How the Metal Wall in Furnace Is Corroded?

The agricultural straw contains 1% higher potassium and other metals. The chlorine content in straw reaches to 0.2% or 3%. High chlorine content is the feature to differentiate the agricultural straw from other mineral fuels like coal. During the working process of heating furnace, chlorine and other chlorides can greatly corrode the cooling pipe.

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While, the oxidizing atmosphere can be produced in furnace and cover the cooling pipe with a layer of thick oxide-protective film. The film can protect the metals from being corroded. While, the HCI and Chlorine can penetrate the protective film and react with steel to produce the ferric chloride.

Since temperature in furnace is very high and oxidizing atmosphere is intense, the ferric chloride is rapidly oxidized into the ferric oxide. As time goes by, the layer of ferric oxide will become more and more thick. If sulfur dioxide and sulfur trioxide exist in furnace, the ferric chloride will react with them and produce the ferric sulfate and chlorine.

The chlorine will corrode the metal pipe again. Alkali chloride can react with the metal pipes or metallic oxide to produce the eutectic compounds. The melting point of eutectic compounds is very low, just about 350-450℃. The low melting point of eutectic compounds can worsen the slag-bonding problem.

Due to the difference of atmosphere and straw contents, the seriousness of slag-bonding and corrosion is different, too. No matter for what kind of materials or furnaces, the above two problems always exist. Price of wood pellet mill is in website!

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