Abstract: Experiments investigating transformation,deposition and corrosion behaviour of ash were carried out in a large-scale wastewater incineration plant.Ash deposited samples were collected from the surfaces of heat transfer tubes after operating period of 15 d and characterized using analytical techniques such as X-ray fluorescence spectrometer(XRF),scanning electron microscope coupled with energy dispersive spectroscopy(SEM-EDS)and X-ray powder fluorescence(XRD),to determine their chemical composition,morphology and mineralogy.The results show that Na which volatilizes during wastewater incineration has an even distribution on whole region flue gas flows,while non-volatile elements,Ni and Fe which are transported by ash particles have strong deposition trends at region of high temperatures.Element S is significantly enriched at region of low temperatures.Release and transformation of numerous Na and S as well as heat transfer process during incineration are the key issues for fouling/slagging and deposits growth in the HRSG.Condensation of Na species on surface of heat transfer tube forms a sticky deposition layer,which increases sticking probability of ash particles.At region of high temperatures,main components in ash deposits are Na₂SO₄,NiO and Fe₂O₃.While at 660-900℃,eutectic mixtures with much lower melting temperatures,such as sodium iron sulfate(Na₃Fe(SO₄)₃),nickelblodite(Na₂Ni(SO₄)₂·4H₂O)are formed.They are temperature-dependent and can enhance formation of sintered deposits.Acidic salt sodium sesquisulfate Na₃H(SO₄)₂ is generated at low temperatures and should be responsible for the initiation of low temperature corrosion.

Key words: wastewater incineration, fouling and slagging, volatile/non-volatile elements, eutectic mixture, corrosion

摘要： 以一台化工废液焚烧炉为研究对象,研究炉内的积灰、结渣与腐蚀行为。利用X荧光光谱仪、扫描电镜、X射线衍射仪对样品的元素组成、微观相貌以及矿物组成进行分析。结果表明,化工废液中高浓度的Na、S在焚烧和换热过程中的转化机理是影响飞灰粒子沉积和管壁腐蚀的关键因素。XRF元素分析显示,沉积物样品中的元素成分基本相似,但是由于挥发性不同,表现出不同的分布、沉积特征,Na在整个取样范围内分部均匀,而Fe、Ni沿烟气流动方向逐渐降低,S则在低温段表现出富集的特征。在660~900℃,碱金属硫酸盐与气相SO₂/SO₃以及Fe₂O₃和NiO发生反应生成的低熔点共晶体,即碱-铁硫酸盐Na₃Fe(SO₄)₃和硫酸镍钠Na₂Ni(SO₄)₂,能够加剧已沉积粒子的烧结和诱发高温腐蚀;在低温段检测到的Na₃H(SO₄)₂表明低温腐蚀的出现。

关键词: 废液焚烧, 积灰结渣, 挥发/非挥发元素, 低熔点共晶体, 腐蚀