Spontaneous emission intensities of Na*, Ca*, and K* during the combustion of single wood and straw pellets doped with known concentrations of Na, Ca, and K were measured using optical bandpass filters mounted on an intensified charge-coupled device camera. The impregnated biomass pellets were suspended in a natural gas flat flame at 750 and 1000 °C. Before the pellets were made, the biomass samples were washed and soaked to demineralize and doped with different concentrations of Na, Ca, and K (0.5, 2, and 5 wt %). During the experiments, the temperature at the center of the pellets was measured with a thermocouple and the combustion stages were identified with the help of the temperature derivative. The results reveal that, at the lower gas temperature, the emission of the selected alkalis is marginal, in agreement with previous studies. At the higher gas temperature, the emission profiles reveal that K and Na are released distinctively in the volatile combustion and char combustion stages. The presence of large amounts of silica and alumina may trap the alkalis in the solid phase, leading to a reduced emission of these species during the char combustion. Calcium does not evaporate at the tested temperature conditions, but the temperature is high enough to promote the decomposition of calcium oxalate in the outer layer of the pellet, leading to a flat emission profile during the combustion stages. Finally, the total integrated emission increased proportionally with the increase of the doping concentration for all species.

中文翻译：

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单个生物质团块燃烧过程中某些碱自由基的自发发射测量

使用安装在增强型电荷耦合器件照相机上的光学带通滤光片，可以测量掺杂了已知浓度的Na，Ca和K的单个木材和秸秆颗粒燃烧过程中Na *，Ca *和K *的自发发射强度。将浸渍的生物质颗粒悬浮在750和1000°C的天然气平焰中。在制备颗粒之前，将生物质样品洗涤并浸泡以脱盐并掺杂不同浓度的Na，Ca和K（0.5、2和5 wt％）。在实验过程中，使用热电偶测量颗粒中心的温度，并借助温度导数确定燃烧阶段。结果表明，与以前的研究一致，在较低的气体温度下，所选碱的排放量很小。在较高的气体温度下，排放曲线表明，K和Na在挥发性燃烧和炭燃烧阶段显着释放。大量二氧化硅和氧化铝的存在可能会将碱捕获在固相中，从而导致在炭燃烧过程中减少这些物质的排放。钙在测试的温度条件下不会蒸发，但是温度足够高以促进草酸钙在颗粒外层中的分解，从而在燃烧阶段产生平坦的排放曲线。最后，所有物种的总累积发射量与掺杂浓度的增加成比例地增加。大量二氧化硅和氧化铝的存在可能会将碱捕获在固相中，从而导致在炭燃烧过程中减少这些物质的排放。钙在测试的温度条件下不会蒸发，但是温度足够高以促进草酸钙在颗粒外层中的分解，从而在燃烧阶段产生平坦的排放曲线。最后，所有物种的总累积发射量与掺杂浓度的增加成比例地增加。大量二氧化硅和氧化铝的存在可能会将碱捕获在固相中，从而导致在炭燃烧过程中减少这些物质的排放。钙在测试的温度条件下不会蒸发，但是温度足够高以促进草酸钙在颗粒外层中的分解，从而在燃烧阶段产生平坦的排放曲线。最后，所有物种的总累积发射量与掺杂浓度的增加成比例地增加。但是温度很高，足以促进草酸钙在颗粒外层中的分解，从而导致燃烧阶段的排放曲线平坦。最后，所有物种的总累积发射量与掺杂浓度的增加成比例地增加。但是温度很高，足以促进草酸钙在颗粒外层中的分解，从而导致燃烧阶段的排放曲线平坦。最后，所有物种的总累积发射量与掺杂浓度的增加成比例地增加。