PDF《博士学位论文公示材料》

温度高于

600 ℃时,生物质灰 样出现烧结结构,815 ℃时,随灼烧时间增加,灰粒表面逐渐熔化;

同一温度下灼烧时,灰颜色先由黑 变为灰白,最后呈浅红;

气化灰的熔融过程具有分段失重机制,其总失重和最大失重速率随氧含量升 高而增加;

灼烧灰在有氧气氛中熔融时出现分段失重规律,而惰性气氛中未见明显的分段规律. 在上述研究的基础上,利用扫描电子显微镜和能谱分析联用技术对生物质灰在沾污结渣过程中的 微观结构演化以及碱/碱土金属的热迁移和转化规律进行了研究,同时基于飞灰的颗粒特性、烧结和熔 融粘结特性、微观结构演化等分析结果深入探讨了生物质灰的沾污结渣机理,提出了有效减少沾污结 渣的新途径和新措施,并运用多指标判别法对不同生物质灰的沾污结渣倾向进行了预测和对比,获得 了灰化温度对沾污结渣及碱/碱土金属热迁移的影响.灰化温度升高,生物质灼烧灰中出现明显的团聚 结渣,灰渣表面逐渐有碱金属物质析出并以熔融态存在,进一步加剧灰沾污结渣现象,而生物质气化 灰熔融时,氯化物从飞灰颗粒内部析出并移向外表面,这是造成渣块内部多孔和外部凸起结构的主要 原因. ―2― 最后针对生物质气化站旋风除尘器内高温流场运动复杂、飞灰颗粒浓度测量受限等问题,基于计 算流体动力学原理,提出了对高温气相流场采用 RNG-RSM 联用的强旋湍流模型,对颗粒场采用多相 流-单元内源项颗粒群模型,以气化炉产出的高温粗燃气为研究对象,借助 FLUENT 软件应用气体-颗 粒耦合数学模型对高温旋风除尘器内风流-飞灰耦合运移规律进行了模拟研究,获得了高温强旋湍流场 的三维速度分布和飞灰颗粒的浓度分布规律,较好地预测了高温燃气进口速度与分离效率的关系,结 果表明分离效率随燃气进口速度的增加而呈现先升后降的趋势,模拟结果与相关实验数据吻合较好, 结合数值模拟结果提出了适用于高温旋风除尘器捕集和脱除生物质飞灰颗粒的优化措施和建议,以减 轻后续设备的沾污结渣程度,这对于工程实际具有重要实用价值. 论文摘要(英文) A large amount of biomass ashes can be generated during the thermochemical conversion of biomass. These fly ashes are prone to melt and volatilize at high temperatures, which easily causes great harm for the heat transfer surface of boilers and equipments, such as fouling, slagging, and corrosion, etc. This poses a great threat to the safe and steady operation of biomass thermochemical conversion system. So it is of important and practical significance to conduct an investigation on the ash fouling and slagging problems, as well as removal of fly ashes. Aiming at preventing and controlling the harm of fouling, slagging, and corrosion, this paper proceeded a fundamental study on the key scientific issues on ash-induced problems from the point of problems of existing studies, including particle characteristics of fly ashes from biomass conversion, pyrolysis behavior of biomass, optimal condition for reducing fly ash generation, sintering and melting properties of various biomass ash, ash fouling and slagging properties, thermal migration and transformation behavior of alka........