【作者】 张锐；

【导师】 刘巽俊；

【作者基本信息】 吉林大学 ， 动力机械与工程， 2004， 博士

【摘要】 在火力发电厂的电能生产过程中，约有5%10%的能量被其自身的辅助设备所消耗，其中制粉系统的能耗在辅助设备中占有较大的份额， 作为火力发电厂中间储仓式制粉系统中的重要设备-粗粉分离器，其结构设计以及分离性能的优劣，对磨煤机的寿命、电耗以及炉内燃烧等有重大影响，因此，粗粉分离器的工作性能直接影响到发电厂的运行安全性和经济性。一个性能理想的粗粉分离器一方面要把合格煤粉随气流输出，另一方面要把大于规定粒度级的过粗煤粉分离出来，返回磨煤机重磨，而不随合格煤粉进入炉膛，以免影响锅炉燃烧稳定性和燃烧效率。目前我国大多数电厂采用的粗粉分离器源于前苏联20世纪5060年代常见的径向型分离设备，其中如吉林省浑江发电厂3、4锅炉的粗粉分离器就是这一类型，它们的结构特点是采用内外筒体双回粉管。气粉混合物在内外筒体间进行一级重力分离，使粗粉落入外回粉管。分离器顶部有径向螺旋形导流档板，使气流产生旋转运动，使不合格的煤粉落入内回粉管。这种粗粉分离器的主要缺点是分离效率不高，流动阻力较大。在运行过程中，这种分离器的内回粉管易于堵塞，不易清理，造成分离效率进一步下降。本文围绕这种粗粉分离器的改进，进行了下列理论研究和现场试验工作：（1）技术改造根据国内外现有的资料和电厂现场的运行经验，对现场的径向型粗粉分离器进行技术改造。分离器的螺旋档板由原来的顶部径向布置改为在内外筒体间的上部轴向布置，一方面加强旋流作用，同时保持较小的阻力损失。内外筒体<WP=105>间的下部加装两级惯性档板，取消内筒体中的回粉管，只用一个外筒体回粉管。气流入口管由原来的直管改为扩口管。含煤粉的气流从入口管自下而上流入整个筒体间的分离腔，由于入口管断面渐扩，流速下降，最粗的煤粉在重力作用下落入回粉管。气流撞到惯性档板时，一部份粗煤粉被惯性分离。气流继续上升，流经上部螺旋档板时，产生强烈旋流，又一部份粗煤粉经离心分离作用甩到外筒壁面上，进而落入回粉管。新型粗粉分离器的特点是分离效率高，流动阻力小，降低制粉系统能耗。（2）数值模拟对改造前和改造后的粗粉分离器进行三维两相流的对比性数值模拟。采用GAMBIT网格生成软件对复杂的分离器流场进行网格化。采用FLUENT商品软件，将气相流动模拟与颗粒相的随机轨道模型相结合，进行三维的两相流模拟计算。首先针对一组边界条件和单一粒度的煤粉进行分离器改造前后流场中的气流速度场、颗粒速度场、压力场和颗粒体积分数场的模拟，求出数值解，并进行分析和讨论。算出了分离器的流动阻力和单分散分离比率。然后针对实际煤粉粒度范围内的多种粒度进行类似的计算，得出相应的各粒度煤粉分离比率，按粒度分布加权得出多分散分离比率，最后算出粗粉分离器的工作效率。（3）变参数研究对改造前后的粗粉分离器进行变参数数值模拟。结果表明，改造后粗粉分离器的工作效率从改前的33.41%提高到53.49%，阻力损失从1150Pa降低到750Pa。按照已确定的模拟方法，针对不同结构参数（如螺旋档板倾斜角）和不同运行参数（进风速度、入口体积分数）进行数值模拟，得出这些参数变化对分离器工作效率和流动阻力的影响，经过数学回归，导出了反映这些变化关系的回归公式。（4）试验验证在浑江发电厂针对改造前后的粗粉分离器进行了现场试验，测定了粗粉分离器的工作效率和流动阻力。试验证明，技术改造后，粗粉分离器工作效率提<WP=106>高10%以上，流动阻力降低400Pa以上。虽然试验数据与数值模拟结果有一些差别，但改造的成功得到了完全的证实。粗粉分离器改造后，制粉系统能耗率大大下降。根据浑江以电厂4号炉乙制粉系统统计，制粉能耗从改造前的30 kW·h/t降到改造后的24 kW·h/t。按制粉量50t/h，锅炉年运行6000h计算，一台锅炉年节电180万kW·h,约合人民币45万元。把三维两相流数值模拟技术应用于本文的新型粗粉分离器的结构改进和性能评估，在国内还未见报导。这种研究，加强了对粗粉分离器中复杂的两相流动的认识，得到了由于现场条件的限制，不易实测的大量数据，为粗粉分离器及类似设备的技术改造和新结构的开发提供了有用的技术平台。更多还原

