Inhibition of lignite ash slagging and fouling upon the use of a silica-based additive in an industrial pulverised coal-fired boiler. Part 1. Changes on the properties of ash deposits along the furnace
Inhibition of lignite ash slagging and fouling upon the use of a silica-based additive in an industrial pulverised coal-fired boiler. Part 1. Changes on the properties of ash deposits along the furnace
复制标题
在工业煤粉锅炉中使用二氧化硅基添加剂可抑制褐煤灰结渣和结垢。
DOI：
10.1016/j.fuel.2014.06.054
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发表时间：
2015-01-01
期刊：
影响因子：
7.4
通讯作者：
Zhang, Lian
中科院分区：
文献类型：
--
作者：
Dai, Bai-Qian;Wu, Xiaojiang;Zhang, Lian
在本文中，我们首次报告了在亚临界蒸汽条件下的 30 MWth 粉状燃料锅炉中燃烧褐煤与二氧化硅添加剂时收集的灰沉积物的特性。燃烧试验连续进行了十个月，并从锅炉内的各个位置采集了灰烬沉积物样本。经证实，与灰有关的结渣和结垢已得到有效控制。除了捕获挥发性碱金属和碱土金属外，过量添加的二氧化硅有利于与熔融液相线混合，促进其团聚，而不是粘附在燃煤器附近结渣。与原煤情况下容易粘附在燃煤器附近形成大量Fe2+-炉渣相比，二氧化硅与煤的混合更有利于在炉边沉积物中形成易碎的硫酸钙，甚至在炉边灰沉积物中也占主导地位。形成的硫酸钙在周层结构中呈高度层状，其中硅酸钙为核，硫酸钙为壳。游离钙在硅酸盐表面上的物理吸附可以提高其比表面积，从而加快硫酸盐化。二氧化硅对 Na 的捕获也很有效，导致大部分 Na 转化为粗底灰，而很少被硫酸化。这反过来又减轻了对流区水管表面与硫酸盐相关的结垢倾向。值得注意的是，相当一部分 Fe 仍以离散颗粒形式保留在富钙炉渣基质之外。相比之下，大部分镁高度结晶为亚微米钙/镁硅酸盐和氧化物颗粒，存在于炉渣基质中，这反过来又增加了粘度并降低了熔渣的粘附倾向。 (C) 2014 Elsevier Ltd. 保留所有权利。
In this paper, we, for the first time report the properties of ash deposits collected from the combustion of lignite mixed with silica additive, in a 30 MWth pulverised-fuel boiler with sub-critical steam conditions. The combustion test was carried out continuously over ten months, and ash deposits were sampled from various locations in the boiler. As has been confirmed, the ash-related slagging and fouling have been controlled effectively. Apart from capturing volatile alkali and alkaline earth metals, silica added in an excess amount is beneficial in mixing with molten liquidus to promote their agglomeration, rather than adhering to the vicinity of coal burners for slagging. Compared to the formation of abundant Fe2+-slag that is prone to stick to coal burner vicinity in the raw coal case, the formation of friable calcium sulfate in fireside deposit is favored upon the mixing of silica with coal, which is even predominant in the fireside ash deposit. The calcium sulfate formed is highly layered in a plerospheric structure in which Ca-silicate is present as the core with calcium sulfate being the shell. The physical adsorption of free Ca on silicate surface is supposed to enhance its specific surface area for a quicker sulfation. The capture of Na by silica is also efficient, leading to the transformation of a remarkable portion of Na into coarse bottom ash with less being sulfated. This in turn alleviates the sulfate - relating fouling propensity on the water tube surface in the convection zone. A noticeable portion of Fe was noticed to remain as discrete grains outside the Ca-rich slag matrix. In contrast, the majority of Mg is highly crystallised as sub-micrometer Ca/Mg-silicate and oxide particles residing within slag matrix, which in turn increase the viscosity and decrease the sticking propensity of the molten slag. (C) 2014 Elsevier Ltd. All rights reserved.