燃用渣油锅炉炉内灰沉积的形成原因

Formation of Ash Deposit Within Residual Oil Burning Boilers

研究了某燃用渣油锅炉不同受热面的多个灰沉积样品,对燃料油灰和燃料油固体沉淀物的组成做了分析,得到了不同受热面灰渣沉积组分分布。分别用X射线荧光光谱(XRF)分析仪,扫描电镜及能谱仪(SEM-EDX)和X射线衍射分析仪(XRD)鉴定了样品的元素组成、形貌学以及晶相。并用热分析(DSC和TG)确定油灰矿物质转变温度。结果表明:炉膛内主要沉积矿物为莫来石,燃料油灰主要晶相为八面沸石,油灰约在980℃开始出现明显的放热峰,表明油灰中主要组分这时开始转变为莫来石晶相,这一晶相转变过程伴随着强烈的放热效应,从而表明辐射受热面莫来石沉积主要来源于原油催化裂化阶段的添加剂;高温过热器沉积物主要为莫来石和一些玻璃体,方石英与斜长石(钾铝硅酸盐);而低温过热器与省煤器上则出现一些钒酸钠、钒酸铁与硫酸钙沉积,它主要由燃料油本身所含矿物质经高温转化而来。

Chemical compositions of ash deposited on different heat delivery surfaces of a certain residual oil burning boiler are found to differ from on another according to an deposits were revealed. With XRF （ X-ray fluorescence） analysis of respective samples wherewith their origins of these spectroscopy, SEM-EDX （ scanning electronic microscopy with energy dispersive X-ray） spectrometetry and XRD techniques, the chemical composition as well as the morphology and mineralogy characteristics were identified. The oil ash was also subjected to a thermal analysis （DCS plus TG） to determine the transition temperature of the minerals contained. Results show that the main crystalline phase of deposited ash in the surface is of the mullite type, while tha tof the oil ash is faujasite. Obvious exothermic peak, observed at 980~C on the DSC curve, indicates that the main content of 0il ash starts to turn into mullite at 980~C, during which large amount of heat is released. This proves that mullite deposits in the radiation heat absorption area mainly comes from additives used in the original oil＇s cracking stage. Deposits on the second stage （high temperature） superheater surface mainly contaiin mullite（mostly coming from cracking additives）, vitreous matter, cristobalite and microcline （potassium aluminosilicate）, while those on the first stage（low temperature） superheater and economizer surfaces, consist of sodium vanadate, ferrite vanadate and calcium sulfate, which mainly come from minerals contaiined in the original oil itself and are deposited in the rear part of the boiler after having undergone a conversion under high temperature conditions in the furnace. Figs 3, tables 4 and refs 9.