【作者】 孟凡珂；

【导师】 王永征；

【作者基本信息】 山东大学 ， 热能工程， 2008， 硕士

【摘要】 煤炭在我国一次能源消费中占据主导地位。燃煤产生的SO₂带来的大气污染问题已经严重影响到我国的经济发展和生产生活。电厂燃煤则是产生SO₂的主要污染源,因此研究动力煤燃烧硫析出规律和SO₂控制技术具有非常重要的意义。近年来,由于全国动力用煤供应紧张,很多电厂无法燃用固定煤种,普遍存在燃用混煤现象。目前,虽然对燃煤硫污染物控制已有大量的研究,但对混煤燃烧及其硫污染物控制的研究则较少。因此研究动力煤及其混煤的SO₂析出特性具有非常重要的现实和理论意义。首先采用热重分析法（TGA）,对所选择的8种山东省内主要动力煤及其混煤的燃烧过程进行了研究,并求取出单煤及其混煤的燃烧特性参数。对比研究了混煤与组分单煤燃烧特性之间的联系与不同。煤阶越高的煤种其着火温度越高,可燃性指数越差。混煤的燃烧特性基本介于两组分煤之间,着火温度相对接近着火温度低的组分煤种,可燃性指数相对接近可燃性差的组分煤种。当煤阶相近的煤种掺配时,混煤的燃烧特性与两组分煤相似;当煤阶相差较大的煤种掺配时,混煤的燃烧特性呈现阶段相似性:在挥发分析出并燃烧阶段,燃烧失重过程与低煤阶组分煤种相似,在焦炭燃烧直至燃尽阶段,失重过程又逐渐接近高煤阶组分煤种。当燃烧特性相差较大的煤种掺混时,其可燃性指数变差。其次在高温管式炉上,对不同煤种燃烧SO₂析出的动态特性进行了研究,并分析了煤质与SO₂析出的关系以及燃烧工况对SO₂析出的影响。煤燃烧SO₂的析出呈现出明显的双峰结构。通过这两个峰可将煤中所含的硫划分为低温硫和高温硫。虽然低温硫和高温硫不能直接等同为有机硫和黄铁矿硫,但可通过有机硫与黄铁矿硫的组成大体判断低温硫与高温硫的析出情况。煤中含硫量越高,SO₂析出速率越高,SO₂析出总量也越多,但硫析出率不一定越高。煤阶与SO₂析出的关系主要体现在:不同煤阶的煤有着差异较大的燃烧特性和形态硫组成,进而影响到SO₂的析出特性。低阶煤SO₂析出开始时间较早,峰值较高,峰宽较窄,硫析出比较集中。高阶煤SO₂析出较平缓,峰值较低,峰宽较大,析出持续时间长。提高温度可使SO₂析出提前并可提高SO₂析出率。温度的提高对高温硫析出的影响比较明显。在1200℃以下时,提高温度对增大硫析出率作用显著,但超过1200℃时,温度的提高则对增大硫析出率的作用不明显。燃烧时氧浓度越高,SO₂析出速率越高,析出量越大,硫析出率越高。然后在高温管式炉上,对混煤燃烧SO₂的析出特性进行了研究。分析了不同掺配方式下混煤燃烧SO₂的析出特性,并分析了燃烧工况对SO₂析出的影响。混煤SO₂析出特性介于两组分煤之间,且相对接近比例大的组分煤。混煤中高硫煤比例越大,SO₂析出速率越高,析出量越大,但硫析出率不一定越高。高硫煤中掺烧低硫煤可明显降低SO₂析出速率和析出总量。煤阶相差较大的煤种掺配时,混煤SO₂析出动态特性随掺配比例变化很大。低阶煤中掺烧高阶煤可明显减缓SO₂的析出。煤阶相近煤种掺配时,混煤SO₂析出动态特性与两组分煤相近。燃烧工况对混煤SO₂析出的影响与对单煤的影响相似。最后,应用BP神经网络模型对混煤燃烧硫析出率进行了预测。分别以煤质因数:挥发分含量、固定炭含量、有机硫含量、黄铁矿硫含量和工况因数:管式炉温度、供气氧浓度以及掺配比例作为输入变量,以硫析出率作为输出量。用54组样本数据进行训练,用10组测试数据进行检验。检验结果表明,经过训练的神经网络模型对检验样本集的预测具有较高准确性,满足试验误差要求。本文建立的BP神经网络可以用来预测混煤燃烧SO₂的析出率。更多还原

