【作者】 杨阳；

【导师】 安连锁；

【作者基本信息】 华北电力大学 ， 流体机械及工程， 2014， 博士

【摘要】 石膏旋流器是火电厂石灰石-石膏湿法烟气脱硫系统的重要设备,主要作用是对吸收塔中脱硫反应的副产物石膏浆液进行浓缩和分级,经真空皮带机脱水后生成的脱硫石膏广泛应用于水泥、建筑等领域。石膏旋流器在实际生产过程中存在底流夹细、分级效果不理想等问题,不仅干扰整个脱硫系统的正常运行,还会影响生成石膏的品质。因此正确认识旋流器内部的流动特性,设计高效节能的石膏旋流器具有重要意义。本文阐述了旋流器内流场的流动特性,对不同排口比的石膏旋流器进行性能实验,得到了分股比、底流浆液密度、底流排出方式、底流含固量等参数的变化规律,拟合得出分股比与排口比之间的关系式,并对排口比在0.3～1之间时,石膏旋流器的分级效率曲线进行了比较,分析了底流夹细现象的产生原因。利用Fluent软件,选取RSM雷诺应力模型与VOF流体体积模型,对固液旋流器中的重要现象——空气柱进行了数值模拟,包括其形成的整个过程、外观形状、三维速度场随时间、空间的变化,分析了空气柱对旋流器工作性能、能耗的影响,得到了空气柱直径随入口速度、溢流管与底流管直径以及介质密度的变化规律。基于空气柱带来的负面影响,设计倒锥形中心棒并选择合理的安装方式。对插入不同结构尺寸中心棒的石膏旋流器进行性能实验,得到入口压强、生产能力、底流与溢流浆液特性参数的变化情况,分析了中心棒对旋流器分级性能的影响,并以某4×600MW火电厂石膏旋流器的石膏生产情况为基础,通过计算得到了中心棒对整个实验系统的节能效果。为提高石膏旋流器的分级性能,设计具有分离块和隔板的新型旋流器入口结构。采用DPM离散相模型,对不同粒径石膏颗粒在新型入口中的运动情况进行数值模拟,分析了入口结构与入口速度对颗粒运动的影响,并对具有新型入口结构的石膏旋流器进行性能实验,得到了入口结构对指标参数的影响,通过分级效率曲线反映出该入口结构对中等粒度石膏颗粒的分级效率有明显的提高。更多还原

【Abstract】 Gypsum cyclone is an important equipment of wet flue gas desulfurization system (WFGD) in power plant, it’s main function is concentration and classification of gypsum slurry from absorber tank and the final production is widely used in cement and construction field. The operation of WFGD system will be disturbed and the quality of final gypsum will be affected because of the serious problems as air core and fish-hook in cyclone’s operation. Therefore, it’s very important to have a correct understanding of the flow characteristics in cyclone, and it’s imperative to design new and efficient cyclone.The flow mechanisms of hydrocyclone were studied. In addition, the performance tests of gypsum cyclone with different structures were carried out in order to deserve the variation of indicator parameters, such as split flow ratio, underflow density, discharge style and so on, the classification efficiency curves with different structures were compared and analyzed, and the reasons of fish hook phenomenon were discussed.Air core is an inevitable problem in hydrocyclone, it’s shape and diameter always changed in cyclone’s operation. It may cause some problems such as:waste of energy, unsteady flow condition, lower separation efficiency and so on. The development process of air core were simulated with RSM and VOF model by Fluent. The simulation results contained certain aspects of the velocity and pressure distribution, the diameter of air core on different axial position, and the energy consumption, et al.A new style of central solid rod with a conical shape was designed aimed at eliminating the air core and imp roving the performance of gypsum cyclone. Experiments were conducted in order to have a further understand about the negative influences by air core. At the same time, the performances of gypsum cyclones with different central solid rod include production capacity, concentration of underflow, solid-containing content in underflow and particle size distribution were measured and compared, the effects on above-mentioned parameters by inlet pressure were studied also. A simple calculation of energy consumption with different central solid rods indicate that:the energy consumption can be reduced about13.41%with conical central solid rod.A new inlet with separation block and bulkhead was designed in order to improve the classification efficiency of gypsum cyclone. The trajectory of particles in new inlet were simulated with Discrete Phase Mode by Fluent, the effects on particles with different inlet structures and velocity were discussed also. The change of characteristics about gypsum cyclone with different inlet structures were tested by experiment, the results indicate that:there is an apparent improvement of classification efficiency about medium-grained particles.更多还原