多分支石灰石输送管路偏流特性的CPFD数值模拟
发布时间：2018-09-05 07:58
【摘要】：气力输送是一项广泛应用于各行各业的技术，在火电厂中的一个重要应用就是循环流化床（CFB）锅炉的喷钙脱硫系统。石灰石粉气力输送系统是CFB机组最重要的辅机系统之一，对CFB的运行具有重要意义。石灰石系统采用多分支形式的输送管路，以实现一条管路多个喷口的需要。在分流输送的过程中，存在明显的偏流现象，导致石灰石粉进入炉膛后分布严重不均，脱硫剂和SO2在炉内无法高效混合，脱硫效率降低。 本文采用专门针对工业气固流动系统的新型CPFD软件—Barracuda，模拟研究了宽筛分特性的石灰石粉在工业尺度下的一分二、二分四式分支管路中进行稀相气力输送时的流动特性。本文获得以下主要成果： （1）深入分析了引起管路偏流的原因，获得了整体管路的偏流特性。其偏流特性体现在气固流量和颗粒粒径的双重分配不均。在本文中带弯头的一分二管路结构下，流量呈现右多左少的分配趋势，，粒径呈现右细左粗的分配特性。 （2）系统研究了运行操作条件对其偏流特性的影响。以输送浓度，输送气速，输送压力，粒径分散特性四种参数作为变量因素获得了其偏流规律。 输送浓度对管路偏流特性的影响不是一种单调的趋势，对于特定的气速，都存在一个出现明显的偏流现象对应的浓度区；随输送气速增大，管路的偏流程度降低，但在不同的浓度区，降低的幅度明显不同；压力对偏流特性的影响以0.1MPa为临界值区分为两种情况，压力小于0.1MPa时，偏流特性明显，压力大于0.1MPa时，流量分配趋于均匀；粒径分散特性主要影响偏流时的粒径范围和其中位粒径d0.5。 （3）研究了分配器的结构对管路系统流动的影响，得到了分配器的结构优化方案，加装倾斜导流挡板的优化方案经过多重验证后证明其可以实现分配器左右支管气固两相流量均流，同时合理的挡板角度还可以一定程度改善粒度分布不均的现象。 （4）得出了加装挡板的分配器结构设计准则，其关键几何参数是挡板距离支管中心轴的高度H。
[Abstract]:Pneumatic conveying is a widely used technology in various industries. One of the important applications in thermal power plants is the calcium injection desulfurization system of circulating fluidized bed (CFB) boilers. The pneumatic conveying system of limestone powder is one of the most important auxiliary machine systems for CFB units, which is of great significance to the operation of CFB. The limestone system adopts multi-branch delivery lines to meet the needs of multiple vents in one pipeline. In the process of separation and transportation, there is obvious phenomenon of biased flow, which leads to the serious uneven distribution of limestone powder after entering the furnace, and the desulfurization efficiency is reduced because the desulphurizer and SO2 can not be mixed efficiently in the furnace. In this paper, a new CPFD software, Barracuda, is used for industrial gas-solid flow system. The flow characteristics of limestone powder with wide sieving characteristics are simulated and studied during the dilute phase pneumatic transport in a branch pipeline of two or two parts in industrial scale. In this paper, the main results are as follows: (1) the causes of pipe deflection are analyzed in depth, and the deflection characteristics of the whole pipeline are obtained. The bias flow characteristics are reflected in the uneven distribution of gas solid flow rate and particle size. In this paper, under the two-pipe structure with bends, the flow rate shows a distribution trend of right, more left and less left. (2) the influence of operation conditions on the bias characteristics is systematically studied. Four parameters, such as transport concentration, gas velocity, pressure and particle size dispersion, are taken as variable factors to obtain the law of bias. The influence of transport concentration on the flow characteristics of pipeline is not a monotonic trend. For a particular gas velocity, there exists a concentration region corresponding to the phenomenon of obvious deviation, and the degree of deviation decreases with the increase of gas velocity. However, in the different concentration regions, the amplitude of the decrease is obviously different, the influence of pressure on the bias flow characteristics is divided into two cases with 0.1MPa as the critical value. When the pressure is less than 0.1MPa, the bias characteristic is obvious, and when the pressure is greater than 0.1MPa, the flow distribution tends to be uniform. The particle size dispersion characteristics mainly affect the particle size range and the particle size D _ (0.5). (3) the influence of the structure of the distributor on the flow of pipeline system is studied, and the optimization scheme of the distributor structure is obtained. The optimization scheme with inclined baffle is proved to be able to realize the gas-solid two-phase flow equalization of the right and left branches of the distributor after multiple verification. At the same time, reasonable angle of baffle can improve the uneven distribution of particle size to some extent. (4) the structural design criterion of distributor with baffle is obtained. The key geometric parameter is the height of baffle from the center axis of branch pipe.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ022.3;TM621
本文编号：2223665
[Abstract]:Pneumatic conveying is a widely used technology in various industries. One of the important applications in thermal power plants is the calcium injection desulfurization system of circulating fluidized bed (CFB) boilers. The pneumatic conveying system of limestone powder is one of the most important auxiliary machine systems for CFB units, which is of great significance to the operation of CFB. The limestone system adopts multi-branch delivery lines to meet the needs of multiple vents in one pipeline. In the process of separation and transportation, there is obvious phenomenon of biased flow, which leads to the serious uneven distribution of limestone powder after entering the furnace, and the desulfurization efficiency is reduced because the desulphurizer and SO2 can not be mixed efficiently in the furnace. In this paper, a new CPFD software, Barracuda, is used for industrial gas-solid flow system. The flow characteristics of limestone powder with wide sieving characteristics are simulated and studied during the dilute phase pneumatic transport in a branch pipeline of two or two parts in industrial scale. In this paper, the main results are as follows: (1) the causes of pipe deflection are analyzed in depth, and the deflection characteristics of the whole pipeline are obtained. The bias flow characteristics are reflected in the uneven distribution of gas solid flow rate and particle size. In this paper, under the two-pipe structure with bends, the flow rate shows a distribution trend of right, more left and less left. (2) the influence of operation conditions on the bias characteristics is systematically studied. Four parameters, such as transport concentration, gas velocity, pressure and particle size dispersion, are taken as variable factors to obtain the law of bias. The influence of transport concentration on the flow characteristics of pipeline is not a monotonic trend. For a particular gas velocity, there exists a concentration region corresponding to the phenomenon of obvious deviation, and the degree of deviation decreases with the increase of gas velocity. However, in the different concentration regions, the amplitude of the decrease is obviously different, the influence of pressure on the bias flow characteristics is divided into two cases with 0.1MPa as the critical value. When the pressure is less than 0.1MPa, the bias characteristic is obvious, and when the pressure is greater than 0.1MPa, the flow distribution tends to be uniform. The particle size dispersion characteristics mainly affect the particle size range and the particle size D _ (0.5). (3) the influence of the structure of the distributor on the flow of pipeline system is studied, and the optimization scheme of the distributor structure is obtained. The optimization scheme with inclined baffle is proved to be able to realize the gas-solid two-phase flow equalization of the right and left branches of the distributor after multiple verification. At the same time, reasonable angle of baffle can improve the uneven distribution of particle size to some extent. (4) the structural design criterion of distributor with baffle is obtained. The key geometric parameter is the height of baffle from the center axis of branch pipe.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ022.3;TM621
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