【Abstract】 It is well known that coal is the primary energy resource in China. Meanwhile, SO₂ produced by coal combustion has always had serious effects on the economic development and production and life. coal combustion in power plants has always been a dominant contributor to the release of sulfur dioxide, in so saying, investigations on the rule of sulfur released from power coal and the technology of control technology of SO₂ have important significance. In recent years, due to short supply of power coals in China, many power plants are able to apply with fixed coal as combustion use. So it is universal for power plants to use blended coals. At present, there are scarce investigations on the rule of sulfur dioxide released from blended coals. As result, investigation on the characteristics of combustion of blended coals and the rule of the release of sulfur dioxide from blended coal is of great signification in realistic and theoretical meaning.Firstly, the characteristic of combustion process of eight primary power coals from Shandong province and their blended samples have been studied using the thermo-gravimetric analysis （TGA） method respectively, their burning performance parameters are in turn gained . The relationship and difference between single and blended coals are studied comparatively. As coal ranks increase, ignition temperatures and temperatures at largest weight loss accelerate, flammability index of coals have a trend of decrease. The combustion characteristic of blended coal lies between the two single coals, the ignition temperature of blended coal is close to that of component coal which is easier to catch fire, and the flammability index of blended coal is more influenced by component coal of poor combustibility. When blended coal is mixed with two component coals of similar rank, the combustion characteristic of the blended coal is similar to the two single components. When the ranks of two component coals are largely different, the combustion characteristic of the blended coal is similar to the two single components by stage. In the phase of precipitation and combustion of volatile, the combustion process is similar to that of low rank coal; in the phase of combustion of the coke, the combustion process is similar to that of high rank coal. The flammability index of blended coal becomes less when the combustion characteristics of component coals are largely different.Secondly, dynamic characteristics of SO₂ released from different coals are studied by high temperature pipe furnace, the relationship between coal qualities and the characteristic of SO₂ released from different coals is studied, the influence of combustion conditions on the characteristic of SO₂ released from different coals is studied too. The characteristic of SO₂ released from different coals presents obvious double-peak structure by which the sulfur in the coal falls into low sulfur coal and high sulfur coal. Although low sulfur coal and high sulfur coal can not is divided into organic sulfur and pyritic sulfur, the release characteristic of low sulfur coal and high sulfur coal can be judged by the composition of organic sulfur and pyritic sulfur. As the sulphur content increases, the releasing rate and the release total quantity are higher, however, there is little regularity between the sulphur content and the release rate of sulfur. The relationship between coal rank and the release characteristic of SO₂ is showed as followed: coal samples with different ranks have different combustion characteristic and sulfur forms, which has great effects on the characteristic of release of SO₂. It is significant that increasing temperature is able to increase the release rate of sulfur dioxide. Furthermore, this effect is more obvious at the stage of the release of high temperature sulphur. However, the influence is little after 1200℃. As the oxygen density increases, coarsening rate of SO₂ is higher; the release rate of sulfur is higher too.Thirdly , the characteristic of SO₂ released from blended coals is studied by high temperature pipe furnace, the release characteristic of SO₂ during the combustion of blended coals with different mixing ways is analyzed , moreover, the influence of combustion conditions on the characteristic of SO₂ released from blended coals is studied. The release characteristic of SO₂ from blended coal lies between that from the two component coals and is close to the characteristic of the component coal with larger proportion. When coals with different ranks to a large extent are blended, the time when SO₂ reach to the peak delays as the proportion of the coal with high rank increases. When coals with different sulfur contents are blended, coarsening rate of SO₂ and the release quantity of sulfur decrease as the proportion of the low sulfur coal increases. However, there is little effect on the release rate of sulfur. The influence of combustion condition on the release characteristic of SO₂ from blended coals is similar to that from single coals.Moreover, the release characteristic of SO₂ from blended coals is forecasted by BP neural network model. In this study , coal property parameters （volatile content、fixed carbon content\ organic sulfur content\pyrite sulfur content） and combustion condition parameters （temperature\ oxygen density） are used as input variable , meanwhile, the release rate of sulfur is used as output variable. 54 groups of sample data are applied to be exercised, and 10 groups of test data are used to inspect the model. The result is shown that the neural network model exercised meets the experimental error and has relatively high accuracy. as such , the BP neural network model set by this study can be used to forecast the release rate of SO₂ from blended coals.更多还原