稀土掺杂Mn-Zn-O固溶体制备、改性并在循环流化床锅炉燃烧中降磨损作用机理研究

The pipe bursting and boiler closing down which were caused by pipe wearing in the heating surface had been seriously affected the operation of coal-fired circulating fluidized bed (CFB) boiler in Innermongolia area. Based on the preceding work, RE-doped Mn-Zn-O solid solution would be prepared and modified in this project. Then the melt structure of coal ash in the simulating combustion of CFB were controlled and its pattern were changed from irregularity to spheric or ellipsoidal shape in order to reduce the pipe wearing in heating surface. This project include three parts. Firstly, the RxOy (CeO2, La2O3) doped MnO2-ZnO(or MnO2-Fe2O3, MnO2-CuO, ZnO-CuO) were prepared and modified. Their physicochemical properties were characterized. Secondly, the solid solution, raw coal and limestone flour were mixed and combusted in the simulating operation mode of CFB. The melt structure of coal ash and desulphurizing efficiency were characterized. The mechanics of melt structure of coal ash and its pattern were also analysed. Thirdly, the theory model of the component and stucture of RE-doped Mn-Zn-O solid solution, the modified technology and the patterns of coal ash would be builted. According to this model, the patterns of coal ash were disigned and controlled in the combustion of CFB. The research findings of this project would be applied in the large-scale coal-fired CFB boiler.

本项目基于内蒙古地区循环流化床燃煤发电锅炉运行中受热面管材磨损严重导致爆管停机重大生产难题，在前期工作基础上制备稀土掺杂Mn-Zn-O固溶体并改性处理，进而在循环流化床锅炉模拟燃烧过程中控制煤灰固熔体结构生成并促使其形貌从不规则状向球形、椭球形转变，从而降低受热面管材磨损减少爆管停机事故，从根本上解决循环流化床锅炉受热面磨损爆管难题。具体研究内容包括：①制备不同组分RxOy(CeO2,La2O3)掺杂MnO2-ZnO(或MnO2-Fe2O3,MnO2-CuO,ZnO-CuO等)固溶体结构并改性处理，进行理化性能测试分析。②混合固溶体、原煤、脱硫剂石灰石粉开展模拟燃烧试验并测试煤灰结构及脱硫效率，分析燃烧过程中煤灰固熔体结构形貌及生成机理。③建立稀土掺杂Mn-Zn-O固溶体组分构成、改性工艺及煤灰形貌改变之间的理论模型，实现循环流化床锅炉燃烧煤灰形貌改变可控性，为工业化应用奠定基础。

本项目基于循环流化床燃煤发电锅炉运行中受热面管材磨损严重导致爆管停机事故以及炉膛内燃烧脱硫效率低下重大生产技术难题，采用共沉淀方法制备了CeO2掺杂MnO2-Fe2O3、MnO2-Al2O3、MnO2-CuO三种固溶体结构，并分别以5%柠檬酸钠、5%乙醇溶液、5%十二烷基硫酸钠溶液、5%十二烷基磺酸钠溶液为改性剂进行改性处理，进而与煤粉、脱硫剂石灰石混合进行燃烧改性及脱硫试验，在此基础上确定CeO2掺杂固溶体结构各组分最佳配比并成型加工至Φ0.8-1.2mm微球，然后开展循环流化床锅炉中试试验，项目最后在实验室及中试试验基础上，在神华神东萨拉齐电厂330MW机组开展了工业试验，取得较好的试验效果。.本项目所制备CeO2掺杂固溶体结构分别以羧甲基纤维素钠、水玻璃为粘结剂通过高速混合、挤压制粒、滚圆成型工艺的球状成品，其中以羧甲基纤维素钠作为粘结剂得到CeO2掺杂MnO2-Fe2O3微球效果最佳，其堆积密度、比表面积、抗压强度分别为1.84g/cm3、67.52m2/g、2.88MPa。分别以不同 CeO2掺杂固溶体添加量（0.3%、1.0%、2.0%）、不同钙硫比（Ca/S=2.0,2.5)、不同燃烧温度（850℃、950℃、1050℃）在循环流化床锅炉燃烧后灰渣微观形貌、能谱分析结果与未添加时相似，均为块状、不规则状，且灰渣中均含O、Ca、Si、Al、Fe、S、Na、Te等元素，说明CeO2掺杂固溶体对燃烧中灰渣形貌改变效果一般，但对提高脱硫效果有较明显改善，在330MW循环流化床燃煤发电锅炉工业化试验中，可将万度发电量所耗石灰石粉量由0.20吨/万度左右降低至0.17吨/万度。.本项目通过实验室制备CeO2掺杂固溶体粉体及模拟燃烧试验，然后成型加工至成品进行中试试验，并在此基础上进行总结调整，最后进行工业化推广应用，形成了较完整的研发路线，通过在神华神东萨拉齐电厂#2机组应用，初步证明本课题技术路线可行，为解决循环流化床燃煤发电机组脱硫效率低下及受热面管材磨损严重技术难题提供了技术可行途径。