多变气氛下SiO2-Al2O3-CaO-K2O体系内生物质三重诱导结渣机制下的动力学耦合机理

Biomass slagging has became a restrictive factor in the safe and efficient operation of the power plants. However, due to the over-focus on the separated alkali-induced or silicates melt-induced slagging and the underestimation on interactions, the biomass slagging is pending until now. Recently, we found that the alkali-induced slagging, high- and low-temperature silicate melt-induced slagging are co-existed during the slagging process in biomass fired boilers, and there also exist complicate interactions between the triple slagging. Therefore, on basis of the results of the experiment conducted in drop-tube furnace and the coupling calculations of the self-complied intrinsic kinetics burning mode of particle, cellular automate theory, and alkali kinetic reaction mechanisms, a sophisticated intrinsic kinetics combustion-slagging code considering the triple slagging mechanisms and the dynamic combustion process of biomass particle are developed, meanwhile, the comprehensive effects of dynamic changed combustion temperature, atmospheres, ash components and melting properties on the triple slagging are revealed. In addition, according to the effects of SiO2、Al2O3、CaO and K2O on the kinetic generation properties of KCl and K2SO4 measured in tube furnace, the existed alkali kinetic reaction mechanisms are further perfected, and the skeleton reaction mechanisms and kinetic controlling reactions on the generations of KCl and K2SO4 are also acquired; take fully into account the experiment results of sintering tester, the evaluation indexes of the triple slagging are proposed. All those provide theoretical guidelines for biomass selection, mix, match and slagging prediction.

生物质结渣严重制约电站安全高效运行。当前研究主要聚焦于单一碱金属或者硅酸盐熔融诱导性结渣，而忽视彼此交互作用，导致生物质结渣问题至今未能合理解决。申请人前期预研表明碱金属诱导性、高温及低温硅酸盐熔融诱导性三重结渣并存于生物质锅炉内，且存在复杂交互作用。此外，生物质结渣评价指标还相对模糊。鉴于此，本项目借助沉降炉实验与颗粒本征动力学燃烧模型、元胞自动机理论及碱金属动力学反应机理模型的耦合计算，发展生物质颗粒动态燃烧过程中三重结渣相耦合的本征动力学燃烧结渣模型，揭示动态变化的温度、气氛、灰组分与熔融特性对三重结渣的综合影响。同时，基于管式炉内SiO2、Al2O3、CaO与K2O对KCl和K2SO4动力学生成特性的影响，完善现有碱金属动力学反应机理，并简化获取骨架机理与KCl和K2SO4动力学生成控制步骤；结合烧结仪熔融结渣研究提出三重结渣评价指标。为生物质选择、组合搭配与结渣预测提供理论支撑。

结渣已成为生物质燃烧发电的主要技术障碍与电站安全运行的制约因素。本项目将生物质燃烧结渣概括为碱金属诱导性，高温及低温硅酸盐熔融诱导性结渣机理三类，并通过实验与动力学模拟研究获得如下主要结论：.随温度升高，KCl硫酸化率呈指数增加，KCl硅酸化程度升高至1300℃后受反应时间控制。硫酸化反应抑制硅酸化，但1000℃后抑制作用减弱。碱金属诱导性结渣主要受碱金属气溶胶（气相K）影响。链条炉内（1273K），添加高岭土可使~79.2%气相K转化为水不溶性K，SiO2（~77.6%）次之；流化床内（1088K），SiO2可转化62.5%的气相K，高岭土(~42.7%)次之。SiO2呈现较高的气相K移除效果，但SiO2可与KCl反应促进低温硅酸熔融诱导性结渣。基于气溶胶生成特性，发展了焦炭颗粒本征动力学燃烧模型与矿物质气化-同相成核-异相冷凝沉积-团聚模型相配合的超细颗粒物生成模型，为碱金属气溶胶颗粒生成研究提供基础。.IDT与FT分别可作为低温与高温硅酸盐熔融诱导性结渣评价指标，IDT和FT越高，低温和高温硅酸盐熔融诱导性结渣倾向越弱。灰组分对IDT影响显著性为：Al2O3 > -K2O > -SiO2 > SiO2/K2O > -SiO2/Al2O3 > -(SiO2+K2O)/Al2O3；对FT影响显著性为：-Al2O3 > K2O > SiO2/K2O > -SiO2/Al2O3 > -SiO2 > -(SiO2+K2O)/Al2O3。基于显著性影响水平分析，提出了低温与高温硅酸盐熔融诱导性结渣评价方法。另外，结合生物质灰特性与模拟灰特性分别绘制了K2O-SiO2-Al2O3三元相图与SiO2-Al2O3-CaO-K2O四元相图，提出了熔融颗粒粘附判定机制，并结合惯性碰撞沉积模型，建立了受热管壁沉积生长综合模型。.生物质结渣过程为含高浓度K、Na、Cl和S或者KCl和K3Na(SO4)2的微细粒子对含高浓度Si和Al浓度粗大飞灰粒子的捕捉，以及微细粒子的再富集与对粗灰粒子的再捕捉。当氯率(Cl+K2O+Na2O)/(SiO2+Al2O3)与硫率(Svolatile+K2O+Na2O)/(SiO2+Al2O3)分别高于2.4与1.9时，结渣严重；但当氯率与硫率分别低于1.0与0.5时，结渣轻微。.该研究为生物质燃料选择与组合搭配，进而全面预测并解决三重结渣提供理论支撑。