On trimodal particle size distributions in fly ash from pulverized-coal combustion
On trimodal particle size distributions in fly ash from pulverized-coal combustion
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DOI：
10.1016/s1540-7489(02)80058-x
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发表时间：
2002-01-01
影响因子：
3.4
通讯作者：
Miyamae, S
中科院分区：
文献类型：
--
作者：
Linak, WP;Miller, CA;Miyamae, S
燃烧产生的细颗粒物，定义为那些空气动力学直径小于2.5微米，已经受到越来越多的监管审查，因为怀疑与人类健康的不利影响。而经典理论煤燃烧表明，灰蒸发和破碎的机制导致双峰灰粒度分布（PSD），本文提出的实验结果支持其他现有的假设，三种不同的灰模式可能更合适。本文着重于一个中心模式的存在和一般性，约0.7和3.0妈妈直径之间。这种中心模式可能是由破碎机制引起的，但从健康的角度来看仍然很重要，因为大部分包含在2.5 μ m的颗粒尺寸部分内。本文介绍了两个不同的实验室燃烧室和一个工业锅炉的实验结果，都燃烧煤粉。使用各种颗粒取样和尺寸分类方法，包括电迁移率、战斗时间和惯性（低压冲击）方法，证实了中央模式不是所用颗粒取样和尺寸测量方法的伪影。10种不同煤种的燃烧结果一致表明，这一中心模式是显着的高和低阶煤。钙、铁和铝的尺寸隔离元素分布提供了对每种模式形成机制的额外见解。现场试验表明，中心模式可以是细颗粒排放离开静电除尘器（ESP）的主要贡献者。这里提出的新的实验结果解释补充现有的数据和现有的理论文献。
Combustion-generated fine particles, defined as those with aerodynamic diameters less than 2.5 mum, have come under increased regulatory scrutiny because of suspected links to adverse human health effects. Whereas classical theories regarding coal combustion suggest that mechanisms of ash vaporization and fragmentation lead to bimodal ash particle size distributions (PSDs), this paper presents experimental results supporting other existing hypotheses that three distinct ash modes may be more appropriate. This paper focuses on the existence and generality of a central mode, between approximately 0.7 and 3.0 mum diameter. This central mode is presumably caused by fragmentation mechanisms, but is still important from a health perspective, because a large portion is contained within the 2.5 mum particle size fraction. Presented here are experimental results from two different laboratory combustors and one industrial boiler, all burning pulverized coals. Use of a variety of particle-sampling and size classification methods, including electrical mobility, time-of-fight, and inertial (low-pressure impaction) methods, confirms that the central mode is not an artifact of the particle-sampling and -sizing methods used. Results from the combustion of 10 different coals consistently show that this central mode is significant for both high- and low-rank coals. Size-segregated elemental distributions of calcium, iron, and aluminum provide additional insight into mechanisms of formation of each mode. Field tests show that the central mode can be the major contributor to fine particle emissions leaving an electrostatic precipitator (ESP). The new experimental results presented here are interpreted in the light of complementary existing data and available theories from the literature.