【作者】 张小辉；

【导师】 刘正；

【作者基本信息】 沈阳工业大学 ， 材料加工工程， 2012， 博士

【摘要】 生物质资源的规模化利用对于解决化石能源日趋紧张和环境污染日益严重问题具有重大意义。农作物秸秆是我国生物质资源的重要组成部分之一，秸秆直燃热利用是生物质资源规模化利用的有效途径。然而由于我国秸秆资源高氯高碱金属的特点，在直燃热利用过程中引起受热面沉积以及高温腐蚀等问题，已经成为提高主蒸汽温度和压力来提高秸秆锅炉能源利用效率所必须面临的难题。为此，探讨了解秸秆直燃沉积腐蚀过程及腐蚀机理，探索沉积腐蚀防护技术是十分有必要的。本文先分析了我国生物质秸秆资源的数量及分布特征，主要以集中于北方地区的玉米、南方地区的水稻和小麦三大秸秆为主。探讨了生物质燃料检验标准及分析方法，对比分析了秸秆与原煤的燃料特性，分析结果表明：欧盟CET/TS和美国ASTM生物质燃料检验分析标准并不完全适合我国以农业资源为主的生物质燃料的检验分析，我国急需制定相应的生物质燃料检验标准和分析方法。我国生物质秸秆属于高氯高钾钠低硫燃料，其燃烧飞灰产物主要是碱金属氯化物；与生物质燃料相比，我国原煤属于高硫高钠钾、低氯或特低氯燃料，其燃烧飞灰产物主要是碱金属硫化物。根据生物质秸秆燃烧特性，本文还建立了基于秸秆燃料特性分析和一次供风配置的秸秆燃料层燃锅炉燃烧数值模型。通过床层燃烧模型，炉膛气相燃烧模型，以及两者之间的流动传热耦合，建立了层燃锅炉一体化燃烧模型，模拟分析秸秆燃料锅炉受热面热力学状态，研究炉内温度场。比较纯烧秸秆锅炉炉内截取的受热面管的积灰腐蚀成分分析检验结果，选择KCl、NaCl、K₂SO₄和Na₂SO₄等四种碱金属盐作为腐蚀介质并通过计算确定其质量配比为63:13:5:1；以500℃、550℃、600℃和650℃作为腐蚀反应温度，建立了秸秆燃料锅炉受热面沉积腐蚀模拟试验环境。选择锅炉厂提供的生物质锅炉常用管材1Cr19Ni11Nb、10Cr9Mo1VNb、12Cr1MoVG和20G，制备腐蚀试样进行腐蚀试验研究，探讨生物质秸秆锅炉受热面沉积腐蚀过程及腐蚀机理。根据生物质秸秆锅炉受热面沉积腐蚀模拟环境和元素的物理化学性质，选择Ni、Cr、Mo、Al和稀土等金属元素粉末作为粉芯材料、设计Ni-Cr粉芯丝材、电弧喷涂防护涂层进行秸秆燃料锅炉受热面沉积腐蚀防护技术的探索研究。四种管材腐蚀试验结果表明，各管材的抗腐蚀性能随着反应温度的升高而降低，四种管材的抗腐蚀能力1Cr19Ni11Nb＞10Cr9Mo1VNb＞12Cr1MoVG＞20G。运用热分析动力学分析理论建立了腐蚀过程动力学方程分析模型，通过腐蚀增重曲线求得热分析α-t曲线，根据G（α）-t曲线线性拟合及拟合误差分析得到腐蚀反应类型为D4类型，腐蚀机理函数符合G （α）=1-2/3α- （1 -α）^2/3函数模式。通过数学计算求得，试验模拟沉积腐蚀条件下，1Cr19Ni11Nb、10Cr9Mo1VNb、20G和12Cr1MoVG四种管材的反应活化能E分别为3632.88J/mol、1421.92J/mol、635.30J/mol和1027.70J/mol；指前因子A分别为0.026181558s^-1、0.019152922s^-1、0.017641521s^-1和0.018077269s^-1。通过扫描电镜对腐蚀试样的微观组织及元素组成进行分析，结果表明，腐蚀产物主要是Fe、Cr、Ni等元素的氧化物。防护涂层耐蚀性试验结果表明，两种Ni-Cr涂层的耐蚀性能随着反应温度的升高而降低，防护涂层明显提高了基体材料的抗腐蚀能力，同时发现1#涂层耐蚀能力要略优于2#涂层。运用热分析动力学分析理论，确定防护涂层腐蚀反应类型为D4类型，腐蚀机理函数符合G （α）=1-2/3α-（1-α）^2/3函数模式，1#和2#防护涂层的反应活化能E分别为4383.19J/mol和4284.97J/mol；指前因子A分别为0.022393154s^-1和0.020931502s^-1。结合光学显微镜和扫描电镜分析结果，可知高Ni-Cr材料耐氯腐蚀性能要优于普通合金材料，Cr元素虽然与Cl元素的亲和力强，但仍然具有一定的耐腐蚀性能，同时发现，Ni元素的耐氯腐蚀性能要优于Cr元素。总之，根据秸秆燃料特性，秸秆燃料锅炉受热面沉积腐蚀防护技术，要综合考虑碱金属的氯化物和硫化物的腐蚀特性，以氯化腐蚀防护为主、兼有硫化腐蚀防护。更多还原