【Abstract】 Nearly 5%～10% of generated energy is consumed by its own auxiliary equipments during the energy generation in the power plant. The great portion of energy is consumed by the coal powder preparation system.The coarse coal powder separator as the major equipment of the intermediate storehouse type coal powder preparation system in the power plant, its structural design and working performance have great influence on the performances of the total power plant, such as the life-span of coal mill, the consumed electric power, and the burning of the coal powder in the boiler furnace, etc. Therefore, the quality of the coarse power separator directly affects the security and economy of the power plant operation. An ideal coarse coal power separator should have two unique characteristics as follows: on the one hand, the acceptable fine coal powder can be exported fully with the air flow; on the other hand, the over-sized coal powder can be returned fully to the coal mill to mill again. In the condition of the over-signed coal powder is not allowed to supply into the boiler furnace with the acceptable fine coal powder, the burning efficiency and stability in the furnace will be assured. In the recent years, many coarse coal powder separators used in China power plants, such as the original coarse coal powder separator in No.3 and No.4 boilers in Hunjiang power plant of Jilin province, were derived from the radial-type separator commonly in the former Soviet Union in 1950s~1960s of the 20 century. The separator structure is characterized by internal and external double coal powder retrieving pipelines. The gravitational separation of the air-coal powder mixture <WP=108>occurs between the internal and external cylinders of the separator at first, and the most coarse coal powder returns into the external retrieving pipeline. At the top of the separator there is a ring of radial spiral barriers, which make the air-coal powder mixture rotate around the vertical axis, thus the finer but still unacceptable coal powder falls into the internal retrieving pipeline under the action of the centrifugal force. The main disadvantages of this type of separator are low working efficiency and high flow resistance. Besides, the internal coal powder retrieving pipeline is prone to clog and difficult to clean, resulting in further deterioration of separator performance.In this dissertation, around the topic of the improvement of coarse coal powder separator, following tasks has been accomplished:Modification of separator structure Based on domestic and foreign literatures and the operation experience at the power plants in our province, technical modification was made to the original radial type coarse coal powder separator to form the novel combinational coarse powder separator. The swirling barriers of the separator change from the radial mount on the top to the axial mount between the internal and external cylinders. The axial swirling barriers enhance the rotational movement of the air, coal powder mixture and at the same time exert relatively little resistance on the mixture flow. Two rings of inertia barriers are added in the lower part of separator on the internal cylinder. The internal coal powder-retrieving pipeline is removed and the external retrieving pipeline around the inlet of flow retrieves the all of the over-sized coal powder. The expanding mouth pipeline replaces the original simple straight entry pipeline. The flow of air with coal powder passes through the entry and performs the gravitational separation of the most coarse coal powder in the expanded space between the internal and external cylinders. The <WP=109>air-coal powder mixture flow rises from the bottom to the top of the separator. When the mixture flow strikes on the inertia barriers, a part of the coarse coal powder is separated further by the particle inertia. As the mixture flow rises further and passes through the top axial swirling barriers of the separator, a strong helical rotating ascending mixture flow forms. After the mixture flow enters更多还原