【作者】 刘长江；

【导师】 谢峻林； 肖天来；

【作者基本信息】 武汉理工大学 ， 生态环境材料， 2006， 硕士

【摘要】 煤是水泥工业分解炉中的主要燃料,随着优质资源的日益稀少,水泥工业正逐步向使用低活性煤的方向发展,然而煤质的变化必然会影响到分解炉内工况的稳定。因此,科学地评价不同煤质煤粉在分解炉环境下的燃烧特性,对于分解炉的稳定生产具有重要意义。本文结合不同的煤质,进行了煤焦燃烧特性的评价方法研究,力求找到一种或几种科学、可靠的方法来指导水泥窑的设计与生产,具有重要的现实意义。 本文通过非临界条件着火理论确定dT/dt≠0,d²T/dt²=0的点为着火所对应定义的时刻,求取了随炉升温和高温进样下的煤焦的着火点。结合热天平和煤燃烧综合测试仪,对煤焦柱的着火特性——着火温度和着火所需时间进行了确定方法的研究。同时利用美国NI公司推出的图形化软件编程平台LabVIEW编写了热天平质量/温度采集软件。结果表明:该方法重现性好,煤焦中含灰越高,着火所需时间越长。具有相近着火点的煤焦,着火所需时间却不一样,说明仅用煤的工业分析来评价煤质的优劣是不科学的。 运用热天平对煤焦粉的燃烧过程研究表明:改变热天平的温度和气流量的大小,通过观察煤焦粉从进样到燃烧失重最快的时间的变化,就可以判断煤焦燃烧是属于扩散燃烧过程还是动力燃烧过程或者两者兼而有之。 本文结合通用的计算流体力学软件Fluent设计出了一套煤悬浮燃烧装置,并利用美国NI公司推出的图形化软件编程平台LabVIEW编写了CO₂气体浓度采集软件。通过实验得出了六种煤焦在悬浮动态下燃烧的难易程度;结合工业分析的研究表明,即使是工业分析值很相近的煤,在动态燃烧条件下,其燃烧难易程度仍然相差很大;实验还探讨了气流量对不同煤焦粉燃尽度的影响,结果表明,某些煤焦的燃尽度随气流量的增加而降低,而某些煤焦的燃尽度则随着气流量的增加先增加后减少。 本论文的特色在于:一方面运用图形化软件编程平台LabVIEW编写了符合实验需要的多功能数据采集软件,并结合计算流体力学软件Fluent自制设计出一台基于分解炉环境的煤悬浮燃烧炉;另一方面,通过模拟水泥分解炉内的温度、气流环境,进行了煤悬浮燃烧特性的初步探讨。更多还原

【Abstract】 Coal is the main fuel used in the cement industries. With the reduction of high quality coal, the inert coal is used more and more, however, the change of the coal quality will certainly influence the stable of the kiln’s condition. In order to well know the combustion characteristics of coal in precalciners, in this article, the methods of evaluating the combustion characteristics of different quality of coal were studied, aiming to find one or more scientific and reliable methods for guiding the design and operating of cement kiln, which have important real significance.Using the graphics software programming platform LabVIEW invented by American NI corporation, two data acquisition softwares, the Thermobalance Mass / Temperature collect software and the Thermobalance / CO₂ Gas concentration collect software, were wrote with many functions such as high speed acquisition and automatic storage. Also other functions can be added whenever need.According to the theory of non-critical catching fire, defining the point where dT/dt≠0 and d²T/dt²=0 as the moment of catching fire, the kindling point of char, with the char temperature rising along with the furnace and with the char injected into the furnace at high temperature, is obtained respectively. By using thermobalance and coal comprehensive test instrument, the coal ignition information of both the kindling point and the burning time were studied. The results show that these methods have good reproducibility, the more ash the char contains, the kindling point is higher and the time for ignition is longer. Although there are similar kindling point and industrial analysis value of two kinds of chars, the time for ignition is different, illustrating that it is unscientific to evaluate coal quality only by the industrial analysis.The studying on combustion mechanism of char particles by using the thermobalance indicates that by observing the time which from the moment of the sample injected to the furnace to the moment of fast rate of loss of char weight via changing the thermobalance temperature and the gas flow rate, we could estimated whether the combustion mechanism is controlled by the diffusion combustion process or the dynamics combustion process or the both two.By using the CFD software FLUENT a set of coal suspension combustion implement was designed with the CO2 concentration collected by a certain software wrote by the graphics software programming platform LabVIEW. Through the experiments on five kinds of char, we know wherther the char is hard or easy to combust under the suspension combustion, combiningthe industrial analysis data it can be seen that under dynamic combustion conditions, there are widely different combustion results between different kinds of char although their industrial analysis data are very similar. Also the influence of the gas flow rate on the burnout degree of different char were discussed, showing that when the gas flow rate increases the burnout degree of some char fall, while some others increase firstly and then fall.The characteristic of this thesis are as follows: one one hand, by using the graphics software programming platform Lab VIEW, the multifunctional data-acquisition softwares were wrote and by the CFD software Fluent a set of coal suspension combustion implement was design;On the other hand, by modeling both the temperature and the gas flow circumstance in the precalciner of cement kiln, the initial research about the char combustion characters under suspension condition is processed.更多还原