【作者】 王琦；

【导师】 赵虹； 杨建国；

【作者基本信息】 浙江大学 ， 工程热物理， 2008， 硕士

【摘要】 煤炭是我国目前乃至将来较长一段时间内电力生产的主要一次能源。我国煤炭资源较为丰富,但是随着我国煤炭消耗量的大幅增长和煤炭生产、运输水平的制约,以及国际煤炭市场的变化,我国煤炭价格近年来呈现大幅上涨的趋势。燃料成本一般占燃煤电厂发电成本的70%以上,因此,降低发电煤耗、提高燃煤经济性,已成为燃煤电厂迫切需要关注的问题。同时,我国煤炭资源及煤炭市场复杂,动力煤炭的煤种供应不稳定,煤质变化较大,煤粉锅炉基本上很难燃用到设计煤种,甚至燃用煤种与设计煤种相差甚远,严重影响了锅炉的燃烧安全性和经济性。因此,对不同煤种燃烧特性进行试验研究,从而得出不同煤种及其混煤的燃尽特性,就显得非常必要。本文采用热分析方法,研究了几种单煤和混煤的燃烧特性,阐述了氧浓度和温度对煤粉燃烧的影响。煤粉锅炉内为动态的悬浮燃烧,煤粉从燃烧器喷嘴喷出到离开炉膛,经历的氧浓度和温度变化十分复杂,而氧浓度和温度对煤粉燃烧特性又有至关重要的影响,所以本文针对煤粉在不同氧浓度和温度下的燃烧特性进行试验研究。考虑到从燃烧器喷出到开始着火的时间极短,而着火后煤粉即可达到很高的温度,并且因焦炭占据了煤的大部分重量和发热量,煤粉的燃烧时间均主要由焦炭决定。本文采用恒温热重分析方法,使煤焦在设定温度下进行燃烧。本文对煤质特性差异较大的无烟煤和平朔5000烟煤进行了变氧浓度的恒温热重试验,根据试验结果得到了煤焦的燃烧时间,利用煤焦燃烧时间计算煤粉的平均燃烧速度,作为判定煤粉燃烧特性的依据。通过分析两种煤粉平均燃烧速度随氧浓度的变化规律,得到不同氧浓度气氛下煤粉燃烧特性的差异。同时,推导了单颗粒煤粉燃烧特性,与实际煤粉炉内煤粒燃烧更加贴近。在分析氧浓度对煤粉燃烧特性影响的基础上,本文对无烟煤、平朔5000烟煤和温家梁神木煤进行变温度和变氧浓度的恒温热重试验,主要研究了温度对煤粉燃烧特性的影响。通过分析煤焦平均燃烧速度随温度的变化规律,阐述了不同煤种燃烧特性受温度影响的差异。对比了不不同温度和氧浓度下煤焦和煤粉平均燃烧速度的差异,提出了固定碳的影响作用。最后,本文研究了无烟煤和平朔5000烟煤按照1:1比例掺混后的燃烧特性。对混煤进行变温度和变氧浓度的恒温热重试验,分析了温度和氧浓度分别对混煤煤焦和煤粉平均燃烧速度的影响。并将混煤和单煤的燃烧速度进行对比,阐述了混煤和单煤之间燃烧特性的差异。为混煤燃烧的研究提供一定的参考依据。更多还原

【Abstract】 Coal is the main primary energy of electric industry in current and future longer period of time in China. China is rich in coal resources, but as the growth of coal consumption and the constraint of coal production level and transport, as well as the change of the international coal market, the price of the coal rose sharply in recent years in China. The cost of the fuel accounted for the general expense of coal-fired power plant more than 70 percent. Thus, the reduce of coal consumption and the improving of the economy of coal had become a focus for coal-fired power plant. Usually, pulverized coal-fired boiler can not use the normal designed coal, and even coal is far from the design coal. Consequently it will impact the stability of the combustion in the boiler, and reduce the thermal efficiency of boiler. Thus, it is very important to study the combustion characteristics of different coal. In this paper, thermal analysis method is used to analyze the combustion characteristics of several single coal and mixed coal.The change of oxygen concentration and temperature which is pulverized-coal come through from the burner nozzle to end the furnace, is very complicated, and the oxygen concentration and temperature are very important factors on pulverized-coal combustion. Therefore, in this paper, the combustion characteristics of pulverized coal in different oxygen concentration and temperature were studied. The time of pulverized-coal when ejected from the burner nozzle until ignited is very short, and pulverized-coal will achieve to a high temperature speedily after bursting into flame. In the process of coal combustion, burning rate and burnout time of pulverized-coal is mainly deiced by the char because the char occupies most of the weight and heat of pulverized-coal’s combustion. Based on the above consideration, the constant temperature thermal analysis method was used in this paper, warming up through the procedures, so that the char will burn in a set constant temperature. In this paper, Pingshuo 5000 and anthracite were tested in different oxygen concentration by constant temperature TGA. According to result of test, the burnout time and average burning rate of coal coke was computed. By analyzing the law of oxygen concentration’s influence on average burning rate, the difference combustion characteristics of pulverized-coal was studied. At the same time, in order to close to the condition of the practical combustion, the combustion characteristic of single particle coal was deduced. On the base of research on oxygen concentration’s influence on coal combustion, the constant temperature thermal test was been done. Anthracite, Wenjialiang coal and Pingshuo 5000 bituminous were tested in different oxygen concentration and temperature condition, and the temperature’s influence on characteristics of pulverized-coal was mainly studied. According to analyze the change of average burning rate with the different temperature, the optimally combustion temperature region of the char was researched. Through comparing the average burning rate between the char and the coal, the influence of carbon fixation on combustion was also studied.Finally, the combustion characteristic of mixed coal which was composed by anthracite and Pingshuo 5000 (1:1) was researched. By the thermal test on mixed coal in different oxygen concentration and temperature condition, analyzing the influence of oxygen concentration and temperature on mixed pulverized-coal’s combustion. The difference characteristic of combustion between mixed coal and single coal was also been studied. The research on above will be give a reference suggestion on the research of combustion of mixed coal.更多还原