【作者】 陆斌；

【导师】 桑芝富； 张卫华；

【作者基本信息】 南京工业大学 ， 化工过程机械， 2004， 硕士

【摘要】 废旧轮胎作为一种特殊的固体废弃物,不同于一般的城市生活垃圾,很难自然降解。目前,废旧轮胎的处理主要分为物理回收和化学回收,而其中把废旧轮胎作为燃料使用,在废旧轮胎的处理中发挥了重要的作用。本文选用某轮胎回收工厂加工的废旧轮胎胶粉作为研究对象,对废旧轮胎胶粉、煤粉以及二者混合物的热解特性和燃烧特性进行了实验研究。在此基础上,采用计算流体力学软件FLUENT模拟了废旧轮胎胶粉、煤粉以及废旧轮胎胶粉和煤粉混合物在大型四角切向燃烧炉中的燃烧特性。通过热重实验,初步研究了废旧轮胎胶粉、煤粉以及废旧轮胎胶粉和煤粉混合物在氮气气氛下的热解特性,以及升温速率对废旧轮胎胶粉热解性能的影响,获得了热解过程中试样的反应机理。通过分析认为,在废旧轮胎胶粉和煤粉的混合物热解过程中,废旧轮胎胶粉和煤粉相互影响较小,混合物的热解特性可以用废旧轮胎胶粉和煤粉的热解特性的线性组合表示,而且在不同温度区间用不同区段的一级反应来描述,均能得到拟合良好的直线关系。同时,利用热重分析仪对废旧轮胎胶粉、煤粉以及二者混合物在空气气氛下的燃烧特性进行了初探,获得了燃烧反应的反应机理,该机理可通过反应速率方程来表示。同样,在空气气氛下废旧轮胎胶粉和煤粉的混合物燃烧特性可以用单组分的物质燃烧特性的线性组合表示,而且在不同燃烧区段,反应可以用一级反应来描述。四角切向燃烧炉是火力电厂的重要设备之一,本文采用计算流体力学软件FLUENT分别模拟废旧轮胎胶粉、煤粉以及废旧轮胎胶粉和煤粉在不同配比下的混合物在四角切向燃烧炉中燃烧过程,得到了它们在炉内燃烧的温度场分布、速度场分布以及CO和CO2等产物的分布。通过数值模拟发现,炉膛区域的平均温度随着混合物中煤粉比例的增大而下降,其中单烧胶粉时,炉膛平均温度最高;分析CO的分布发现在燃烧炉的出口处没有CO出现,这说明生成的CO都完全燃烧了,在炉膛中产生的CO总量也是随着燃料中煤粉比例的增大而下降;分析CO2的分布发现,单烧胶粉时,产生CO2量最多,在燃烧胶粉和煤粉混合物时,随着混合物中煤粉比例增大,CO2生成量呈下降趋势;CO,CO2和O2的质量浓度分布和温度分布有很大关系,高温区对应着高的CO质量浓度和低的O2、CO2质量浓度;从速度分布图可以看出,在炉膛内存在强烈的旋流,旋流强度自底到上由弱到强,然后减弱,但到达出口时还存在残余旋流。 <WP=4>另外,本文还对废旧轮胎胶粉燃烧时NO的生成进行了数值模拟,通过模拟发现,随着混合燃料中煤粉比例的增大,NO排放量呈现减少的趋势;最后分析了影响NO生成的几个因素。通过模拟计算分析可见,把废旧轮胎胶粉和煤粉混合物作为燃料用于四角切向燃烧炉是可行的,但也发现在它们燃烧过程中NO的排放量比单烧煤粉时产生的NO多,在实际使用中要注意废旧轮胎胶粉和煤粉之间的比例搭配。更多还原

【Abstract】 As a special kind of waste solid, waste tyre differs from common MSW (municipal solid waste). It can not degrade spontaneously and isn’t suitable for land-filling because of its large capacity and low density. At present, the treatments of waste tyre can be included as physical methods and chemical methods, and TDF (Tire-derived fuel) plays an important role in the waste tyre treatment. This paper aims at enhancing the fundamental understanding of the combustion behavior of pulverized waste tyres. And using a CFD software Fluent V6.1.18, combustion characteristics were investigated in a tangentially fired furnace.In this paper a thermo-gravimetric analyzer (TGA) was used as experimental means. In a thermo-gravimetric analyzer, a series of experiments were conducted. The pyrolysis tests of pulverized waste tyre and pulverized coal in an inert atmosphere of nitrogen gas were conducted respectively. And then the co-pyrolysis tests of pulverized waste tyre and pulverized coal in an inert atmosphere of nitrogen gas were also conducted at different proportioning. The experiment results indicate that the interaction of pulverized waste tyre and coal at different proportioning during the co-pyrolysis process can be ignored. It is suggested that the kinetic analysis in pyrolysis can be handled with first order reaction. It can be concluded that the pyrolysis characteristics of mixtures of pulverized waste tyre and pulverized coal in TGA can be expressed by the plus of pyrolysis characteristics of individual components of the mixture. And also, in the thermogravimetric analyzer, in air, combustion studies on single fuel particles and mixed fuel were conducted at a heating rate of 10K/min. The combustion activation energy and frequency factor are obtained. It is suggested that the kinetic analysis in combustion the samples can be handled with the first order reaction.Using a CFD software Fluent v6.1.18, an Eulerian/Lagrangian approach was employed to investigate numerically the flow field, heat transfer and combustion process in a tangentially fired furnace. Six different cases were simulated. The distributions of the velocity, temperature, CO, O2, CO2 were obtained and analyzed. Because heating value of tire-derived fuel is higher than that of coal, the average temperature of mixtures in the furnace decreases gradually with the increasing of fraction of coal in the mixtures; By investigating the <WP=6>distributions of CO and CO2, it can be concluded that the amount of CO and CO2 in the furnace decreases with the increasing of fraction of coal because of the different C content and different volatile matter content; And also the distribution of CO, O2 and CO2 concentration are strongly realated to the temperatur field; It can be seen that from bottom to top, the intensity of a swirl firstly strengthens and then weakens, but residual swirl still exists at the exit of the furnace.In addition, the yielding of NO was also simulated. The results show that the amount of NO decreases with the increasing of fraction of coal in the mixture. At last the influencing factors which affect the yielding of NO were analysed. It is feasible to use pulverized waste tyre as a kind of supplementary fuel in a tangentially fired furnace by numerical simulation. But the mixed fraction should be controlled.更多还原