Ignition and volatile combustion behaviors of a single lignite particle in a fluidized bed under O-2/H2O condition
Ignition and volatile combustion behaviors of a single lignite particle in a fluidized bed under O-2/H2O condition
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O-2/H2O条件下流化床中单个褐煤颗粒的着火及挥发燃烧行为
DOI：
10.1016/j.proci.2018.05.038
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发表时间：
2019
影响因子：
3.4
通讯作者：
Zhao Changsui
中科院分区：
文献类型：
--
作者：
Li Lin;Duan Lunbo;Zeng Dong;Lu Dennis Y;Bu Changsheng;Zhao Changsui
O2/H2O燃烧作为全氧燃烧的新发展，近年来在燃煤电厂的碳捕获方面逐渐受到越来越多的关注。蒸汽的物理和化学性质，例如反应性、热容量、扩散率，都会影响煤的燃烧过程。在这项工作中，首先在 O2/H2O 气氛下的流化床燃烧室中研究了单个褐煤颗粒的着火和挥发性燃烧特性。火焰和颗粒温度分别通过校准的双色高温计和预埋热电偶测量。结果表明，随着氧气浓度的增加，挥发火焰变得更小、更亮。由于传热系数较高，密相颗粒的着火延迟时间比稀相颗粒短。此外，在密相中，挥发性火焰与颗粒完全分离（定义为离火），而在稀相中，火焰位于颗粒表面（定义为着火）。燃料颗粒在稀相中着火时的自加热作用比密相中更明显，导致焦炭较早燃烧。在低氧浓度下，H2O气氛中的火焰比N2气氛中的火焰颜色更深，因为H2O的热容量比N2的热容高。随着氧浓度的增加，O2/H2O气氛中的火焰温度比O2/N2气氛中的火焰温度显着升高，其中氧在O2/N2气氛中的扩散速率成为主导因素。
O2/H2O combustion, as a new evolution of oxy-fuel combustion, has gradually gained more attention recently for carbon capture in a coal-fired power plant. The physical and chemical properties of steam e.g. reactivity, thermal capacity, diffusivity, can affect the coal combustion process. In this work, the ignition and volatile combustion characteristics of a single lignite particle were first investigated in a fluidized bed combustor under O2/H2O atmosphere. The flame and particle temperatures were measured by a calibrated two-color pyrometry and pre-buried thermocouple, respectively. Results indicated that the volatile flame became smaller and brighter as the oxygen concentration increased. The ignition delay time of particle in dense phase was shorter than that in dilute phase due to its higher heat transfer coefficient. Also, the volatile flame was completely separated from particles (defined as off-flame) in dense phase while the flame lay on the particle surface (defined as on-flame) in dilute phase. The self-heating of fuel particles by on-flame in dilute phase was more obvious than that in dense phase, leading to earlier char combustion. At low oxygen concentration, the flame in the H2O atmosphere was darker than that in the N2atmosphere because the heat capacity of H2O is higher than that of N2. With the increase of oxygen concentration, the flame temperature in the O2/H2O atmosphere was dramatically enhanced rather than that in the O2/N2atmosphere, where the diffusion rate of oxygen in O2/N2atmosphere became the dominant factor.