【作者】 李进春；

【导师】 李双跃；

【作者基本信息】 西南科技大学 ， 机械制造及其自动化， 2009， 硕士

【摘要】 涡流空气分级机广泛应用于粉煤灰分选,但较细的分级粒度要求与分级效率、分级精度、大处理量之间的矛盾,以及能耗高和部件磨损严重等仍亟待解决。本文根据与分级相关的粉煤灰物化特性,以气-固两相流理论为基础,研究颗粒的分级原理,提出SLK分级原理,通过气-固两相流数值模拟分析,结合实践经验进行SLK分级机结构设计,并进行模型机实验和工业应用实例分析。根据粉煤灰利用及其相关物化特性,以气体-固体颗粒两相流理论为基础,提出了集强制涡流分级、迅速分级、惯性预分级、气流密封、颗粒的气流预分散原理于一体的SLK分级原理和技术。运用强制涡流分级原理并进行改进,保证较高的分级效率和精度,以及较低的能耗;迅速分级以减少颗粒在分级区域内的滞留时间,从而减少团聚,减少颗粒反混,提高分级效率和精度,同时减少分级区速度梯度,分级构件的磨损小;惯性预分级可预分离部分粗颗粒,提高分级机的处理量;气流密封高速旋转叶片产生的高压气流进行密封,提高分级精度;气流预分散对物料进行预分散,有利于后续的分级,同时分离部分硬杂物,避免分级机构件损坏。运用两相流数值模拟技术对SLK分级结构进行分析,结果表明:内、外侧倾角均为30o的“Z”形转子叶片能有效消除强制涡流区易产生的惯性反旋涡现象,分级流场更加均匀和稳定;“L”形导流叶片使进入分级区的气流速度与转子边缘速度相当,实现迅速分级,同时缩小分级区气流速度差,减少叶片磨损;安装倾角为55o的“L”形导流叶片,使含料气体路径发生偏转,实现惯性分级;后倾角为60o的密封叶片、密封环低于叶片15～20mm的气流密封结构能有效阻止粗颗粒穿过;气流预分散系统采用凹形空腔物料分散锥和粗粉流化清洗装置,可实现颗粒的分散和预分离硬杂物。以分级理论分析和数值模拟结果为指导,并结合实践经验进行SLK分级机结构设计,包括“L”形导流叶片、“Z”形转子叶片、分级室结构、分级区环流空间结构、气流密封结构、悬浮式气流预分散系统、粗粉流化清洗装置。通过SLK-50型模型机实验和SLK-85应用实例,结果表明:SLK型分级机在较低转速下,所分选的成品就可达到Ⅰ级粉煤灰的粒度要求,而且分级效率平均可达85%左右。SLK分级机在较高的分级浓度下,仍能获得较高的分级细度、分级效率和分级精度,且分级磨损小、分级能耗有所改善。更多还原

【Abstract】 Vortex air classifier is wide used to classify coal ash, but the contradiction among fine particle size and high classifying efficiency, high precise, high feeding capacity, as well as the high energy consumption and parts abrasion are all demanding prompt solution. Based on the physical and chemical characteristics related to particle classification of coal ash, theory of air solid two-phase was took to study classification principle, and SLK classification principle was put forward, air solid two-phase numerical simulation was adopted to analyze classification principle. With the combination of numerical simulation result and design experience, the structure of SLK classifier was designed, then put on classifying experiments on model SLK classifier and industry application analyze.Based on the application of coal ash, as well as physical and chemical characteristics related to particle classification of coal ash, SLK classification principle which was united forced vortex classification, rapid classification, inertia pre-classification, air sealing and material pre-dispersion by air flow was put forward. Forced vortex classification principle was applied and improved, in order to guarantee higher classifying efficiency and precise and lower energy consumption. Rapid classification was applied to the classification housing, to shorten the time particles resort in the classification zone, so particles agglomeration and back mixing can be reduced, to improve classifying efficiency and precise. And by applying of rapid classification, velocity gradient in the classification zone can be decreased, so lessen the parts abrasion. Parts of coarse particle can be separated by inertia pre-classification, and the result was promoting feeding capacity of classifier. High pressure air flow generated by high rotate speed vanes were applied to air sealing, improving classification precise. Material pre-dispersion by air flow was profit for later classification, and simultaneity parts of big stone mixing in the material were separated, avoiding damage of structure in the classifier housing.Air solid two-phase numerical simulation was adopted to analyze SLK airflow guiding structure, the results show that: inertia counter-rotation between plane rotor vanes could be reduced by using of Z-shape rotor vanes, the airflow between vanes was steady and uniformity. The velocity of airflow into the classification zone was close to velocity of outer edge of rotor by using of L-shape guide vanes, this principle could achieve rapid classification, and simultaneity speed difference in the classification zone could be reduced, to lessen abrasion of rotor vanes and guide vanes. Path of the air-solid flow was deflected by using of L-shape guide vanes which installing obliquity is 55o, this principle could achieve inertia pre-classification. The bypass of classifier was reduced by applying of air sealing structure which was composed of 60o obliquity vanes and seal ring whose height is lower 15～20mm than vanes. Particle dispersion and separation of big stone mixing in the material could be achieved by using of material dispersion concave cone in the material-dispersion-by-air-flow system.Based on the theoretical analyze and numerical simulation results, and combine with classifier design experience, the structure of SLK classifier was designed, which was composed of L-shape guide vanes, Z-shape rotor vanes, classification housing structure, circumfluence structure in the classification zone, air seal structure, structure of suspending material dispersion by airflow and device of coarse particles washed by airflow.The experiment results of SLK-50 model type and application program of SLK-85 proved that: the fine product of SLK classifier could achieveⅠgrade of national standard of coal ash under low rotor speed, and average classification efficiency was about 85%. The SLK classifier could achieve high degree of fineness and high classification efficiency and precise under large feeding capacity,更多还原