe20231222156878

Cite this

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title = "Cold-end corrosion in biomass combustion - role of calcium chloride in the deposit",

abstract = "Using sustainable fuels in power production may lead to an increased risk of corrosion of various boiler parts. In biomass and waste combustion, hygroscopic and deliquescent deposits can cause corrosion of, e.g., preheaters and flue gas cleaning equipment. In the colder part of the boiler, calcium chloride (CaCl2) may form when utilizing fuels containing chlorine. Calcium chloride is a deliquescent salt which can absorb moisture from the flue gas leading to the dissolution of the salt itself. When calcium chloride deliquesces, it forms a corrosive electrolyte that can cause severe corrosion. In this work, full-scale corrosion probe measurements in a biomass boiler and laboratory experiments were carried out to study whether calcium compounds and especially CaCl2 might cause corrosion at different temperatures and humidity conditions. The impact of CaCl2 on the corrosion of carbon and stainless steel was studied in more details at various temperatures (80, 100 and 120 ◦C) and flue gas moisture levels (15–25 vol\% H2O) in a laboratory furnace. Different exposure times were used (24, 72 and 168h), and the effect of mixtures of CaCl2 and calcium carbonate (CaCO3) was also studied. The corrosion rate was gravimetrically measured, and the sample cross-sections were analysed with SEM-EDX to verify the impact of different elements on the corrosion. Full-scale measurements showed chlorine-induced low-temperature corrosion. The main species in the deposit were calcium and chlorine, and corrosion was observed at conditions at which CaCl2 deliquesces. The laboratory work showed that although the deposit contains mainly calcium carbonate, which is not deliquescent, the highest corrosion rate (>1 mm/year) was found with 5 wt\% CaCl2 in the salt deposit mixture. The tests showed that the corrosion rate is linear with time, and severe corrosion of carbon steel occurs when CaCl2 deliquesces. Stainless steel did not show any measurable corrosion at the conditions tested. ",

keywords = "CaCl2, Cold-end corrosion, Hygroscopic deposits, Biomass combustion, Deliquescent salts",

author = "Alessandro Ruozzi and Emil Vainio and Hanna Kinnunen and Leena Hupa",

year = "2023",

month = oct,

day = "1",

doi = "10.1016/j.fuel.2023.128344",

language = "English",

volume = "349",

journal = "Fuel",

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TY - JOUR

T1 - Cold-end corrosion in biomass combustion - role of calcium chloride in the deposit

AU - Ruozzi, Alessandro

AU - Vainio, Emil

AU - Kinnunen, Hanna

AU - Hupa, Leena

PY - 2023/10/1

Y1 - 2023/10/1

N2 - Using sustainable fuels in power production may lead to an increased risk of corrosion of various boiler parts. In biomass and waste combustion, hygroscopic and deliquescent deposits can cause corrosion of, e.g., preheaters and flue gas cleaning equipment. In the colder part of the boiler, calcium chloride (CaCl2) may form when utilizing fuels containing chlorine. Calcium chloride is a deliquescent salt which can absorb moisture from the flue gas leading to the dissolution of the salt itself. When calcium chloride deliquesces, it forms a corrosive electrolyte that can cause severe corrosion. In this work, full-scale corrosion probe measurements in a biomass boiler and laboratory experiments were carried out to study whether calcium compounds and especially CaCl2 might cause corrosion at different temperatures and humidity conditions. The impact of CaCl2 on the corrosion of carbon and stainless steel was studied in more details at various temperatures (80, 100 and 120 ◦C) and flue gas moisture levels (15–25 vol% H2O) in a laboratory furnace. Different exposure times were used (24, 72 and 168h), and the effect of mixtures of CaCl2 and calcium carbonate (CaCO3) was also studied. The corrosion rate was gravimetrically measured, and the sample cross-sections were analysed with SEM-EDX to verify the impact of different elements on the corrosion. Full-scale measurements showed chlorine-induced low-temperature corrosion. The main species in the deposit were calcium and chlorine, and corrosion was observed at conditions at which CaCl2 deliquesces. The laboratory work showed that although the deposit contains mainly calcium carbonate, which is not deliquescent, the highest corrosion rate (>1 mm/year) was found with 5 wt% CaCl2 in the salt deposit mixture. The tests showed that the corrosion rate is linear with time, and severe corrosion of carbon steel occurs when CaCl2 deliquesces. Stainless steel did not show any measurable corrosion at the conditions tested.

AB - Using sustainable fuels in power production may lead to an increased risk of corrosion of various boiler parts. In biomass and waste combustion, hygroscopic and deliquescent deposits can cause corrosion of, e.g., preheaters and flue gas cleaning equipment. In the colder part of the boiler, calcium chloride (CaCl2) may form when utilizing fuels containing chlorine. Calcium chloride is a deliquescent salt which can absorb moisture from the flue gas leading to the dissolution of the salt itself. When calcium chloride deliquesces, it forms a corrosive electrolyte that can cause severe corrosion. In this work, full-scale corrosion probe measurements in a biomass boiler and laboratory experiments were carried out to study whether calcium compounds and especially CaCl2 might cause corrosion at different temperatures and humidity conditions. The impact of CaCl2 on the corrosion of carbon and stainless steel was studied in more details at various temperatures (80, 100 and 120 ◦C) and flue gas moisture levels (15–25 vol% H2O) in a laboratory furnace. Different exposure times were used (24, 72 and 168h), and the effect of mixtures of CaCl2 and calcium carbonate (CaCO3) was also studied. The corrosion rate was gravimetrically measured, and the sample cross-sections were analysed with SEM-EDX to verify the impact of different elements on the corrosion. Full-scale measurements showed chlorine-induced low-temperature corrosion. The main species in the deposit were calcium and chlorine, and corrosion was observed at conditions at which CaCl2 deliquesces. The laboratory work showed that although the deposit contains mainly calcium carbonate, which is not deliquescent, the highest corrosion rate (>1 mm/year) was found with 5 wt% CaCl2 in the salt deposit mixture. The tests showed that the corrosion rate is linear with time, and severe corrosion of carbon steel occurs when CaCl2 deliquesces. Stainless steel did not show any measurable corrosion at the conditions tested.

KW - CaCl2

KW - Cold-end corrosion

KW - Hygroscopic deposits

KW - Biomass combustion

KW - Deliquescent salts

U2 - 10.1016/j.fuel.2023.128344

DO - 10.1016/j.fuel.2023.128344

M3 - Article

SN - 0016-2361

VL - 349

JO - Fuel

JF - Fuel

M1 - 128344

ER -

Cold-end corrosion in biomass combustion - role of calcium chloride in the deposit

Abstract

Funding

Keywords

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