Role of Sodium in Coal in Determining Deposition Rates
Role of Sodium in Coal in Determining Deposition Rates
复制标题
煤中钠在确定沉积率中的作用
DOI：
10.1021/acs.energyfuels.6b02183
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发表时间：
2017
期刊：
影响因子：
5.3
通讯作者：
Wendt, Jost O.
中科院分区：
文献类型：
--
作者：
Zhan, Zhonghua;Wendt, Jost O.
灰中的碱含量通常被认为是决定煤灰在锅炉传热表面上沉积速率的“坏演员”。本文报道了16个试验的结果，其中灰气溶胶沉积速率测量三种煤，在空气和氧燃烧条件下燃烧。一个100千瓦的向下燃烧的实验室燃烧室与一个专门设计的沉积探针。灰气溶胶的粒度分布和尺寸隔离的组合物进行了测量，使用电迁移率，光散射，和低压冲击器技术。将净钠蒸发（假设为以<0.6 μm烟气形式收集的钠分数）与文献数据进行比较。关于灰沉积速率，重点是紧密结合的“内部”沉积物，而不是松散结合的“外部”沉积物，后者无法精确收集或称重。在这些试验的有限范围内，PM 1确实大大富集了钠，沉积速率确实与PM 1的钠含量和煤中Na/（Al + Si）的比率相关，如文献中所提出的。然而，在整个范围内的沉积速率的调查，测得的速率没有相关性以及与钠含量的煤或与钠含量的细灰气溶胶（PM 1或PM0.6），但相关性以及与总的烟气浓度的PM 1，其中的碱性成分变化显着超过16个测试。这表明存款粘附的机理仅仅取决于任何组成的亚微米颗粒的存在。进一步的研究来证实这一点将是有用的，因为这一结论与大多数现有的火山灰沉积模型不一致。本工作的重点是内部污垢沉积，这可以被看作是污垢沉积物的初始层。结渣沉积不在本工作范围内。
The alkali content in the ash is commonly thought to be the “bad actor” in determining coal ash deposition rates on boiler heat transfer surfaces. This paper reports results of 16 tests in which ash aerosol deposition rates were measured for three coals, burned under air- and oxy-fired combustion conditions. A 100 kW down-fired laboratory combustor coupled with a specially designed deposition probe was employed. Ash aerosol particle size distributions and size-segregated compositions were measured using electric-mobility, light-scattering, and low-pressure impactor techniques. Net sodium vaporization (assumed to be the fraction of sodium collected as a <0.6 μm fume) was compared to literature data. For ash deposition rates, emphasis was on the tightly bonded “inside” deposits rather than the loosely bound “outside” deposits, which could not be collected or weighed precisely. Over a limited range of these tests, where PM1was indeed greatly enriched in sodium, deposition rates did correlate with the sodium content of PM1and the ratio of Na/(Al + Si) in the coal, as proposed in the literature. However, over the entire range of deposition rates investigated, the measured rates did not correlate well with the sodium content of the coal or with the sodium content of the fine ash aerosol (PM1or PM0.6) but did correlate well with the overall flue gas concentration of PM1, of which the alkali composition varied significantly over the 16 tests. This suggests a mechanism of deposit adhesion that depends simply upon the presence of sub-micrometer particles of any composition. Additional research to confirm this would be useful because this conclusion disagrees with most existing models for ash deposition. This work focuses on the inside fouling deposition, which could be seen as the initial layer of the fouling deposits. Slagging deposition is not within the scope of this work.