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Measurement and theoretical prediction of char temperature oscillation during fluidized bed combustion

机译：流化床燃烧过程中焦炭温度振荡的测量和理论预测

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There is experimental evidence of oscillations of the char particle temperature during combustion in a fluidized bed (FB), resulting from the movement of the char throughout the bed. However, in most theoretical FB combustion studies the char particle is assumed to always stay in the emulsion phase, and existing models do not take into account the movement of the char particle explicitly. Moreover, it is difficult to quantify the magnitude and frequency of these temperature oscillations with the common measurement techniques employed in FB (thermocouple and pyrometry with optical probe). In this work, the combustion of single char particles (8 mm) from beech wood and sub-bituminous coal is carried out in a 2-dimensional FB made of quartz, using two O-2 concentrations (11 and 21%(v)) in N-2. The time-evolution of the temperature and the size of the char in the different phases are estimated by the analysis of images resulting from a new method combining pyrometry with readings from a digital camera. It is found that the combustion temperature oscillates in hundredths of seconds with an amplitude varying from 10 to 100 degrees C, resulting from the movement of a particle between the emulsion, bubble and splash phases. The amplitude increases with higher O-2 concentration and smaller char-particle size. A combustion model is developed using the experimental characterization of the movement of the char particle through the bed as input. The temperature and burnout time predicted by the model compare well (within 15 %) with measurements obtained from this work and from literature. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
机译：有实验证据表明，炭在整个流化床中的运动会导致流化床（FB）在燃烧过程中炭颗粒温度发生振荡。但是，在大多数理论FB燃烧研究中，假定炭颗粒始终停留在乳液相中，并且现有模型未明确考虑炭颗粒的运动。而且，很难用FB中使用的常用测量技术（带光学探针的热电偶和高温测定法）来量化这些温度振荡的幅度和频率。在这项工作中，使用两种O-2浓度（11％和21％（v））在由石英制成的二维FB中燃烧山毛榉木和次烟煤中的单个焦炭颗粒（8毫米）。在N-2中通过分析将高温测定法与数字照相机的读数相结合的新方法得到的图像，可以估算出不同相中炭的时间演变和温度的变化。发现燃烧温度以百分之一秒的幅度振荡，幅度在10到100摄氏度之间变化，这是由于粒子在乳化相，气泡相和飞溅相之间移动所致。 O-2浓度越高，炭颗粒越小，振幅越大。使用炭颗粒通过床的运动的实验表征作为输入来开发燃烧模型。该模型预测的温度和燃尽时间与从这项工作和文献中获得的测量值进行了很好的比较（在15％以内）。 （C）2018年燃烧研究所。由Elsevier Inc.出版。保留所有权利。

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