【作者】 裴晓冲；

【导师】 陈冬林；

【作者基本信息】 长沙理工大学 ， 动力机械及工程， 2009， 硕士

【摘要】 卫燃带是实现低质燃煤锅炉稳定高效燃烧最有效最简单的方法,国内外低质燃煤锅炉几乎都采用卫燃带稳燃,但卫燃带容易引起炉内结渣。针对低质燃煤锅炉卫燃带的防结渣设计难题,提出了研究卫燃带材料上沉积煤灰渣粘接特性的煅烧实验与振动测试方法,研究并设计了振动式灰渣粘接特性测量装置。该装置的特点是振源的振幅和频率可控,实验原理简单,结构简单紧凑,装置部件较少,自动化程度高,实际动手操作起来也较为简单。该装置可以克服目前测试耐火材料上粘接特性的方法(目测法,气流冲刷法,刮铲法等)的共同缺点:主要依靠测试人员的经验判断,对同种结渣试样检测的重复性较差,对不同温度下对灰渣的区分度较差等。定义了描述耐火材料上灰渣粘接特性的灰渣振落率指标。煤粉燃烧过程中的结渣主要与煤灰粒子及卫燃带的表面温度有关,当温度逐渐升高时,煤灰在卫燃带表面上的沉积将由疏松的积灰逐渐过渡到紧密的结渣。疏松的积灰很容易通过振动振落,振落率近100%,紧密结合的渣则很难通过振动振落,其振落率很小,接近于0%,而介于疏松积灰与紧密结渣两者之间的灰渣沉积,其灰渣振落率在100～0%。显然,如果能获得不同燃烧温度条件下煤灰在卫燃带材料上的沉积试样,通过振动测试这些试样的灰渣振落率,则可判断不同温度条件下煤灰在卫燃带材料上的粘接特性,并提出了用于指导卫燃带防结渣设计的结渣临界温度概念及其测试方法从而为卫燃带的优化设计提供依据。实验选取了6种不同煤质的典型燃煤电站燃料煤,将过100目筛的煤粉(最大粒度为150μm)高温灰化,进行元素分析和工业分析。取灰样0.2克疏松撒播在高铝质耐火材料板上,制成煤灰/耐火材料试样对,在高温电加热炉中恒温烧结20小时,实验结束后试样自然冷却到室温。对结渣试样进行振动测试分析,得到6种煤灰的灰渣振落率测试结果,进而分析得到结渣临界温度(带)。该结论适用于敷设此种卫燃带耐火材料的锅炉,当燃用此种或性质类似煤种时,若恰当控制炉膛温度,可有效避免结渣。更多还原

【Abstract】 Almost all PC-fired boilers, burning low rank coals, have been adopting heat-insulating refractory liner on their furnace waterwalls to improve combustion. Although the refractory liner is very effective for stabilizing combustion of low rank coal, it is very easy to cause slagging on the liner. Present methods may be used to test adhesion performance of coal ash with refractory include: visual observation, airflow scouring, mechanical scraping etc. These methods are simple, but have a mutual shortcoming that the adhesion performance is estimated mainly by operators’experiences, in addition, the repeatability of tested results for identical coal ash/refractory sample under same conditions is not satisfactory. To overcome the disadvantages of the above-mentioned methods, a vibration based testing method is proposed and a vibration-based testing device was developed.The concept of drop-off ratio and critical temperature for slagging and its testing method are also proposed to prevent slagging for the refractory design. If drop-off ratio and critical slagging condition of coal ash slagging on refractory could be associated, it is possible to confirm critical slagging temperature for special coal on special refractory. The analysis above indicates that drop-off ratio may be used to list the adhesion performance between coal ash and refractory under different temperatures. When drop-off ratio is equal to 100%, the corresponding temperature will not bring slagging as there is only loose dust stratification; when drop-off ratio is equal to 0%, the corresponding temperature will bring serious slagging as tight adhesion produced. Obviously, the transformation of drop-off ratio from 100% to 0% corresponds to the transformation of slagging behavior from loose deposition to serious slagging and the change is process of a gradual change.Six typical coal samples used in power plant were selected and then tested by proximate and ultimate analysis. Ash of the pulverized coal with size of no more than 150μm (similar with the coal burned in power plant) was made by high temperature dry ashing. 0.2g ash of coal was spread on the surface of the refractory to form coal ash/refractory sample and then the sample was put into the muffle furnace to be sintered for 20h. After cooled down naturally, eyeballing, vibration tests analysis were used to determine the drop-off ratio and critical temperatures (or temperature zones). Above all, the result can be used when this kind of refractory was laid in furnaces, if these coals or coals with similar characteristics are used as fuels, slagging may be avoided effectively by controlling the temperatures on the refractory surface less than the critical temperatures.更多还原