自激式除尘器内流气液耦合及压力波动特性研究

发布时间：2018-09-13 08:03

【摘要】：除尘器是一种从含尘气流中分离并捕集粉尘的装置,它是粉尘治理工程的核心设备,并广泛应用于过程工业。随着人们对环境的要求越来越高,除尘器在工业生产中的应用越来越受到人们的重视。自激式除尘器作为众多除尘器中的一种,具有结构简单、造价低、运行维护方便,适用于高温、易燃易爆除尘等优势,因此不断开展理论研究和试验研究,对提高其除尘性能具有重要意义。本文依托国家自然科学基金项目“自激式除尘器液滴形成机制与微细化调控”,以自激式除尘器模型为研究对象,通过理论推导、试验研究、验证性试验研究,对自激式除尘器工作过程中气流与除尘液的耦合过程进行了分析研究。通过理论分析,自激式除尘器的除尘过程可以分为不同机理作用下的两个除尘阶段:惯性除尘和液滴捕尘。在惯性除尘阶段,依赖的是弧形过流通道下粉尘的离心力作用从而实现除尘,并且这一过程只对100μm以上的粉尘才具有90%以上的除尘效率,而100μm以下的粉尘主要依靠除尘腔内的液滴来捕集。液滴捕尘阶段的分级除尘效率主要受到液气比、气液相对速度、液滴大小的影响,但这些因素的前提是气液两相充分耦合接触。试验研究认为,除尘器脱水板的正确安装是保证气流二次冲击液幕,促进气流与除尘液接触的必备条件。在试验中观察到,自激式除尘器的气液耦合分为5种典型的模式,分别是微弱波动模式、静液位差模式、气锤模式、剪切液幕模式和卷吸气泡模式。这5种模式是在不同的初始液位h0和不同的流量Q下发生的,代表了除尘器的工作状态。自激式除尘器工作过程中,节流气速Uj等在全节流、强节流、弱节流下随着Q的变化体现出不同的变化规律。又由于节流板的柔性节流作用,除尘器在不同的气液耦合程度下,其内部的压力表现出明显相区别的波动特征,主要分为低时均值高频脉动区、双波叠加区、大时均值高频脉动区三种波动特征区域,这种波动特征能够定性地描述气液耦合状态。初始液位h0和气流量Q决定除尘器内部的气液两相耦合状态,h0越高越易形成节流液位差,有利于惯性除尘;而Q越大气液耦合越剧烈。但最佳的除尘液幕并不是液位最高或气流量最大时形成的。试验结果认为,初始液位高度为0~20mm较为适宜,而最佳气流量根据初始液位不同而不同。自激式除尘器的除尘效率随着初始液位的提高或者气流量的增大而增大。
[Abstract]:Dust catcher is a kind of equipment for separating and collecting dust from dust-containing airflow. It is the core equipment of dust treatment engineering and is widely used in process industry. With the increasing requirement of environment, the application of dust collector in industrial production has been paid more and more attention. As one of the many kinds of precipitators, the self-excited precipitator has the advantages of simple structure, low cost, convenient operation and maintenance, suitable for high temperature, flammable and explosive dust removal and so on. It is of great significance to improve its dust removal performance. Based on the project of National Natural Science Foundation, "the mechanism of droplet formation and fine control of self-excited precipitator", this paper takes the model of self-excited precipitator as the research object, through theoretical derivation, experimental research, confirmatory experimental research. The coupling process of air flow and dust remover in self-excited precipitator is analyzed and studied. Through theoretical analysis, the dust removal process of self-excited dust collector can be divided into two stages under different mechanism: inertial dust removal and droplet dust capture. In the stage of inertial dust removal, it depends on the centrifugal force of the dust under the arc flow channel to realize the dust removal, and this process only has more than 90% dust removal efficiency for the dust above 100 渭 m. The dust below 100 渭 m mainly depends on the droplets in the dust removal chamber. In the stage of droplet dust capture, the efficiency of graded dust removal is mainly affected by the ratio of liquid to gas, the relative velocity of gas and liquid, and the size of droplet, but the premise of these factors is that the gas-liquid two phases are fully coupled with each other. The experimental study shows that the correct installation of the dewatering plate of the dust collector is a necessary condition to ensure the secondary impact of the gas flow and to promote the contact between the gas flow and the dedusting liquid. It is observed in the experiment that the gas-liquid coupling of the self-excited precipitator can be divided into five typical modes, namely, weak wave mode, static liquid level difference model, air hammer mode, shear liquid curtain mode and entrainment bubble mode. These five models occur at different initial liquid level h _ 0 and different flow rate Q, which represent the working state of the dust collector. In the working process of self-excited precipitator, the variation of throttling gas velocity (Uj) shows different laws with the change of Q under the condition of full throttling, strong throttling and weak throttling. Because of the flexible throttling effect of the throttle plate, the internal pressure of the dust collector shows distinct fluctuation characteristics under different gas-liquid coupling degree, which is mainly divided into the low mean high frequency pulsation region and the double wave superposition region. There are three kinds of fluctuating characteristic regions in the high frequency pulsation region with large mean value, which can describe the gas-liquid coupling state qualitatively. The higher the initial liquid level h _ 0 and the gas flow Q determine the gas-liquid two-phase coupling state in the precipitator, the more easy it is to form the throttling liquid level difference, which is favorable to the inertia dust removal, and the greater the Q is, the more intense the gas-liquid coupling is. But the best dedusting liquid curtain is not formed when the liquid level is the highest or the gas flow is the largest. The experimental results show that the initial liquid level height is 0~20mm and the optimal gas flow rate is different according to the initial liquid level. The dust removal efficiency of self-excited precipitator increases with the increase of initial liquid level or gas flow rate.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X701.2

【参考文献】