This experimental study explores the burning characteristics of single pellets made of wood and coal mixtures for co-firing. Three types of pellets were prepared with different wood–coal ratios (100:0, 80:20, and 50:50). Experiments were carried out in a laboratory reactor at rapid heating rates and under oxygen concentrations between 10 and 40%. To investigate their combustion behavior, single pellets were suspended on a wire injected into a hot gas stream at 1340 K and flame and char combustion were recorded through an observation window by means of a high-resolution (4K) camera. The sequential combustion time, volatile flame characteristics, and mass reduction rate were obtained over a time profile by carefully controlled particle injection. The results demonstrated that the char combustion time increased significantly in comparison to the volatile combustion time, which only varied a little, when the pellets contained coal in the mixture. Partially detached flames were also predominantly observed on pure biomass pellets at oxygen concentrations between 21 and 40%. During the homogeneous combustion period, the cross-sectional area of a pellet shrunk by 26.3–37.5% depending upon the type of pellet.

中文翻译：

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煤木混合物单颗粒在热气流场中的燃烧行为

这项实验研究探索了由木材和煤炭混合物制成的单一颗粒用于共烧的燃烧特性。制备了三种具有不同木煤比（100：0、80：20和50:50）的颗粒。实验是在实验室反应器中以快速加热速率并在10％至40％的氧气浓度下进行的。为了研究它们的燃烧行为，将单个颗粒悬浮在以1340 K注入热气流中的金属丝上，并通过高分辨率（4K）摄像机通过观察窗记录火焰和炭燃烧。通过仔细控制颗粒的喷射，可以在一定的时间范围内获得顺序燃烧时间，挥发性火焰特性和质量降低率。结果表明，与挥发性燃烧时间相比，焦炭燃烧时间显着增加，而挥发性燃烧时间仅在颗粒中含有煤时才有所变化。在纯生物质颗粒上，在氧气浓度介于21％和40％之间的情况下，也主要观察到部分脱离的火焰。在均质燃烧期间，取决于颗粒的类型，颗粒的横截面收缩了26.3–37.5％。