【Abstract】 It is of great significance to utilize biomass resource in a large scale for substitutingthe fossil fuel and solving the environmental problems.Crop straw is one of the mostimportant parts of biomass resource in China.Direct combustion of straw is suit forutilizing straw in a large scale.However,during direct combustion of straw,its high contentof chlorine and alkali metal causes many problems,such as deposition of the heatingsurface and high temperature corrosion. All these problems must be faced when peoplewant to develop the straw fuel boiler energy utility efficiency with the developedtemperature and pressure of main steam.Therefore, it’s necessary to research themechanism and protection technique of the deposition corrosion of the heating surface.Firstly, this paper analyzes the quantity and distribution of straw resource. It givespriority to the straw of maize, rice and wheat, in which the maize straw is the largest innumber and distributes mainly in the north of China. It is followed by rice and wheatstraws which concentrate mainly in the south.This paper also discusses the inspectionstandard and analysis method of biomass fuel, and compares fuel properties of the strawand coal in China. The analysis discovers that CET/TS and ASTM are not suitable forinspection analysis of agriculture resources in our country, so inspection standard andanalysis method of biomass fuel urgently needs to be developed in our country.Thecharacteristics of the biomass straw in our country lie in high chlorine,high potassium,highsulphur and low sulphur. So its combustion products are mainly alkali chlorine.However,coals in our country contain high sulphur, high sulphur,high potassium and low chlorine.Itscombustion products are mainly alkali sulphur.According to the characteristics of the biomass straw，this paper develops a numericalmodel of travelling grate boiler combustion of the straw fuel, based on the straw fuelanalysis and primary air as the input conditions. The model of integrated travelling grateboiler combustion comprises bed model, furnace model and their coupling model. The simulation analysis focuses on its thermodynamic state and temperature field in the furnaceof boiler. Compare of composion test results of deposition corrosion of the heating surfacein pure straw burning boiler, this paper establishes corrosion sedimentary environment ofthe straw fuel boiler, the corrosive compound is made of KCl,NaCl,K₂SO4and Na2SO4,mass ratio of KCl: NaCl: K₂SO4: Na2SO4is 63:13:5:1, and corrosion reaction temperatureis 500℃, 550℃, 600℃and 650℃. In order to explore depositon corrosion process andcorrosion mechanism of heating surface in straw boiler,the experiments of hightemperature corrosion are conducted to simulate deposition condition in biomass boilerheating surface for four kinds of materials: 1Cr19Ni11Nb, 10Cr9Mo1VNb,12Cr1MoVGand 20G. According to the biomass straw boiler heating surface deposion corrosionenvironment and physical and chemical properties of elements,Ni,Cr,Mo,Al and rare-earchmetal elements fine powders are used as corrosion pretection matericals.The Ni-Crprotection coatings are prepared with arc spraying to research its corrosion resistance indeposition condition in biomass boiler heating surface.The results show that corrosion resistance decreases as temperature rises andcorrosion resistance of four kinds of materials is 1Cr19Ni11Nb＞10Cr9Mo1VNb＞12Cr1MoVG＞20G.According to thermal analysis and kinetic theory，it sets the model ofdynamics analysis for corrosion process.The thermal analysisα-t curves are plotted byusing the mass gain curves.The D4 corrosion reaction type is plotted by using G（α）-t linearfitting curves and fitting error. The corrosion mechanism function isG （α）=1-2/3α- （1-α）^2/3.Under simulation test of deposition corrosion of heatingsurface in straw boiler conditons, these kinds of 1Cr19Ni11Nb,10Cr9Mo1VNb,20G and12Cr1MoVG materials activation energy E and pre-exponential factor A in the reactionhave been calculated,which are 3632.88J/mol,1421.92J/mol,635.30J/mol,1027.70J/moland0.026181558s-1,0.019152922s-1,0.017641521s-1,0.018077269s-1.The metal elements areanalyzed after the experiment using SEM-EDS method to detect the appearance，theelement contents and the compositions of the corrosion products. The results show that thecorrosion products are mainly Fe oxide，Cr oxide and Ni oxide.The results of arc spraying protection coatings corrosion test show that two kinds ofNi-Cr coatings corrosion resistance decreases as temperature rises.The anti-corrosionabilities of two coatings are better than body metal. And the anti-corrosion abilities of 1#coating are better than 2# coating. The D4 corrosion reaction type are plotted by usingthermal analysis and kinetic theory. The function of corrosion mechanism is G （α）=1- 2/3α- （1-α）^2/3.The kinds of materials activation energy E andpre-exponential factor A in the reaction have been calculated,which are 4383.19J/mol,4284.97J/mol and 0.022393154s^-1,0.020931502s^-1.The activation energy value shows twokinds of protection coatings corrosion ability and mass gain curves are in agreement. Theelements of protection coatings are analyzed after the experiment by using Opticalmicroscope and SEM-EDS method to detect the appearance,the element contents and thecompositions of the corrosion products.The results show that the anti-corrosion resistanceof high Ni and Cr metals is better than that of common metal materials. Although thereaction activity of Cr and Cl is large,Cr still has some of the anti-corrosion resistance.And Ni’s corrosion resistance is more excellent than Cr in the chlorine corrosionenvironment.In conclusion, according to the characteristics of the biomass straw fuel,the corrosionmechanism and protection technology of deposition of the straw boiler heating surfaceneed take chloride and sulfide corrosion of alkali into consideration, given priority tochlorinated corrosion incorporated with sulfide corrosion.更多还原