2025/6/2127.5AshdepositandcorrosionofhightemperatureSH

§7-5过热器、再热器的高温积灰与高温腐蚀1.Ashdeposit高温积灰在高温烟气环境(700~800oC)中飞灰沉积在管束外表面的现象。（Fly-ash飞灰）Basedonashfusibility根据煤灰的易熔程度Low-melting低熔灰：金属氯化物和硫化物(NaCl,CaCl2,MgCl2,Na2SO4,Al2(SO4)3)等，其熔点在700~850oC;Middle-melting中熔灰：FeS,Na2SO3,K2SO4等，其熔点在900~1100oCHigh-melting高熔灰：纯氧化物(SiO2，Al2O3,CaO,MgO,Fe2O3),熔点在1600~2800oC。Particlesize飞灰直径分:细径灰群(10微米)、中径灰群(10-30微米)和粗径灰群(30微米)三个灰群。

2025/6/2137.5AshdepositandcorrosionofhightemperatureSH

§7-5过热器、再热器的高温积灰与高温腐蚀Corrosionisnearlyalwaysassociatedwithsinteredorslagtypedepositsthatarestronglybondedtothetubes.Suchdepositsconsistofatleastthreedistinctlayers.Outerlayer外层灰：elementalcompositionconstitutesthebulkofthedepositandhasansimilartothatofash.松散，容易清除Intermediatelayer中间层：frequentlycalledthewhitelayer,isawhitetoyellowcoloredmaterialwhichvariesinthicknessfrom0.76to6.35mm.Itusuallyhasachalkytexturewherecorrosionismildornonexistent,butisfusedandsemi-glossywherecorrosionissevere.Inthelatterconditionthislayerisdifficulttoremoveasitissofirmlybondedtothecorrodedsurfacebeneath.紧密，与管子粘结牢固，不容易清除。Innerlayer内层灰：Thislayeriscomposedprimarilyofcorrosionproducts,i.e.,oxides,sulfides,andsulfatesofironandotheralloyingconstituentsinthetubemetal.Itseldomexceeds1.59mmthicknessoncorroded18Cr-8Nistainlesssteeltubes,probablybecauseofitsstrongtendencytospallwhenthetubescool.主要的腐蚀。

2025/6/2147.5AshdepositandcorrosionofhightemperatureSH

§7-5过热器、再热器的高温积灰与高温腐蚀1.Ashdeposit高温积灰HarmDisadvantage积灰的危害增加传热热阻增加烟气流动阻力引起受热面高温腐蚀

2025/6/2157.5AshdepositandcorrosionofhightemperatureSH

§7-5过热器、再热器的高温积灰与高温腐蚀1.Corrosionmechanisms高温积灰形成机理Theelementsincoalashcorrosion(sodium,potassium,aluminum,sulfurandiron)arederivedfromthemineralmatterincoal.Duringthecombustionofcoal,thesemineralsa