Low-Temperature Corrosion in Biomass Boilers Fired with Chemically Untreated Wood Chips and Bark

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• 作者：Stefan Retschitzegger ; Thomas Brunner ; Ingwald Obernberger
• 刊名：Energy & Fuels
• 出版年：2015
• 出版时间：June 18, 2015
• 年：2015
• 卷：29
• 期：6
• 页码：3913-3921
• 全文大小：504K
• ISSN：1520-5029

文摘

Low-temperature corrosion often causes failures of cold-end parts (economizers, air pre-heaters, and fire tubes of hot water boilers) in biomass boilers firing chemically untreated wood chips and bark. The most relevant mechanisms causing low-temperature corrosion are condensation of acids and hygroscopic salts in the deposits on heat-exchanger surfaces. This article offers a short review on acid condensation and presents a detailed study on the formation of hygroscopic salts, which may absorb moisture from the flue gas to such an extent that they are dissolved and form highly concentrated salt solutions. Typical fuel compositions of wood chips and bark in combination with typical operating conditions of biomass grate furnaces have been used to estimate the compositions of ash deposits on heat-exchangers. Based on these compositions, thermodynamic equilibrium calculations have been conducted in the range of 70鈥?00 掳C, which have revealed that the hygroscopic salts K₂ZnCl₄, KCaCl₃, and CaCl₂ can be formed at these conditions. Finally, recommendations are given on how to minimize the risk for low-temperature corrosion.