基于灰颗粒的物理特性为分类原则的试验研究

循环流化床(CFB)锅炉炉内的燃烧及传热与炉内床料的状态密切相关,而炉内床料主要是由燃煤含有的矿物组分经过燃烧、爆裂和磨耗过程形成的。文中对6种煤样在固定床燃烧后,使用可视化显微仪,获取了灰颗粒的微观形貌特征,根据灰颗粒的机械强度和耐磨性能的不同,将灰颗粒定义为3类不同性质的灰。以此为基点,采用固定床燃烧后冷态振动筛分和流化床实验台热态流化后筛分的方法,研究了不同燃烧温度下升温速率对灰颗粒粒径变化的影响,以及不同燃烧温度下燃烧时间对灰颗粒粒径变化的影响,推演了不同煤样在燃烧过程中的演化特征。结果表明:3类灰颗粒在不同的燃烧温度和时间的演化过程存在明显的不同,从而为预测循环流化床中的床料粒径分布提供了理论依据。

An Experimental Study of the Classification Principle of Ash Particles Based on Their Physical Properties

The combustion and heat transfer in a circulating fluidized bed(CFB) boiler is closely related to the status of the in-boiler bed material,which is formed mainly in the course of combustion,explosive fragmentation and wear abrasion of mineral constituents contained in fuel coal.The microscopic morphological characteristics of ash particles were obtained by using a visual microscope after six kinds of coal samples have been burned in a fixed bed.The ash particles were classified into three kinds with different characteristics according to their mechanical strength and wear-resistant properties.On this basis,a study was conducted of the impact of temperature rise speed and combustion time at different combustion temperatures on the change of ash particle diameter.The study has been undertaken by adopting a cold-state vibration sifting method after combustion on a fixed bed and a sifting process following a hot-state fluidization on a fluidized bed test rig.Moreover,the evolution characteristics of different ranks of coal in the course of combustion have been deduced.The results show that with respect to the evolution process of different combustion temperatures and durations the three kinds of ash particles exhibit a conspicuous difference.As a result of the foregoing,a theoretical basis is provided for the forecast of a particle diameter distribution of bed materials in the circulating fluidized bed.